LU81669A1 - APPLICATION ON RUBBER OF A NON-ADHESIVE AND WATER-RESISTANT COATING BASED ON CARBOXYL POLYMERS - Google Patents

Description

"t>. 50.765

-ΊΓ — 2 — Ä-Â "^. GRAND-DUCHÉ DE LUXEMBOURG

Patent No .......... Q ...... j ...... Q ....... U

du lo · September ... 19.7 9 (¾¾¾¾ Minister ..... 0¾¾¾ of the National Economy and the Middle Classes çÿLAgj Industrial Property Service

SM LUXEMBOURG

Patent Application

Request d, a3aitioa..à..la..dgnande .. ^ 81.468 of 5, o7.197S

I. Request

..... La .... soclêtê ..... say ...... T.HE ..... GEUERAL .... TIBE ... & ..... RU.3BER. ... CQMPAÎÎ.Y., ..... Qne.Gene- (D

..... r.al .... s treet., ... at. akrqh, ..... Ohio, ...... 4432.9 .., ... E.tatsr.ünis ...... d ..!. Méi: .igue., ...... ..........................

..... represented ..... by ... Hon.si.eur .... J.acques..de ... MiiYser. / ...... a.giss.ant ... ..oR .......................... (2) ..... quality ± t .... of .... authorized representative .................................................. .................................................. .................................................. ...................................

drop off ........ this ..... & ix .... septerabre ..... 19oo ..... seventy-nine ............. ............................ (3d to .......... 1.5 ........ .... ... hours, at the Ministry of National Economy and Middle Classes, in Luxembourg: 1. this request for obtaining a patent for an invention concerning: .....,!. Applicatio.n .... s.ur ..... dn ... rubber ... d, un.uterement ... non .... tacky ............. . (4i .......... and .... r.ësistan.t .... â .... water ..., ...... at ... base. of ... polymers ..... carboxylated "...................................... .

"................................................. .................................................. .................................................. .................................................. .................................................. .......................................

declares, assuming responsibility for this declaration, that T (es) inventor (s) is (are): i ......................... .................................................. .................................................. .................................................. .................................................. .................................................. ..... (5); 2. the delegation of power, dated_______________________________________________________________________ on ........................................ .............................

3. the description in language ______________ fxailÇâiS & ............................. of the invention in two copies; 4 ........ /. / .-------------- drawing boards, in two copies; i 5. the receipt of the taxes paid to the Luxembourg Registration Office, the —lo ..... sep.tembra .... l9..7.9 .------------- ---------------------------------------------------------- ---------------------------------------------------------- ---------------------------------------------------------- --------------- claims for the above patent application the priority of one (s) request (s) of (6) ............ ............patent..................................... .... filed (s) / ^ (7). in .... United States ..... d iAmerica ....................

on ....... 1.9 ..... March ..... 1.9.39 ........... (No * ..... llSSolÎc-i-papplicatioiL) - ----------------------------------------------- (8) in the name of .s ..... inventors --------------------------------------- ---------------------------------------------------------- ---------------------------------------------------------- --------------------------------------------- (9) elect domicile for him (her) and, if appointed, for his representative, in Luxembourg ---------------------------------. ..... 35./.....bld........Royal--------------------------- ----------------------------------------------- (io) requests the issuance of a patent for the subject described and represented in the abovementioned appendices, - with postponement of this grant to ... // ................ .......month.

LL .... iaariaatair.e ..... L ....... L ...... L K

Π. Deposit Minutes

The above application for a patent for invention has been filed with the Ministry of National Economy and the Middle Classes, Industrial Property Service in Luxembourg, on: btßH September 1, 1979 / .. · ..... ..... Pr. the Minister ((JY / at .......... 1.5 ........... hours / \ of the National Economy and the Middle Classes, I:: p. d.

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C ^ (i ï) a 68007 "....... ·” "OC 5o.765

'' CLAIM OF PRIORITY

♦ of the patent application / dt / rfiérVté / Vi / fifiiV

£ fi IN THE UNITED STATES OF MARCH 19, 1979

Request for addition to the Luxembourg patent application No. 81.468 of July 5, 1979 Brief Description filed in support of a request for

PATENT

at

Luxembourg

on behalf of: THE GENERAL TIRE & RUBBER COMPANY

for: "Application on rubber of a non-sticky and water-resistant coating, based on carboxylated polymers".

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The subject of the present invention is a method of applying a water-resistant coating to a hot rubber composition which makes it possible to rapidly cool the rubber with water and to assemble or stack the 5 rubber sheets cooled without sticking to each other.

In the preparation of rubber compositions, the gum is usually mixed in a Banbury with the usual ingredients or only some of them, 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 yield of a Banbury, for a 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 Banbury 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 to prevent the sheets from sticking together when stacked and stored until used for manufacturing. The installation of power integrators on the Banburys 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 ability. However, the cooling of rubber mixtures 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 Banbury and the grinder to the desired temperature of about 50 ° C maximum and preferably not exceeding not approximately 45 ° C, in order to prevent the rubber from scorching. A cooling system with water spray stations placed between the sheet immersion tank 5 and the air blowers well reduces the cooling time to less than 5 minutes, but spraying water removes the coating from clay left by ordinary immersion baths, which are aqueous dispersions of clay.

The baths for coating the sheets are generally suspensions or aqueous emulsions of suitable inorganic or organic materials, the most common of which are, for example, limestone, clay and / or paraffin wax. The effectiveness of 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 leaves. Many products would no doubt 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 water limits the number of possible products. An aqueous suspension of zinc stearate can be used as a coating bath, this salt forming a uniform film on the rubber surface 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 Banbury mixer.

In the main patent it has been shown that by using a carboxylated polymer latex containing a relatively small proportion of a heat-sensitizing agent, sufficient to gel the particles of the latex polymer, preferably also containing fillers, stabilizers and wetting agents, a well adherent and water resistant coating can be formed on a hot rubber surface which can then be cooled with water, by immersion and preferably by spraying, then dried, the layers rubber thus treated can then be assembled without risk that the rubber sticks to itself, that is to say that the layers stick together. The 4 f 3 film obtained after hot drying is not removed by spraying with water, and is believed to be formed by the heat of the freshly mixed, ground or worked rubber. This film adheres well to the rubber, 5 of which it prevents the layers from sticking to each other, and moreover the fillers possibly present in the latex are effectively linked to the drying by the carboxylated polymer and thus do not form powder or dust on coating surface. This process thus makes it possible to increase the production of a Banbury.

The preparation of the carboxylic polymer, by radical copolymerization in aqueous emulsion, is described in detail in the main patent, where it is also said that the latex of carboxylated polymer provided by the polymerization can be used as it is as a rubber immersion bath. but it is better to use a compound latex, that is to say 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, anti-foaming agents, agents for reducing stickiness, antioxidants, bactericides, etc., in order to obtain a charged, stable latex composition having good covering power and giving on a hot, sticky rubber mixture. to itself, a coating, film or layer, which, once dried, does not stick to itself but adheres well to the rubber.

The Applicant has now found, and this is the purpose of this certificate of addition, that by adding a chelating or sequestering agent to the latex bath described in the main patent, it is possible to eliminate any risk of coagulation. or precipitation of said bath.

A subject of the present invention is therefore a process consisting in applying to a hot rubber composition with a tacky surface an aqueous thermosensitized composition of a polymer latex, in drying the layer applied until at least 80% of the water is evaporated to form a coating of gelled polymer which is not sticky to itself, water resistant and adherent,

It is 4 to cool the rubber composition with water and dry it at a temperature low enough to prevent the rubber from scorching, then to stack it in layers which do not stick to each other, the latex polymer being 5 a copolymer comprising (1) at least 45% by weight of a monomer chosen from styrene, vinyl toluene, acrylonitrile and methacrylonitrile, acrylamide and methacrylamide, methyl methacrylate and methacrylate ethyl and their mixtures, (2) up to 10% by weight of a copolymerizable monomer chosen from 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.

* 15 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, this copolymer having a temperature glass transition temperature not lower than about -30 ° C, process characterized in that the thermo-stabilized aqueous composition of a polymer latex which is used contains a chelating or sequestering agent.

The fillers which it is advantageous to add to the latex are described in the main patent.

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., * 30 present during the polymerization) to stabilize the latex even better for the addition of fillers. These other ingredients can have several functions in the latex, which can act for example ''. 5 * as dispersing agents as well as wetting agents, and in general, for example stabilizers and wetting agents, are added in an amount of about 1 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, Defoamer Y-250 (mixture of emulsifiable mineral oil, silica derivatives and esters, 10 from Draw Chemical Corp.). Examples of some 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 a polymerization product of a sulfonated alkyl naphthalene, sodium stearate, nonyl phenol and mixtures thereof, while examples of certain suspending agents and organic thickeners are 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 processing 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 in the dry state. We can also em-. '6 * fold 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 , 1966, 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 about 10 to 40%. Deionized or distilled dilution water must be used to avoid introducing foreign ions which could make the latex and the film formed unstable.

’. 7

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 with water or 10 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 Baribury, 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-ester copolymers acrylic, polychloroprene, ethylene-propylene-diene copolymers, (EPDM), isobutylene-isoprene (butyl rubber), chlorinated or brominated butyl rubber, butadiene-styrene-vinyl-pyridine copolymers or butadiene-acrylonitrile carboxylated copolymers, carboxylated butadiene polymers, carboxylated butadiene-styrene copolymers, etc., and mixtures thereof.

8

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 one 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 about one second, then allowed to air dry for 30 to 40 seconds or until that at least 80% of the water is evaporated, or preferably all, and that 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, 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.

The main advantage of adding chelating and / or sequestering agents to the latex of the carboxylic polymer is to prevent foreign ions, such as metal cations, from causing the coagulation of said latex or the precipitation of soaps, a disadvantage which has been tried to remedy previously. by applying a protective coating, for example an epoxy resin, glass or the like, to the walls of the immersion tank as well as pipes, agitators, pumps etc. which can be used with tank. For more security, these two measures can of course be used, although this is of little interest.

If, moreover, there is an agitation system, which is started continuously or only when necessary, it may not be necessary to add an agent for suspending the charges.

The following example illustrates the present invention. In this example, the parts of the materials indicated are parts by weight unless otherwise indicated. The abbreviation TTS stands for "total solids content".

In this example, the ingredients constituting the bath are mixed using an air or electric stirrer. The operations are summarized below.

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

2. Soap and wetting agent are added and dissolved. Dissolution usually requires less than 5 minutes. 3. The thermosensitizer is also added.

4. The filler and the wax emulsion are added.

5. Add the anti-foam.

• 30 6. Stirring is continued until the latex dispersion appears homogeneous.

This mixture should not take more than about 30 minutes for the operations indicated.

The rubber mixtures or samples used to study the baths include chewed samples of natural rubber gum and chewed samples of natural rubber loaded with carbon black, both types of samples being ground on a laboratory apparatus before be 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, 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 rubber layers are stacked * so as to simulate the conditions of production; two samples covered with the dried gelled composition are placed one on top of the other, then a pressure of approximately 150 g / cm is applied by means of a special beaker mold (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 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:

The following ingredients are mixed to form a bath as shown below:

Ingredients Weight parts

Latex 100

Aluminum silicate hard clay 430 "Valpro" SD 3 '30 "Sequestrene" NA3 0.5 "Lubrex" PE-40 12 "Triton" X-114 4 NMP 2 Y-250 0.1 35 Water (deionized) 1915% TTS, of the bath weight 20% by weight of rubber relative to the total bath 2.0% by weight of rubber relative to 40 dry solids of the bath 10.1 11

The surface is treated with hot mastic rubber using this bath. When water is sprayed to cool the rubber / the bath is not removed. After this spraying intended to cool the rubber / 5, it is dried and stacked. The rubber of the different layers does not stick and can therefore be easily separated. Notes for the previous example:

Latex of the example: high molecular weight copolymer formed by radical polymerization in aqueous emulsion and comprising approximately 64% by weight of styrene, approximately 2% by weight in total of a mixture of itaconic acid and methacrylic acid, the remainder consisting of 1,3-butadiene. About 50% by weight of solid matter, pH 9. Viscosity Broockfield (N ° 2 to 60 LVF) 60 to 90. ·, Glass transition temperature Tg of approximately -15.9 ° C by differential thermal analysis and approximately -10.2 ° C by differential scanning calorimetry.

"Valpro" SD: Sodium linoeate at least 94% anhydrous soap, Valley Products Co, added as a stabilizing, dispersing and wetting agent.

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 a heat-sensitizing additive.

"Triton" X-114: alkyl aryl polyether alcohol, adduct of 7 to 8 moles of ethylene oxide on t-octylphenol, Rohm & Haas Company, wetting agent.

"Seguestrene" NA3: dihydrate of the tri-, sodium salt of ethylene diamine-tetracetic acid. Chelating agent -Ciba-Geigy Corp.

"Lubrex" PE-40: 30% polyethylene emulsion in water. Harwich Chemical.

"Y-25Q: defoamer. Specific weight 0.91 to 35 0.93; boiling point 121 ° C; flash point above 121 ° C; COC; dispersible in water; mixture of oils mineral, silica derivatives and esters in emulsion.

Drew Chemical Corp.

12

To sum up, it can be said that the baths used in the process of the invention leave a coating on the surface of rubber compositions which is not removed by spraying with water. These baths, which are based on a latex of a carboxylated polymer and of a thermosensitizer and which optionally contain wetting agents, stabilizers and suitable fillers, contain che-latants and / or sequestrants whose role is to prevent coagulation of the bath and the precipitation of soaps. The heat of the freshly mixed rubber composition 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. to stick to each other when they are 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.

Claims (14)

13 1.- Method consisting in applying to a hot rubber composition, with a tacky surface, a thermosensitized aqueous composition of a polymer latex, in drying the applied layer until at least 80% of the water are evaporated to form a coating of non-sticky, water-resistant and adherent gelled polymer, cooling the rubber composition with water and drying it at a temperature low enough to prevent scorching of the rubber, and 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, vinyl toluene, l acrylonitrile and methacrylonitrile, acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and mixtures thereof (2) up to 10% by weight of a copolymerizable monomer chosen from acrylic, methacrylic, ethacrylic, maleic, fumaric acids, itaconic, citric-conical, sorbic and crotonic and their mixtures, and (3) 20 the remaining part of the copolymer, in a proportion sufficient to give it a certain flexibility and to allow its vulcanization, being a copolymerizable monomer chosen from butadiene-1 , 3, isoprene, 2,3-dimethyl-butadiene-1,3 and piperylene and their mixtures, this copoly-mother having a glass transition temperature of not less than approximately -30 ° C, process characterized in that that the thermo-stabilized aqueous composition of a polymer latex which is used contains a chelating or sequestering agent. 2. A method according to claim 1, characterized in that the chelating agent is ethylene diamine-tetra-trisodium acetate dihydrate. 3.- Method consisting in applying to a hot crushed rubber composition with a tacky surface, a thermosensitized aqueous 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 whose weight does not exceed 7% by weight of the rubber composition, to cool the rubber composition with water and drying it at a temperature not exceeding about 50 ° C., then stacking it in layers which do not stick to each other, the latex polymer being a copolymer comprising (1) at least 45% by weight of a monomer chosen from styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and their mixtures, (2) up to 10% by weight of a deservable copoly-10 monomer chosen from acrylic acids, m ethacrylic, ethacrylic, maleic, fumaric, itaconic, citraconic, sorbic and crotonic and their mixtures, and (3) 1a. 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 butadiene-1,3, isoprene, 2,3-dimethyl- butadiene-1,3 and piperylene and their mixtures, this copolymer having a glass transition temperature of not less than approximately -30 ° C., the latex composition containing, for 100 parts by weight of the copolymer, approximately 150 to 1000 parts by weight non-black mineral pigments for rubbers, about 1 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, a process characterized in that the thermo-stabilized aqueous composition of a polymer latex which is used contains a chelating or sequestering agent. 4. Method according to claim 3, 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 approximately 45 ° C, and the total solid content of latex 35 is of the order of 10 to 40% by weight. 5. Method according to claim 4, 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 approximately -20 ° C. 6. The method of claim 4, wherein the latex copolymer comprises about 64% by weight of styrene, about 2% by weight in total of a mixture of itaconic acid and methacrylic acid, the remainder being butadiene -1.3, this copolymer having a glass transition temperature of approximately -15.9 ° C by differential thermal analysis and approximately -10.2 ° C by differential scanning calorimetry. 7. Product obtained by the process of claim 1. 8. Product obtained by the process of claim 2. 9. 9. Product obtained by the process of claim 3. 10. -Product obtained by the process of claim 4. 11. Product obtained by the process of claim 5. 12. Product obtained by the process of claim 6. 13. Composition comprising an aqueous polymer latex which contains a small proportion by weight of a thermosensitizer sufficient to gel the polymer when hot, the polymer having a glass transition temperature of not less than approximately -30 ° C. and being a copolymer which comprises (1) at least 45% by weight of a monomer chosen from styrene, vinyl-toluene, acryl-. Lonitrile and methacrylonitrile, acrylamide and methacrylamide, methyl methacrylate and ethyl methacrylate and their mixtures, (2) up to 10% by weight of a copolymerizable monomer chosen from acrylic acids, 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 copolymerizable monomer chosen from butadiene-1, 3, isoprene, 2,3-dimethyl-butadiene-1, 3 and piperylene and their mixtures, 4 16 <“- s composition characterized in that it contains in addition to a chelating agent. 14. -Composition according to claim 13, characterized in that it contains, as a chelating agent, ethylene diamine-trisodium dihydrate tetracetate. 15. The composition as claimed in claim 13, 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 1 to 30 parts by weight of stabilizing and wetting agents, the 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 solid content of the latex being approximately 10 to 75% by weight. 16. The composition of claim 15, 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 about d methacrylic and itaconic acids, the remaining part being 1,3-butadiene, this copolymer having a glass transition temperature of the order of -20 ° C. 17. The composition of claim 15, wherein the total solids content of the latex is from about 10 to 40% by weight and the latex copolymer comprises from about 64% by weight of styrene, from about 2% by weight to the total of itaconic acid and methacrylic acid, the remainder being 1,3-butadiene, this copolymer having a glass transition temperature of approximately -15.9 ° C by differential thermal analysis, and approximately - 10.2 ° C by differential scanning calorimetry. v