Textile auxiliaries are defined as chemicals of formulated chemical products which enables a processing operation in preparation, dyeing, printing of finishing to be carried out more effectively or which is essential if a given effect is to be obtained. Certain Textile Auxiliaries are also required in order to produce special finishing effects such as wash & wear, water repellence, flame retardancy, aroma finish, anti odour, colour deepening etc. The prime consideration in the choice of Textile materials is the purpose for which they are intended, but colour has been termed the best salesman in the present scenario. The modern tendency is towards an insistence on colour which is fast to light, washing, rubbing, and bleaching; this movement makes a great demand on the science of dyeing. Auxiliaries, dyes and dye intermediates play a vital role in textile processing industries. The manufacture and use of dyes is an important part of modern technology. Because of the variety of materials that must be dyed in a complete spectrum of hues, manufacturer now offer many hundreds of distinctly different dyes. The major uses of dyes are in coloration of textile fibers and paper. The substrates can be grouped into two major classes-hydrophobic and hydrophilic. Hydrophilic substances such as cotton, wool, silk, and paper are readily swollen by water making access of the day to substrate relatively easy. On other hand hydrophobic fibers, synthetic polyesters, acrylics, polyamides and polyolefin fibers are not readily swollen by water hence, higher application temperatures and smaller molecules are generally required. Dye, are classified according to the application method. Some of the examples of dyes are acid dyes, basic or cationic dyes, direct dyes, sulfur dyes, vat dyes, reactive dyes, mordant dyes etc. Colorants and auxiliaries will remain the biggest product segment, while faster gains will be seen in finishing chemicals. World demand for dyes and organic pigments is forecast to increase 3.9 percent per year through 2013, in line with real gains in manufacturing activity. Volume demand will grow 3.5 percent annually. While the textile industry will remain the largest consumer of dyes and organic pigments, faster growth is expected in other markets such as printing inks, paint and coatings, and plastics. Market value will benefit from consumer preferences for environmentally friendly products, which will support consumption of high performance dyes and organic pigments.
Some of the fundamentals of the book are antimony and other inorganic compounds, halogenated flame retardants, phosphorous compounds, dyes and dye intermediates, textile fibers, pigment dyeing and printing, dry cleaning agents, dry cleaning detergents, acrylic ester resins, alginic acid, polyvinyl chloride, sodium carboxy methyl cellulose, guar gum, industries using guar gum, gum tragacanth, hydroxyethyl cellulose, polyethylene glycol, industries using polyethylene glycols, etc.
The book covers details of antimony and other inorganic compounds, halogenated flame retardants, silicone oils, solvents, dyes and dye intermediates, dry cleaning agents, different types of gums used in textile industries, starch, flame retardants for textile and many more. This is very resourceful book for new entrepreneurs, technologists, research scholars and technical institutions related to textile.
Antimony and Other Inorganic Compounds
In many polymers
the high concentration of halogenated
organic compounds needed to impart flame retardancy adversely affects
physical properties. In practice halogen containing flame retardants
formulated with inorganic compounds that behave synergistically with
halogen. This enables formulators to use less additives without
flame retardance. Indeed in many instances flame retardancy is improved
inorganic halogen synergists are used.
Trioxide. In 1979
approximately 15 900 metric
tons of antimony trioxide (commonly referred to as antimony oxide) was
impart flame retardance to a variety of plastics. Antimony trioxide is
manufactured by oxidizing molten antimony sulfide ore and/or antimony
air at 600 800°C. Typical properties for antimony trioxide are listed
trioxide is a white pigment (qv). Its pigment
strength is a function of the average particle size and the particle
Particle size can be controlled during its manufacture to produce
either a high
tint or a low tint product. The difference in the particle size and
size distribution between high tint and low tint antimony trioxide is
illustrated in Figure 1. Both grades have the same flame inhibiting
but have different effects on pigmentation and physical properties.
products and trade names of antimony trioxide are
summarized in Table 2.
are available at higher costs. They include
White Star S15 from the Harshaw Chemical Company and ultra fine
from PPG Industries.
Trioxide in Cellulosics. Antimony
trioxide can be used as a condensed phase flame retardant in cellulosic
materials. In these substrates it reacts endothermically with the
groups and forms a variety of products. The endothermic reaction
needed to propagate the flame. The products formed are difficult to
shield the underlying cellulose from the flame minimizing pyrolytic and
manufactured by the oxidation of antimony trioxide with nitrates or
(5 9). For Sb205 the
wt % of antimony is 72.8 and the specific
gravity is 3.8.
pentoxide is heated above 380°C it disproportionates
into antimony tetroxide with the evolution of oxygen.
antimony pentoxide is primarily available as a
stable colloid (Nyacol Inc.) or as a redispersible powder (Nyacol Inc.
Industries Inc.). It is significantly more expensive than antimony
is designed primarily for highly specialized applications. Antimony
manufacturers suggest fiber and fabric treatment applications as a
area for its use. The redispersible powder form of antimony pentoxide
also recommended for plastics contains 88% antimony pentoxide and 12%
dispersing agents. Care must be exercised when this product is
into plastic since the dispersing agents can adversely affect the
stability and physical properties.
antimonate Na2OSb2O5.½H2O is a free
flowing white powder
made by the oxidation of antimony trioxide in a basic medium. A few of
properties are shown in Table 3.
strength of sodium antimonate is less than
antimony trioxide. It is recommended for formulations in which deep
are required. Because it contains 62 wt % antimony somewhat higher
concentrations are needed to make it as effective as antimony trioxide
83 wt % antimony.
Antimony Compounds. Recent
developments in inorganic flame retardant synergists have centered on
products that contain antimony and other metals which reportedly give
performance at reduced cost.
(M & T Chemicals
Inc.) appears to be as effective as antimony trioxide in most flame
applications and has a significantly lower price. Although it contains
level of antimony compared to antimony trioxide other metals contained
product significantly boost its flame retarding properties.
has developed a series
of antimony silico complexes under the trade name Oncor. These products
up to 50% antimony trioxide. They are less opacifying than either high
or low tint
antimony oxide. Generally antimony silico complexes are less effective
than antimony trioxide. Therefore although the cost per kilogram is
antimony trioxide the cost effectiveness of the antimony silico
trioxide is used almost exclusively with heat labile
halogen compounds. Most of the mechanisms proposed indicate that
trioxide is activated by reaction with halogens forming antimony
trichloride and antimony oxychloride work primarily
as flame phase flame retarders. The type of antimony halide formed
the concentration of the hydrogen halide and the temperature of the
In this study a
chlorinated paraffin containing 70 wt % chlorine (Chlorowax Diamond
was heated alone at a rate of 20°C/min. A 67% weight loss was noted at
(see Fig. 2). The loss is equivalent to 93 wt % of the theoretical
stoichiometric quantity of hydrogen chloride.
When an equal
weight of antimony
trioxide was added to the chlorinated paraffin and the mixture was
the same rate a 76% weight loss at 310 400°C was noted (see Fig. 3). If
were no reaction the loss would have been only 37.5% since only half of
mixture was the chlorinated paraffin and antimony trioxide does not
below 656°C. The higher weight loss indicates that some reaction
the decomposition products of the chlorinated paraffin or the
paraffin itself and antimony trioxide have taken place. The gas
the reaction has been analyzed and identified as antimony trichloride.
weight loss is equivalent to 90% of the theoretical quantity of
trichloride that can be formed from the mixture. From this thermal
is apparent that antimony trichloride is the predominate antimony
formed from combinations of antimony trioxide and aliphatic chlorine
that generate high concentrations of hydrogen chloride upon thermal
When a cyclic
halogenated organic compound Dechlorane 5 10
(Hooker) that contains 77% chlorine was heated at a rate of 20°C/min
90% of its
weight was lost between 280 and 400°C. It does not generate hydrogen
upon decomposition (see Fig. 4). When equal weights of Dechlorane 5 10
antimony trioxide were heated at the same rate a different weight loss
was noted (see Fig. 5).
Instead of the
smooth continuous decomposition pattern
observed for either the chlorinated paraffin antimony trioxide mixture
Dechlorane 5 10 itself a two stage decomposition pattern was observed.
was a 45% weight loss between 305 and 410°C and another between 490 and
It appears that
antimony oxyhalides are the primary antimony
compounds formed when organic halogen compounds which do not generate
chloride directly upon thermal exposure and antimony trioxide are
trihalides are the flame retarding species whether
they are generated directly from the starting antimony halogen mixture
antimony oxyhalide. They inhibit combustion by altering the manner and
decomposition products formed by the plastic and by modifying the
the flame to make them less exothermic. In the condensed phase or
polymer just beneath the flame antimony trihalide promotes reactions
carbonaceous chars instead of highly volatile reactive gases. The chars
heat shields which deflect the heat of the flame and slow down the
oxidative decomposition of the polymer. The chars also form a seal
polymer preventing potentially flammable gas from escaping and entering
Once in the
flame the antimony trihalides decompose into
various antimony oxides and halogen compounds. The decomposition
not been completely determined.
oxides formed also participate directly in
reactions with the hydrocarbons to give water and molecular hydrogen
flame propagating radicals. Since the formation of the nonpropagating
is less exothermic than the formation of flame propagating radicals
2700 metric tons of borates was used as flame
retarders for poly(vinyl chloride) cellulosics and unsaturated
polyesters in 1979. Zinc borate is by far the most widely used of this
compounds (see Boron compounds). There are a variety of zinc borates
that vary in zinc boron and water content.
and trade names of commercially available
borate flame retardants are shown in Table 4.
Zinc borate is
rarely used alone. It acts synergistically
with antimony oxide enabling compounders to extend antimony trioxide in
Zinc borate is
also used with high levels of alumina
trihydrate in some halogenated unsaturated polyester resins.
Sodium Borate. Boric acid and
(borax) are two of the oldest known flame retardants. They are used
to flame retard cellulosics such as cotton (qv) and paper (qv). Both
are inexpensive and fairly effective in these applications. Their use
limited to products for which nondurable flame retardancy is acceptable
both are very water soluble.
Boron Mechanism. Boron compounds
function as flame retardants
in both the flame and condensed phases. Flame phase active boron
generated from combination of borates and halogenated organic
compounds usually generate boron trihalides which have been used to
flame volatility of air hexane mixtures.
Boric acid and
borax are effective condensed phase flame retardants
in polyhydroxyl compounds especially in cellulosic fibers. When these
are exposed to a flame they melt and form a glasslike coating around
fibers. Prolonged exposure causes the coating to dehydrate generating
cools the flame and cause it to extinguish. The boron residue also
the hydroxyl groups of the cellulose to generate additional quantities
and form an inorganic char that is difficult to ignite and burn. The
char is an
insulator that slows down the rate of polymer degradation and fuel
that also contain other metals are active in
both phases. Although zinc borate is not used alone to flame retard PVC
inhibit flammability in the condensed and flame phases. Upon exposure
flame the PVC generates hydrogen chloride which can react with the zinc
to form nonvolatile zinc compounds as well as volatile and nonvolatile
zinc compounds and boric acid promote char reducing
fuel formation and the boron trichloride and water cool and extinguish
fluoroborate NH4BF4 is
another boron containing compound that has
some utility as a flame retardant. It can decompose to yield both
boron functionalities to the flame retarding process. Flame retardant
formulations recently published suggest that ammonium fluoroborate
used primarily in combination with antimony trioxide. Manufacturers
that the following reaction describes functionally what takes place
two products are exposed to flaming conditions.
formed contribute to extinguishing the flame by
the mechanisms proposed in proceeding paragraphs.
159 000 metric tons of alumina trihydrate
(ALTH) was used to flame retard unsaturated polyesters and foam carpet
in 1979. ALTH is made either from bauxite by the Bayer process from
aluminum by the sinter process. Physical properties listed in Table 5
principal suppliers in Table 6.
trihydrate is the only aluminum compound of
commercial significance as a flame retardant. It functions as a flame
in both the condensed and flame phases.
trihydrate is exposed to temperatures above 250°C it forms water and
The evolution of
water absorbs heat. The water cools the
flame and dilutes the flammable gases and oxidant in the flame. The
residue an excellent heat conductor increases removal of heat from the
Although ALTH is
an inexpensive compound it is a
comparatively inefficient flame retardant. High add on levels up to
as much as the plastic itself are needed to impart acceptable flame
It is used alone only in polymers in which large amounts of filler can
tolerated and increased weight (or density) is desired. The major
areas for ALTH are filled thermoset polyesters and styrene butadiene
latex rug backing.
trihydrate is also used as a secondary synergist to
improve the flame retardance of polymer systems that already contain
trioxide zinc borate or some phosphorus flame retardants.
compounds have been used
as flame retardants of cellulosics for many years. Recently they have
some use in other polymers. Molybdenum compounds appear to function as
condensed phase flame retarders (32). After ignition of PVC
containing molybdenum oxide (MoO3) and antimony
oxide 90% of the molybdenum remained in
the ash and only 10% of the antimony was found.
Since most of
remained in the ash and the formulation did have flame retardant
is probably a condensed phase flame retardant that promotes char. The
mechanism of action has not been sufficiently defined to warrant
Halogenated Flame Retardants
and extensive use of
synthetic polymers in both old and new types of applications has
the concern for combustibility. Although these new polymers are not
more flammable than natural polymers they are more readily used in
forms eg foams
electrical applications etc that can result in an increased fire
Along with the
development of many
synthetic polymer systems during the 1930s and 1940s a significant
the science of imparting flame resistance occurred ie the use of
organic materials to impart ignition resistance to these new polymer
plastics applications the
small size of fabricated articles and the relative scarcity of these
made fire retardancy a secondary consideration. Advances in plastics
have led to increasingly large scale applications especially in the
construction industry. Since many polymers have fuel values (heats of
combustion) comparable to common fuels eg wood oil alcohol etc. it is
understandable that they contribute to the burning process in a typical
halogenated products used
as flame retardants for plastics currently in use are mainly compounds
containing high (50 85 wt %) levels of either chlorine or bromine ie
oxide chlorendic acid tetrabromophthalic anhydride etc. These materials
into two distinct types additives and reactives. The additives have the
advantage of being readily added to a polymer by mechanical means with
minimum of reformulation being required. The reactives on the other
the development of essentially new polymer systems.
polymer forms are considered though the
materials and concepts discussed are almost similarly applicable to
coatings and elastomers. Halogenated phosphorus compounds are included
Flame retardants phosphorus compounds.
of Developing Flame Retardant Polymers
of the principles of developing flame retardant
polymer systems must acknowledge the chaotic situation that exists at
This situation has arisen for a variety of reasons technical economic
problem is the worst in that it is at the root
of most of the other problems and is caused by the fact that the term
flame retardant may be perceived in a variety of ways depending upon
the user s
viewpoint. The term as defined above means simply that some change has
made in a polymer system so that it will pass one or more of at least a
different flammability tests. These tests are normally designed to
not eliminate the fire risk associated with the use of a polymer in
specific use or product. As a consequence a modification of a polymer
makes it suitable for one use does not necessarily make it suitable for
There is no single fire retardant chemical or method that is applicable
polymer systems or even to all uses of a single polymer.
It is therefore
necessary that early in the development of a
flame retardant polymer system the question Why? is answered before
is put into answering the question How? .
It is not
unusual to see many compounds proposed as flame retardant
chemicals that are clearly unusable in any practical sense but that
polymer system to pass a specific flammability test. A polymer system
easily modified so that it can be called flame retardant by some test.
difficult however to do so and keep a polymer system that is low cost
and physiologically acceptable and also mechanically and esthetically
dissimilar from nonfire retardant counterparts.
One of the
most common approaches used to modify the burning properties of
polymers at the
present time is by incorporation of halogen into the polymer matrix
directly or through the use of halogenated additives. The usual
the use of the halogens as flame retardants is based on the theory that
function in the gas phase as radical traps. It is generally agreed that
combustion of gaseous fuels is a high temperature process which
proceeds via a
free radical mechanism.
In the radical
trap theory of flame inhibition it is thought
that equations 6 10 effectively compete with equations 2 5 for those
species that are critical for flame propagation ie .OH and .0. thereby
the rate of energy production and resulting in the extinction of the
Hydrogen fluoride does not significantly enter into the flame chemistry
fully fluorinated compounds are generally considered to be ineffective
retardant agents. The radical trap theory of flame inhibition although
attractive in that it can be adapted to any situation tends to lead to
belief that the simple inclusion of small amounts of halogen into a
system will render the system flame retardant.
physical theory of flame suppression by the halogens
although conceding that the halogens enter into flame chemistry
this participation per se cannot be the primary
mechanism by which the
halogens function. Rather it is postulated that the halogens act by
the physical properties ie the density and mass heat capacity of the
fuel oxidant mixture so that flame propagation is effectively
physical theory is primarily based on the observations that any gaseous
of fuel and halogenated agent generally propagates flame when mixed
with air as
long as the mass fraction of halogen in the mixture is less than ca 0.7
relative effectiveness of the halogens is directly proportional to
weights ie F CI Br I = 1.0 1.9 4.2 6.7. The halogenated agents probably
the same basic mechanisms as the inert gases ie CO2 N2 etc
suppressant effects are additive to those of the inert gases.
the mass fraction of oxygen in the
combustion zone Hc is
the net heat of combustion of the sample
(J/g) r is the stoichiometric mass oxygen/fuel ratio Cp is
the specific heat of the gases in the
combustion zone Ts
surface temperature of the sample (ºC) Ta is
temperature (ºC) and HG is
the apparent heat of gasification (J/g).
The B number contains the fundamental properties of the polymeric
Thus the mass burning rate or burning intensity can be related to the
fundamental properties of the material.
Where Mi is
the mass fraction of the inert components
of the mixture and ma mN mf
of agent nitrogen fuel and oxygen respectively. If all of the terms in
number remain constant an increase in the mass of inert gas in the
zone (ma O)
results in a lower oxygen mass fraction mo a
lower B number and a corresponding reduction
in the polymer burning rate.
When applied to
liquid fuels the Spalding B number in its
simplest form can be visualized as the ratio of the heat of combustion
heat of vaporization (Hc/Hv). Table 1 shows
the significance of
this ratio applied to several halogen containing fuels. In Table 1 the
and fire points are expressed both in °C as normally reported and as
of compound present in the gas phase over the surface of the liquid at
temperature (mg/L). The introduction of halogen has a lesser effect
upon Hv per
milligram of compound evaporated. The ratio Hc/ Hv decreases
with added halogen indicating that
less energy is available from the flame for gasification and in order
the flame burning additional heat from some outside source is required.
the amount of
heat required to vaporize the weight of fuel (latent heat of
present in the gas phase at the appropriate flash and fire points after
fuels have been raised to these temperatures by the outside source.
large increase in mass that must be vaporized in order to obtain
burning in the case of bromobenzene at least 100 times the mass that
vaporized in the case of benzene itself.
theory apparently accounts for the effects seen
when halogenated agents are used as flame retardants. In view of the
the halogen content of a typical plastic is generally ca 1 30 wt % it
obvious that if the typical polymer were totally vaporized the gases
would be quite capable of flame propagation.
In order to
visualize the role of halogen it is necessary to
examine the heat balance that occurs at the surface of the polymer.
shows a schematic of this balance (10). Heat received by the polymer
may arise either as a heat flux from the flame (T) or as an
externally applied heat flux (E) derived from
another source. Heat
is lost either as the heat required for gasification (G) of the polymer
or as heat lost L through
radiation conduction convection dripping
etc. T and
dependent whereas E is
obviously agent independent except in char forming
systems. L may
be agent dependent if the agent acts by
increasing the drip rate of the burning polymer. Halogenated agents
heat balance through T G and
phosphorus may act in the
gas phase it appears to be the most important element affecting G and
the burning process involves heating of the
substrate to a temperature high enough to drive off flammable vapors.
rate of vapor evolution becomes high enough to generate a flammable
mixture ignites. If the rate of vapor or gas evolution becomes
high the heat produced by the combustion process may return enough heat
substrate so that the evolution offuel becomes self sustaining.
When a flame
retardant that acts in the vapor phase is added
to the system part of the vapor that distills from the polymer does not
contribute to the heat of combustion but results only in a reduction in
mass fractions of the oxygen and fuel in the combustion zone. Hence
there is an
increase in the total mass of material that must be vaporized per unit
order to keep the fire burning. A corresponding increase in the amount
energy must be added to the system from an external heat source (E Figure
1) in order to vaporize the extra
and char formation interfere with the energy
feedback cycle (T and
consequently cause an increase in the intensity
of the external heat flux required to balance the energy fuel cycle.
Where the flame
is actively spreading over the surface of a
material the elemental composition of the vapor being evolved ahead of
moving flame is not necessarily the same as the elemental composition
polymer. The composition of the vapors may vary considerably between
temperature at which the material first begins to evolve vapors and the
temperature at which the rate of evolution supports the flame. With
of dynamic burning condition changes in the substrate and the structure
agent are more important than they are under steady state conditions.
There are five
fundamental methods used to fire retard both
natural and synthetic polymer systems. They are
decomposition temperature of the polymer. This is
generally accomplished by increasing the cross linking density of the
with ladder polymers (increase G).
Reduce the fuel
content of the system. This
approach generally involves halogenating the polymer backbone adding
halogenated additives adding inert fillers or by resorting to inorganic
(increase G decrease
flow by selective chain scission. This
approach is generally applicable to thermoplastic polymer systems where
interrupting the polymer backbone results in reduction of the viscosity
polymer and promotes dripping (increase L).
decomposition pathways. This method
is most applicable to cellulosics where the introduction of phosphorus
compounds generates phosphorus acids which catalyze the loss of water
retention of the carbon as char (increase G decrease
include (1) bonding a
skin on the polymer (2) covering the polymer with an intumescent
design of the system and (4) the use of sprinklers (decrease E).
Synergism. Antimony oxide
employed fire retardant adjunct for halogen containing polymer systems
usually employed as a means of reducing the halogen levels required to
given degree of flame retardancy with the polymer system. This
often desirable since the required halogen content for the system may
it affects the physical properties of the system. In other cases the
oxide is used simply to give a more cost effective system.
systems have been widely studied in attempts
to explain the apparent synergistic effects obtained with this
elements. No completely satisfactory theory is available as yet but it
generally agreed that the active agents antimony trihalides or antimony
oxyhalides act principally in the gas phase (12 13). As with the
halogens it is
generally postulated that the antimony halides act as radical traps.
tests show that the optimum halogen (CI
Br)/antimony atom ratio in most systems is 3/1 (14) corresponding to
ratio found in the antimony trihalides ie SbCI3 SbBr3. On the usual
weight basis this
corresponds to a ratio of ca 0.9/1 for the chlorine antimony system and
for the bromine antimony systems.
antimony halides appear
to act principally in the gas phase some effect on the condensed phase
cannot be ruled out. Antimony halogenflameretardant compositions
produce a carbonaceous residue even in polymers such as polypropylene
produces none in the absence of fire retardants. The production of the
carbonaceous residue probably results from the antimony trihalides
acid catalysts which are capable of promoting the dehydrohalogenation
organic halides and coupling and rearrangement reactions in organic
Halogen Systems. A large
number of phosphorus containing compounds have been used in halogen
polymer systems as a means of improving their ignition resistance. In
these cases both the phosphorus and the halogen reside in the same
there is little if any evidence to indicate that having both elements
same molecule has any particular advantage. Because there is no fixed
phosphorus halogen ratio in contrast to the antimonyhalogen system it
frequently easier to optimize the ignition resistance when the
halogen are adjusted separately.
phosphorus appears to act
as an acid precursor in the solid phase to induce selective
pathways that result in a reduction in the rate of fuel formation and
increase in charring. This mode of action is most applicable to
may also be important in other oxygen or nitrogen containing polymers
polyesters (qv) polyamides (qv) and polyethers (qv).
In polymers such
as polyolefins and
polystyrene the formation of acids has little affect on the mode of
decomposition and much of the phosphorus may be volatilized in some
much as 50 99%. Even in these cases some of the phosphorus may end up
polyphosphoric acids which serve to protect the substrate from the heat
produced by the burning gases. The phosphorus that volatilizes will
beneficial flame retarding effects in that it has gas phase flame
activity similar to the halogens.
The main fire
retardants currently used in plastics and
textiles fall into several distinct classes (1) alumina trihydrate (2)
halogenated compounds usually used in combination with antimony oxide
and boric acid and (4) the phosphorus phosphorus nitrogen and
of Action of Phosphorus Flame Retardants
article presents a broad discussion of flame retardant
mechanisms. The following discussion deals specifically with phosphorus
Mechanisms. The mode of
action of phosphorus based flame retardants in cellulose has been more
extensively studied and is better understood than in most other polymer
systems. Two alternative routes of cellulose (qv) pyrolysis are known
to occur one
route proceeds first to a tarry depolymerization product called
(1) which decomposes to volatile combustible fragments the other route
(catalyzed by acids) leads primarily to water and difficultly
general catalyze the desired water and char forming pyrolysis route
acid is particularly advantageous because of its low volatility. Also
strongly heated phosphoric acid yields polyphosphoric acid which is
effective in catalyzing the desired dehydration reaction. The flame
action of phosphorus compounds in cellulose is believed to proceed by
initial phosphorylation of the cellulose. The phosphorylated cellulose
breaks down to water phosphoric acid and an unsaturated cellulose
char by repetition of these steps. Certain nitrogenous compounds such
melamines guanidines ureas and other amides appear to catalyze the
phosphate forming steps and are found to enhance or synergize the flame
action of phosphorus on cellulose.
terephthalate) and poly (methyl methacrylate) the mechanism of action
phosphorus based flame retardants has been shown to involve both a
decrease in the amount of combustible volatiles and a similar increase
amount of residue (aromatic residues and char). The char thus formed
as a physical barrier to heat and gases.
polyurethane foams the
action of phosphorus flame retardants also appears to involve char
character of the
char from rigid urethane foams was found to be affected by the
presence of a phosphorus containing flame retardant caused rigid
to produce a more coherent char possibly serving as a physical barrier
combustion process. There is evidence that a substantial fraction of
phosphorus may be retained in the char.
In polymers such
polystyrene that do not readily undergo charring phosphorus based flame
retardants tend to be less effective and such polymers are usually
retarded by antimony halogen combinations. However even in noncharring
phosphorus additives exhibit some activity that suggests at least one
mechanism of action. It has been proposed and some evidence adduced
phosphorus compounds may produce a barrier layer of polyphosphoric acid
phosphorus containing additives can act in some cases by catalyzing
breakdown of the polymer melt reducing its viscosity and favoring the
drip of molten polymer from the combustion zone. In polystyrene tris(2
phosphate acts at least in part by this mechanism.
commercial polyester fabrics are flame retarded with
low levels of phosphorus additives or reactives which cause them to
drip more readily than fabrics without the flame retardant. This
be counteracted or completely defeated by the presence of
fibers such as cotton which can serve as wicks or by silicone oils
form pyrolysis products capable of impeding melt flow.
Mechanisms. In addition
to the condensed phase mechanisms discussed above phosphorus flame
can exert vapor phase flame retardant action. It has been demonstrated
trimethyl phosphate retards the velocity of a methane oxygen flame with
the same molar efficiency as SbCl3. Both physical
and chemical vapor phase mechanisms
have been proposed for the flame retardant action of certain phosphorus
compounds. Since tris(dibromopropyl) phosphate was found not to change
activation energy of thermo oxidative degradation of polypropylene
raised the oxygen index a vaporphase physical shielding action was
Possibly this action may be produced by bromine containing pyrolysis
rather than by the phosphate itself.
triphenyl phosphate as model phosphorus flame retardants were shown by
spectroscopy to break down in a flame to give small molecular species
PO HPO2 PO2 and
P2. The rate
controlling hydrogen atom
concentration in the flame was shown spectroscopically to be reduced
phosphorus species were present. These data indicate the existence of a
mechanism however the stable volatile compounds used in this study are
typical of many of the phosphorus based flame retardants used
Physical or chemical vapor phase mechanisms may be reasonably
cases where a phosphorus flame retardant is found to be effective in a
polymer and especially where the flame retardant or phosphorus
breakdown products are capable of being vaporized at the temperature of
pyrolyzing surface. In General Electric s engineering thermoplastic
consists of a blend of a charrable poly (phenylene oxide) and a
polystyrene experimental evidence indicates that effective flame
such as triphenyl phosphate act in the vapor phase to suppress the
of the polystyrene pyrolysis products.
A comparison of
a variety of
phosphorus additives at equivalent phosphorus loadings was made in poly
methacrylate) which can be retarded by condensed phase action but
be subject to vapor phase inhibition because it depolymerizes to
flame retardancy was found with trimethylphosphine oxide a volatile
species whereas a much larger oxygen index elevation was observed with
phosphoric acid this result suggests that the condensed phase mechanism
more efficient one in poly (methyl methacrylate).
terephthalate) exhibits a higher oxygen index
with 5 wt % phosphorus incorporated in the backbone of the polymer as
phenylphosphinyl groups as contrasted to 5 wt % phosphorus incorporated
relatively volatile additive triphenylphosphine oxide. This result
that a condensed phase mechanism is more effective than a vapor phase
in this polymer.
The question as
to whether a flame retardant operates mainly
by a condensedphase mechanism or mainly by a vapor phase mechanism is
especially complicated in the case of the haloalkyl phosphorus esters.
of these compounds upon thermal degradation release volatile
hydrocarbons which are plausible flame inhibitors. At the same time
content remains as relatively nonvolatile phosphorus acids which are
condensed phase flame retardants. There is no evidence for the
With Other Flame Retardants. Some claims
have been made for a phosphorus halogen synergism but unlike the firmly
established antimony halogen synergism phosphorus halogen interactions
often merely additive and in some instances slightly less than
of phosphorus halogen synergism (ie activity greater than that
some additivity model) usually do not hold up to careful analysis and
supposed cases are artifacts of nonlinear response concentration
Nevertheless combinations of phosphorus and halogen in separate
compounds or in
a single compound are often quite useful even if not truly synergistic.
between antimony oxide and phosphorus flame retardants
has been reported in several polymer systems and has been explained on
basis of phosphorus interfering with the formation or vaporization of
halide. This phenomenon is also not universal and some useful
formulations have been described for antimony oxide and triaryl
case of synergism has been described involving
a bisphosphine oxide American Cyanamid s RF 699 and ammonium
Based Flame Retardants in Commercial Use
original report of
ammonium phosphate as a flame retardant by Gay Lussac in 1821 and the
commercial introduction of tricresyl phosphate as a flame retardant
for cellulosics early in the present century many thousands of
compounds have been described as having flame retardant utility. A
sampling of these is covered in ref. 33. The more specialized topics of
phosphorus monomers and polymers containing built in phosphorus have
reviewed. This article is confined to the much more limited groups of
that found commercial or semi commercial use.
Compounds. Red Phosphorus. This allotropic
form of phosphorus
is relatively nontoxic and unlike white phosphorus is not spontaneously
flammable (although easily ignited). It is a polymeric form of
thermal stability up to ca 450°C. In finely divided form it has been
be outstandingly effective as a flame retardant additive. In Europe it
found commercial use in molded nylon electrical parts. Handling hazards
flammability odor partial reversion to toxic white phosphorus and the
of color have deterred broader usage. A product Exolit 505 available
Hoechst (FRG) consists of red phosphorus treated with caprolactam and
reported to be safer than the untreated material (38). Related products
marketed in Japan.
Phosphates. These salts
were recommended for treating theater
curtains in 1821. Their use in forest fire control is well established.
Monoammonium phosphate and diammonium phosphate or mixtures of the two
are more water soluble and nearly neutral are still used in large
nondurable flame retarding of paper textiles disposable nonwoven
fabrics and wood products. Their advantage is high efficacy and low
Ammonium phosphate finishes are not resistant to laundering or even to
by water but they are resistant to organic solvents such as dry
solvents. One important advantage of ammonium phosphates as flame
phosphorus flame retardants in general over borax (also used for
cellulosic flame retardants) is their effectiveness in preventing
ammonium phosphates may produce a gritty texture on the surface of some
substrates. This characteristic is lessened by commercial ammonium
formulations containing softening and penetrating agents.
latexes have been formulated with diammonium phosphate and organic
to obtain flame retardant textile backcoatings and nonwoven binders
small but useful degree of durability to laundering and dry cleaning.
ammonium polyphosphate. When
ammonium phosphates are heated with urea or by themselves under ammonia
pressure relatively water insoluble ammonium polyphosphate (Phoschek
is produced. These products are long chains having repeating units of
structure OP(O)(ONH4) . This
product a finely divided solid is a principal ingredient of intumescent
and mastics. In such formulations ammonium polyphosphate is considered
function as a catalyst. Thus when the intumescent coating is exposed to
temperature the ammonium polyphosphate yields a phosphorus acid which
interacts with an organic component such as dipentaerythritol to form a
carbonaceous char. A blowing (gas generating) agent such as melamine or
is also present to impart a foamed characteristic to the char thus
fire resistant insulating barrier to protect the substrate. In addition
intumescent formulations typically contain resinous binders pigments
fillers. Mastics are related but generally more viscous formulations
to be applied in thick layers to girders trusses and decking they
contain mineral fibers to increase their coherence.
Ammonia/P2O5 products. The reaction
of ammonia gas
with phosphorus pentoxide at high temperature yields an amorphous
solid slowly soluble in water to form a nearly neutral solution. The
consists of a mixture of ammonium salts of metaphosphorimidic acid.
shows about two ammonium nitrogen atoms and one imide nitrogen atom for
two phosphorus atoms. Stauffer s Victamide is known to be a complex
a typical component is believed to have structure (2).
Victamide as an
aqueous solution can
be applied to paper cotton cloth cotton batting and nonwovens. When dry
produces a smoother surface texture than that produced by the
ammonium phosphates. Proprietary formulations have been developed
some degree of water resistance presumably the Victamide acts therein
as a phosphorylating
agent. Ammoniation of Victamide by concentrated ammonia produces a
which when applied to a cellulosic substrate and heated yields a
flame retardant finish that withstands several aqueous washes.
Acid Based Systems for Cellulosics. Semidurable
treatments for cotton can be attained by phosphorylation of cellulose.
originally accomplished by heating cotton or paper with phosphoric acid
presence of basic compounds such as urea at ca 145 180°C. Commercial
formulations have been developed utilizing as coreactants either
acid and cyanamide or phosphoric acid and a dicyandiamide formaldehyde
The nitrogenous component catalyzes the phosphorylation of cellulose
the acid degradation of the cellulose and synergizes the flame
of the phosphorus. A fair degree of durability to laundering is
such treatments. Typically several launderings can be tolerated and dry
resistance is good. A substantial part of the decline in flame
during laundering is caused by ion exchange of the protons of the
acid groups by sodium calcium and magnesium cations that suppress the
effectiveness of the phosphorus groups. Such finishes also have limited
because of fabric damage during cure although applications have been
draperies nonwoven fabrics and paper products.
been developed based on phosphoric acid ureaformaldehyde resins and
dicyandiamide as leach resistant clear flame retardant coatings for
Retardants Additive Types. Alkyl
Acid Phosphates. The lower alkyl
acid phosphates have found some limited use as additive flame
cast thermoplastics and polyester resins. In cast poly(methyl
and haloalkyl acid phosphates are effective in combination with halogen
phosphate is a colorless liquid boiling at
209 218°C and containing 17 wt % phosphorus. It is manufactured from
ether and phosphorus pentoxide via a metaphosphate intermediate.
phosphate has been used commercially as an additive for polyester
in cellulosics. In polyester resins it functions as a viscosity
as a flame retardant. The viscosity depressant effect of triethyl
polyester resin permits high loadings of alumina trihydrate a fire
smoke suppressant filler. Triethyl phosphate has also been employed as
a flame resistant
plasticizer in cellulose acetate. Because of its water solubility the
triethyl phosphate is limited to situations where weathering resistance
unimportant. The halogenated alkyl phosphates are generally used for
applications where lower volatility and greater resistance to leaching
phosphate has been employed
as a specialty flame retardant plasticizer for vinyl compositions where
temperature flexibility is critical eg in military tarpaulins. It can
included in blends with general purpose plasticizers such as phthalate
to improve low temperature flexibility.
methylphosphonate (DMMP) is made by molecular rearrangement of
phosphite. It contains 25 wt % phosphorus (near the maximum possible
phosphorus ester) and it is therefore highly efficient on a weight
basis as a
flame retardant. DMMP is a low viscosity colorless liquid bp 185°C.
its volatility it has been useful mainly in thermoset systems. DMMP is
efficient viscosity depressant in polyester resins and epoxy resins. As
retardant it has somewhat greater efficiency than triethyl phosphate
used in similar systems. DMMP is used commercially in mineral filled
and glass reinforced
polyester compounds where its viscosity depressant effect permits use
filler loadings. The use of alumina trihydrate as filler and DMMP in
role of viscosity depressant and flame retardant affords reinforced
resin formulations with low flame spread suitable for bathtubs and
stalls. DMMP has been used commercially for boosting the phosphorus
flame retardants used in rigid foams. DMMP is also used as a chemical
intermediate for the manufacture of several other flame retardants.
Urea Formaldehyde Resins
urea and melamine resin reactions have certain
similarities they also have definite differences therefore it will be
describe them separately. One mole of urea may be reacted with 1 or 2
formaldehyde to produce different products. The reactions may be
under either acidic or basic conditions and again different products
obtained. In addition the dimethylol urea may be produced from urea and
formaldehyde and etherified with butanol separately or the
be carried out simultaneously with the condensation by reacting the
and butanol together. Figure 1 illustrates the condensation reactions
mole of urea and both 1 and 2 moles of formaldehyde under acidic and
conditions insoluble compounds are formed which
cannot be used for coating resins. Under basic conditions the monoor
ureas are produced which can be used as intermediate products for
resins and other purposes. The dimethylol urea is known commercially as
is available as a white solid containing 88 90% DMU and 10 12% water.
soluble in water and alcohol but it polymerizes slowly at room
the insoluble stage.
The usual source
of formaldehyde is formalin which is a 37%
solution of formaldehyde in water. The urea is a white crystalline
a melting point of 133°C and soluble in water to the extent of 80
gm/100 ml it
has a molecular weight of 60. For the production of DMU the correct
urea and formalin are adjusted to a pH of 7 8.5 and reacted at about
Sodium hydroxide is the usual basic catalyst but others may be used
various amines. When the reaction is complete the mass is concentrated
vacuum to the desired solid content and may be tray dried spray dried
crystallized. The DMU is used in some of the non coating applications
to earlier since it may be polymerized to the insoluble stage by
structure of the insoluble polymer has not been proved but there can be
doubt that it is highly complex. It is probable that the structure
cross linked linear polymers and six membered rings as indicated in
Fig. 2 A
and B respectively.
In order to form
the six membered ring structure (B Fig. 2)
the two –NH2 of
urea may react differently with
formaldehyde. One may react as a primary amine to form the Schiff s
by trimerization to the ring structure. The other may then react as an
by elimination of water and formation of methylene linkages connecting
structures as indicated in Fig. 2 B. Until more positive evidence is
regarding the structure of these insoluble polymers the above theories
some idea of their possibilities and their complexity.
Etherification. In order to
change the DMU from a water soluble material to an organic solvent
material it must be made less polar. This is accomplished by alkylation
alcohols. Obviously the lower alcohols with very short carbon chains or
non polar groups are less effective than the higher alcohols with
chains. For example the methoxy methylol ureas are water soluble the
products are soluble in ethanol but good solubility in organic solvents
obtained until butyl alcohol is used. It will be shown later that
solubility and compatibility with other resins are obtained if the
alcohols are used such as capryl or octyl. However these are more
they retard the curing rate of the resin.
Resin. A typical urea
suitable for use in baking coatings may be prepared by dispersing the
butanol which has been slightly acidified. The dispersion is heated and
etherification and polymerization reactions occur. It is essential that
sufficient etherification take place before excessive polymerization
that the product will have good solubility and stability. Conversely if
degree of etherification occurs and relatively low polymerization the
will have low viscosity and will be slower curing. These factors are
by the amount and type of acidic catalyst the temperature and the ratio
components. A variety of acids may be used including phosphoric formic
phthalic. In general the ratio of combined butanol in the final resin
0.5 to 1.0 moles per mole of DMU but of course a considerable excess of
is used during the resin manufacture.
eliminated in the etherification and polymerization
reactions together with any water with the original DMU is removed
straight azeotropic distillation or by a continuous decantation
the desired degree of etherification and polymerization is reached as
by solubility and compatibility tests the resin is neutralized and
concentrated. For a resin solution which is marketed as 50% resin 30%
20% xylol the original butanol solution would need to be concentrated
resin and 37.5% butanol. When 100 parts of this solution are thinned
parts of xylol the resulting product would meet the requirements
above. Every effort is made to remove as much water and free
possible because these detract from stability curing speed and gloss in
finished enamel. In general the final resin solution does not contain
0.5% water and somewhat less of free formaldehyde. Resins of this type
prepared from the original ingredients without first preparing the DMU
intermediate. In such cases the ingredients are reacted first under
conditions to permit the necessary amount of condensation then finished
slightly acidic conditions as indicated above.
formulas for a butylated urea formaldehyde
resin are shown in Fig. 3. This resin is based on a mole ratio of 1
mole urea 2
moles formaldehyde and 1 mole butanol.
polymerized product in Fig. 3 is a highly
simplified and idealized representation. The actual product would be
complex and cross linked and would probably contain ring structures as
indicated in Fig. 2. However the diagram will serve to illustrate the
the type of alcohol and the degree of etherification on the solubility
of cure of the resin.
Compatibility. It should be
apparent that the 4carbon chain alkyl group in the butoxymethylol urea
three purposes (1) it decreases the amount of cross linking (2) it
hydrocarbon solubility on the resin (3) it increases compatibility with
and other resins. . Decreasing the possible cross linkages retards the
rate and hydrocarbon solubility permits the use of xylol to replace
part of the
more expensive butanol. In the manufacture of the resin isobutanol may
be used but
the secondary and tertiary butanols react too slowly. If the ratio of
were reduced from the 1 mole shown in Fig. 3 to 2/3 mole there would be
butoxyl groups in the resin. This would reduce the hydrocarbon
would provide another point for cross linking in the trimer
ratios than 1 mole of butanol would increase the solubility but these
seldom used since they would retard the curing rate and amount of
It should be
apparent that increasing the carbon chain from a
4 to a 10 or 12 carbon chain would provide another method for
hydrocarbon solubility without reducing the number of possible cross
This may be done by using capryl octyl or other alcohols instead of
However these longer chain alcohols are not good solvents for the
DMU. Therefore the DMU polymerizes excessively before any appreciable
etherification takes place and a heterogeneous product is obtained
which is not
suitable for coating resins. However the higher alcohols may be
into the resin by the transetherification procedure. The resin is
first with one of the lower alcohols such as methanol and the
methylol urea reacted with capryl or octyl alcohol. The
takes place because the liberated methanol may be removed by
distillation at a
temperature low enough not to affect the higher boiling alcohol.
Tolerance. Amino resins are
frequently with the medium oil length alkyd resins which are thinned
mineral spirits instead of xylol. Since mineral spirits is not as
solvent as xylol it will be necessary for the amino resins to have
hydrocarbon solubility. One method for accomplishing this is the use of
higher alcohols referred to above. The long carbon chain on the resin
much more non polar and therefore more soluble in aliphatic
degree of solubility of the resin is referred to as its mineral spirits
tolerance. This is measured by adding mineral spirits to the resin
slowly until turbidity develops.
spirits tolerance is usually expressed as the
pounds of mineral spirits tolerated by 100 lb of resin solution before
turbidity develops. The mineral spirits tolerance may also be increased
increasing the ratio of formaldehyde to urea (b) reducing the degree of
polymerization of the resin (c) increasing the amount of alkylation. It
evident that all these methods tend to reduce the curing rate of the
means a longer baking time for the finish in order to obtain the same
variation in type of alcohol was the only composition variable
the preceding discussion of urea resins. However both the amino and the
aldehyde components may also be changed. The only other amino resin
achieved commercial importance to date is the melamine formaldehyde
described in the following section. . However mention should be made of
thiourea since it was one of the early amino compounds investigated for
formula shows that the oxygen of urea has been replaced with sulfur.
made with thiourea have slightly better water and alkali resistance
comparable urea resins but they are not as pale in color are somewhat
are inferior in exterior durability.
the most useful aldehyde for amino resins
utilized in surface coatings. An aldehyde with more carbons such as
acetaldehyde may be expected to increase the solubility of the resin
curing rate color retention and film properties have been reported to
inferior (8). Parker (8) also points out that mixtures of formaldehyde
acetaldehyde are impractical because very little of the higher aldehyde
combined under such conditions. It can be removed quite readily by
of the resinous material. Furfural has not been used extensively in
resins to date but it is employed in amino resins for adhesives and
In 1834 Justus
von Liebig (9) produced a new chemical which
he believed was the amine of melam and which he called melamine.
investigations have shown that his analysis was not entirely correct
chemical has retained its original name. It is a member of the class of
compounds known as triazines and may be designated 2 4 6 triamino 1 3 5
It may also be considered a trimer of cyanamide. It may be prepared
dicyandiamide by heating under pressure in the presence of a diluent
alcohol or ammonia. The relation of melamine to cyanamide and
shown in Fig. 4.
development and methods of production of melamine are given in
detail by McClellan (11). Hughes (12) studied crystalline melamine and
to be a resonance hybrid with the position of the atoms as shown in
Fig. 5 (a).
Ostrogovich (13) suggested both amino and imino structures in view of
possibility of tautomerism Fig. 5 (b). The amino form is generally used
discussion of melamine in coating resins because its highmelting point
stability suggest this benzenoid structure. Melamine is a white
powder with a melting point of 354°C. It has a molecular weight of 126
specific gravity of 1.57 at 25°C. Its solubility in water has been
Chapman (14) to be 0.5% at 25°C 1.0% at 50°C 2.5% at 75°C and. 4.0% at
Solvents. The terpene
solvents are the oldest in use by the paint industry and are obtained
trees. They have been replaced by lower cost aliphatic hydrocarbon
many coatings. Their chemical properties make them quite valuable as
materials for synthetic resins and other compounds. The chemical
important constituents of terpene solvents are shown in Fig. 1.
the most widely used terpene solvent its principal use being in house
and in some varnishes. The production of gum turpentine from the
the pine tree is described. The production of wood turpentine dipentene
pine oil from solvent extraction of pine stumps followed by steam
contains 60 65% a pinene and 30 35% pinene.
Wood turpentine contains about 80% a pinene the remainder being
and terpene alcohols. Dipentene has a higher boiling point than
excellent solvent properties. It is also used to retard the skinning of
varnishes synthetic resins and enamels. The heavy fractions obtained
production of wood turpentine are known as pine oil. These fractions
terpene tertiary and secondary alcohols plus varying percentages of
terpene hydrocarbons. Small percentages of phenol ethers and ketones
present. The polar non polar structure of pine oil makes it suitable
for a wide
range of uses. It has excellent solvent properties improves the flow of
retards skinning is an antifoaming agent and has some bactericidal
action. A typical
group of terpene alcohol solvents is given in Table 1.
p Cymene and p
menthane are obtained from the
catalytic disproportionation of dipentene. As a result they have a
degree of purity and are used as chemical raw materials as well as
p Menthane is a
saturated terpene and therefore not
susceptible to oxidation like the unsaturated terpenes.
uses for terpene solvents in varnishes resins and
coatings are given in other sections of this book and in Volume II. The
physical characteristics of a typical group of commercial terpene
given in Table 2.
Solvents. The petroleum
and coal tar
hydrocarbon solvents are used extensively because of their low cost
solvent power for oils and resins and effectiveness as diluents for
nitrocellulose lacquers. The petroleum solvents are the lighter
obtained by the distillation and fractionation of the crude oil. They
the original turpentine substitutes Varnish
Makers and Painters Naphtha (VM &
P Naphtha) and mineral spirits. Vast improvements have been made in
fractionation apparatus with the result that today many grades of
solvents are available as shown in Tables 3 and 4.
The coal tar
hydrocarbons are obtained by distillation of the
material from the coke oven by product recovery process. They include
(benzol) toluene (toluol) xylene (xylol) and other aromatic
tremendous wartime demand for toluene to make explosives stimulated
produce it from other sources. Today more aromatics are produced from
than from coal tar.
solvents may be classified chemically in
Aliphatics straight or open chain
cyclic saturated hydrocarbons with or without alkyl side chains.
cyclic hydrocarbons carbons containing the benzene ring structure.
hydrocarbon solvents are usually mixtures of
closely related compounds and isomers hence the range in distillation
for single solvents shown in Tables 3 and 4. The structures of typical
hydrocarbons are shown in Fig. 2 with the boiling points of the pure
points increase with increase in molecular weight
in a given series but the effect of molecular shape is shown by the
compounds in Fig. 2. They are isomers of hexane and therefore have the
composition and molecular weight but the boiling point decreases with
shortening of the main carbon chain. The increase in boiling point of
normal straight chain saturated hydrocarbons or alkanes is shown in
Fig. 3. The
normal alkanes containing from 5 to 16 carbon atoms in the chain are
room temperature. The solid paraffin wax contains from 18 to 25 carbons
chain and polyethylene contains several hundred carbons. This topic was
discussed in Chapter 1 with respect to the secondary valence forces and
length and their effect on the physical properties.
The wide range
of properties in hydrocarbon solvents which
are available commercially is illustrated in Table 3 with the Amsco
the American Mineral Spirits Co. ASTM Designation D86 46 gives the
for distillation of petroleum hydrocarbons. The report usually contains
temperatures of the initial boiling point (when the first drop falls
end of the condenser) the points at which 50% and 90% by volume have
distilled the dry point (at which the bottom of the flask becomes dry)
end point or temperature at which the last drop is obtained. Additional
must be applied after the bottom of the flask is dry to obtain the last
It is advantageous in many cases to have the spread in distillation
temperatures kept as small as possible but this requires closer
with an increase in cost.
In Table 3 the
solvent power is indicated by the range of KB
values from 34 to 37 for the regular mineral spirits type of solvent to
toluol. The straight aniline point is used for the aliphatic or mineral
ype solvents and the mixed aniline point for the aromatic type as
previously. The results from the nitrocellulose dilution ratio test are
for the solvents having fast enough evaporation rates and sufficient
power to be used as diluents. The test was run with butyl acetate as
solvent portion. The values would be different if another solvent were
explained previously. It will be noted that the aromatics are higher in
per gallon than the aliphatics.
A typical set of
characteristics of aromatic solvents as
produced by the coal tar industry is given in Table 4.
Explosion Hazard. A comparison of
point autoignition temperature and explosive limits in air for a
hydrocarbon solvents may be obtained from Table 5. The fire hazard is
to the volume of vapor in the air the volumes of solvent vapor per
solvent evaporated at 80°F and 212°F are given. Also given is the
density in comparison with air.
The volume of
solvent vapor at a given temperature may be
calculated from the relationship between molecular weight and volume.
example when the molecular weight is expressed in pounds 1 lb mole of
occupies 400 cu ft at 80°F and 500 cu ft at 212°F. These factors are
in the following formula
formula to calculate the concentration of toluol
at 80°F one obtains about 31 cu ft of vapor per gallon evaporated. When
factor of safety of 4 this means that 4 × 100 × 31 = 12 400 cu ft of
be supplied for each gallon of toluol evaporated to keep the
safely below the explosive point.
Dyes and Dye Intermediates
intensely colored substances that can be used to
produce a significant degree of coloration when dispersed in or reacted
other materials by a process which at least temporarily destroys the
structure of the substances. This latter point distinguishes dyes from
which are almost always applied in an aggregated or crystalline
Modern dyes are products of synthetic organic chemistry. To be of
interest dyes must have high color intensity and produce dyeings of
permanence. The degree of permanence required varies with the end use
absorb energy over various parts of the
electromagnetic spectrum. The characteristic of dye molecules is that
absorb radiation strongly in the visible region which extends from 4000
angstroms. Only organic molecules of considerable complexity which
extensive conjugation systems linked to electron withdrawing and
groups give sufficient absorption (tinctorial value) in the visible
be useful as dyes. The shade and fastness of a given dye may vary
the substrate due to different interactions of the molecular orbitals
dye with the substrate and the ease with which the dye may dissipate
absorbed energy to its environment without itself decomposing.
The primary use
for dyes is textile coloration although
substantial quantities are consumed for coloring such diverse materials
leather paper plastices petroleum products and food.
and use of dyes is an important part of
modern technology. Because of the variety of materials that must be
dyed in a
complete spectrum of hues manufacturers now offer many hundreds of
different dyes. An understanding of the chemistry of these dyes
they be classified in some way. From the viewpoint of the dyer they are
classified according to application method. The dye manufacturer on the
hand prefers to classify dyes according to chemical type.
Both the dyer
and the dye manufacturer must consider the
properties of dyes with relation to the properties of the materials to
In general dyes must be selected and applied so that color excepted a
of change is produced in the properties of the substrate. It is
to consider the chemistry of textile fibers as a background for an
understanding the chemistry of dyes.
The major uses
of dyes are in coloration of textile fibers
and paper. The substrates can be grouped into two major classes
hydrophilic. Hydrophilic substances such as cotton wool silk and paper
readily swollen by water making access of the day to the substrate
easy. On the other hand the ease of penetration also allows easy
aqueous systems and special techniques must be used where a high degree
of wet fastness
On the other
hand hydrophobic fibers such as the synthetic
polyesters acrylics polyamides and polyolefin fibers are not readily
water hence higher application temperatures and smaller molecules are
chemist has increased the versatility of the
newer fibers by incorporating dye sites of a varying nature as needed
achieve dyeability with a predetermined class of dyes. It is now
have polyesters acrylics and polyamide fibers which can be dyed with
(basic cationic) negative (acid anionic) or neutral (disperse) dyes.
recent developments have allowed the fabric designer to produce
(textiles carpets) fabricated in patterns which can be dyed three
colors from one dyebath containing three types of dyes. This concept is
dyeing and is becoming increasingly popular as a low cost method of
Cotton and rayon
(regenerated cellulose) fibers are composed
of cellulose in quite pure from. Cellulose lacks significant acidic or
but has a large number of alcoholic hydroxyl groups. It is hydrolyzed
acid and swollen by concentrated alkali. When cotton is swollen by
alkali under tension so that the fibers cannot shrink lengthwise it
silk like luster. This process is called mercerization. The affinity of
mercerized cotton for dyes is greater than that of untreated cotton.
Cotton and rayon
fibers are easily wetted by water and afford
ready access to dye molecules. Dyeing may takes places by adsorption
reaction with the hydroxyl groups. It is also possible to make cotton
receptive to a variety of dyes by pretreatment or mordanting with a
capable of binding the dyes.
Wool and silk
fibers are protein substances with both acidic
and basic properties. They are destroyed by strong alkali. Strong acid
hydrolysis but the process may be controlled to permit dyeing from
Wool and silk
are wetted by water and are dyed with either
acid or basic dyes through formation of salt linkages. They may also be
with reactive dyes that from covalent bonds with available amino
Mordanting is sometimes used to alter the dyeability of wool and slik.
cellulose fibers differ from cellulose fibers in
that they are more hydrophobic and lack large numbers of free hydroxyl
The higher the degree of acetylation the more unlike cotton and rayon
acetates become. Strong acid and strong alkali degrade cellulose
the initial attack is slow under moderate conditions because of the
of wetting the fiber. The triacetate is the most hydrophobic and the
cellulose actetates is effected with dyes of low
water solubility which become dissolved in the fiber or by occlusion of
formed in situ. Acid basic and reactive dyes cannot
be used because of
the lack of sites for attachment.
(nylon) are synthetic fibers possessing
properties somewhat like those of wool and slik. They are more
with only a limited numbers of basic or acidic groups. Polyamides are
by strong acid but may be dyed from acidic dye baths under controlled
are dyeable near the boiling point of water
with acid dyes that from salt linkages with basic sites. Dyeing by this
is limited by the availability of these sities. Dyes like those used on
cellulose acetates (i.e. that dissolve in the fiber) or reactive dyes
to available amino groups may also be used.
synthetic fibers unlike any produced in nature. They are hydrophobic
good stability to acid and alkali as a result of this hydrophobicity.
hydrolyzed under sufficiently drastic conditions however. Some
lack functional groups others are provided with acidic groups or
modified to make them more hydrophilic.
are dyed by solution of dyes in the fiber or to a limited extent by
of dyes formed in situ. Modified polyester fibers may be dyed in these
with dyes selected according to the nature of the sites introduced by
modification. Both unmodified and modified polyester fibers must be
vigorous conditions often with the assistance of a swelling agent to
hydrophobic synethetic fibers with excellent chemical stability. They
resemble any natural product. The only funcational groups pressent are
introduced for the purpose of providing sites for dyeing.
are dyed by
solution of dyes in the fiber by occlusion of dyes formed in
situ and by
formation of salt linkages with dyes capable of attachement to sites
for that purpose. Basic dyes are used on acrylic fibers bearing
groups for examples.
make up a class of fiber forming materials that varies greatly in
on constitution. Some vinyl fibers are very resistant to degradation by
Dyes are selected accoding to the nature of the specific polymer to be
fibers are formed
from the products of polymerization of unsaturated compounds of carbon
hydrogen for example propylene. They do not absorb water and are
quite inert. They can be dyed with special disperse dyes but are
by introducing a colorant into the polymer before the fibers are spun.
types of polypropylene incorporate metal ions such as Ni++ to
act as dye sites for chelatable dyes.
Glass fibers are
used for special purpose for example where
flammable materials cannot be tolerated. They are often colored during
manufacture but can be dyed by special techniques which involve the use
surface coatings that have affinity for dyes.
Paper is a
nonwoven material made up primarily from cellulose
of varying degress of refining (see chapter 15). Paper may be colored
pulp as a watery fibrous slurry by either continuous or batch methods.
dyeing process takes place at ambient temperature and the dyes are
the pulp by their affinity for the cellulose. Direct dyes are most
used. In continuous coloration the dye solutions are metered directly
into a moving
stream of pulp. In batch operations dye is added to a pulper beater or
chest containing a given quantity of slurry.
Paper may also
be colored on its surface after the inital
sheet is formed pressed and partially dried. This can be done at the
of the paper machine or color can be carried by a calender roll for
sheets. A wide vareiety of low cost dyes can be used for surface
Properties of Dyes
of dyes may be classified as application
properties and end use properties. Application properties include
and dyeing rate. End use properties include hue and fastness to
influences such as light washing heat (sublimation) and bleaching. Dyes
selected for acceptable end use properties at minimum expense. Involved
application procedures are used only when necessary to acheive
It has become
common practice to treat dyed textiles with
agents designed to improve resistance to shrinking wrinkling and the
These agents frequently alter the appearnce and fastness of dyes.
after treatments must therefore be considered as an important end use
The amount of
dye required to obtain a light shade is usually
about 1 per cent of the weight of the fiber heavier shades may require
as 8 per cent. These values are very approximate since dyes differ in
strength and are usually sold in diluted form. These amounts of dye are
sufficient in most cases to markedly affect the properties other than
the fiber. Care must be exercised however to apply the dye under
that do not cause fiber degradation.
It is obvious
from the list
above that many basic dyes have about 10 20 times the color value per
as the anthraquinone types. Unfortunately light fastness is in the
order the anthraquinones being used where maximum durability to light
needed. The challenge to be dye chemist or engineer is to increase the
of the light fast dyes or to increase the fastness of the strongest
to application method for the convenience of the dyer. The best
method available is that used in the color index a publication
sponsored by the
society of dyers and colourists (England) and the American Association
Textile Chemists and Colorists.
dyes depened on the presence of one or more acidic groups for their
to textile fibers. These are usually sulfonic acid groups which serve
the dye soluble in water. An example of this class is Acid yellow 36
Acid dyes are
used to dye fibers containing basic groups such
as wool slik and polyamides. Application is usually made under acidic
conditions which cause protonation of the basic cause protonation of
It should be
noted that this process is reversible. Generally
acid dyes can be removed from fibers by washing. The rate of removal
the rate at which the dye can diffuse through the fiber under the
washing. For a given fiber the diffusion rate is determined by
and shape of the dye molecules and the number and kind of linkages
Chrome dyes. A special kind
of acid dye used mainly
on wool they posses improved fastness when converted to chromium
suitable chromium salt is applied to the fiber (1) before the dye (2)
same time as the dye or (3) after the dye. All these methods are
more complicated than is desired. In recent years manufactures have
available dyes in which chromium is already a part of the molecule.
are simpler to apply than the older types and as a consequence are
or Cationic Dyes
become attached to fibers by formation of salt
linkages with anionic or acidic groups in the fibers. Basic dyes are
have a basic amino group which is protonated under the acid conditions
dyebath. Cationic dyes can be divided into the three classes which are
brown 1 (Bismark brown) is an amino containing dye which is redily
under the pH 2 5 conditions of dyeing.
violet (Basic violet3) is an example of a cationic
dye in which the cationic charge is delocalized by resonance and may be
at any one of the basic centers at any time. These resonance forms of
equivalent energy are one of the reasons that crystal violet is among
strongest dyes known. This high color value (tinctorial strength) has
commercial interest in the hectograph copying system. In this system
violet in a wax base is transferred to the back of a typewritten copy
using paper moistened with alcohol more than 200 good copies may be
Dry Cleaning Agents
garments is done in much the same manner as
laundering except that organic solvents are used in place of water. As
laundering detergents are added to the solvent to enhance its cleaning
Other solvent additives are used to give the textile the desired
may be done merely to improve the hand or drape of the textile or
additives may be used to acheive water repellency insect repelleney or
washes are similar in construction to commercial
laundry washers but in drycleaning provision is made for clarifying the
for reuse. In laundering the used wash water is discarded this cannot
with the more expensive drycleaning solvents.
drycleaning system the solvent is continuously pumped
through the washes and then through some type of after designed to
suspended soil. Provision is also made for distillation of the solvent
it form the solvent soluble soil.
The filters also
contain activated carbon to absorb dissolved
dye which would otherwise build up in the solvent.
products used in small quantities by
drycleaners are formulted to remove stains by local appplicaton to the
area of the garment.
Only two classes
of solvents have proved suitable for
drycleaning petroleum fractions and a few halogenated hydrocarbons. All
classes of solvents fail to meet the following eight major requirements
must not weaken dissolve or shrink the ordinary textile fibers.
must not remove the common dyes from fibers.
must be an acceptable solvent for fat and oils.
must not impart an objectionable order to drycleaned textiles.
must be sufficiently volatile to permit reclamation by distillation and
permit garments to be tried without prolonged heating at excessive
must be noncorrosive to metals either when dry or in the presence of
must be relatively nontoxic.
must have a flash point of 1000F or above.
drycleaning solvents used in the U.S. are the
petroleum fraction called Stoddard solvent of which there are four
perchlorethylene and to a limited extent trichlorethylene and
exceptions of the solvents the chemicals used in
drycleaning are sold as brand name formulations and the only tests
them are the determination of the amount of detergent in the solvent
amount of water in a solution of detergent in solvent. However these
are tested to determine how well they perform the function they are
for according to a number of procedurs developed by the National
Much of the
drycleaning done in the United States employs a solvent
corresponding to a petroleum fraction with a minimum flash point of 1000C.This solvent
has been named
Stoddard solvent for W.J. Stoddard. The first commercial standard for a
drycleaning solvent CS3 28 was issued in 1928 by the National Bureau of
The latest revision of this specification is CS3 41 it also became an
Table 1 summarizes the current specifications of regular Stoddard
other petroleum fractions are also broadly termed
as Stoddard solvents. These are the 1400F solvent the
low end point solvent and the ordoless
1400F Solvent. This
solvent is safer than the regular stoddard solvent. Therefore it may be
locations where stoddard solvent is prohibited. Also building codes for
using 1400F solvent
are not so rigorous. For example explosion proof motors and other
fixtures are not required. Specifications of 1400F solvent which
differ from the specificantions of the
regular stoddard solvent are listed in Table 2.
Low End Point
Solvent. This type of
has a dry point in the range of 330 3620F compared with
368 4090F for the
regular stoddard solvent. The result is a
rapid drying solvent. There is no specification covering this solvent.
regaeded as a premium grade because of the fast drying feature.
Solvent. Whereas regular
stoddard solvetn is
specified to be free of objectionable odor this new class of stoddard
is free of all odors. This is acheived by removing or hydrogenating all
aromatic compounds. The solvent also meets all requitements for a
solvent since smog production is related to the aromatic content.
is also regarded as a premium grade of
stoddard and is not conered by a separate specification.
Some comments to
the specification tests for stoddard solvent
are given here.
Odor. The term sweet
as used in the specification means the
opposite of rancid or sour. Although the usual methods of clarifying
a drycleaning plant remove odors that accumulate during continued
processes do not always remove dodrs caused by improper refining.
solvent when received from the refinery should be free from undesirable
There is nothing to show whether or not a solvent meets the requirement
the opinion of the examining chemist. Many samples of stoddard solvent
rather strong odor but it is easily removed from the fabric by
Flash point. The flash point
is governed by those
portions of the solvent that have the lowest boiling points and are
the most volatile. Since these portions evaporate more rapidly than the
the solvent the flash point of Stoddard solvent in a drycleaning system
gradualy rises with use. Soaps prespotters or other added materials
contain low flash solvents (such as some alcohols) that lower the flash
of the solvent and increase the fire hazard. The introduction of even
amounts of methyl ethyl or isopropyl alcohol into a washer lowers the
point of the solvent below normal room temperatures.
A lighted match
held over Stoddard solvent at ordinary room
temperatures does not ignite the solvent because the solvent is not
enough vapor to form a combustible mixture with the air. If the
the solvent is raised vapor pressure is increased and the air above the
becomes richer in solvent vapors. Finally a temperature is reached
solvent has vaporized to form a combustible mixture with the air If a
then introduced above the solvent the vapors will flash. The lowest
at which this occurs is called the flash point. Since the flash point
stoddard may not be under 1000F there is
no danger of fire from solvent vapors until the temperature of the
rises to 1000F or above.
The flash point
specification is frequently violated. In some
cases the refinery may have set the lower limit of the distillation
low. Such violations usually result in a solvent with a flash point of
98 or 990F. A more
dangerous type of
violation however results from careless handling of the solvent. For
is sometimes transported in tank trucks that were previously used for
gasoline and still contain small quanities of gasoline. As little as 1%
gasoline in stoddard solvent lowers its flash point considerably.
The flash point
by ASTM method.
refined solvent may contain traces of dissolved free sulfur which can
the metals of storage tanks and equipment. The corrosion test is
according to ASTMD 1616 60 at an elevated temperature 121ºF. Under
conditions corrosion that would be apparent after considerable use of
solvent at room temperature can be seen after only 3 hr.
Range. From the
standpoint of a drycleaning solvent there are disadvantages in products
containing very low or very high boiling hydrocarbons. Low boiling
petroleum ether and gasoline cause fires and high evaporation loss high
hydrocarbons such as kerosene cause excessive drying time. The
range for Stoddard solvent is between 300 and 4100F a range not
low enough to cause undue fire hazard and
evaporation loss or high enough to prolong the drying time.
stoddard solvent is determined according to ASTM D 86 66 and D 1078 67.
nonvolatile matter in the solvent often contributers to odors and
drying time. Because of the high temperatures used a small amount of
residue is usually formed during the distillation test. A sample of the
solvent evaporated on a steam bath where temperature is not raised
above 2120F yields a
smaller and less odorous
Acidity. If the
solvent is given a sulfuric acid treatment in the refinery and not
a neutralizing treatment (such as with caustic soda) it will contain
amounts of sulfuric acid or other acidic materials. Even small amounts
sulfuric acid are undesirable in a drycleaning solvent as they corrode
equipment and damage garments. Fortunately almost without exception
solvents pass the acidity test.
has a very high
boiling point. The presence of this substances in the solvent will be
residue in the flask after the distillation. If a residue of 1 ml
distilling 100 ml of solvent any sulfuric acid present is concentarted
100 times. Thus it is logical to test the residue from distillation for
ASTM D 1093 65 the solvent sample is shaken with
water and one drop of a 0.1% methyl orange indicator solution is added
aqueous layer there should be no change in the color of the indicator.
Doctor Test. Mercaptans
impart to the solvent
unpleasant odors which may be absorbed onto the garments during
The doctor test is a qualitative method to determine whether the
mercaptans was properly done in the refinary. Sulfur and sodium
added to the solvent in a test tube. If mercaptans are present in the
reaction proceeds and the black lead sulfide formed is indicative of a
Absorption Test. This test
determines if the solvent contains appreciable amounts of unsaturated
hydrocarbons. These would be in the solvent if it was inadequately
sulfuric acid during refining. Since unsaturated hydrocarbons turn
cause undesirable odors in drycleaned garments it is imperative that
removed before the solvent leaves the refinery.
In the test
concentrated sulfuric acid is added in a
graduated cylinder to the solvent and shaken. Sulfuric acid reacts with
unsaturated hydrocarbons present and most of the products of the
settle into the acid layer thus the volume of the solvent is decreased.
some of the products formed from the reaction remain in the solvent
test does not give a quantitative measure of unsaturated hydrocarbons
that is a
5% absorption of the solvent by sulfuric acid actually represents a
percentage of unsaturated hydrocarbons in the solvent.
the strength of commerically available
concentrated sulfuric acid cause variations in the sulfuric acid
test. Therefore the acid strength must be standardized if
(tetrachloroethylene) became an important drycleaning
solvent because of its nonflammability which permits its use in places
all types of flammable solvent are either forbidden by codes or
high insurance rates. Its general properties are given in Table 3 and
specifications proposed by the NID are listed in Table 4.
Residual Odor. Any residual
odor left in a fabric
after treatment in the solvent is objectionable. Detection of such
smelling is more sensitive if the fabric is steamed immediately prior
test. A swatch of bleached but unfinished cotton poplin Style A 400W
Inc. is used and subjected to the following test.
cotton at 60% relative humidity for at least 8
hr prior to use. Soak the swatch in perchlororthylene for 5 min then
and hang it to drain dry for about 4 hr. Tumble the swatch in a tumble
for 30 min at 1400F.
To test for odor
grasp the swatch in the center with a
forceps hold it in live steam for 5 sec and smell it immediately. Test
untreated swatch smiultaneously. There should be no discernible
odor between the two swatches.
Residue. This test
detects the presence of
nonvolatile impurities in the solvent. It is determined gravimetrically
evaporating a measured quantity of solvent and weighing the residue as
Dry a 4 in.
diameter evaporating dish and weigh it to the
nearest 0.1 mg. Place it on a steam bath in a hood and add the
perchloroethylene to be tested by pipet in two 50 ml portions.
has a high specific gravity. 1.62 and is difficult to handle in a 100
Add the second portion afted the first is partially evaporated.
solvent has completely evaporated on the steam bath
heat the dish further in an oven at 1050C for I hr then
cool it in a desiccator and weigh. The
increase in weight of the dish in grams for a 100 ml sample is %
Perchloroethylene is stabilized by
adding traces of chemicals known to inhibit its decomposition. Loss of
stabilizer or the pressure of certain impurities can lower the
stability of the
Wash two strips
foil 2.0×7.5×0.005 cm in concentrated
hydrochloric acid. Rinse dry and weigh to the nearest 0.1 mg. Add 75 ml
test solvent and 3 ml of water to a 300ml Soxhlet extractor. Place one
strip in the flask and the other into the condenser of the soxhlet.
Soxhlet at a rate that will cause it to empty 8 10 min.
After 24 hr
remove the strips wash them again in concentrated
hydrochloric acid and weigh. The combined weight loss of the two strips
not exceed 30 mg.
Note Do not fail to
add the water with the solvent. The
test is worthless in the absence of water.
Around 1960 du
pont introduced trichlorotrifluoroethane as a
drycleaning solvent under the trade name valclene. This solvent has
much interest because of its ideal properties but it is too volatile to
in machines designed for perchloroethylene. Therefore its full
a wait machine development. A number of companies have introduced small
machines for the solvent but it will be several years before use of the
specifications or test methods have been developed
for this solvent.
In addition to
the tests given under the specifications there
are several analytical methods designed for quality control purposes in
drycleaning operations. These methods are normally performed on used
taken from plant washers. The following tests are made routinely on
Concentration. The method of
anionic detergents is used. There is no satisfactroy method for
detergents that are all nonionic however manufacturers of niononic
normally include some anionic surfactant in the mixture to serve as a
This serves the purpose of quality control with a known product but not
analysis of an unknown mixture.
Residure. Except that
10ml samples are used
instead of 100 ml.
Content. The moisture
content of the used
solvent can be determined by the Karl Fischer method.
Acid Number. This test was
originally designed to
measure the buildup of fatty acids in the solvent. Its value has
recent years because of the widespread use of amine sulfonate
detergents react quantitatively with the titrant giving a high value
fatty acid content of the solvent. However the test is still useful for
purposes where proper correction can be applied for interfercence by
In other fields
acid number is defined as the mg of potassium
hydroxide neccessary to neutralize l g of sample. In drycleaning. The
defined acid number as the mg of potassium hydroxide necessary yo
1.28 ml of solvent.
The titration is
made in the usual manner using a 0.06 N
alcoholic solution of potassium hydroxide and phenolphthalein
indicator. It was
found that 2 methyl 2 4 pentanediol is a better solvent than ethanol
its solubility in petroleum solvents.
Residual Odor. The test is
carried out according to the procedure given on p 608.
Color. The color
of used drycleaning solvents may be due chiefly to dyes dissolved from
textiles. The balance is caused by colored soils or colloidally
pigments. The latter are removed by microfiltration prior to
At NID color is determined on a Coleman universal spectrophotometer
using a 40 mm
cuvet at 500nm. The instrument is standardized against water.
Cotton. The cotton
fabric used for the residual odor test is read on the reflectometer to
determine the decrease in % green reflectance. Although this is called
is actually a measure of the amount of dye and colored impurities
the solvent because the insoluble material has been removed by
through 0.2 µm membranes.
drycleaners use certain resins in the solvent as sizes or bodying
fabrics to replace the finishing materials removed during wear or
Natural terpene resins are widely used and the amount of resin in the
is determined at NID by extracting the nonvolatic residue with boiling
This reagent dissolves everything except the terpene resins. The
not been validated however for all types of sizes.
Suspended Soilds. After
microfiltration of a measured volume of the solvent the membrane witch
previously weighed is oven dried at 1050C and weighed to
determine the quantity of insoluble
material suspemded in the solvent. The NID standard for this is
Larger quantities can cause excessive greying of white fabrics and is
indication of poor solvent filtration.
solvents follows much the same principles as in water particularly in
removal of insoluble soil. The major differences come in the attack on
and solvent soluble soils. In aqueous detergency the major attack is on
oily soils because the water soluble soils are removed by simple
drycleaning on the other hand the major attack by detergents is on the
soil because the soil is removed by simple solution.
lanundering and drycleaning the
process of emulsification and solubilization effects the removal of
the fiber surface. In both types of eleaning the detergents used are
surface active agents.
detergents generally contain
not more than 20% surface active agents (surfactants) the balance being
types of builders. Drycleaning detergents may consist of a single
The product may also contain a consolvent or coupling agent to enhance
capacity for dissolving or emulsifying water and a fluorescent
Frequently two or more surfactants are mixed.
three functions in the cleaning process. It acts as a dispersant or
agent for insoluble soils. It not only disperses this kind of soil but
keeps it in suspension while it is being flushed out of the fabric and
to the filter. Insoluble soils may be dispersed to particle size in the
submicron range by good detergents and while so dispersed the particles
are small enough to escape between the tightly packed fibers in textile
the absence of a good detergent this kind of soil is difficult to
readily redeposits on other fiber surfaces causing what is generally
greying a phenomenon also common in laundering particularly with
fibers. Thus the first two roles of a drycleaning detergent are to
the removal of insoluble soil and to prevent it from redepositing on
fabrics in the bath.
function of a drycleaning
detergent is to emulsify water in the solvent and promote the removal
of water soluble
soil by the emulsified or solubilized water. Although the water plays
role in detaching water soluble soil from the fiber surface the
itself can dissolve some of these soils within its micelles.
Progress in the
drycleaning detergents is slow compared to the formulation of laundry
detergents. One reason for the lack of progress has been the absence of
reliable test methods for drycleaning detergents. The literature on
detergent test methods is scanty and the few methods that have been
have received little attention or use. The methods described here have
use at the National Institute of Drycleaning and are designed to test
ability of a detergent to perform its three functions.
The tests to be
carried out on drycleaning detergents can be
divided into two groups specification tests resulting in information on
properties of the detergnets and performance tests.
without exception are liquids so it is describle to know how much of
material consists of an active ingredient and how much is solvent or
determination is made on a perchloroethylene solution of known
the detergent. An aliquot is evaporated to dryness as described on p.
the determination of the nonvolatile residue of a solvent. The amount
is determined on a separate sample by the karl fischer titration.
detergents are diluted with mineral oil so
that the nonvolatile residue is not all surfactant but it still
upper limits of surfactant concentration.
Specific Gravity. The main
purpose of this test is to
establish what types of solvents are used as diluents. Most surfactants
specific gravities close to unity whereas drycleaning solvents have a
gravity of about 0.8 (Stoddard solvent) or 1.62 (perchloroethylene).
determination can be carried out by any of the conventional methods.
pH. A drycleaning
detergent should be essentially neutral
because of the adverse effect of acids and alkalis on some types of
test is made by thoroughly shaking the detergent with water and
ph of the water phase.
Test. Since used
dryeleaning solvent is
reclaimed by distillation it is important that the detergent cause no
in the still. This is checked qualitatively by distilling a 1% solution
detergent in perchloroethylene in an all glass laboratory still. The
observed for any signs of foaming flooding over or decomposition. The
distillate should be pure perchloroethylene presence of other volatile
intended for use in Stoddard solvent must be
tested by vacuum distilling a 1% solution in this solvent.
Dryeleaning Solvents. The purpose
of this test is to ascertain that the detergent is soluble in both
simple qualitative test is sufficient.
Chemical Type. It is desirable
to know whether the
sufactant in the detergent is anionic cationic nonionic or a mixture of
and nonionic surfactants. This can be determined by studying the
spectrum of the sample as well as the methylene blue titration method
Concentration by Methylene Blue Titration. This method
is widely used as a control test to determine the amount of a prticular
detergent in a drycleaning solution. It was originally described by
1951. The following procedure is from an NID publication.
Surfactants. Place 25ml of
chloroform into a 100
ml glass stoppered graduated cylinder. Take at least a 5 ml sample of
to be tested dilute to 100 ml and then add a proper aliquot to the
Add 25 ml of water containing 1 drop of a 0.5% methylene blue solution
shake. The methylene blue enters the chloroform layer as a result of
solubilization by the surfactants. Start to add a 0.02% aqueous
chloride solution in 0.5 ml increments and shake the mixture vigorously
each addition. As long as any free anionic surfactant remains in the
layer its blue color will presist. Near the end point the methylene
to pass into the aqueous layer. Eventually this is complete and the
is colorless. A sharp and reproducible end point is the point of equal
distribution between the two phases. Prepare a calibration curve for
detergent by titrating a number of samples of known volume volume
over the expected range and plotting ml of titrant againt deteregent
Surfactants. Carry out the
determination in a
similar way but by using a standard anionic surfactant such as Aerosol
surfactants cannot be titrated in this manner. However
detergents consisting of nonionic surfactants generally contain a small
of anionic surfactant as a tracer so the solution can be titrated to
As early as 600
B.C. seaweed was used as a food for man but
algin a component of seaweed was first discovered by British chemist E.
Stanford in 1880. In 1896 A Krefting prepared a pure alginic acid. In
Company began commercial production of alginates and introduced milk
again as an ice cream stabilizer in 1934. In 1944 propylene glycol
Algin is a
polysaccharide found in all brown seaweeds phaeophycea
which grow on rocky shores or in ocean areas that have clean rocky
Although some species can be found at the high tide line other exist
shore where depths are less than about 40 m (125 ft) the maximum depth
sunlight will penetrate. (Since algae do not have true roots stems or
comes directly from sunlight and mineral nutrients in ocean water.)
Only a few
species of brown seaweeds are used for commercial
production of algin. The principal source of the world s supply of
algin is the
giant kelp Macrocystis pyrifera found along the
coasts of North and
South America New Zealnd Austrila and Africa. Other seaweeds used for
manufacture are Ascophyllum nodosum and species of
Algin exists in
the kelp cell wall as the insoluble mixed
salt (calcium magnesium sodium potassium) of alginic acid. Alginic acid
high molecular weight linear glycuronan comprising solely D mannuronic
L guluronic acid.
Algin is used in
foods and general industrial applications
because of its unique colloidal behaviour and its ability to thicken
suspend form films and produce gels. These properties are discussed in
detail in later sections of this chapter such as solution Properties
It has been in
recent years only that the composition of
alginic acid has become understood. Table 1 shows the composition of
acid whereas Table 2 shows the proportions of polymannuronic acid
acid segments and alternating segments of these two uronic acids in
commercial samples of alginic acid. Figures 1 to 3 illustrate the
mannuronic and guluronic acids the apparent discrepancies between the
Tables 2 and 3 are accounted for by variations between alginates
different species of brown algae.
derivatives The propylene
glycol ester of
alginic acid is the only orgainc derivative of alginic acid currently
market. Propylene glycol alginate has improved acid stability and
precipitation by calcium and other polyvalent metal ions.
can be made by reacting alginic acid with
orgainc amines. Suitable amines are triethanolamine triisopropanolamine
dibutylamine and dimylamine. Algin acetate and algin sulfate esters
prepared but have no known applications. Carboxymethyl alginate can be
treating sodium alginate with chloroacetic acid and alkali. A number of
alkylene glycol esters of alginic acid have been prepared and evaluated.
can be reacted with alginic acid to form 2 hydroxyethyl
alginate. Alginamides can be prepared by reacting propylene glycol
with primary amines such as ammonia ethanolamine ethylenediamine
isopropyl amine and butylamine. Very little reaction occurs with
pyrifera the brown
seaweed that is the main
source of algin grows in relatively calm waters and in large dense
plant is a perennial and can be harvested on a continuing basis. Its
growth permits up to four cuttings per year.
Only mature beds
are cut. At the time harvesting a dense mat
of fronds floats on the ocean surfac. Cutting the dense mat on the
allows light to penetrate the water and reach the immature fronds this
stimulates their growth. Harvesting is actually a massive pruning of
bed. Underwater blades mow the kelp approximately 3 ft below the water
the cut kelp is automatically conveyed into the hold of the barge by a
commercial methods of producing sodium alginate from
seaweed are proprietary the fundamental steps in a typical process
one of ion exchange are shown in Fig. 4. In the seaweed the algin is
present as a mixed salt of sodium and /or potassium calcium and
is a high molecular weight polymer. The exact composition varies
with the type of seaweed but does not affect processing.
It is possible
to extact sodium alginate from seaweed with a
strong solution of a sodium salt however for the production of purfied
alginates the commercial processes are much more efficient. Alginic
also be neutralized with bases to give salts and reacted with propylene
to make propylene glycol alginate.
available water soluble alginates include the sodium
potassium ammonium calcium and mixed ammonium calcium salts of alginic
glycol alginate and alginic acid itself. The physical properties of
these alginates are given in Table 3.
Alginates Alginate as a
absorbs moisture from the atmosphere therefore equilibrium moisture
related to relative humidity as shown in Fig. 5. The dry storage
alginates is excellent at moderate temperatures 25oC (77oF) or less
however they should be stored in a cool dry
place. Table 4 gives datea showing the effects of storage for 1 year at
24.9oC (75oF) on typical
alginates. Table 5 shows the effects of
variious storage temperatures on the stablilities of alginates.
dissloved indistilled water from smooth
solutions with long flow characteristics. The physical variables that
the flow properties of alginate solutions are temperature shear rate
size concentration and the presence of solvents miscible with the
water. The chemical variables that affect algin solutions are pH and
presence of sequestrants monovalent salts polyvalent cations and
Properties The flow
properties of sodium
alginate solutions are concerntration dependent. A 25% medium viscosity
alginate solution is pseudoplastic over a wide range of shear rates (10
000s 1) wheras a
0.5% solution is Newtonian at low shear rates (1 to 100s 1) and
pseudoplastic only at high
shear rates (1000 to 10 000s 1) as shown
in fig. 6.
Because of high
molecular weight and molecular rigidity sodium
alginate forms solutions of unusally high apperant viscosity even at
concentraions. Propylene glycol alginate solutions are shear thining
wide range of shear rates at 3% concentrations. However at 1% or lower
concentrations solutions have almost constant viscosity below shear
100 s 1(fig. 7).
Figure 8 shows
that viscosity shear curves of medium viscosity
sodium and potassium alginates are virtually the same over the entire
range. On the other hand in comparing low viscosity propylene glycol
alginates the curves are indentical at shear rates greater than 10 000s
diverge at low shear rates.
The effects of
solution soilds on shear thinking are
illustrated in fig. 9. The viscosity shear curves of a 2% solution of
sodium alginate were the same as those of a 9% solution of a low
sodium alginate. Measurements were taken using shear rates in the
range (1 to10 000 s 1). At high
shear rates such as those experienced at 100 000 s 1 measured
with a capillary viscometer the
illustrates the effect of temperature on the flow
of a high viscosity propylene glycol alginate. Addition of a
hexametaphosphate to a medium viscosity sodium alginate (fig. 11) gives
viscosity shear curve comparable to that of a low calcium sodium
Xanthan gum can
be used to modify the rhelogical behavior of
sodium alginate solutions (fig. 12) As shown the curves for the 0.5%
of sodium alginate and xanthan differ greatly. A combination of the two
produces flow properties intermediate between the two materials.
illustrate the importance of rheological
properties to the design of product performance. If the paint is highly
pseudoplastic application will be easy and sagging will be prevented
and leveling will be minimal and brush marks will be left on the dried
Elimination of the yield value will result in setting out of the
the can. If dilatancy occurs stirring will be difficult and brush drag
temperature The viscosities
of algin solutions
decrease as temperatures increas approximately 12% for each 5.6ºC (100F) increase in
decrease is reversible if the high temperatures are not held for long
Table 6 shows the effect of time and temperature on solution viscosity.
apparent that the heating of sodium alginate results in some thermal
depolymerization the amount being related to both temperature and time.
reducation in temperature of an alignate solution
in an increase in viscosity it does not produce a gel. A sodium
can be frozen and thawed without any change in its appearance or
after remelting. It is possible to form a freeze dried sodium calcium
gel with an absorptive capacity of more than 5000%.
Solvents Addition of
increasing amounts of
nonaqueous water miscible solvents such as alcohols glycols or acetone
aqueous alginate solution increases solution viscosity and eventually
precipitation of the aligante. Tolerance of the alignate solution to
solvents is influenced by the source of the alginate the degree of
polymerization the cation type present and the solution concentration.
gives data on solvent tolerances of various types of alginates in
Concentration Figure 13 shows
the effect of
solution concentration on selected grades of sodium ammonium postassium
propylene glycol alginates.
Effect of pH Sodium alginates
with some residual
calcium content increase in viscosity at a ph of 5.0 and are unstable
levels of about 11.0. Sodium alginates with minimal calcuim content do
the viscosity increase until the pH reaches 3.0 to 4.0 Lower molecular
sodium alginates are stable at a pH as low as 3.0 if calcuim is
alginates do not gel until the pH is below
3.0 but they do saponify at pH levels above 7.0 The long term stability
sodium alignate solutions is poor when the pH reaches 10.0. At even
values there is depolymerization with an accompanying viscosity loss.
illustrates the effect of pH on viscosity for several types of
Gelation Algin polymers
will react with most polyvalent cations
(magnesium excepted) to form crosslinkages. As the content of
increases the algin solutions thicknes then gels and finally there is
precipition. The proposed
structure of an alignate gel in which the calcuim ions are bound
associated segments of the polymer chain is shown in fig. 15.
gets are the result of interactions between the
alginate molecules which produce a three dimensional structure
mobility of the water molecules. They are not thermally reversible. By
proper selection of gelling agent gel structure and rigidity are
Loss of water to the atomsphere and resulatant shrinkage is very slow
polyvalent ions e.g. zinc aluminum copper and silver
from complexes with aliginates in the presence of excess ammonium
When the ammonia is driven from the system the insoluble metal
formed. Calcium is the polyvalent cation most often used to change the
rheological properties and get characteristics of algin solutions.
also used to form insoluble aliginate filaments and films.
The method of
calicum addition to an alginate system greatly
influcences the properties of the final gel. If calcium is added too
result is spot gelation and a discontinuous gel structure. The rate of
addition can be controlled by use of a slow dissloving calcium salt or
addition of a sequestrant such as tetrasodium pyrophosphate or sodium
sequestrants The purpose of
alginate solutions can be either to prevent the alginatic from reacting
polyvalent ions present in the solution or to sequester the calcium
the alginate. Polyvalent ion contaminants can come from water chemicals
or various natural origin materials. Figure 16 and 17 show viscosity
relationships for two types of alginates which and without sodium
hexametaphosphate as the sequestrant.
In fig. 16 a low
calcium sodium alginate shows a very small
viscosity change up addition of the ployphosphate sequestrant to the
In contrast fig. 17 should that a sodium calcium alginate solution has
change in viscosity when the sequestrant is added. Sequestered alginate
solutions are more Newtonian in behavior than are those with some
Monovalent Salts Monovalent salts
depress the viscosities
of dilute sodium alginate solutions. The maximum effect on viscosity is
attained at a salt level of 0.1N in the solution. Except for alginates
calcium an increase in alginates concentration decreases the effect of
Figure 18 shows
the effect of sodium chloride on the
viscosity of several kinds of alginate solutions whereas Table 8 shows
effects of 1% and 5% sodium chloride concentrations over a 210 day
temperatures of 4.4 23.9 and 48.90C (40 75 and 1200F). The effect
of a salt on an alginate solution will
vary with the source of the alginate as well as with its degree of
polymerization the concentration of alignate in the solution and the
insoluble adducts result
when sodium alginate reacts with cationic organic ammonium compounds.
insolubilization can be prevented by adding an electroylte e.g. NaCl to
suppress the activity of the cation. Salt concentrations needed to
insoluble alginate adducts are listed in Table 9.
solution have compatibility with a wide variety
of materials including other thickeners synthetic resins latices sugar
waxes pigments various surfactants and alkali metal solutions.
are generally the result of a reaction with divalent cations (except
or other heavy metal ions cationic quaternary amines or chemicals that
alkaline degradation or acid precipitation. In many cases the
can be avoided by sequestration of the metal ion or by careful control
Table 10 lists
materials that were tested for compatibility
with solutions of a medium viscosity purified sodium alginate.
Preservaties Alginates have
most commonly used preservatives except quaternary ammonium compounds.
polysaccharide is quite resistant to the common enzyme systems produced
bacteria however since the solutions will support microbiological
preservative should be used if alginate solutions are to be stored for
considerable period of time. The preservatives listed in Table 10
can be used to protect against bacterial
action in acid systems. For additional protection against yeast and
sorbate or calcium or sodium propionate can be effective.
Thickeners The alginates
with most commercially available thickeners both synthetic and natural.
some thickeners a synergistic viscosity increase may be noticed. If the
residual polyvalent ion content of a natural gum causes gelation of an
solution the gelation can be controlled by the proper use of a
compatibility of the alginates
with most water soluble resins is excellent. Polyvinyl alcohol exhibits
definite synergism with sodium alginate in the formulation of grease
Latices Those latices
normally used in the formulation of
paints paper coatings and adhesives have compatibility with the
latex emulsions with pH of 4.0 or less will cause gelation of the
apparent incompatibility may be overcome by proper buffering. High
ammonium alginate may be used as a creaming agent for natural rubber
for several types of synthetic latex.
As shown in
Table 10 alginate
solutions will tolerate up to 30% water miscible solutions. However
increases may occur with long term storage. To prevent localized
is necessary that there is good agitation of the solution at the time
organic solvent is added.
Enzymes Enzymes commonly
encountered as by products or as
commercially available products e.g. protease cellulase amylase
have no effect on the alginate molecule. Storage test data is given in
for representative enzymes.
alginate solutions have
compatibility with anionic non ionic and amphoteric surfactants high
concentrations of surfactants will result in a loss of viscosity and
the aliginate will out salt of solutions.
surfactants can be used at concentrations higher
than those allowable for the anionics or amphoterics. Some cationic
may be used if approximately 2.5% of a soluble salt such as sodium
added to the system. The exact salt level required depends upon the
cationic material in the system.
such as glycols or
glycerol may be used to improve the flexibility of alignate films. Data
number of plasticizers and their effects on alginate solutions are
Inorganic Salts The
compatibility of alginate
solutions with inorganic salts is limited to ammonium magnestium or the
metal salts. Divalent or higher valence cationic salts will unless
gelation or precipitation of the alginate. The alginates will also be
precipitated by molar solutions of monovalent salts.
Salts which are
sightly acidic may produce large viscosity
increase after prolonged storage. Sequenstrants in many cases will
salt compatibility and stability of the sodium alginate. Mixed alginate
(sodium/calcium alginate) are much more salt sensitive than are the
large volume renewable agricultural raw material is
transformed into hundreds of products affecting every phase of daily
use and versatility are exploited by the chemical industry much as the
industry exploits its raw materials using everything but the squeal.
of water soluble cellulose derivatives in
contrast to that of polymers based on petrochemical resources starts
preformed polymer backbone of either wood or cotton cellulose instead
monomer. Cellulose is a linear polymer of anydroglucose with the O
structure shown below
of a specific cellulose ether depend on the
type distribution and uniformity of the substituent groups. For each
ring there are three hydroxyl groups available for the nucleophilic
substitution reaction. Reactions at these sites can occur either on a
one to one
basis or with formation of side chains depending on choice of reagent
to modify the cellulose. In the former case the term degree
substitution (DS) is used to identify the average number of
per ring. The maximum value is 3 corresponding to the number of
available for reaction. When side chain formation is possible the term molar
substitution (MS) is used and the value can exceed 3.
soluble cellulose ethers
possess a range of multifunctional properties resulting in a broad
This family of
commercial water soluble
cellulose ethers comprises methylcellulose (MC) and the methylcellulose
hydroxypropylmethylcellulose (HPMC) hydroxyethylmethyl cellulose (HEMC)
possesses many properties and end uses in common with the
products and is included in this section.
hydroxypropylmethylcellulose are two examples of this versatile class
of water soluble
hydrocolloids derived from the etherification of cellulose. MC and HPMC
polymers having the useful properties of thickening thermal gelation
film formation and adhesion. Those characteristics earn them
areas such as foods cosmetics paints construction pharmaceuticals
products agriculture adhesives textiles and paper. Additionally to
product for a specific end use the properties of MC and HPMC may be
changing the molecular weight or the relative amounts of etherifying
products have an
average degree of substitution (DS) ranging from 1.5 to 2.0 hence one
two thirds of the available hydroxyl units are substituted with methyl
(Table 1). In commercial HPMC products the DS for methyl groups ranges
to 1.8 and the substitution (MS) of hydroxypropyl groups range from 0.1
MC and HPMC
possess the rather
unusual property of solubility in cold water and insolubility in hot
that when a solution is heated a three dimensional gel structure is
modifying production techniques and by altering the ratios of methyl
hydroxypropyl substitutions it is possible to produce products whose
temperature ranges from 50 to 900C (122 to 1940F) and whose gel
texture ranges from firm to rather
amounts of methyl and hydroxypropyl substitution
also affects the solubility properties of the cellulose ether.
Decreasing the substituent
groups below a DS of 1.4 gives products whose solubility in water
Concentrations of 2 to 8% sodium hydroxide are required for solubility
level of substitution decreases. Increasing the substitution above an
MS of 2.0
improves solubilty in polar organic solvents.
Co. A. G. of west Germany also produces
hydroxyethylmethylcellulose. The small amount of hydroxyethyl
increases the solubility of the polymer and raises the thermal gel
about 55oC to about
70oC. The more
polar nature of the hydroxyethyl group versus the hydroxypropyl group
for the formation of a slightly stiffer gel than is possible with an
material of comparable gelation temperature.
A third product
ethylhydroxyethylcellulose is similar in many
properties to MC and HPMC. The small amout of hydroxyethyl substitution
the thermal gel point from about 55ºC (131ºF) to about 70ºC (158ºF).
polar nature of the hydroxyethyl group allows for the formation of a
gel than is possible with an HPMC material of comparable gelation
In many respects
the properties and uses of EHEC are also
very similar to those of methylcellulose and
product has the characteristic properties of thickening surfactancy
forming binding solubility in cold water and insolubility in hot water
broad range of solubility in many organic solvents.
of EHEC are quite dependent upon the relative
amounts of ethyl and hydroxyethyl substitution. By varying the ratio of
substituents the gelation temperature the gel characteristics the
properties in different solvents and the surfactancy can be modified.
Increasing the amount of ethyl substitution increases the solubility in
media and the tendency to form a firm gel while increasing the
substitution improves the water solubility reduces the tendency to from
on heating and improves the brine tolerance of the polymer in various
was first produced commercially in the United
States in 1938 by The Dow Chemical Co. under the registered trademark
Methocel. Hydroxypropylmethylcellulose achieved commerical significance
early fifties. In additon to The Dow Chemical Co. other suppliers of
products are Shin Etsu Chemical Products Ltd. (Metolose) of Japan
Celanese Ltd. (Celacol) of Great Britain and Kalle & Co. A G.
and Cie GmbH (Culminal) and Wolff A. G. of Germany.
capacity of MC and HPMC in 1979 is estimated to
be about 159 million pounds per year and is growing. Water soluble
ethylhydroxyethylcellulose is produced by Berol Kemi AB (formerly
amounts of methyl and hydroxypropyl substitution
are controlled by the weight ratio and concentration of sodium
the weight ratios of methyl chloride and propylene oxide per unit
EHEC is prepared
by reacting dissolving grade wood pulp with
aqueous sodium hydroxide and then with ethyl chloride and ethylene
schematically illustrated below
The amount of
ethylation is controlled by the amount of
caustic used in the formation of alkali cellulose and the amount of
hydroxyethylation is controlled mainly by the amount of ethylene oxide
the reactor. The addition is stepwise since ethylene oxide is far more
than ethylene chloride and hence reacts with the cellulose first.
There are three
main steps used in the manufacture of MC and
Alkali Cellulose Alkali
cellulose is prepared by contacting cellulose and 35 to 60% aqueous
according to several procedures that include dipping a cellulose sheet
caustic solution spraying the caustic onto agitated cellulose flock
the cellulose in aqueous caustic and removing the excess or mixing the
cellulose and aqueous caustic in an inert diluent.
control of the
final product is obtained by choice of pulp by aging the alkali
warm air and by controlling the amount of oxygen left in the reactor
methylation. For high viscosity products the higher molecular weight
linters are used with minimum aging. Since alkali cellulose is
oxidative degradation exposing it to air for varying time peroids is an
effective method for viscosity reduction.
Reaction The alkali
cellulose methyl chloride and (if required propylene oxide are loaded
jacketed nickel clad agitated vessel and heated under controlled
a maximum pressure of 1.38 MPa (200 psig.) The heat of reaction is
condensation of the solvents. In additon to controlling the
variations in the amounts of methyl chloride and changes in the
will affect the properties of the final product.
Purification Since MC and
HPMC are insoluble in hot water the reaction by products are removed by
slurrying the crude product in water heated to above 900C (1940F) and then
filtering. The purified wet product in then
dried ground to > 95% through 40 mesh screen and commonly
packaged in 22.68
kg (50 lb) bags.
Toxicity and Handling
products have been used by the food pharmaceutical and cosmetic
many years. They are odorless. Tasteless powders and are considered to
MC products are
listed in the
United States Pharmacopeia XIX and Food Chemicals Codex and
by the FDA as Generally Recognized as Safe (GRAS).
substitution ranges from 19 to 30% and hydroxypropyl substitution
ranges from 4
to 12% are also listed in the United States Pharmacopeia XIX
Chemicals Codex. Both products can meet the requirements of
Regulations 182.1480 and 172.874 as a miscellaneous and/or general
additive for nonstandardized foods.
While a gross
exposure to MC
or HPMC can conceivably cause temporary mechanical irritation to skin
and eyes exposure
to normal amounts presents no significant health hazards from either
In storage good
housekeeping is suggested to prevent dusts
from building up to possibly explosive levels. All the cellulose ethers
organic materials that will burn under the right conditions of heat and
supply. Fires can be extinguished by conventional means. Gross powder
should be swept up to avoid accidents caused by slippery floors or
the trace residual product can be flushed to a sewer. These products
biochemical oxygen demand (BOD) with the standard 5 day test. However
tests with activated sludge showed breakdown over a 15 to 20 day
products should provide no ecological hazard. The products may be
by either landfill or incineration.
viscosity is known at one concentration the
viscosity can be calculated for any other concentration by using Eq.
first calculate K for the sample at the concentration for which the
is known and then using Eq. (2) again to calculate the viscosity at the
concentration knowing the value of k.
EHEC may be
dissolved in cold water to yield clear smooth
solutions. Commercial products range in viscosity from 0.050 to
to 12 000 cP) at 2% concentration. The solutions are pseudoplastic in
apparent viscosity decreases with increasing rate of shear the
not thixotropic unless they are gelled. (see fig. 1)
Rheology Solutions of MC
and HPMC generally show pseudoplastic
nonthixotropic flow properties at 200C (680F) that is
not a function of substitution within the range of available commercial
products and whose deviation from Newtonian character increases with
molecular weight (figs. 2 and 3). Dilute solutions of low viscosity
(fig. 4) do closely approach Newtonian flow but increasing the
the gum to over 5% may give a solution showing same thixotropy due to
chain to chain interactions. Since flow properties are dependent on the
molecular weight and the molecular weight distribution of the polymer a
of high and low molecular weight polymers can have different flow
than a polymer having the same solution viscosity as the blend but
narrow molecular weight distribution (fig. 5). This effect is generally
important for dilute solutions of higher viscosity materials (fig. 6)
be significant when applied to solutions of over 5% of the low
solution of MC or HPMC shows the normal effect of
lower viscosity until the gelation temperature is reached at that point
viscosity of the solution increases rapidly and highly thixotropic flow
effect of temperature in the range of 0 to 450C (32 to 1130F) is roughly a
3% reduction in
viscosity for every degree celsius increase in the temperature of the
(when applied to aqueous solutions containing no added solutes and
evidence of gelation).
MC and HPMC
solutions show the
unusual property of forming a structured gel when heated.
these polymers exist as aggregates of long
colloidal molecules. These molecules are highly hydrated with the
in layers that are held through hydrogen bonding thereby giving the
lubricity and smooth flow. As the temperature is raised the hydrogen
between the water molecules weakens and the interactions between chains
significant eventually leading to the formation of a structured gel.
many chemical gels those made from MC and HPMC are primarily a result
separation and are susceptible to shear thinning (a mechanical breaking
the gel without affecting the molecular weight). With cooling this
reversible and the gel reverts back to a solution whose flow properties
temperature is dependent on the relative amounts
of methyl and hydroxypropyl substitution and may be used as an
the relative hydrophilicity of the derivative. In general the more
substituted derivatives have lower gelation temperatures and will be
compatible with added solutes or electrolytes. The gelation temperature
products currently produced varies from about 50 to 850C (122 to 1850F) with the
resultant gels ranging
from firm to rather mushy in consistency (when determined by heating a
solution of the gum in pure water). The gelation temperature of a
affected by the concentration of the gum and more importantly by other
dissolved solutes. Presence of salts (Table 3) will lower the gel point
of ethanol or propylene glycol can raise the gel point as much as 200C (36OF).
the thermal gelation temperature EHEC will
separate out of solution as either a floc or a gel depending upon
weight and the concentration (see Table 4).
Surface Activity MC and HPMC
reduce the surface
tension and interfacial tension of aqueous sustems to values of 41 to
and 18 to 28 dyn/cm respectively (depending on chemical structure)
functioning as moderate emulsifiers for two phase mixtures. Since they
polymeric materials they are active surfactants at very low use levels
from 0.001 to 1.0%. Their status as approved additives in foods makes
useful as edible surfactants. EHEC also behaves as a moderate
the surface tension of water to 47 to 52 dyn/cm.
is usually encountered. This can be
controlled if desired by use of commercially available defoamers
Polyglycol P 1200
(The Dow Chemical Co.) Antifoam A AF B or FG (Dow corning corp.) Nopco
(Nopco Chemical Co.) or tril n butylphosphates.
Sodium Carboxy Methyl Cellulose
methyl cellulose is a water soluble anionic
linear polymer. It is universally known as CMC and will sometimes be so
designated here. In the food pharmaceutical and cosmetic industries the
purified types required are referred to as cellulose gum. The
States Food and Drug Administration (FDA) has defined cellulose gum
section on toxicological properties) also the Food Chemicals
the Food and Agriculture Organization (FAO) of the United Nations have
established specifications for identity and purity of sodium
carboxymethylcellulose for food uses worldwide.
carboxy methyl cellulose is a white to buff colored
tasteless odorless free flowing powder. Less purified grades contain
reaction salts (sodium chloride and sodium glycolate) and can be off
white to a
light brown for the low assay types (50% purity).
methyl cellulose is probably used in more
varied applications worldwide than any other water soluble polymer
today. Applications vary from the large worldwide detergent use to the
specialized barium sulfate suspension for medical diagnosis.
applications of CMC in order of size of estimated
end use are given in Table 1. These estimated usages demonstrate the
versatility throughout the world for this modified natural long chain
It is estimated
that over 250 types of sodium
carboxymethylcellulose are manufactured throughout the world by over 50
producers with outputs ranging from as little as 200 metric tons to
over 35 000
metric tons per year.
The growth of
CMC was accelerated by the world conflict in
the early 1940s when fatty acids usage was drastically shifted from
soap manufacture to wartime manufacture of explosives. Even though CMC
developed shortly after World War I as a possible replacement for some
uses the major growth in the use of CMC began after it was discovered
improved the efficiency of synthetic detergents. Usage during the early
was primarily for detergent systems although many new applications were
developed on a laboratory scale where control of water movement was
With the end of
the world conflict in 1945 and with the huge
demand for consumer products CMC backed with several years of
studies began finding uses in all types of areas requiring water
systems with various levels of soluble and insoluble solids.
In the United
States a landmark in the growth of purified
sodium carboxymethylcellulose (cellulose gum) was the approval by the
its use as an intentional food additive (see section on toxicological
properties for details). Following this was the definition in the United
States Pharmacopoeia for subsequent use in pharmaceutical
Cellulose is a
linear polymer of
anhydroglucose units. Each anhydroglucose unit contains three hydroxyl
The extent of
the reaction of
cellulose hydroxyls to form a derivative is called the degree
substitution (DS) and is defined as the average number of
hydroxyl groups in the anhydroglucose unit which have reacted. Thus if
of the three hydroxyl groups has been carboxymethylated the DS is 1.0.
Commercial products have DS values ranging from 0.4 to about 1.4. The
common grade has a DS of 0.7 to 0.8 and if the DS is not specifically
it can be assumed to be in this range. CMC is commercially available in
different viscosity grades ranging from 4.5 Pa.s (4500 cP) in 1%
0.010 Pa.s (10 cP) in 2% solution. The various viscosity grades
products having molecular weights from about 1 000 000 to 40 000. Table
that 19 different DS viscosity combinations are available from one
CMC is a salt of
a carboxylic acid
having approximately the same acid strength as acetic acid. The pK
somewhat with degree of substitution. The pure commercial product of DS
a pK value of 4.4 the corresponding value of K
constant is 4 × 10–5. A dilute
solution of such a product has a pH of about 7 and has over 99% of its
carboxylic acid groups in the sodium salt form and very few in the free
soluble salts with alkali
metal and ammonium ions. Calcium ion present in concentrations normally
in hard water prevents CMC from developing its full viscosity and thus
dispersions are hazy. At much higher concentrations calcium ions
CMC from solution.
ferrous ion have a
similar effect on CMC dispersions. Heavy metal ions like silver barium
lead and zirconium precipitate CMC from solution. Quaternary salts
a long hydrocarbon chain such as dimethylbenzylcetylammonium chloride
precipitate CMC from solution.
precipitated from solution by the polyvalent cations
Al3+ Cr3+ or
Fe3+. If the ion
carefully controlled for example by the presence of a chelating agent
citric acid it is possible to form more viscous solutions soft gels or
rigid gels. In these instances the polyvalent ion functions as a
CMC reacts with
certain proteins. For example soy protein which
is insoluble in its isoelectric range can be solubilized by CMC. Thus
solubility can be extended over a wider pH range. CMC has a similar
solubilizing effect on casein but in the case of gelatin which is a
soluble protein the reaction with CMC manifests itself as a rise in
polymers CMC may be salted out of solution. However CMC
being a very hydrophilic polymer is more tolerant of alkali metal salts
many other water soluble polymers. Its salts compatibility is much
the salt is dissolved in the CMC solution than if the CMC is dissolved
salt solution (see Figure 1). Such behavior relates to the fact that
CMC of DS
0.7 is aggregated in solution. This is discussed later in connection
grades of CMC have most of their carboxyl groups
in the sodium salt form. Such products may be converted into the free
e.g. by passing a solution through a suitable ion exchange resin. If
resulting free acid is freed from water by drying a film or
alcohol and drying the product is no longer water soluble. It may be
in aqueous NaOH that is by re forming a soluble salt.
physical properties of CMC are summarized in
Table 3. Other physical properties follow.
Moisture Content CMC is a
very hydrophilic polymer whose equilibrium moisture increases with DS.
gives the equilibrium moisture content for products of DS 0.4 0.7 and
different humidities. These data were obtained on dry commercial
conditioning the powder to constant weight at 25°C.
Weights The molecular
weights shown in Table
4 were calculated from intrinsic viscosity measurements in 0.1% NaCl at
using the relationship [M] = 2.9 × 10–4 M0.78 where
M is the weight average molecular
Solubility The only good
common solvent for CMC
is water. The degree of dispersion in water varies with the DS and the
molecular weight. CMC with a DS of 0.7 may be dissolved in glycerin
in the presence of a slight amount of water by heating with good
Aqueous solutions of CMC will tolerate considerable quantities of water
organic solvents such as methanol ethanol and acetone. For example a 1%
solution of the high viscosity grade will tolerate 1.6 volumes of
volume of CMC solution before it becomes hazy and precipitates. Low
grades will tolerate as much as 3.5 volumes. Aqueous solutions of CMC
tolerate large amounts of alkali metal salts and small amounts of
magnesium salts. Heavy metals and multivalent salts precipitate CMC as
discussed earlier under Chemical Nature.
Film Properties Table 5 gives
of 0.508 mm (2 mil) films containing about 18% moisture for three
viscosity grades of CMC with a DS of 0.7. It is evident that the
flexibility are greater for the types which have high viscosities or
weights. Films may be insolubilized by crosslinking at the hydroxyl
using suitable water soluble resins such as Hercules Kymene 917 and
Resin or Aerotex M 3. The crosslinks are formed by reaction of
hydroxyls with the aldehyde functionality of the resins. A film is cast
aqueous solution of the resin and CMC. Upon drying and further curing
becomes insoluble. The degree of insolubilization depends on the extent
curing treatment. Dry CMC films may be insolubilized by treatment with
solutions of aluminum salts.
of CMC involves treatment of cellulose with
aqueous sodium hydroxide followed by reaction with sodium chloroacetate
Cellulose is a
fibrous solid. Chemical cellulose which is
used for the manufacture of CMC is derived from cotton linters or wood
obtain uniform reaction it is essential that all the fibers be wetted
the aqueous NaOH. One process for accomplishing this is to steep
cellulose in aqueous NaOH and then press out the excess. The sheets are
shredded and the sodium chloroacetate is added. Reactions are generally
conducted at 50 to 70°C. In some cases a greater amount of NaOH is
the monochloroacetic acid is added as such the sodium salt being formed
presence of the cellulose.
In an alternate
process the steeping and pressing steps are
eliminated by conducting the reaction in the presence of an inert water
diluent such as tertiary butyl alcohol or isopropanol. At the end of
reaction the excess alkali is neutralized and the crude product which
sodium chloride and sodium glycolate is purified or partially purified
Table 6). There are many variations of these processes depending on the
level and the quality of the product desired.
cellulose derivatives are all subject to
microbiological attack under certain conditions. The magnitude of the
microbiological degradation is influenced by a number of factors which
contaminants present temperature pH of system oxygen available and
concentration. The first sign of biological degradation is usually loss
viscosity (i.e. chain length). This loss can be rapid under extreme
very slow under much less severe conditions. Biological attack is
solution systems than on the dry form of sodium carboxymethylcellulose.
the moisture content of sodium carboxymethylcellulose is from 5 to 10%
biological degradation is generally not severe under normal dry storage
conditions at this moisture level.
conditions and subsequent packaging systems can
greatly influence the microbiological stability of the final product.
commercial manufacturing systems using solvents the final packaged
carboxymethylcellulose is essentially aseptic. In the dry process
CMC there is a greater possibility of residual biological
Generally however the caustic present in the system necessary for the
cellulose stage is detrimental to any microorganisms present.
environment is also extremely important. Clean containers
and air free of microbiological organisms are necessary in the
CMC. Generally speaking the product as produced and packaged is
of microbiological organisms which would promote degradation of the
chain. It has been found in actual application that most biological
causing CMC degradation have been introduced from outside sources
in the CMC). Each manufacturer of sodium CMC usually runs periodic
bacteriological examinations. An example of these analyses is as
bacteriological testing has been done on the
example purified sodium carboxymethylcellulose testing for the presence
coliforms thermophilic anaerobic spores pathogenic staphylococci beta
streptococci Salmonella species and Pseudomonas
It is stressed
that most individual manufacturers of CMC
throughout the world have had bacteriological examination of their
will have data comparable to the preceding. Varying manufacturing
(i.e. different solvents and dry process techniques) will yield
biological analyses but generally speaking most known processing does
promote or support bacterial growth.
bacteriological problems are generally caused when
the sodium carboxymethylcellulose is used in solution. Contaminating
be introduced in the system from influent water used for solution
well as from the air surrounding the mixing and makeup vessels. This is
especially true in warm humid climates which are supportive of
spores. Care should always be taken in handling containers of sodium
carboxymethylcellulose that are stored in locations exposed to warm
bacteriological contamination has been observed
in plant operations where the vessels piping pumps etc. have not been
after each use. In many fluid handling systems the possibility exists
which could retain residual product. In these areas under the proper
microbiological growth can take place at a rapid rate thus
subsequent batches pumped or handled in the same system. Industrial
has shown that this is a major source of microbiological contamination.
clean out measures in any solution handling system where CMC is used
that are necessary to prevent subsequent contamination of other batches
In the United
States toxicological information on sodium
carboxymethylcellulose has primarily been developed on the food
additive grade or
cellulose gum which is of 99.5% purity. Extensive testing has been
this purified grade of sodium carboxymethylcellulose to assess its
foods as an additive. Details on testing and results follow. However a
definition of food grade sodium carboxymethylcellulose is necessary to
safe use. The United States Food and Drug Administration defines
as the sodium salt of carboxymethylcellulose not less than 99.5% on a
weight basis with a maximum substitution of 0.95 carboxymethyl groups
anhydroglucose unit and with a minimum viscosity of 0.025 Pa.s (25 cP)
in a 2%
(dry weight) aqueous solution at 25°C.
carboxymethylcellulose (cellulose gum) is classified
under Substances That Are Generally Recognized As Safe (GRAS) by Title
182.1745 (formerly 121.101) of the Code of Federal