MXPA98003637A - Composition of rubber based on black carbon which has silice fixed to its surface and a dienic polymer functionalized or modified by the sila functions - Google Patents

Abstract

Rubber composition having improved hysteresis and physical properties, which make it particularly suitable for constituting a tread of a tire having especially a low rolling resistance, comprising a carbon black having silica fixed to its surface in quality of majority reinforcing filler material, and at least one functionalized diene polymer bearing at the end of its chain a silanol function, or a modified diene polymer along its chain with silanol functions

Description

COMPOSITION OF RUBBER BASED ON BLACK DB CARBON THAT HAS A SILICA FIXED TO ITS SURFACE AND A FUNCTIONALIZED OR MODIFIED DIENIGE POLYMER FOR THE FUNCTIONS SILANOL FIELD OF THE INVENTION The present invention relates to a rubber composition usable especially for the manufacture of tire covers, having improved hysteresis and physical properties in the vulcanized state, which comprises a diene polymer functionalized or modified with silanol functions and , as a reinforcing material, a carbon black that has silica fixed to its surface.

BACKGROUND OF THE INVENTION Since fuel savings and the need to protect the environment have become a priority, it is desirable to produce polymers possessing good mechanical properties and as small a hysteresis as possible, in order to be able to employ them in form compositions of rubbers usable for the manufacture of various semi-encapsulated products that come into the constitution of tire covers, such as, for example, sublayers, rubbers and the union between rubbers ie different natures or the lining of metal or textile reinforcements, gcrr eas flanks or bands to REF: 27425, and obtain tires with improved properties, which have especially low rolling resistance. To achieve this goal, numerous solutions have been proposed, which consist in particular of modifying the nature of the diene polymers and copolymers at the end of the polymerization, by coupling or crossover or functionalization agents. The very large majority of the solutions have been concentrated essentially on the use of polymers modified with a carbon black reinforcing filler material, in order to obtain a good interaction between the modified polymer and carbon black, the use of which has been shown to be inappropriate. of a white filler material, especially silica, because of the small level of certain properties of such compositions and, as a consequence, of certain properties of the tires that employ these compositions, such as the small wear resistance. Illustrative of this prior art, mention may be made of Patent US-B-4,677,165 which describes the reaction of living functionalized polymers with benzophenone derivatives to obtain improved properties in carbon black-containing compositions. With the same purpose, the patent US-B-4. 625 describes the functionalization of an elastomer by reaction of living polymers with N-methyl-pyrrolidine. Patent applications EP-A-0 590 491 and EP-A-0 593 049 describe polymers carrying amine functions, which allow a better interaction between the polymer and the carbon black. Some solutions have also been proposed which concern the use of silica as reinforcing filler material in compositions intended to constitute tire treads. Thus, patent applications EP-A-0 .299,074 and EP-A-0 .447,066 describe functionalized polymers comprising alkoxysilane functions. These functionalized polymers have been described in the prior art as effective in reducing hysteresis and improving abrasion resistance, but their properties are still insufficient to allow the use of these polymers in compositions intended to form tire treads. In addition, the formulation of these polymers poses problems of evolution of macrostructures when effecting the elimination of the polymerization solvent, which leads to a serious degradation of potentially interesting properties. In addition, this evolution is very little controllable.

Otherwise, coupling reactions have been frequently observed in the course of such functionalization reactions and, in order to minimize those, an excess of alkoxysilane and / or intense mixing are generally used. This interest for compositions containing silica has been made with the publication of the patent application EP-AO 501,227, which discloses a composition of rubber vulcanizable with sulfur, obtained by the thermomechanical work of a copolymer of conjugated diene and a compound vinylaromatic and by the use of a particular precipitated silica, obtained according to the procedure detailed in the patent application EP-AO .. 157.703. This composition, which has an excellent compromise between several contradictory properties, allows the manufacture of tires having a tread band provided with a loading material of the particular silica type. However, in silica-based compositions, relatively high amount of binding agents must be used, so that these compositions maintain good mechanical strength properties. These materials have very electrical conductivities which, in certain particular circumstances, do not allow the accumulated static electricity to be effectively evacuated by the soil, and make a more complex production of tires that use old solutions and collected especially in US-B-5,518 publications desirable. 055, EP-A-0,705,722 or EP-AO .718.126 in the form of a scratch or strip of conductive rubber running through the tread, or in the patent application EP-AO .556,890 in the form of an addition of particular conducting polymers to the rubber composition constituting the tread of the tires. More recently, the patent application WO 96/37547 has described a rubber composition which uses as a reinforcing filler material a carbon black having silica fixed on its surface, based on a diene polymer, functionalized or not, and of a coating and coupling agent based on a silane. This composition appears to have improved hysteresis properties in relation to compositions containing a carbon black as reinforcing filler material. However, it is always necessary to use a coating and coupling agent of the syllable type, in a relatively high amount.

The applicant has surprisingly discovered that diene polymers carrying at the end of their chain a silanol function or a block of polysiloxane having a silanol end, or modifier along its chain with silanol functions, which do not In addition, they present no macrostructural evolution in carrying out their functionalization, they confer to the vulcanized compositions, which comprise a carbon black having silica fixed on its surface as a reinforcing filler, properties of the rubber sector, and in particular properties of hysteresis and physics, improved in relation to compositions based on non-functional or functional diene polymers that have been adapted to carbon black, and of the same level as compositions based on diene polymers, functionalized or not, comprising a binding agent and silica as reinforcing filler material, also having a clear increase in conductivity electric activity in relation to these latter compositions.

DESCRIPTION OF THE INVENTION The invention concerns a vulcanizable rubber composition comprising at least one functionalized or modified diene polymer, a carbon black having silica fixed on its surface as reinforcing filler material and the other usual constituents of such compositions, characterized in that the diene polymer is a functionalized diene polymer bearing at the end of its chain a silanol function or a polysiloxane block having a silanol end or a modified diene polymer along its chain with silanol functions. As a preferential polysiloxane block having a silanol end, the compounds according to the following general formula are suitable: wherein: Ri and R2, identical or different, represent an alkyl group having from 1 to 8 carbon atoms, x is an integer comprised between 1,000 and 1,500 and preferably from 1 to 50. By diene polymers capable of to be used in the composition according to the invention, is meant any homopolymer obtained by polymerization of a monomer of the conjugated diene type having from 4 to 12 carbon atoms, any polymer obtained by copolymerization of one or several conjugated dienes with each other or with one or various vinylaromatic compounds having 8 to 20 carbon atoms. Suitable conjugated dienes are, in particular, butadiene-1,3-butadiene, 2,3-di (alkyl of dA C5) -1, 3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene, 2, 3-diethyl-l, 3-butadiene, 2-methyl-3-ethyl-l, 3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1, 3-pentadiene, 2, 4-hexadiene, etc. Particularly suitable as vinylaromatic compounds are styrene, ortho-, meta- and para-methyl-styrene, the commercial mixture known as "vinyltoluene", para-tere. -butyl styrene, methoxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene, etc. The copolymers can contain between 99% and 20 * by weight of diene units and from 11 to 80% by weight of vinylaromatic units. Functionalized diene polymers carrying at the end of their chain a silanol function or a block of polysiloxane having a silanol end, or modified along their chain with silanol functions, may have any microstructure which is a function of the conditions used in polymerization. The polymers can be block, statistical, sequenced, microsequenced, etc., and have been prepared in dispersion or in solution. When it comes to an anionic polymerization, the microstructure of these polymers can be determined by the presence or not of a modifying and / or alloying agent and the amounts of this modifying and / or alloying agent used. To preferential titles, polybutadienes are convenient and in particular those that have a content of 1,2 units comprised between 4% and 80%, the polyisoprene, the butadiene and styrene copolymers and in particular those having a styrene content between 4% and 50% by weight and more particularly between 20% and 40% by weight, a 1,2-link content of the butadiene part comprised between 4% and 65%, a content of trans-1,4 bonds comprised between 30% and 80%, the butadiene and isoprene copolymers and especially those having an isoprene content comprised between 5% and 90- weight and a glass transition temperature (Tg) of -40'C to -80 ° C, isoprenc and styrene copolymers and especially those having a styrene content comprised between 5% and 50% by weight and a Tg comprised between -25 ° C and -50 ° C. In the case of copolymers of butadiene, styrene and isoprene, those having a styrene content between 5% and 50 by weight and more particularly comprised between 10% and 43, an isoprene content between 20% and 50% are suitable. by weight, a butadiene content between 5% and 50% and more particularly comprised between 20% and 40% by weight, a content of 1.2 units of the butadiene part comprised between 4% and 85%, a content of units trans-1,4 of the butadiene part 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 trans-1,4 units of the isoprene part comprised between 10% and 50%, and more generally any copolymer of butadiene, styrene and isoprene having a Tg comprised between -20 ° C and -70 ° C. As the polymerization initiator, any anionic or non-monofunctional or polyfunctional initiator, which is known, can be used. However, an initiator containing an alkali metal such as lithium or an alkaline earth metal such as barium is used preferentially. As initiators of the type of organic lithium compounds, those comprising one or more bonds between carbon and lithium are particularly convenient.

Representative compounds are organic aliphatic lithium compounds such as ethyl lithium, n-butyl lithium (n-BuLi), isobutyl-lithium, dilithios-polymethylenes such as 1,4-dilithio-butane, etc. The lithium idides are also preferred initiators, which lead to polymers having a polar group at the chain end which does not carry the silanol function nor the polysiloxane block having a silanol end. The lithium amide is obtained from an acyl or cyclic secondary amine, in the latter case pyrrolidine and hexamethyleneimine are highly preferred; said amide being able to be made soluble in a hydrocarbon solvent thanks to the joint use of a solvating agent, for example an ether, such as described in Patent FR 2,250,774. Representative compositions containing barium are those described, for example, in patent applications FR-A-2,302,311 and FR-A-2,273,822 and the certificates of addition FR-A-2,338,953 and FR-A-2,340,958 , whose content is incorporated into this document. The polymerization, as is known per se, is preferably carried out in the presence of an inert solvent which can be exemplified by an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane or cyclohexane, or an aromatic hydrocarbon such as benzene, toluene or xylene. The polymerization can be carried out in a continuous or batchwise regime. Generally, the polymerization is carried out at a temperature comprised between 20JC and 120 C and preferably close to 30 ° C to 980 ° C. Of course, a transmetallation agent can also be added at the end of the polymerization to modify the reactivity of the end of the living chain. Functionalized diene polymers carrying at the end of their chain a silanol function, used in the invention, can be obtained by analogy by various methods. A first way is to react, as described in Journal of Polymer Science, part A, volume 3, pages 93, -103 (1965), the living diene polymer with an organosilane-type functionalization agent, preferably at the polymerization reactor outlet and at a temperature identical or different and preferably close to the polymerization temperature, to form a diene polymer having at one end of its chain a halogenosilane function, and subjecting it, as described in the manual " Chmistry and Technology of Silicones, "Academic Press, New York, NY (1968), page 95, to the action of a proton donor, to obtain the dianium polymer functionalized with silanol at one end of its chain. The chaining of these 2 reactions already described by Messrs. Greber and Balciunas in Makromol. Chem. 69, pages 193-205 (1963). Examples of organophosilane type fermentation agents capable of reacting with the living diene polymer include linear dihalogensilanes which correspond to the formula: Ri R2 Yes? 2 wherein: Ri and R2, identical or different, represent an alkyl group having from 1 to 8 carbon atoms, X represents an atom of halogen and preferably chlorine or bromine. Preferred dihalogensilane compounds include dichlorodimethylsilane, dichlorodiethyl silane, dichlorodiphenylsilane, dichlorophenylmethylsilane and dichlorovinylmethylsilane. A second way consists in reacting the living polymer with a cyclic polysiloxane-type functionalization agent to obtain a polymer having an SiO "end, and specifically in a medium that does not allow the polymerization of said cyclo-polysiloxane, as cyclic polysiloxanes. can cite those that respond to the formula: wherein: - R and R2, identical or different, represent an alkyl group having from 1 to 8 carbon atoms, - m represents an integer with a value from 3 to 8, and preferably as cyclic polysiloxane compounds, can hexamethyl-cyclotrisiloxane, trimethyl-triethyl-cyclotrisiloxane, octamethylcyclotetrasiloxane, decamethyl-cyclopentasiloxane and mixtures. The polymer comprising an SiO "end is then reacted with a proton donor compound to drive the silanol-functionalized diene polymer at one end of its chain.A third way consists in preparing by block polymerization block copolymers comprising a block of polysiloxane having a silanol end These block copolymers are obtained by the preparation, as described for example in US-B-3,483,270, US-B-3,051,684 and J. Appl. Sei. Vol. .8, pages 2. 707-2.716 (1964), of a first block of a living diene polymer, which is then reacted, in a polar medium, with a cyclic polysiloxane that is anionically polymerized to form a second block to conduct a block copolymer sequenced, comprising a block of polysiloxane having one end (SiO ") which is then reacted with a proton donor to conduct the diene copolymer of blocks comprising a polysiloxane block having a silanol function at one end of its chain. A fourth way consists of preparing block copolymers comprising a block of polysiloxane having a silanol end, by grafting 2 polymers, for example, by grafting a polysiloxane diluted or disodiated with a diene polymer having one end (SiX), X representing a halogen atom, the graft product then being reacted with a donor to drive the block copolymer comprising a polysiloxane block having a silanol end, as described for example by Messrs. Greber and Balciunas in Makro ol Chem. 79, pages 149-160 (1964) or is cited by Messrs. Plumb and Atherton in the "Block Copolymers" manual, Applied Science, England (1973) page 339. Diene polymers modified throughout of its chain with silanoid functions can also be obtained by various methods such as, for example, the first and third pathways that have been presented previously in this memory, performing a previous stage of metalation of the polymer chain. Of course, one or more antioxidant agents can be added to the reaction mixture before recovering the functionalized polymer by conventional techniques, i.e. either by coagulation, or by evaporation by any means considered such as, for example, evaporation. in vacuum and subsequently drying, if necessary, and even separation of the solvent by stripping with water vapor, which is entirely for a person skilled in the art who could have expected a macrostructural evolution as usually happens with the polymers functionalized by alkoxysilanes. Functionalized diene polymers carrying at the one end of their chain a silanol function or a polysiloxane block having a silanol end, or modified along their chain with silanol functions, have a particular aptitude for being used in order to constitute compositions of rubber comprising as a reinforcing filler material a carbon black having silica fixed on its surface.

The proportion of the carbon black having silica fixed on its surface is at least equal to 30 parts by weight of the polymer. This carbon black having silica fixed on its surface can be used in admixture with other reinforcing fillers such as a carbon black or white fillers, especially silica. The relative percentage of these fillers can be adjusted depending on the compromise of properties of the composition that is desired by the person skilled in the art. The concentration of silica present on the surface of the carbon black constitutes from 0.1 to 50% by weight, preferably from 0.3 to 30%. This carbon black having silica fixed on its surface can be obtained by different manufacturing modes. Mention will be made, by way of example, of the manufacturing methods described in the patent application EP-A-0.711.805, in the Japanese patent application N 63-63755, or the manufacturing procedure of the ECOBLACK CRX200C, sold by the company. CABOT and described in the patent application Wo 96/37547. As the silica suitable for use in the invention, precipitated, pyrogenicized silicas known to a person skilled in the art and, in particular, highly dispersible silicas are suitable. A highly dispersible silica is understood to be any silica which has a very important ability for deagglomeration and for dispersion in a polymeric matrix, observable by electron microscopy or optics, in thin sections. The dispersibility of the silica is also evaluated by means of an aptitude test for deagglomeration against ultrasound followed by a measurement, by diffraction in a glanulometer, of the size of those of the silica particles to determine the average diameter (D50). of the particles and the deagglomeration factor (FD) after the deagglomeration, as described in patent application EP-AO .520,860, the content of which is incorporated herein, or in the article appearing in the Reviosta Rubber World, June 1994, pages 20-24, entitled "Dispersibility measurements of prec. Sílicas".

As non-limiting examples of such silica, mention may be made of the silica Perkasil KS 430 of the company AKZO, the silicas Zeosil 1165 MP and 85 MP of the company Rhone-Poulenc, the silica Hl-Sil 2000 of the company PPG and the silicas Zeopol 8741 u 8745 of the Huber company.

Suitable carbon blacks are all carbon blacks commercially available or conventionally used in tires and particularly in tire treads. Non-limiting examples of such blacks include blacks N 234, N 339, N 326, N 375, etc. The diene polymer functionalized or modified with a silanol can be used alone in the composition according to the invention or can be used in mixture with any other elastomer conventionally used in tires, such as a natural rubber, or in a mixture based on natural rubber and a synthetic elastomer or else another diene polymer optionally coupled and / or crashed or also partially or entirely functionalized with a function other than a silanol function. It is evident that the higher the proportion of conventional elastomer present in the composition according to the invention, the lower the improvement in properties. For this reason, the conventional elastomer can be present in proportions of 1 to 50 parts by weight per 100 parts by weight of functionalized or modified silanes with a silanol. The compositions according to the invention contain, in addition to one or more diene polymers and carbon black having silica fixed on their surface, in whole or in part other constituents and additives commonly used in rubber mixtures, such as plasticizers, pigments, antioxidants, antioxidant waxes, a vulcanization system, extender oils, one or more agents for binding to the elastomer and / or coating the silica, such as alkoxysilanes, polyols, amines, etc. The invention also relates to tire treads, which have a reduced rolling resistance. The invention is illustrated in a non-limiting manner by the Examples which should not constitute any limitation on the scope of the invention. In the Examples, the properties of the compositions are evaluated in the following manner: - Mooney viscosity ML (1 + 4) at 100 ° C, measured according to the ASTM standard: D-1646, entitled Mooney in the Tables. - Lengthening modules of 300 * (MA 300), 100% (MA 100) and 10% (MA 10): measurements made according to ISO 37.

- Scott breakage indexes: measured at 20 ° C (force at break in MPa, Fr, elongation at break in%, Ar). Hysteresis losses measured at 60 ° C in%. The deformation for the measured losses is 35%.

- Shore A hardness: measurements made in accordance with DIN 53505. - Dynamic properties in shear: Measurements made as a function of deformation at 10 to 23 ° C. Non-linearity? G expressed in MPa is the difference of shear moduli between 0.15% and 50% deformation from peak to peak. The hysteresis is expressed by the measurements of the maximum of G "and the maximum of tg at 23JC and with a deformation of approximately 7%, which are respectively indicated as G '' max 23o 'and tg5 ma. 232 according to ASTM D2231-71 (return to Drobar in 1977). - The volume resistivity (Pv) is measured in ohm.cm, according to the ASTM D257 standard, its value being between 10: and 10 '° Ocm. Its expression will be given in the form of its logarithm of base 10, and it will be designated by Log resistivity. EXAMPLE 1 This Example has the purpose of comparing the properties of a composition based on a functionalized polymer that carries at one end of its chain a silanol function with the other two compositions based on the same polymers but in which respectively one of these does not it is functionalized and the other is functionalized with a functionalization agent known in the state of the art, these three compositions possessing, as reinforcing filler material, a carbon black having silica fixed to its surface. In all the tests of this example, the diene polymer is a copolymer of butadiene and styrene having a proportion of 1,2-butadiene of 40%, a proportion of styrene of 25%, a glass transition temperature Tg of -38 ° C and a Mooney viscosity of 60. The butadiene-styrene copolymers which are employed in the three compositions are: for test A, a copolymer carrying a terminal, functionalized silanol function (SBR-A) for this purpose with the aid of a functionalizing agent of the cyclic siloxane type consisting of hexamethylcyclotrisiloxane, D3, - for test B, a functionalized copolymer (SBR-B) with bis-diethylamino-benzophenone, DEAB, recognized for allowing the preparation of compositions having good hysteresis properties with carbon black, - for test C, a copolymer These SBRs have been synthesized in continuous form in toluene as a polymerization solvent and as a lithium initiator, thus, for all tests, the copolymer is prepared in a 32 liters of useful capacity with a turbine-type stirrer, in which toluene, butadiene, styrene and THF are continuously introduced in a mass ratio of 100: 10: 4.3: 0.3 and a solution of 500 micromoles of active n-BuLi per one hundred grams of monomers The flow rates of the different solutions are calculated to have an average residence time of 45 minutes under intense agitation.The temperature is kept constant at 60 ° C. At the output of the reactor r, the measured conversion is 88% and the SBR contains 25% (by mass) of incorporated styrene and has a content of 40% of 1,2 bonds for the butadiene part.

To obtain the SBR-A, hexamethyl-cyclotrisiloxane (D3) is added at the outlet of the reactor and at the inlet of a static mixer at a ratio of active D3 / n-BuLi = 0.48. Within the framework of the synthesis of SBR-C, D3 is replaced by methanol in an active MeOH / n-BuLi ratio = 1.5. Within the framework of the synthesis of SBR-B, DEAB is added instead of methanol in an active DEAB / n-BuLi ratio = 1.5. The degrees of functionalization (Fn) are calculated by NMR ^ and as a continuation of the determination of the molar mass obtained by osmometry. The molecular mass is in the three cases of 175,000 g.mol. "The number of milliequivalents per kilogram corresponding to the rest [Si (CH3) 2OH] for the functionalized polymer SBR-A is 4.6, that is, one degree of functionalization of 80%, and the number of milliequivalents per kilogram corresponding to the rest [(C2H5) 2N-C < -H4] C0H for the functionalized polymer SBR-B is 4.7, that is, a functionalization degree of 82 %.

In all three cases, after 5 minutes, 0.8 parts per hundred parts of elastomers (pee) of 2,2'-methylene-bis (4-methyl-6-tert-butyl-phenol) and 0 are added, 2 pee of N- (1, 3-methylene-bis (4-methyl-butyl-N '-phenyl-p-phenylenediamine as antioxidants.) Polymers are recovered by the classical operation of recovery by stripping the solvent with steam. water and then dried in a cylinder machine at 100 ° C for 10 minutes With the help of the three copolymers SBR-A, B and C, 3 rubber compositions, respectively Al, are prepared as is known. Bl and Cl, reinforced by a carbon black having silica fixed to its surface, according to the following formulation, in which all parts are expressed by weight: Elastomer: 100 Black treated with silica (*): 60 Aromatic oil 25 Bonding agent (** 1/8 Zinc oxide 2, 5 Stearic acid 1 5 Antioxidant (a) 1/9 Paraffin (b) 1/5 Sulfur 1 / 1 Sulfenamide (c) 2 Diphenylguanidine 0.42 (*) The carbon black that has silica fixed to its surface is a black sold by the company CABOT under the denomination NOIR ECOBLACK CRX2000 (% of Si: 2.74 without treatment with HF / 0.33% after treatment with HF; specific surface (with N2): 138.9 mVg without treatment with HF, 179, 6 m / g after treatment with HF). (**) Polysulfurized oganosilane sold by the company Degussa under the name S169. (a): Antioxidant: N- (1,3-dimethyl-butyl) -N'-phenyl-p-phenylene-diamine (b): Paraffin: mixture of macrocrystalline and microcrystalline waxes (c): Sulfenamide: N-cyclohex? l-2-benzothiazyl-sulfenamide The 3 copolymers described above are used in a composition produced according to the method described in patent application EP-AO 501,227, which has been incorporated in the present application, indicating that a thermomechanical work is carried out in two stages that last respectively 5 and 4 minutes, for an average speed of the blades of 45 revolutions per minute until reaching an identical maximum fall temperature of 160 ° C, while the introduction of the vulcanization system is carried out at 30 ° C in a cylinder machine. The vulcanization is carried out at 150CC for 50 minutes. The properties of these 3 compositions are compared with each other, both in the unvulcanized state and in the vulcanized state. The results are reported in Table 1.

TABLE 1 Compositions A1 Bl C1 Detention agent D3 DEAB MeOH It is found, at the level of the properties in the vulcanized state, that the composition Al based on SBR-A (functionalized with silanol) has hysteresis properties clearly better than the composition Cl comprising the SBR-C (stopped with methanol) with small deformations (G "MX; 3 °; tg $ (max 23 °) and large (PH 60 ° C) without degrading the other properties in relation to the mixture with the SBR-C. better than those obtained with the composition Bl (SBR-B) functionalized with DEAB).

EXAMPLE 2 The purpose of this example is to compare the composition of rubber Al according to the invention (containing a polymer functionalized with silanol and carbon black having silica fixed on its surface) with a composition B2 containing respectively the SBR-B functionalized with DEAB and a filler material consisting of carbon black, and a C2 composition comprising SBR-C, a filler material consisting of silica and a coating and coupling agent of the silane type. These last two compositions being recognized, B2 and C2, for giving good hysteresis properties respectively for carbon black and silica.

The same manufacturing method is followed as that described in Example 1 for the composition Cl. These compositions have the following formulations: TABLE 2 Compositions A1 B2 C2 Detention agent 03 DEAB MeOH Charging material Black treated with silica Black Silica The results obtained are reported in the Table It is found that the composition Al (with the SBR-A functionalized with silanol) comprising the black ECOBLACK CRX2000, has a very large decrease in hysteresis (with small and large deformations) of the order of 30% in relation to that obtained with the B2 composition based on carbon black, without deteriorating to the other properties. Furthermore, it is observed that Al composition has improved hysteresis properties even in relation to silica-based composition C2 with a greatly reduced conductivity level.

Example 3 In this example, three compositions are compared A3, C3 and B3, respectively based on the SBR-A (functionalized with D3), SBR-C (stopped with MeOH) and SBR-3 (functionalized with DEAB), which do not contain any binding agent but carbon black having silica fixed to its surface as reinforcing filler material. The compositions A3, C3 and B3 are produced according to the method presented in Example 1, and have the following formulation: Elastomer 100 Black treated with silica 60 Aromatic oil 25 Bonding agent 1.0 Oxide of zinc 2,5 Stearic acid 1/5 Antioxidant (a) 1,9 Paraffin (b) 1,5 Sulfur 1,1 Sulfenamide (C) 2 Diphenylguanidine: 0.42 (*) The carbon black that has silica fixed to its surface is a black sold by the company CABOT under the denomination NOIR ECOBLACK CRX2000 of Si: 2.74 without treatment with HF / 0.33% after treatment with HF; surface area (with N2): 138.9 m2 / g without treatment with HF, 179.6 m2 / g after treatment with HF).

The results are recorded in Table 3 It is found that even without the use of any coating and bonding agent, the A3 composition using the SBR-A (functionalized with silanol) has a level of hysteresis, with small deformations (G "ma 2 - ***; tg £ (max 23) and large (PH 60 °), very low in relation to those of the other two compositions that also comprise a carbon black having silica fixed to its surface as a reinforcing filler, without any degradation occurring In addition, a slight deterioration of the hysteresis properties of the compositions B3 and C3 constituted respectively based on SBR-B and SBR-C, is observed with respect to the compositions B2 and C2 of Example 2 on the basis of of the same polymers but containing a coating and binding agent, while on the other hand the hysteresis properties of the composition A3 are almost as good as those of the composition Al containing a coating agent It should also be emphasized that the other properties of mechanical cohesion (MA300, strength and elongation at break) of the A3 composition are no longer degraded in relation to the Al composition, nor are the properties of the conductivity level. .Example 4. This example has the purpose of comparing compositions Al and Cl of Example 1 respectively based on SBR stopped with methanol and functionalized with silanol, with a composition of the same formulation Fl but which uses a different SBR This SBR-F is synthesized in a continuous regime as in Example 1, having the cyclohexane as the polymerization solvent and the hexamethyleneimine-lithium (HMIMLi) as the initiator. This is functionalized with the help of hexamethylcyclotrisiloxane (D3), the method of preparation of the composition Fl being identical to that used for the compositions Al and Cl. The results are reported in Table 4.

TABLE 4 Compositions A1 C1 F1 Catalyst BuLi BuLi HMIMLi Stop Agent D3 MeOH -D In view of the properties in the vulcanized state, it is observed that the composition Fl, which uses the polymer SBR-A functionalized with silanol but with a catalyst different from that of the composition Al, has hysteresis properties with small and large deformations, greatly improved in relation to the Cl composition based on the SBR-C stopped with methanol, and as good, if not better, as those obtained with the composition Al. Thus, it is clearly shown that the improvement of hysteresis properties, without degradation of the other properties, obtained by the use of a polymer functionalized with silanol in the presence of a reinforcing filler material constituted by carbon black having silica fixed on its surface, is independent of the choice of the catalyst.

EXAMPLE 5 This Example has the purpose of comparing a composition G5 according to the invention with two other compositions S5 and 15 based on commercial SBR. The compositions G5, H5 and 15 are synthesized on a discontinuous basis based, respectively, on the following SBRs: - the SBR-G is synthesized in a discontinuous regime within cyclohexane and is functionalized with the help of D3 according to the method indicated in that follows, - the T0589 manufactured by the company JAPAN SYNTHETIC RUBBER, is a polymer modified specifically to react with silica, which has the following characteristics: Tg = -32 ° C,% of 1,2 = 41%,% of est = 33%, ML (l-4) 100 ° = 45, - the NS116 manufactured by the company NIPPON ZEON, is a polymer modified specifically to react with carbon black, which has the following characteristics: Tg = -25 ° C, % of 1,2 = 60%,% of est = 21%, ML (1 + 4) 100 ° C = 50. The SRB-G is synthesized in batch mode as follows: In a reactor of 10 liters capacity containing 4.6 liters of deaerated cyclohexane, 211 g of styrene, 429 g of butadiene and 2,000 ppm of THF are injected. The impurities are neutralized with the aid of n-BuLi and then 0.0033 moles of n-BuLi as well as 0.001 moles of sodium tert-butylate used as a randomizing agent are added, and the polymerization is carried out at 55 ° C. . With a conversion of 90%, 0.0011 moles of hexamethyl-cyclotrisiloxane (D3) are injected into the reactor. The polymer solution is stirred for 15 minutes at 55 ° C. The polymer is subjected to antioxidant treatment by the addition of 0.80 pee of 3, 3-methylene-b? S (4-methyl-6-tert-butyl-meth? L-phenol) and 0.20 pee of N- ( 1,3-dimethyl-butyl) -N'-phenyl-p-phenylene diamine and then recovered by stripping with steam and drying in a cylinder machine at 100 ° C. The Mooney viscosity (ML (1 + 4) 100 °) is 46, the mass percentage of styrene incorporated (% of esti), determined by RMN1H, is 33% and the degree of vinyl chaining of the butadiene part (% of 1.2) is 41%. The NMR analysis gives a degree of functionalization with [-Si (CH2) 2] -OH of 4 meg / g, which, taking into account the molecular mass of the copolymer given by osmometry (175,000 g / mol), corresponds to a degree of functionalization with [SiOH] of approximately 70%. The three compositions G5, H5 and 15 have the same formulation as indicated in Example 1 based on a carbon black having silica fixed on its surface (ECOBACK CRX2000), the method of preparation of these compositions being identical to that used for composition Al of example 1. The results obtained are shown in Table 5.

In view of the properties in the vulcanized state, it can be seen that only the composition G5 based on an SBR-G according to the invention makes it possible to obtain very small hysteresis properties and very high reinforcing properties. It is therefore evident that the use of any functionalized polymer adapted to carbon black does not allow any improvement of the hysteresis and physical properties when using it in a composition based on silica-treated black (here ECOBLACK CRX2000), nor does it the transformation of any polymer functionalized specifically for silica with a composition comprising silica-treated black as a reinforcing filler.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (11)

1. Composition of vulcanizable rubber containing at least one diene polymer, and a carbon black having silica fixed on its surface as a reinforcing filler material, characterized in that the diene polymer is a functionalized diene polymer bearing at one end of its chain a silanol function or a polysiloxane block having a silanol end or a modified diene polymer along its chain with silanol functions.

2. Composition according to claim 1, characterized in that the polysiloxane block having a silanol end corresponds to the formula: wherein: Ri and R2, identical or different, represent an alkyl group of 1 to 8 carbon atoms, x is an integer between 1 and 1,500.

3. Composition according to claim 2, characterized in that Ri and R2 represent an alkyl group having from 1 to 5 carbon atoms and preferably represent the methyl group.

4. Composition according to any one of claims 1 to 3, characterized in that the diene polymer is a copolymer of butadiene and styrene or of butadiene, styrene and isoprene.

5. Composition according to claim 4, characterized in that it also comprises a polybutadiene and / or a copolymer of butadiene and isoprene and / or a natural rubber.

6. Composition according to any one of claims 1 to 5, characterized in that the percentage of silica present on the surface of the carbon black constitutes 0.1 to 50% by weight.

7. Composition according to claim 6, characterized in that the percentage of silica present on the surface of the carbon black constitutes from 0.3 to 30% by weight.

8. Composition according to any one of claims 1 to 7, characterized in that the carbon black having silica fixed on its surface is used in admixture with other reinforcing fillers.

9. Tire comprising a vulcanized rubber composition which comprises at least one diene polymer, and a carbon black having silica fixed on its surface as a reinforcing filler, characterized in that the diene polymer is a functionalized diene polymer bearing at one end of its chain a silanol function or a polysiloxane block having a silanol end or a modified diene polymer along its chain with silanol functions.

10. Tire according to claim 9, characterized in that the composition enters the constitution of the tread.

11. Tire tread compound consisting of a vulcanized rubber composition comprising at least one diene polymer, and a carbon black having silica fixed on its surface, characterized in that the diene polymer is a functionalized diene polymer bearing at one end of the tire. its chain a silanol function or a polysiloxane block having a silanol end or a modified diene polymer along its chain with silanol functions.