Rubber composition

Abstract

A rubber composition, which unexpectedly provides an improved balance between hysteresis performance and processability, is based on at least one elastomeric matrix; a reinforcing filler; and a granular rubber; wherein the total amount of the reinforcing filler is less than 50 phr; wherein the reinforcing filler comprises at least one carbon black and at least one silica; and wherein the total amount in phr of carbon black is lower than that of the silica.

Description

Description Title of the invention: A RUBBER COMPOSITION

[0001] The field of the invention is that of rubber compositions, particularly rubber compositions for rubber products, more particularly rubber compositions for rubber products coming into contact with ambient air, even more particularly rubber compositions for tires, shoes, conveyor belts or rubber tracks, specifically rubber compositions for tires, more specifically rubber compositions for tire sidewalls.

[0002] Generally, regarding the performance of rubber products such as tires, several excellent characteristics are required. However, it is known that these characteristics are in antinomic relationship with each other, for example between hysteresis and processability.

[0003] Patent document WO2006 / 052035 discloses a sidewall rubber composition composed of a novel vinyl-cis-polybutadiene, which has low matrix swelling and excellent extrusion processability and can improve low fuel consumption.

[0004] A constant goal of rubber product manufacturers is to improve the balance between hysteresis performance and processability.

[0005] In the course of their research, the inventors discovered that a specific rubber composition intended particularly for a rubber product, more particularly for a tire, a shoe, a conveyor belt or a rubber track, more particularly still for a tire sidewall, allows an improved and unexpected balance between hysteresis performance and processability.

[0006] The expression "based on" or "composition based on" must be understood as meaning a composition comprising the mixture, the product of the in situ reaction of the different basic constituents used or both, certain of these constituents being able to react, being intended to react, or being intended to react and being intended to react with each other, at least partially, during the different phases of manufacture of the composition or during subsequent hardening, modifying the composition as it is initially prepared. Thus, the compositions used for the invention may be different in the non-crosslinked state and in the crosslinked (vulcanized) state.

[0007] The term "pce" means part by weight per hundred parts of elastomers, in the sense of the preparation of the composition before curing. That is to say, in the case of the presence of granular rubber, the term "pce" means part by weight per hundred parts of "new" elastomers, thus excluding from the base 100 the elastomers contained in the granular rubber.

[0008] In this description, unless expressly stated otherwise, all percentages (%) indicated are percentages by weight (% by weight).

[0009] The expression "elastomer matrix" means, in a given composition, all of the elastomers present in said rubber composition.

[0010] In this description, unless expressly stated otherwise, each TgDSC (glass transition temperature) is measured in a known manner by DSC (differential scanning calorimetry) according to ASTM D3418-08.

[0011] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​greater than "a" and less than "b" (i.e., excluding the limits a and b) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0012] When reference is made to a "predominant" compound, this means, for the purposes of the present invention, that this compound is predominant among the compounds of the same type in the composition, i.e. it is the one which represents the greatest amount by weight among the compounds of the same type, and preferably more than 50% by weight, more preferably more than 75% by weight. Thus, for example, a predominant polymer is the polymer representing the greatest weight, relative to the total weight of the polymers in the composition. Similarly, a “predominant” filler is one that represents the greatest weight among the fillers in the composition. For example, in a system comprising a single polymer, the latter is predominant within the meaning of the present invention and, in a system comprising two polymers, the predominant polymer represents more than half the weight of the polymers. On the contrary, a “minor” compound is a compound that does not represent the largest weight fraction among the compounds of the same type.

[0013] For the purposes of the present invention, when reference is made to a “predominant” unit (or monomer) within the same compound (or polymer), this means that this unit (or monomer) is predominant among the units (or monomers) forming the compound (or polymer), that is to say that it is the one which represents the largest fraction by weight among the units (or monomers) forming the compound (or polymer). Thus, for example, a resin composed mainly of units derived from C5 monomers is a resin in which the C5 units represent the largest quantity by weight among all the units composing said resin. In other words, a “predominant” monomer or an assembly of “predominant” monomers is a monomer (or an assembly of monomers) which represents the largest fraction by weight in the polymer. On the contrary, a “minor” monomer is a monomer which does not represent the largest molar fraction in the polymer.

[0014] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. This particularly concerns polymers, plasticizers, fillers and others.

[0015] A first aspect of the invention is a rubber composition based on at least one elastomer matrix; a reinforcing filler; and a granular rubber; the total amount of the reinforcing filler being less than 50 phr; the reinforcing filler comprising at least one carbon black and at least one silica; and the total amount of carbon black being less than that of the silica.

[0016] The specific composition of the rubber allows for an improved and unexpected balance between hysteresis performance and processability.

[0017] Each of the aspects, embodiments, instantiations, and variations below, including each of the preferred ranges, materials, or both, may be applied to any of the other aspects, embodiments, instantiations, and variations of the invention, unless expressly indicated otherwise.

[0018] The rubber composition according to the invention is based on an elastomer matrix.

[0019] As is customary, the terms "elastomer" and "rubber", which are interchangeable, are used without distinction in the text.

[0020] By elastomer (or more loosely "rubber", the two terms being considered synonymous) of the "diene" type, we mean in a known manner one (or more) elastomer(s) derived at least partially (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0021] These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally speaking, the expression "essentially unsaturated" means 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 15% (mol %); thus, diene elastomers such as butyl rubbers or diene / α-olefin copolymers of the EPDM type do not meet the previous definition and can in particular be described as "essentially saturated" diene elastomers (low or very low content of units of diene origin, always less than 15%).In the category of "essentially unsaturated" diene elastomers, a "highly unsaturated" diene elastomer means in particular a diene elastomer whose content of units of diene origin (conjugated dienes) is greater than 50%.

[0022] Although it applies to any type of diene elastomer, it is preferably used with essentially unsaturated diene elastomers.

[0023] Taking into account these definitions, the expression diene elastomer capable of being used in the compositions according to the invention is understood to mean in particular: - (a) any homopolymer obtained by polymerization of a conjugated diene monomer, preferably having from 4 to 12 carbon atoms; - (b) any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinyl aromatic compounds preferably having from 8 to 20 carbon atoms.

[0024] The following compounds are particularly suitable as conjugated dienes: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C1-C5 alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene or 2-methyl-3-isopropyl-1,3-butadiene, an aryl-1,3-butadiene, 1,3-pentadiene or 2,4-hexadiene. The following vinyl aromatic compounds, for example, are suitable: styrene, ortho-methylstyrene, meta-methylstyrene or para-methylstyrene, the commercial mixture "vinyltoluene", para-(tert-butyl)styrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene or vinylnaphthalene.

[0025] A second aspect of the invention is the rubber composition according to the first aspect, the elastomer matrix comprising at least one elastomer selected from the group consisting of an isoprene elastomer and a butadiene elastomer.

[0026] A third aspect of the invention is the rubber composition according to the first aspect or the second aspect, the elastomer matrix comprising at least one isoprene elastomer, preferably the total amount of the isoprene elastomer being greater than 30 phr and less than 70 phr.

[0027] Isoprene elastomer means all elastomers composed mainly of isoprene monomers.

[0028] According to a preferred embodiment of the second aspect or the third aspect, the isoprene elastomer is selected from the group consisting of isoprene polymers, isoprene copolymers and corresponding combinations.

[0029] According to a more preferred embodiment of the above preferred embodiment, the isoprene copolymers are selected from the group consisting of butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and combinations thereof.

[0030] According to an even more preferred embodiment of the above more preferred embodiment, the butadiene-isoprene (BIR) copolymers have an isoprene content of greater than 50% by weight and less than 90% by weight per 100% by weight of the butadiene-isoprene (BIR) copolymers.

[0031] According to an even more preferred embodiment of the above more preferred embodiment, the butadiene-isoprene copolymers (BIR) have a TgDSC of -80°C to -40°C.

[0032] According to an even more preferred embodiment of the above more preferred embodiment, the styrene-isoprene (SIR) copolymers have a styrene content of greater than 5 wt% and less than 50 wt% per 100 wt% of the styrene-isoprene (SIR) copolymers.

[0033] According to an even more preferred embodiment of the above more preferred embodiment, the styrene-isoprene copolymers (SIR) have a TgDSC greater than -50°C and less than -25°C.

[0034] According to an even more preferred embodiment of the above more preferred embodiment, the styrene-butadiene-isoprene (SBIR) copolymers have an isoprene content which is greater than the styrene and butadiene content.

[0035] According to an even more preferred embodiment of the above more preferred embodiment, the styrene-butadiene-isoprene (SBIR) copolymers have an isoprene content of greater than 50% by weight and less than 60% by weight per 100% by weight of the styrene-butadiene-isoprene (SBIR) copolymers.

[0036] According to a preferred embodiment of the second aspect or the third aspect, the isoprene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprenes and combinations thereof. corresponding, preferably the isoprene elastomer is made of natural rubber.

[0037] According to a more preferred embodiment of the preferred embodiment, the synthetic polyisoprene is a synthetic polyisoprene, preferably having a content (mol%) of cis-1,4 bonds greater than 90%, more preferably greater than 95%, even more preferably greater than 98%.

[0038] A fourth aspect of the invention is the rubber composition according to any one of the first to third aspects, the elastomer matrix comprising at least one butadiene elastomer, preferably the total amount of the butadiene elastomer being greater than 30 phr and less than 70 phr.

[0039] Butadiene elastomer means all elastomers composed mainly of butadiene monomers.

[0040] According to a preferred embodiment of the second aspect or the fourth aspect, the butadiene elastomer is selected from the group consisting of butadiene polymers, butadiene copolymers and combinations thereof, preferably selected from the group consisting of polybutadienes (BR), styrene-butadiene copolymers (SBR) and combinations thereof.

[0041] According to a more preferred embodiment, the butadiene elastomer is selected from the group consisting of polybutadienes (BR) and corresponding combinations.

[0042] According to an even more preferred embodiment of the above more preferred embodiment, the polybutadienes have a content (mol%) of 1,2-units of more than 4% and less than 80%.

[0043] According to an even more preferred embodiment of the above more preferred embodiment, the polybutadienes have a cis-1,4 content (mol%) of more than 80%.

[0044] According to a more preferred embodiment of the preferred embodiment, the butadiene copolymer is selected from the group consisting of copolymers styrene-butadiene (SBR), butadiene-isoprene (BIR) copolymers, styrene-butadiene-isoprene (SBIR) copolymers and corresponding combinations.

[0045] According to an even more preferred embodiment of the above more preferred embodiment, the butadiene copolymer is selected from the group consisting of styrene-butadiene copolymers (SBR) and combinations thereof.

[0046] According to a particular embodiment of the even more preferred embodiment above, the styrene-butadiene copolymers (SBR) have a glass transition temperature TgDSC greater than -100°C and less than 0°C, preferably greater than -90°C and less than 0°C, more preferably greater than -80°C and less than 0°C, even more preferably greater than 70°C and less than 0°C, in particular greater than -60°C and less than -10°C.

[0047] According to a particular embodiment of the above even more preferred embodiment, the styrene-butadiene copolymers (SBR) have a styrene content of more than 5% by weight and less than 60% by weight, more particularly more than 20% by weight and less than 50% by weight, per 100% by weight of the styrene-butadiene copolymers (SBR).

[0048] According to a particular embodiment of the even more preferred embodiment above, the styrene-butadiene copolymers (SBR) have a content (mol%) of 1,2-linkages of the butadiene part greater than 4% and less than 75% and a content (mol%) of trans-1,4-linkages greater than 10% and less than 80%.

[0049] According to an even more preferred embodiment of the above more preferred embodiment, the butadiene copolymer is selected from the group consisting of butadiene-isoprene (BIR) copolymers and combinations thereof.

[0050] According to a particularly preferred embodiment of the above even more preferred embodiment, the butadiene-isoprene (BIR) copolymers have an isoprene content of greater than 5% by weight and less than 50% by weight per 100% by weight of the butadiene-isoprene (BIR) copolymers.

[0051] According to a particular embodiment of the above even more preferred embodiment, the butadiene-isoprene copolymers (B IR) have a TgDSC ranging from -80°C to -40°C.

[0052] According to an even more preferred embodiment of the above more preferred embodiment, the butadiene copolymer is selected from the group consisting of styrene-butadiene-isoprene (SBIR) copolymers and combinations thereof. The styrene-butadiene-isoprene (SBIR) copolymers have a butadiene content greater than the styrene and isoprene contents.

[0053] A fifth aspect of the invention is the rubber composition according to any one of the first to fourth aspects, the elastomer matrix comprising at least one isoprene elastomer and at least one butadiene elastomer, preferably the total amount of the isoprene elastomer being greater than 30 phr and less than 70 phr, and the total amount of the butadiene elastomer being greater than 30 phr and less than 70 phr.

[0054] According to a preferred embodiment of the third aspect or the fifth aspect, the total amount of the isoprene elastomer is less than or equal to 65 phr, preferably less than 65 phr, more preferably less than or equal to 60 phr, even more preferably less than 60 phr, in particular less than or equal to 55 phr, more particularly less than 55 phr.

[0055] According to a preferred embodiment of the third aspect or the fifth aspect, the total amount of the isoprene elastomer is greater than or equal to 35 phr, preferably greater than 35 phr, more preferably greater than or equal to 40 phr, even more preferably greater than 40 phr, particularly greater than or equal to 45 phr, more particularly greater than 45 phr.

[0056] According to a preferred embodiment of the fourth aspect or the fifth aspect, the total amount of the butadiene elastomer is less than or equal to 65 phr, preferably less than 65 phr, more preferably less than or equal to 60 phr, even more preferably less than 60 phr, in particular less than or equal to 55 phr, more particularly less than 55 phr.

[0057] According to a preferred embodiment of the fourth aspect or the fifth aspect, the total amount of the butadiene elastomer is greater than or equal to 35 phr, preferably greater than 35 phr, more preferably greater than or equal to 40 phr, even more preferably greater than 40 phr, particularly greater than or equal to 45 phr, more particularly greater than 45 phr.

[0058] According to a preferred embodiment of the invention, the elastomer matrix in the rubber composition according to the invention consists of isoprene elastomer and butadiene elastomer.

[0059] According to another preferred embodiment of the invention, the elastomer matrix in the rubber composition according to the invention comprises another elastomer or an elastomer other than the isoprene elastomer and the butadiene elastomer.

[0060] Any elastomer known to those skilled in the art which is not defined above as isoprene elastomer or butadiene elastomer may be used as such.

[0061] The rubber composition according to the invention is based on a reinforcing filler, and the total amount of the reinforcing filler is less than 50 phr, preferably less than or equal to 45 phr, more preferably less than 45 phr, even more preferably less than or equal to 40 phr, particularly less than 40 phr.

[0062] A sixth aspect of the invention is the rubber composition according to any one of the first to fifth aspects, wherein the total amount of the reinforcing filler is greater than 5 phr, preferably greater than or equal to 10 phr, more preferably greater than 10 phr, even more preferably greater than or equal to 15 phr, particularly greater than 15 phr, more particularly greater than or equal to 20 phr, even more particularly greater than 20 phr, advantageously greater than or equal to 25 phr, more advantageously greater than 25 phr, even more advantageously greater than or equal to 30 phr, particularly greater than 30 phr, more particularly greater than or equal to 35 phr, even more particularly greater than 35 phr.

[0063] Any type of reinforcing filler known for its ability to reinforce a rubber composition that can be used for the manufacture of the rubber product may be used, for example an organic reinforcing filler, such as at least one carbon black, or an inorganic reinforcing filler, such as a silica (SiO2), an alumina (AI2O3) or a combination thereof, with which at least one coupling agent is combined in a known manner.

[0064] The reinforcing filler in the rubber composition according to the invention comprises at least one carbon black.

[0065] A seventh aspect of the invention is the rubber composition according to any one of the first to sixth aspects, wherein the total amount of carbon black in the reinforcing filler is greater than 0 phr, preferably greater than or equal to 1 phr, more preferably greater than 1 phr, even more preferably greater than or equal to 2 phr, especially greater than 2 phr, more particularly greater than or equal to 3 phr, and wherein the total amount of carbon black in the reinforcing filler is less than 20 phr, preferably less than or equal to 15 phr, more preferably less than 15 phr, even more preferably less than or equal to 10 phr, especially less than 10 phr, more particularly less than or equal to 5 phr, even more particularly less than 5 phr.

[0066] The weight fraction of carbon black can be measured by thermogravimetric analysis (TGA) according to standard NF T-46-07, on a Mettler Toledo instrument, model "TGA / DSC1". Approximately 20 g of sample can be introduced into the thermal analyzer, then subjected to a thermal program from 25 °C to 600 °C under an inert atmosphere (pyrolyzable phase), then from 400 °C to 750 °C under an oxidizing atmosphere (oxidizable phase). The weight of the sample can be measured continuously throughout the thermal program. The organic matter content can correspond to the weight loss measured during the pyrolyzable phase relative to the initial weight of the sample. The quantity of carbon black can correspond to the weight loss measured during the oxidizable phase relative to the initial weight of the sample.

[0067] As carbon blacks, all carbon blacks, in particular SAF, ISAF, HAF, FEF, GPF, HMF, SRF, and SRF type blacks, conventionally used in tires (so-called "tire quality" blacks) are suitable, such as, for example, reinforcing carbon blacks of the 100, 200 or 300 series in ASTM qualities (such as, for example, blacks N115, N134, N234, N326, N330, N339, N347 or N375), or carbon blacks of higher series, the 500, 600, 700, 800 or 900 series in ASTM qualities (such as, for example, blacks N550, N660, N683, N772, N774, N880, N990, N991).

[0068] According to a preferred embodiment of the invention, the carbon black has a BET surface area (according to ASTM D6556-10) greater than 80 m2 / g (e.g., between 80 and 160 m2 / g), preferably greater than 90 m2 / g (e.g., between 90 and 150 m2 / g), more preferably greater than 100 m2 / g (e.g., between 100 and 140 m2 / g), even more preferably greater than 110 m2 / g (e.g., between 110 and 130 m2 / g).

[0069] According to a preferred embodiment of the invention, the carbon black has a compressed sample oil absorption number (COAN) (according to ASTM D3493-16) greater than 90 ml / 100g (e.g., between 90 and 120 ml / 100g), preferably greater than 95 ml / 100g (e.g., between 95 and 115 ml / 100g), more preferably greater than 100 ml / 100g (e.g., between 100 and 110 ml / 100g).

[0070] The reinforcing filler in the rubber composition according to the invention comprises at least one silica.

[0071] An eighth aspect of the invention is the rubber composition according to any one of the first to seventh aspects, wherein the total amount of silica in the reinforcing filler is greater than 20 phr, preferably greater than or equal to 25 phr, more preferably greater than 25 phr, even more preferably greater than or equal to 30 phr, particularly greater than 30 phr, and wherein the total amount of silica in the reinforcing filler is less than 50 phr, preferably less than or equal to 45 phr, more preferably less than 45 phr, even more preferably less than or equal to 50 phr, equal to 40 pce, particularly less than 40 pce, more particularly less than or equal to 35 pce, even more particularly less than 35 pce.

[0072] According to a preferred embodiment of the invention, the silica is any reinforcing silica, in particular any precipitated or fumed silica having a BET surface area and a CTAB specific surface area which are both less than 450 m2 / g, preferably from 20 to 400 m2 / g, more preferably from 50 to 350 m2 / g, even more preferably from 100 to 300 m2 / g, particularly between 150 and 250 m2 / g. The BET surface area can be measured according to a known method, i.e. by gas adsorption according to the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society", Vol. 60, page 309, February 1938, and more particularly according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points); where gas: nitrogen, degassing: 1 hour at 160 °C, relative pressure range p / po: 0.05 to 0.17). The CTAB specific surface area can be determined according to the French standard NF T 45-007 of November 1987 (method B).

[0073] According to a preferred embodiment of the invention, the silica is formed from particles whose weight average size is less than 1000 nm, preferably less than 500 nm, more preferably less than 200 nm, even more preferably between 20 nm and 200 nm.The weight average size can be measured in a known manner after dispersion by ultrasonic deagglomeration of the filler to be analyzed in water (or an aqueous solution containing a surfactant), for example by means of an X-ray detection centrifugal sedimentometer type XDC (X-ray disc centrifuge), sold by Brookhaven Instruments, according to the following procedure: 3.2 g of sample of inorganic filler to be analyzed are suspended in 40 ml of water by the action, for 8 minutes, at 60% power (60% of the maximum position of the "output control"), of a 1500 W ultrasonic probe (Vibracell 3 / 4 inch sonicator sold by Bioblock); after sonication, 15 ml of the suspension are introduced into the rotating disc; after sedimentation for 120 minutes, the weight distribution of the particle sizes and the size. weight average of particles dw are calculated by the XDC sedimentometer software.

[0074] The total amount in pce of carbon black in the reinforcing filler of the rubber composition according to the invention is less than that of silica.

[0075] According to a preferred embodiment of the invention, the total amount of carbon black in the reinforcing filler of the rubber composition according to the invention is less than 90% by weight, preferably less than 80% by weight, more preferably less than 70% by weight, even more preferably less than 60% by weight, particularly less than 50% by weight, more particularly less than 40% by weight, even more particularly less than 30% by weight, advantageously less than 20% by weight, more preferably less than 10% by weight, per 100% by weight of the reinforcing filler.

[0076] According to a preferred embodiment of the invention, the rubber composition according to the invention is based on a silane-type coupling agent.

[0077] The silane coupling agent is intended to provide sufficient chemical connection, sufficient physical connection, or both between the silica and the elastomer matrix.

[0078] The silane coupling agent, by definition at least bifunctional, has the simplified general formula “Y-AX”, in which: - Y represents a functional group (functionality “Y”) which is capable of physically bonding, chemically bonding or both to the silica, such bonding being able to be established, for example, between a silicon atom of the silane coupling agent and the surface silanol groups of the silica; - X represents a functional group (function “X”) which is capable of physically binding, chemically binding or both to the elastomer matrix, for example via a sulfur atom; - A represents a divalent group allowing Y and X to be linked.

[0079] Bifunctional organosilanes or polyorganosiloxanes are usually used, and most often silane polysulfides, called "symmetrical" or "asymmetrical" depending on their specific structure, as described in numerous patent documents (see, for example, WO 03 / 002648, WO 03 / 002649 or WO 2004 / 033548).

[0080] As a reminder, the most used are the so-called symmetrical silane polysulfides corresponding to the following general formula (I): Z - A - Sx - A - Z (I); in which: - x is an integer from 2 to 8 (preferably from 2 to 5); - A is a divalent hydrocarbon radical (preferably C1-C18 alkylene groups or C6-C12 arylene groups, more particularly C1-C10 alkylenes, in particular C1-C4, in particular propylene); - Z corresponds to one of the formula below:

[0081] [Chem. 1] in which: - the radicals Ra, substituted or not, identical or different from each other, represent a C1-C18 alkyl group, a C5-C18 cycloalkyl group or a C6-C18 aryl group (preferably, C1-C6 alkyl, cyclohexyl or phenyl groups, in particular C1-C4 alkyl groups, more particularly methyl, ethyl or both), - the radicals Rb, substituted or not, identical or different from each other, represent a C1-C18 alkoxyl or C5-C18 cycloalkoxyl group (preferably a group chosen from C1-C8 alkoxyls and C5-C8 cycloalkoxyls, more preferably a group chosen from C1-C4 alkoxyls, particularly methoxyl and ethoxyl), are particularly suitable, without limitation of the above definition.

[0082] In the case of a mixture of alkoxysilane polysulfides of formula (I) above, in particular normal commercially available mixtures, the average value of the indices "x" is a fractional number preferably between 2 and 5, more preferably about 4. However, the invention can also advantageously be carried out, for example, with alkoxysilane disulfides (x = 2).

[0083] Examples of silane polysulfides that may be mentioned more particularly are bis((C1-C4)alkoxyl(C1-C4)alkylsilyl(C1-C4)alkyl) polysulfides (in particular disulfides, trisulfides or tetrasulfides), such as, for example, bis(3-trimethoxysilylpropyl) or bis(3-triethoxysilylpropyl) polysulfides. Among these compounds, bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula [(C2H5O)3Si(CH2)3S2]2, or bis(3-triethoxysilylpropyl) disulfide, abbreviated to TESPD, of formula [(C2HSO)3Si(CH2)3S]2. Mention will also be made, as preferred examples, of bis(mono(C1-C4)alkoxydi(C1-C4)alkylsilylpropyl) polysulfides (in particular disulfides, trisulfides or tetrasulfides), more particularly bis(monoethoxydimethylsilylpropyl) tetrasulfide, as described in patent application WO 02 / 083782 (or US 7,217,751).

[0084] Mention may in particular be made, as coupling agent other than an alkoxysilane polysulfide, of bifunctional POS (polyorganosiloxanes) or hydroxysilane polysulfides (Rb = OH in formula (I) above), as described in patent applications WO 02 / 30939 (or US 6,774,255) and WO 02 / 31041 (or US 2004 / 051210), or silanes or POS bearing azodicarbonyl functional groups, as described for example in patent applications WO 2006 / 125532, WO 2006 / 125533 and WO 2006 / 125534.

[0085] Examples of other silane sulfides include, for example, silanes bearing at least one thiol function (-SH) (called mercaptosilanes), at least one blocked thiol function, or both, as described, for example, in patents or patent applications US 6,849,754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2008 / 055986, and WO 2010 / 072685.

[0086] Of course, it is also possible to use mixtures of the silane coupling agents described above, as described in particular in the patent application WO 2006 / 125534 mentioned above.

[0087] According to a more preferred embodiment, the amount of silane coupling agent in the rubber composition according to the invention is between 5% and 20% by weight per 100% by weight of the silica.

[0088] According to a preferred embodiment of the invention, the amount of the silane-type coupling agent is between 1 and 10 phr, preferably between 1 and 5 phr.

[0089] The rubber composition according to the invention is based on a granular rubber. (Abbreviated as “granular” in the rest of the text).

[0090] A ninth aspect of the invention is the rubber composition according to any one of the first to eighth aspects, wherein the total amount of granular rubber is greater than 0 phr, preferably greater than or equal to 1 phr, more preferably greater than 1 phr, even more preferably greater than or equal to 2 phr, in particular greater than 2 phr, more particularly greater than or equal to 3 phr, even more particularly greater than 3 phr, and wherein the total amount of granular rubber is less than 50 phr, preferably less than or equal to 40 phr, more preferably less than 40 phr, even more preferably less than or equal to 30 phr, in particular less than 30 phr, more particularly less than or equal to 20 phr, even more particularly less than 20 phr, advantageously less than or equal to 15 phr, more advantageously less than 15 phr, even more advantageously less than or equal to 10 phr,in particular less than 10 pce.,

[0091] A tenth aspect of the invention is the rubber composition according to any one of the first to ninth aspects, wherein the total amount, in phr, of the crumb rubber is greater than that of the carbon black, and wherein the total amount, in phr, of the crumb rubber is less than that of the silica.

[0092] Granular rubbers are in the form of granules, possibly processed into a rubber sheet. Usually, granular rubbers are derived from the grinding or micronization of vulcanized rubber compositions already used for a first application, for example in tires; they are products of material recycling.

[0093] Crumb rubber can be obtained by grinding used tires or other rubbers into granules from which reinforcing materials such as steel or fibers have been removed, as well as any other contaminants such as dust, glass, or stones. The book "Rubber Chemistry and Technology" discloses numerous methods for grinding vulcanized or crosslinked rubbers to obtain crumb rubber.

[0094] According to a preferred embodiment of the invention, the crumb rubber is generated from used tires.

[0095] According to a preferred embodiment of the invention, the granular rubber is in the form of microparticles.

[0096] By "microparticles" we mean particles which have a size, namely their diameter in the case of spherical particles or their largest dimension in the case of anisometric particles, of a few microns or a few tens of microns or a few hundreds of microns.

[0097] An eleventh aspect of the invention is the rubber composition according to any one of the first to tenth aspects, wherein the crumb rubber comprises no crumb rubber particles remaining on a 40 mesh sieve, or the crumb rubber comprises crumb rubber particles remaining on a 40 mesh sieve and the total amount of the crumb rubber particles remaining on the 40 mesh sieve is less than 10% by weight relative to 100% by weight of the crumb rubber, preferably wherein the crumb rubber comprises no crumb rubber particles remaining on a 60 mesh sieve, or the crumb rubber comprises crumb rubber particles remaining on a 60 mesh sieve and the total amount of the crumb rubber particles remaining on the 60 mesh sieve is less than 10% by weight relative to 100% by weight of the crumb rubber, more preferably wherein the rubber granular does not include granular rubber particles remaining on an 80 mesh screen, or the granular rubber includes granular rubber particles remaining on an 80 mesh screen and the total amount of the granular rubber particles remaining on the 80 mesh screen is less than 10% by weight per 100% by weight of the granular rubber.

[0098] The total amount of crumb rubber particles remaining on the 40 mesh screen is less than 10% by weight per 100% by weight of crumb rubber, which means that more than 90% by weight of the crumb rubber particles per 100% by weight of crumb rubber can pass through the 40 mesh screen.

[0099] The total amount by weight of the granular rubber particles in the granular rubber of the rubber composition according to the invention can be obtained from the particle size distribution of the granular determined in accordance with ASTM-D5644-01.

[0100] Alternatively, the particle size distribution of the granular, i.e. the weight distribution of the particle size of the granular, can be measured by laser particle size analysis, on a Malvern Mastersizer 3000 device. The measurement can be carried out by the liquid route, diluted in alcohol after an ultrasonic pretreatment for 1 minute to ensure particle dispersion. The measurement can be carried out according to ISO- 13320-1 and can allow the determination in particular of the D10 and D50, i.e. the average diameter below which respectively 10% by weight and 50% by weight of the total particle population may be present.

[0101] According to a preferred embodiment of the invention, the crumb rubber in the rubber composition according to the invention is mechanically treated, cryogenically treated, or mechanically and cryogenically treated, i.e., the crumb rubber is ground using a mechanical grinding process, a cryogenic process, or both processes. In both processes, the steel components are removed using a magnetic separator and the fiber components are separated by air classifiers or other separation apparatus. The mechanical grinding process uses various grinding techniques, such as cracking mills, granulators, etc., to mechanically break down the rubber into small particles. In the cryogenic process, the shredded rubber is frozen to an extremely low temperature and then broken into small particles.

[0102] According to a more preferred embodiment of the above preferred embodiment, the granular rubber is cryogenically treated in accordance with the micronization processes described in US7445170 and US7861958.

[0103] Commercially available granular rubber is for example "PolyDyne 40", "PolyDyne 80", "PolyDyne 140" or "PolyDyne 200" from Lehigh Technologies.

[0104] The granular rubber in the rubber composition according to the invention may consist of a composition based on all the ingredients normally used in rubber compositions for rubber products.

[0105] According to a preferred embodiment of the invention, the granular rubber in the rubber composition according to the invention consists of a composition based on an elastomer.

[0106] According to a more preferred embodiment of the above preferred embodiment, the granular rubber comprises an elastomer which represents more than 30% by weight, preferably more than 35% by weight, more preferably more than 40% by weight, per 100% by weight of the granular rubber, said percentage being determined according to ASTM E1131-03.

[0107] According to a further preferred embodiment of the above preferred embodiment or the more preferred embodiment above, the granular rubber comprises an elastomer which comprises, preferably consists of, a diene elastomer.

[0108] According to a particular embodiment of the above even more preferred embodiment, the diene elastomer in the granular rubber is selected from the group consisting of polybutadienes, polyisoprenes, including natural rubber, butadiene copolymers and isoprene copolymers.

[0109] According to a particular embodiment of the even more preferred embodiment above, the molar content of units of diene origin (dienes conjugated) present in the diene elastomer in the granular rubber is greater than 50%, preferably greater than 50% and less than 70%.

[0110] According to a preferred embodiment of the invention, the granular rubber in the rubber composition according to the invention consists of a composition based on a filler.

[0111] According to a more preferred embodiment of the above preferred embodiment, the above amount of the filler in the crumb rubber is greater than 5% by weight and less than 80% by weight, preferably greater than 10% by weight and less than 75% by weight, more preferably greater than 15% by weight and less than 70% by weight, of a filler per 100% by weight of the crumb rubber, said percentage being determined in accordance with ASTM E1131-03.

[0112] The term "filler" herein refers to any type of filler, whether reinforcing filler (usually having nanometric particles, having a weight average size preferably less than 500 nm, in particular greater than 20 nm and less than 200 nm) or non-reinforcing filler or inert filler (usually having micrometric particles, having a weight average size preferably greater than 1 pm, for example greater than 2 pm and less than 200 pm). The weight average size of the nanometric particles is measured in a manner well known to those skilled in the art (for example, according to patent application WO 2009 / 083160 paragraph 1.1). The weight average size of the micrometric particles can be determined by mechanical sieving.

[0113] According to a more preferred embodiment of the above preferred embodiment, the filler in the crumb rubber comprises a reinforcing filler, preferably the reinforcing filler comprises an organic reinforcing filler, an inorganic reinforcing filler or a combination thereof.

[0114] Any type of reinforcing filler known to have the ability to reinforce a rubber composition that can be used in the manufacture of the rubber product may be used, for example, an organic reinforcing filler, such as at least one carbon black, or an inorganic filler. reinforcing material, such as silica (SiO2), alumina (AI2O3) or a combination thereof, with which at least one coupling agent is combined in a known manner.

[0115] According to an even more preferred embodiment of the above more preferred embodiment, the reinforcing filler in the granular rubber comprises an organic reinforcing filler, preferably at least one carbon black, representing more preferably more than 50% by weight, even more preferably more than 60% by weight, in particular more than 70% by weight, more particularly more than 80% by weight, even more particularly more than 90% by weight, advantageously 100% by weight, per 100% by weight of the reinforcing filler.

[0116] According to an even more preferred embodiment of the above more preferred embodiment, the reinforcing filler in the crumb rubber comprises an organic reinforcing filler, preferably at least one carbon black, more preferably representing from 20% by weight to 40% by weight, even more preferably from 25% by weight to 35% by weight, per 100% by weight of the crumb rubber.

[0117] The weight fraction of carbon black can be measured by thermogravimetric analysis (TGA) according to standard NF T-46-07, on a Mettler Toledo instrument, model "TGA / DSC1". Approximately 20 g of sample can be introduced into the thermal analyzer, then subjected to a thermal program from 25 °C to 600 °C under an inert atmosphere (pyrolyzable phase), then from 400 °C to 750 °C under an oxidizing atmosphere (oxidizable phase). The weight of the sample can be measured continuously throughout the thermal program. The organic matter content can correspond to the weight loss measured during the pyrolyzable phase relative to the initial weight of the sample. The quantity of carbon black can correspond to the weight loss measured during the oxidizable phase relative to the initial weight of the sample.

[0118] As carbon blacks, all carbon blacks, including SAF, ISAF, HAF, FEF, GPF, HMF, SRF, and SRF types, conventionally used in tires (so-called "tire quality" blacks) are suitable, such as, for example, 100, 200 series reinforcing carbon blacks. or 300 in ASTM grades (such as blacks N115, N134, N234, N326, N330, N339, N347 or N375), or higher series carbon blacks, series 500, 600, 700, 800 or 900 in ASTM grades (such as blacks N550, N660, N683, N772, N774, N880, N990, N991).

[0119] According to a more preferred embodiment of the above preferred embodiment, the filler in the crumb rubber comprises a non-reinforcing filler, preferably chalk, kaolin or a combination thereof.

[0120] The granular rubber in the rubber composition according to the invention may consist of a composition based on usual additives generally used in rubber compositions intended for rubber products. The additives may also be present in the granular rubber in the form of a residue or a derivative, since they may have reacted during the stages of production of the composition or of crosslinking of the composition from which the granular rubber is derived.

[0121] The granular rubber in the rubber composition according to the invention may be simple ground / micronized rubber materials, without any further treatment.

[0122] A twelfth aspect of the invention is the rubber composition according to any one of the first to eleventh aspects, wherein the crumb rubber has not undergone any modification by a treatment selected from the group consisting of thermal, mechanical, biological and chemical treatments and combinations thereof.

[0123] According to a preferred embodiment of the twelfth aspect, the crumb rubber has an acetone extract of greater than 3% by weight and less than 30% by weight, preferably greater than 3% by weight and less than 15% by weight, more preferably greater than 3% by weight and less than 10% by weight, per 100% by weight of the crumb rubber.

[0124] According to a preferred embodiment of the twelfth aspect, the granular rubber has a chloroform extract of more than 3% by weight and less than 85% by weight, preferably more than 3% by weight and less than 20% by weight, more preferably more than 5% by weight and less than 15% by weight, by weight per 100% by weight of the crumb rubber.

[0125] According to a preferred embodiment of the twelfth aspect, the granular rubber has a chloroform extract whose weight average molecular weight (Mw) is less than 10,000 g / mol, preferably less than 8,000 g / mol.

[0126] According to a preferred embodiment of the twelfth aspect, a weight ratio of a chloroform extract to an acetone extract in the granular rubber is less than 1.5.

[0127] According to a preferred embodiment of the invention, the granular rubber in the rubber composition according to the invention undergoes a treatment in order to modify it. This treatment may consist of chemical functionalization or modification by devulcanization. It may also be a thermomechanical, thermochemical, biological treatment, and the like.

[0128] According to one embodiment of the invention, the granular rubber of the rubber composition according to the invention has a morphology modified by heat treatment, mechanical treatment, biological treatment, chemical treatment or a combination thereof. Preferably, the modified granular rubber has an acetone extract of more than 5% by weight and less than 20% by weight, more preferably from 10% by weight to 18% by weight. Also, preferably, the modified granular rubber has a chloroform extract of more than 15% by weight and less than 85% by weight, more preferably from 15% by weight to 50% by weight. Preferably, the chloroform extract of the modified granular rubber has a weight average molecular weight (Mw) of more than 10,000 g / mol, more preferably more than 20,000 g / mol and even more preferably more than 30,000 g / mol.Preferably, a weight ratio of chloroform extract to acetone extract in the modified granular rubber is greater than or equal to 1.5, preferably greater than 2.

[0129] The amount of acetone or chloroform extract can be measured according to ISO1407 using a Soxhlet extractor. A test sample (more than 500 mg and less than 5 g) can be introduced into a chamber extraction tube and then placed in the Soxhlet extraction tube. A volume of acetone or chloroform equal to two or three times the volume of the extraction tube can be placed in the Soxhlet collector. The Soxhlet can then be assembled and heated for 16 h. The sample can be weighed after extraction. The amount of acetone or chloroform extract can correspond to the weight loss of the sample during extraction, compared to its initial weight.

[0130] Molecular weights can be determined by size exclusion chromatography, according to a Moore calibration and in accordance with ISO16014. The weight average molecular weight (Mw) of the chloroform extract can be measured by size exclusion chromatography (SEC) with a refractive index (RI) detector. The system can consist of a Waters Alliance 2695 line, a Waters column oven and also a Waters RI 410 detector. The column set used can consist of two PL Gel Mixed D columns (300x7.5 mm 5 µm), followed by two PL Gel Mixed E columns (300x7.5 mm 3 µm) from Agilent. These columns can be placed in a column oven thermostatically controlled at 35 °C. The mobile phase used can be non-antioxidized tetrahydrofuran. The flow rate of the mobile phase can be 1 ml / minute. The RI detector can also be thermostated at 35°C. The chloroform extract can be dried under a nitrogen stream.The dry extract can then be taken up at 1 g / l in unantioxidized tetrahydrofuran at 250 ppm with stirring for 2 hours. The resulting solution can be filtered using a syringe and a disposable 0.45 µm PTFE syringe filter. 100 µl of the filtered solution can be injected into the conditioned chromatographic system at 1 ml / minute and 35 °C. Mw results can be provided by integrating the chromatographic peaks detected by the RI detector above a value of 2000 g / mol. The Mw can be calculated from a calibration carried out using polystyrene references.

[0131] The total amount of the reinforcing filler and the granular rubber in the rubber composition according to the invention is greater than 30 phr and less than 70 phr.

[0132] According to a preferred embodiment of the invention, the total amount of the reinforcing filler and the granular rubber in the rubber composition according to the invention is greater than or equal to 35 phr, preferably greater than 35 phr, more preferably greater than or equal to 40 phr, even more preferably greater than 40 phr, particularly greater than or equal to 45 phr, more particularly greater than 45 phr.

[0133] According to a preferred embodiment of the invention, the total amount of the reinforcing filler and the granular rubber in the rubber composition according to the invention is less than or equal to 65 phr, preferably less than 65 phr, more preferably less than or equal to 60 phr, even more preferably less than 60 phr, in particular less than or equal to 55 phr, more particularly less than 55 phr, even more particularly less than or equal to 50 phr, in particular less than 50 phr.

[0134] A weight ratio of the total amount of granular rubber to the total amount of reinforcing filler in the rubber composition according to the invention is greater than 0.20 and less than 2.50, preferably less than or equal to 2.00, more preferably less than 2.00, even more preferably less than or equal to 1.50, particularly less than 1.50, more particularly less than or equal to 1.00, even more particularly less than 1.00.

[0135] The rubber compositions according to the invention may be based on all or at least some of the usual additives generally used in rubber compositions intended for rubber products (e.g., tires, shoes, conveyor belts or caterpillars), such as plasticizing agents (e.g., liquid plasticizers (e.g., oils), solid plasticizers (e.g., hydrocarbon resins with or without tackifying resin characteristics) or combinations thereof), protective agents (e.g., anti-ozonating waxes, chemical anti-ozonating agents, antioxidants or combinations thereof), pigments, anti-fatigue agents, reinforcing resins, methylene acceptors (e.g., phenolic novolak resin), methylene donors (e.g., hexamethylenetetramine (HMT), hexamethoxymethylmelamine (H3M) or combinations thereof), processing acids, a crosslinking (vulcanization) system or corresponding combinations.

[0136] A thirteenth aspect of the invention is the rubber composition according to any one of the first to twelfth aspects, wherein the rubber composition is further based on an anti-ozone wax, preferably wherein the total amount of the anti-ozone wax is greater than 1 phr in order to maintain or further improve the ozone resistance performance.

[0137] The ozone resistance performance of rubber compositions can be measured by the following method: 10 test pieces for each of the rubber compositions are prepared by curing in a bell press, cooling at room temperature for 1 day, and placing in an oven under air at a temperature of 77°C for 28 days. The 10 test pieces for each of the rubber compositions are placed on a trapezoid at different elongations ranging from 10% to 100% in steps of 10% elongation. The test pieces called "B15" were from an MFTR plate (known as Monsanto), the two end beads of which are used to hold the test piece. The "B15" test pieces have the following dimensions: 78.5 mm*15 mm*1.5 mm.After exposure for 192 hours to a temperature of 38°C and an ozone content of 50 ppmm (parts per hundred million), the facies of each specimen is rated according to the number and depth of cracks. This subjective rating ranges from 0 to 5 (0: absence of cracks; 1 to 4: presence of increasingly wide and deep cracks; 5: fracture of the specimen). This means that the lower the subjective rating, the better the ozone performance.

[0138] According to a preferred embodiment of the fourteenth aspect, the total amount of the anti-ozonant wax in the rubber composition according to the invention is greater than or equal to 1.1 phr, preferably greater than 1.1 phr, more preferably greater than or equal to 1.2 phr, even more preferably greater than 1.2 phr, particularly greater than or equal to 1.3 phr, more particularly greater than 1.3 phr.

[0139] Anti-ozone wax is called anti-ozone wax and is well known to those skilled in the art as film-forming anti-ozone wax. These film-forming anti-ozone waxes may, for example, be paraffin waxes, microcrystalline waxes or mixtures of paraffin and microcrystalline waxes. They consist of a mixture of linear alkanes and non-linear alkanes (isoalkanes, cycloalkanes, branched alkanes) derived from petroleum refining or the catalytic hydrogenation of carbon monoxide (Fischer-Tropsch process) comprising mainly chains of at least 20 carbon atoms.

[0140] Any anti-ozone wax known to those skilled in the art may be used, including natural waxes, such as, for example, candelilla wax or carnauba wax. These waxes may, furthermore, be used as mixtures.

[0141] Commercially available wax removers include, for example, "Varazon 4959", "Varazon 6500" and "Varazon 6810" from Sasol, "Ozoace 0355" from Nippon Seiro, "Negozone 9343" from H&R, and "H3841" from Yanggu Huatai.

[0142] According to a preferred embodiment of the fourteenth aspect, the antiozonant wax comprises from 50% by weight to 75% by weight of linear alkanes comprising from 30 carbon atoms to 38 carbon atoms, relative to the total amount of linear alkanes.

[0143] According to a preferred embodiment of the fourteenth aspect, the total amount of the anti-ozone wax is less than 3 phr in order to improve the efflorescence performance. Efflorescence is a phenomenon whereby the anti-ozone wax has the disadvantage of migrating to the outside of rubber products comprising rubber compositions, revealing whitish stains which penalize the aesthetics of the rubber products.

[0144] The efflorescence performance of rubber compounds can be measured using the following method: After cutting into the slabs of the cured rubber compounds, the 2.5 mm thick specimens are baked at 70 °C in air for 12 hours. They are then cured at 40 °C in air for 4 weeks. After removal from the oven and exposure to room temperature for 15 minutes, the specimens are each scraped with a metal blade to reveal the efflorescence of the anti-ozone wax. The extent of the efflorescence phenomenon (white discoloration of the surface) is then assessed using a subjective scale of values representative of the final appearance of the samples. The values ​​of this subjective scale obtained respectively for the tested samples can vary from 0 to 3 and correspond to the “efflorescence classification”. These values, ranging from 0 to 3, correspond to the following aspects for the samples: 0: No efflorescence. The scraped surface remains black. 1: Slight efflorescence. 2: Moderate efflorescence. 3: Total efflorescence. The scraped surface is white.

[0145] The lower the value, the better the appearance of efflorescence, i.e. the lower the efflorescence.

[0146] According to a preferred embodiment of the above preferred embodiment, the total amount of the anti-ozonant wax in the rubber composition according to the invention is less than or equal to 2.8 phr, preferably less than 2.8 phr, more preferably less than or equal to 2.6 phr, even more preferably less than 2.6 phr, particularly less than or equal to 2.4 phr, more particularly less than 2.4 phr, even more particularly less than or equal to 2.2 phr, advantageously less than 2.2 phr, more advantageously less than or equal to 2.0 phr, even more advantageously less than 2.0 phr, especially less than or equal to 1.8 phr, more especially less than 1.8 phr, even more especially less than or equal to 1.6 phr, especially less than 1.6 phr, more especially less than or equal to 1.4 phr.

[0147] According to a preferred embodiment of the invention, the rubber composition according to the invention is further based on a crosslinking system.

[0148] According to a more preferred embodiment of the above preferred embodiment, the crosslinking system in the rubber composition according to the invention comprises a vulcanizing agent, preferably selected from the group consisting of sulfur, a sulfur donor, a peroxide, a bismaleimide and a combination thereof, more preferably selected from the group consisting of sulfur and a combination thereof. The vulcanizing agent is referred to as a "vulcanizing agent", "hardener" or "curing agent". According to an even more preferred embodiment of the above more preferred embodiment, the sulfur donor is an alkylphenol disulfide (abbreviated as "APDS"), more preferably paracert butylphenol disulfide. According to an even more preferred embodiment of the above more preferred embodiment, the total amount of vulcanizing agent is greater than 0.5 phr and less than 10 phr, preferably greater than 0.5 phr and less than 3 phr.

[0149] According to a more preferred embodiment of the above preferred embodiment, the crosslinking system in the rubber composition according to the invention comprises a vulcanization accelerator, preferably a primary vulcanization accelerator, more preferably selected from the group consisting of a sulfenamide type accelerator, a thiazole type accelerator, a thiuram type accelerator, a dithiocarbamate type accelerator and a combination thereof, more preferably selected from the group consisting of a sulfenamide type accelerator and a combination thereof.According to an even more preferred embodiment of the above more preferred embodiment, the sulfenamide accelerator is selected from the group consisting of N-cyclohexyl-2-benzothiazolesulfenamide (abbreviated as "CBS"), N-(tert-butyl)-2-benzothiazolesulfenamide (abbreviated as "TBBS"), N-tert-butyl-2-benzothiazolesulfenimide (abbreviated as "TBSI"), N-oxydiethylene-2-benzothiazolesulfenamide (abbreviated as "MBS"), N,N'-dicyclohexyl-2-benzothiazolesulfenamide (abbreviated as "DCBS") and a combination thereof. According to an even more preferred embodiment of the above more preferred embodiment, the thiazole accelerator is selected from the group consisting of 2-mercaptobenzothiazole (abbreviated as "MBT"), 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), zinc-2-mercaptobenzothiazole (abbreviated as "ZMBT"), 2-(morpholinothio)benzothiazole (abbreviated as "MDB") and a combination thereof.According to an even more preferred embodiment of the above more preferred embodiment, the thiuram accelerator is selected from the group consisting of tetramethylthiuram disulfide (abbreviated as "TMTD"). tetraethylthiuram disulfide (abbreviated as “TETD”), tetrabutylthiuram disulfide (abbreviated as “TBTD”), tetrakis(2-ethylhexyl)thiuram disulfide (abbreviated as “TOT-N”), tetramethylthiuram monosulfide (abbreviated as “TMTM”), dipentamethylenethiuram tetrasulfide (abbreviated as “DPTT”), tetrabenzylthiuram disulfide (abbreviated as “TBzTD”) and a combination thereof. According to an even more preferred embodiment of the above more preferred embodiment, the dithiocarbamate accelerator is selected from the group consisting of zinc dimethyldithiocarbamate (abbreviated as "ZDMC"), zinc diethyldithiocarbamate (abbreviated as "ZDEC"), zinc dibutyldithiocarbamate (abbreviated as "ZDBC"), zinc ethylphenyldithiocarbamate (abbreviated as "ZEPC"), zinc dibenzyldithiocarbamate (abbreviated as "ZDBzC"), zinc N-pentamethylenedithiocarbamate (abbreviated as "ZPDC") and a combination thereof.According to an even more preferred embodiment of the above more preferred embodiment, the total amount of the vulcanization accelerator is greater than 0.5 phr and less than 5.0 phr.

[0150] According to a more preferred embodiment of the above preferred embodiment, the crosslinking system in the rubber composition according to the invention comprises a vulcanization retarder, for example N-cyclohexylthiophthalimide (abbreviated as "CTP").

[0151] According to a more preferred embodiment of the above preferred embodiment, the crosslinking system in the rubber composition according to the invention comprises a vulcanization activator, preferably selected from the group consisting of zinc oxide, a fatty acid, a zinc fatty acid ester, a guanidine derivative or a combination thereof. According to an even more preferred embodiment of the above more preferred embodiment, the fatty acid is stearic acid, lauric acid, palmitic acid, oleic acid, naphthenic acid or a combination thereof. According to an even more preferred embodiment of the above more preferred embodiment, the zinc fatty acid ester is zinc stearic acid, zinc lauric acid, zinc palmitic acid, zinc oleic acid, zinc naphthenic acid or a combination thereof. According to an even more preferred embodiment of the above more preferred embodiment, the zinc fatty acid ester is zinc stearic acid, zinc lauric acid, zinc palmitic acid, zinc oleic acid, zinc naphthenic acid or a combination thereof. preferred of the more preferred embodiment above, the guanidine derivative is diphenylguanidine.

[0152] A fourteenth aspect of the invention is the rubber composition according to any one of the first to thirteenth aspects, wherein the rubber composition is further based on a crosslinking system which comprises a vulcanization activator comprising a guanidine derivative, preferably the total amount of the guanidine derivative is greater than 0.5% by weight and less than 5% by weight per 100% by weight of the silica in the reinforcing filler.

[0153] The rubber compositions according to the invention may be used alone or in admixture (i.e. as a mixture) with any other rubber composition which may be used for the manufacture of rubber products.

[0154] It goes without saying that the invention relates to the rubber compositions described above both in the unvulcanized or uncrosslinked state or in the raw state (i.e. before vulcanization) and in the vulcanized or crosslinked or vulcanized state (i.e. after crosslinking or vulcanization).

[0155] According to a preferred embodiment of the invention, the rubber composition according to the invention is further based on a crosslinking system comprising a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, a vulcanization activator or a corresponding combination, and the rubber composition according to the invention is manufactured in a mixer using two successive preparation phases: a first thermomechanical working or kneading phase (called "non-productive" phase) at high temperature, up to a maximum temperature above 110°C and below 200°C, preferably above 110°C and below 190°C, more preferably above 130°C and below 180°C, followed by a second mechanical working phase (called "productive" phase) at a lower temperature below or equal to 110°C, preferably above 40°C and below 100°C,more preferably above 60°C and below 100°C, finishing phase during which the vulcanizing agent, the vulcanization accelerator and the vulcanization retarder are incorporated or, their combination in the crosslinking system. According to a more preferred embodiment of the above preferred embodiment, the vulcanization activator is incorporated during the first non-productive phase, during the productive phase or during both phases, preferably during the first non-productive phase.

[0156] According to a more preferred embodiment of the above preferred embodiment, the first phase (the non-productive phase) is carried out in several thermomechanical steps: during the first step in the several thermomechanical steps, the elastomer matrix, the reinforcing filler, the granular rubber (and optionally the plasticizing agent, the other ingredients or combinations thereof, except the vulcanizing agent, the vulcanization accelerator, the vulcanization retarder or their combination in the crosslinking system) are introduced into a mixer (preferably an internal mixer) at a temperature above 20°C and below 100°C, preferably above 25°C and below 100°C;and after a few minutes, preferably from 0.5 minutes to 2 minutes, and a temperature rise to 90°C or more (preferably, 100°C), the elastomer matrix, the other ingredient and their combination (i.e. those remaining, in case not all of them were introduced into the mixer in the first stage (the non-productive phase)) are added all at once or in portions, with the exception of the vulcanizing agent, the vulcanization accelerator, the vulcanization retarder or their combination in the crosslinking system, during a mixing ranging from 20 seconds to a few minutes; wherein the total mixing time, in the first phase (the non-productive phase), is preferably greater than 1 minute and less than 15 minutes, more preferably greater than 2 minutes and less than 10 minutes, at a temperature less than or equal to 190°C, preferably less than or equal to 180°C, more preferably less than or equal to 170°C.;

[0157] According to an even more preferred embodiment of the preferred embodiment or the more preferred embodiment above, after cooling the mixture thus obtained, the vulcanizing agent, the vulcanization accelerator, the vulcanization retarder or their combination in the system of crosslinking is then incorporated at low temperature, preferably less than or equal to 100°C, more preferably less than or equal to 90°C, in an external mixer, preferably an open mill; the whole is then mixed in the second phase (the productive phase) for a few minutes, preferably more than 2 minutes and less than 15 minutes, more preferably more than 5 minutes and less than 15 minutes.

[0158] According to a particular embodiment of the above preferred embodiment, the above more preferred embodiment or the above even more preferred embodiment, the rubber composition thus obtained in the mixer using two successive preparation phases is then calendered, for example in the form of a sheet or a plate, in particular for laboratory characterization, or extruded in the form of a profiled rubber element suitable for direct use as a rubber product, for example a tire sidewall, a tire tread, a shoe sole, a conveyor belt covering and a rubber track tread.

[0159] According to a more particular embodiment of the above preferred embodiment, the above more preferred embodiment, the above even more preferred embodiment or the above particular embodiment, the crosslinking (or curing) is carried out in a known manner at a temperature above 110°C and below 200°C, preferably above 130°C and below 190°C, under pressure, for a sufficient time which may be, for example, between 5 and 90 mm, depending in particular on the curing temperature, the crosslinking system adopted, the crosslinking kinetics of the rubber composition in question or the size of the rubber product.

[0160] According to a preferred embodiment of the invention, the rubber composition is a rubber composition for a rubber product coming into contact with ambient air, particularly a rubber composition for a tire, a shoe, a conveyor belt or a rubber track, more particularly for a tire sidewall, a tire tread, a shoe sole, a tread covering transport or a rubber track tread, more particularly a rubber composition for a tire sidewall.

[0161] A fifteenth aspect of the invention is a rubber product comprising a rubber composition according to any one of the first to fourteenth aspects, preferably wherein the rubber product comprises a rubber part comprising a rubber composition according to any one of the first to fourteenth aspects, more preferably wherein the rubber product is a tire, a shoe, a conveyor belt or a rubber track, more preferably wherein the rubber part is a tire sidewall, a tire tread, a tire rim cushion, a shoe sole, a conveyor belt cover or a rubber track tread, particularly wherein the rubber product is a tire comprising a rubber part which is a tire sidewall comprising a rubber composition according to any one of the first to fourteenth aspects.The tire sidewall is one of the parts of the tire and is intended to come into contact with the ambient air, but not with the ground. The tread is one of the parts of the tire and is intended to come into contact with the ambient air and the ground. The tire rim cushion is one of the parts of the tire and is intended to come into contact with the tire rim and the ambient air, but not with the ground. The conveyor belt is a means of transport of a belt conveyor system. The conveyor belt cover is one of the parts of the conveyor belt, also called cover rubber or "rubber cover", and is intended to come into contact with the ambient air. The rubber track is one of the continuous tracks, also called rubber track or rubber track band or rubber track and intended to equip a tracked vehicle.The rubber track tread is one of the parts of the rubber track and is intended to come into contact with the surrounding air and the ground.

[0162] According to a preferred embodiment of the invention, a tire comprises a rubber composition according to any one of the first to fourteenth aspects, preferably wherein the tire comprises a sidewall comprising a rubber composition according to any one of the first to fourteenth aspects.

[0163] The aforementioned tires of the invention are particularly intended for equipping passenger motor vehicles, including 4x4 (four-wheel drive) vehicles and SUV (Sport Utility Vehicles), and industrial vehicles, in particular vans and heavy-duty vehicles (i.e. buses or heavy-duty road transport vehicles (trucks, tractors, trailers)).

[0164] The invention is also illustrated by the following non-limiting examples. Examples

[0165] In order to confirm the effect of the invention, six rubber compositions (C1, C2 and C3: examples according to the invention, T1 and T2: references, and T3: a comparative example) were used. Each of the rubber compositions is based on diene elastomers (a combination of natural rubber (abbreviated as "NR") and polybutadiene rubber (abbreviated as "BR") as the elastomer matrix) reinforced with a combination of carbon black and silica (as a reinforcing filler), with or without crumb rubber. Each of the formulations of the rubber compositions is shown in Table 1 with the amount of the various products expressed in phr.

[0166] Each rubber composition was produced as follows: The reinforcing filler, elastomer matrix, anti-ozone wax, crumb rubber, plasticizing agent and various other ingredients, except for sulfur (as vulcanizing agent) and N-Cyclohexyl-2-benzothiazolesulfenamide (abbreviated as “CBS”) (as vulcanization accelerator) in a crosslinking system, were successively introduced into an internal mixer having an initial tank temperature of about 60 °C; the mixer was therefore filled to about 70% (% by volume). The thermomechanical working (non-productive phase) was then carried out in a single step, lasting a total of about 3 minutes to 4 minutes, until a maximum “fall” temperature of 165 °C was reached. The resulting mixture was recovered and cooled, and then the vulcanizing agent and vulcanization accelerator from the crosslinking system were added. crosslinking were incorporated on an external mixer (homofinisseur) at a temperature of 20°C to 30°C, the whole being mixed (productive phase) for an appropriate time (e.g., more than 5 minutes and less than 12 minutes).

[0167] The rubber compositions thus obtained were then calendered, either in the form of sheets (thickness of 2 to 3 mm) or thin rubber sheets, for the measurement of their physical or mechanical properties, or in the form of profiled elements which could be used directly, after cutting, assembly, or both to the desired dimensions, for example as semi-finished products for tires.

[0168] The dynamic properties (G 1: dynamic shear modulus (or dynamic modulus), G”: viscous shear modulus, tan 5: loss factor, and G*: complex modulus) of the rubber compositions were obtained from measurements carried out on a Metravib VA4000 visco-analyzer on specimens bonded from the cured rubber compositions. The specimens such as those described in ASTM D 5992-96 (the version published in September 2006, originally approved in 1996) in Figure X2.1 (circular shape) were used. The diameter “d” of the specimen was 10 mm (it therefore has a circular cross-section of 78.5 mm 2), the thickness "L" of each portion of the rubber composition was 2 mm, which gives a "d / L" ratio of 5 (contrary to ISO 2856 mentioned in ASTM standard, paragraph X2.4, which recommends a d / L value of 2). The response of a specimen of vulcanized rubber composition subjected to a simple alternating sinusoidal shear load at a frequency of 10 Hz and a temperature stabilized at 23 °C was recorded. The specimens were loaded symmetrically around their equilibrium position. The scanning covered strain amplitudes from 0.1% to 50% (peak-peak: on the forward cycle; 12 measurement points), then from 50% to 0.1% (peak-peak; on the return cycle; 11 measurement points). After each data acquisition, the dynamic shear elastic modulus (G 1) and the viscous shear modulus (G”) on the return cycle, as well as the loss factor (tan 5), which corresponds to the ratio G" / G', were calculated. Similarly, the complex modulus (G*) is defined as the absolute value of the complex sum of the elastic modulus (G 1 ) and the viscous modulus

[0169] Each value of G” at a frequency of 10 Hz, a stabilized temperature of 23 °C and a deformation of 10% is representative of the hysteresis performance of the rubber compositions each, and it is representative of the rolling resistance performance in the case where tires, conveyor belts or rubber tracks comprise the rubber compositions.

[0170] The results (hysteresis performance) are expressed in base 100, i.e. the value 100 is arbitrarily assigned to the reference (T1), then the values ​​of the examples (C1, C2 and C3) according to the invention, of the other reference (T2) and of the comparative example (T3) are indicated in Table 2. The values, which each correspond to G" (T1, 10 Hz, 23 °C, 10 %) / G"(X, 10 Hz, 23 °C, 10 %) x 100, where X is C1, C2, C3, T1, T2 or T3, are calculated. The higher the value, the lower the hysteresis loss, which means that the hysteresis performance is better.

[0171] For the processability test, each of the samples made from the rubber compositions was subjected to extrusion under conditions of barrel temperature of 90 °C, capillary diameter of 1 mm, capillary length of 10 mm and shear rate of 80 sec-1 , in accordance with Method A (capillary dies) of ISO 11443:2014, and the swelling ratio of the die was calculated using “extrudate diameter / capillary diameter”.

[0172] The results (processability) are expressed in base 100, i.e. the value 100 is arbitrarily assigned to the reference (T2), and then the values ​​of the examples (C1, C2 and C3) according to the invention, of the other reference (T1) and of the comparative example (T3) are indicated in Table 2. The values, which each correspond to the matrix swelling rate (T2, 10 Hz, 23 °C) / matrix swelling rate (X, 10 Hz, 23 °C) x 100, where X is C1, C2, C3, T1, T2 or T3, are calculated. The higher the value, the lower the matrix swelling rate, which means that the processability is better.

[0173] The results in Table 2 show that the examples (C1, C2 and C3) according to the invention have a better balance between hysteresis performance and processability than the references and the comparative example (T1, T2 and T3).

[0174] In conclusion, the rubber composition according to the invention allows an unexpectedly improved balance between hysteresis performance and processability.

[0175] [Table 1] (1) Natural rubber; (2) Nd butadiene rubber (3) Carbon black (ASTM Cabot grade N234, BET (in accordance with ASTM D6556-10): 119 m2 / g, COAN (in accordance with ASTM D3493-16): 102 m 1 / 100g) (4) Silica (“Ultrasil ® 7000GR” from Evonik; (5) Granular rubber (“Polydyne 80” from Lehigh Technologies); (6) Oleic sunflower oil (“Lubrirob Tod 1880” from the Novance company); (7) Silane coupling agent TESPT (“Si69” from Evonik); (8) Combination of two antioxidants ((N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine (“Santoflex 6-PPD” from Flexsys) and 2,2,4-trimethyl-1,2-dihydroquinolone (“TMQ” from Lanxess)); (9) Anti-ozone waxes (“Varazon 4959” from Sasol); (10) Diphenylguanidine (“Perkacit DPG” from Flexsys); (11) Stearic acid (“Pristerene 4931” from Uniqema); (12) Zinc oxide (industrial grade from Umicore); (13) N-dicyclohexyl-2-benzothiazolesulfenamide (“Santocure CBS” from Flexsys).

[0176] [Table 2]

Claims

Claims

1. Rubber composition based on at least: - an elastomer matrix; - a reinforcing charge; and - a granular rubber; the total quantity of the reinforcing filler being less than 50 pce; the reinforcing filler comprising at least one carbon black and at least one silica; and the total quantity in pce of carbon black being less than that of the silica.

2. A rubber composition according to claim 1, the elastomer matrix comprising at least one elastomer selected from the group consisting of an isoprene elastomer and a butadiene elastomer.

3. A rubber composition according to claim 1 or claim 2, the elastomer matrix comprising at least one isoprene elastomer, preferably the total amount of the isoprene elastomer being greater than 30 phr and less than 70 phr.

4. A rubber composition according to any one of claims 1 to 3, the elastomer matrix comprising at least one butadiene elastomer, preferably the total amount of the butadiene elastomer being greater than 30 phr and less than 70 phr.

5. A rubber composition according to any one of claims 1 to 4, the elastomer matrix comprising at least one isoprene elastomer and at least one butadiene elastomer, preferably the total amount of the isoprene elastomer being greater than 30 phr and less than 70 phr, and the total amount of the butadiene elastomer being greater than 30 phr and less than 70 phr.

6. A rubber composition according to any one of claims 1 to 5, the total amount of the reinforcing filler being greater than 5 phr.

7. A rubber composition according to any one of claims 1 to 6, wherein the total amount of carbon black in the reinforcing filler is greater than 0 phr and less than 20 phr.

8. A rubber composition according to any one of claims 1 to 7, the total amount of silica in the reinforcing filler being greater than 20 phr and less than 50 phr.

9. A rubber composition according to any one of claims 1 to 8, the total amount of the granular rubber being greater than 0 phr and less than 50 phr.

10. A rubber composition according to any one of claims 1 to 9, wherein the total amount in phr of the granular rubber is greater than that of the carbon black, and the total amount in phr of the granular rubber is less than that of the silica.

11. A rubber composition according to any one of claims 1 to 10, wherein the crumb rubber comprises no crumb rubber particles remaining on a 40 mesh screen, or the crumb rubber comprises crumb rubber particles remaining on a 40 mesh screen and the total amount of the crumb rubber particles remaining on the 40 mesh screen is less than 10% by weight per 100% by weight of the crumb rubber.

12. A rubber composition according to any one of claims 1 to 11, the granular rubber not having undergone any modification by a treatment selected from the group consisting of thermal, mechanical, biological and chemical treatments and combinations thereof.

13. A rubber composition according to any one of claims 1 to 12, the rubber composition further being based on an anti-ozonating wax.

14. A rubber composition according to any one of claims 1 to 13, the rubber composition further being based on a crosslinking system which comprises a vulcanization activator comprising a guanidine derivative, preferably the total amount of the guanidine derivative being greater than 0.5% by weight per 100% by weight of the silica in the reinforcing filler.

15. A rubber product comprising a rubber composition according to any one of claims 1 to 14, preferably the product comprising a rubber part comprising a rubber composition according to any one of claims 1 to 14, more preferably the rubber product being a tire, a shoe, a conveyor belt or a rubber track, even more preferably the rubber part being a tire sidewall, a tire tread, a tire rim cushion, a shoe sole, a conveyor belt liner or a rubber track tread, particularly the rubber product being a tire comprising a rubber part which is a tire sidewall comprising a rubber composition according to any one of claims 1 to 14.

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