Patent Description:
In a known way (for example, the following patent literature <NUM>), liquid diene polymers have been used in rubber compositions of rubber articles in order to improve the processability.

However, the improvement by the liquid diene polymer can be disadvantageous to the hysteresis property of the rubber compositions, and thus a constant objective of the manufactures of the articles is improvement of balance of performances (the processability and the hysteresis property). <CIT> discloses a rubber composition for the tread of a tire that improves the grip performance of the tire on snow. The rubber composition is based on at least an elastomer matrix comprising more than <NUM> phr and up to <NUM> phr of a first diene elastomer bearing at least one SiOR function, R being a hydrogen atom or a hydrocarbon radical, the SiOR function not located at the chain ends of the first diene elastomer, and optionally, <NUM> to less than <NUM> phr of a second diene elastomer which is different from the first diene elastomer; a reinforcing filler comprising <NUM> to <NUM> phr of a reinforcing inorganic filler; and a plasticizing agent comprising <NUM> to <NUM> phr of a liquid diene polymer having a glass transition temperature of less than -<NUM>. The liquid diene polymer is not functionalized. <CIT> discloses a rubber composition for the tread of a tire that improves the grip performance of the tire on snow without deteriorating the grip performance on wet. A tire has a tread comprising at least two radially superposed portions which comprise radially external/internal portions. The external portion is made of a first rubber composition which is based on at least an elastomer matrix, a reinforcing filler comprising between <NUM> and <NUM> phr of a reinforcing inorganic filler, and a plasticizing agent. The internal portion is made of a second rubber composition which is based on an elastomer matrix comprising <NUM> to <NUM> phr of a first diene elastomer bearing at amine and SiOR functions, and optionally, <NUM> to <NUM> phr of a second diene elastomer which is different from the first diene elastomer, a reinforcing filler comprising <NUM> to <NUM> phr of a reinforcing inorganic filler, and a plasticizing agent comprising <NUM> to <NUM> phr of a liquid plasticizer having a glass transition temperature of less than -<NUM>. The liquid plasticizer may be a liquid diene polymer that is not functionalized. <CIT> discloses a rubber composition for the tread of a tire that improves off-road performance while maintaining on-road performance. The tire has a tread comprising at least two radially superposed portions which comprise a radially external portion intended to come into contact with ground during rolling, the radially external portion being made of a first rubber composition, and a radially internal portion made of a second rubber composition; wherein the first rubber composition is based on at least an elastomer matrix; and a reinforcing filler comprising between <NUM> and <NUM> phr of a reinforcing inorganic filler; wherein the second rubber composition is based on at least: an elastomer matrix comprising <NUM> to <NUM> phr of a first diene elastomer bearing at least one SiOR function, R being a hydrogen atom or a hydrocarbon radical, <NUM> to <NUM> phr of a second diene elastomer which is polyisoprene, and comprising no third diene elastomer or at most <NUM> phr; a reinforcing filler comprising a reinforcing inorganic filler. The first and the second compositions may comprise a liquid plasticizer. The liquid plasticizer may be a liquid diene polymer that is not functionalized. <CIT> discloses a tire tread rubber composition for a pneumatic tire having reduced rolling resistance. The composition comprises the following components in parts by weight: <NUM>-<NUM> parts of neodymium-based cis-polybutadiene rubber, <NUM>-<NUM> parts of modified soluble polymerized styrene-butadiene rubber, <NUM>-<NUM> parts of white carbon black, <NUM>-<NUM> parts of carbon black, <NUM>-<NUM> parts of environment-friendly aromatic hydrocarbon oil, <NUM>-<NUM> parts of a silane coupling agent, <NUM>-<NUM> parts of road holding resin, <NUM>-<NUM> parts of zinc oxide, <NUM>-<NUM> parts of stearic acid, <NUM>-<NUM> parts of a white carbon black dispersing agent, <NUM>-<NUM> parts of alkoxy silicon modified polybutadiene liquid rubber, <NUM>-<NUM> parts of an anti-aging agent, <NUM>-<NUM> parts of protective wax, <NUM>-<NUM> parts of an accelerant and <NUM>-<NUM> parts of sulfur.

During the research, the inventor has discovered a specific rubber composition which allows an unexpectedly improved balance of performances between the processability and the hysteresis property.

In the present description, unless expressly stated otherwise, all the percentages (%) indicated are percentages by weight (wt%).

The expression "elastomer matrix" is understood to mean, in a given composition, all of the elastomers present in said rubber composition.

The abbreviation "phr" signifies parts by weight per hundred parts by weight of the elastomer matrix in the considered rubber composition.

In the present description, unless expressly indicated otherwise, each TgDSC (glass transition temperature) is measured in a known way by DSC (Differential Scanning Calorimetry) according to Standard ASTM D3418-<NUM>.

Any interval of values denoted by the expression "between a and b" represents the range of values of more than "a" and of less than "b" (i.e. the limits a and b excluded) whereas any interval of values denoted by the expression "from a to b" means the range of values going from "a" to "b" (i.e. including the strict limits a and b).

The expression "based on" should be understood in the present application to mean a composition comprising the mixture(s) and/or the product of the reaction of the various constituents used, some of the constituents being able or intended to react together, at least partly, during the various manufacturing phases of the composition, in particular during the vulcanization (curing).

A first aspect of the invention is a rubber composition based on at least:.

The specific rubber composition allows improving the balance of performances between the processability and the hysteresis property.

Each of the below aspect(s), the embodiment(s) and the variant(s) including each of the preferred range(s) and/or matter(s) may be applied to any one of the other aspect(s), the other embodiment(s) and the other variant(s) of the invention unless expressly stated otherwise.

Elastomer (or loosely "rubber", the two terms being regarded as synonyms) of the "diene" type is to be understood in a known manner as an (meaning one or more) elastomer derived at least partly (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).

These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally, the expression "essentially unsaturated" is understood to mean a diene elastomer resulting at least in part from conjugated diene monomers having a content of units of diene origin (conjugated dienes) which is greater than <NUM>% (mol %); thus it is that diene elastomers such as butyl rubbers or diene/ α -olefin copolymers of the EPDM type do not fall under the preceding definition and may especially be described as "essentially saturated" diene elastomers (low or very low content of units of diene origin, always less than <NUM>%). In the category of "essentially unsaturated" diene elastomers, the expression "highly unsaturated" diene elastomer is understood to mean in particular a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than <NUM>%.

Although it applies to any type of diene elastomer, a person skilled in the art of rubber articles (for example, tires) will understand that the invention is preferably employed with essentially unsaturated diene elastomers.

Given these definitions, the expression diene elastomer capable of being used in the compositions in accordance with the invention is understood in particular to mean:.

The following are suitable in particular as conjugated dienes: <NUM>,<NUM>-butadiene, <NUM>-methyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-di(C<NUM>-C<NUM> alkyl)-<NUM>,<NUM>-butadienes, such as, for example, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-butadiene, <NUM>-methyl-<NUM>-ethyl-<NUM> ,<NUM>-butadiene or <NUM>-methyl-<NUM>-isopropyl-<NUM> ,<NUM>-butadiene, an aryl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-pentadiene or <NUM>,<NUM>-hexadiene. The following, for example, are suitable as vinylaromatic compounds: styrene, ortho-, meta- or para-methylstyrene, the "vinyltoluene" commercial mixture, para-(tert-butyl) styrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene or vinylnaphthalene.

The first diene elastomer may be selected from the group consisting of polybutadiene(s) (BR(s)), synthetic polyisoprene(s) (IR(s)), natural rubber (NR), butadiene copolymers, isoprene copolymers and the combinations thereof; such copolymer(s) is selected more preferably from the group consisting of styrene-butadiene copolymer(s) (SBR(s)) and the combinations thereof.

The first diene elastomer may have any microstructure which depends on the polymerization conditions used, in particular on the presence or absence of a modifying and/or randomizing agent and on the amounts of modifying and/or randomizing agent employed. This elastomer may, for example, be a block, statistical, sequential or micro sequential elastomer and may be prepared in dispersion or in solution.

The first diene elastomer bears at least one SiOR function, R being a hydrogen atom or a hydrocarbon radical.

The expression "hydrocarbon radical" means a monovalent group essentially consisting of carbon and hydrogen atoms. Such a group may comprise at least one heteroatom, and it is known that the assembly formed by the carbon and hydrogen atoms represents the major number fraction in the hydrocarbon radical, for example alkyl or alkoxyalkyl; preferably assembly formed by the carbon and hydrogen atoms represents the entirety of the hydrocarbon radical(s), for example alkyl. Such a SiOR (R is alkyl or alkoxyalkyl) is referred as an "alkoxysilane" function. While, a SiOH (R is a hydrogen atom) is referred as a "silanol" function.

The SiOR function borne by the first diene elastomer is not located at the chain ends of the first diene elastomer.

According to a first variant of the first aspect, the SiOR function borne by the first diene elastomer may be a pendant group, which is equivalent to saying that the silicon atom of the SiOR function may not be inserted between the carbon-carbon bonds of the elastomer chain of the first diene elastomer. A diene elastomer bearing a pendant SiOR function may for example be prepared by hydrosilylation of the elastomer chain by a silane bearing an alkoxysilane group, followed by hydrolysis of the alkoxysilane function to give a SiOR function.

According to a second variant of the first aspect, the SiOR function borne by the first diene elastomer may not be a pendant group, but maybe be situated in the elastomer chain, that is, may be within the elastomer chain, which is equivalent to saying that the silicon atom of the SiOR function may be inserted between the carbon-carbon bonds of the elastomer chain of the first diene elastomer. Such a diene elastomer may be prepared according to the procedure described in a patent <CIT>. This second variant is preferential and applies to the first aspect.

A second aspect of the invention is the rubber composition according to the first aspect, wherein the first diene elastomer is a styrene-butadiene copolymer (SBR), preferably a solution styrene-butadiene copolymer which is a copolymer of butadiene and styrene, prepared in solution.

A third aspect of the invention is the rubber composition according to the first aspect or the second aspect, wherein the first diene elastomer further bears at least one amine function, preferably at least one tertiary amine function.

According to a preferred embodiment of the third aspect, the amine function borne by the first diene elastomer may be a tertiary amine function. Mention will be made, as tertiary amine function, of the amines substituted with C<NUM>-C<NUM> alkyl radicals, preferably C<NUM>-C<NUM> alkyl, more preferably methyl or ethyl radical(s).

Generally, such a function borne by an elastomer, particularly a diene elastomer, may be located on the elastomer chain end(s) or may not be located at the elastomer chain ends, that is, may be away from the chain ends. The first case occurs for example when the diene elastomer is prepared using a polymerization initiator bearing the function or using a functionalizing agent. The second case occurs for example when the diene elastomer is modified by the use of a coupling agent or star-branching agent bearing the function.

According to this embodiment or a preferred embodiment of the third aspect, the amine function borne by the first diene elastomer may be a pendant group. The pendant position of the amine function means, in a known way, that the nitrogen atom of the amine function may not be inserted between the carbon-carbon bonds of the elastomer chain of the first diene elastomer.

A fourth aspect of the invention is the rubber composition according to the third aspect, wherein the SiOR function bears the amine function.

Such a diene elastomer may result from the modification of a diene elastomer by a coupling agent that introduces, the elastomer chain, an alkoxysilane group bearing an amine function according to the operating procedure described in a patent <CIT>. The following are suitable for example as coupling agent: N,N-dialkylaminopropyltrialkoxysilanes, C<NUM>-C<NUM>, preferably C<NUM>-C<NUM>, dialkyl groups, the compounds <NUM>-(N,N-dimethylaminopropyl)trimethoxysilane, <NUM>-(N,N-dimethylaminopropyl)triethoxysilane, <NUM>-(N,N-diethylaminopropyl)trimethoxysilane, <NUM>-(N,N-diethylaminopropyl)triethoxysilane being most particularly preferred, irrespective of the embodiment of the invention.

A fifth aspect of the invention is the rubber composition according to any one of the first to the fourth aspects, wherein R of the SiOR function is a hydrocarbon radical.

According to a preferred embodiment of the fifth aspect, the hydrocarbon radical may be an alkyl radical, preferably an alkyl radical having <NUM> to <NUM> carbon atoms, more preferably a branched, linear or else cyclic alkyl radical having <NUM> to <NUM> carbon atoms, still more preferably <NUM> to <NUM> carbon atoms, particularly <NUM> to <NUM> carbon atoms, more particularly methyl or ethyl radical(s).

A sixth aspect of the invention is the rubber composition according to any one of the first to the fifth aspects, wherein the first diene elastomer has a glass transition temperature (TgDSC) of lower than -<NUM>, (for example, between -<NUM> and -<NUM>), advantageously less than -<NUM> (for example, between -<NUM> and -<NUM>).

A seventh aspect of the invention is the rubber composition according to any one of the first to the sixth aspects, wherein the elastomer matrix optionally comprises at least one second diene elastomer different from the first diene elastomer, that is, the elastomer matrix does not comprise any second diene elastomer different from the first diene elastomer, or the elastomer matrix further comprises at least one second diene elastomer different from the first diene elastomer, and wherein the amount of the first diene elastomer is from <NUM> to <NUM> phr, preferably between <NUM> and <NUM> phr, more preferably from <NUM> to <NUM> phr, still more preferably from <NUM> to <NUM> phr, particularly from <NUM> to <NUM> phr, and wherein the amount of the second diene elastomer is <NUM> to <NUM> phr, preferably between <NUM> and <NUM> phr, more preferably from <NUM> to <NUM> phr, still more preferably from <NUM> to <NUM> phr, particularly from <NUM> to <NUM> phr.

According to a preferred embodiment of the seventh aspect, the second diene elastomer is selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and the combinations thereof, preferably selected from the group consisting of polybutadienes and the combinations thereof.

The rubber composition according to the invention is based on a reinforcing filler.

Use may be made of any type of reinforcing filler known for its capabilities of reinforcing a rubber composition which can be used for the manufacture of rubber articles, for example a reinforcing organic filler, such as carbon black, or a reinforcing inorganic filler, such as silica, with which a coupling agent is combined in a known way.

According to a preferred embodiment of the invention, the amount of the reinforcing filler is more than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), advantageously more than <NUM> phr (for example, between <NUM> and <NUM> phr).

The reinforcing filler in the rubber composition according to the invention comprises a reinforcing inorganic filler, preferably the reinforcing filler predominately comprises the reinforcing inorganic filler, that is, the reinforcing filler comprises more than <NUM>%, more preferably more than <NUM>%, still more preferably <NUM>%, particularly more than <NUM>%, more particularly more than <NUM>%, by weight of the reinforcing inorganic filler per <NUM>% by weight of the reinforcing filler.

The expression "reinforcing inorganic filler" should be understood here to mean any inorganic or mineral filler, whatever its color and its origin (natural or synthetic), also referred to as "white filler", "clear filler" or even "non-black filler", in contrast to carbon black, capable of reinforcing by itself alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of rubber articles (for example, tires), in other words capable of replacing, in its reinforcing role, a conventional tire-grade carbon black; such a filler is generally characterized, in a known manner, by the presence of hydroxyl (-OH) groups at its surface.

The physical state under the presence of this filler is unimportant, whether it is in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the reinforcing inorganic filler of the combinations of various reinforcing inorganic fillers, preferably of highly dispersible siliceous and/or aluminous fillers is described hereafter.

Mineral fillers of the siliceous type, preferably silica (SiO<NUM>) and/or the aluminous type, preferably alumina (Al<NUM>O<NUM>) are suitable in particular as the reinforcing inorganic fillers.

An eighth aspect of the invention is the rubber composition according to any one of the first to the seventh aspects, wherein the amount of the reinforcing inorganic filler is between <NUM> and <NUM> phr, still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), advantageously more than <NUM> phr (for example, between <NUM> and <NUM> phr).

A ninth aspect of the invention is the rubber composition according to any one of the first to the eighth aspects, wherein the reinforcing inorganic filler predominately comprises silica, that is, the reinforcing inorganic filler comprises more than <NUM>%, preferably more than <NUM>%, more preferably <NUM>%, by weight of silica per <NUM>% by weight of the reinforcing inorganic filer. The reinforcing inorganic filler may comprise a type of silica or a blend of several silicas. The silica used may be any reinforcing silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface area and a CTAB specific surface area that are both less than <NUM><NUM>/g, preferably from <NUM> to <NUM><NUM>/g, more preferably from <NUM> to <NUM><NUM>/g, still more preferably from <NUM> to <NUM><NUM>/g, particularly from <NUM> and <NUM><NUM>/g. Such silica may be covered or not.

The BET surface area is measured according to a known method, that is, by gas adsorption using the Brunauer-Emmett-Teller method described in "<NPL>, and more specifically, in accordance with the French standard NF ISO <NUM> of December <NUM> (multipoint volumetric method (<NUM> points); where gas: nitrogen, degassing: <NUM> hour at <NUM>, relative pressure range p/po: <NUM> to <NUM>). The CTAB specific surface area is determined according to the French standard NF T <NUM>-<NUM> of November <NUM> (method B).

A person skilled in the art will understand that a reinforcing filler of another nature, in particular organic nature, such as carbon black, might be used as filler equivalent to the reinforcing inorganic filler described in the present section, provided that this reinforcing filler is covered with an inorganic layer, such as silica, or else comprises, at its surface, functional sites, in particular hydroxyls, requiring the use of a coupling agent in order to form the connection between the filler and the elastomer. By way of example, mention may be made of carbon blacks for rubber articles (for example, tires), such as described in patent applications <CIT> and <CIT>.

A tenth aspect of the invention is the rubber composition according to any one of the first to the ninth aspects, wherein the reinforcing filler further comprises carbon black, and wherein the amount of carbon black is less than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably less than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably less than <NUM> phr (for example, between <NUM> and <NUM> phr).

Within the ranges indicated, there is a benefit of coloring properties (black pigmentation agent) and anti-UV properties of carbon blacks, without furthermore adversely affecting the typical performance provided by the reinforcing inorganic filler, namely low hysteresis (reduced rolling resistance).

In order to couple the reinforcing inorganic filler to the elastomer matrix, for instance, the diene elastomer, use can be made, in a known manner, of a coupling agent (or bonding agent) intended to provide a satisfactory connection, of chemical and/or physical nature, between the reinforcing inorganic filler (surface of its particles) and the elastomer matrix, for instance, the diene elastomer. This coupling agent is at least bifunctional. Use can be made in particular of at least bifunctional organosilanes or polyorganosiloxanes.

Use can be made in particular of silane polysulphides, referred to as "symmetrical" or "asymmetrical" depending on their particular structure, as described, for example, in applications <CIT>, <CIT> and <CIT>.

Particularly suitable silane polysulphides correspond to the following general formula (I):.

In the case of a mixture of alkoxysilane polysulphides corresponding to the above formula (I), in particular normal commercially available combinations, the mean value of the "x" indices is a fractional number preferably of between <NUM> and <NUM>, more preferably of approximately <NUM>. However, the present invention can also advantageously be carried out, for example, with alkoxysilane disulphides (x = <NUM>).

Mention will more particularly be made, as examples of silane polysulphides, of bis((C<NUM>-C<NUM>)alkoxyl(C<NUM>-C<NUM>)alkylsilyl(C<NUM>-C<NUM>)alkyl)polysulphides (in particular disulphides, trisulphides or tetrasulphides), such as, for example, bis(<NUM>-trimethoxysilylpropyl) or bis(<NUM>-triethoxysilylpropyl)polysulphides. Use is in particular made, among these compounds, of bis(<NUM>-triethoxysilylpropyl)tetrasulphide, abbreviated to TESPT, of formula [(C<NUM>H<NUM>O)<NUM>Si(CH<NUM>)<NUM>S<NUM>]<NUM>, or bis(<NUM>-triethoxysilylpropyl)disulphide, abbreviated to TESPD, of formula [(C<NUM>HSO)<NUM>Si(CH<NUM>)<NUM>S]<NUM>. Mention will also be made, as preferred examples, of bis(mono(C<NUM>-C<NUM>)alkoxyldi(C<NUM>-C<NUM>)alkylsilylpropyl)polysulphides (in particular disulphides, trisulphides or tetrasulphides), more particularly bis(monoethoxydimethylsilylpropyl)tetrasulphide, as described in patent application <CIT> (or <CIT>).

Mention will in particular be made, as coupling agent other than alkoxysilane polysulphide, of bifunctional POSs (polyorganosiloxanes) or of hydroxysilane polysulphides (R<NUM> = OH in the above formula (I)), such as described in patent applications <CIT> (or <CIT>) and <CIT> (or <CIT>), or of silanes or POSs carrying azodicarbonyl functional groups, such as described, for example, in patent applications <CIT>, <CIT> and <CIT>.

As examples of other silane sulphides, mention will be made, for example, of the silanes bearing at least one thiol (-SH) function (referred to as mercaptosilanes) and/or at least one blocked thiol function, such as described, for example, in patents or patent applications <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Of course, use could also be made of combinations of the coupling agents described previously, as described in particular in the aforementioned patent application <CIT>.

According to a preferred embodiment of the invention, the content of coupling agent is from <NUM> to <NUM>% by weight per <NUM>% by weight of the reinforcing inorganic filler, particularly silica.

According to a preferred embodiment of the invention, the rubber composition of the tread of the rubber composition according to the invention is based on less than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably less than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more less than <NUM> phr (for example, between <NUM> and <NUM> phr), of coupling agent.

The rubber composition according to the invention is based on a plasticizing agent.

The role of the plasticizing agent is to soften the matrix by diluting the elastomer and the reinforcing filler.

According to a preferred embodiment of the invention, the amount of the plasticizing agent is more than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr).

The plasticizing agent in the rubber composition according to the invention comprises the liquid plasticizer.

The liquid plasticizer is liquid at <NUM> by definition, and its TgDSC is by definition less than -<NUM>, preferably less than -<NUM>, more preferably less than -<NUM>.

Any extending oil, whether of aromatic or non-aromatic nature, any liquid plasticizing agent known for its plasticizing properties with regard to elastomer matrix(es) (for instance, diene elastomer), can be used as the liquid plasticizer. At ambient temperature (<NUM>) under atmospheric pressure, these plasticizers or these oils, which are more or less viscous, are liquids (that is to say, as a reminder, substances that have the ability to eventually take on the shape of their container), as opposite to plasticizing hydrocarbon resin(s) which are by nature solid at ambient temperature (<NUM>) under atmospheric pressure.

According to a preferred embodiment of the invention, the amount of the liquid plasticizer is more than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr).

The liquid plasticizer in the plasticizing agent in the rubber composition according to the invention comprises a liquid diene polymer.

The liquid diene polymer is a diene polymer, and is liquid at <NUM> by definition.

An eleventh aspect of the invention is the rubber composition according to any one of the first to the tenth aspects, wherein the amount of the liquid diene polymer is at most <NUM> phr (for example, from <NUM> to <NUM> phr), preferably at most <NUM> phr (for example, from <NUM> to <NUM> phr), more preferably at most <NUM> phr (from <NUM> to <NUM> phr).

A twelfth aspect of the invention is the rubber composition according to any one of the first to the eleventh aspects, wherein the liquid diene polymer has a glass transition temperature of less than -<NUM> (for example, between -<NUM> and -<NUM>), preferably less than -<NUM> (for example, between -<NUM> and -<NUM>), more preferably less than -<NUM> (for example, between -<NUM> and -<NUM>), still more preferably less than -<NUM> (for example, between -<NUM> and -<NUM>).

A thirteenth aspect of the invention is the rubber composition according to any one of the first to twelfth aspects, wherein the liquid diene polymer has a number average molar mass of between <NUM> and <NUM>/mol, preferably less than <NUM>/mol (for example, between <NUM> and <NUM>/mol), more preferably less than <NUM>/mol (for example, between <NUM> and <NUM>/mol), still more preferably less than <NUM>/mol (for example, between <NUM> and <NUM>/mol).

The number average molar mass (Mn) can be measured by gel permeation chromatography (GPC).

In case of gel permeation chromatography (GPC) of hydroxyl-terminated polybutadienes: The measurements can be carried out at <NUM> in tetrahydrofuran (THF) at a concentration of <NUM>/L and a flow rate of <NUM>/min. Chromatographic separation can be achieved using a PSS SDV Micro <NUM> µ /<NUM> × <NUM> precolumn and a PSS SDV Micro linear S <NUM> µ /<NUM>×<NUM> (<NUM>×) separation column. Detection can be by means of an RI detector. Calibration can be carried out by means of a polybutadiene standard (PSS-Kit polybutadiene-<NUM>,<NUM>, Mp <NUM><NUM>-<NUM>, Part No.:PSS-bdfkit, Mn: <NUM>/<NUM>/<NUM>/<NUM>/<NUM>).

In cast of gel permeation chromatography (GPC) of silane terminated polybutadienes: The measurements can be carried out at room temperature in tetrahydrofuran (THF) at a concentration of <NUM>/L and a flow rate of <NUM>/min. Chromatographic separation can be effected using a combination of styrene-divinylbenzene columns (<NUM>×<NUM>, <NUM> µ n, linear; 1x30 cm <NUM> µ m, <NUM>Å). Detection can be by means of an RI detector. Calibration can be carried out by means of polystyrene standards and absolute molecular weights obtained via Mark-Houwink constants (a=<NUM>; k=<NUM>/g).

According to a preferred embodiment of the invention, the liquid diene polymer is selected from the group consisting of liquid polybutadiene(s), liquid polyisoprene(s), liquid styrene-butadiene copolymer(s), and the combinations thereof.

According to a more preferred embodiment of the preferred embodiment, the liquid diene polymer is preferably selected from the group consisting of liquid polybutadiene(s), liquid polyisoprene(s), and the combinations thereof.

According to another more preferred embodiment of the preferred embodiment, the liquid diene polymer is preferably selected from the group consisting of liquid polybutadiene(s), liquid styrene-butadiene copolymer(s), and the combinations thereof.

A fourteenth aspect of the invention is the rubber composition according to any one of the first to thirteenth aspects, wherein the liquid diene polymer comprises the <NUM>,<NUM>-butadiene derived monomer units being <NUM>,<NUM>-vinyl, <NUM>,<NUM>-trans and <NUM>,<NUM>-cis, and wherein the proportion of <NUM>,<NUM>-vinyl in the entirety of the <NUM>,<NUM>-butadiene derived monomer units present in the liquid diene polymer is less than <NUM> mol% (for example, between <NUM> and <NUM> mol%), preferably less than <NUM> mol% (for example, between <NUM> and <NUM> mol%), more preferably less than <NUM> mol% (for example, between <NUM> and <NUM> mol%), and wherein the sum of the proportions of <NUM>,<NUM>-trans and <NUM>,<NUM>-cis in the entirety of the <NUM>,<NUM>-butadiene derived monomer units present in the liquid diene polymer is more than <NUM> mol% (for example, between <NUM> and <NUM> mol%), preferably more than <NUM> mol% (for example, between <NUM> and <NUM> mol%), more preferably more than <NUM> mol% (between <NUM> and <NUM> mol%).

According to a preferred embodiment of the fourteenth aspect, wherein the proportion of <NUM>,<NUM>-trans in the entirety of the <NUM>,<NUM>-butadiene derived monomer units present in the liquid diene polymer is more than <NUM> mol% (for example, between <NUM> and <NUM> mol%), preferably more than <NUM> mol% (for example, between <NUM> and <NUM> mol%), more preferably more than <NUM>% (for example, between <NUM> and <NUM> mol%), still more preferably more than <NUM>% (for example, between <NUM> and <NUM> mol%), particularly more than <NUM> mol% (for example, between <NUM> and <NUM> mol%).

The features of the above microstructure (<NUM>,<NUM>-vinyl content; <NUM>,<NUM>-cis content; and <NUM>,<NUM>-trans content) can be determined after completion of synthesis of the liquid diene polymer by nuclear magnetic resonance (NMR) with <NUM>H, <NUM>C or the both, for example, <NUM>C NMR (<NUM>; relaxation agent: Cr (acac)<NUM>; solvent: deuterated chloroform (CDC<NUM>), Bruker <NUM>).

A fifteenth aspect of the invention is the rubber composition according to any one of the first to the fourteenth aspects, wherein the liquid diene polymer is a liquid polybutadiene.

According to a preferred embodiment of the fifteenth aspect, the term "liquid polybutadiene" as used herein is to be understood as meaning a product obtainable by polymerization of monomer units each having at least two conjugated double bonds, wherein in order of increasing preference, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>% of the monomer units are <NUM>,<NUM>-butadiene.

The liquid diene polymer in the liquid plasticizer in the plasticizing agent in the rubber composition according to the invention bears at least one function.

A sixteenth aspect of the invention is the rubber composition according to any one of the first to the fifteenth aspects, wherein the liquid diene polymer is such that the function comprises at least one function selected from the group consisting of silane function(s), hydroxyl function(s), anhydride function(s) (for example, maleic anhydride functions), and the combinations thereof.

According to a preferred embodiment of the invention, the liquid diene polymer has an average functionality of more than <NUM> (for example, between <NUM> and <NUM>), preferably at least <NUM> (from <NUM> to <NUM>). The average functionality can be calculated via the number average molar mass (Mn) of the liquid diene polymer and the function number (for example, the number of silane groups, the number of hydroxyl groups, and the number of anhydride groups).

According to a preferred embodiment of the sixteenth aspect, the liquid diene polymer is such that the function comprises at least one function selected from the group consisting of silane function(s), hydroxyl function(s), and the combinations thereof.

According to a more preferred embodiment of the sixteenth aspect or the preferred embodiment, the liquid diene polymer is a liquid diene polymer produced by free-radical polymerization.

According to a still more preferred embodiment of the more preferred embodiment, the liquid diene polymer is a liquid polybutadiene that comprises at least one hydroxyl function produced by polymerization of <NUM>,<NUM>-butadiene in the presence of peroxide, water and an organic solvent, preferably the liquid polybutadiene is a hydroxyl-terminated liquid polybutadiene ,as described in <CIT>,.

According to another still more preferred embodiment of the more preferred embodiment, the liquid diene polymer a liquid polybutadiene that comprises at least one silane function produced by reacting at least one organosilane compound (preferably, <NUM>-isocyanatopropyltrimethoxysilane, isocyanatopropyltriethoxysilane or the combinations thereof) with the liquid polybutadiene comprising at least one hydroxyl function (preferably, a hydroxyl-terminated liquid polybutadiene), preferably a triethoxysilane-terminated liquid polybutadiene, as described in <CIT>.

A seventeenth aspect of the invention is the rubber composition according to any one of the first to the sixteenth aspects, wherein the liquid diene polymer is such that the function is a silane function.

According to a preferred embodiment of the invention, the liquid plasticizer optionally comprises at least one liquid plasticizer other than the liquid diene polymer, that is, the liquid plasticizer does not comprise any liquid plasticizer other than the liquid diene polymer, or comprises at least one liquid plasticizer other than the liquid diene polymer. Preferably, the liquid plasticizer other than the liquid diene polymer is selected from the group consisting of liquid diene polymer(s) not bearing any function, polyolefinic oil(s), naphthenic oil(s), paraffinic oil(s), Distillate Aromatic Extracts (DAE) oil(s), Medium Extracted Solvates (MES) oil(s), Treated Distillate Aromatic Extracts (TDAE) oil(s), Residual Aromatic Extracts (RAE) oil(s), Treated Residual Aromatic Extracts (TRAE) oil(s), Safety Residual Aromatic Extracts (SRAE) oil(s), mineral oil(s), vegetable oil(s), ether plasticizer(s), ester plasticizer(s), phosphate plasticizer(s), sulphonate plasticizer(s) and the combinations thereof, preferably selected from the group consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and the combinations thereof, more preferably selected from the group consisting of MES oils, vegetable oils and the combinations thereof, still more preferably selected from the group consisting of vegetable oils and the combinations thereof.

An eighteenth aspect of the invention is the rubber composition according to any one of the first to the seventeenth aspects, wherein the liquid plasticizer further comprises a vegetable oil, and wherein the amount in phr of vegetable oil is higher than one-third of the amount in phr of the liquid diene polymer.

According to a preferred embodiment of the eighteenth aspect, the amount in phr of vegetable oil is higher than that of the liquid diene polymer, preferably the amount in phr of vegetable oil is higher than twice of the amount in phr of the liquid diene polymer.

According to a preferred embodiment of the eighteenth aspect, the amount of the vegetable oil is more than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr).

According to a preferred embodiment of the eighteenth aspect, the vegetable oil(s) is made of an oil selected from the group consisting of linseed, safflower, soybean, corn, cottonseed, turnip seed, castor, tung, pine, sunflower, palm, olive, coconut, groundnut and grapeseed oils, and the combinations thereof, preferably sunflower oil(s), more preferably sunflower oil(s) containing over <NUM>%, still preferably more over <NUM>%, particularly over <NUM>%, more particularly over <NUM>%, still more particularly <NUM>%, by weight of oleic acid.

A nineteenth aspect of the invention is the rubber composition according to any one of the first to the eighteenth aspects, wherein the plasticizing agent further comprises a hydrocarbon resin, and wherein the amount in phr of hydrocarbon resin is higher than that of the liquid diene polymer.

According to a preferred embodiment of the nineteenth aspect, the amount in phr of hydrocarbon resin is higher than twice of the amount in phr of the liquid diene polymer, preferably the amount in phr of hydrocarbon resin is higher than triple of the amount in phr of the liquid diene polymer.

According to a preferred embodiment of the nineteenth aspect, the amount in phr of hydrocarbon resin is higher than the total amount in phr of the liquid plasticizer.

According to a preferred embodiment of the nineteenth aspect, the amount of the hydrocarbon resin is more than <NUM> phr (for example, between <NUM> and <NUM> phr), preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more preferably more than <NUM> phr (for example, between <NUM> and <NUM> phr), particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more particularly more than <NUM> phr (for example, between <NUM> and <NUM> phr), advantageously more than <NUM> phr (for example, between <NUM> and <NUM> phr), more advantageously more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more advantageously more than <NUM> phr (for example, between <NUM> and <NUM> phr), especially more than <NUM> phr (for example, between <NUM> and <NUM> phr), more especially more than <NUM> phr (for example, between <NUM> and <NUM> phr), still more especially more than <NUM> phr (for example, between <NUM> and <NUM> phr).

The hydrocarbon resin(s) are polymer well known by a person skilled in the art, which are essentially based on carbon and hydrogen, and thus miscible by nature in rubber composition(s), for instance, diene elastomer composition(s). They can be aliphatic or aromatic or also of the aliphatic/aromatic type, that is to say based on aliphatic and/or aromatic monomers. They can be natural or synthetic and may or may not be petroleum-based (if such is the case, also known under the name of petroleum resins). They are preferably exclusively hydrocarbon, that is to say, that they comprise only carbon and hydrogen atoms.

Preferably, the hydrocarbon resins as being "plasticizing" exhibit at least one, more preferably all, of the following characteristics:.

The macrostructure (Mw, Mn and PI) of the hydrocarbon resins is determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature <NUM>; concentration <NUM>/l; flow rate <NUM>/min; solution filtered through a filter with a porosity of <NUM> µ m before injection; Moore calibration with polystyrene standards; set of <NUM> "Waters" columns in series ("Styragel" HR4E, HR1 and HR0. <NUM>); detection by differential refractometer ("Waters <NUM>") and its associated operating software ("Waters Empower").

According to preferred embodiment of the nineteenth aspect, the hydrocarbon resin is selected from the group consisting of cyclopentadiene (abbreviated to CPD) homopolymer or copolymer resins, dicyclopentadiene (abbreviated to DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C<NUM> fraction homopolymer or copolymer resins, C<NUM> fraction homopolymer or copolymer resins, alpha-methyl styrene homopolymer or copolymer resins and the combinations thereof. Use is more preferably made, among the above copolymer resins, of those selected from the group consisting of (D)CPD/vinylaromatic copolymer resins, (D)CPD/terpene copolymer resins, (D)CPD/C<NUM> fraction copolymer resins, (D)CPD/C<NUM> fraction copolymer resins, terpene/vinylaromatic copolymer resins, terpene/phenol copolymer resins, C<NUM> fraction/vinyl-aromatic copolymer resins, C<NUM> fraction/vinylaromatic copolymer resins, and the combinations thereof.

The term "terpene" combines here, in a known way, the α -pinene, β -pinene and limonene monomers; use is preferably made of a limonene monomer, which compound exists, in a known way, in the form of three possible isomers: L-limonene (laevorotatory enantiomer), D-limonene (dextrorotatory enantiomer) or else dipentene, the racemate of the dextrorotatory and laevorotatory enantiomers. Styrene, α -methylstyrene, ortho-, meta- or para-methylstyrene, vinyltoluene, para-(tert-butyl)styrene, methoxystyrenes, chlorostyrenes, hydroxystyrenes vinylmesitylene, divinylbenzene, vinylnaphthalene, or any vinylaromatic monomer resulting from a C<NUM> fraction (or more generally from a C<NUM> to C<NUM> fraction) are suitable, for example, as vinylaromatic monomer. Preferably, the vinylaromatic compound is styrene or a vinylaromatic monomer resulting from a C<NUM> fraction (or more generally from a C<NUM> to C<NUM> fraction). Preferably, the vinylaromatic compound is the minor monomer, expressed as molar fraction, in the copolymer under consideration.

Mention may also be made, as examples of other preferred resins, of phenol-modified α - methylstirene resins. It should be remembered that, in order to characterize these phenol-modified resins, use is made, in a known way, of a number referred to as "hydroxyl number" (measured according to Standard ISO <NUM> and expressed in mg KOH/g). α - Methylstirene resins, in particular those modified with phenol, are well known to a person skilled in the art and are available commercially.

The rubber compositions according to the invention may be based on all or a portion(s) of the usual additives generally used in the elastomer compositions intended in particular for rubber articles (for example, tires, shoes or caterpillar tracks), in more particular for tires, in still more particular for tire treads, such as, for example, protection agents, such as antiozone waxes, chemical antiozonants, antioxidants, reinforcing resins, methylene acceptors (for example phenolic novolak resin) or methylene donors (for example hexamethylenetetramine (HMT) or hexamethoxymethylmelamine (H3M)), a crosslinking system based either on sulphur or on donors of sulphur and/or per oxide and/or bismaleimides, vulcanization accelerators, or vulcanization activators.

The composition can be also based on coupling activators when a coupling agent is used, agents for covering the reinforcing inorganic filler or more generally processing aids capable, in a known way, by virtue of an improvement in the dispersion of the filler in the rubber matrix and of a lowering of the viscosity of the compositions, of improving their property of processing in the raw state; these agents are, for example, hydrolysable silanes, such as alkylalkoxysilanes, polyols, polyethers, amines, or hydroxylated or hydrolysable polyorganosiloxanes.

The rubber composition according to the invention may be manufactured in appropriate mixers using two successive preparation phases well known to a person skilled in the art: a first phase of thermomechanical working or kneading (referred to as "non-productive" phase) at high temperature, up to a maximum temperature of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, followed by a second phase of mechanical working (referred to as "productive" phase) at a lower temperature, typically of less than <NUM>, for example between <NUM> and <NUM>, finishing phase during which the crosslinking or vulcanization system is incorporated.

A process which can be used for the manufacture of such compositions comprises, for example and preferably, the following steps:.

According to a preferred embodiment of the invention, the first (non-productive) phase is carried out in a single thermomechanical stage during which all the necessary constituents may be introduced into an appropriate mixer, such as a standard internal mixer, followed, in a second step, for example after kneading for <NUM> to <NUM> minutes, by the other additives, optional additional filler-covering agents or processing aids, with the exception of the crosslinking system. The total kneading time, in this non-productive phase, is preferably between <NUM> and <NUM>.

After cooling the mixture thus obtained, the crosslinking system may be then incorporated at low temperature (for example, between <NUM> and <NUM>), generally in an external mixer, such as an open mill; the combined mixture is then mixed (the second (productive) phase) for a few minutes, for example between <NUM> and <NUM>.

The crosslinking system is preferably based on sulphur and on a primary vulcanization accelerator, in particular on an accelerator of sulphenamide type. Added to this vulcanization system are various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine), and the like, incorporated during the first non-productive phase and/or during the productive phase. The content of sulphur is preferably between <NUM> and <NUM> phr, more preferably between <NUM> and <NUM> phr, and that of the primary accelerator is preferably between <NUM> and <NUM> phr.

Use may be made, as accelerator (primary or secondary) of any compound capable of acting as accelerator of the vulcanization of elastomer matrix, for instance, diene elastomers, in the presence of sulphur, in particular accelerators of the thiazoles type and their derivatives, accelerators of thiurams types, or zinc dithiocarbamates. These accelerators are more preferably selected from the group consisting of <NUM>-mercaptobenzothiazyl disulphide (abbreviated to "MBTS"), N-cyclohexyl-<NUM>-benzothiazole sulphenamide (abbreviated to "CBS"), N,N-dicyclohexyl-<NUM> benzothiazolesulphenamide ("DCBS"), N-tert-butyl-<NUM>-ben zothiazolesulphenamide ("TBBS"), N-tert-butyl-<NUM> benzothiazolesulphenimide ("TBSI"), zinc dibenzyldithiocarbamate ("ZBEC"), Tetrabenzylthiuram disulfide ("TBZTD") and the combinations thereof.

The final composition thus obtained is subsequently calendered, for example in the form of a sheet or of a plaque, in particular for laboratory characterization, or else extruded in the form of a rubber profiled element which can be used directly as a laminate or an article, for example, a tire tread, a shoe sole and a caterpillar track tread.

The vulcanization (or curing) is carried out in a known way at a temperature generally of between <NUM> and <NUM> for a sufficient time which may vary, for example, between <NUM> and <NUM> depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition under consideration.

According to a preferred embodiment of the invention, an article comprises a rubber composition according to any one of the first to the nineteenth aspects.

According to a more preferred embodiment of the preferred embodiment, the article is a tire, a shoe, a conveyor or a caterpillar track, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread.

According to a still more preferred embodiment of the more preferred embodiment, the article is a tire, preferably a tire in which the rubber composition according to any one of the first to the nineteenth aspects is comprised in its tread, sidewall(s) or the both.

The tires of the invention are particularly intended to equip passenger motor vehicles, including <NUM>×<NUM> (four-wheel drive) vehicles and SUV (Sport Utility Vehicles) vehicles, and industrial vehicles particularly selected from vans and heavy duty vehicles (i.e., bus or heavy road transport vehicles (lorries, tractors, trailers)).

A twentieth aspect of the invention is a tire tread comprising a rubber composition according to any one of the first to the nineteenth aspects.

According to a preferred embodiment of twentieth aspect, the tire tread comprising at least two radially superposed portions which comprises a radially external portion and a radially internal portion, the radially external portion intended to come into contact with the ground, the radially external portion being made of a first rubber composition, and the radially internal portion being made of a second rubber composition different from the first rubber composition.

According to a more preferred embodiment of the preferred embodiment, the first rubber composition is a rubber composition any one of the first to the nineteenth aspects.

According to another more preferred embodiment of the preferred embodiment, the second rubber composition is a rubber composition any one of the first to the nineteenth aspects.

According to an embodiment of the other more preferred embodiment, the radially external portion is intended to come into contact with the ground during service life of the tire.

According to another embodiment of the other more preferred embodiment, the radially external portion is not intended to come into contact with the ground during service life of the tire.

A radial direction is defined as a direction perpendicular to the axis of rotation of the tire, and the expression "radially" means "in radial direction". The expressions "radially on the inside (radially inner or radially internal), or respectively radially on the outside (radially outer or radially external)" mean "closer or, respectively, further away, from the axis of rotation of the tire, in the radial direction, than".

The service life of the tire means the duration to use the tire (for example, the term from the new state to the final state of the tire, the final state means a state on reaching the wear indicator bar(s) in the tread of tire).

The invention relates to the rubber compositions in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization).

In order to confirm the effect of the invention, four rubber compositions (identified as C-<NUM> (a reference), C-<NUM> and C-<NUM> (examples according to the invention), and C-<NUM> (a comparative example)) are compared for Mooney plasticity (as an index of processability before curing) and tan(δ)max (as an index of hysteresis property after curing). They are based on a blend of BR and SBR bearing a SiOR function (as an elastomer matrix) reinforced with a blend of silica (as a reinforcing inorganic filler) and carbon black, and a plasticizing agent comprising a liquid polybutadiene (as a liquid diene polymer), a sunflower oil (as vegetable oil) and a C<NUM>/C<NUM> hydrocarbon resin (as hydrocarbon resin. The formulations of the three rubber compositions are given at Table <NUM> with the content of the various products expressed in phr.

Each rubber composition was produced as follows: The reinforcing filler, its associated coupling agent, the plasticizing agent, the elastomer matrix and the various other ingredients, with the exception of the vulcanization system, were successively introduced into an internal mixer having an initial vessel temperature of approximately <NUM>; the mixer was thus approximately <NUM>% full (% by volume). Thermomechanical working (non-productive phase) was then carried out in one stage, which lasts in total approximately <NUM> to <NUM> minutes, until a maximum "dropping" temperature of <NUM> was reached. The mixture thus obtained was recovered and cooled and then sulphur and an accelerator of sulphenamide type were incorporated on an external mixer (homofinisher) at <NUM> to <NUM>, everything being mixed (productive phase) for an appropriate time (for example, between <NUM> and <NUM>).

The rubber compositions thus obtained were subsequently calendered, either in the form of sheets (thickness of <NUM> to <NUM>) or of fine sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of profiled elements which could be used directly, after cutting and/or assembling to the desired dimensions, for example as tire semi-finished products, in particular as tire treads.

As the measurement of Mooney plasticity of each rubber composition before curing, the use was made of an oscillating consistometer as described in French Standard NF T <NUM>-<NUM> (November <NUM>). The Mooney plasticity measurement was carried out according to the following principle: the composition in the raw state (before curing) was molded in a cylindrical chamber heated to <NUM>. After preheating for one minute, the rotor rotated within the test specimen at <NUM> revolutions/minute and the working torque for maintaining this movement was measured after rotating for <NUM> minutes. The Mooney plasticity (ML1+<NUM>) is generally expressed in "Mooney unit" (MU, With <NUM> MU: <NUM> Newton-meter), and is representative of the processability. The lower Mooney plasticity is, the better processability is, therefore, a value (Mooney plasticity (C-<NUM>)/Mooney plasticity (C-n)×<NUM>; where n=<NUM>, <NUM>, <NUM> and <NUM>) greater than that of the reference (C-<NUM>), set at <NUM>, indicates an improved performance.

Each rubber composition was placed in a press with heated platens at a temperature (typically <NUM>), and for the time that was necessary for the crosslinking of these rubber compositions (typically several tens of minutes), at a pressure (typically <NUM> bar), and then, that is after curing, tan(δ)max of Each rubber composition was measured on a viscosity analyser (Metravib VA4000), according to the standard ASTM D <NUM>-<NUM>. A recording was made of the response of a sample of vulcanized composition (cylindrical test specimen with a thickness of <NUM> and a cross section of <NUM><NUM>), subjected to a simple alternating sinusoidal shear stress, at the frequency of <NUM>, under defined temperature conditions, for example at <NUM> according to the standard ASTM D <NUM>-<NUM>. A strain amplitude sweep was carried out from <NUM>% to <NUM>% (outward cycle), then from <NUM>% to <NUM>% (return cycle). For the return cycle, the maximum value of tan(δ) observed, identified as tan(δ)max at <NUM>, was indicated. The value of tan(δ)max at <NUM> is representative of the hysteresis property, and therefore of the rolling resistance. The lower tan(δ)max at <NUM> is, the better the hysteresis property (relative to rolling resistance) is, therefore, a value (tan(δ)max (C-<NUM>)/ tan(δ)max (C-n) × <NUM>; where n=<NUM>, <NUM>, <NUM> and <NUM>) greater than that of the reference (C-<NUM>), set at <NUM>, indicates an improved performance.

The results from Table <NUM> demonstrate that the rubber compositions (C-<NUM> and C-<NUM>) according to the invention have an unexpectedly improved balance of performances between the processability and the hysteresis property than that of the reference or the comparative example (C-<NUM> and C-<NUM>). The balance between the processability and the hysteresis property in Table <NUM> is a sum of the both performances.

In conclusion, the rubber composition according to the invention allows an improvement of the balance of performances between the processability and the hysteresis property.

Claim 1:
A rubber composition based on at least:
- an elastomer matrix comprising at least one first diene elastomer bearing at least one SiOR<NUM> function, R<NUM> being a hydrogen atom or a hydrocarbon radical, the SiOR<NUM> function not located at the chain ends of the first diene elastomer;
- a reinforcing filler comprising a reinforcing inorganic filler; and
- a plasticizing agent comprising a liquid plasticizer comprising a liquid diene polymer bearing at least one function
wherein the amount of the reinforcing inorganic filler is more than <NUM> phr;
wherein the liquid diene polymer is a diene polymer;
wherein the liquid diene polymer is liquid at <NUM>; and
wherein the liquid diene polymer has a number average molar mass of less than <NUM>/mol.