MXPA00000254A - Colour rubber composition for tyre - Google Patents

Abstract

The invention concerns a white, light-coloured or colour tyre rubber composition devoid of carbon black, comprising at least a diene elastomer, a reinforcing white or coloured filler, an anti-photooxidation protective system, characterised in that said protective system is based at least on:(A) a 2,2'-methylene-bis-[4-alk yl(C1-C10)-6-alkyl(C1-C12)phenol];(B) a dialkylthiodipropionate whereof the alkyl radicals, identical or different are (C1-C30), preferably (C8-C20), radicals;(C) a 2-(2-hydroxyphenyl)benzotriazole;(D) a"HALS"amine derived from 2,2,6, 6-tetramethylpiperidine.

Description

COMPOSITION OF COLOR RUBBER FOR PNEUMATICS Description of the invention The present invention is concerned with the rubber or rubber compositions of tires, as well as with the anti-degradation agents intended to protect these compositions against atmospheric photo-oxidant aging due to the combined action of the oxygen and light. * It is more particularly concerned with the anti-photo-oxidant protection of white, clear or colored dienic rubber or rubber compositions devoid of carbon black and reinforced with at least one white or colored filler, in particular silica, such Compositions are vulcanizable with sulfur and enter the constitution of colored tires. As is known, the vulcanizates of rubbers or diene rubbers essentially unsaturated, natural or synthetic, due to the presence of double bonds in their molecular chains, are susceptible to deteriorating more or less rapidly after a prolonged exposure to the atmosphere if they are not protected , due to the known oxidation mechanisms. These complex mechanisms have already been described, for example, in the following documents: ref. [1]: "Antidegradants for tire applications" in "Tire compounding", Education Symposium No. 37 (ACS), Cleveland, REF .: 32485 Communications I, October 1995; ref. [2]: Non-blooming high performance antidegradants ", Kautschu Gummi Kunststoffe, 47. Jahrgang, No. 4, 1994, 248-255; ref. [3]: "Antioxidants" in Encycl. Polym. Sci. And Eng., 2a. edition, Vol. 2. 73-91. They cause immediately after the breakdown of these double bonds and the oxidation of the sulfur bridges, a rigidification and embrittlement of the vulcanized ones, degradation that is also accelerated under the conjugated action of the heat by means of "thermo-oxidation" or even of the light through "photo-oxidation" (see, for example, ref [4]: "Photooxidation and stabilization of polymers", Trends in Polym, Sci., Vol. 4, No. 3, 1996, 92-98; ref. '[5 ]: "Degradation mechanisms of rubbers" ', Int. Polym, Science and Technol., Vol. 22. No 12, 1995, 47-57). These oxidation phenomena have been inhibited little by little thanks to the clarification and commercialization of various antioxidant agents where the most effective ones are in known manner quinoline derivatives ("TMQ") or p-phenylenediamine derivatives ("PPD" or "PPDA") even more active than the former, such as, for example, Nl-3-dimethylbutyl-N '-phenyl-p-phenylenediamine (6-PPD). These sometimes associated TMQ and PPD type antidegradants are now scattered and are used almost systematically (see for example ref [1] to [3] above) in conventional tire compositions, filled or filled at least part of carbon black that gives it its characteristic black color. Since the need to save fuel and the need to protect the environment have become a priority and in particular after the publication of the European patent EP-A-0 501 227 the interest for the silica reinforced compositions has resurfaced. This application describes a rubber composition or vulcanizable rubber with reinforced sulfur, preferably mostly of a particulate precipitated silica, which makes it possible to manufacture a tire that has a clearly improved rolling resistance, without affecting the other properties, in particular the adhesion * , of hardness and resistance to wear or wear. The recently published European patent application EP-A-0 810 258 discloses a new reinforced dienic rubber composition of another white particulate filler, in the presence of alumina (A1203) specific for high dispersibility, which also allows obtaining tires or of treads that have an excellent exchange of such contradictory properties. One can thus envision the commercialization of color tires, which for aesthetic reasons, particularly in the domain of passenger cars, correspond to a real expectation of the users, while the latter can be offered a substantial fuel economy.

It is found that the antioxidant agents described above, tuned and optimized after many years of research in conventional black rubber compositions, are not suitable for the protection of tire rubber compositions loaded exclusively with white loads, particular of silica or alumina. In fact, most of them and in particular the TMQ or PPD derivatives mentioned above are not stable to light; under the effect of ultraviolet radiation (U.V.) they present a color alteration and stain the rubber compositions, which does not allow contemplating their use in white, clear or colored compositions. On the other hand, the absence of carbon black, which up to now played a U.V. very effective - in conventional compositions, it has the consequence of aggravating all the degradation processes described above, in particular those of photo-oxidation. Thus, it is necessary, in order to develop colored tires, to develop new photo-oxidant aging protection systems, which have an exchange of new properties, displaced in relation to those used for black tires, particularly effective ones in front of UV radiation while they are stable to light and do not stain in front of the compositions to be protected. After an investigation, the applicant found an anti-photo-oxidant protection system that meets the requirements defined above, this system is compatible on the one hand with a vulcanization of sulfur and on the other hand with the severe conditions of tire use (temperature, fatigue due to dynamic restrictions). Accordingly, a first object of the invention consists of a white, clear or colored tire rubber composition, devoid of carbon black, "comprising at least one diene elastomer, a white or colored reinforcing filler, a system of anti-photo-oxidant protection, this composition is characterized in that the protection system is based on at least: (A) a 2, 2'-methylene-bis- [4-alkyl (of 1 to 10 carbon atoms) -6-alkyl (from 1 to 12 carbon atoms) phenol]; (B) a dialkylthiopropionate wherein the alkyl radicals, identical or different, are radicals of 1 to 30 carbon atoms, preferably 8 to 20 carbon atoms; (C) a 2- (2-hydroxyphenyl) benzotriazole; (D) an amine "HALS" derived from 2,2,6,6-tetramethylpiperidine.

The invention also relates to colored tires or colored rubber articles of such tires, when they comprise a rubber composition according to the invention, such articles consist in particular of treads, sublayers intended for example to be placed under the treads, flanks, protectors, heels, more generally any layer or rubber cover that can enter the constitution of the tires. Tires or rubber articles "colored" or "colored" in the present description means tires or rubber articles where at least one part is of a different color from conventional black and comprises a white color. Another subject of the invention is a method for protecting against photo-oxidant aging a tire rubber composition, white or colored, devoid of carbon black, this process is characterized in that it incorporates by mixing into the composition, before its vulcanization, an anti-photo-oxidant system such as that described hereinabove. Finally, the invention has for its object the use of an anti-photo-oxidant system which meets the definition mentioned above for the protection against photo-oxidation of these white, clear or colored tire rubber compositions. Thus the invention and its advantages will be better understood in the light of the description and the following examples of embodiment.

I. MEASURES AND TESTS USED The properties of the rubber compositions are evaluated as indicated hereinafter. During the photo-oxidation, thermo-oxidation and colorimetry tests, the samples used are non-standardized samples consisting of rubber strips with dimensions (L x 1 xe) equal to (110 x 15 x 2.5) in mm (millimeters) ). 1-1. Tensile tests These tests make it possible to determine the elastic tensions and the properties at break; those made in the cooked mixtures are made according to the standard AFN0R-NF-T46-002 of September 1988. The drying modules (in MPa) at 10% elongation (MIO) and at 100% elongation (MlOO) are measured . Unless otherwise stated in the text, all these traction measures are carried out under normal conditions of temperature and humidity according to the standard AFNOR-NF-T40-101 of December 1979. 1-2. Shore A hardness tests These measurements allow to assess the hardness of the compositions after cooking, according to ASTM D 2240-86. 1-3. Hysteresis losses Hysteresis losses (PH) are measured by bouncing at 60 ° C at the sixth shock and are expressed in% according to the following relationship: PH (%) = 100 [(c W?) / W0] where W0: energy provided; Wi: energy restored. 1-4. Photo-oxidation tests The compositions in the cooked state are subjected to accelerated photo-aging in the following manner: one face of the samples is exposed for 12 days under 4 high-pressure mercury vapor lamps (MAZDA MA400) at 60 ° C, in SEPAP 12/24 (MPC). The evolutions of the mechanical and colorimetric properties are measured immediately. In particular, tensile tests after accelerated photo-aging are performed by extensometry of the samples at reduced elongation stresses (10% and 25%) at the first elongation, on an Instron 1122 machine, at low traction speed (10 mm / min). The measured voltages are indicated as FIO and F25. 1-5. Thermo-oxidation tests These tests allow to evaluate the resistance of the tested materials to the thermo-oxidation. The MINE, MlOO and PH parameters are measured for this after a 30-day thermo-oxidant aging at a constant temperature of 70 ° C in an air-ventilated oven. 1-6. Colorimetric tests The colorimetric values are determined with the aid of a spectrocolorimeter Microflash 200 D DATA COLOR of configuration D65 / 10 (daylight, observation angle 10 °). The colorimetric properties are measured in a known manner, according to the instruction manual of the colorimeter (May 1995) by analysis of the reflectance spectrum of the samples. These measurements are reported in the "CIÉ LAB" system of 3 colorimetric three-dimensional coordinates, L *, a *, b *, system in which: the axis a * represents the coordinate of green-red chromaticity, with a scale of -100 (green) to +100 (red), - the b * axis represents the blue-yellow chromaticity coordinate, with a scale of -100 (blue) to +100 (yellow), the L * axis represents the brightness coordinate, with a scale of 0 (black) to 100 (white); -? E = [(? L *) 2 + (? A *) 2 + (? B *) 2J1 2 represents the global average colorimetric deviation of each sample in relation to a non-aged control; the older it is? E, the more the composition has lost its initial color.

II. CONDITIONS OF CARRYING OUT THE INVENTION In addition to the usual additives and optionally a coloring agent (or several), the compositions according to the invention comprise at least one diene elastomer, a white or colored filler as a reinforcing filler, an anti-seize system, and photo-oxidant, photo-stable and non-staining against the protected compositions, the system comprises at least, in combination, the compounds A, B, C and D mentioned above.

II-l. Diene elastomer Elastomer or "diene" rubber means in a known manner a resulting elastomer at least in part (ie a homopolymer or a copolymer) of diene monomers (monomers bearing carbon-carbon double bonds), conjugated or not). Generally, "essentially unsaturated" diene elastomer is understood to mean a diene elastomer resulting at least in part from conjugated diene monomers having a proportion of portions or units of diene origin (conjugated dienes) which is greater than 15% (% by weight). moi). Thus, for example, diene elastomers such as butyl rubbers or copolymers of dienes and alpha olefins of the EPDM type do not fall within the above definition and can be particularly qualified as "essentially saturated" diene elastomers (proportion of diene-based portions). reduced or very reduced, always less than 15%). In the category of diene elastomers "essentially unsaturated" is understood in particular by "strongly unsaturated" diene elastomer, a diene elastomer having a proportion of portions of diene origin (conjugated dienes) which is greater than 50%.

As indicated above, the present invention is concerned primarily with the anti-photo-oxidant protection of pneumatic compositions based on essentially unsaturated diene elastomers. Among the latter, the homopolymers obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms, as well as the copolymers obtained by copolymerization of one or several conjugated dienes or with one or more compounds are preferably used. vinyl aromatics having 8 to 20 carbon atoms. Suitable conjugated dienes are, in particular, 1, 3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (alkyl of 1 to 5 carbon atoms) -1, 3-butadienes, such as for example 2, 3-dimetii-l, 3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-l, 3-butadiene, 2-methyl-3 -isopropyl-1, 3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert.-thiobutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene. , vinylnaphthalene.

The copolymers can contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl aromatic units. The elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or not of a modifying and / or disrupting agent and the amounts of the modifying and / or disrupting agent employed. The elastomers may be, for example, blocks, statistics, sequences, microsequences and be prepared in dispersion or in solution. Preferably, polybutadienes are desirable, and in particular those having a content of 1,2- units comprised between 4% and 80% or those having a 1,4-cis content greater than 80%, polyisoprenes, copolymers butadiene-styrene and in particular those having a styrene content comprised between 5% and 50% by weight and more particularly between 20% and 40%, a content of 1,2-bonds of the butadiene part included between 4% and 65%, a content of 1,4-trans bonds between 20% and 80%, the butadiene-styrene copolymers and in particular those having an isoprene content between 5% and 90% by weight and a vitreous transition temperature (Tg) of -40 ° C to -80 ° C, isoprene-styrene copolymers and in particular those having a styrene content between 5% and 50% by weight and a Tg comprised between - 25 ° C and -50 ° C. In the case of butadiene-styrene-isoprene copolymers, in particular those having a styrene content between 5% and 50% by weight and more in particular between 10% and 40%, an isoprene content of between 15% and 60% by weight and more in particular between 20% and 50%, a butadiene content between 5% and 50% by weight and more in particular between 20% and 40%, a content of units 1,2 - of the butadiene part comprised between 4%, and 85%, a content of 1,4-trans units of the butadiene part comprised between 6% and 80%, a content of 1,2-units plus 3,4- of the isoprene part comprised between 5% and 70% and a content of 1,4-trans units of the isoprene part comprised between 10% and 50% and more generally any butadiene-styrene-isoprene copolymer having a Tg comprised between -20 ° C and -70 ° C. Of course, the elastomer can be coupled and / or starred or even rendered functional with a coupling and / or star forming or function forming agent. The elastomer can also be made of natural rubber or a mixture based on natural rubber with any elastomer, in particular diene, synthetic.

In a particularly preferred manner, the diene elastomer of the composition according to the invention is chosen from the group of strongly unsaturated diene elastomers consisting of polybutadienes, polyisoprenes or natural rubber, butadiene-styrene copolymers, butadiene-styrene copolymers, the isoprene-styrene copolymers, the butadiene-styrene-isoprene copolymers or a mixture of two or more of these compounds. When the composition according to the invention is in the form of a tread, the diene elastomer is preferably a butadiene-styrene copolymer prepared from a solution having a styrene content of between 20% and 30% by weight , a content of yinyl bonds of the butadiene part comprised between 15% and 65%, a content of 1,4-trans bonds comprised between 15% and 75% and a Tg comprised between -20 ° C and 55 ° C, this copolymer of butadiene-styrene is optionally used in admixture with a polybutadiene which preferably has more than 90% 1,4-cis bonds.

II-2. Reinforcing load As a reinforcing filler, any white fillers (even so-called clear fillers) capable of reinforcing (or filling), alone or in a mixture with one another, more or less according to the applications contemplated, are suitable for a tire rubber composition, such as for example silica, alumina, clays, hydrates or oxides of aluminum and / or magnesium, bentonite, talc, chalk, kaolin, titanium oxide. Preferably, the proportion of reinforcing filler is comprised in a domain of 30 to 150 pee (parts by weight per one hundred parts of elastomer), more preferably 30 to 100 pee, the optimum being different according to the contemplated applications: the level of reinforcement (or level of filling) expected in a bicycle tire, for example, is of course significantly lower than that required in a tire apt to roll at a high speed in a sustained manner, for example a motorcycle tire, a tire for vehicle for tourism or for utility vehicle such as a heavy vehicle. Preferably, in particular when the composition of the invention is concerned with such a tire suitable for high-speed rolling, silica (SiO2) or alumina (Al203), in reality the two associated, constitute (n) the majority, ie more 50% by weight of the total reinforcing (or filler) load. More preferably still, the silica and / or alumina constitute more than 80% by weight of this total reinforcing filler.

The silica and / or the alumina can constitute the entire reinforcing load; however, other white loads can, according to the applications contemplated, advantageously represent a more or less important fraction of the reinforcing load. Thus, it has been found that another white charge associated for example with silica or alumina can have the effect of dulling the colors, in other words, of decreasing the clear, ie more or less translucent, nature of the compositions charged with silica or alumina. This other white filler is preferably chosen from chalk, talc or kaolin, more preferably kaolin; it is preferably used in a proportion of 2.5 to 12.5%, more preferably 5 to 10% (% by weight in relation to the weight of the silica and / or alumina), according to the contemplated applications; for a proportion lower than 2.5% the effect is generally not very visible whereas for proportions greater than 12.5%, the mechanical properties of the vulcanized ones can decrease. It has also been found that the use of titanium oxide (Ti02) has the effect of giving pastel colors, particularly aesthetic, to the chosen colors; the proportion of titanium oxide preferably ranges from 0.5 to 7%, more preferably from 1 to 3% (% by weight in relation to the weight of silica and / or alumina), according to the applications contemplated. For a proportion lower than 0.5%, the effect is generally not very visible, while for proportions greater than 7%, it is exposed to a risk of blooming on the surface of the vulcanized. Of course, the invention also applies to the case where a colored reinforcing filler is chosen, compatible with the desired color for the tire, this colored filler can be a naturally colored filler or even obtained by a prior coloring operation, for example a silica or a pre-colored alumina. The silica used can be any reinforcing silica known to those skilled in the art, particularly any precipitated or calcined silica having a BET surface as well as a CTAB specific surface the two .. less than 450 m2 / mg, even if the silicas precipitated highly dispersible are preferred, in particular when the invention is concerned with tires that have a low rolling resistance. Highly dispersible silica means any silica having a very important capacity of deagglomeration and dispersion in a polymer matrix, observable in a known manner by electron microscopy or optical, in thin layers. Non-limiting examples of such preferred highly dispersible silicas include silica Perkasil KS 430 from Akzo, silica BV 3380 from Degussa, silicas Zeosil 1165 MP and 1115 MP from Rhóne Poulenc, Silica Hi Sil 2000 from the company PPG, silicas Zeopol 8741 or 8745 from the company Huber, precipitated silicas treated, such as for example the silicas "impurified" with aluminum described in the application EP-A-0 735 088. The reinforcing alumina used it is preferably a highly dispersible alumina having a BET surface of 30 to 400 m2 / mg, more preferably 80 to 250 m2 / mg, an average particle size of at least 500 nm, more preferably at least equal to 200 nm, a high proportion of reactive Al-OH surface functions, as described in the aforementioned EP-A-0 810 258 application. As non-limiting examples of such reinforcing aluminas, mention may be made in particular of the aluminas A125, CR125, D65CR from the company Baikowski. The physical state in which the reinforcing white charge occurs is irrelevant, whether in the form of dust, microbeads, granules or even billiard balls. Of course, white reinforcing filler is also generally understood as mixtures of different reinforcing white fillers, in particular highly dispersible silicas and / or aluminas such as those described hereinabove.

Any known coupling agent can be used to ensure the bond between the reinforcing white filler and the diene elastomer, such as the organosilanes, in particular polysulfurized alkoxysilanes, such as the bis (trialkyl (1- to 4-carbon atoms) silylpropyl tetrasulfides) , in particular bis (tpmethoxy-silylpropyl) or bis (triethoxysilylpropyl), in particular the last of these compounds, of formula [(C2H50) Si (CH2) 3S2] 2 marketed, for example, by the company Degussa under the name Si69 or by the company Osi under the name URC2.

II-3. Anti-photo-oxidant system As mentioned above, the tire composition according to the invention is protected against photo-oxidant aging by means of an anti-photo-oxidant, photo-stable and non-staining system against this composition, base of at least: (A) a 2, 2'-methylene-bis- [4-alkyl (from 1 to 10 carbon atoms) -6-alkyl (from 1 to 12 carbon atoms) phenol]; (B) a dialkylthiopropionate wherein the alkyl radicals, identical or different, are radicals of 1 to 30 carbon atoms, preferably 8 to 20 carbon atoms; (C) a 2- (2-hydroxyphenyl) benzotriazole; (D) an amine "HALS" derived from 2,2,6,6-tetramethylpiperidine. The phenolic compounds A are known antioxidants. Preferred A compounds are those corresponding to the following general formula (I): wherein: R1 = alkyl of 1 to 4 carbon atoms, preferably methyl or ethyl; R2 = alkyl of 1 to 6 carbon atoms or cycloalkyl of 5 to 12 carbon atoms. Preferably, compound A is a 2, 2'-methylenebis- [4- (methyl or ethyl) -6-alkyl (1 to 4 carbon atoms) phenol] or a 2,2 '-methylene-bis- [ 4- (methyl or ethyl) -6-cycloalkyl (from 7 to 8 carbon atoms) phenol]. Compound A is advantageously chosen from the group consisting of 2,2 '-methylene-bis- [4-methyl-6-t-butylphenol), 2,2'-methylene-bis- [4-ethyl-6-t -butylphenol], 2, 2'-methylene-bis- [4-methyl-6-cyclohexylphenol], 2,2'-methylene-bis- [4-methyl-6-alpha-methyl-cyclohexylphenol], , 2'-methylene-bis- [4-methyl-6-nonylphenol]. Even more preferably, the compound A selected is 2,2'-methylene-bis- [4- (methyl) -6-t-butylphenol]. The dialkylthiodipropionates (Alkyl-0-CO-CH2-CH2-S-CH2-CH2-CO-0-alkyl) are also known antioxidants. As preferred examples B, those in which the two alkyl radicals are identical radicals of 8 to 20 carbon atoms, advantageously dilauryl (of 12 carbon atoms) -thiodipropionate or distearyl (of 18 carbon atoms) - are particularly cited thiodipropionate (or dioctadecyl-2, 2'-thiodipropionate). Compound C is a U.V. ("UVA") of the known family of the 2- (2-hydroxyphenyl) benzotriazoles, which respond preferably to the following general formula (III): wherein R3 and R4, identical or different, represent various straight or branched chain hydrocarbon radicals, substituted or unsubstituted, in particular alkyl of 1 to 4 carbon atoms, in particular methyl or ethyl or alkylaryls of 7 to 20 carbon atoms carbon. The benzotriazole nucleus can itself be substituted in position 4, for example by a halogen, in particular chlorine. Compound D is an amine "HALS" ("Hindered Amine Light Stabilizers") derived from 2,2,6,6-tetramethylpiperidine which preferably responds to the following general formula (III) (X chosen preferably from hydrogen or a hydrocarbon group comprising 1 to 2"0 carbon atoms, for example an alkoxy of 1 to 20 carbon atoms): (D) Such HALS amines can be polymeric, can carry a very large variety of substituents in position 4; they are well known in the U.V. stabilizer domain. and have been described in a large number of documents, for example in "Polymer Stabilization and Degradation", ACS symposium series 280, Ed. P.P. Klemchuk (1985). The anti-photo-oxidant system such as that described above is tested sufficiently effective by itself for the anti-photo-oxidant protection of the tire compositions according to the invention; it can therefore advantageously constitute the only anti-photo-oxidant system, that is to say both anti-(thermo) oxidant and anti-U.V present in the compositions according to the invention. According to the contemplated applications and the nature of the diene elastomer to be protected, the compounds A, B, C and D are present in the compositions according to the invention in the preferred proportions that follow (in pee): A 1 to 5, more preferably 1.5 to 2.5; B 0.5 to 3, more preferably 0.5 to 1.5; C 0.5 to 3, more preferably 0.5 to 1.5; D 0.5 to 3, more preferably 0.5 to 1.5, the total content of the anti-photo-oxidant system (A + B + C + D) is preferably comprised in a domain of 2.5 to 10 pee, more preferably 3.0. at 7.0 pee. At a level lower than the minimum proportions indicated, the effect of the system may be insufficient, while beyond the maximum proportions indicated, no improvement in protection is observed while the formulation costs increase.

II-4. Coloring agent For the application of the invention, any type of coloring agent known to those skilled in the art can be used, this coloring agent can be organic or inorganic, soluble or not in the compositions according to the invention. As an example, mention may be made of mineral colorants such as, for example, powdered metals, in particular copper or powdered aluminum or various metal oxides, in particular iron silicates, aluminates, titanates, oxides or hydroxides, mixed oxides of metal elements different such as Co, Ni, Al, Zn. Mention may also be made of organic pigments such as indantrones, diketo-pyrrolo-pyrroles or diazo condensates, organometallic pigments such as phthalocyanines. The color of the compositions according to the invention can thus vary in a very large range, as an example of the different dyes of red, orange, green, yellow, blue or even brown or gray .. It is also possible not to use a coloring agent and choose to preserve the original color of the reinforcing load whether the latter is white or colored.

II-5. Miscellaneous additives Of course, the compositions according to the invention containing in addition to the compounds described above all or part of the usual constituents used in tire diene rubber compositions, such as plasticizers, a crosslinking system based on either sulfur, either sulfur donors, vulcanization accelerators, aromatic or paraffinic extension oils, other anti-degradation agents that do not stain, in particular antiozone waxes and chemically active antiozonants, in particular cyclic acetals or even various anti-fatigue agents. The compositions according to the invention can contain coupling and / or coating agents of the reinforcing filler in addition to those mentioned above, in combination or in place of the latter, such as, for example, polyols, amines, alkoxysilanes.

III. EXAMPLES OF EMBODIMENT OF THE INVENTION In the following examples, the rubber compositions are prepared by applying the diene elastomers according to well known techniques, by thermomechanical process in an internal paddle mixer followed by an external mixer mix. As an example, the procedure is as follows: the elastomer or the mixture of elastomers is introduced into an internal mixer, filled at 70% and where the temperature is about 60 ° C, then, after an appropriate mixing time, for example in the order of 1 minute, all the other ingredients are added with the exception of the vulcanization system; the thermomechanical mixing process is continued until a temperature drop of 175 ° C; the mixture thus obtained is recovered, then the vulcanization system is added in an external mixer (homo-terminator) at 30 ° C. The vulcanization is carried out at 150 ° C for 45 minutes. Seven red rubber compositions for the manufacture of tire treads are compared in this test. These compositions are identical, with the exception of the anti-photo-oxidant protection system that is absent in the case of composition No. 1 (control, not protected), based on an antioxidant type PPD for composition No. 2 (reference composition) and based on different associations that involve all or part of the compounds A to D for the other compositions. Composition No. 7 is the only composition according to the invention, it comprises the four compounds (A + B + C + D). Compounds A to D used, all commercially available, are the following: (A): 2, 2'-methylene-bis- (4-methyl-6-t-butylphenol); (B): distearylthiodipropionate; (C): 2- (2-hydroxyphenyl) benzotriazole according to formula (II) in which: - R 3 = t-butyl; - R4 = CH2-CH2-CO-O- [(C-H2) 2-0] n-H; (D): tertiary "HALS" amine derived from 2,2,6,6-tetramethylpiperidine, according to formula (III) in which: - substituent in position 1 (X): 0-C8H? 7 (capriloxyl), - substituent in position 4: [0-C0- (CH2) 4] 2 • The diene elastomer is a SBR / BR mixture. The SBR elastomer (styrene butadiene copolymer) is prepared in solution and comprises 25.6% styrene, 60% 1,2-butadiene portions and 23% 1,4-trans polybutadiene portions. The BR (polybutadiene) elastomer is a commercial product comprising more than 90% 1,4-cis linkages (approximately 98%). Tables 1 to 3 provide successively the formulation of the different compositions (table 1, proportion of the different products expressed in pee), their properties after cooking and the evolution of their mechanical properties after the thermo-oxidation and after the photo -oxidation (table 2) and finally the evolution of its colorimetric properties after photo-oxidation (table 3). When reading these different tables of results, you can see the following: - the classic properties of rubber (table 2) after cooking and before aging are little different from one composition and the other, whether they are protected or not by one or several antidegradant agents. - after the thermo-oxidation (table 2) it is found that the results obtained in the composition according to the invention (No. 7) are those closest to the results obtained with the classical anti-oxidant agent (6-PPD) which serves as a reference. It should be noted here that the lowest% evolution of MIO and MlOO, verified in the unprotected control (composition No. 1) are not revealing here more than a low degradation; on the other hand, associated with PH losses that do not decrease, these low% evolution are linked in a manner known to those skilled in the art to a degradation by clge of elastomeric chains in the control composition; - after the photo-oxidation (table 2), it is noted that even better results are obtained thanks to the anti-photo-oxidant system that combines the 4 compounds A, B, C and D (composition No. 7); these results are comparable to those obtained in reference composition No. 2; see evolution of Shore A hardness, FIO and more particularly F25; - finally concerning the evolution of the colorimetric properties (table 3), it is verified that the composition No. 2 protected by the PPD derivative degrades in a very important and redhibitory way (pronounced blackening) while the composition No. 7 in accordance with the invention shows, on the contrary, an excellent color stability (no visible stain) almost equivalent to that registered in the control composition lacking an antidegradant agent; the parameter? E is close to 10 for the composition according to the invention, while it is greater than 30 for the composition based on the PPD derivative. These tests clearly show that the compounds A to D, in the composition No. 7 according to the invention, reinforce each other's effects, thus allowing to obtain a better exchange of properties after aging than for the other compositions. Finally, long-term rolling tests have been carried out on passenger vehicles with numerous color tires according to the invention (dimensions 155/70 SR 13; 175/70 SR 13; 185/65 HR 14); These tires include treads and / or colored sidewalls in different colors (red, yellow or green). These rolling tests have led to the following results: - hardness properties equivalent to those observed in conventional black compositions, charged (or filled) at least in part with carbon black; Adhesion performances, particularly in wet soil and rolling resistance better than those obtained with conventional compositions loaded with carbon black, these performances are also good as those obtained in silica-based compositions such as described in the EP-A patent -0 501 227 cited above; - no degradation of colors after several tens of thousands of kilometers. In conclusion, the compositions according to the invention, thanks to a synergistic combination of four specific compounds, offer color tires a very good resistance to atmospheric aging due to the combined action of oxygen and UV light, this resistance is comparable to that obtained with the aid of a derivative of the PPD type, while guaranteeing these tires an excellent color stability impossible with a conventional antidegradant agent type 6-PPD.

Table 1 (1) styrene-butadiene copolymer; (2) polybutadiene Europene Cis (Enichem company); (3) Zéosil Silica 1165MP (Rhóne Poulenc company); (4) Si69 (society Degussa); (5) N-1, 3-dimethylbutyl-N '-phenyl-p-phenylenediamine; (6) 2, 2'-methylene-bis (4-methyl-6-t-butylphenol) (Vulkanox BKF from Bayer); (7) diocta-decyl-2, 2-thiodipropionate (Irganox PS 802 from Ciba Geigy); (8) 2- (2-hydroxyphenyl) benzotriazole (UVA Tinuvin 213 from Ciba Geigy); (9) HALS amine derived from 2, 2, 6, 6-tetramethylpiperidine (Tinuvin 123 from Ciba Geigy); (10) anti-ozone wax (Redezon 500 of the Repsol company); (11) Pig ophtal Red BRN CI-Red 144 (Ciba-Geigy company); (12) N-cyclohexyl-benzothiazyl-sulfenamide; (13) 1,3-diphenylguanidine.

Table 2 Composition No. Before the MIO thermo-oxidation (MPa) 5 5.1 4. 9 5. Four. Five . 2 5. 3 5. 4 MlOO (MPa) 2 2.1 2 2. 1 2 2. 2 2. 2 Shore hardness A 65 65 66 68 66 66 65 PH60 31 30 31 32 32 32 32 After thermo-oxidation (30 days at 70 ° C) MIO (MPa)% of 5.5 5.9 6.2 6.3 6.2 6.3 6.2 evolution 10 16 27 17 19 19 15 MlOO (MPa)% of 2.5 2.8 2.8 2.8 2.7 3.0 2.9 evolution 25 33 40 33 35 36 32 PH60 33 26 28 27 27 28 27 Before photo-oxidation FIO (MPa) 0.55 0.59 0.58 0.6 0.6 0.62 0.55 F25 (MPa) 0.85 0.88 0.86 0.9 0.87 0.88 0.79 After photo-oxidation (12 days) FIO (MPa) 0.95 0.95 0.97 1.02 0.99 1.03 0.9 % evolution 72 61 67 70 65 66 64 F25 (MPa) 1.45 1.37 1.44 1.41 1.42 1.42 1.23 % evolution 71 56 67 64 63 61 56 Shore hardness A 78 76.8 78.5 81 77.8 78.5 76 % evolution 20 18 19 19 19 1-7 Table 3 Composition No. 1 Initial colorimetric properties: L * +38 + 34 + 35 a * +36 + 31 +34 b * +22 + 18 +20 After photooxidation, 12 days:? L -5 - 14 -5? A * -5 -28 -8? B * -2 -14 -5? E +7 + 34 + 11 It is noted that, in relation to this date, the best method known to the applicant to carry the practice said invention is that which is clear from the present description of the invention.

Claims (22)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A tire composition, white, clear or colored, devoid of carbon black, comprising at least one diene elastomer, a reinforcing filler or filling charge, white or colored, an anti-photo-oxidant protection system, characterized in that the protection system is based on at least: (A) a 2, 2 '-methylene-bis- [4] -alkyl (from 1 to 10 carbon atoms) -6-alkyl (from 1 to 12 carbon atoms) phenol]; (B) a dialkylthiopropionate, wherein the alkyl radicals, identical or different, are radicals of 1 to 30 carbon atoms, preferably of 8 to 20 carbon atoms; (C) a 2- (2-hydroxyphenyl) benzotriazole; (D) an amine "HALS" derived from 2,2,6,6-tetramethylpiperidine.
2. 2. The composition according to claim 1, characterized in that the compound A is a 2, 2'-methylene-bis- [4-alkyl (1 to 4 carbon atoms) -6-alkyl (1 to 7 atoms carbon) phenol].
3. 3. The composition according to claim 2, characterized in that compound A is 2,2'-methylene-bis- [4- (methyl) -6-t-butylphenol].
4. 4. The composition according to any of claims 1 to 3, characterized in that the compound B is a dialkyl (of 8 to 20 carbon atoms) thiodipropionate.
5. 5. The composition according to claim 4, characterized in that the compound B is the dilaurylthiopropionate or the distearylthiodipropionate.
6. The composition according to any of claims 1 to 5, characterized in that the diene elastomer is selected from the group consisting of polybutadienes, polyisoprene or natural rubber, butadiene-styrene copolymers, butadiene-isoprene copolymers, copolymers of isoprene-styrene, butadiene-styrene-isoprene copolymers or a mixture of two or more of these compounds.
7. The composition according to claim 6, characterized in that the diene elastomer is a butadiene-styrene copolymer prepared in solution having a styrene content comprised between 20% and 30% by weight, a content of vinyl bonds of the part of butadiene comprised between 15% and 65%, a content of 1,4-trans bonds comprised between 15% and 75% and a glass transition temperature between -20 ° C and -55 ° C, this butadiene-styrene copolymer it is optionally used in admixture with a polybutadiene which preferably has more than 90% 1,4-cis bonds.
8. The composition according to any of claims 1 to 7, characterized in that the reinforcing filler or filling filler consists mainly of silica and / or alumina.
9. 9. The composition according to claim 8, characterized in that another white charge chosen from chalk, talc or kaolin is associated with silica and / or alumina, preferably at a proportion of 2.5 to 12.5% (by weight). in relation to the weight of the silica and / or alumina).
10. The composition according to any of claims 8 or 9, characterized in that a titanium oxide is associated with the silica and / or alumina, preferably at a ratio of 0.5 to 7% (% by weight in relation to the weight of silica and / or alumina).
11. A color tire or rubber article such as a tire, characterized in that it comprises a rubber composition according to any of claims 1 to 10.
12. 12. A rubber article according to claim 11, characterized in that it is chosen of the group constituted by the treads, the sublayers, the flanks, the protectors and the heels.
13. 13. A method for protecting against photo-oxidant aging a rubber composition of white tire, clear or colored and devoid of carbon black, characterized in that an anti-photo system is incorporated by mixing into the composition before vulcanization. -oxidant based on at least: (A) a 2, 2'-methylene-bis- [4-alkyl (of 1 to 10 carbon atoms) -6-alkyl (of 1 to 12 carbon atoms) phenol]; (B) a dialkylthiopropionate wherein the alkyl radicals, identical or different, are radicals of 1 to 30 carbon atoms, preferably 8 to 20 carbon atoms; (C) a 2- (2-hydroxyphenyl) benzotriazole; (D) an amine "HALS" derived from 2,2,6,6-tetramethylpiperidine.
14. The process according to claim 13, characterized in that compound A is a 2, 2'-methylene-bis- [4-alkyl (1-4 carbon atoms) -6-alkyl (from 1 to 7 atoms carbon) phenol].
15. 15. The process according to claim 14, characterized in that compound A is 2,2'-methylene-bis- [4- (methyl) -6-t-butylphenol].
16. 16. The process according to any of claims 13 to 15, characterized in that the compound B is a dialkyl (of 8 to 20 carbon atoms) thiodipropionate.
17. 17. The process according to claim 16, characterized in that the compound B is the dilaurylthiopropionate or the distearylthiodipropionate.
18. 18. The use, for the protection against photo-oxidation of rubber compositions of white, clear or colored tires and devoid of carbon black, of an anti-photo-oxidant system based on at least: (A) a 2, 2'-methylene-bis- [4-alkyl (from 1 to 10 carbon atoms) -6-alkyl (from 1 to 12 carbon atoms) phenol]; (B) a dialkylthiopropionate wherein the alkyl radicals, identical or different, are radicals of 1 to 30 carbon atoms, preferably 8 to 20 carbon atoms; (C) a 2- (2-hydroxyphenyl) benzotriazole; (D) an amine "HALS" derived from 2,2,6,6-tetramethylpiperidine.
19. 19. The use according to claim 18, characterized in that compound A is a 2, 2'-methylenebis- [4-alkyl (1-4 carbon atoms) -6-alkyl (1-7 carbon atoms) ) phenol].
20. 20. The use according to claim 19, characterized in that compound A is 2,2'-methylenebis- [4- (methyl) -6-t-butylphenol].
21. 21. The use according to any of claims 18 to 20, characterized in that the compound B is a dialkyl (of 8 to 20 carbon atoms) thiodipropionate.
22. 22. The use according to claim 21, characterized in that the compound B is the dilaurylthiopropionate or the distearylthiodipropionate.