Title of Invention

"A PROCESS FOR PREPARING A CROSS-LINKABLE OR CROSS-LINKED RUBBER COMPOSITION"

Abstract

The present invention relates to a cross-linkable or cross-linked rubber composition having improved hysteresis properties in the cross-linked state which is usable for constituting a tyre tread, to a process for preparation of such a cross-linkable composition, to a tread of this type and to a tyre having reduced rolling resistance. This rubber composition according to the invention is based on: - at least one diene elastomer having a molar ratio of units originating from conjugated dienes which is greater than 30% and comprising carboxylic acid functions along its chain, and a reinforcing inorganic filler.

Full Text

The present invention relates to composition for a tyre tread and process for its preparation. The present invention relates to a cross-linkable or cross-linked rubber composition having improved hysteresis properties in the cross-linked state which is usable for constituting a tyre tread, to a process for preparation of such a cross-linkable composition, to a tread of this type and to a tyre having reduced rolling resistance. Since fuel economies and the need to preserve the environment have become priorities, it has become desirable to produce mixes having good mechanical properties and as low a hysteresis as possible so that they can be processed in the form of rubber compositions usable for the manufacture of various semi-finished products involved in the constitution of tyres, such as, for example, underlayers, sidewalls or treads, and in order to obtain* tyres having reduced rolling resistance. To achieve such -an objective, numerous solutions have been proposed, consisting in particular of modifying the structure of the diene polymers and copolymers at the end of polymerisation by means of functionalising, coupling or starring agents. The very great majority of these solutions have concentrated on the use of functionalised polymers which are active with respect to carbon black, with the aim of obtaining a good interaction between the polymer thus modified and the carbon black. By way of illustration of this prior art relating to reinforcing fillers formed of carbon black, mention may for example be made of US Patent Specification US-A-3 135 716, which describes the reaction of living diene polymers at the end of a chain with a polyfunctional organic coupling agent in order to obtain polymers having improved properties. Mention may also be made of US Patent Specification US-A-3 244 664, which discloses the use of tetra-alkoxysilanes as coupling agent or starring agent for diene polymers. Silica has been used as reinforcing filler in cross-linkable rubber compositions, in particular those intended to constitute tyre treads, for a long time. However, this use has remained very limited, owing to the unsatisfactory level of certain physical properties of such compositions, in particular abrasion resistance. This is why it has been proposed, in order to overcome these drawbacks, to use functionalised diene polymers instead of the non-functionalised polymers which were used before, and in particular polymers functionalised by alkoxysilane derivatives, such as tetraethoxysilanes. For example, mention may be made of U.S. Patent Specification US-A-5.066.721, which describes a rubber composition comprising a diene polymer functionalised by an alkoxysilane having at least one non-hydrolysable alkoxyl radical, which makes it possible to eliminate the polymerisation solvent by steam stripping. One disadvantage of these functionalisation reactions lies in the coupling reactions which accompany them, which generally makes it necessary to use an excess of alkoxysilane and/or intensive mixing, in order to minimise these coupling reactions. Another drawback of these reactions lies in the later implementation of the steam stripping operation, which is necessary to eliminate the polymerisation solvent. In fact, generally, experience shows that the functionalised polymers obtained undergo changes in macrostructure during this stripping operation, which results in serious degradation of their properties, unless one is limited to using as functionalising agent an alkoxysilane belonging to a restricted family, such as that described in the aforementioned document US-A-5 066 721. Consequently, it emerges from the above that the use of diene polymers comprising an alkoxysilane function to obtain rubber compositions comprising silica as reinforcing filler is not satisfactory, despite the improved physical properties of these compositions. This is why research has been carried out on other functionalisation reactions, always with a view to obtaining such rubber compositions. By way of example, mention may be made of French Patent Specification FR-A-2 740 778 in the name of the Applicant, which discloses the incorporation, in rubber compositions comprising as reinforcing filler silica in a majority proportion (for example comprising a blend of silica and carbon black), of diene polymers bearing at the chain end a silanol function or a polysiloxane block having a silanol end. For example, a functionalising agent consisting of a cyclic polysiloxane is used, such as hexamethylcyclotrisiloxane. The functionalised polymers obtained can be separated from the reaction medium resulting in their formation by steam extraction of the solvent, without their macro structure and, consequently, their physical properties, changing. Mention may also be made of European Patent Specification EP-A-877 047, which discloses the incorporation of such polymers having a silanol function in rubber compositions comprising as reinforcing filler carbon black having silica fixed to its surface. It has been possible to establish that these polymers impart rubber properties, in particular hysteresis and reinforcement properties in the cross-linked state, which are improved compared with those of control compositions based on non-functionalised diene polymers, and which are at least analogous to those of compositions based on diene polymers comprising an alkoxysilane function. Mention may also be made of European Patent Specification EP-A-692 493, which establishes that diene polymers bearing at the chain end alkoxysilane groups and an epoxy group result in improved reinforcement properties and in reduced hysteresis losses at small and large deformations. One disadvantage of these polymers, which comprise a functional group which is active for coupling to silica or to carbon black surface-modified by silica, is that the improvement in the hysteresis and reinforcement properties which they impart to the rubber compositions incorporating them is generally accompanied by a processing ability of the non-cross-linked mixes which is compromised relative to that of non-functionalised "control" polymers. Among the other functionalisation reactions studied, mention may be made, for example, of the functionalisation of the diene polymers along the chain by COOH functions. The functionalisation along the chain can be effected by direct metallation, in the presence of N,N,N',N'-tetramethylethylenediamine (TMED), by means of butyllithium or metallic sodium (as described in US Patent Specifications US-A-3 978 161 and US-A-3 976 628, respectively), followed by a carbonation reaction by means of carbonic gas. Such a process has the disadvantage of generally resulting in cuts in the chain of the modified polymer. Two specific reagents, of the respective formulae HSCH2CO2CH3 and N2CHCO2CH2CH3, were also used to graft COOH functions along the chain of a diene polymer. For the description of the reaction mechanisms relating to the use of these two reagents, reference may be made respectively to the articles "K. Sanui, R.W. Lenz, W.J. MacKnight, J. Poly. Sci., Polym. Chem. Ed. 12, 1965 (1974)" and "H. Tanaka, W.J. MacKnight, J. Poly. Sci., Polym. Chem. Ed. 17, 2975 (1979)". One major disadvantage of using one or the other of these two reagents is that it results in significant changes of macro structure for the modified polymer. This functionalisation along the chain may also be implemented by means of carbon monoxide, either by hydroformylation followed by oxidation of the aldehyde formed (as described in US Patent Specification US-A-4 912 145), or by direct hydrocarboxylation of the polymer (as described in the article "A. Nait Ajjou, H. Alper, Macromolecules 29, 1784 (1996)"). The catalysts used for these reactions are based on rhodium or palladium. One disadvantage of this functionalisation by carbon monoxide lies, on one hand, in the drastic nature of the operating conditions and, on the other hand, in the frequent formation of a gel in the reaction medium. Functionalisation by means of maleic anhydride is more widespread. It makes it possible to obtain succinic anhydride units along the chain, which are precursors of the COOH functions. Reference may be made to US Patent Specifications US-A-4 082 817 and US-A-4 082 493 for examples of implementation of such functionalisation. However, this method of functionalisation may also result in the formation of a gel. The use of diene elastomers comprising COOH functions along the chain, for the preparation of rubber compositions usable in tyres, is in particular disclosed by US Patent Specification US-A-5 494 091. This document in fact discloses a rubber composition filled with carbon black comprising 25 to 55 phr of polyisoprene and 45 to 75 phr (phr: parts by weight per hundred parts of elastomeric matrix) of a diene polymer belonging to the group consisting of homopolymers of conjugated dienes and copolymers of conjugated dienes with mono-olefins, such as EPDM terpolymers (of ethylene, propylene and a diene), part of at least one of these polymers comprising COOH functions grafted along the chain by reaction with a metal salt of unsaturated carboxylic acid, for example zinc dimethacrylate. The composition thus obtained is supposed to have a sufficiently high rigidity to be used in an internal reinforcement rubber for tyre sidewalls, so as to permit travel with a flat tyre under satisfactory conditions. The Applicant unexpectedly discovered that a cross-linkable or cross-linked rubber composition obtained by the association with a reinforcing inorganic filler of at least one diene elastomer having a molar ratio of units originating from conjugated dienes greater than 30% and comprising carboxylic acid functions along its chain, has reduced hysteresis losses at small and large deformations, which are similar to those of known compositions based on polymers comprising functional groups which are active for coupling to silica (such as the alkoxysilane or silanol groups mentioned above), while having processing properties in the non-cross-linked state which are improved compared with those of these known compositions filled with silica and which are comparable to those of compositions filled with silica based on non-functionalised polymers. These advantageous characteristics make the composition according to the invention usable to constitute a tyre tread. It will be noted that certain diene elastomers, such as butyl rubbers, nitrile rubbers or copolymers of dienes and alpha-olefins of the EPDM type, for example, cannot be used in the compositions according to the invention, owing to their reduced content of units of diene origin which makes the corresponding compositions unsuitable for constituting tyre treads. Even more preferably, said diene elastomer of the composition according to the invention is a "highly unsaturated" diene elastomer, that is to say, a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%. The following may be used as diene elastomer capable of being used in the compositions according to the invention: - a homopolymer obtained by polymerisation of a conjugated diene monomer having 4 to 12 carbon atoms, or - a copolymer obtained by copolymerisation of one or more dienes conjugated together or with one or more vinyl-aromatic compounds having 8 to 20 carbon atoms. It will be noted that the diene elastomer used in the compositions according to the invention may be prepared anionically or by any other method, provided that it has the aforementioned characteristics. Mention may be made, for example, of synthesis by radical polymerisation effected in emulsion, which is known to give polymers having COOH functions along the chain and which is described in particular in the work "Emulsion Polymerization and Emulsion Polymers", P. A. LOVELL and M. S. EL-AASSER, John Wiley and Sons (1997), pp. 558-561 (see also the references cited therein). Suitable conjugated dienes are, in particular, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(Cl to C5 alkyl)-1,3-butadienes such as, for instance, 2,3-dimethyl-1,3-butadiene, 2,3 -diethyl-1,3 -butadiene, 2-methyl-3 -ethyl-1,3 -butadiene, 2-methyl-3 -isopropyl-1,3 -butadiene, an aryl-1,3-butadiene, 1,3-pentadiene and 2,4-hexadiene. Suitable vinyl-aromatic compounds are, for example, styrene, ortho-, meta- and para-methylstyrene, the commercial mixture "vinyltoluene", para-tert. butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene and vinylnaphthalene. The copolymers may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl-aromatic units. The elastomers may have any microstructure, which is a function of the polymerisation conditions used, in particular of the presence or absence of a modifying and/or randomising agent and the quantities of modifying and/or randomising agent used. The elastomers may for example be block, statistical, sequential or micro sequential elastomers, and may be prepared in dispersion or in solution. They may be coupled and/or starred or alternatively functionalised with a coupling and/or starring or functionalising agent. Preferred are polybutadienes, and in particular those having a content of 1,2-units of between 4% and 80%, or those having a content of cis-1,4 [bonds] of more than 80%, synthetic polyisoprenes, butadiene-styrene copolymers, and in particular those having a styrene content of between 5% and 50% by weight and, more particularly, between 20% and 40%, a content of 1,2-bonds of the butadiene fraction of between 4% and 65%, and a content of trans-1,4 bonds of between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a glass transition temperature (Tg) of between -40°C and -80°C, isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between -25°C and -50°C. In the case of butadiene-styrene-isoprene copolymers, those which are suitable are in particular 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% and 60% by weight, and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight, and more particularly between 20% and 40%, a content of 1,2-units of the butadiene fraction of between 4% and 85%, a content of trans-1,4 units of the butadiene fraction of between 6% and 80%, a content of 1,2- plus 3,4-units of the isoprene fraction of between 5% and 70%, and a content of trans-1,4 units of the isoprene fraction of between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer having a Tg of between -20°C and -70°C. Particularly preferably, the diene elastomer of the composition according to the invention is selected from the group of highly unsaturated diene elastomers which consists of polybutadienes (BR), synthetic polyisoprenes (IR), butadiene-styrene copolymers (SBR), butadiene-isoprene copolymers (BIR), isoprene-styrene copolymers (SIR), butadiene-styrene-isoprene copolymers (SBIR), or a mixture of two or more of these compounds. Even more preferably, the diene elastomer belongs to the family consisting of polybutadienes, butadiene-styrene copolymers and butadiene-styrene-isoprene copolymers. According to an advantageous example of embodiment of the invention, the diene elastomer used is a butadiene-styrene copolymer prepared in solution having a styrene content of between 20% and 30% by weight, a content of vinyl bonds of the butadiene fraction of between 15% and 65%, a content of trans-1,4 bonds of between 15% and 75% and a Tg of between -20°C and -55°C According to another advantageous example of embodiment of the invention, the diene elastomer used is a butadiene-styrene copolymer prepared in emulsion, and it preferably has a total quantity of emulsifier which is less than 3.5 phr (phr: parts by weight per hundred parts of elastomer). There are considered in the invention the aforementioned diene elastomers which are obtained from any anionic initiator, whether it be monofunctional or polyfunctional, or non-anionic initiator. However, preferably an anionic initiator containing an alkali metal such as lithium, or an alkaline-earth metal such as barium is used. Suitable organolithium initiators are in particular those comprising one or more carbon-lithium bonds. Mention may be made, for example, of aliphatic organolithiums, such as ethyllithium, n-butyllithium (nBuLi), isobutyllithium, and dilithium polymethylenes such as 1-4 dilithiobutane. Lithium amides, which are obtained from an acyclic or cyclic secondary amine, such as pyrrolidine or hexamethyleneimine, may also be used. Also considered to be within the invention are diene elastomers which are initiated by compounds of transition metals, such as compounds of titanium for example, or by rare earths, such as neodymium. The polymerisation, as is known to the person skilled in the art, is preferably effected in the presence of an inert solvent which may for example be an aliphatic or alicyclic hydrocarbon such as pentane, hexane, iso-octane, cyclohexane, methylcyclohexane, cyclopentane, or an aromatic hydrocarbon such as benzene, toluene or xylene. This polymerisation may be effected continuously or discontinuously. It is generally effected at a temperature of between 20°C and 120°C, preferably between 30°C and 100°C. The functionalisation of the diene elastomers thus obtained by COOH functions along the chain may advantageously be effected using the process which is described in French Patent Application No. 99 05746 in the name of the Applicant, which relates generally to the functionalisation of any polymers comprising at least one double bond, for example polymers obtained from monomers such as isoprene, butadiene, isobutylene, a vinyl-aromatic compound or terpolymers of ethylene, propylene and a diene. This process consists essentially: - in a first step, of subjecting the starting polymer to a hydroalumination or carboalumination reaction along its chain in an inert hydrocarbon solvent, by addition of an agent derived from aluminium to said starting polymer, - in a second step, of adding to the product of this reaction at least one electrophilic agent intended to react with said agent derived from aluminium, - in a third step, of later stopping the functionalisation reaction of the second step and recovering the polymer functionalised along its chain. 0 In order to implement the hydroalumination or carboalumination reactions relating to the first step of the process, which results respectively in the addition of an Al-H or Al-C bond to a double bond of said starting polymer in accordance with the reactions Al-H + C=C —> H-C-C-Al or Al-C + C=C —> C-C-C-Al, in particular an alkyl aluminium or an aluminate may be used for said agent derived from aluminium. Preferably, diisobutyl aluminium hydride is used. This first step is advantageously implemented in an inert hydrocarbon solvent, such that the number of moles of agent derived from aluminium per 1000 g of starting polymer is between 0.05 and 5 moles, and preferably between 0.05 and 0.5 mole. In particular toluene, xylene, heptane, or alternatively cyclohexane may be used as inert hydrocarbon solvent. Preferably, this first step is implemented at a temperature of between 20°C and 100°C and, even more preferably, between 50°C and 70°C. To implement said second step of the process, preferably anhydrides are used as electrophilic agent, in particular carbon dioxide, to obtain a polymer having carboxylic acid functions along the chain. A cyclic anhydride may also be used, such as succinic anhydride. This second step is advantageously implemented such that the molar ratio of the number of moles of electrophilic agent to the number of moles of agent derived from aluminium is equal to or greater than 3. Preferably, this second step is implemented at a temperature of between 20°C and 100°C and, even more preferably, between 50°C and 70°C. 0 For stopping the functionalisation reaction of this second step, there is preferably added a metallic complexing agent which furthermore has the effect of liquefying the reaction medium. This complexing agent is preferably formed of a metallic chelate capable of releasing at least one proton during the complexing reaction. Preferably, acetylacetone is used for said chelate. Benzoyl acetone or 8-hydroxyquinoline may also be used. The molar ratio of the number of moles of this complexing agent to the number of moles of agent derived from aluminium is then equal to or greater than 3. In the case of carboxylic acid functionalisation with carbon dioxide as electrophilic agent and following the addition of said metallic complexing agent, there is added to the reaction medium a highly protonic acid to finish said stopping, for example hydrochloric acid. The molar ratio of the number of moles of highly protonic acid to the number of moles of agent derived from aluminium is then equal to or greater than 3. For the carboxylic acid functionalisation of a diene elastomer, such as a styrene-butadiene copolymer prepared in emulsion, there may be used as functionalising agent an unsaturated aliphatic monocarboxylic or dicarboxylic acid, for example acrylic acid, maleic acid or fumaric acid, or alternatively a carbocyclic carboxylic acid, such as cinnamic acid. Of course, the compositions of the invention may contain a single diene elastomer such as the aforementioned one or a mixture of several of these diene elastomers. The diene elastomer(s) according to the invention having COOH functions along the chain may be used on their own in the composition according to the invention, or be used in a blend with any other elastomer conventionally used in tyres, such as natural rubber or a blend based on natural rubber and a synthetic elastomer, or alternatively another diene elastomer which may possibly be coupled and/or starred or alternatively partially or entirely functionalised other than with COOH functions along the chain. It will be noted that the improvement in the properties of the rubber composition according to the invention will be all the greater, the lower the proportion of said conventional elastomer(s) in the composition according to the invention. Advantageously, this or these conventional elastomer(s) may if applicable be present in the composition according to the invention in a quantity of from 1 to 70 parts by weight per 100 parts by weight of diene elastomer(s) according to the invention having COOH functions along the chain. In the present application, "reinforcing inorganic filler", in known manner, is understood to mean an inorganic or mineral filler, whatever its colour and its origin (natural or synthetic), also referred to as "white" filler or sometimes "clear" filler in contrast to carbon black, this inorganic filler being capable, on its own, without any other means than an intermediate coupling agent, of reinforcing a rubber composition intended for the manufacture of tyres, in other words which is capable of replacing a conventional tyre-grade carbon black filler in its reinforcement function. Preferably, the reinforcing inorganic filler is present in the composition of the invention in a quantity equal to or greater than 40 phr (phr: parts by weight per hundred parts of diene elastomer(s)). Also preferably, this reinforcing inorganic filler is present in a majority proportion in the reinforcing filler of the composition of the invention, such that its mass fraction in said reinforcing filler is greater than 50%. Advantageously, the entirety or at the very least a majority proportion of said reinforcing inorganic filler is silica (SiO2). The silica used may be any reinforcing silica known to the person skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a specific CTAB surface area both of which are less than 450 m2/g, even if the highly dispersible precipitated silicas are preferred. In the present specification, the BET specific surface area is determined in known manner, in accordance with the method of Brunauer, Emmet and Teller described in "The Journal of the American Chemical Society", vol. 60, page 309, February 1938, and corresponding to Standard AFNOR-NFT-45007 (November 1987); the CTAB specific surface area is the external surface area determined in accordance with the same Standard AFNOR-NFT-45007 of November 1987. "Highly dispersible silica" is understood to mean any silica having a very substantial ability to disagglomerate and to disperse in an elastomeric matrix, which can be observed in known manner by electron or optical microscopy on thin sections. As non-limitative examples of such preferred highly dispersible silicas, mention may be made of the silica Perkasil KS 430 from Akzo, the silica BV 3380 from Degussa, the silicas Zeosil 1165 MP and 1115 MP from Rhodia, the silica Hi-Sil 2000 from PPG, the silicas Zeopol 8741 or 8745 from Huber, and treated precipitated silicas such as, for example, the aluminium-"doped" silicas described in application EP-A-0 735 088. The physical state in which the reinforcing inorganic filler is present is immaterial, whether it be in the form of a powder, microbeads, granules or alternatively balls. Of course, "reinforcing inorganic filler" is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible silicas such as described above. It will be noted that the reinforcing filler of a rubber composition according to the invention may contain in a blend (mixture), in addition to the aforementioned reinforcing inorganic filler or fillers, carbon black in a minority proportion (that is to say, in a mass fraction of less than 50%). Suitable carbon blacks are any carbon blacks, in particular the blacks of the type HAF, ISAF and SAF, which are conventionally used in tyres, and particularly in tyre treads. As non-limitative examples of such blacks, mention may be made of the blacks Nl 15, N134, N234, N339, N347andN375. For example, black/silica blends or blacks partially or integrally covered with silica are suitable to form the reinforcing filler. Also suitable are reinforcing inorganic fillers comprising carbon blacks modified by silica such as, and this is non-limitative, the fillers sold by CABOT under the name "CRX 2000", which are described in International Patent Specification WO-A-96/37547. As reinforcing inorganic filler, there may also be used, in non-limitative manner, - aluminas (of formula Al203), such as the aluminas of high dispersibility which are described in European Patent Specification EP-A-810 258, or alternatively - aluminium hydroxides, such as those described in International Patent Specification WO-A-99/28376. In the event that the reinforcing filler contains only a reinforcing inorganic filler and carbon black, the mass fraction of this carbon black in said reinforcing filler is preferably selected to be less than or equal to 30%. However, experience shows that the aforementioned properties of the composition according to the invention are improved all the more, the higher the mass fraction of reinforcing inorganic filler contained in the reinforcing filler which the composition comprises, and that said properties are optimum when said composition contains solely a reinforcing inorganic filler, for example silica, as reinforcing filler. This latter case therefore constitutes a preferred example of a rubber composition according to the invention. The rubber composition according to the invention furthermore comprises, in conventional manner, a reinforcing inorganic filler/elastomeric matrix bonding agent (also referred to as coupling agent), the function of which is to ensure sufficient chemical and/or physical bonding (or coupling) between said inorganic filler and the matrix, while facilitating the dispersion of this inorganic filler within said matrix. "Coupling agent" is more precisely understood to mean an agent capable of establishing a sufficient chemical and/or physical connection between the filler in question and the elastomer, while facilitating the dispersion of this filler within the elastomeric matrix. Such a coupling agent, which is at least bifunctional, has, for example, the simplified general formula "Y-T-X", in which: - Y represents a functional group ("Y" function) which is capable of bonding physically and/or chemically with the inorganic filler, such a bond being able to be established, for example, between a silicon atom of the coupling agent and the hydroxyl (OH) surface groups of the inorganic filler (for example, surface silanols in the case of silica), - X represents a functional group ("X" function) which is capable of bonding physically and/or chemically with the elastomer, for example by means of a sulphur atom, - T represents a group making it possible to link Y and X. The coupling agents must particularly not be confused with simple agents for covering the filler in question which, in known manner, may comprise the Y function which is active with respect to the filler but are devoid of the X function which is active with respect to the elastomer. Such coupling agents, of variable effectiveness, have been described in a very large number of documents and are well-known to the person skilled in the art. In fact, any known coupling agent known to or likely to ensure, in the diene rubber compositions which can be used for the manufacture of tyres, the effective bonding or coupling between a reinforcing inorganic filler such as silica and a diene elastomer, such as, for example, organosilanes, in particular polysulphurised alkoxysilanes or mercaptosilanes, or alternatively polyorganosiloxanes bearing the X and Y functions mentioned above may be used. Silica/elastomer coupling agents in particular have been described in a large number of documents, the best known being bifunctional alkoxysilanes such as polysulphurised alkoxysilanes. In particular polysulphurised alkoxysilanes, which are referred to as "symmetrical" or "asymmetrical" depending on their specific structure, are used, such as those described for example in patents US-A-3 842 111, US-A-3 873 489, US-A-3 978 103, US-A-3 997 581, US-A- 4 002 594, US-A-4 072 701, US-A-4 129 585, or in the more recent patents US-A-5 580 919, US-A-5 583 245, US-A-5 650 457, US-A-5 663 358, US-A-5 663 395, US-A-5 663 396, US-A- 5 674 932, US-A-5 675 014, US-A-5 684 171, US-A-5 684 172, US-A-5 696 197, US-A-5 708 053, US-A-5 892 085, EP-A-1 043 357, which describe such known compounds in detail. Particularly suitable for implementing the invention, without the definition below being limitative, are symmetrical polysulphurised alkoxysilanes which satisfy the following general formula (I): (I) Z-A-S„-A-Z, in which: - n is an integer from 2 to 8 (preferably from 2 to 5); - A is a divalent hydrocarbon radical (preferably C1-C12 alkylene groups or C6-C12 arylene groups, more particularly C1-C10 alkylenes, in particular C1-C4 alkylenes, in particular propylene); - Z corresponds to one of the formulae below: (Formula Removed) in which: - the radicals R1, which may or may not be substituted, and may be identical or different, represent a C1-C18 alkyl group, a C5-C18 cycloalkyl group, or a C6-C18 aryl group, (preferably C1-C6 alkyl groups, cyclohexyl or phenyl, in particular C1-C4 alkyl groups, more particularly methyl and/or ethyl). - the radicals R2, which may or may not be substituted, and may be identical or different, represent a C1-C18 alkoxyl group or a C5-C18 cycloalkoxyl group (preferably C1-C8 alkoxyl groups or C5-C8 cycloalkoxyl groups, more preferably C1-C4 alkoxyl groups, in particular methoxyl and/or ethoxyl). In the case of a mixture of polysulphurised alkoxysilanes in accordance with Formula (I) above, in particular conventional, commercially available, mixtures, it will be understood that the average value of the "n"s is a fractional number, preferably within a range from 2 to 5. As polysulphurised alkoxysilanes, mention will be made more particularly of the polysulphides (in particular disulphides, trisulphides or tetrasulphides) of bis-(alkoxyl(C1-C4)-alkyl(C1-C4)silylalkyl(C1-C4)), such as for example the polysulphides of bis(3-trimethoxysilylpropyl) or of bis(3-triethoxysilylpropyl). Of these compounds, preferably bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated TESPT, of the formula [(C2H5O)3Si(CH2)3S2]2, or bis(triethoxysilylpropyl) disulphide, abbreviated TESPD, of the formula [(C2H5O)3Si(CH2)3S]2, are used. TESPD is sold, for example, by Degussa under the names Si266 or Si75 (in the latter case, in the form of a mixture of disulphide (75% by weight) and of polysulphides), or alternatively by Witco under the name Silquest A1589. TESPT is sold, for example, by Degussa under the name Si69 (or X50S when it is supported to 50% by weight on carbon black), or alternatively by Osi Specialties under the name Silquest A1289 (in both cases, a commercial mixture of polysulphides having an average value of n which is close to 4). The compositions according to the invention also comprise, in addition to the diene elastomers having carboxylic acid functions along the chain and said reinforcing inorganic filler, plasticisers, pigments, antioxidants, anti-ozone waxes, a cross-linking system based either on sulphur and/or on peroxide and/or on bismaleimides, cross-linking activators comprising zinc monoxide and stearic acid, extender oils, one or more agents for covering the silica, such as alkoxysilanes, polyols or amines. In particular, these compositions may be such that the diene elastomer having carboxylic acid functions is extended using a paraffmic, aromatic or naphthenic oil, with a quantity of extender oil of between 0 and 50 phr. Another subject of the invention is a process for the preparation of a cross-linkable rubber composition according to the invention. In known manner, such a process consists essentially in a first phase of thermomechanical working of the constituents of said composition with the exception of the cross-linking system and at a maximum temperature of between 130°C and 200°C, followed by a second phase of mechanical working effected at a temperature less than that of said first phase and during which said cross-linking system is incorporated, said first phase comprising: - a first step in which said constituents of said first phase, with the exception of the antioxidant, are mixed together, and - a second step in which the antioxidant is incorporated and mixed with the constituents of said first step. Furthermore, zinc monoxide is conventionally added during said second step to activate the later cross-linking. The Applicant unexpectedly discovered that incorporating all the zinc monoxide during the first step of thermomechanical working, contrary to the convention in which it is incorporated during the second step of thermomechanical working, makes it possible to minimise further the hysteresis losses at low deformations of the composition according to the invention in the cross-linked state which corresponds to the above definition, while imparting to this composition according to the invention processing properties in the non-cross-linked state which are still improved compared with those of compositions based on known functional elastomers and which are comparable to those of the compositions according to the invention obtained by incorporation of zinc monoxide during the second step of thermomechanical working. The Applicant furthermore unexpectedly discovered that the incorporation of magnesium monoxide in the first step of thermomechanical working makes it possible to minimise further the hysteresis losses at low and high deformations of the composition according to the invention in the cross-linked state corresponding to the aforementioned definition, while imparting to this composition according to the invention processing properties in the non-cross-linked state which are similar to those of compositions based on non-functional elastomers. Another subject of the invention is also a tread for a tyre, which is such that it comprises a cross-linkable or cross-linked rubber composition such as that mentioned above, or alternatively which is such that it is formed of this composition. Owing to the reduced hysteresis which characterises a rubber composition according to the invention in the cross-linked state, it will be noted that a tyre, the tread of which comprises said composition, has an advantageously reduced rolling resistance. A tyre according to the invention is such that it comprises this tread. The aforementioned characteristics of the present invention, as well as others, will be better understood on reading the following description of several examples of embodiment of the invention, which are given by way of illustration and not of limitation. For the polymers, the viscosities indicated are inherent viscosities which are measured at a concentration of 1 g/1 in toluene at 25°C. The following experimental techniques have in particular been used for characterising the polymers obtained. a) The SEC technique (size exclusion chromatography) was used to determine the distributions of molecular weights relative to samples of these polymers. Starting from standard products whose characteristics are described in Example 1 of European Patent Specification EP-A-692 493, this technique made it possible to evaluate, for a sample, a number-average molecular weight (Mn) which has a relative value, unlike the one determined by osmometry, and also a weight-average molecular weight (Mw). The polydispersity index (Ip=Mw/Mn) of this sample was deduced therefrom. According to this technique, the macromolecules are separated physically according to their respective sizes when swollen, in columns filled with a porous stationary phase. Before implementing this separation, the sample of polymer is solubilised at a concentration of about 1 g/1 in tetrahydrofuran. A chromatograph sold under the name "WATERS" and under the model "150C" was used for the aforementioned separation. The elution solvent is tetrahydrofuran, the flow rate is 1 ml/min, the temperature of the system is 35°C and the duration of analysis is 30 min. A set of two "WATERS" columns is used, the type being "STYRAGEL HT6E". The injected volume of the solution of polymer sample is 100 µl. The detector is a "WATERS" differential refractometer, the model number of which is "R401". Software for processing the chromatographic data is also used, the trade name of which is "WATERS MILLENIUM". b) With the aim of calculating the amount of COOH functions (in meq/kg of polymer) and the number of corresponding functional units per chain of polymer, a metering method using the *H NMR technique was used, after esterification with an excess of diazomethane, which reagent is known to react with COOH functions. More precisely, this method consists of obtaining, using diazomethane, methyl ester functions from the COOH functions which have been fixed to the elastomer, in order to provide access indirectly and quantitatively to the amounts of COOH functions by 1H NMR. (i) First, the diazomethane is prepared as follows: It is obtained by action of alcoholic potassium hydroxide solution on N-methyl-N-nitrosoparatoluenesulphonamide, in the presence of diethyl ether at the temperature of melting ice. Then the ether phase containing the reagent is recovered by simple distillation. The esterification reaction is then carried out in the following manner. (ii) A sample of the elastomer which has been washed and dried in specific manner is solubilised in toluene, so as to be able to characterise it by analysis. (iii) This specific preparation consists of treating the elastomer by three successive dissolution operations in toluene, respectively followed by coagulation operations in a mixture formed of acetone and water and which is acidified to pH=2 with hydrochloric acid, in order to eliminate any traces of acidic compounds (stopper, antioxidant, catalytic residues, by-products such as isovaleric acid, in particular). Then the elastomer thus treated is dried in an oven at 50°C, in a vacuum and under a nitrogen atmosphere. (iv) Then the ethereal solution containing the diazomethane is added thereto, such that there is an excess of reagent relative to the COOH functions. The polymer thus treated is subsequently coagulated in methanol, then redissolved twice in toluene and methanol to coagulate it. The polymer is then dried in a desiccator at ambient temperature and under a high vacuum by means of a vane pump. (v) 'H NMR analysis is then performed in the following manner. A sample of the polymer esterified in this way is solubilised in carbon disulphide. The 'HNMR signal is analysed using a spectrometer marketed under the name BRUKER AC200. The characteristic signal of the three methyl protons of COOCH3 provides quantitative access to the initial proportion of COOH functions in the functional polymer. In the following examples, the properties of the compositions of the invention are evaluated as follows: - Mooney viscosity ML (14) at 100°C, measured in accordance with ASTM Standard D-1646, referred to as Mooney in the tables. - Moduli of elongation at 300%, (ME 300), at 100%, (ME 100) and at 10% (ME 10): measurements taken in accordance with Standard ISO 37. - Scott break indices: measured at 20°C Breaking load (BL) measured in MPa, Elongation at break (EB) in %. - Hysteresis losses (HL): measured by rebound at 60°C in %>. The deformation for the losses measured is about 40%,. - Shore A hardness: measurements taken in accordance with Standard DIN 53505. - Dynamic shear properties: These are measurements as a function of the deformation: performed at 10 Hertz with a peak-to-peak deformation of from 0.15% to 50%,. The non-linearity expressed is the difference in the shear modulus between 0.15%, and 50%, deformation, in MPa. The hysteresis is expressed by the measurement of tan 8 max. at 23°C in accordance with Standard ASTM D2231-71 (reapproved in 1977). I. Preparation of styrene/butadiene copolymers (SBR), whether functionalised or not: A/ Preparation discontinuously and in solution of a non-functional SBR (S-SBR A): In a first phase, a styrene/butadiene copolymer is prepared by injecting 167 g of styrene, 476 g of butadiene and 2000 ppm of tetrahydrofuran (THF) into a 10 litre reactor containing 6.4 litres of deaerated heptane. The impurities are neutralised using n-BuLi, then 0.0038 mol of n-BuLi and 0.0011 mol of sodium tert. butylate used as randomising agent are added. The polymerisation is carried out at 55°C. In a second phase, at 90% conversion, 0.006 mol of methanol is injected into the reactor. The polymer solution is stirred for 15 minutes at 55°C. The polymer is antioxidised by the addition of 0.8 phr 2,2'-methylene bis(4-methyl-6-tert. butylphenol) and 0.2 phr N-(l,3-dimethylbutyl)-N'-p-phenylenediamine, then recovered by steam stripping and dried on an open mill at 100°C. The S-SBR A thus obtained has the following characteristics: - Incorporated styrene 26% by weight - Number of vinyl units of the butadiene fraction 41% - Viscosity measured in toluene at 25°C (dl/g) 1.4 - Mooney viscosity ML( 14, 100°C) 26 - Mn measured by osmometry 155,000 g/mol. - polydispersity index 1.07. B/ Preparation discontinuously and in solution of a functionalised SBR by reaction with hexamethylcyclotrisiloxane (S-SBR B): In a first phase, operation is under conditions identical to those described for the preparation of the S-SBR A. In a second phase, at 90% conversion, an aliquot part is taken from the reactor, the reaction is stopped by adding methanol and the viscosity of the polymer is measured, it being 1.4 dl/g. 0.0013 mol of hexamethylcyclotrisiloxane (D3) is injected into the rest of the contents of the reactor. The polymer solution is stirred for 15 minutes at 55°C. The polymer is antioxidised by the addition of 0.8 phr 2,2'-methylene bis(4-methyl-6-tert. butylphenol) and 0.2 phr N-(l,3-dimethylbutyl)-N'-p-phenylenediamine, then recovered by steam stripping and dried on an open mill at 100°C. The S-SBR B thus obtained has the following characteristics: - Incorporated styrene 26% by weight - Number of vinyl units of the butadiene fraction 41% - Viscosity measured in toluene at 25°C (dl/g) 1.4 - Mooney viscosity ML( 14, 100°C) 26 - Mn measured by osmometry 155,000 g/mol. - Polydispersity index 1.07. The amount of functionalised chains is measured by 1H NMR, after purification of the polymer sample by a series of three coagulation operations in methanol, redissolving in toluene. This amount of functionalised chains is expressed by means of this technique in milli-equivalents per kilogramme of polymer (meq/kg). The XH NMR spectrum is characterised by blocks at 0 and -0.1 ppm corresponding to the -Si(CH3)2-OH group. For the S-SBR B, lH NMR analysis provides an amount of functions of 4.5 meq/kg which, taking into account the molecular weight Mn of the polymer, corresponds to approximately 70% of functionalised chains. C/ Preparation discontinuously and in solution of several SBRs comprising carboxylic acid functions along the chain fS-SBR C. S-SBR D and S-SBR E): In this section, the number-average molecular weights (Mn) of the starting polymers and the corresponding functional polymers were determined precisely by osmometry. The aforementioned SEC technique was also used to determine the distributions of molecular weights relative to samples of these polymers. Each of the three functional copolymers S-SBR C, S-SBR D and S-SBR E was prepared using the same deoxygenated solution of a starting styrene/butadiene copolymer, the number-average molecular weight of which, determined by osmometry, is Mn= 180,000 g/mole and the polydispersity index of which, determined by the SEC technique, is Ip=1.09. The percentages of styrene, of 1,4-cis linkages, 1,4-trans linkages and 1,2 linkages of this starting copolymer are respectively 25%, 28%, 32% and 40%. Furthermore, this starting solution contains 0.2 phr of the antioxidant N-l,3-dimethylbutyl-N'-phenyl-p-phenylenediamine and 0.2 hr of the antioxidant 2,2'-methylene-bis (4-methyl-6-t. butylphenol). In accordance with the techniques known to the person skilled in the art and under the conditions mentioned in Table I below, there is introduced, at ambient temperature into a 10 litre reactor containing 7 litres of said deoxygenated solution, the necessary quantity of a molar toluene solution of diisobutylaluminium hydride (HDiBA), the weight fraction of the polymeric solution in the toluene being 10%. The reaction medium is kept stirred for 10 minutes in order to homogenise it sufficiently. Then the stirring is stopped and the hydroalumination is effected under static conditions, at 65 °C for 64 hours. It will be noted that the value of the ratio "number of moles of HDiBA /kg of polymer" was varied in order to prepare the three functional elastomers S-SBR C, S-SBR D and S-SBR E (this ratio is 0.05 mol/kg, 0.1 mol/kg and 0.2 mol/kg for S-SBR C, S-SBR D and S-SBR E, respectively). Then the functionalisation is effected in the same reactor, at 65°C and for 6 hours, by means of pressurisation of 6 bars with carbon dioxide. This functionalisation is performed under identical operating conditions, for the preparation of the elastomers S-SBR C, S-SBR D and S-SBRE. Then the reaction is stopped, firstly with acetylacetone in a molar ratio of acetylacetone/aluminium of 12, then with hydrochloric acid in a molar ratio of hydrochloric acid/aluminium of 7.5. Then the elastomer solution obtained is treated with 0.3 phr of an antioxidant consisting of 2,2'-methylene-bis (4-methyl-6-t. butylphenol), then stripping, preferably with steam, is effected in acidic medium (pH=2). Then the elastomer is re-dissolved in toluene, with concentrated aqueous hydrochloric acid, such that the molar ratio of hydrochloric acid/aluminium is equal to 5. Then a second stripping in acidic medium is effected in order to be able to eliminate the residual isovaleric acid completely, this being a by-product of the carboxylation of the isobutyl radicals contained in the HDiBA. Then the elastomer thus treated is drained on a open mill at 100°C, and is dried in a vacuum at 60°C (inert nitrogen atmosphere) for 18 hours. The amount of carboxylic acid functions was calculated (in meq/kg of polymer) and the number of corresponding functional units per chain of copolymer was calculated (with Mn= 180,000 g/mole determined by osmometry) using two different methods for each of these two calculations. - A first method consisted of metering the carboxylic acid functions by acidimetry and calculating^ on one hand, the amount of these COOH functions per kg of polymer and, on the other hand,yhe number of units per chain on the basis of a Mn (determined by osmometry) of 180,000 g/mole. This metering by acidimetry was effected by dissolving a sample of the elastomer thus prepared in a mixture of toluene and orthodichlorobenzene. The COOH functions are neutralised in the presence of pyridine, with a solution of tetrabutylammonium hydroxide in isopropanol. The equivalence is detected by potentiometry. - A second method consisted in effecting metering in accordance with the *H NMR technique described in section b) above. The results obtained are set forth in Table 1 below, which refers to said starting styrene-butadiene copolymer and to the three copolymers S-SBR C, S-SBR D and S-SBR E which were hydroaluminised and functionalised. The amounts of COOH functions and the numbers of COOH units per chain were determined in accordance with one or the other of the above two methods indicated in Table 1 below. Table 1: (Table Removed) It will be noted that the functional polymers S-SBR C, S-SBR D and S-SBR E obtained have a macrostructure which is practically identical to that of the starting polymer, as the results of the distribution of the molecular weights show (polydispersity indices Ip). A/ Preparation in emulsion of a non-functional SBR (E-SBR F): The polymerisation operations are effected at 5°C with stirring, in 250 ml Steinie bottles, in accordance with the methods known to the person skilled in the art. The water used is deionised and bubbled through in a current of nitrogen to eliminate any trace of dissolved oxygen. An emulsifying solution consisting of 5.45 g n-dodecylamine, 1.59 g acetic acid and 543.5 ml water is introduced into a 750 ml Steinie bottle, which has previously been bubbled through with nitrogen. This emulsifying solution is heated to 60°C and stirred until the n-dodecylamine has completely dissolved. Then 6.5 ml of a solution of 100 g/1 KC1, 6.5 ml of a solution of l00g/l A1C13 and 23 ml of a molar solution of hydrochloric acid are added to this bottle. 45 ml of this stock solution is placed in a 250 ml Steinie bottle and cooled to 5°C. Then 13 g liquid butadiene and 12 g styrene are added thereto. The whole is stirred in a tank at 5°C until a stable emulsion forms. Finally, 2 ml of a solution of 31.25 g/1 n-dodecylmercaptan and 14.25 g/1 paramenthane hydroperoxide is added, and the polymerisation is started at 5°C with stirring. The polymerisation is stopped after 6 hours and 30 minutes by adding 0.025 g hydroquinone. 10 g NaCl per 100 g elastomer is added to this emulsion and the mixture is stirred for several minutes. Then 150 ml toluene and 1 phr of an antioxidant mixture comprising 80% of the product named "A02246" and 20% N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (commonly called "6PPD"). The solution is stirred once again. It is finally stripped and the polymer is dried at between 30 and 50°C. 15 g of a polymer having the characteristics indicated below are obtained. (Table Removed) * the percentage is a mass percentage ** the percentages are mass percentages relative to the incorporated butadiene. E/ Preparation in emulsion of an SBR comprising carboxylic acid functions along the chain (E-SBR G): The procedure is as in section D/ above, except that 55 meq/kg of monomers of acrylic acid is added to the emulsifying solution, at the same time as the KC1 and the AICI3. The polymerisation is stopped after 18 hours by adding 0.025 g hydroquinone. The polymer is recovered in the same manner as in said section D/. 15 g of a polymer having the characteristics indicated below is obtained. (Table Removed) Furthermore, the E-SBR G thus obtained has a total quantity of emulsifier which is less than 3 phr (as the treatment of the polymer obtained by solubilisation and stripping has the effect of reducing the final quantity of emulsifier in the E-SBR G). F/ Preparation in emulsion of a non-functional SBR extended with oil (E-SBR H): The polymerisation operations are effected at 5°C with stirring, in a 10 1 stainless steel reactor, in accordance with the methods known to the person skilled in the art. 1 The water used is deionised and bubbled through in a current of nitrogen to eliminate any frace of dissolved oxygen. An emulsifying solution consisting of 37.19 g n-dodecylamine, 10.95 g acetic acid and 5*40 ml water is introduced into a 750 ml Steinie bottle, bubbled through with nitrogen. This emulsifying solution is heated to 60°C and stirred until the n-dodecylamine has completely dissolved. 3 1 water is added to a 10 1 reactor and is bubbled through under nitrogen for 30 minutes. All the soap solution is introduced into the reactor, as is 90 ml of a solution of 50 g/1 KCl, 90 ml of a solution of 100 g/1 AIC13, 114 ml of a solution of 14 g/1 FeCb and 177 ml of a molar solution of hydrochloric acid. The reactor is cooled to 12°C and 1164 g butadiene and 1006 g styrene is added thereto. The temperature of the reactor is lowered to 5°C. After 5 minutes' stirring, 2.55 g paramenthane hydroxide and 10.52 g mercaptan both diluted in 68 g styrene are added. After 9 hours, the polymerisation is stopped by adding 128 ml of a solution of 40 g/1 hydroquinone. There is added thereto successively, with stirring, 7 1 toluene, 15 phr NaCl (15 g per 100 g of elastomer), another 7 1 toluene and 1 phr of a mixture of antioxidants composed of 80% of the product "AO 2246" and 20% "6PPD". The solution obtained is stripped and dried. The final conversion is 74%. The polymer is then solubilised in toluene and extended with 27.5 phr of an aromatic oil sold by BRITISH PETROLEUM under the name "EXAROL". The polymer is finally dried in an oven in a vacuum at a temperature of between 40 and 50°C. The characteristics of the polymer obtained are indicated below. (Table Removed) Gl Preparation in emulsion of an SBR comprising carboxylic acid functions along the chain and extended with oil (E-SBR Is): Procedure for the polymerisation is as in section VI, except that 5.78 g of methacrylic acid is added to the emulsifying solution. The polymerisation is stopped after nine hours and thirty minutes, and the conversion is 70%. Contrary to section VI above, 27.5 phr of said aromatic oil "EXAROL" is added to the polymer obtained before proceeding with the stripping, the pH of the stripping water being kept at pH=2. The polymer is dried in an oven under nitrogen at 30°C and is used in this form for the rubber properties tests (see section 11/ below). The characteristics of the dry polymer are set forth in the table below. The Mooney viscosity ML(l4) of the polymer extended with oil is 48. (Table Removed) Furthermore, the E-SBR I thus obtained has a total quantity of emulsifier which is less than 3 phr (as the treatment of the polymer obtained by solubilisation and stripping has the effect of reducing the final quantity of emulsifier in the E-SBR G). II. Rubber compositions comprising an inorganic reinforcing filler and the aforementioned elastomers : A/ First comparative example: In this example, the five elastomers of section I (S-SBR A, S-SBR B, S-SBR C, S-SBR D and S-SBR E) were used for the preparation of rubber compositions A, B, C, D and E of the passenger-car-tread type. Each of these compositions A, B, C, D and E has the following formulation (expressed in phr: parts by weight per hundred parts of elastomer): Elastomer 100 Silica (1) 80 Aromatic oil ("ENERFLEX 65") 40 Bonding agent (2) 6.4 ZnO 2.5 Stearic acid 1.5 Antioxidant (3) 1.9 Anti-ozone wax "C32ST" 1.5 Sulphur 1.1 Sulphenamide (4) 2 Diphenylguanidine 1.5 with (1) = silica "Zeosil 1165MP" manufactured by Rhodia, (2) = bonding agent "Si69" from Degussa, (3)= N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and (4) = N-cyclohexyl-2-benzothiazylsulphenamide. Each of the following compositions is produced, in a first phase of thermomechanical working, by two steps separated by a cooling phase, then, in a second, finishing, phase, by mechanical working. There are introduced in succession into a laboratory internal mixer of the "Banbury" type, the capacity of which is 400 cm3, which is 70% filled and the initial temperature of which is approximately 90°C, the elastomer, two-thirds of the reinforcing filler, the coupling agent, the diphenylguanidine and the stearic acid, then, approximately one minute later, the rest of the reinforcing filler, the aromatic oil and the anti-ozone wax "C32ST". The first thermomechanical working step is performed for 4 to 5 minutes, until a maximum dropping temperature of about 160°C is achieved. The elastomeric block is then recovered and cooled. Then a second step of thermomechanical working is performed in the same mixer for 3 to 4 minutes, with addition of the antioxidant and the zinc monoxide, until a maximum dropping temperature of about 160°C is achieved. The aforementioned first phase of thermomechanical working is thus effected, it being specified that the average speed of the blades during this first phase is 45 rpm. The mixture thus obtained is recovered, is cooled and then, in an external mixer (homo-finisher), the sulphur and sulphenamide are added at 30°C, by mixing everything for 3 to 4 minutes (second aforementioned phase of mechanical working). The compositions thus obtained are then calendered either in the form of sheets (of a thickness of 2 to 3 mm) or of fine films of rubber in order to measure their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting out and/or assembly to the dimensions desired, for example as semi-finished products for tyres, in particular for treads. The cross-linking is carried out at 150°C for 40 min. The results are set forth in Table 2 below. (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 relating to compositions B, C, D and E (based respectively on S-SBR B, S-SBR C, S-SBR D and S-SBR E) is greater than that relating to composition A and, on the other hand, that the hysteresis properties (at low and high deformations) are greatly improved compared with those of said composition A. It will also be noted that the compositions C, D and E according to the invention have values of Mooney "mixture" which are distinctly less than that of composition B based on an elastomer functionalised by reaction with hexamethylcyclotrisiloxane. These Mooney values are indicative of a processing ability for the compositions of the invention which is improved compared to that of a composition based on a known functional elastomer. These Mooney values for compositions C, D and E are closed to that of composition A based on a non-functional elastomer S-SBR A, in particular as far as said compositions C and D are concerned (the Mooney value of composition E according to the invention being between those of compositions A and B). In other words, the elastomers S-SBR C, S-SBR D and S-SBR E which comprise COOH functions along the chain and, more particularly, S-SBR D, impart to compositions filled with silica practically the same rubber properties in the cross-linked state as those imparted to such a composition by a known functional elastomer, and furthermore with a processing ability close to that imparted by a non-functional elastomer. B/ Second comparative example: In this example, the non-functional S-SBR A of section I was used to prepare a rubber composition A' of the passenger-car-tread type, which is distinguished from the aforementioned composition A in that it furthermore comprises a carboxylic acid. An attempt was made to compare the properties of the aforementioned composition D according to the invention with those of composition A'. Each of the compositions A and D has the following formulation (expressed in phr: parts by weight per hundred parts of elastomer): Elastomer 100 Silica (1) 80 Aromatic oil ("ENERFLEX 65") 40 Bonding agent (2) 6.4 ZnO 2.5 Stearic acid 1.5 Antioxidant (3) 1.9 Anti-ozone wax "C32ST" 1.5 Sulphur 1.1 Sulphenamide (4) 2 Diphenylguanidine 1.5 with (1) = silica "Zeosil 1165MP" manufactured by Rhodia, (2) = bonding agent "Si69" from Degussa, (3)= N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and (4) = N-cyclohexyl-2-benzothiazylsulphenamide. More precisely, the carboxylic acid used for composition A is oleic acid, and it is incorporated in the S-SBR A prior to the addition of the other additives, so as to be able to effect a first joint mastication of the S-SBR A and the oleic acid. The amount of oleic acid which is added to the S-SBR A is 0.62 phr, which corresponds to a stoichiometry of 4 units which are fixed to the elastomer chain, by analogy with the S-SBR D of the invention (the composition A' has the formulation shown above for the compositions A and D, with furthermore 0.62 phr of oleic acid.). Each of the following compositions is produced, in a first phase of thermomechanical working, by two steps separated by a cooling phase, then, in a second, finishing, phase, by mechanical working. There are introduced in succession into a laboratory internal mixer of the "Banbury" type, the capacity of which is 400 cm3, which is 70% filled and the initial temperature of which is approximately 90°C, the elastomer, two-thirds of the reinforcing filler, the coupling agent, the diphenylguanidine and the stearic acid, then, approximately one minute later, the rest of the reinforcing filler, the aromatic oil and the anti-ozone wax "C32ST". The first thermomechanical working step is performed for 4 to 5 minutes, until a maximum dropping temperature of about 160°C is achieved. The elastomeric block is then recovered and cooled. Then a second step of thermomechanical working is performed in the same mixer for 3 to 4 minutes, with addition of the antioxidant and the zinc monoxide, until a maximum dropping temperature of about 160°C is achieved. The aforementioned first phase of thermomechanical working is thus effected, it being specified that the average speed of the blades of this first phase is 45 rpm. The mixture thus obtained is recovered, is cooled and then, in an external mixer (homo-finisher), the sulphur and sulphenamide are added at 30°C, by mixing everything for 3 to 4 minutes (mechanical working). The compositions thus obtained are then calendered, either in the form of sheets (of a thickness of 2 to 3 mm) or of fine films of rubber in order to measure their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting out and/or assembly to the dimensions desired, for example as semi-finished products for tyres, in particular for treads. The cross-linking is carried out at 150°C for 40 min. The results are set forth in Table 3 below. TABLE 3 (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 relating to composition A' is very close to that of composition A and, on the other hand, that the hysteresis properties of composition A are not substantially improved compared with those of composition A. In the light of these results, it will be noted that the elastomer S-SBR D which comprises COOH functions along the chain imparts to a composition filled with silica a combination of characteristics "processing ability/properties at low deformations" which is overall improved relative to the same combination of characteristics relative to composition A comprising a carboxylic acid. C/ Third comparative example: In this example, the S-SBR B (functionalised by reaction with hexamethylcyclotrisiloxane) and the S-SBR D of section I (comprising 4 COOH units along the chain) were used for the preparation of two rubber compositions B' and D' of the passenger-car-tread type, respectively, these compositions B' and D' being distinguished only from the compositions B and D mentioned above in section II. A/ by their respective preparation processes (Each of these compositions B' and D' has the same ingredients and the same formulation as in the preceding sections II. A/ and II. B/). Each of compositions B' and D' is produced, in a first phase of thermomechanical working, by two steps separated by a cooling phase, then, in a second, finishing, phase, by mechanical working. There are introduced in succession into a laboratory internal mixer of the "Banbury" type, the capacity of which is 400 cm3, which is 70% filled and the initial temperature of which is approximately 90°C, the elastomer, two-thirds of the reinforcing filler, the coupling agent, the diphenylguanidine and the stearic acid, then, approximately one minute later, the rest of the reinforcing filler, the aromatic oil and the anti-ozone wax "C32ST". The first thermomechanical working step is performed for 4 to 5 minutes, until a maximum dropping temperature of about 160°C is achieved. The elastomeric block is then recovered and cooled. Then a second step of thermomechanical working is performed in the same mixer for 3 to 4 minutes, with addition of the antioxidant and the zinc monoxide, until a maximum dropping temperature of about 160°C is achieved. The aforementioned first phase of thermomechanical working is thus effected, it being specified that the average speed of the blades of this first phase is 85 rpm (unlike in the examples of section II. A/). The mixture thus obtained is recovered, is cooled and then, in an external mixer (homo-finisher), the sulphur and sulphenamide are added at 30°C, by mixing everything for 3 to 4 minutes (mechanical working). The compositions thus obtained are then calendered either in the form of sheets (of a thickness of 2 to 3 mm) or of fine films of rubber in order to measure their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting out and/or assembly to the dimensions desired, for example as semi-finished products for tyres, in particular for treads. The cross-linking is carried out at 150°C for 40 min. It will be noted that all the zinc monoxide (ZnO) is introduced conventionally in the second step of thermomechanical working, in order to obtain cross-linkable compositions B' and D'. - In this comparative example, said S-SBR D was also used for the preparation of a composition D" of the passenger-car-tread type, this composition D" being distinguished from the abovementioned composition D' solely in that the introduction of all the zinc monoxide takes place during the first step of thermomechanical working, and not, in conventional manner, during the second step of thermomechanical working (this composition D" also has the same ingredients and the same formulation as in sections II. A/ and II. B/ above). An attempt was made to compare the properties of compositions D' and D" according to the invention with each other, on one hand, and with those of composition B', on the other hand. The results are set forth in Table 4 below. TABLE 4: (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 relating to the preferred composition D" according to the invention is greater than that of the other composition D1 according to the invention and, on the other hand, that the hysteresis properties at low deformations of composition D" are improved compared with those of composition D' and also compared with those of composition B' (based on a functionalised elastomer by reaction with hexamethylcyclotrisiloxane. It will also be noted that composition D" according to the invention has a value of Mooney "mix" which is distinctly less than that of composition B'. This Mooney value indicates a processing ability for the composition D" of the invention which is always improved compared to that of a composition based on a known functional elastomer. In other words, the elastomer S-SBR D which comprises COOH functions along the chain imparts to composition D", which is filled with silica and is obtained by introducing ZnO during the first step of thermomechanical working, hysteresis properties at low deformations which are improved compared with those imparted to such a composition by a known functional elastomer, and furthermore has a processing ability which is identical, or even improved, compared with that of composition D', which is also based on elastomer S-SBR D, being filled with silica but is obtained by conventional introduction of ZnO during the second step of thermomechanical working. D/ Fourth comparative example: In this example, the properties of a new composition D'" of the "passenger-car"-tread type based on said S-SBR D were compared with those of compositions A, B' and D1 tested in the preceding sections (see section C/ above for B' and D', with introduction of the ZnO during the second step of thermomechanical working). Composition D'" is produced in accordance with the method described in section C/ above for composition D', it being stated that this composition D'" is furthermore characterised by the fact that magnesium oxide (MgO) is added in a quantity of 1.33 phr in one go, right at the beginning of the first step of thermomechanical working (namely at t=0 minutes in the internal mixer). The results are set forth in Table 5. TABLE 5 (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 relating to composition D"' according to the invention (based on S-SBR D with addition of the MgO during the first step of thermomechanical working) is substantially identical to that of composition B' and, on the other hand, that the hysteresis properties (losses at 60°C and tg8 max at 23°C) are greatly improved compared with those of composition A. It also proves that composition D"' makes it possible to obtain hysteresis properties at low and high deformations which are improved compared with those of composition D' but also relative to composition B' for the low deformations. On the other hand, it would appear that composition D"' has, in the non-cross-linked state, a value of Mooney viscosity of mix which is distinctly less than that of composition B' and substantially close to that of composition A based on a non-functional S-SBR. This composition D'" consequently has a processing ability which is distinctly improved compared with that of the compositions based on conventional functional elastomers. In other words, composition D"' according to the invention has hysteresis properties at low deformations which are improved compared with those of a composition based on a conventional functional elastomer while considerably improving the hysteresis properties at high deformations (losses at 60°C) compared with those of composition D' without MgO. This composition D"' furthermore has a processing ability which is close to that of the "control" composition A based on a non-functional elastomer. E/ Fifth comparative example: In this example, the properties of a new composition D"" of the "passenger-car"-tread type based on said S-SBR D were compared with those of compositions A, B', D' and D"' tested in the preceding sections. Composition D"" is produced in accordance with the method described in section D/ above for composition D"', it being specified that this composition D"" differs from said composition D"' solely by the fact that the aforementioned 1.33 phr of magnesium oxide (MgO) is added in a single go to the internal mixer during the first step of thermomechanical working, only when the temperature in the internal mixer has reached 120°C (i.e. after about 2 to 3 minutes, contrary to composition D"1, in which this addition of MgO took place at t=0 minutes). The results are set forth in Table 6. (Table Removed) composition D"" according to the invention makes it possible to obtain properties in the non-cross-linked and cross-linked state which are similar to those of the other composition D'" according to the invention. Consequently, the moment of introduction of the MgO during the first step of thermomechanical working does not change the Mooney viscosity, the ratio ME300/ME100 and the hysteresis properties obtained with said composition D"In other words, composition D"" makes it possible to obtain hysteresis properties (tgS max at 23°C) which are largely improved compared with those of compositions A, B' and D', with a distinct improvement of the processing ability compared with that of composition B' based on a known functional elastomer. Furthermore, the compositions D'" and D"" according to the invention have hysteresis properties at high deformations which are improved compared with those of compositions A or D'. F/ Sixth comparative example: In this example, the properties of two rubber compositions F and G of the "passenger-car"-tread type were compared, composition F being based on the non-functional E-SBR F of section I. D/ above and composition G being based on E-SBR G comprising acrylic acid functions along the chain (see section I. E/ above). The formulation used for each of these two compositions F and G is the one mentioned in section II. A/ above. Each of these two compositions F and G is produced, in a first phase of thermomechanical working, by two steps separated by a cooling phase, then, in a second, finishing, phase, by mechanical working. There are introduced in succession into a laboratory internal mixer of the "Banbury" type, the capacity of which is 400 cm3, which is 70% filled and the initial temperature of which is approximately 90°C, the elastomer, two-thirds of the reinforcing filler, the coupling agent, the diphenylguanidine and the stearic acid, then, approximately one minute later, the rest of the reinforcing filler, the aromatic oil and the anti-ozone wax "C32ST". The first thermomechanical working step is performed for 4 to 5 minutes, until a maximum dropping temperature of about 160°C is achieved. The elastomeric block is then recovered and cooled. Then a second step of thermomechanical working is performed in the same mixer for 3 to 4 minutes, with addition of the antioxidant and the zinc monoxide, until a maximum dropping temperature of about 160°C is achieved. The aforementioned first phase of thermomechanical working is thus effected, it being specified that the average speed of the blades of this first phase is 85 rpm. The mixture thus obtained is recovered, is cooled and then, in an external mixer (homo-finisher), the sulphur and sulphenamide are added at 30°C, by mixing everything for 3 to 4 minutes (mechanical working). The compositions thus obtained are then calendered, either in the form of sheets (of a thickness of 2 to 3 mm) or of fine films of rubber in order to measure their physical or mechanical properties, or in the form of profiled elements which can be used directly, after cutting out and/or assembly to the dimensions desired, for example as semi-finished products for tyres, in particular for treads. The cross-linking is carried out at 150°C for 40 min. It will be noted that all the zinc monoxide (ZnO) is in this case introduced conventionally during the second step of thermomechanical working, in order to obtain the cross-linkable compositions F and G. The results are set forth in Table 7. TABLE 7 (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 of composition G according to the invention (based on E-SBR G having acrylic acid functions along the chain) is greater than that of composition F (based on non-functional E-SBR F) and, on the other hand, that the hysteresis properties (losses at 60°C and tan(S) max at 23 °C) are improved compared with those of composition F. It would also appear that this composition G has a Mooney viscosity of mix which is similar to that of composition F, that is to say a processing ability which is close to that of said composition F. In other words, the elastomer E-SBR G, which comprises acrylic acid functions along the chain, makes it possible to obtain compositions having rubber properties in the cross-linked state which are improved compared with those of the "control" compositions based on a non-functional elastomer prepared in emulsion, and furthermore having a processing ability which is close to that of such "control" compositions. G/ Seventh comparative example: In this example, the properties of three rubber compositions F, G and G of the "passenger-car"-tread type are compared with each other, the compositions F and G having been defined in the preceding section and the new composition G also being based on the elastomer E-SBR G having acrylic acid functions along the chain and differing only from composition G by the fact that all the ZnO is introduced into the internal mixer during the first step of thermomechanical working and at a temperature of 120° C. The results are set forth in Table 8. TABLE 8 (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted, on one hand, that the ratio ME300/ME100 of composition G1, based on E-SBR G and with the addition of ZnO during the first step of thermomechanical working, is greater than that of the "control" composition F and, on the other hand, that the hysteresis properties (losses at 60°C and tan(5) max at 23°C) are greatly improved compared with those of said composition F. It also proves that composition G' has hysteresis properties at low deformations which are improved compared with those of composition G. Furthermore, it would appear that this composition G' according to the invention has a Mooney viscosity of mix which is substantially identical to that of composition F (based on a nonfunctional elastomer prepared in emulsion). In other words, this composition G' has hysteresis properties at low deformations which are improved compared with those obtained with the compositions F and G, and furthermore a processing ability which is close to that of said "control" composition F. H/ Eighth comparative example: In this example, the properties of two rubber compositions H and I of the "passenger-car"-tread type were compared, composition H being based on the non-functional E-SBR H and extended with the oil of section I. F/ above and composition I being based on E-SBR I comprising methacrylic acid functions along the chain (see section I. G/ above). The formulation used for each of these compositions H and I is as follows (in phr): Elastomer extended with oil 127.5 Silica (1) 80 Aromatic oil "ENERFLEX 65" 10 Bonding agent (2) 6.4 ZnO 2,5 Stearic acid 1.5 Antioxidant (3) 1.9 Ozone wax "C32ST" 1.5 Sulphur 1.1 Sulphenamide(4) 2 Diphenylguanidine 1.5 with (1) = Silica ZEOSIL 1165 (RP) (2) = Bonding agent: Si69 Degussa (3)= N-( 1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (4) = N-cyclohexyl-2-benzothiazylsulphenamide Each of these compositions H, I is produced in the manner described in section II. F/ above (in particular with conventional introduction of the ZnO during the second step of thermomechanical working). The results are set forth in Table 9. TABLE 9 (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted that the hysteresis properties (losses at 60°C and tan(8) max at 23° C) of composition I according to the invention (based on an elastomer having methacrylic acid functions along the chain) are improved compared with those of the "control" composition H (based on a non-functional elastomer prepared in emulsion). It would also appear that this composition I according to the invention has a Mooney viscosity of mix which is substantially identical to that of the "control" composition H, that is to say a processing ability which is close to that of said composition H. In other words, the elastomer E-SBR I makes it possible to obtain compositions having rubber properties in the cross-linked state which are improved compared with those of the "control" compositions based on a non-functional elastomer prepared in emulsion, and furthermore having a processing ability which is close to that of such "control" compositions. H/ Ninth comparative example: In this example, the properties of three rubber compositions H, I and I' of the "passenger-car"-tread type are compared with each other, the compositions H and I having been defined above and the new composition I' differing from composition T solely in that all the ZnO is added during the first step of thermomechanical working. The results are set forth in Table 10. (Table Removed) As far as the properties in the cross-linked state are concerned, it will be noted that the hysteresis properties (losses at 60°C and tan(8) max at 23 °C) of composition I' according to the invention are improved compared with those of composition H. It also proves that this composition I' makes it possible to obtain hysteresis properties at low deformations which are improved compared with those of composition I. Furthermore, it would appear that composition I' has a Mooney viscosity of mix which is substantially identical to that of said "control" composition H based on a non-functional elastomer prepared in emulsion. In other words, composition I' has hysteresis properties at low deformations which are improved compared with those obtained with the compositions H and I, and it furthermore has a processing ability which is close to that of said "control" composition H. We claim: 1. A process for preparing a cross-linkable or cross-linked rubber composition usable to constitute a tread for a tire, characterised in that said process comprises: (i) preparing, in solution, at least one diene elastomer having a molar ratio of units originating from conjugated dienes which is greater than 30% and comprising carboxylic acid functions along its chain, by implementing the following steps: • in a first step, subjecting the initial diene elastomer in an inert hydrocarbon solvent to a hydroalumination or carboalumination reaction along its chain, by adding an agent derived from aluminum to said initial diene elastomer; • in a second step, adding to the product of said hydroalumination or carboalumination reaction at least one electrophilic agent, wherein said electrophilic agent reacts with said agent derived from aluminum; and • in a third step, stopping the reaction of said electrophilic agent and said agent derived from aluminum and recovering said at least one diene elastomer comprising carboxylic acid functions along its chain; (ii) subjecting the constituents of said composition comprising said diene elastomer having carboxylic acid functions along its chain and a reinforcing filler comprising a reinforcing inorganic filler, wherein the mass fraction of said reinforcing inorganic filler in said reinforcing filler is greater than 50%,, with the exception of the cross-linking system, to a first phase of thermomechanical working, wherein the maximum temperature during the first phase of thermomechanical working is between 130°C and 200°C; and (iii) subjecting to a second phase of mechanical working at a temperature that is less than the maximum temperature, wherein a cross-linking system is added. 2. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in claim 1, said process consisting essentially in a first phase of thermomechanical working of the constituents of said composition with the exception of the cross-linking system at a maximum temperature of between 130°C and 200°C, followed by a second phase of mechanical working effected at a temperature less than that of said first phase and during which said cross-linking system is incorporated, said first phase comprising: • a first step in which said constituents of said first phase, with the exception of the antioxidant, are mixed together, and • a second step in which the antioxidant is incorporated and mixed with the constituents of said first step, zinc monoxide being added during said first phase to activate the later cross-linking, wherein it consists of incorporating all said zinc monoxide during said first step of said first phase of thermomechanical working. 3. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, said process consisting essentially in a first phase of thermomechanical working of the constituents of said composition with the exception of the cross-linking system at a maximum temperature of between 130°C and 200°C, followed by a second phase of mechanical working effected at a temperature less than that of said first phase and during which said cross-linking system is incorporated, said first phase comprising: • a first step in which said constituents of said first phase, with the exception of the antioxidant, are mixed together, and • a second step in which the antioxidant is incorporated and mixed with the constituents of said first step, zinc monoxide being added during said first phase to activate the later cross-linking, wherein it consists of incorporating magnesium monoxide during said first step of said first phase of thermomechanical working. 4. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said reinforcing inorganic filler is instep (ii) in a quantity equal to or greater than 40 parts by weight per hundred parts of diene elastomer. 5. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said reinforcing inorganic filler comprises carbon black surface-modified by silica. 6. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said reinforcing inorganic filler comprises silica. 7. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein a reinforcing inorganic filler/diene elastomer bonding agent is added in step (ii). 8. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said diene elastomer comprises carboxylic acid functions along its chain has a molecular weight exceeding 100,000 g/mol. 9. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said at least one or each diene elastomer is selected from the group consisting of polybutadienes, butadiene/styrene copolymers and butadiene/styrene/isoprene copolymers. 10. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said diene elastomer further comprises an extender oil in an amount that ranges between 0 and 50 parts by weight per hundred parts of diene elastomer, said extender oil being selected from the group consisting of paraffinic oil, aromatic oil, and naphthenic oil. 11. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said diene elastomer comprises along its chain acrylic acid functions. 12. A process for the preparation of a cross-linkable or cross-linked rubber composition as claimed in one of the preceding claims, wherein said rubber composition comprises an elastomeric matrix comprising in majority or formed by said diene elastomer. 13. A tyre tread, wherein it comprises a cross-linkable or cross-linked rubber composition prepared by a process as claimed in one of the preceding claims 1-12.

Documents:

IN PCT-2002-01130-DEL-CorrespondenceOthers-(08-04-2011).pdf

in-pct-2002-1130-del-abstract.pdf

in-pct-2002-1130-del-claims.pdf

in-pct-2002-1130-del-complete specification (granted).pdf

in-pct-2002-1130-del-correspondence-others.pdf

in-pct-2002-1130-del-correspondence-po.pdf

in-pct-2002-1130-del-drawings.pdf

in-pct-2002-1130-del-form-1.pdf

in-pct-2002-1130-del-form-18.pdf

in-pct-2002-1130-del-form-2.pdf

in-pct-2002-1130-del-form-3.pdf

in-pct-2002-1130-del-form-5.pdf

in-pct-2002-1130-del-gpa.pdf

in-pct-2002-1130-del-petition-137.pdf