MXPA01000927A - Rubber composition for tyre, based on diene elastomer and a reinforcing titanium oxide - Google Patents

Abstract

The invention concerns a rubber composition to be used for making tyres, comprising at least (i) a diene elastomer, (ii) a white filler as reinforcing filler and (iii) a coupling agent ( white filler/elastomer). The invention is characterised in that said white filler consists entirely or partly of a titanium oxide having the following characteristics:(a) it comprises more than 0.5%in volume of a metal element other that titanium selected from the group consisting of Al, Fe, Si, Zr ora mixture of those elements;(b) its BET surface specific area ranges between 20 and 200 m2/g;(c) its average particle size (in volume), recorded as dw, ranges between 20 and 400 nm;(d) its speed of ultrasonic deagglomeration, recorded asa, measured according to the so-called ultrasonic deagglomeration test, at an amplitude of an ultrasonic probe of 600 W, is higher than 2. 10-2µm-1/s. The invention also concerns the use of said rubber composition for making rubber articles, in particular tyres or semi-finished products designed for those tyres. The inventive composition is used in particular for making coloured tyres or semi-finished articles such as running treads of tyre sidewalls.

Description

COMPOSITION OF RUBBER FOR TIRE, BASED ON DIANETIC ELASTOMER AND OF A TITANIUM OXIDE OF REINFORCEMENT Description of the Invention The present invention relates to compositions of diene rubbers which can be used for the manufacture of tires or semi-finished products for tires, in particular of treads of these tires, as well as reinforcement loads capable of reinforcing such compositions. of rubber. In order to reduce fuel consumption and harmful emissions from motor vehicles, significant efforts have been made by tire designers in order to obtain tires that exhibit both very low rolling resistance and improved grip. in dry soil as in wet soil and a very good resistance to wear. Thus, numerous solutions have been proposed to lower the rolling resistance and improve the grip of the tires, but these generally result in a very significant loss of wear resistance. It is well known in particular Ref: 126829 that the incorporation of conventional white fillers, such as, for example, conventional silicas or aluminas, chalk, talcum, titanium oxides, clays such as bentonite or kaolin, for example, in the rubber compositions used for the manufacture of tires and in particular of treads, are certainly translated by a reduction of rolling resistance and by an improvement of the adhesion on wet, snow-covered or ice-covered ground, but also by an unacceptable loss of the wear resistance linked to the fact that these conventional white fillers do not have sufficient reinforcing capacity against such rubber compositions; for this reason, these white charges of non-reinforcing charges, called still inert charges, are generally qualified. An effective solution to this problem has been described in the patent application EP-A-0 501 227 disclosing a diene rubber composition reinforced with a particular precipitated silica (Si02), which makes it possible to manufacture a tire that has a rolling resistance. Improved, without affecting the other properties in particular those of adhesion, durability and wear resistance. European patent application EP-A-0 810 258 discloses a composition of dienic rubber reinforced with another particular white filler, in the presence of an alumina (A1203) specific of high dispersibility, which also allows obtaining tires or of treads that have such an excellent compromise of contradictory properties. Thanks to these new white loads qualified as reinforcers, it was also possible to consider the marketing of colored tires, in particular of colored treads, which for aesthetic reasons correspond to a real expectation of users, particularly in the vehicle domain. of tourism, all that can offer users a substantial fuel economy. The applications O99 / 02590 and WO99 / 06480 describe in particular the colored rubber compositions, based on silicas or reinforcing aluminas, used for the manufacture of tires containing treads or flanks of different colors. As complementary white fillers, one or more inert (i.e., non-reinforcing) fillers having the function of a pigment or a pastelizing agent, such as, in particular, kaolin, talcum, titanium oxide, were used in these compositions. Among these inert fillers, titanium oxides, in particular, have long been known as white pigments in different matrices such as paints, inks, cosmetics, plastics and polymers, included in the rubber compositions intended in particular for incorporation into the tire sidewalls (see for example CA-A-2054059, CA-A-2058901, CA-A-2228692, GB-A-836716, EP-A-697432, applications JP 1991/006247, JP 1995/149950, JP 1996/059894). In addition to their properties of pigmenting agent or pastelization, the titanium oxides have the advantage of having effective anti-UV properties, particularly favorable in the anti-aging protection of the colored rubber compositions.; these compositions are normally devoid of carbon black (in addition to excellent U.V. absorber), they are in fact very sensitive to the degradative action of sunlight (see WO99 / 02590 and WO99 / 06480 above); in addition, they can not be protected by antioxidant agents (paraphenylenediamine type) conventionally used in black tires, because of the staining effect of these antioxidants. Now, the Applicant has discovered in its investigations that there are particular titanium oxides which, in the rubber compositions for tires, can be used not only as an anti-aging or pigmentation agent, but also and above all, and that is what is required. considers the contribution of the invention, as a real reinforcement load capable of replacing conventional carbon blacks. These titanium oxides thus represent, unexpectedly, an advantageous alternative in the use of reinforcing silicas or aluminas, in particular in colored rubber compositions where a single white charge can thus replace several of these, which simplifies in particular the processes. Accordingly, a first objective of the invention relates to a rubber composition usable for the manufacture of tires, which contains at least (i) a diene elastomer, (ii) a white charge as reinforcement load r and (iii) a coupling agent (white filler / elastomer) that ensures the union between the reinforcement carf Ia and the elastomer, this composition is characterized in that the white filler is constituted all or in part of a titanium oxide having the following characteristics: - ( a) contains more than 0.5% by mass of a metallic element different from titanium, chosen from the group consisting of Al, Fe, Si, Zr or a mixture of these elements; - (b) its specific surface BET is between 20 and 200 m2 / g; - (c) its average (mass) particle size, denoted dw, is between 20 and 400 nm; - (d) its rate of deagglomeration, denoted a, measured in the so-called deagglomeration test with ultrasound, at 100% power of an ultrasound probe of 600, is greater than 2.10"2 μm" Vs. The state of the art does not describe or suggest in any way the use in rubber composition for tire of a titanium oxide such as the above, hereinafter referred to as "reinforcing titanium oxide", capable, without other means than that of a coupling agent (white charge / elastomer) intermediary, of reinforcing only the rubber compositions usable for the manufacture of tires, in particular of treads of such tires and which therefore have a high resistance to wear. For example, it will be reported the indication of the aforementioned CA-A-2054059, CA-A-2058901 or CA-A-2228692 requests which, on the contrary, highlight the non-strengthening character of the titanium oxides and the need to add a reinforcing filler of the black smoke or silica type to give a minimum level of reinforcement to the rubber compositions described. Another object of the invention is the use of a rubber composition according to the invention for the manufacture of rubber articles, in particular of tires or semi-finished rubber products intended for these tires, these semi-finished articles are In particular, they choose from the group consisting of the treads, the substrates intended for example to be placed below these treads, the upper layers, the sidewalls, the frame layers, the heels, the protectors, the air chambers or the inner tires stopped for tubeless tires. The composition according to the invention is particularly adapted to the manufacture of sidewalls or tire treads intended to equip passenger cars, trucks, 4x4 vehicles, two wheels and heavyweight, airplanes, civil engineering machines, agricultural machinery, or of maintenance, these treads can then be used in the manufacture of new tires or for the retreading of used tires. The invention also aims at these tires and these semi-finished rubber products, when they contain a rubber composition according to the invention. Another object of the invention is the use as reinforcing filler, in a diene rubber composition usable for the manufacture of tires, of a reinforcing titanium oxide. The invention also aims at a process for reinforcing a diene rubber composition usable for the manufacture of tires, this process is characterized in that a titanium reinforcing oxide is incorporated in this crude state, by thermo-mechanical mixing. The composition of the invention is used in particular for the manufacture of colored tires or colored semi-finished articles such as treads or flanks. By compositions of rubber, tires or rubber articles of "colored" or "colored", it is understood in the present description compositions, tires or rubber articles in which at least a part is of a color different from conventional black, in which is understood a white color. The invention, as well as its advantages, will be easily understood in the light of the description and the following examples of embodiment, as well as of figures 1 to 5 relating to these examples, which represent: a device scheme suitable for measuring speed of deagglomeration with ultrasound (a) of a load that occurs in the form of agglomerates (Fig. 1); - curves of evolution of the size of the agglomerates in the course of a sonication with the help of the device of figure 1, for the loads according to the invention or not, curves from which the deagglomeration rates are determined (fig. 2 and Fig. 3); - modulus curves according to the elongation for different diene rubber compositions, according to the invention or not (Figure 4 and Figure 5).

I. MEASURES AND TESTS USED 1-1. Characterization of the reinforcing fillers The fillers described below consist in known manner of agglomerates of particles susceptible to deagglomerate in these particles under the effect of an external force, for example under the action of mechanical or ultrasound work. The term "particle" used in the present application must be understood in its usual generic sense of aggregate, and not in that of the eventual elementary particle that can form, if necessary, a part of this aggregate; by "aggregate", the indivisible set (i.e., which can not be cut, divided, split) must be understood in a known manner, which is then produced by the synthesis of the charge, generally composed of elementary particles aggregated between them. These charges are characterized as indicated below. a) BET specific surface: The BET specific surface is determined in a known manner, according to the Brunauer-Emmet-Teller method described in "The Journal of the Ameri can Soci ety" Vol. 60, page 309, February 1938 and which corresponds to standard AFNOR-NF-T 45 007 (November 1987). b) average particle size d ": The average (mass) size of the particles, denoted dw, is measured in a classical manner after the dispersion, by deagglomeration with ultrasound, of the load to be analyzed in an aqueous solution of 0.6% by weight sodium hexametaphosphate. The measurement is made by means of a centrifuge sedimentation meter with X-ray detection type "XDC" ("X-rays Disk Centrifuge"), marketed by Brookhaven Instruments, according to the operation mode that follows. A suspension of 0.8 g of sample of the load to be analyzed is made in 40 ml of water, which contains as surfactant 6 g / l of sodium hexametaphosphate, per action for 8 minutes, at 60% power (60% of the maximum position of the "control of output", in English: ou tpu t con trol "), of a 1500 W ultrasound probe (Vibracell 3/4 inch sonicator marketed by the company Bioblock); after sonication, 15 ml of the suspension is introduced into the rotation disc; after sedimentation for 120 minutes, the mass distribution of the particle sizes and the average mass size of the dw particles are calculated by the programming element of the sedimentation meter "XDC" (dw =? (n¿d¿ 5) / S (nor d) with nx number of objects of the size or diameter class d ±). c) speed of deconsolidation a: The deagglomeration speed denoted OI was measured in the test called "deagglomeration test with ultrasound", at 100% power of a 600 W (watts) probe. This test allows continuous measurement of the evolution of the average size (in volume) of the particle agglomerates during sonication, according to the following indications. The assembly used consists of a laser granule meter (type "Mastersizer S", marketed by Malvern Instruments - He-Ne laser source that emits red, wavelength 632.8 nm) and its preparer ("Malvern Small Sample" Unit MSX1") / between which a continuous flow treatment cell (Bioblock M72410) equipped with an ultrasound probe (Vibracell® 600-inch type Sonicator sold by the company Bioblock) has been interposed. A small amount (40 mg) of the charge to be analyzed is introduced into the preparator with 160 ml of an aqueous solution containing 0.5 g / l of sodium hexametaphosphate., the speed of circulation is fixed at its maximum. At least three consecutive measurements are made to determine according to the known calculation method of Fraunhofer (Malvern calculation matrix 3 $$ D) the average initial diameter (in volume) of the agglomerates, denoted dv [0]. The sonication is established immediately at a power of 100% (either 100% of the maximum position of "tip amplitude") and the evolution of the average diameter in volume dv [t] as a function of time is followed for approximately 8 minutes "t "at a rate of one measurement every 10 seconds approximately. After a period of induction (approximately 3-4 minutes), it is observed that the inverse of the average diameter in volume l / dv [t] varies linearly, or in a substantially linear manner, with time "t" (stable regime of deagglomeration ). The rate of deagglomeration a is calculated by linear regression of the evolution curve of l / dv [t] as a function of time "t", in the zone of stable regime of deagglomeration (in general, between approximately 4 and 8 minutes) . It is expressed in μrrrVs. Figure 1 schematizes the measuring device used to perform this deagglomeration test with ultrasound. This device consists of a closed circuit 1 in which a flow 2 of particle agglomerates in suspension in a liquid 3 can circulate. This device essentially comprises a sample prepper 10, a laser granule meter 20 and a treatment cell 30. Positioned at atmospheric pressure (13, 33), at the level of the sample prepper 10 and of the treatment cell 30, allows the continuous removal of air bubbles that are formed during sonication (ie the action of the ultrasound). The sample preparation 10 ("Malvern Small Sample Unit MSXl") is intended to receive the sample of the load to be tested (in suspension in the liquid 3) and to circulate it through the circuit 1 at the pre-regulated speed (potentiometer 17 - maximum speed of about 3 l / min), in the form of a flow 2 of liquid suspension. This preparer 10 consists simply of a reception tank containing, and through which circulates, the suspension to be analyzed. It is equipped with a stirring motor 15, capable of modulating speed, in order to avoid sedimentation of particle agglomerates of the suspension; a centrifugal mini-pump 16 is intended to ensure the circulation of the suspension 2 in circuit 1; the inlet 11 of the preparer 10 meets with the open air via an opening 13 intended to receive the sample of load to be tested and / or the liquid 3 used for the suspension. A laser granule meter 20 ("Mastersizer S") is connected to the preparer 10 in which the function is to continuously measure, at regular time intervals, the average volume size "dw" of the agglomerates, in the step of flow 2, thanks to a measuring cell 23 in which automatic recording and calculation means of the granule meter 20 are coupled. It is briefly recalled here that the laser granule meters exploit, in a known manner, the principle of diffraction of light by solid objects suspended in a medium in which the refractive index is different from that of the solid. According to Fraunhofer's theory, there is a relation between the size of the object and the angle of diffraction of light (the smaller the object, the higher the diffraction angle). Practically, it is enough to measure the amount of light diffracted by different diffraction angles in order to determine the size distribution (in volume) of the sample, which corresponds to the average size in volume of this distribution (dv = S (nL d) / S (nA dj.3) with nx number of objects of the size or diameter class dx). Interspersed between the preparer 10 and the laser granule meter 20 is located at the end of a treatment cell 30 equipped with an ultrasound probe 35 (converter 34 and probe head 36) intended to continuously break up the agglomerates of particles in the passage of the flow 2. The treatment cell 30 is arranged between the outlet 22 of the granule meter 20 and the inlet 11 of the preparer 10, such that, in operation, the flow 2 of particles exiting the preparer 10 traverse first the laser pellet meter 20 before entering the treatment cell 30. This arrangement has two main advantages for the measurements: on the one hand, the air bubbles due to the action of the ultrasound probe are eliminated when passing through the preparer 10 (which is outdoors), that is to say before the entrance of the granule meter 20, and thus do not disturb the measurement of the laser diffraction; on the other hand, the homogeneity of the suspension is improved by a previous step in the preparer 10. The treatment cell 30 is arranged in such a way that the particle flow 2 penetrating there, through an inlet 31, passes first in front of the head 36 of the ultrasound probe 35; this unconventional arrangement (the flow 2 enters the lower part 31 of the cell, and not the upper part 32) has the following advantages: on the one hand, the whole circulating suspension 2 is forced to pass in front of the end 36 of the ultrasound probe 35, the most active zone in terms of deagglomeration; on the other hand, this arrangement allows a first degassing after sonication in the body of the treatment cell 30, the surface of the suspension 2 is then brought into contact with the atmosphere by means of a tube 33 of small diameter. The flow 2 is preferably thermostatic by the intermediary of a cooling circuit 40 arranged, at the level of the cell 3, in a double envelope surrounding the probe 35, the temperature being controlled for example with a temperature probe 14 which is submerged in the liquid 3 at the level of the preparer 10. The arrangement of different elements of the measuring device is optimized so as to limit as much as possible the circulating volume, ie the length of the connecting tubes (for example of the flexible tubes ). 1-2. Characterization of rubber compositions The rubber compositions are characterized, before and after curing, as indicated below. a) Mooney plasticity: A consistency meter is used that oscillates as described by the AFNOR-NFT-43005 standard (November 1980). The measurement of Mooney plasticity is made according to the following principle: the composition in the raw state is milled in a cylindrical vessel heated to 100 ° C. After one minute of preheating, the rotor rotates inside the test tube at 2 turns / minute and the useful torque is measured to maintain this movement after 4 minutes of rotation. The Mooney plasticity (MS 1 + 4) is expressed in "Mooney units" (UM) with 1 MU = 0.83 N.m (Newton.metro). b) tensile tests: These tests allow determining the limits of elasticity and the properties at break. They are carried out, except for different indications, according to the AFNOR-NFT-46002 standard (September 1988). The drying modules are measured at 10% elongation (MIO), 100% elongation (M100) and 300% elongation (M300); these modules are calculated and carried to the actual section of the test tube and, unless otherwise indicated, they are measured in the second elongation (i.e. after a preparation cycle). All these traction measurements are carried out under normal conditions of temperature and humidity according to the standard ÁFNOR-NFT-40101 (December 1979). A treatment of traction records also allows tracing the curve of the module as a function of elongation (see figure 4 attached), the module used here is the secant modulus measured in the first elongation (ie without preparation cycle), calculated it is taken to the Real section of the test tube. c) hysteretic losses: Hysteretic losses (PH) are measured by bouncing at 60 ° C at the 6th shock, and are expressed in% according to the following relationship: PH. { %) = 100 [(W0 - W / 0], with W0: power supplied, Wx: power restored.

II. CONDITIONS FOR CARRYING OUT THE INVENTION In addition to the usual additives or those that can be used in a rubber composition capable of crosslinking with sulfur and usable for the manufacture of tires, the compositions according to the invention contain, as basic constituents, (i) ) at least one diene elastomer, (ii) at least one white reinforcing filler and (iii) at least one coupling agent between the filler and the elastomer, the reinforcing filler is all or part of a titanium oxide of reinforcement, as described in detail below.

II-l. Diene elastomer By "elastomeric" rubber or elastomer, it is understood in a known manner that an elastomer exits at least in part (i.e. a homopolymer or a copolymer) of diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not). Generally, here by "essentially unsaturated" diene elastomer is meant a diene elastomer derived at least in part from conjugated diene monomers, which have a rate of radicals or units of diene origin (conjugated dienes) which is greater than 15% ( % in mol). 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 described in particular as "essentially saturated" diene elastomers (radical rate). of low or very low dienic origin, always lower than 15%). In the category of "essentially unsaturated" diene elastomers, it is understood in particular by "strongly unsaturated" diene elastomer a diene elastomer having a rate of radicals of diene origin (conjugated dienes) which is greater than 50%. Of these definitions that are given, it is understood in particular by diene elastomer capable of being used in the compositions according to the invention: (a) - any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; (b) - any copolymer obtained by copolymerization of one or more dienes conjugated to one another or to one or more aromatic vinyl compounds having from 8 to 20 carbon atoms; (c) - any ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having from 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, such as, for example, the elastomers obtained from ethylene, from propylene with a non-conjugated diene monomer of the aforesaid type, such as, in particular, hexadiene-1,4, ethylidene norbornene, dicyclopentadiene; (d) - all copolymer of isobutene and isoprene (butyl rubber), as well as halogenated, in particular chlorinated or brominated, versions of this type of copolymer. Although it is applied to all types of diene elastomer, it will be understood by the person skilled in the art that the present invention, in particular when the rubber composition is intended for a tire tread, is primarily used with the diene elastomers essentially unsaturated, in particular of type (a) or (b) above. Suitable conjugated dienes are, in particular, butadiene-1, 3, 2-methyl-1,3-butadiene, 2,3-di (C1 to C5 alkyl) -1, 3-butadienes, such as 2, 3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-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-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene. . The copolymers can contain between 99% and 20% by weight of diene units and from 1% to 80% by weight of vinylaromatic units. The elastomers can have all the microstructure that is a function of the polymerization conditions used, in particular of the presence or not of a modifying and / or randomizing agent and of the amounts of modifying and / or randomizing agent employed. The elastomers can be, for example, blocks, statistics, sequences, microsequences and can be prepared in dispersion or in solution; they can be coupled and / or form a star or even be functionalized with a coupling agent and / or star or functionalization agent. Preferred are polybutadienes and in particular those having a content of -1.2 units comprised between 4% and 80%, or those having a content of cis-1,4, greater than 80%, polyisoprenes, butadiene copolymers -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 ligatures -1,2 of the butadiene part comprised between 4% and 65% , a content of trans-1,4 ligatures between 20% and 80%, the butadiene-isoprene copolymers and in particular those having an isoprene content between 5% and 90% by weight and a glass transition temperature ( Tg) between -40 ° C and -80 ° C, the isoprene-styrene copolymers and in particular 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 the butadiene-styrene-isoprene copolymers, those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15%, are particularly suitable. and 60% by weight and more particularly between 20% and 50%, a butadiene content comprised between 5% and 50% by weight and more particularly comprised between 20% and 40%, a content of units -1.2 of the part butadiene comprised between 4% and 85%, a content of trans-1,4 units of the butadiene portion comprised between 6% and 80%, a content of units -1,2 plus -3,4 of the isoprene part comprised between 5 and % and 70% and a content of trans-1 units, 4 of the isoprene part comprised between 10% and 50%, and more generally all butadiene-styrene-isoprene copolymer having a Tg comprised between -20 ° C and -70 ° C. According to a preferred embodiment of the invention, the diene elastomer of the composition according to the invention is selected from the group of strongly unsaturated diene elastomers consisting of polybutadienes (BR), polyisoprene (IR) or natural rubber. (NR), the butadiene-styrene copolymers (SBR), the butadiene-isoprene copolymers (BIR), the butadiene-acrylonitrile copolymers (NBR), the isoprene-styrene copolymers (SIR), the butadiene-styrene copolymers -isoprene (SBIR) or a mixture of two or more of these compounds.

When the composition according to the invention is intended for a tire tread, the diene elastomer is preferably a butadiene-styrene copolymer prepared in solution having a styrene content between 20% and 30% by weight, content of vinyl bonds of the butadiene part between 15% and 65%, a content of trans-1,4 bonds between 20% and 75% and a glass transition temperature between -20 ° C and -55 ° C, this butadiene-styrene copolymer is optionally used in admixture with a polybutadiene which preferably has more than 90% cis-1,4 bonds.

According to another advantageous embodiment of the invention, in particular when it is intended for a tire, the composition according to the invention can contain at least one essentially saturated diene elastomer, in particular at least one EPDM copolymer, either whether or not this copolymer is used, for example, in admixture with one or more of the strongly unsaturated diene elastomers mentioned above. Of course, the compositions of the invention may contain a single diene elastomer or a mixture of several diene elastomers, the diene elastomer (s) may be used in association with all types of synthetic elastomer different from the diene, even with different elastomer polymers, by example, thermoplastic polymers.

II-2. Reinforcing charge In the present application, white charge of "reinforcement" is understood as a white charge (ie inorganic, in particular mineral, sometimes also called clear charge), capable of reinforcing by itself, without any other means than an agent of intermediate coupling, a rubber composition intended for the manufacture of tires, in other words capable of replacing a conventional load of pneumatic-grade carbon black in its reinforcing function. The composition according to the invention is reinforced by a white reinforcing filler consisting wholly or in part of a reinforcing titanium oxide, that is to say having the following characteristics: - (a) it contains more than 0.5% by mass of an element metallic different from titanium, chosen from the group consisting of Al, Fe, Si, Zr or a mixture of two or more of these elements; - (b) its specific surface BET is between 20 and 200 m2 / g; - (c) its average (mass) particle size, denoted dw, is between 20 and 400 nm; - (d) its rate of deagglomeration, denoted by, measured in the so-called deagglomeration test with ultrasound, at 100% power of a 600W ultrasound probe, is greater than 2.10"2 μm_1 / s. is meant any compound that responds to the known formula of Ti02 as well as its optional hydrated forms, regardless of the crystalline form of this titanium oxide (for example rutile, anatase or mixture of two crystalline varieties). , in combination, all characteristics (a) to (d) above.An essential feature of this titanium oxide reinforcement is that it combines with at least one metal element specifically denoted "dopant", in other words, its reinforcing function it is activated, it is increased by the presence of this doping element By "combined" titanium oxide is meant in the present application a titanium oxide in which the particles contain, on the surface and / or in its mass, more than 0.5% by mass of a metallic element different from Ti chosen from the group consisting of Al, Fe, Zr or a mixture of two or more of these elements, this metallic doping element can be integrated into the structure or Crystal mesh of titanium oxide, or be fixed, deposited in an adherent layer to the surface of its particles. In other words, the reinforcing titanium oxide particles may contain the doping metal element within its structure or only be coated, at least in part, with the latter. The mass% indicated is the content of the metallic element (atom) determined in a known manner by elemental chemical analysis. Below the indicated minimum rate of 0.5%, titanium oxide behaves as a non-combined product and shows significantly lower reinforcing functions; thus, the rate of metallic doping element in the reinforcing titanium oxide (% by mass of reinforcing titanium oxide) is preferably chosen to be greater than 1%. The maximum rate, according to the nature of the doping element, can reach values as high as 10% to 15%, even more. Of course, the person skilled in the art will easily understand that if the metallic doping element is not distributed substantially uniformly in the mass of the reinforcing titanium oxide, then it must be present at least on the surface and / or on the periphery of its particles . It is generally known that in order to obtain the optimal reinforcing properties conferred by a filler, it is particularly desirable that the latter be present in the rubber matrix in a final form which is both as finely divided as possible and distributed in the same way as more homogeneous as possible. However, such conditions can only be carried out insofar as the load has a very good capacity, on the one hand when it is going to be incorporated in the matrix of the mixture with the elastomer and on the other hand when it is going to de-agglomerate. order to disperse homogeneously in this matrix. The intrinsic dispersibility of a charge can be evaluated with the help of the deagglomeration test with ultrasound described in chapter I above, by measuring its deagglomeration speed. It was found that for an OI speed higher than 2.10"2 μprVs, the titanium oxide exhibits a good dispersibility, that is to say that few micronic agglomerates were observed by reflection in optical microscopy in a cut of the rubber composition prepared according to the rules For an even better dispersion of the titanium oxide reinforcement in the diene rubber matrix, and therefore for optimum reinforcement, it is preferred that the deagglomeration speed OI be greater than 5.10"2 μm_1 / s. For a BET surface of less than 20 m2 / g, the compositions have a facilitated use and a reduced hysteresis, but there is a loss of breaking properties and a decreasing wear resistance in the tire; for BET surfaces greater than 200 m2 / g, the use in the raw state becomes more difficult (higher Mooney plasticity) and the dispersion of the load is degraded. For very high dw sizes, greater than 400 nm, the particles behave as defects that localize the constrictions and are detrimental to wear; very small dw sizes, less than 20 nm, on the contrary will penalize the use in raw state and the dispersion of the load in the course of this use. For all the reasons discussed above, the BET surface is preferably comprised in a domain ranging from 30 to 150 m2 / g and the particle size dw is preferably comprised in a domain ranging from 30 to 200 nm. Even more preferably, in particular when the compositions of the invention are intended for tire treads which have low rolling resistance, the titanium reinforcing oxides verify at least one of the following characteristics, preferably both: BET comprised in a domain of 70 to 140 m2 / g; - dw particle size comprised in a 50 to 100 nm domain. The reinforcing titanium oxide particles also have a sufficient surface reactivity, i.e. a sufficient rate of surface hydroxyl functions (-0H) reactive with the coupling agent, which is particularly favorable to the reinforcing function performed by the load, and therefore with mechanical properties of the rubber compositions of the invention. Of course, the physical state under which the reinforcing titanium oxide may be present is indifferent, whether in the form of a powder, microbeads, granules, particles, pellets or any other densified form. The titanium reinforcing oxide described above can be used alone or associated with one or more reinforcing fillers, for example a second white filler such as a silica or reinforcing alumina. In the case of a silica, a highly dispersible precipitated silica is preferably used, in particular when the invention is used for the manufacture of tires that have low rolling resistance; as non-limiting examples of such preferred highly dispersible silicas, mention may be made of the silicas BV3380 and Utrasil 7000 of the company Degussa, the silicas Zeosil 1165MP and 1115MP of the company Rhdne Poulenc, the silica Hi-Sil 2000 of the company PPG, the silicas Zeopol 8715 or 8745 of the Huber Society. If a reinforcing alumina is used, it is preferably a highly dispersible alumina such as that described in the aforementioned EP-A-0 810 258, for example the aluminas A125 or CR125 (Ba? Kowski company), APA-100RDX ( Condéa society), Aluminoxid C (Degussa company) or AKP-G015 (Sumitomo Chemicals). The titanium oxide, alone or optionally associated with a second white charge, can also be used in mixing, i.e. in mixture, with one or several conventional pneumatic-grade carbon blacks. All the carbon blacks are suitable as carbon blacks, in particular blacks of the type HAF, ISAF, SAF, conventionally used in tires and particularly in tire treads. As non-limiting examples of such blacks, mention may be made of blacks N115, N134, N234, N339, N347, N375. The amount of carbon black present in the total reinforcing filler can vary over large limits, this amount is however preferably less than the amount of reinforcing white filler present in the rubber composition. Preferably, in the compositions according to the invention, the titanium oxide of reinforcement constitutes the majority, i.e. more than 50% by weight, of the total reinforcement load; it can advantageously constitute the entire reinforcing load. Preferably, the total reinforcing fillers in the compositions of the invention are comprised in a domain ranging from 20 to 400 pee, more preferably from 30 to 200 pee, the optimum is different according to the indicated applications: known, the level of expected reinforcement in a bicycle tire, for example, is clearly lower than that required in a tire for a passenger car or for a utility vehicle such as a heavyweight. Even more preferably, in particular when the compositions of the invention are intended for the tire treads, the reinforcing white charge rate is chosen between 50 and 150 pee. The metallic doping element, chosen from the group consisting of Al (aluminum), Fe (iron), Si (silicon), Zr (zirconium) or consisting of a mixture of two or more of these elements, is preferably Al (aluminum) and / or Si (silicon). As examples of reinforcing titanium oxides which are suitable for the rubber compositions of the invention, mention may be made of titanium oxides marketed as anti-UV agents, for varnish or paints, by the company Sachtleben Chemie, under the trade names Hombitec RM300 and RM400 (approximately 88% and 78% by weight of rutile Ti02, respectively). Titanium oxide Hombitec RM400 is particularly preferred, in particular because of its combined BET surface characteristics, average dw particle size as well as agglomeration speed a. This compound was developed especially (technical documentation of the supplier) for the anti-UV protection of wood (incorporated in the varnish or paints for wood); its elemental chemical analysis reveals that it contains (% by weight of reinforcing titanium oxide) as metallic doping elements of aluminum (approximately 14.3% of the Al element) and of iron (approximately 5.3% of the Fe element).

II-3. Coupling agent It is well known to the person skilled in the art that it is necessary to use, for a reinforcing white filler such as for example a silica or a reinforcing alumina, a coupling agent (white filler / elastomer), also referred to as a filler agent. link, whose function is to ensure the link (or "coupling") between the white charge and the elastomer, all that facilitates the dispersion of this white charge within the elastomeric matrix. The titanium reinforcing oxide described above also requires the use of such a coupling agent to fully ensure its reinforcing filler function in the rubber compositions according to the invention. By "coupling" agent (filler / elastomer), it is understood more precisely an agent able to establish a sufficient connection, chemical and / or physical, between the considered load and the elastomer, all that facilitates the dispersion of this load in the bosom of the elastomeric matrix; such a coupling agent, at least bifunctional, has for example as a simplified general formula "YTX", in which: - Y represents a functional group ("Y" function) that is capable of physically and / or chemically binding to the white charge , such a linkage can be stable, for example, between a silicon atom of the coupling agent and the hydroxyl groups (OH) on the surface of the filler (for example the silanols on the surface when treated with silica); - X represents a functional group (function "X") capable of physically and / or chemically bonding to the elastomer, for example by means of a sulfur atom; - T represents a hydrocarbon group that allows joining Y and X. Coupling agents should not be confused with simple coating agents of the charge in question which, in a known manner, can contain the active Y function in relation to the charge but are devoid of the active X function vis-à-vis the elastomer. Such coupling agents, of variable efficiency, are described in a very large number of documents and are well known to the person skilled in the art. In fact, any coupling agent known to be capable of effectively securing, in the diene rubber compositions useful for the manufacture of tires, the bond or coupling between silica and diene elastomer, such as, for example, organosilanes, in particular those alkoxysilanes polysulfides or mercaptosilanes, or the polyorganosiloxanes bearing X and Y functions mentioned. Particularly used are the polysulphurized alkoxysilanes as described, for example, in US-A-3 842 111, US-A-3 873 489, US-A-3 978 103, US-A-3 997 581, US Pat. A-4 002 594, or in the most recent patents US-A-5 580 919, US-A-5 583 245, US-A-5 663 396, US-A-5 684 171, US-A-5 684 172, US-A-5 696 197, which describe in detail such known compounds. They agree in particular for the use of the invention, without the limiting definition being limiting, the polysulphurized alkoxysilanes referred to as "symmetrical" which correspond to the following general formula (I): (I) Z - A - Sn - A - Z, in the one: - n is an integer from 2 to 8 (preferably from 2 to 5); - A is a divalent hydrocarbon radical (preferably alkylene groups of Cx-Cxo or arylene groups of C6-C1Z, more particularly C-C ^ alkylene, in particular of C2-C4, in particular propylene); - Z responds to one of the following formulas: R1 R1 R2 -R1 -Si-R2 -Si-R2 R2 i R2 i R2 in which: - the radicals R1, substituted or unsubstituted, identical or different from each other, represent an alkyl group of Cj-Cia, cycloalkyl of C5 -C18 or C6-C18 aryl (preferably the C?-C6 alkyl, cyclohexyl or phenyl groups, in particular the C?-C 4 alkyl groups, more particularly the methyl and / or the ethyl). - the radicals R 2, substituted or unsubstituted, identical or different from each other, represent an alkoxyl group of Cx-Cxg, C3-C18 cycloalkoxy (preferably Cx-Cxg or C5-C8 cycloalkoxy groups), more particularly methoxy and / or ethoxy). In the case of a mixture of polysulfurized alkoxysilanes corresponding to the above formula (I), in particular the usual commercially available mixtures, it will be understood that the average value of the "n" is a fractional number, preferably comprised between 2 and 5. As polysulfurized alkoxysilanes, mention may be made more particularly of the polysulphides (in particular the disulphides or tetrasulfides) of bis (C 1 -C 4 alkoxy) -silylpropyl), in particular of bis (trialkoxyl (C 4 -C 4) -silylpropyl), in in particular the bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides. Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated TESPT, of formula [(C2H50) 3Si (CH2) 3S2] 2 or the bis (triethoxysilylpropyl) disulfide, abbreviated TESPD, of formula [3] is preferably used. (C2H50) 3Si (CH2) 3S] 2. The TESPD is marketed, for example, by the company Degussa under the names Si266 or Si75 (in the second case, in the form of a mixture of disulphide (at 75% by weight) and polysulfides), or also by the Witco company under the name Silquest A1589. The TESPT is marketed, for example, by the company Degussa under the name Si69 (or X50S when 50% by weight of carbon black is supported), or also by the company Witco under the name Silquest A1289 (in both cases, the mixture commercial polysulfides with an average value so that n is close to 4). The person skilled in the art will know how to adjust the content of the coupling agent in the compositions of the invention, depending on the application indicated, on the nature of the elastomer used and on the amount of titanium oxide reinforcing, if necessary if necessary. any white load used as a complementary reinforcement load. In order to take into account the differences in specific surface area and density of the white reinforcing fillers that can be used, as well as the molar masses of the coupling agents, it is preferable to determine the optimum rate of coupling agent in moles per square meter. of white reinforcement load, for each white load used; this optimum rate is calculated from the weighting report [coupling agent / white reinforcement load], the BET surface of the load and the molar mass of the coupling agent (denoted after M), according to the following relationship: (moles / m2 of white charge) = [coupling agent / white charge] (1 / BET) (1 / M) Preferably, the amount of coupling agent used in the compositions according to the invention is comprised between 10 ~ 7 and 10"5 moles per square meter of total reinforcing white filler, which is per square meter of titanium oxide reinforcing when the latter constitutes the only white reinforcing filler present Even more preferably, the amount of coupling agent is comprised between 5.10"7 and 5.10" 6 moles per square meter of total reinforcing white filler, taking into account the amounts expressed above, In general, the coupling agent rate, carried to the weight of the diene elastomer, will preferably be between 1 and 20 pee, more preferably between 3 and 15 pee, Of course, the coupling agent used could be pre-inserted ( via the "X" function) in the diene elastomer of the composition of the invention, the elastomer thus functionalized or "pre-coupled" contains the free "Y" anointing for titanium oxide reinforcement. The coupling agent could also be pre-inserted (via the "Y" function) into the titanium reinforcing oxide, the charge "pre-coupled" can then be linked to the diene elastomer by means of the free functions "X". However, it is preferred to use the coupling agent in the free state (ie, not inserted) or inserted into the reinforcing titanium oxide, in particular for the reasons of best use ("processabili ty", "susceptible to be processed") of the compositions in the raw state.

II-4. Miscellaneous additives Of course, the compositions according to the invention contain, in addition to the compounds already described, all or part of the constituents used in the diene rubber compositions intended for the manufacture of tires, such as, for example, plasticizers, pigments, of protection agents of the antioxidant, antiozonant type, a cross-linking system based on either sulfur, either sulfur and / or peroxide and / or bismaleimide donors, vulcanization accelerators, vulcanization activators, oils extension, etc. The white reinforcing filler of the invention can also be combined, if necessary, with a conventional non-reinforcing white filler, such as clays, bentonite, talc, chalk, kaolin, up to conventional titanium oxides which fulfill a function known as pigmentation agent or anti-UV protection. For the production of colored rubber compositions, any type of coloring agent known to the person skilled in the art can also 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. Organic pigments such as indantrones, diketo-pyrrolo-pyrroles or diazo condensates, organometallic pigments such as phthalocyanines may also be mentioned. The color of the compositions according to the invention can also vary in a very large range, as an example in different inks of red, orange, green, yellow, blue or even brown or gray. You can not use coloring agent, and choose to keep the original color of the reinforcement load, whether it is white or has been pre-colored. For the anti-aging protection of the colored rubber compositions according to the invention, protection systems such as those described in the aforementioned WO99 / 02590 and WO99 / 06480 can be advantageously used. The rubber compositions according to the invention can also contain, in addition to the aforementioned coupling agents, coating agents (containing, for example, the only Y function) of the reinforcing white filler or more generally susceptible agents that help the employment in a known way, thanks to an improvement in the dispersion of the white filler in the rubber matrix and to a decrease in the viscosity of the compositions, they improve their ability to be used in the raw state, these agents for example the alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines of hydroxylated or hydrolyzable polyorganosiloxanes, for example,? -dihydroxy-polyorganosiloxanes (in particular?,? -dihydroxy-polydimethylsiloxanes).

II-5. Preparation of the compositions The rubber compositions are prepared using the diene elastomers according to all techniques known to the person skilled in the art, for example by one or two stage thermomechanical work in an internal mixer with blades, followed by mixing in a mixer. external during which the vulcanization system (crosslinking) is incorporated, as described for example in the aforementioned EP-A-0 501 227. According to a classical process in one stage, for example, all the necessary constituents are introduced in a conventional internal mixer with the exception of the vulcanization system; When the bulk density of the charge is low, it may be preferable to fractionate its introduction of several parts. The result of this first mixing step is then continued in an external mixer, in general a cylinder mixer, and then the vulcanization system is added thereto. A second stage can be added in the internal mixer, essentially with the aim of subjecting the mixture to a complementary thermo-mechanical treatment. It is evident that the invention relates to the compositions described above both in the crude state (i.e., before curing) and in the cured state (i.e., after cross-linking or vulcanization). Of course, the compositions according to the invention can be used alone or mixed with any rubber composition useful for the manufacture of tires.

III. EXAMPLES OF EMBODIMENT OF THE INVENTION III-1. Charges used The characteristics of the charges used in the following examples are summarized in Table 1. The denoted charges and D are the reinforcing titanium oxides (Hombitec RM400 and RM300, respectively) chosen for the compositions according to the invention. The filler B is a conventional titanium oxide (i.e., is not reinforcing) usually used as a white pigment (Pronox RKB6 from Bayer). The load C is a pneumatic-grade carbon black (N234), conventionally used in tire treads. It is observed in particular that the loads A and D have a particle size dw much lower than that of the load B, of the same order of magnitude as that of the load C. The speed of deagglomeration of the charges A and D is very high, approximately ten and three times higher, respectively, than that of load B. The deagglomeration capacity of the carbon blacks is in a known way clearly superior to that of white loads, which explains that the measurement of the speed for the load C has no place to perform. It is further observed that the load A advantageously verifies the set of preferential characteristics that follow: - metal dopant element rate greater than 1%; - BET surface comprised in a domain of 70 to 140 m2 / g; - dw particle size comprised in a 50 to 100 nm domain; - speed of deagglomeration ce greater than 5.10"2 μpr s.

As an example, figures 2 and 3 reproduce the evolution curves [l / dv (t) = f (t)] of the size of the agglomerates, recorded in the deagglomeration test with ultrasound, respectively for loads A and B. see well in these figures 2 and 3 (see in particular Fig. 3) that the first recorded points ("t" varying from 0 to 30 s approximately) correspond to the measure of the initial average diameter dv [0], followed (after to operate the ultrasound probe) from a progressive step (here, "t" from approximately 30 to 4 minutes for load 4) to a stable deagglomeration regime during which the inverse of "dv" varies very linearly with time " t "; the data record stops here after approximately 8 minutes. It is deduced by an elementary linear regression calculation, performed by the granulometer calculator, the rate of deagglomeration at the steady state deagglomeration zone (between 4 and 8 minutes approximately). A quick comparison of Figures 2 and 3 immediately illustrates the superiority of load A.

III-2. Preparation of the compositions The compositions prepared below are prepared in a known manner, as follows: the diene elastomer is introduced into an internal mixer with a capacity of 300 ml, filled to 75% and in which the initial temperature of the cell is of approximately 90 ° C; then, after an appropriate mixing time, for example in the order of 1 minute, the other ingredients are added, in which the charge and the associated coupling agent are contained, with the exception of the vulcanization system. A thermomechanical work of a duration of approximately 10 minutes is then conducted, with an average pallet speed of 70 turns / min, until a fall temperature of approximately 160 ° C is obtained. The mixture thus obtained is recovered and then the vulcanization system (sulfur and sulfenamide type primary accelerator) is added in an external mixer (homo-terminator) at 30 ° C. The vulcanization (curing) is carried out at 150 ° C for 40 minutes.

III-3. Tests A) Test 1 Three compositions of diene rubber intended for the manufacture of tires or treads for tires, useful in particular for the manufacture of colored tires, are then compared.

The diene elastomer is an SBR (styrene-butadiene copolymer) prepared in solution and containing 25% styrene, 58% polybutadiene 1-2 radicals and 23% polybutadiene 1-4 radicals after. These three compositions are identical with the following differences: composition No. 1 (according to the invention): charge A (with coupling agent); - composition No. 2 (not according to the invention): load B (with coupling agent); - composition No. 3 (not according to the invention): load C (without coupling agent). The coupling agent TESPT (Si69) was introduced here at a rate corresponding to a surface coverage of approximately 11.6.10"7 mol / m2 of white charge (titanium oxide A or B), in which the white charge is of reinforcement (load A) or not (load B): indeed, for the needs of this comparative test, the coupling agent was also used in the control composition No. 2 which did not contain more than one conventional titanium oxide (no it is reinforcement.) In these compositions, the titanium oxides (charges A and B) are used at iso-volume with respect to the carbon black (charge C).

The composition No. 3 which serves here as a reference does not require the coupling agent as it is loaded with carbon black. Tables 2 and 3 give successively the formulation of different compositions (table 2 - rate of different products expressed in pee), their properties before and after curing at 150 ° C for 40 minutes (table 3). Figure 4 reproduces the modulus curves (in MPa) as a function of elongation (in%); these curves are indicated Cl to C3 and correspond respectively to rubber compositions No. 1 to No. 3.

The study of different results shows that the composition No. 1 presents after the curing a level of reinforcement clearly superior to that of the control composition No. 2, substantially equivalent, even higher than that of the reference composition No. 3: - effort to the rupture approximately three times higher with respect to composition No. 2, of the same order of magnitude as that of composition No. 3; - modules with strong deformations (M100 and M300) higher not only those of composition No. 2 but also those of reference composition No. 3; ratio (M300 / M100) clearly superior to that of composition No. 2, close to composition No. 3; these are clear indicators for the skilled artisan of a high quality reinforcement for the composition according to the invention; - Figure 4 annexed confirms well the previous results: it is observed that the curves Cl and C3, very close, are located very above the curve C2, the difference is that the steeper the more the elongation increases; this clearly illustrates an excellent interaction between the reinforcing titanium oxide and the elastomer in the composition No. 1, of the same level as the upper one (visible beyond 200% elongation) in which it reaches carbon black (composition No. 3), in all cases much higher than that offered by conventional titanium oxide in the composition No. 2 Compared to reference composition No. 3, the composition according to the invention has, in addition to a higher level of reinforcement, lower hysteretic losses (PH) (26% instead of 32%). The use in the raw state is also more advantageous thanks to a clearly lower level of plasticity (52 MU instead of 60 MU). As for the very low viscosity and hysteresis values of composition No. 2, of course they are explained by a very weak level of reinforcement, compared to that achieved in the composition according to the invention.

B) Test 2 The objective of this test on the one hand is to test a titanium oxide reinforcement different from that of test 1, on the other hand to demonstrate that the capacity of reinforcement or not of such white charge can only be revealed in the presence of a coupling agent capable of securing the bond between this white filler and the diene elastomer. For this, three diene rubber compositions similar to those of test 1 above, intended for the manufacture of tires or treads for tires, are compared, these three compositions are identical with the following differences: - composition No. 4 (from according to the invention): loading D, with coupling agent; - composition No. 5 (not according to the invention): loading D, without coupling agent; - composition No. 6 (not according to the invention): load D (without coupling agent). In the composition according to the invention, the coupling agent (TESPT) has been introduced at a rate corresponding to a surface cover of approximately 11.6.10"7 mol / m2 of white charge (titanium oxide D), as for the previous test 1. For the needs of this comparative test, the coupling agent in the control composition No. 5 was suppressed.As for the control composition No. 6, charged with carbon black, it is the same composition than the one used in the previous test (composition No. 3) Tables 4 and 5 give successively the formulation of different compositions (table 4 - rates of different products expressed in pee), their properties before and after curing at 150 ° C Figure 40 shows the curves of the module (in MPa) as a function of the elongation (in%), these curves were denoted C4 to C6 and correspond respectively to the compositions of rubber No. 4 and No. 6 The study of different results shows that the composition No. 4 presents after the curing a reinforcement level clearly superior to that of the control composition No. 5, substantially equivalent to that of the reference composition No. 6: - modules with strong deformations (M100) and M300) and ratio (M300 / M100) clearly superior to that of composition No. 5, very close but slightly lower than those of reference composition No. 5; - better hysteresis (much smaller PH losses) for the composition according to the invention, with respect to the control composition No. 6 charged with carbon black, as might be expected by reason of the very nature of the reinforcing filler, but also with respect to the composition No. 5 (devoid of coupling agent), the attached figure 5 confirms well the previous observations: it is observed that the curves C4 and C6, very close one to the other, are located both very above the curve 5. All these results clearly demonstrate the fact that the ability to reinforce or not a titanium oxide, as another additional white charge, can only be revealed in the presence of a coupling agent capable of ensuring the link between this white charge and the diene elastomer. It is further noted that the functions of the reinforcing load D (composition No. 4 and curve C4 of figure 5), although substantially equivalent to those of a conventional pneumatic-grade carbon black, thus satisfying all the application indicated , however, are slightly lower than those of the previous load A (composition No. 1 and curve Cl of figure 4): curve Cl located beyond curve C3, which is not the case of curve C4 compared with C6; higher values of module M100 and M300 in the case of load A. The superior performance of load A is explained by a better compromise of characteristics in terms of the specific surface area of BET, the average particle size dw and the Deagglomeration speed a. In summary, the specific titanium oxides of the compositions according to the invention confer to the latter very interesting properties: first of all, a reinforcing capacity and therefore of wear resistance for the compositions containing them, at least equal but higher than those achieved with the carbon black, hitherto unknown with the titanium oxides, conventionally used in the rubber compositions for prior art tires; - next, advantageously, an improvement in the resistance to aging and to the action of UV rays, favorable in particular to the aesthetics and to the preservation of colors in the case of colored rubber articles such as tires or colored treads. Thanks to the reinforcing and anti-UV properties of the titanium oxides described, the compositions according to the invention represent an interesting alternative of the use of reinforced rubber compositions of white fillers such as silicas or reinforcing aluminas. In particular, it is possible to consider the manufacture of tires with low rolling resistance, or of treads intended for such tires, in particular tires with colored treads, from rubber compositions loaded exclusively with titanium oxides.

Table 1 Table 2 (1) Copolymer of styrene butadiene (2) N-1, 3-dimethylbutyl N-phenylparaphenylenediamine (3) Diphenylguanidine (4) N-cyclohexy1-2-benzothiazisulfenamide Table 3 Table 4 (1) 4) idem table 1 Table 5 It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (27)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1.
2. Composition of rubber useful for the manufacture of tires, containing at least (i) a diene elastomer, (ii) a white charge as a reinforcing filler and (iii) a coupling agent (white filler / elastomer) which ensures the bond between the reinforcing filler and the elastomer, characterized in that the white filler is constituted all or in part of a titanium oxide having the following characteristics: (a) it contains more than 0.5% mass of a metallic element different from titanium, chosen from the group constituted by Al, Fe, Si, Zr or a mixture of these elements; - (b) its specific surface BET is between 20 and 200 m2 / g; - (c) its average (mass) particle size, denoted dw, is between 20 and 400 nm; - (d) its rate of deagglomeration, denoted a, measured in the so-called de-agglomeration test with ultrasound, at 100% power of a 600W ultrasound probe, is greater than 2.10"2 μm_1 / s. with claim 1, characterized in that the amount of total reinforcing filler is between 200 and 400 pee (parts by weight per one hundred parts of elastomer)
3. 3. Composition according to any of claims 1 or 2, characterized in that the surface BET is comprised in a domain ranging from 30 to 150 m2 / g
4. 4. Composition according to any of claims 1 to 3, characterized in that the size dw is comprised in a domain ranging from 30 to 200 nm.
5. 5. Composition according to any of claims 1 to 4, characterized in that the deagglomeration speed a is greater than 5.10"2 μrtrVs 6.
6. Composition according to any of claims 1 to 5, characterized in that the titanium oxide represents more than 50% by weight of the total reinforcing filler 7.
7. Composition according to claim 6, characterized in that the titanium oxide represents the total reinforcing filler 8.
8. Composition according to any of claims 1 to 6, characterized in that it contains, in addition to titanium oxide, the silica and / or alumina as white reinforcing filler 9.
9. Composition according to any of claims 1 to 6, characterized in that it contains, in addition to the titanium oxide, one or more carbon blacks as reinforcing filler 10.
10. Composition according to any of claims 2 to 9, characterized in that the amount of filler Total reinforcement is between 30 and 200 pee.
11. Composition according to any of claims 1 to 10, characterized in that the amount of coupling agent is between 10"7 and 10 ~ 5 mol per square meter of white reinforcing filler 12.
12. Composition in accordance with the claim 11, characterized in that the amount of coupling agent is between 5.10"7 and 5.10" 6 mol per square meter of white reinforcing filler 13.
13. Composition according to any of claims 4 to 12, characterized in that titanium oxide verify at least one of the following characteristics: - its BET surface is in a domain of 70 to 140 m2 / g, - its dw particle size is within a domain of 50 to 100 nm 14.
14. Composition in accordance with the claim 13, characterized in that the titanium oxide verifies the set of the following characteristics: it contains more than 1% by mass of a metallic element different from the tita child chosen from the group consisting of Al, Fe, Si, Zr or a mixture of these elements; - its BET surface is comprised in a domain of 70 to 140 m2 / g; its dw particle size is comprised in a 50 to 100 nm domain; - its deagglomeration speed a is greater than 15.
15. Composition according to any of claims 1 to 14, characterized in that the coupling agent is a polysulfurized alkoxysilane.
16. Composition according to any of claims 1 to 15, characterized in that the diene elastomer is selected from the group consisting of polybutadienes, polyisoprenes or natural rubber, butadiene-styrene copolymers, butadiene-isoprene copolymers, copolymers of butadiene-acrylonitrile, isoprene-styrene copolymers, butadiene-styrene-isoprene copolymers or a mixture of two or more of these compounds.
17. 17. Composition accordto claim 16, characterized in that the diene elastomer is a butadiene-styrene copolymer prepared in solution hava styrene content comprised between 20% and 30% by weight, a content of vinyl bonds of the butadiene part included 15% and 65%, a content of trans-1,4 bonds comprised between 20% and 75% and a glass transition temperature comprised between -20 ° C and -55 ° C, this butadiene-styrene copolymer is optionally used in mixture with a polybutadiene which preferably has more than 90% cis-1 bonds,.
18. 18. Composition accordto any of claims 1 to 15, characterized in that the diene elastomer is a copolymer EPDM.
19. 19. Use of a rubber composition accordto any of claims 1 to 18, for the manufacture of rubber articles.
20. 20. Use accordto claim 19, for the manufacture of tires or rubber semi-finished products intended for tires, these semi-finished products are chosen from the group consistof treads, sub-layers of treads , the upper layers, the flanks, the frame layers, the heels, the protectors, the air chambers or the inner tires stopped for tubeless tires.
21. 21. Use as reinforcfiller, in a diene rubber composition useful for the manufacture of tires, of a titanium oxide havthe followcharacteristics: (a) it contains more than 0.5% mass of a metallic element different from titanium, chosen of the group consistof Al, Fe, Si, Zr or a mixture of these elements; - (b) its BET specific surface area is between 20 and 200 m2 / g; - (c) its average (mass) particle size, denoted dw, is between 20 and 400 nm; - (d) its de-agglomeration speed, denoted c, measured in the so-called de-agglomeration test with ultrasound, at 100% power of a 600W ultrasound probe, is greater than 2.10"2 μm'Vs. reinforca diene rubber composition useful for the manufacture of tires, characterized in that this composition is incorporated in the raw state, for thermo-mechanical mix of a titanium oxide havthe followcharacteristics: (a) it contains more than 0.5% mass of a metallic element different from titanium, chosen from the group consistof Al, Fe, Si, Zr or a mixture of these elements - (b) its specific surface BET is between 20 and 200 m2 / g; - (c) its average size (in mass) of particles, denoted dw, is between 20 and 400 nm; - (d) its deagglomeration speed, denoted, measured in the so-called de-agglomeration test with ultrasound, at 100% power of a probe 600W ultrasound , is greater than 2.10"2 μ 'Vs. 23. Rubber article containa composition accordto any of claims 1 to 18. 24. Tire containa rubber composition accordto any of claims 1 to 18. 25. Colored tire containa rubber composition accordto any of claims 1 to 18. 26. Tire tread on the basis of a rubber composition accordto any of claims 1 to 18. 27. Colored tire tread band based on a rubber composition accordto any of claims 1 to 18. SUMMARY OF THE INVENTION Composition of rubber useful for the manufacture of tires, containat least (i) a diene elastomer, (ii) a white charge as a reinforcfiller and (iii) a couplagent (white filler / elastomer), characterized in that the filler White is constituted all or in part of a titanium oxide that has the followcharacteristics: - (a) contains more than 0.5% mass of a metallic element different from titanium, chosen from the group consistof Al, Fe, Si, Zr or a mixture of these elements; - (b) its BET specific surface area is between 20 and 200 m2 / g; - (c) its average (mass) particle size, denoted dw, is between 20 and 400 nm; - (d) its deagglomeration rate, denoted OI, measured in the so-called deagglomeration test with ultrasound, at 100% power of a 600W ultrasound probe, is greater than 2.10"2 μm'Vs. rubber according to the invention for the manufacture of rubber articles, in particular pneumatic or semi-finished rubber products intended for these tires The composition of the invention is used in particular for the manufacture of colored tires or semi-finished articles. Colored finishes, such as treads or tire sidewalls.