Note: Descriptions are shown in the official language in which they were submitted.
l:~lS~ 7~7
IT_ 1400
COATING RUBBER WITH A COMPOSITION
WHICH RESISTS REMOVAL BY WATER
BACKGROUND
In preparing rubber stocks for use they are
generally mixed in a Banbury with some or all of the
compounding ingredients, and the rubber stock is sheeted
on a sheetOff mill and cooled for further use. If it is
to be stacked or stored before further handling, it must
be dusted or coated with a material like clay to prevent
sticking. The output of a Banbury for a particular rubber
compound has generally been measured by the time or by
the temperature required. It has been found that measure-
ment of the energy consumed by the Banbury by means of a
power integrator (Monsanto) gives a better indication of
mixing. Mixing of the rubber compound or mix in the
Banbury usually results in a large heat build-up with the
temperature of the compound increasing to about 90C., and
higher most of the time, even up to at least about 150C.
Slab dips are used in the tire industry for
coating freshly mixed rubber compounds to prevent them
from sticking together when piled and shelved for subsequent
processing. The installation of power integrators
on Banburys significantly reduces the mixing time of
rubber stocks, and hence it increases throughput, increases
savings or reduces the need for more Banburys or mixing
capacity. However, the method of cooling the rubber com-
pounds by forced air (fans) is not adequate generally to
accommodate the increased throughput for a given factory space.
~ '.
1~15~7i7
It requires more than 12 minutes to cool a stock from the
l~an~ury and s~leetoff ~lill with forced air to a desired
laydown temperature of a~out 50C. maximum, preferably
of about 45C. rnaximum,to prevent scorch. A cooling
system incorporating water spray units between the slab dip
tank and the air cooling fans effectively reduces the cool-
ing time to less than 5 minutes. The use of water sprays,
however, renders the usual slab dip, a clay dispersion in
water, ineffective as it is easily washed away when sprayed
with water.
Slab dips usually come in the form of an aqueous
suspension or emulsion containing suitable inorganic or
organic substances. Most commonly used additives include
whiting, clay and/or paraffin wax. The effectiveness of
a slab dip depends on the uniformity of the coating deposited
on the rubber surface, particularly on drying, and on its
resistance to flow or displacement under stress as a
result of stacking. Many compositions probably would work
if they were dried by air or forced air after deposition on
the rubber surface. The requirement of resistance to removal
by water spray would limit the number of usable candidates.
Zinc stearate slurry in water can be used as a coating.
When deposited on the rubber surface, the zinc stearate
forms a uniform, anti-sticking film which resists rer.loval
by water. However, the cost of zinc stearate even in thin
coatings outweights the benefits resulting from the use of
a power integrator on a ~anbury.
Accordingly, it is an object of the present
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invention to overcome the difficulties alluded to herein-
above and to provide a method for coating a hot rubber
compound with a coating which resists removal by water,
which enables the rubber to be cooled substantially rapidly
by water and which enables the cooled rubber to be assembled
or stacked without sticking.
These and other objects and adv.lntages of the
present invention will become more apparent to those skilled
in the art from the following detailed description and
working examples.
DISCUSSION OF THE PRIOR ART
U.S. Patent No. 2,791,519 discloses a lacquer
comprising a solution of a copolymer of 40-80% butadiene,
10-50~ acrylonitrile, and 2-25~ methacrylic acid dissolved
in a solvent to be used as a coating for cured or uncured
curable rubber compositions to improve the abrasion resist-
ance and gloss of such rubber articles as hose, fuel cells,
auto mats, seat covers, shoe soles and uppers and tires.
While silica and some compounding ingredients can be
added to the lacquer, materials which react with the COOH
groups are less suitable. If uncured, the lacquer coating
can be removed by a solvent. Example 3 shows application
of the lacquer to a curable rubber stock which was
vulcanized and shows after curing the removal of the lacquer
by a solvent.
U.S. Patent No. 4,092,279 (O.G. May 30, 1978)
shows a coating for treating the outer surface of a rubber
article prior to vulcanization comprising an aqueous
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compositiol-l Or 2-7~/(' solids of (A) a ru~ber from a latex
(natural, con~ugated diene polymers, copolymers of dienes,
and copolymers of dienes and styrene, substituted styrene,
acrylic and methacrylic acid, esters, nitriles and amides
thereof and vinyl pyridine), (B) emulsifying agents, (C)
graphite, carbon black or mineral fillers, (D) a thickening
agent and (E) casein.
Japanese Patent Specification No. 057625
(May 22, 1974) discloses a process for preventing sticking
of rubber sheets or granules together by passing the rubber
through a dip tank comprising an aqueous dispersion of 10
light calcium carbonate and 0.2~ (rubber solids) of a
butadiene-styrene copolymer (latex, 23.5~ styrene). The
latex, also, can be a polyisoprene, polybutadiene, acryloni-
trile-butadiene copolymer or polychloroprene latex (0.1-5
wt. ~ solids rubber in the dispersion). The filler, also,
can be talc, clay, silica or magnesium carbonate and can
be present in the dispersion in an amount of 1-30 wt. ~.
Japanese Patent Application 51489 (Ma~ 8, 1973)
discloses a process for the preparation of tack free pellets
or strands of uncured rubber (which is tacky at normal
temperatures) which comprises coating the same with a
thermoplastic polymer having a softening point of 40 to
170C. The thermoplastic polymer can be applied from
solvent or emulsion, should be tack-free at normal temperatures
and should be capable of being plasticized or processed by
rubber processin~ machines. The thermoplastic polymer can
be polyethylene, polypropylene, their chlorinated polymers,
ethylene-propylene copolymers, ethylene-vinyl acetate
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copolymers, styrene-outadiene block copolymers, trans-
1,4-polyisoprene, thermoplastic polyurethanes, thermo-
plastic polyesters, chlorosulfonated polyethylene, polyvinyl
chloride, polyvinylidene chloride and vinyi alcohol type
polymers and mixtures thereof. The amount of thermoplastic
polymer should be less than 50~, preferably less than 30~,
by weight based on the sum of the thermoplastic polymer and
the uncured rubber.
"Chemical Abstracts," Vol. 87, 153215v discloses
a release agent for unvulcanized rubber. When a milled
dispersion comprising 10 parts of powdered co~.arone resin,
30 talc, 1.2 magnesium silicate hydrate, 4 nonionic surfact-
ant and 54.8 parts water was sprayed onto unvulcanized
butyl rubber sheets at 130-40 and piled up, the sheets
did not stick together.
STATEMENT OF THE INVENTION
.
According to the present invention it has been
found that a carboxylated polymer latex conl;aining
a minor amount by weight of a heat sensitizer sufficient to
gel the pol~merparticles of the latex on the application of
heat, preferably containing also fillers, stabilizers and
wetting agents, can be used, to form an adherent water
resistant coating on a hot rubber surface which subsequently
can be water cooled, by dipping, preferably by spraying,dried
and assembled without danger of the rubber (layers)
sticking to itself. The film formed on heat drying resists
removal by water spray. Film formation is believed due to
the heat from the freshly mixed (milled or worked) rubber.
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The film is adherent to the rubber and prevents layers of rubber from sticking
together. Also, any filler in the rubber latex is effectively bound by the
carboxylated polymer on drying so that dusting does not occur to any ap-
preciable extent when a filler is present in the coating. The use of the
present process thus provides a method for increasing the production of a
Banbury.
Thus, this invention provides for the method which comprises coat-
ing a hot, sticky rubber compound with a heat sensitized aqueous polymer
latex composition, drying said coated rubber compound until at least 80% of
the water has evaporated to form a gelled, non-tacky, water resistant and
adherent polymeric coating from said latex on said rubber compound, cooling
said coated rubber compound with water and drying the same to a temperature
sufficiently low to prevent scorch of said rubber compound and stacking
said coated rubber compound to provide layers of said rubber compound which
do not stick together, the polymer of said latex being a copolymer of (1)
at least 45% by weight of a monomer selected from the group consisting of
styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide,
methacrylamide, methyl methacrylate, and ethyl methacrylate and mixtures
thereof, (2) up to 10% by weigh~ of a copolymerizable monomer selected from
the group consisting of acrylic acid, methacrylic acid, ethacrylic acid,
maleic acid, fumaric acid, itaconic acid, citraconic acid, sorbic acid and
crotonic acid and mixtures thereof and (3) the balance, in an amount suffici-
ent to provide some flexibility to and for w lcanization of said copolymer,
a copolymerizable monomer selected from the group consisting of butadiene-
1,3, isoprene, 2,3-dimethyl-butadiene-1,3 and piperylene and mixtures thereof,
said copolymer having a glass transition temperature of not less than about
_30C.
In a further aspect, this invention provides for the method which
comprises coating a hot, milled sticky rubber compound with a heat sensitized
aqueous compounded polymer latex composition, drying said coated rubber com-
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1~15877
pound to form a gelled, non-tacky, water resistant and adherent polymeric
coating from said latex on said rubber compound, the amount of said coating
being not over about 7% by weight of said rubber compound, cooling said
coated rubber co~pound with water and drying the same to a temperature not
above about 50C., and stacking said coated rubber compound to provide layers
of said rubber compound which do not stick together, the polymer of said
latex being a copolymer of (1) at least 45% by weight of a monomer selected
from the group consisting of styrene, vinyl toluene, acrylonitrile, meth-
acrylonitrile, acrylamide, methacrylamide, methyl, methacrylate, and ethyl
methacrylate and mixtures thereof, (2) up to 10% by weight of a copolymer-
izable monomer selected from the group consisting of acrylic acid, meth-
acrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid,
citraconic acid, sorbic acid and crotonic acid and mixtures thereof and (3)
the balance, in an amount sufficient to provide some flexibility to and for
vulcanization of said copolymer, a copolymerizable monomer selected from the
group consisting of butadiene-1,3, isoprene, 2,3-dimethyl-butadiene-1,3 and
piperylene and mixtures thereof, said copolymer having a glass transition
temperature of not less than about -30C., said latex composition containing
from about 150 to 1000 parts by weight of inorganic, non-black rubber com-
pounting pigments per 100 parts by weight of said copolymer in said latexand from about 2 to 30 parts by weight of stabilizers and wetting agents per
100 parts by weight of said copolymer in said latex, the heat sensitizer in
said latex being present in an amount of from about 0.75 to 15 parts by
weight per 100 parts by weight of said copolymer in said latex and the total
solids content of said latex being from about 10 to 75% by weight.
In a further embodiment, this invention provides for a composition
of matter comprising an aqueous polymeric latex containing a minor amount
by weight of a heat sensitizer sufficient to gel the polymer of said latex
on heating, the polymer of said latex having a glass transition temperature
of not less than about -30C., and the polymer of said latex being a copolymer
I B (6a)
~i5877
of (1) at leas~ 45% by weight of a monomer selected from the group consisting
of styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide,
methacrylamide, methyl methacrylate and ethyl methacrylate and mixtures
thereof, (2) up to 10% by weight of a copolymerizable monomer selected from
the group consisting of acrylic acid, methacrylic acid, ethacrylic acid,
maleic acid, fumaric acid, itaconic acid, citraconic acid, sorbic acid and
crotonic acid and mixtures thereof and (3) the balance, in an amount suffic-
ient to provide some flexibility to and for w lcanization of the copolymer,
a copolymerizable monomer selected from the group consisting of butadiene-
1,3, isoprene, 2,3-dimethyl-butadiene-1,3, and piperylene and mixtures there-
of.
DISCUSSION OF DETAILS AND
PR~FERRED EMBODIMENTS
The carboxylated polymer is prepared by free radical aqueous em-
ulsion copolymerization. It should be capable of forming an essentially
non-tacky, essentially water insoluble film when cast as a latex and dried,
and the copolymer per se should be sulfur w lcanizable and have a glass
transition temperature (Tg) of not less than about -30C. The copolymer
contains (1) at least 45% by weight of styrene, vinyl toluene, acrylonitrile,
methacrylonitrile, acrylamide, methacrylamide, methylmethacrylate, or ethyl
methacrylate or mixture thereof, (2) up to 10% by weight of a copolymerizable
acidic monomer like acrylic acid, methacrylic acid, ethacrylic acid, maleic
acid, fumaric acid, itaconic acid~ citraconic acid, sorbic acid or crotonic
acid or mixture thereof, and (3) the balance a copolymerizable conjugated
diene monomer in sufficient amount by weight to afford some flexibility and
to provide for vulcanization, crosslinking or curing, e.g., sulfur, or
peroxide curing, such as butadiene-1,3, isoprene, 2,3-dimethyl-butadiene-1,3,
or piperylene or mixture thereof. Very minor amounts of a 4th, 5th etc.,
monomer such as methyl acrylate, hydroxy ethyl acrylate, and so forth can
D (6b)
l~lS~77
be copolymerized with the above monomers so long as these
additional monomers do not adversely affect the properties
of the resu]ting copolymer or latex. Methods for making
carboxylated polymers are disclosed in U.S. Patents Nos.
2,604,668; 2,669,550; 2,710,292; 2,724,707; 2,849,426;
2,868,754; 3,392,o48; 3,404,116; 3,409,569 and 3,468,833;
in "Rubber World," September, 1954, pages 784 to 788; and in
"Industrial and Engineering Chemistry," May 1955, pages
1006 to 1012. Mixtures of carboxylated latices may be
used. While an ester of the acid or its anhydride etc.,
can be copolymerized instead of the acid and then hydrolyzed
and neutralized to form free acid groups in the copolymer,
this procedure is not as convenient as directly copolymerizin r
the acidic monomer with the other copolymerizable monomers.
Polymerization of the monorners is effected by
free-radical catalysts (free-radical formers or free-radical
forming systems) such as ammonium, potassium or sodium per-
sulfate, H202 and the like in an amount sufficient for
polymerization of the monomers and to obtain the desired
molecular weight. Other free-radical catalysts can be used
which decompose or become active at the temperature used
during polymerization. Examples of some other free-radical
catalysts are cumene hydroperoxide, dit)enzoyl peroxide,
diacetyl peroxide, didecanoyl peroxide, di-t-~utyl peroxide,
dilauroyl peroxide, bis (p-methoxy benzoyl) peroxide, t-
butyl peroxy pivalate, dicumyl peroxide, isopropyl per-
carbonate, disec-butyl peroxydicarbonate, azobisdimethyl-
valeronitrile, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-
methylbutyronitrile and 2,2'-azobis (methylisobutyrate) and
the like and mixtures of the same. Only minor amounts of
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catalyst ~r(~ rlecessary to effec~ p~lymeriza~ion. L~r~(-
radical catalysis is well known as shown ~y "Encyclopedia
of Polymer Science and Technology," Interscience Publishers
a division of John Wiley & Sons, Inc., New York, Vol.2
(1965) pages 278-295, Vol. 3 (1965) pages 26-29, Vol. 7
(1967) pages 361-431, and Vol. 9 (1968) pages 814-841.
Emulsifiers such as soaps, surfactants or dispersing
agents are used in an amount sufficient to obtain an aqueous
emulsion of the water and monomers and resulting copolymer.
Examples of some emulsifiers are potassium laurate, potassium
stearate, potassium oleate, sodium dodecyl sulfonate, sodium
decyl sulfate and sodium rosinate and the like and mixture
thereof. Other well known surfactants can be used. See~
also, "Materials, Compounding Ingredients and Machinery
for Rubber," Publ. by "Rubber World", Bill Communications,
Inc., New York, 1977, pages 291-294 and "Encyclopedia of
Polymer Science and Technology," Vol. 5, 1966.
Chain transfer agents or modifiers are well known
in the emulsion copolymerization of vinyl and diene monomers
to make copolymers. They are used generally to modify
the molecular weight and to reduce cross-linking. While
many types have been proposed, it is preferred to use the
alkyl and/or aralkyl mercaptans having from 8 to 18 carbon
atoms. Of these, the tertiary alkyl mercaptans are much
preferred. Examples of some mercaptans are n-octyl mercaptan,
n-dodecyl mercaptan, t-octyl mercaptan, t-dodecyl mercaptan,
p-tridecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan
and so forth and mixtures thereof. If little or no mercaptan
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is used and polymerization is continued to completion, ~el
may occur and the molecular weight can be very high or
infinitè although some low m.w. fractions may be found.
In other words, m.w. may range from 50,000 to 2,000,000
or more.
NaOH, KOH, NH40H and so forth may be added to
the polymerization reactor before, during or after
polymerization to control the pH as desired. Polymerization
may be conducted under acidic conditions.
The water should be free of deleterious materials,
and preferably should be distilled or ion exchanged.
Sufficient water is used to enable formation of the emulsion
and to enable proper mixing or stirring of the ingredients
during polymerization to obtain the desired rate and degree
of polymerization, heat transfer and so forth. The solids
content (after removal of water) of the resulting latex,
thus, may vary from about 25 to 60% by weight, and the pH
can be from about 7.5 to 11.5.
Stabilizers, antioxidants and chelating agents may
be used during polymerization. Also shortstops in free radical
polymerizatlon are well known. They are not only used to
stop the polymerization in the reactor at the desired
conversion but also to prevent further polymerization,
cross-linking etc., during stripping,work-up and so forth.
Examples of some shortstops are hydroquinone, sodium sulfide,
hydroxyl ammonium acid sulfate, hydroxyl ammonium sulfate,
sodium diethyl dithiocarbamate, diethylhydroxylamine,
sodium dimethyl dithiocarbamate, potassium dimethyl dithio-
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l~lS877
carbamate, dimethylammonium dimethyldithiocarbamate, hydroxyl-
amine sulfate plus sodium hydrosulfite and so forth.
Temperatures used during polymerization should
be sufficient to effect polymerization by activation of the
catalyst and double bonds of the monomers. They should
not be too high to cause a run-away reaction and not too
low to retard polymerization. In general, the temperature
may be from about 2 to 90C. If even lower temperatures
are used, it may be desirable to add an anti-freeze material
to the polymerization media such as methyl alcohol, ethyl
alcohol, propyl alcohol, ethylene glycol or other inert
water soluble antifreeze material and so forth.
Polymerization should preferably be conducted in
a closed reactor, such as a pressure reactor, fitted with
a stirrer or other agitating means, heating and cooling
means, with means to flush with or pump in an inert gas
such as nitrogen, helium, argon, neon and the like in
order to polymerize preferably under inert or non-reactive
conditions, with means to charge the monomers, water,
catalysts and so forth, venting means, and with means to
recover the polymer and so forth. The reactor should be
cleaned or flushed out between polymerization runs to remove
traces of shortstops, catalysts, modifier, residues and so
forth which might interfere with subsequent polymerizations.
There should be sufficient agitation or stirring of the
polymerization media to ensure thvrough mixing, diffusion~
contact and so forth. All of the polymerization ingredients
except the shortstop may be charged to the reactor at the
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same time, intermittently, incrementally or continuously.
Also, the ingredients may be added separately or in a
mixture.
Free radical aqueous emulsion copolymerization of
dienes and vinyl monomers is well known to those skilled
in the art. In this connection please see Bovey et al,
"Emulsion Polymerization," Interscience Publishers, Inc.,
New York, 1955; Whitby et al, "Synthetic Rubber," John
Wiley & Sons, Inc., New York, 1954; Schildknecht, "Vinyl
and Related Polymers," John Wiley & Sons, Inc., New York,
1952 and "Encyclopedia of Polymer Science and Technology,"
Vol. 5 (1966), pages 801-859, Interscience Publishers, a
division of John Wiley & Sons, Inc., New York.
The polymers made by the emulsion copolymerization
process dlscussed above include not only randcm,linear, and
branched copolymers and the like but also graft polymers.
The techni~ue of polymerizing or copolymerizing one or more
monomers in the presence of a polymer or a substrate,
"grafting technique," is known and is frequently called
graft polymerization or graft copolymerization. In th:s
connection, please see "Copolymerization," High Polymers,
Vol. XVIII, Ham, pages 323-324, 335-420 and 573, Interscience
Publishers a division of John Wiley & Sons, New York, 1964;
"Block and Graft Polymers," Burlant and Hoffman, Reinhold
Publish:ing Corporation, New York, 1960; "Block and Graft
Copolymers," Ceresa, Butterworth & Co. (Publishers) Ltd.,
London, 1962j and "Graft Copolymers," Polymer Reviews,
Vol. 16, Battaerd and Tregear, Interscience Publishers, a
division of John Wiley & Sons, New York, 1967. Block
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copolymers, also, may be prepared in water by using certain
a7.0amidino compounds which have surfactant properli~s and
also act as free radical catalysts, opti~:.nally with an
added emulsifying agent, as shown by U.S. Patent No. 3,914,340.
While the above carboxylated latex or a mixture
of the above latices can be used alone for the dip, it is
preferred to employ a compounded latex. In other words, it
is preferred to compound the latex with rubber fillers or
extending agents along with the desired rubber stabilizers,
wetting or dispersing agents, suspending agents, defoamers,
antisticking agents, antioxidants, bactericides, and the
like to provide a stable, filled, compounded latex composition
which has good covering power and which provides a non-
tacky, non-sticky or releasable, but adherent coating, film
and/or layer on a hot tacky rubbery substrate when dried.
Some latex compounding ingredients are shown by "Materials,
Compounding Ingredients and Machinery for Rubber,""Rubber
World" publication, 1977, Bill Communications, Inc., New York.
The fillers which are desirably added to the
latex to extend it are non-black, inorganic rubber compounding
pigments or fillers. The fillers, also, may help as
antisticking agents and may serve to thicken the latex as
well as to modify the viscosity of the latex. The filler
should be finely divided. Examples of fillers are calcium
carbonate, clay, precipitated hydrated silica, fumed silica,
mica, barytes, perlite, magnesium silicate or talc, feldspar,
hydrous calcium magnesium silicate, magnesium carbonate,
magnesium oxide, titanium dioxide, and the like and mixtures
of the same. Of these
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rr.aterials it is preferred to use calcium carbonate, clay
fumed silica or hydrated precipitated silica and mixtures
thereof. These fillers are used in an amount necessary to
provide the desired extension, thickening, viscosity and/or
additional anti-sticking properties for the latex and to
reduce cost. Too large an amount should be avoided since
the rubber particles of the latex (rubber dispersion or
suspension) on drying will not be present in sufficient
amount to form a film and to bind all of the filler particles
together to the substrate. In general the amount of filler
can vary from about ~50 to l,000 parts by weight per lO0
parts by weight of dry copolymer (from the latex).
The otherjas mentioned above, latex compounding
ingredients (besides the pigments) are used in a minor
amount by weight as compared to the copolymer (dry basis).
They are desired (for example, in addition to any stabilizers,
emulsifiers etc., used during polymerization) to further
stabilize the latex in view of the addition of the fillers.
These other compounding ingredients may provide more than
one function in the latex, e.g., they may act as dispersing
agents as well as wetting agents. In general, these other
compounding ingredients such as stabilizers and wetting agents
are used in an amount of from about 2 to 30 parts by weight
per lO0 parts by weight of the copolymer on a dry basis.
Examples of some of these other latex compounding ingredients
are anti-foaming or defoaming agents such as polyalkylene-
ether glycols, triols and tetrols, 2,4,7,9-tetramethyl-5-
decyn-4, 7-diol, Defoamer Y-250 (blend of emulsi~iable
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mineral oil, silica derivatives and esters, Drew Chemical
Corp.), and the like. Examples of some stabilizing,
dispersing and wetting agents are sodium linoleate, octyl-
phenoxy polyethoxy ethanol, polyoxypropylene oxyethylene
glycol, casein, alkyl aryl sulfonates, sodium dioctyl sulfon-
succinate, sodium salt of polymerized alkyl naphthalene
sulfonate, sodium stearate, and nonyl phenol and the like
and mixtures thereof. Examples of some suspending and
organic thickening agents are ammonium poly acrylate, sodium
polyacrylate, hydroxyethyl cellulose, potassium alginate,
polysaccharides, sodium alginate and the like and mixtures
thereof. Examples of some antisticking agents are zinc
stearate, saponified fatty acids and so forth.
The heat sensitizer is required so that the
copolymer will form a film (coagulate or gel) at the desired
temperature, e.g., on contacting the hot rubber stock. The
heat sensitizer, also, acts to form (accelerate) a str~nger
film faster at a given temperature and thus reduces time
of processing. Examples of heat sensitizers are the zinc
ammine system, polyvinyl methylether, polypropylene
glycol, 2-nitro-2-methyl-1-propanol and so forth. Polyoxy
propylene oxyethylene glycols and similar alkylene oxide
polyols, also, may act as heat sensitizers. The heat
sensitizer is used in a minor amount by weight dry as
compared to the polymer of the latex sufficient to gel or
coagulate the polymer. Preferably, there are used about 0.75
to lsparts by weight of the sensitizer to 100 parts by
weight of the carboxylated polymer on a dry weight basis.
Mixtures of heat sensitizers can be used.
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A minor amount by weight (up to about 25~ by
weight on a dry weight basis) of the carboxylated latex
may be replaced with other polymeric latices which are
compatible with the carboxylated latex and the rubber
stock to be dipped and which when mixed with the carboxylated
latex do not cause the overall rubber mixture to have a
cornbined glass transition temperature below about -30C.
Examples of such other latices are those of polybutadiene,
polyisoprene, natural rubber, butadiene-styrene copolymer,
butadiene-acrylonitrile copolymer, butadiene-styrene-acrylo-
nitrile copolymer, butadiene-acrylic ester copolymer,
polychloroprene, ethylene-propylene-diene copolymers (EPDM),
isobutylene-isoprene copolymers, butadiene-styrene-vinyl
pyridine copolymer, chlorobutyl rubber, bromobul;yl rub~er
and so forth and mixturesthereof. Some of these polymers
may be made by solution processes and then converted to
emulsions by processes well known to the art.
For more information on methods of compounding
and treating latex or latices see "Latex In Industry,"
Noble, 2nd Ed. 1953, Rubber Age, Palmerton Publishing Co.,
New York and "High Polymer Latices," Blackley, 1966, Vols.
1 and 2, Maclauren & Sons Ltd., London.
The amount of water used in making or added to
the compounded latex will depend on the desired viscosity,
handling characteristics of the compounded latex, the
thickness of the film which it is desired to lay down on the
rubber substrate and the time required for drying and film
formation. Thin films and low viscosity compounded latices
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are desirable; however, t~lese propertieC n~y ~ary coll~i(1er-
able with needs, coating equipment, storing, pumping,
speeds of coating, drying times and temperatures, fi~m
thickness and so forth. In general, the total solids
content in the aqueous compounded latex may be from aoout
10 to 75%,preferably from about 10 to 40~, by weight.
Deionized or distilled water should be used as the diluent
to avoid introducing extraneous ions which might cause
instability to the latex, resulting film and so forth.
The compounded aqueous latex dip may be applied
to the rubber substrate by dipping, spraying, roller coating,
painting or by any means which will provide a suitable
coating. Thin coatings are preferred since they will
gel in a short time. On the other hand, while thick coatings
may be used, only the surface layers nearest to or adjacent
the rubber stock may be gelled in sufficient time so that
the bulk of the coating may be washed off during the
subsequent water(spray or dip)cooling step. Moreover, excess
dip coating may require further compounding of the rubber
stock itself to overcome the effects of the dip c~ ting
if the rubber compound is fu-~ther mixed with curing agents
such as sulfur and rubber accelerators. In general,
not over about 7%, preferably not over about 2~,by weight
dry of the dried latex composition from the dip on the
rubber stock substrate will be enough to prevent sticking.
While the dip of the present invention can be
applied to any polymeric surface and heated to prevent
sticking of the surfaces, it is particularly applicable to
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rul)~ r s~o~ks wh;ch havt-~ ~)e~t~ ~n~u~yed, mastica~d,milled
or which are freshly mixe~ and hot so that their surfaces
are sticky or tacky. The stocks may be in the form of
milled, masticated or broken down rubber, partially
or fully compounded with carbon black, zinc oxide, stearic
acid, silica, extender oil, styrenated phenol antioxidant
and so forth. Examples of the rubber polymers which may be
used in the stocks are natural rubber, polyisoprene,
polybutadiene, butadiene-styrene copolymer, butadiene-
acrylonitrile copolymer, butadiene-styrene-acrylonitrile
copolymer, butadiene-acrylic ester copolymer, polychloroprene,
ethylene-propylene-diene copolymers (EPDM), isobutylene-
isoprene copolymers (butyl), chlorinated butyl, brominated
butyl, butadiene-styrene-vinyl pyridine copolymers, carboxyl-
ated butadiene-acrylonitrile copolymers, carboxylated
butadiene polymers, carboxylated butadienc-styrene
copolymers and the like and mixtures thereof. While the
process of the present invention is particularly useful
for treating hot rubber which has ~ust been ~anburyed and
passed through a sheeting mill to form a continuous hot
sheet or slab, it will be appreciated that it can apply
to any milled, extruded, calendered, laminated or warmed,
tacky rubber stocks to prevent the rubber stocks from
sticking together when piled, shelved or stored awaiting
subsequent processing, e.g., the manufactures of tires,
belts and so forth. Moreover, while the dip of the present
invention is useful with slab, strip or sheet rubber
stock, especially in continuous form, it, also, can be
used on separate pieces, formed or not, or in the form of
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l~lS877
powders, pellets, crumb or particles and so forth to prevent
them from sticking together.
In one enlbodiiment of the present invention the
hot (abaut 90-l~P C.) masticated rubber stock from the Banbury
is passed through a sheeting mill to form a continuous hot
sheet or slab and the continuous hot slab is dipped in a
dip tank containing the latex slab dip composition of
this inven.tion for about 1 second or so and is then allowed
to air dry for 30 to 40 seconds or until at least about 80~
of the water has evaporated (preferably all the water should
evaporate) and the heat sensitizer in the latex has caused
it to coagulate or gel. The gelled latex composition coated
slab is then sprayed with water for about 30 to 40 seconds
to cool it down without removing the latex coating and then
air dried and stacked at a lay down temperature of about
50C. maximum, preferably of about 45QC. maximum,
(to prevent scorch) to form stacks or layers of rubber
which do not stick kogether. During air drying step and
water spraying step the rubber sheet or slab may be carried
on a series of rotating æhafts with long loops between the
shafts (festooned) to save space.
Since the carboxylated latex may be sensitive
to extraneous ions such as metallic cations which may
cause it to coagulate or cause the precipitation of soaps,
the dipping tank and piping, stirrers, pumps and so forth
which may be use~d in connection with a dip tank should pre-
ferably contain a protective coating such as an epoxy resin,
glass
~18)
1~1587~7
etc. If stirring or agitating means are available and used
continuously or when needed, filler suspending agents for
the filled latex may not be necessary.
The following examples will serve to illustrate
the present invention with more particularity to those
skilled in the art. In the examples, parts are parts by
weight unless otherwise indicated.
The mixing of the ingredients of the slab dip
composition for the examples was done with a portable air
or electric stirrer. The procedureis outlined below:
1. The latex was diluted with the predetermined
amount of deionized water using moderate stirring.
2. The soap and wetting agents were added until they
dissolved, the rate of solution depending on the
nature of the materials and usually taking less
than 5 minutes.
3. The heat-sensitizing additive was added.
4. The filler(s), wax emulsion and/or zinc stearate
were added.
5. The polysaccharide thickener was added if used.
6. The defoamer was added if used.
7. Stirring was maintained until the latex dispersion
appeared homogeneous.
The mixing procedure should not take longer than about 30
minutes for the batches shown in the working examples.
The viscosity of the slab dips was measured
using the Brookfield viscometer. Model HB was used for high
viscosity dips while model ~V was used for the low viscosity
(19)
1115877
dips. The rate of shearing and spindle type used were
dictated by the nature of the dip. The slab dip formulation
should be stable mechanically under conditior~s of high
shear rate agitation. To establish this about 100 cc of
the slab dip was stirred vigorously (~ 10,000 rpm) using
a "milk shake" type apparatus while observing for a change
in the slab dlp.
pH determination of the slab dips were made by
means of pH indicating paper strips.
Rubber compounds or samples used to test the slab
dips included masticated natural rubber gum stocks and
masticated natural rubber-carbon black filled stocks,
both milled in the laboratory prior to dipping to provide
a hot fresh rubber surface.
Then the freshly milled rubber samples were dipped
in a bath of the latex slab dip composition for about 1
second, dried in air at about 25C. for about 30 seconds,
cooled in water at about 25C. for 30 seconds, and then
dried in air for 60 seconds and stacked.
The stacked rubber layers (stacking) was
made to simulate conditions in production. Two samples
coated with the dried gelled slab dip were stacked on top
of each other and ab~jut 2 psi was applied using a special
bladder mold in a press. The press was heated to about 54.50C.
Samples were treated this way for as long as three days
before they were taken out for observation. The condi1~ions
of simulated stacking are actually much more severe than in
production. In production a regular batch weighing about
1800 lbs., when folded and stacked in the normal way,
(20)
l~lS~77
probably experiences about 1 psi of pressure, particularly
those confined to the bottom of the stack. The temperature
of the stock during laydown is not supposed to exceed about
50~C.
EXAMPLE I
The following ingredi~nts were mixed together
to form sla~ dips having a total solids content (TSC)
of over 50% as shown in Table I below:
Table I
Parts by Weight
Ingredients Run 1 Run 2 Run 3
Latex 100 100 100
"Valpro" SD 1.5 1.5 1.5
"Pluronics" L101 1.5 1.5 1.5
Sodium lauryl sulfate 1.0 1.0 1.0
I~:aolin clay - - 150
Whiting 300 300
"Cab-0-Sil" M5 2.5 2.5
NMP 1.5 ~ 1.5
2.5~ "Kelzan" aqueous solution - 10
"Surfynol" 104H - _ o.5
Water (deionized) 100 100 150
Total 508.0 516.5 406.0
%TSC, by weight of dip 70.6 69.2 50.9
% Rubber, dry basis, by weight
in dip 14.1 14.2 24.6
% Rubber, wet basis, by weight
in dip 10.0 9.8 12.5
(21)
5~77
n starl~ing overni~,h~, ~t~e w~ in" in sla~J ~ip Run 1
settled out due to lack of suspending agent while Run 2
and Run 3 remained homogeneous. The incorporation of a
polysaccharide ("Kelzan") in Run 2 effectively maintained
the filler in suspension. Run 3, on the other hand, had
a much lower total solids content than Run 1. The type
of filler used ":~lso, was different in both cases. The
mechanical stability of the above dips was excellent. When
subjected to vigorous stirring for more than 30 minutes,
very little change in viscosity was observed. Foaming was,
however, extensive in all cases but collapse of the foams
r~ccurred in 10-30 minutes after stirring had ceased.
When freshly masticated hot natural rubber samples
(gum and black lo~ded) were immersed in the dips, heavy
coatings were obtained due to the high solids content.
The viscosity of the above dips were all about 3000 cps,
based on an HB model Brookfield viscometer with a number 2
spindle and 10 rpm. Subsequent spraying with water washed
off part of the dips, leaving fairly thin continuous coatings
on drying. The coated samples did not stick together in
the heated bladder mold test. The dried coatings were not
removed on treat~nent with water.
The stability of these latex dips, when exposed
to a sandblasted steel panel, was poor. Destabilization
obviously occurred after exposure overnight as indicated
by the thick deposit on the surfaces of the panel. This
problem was eliminated when a similar steel panel was coated
with an epoxy based paint prior to exposure to the slab dips.
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i~iS~77
EXAl`~PL~ II
The following ingredients were mixed together
to form slab dips having varying TSC as shown in Table II,
below:
Table II
Parts By Weight
Run No 10 11 12 13 14
In~redients
Latex 100 100 100 100 100
'IValpro'' SD 1.0 1.0 1.0 1.0 1.0
"Triton" X-114 0.5 0.5 0.5 0.5 0.5
"Kelzan" 0~25 0.25 0.25 0.25 0.25
Whiting 275 275 275 275 275
"Cab-0-Sil" EH5 5 5 5 5 5
NMP 2 2 2 2 2
Deionized water 285.4 359.7 452.6 572.1 731.4
Total 669.15 743.45 836.35 955.85 1115.15
% TSC, by weight 50 45 40 35 3
% Rubber (wet), by
weight 7.6 6.8 6.o 5-3 4.6
% Rubber (dry), by
weight 15 15 15 15 15
The above dips were then evaluated for coating efficiency
or behavior and for viscosity. Uncured (carbon black
loaded natural rubber) tire compounds die-cut into l"x6"xl/4"
specimens were accurately weighed and heated prior to dipping
and drying. After spraying with water and final drying,
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~15~77
the dipped speclmens were reweighed to obtain the coating
retained. The results are summarized in Table II, A, below:
Table II, A
Slab Dip 10 11 12 13 14
Run No. - - - -
Brookfield Visc.
centipoise HB
Model, Spindle ~1
10 rpm 105 50 3 15 <10
Deposit on rubber
specimens, ~ by wt. 3 9 2.3 1.65 0.95 poor
wetting
The weight of the rubber specimens used averaged 16.56 grams
with deviations from this average of no more than 5~. It
was apparent from the results shown that the deposit from
the slab dips increases with increasing total solids
content. An ideal dip would be one which works with the
least amount of deposit from a cost standpoint. Inadequate
wetting becomes a problem with increasing dilution. However,
this can easily be circumvented by adjusting the amount of
wetting agent accordingly. The increase in viscosity wlth
increasing TSC is rather expected. The surfaces of the
dried latex coated samples of Runs 10 to 13 were not
tacky, and, also, the dried coatings were not removed on
washing or rinsing in water. The wetting of Run 14 could
be increased by adding more surfactant or wetting agent.
EXAMPLE III
The foll~wing ingredients were mixed together to
form slab dips having constant TSC by keeping the latex
content constant and by varying the whiting content and
(24)
~lS~77
the water content as shown in Table III, below:
Table III
Parts By Weight
Run No. _ 21 22_
Ingredients
Latex 100 100 100
"Valpro" SD 1.0 1.0 1.0
"Triton'l X-114 0.5 0.5 0.5
"Kelzan" 0.25 0.25 0.25
Whiting 275 210 185
"Cab-0-Sil" EH5 5 5 5
NMP 2 2 2
Water 452.6 355 317.6
Total 836.35 673.75611.35
~TSC, by weight 40 40 40
Rubber (dry), by wt. 15 18.8 20.7
% Rubher (wet), by wt. 6 7.5 8.3
Brookfield Viscosity Model
HB Spindle #1, lo rpm ~30 ~4 ~25
Deposit of latex
compound on rubber 1.65 1.40 1.25
~ by wt.
In contrast to previous examples, the amount of slab dips
deposited on hot and dried carbon black filled natural
rubber sample stocks appears to decrease with increasing
rubber content. Closer examination of the formulations
(25)
1~15~77
showed tha~ thl e~fect of t.he rubber con~en~ was actually
confounded with the differences in the whiting leve]. The
increase in rubber corltent was obtained at the expense
of decreasing whiting level. Hence, the decrease in the
amount of dip deposit with increasing rubber cGntent may
in some way be related to the decrease in the whiting level.
The slab dips in Tables II plus II A and III, except Run 14
in Tables II plus II A, effectively prevented the rubbers
from sticking in the bladder mold test. Based on the results
of these examples, decreasing the solids content does
not impair the slab dip performance. The surfaces of the
dried latex coated rubber samples of this Example were not
sticky nor tacky, and, also, after drying the surface
films or coatings were not removed by treatment with water.
EXAMPLE IV
In this example relatively low TSC slab dips
were prepared in which were dipped natural rubber gum
stocks or compounds as well as carbon black filled natural
rubber stocks. The dried latex coated rubber samples were
tested according to the bladder mold test mentioned
above and all of the dried latex coated rubber samples
of the runs of this example did not stick together, and even
though the surface films were thin, they were uniform.
Moreover, after drying, these surface films on the rubber
stocks were not removed by water. The ingredients of the
dips are shown in Table IV, below:
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1~15877
Tat~lc ~v
Parts by Weight
Run No. 3 31 32 33
Ingredients
Latex 100 100 100 100
"Valpro" SD 2.5 2.5 2.5 2.5
"Triton" X-114 3.0 3.0 3.0 3.0
Whiting 430 430 430 450
"Hi-Si~'215 15 - 15
Emulsion - - 15
Zinc stearate - - - 5
"Gantrez" M-154 4.0 5.0 4.0 3.0
Deionized water 1972 1916 2032 2008
Total 2526.5 2456.5 2601.5 2571.5
~ TSC, by wt. 20 20 20 20
% Rubber (dry), by wt. 10.05 10.3 9.8 9.9
Rubber (wet), by wt. 2.01 2.07 1.95 1.98
The emulsion contained the following ingredients in parts
by weight:
"Epolene" E-15 40
"Triton" X-114 13
43~ KOH in deionized water 1.3
Deionized water 150
Total 204.3
The emulsion was prepared by first melting the "Epolene"
at about 130C., in the presence of the "Triton" and then
. (27)
1~15877
slowly adding the KOH solution. The mixture was stir~ed
until bubbling stopped. It was then reheated back to about
130C., before final blending, with vigouous stirrin~, into
the boiling water. The stirring was maintained until the
emulsion cooled to about 450C.
The pH of the dips of this example ranged from
8.2 to 8.4. The heat sensitizer, "Gantrez", is
most effective at a pH of about 8 although
at a pH of above about 8 the compounded latex can become
marginal in stability unless amply stabilized. The wetting
agents in appreciable amounts are necessary to get good
wetting at high filler loading ( note Run 14).
With respect to the dips of the runs of this
example all were vigorously stirred ( ~10,000 rpm) between
one half to about one hour using a milk shake type apparatus
without any observable change in their appearance showing
that they were resistant to destabilization at high speed
agitation even at relatively low pH. Although foaming
occurred in all instances duc to air entrapment, the
foams collapsed on standing. The dips of the runs of this
example were aged in closed cont~iners in an oven at 50C.,
wlthout any observed change after three weeks. Thus the
dips can be stable to the pumping, stirring, and temperatures
which might be encountered in s~rage and in dipping during
tire factory operations.
Using a Brookfield Model LV viscometer with a
#1 spindle rotating at 30 rpm the viscosity of all of the
dips of this example was less than 10 centipoises.
(28)
1~15~37'~
Specimens of uncoated steel panels were immersed
in the sla~ dips of this example, and no change was observed
after the first 3 days. Later some green deposits started
to appear on the steel and the pH of the dips was found to
be reduced from above 8 as shown above to slightly above
7. In contrast to these observations there was no
apparent change in the physical state of painted steel panels
when immersed in these dips, and the pH of the dips was
unchanged after immersion for a week.
A rubber slab (natural rubber-carbon black master-
batch) was dipped in a slab dip the same as Run 31 above
but at a somewhat higher total solids content, dried and
cooled. The coated slab and a similar uncoated slab
were separately mixed, based on 100 parts by weight of
the rubber slab, with 5 parts of zinc oxide, 2 parts
of stearic acid, 0.5 part of MBT, and 2.5 parts of sulfur.
The resulting compounded slabs were then each molded,
cured and tested. The results are shown in Table IV, A
below:
Table IV,A
Slab + Dip Slab
of Run 31 Without Dip
Cure at 141.7C14 min. 14.5 min.
10% Modulus, MPa0.62 0.5!
100% Modulus, MPa 3-52 3.40
300% Modulus, MPa 12.82 12.35
Tensile, MPa 15.63 18.31
Elongation, % 355 420
Shore A, hardness 72 71
Trouser Tear, kN/m 3.01 2.92
(29)
l~lS877
With the exception of the tensile strength and elongation,
the two cured compounds appear to have essentially the same
properties. The differences in tensile strength and
elongation are not significant and generally are within
the experimental error normally expected for these properties.
These tests show that the coating on the slab does not
materially affect the cured properties of the rubber. Of
course, allowance in compounding for these differences may
narrow and eliminate the same.
A run was made using the same dip as Run 31
but with a slightly higher concentration of whiting. The
rubber stock was milled, calendered and extruded as
a tire puncture sealing strip and passed through the dip,
dried, cooled with water, dried and piled up on itself or
stacked. After several hours (overnight), it was inspected
and the lengths or strips of the coated rubber puncture
sealant compound could readily be separated from each other
or unstacked. The puncture sealant is of a type which
flows excessively in storage. This experiment indicates
the importance of compliance and ~etention of film contiguity
that the film from the present slab dip possesses since a
non-film forming dip would not work in the case of such a
rubber compound which was an oil extended ethylene-propylene-
diene monomer rubber composition (see U.S. Patent No. 3,903,947).
(3o)
1~15~77
EXAMPLE V
A natural rubber carbon black masterbatch compound
was cut into pellets or cubes approximately 4 ~I in size.
Four lots of these pellets each weighing about 25 grams were
loosely put in a steel mesh container and dipped in various
dips and dried for 1-2 minutes, the rubber samples being
accurately weighed to the nearest 0.1 mg before and after
coating. The samples were then transferred to their
respective graduated cylinders measuring about 12" long x
1.5" diameter to simulate storage bins. On top of the
rubber pellets was added a metal dish and then there
were added lead beads on top of the dish - which thus
separated the pellets from the beads. The dish and
beads together exerted about 2.4 p.s.i., of pressure on the
rubber pellets. The entire assemblies were then aged in a
heated oven at about 450C., for four days. After this
period the rubber pellets were taken out for observation.
The data are shown below:
V-l. Control.No dip nor coatlng. The pellets adhered
together forming a solid mass in the s~ape of the cylinder.
V-2. Rubber pellets not heated prior to dipping. Dip
was clay suspension or slurry (10~ TSC) in water containing
surfactant. o.6g% by weight of dip coating on rubber pellets
picked up on drying. Coated pellets did not stick together.
V-3. Rubber pellets not heated prior to dipping. Dip
was zinc stearate (not readily water dispersible, "Quikote''
Ventron Corp.) slurry (10~ TSC) in water. 0.13~ by weight
of dip coating on rubber pellets picked up on drying. Coated
(31)
1~1587'7
pellets did not stick together.
V-4. Rubber pellets heated above about 7~C. with a hot-
air blow gun before dipping. Dip was the dip of Example IV,
Run 31, above. 0.45% by weight of dip coating on rubber
pellets picked up on drying. Co~ted pellets did not stick
together.
The following comments can be made:
V-2. This dip not only deposited more solids
on the rubber which can adversely affect vulcanizate properties
for some applications, but it is readily removed by water
washing.
V-3. While this dip deposited less solids on
the rubber stock than the dip of V-4, it is about 6 times
more expensive than the dip of V-4 even at the lower solids
deposit. While zinc stearate is water insoluble, it apparently
adheres to the rubber because of its fine particle size
and of its density being low, e.g., lower than the clay.
In summary, slab dips have been disclosed which
when deposited on the surface of rubber compounds, become
resistant to removal by water spray. The dips are based
on a carboxylated polymer latex and a heat sensitizer and
preferably contain suitable wetting agents, stabilizers
and fillers. The high temperature of the freshly-mixed rubber
compound causes the slab dip to form an adherent, non-
tacky water resistant film. 'I'h- film deposi~ed on t~lC rutJt)fr
compounds effectively prevents the layers of rubber from
sticking during stacking and storage. The dips are low in
cost and are easy to prepare. The rubber compound containing
(32)
~15~37'7
the rilm f~ e (tip e~ar~ r~pro~(~ss~ asily wi~l rlo
adverse effect on the final vulcanizate properties based
on laboratory tests.
NOTES:
Latex - ~queous emulsion free radical polymerized
high molecular weight carboxylated butadiene-styrene
copolymer containing about 55% by weight styrene, not
over about 5~ by weight total of methacrylic and itaconic
acids and the balance butadiene-1,3. Polymer Tg of about
-20C., 50% solids, pH of 9.0, Brookfield viscosity
(#2@ 60 LVF) of 70, and surface tension of 54Ø Contains
antioxidant. Binder and film former.
"Valpro" SD - Sodium linoleate.
94~ min. a nhydrous soap. Valley Products Co. Used as
stabilizing, dispersing and wetting agent.
"Pluronic" L 101 - Liquid polyoxypropylene -
oxyethylene glycol. A n~nionic difunctional block-polymer
terminated in primary hydroxyl groups. Av. mol. wt. of
3800. BASF Wyandotte. Used as wetting agent and possible
heat sensitizer.
Kaolin - China clay. Hydrated alumina silicate.
J. M. Huber. Used as filler and anti-sticking agent.
Whiting - Calcium carbonate. Natural ground.
Sp. gr. 2.71. Mean particle size (microns), 13Ø CC100,
Sylacauga Calcium, Alabama.Used as filler and antist'cking
agent.
"Cab-O-Sil" M-5 - Fumed silica. Surface area
(BET) 200+ 25 m2/gm, particle size 0.012 micron. Cabot
Corp. Used as viscosity modifier and filler.
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1~15877
NMP - 2-Nitro-2-methyl-1-propanol. Water max.
0.5% by wt. ~ree formalde}ly~e max. 0.04% t)y wt. Meltin~
point min. ~O~C. IMC Chemical Group, Inc. Used
as heat-sensitizing additive.
"Kelzan" - Xanthan gum, a high molecular weight
(about over one million) generally linear complex poly-
saccharide. Kelco Company. Used as filler suspending agent.
"Surfynol" 104H - 75% wt. 2,4,7,9-tetramethyl-5-
decyn-4,7-diol in ethylene glycol. Air Products and Chemicals
Inc. Used as defoamer.
"Triton" X-114 - An alkyl aryl polyether alcohol;
the adduct of t-octyl phenol and 7-8 ethylene oxide groups.
Rohm ~ Haas Company. Used as wetting agent.
"Cab-O-Sil" EH-5 - Fumed (vapor phase) silica.
Surface area (BET) 390+ 40 m2/gm. Density 2.3 lbs./cu. ft.
Nominal particle size 0.007 micron. Ignition loss (1000C.,
moisture-free bases)2.5~. Cabot Corp. Used as viscosity
modifier and filler.
"Hi-Sil" 215 - Compacted,precipitated, hydrated
silica. Sp. gr. 2Ø Ultimate particle size 0.022 micron.
Finer than 325 mesh. PPG Industries, Inc. Used as
thickening agent and filler.
"Gantrez 1I M-154 - 50~ water solution of linear
homopoly (vinyl methyl ether); K-value 40, specific viscosity
(1 g/lOOml benzene)O.47. GAF Corp. Used as heat sensitizing
additive.
(34)
1~15877
"Epolene" E-15 - Polyethylene. Emulsifiable.
Approximate molecular weight of 3400. Density at 25C.,
of 0.925. Acid No. 16. Brookfield viscosity, spindle
#3,6 rpm, at 125C., of 520 cp. Eastman Kodak Co.
MBT - 2-mercaptobenzothiazole.
Zinc stearate - wettable. Dispersible in water.
C. P. Hall.
(35)
