LU81468A1 - APPLICATION ON RUBBER OF A NON-ADHESIVE AND WATER-RESISTANT COATING BASED ON CARBOXYL POLYMERS - Google Patents

Description

'y i «. In the preparation of rubber compositions, the gum is usually mixed in a Baribury with the usual ingredients or some of them only, then the mixture is placed on a grinder in the form of sheets which are then cooled. If the sheets are to be stored stacked on top of each other before being used, they should be powdered or covered with a material such as clay to prevent them from sticking together. The performance of a Baribury, for a given particular rubber composition, is generally determined by the time or temperature required, and it has been observed that the measurement of the energy consumed by the apparatus by means of a power integrator (Monsanto) gave a better indication of the mixing operation. The mixing of the rubber composition in the Baribury generally gives rise to a strong accumulation of heat, the temperature of the material rising to around 90 °, or even more most of the time, and possibly even reaching 150 ° C. and more.

In the manufacture of tires, baths are used to coat the freshly mixed rubber compositions in order to prevent the sheets from sticking together when they are stacked and stored until used for manufacturing. The installation of power integrators on the Bariburys greatly reduces the time for mixing the compositions, which increases the processing capacity of the apparatuses and the savings, either decreases the number of apparatuses necessary or avoids having to increase their capacity . However, the cooling of the rubber mixes by air blowers does not generally make it possible to cope with the increased efficiency of the mixing devices for a given space in the workshop. With such air cooling, it takes more than 12 minutes to cool a mixture from the Baribury and the grinder to the desired temperature of about 50 ° C maximum and, preferably, not exceeding 35 45 ° C approximately, to prevent the rubber from scorching. * A cooling system with water spray stations placed between the leaf immersion tank and the air blowers reduces the cooling time to less than 5 minutes, 2 but spraying water removes the coating. clay left by ordinary immersion baths, which are aqueous dispersions of clay.

The baths for coating the sheets are generally aqueous suspensions or emulsions of suitable inorganic or organic materials, the most common of which are, for example, limestone, clay and / or paraffin wax. such a bath depends on the regularity of the layer deposited on the surface of the rubber, in particular after drying, as well as on its more or less great tendency to creep or to move under the pressure resulting from the stacking of the sheets. Many products would probably be satisfactory if they were dried in air or by air blowers * after they were deposited on the surface of the rubber, but the fact that they should not be removed by limiting water the number of possible products. An aqueous suspension of zinc stearate can be used as the coating bath, this salt forming on the surface of the rubber a uniform film preventing adhesion and which is resistant to water, but then the cost of zinc stearate, even for thin films, exceeds the benefit of using a power integrator on a Baribury mixer.

That said, the subject of the present invention is a method of applying, to a hot rubber composition, a coating which is resistant to water and which makes it possible to cool the rubber quickly with water, and to assemble or stack the cooled rubber sheets without Λ sticking to each other o

US Patent No. 057625 describes a varnish 30 which is a solution in a solvent of a copolymer with 40-80% of butadiene, 10 to 50% of acrylonitrile and 2-25% of methyl acid. thacrylic, to form a coating on vulcanizable rubber compositions, vulcanized or not, in order to improve the abrasion resistance and the gloss of rubber articles such as flexible pipes, fuel cell cases, carpets of automobiles, seat covers, soles and combs of shoes and tires, and if one can add to such a varnish silica and certain other ingredients, the materials which react with the carboxylic groups con-40 come less well ", Furthermore, in the uncured state, the 'f 3 S * * * coating can be removed by solvents, and 1 * example 3 of this patent describes 1 * application of the varnish on a mixture of vulcanizable rubber which is then vulcanized, and after vulcanization shows 1 Removal of the coating with a 5 solva nt.

US Patent No. 4,092,279, dated May 30, 1978, describes a surface coating product of rubber articles before vulcanization, which is an aqueous composition at 2-70% solids, (A) a latex rubber (natural, polymers of conjugated dienes, copolymers of dienes and copolymers of dienes and styrene, styrene substitution derivatives, acrylic and methacrylic acids, their esters, nitriles and amides and vinylpyridine), (B ) d * emulsifying agents / (C) graphite, carbon black or mineral fillers, (D) a thickening agent and (E) casein.

Japanese Patent No. 057625 dated May 22, 1974 describes a process for preventing sheets or granules of rubbers from sticking and adhering to each other, process comprising passing the rubber 20 through a bath consisting of an aqueous dispersion with 10% of light calcium carbonate and 0.2% (in solid rubbery material) of a butadiene-styrene copolymer with 23.5% of styrene (latex), the latex possibly also being a latex of polyisoprene, of polybutadiene, of an acrylonitrin-butadiene copolymer or of polychloroprene containing 0.1 ~ 5% by weight of solid rubber, and the filler which may also consist of talc, clay, silica or magnesium carbonate, in a proportion of 1 to 30% by weight.

Japanese patent application No. 51489 of May 8, 1973 describes a process for preparing non-sticky pellets or strands of unvulcanized rubber (which is sticky to itself at normal temperatures) consisting in coating them with a thermoplastic polymer softening between 40 and 170 ° C, polymer which can be applied in solution in a solvent, or in emulsion, which must not be sticky at normal temperatures and which must be able to be plasticized or worked i on processing machines rubbers. This thermoplastic polymer can be polyethylene, polypropylene, optionally chlorinated, an ethylene-propylene copolymer (4 Ψ * or ethylene-vinyl acetate or a styrene-butadiene block copolymer, or alternatively trans-1,4 polyisoprene, a polyurethane or a thermoplastic polyester, chlorosulfonated polyethylene, polyvinyl or polyvinylidene chloride or a polymer of vinyl alcohol type or a mixture of several of these materials, and its proportion must be less than 50%, preferably 30%, the sum of its weight and the weight of unvulcanized rubber.

The "Chemical Abstracts" Vol. 87, 153215V describes a product which prevents unvulcanized rubbers from being sticky: by spraying on unvulcanized butyl rubber sheets which are at a temperature of 130-40 ° C a ground dispersion of 10 parts of resin coumarone powder, 30 parts talc, 1.2 parts hydrated magnesium silicate, 4 parts of a non-ionic surfactant and 54, 8 parts of water, these sheets stacked on top of each other are prevented from sticking and adhere to each other.

The present Applicant has found that it is possible to use a carboxylated polymer latex containing a relatively small proportion of a heat-sensitizing agent, sufficient to gel the particles of the latex polymer by heating, preferably also containing fillers, stabilizers and wetting agents, to form a well adherent and water resistant coating on a hot rubber surface which can then be cooled with water, by immersion and preferably by spraying, then dried, “les rubber layers thus treated can then be assembled without risk that the rubber sticks to itself, that is to say that the layers stick together. The skin obtained after hot drying is not removed by spraying water, and is believed to be formed by the heat of the freshly mixed, ground and worked rubber. This film adheres well to the rubber, the layers of which it prevents from sticking to each other and, moreover, the charges possibly present in the latex are effectively linked to drying by the carboxylated polymer and thus do not form powder or dust on the surface. of the coating. The present process thus makes it possible to increase the production of a Baribury.

* ^ 5 '* ψ *. The carboxylic polymer is prepared by radical copolymerization in aqueous emulsion. It must be able to form a non-sticky and water-insoluble film when it is poured in the latex state and dried, and it must be able to be vulcanized by sulfur by itself and have a glass transition temperature (Tg ) at least equal to -30 ° C. This copolymer comprises (1} at least 45% by weight of styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide or methacrylamide, methyl or ethyl methacrylate, or mixtures thereof , (2) up to 10% by weight of a copolymerizable acid monomer such as acrylic, methacrylic, ethacrylic, maleic, fumaric, itaconic, citraconic, sorbic or crotonic acid or their mixtures, (3) the remaining part being constituted by a conjugated diene in a proportion sufficient to give a certain flexibility and allows vulcanization (crosslinking or hardening) for example by means of sulfur or a peroxide, diene such as 1,3-butadiene, isoprene, 2,3-dimethyl-butadiene-1,3, piperylene or mixtures thereof. Very small proportions of a fourth, a fifth or more monomer, such as methyl acrylate or hydroxy * ethyl and others can also be copolymerized with the above monomers, provided that these mon additional omers do not adversely affect the properties of the copolymer formed or its latex.

Methods of making carboxylic polymers are described in U.S. patents. Nos 2 604 668; 2,669,550; 2,710,292; 2,724,707; 2,849,426; 2,868,754; 3,392,048; 3,404,116; 3,409,569 and 3,468,833; as well as in the work "Rubber World", September 1954, pages 784 to 788 and in the review "Industrial 30 and Engineering Chemistry", May 1955, pages 1006 to 1012, and it is also possible to use latex mixtures of carboxylated polymers. If an acid ester or its anhydride or another derivative can be copolymerized in place of the acid and then hydrolyzed and neutralized to form the free acid groups in the copolymer, this process is not as beneficial as direct copolymerization of the acidic monomer with the other monomers.

I.

fi 6 * '' 'The polymerization is carried out by means of radical catalysts, that is to say catalysts or systems forming free radicals, such as ammonium, potassium or sodium persulfate, peroxide * hydrogen etc., in a proportion sufficient to polymerize the monomers and reach the desired molecular mass. Other free radical catalysts which decompose or become active at the polymerization temperature can be taken, examples of some of the other catalysts being "cumene hydroperoxide, dibenzoyl peroxide, diacetyl peroxide, dideca peroxide -noyl, di-t-butyl peroxide, dilauroyl peroxide, bis (p-methoxy benzoyl) peroxide, t-butyl peroxy-pivalate, dicumyl peroxide, isopropyl percarbonate, di-sec-butyl peroxy-dicarbonate, azo-bis-15 dimethyl-valeronitrile, 2,2 * -azo-bis-isobutyronitrile, 2,2 * -azo-bis-2-methylbutyronitrile and 2 , Methyl 2'-azo-bis isobutyrate and others, or mixtures of these compounds "The polymerization requires only small proportions of the catalyst. The radical catalysis is well known and described ~ 20 for example in the book" Encyclopedia of Polymer

Science and Technology ", Interscience Publishers division of John Wiley & Sons, Inc., New York, Vol. 2 (1965) pages 278-295, Vol. 3 (1965) pages 26-29, Vol07 (1967) pages 361-431 and Vol. 9 (1968) pages 814-841.

Emulsifiers such as soaps, surfactants or dispersants may be added in a sufficient proportion to obtain an aqueous emulsion of the monomers and then of the copolymer formed, examples of certain emulsifiers being laurate, stearate and potassium oleate, dodecyl -30 sodium sulfonate and decyl sulfonate as well as sodium colophenate etc., and mixtures thereof, but one can also choose other well known surfactants and on this subject one can consult for example the publication "Materials, Compounding Ingredients and Machinery for Rubber ", Publ. from "Rubber World", Bill Communications, Inc0, New York, 1977, pages 291-294 and 35 "Encyclopedia of Polymer Science and Technology", Vol. 5, 1966.

Chain transfer agents or modifiers are also well known in emulsion copolymerizations of vinyl monomers and dienes, and they are generally used to modify the molecular weight of the copolymer and to reduce its crosslinking. If many types of such agents have been proposed, it is however preferable to choose alkyl and / or aralkyl mercaptans in Cg to C ^ g, among which tert.-alkyl mercaptans are much preferable, examples of some of these mercaptans being n-octyl-mercaptan, n-dodecyl mercaptan, t-octyl mercaptan, t-dodecyl mercaptan, p-tridecyl mercaptan, tetradecyl mercaptan, * hexadecyl mercaptan etc., and mixtures thereof. If little or no mercaptan is added, and polymerization is continued to completion, gelation may occur and the molecular weight may be very high or even infinite, although the * some low molecular weight fractions can be found. In other words, the molecular weight can be between 50,000 and 2,000,000 or more.

Bases, NaOH, KOH, MH ^ OH etc. can be added before, during or after the polymerization to adjust the pH to the desired value, and the polymerization can be carried out in an acid medium.

20 The water must not contain harmful substances must preferably be distilled water or water which has been treated on an ion exchanger. It must be in sufficient quantity to allow the formation of the emulsion and suitable mixing or stirring of the ingredients during the polymerization in order to have the desired speed and degree of reaction, good heat transfer, etc. After removal of the water, the solid content of latex formed can thus be between approximately 25 and 60% by weight and the pH between 7.5 and 11.5.

Stabilizers, antioxidants and chelating agents can be added during polymerization, and free radical blocking agents are also known, which not only serve to abruptly stop polymerization in the reactor at the desired conversion rates, 35 but also to prevent it from continuing or from crosslinking, etc., during the removal of the water, subsequent treatments, etc. Examples of certain polymerization blocking agents are hydroquinone, sodium sulfide, ammonium hydrogen sulfate, hydro * sulfate. 8 xyl ammonium, sodium diethyl dithiocarbamate, di-ethylhydroxylamine, sodium or potassium dimethyl dithiocarbamate or dimethylammonium 1, hydroxylamine sulfate with sodium hydrosulfite etc.

The polymerization temperature must be sufficient to activate the catalyst and the double bonds of the monomers, but it must not be too high so as not to cause a reaction too sudden, nor too low for the reaction rate to be sufficient. In general, it may be between approximately 2 and 90 ° C., but if the operation is carried out at even lower temperatures, it may be advisable to add an anti-freeze such as methyl, ethyl or propyl alcohol, ethylene glycol or another inert water-soluble anti-freeze, etc.

The polymerization is preferably carried out in a closed apparatus, for example in a reactor allowing to operate under pressure, equipped with any agitation system, with heating and cooling means, with means for bringing in an inert gas. such as nitrogen, helium, argon, neon or the like in order to carry out the polymerization under a non-reactive atmosphere, of means for the introduction of the monomers, of water, of the catalysts, etc. as well as means for degassing and recovery of the polymer and the like. Between the polymerization tests, the reactor 25 must be cleaned or swept to remove traces of blocking agents, catalysts, modifying agents, etc., which could hinder subsequent polymerizations, and the agitation must be sufficient to ensure mixing, diffusion, contact and others satisfactory. All the ingredients of the polymerization except the hLocating agent can be put into the apparatus at the same time, either discontinuously or progressively continuously, or they can be added separately or as mixtures.

The radical copolymers in aqueous emulsion of dienes and of vinyl monomers are well known to specialists, and in this regard one can consult for example:, Bovey et al, "Emulsion Polymerization", Interscience Publishers,

Inc., New York, 1955, Whitby et al, "Synthetic Rubber", f '* 9 t

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, division 5 of John Wiley & Sons, Inc., New York.

The polymers which have been formed by the emulsion copolymerization process which has just been described include not only random, linear or branched copolymers, etc., but also graft polymers. The technique consisting of polymerizing or copolymerizing one or more monomers in the presence of a polymer serving as substrate or trunk, known as "grafting technique", is well known and often called "grafting or grafting" polymerization or "copolymerization" , and on this subject one can consult for example the works: "Copolymerization", High Polymers, Vol.

XVIII, Ham, pages 323-324, 335-426 and 573, Interscience Publishers division of John Wiley & Sons, New York, 1964; "Block and Graft Polymers", Burlant and Hoffman, Reinhold Publishing Corporation, New York, 1960; "Block and Graft Copolymers", 20 Ceresa, Butterworth & Co, (Publishers) Ltd., London, 1962; and "Graft Copolymers", Polymer Reviews, Vol. 16, Battaerd and Tregear, Interscience Publishers, division of John Wiley & Sons, New York, 1967. It is also possible to prepare block copolymers in water with certain azoamide compounds having surfactant properties and which also act as radical catalysts, optionally adding an emulsifier # as stated in US Patent No. 3,914,340.

If the above carboxylated polymer latex, or a mixture of such latexes, can be used alone as a rubber immersion bath, it is preferable to use a compound latex, i.e. a latex which has been mixed with fillers for rubbers or extenders and other additives for rubbers such as stabilizers, wetting or dispersing agents, suspending agents, defoamers, tackifying agents, antioxidants, bactericides etc., in order to obtain a charged, stable latex composition having good covering power and giving on a hot rubbery mixture, sticking to itself, i- 10 s * a coating, film or layer, which when dried, does not stick to itself but adheres well to the rubber. Certain ingredients for mixing with latex are indicated in the publication "Materials, Compounding Ingredients 5 and Machinery for Rubber," "Rubber World" publication, 1977,

Bill Communications, Inc., New York

The fillers which it is advantageous to add to the latex are fillers or mineral pigments for rubbers, not black. The fillers can also serve to reduce the tackiness and to thicken the latex or to modify its viscosity. The charges must be finely divided. Examples of fillers are calcium carbonate, clays, precipitated hydrated silica, pyrogenic silica, mica, barium sulphate, perlite, magnesium silicate or talc, feldspar, silicate of hydrated calcium and magnesium, magnesium carbonate and magnesium oxide, titanium dioxide etc., or mixtures thereof. But among all these materials it is preferable to use calcium carbonate, clay, pyrogenic silica or hydrated precipitated silica or mixtures thereof. These fillers are added in the proportions necessary to lengthen the latex and thicken it as desired, adjust its viscosity and reduce the tackiness, and also to lower the cost. But do not add too much because otherwise the rubber particles of the latex, which is a dispersion or suspension of the rubber, would not be in sufficient quantity on drying to form a good film and to bond to the rubber substrate. all charge particles.

In general, the proportion of the filler can be approximately 30 150 to 1000 parts by weight per 1000 parts of the dry copolymer originating from the latex.

The other latex mixing ingredients which have been indicated above, other than the pigments, are added in small proportions relative to the dry copolymer, and they serve (for example in addition to all stabilizers, emulsifiers, etc., if any present during the polymerization) to stabilize the latex even better with a view to adding the fillers. These other ingredients can have several functions in the latex, which can act for example · '· 11 s *' as dispersing agents as well as wetting agents, and in general, for example stabilizers and wetting agents, are added at a rate of approximately * 2 to 30 parts by weight per 100 parts of the copolymer in the dry state. Examples of some of these other latex blending ingredients are defoamers and defoamers such as polyoxyalkylene glycols, triols and tetrols, 2,4,7,9-tetramethyl-5-decyne-4 , 7-diol, the product Defoamer Y-250 (mixture of emulsifiable mineral oil, silica derivatives and esters, 10 from Derw Chemical Corp.). Examples of certain stabilizers, dispersants and wetting agents are sodium linoleate, octylphenoxy polyethoxy ethanol, polyoxypropylene oxyethylene glycols, casein, alkyl aryl sulfonates, sodium salt of dioctyl sulfosuccinate, sodium salt of dioctyl polymerization product of a sulfonated alkyl naphthalene, sodium stearate, nonyl phenol and mixtures thereof, while examples of certain suspending agents and organic thickeners are the ammonium and sodium polyacrylates , hydroxyethyl cellulose, potassium algi-20 nate, polysaccharides, sodium alginate etc., and mixtures thereof, and examples of certain agents for suppressing or reducing stickiness are zinc stearate, saponified fatty acids, etc.

The thermal sensitizer is necessary for the copolymer to form a film (of coagulated or gelled product) at the desired temperature, for example by contacting with the hot rubber mixture, and it also acts by forming or accelerating the formation of * a more solid film at a given temperature, which reduces treatment times. Examples of thermosensitizers are the zinc ammine system, polyvinyl methyl ether, polypropylene glycol, 2-nitro-2-methyl-1-propanol etc., polyoxypropylene oxyethylene glycols as well as polyoxyalkylene polyols similar can also be used as thermosensitizers. The thermosensitizer is added in a small proportion by weight in the dry state relative to the latex polymer sufficient to gel or coagulate the polymer, preferably about 0.75 to 15 parts by weight per 100 parts of the carboxylated polymer 'dry state. It is also possible to use mixtures of several thermosensitizers.

A smaller proportion (up to about 25% by weight of dry matter) of the carboxylated polymer latex can be replaced by other latexes of polymeric materials which are compatible with the first as well as with the rubber mixture to be treated, and the mixture of which with the carboxylated polymer latex does not have a glass transition temperature below approximately -30 ° C., examples of such other latexes being those of polybutadiene, polyisoprene, natural rubber, butadiene copolymers. styrene, butadiene-acrylonitrile, butadiene-styrene-acrylonitrile, butadiene-acrylic esters, of poly-chloroprene, of ethylene-propylene-diene copolymers (EPDM), isobutylene-isoprene, butadiene-styrene-vinyl-pyridine, of rubber chlorobutyl or bromo-butyl etc. or mixtures thereof, some of these polymers can be formed by solution processes and then be transformed into emulsions by well-known methods.

For more details on the mixing and processing of latex, one can consult the works, "Latex In 20 Industry", Noble, 2nd Ed. 1953, Rubber Age, Palmerton Publishing Co., New York and "High Polymer Latices", Blackley , 1956, Vols. 1 and 2, Maclauren & Sons Ltd. London.

The proportion of water for the preparation or the addition to the latex composition depends on the desired viscosity, on the handling characteristics of this composition, on the thickness of the film to be deposited on the rubber as well as on the time necessary for form and dry the film. Thin films of low viscosity latex compositions are desirable but nevertheless these characteristics can vary greatly depending on the needs with the coating apparatus, storage, pumping, application rates, drying times and temperatures. , the thickness of the film, etc., in general, the total solid content of the aqueous latex composition * 35 can be of the order of 10 to 75% by weight, preferably around 10 at 40%. Deionized or distilled dilution water must be used to avoid introducing foreign ions which could make the latex and the film formed unstable.

AT

13

The aqueous latex composition can be applied to the rubber by immersion, spraying, using a roller or brush, or by any other means allowing a good coating to be obtained. Thin coatings are preferable because they are quickly gelled, while if thick coatings can also be applied, only the part closest to the rubber can be gelled fairly quickly and most of the coating will then be removed by water during the subsequent cooling by spraying water or by immersion in water. In addition, excess coating may require additional mixing ingredients to be added to the rubber composition itself to alleviate its effects if the composition is then mixed with vulcanizers such as sulfur and accelerators. In general, a proportion of the dried latex composition on the rubber, not exceeding about 1% by weight and preferably not exceeding about 2%, will suffice to prevent the rubber from being tacky.

The latexes according to the present invention can be applied to any surface of polymeric material and then heated to prevent the adhesion of the surfaces to each other, but they are particularly applicable to rubber mixtures which have been treated in a Banbury, putty or ground, or which are freshly mixed and hot, their surfaces then being adherent or sticky. These mixtures can be in the form of ground rubber, putty, or in pieces, partially or completely mixed with carbon black, zinc oxide, stearic acid, silica, extension oils, a phenolic antioxidant etc., and examples of rubbery polymers which can be treated are natural rubber, polyisoprene, polybutadiene, butadiene-styrene, butadiene-acrylonitrile, buta-diene-styrene-acrylonitrile and butadiene-acrylic ester copolymers , polychloroprene, ethylene-propylene-diene copolymers, • 35 (EPDM), isobutylene-isoprene (butyl rubber), chlorinated or brominated butyl rubber, butadiene-styrene-1 vinyl-pyridine copolymers or butadiene-acrylonitrile carboxylated copolymers , carboxylated butadiene polymers, carboxylated butadiene-styrene copolymers, etc., and mixtures thereof.

14 f ·,

If the present method is particularly interesting for treating hot rubber which leaves a Baribury and which has just passed over a grinder to be put into a hot continuous sheet or plate, it should be noted that it can also be applied to any mixture of rubber sticking to itself, crushed, extruded, calendered, laminated or heated, to prevent the rubber from sticking to itself when it is stacked for storage while waiting to be used for example for the manufacture of tires, belts etc., and moreover if the latexes can advantageously be used to treat rubber plates, strips or sheets, in particular continuous, they can also be used on separate parts, formed or not, or on rubber in powder, pellets or other fragments or particles, to prevent them from sticking together.

In an embodiment of the present invention, the mixture of hot putty rubber, that is to say at a temperature of about 90 to 150 ° C., leaving the Baribury, passes over a grinder to be put into a continuous hot sheet or plate which is then immersed in a tank containing the latex composition according to the invention for approximately one second, then allowed to air dry for 30 to 40 seconds or until at least 80% of the water is evaporated, or preferably all, and the thermosensitizer 25 has caused coagulation or. latex gelation. On the rubber plate thus coated with the gelled latex composition, water is then sprayed for approximately 30 to 40 seconds to cool it, which does not remove the latex coating, then it is air dried and it is stacked at a maximum temperature of approximately 50 ° C., preferably of the order of 45 ° C. to prevent the toasting of the rubber, the layers thus stacked not sticking together. During air drying and spraying with water, in order to take up less space, the rubber sheet or plate can pass over a series of trees, forming between them long loops or kinds of festoons.

As the latex of the carboxylic polymer can 1 15 f *. be sensitive to foreign ions such as metal cations, which can cause its coagulation or the precipitation of soaps, the immersion tank as well as the pipes, agitators, pumps etc., which can be used with the tank should preferably have a protective coating, for example of epoxy resin, glass or the like. If there is also a stirring system, which is started continuously or only when necessary, it may not be necessary to add an agent for suspending the loads.

The examples which follow, in which the parts of the materials indicated are parts by weight unless otherwise indicated, are given to illustrate the present invention.

In these examples, the ingredients 15 constituting the bath are mixed by means of an air or electric stirrer. The operations are summarized below.

1. The latex is diluted with the desired amount of deionized water, with moderate agitation.

2. The soap and wetting agents are added and dissolved, the dissolution rate depending on the nature of the additives and the dissolution usually requiring less than 5 minutes.

3. The thermosensitizer is also added.

4. The filler (s), the wax emulsion and / or the zinc stearate are added.

5. If a thickening polysaccharide is used, it is added.

6. If you use an anti-foam agent, add it.

7. Stirring is continued until the latex persion appears homogeneous.

This mixture should not take more than approximately 30 minutes for the operations which are indicated in the examples.

The viscosity of the baths is determined using a Brookfield viscometer, Model HB for highly viscous baths and Model LV for low-viscosity baths. The degree of shearing and the type of shaft are determined by the nature of the bath, the composition of which must remain mechanically stable within 16 h. stirring conditions with a high degree of shear / and to examine this stability vigorously stirred at more than 10,000 rpm about 100 ml of the bath with a milk shaker / observing the modification of the bath.

5 The pH of the baths is determined with an indicator paper. 0 * The mixtures or samples of rubber used to study the baths include chewed samples of natural rubber gum and chewed samples of natural cauliflower loaded with carbon black, both kinds of samples being ground on a laboratory apparatus before being immersed in the baths to have a cool and warm rubber surface.

The freshly ground samples are then immersed in a bath of the latex composition for about 1 second and then they are air dried at around 25 ° C for about 30 seconds, cooled in water at around 25 ° C for 30 seconds, and then they are air-dried again for 60 seconds and finally stacked.

The layers of rubber are stacked in such a way as to simulate the conditions of production: two samples covered with the dried gelled composition are placed one on the other and then a pressure of approximately 150 g / cm is applied using a special mold in addition (air bag) in a press heated to around 55 ° C., the samples thus remaining for 3 days before being observed. These conditions are in fact even more severe than in production where a regular 80 kg piece is folded and stacked in the normal way, which is thus probably subjected to a pressure of about 30 70 g per square centimeter, in particular, for the parts which are at the bottom of the stack, the temperature of the material being assumed not to exceed approximately 50 ° C.

EXAMPLE 1 î

The following ingredients are mixed to form ‘35 baths with a total solids content (TTS) greater than 50%, as shown in Table I below:

Parts by weight «17

table I

Ingredients - Trial 1 Trial 2 Trial 3 * Latex 100 100 100 5 "Valpro" SD 1.5 1.5 1.5 "Pluronics" L101 1.5 1.5 1.5

Sodium sulfate and lauryl 1.0 1.0 1.0

Kaolin - M 150

Limestone 300 300 10 "Cab-O-Sil" M5 2.5 2.5 NMP 1.5 - 1.5

2.5% aqueous solution of "Kelzan" - 10 - "Surfynol" 104H - - 0.5

Water (deionized) 100 100 150 15 Total 508.0 516.5 406.0% TTS, of the bath weight 70.6 69.2 50.9% by weight of rubber relative to the dry matter of the bath 14.1 14 2.24.6 20% by weight of rubber in the bath 10.0 9.8 12.5

After an overnight rest, the limestone from bath No. 1 was deposited as a result of the absence of a suspending agent, while baths No. 2 and 3 remained homogeneous, and it can be seen that the addition of a polysaccharide ("Kelzan") in test No. 2 effectively maintains the charge in suspension. Furthermore, in bath No. 3, the total solids content is much lower than in bath No. 1, and in both cases the type of filler is also different. The mechanical stability of these three baths is excellent. When they are subjected to vigorous stirring for more than 30 minutes, only a very slight change in viscosity is observed. The foaming is however very strong in all cases, but the foams formed collapse within 10 to 30 minutes ”18 1 following the end of the agitation.

By immersing in these baths samples of hot natural rubber freshly chewed (gum and black filler), thick coatings are obtained due to the high content of the baths in solid matter. The viscosity of the three baths is approximately 3000 cps with the Brookfield viscometer model HB with the shaft N ° 2 rotating at 10 revolutions per minute. But the spraying of water which follows removes part of the deposits, which leaves after drying fairly thin continuous coatings. 10 The samples thus coated do not stick to each other in the hot mold test in the goat mold (air bag), and the dried coatings are not removed by water.

These latex baths do not remain stable in the presence of a sandblasted steel plate (sensitivity to cations of foreign metals). After having immersed such plates in the baths overnight, we indeed observe on the plates the formation of thick deposits, but this disadvantage can easily be remedied by covering the plates with an epoxy paint before immersing them in the baths .

EXAMPLE 2:

The following materials are mixed to form various TTC baths, as shown in Table II

TABLE II

Weight parts 25 Test. N ° 10 11 12 13 14

Ingredients

Latex 100 100 100 100 100 "Valpro" 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 30 Limestone 275 275 275 275 275 "Cab-O-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 1,115.15% TTS, by weight 50 45 40 35 30 19 ί! ,% by weight of rubber in the bath 7.6 6.8 6.0 5.3 4.6% by weight of rubber-5 based on dry matter 15 15 15 15 15

On these baths, the formation of coatings or behavior and the viscosity are examined. In unvulcanized mixtures for tires (natural rubber loaded with carbon black), samples of 25 x 150 x 6 mm are cut out of the matrix, which are weighed with precision and then heated before being immersed in the baths, the test pieces then being dried. After spraying with water and final drying, the test pieces are re-weighed to obtain the weights of the coatings. The results are grouped in Table II A.

TABLE II * A

Bath N ° 10 11 12 13 14

Brookfield viscosity, HB model with ar-25 bre N ° 1 at 10 rpm (centipoise) 105 50 30 15 ¢ 10 Deposition on rubber test pieces,% by weight 3.9 2.3 1.65 0, 95 poor wetting 30 The weight of the rubber test pieces is on average 16.56 g, the variations around this average not exceeding 5%. It is seen from these results that the deposition on the rubber increases with the total solids content of the bath. From the point of view of cost price, an ideal bath would be one which gives good results with the lowest possible deposit, but an increase in dilution raises the problem of poor wetting. However, this can be easily remedied by adjusting the proportion of wetting agent accordingly. The increase in viscosity with T3 * S is quite expected. In tests 10 to 13, the surfaces of the samples covered with the dried latex are not sticky and the dried coatings are not removed by washing or rinsing with water. In Test 14, wetting can be improved by a greater amount of surfactants or wetting agents. EXAMPLE 3:

The following ingredients are mixed to form baths at constant TTS, keeping the latex content constant and varying only the lime and water contents, as shown in Table III below.

TABLE III

Weight Games

Trial No. 20 21 22 10 Ingredients

Latex 100 100 100 "Valpro" SD 1.0 1.0 1.0 "Triton" X-114 0.5 0.5 0.5 "Kelzan" 0.25 0.25 0.25 15 Limestone 275 210 185 " Cab-O-Sil "EH5 555 NMP 222

Water 452.6 355 317.6

Total 836.35 673.75 611.35 ΟΛ υ% TTS, by weight 40 40 40% by weight of rubber ρ.ΐο to the dry matter of the bath 15 18.8 20.7% by weight of rubber 25 the bath), 6 7.5 8.3

Viscosity Brookfield Model HB, shaft no.1 at 10 rpm v 30 40 25 Latex deposit on the rubber 30% by weight 1.65 1.40 1.25

In contrast to the previous examples, the amount of deposit on hot samples of natural rubber loaded with carbon black, after drying, decreases when the rubber content of the bath increases. But a closer look at the bath formulas shows that the effect of the rubber content is actually confused with the differences between the proportions of lime. The increase in the rubber content results in fact only from the lowering of the scale content, lowering which can therefore be made to depend on the fact that, in a certain way, the quantity deposited decreases with the increase in the content rubber. The baths of Examples 2 and 3, except for No. 14 effectively prevent the rubbers from sticking in the air bag mold test, and from the results of these examples, a lowering of the content solids does not decrease their effectiveness; the surfaces of the rubber samples covered with the dried latex are not sticky and do not adhere to each other, and after drying the coatings are not removed by treatment with water.

15 EXAMPLE 4:

In this example, relatively low TTS baths are prepared in which compositions of natural rubber gum and natural rubber loaded with carbon black are immersed. By then subjecting the rubber samples coated with the dried latex to the test in the air bag mold which has been described above, none of the samples of this example are sticky, and although the films formed are thin, they remain very regular and uniform. In addition, after drying, the dandruff is not removed by water.

The materials constituting these baths are indicated in Table XV.

TABLE IV

Weight Games

Bath N ° 3C> 3JL 32, 33

Ingredients 30 Latex 100 100 100 100 "Valpro" SD 2.5 2.5 2.5 2.5 2.5 "Triton" X-114 3.0 3.0 3.0 3.0 * Limestone 430 430 430 450 "Hi- Sil "215 15-15 '35 Emulsion - - 15

Zinc stearate - - “^ f0" Gantrez "M-154 4.0 5.0 4.0 3.0

Deionized water 1972 1916 2032 2008 9- 30 31 32 33 22 Γ TABLE IV (end)

Total 2526.5 2456.5 2601.5 2571.5% TTS, by weight 20 20 20 20 5% by weight of cauliflower p0r. dry matter 10.5 10.3 9.8 9.9% by weight of rubber in the bath 2.01 2.07 1.95 1.98 10 The cited emulsion contains the following materials, in parts by weight: " Epolene "E ~ 15 40" Triton "X-114 13

Deionized water at 15 43% KOH 1.3

Deionized water 150

Total 204.3

This emulsion is prepared by first melting the product "Epolene" at around 130 ° C. in the presence of 20 "Triton" then slowly adding the potassium hydroxide solution. The * mixture is stirred until the boiling stops and then reheats it to around 130 ° C before finally mixing it in boiling water with vigorous stirring, stirring being continued until the emulsion has cooled to about 45 ° C.

The pH of the baths in this example is between 8.2 and 8.4. The heat sensitizer, the product "Gantrez", is more effective at a pH of about 8, but at pH above about 8, the stability of the latex may become precarious, unless its composition has been well stabilized. If, the loading rate is high, significant proportions of wetting agents are necessary to have good wetting (see test No. 14 above) "

All the baths of this example can be vigorously stirred, at more than 10,000 revolutions / minute, for half an hour to about 1 hour with a 23 * milk shaker apparatus without being able to observe a any change in their appearance, which shows that they remain stable at high agitation rates even at a relatively low pH. In all cases, foaming occurs due to the occlusion of air, but the foams formed fall at rest. These baths can also be aged in an oven at 50 ° C. in closed containers without showing any visible alteration at the end. 3 weeks. They can thus remain stable during pumping and agitation operations as well as at the temperatures at which they can be subjected to storage or when they are used for the immersion of rubber in the manufacture of tires for example.

With the Brookfield Model LV viscometer with the N ° 1 shaft rotating at 30 rpm, the viscosity of all the baths of this example is less than 10 cps

When naked steel plates were immersed in the baths of this example, no change was observed in the first three days, but after it begins to appear on the steel a little green deposit and the pH drops , from a value greater than 8 (as indicated above) to slightly more than 7. On the contrary, there is no apparent change in the physical state of painted steel plates immersed in these baths, and the pH did not change after a week of immersion.

In a bath identical to bath 31 above but containing a little more solids, a rubber plate (natural rubber loaded with carbon black) was immersed which was then dried and cooled, then this plate, as well that a similar plate but which was not immersed in the bath, were mixed separately with, for 100 parts of the plate weight, 5 parts of zinc oxide, 2 parts of stearic acid, 0 , 5 parts MBT, and 2.5 parts sulfur, and the mixtures were molded, vulcanized and tested. The results are given in Table IV A.

* è 24

TABLE IV A

PI. Immersed in PI. untreated bath # 31

Vulcanization at 142 "C 14 mine 14.5 min 5 Module at 10% elongation o. 62 0.59 MPa,

Module at 100%, MPa 3.52 3.40

Module at 300%, MPa 12.82 12.35 Tensile strength 15.63 18.31 10 MPa *

Elongation,% 355 420

Shore A hardness 72 71 Tearing resistance "Trouser", kN / m 3.01 2.92 15 We see that, with the exception of tensile strength and elongation, the two vulcanized mixtures have practically the same characteristics, and even for the tensile strength and for the elongation the differences are not very important and they are generally of the order of magnitude of the experimental errors which one can normally expect in the determination of these properties. These tests therefore show that the coating applied to the plate does not appreciably modify the characteristics * of the rubber in the vulcanized state, and naturally the tolerances 25 accepted for the mixture make it possible to attenuate or even to eliminate the noted differences "

A test was also carried out with bath No. 31 but with a slightly higher limestone content. The rubber mixture is ground, calendered and extruded into a sheet for repairing punctures in tires, which passes through the bath and is then dried, cooled with water and again dried and stacked on itself. After several hours (overnight), the stacked parts of the coated rubber can be easily separated from one another, that is to say, the destacking. The filling product is of a type which undergoes storage very strong creep, and this test shows the importance of the fact that the film which is obtained with the present bath adapts well to the movement of the creep while remaining continuous I * 25 * and contiguous to the rubber, because a bath which would not give such a film would be ineffective with such a rubber composition, which is a mixture of ethylene / propylene / diene rubber extended to the oil (see US patent

5 No. 3,903,947).

EXAMPLE 5:

A mixture of natural rubber and carbon black is cut into pellets or cubes of approximately 6 mm, of which four batches of approximately 25 g are made, which are loosely packed in steel wire baskets, then immersed in various baths and dried for 1 to 2 minutes, the rubber samples being weighed with precision to the nearest 0.1 mg before and after immersion in the baths. These samples are then transferred to respective graduated cylinders 15 of about 300 mm in length and 40 mm in diameter to simulate storage in silos. On top of the rubber pellets a flat metal capsule is placed and lead beads are placed on the capsule which thus separates the pellets from the pearls, the capsule and the beads exerting together on the rubber pellets 2 a pressure of about 170 g to cm. The rubber is aged in an oven at around 45 ° C for 4 days and then the pellets are examined. The results are given below: V “1. Control test without treatment in any bath.

The pellets adhere to each other forming a solid mass which has taken the form of the test piece.

V-2. Unheated rubber pellets before immersion in the bath which is an aqueous suspension of clay (TTS 10%) containing a surfactant. After drying, 0.69% by weight of coating remains on the pellets and the latter do not stick to each other.

V-3 o Unheated rubber pellets before immersion in the bath which is an aqueous suspension (at 10% TTS) of zinc stearate difficult to disperse in water (product "Quikote" from Ventron Corp.). After drying there remains a coating of 0.13% by weight on the rubber pads, which do not stick together.

V — 4. The rubber pads are heated above about 70 ° C with a hot air dryer before being 26

J

en * • immersed in the bath which is bath n ° 31 of Example 4 previouso After drying there remains a coating of 0.45% by weight on the pellets, which do not stick to each other · 5 We can make the following comments on these tests: * V ~ 2. Not only does the bath used deposit more solid material on the rubber, which for some applications can affect the characteristics of vulcanized rubber, but the coating is easily removed by water.

V ~ 3 o The bath used deposits less solid material on the rubber than the bath of test V-4, but it is about 6 times · more expensive, even for this weaker deposit, and 15 if the stearate zinc is insoluble in water, it adheres to rubber, however, because it is in fine particles and has a low density, lower than that of clay, for example.

To sum up, it can be said that the baths which have just been described leave a coating on the surface of rubber composites which is not removed by spraying with water. These baths are based on a latex of a carboxylated polymer and of a thermosensitizer, and preferably they also contain wetting agents, stabilizers and fillers which are "suitable". The warmth of the fresh rubber composition - - Mixed together allows the formation by the bath of a film which adheres to the rubber but which does not stick to itself and which is resistant to water, a film which effectively prevents the layers of rubber from sticking to each other. others 30 when stacked for storage. These baths are inexpensive and easy to prepare, and according to laboratory tests, the coated rubber composition can be easily reprocessed without prejudice to the final characteristics of the vulcanized rubber. NOTES TO EXAMPLES PREVIOUS; "

Latex - Aqueous emulsion of a high molecular weight butadiene-styrene carboxyl copolymer formed by radical polymerization in aqueous emulsion, comprising approximately I * 27 * 55% by weight of styrene and at most approximately 5% * itaconic methacrylic acids, the part remaining being constituted by 1,3-butadiene, glass transition temperature Tg of this polymer of 1 * of the order of -20 ° C., emulsion at 50% of solid material, pH 9.0, Brookfield viscosity (No. 2 to 60 LVF) 70 and surface tension 54.0, containing an antioxidant. Binder and film-forming.

"Valpro" SD - Sodium linoeate at 94% min of anhydrous soap, Valley Products Co, added as stabilizer, dispersing and wetting agent, "Pluronics" L 101 - Liquid polyoxypropylene-oxyethylene glycol, nonionic difunctional block copolymer terminated by primary hydroxy groups, average molecular mass 3800, BASF Wyandotte, product added as a wetting agent, may also be thermosensitizing.

Kaolin "Hydrated aluminum silicate J.M. Huber, as a filler and to prevent sticking.

Limestone - Ground natural carbonate of density 2.71, average grain size 13 microns, CC100, Sylacauga Calcium, 20 Alabama, also as filler and to prevent sticking.

"Cab-O-Sil" M-5 - Pyrogenation silica with specific surface o (BET) of 200 + 25 m / g in particles of 0.012 micron. Cabot Corp. Product used as filler and viscosity modifier.

25 NMP - 2-Nitro-2-methyl-1-propanol at 0.5% by weight maximum water and 0.04% by weight maximum free formaldehyde, minimum melting point 80 ° C, IMC Chemical Group, Inc used as an additive the rmo-s e ns ib i1is ant.

"Kelzan" - Xanthan gum, a highly linear, highly molecular complex poly-saccharide of high molecular weight (greater than about one million), Kelco Company, used as a charge suspending agent.

"Surfynol" 104H - 75% by weight of 2,4,7,9-tetramethyl-5-decyne-4,7-diol in ethylene glycol, Air Products and Chemicals. 35 Inc, anti-foaming agent.

"Triton" X-114 - polyether ethyl aryl alcohol, adduct of 7 to 8 moles of ethylene oxide on t-octyl-phenol,

Rohm & Haas Company, wetting agent.

! '28 * * "Cab-O-Sil" EH ~ 5-Pyrogenic silica (formed from a 2 vapor phase), specific surface (BET) 390 + 40 m / g, density 3 3.7 g / dm, nominal particle size 0.007 micron, loss on ignition at 1000eC on the anhydrous product: 2.5% 5 Cabot Corpe, filler and viscosity modifying agent.

"Hi-Sil" 215 "Precipitated hydrated silica, packed, density 2.0, size of the finest particles 0.022 micron, passing through a mesh screen of 45 microns opening, PPG Industries, Inc, thickener and loaded 10" Gantrez "M-154 - · 50% aqueous solution of a linear homopolymer of methyl vinyl ether, K value 40, specific viscosity (1 g / 100 ml of benzene) 0.47, GAF Corp, heat-sensitizing additive.

"Epolene" E-15 "Polyethylene? emulsifiable, approximate molecular weight 3400, density at 25 ° C: 0.925, acid number 16, Brookfield viscosity with shaft no.3 at 6 rpm, at 125 ° C: 520 cp „Eastman Kodak Co„ MBT - 2 ~ Mercaptobenzothiazole0

Zinc stearate - wettable and water dispersing product, C0Po Hall.

5 c

Claims (4)

29 ι · t 1. * - Method consisting in applying to a hot rubber composition # with a tacky surface, an aqueous thermosensitized composition of a polymer latex # to dry the applied layer until at least 80% of the water is evaporated to form a coating of gelled polymer which is non-oaLlant to itself, water resistant and adherent # to cool the rubber composition with water and to dry it at a temperature sufficiently low to prevent roasting of the rubber! 10 cabbage, then stack in layers which do not stick together, the latex polymer being a copolymer comprising (1) at least 45% by weight of a monomer chosen from styrene # vinyl toluene , acrylonitrile and methacrylonitrile, 11acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and mixtures thereof (2) up to 10% by weight of a copolymerizable monomer chosen from acrylic and methacrylic acids , ethacrylic # maleic, fumaric, itaconic, citraconic, sorbic and crotonic and their mixtures, and (3) the remaining part of the copolymer, in a sufficient proportion to give it a certain flexibility and to allow its vulcanization, being a monomer copolymerizable chosen from butadiene-1,3 # isoprene, 2,3-dimethyl-butadiene-1,3 and piperylene and their mixtures, this copoly-j mother having a glass transition temperature not lower than 25 to ~ 30 ° C approx. V i 2 Process consisting in applying to a hot crushed rubber composition, with a sticky surface, an aqueous thermosensitized composition of a polymer latex, with mixing ingredients, in drying the applied layer to form a coating of gelled polymer non-sticky to itself, water-resistant and adherent, coating the weight of which does not exceed approximately 7% of the weight of the rubber composition, to cool the rubber composition with water and to dry it temperature not exceeding approximately 50 ° C., then stacking it in layers which do not stick together, * the latex polymer being a copolymer comprising (1) at least 45% by weight of a monomer chosen from styrene, 30 "/ vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and mixtures thereof, (2) up to 10% by weight of a copolymerization monomer chosen from acids 5 acrylic, methacrylic, ethacrylic, maleic, fumaric, itaconic, citraconic, sorbic and crotonic and their mixtures, and (3) the remaining part of the copolymer, in a sufficient proportion to give it a certain flexibility and to allow its vulcanization, being a co-polymerizable monomer chosen from 1,3-butadiene, isoprene, 2,3-dimethyl-butadiene-1,3 and piperylene and their mixtures, this copolymer having a glass transition temperature not lower than Approximately -30 ° C., the latex composition containing, per 100 parts by weight of the copolymer, approximately 150 to 1000 parts by weight of non-black mineral pigments for rubbers, approximately 2 to 30 parts by weight of stabilizers and wetting agents and about 0.75 to 15 parts by weight of the heat-sensitizing agent, and the total solids content of the latex being of the order of 10 to 75% by weight. 20. The method according to claim 2, in which the weight of the coating on the rubber does not exceed approximately 2%, the cooling water is applied by spraying, the temperature of the coated rubber composition, after cooling and drying, does not exceed about 45 ° C, and the total solids content of the latex is in the range of ~ 10 to 40% by weight. 4. The process as claimed in claim 3, in which the latex copolymer comprises approximately 55% by weight of styrene and not more than approximately 5% of methacrylic and itaconic acids, the remaining part being 1,3-butadiene, and this copolymer has a glass transition temperature of about -20 ° C. 5. Product obtained by the process of claim lo 6, - Product obtained by the process of claim “35 tion 2„ 7. Product obtained by the process of claim 3. i 31 * ι ..... * 8.-1 Product obtained by the process of claim 4, 9p- Composition comprising an aqueous polymer latex which contains a small proportion by weight of a thermo-sensitizer sufficient to gel the polymer when hot, the polymer having a glass transition temperature - not less than approximately -30 ° C. and being a copolymer which comprises (1) at least 45% by weight of a chosen monomer among styrene, vinyl toluene, 11acrylonitrile and methacrylo-10 nitrile, acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and their mixtures, (2) v up to 10% by weight of a copolymerizable monomer chosen by mi acrylic, methacrylic, ethacrylic, maleic, fumaric, itaconic, citraconic, sorbic and crotonic acids and their mixtures, and (3) the remaining part of the copolymer, in a sufficient proportion to give it a certain flexibility and to allow its vulcanization, being a copolymerizable monomer chosen from 1,3-butadiene, isoprene, 2,3-dimethyl-butadiene-1,3 and piperylene and their mixtures. 10. The composition according to claim 9, further comprising, per 100 parts by weight of the copolymer, approximately 150 to 1000 parts by weight of non-black mineral pigments for rubbers and approximately 2 to 30 parts by weight of stabilizing and wetting agents, proportion of the thermosensitizer being of the order of 0.75 to 15 parts by weight per 100 parts of the copolymer and the total content of solid matter of the latex being approximately 10 to 75% by weight. 11. The composition of claim 10, wherein the total solids content of the latex is about 10 to 40% and the copolymer is a copolymer comprising about 55% by weight of styrene, not more than 5% by weight of about methacrylic acids. and itaconic, the remaining part being 1,3-butadiene, this copolymer having a glass transition temperature of the order of −20 ° C.