WO2021166166A1

WO2021166166A1 - A rubber composition

Info

Publication number: WO2021166166A1
Application number: PCT/JP2020/006812
Authority: WO
Inventors: Tomoya SAKURADA
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2020-02-20
Filing date: 2020-02-20
Publication date: 2021-08-26

Abstract

A rubber composition is based on at least an elastomer matrix, a reinforcing filler predominately comprising a reinforcing inorganic filler, a polyethylene glycol, an epoxy and a crosslinking system based on at least one of a peroxide or a sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator.

Description

A RUBBER COMPOSITION

The field of the invention is that of rubber compositions intended in particular for laminates, in more particular for articles, for example, tires, shoes, conveyors or caterpillar tracks, in still more particular for tires, in especial for treads of tires, in more especial for treads of tires capable of rolling over ground surface covered with snow.

As is known, the snow tires classified in a category of use “snow”, identified by an inscription the alpine symbol (“3-peak-mountain with snowflake”), marked on their sidewalls, mean tires whose tread patterns, tread compounds and/or structures are primarily designed to achieve, in snow conditions, a performance better than that of normal tires intended for normal on-road use with regard to their abilities to initiate, maintain or stop vehicle motion.

JP 2018-188601

Snowy ground has a feature of having a low friction coefficient and a constant objective of manufacturers of rubber articles is improvement of a grip performance of rubber articles on snow-covered (snowy) ground without deteriorating the durability performance of rubber articles.

During their research, the inventor has discovered that a specific rubber composition intended in particular for a laminate, in more particular for a rubber article, for example, a tire tread, a shoe sole, a conveyor belt and a caterpillar track tread, which allows an improved grip performance on snowy ground with the unexpectedly improved durability performance.

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 Tg_DSC (glass transition temperature) is measured in a known way by DSC (Differential Scanning Calorimetry) according to Standard ASTM D3418-08.

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), the product of the reaction of the various constituents used or both, 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 an elastomer matrix, a reinforcing filler predominately comprising a reinforcing inorganic filler, a polyethylene glycol, an epoxy, and a crosslinking system based on at least one of a peroxide or a sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator.

The specific rubber composition allows an improved grip performance on snowy ground with the unexpectedly improved durability performance.

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

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

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 15% (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 15%). 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 50%.

Although it applies to any type of diene elastomer, a person skilled in the art of rubber article (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:
(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 one another or with one or more vinyl aromatic compounds preferably having from 8 to 20 carbon atoms.

The following are suitable in particular 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, 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.

A second aspect of the invention is the rubber composition according to the first aspect, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and combinations thereof.

According to a preferred embodiment of the second aspect, the copolymers are selected from the group consisting of butadiene copolymers, isoprene copolymers and combinations thereof, preferably selected from the group consisting of butadiene copolymers and combinations thereof, more preferably selected from the group consisting of styrene-butadiene copolymers (SBR), butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and combinations thereof, still more preferably selected from the group consisting of styrene-butadiene copolymers (SBR) and combinations thereof.

The diene elastomer may have any microstructure which depends on the polymerization conditions used, in particular on the presence or absence of a modifying agent(s), a randomizing agent(s) or both and on the amount(s) of modifying agent(s), randomizing agent(s) or both employed. This elastomer may, for example, be a block, statistical, sequential or micro sequential elastomer and may be prepared in dispersion or in solution. This elastomer may be coupled, star-branched or both; or else functionalized with a coupling agent(s), a star-branching agent(s) or both; or a functionalizing agent(s).

According to a more preferred embodiment of the preferred embodiment, the elastomer matrix comprises more than 50 phr and up to 100 phr, preferably at least 55 phr, more preferably at least 60 phr, still more preferably at least 65 phr, particularly at least 70 phr, more particularly at least 75 phr, of a first diene elastomer which is a styrene butadiene copolymer(s), preferably a solution styrene butadiene copolymer(s), and the elastomer matrix comprises no second diene elastomer or comprises less than 50 phr, preferably at most 45 phr, more preferably at most 40 phr, still more preferably at most 35 phr, particularly at most 30 phr, more particularly at most 25 phr, of a second diene elastomer which is different from the first diene elastomer.

According to a still more preferred embodiment of the more preferred embodiment, the first diene elastomer exhibits a glass transition temperature (Tg_DSC) of less than -40℃ (for example, between -40℃ and -110℃), preferably less than -45℃ (for example, between -45℃ and -105℃), more preferably less than -50℃ (for example, between -50℃ and -100℃), still more preferably less than -55℃ (for example, between -55℃ and -95℃), particularly at most -60℃ (for example, -60℃ to -90℃).

According to a particular embodiment of the more preferred embodiment or the still more preferred embodiment, the second diene elastomer is a polybutadiene(s) (BR) more preferably having a content (molar %) of 1,2-units of between 4% and 80% or those having a content (molar %) of cis-1,4-units of greater than 80%, more preferably greater than 90% (molar %), still more preferably greater than or equal to 96% (molar %).

According to a more particular embodiment of the more preferred embodiment, the still more preferred embodiment or the particular embodiment, the styrene-butadiene copolymer exhibits a styrene unit of less than 30% by weight (for example, between 3 and 30% by weight) per 100% by weight of the styrene-butadiene copolymer, preferably less than 27% by weight (for example, between 5 and 27% by weight), more preferably less than 23% by weight (for example, between 7 and 23% by weight), still more preferably less than 20% by weight (for example, between 10 and 20% by weight), particularly at most 18% by weight (for example, from 12 to 18%). The styrene unit can be determined by 1H NMR method in accordance with ISO 21561.

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 the article, for example a reinforcing organic filler, such as a carbon black, or a reinforcing inorganic filler, such as silica, with which a coupling agent is combined in a known way.

A third aspect of the invention is the rubber composition according to the first aspect or the second aspect, wherein the amount of reinforcing filler is more than 80 phr, preferably more than 90 phr, more preferably more than 100 phr, still more preferably more than 110 phr, particularly more than 115 phr, more particularly more than 120 phr.

According to a preferred embodiment of the invention, the amount of reinforcing filler is less than 300 phr, preferably less than 280 phr, more preferably less than 260 phr, still more preferably less than 240 phr, particularly less than 220 phr, more particularly less than 200 phr.

The reinforcing filler in the rubber composition according to the invention predominately comprises a reinforcing inorganic filler, that is, the reinforcing filler comprises more than 50%, preferably more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, by weight of the reinforcing inorganic filler per 100% 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 combinations of various reinforcing inorganic fillers, preferably of highly dispersible siliceous fillers, aluminous fillers or both is described hereafter.

Mineral fillers of the siliceous type (preferably silica (SiO₂)), the aluminous type (preferably alumina (Al₂O₃)) or both are suitable in particular as the reinforcing inorganic fillers.

A fourth aspect of the invention is the rubber composition according to any one of the first to the third aspects, wherein the amount of reinforcing inorganic filler is more than 50 phr, preferably more than 60 phr, more preferably more than 70 phr, still more preferably more than 80 phr, particularly more than 90 phr, more particularly more than 100 phr, still more particularly more than 110 phr, advantageously at least 115 phr.

According to a preferred embodiment of the fourth aspect, the amount of reinforcing inorganic filler is less than 300 phr, preferably less than 280 phr, more preferably less than 260 phr, still more preferably less than 240 phr, particularly less than 220 phr, more particularly less than 200 phr, still more particularly less than 180 phr, advantageously at most 165 phr.

A fifth aspect of the invention is the rubber composition according to any one of the first to the fourth aspects, wherein the reinforcing inorganic filler predominately comprises a silica, that is, the reinforcing inorganic filler comprises more than 50%, preferably more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, more particularly more than 100%, by weight of silica per 100% 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 450 m²/g, preferably from 20 to 400 m²/g, more preferably from 50 to 350 m²/g, still more preferably from 100 to 300 m²/g, particularly from 150 to 250 m²/g.

The BET surface area is measured according to a known method, that is, by gas adsorption using the Brunauer-Emmett-Teller method described in “The Journal of the American Chemical Society”, Vol. 60, page 309, February 1938, and more specifically, in accordance with the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points); where gas: nitrogen, degassing: 1 hour at 160℃, relative pressure range p/po: 0.05 to 0.17). The CTAB specific surface area is determined according to the French standard NF T 45-007 of November 1987 (method B).

A person skilled in the art will understand that a reinforcing filler of another nature, in particular organic nature, such as a 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 WO 96/37547 and WO 99/28380.

A sixth aspect of the invention is the rubber composition according to any one of the first to the fifth aspects, wherein the reinforcing filler further comprises a carbon black, and wherein the amount of carbon black is less than 45 phr, preferably less than 40 phr, more preferably less than 35 phr, still more preferably less than 30 phr, particularly less than 25 phr, more particularly less than 20 phr, still more particularly less than 15 phr, especially less than 10 phr, more especially less than 5 phr.

According to a preferred embodiment of the sixth aspect, the amount of carbon black is more than 1 phr, preferably more than 2 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) and high grip on wet.

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 nature, physical nature or both, 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 polysulfides, referred to as “symmetrical” or “asymmetrical” depending on their particular structure, as described, for example, in applications WO 03/002648, WO 03/002649 and WO 2004/033548.

Particularly suitable silane polysulfides correspond to the following general formula (I):
(I) Z - A - Sx - A - Z, 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, in particular C₁-C₄, alkylenes, especially propylene);
- Z corresponds to one of the formulae below:

in which:
- the R¹ radicals which are unsubstituted or substituted and identical to or different from one another, represent a C₁-C₁₈ alkyl, C₅-C₁₈ cycloalkyl or 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 R² radicals which are unsubstituted or substituted and identical to or different from one another, represent a C₁-C₁₈ alkoxyl or C₅-C₁₈ cycloalkoxyl group (preferably a group selected from C₁-C₈ alkoxyls and C₅-C₈ cycloalkoxyls, more preferably a group selected from C₁-C₄ alkoxyls, in particular methoxyl and ethoxyl), are suitable in particular, without limitation of the above definition.

In the case of a mixture of alkoxysilane polysulfides 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 2 and 5, more preferably of approximately 4. However, the present invention can also advantageously be carried out, for example, with alkoxysilane disulfides (x = 2).

Mention will more particularly be made, as examples of silane polysulfides, of 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. Use is in particular made, among these compounds, of 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)alkoxyldi(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).

Mention will in particular be made, as coupling agent other than alkoxysilane polysulfide, of bifunctional POSs (polyorganosiloxanes) or of hydroxysilane polysulfides (R² = OH in the above formula (I)), such as described in patent applications WO 02/30939 (or US 6 774 255) and WO 02/31041 (or US 2004/051210), or of silanes or POSs carrying azodicarbonyl functional groups, such as described, for example, in patent applications WO 2006/125532, WO 2006/125533 and WO 2006/125534.

As examples of other silane sulfides, mention will be made, for example, of the silanes bearing at least one thiol (-SH) function (referred to as mercaptosilanes), at least one blocked thiol function or both, such 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.

Of course, use could also be made of combinations of the coupling agents described previously, as described in particular in the aforementioned patent application WO 2006/125534.

According to a preferred embodiment of the invention, the content of coupling agent is from 0.5 to 15% by weight per 100% 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 40 phr (for example, between 0 and 40 phr), preferably less than 30 phr (for example, between 1 and 30 phr), more preferably less than 20 phr (for example, between 2 and 20 phr), of coupling agent.

The rubber composition according to the invention is based on a polyethylene glycol.

A seventh aspect of the invention is the rubber composition according to any one of the first to the sixth aspects, wherein the amount of polyethylene glycol is more than 1 phr, preferably more than 2 phr, still more preferably more than 3 phr, particularly more than 4 phr, more particularly more than 5 phr, still more particularly more than 6 phr, advantageously more than 7 phr, more advantageously more than 8 phr, still more advantageously more than 9 phr.

According to a preferred embodiment of the invention, the amount of polyethylene glycol is less than 20 phr, preferably less than 19 phr, more preferably less than 18 phr, still more preferably less than 17 phr, particularly less than 16 phr, more particularly less than 15 phr, still more particularly less than 14 phr, advantageously less than 13 phr, more advantageously less than 12 phr, still more advantageously less than 11 phr.

According to a preferred embodiment of the invention, the polyethylene glycol has a weight-average molecular weight of less than 20000 g/mol, preferably less than 10000 g/mol, more preferably less than 5000 g/mol, still more preferably less than 1000 g/mol, particularly less than 500 g/mol.

According to a preferred embodiment of the invention, the polyethylene glycol has a weight-average molecular weight of more than 100 g/mol, preferably more than 150 g/mol, more preferably more than 200 g/mol, still more preferably more than 250 g/mol, particularly more than 300 g/mol.

The weight-average molecular weight of the polyethylene glycol may be measured with Gel Permeation Chromatography (GPC).

The rubber composition according to the invention is based on an epoxy.

The epoxy comprises at least one compound whose molecule comprises at least one epoxide functional group which is a three-membered ring comprising an oxygen atom and two carbon atoms. The epoxy may harden by reacting with at least one co-reactant which is an epoxy hardener.

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 epoxy is at least 1 phr, preferably at least 5 phr, more preferably at least 10 phr, still more preferably at least 15 phr, particularly at least 20 phr, more particularly at least 25 phr, still more particularly at least 30 phr.

According to a preferred embodiment of the invention, the amount of epoxy is at most 50 phr.

A ninth aspect of the invention is the rubber composition according to any one of the first to the eighth aspects, wherein the epoxy comprises at least one epoxy resin comprising at least two, preferably more than two, more preferably at least three, epoxide functional groups in a molecule.

According to a preferred embodiment of the ninth aspect, the epoxy resin is selected from the group consisting of glycidyl ether epoxy resin(s), glycidyl amine epoxy resin(s), glycidyl ester epoxy resin(s), olefin oxidation (alicyclic) epoxy resin(s) and combinations thereof, preferably selected from the group consisting of glycidyl ether epoxy resin(s) and combinations thereof, more preferably selected from the group consisting of di-functional glycidyl ether epoxy resin(s), multi-functional glycidyl ether epoxy resin(s) and combinations thereof, still more preferably selected from the group consisting multi-functional glycidyl ether epoxy resin(s) and combinations thereof, particularly the multi-functional glycidyl ether epoxy resin(s) selected from the group consisting of oligomer epoxy resin(s), monomer epoxy resin(s) and combinations thereof.

According to a preferred embodiment of the ninth aspect, the epoxy resin has a viscosity of less than 2000 mPa・s, preferably less than 1500 mPa・s, more preferably less than 1000 mPa・s, still more preferably less than 500 mPa・s, at 150℃.

The above viscosity at 150℃ can measured in accordance with ASTM D4287.

According to a preferred embodiment of the ninth aspect, the epoxy resin has an epoxy equivalent weight of less than 500 g/eq, preferably less than 400 g/eq, more preferably less than 300 g/eq, still more preferably less than 200 g/eq, particularly less than 190 g/eq, more particularly less than 180 g/eq, still more particularly less than 170 g/eq.

The epoxy equivalent can be determined in accordance with ISO 3001.

The rubber composition according to the invention is based on a crosslinking system based on at least one of a peroxide or a sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator.

According to a preferred embodiment of the invention, the amount of peroxide in the rubber composition is less than 10 phr, preferably less than 9 phr, more preferably less than 8 phr, still more preferably less than 7 phr, particularly less than 6 phr, more particularly less than 5 phr, still more particularly less than 4 phr, advantageously less than 3 phr.

According to a preferred embodiment of the invention, the amount of peroxide in the rubber composition is more than 1 phr, preferably more than 2 phr.

According to a preferred embodiment of the invention, the amount of sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the rubber composition is less than 10 phr, preferably less than 9 phr, more preferably less than 8 phr, still more preferably less than 7 phr, particularly less than 6 phr, more particularly less than 5 phr, still more particularly less than 4 phr, advantageously less than 3 phr.

According to a preferred embodiment of the invention, the amount of sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the rubber composition is more than 1 phr, preferably more than 2 phr.

According to a preferred embodiment of the invention, the peroxide is an organic peroxide, preferably selected from the group consisting of dicumyl peroxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, isopropylcumyl hydroperoxide, 2,5-bis (tert-butylperoxy) -2,5-dimethyl-3-hexyne, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, di-tert-butyl peroxide, 2,5-bis (tert-butylperoxy) -2,5-dimethylhexane, Di (tert-butylperoxyisopropyl) benzene, tert-butylcumyl peroxide, di-tert-amyl peroxide, 4,4-di (tert-butylperoxy) butyl valerate, tert-butyl peroxybenzoate, 2,2-bis (tert-butylperoxy) butane, tert-amyl peroxybenzoate, tertbutyl peroxyacetate, tert-butylperoxy- (2-ethylhexyl) carbonate, tert-butylperoxy isopropyl carbonate, tert-butyl peroxy-3,5,5-trimethyl hexanoate, 1,1-bis (tertbutylperoxy) cyclohexane, tert-amyl peroxyacetate, tert-amyl peroxy- (2-ethylhexyl) carbonate, 1,1-bis (tert-butylperoxy) -3,5,5-trimethylcyclohexane, 1,1-bis (tert-amylperoxy) cyclohexane, tert-butyl peroxy-maleate, 1,1'-azodi (hexahydrobenzonitrile), tert-butyl peroxyisobutyrate, tert-butylperperiodiethylacetate, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, tert-amyl peroxy-2-ethylhexanoate, bis (4-methylbenzoyl) peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, ammonium peroxydisulfate, 2,5-dimethyl-2,5-di- (2-ethylhexanoyl peroxy) hexane, 2,2'-Azodi (2-methylbutyronitrile), 2,2'-Azodi (isobutyronitrile), decanoyl peroxide, dodecanoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, tert-amyl peroxypivalate, tert-butyl peroxyneoheptanoate, 1,1,3,3-tetramethylbutyl peroxypivalate, tert-butyl peroxypivalate, cetyl peroxydicarbonate, dimyristyl peroxydicarbonate, bis (2-ethylhexyl) peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate; diisopropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, tert-amyl peroxyneodecanoate, cumyl peroxyneoheptanoate, bis (3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, cumyl peroxyneodecanoate, diisobutyryl peroxide and combinations thereof.

The sulfur-based vulcanization accelerator is a vulcanization accelerator comprising at least one sulfur atom in a molecule. The vulcanization accelerator can promote the sulfur vulcanization reaction in the rubber composition.

The sulfenamide type vulcanization accelerator may be N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), 2-(4-morpholinothio)-benzothiazole (MBS), N,N’-dicyclohexyl-2-benzothiazole sulfenamide (DCBS) or combinations thereof.

According to a preferred embodiment of the invention, the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator is selected from the group consisting of thiourea type vulcanization accelerator(s), thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and combinations thereof, preferably selected from the group consisting of thiazole type vulcanization accelerator(s), thiuram type vulcanization accelerator(s), dithiocarbamate type vulcanization accelerator(s) and combinations thereof, more preferably selected from the group consisting of dithiocarbamate type vulcanization accelerator(s) and combinations thereof, still more preferably selected from the group consisting of zinc dimethyl dithiocarbamate, zinc diethyl dithiocarbamate, zinc dibutyl dithiocarbamate, zinc ethyl phenyl dithiocarbamate, zinc N-pentamethylene dithiocarbamate, zinc dibenzyl dithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibutyl dithiocarbamate, cupric dimethyl dithiocarbamate, iron dimethyl ditchiocarbamate, tellurium diethyl dithiocarbamate, and combinations thereof, particularly selected from the group consisting of zinc ethyl phenyl dithiocarbamate, zinc dibenzyl dithiocarbamate and combinations thereof, more particularly zinc dibenzyl dithiocarbamate.

The thiourea type vulcanization accelerator(s) may be N,N-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea or combinations thereof.

The thiazole type vulcanization accelerator(s) may be 2-2’-dithiobis(benzothiazole) (MBTS), zinc-2-mercaptobenzothiazole (ZMBT) or combinations thereof.

The thiuram type vulcanization accelerator(s) may be tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis(2-ethylhexyl) thiuram disulfide, dipentamethylenethiuram tetrasulfide (DPTT), tetrabenzylthiuram Disulfide (TBzTD) or combinations thereof.

According to a preferred embodiment of the invention, the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator is a cyclic compound. The cyclic compound is a compound whose molecule comprising at least one ring (for example, homocyclic ring(s), heterocyclic ring(s)) formed with at least three atoms connected.

According to a more preferred embodiment of the preferred embodiment, the cyclic compound is an unsaturated cyclic compound. The unsaturated cyclic compound is a cyclic compound whose molecule comprising at least one ring formed with at least three atoms connected, and the ring has at least one unsaturated bond (for example, benzene, benzothiazole).

According to a still more preferred embodiment of the more preferred embodiment, the unsaturated cyclic compound is selected from the group consisting of 2-2’-dithiobis(benzothiazole) (MBTS), zinc-2-mercaptobenzothiazole (ZMBT), tetrabenzylthiuram disulfide (TBzTD), zinc ethylphenyldithiocarbamate (ZEPC), zinc dibenzyldithiocarbamate (ZDBzC) and combination thereof.

A tenth aspect of the invention is the rubber composition according to any one of the first to the ninth aspects, wherein the crosslinking system is such that the peroxide is present.

According to a preferred embodiment of the tenth aspect, the crosslinking system is free of any sulfenamide type vulcanization accelerator, or the crosslinking system is further based on a sulfur-based vulcanization accelerator of which the amount in phr is lower than that of the peroxide, preferably the crosslinking system is free of any sulfenamide type vulcanization accelerator.

An eleventh aspect of the invention is the rubber composition according to any one of the first to the tenth aspects, wherein the crosslinking system is such that the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator is present.

According to a preferred embodiment of the eleventh aspect, the crosslinking system is free of any sulfenamide type vulcanization accelerator, or the crosslinking system is further based on a sulfur-based vulcanization accelerator of which the amount in phr is lower than that of the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator, preferably the crosslinking system is free of any sulfenamide type vulcanization accelerator.

The crosslinking system may be further based on a vulcanization activator. The vulcanization activator may be based on zinc (pure zinc, zinc derivatives (for example, zinc fatty acid salt)), fatty acid (in particular, stearic acid) or combinations thereof.

A twelfth aspect of the invention is the rubber composition any one of the first to the eleventh aspects, wherein the rubber composition is further based on a plasticizing agent, preferably wherein the amount of plasticizing agent is more than 50 phr, more preferably more than 55 phr, still more preferably more than 60 phr, particularly more than 65 phr, more particularly more than 70 phr, still more particularly more than 75 phr.

According to a preferred embodiment of the twelfth aspect, the amount of plasticizing agent is less than 120 phr, preferably less than 115 phr, more preferably less than 110 phr, still more preferably less than 105 phr, particularly less than 100 phr, more particularly less than 95 phr, still more particularly less than 90 phr, advantageously less than 85 phr.

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 twelfth aspect, the plasticizing agent comprises a liquid plasticizer, a hydrocarbon resin or combinations thereof.

The liquid plasticizer is a liquid at ambient temperature (for example, 20℃) under atmospheric pressure.

According to a more preferred embodiment of the preferred embodiment, the liquid plasticizer has a Tg_DSC of preferably less than -20℃, more preferably less than -30℃, still more preferably less than -40℃.

According to a still more preferred embodiment of the preferred embodiment or the more preferred embodiment, the liquid plasticizer is selected from the group consisting of liquid diene polymer(s), 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), sulfonate plasticizer(s) and combinations thereof, preferably selected from the group consisting of MES oil(s), TDAE oil(s), naphthenic oil(s), vegetable oil(s) and combinations thereof, more preferably selected from the group consisting of MES oil(s), vegetable oil(s) and combinations thereof, still more preferably vegetable oil(s), particularly vegetable oil(s) made of oil(s) 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 combinations thereof, more particularly made of sunflower oil(s), still more particularly made of sunflower oil(s) containing more than 60%, advantageously more than 70%, more advantageously more than 80%, still more advantageously more than 90%, especially, by weight of oleic acid.

According to a particular embodiment of the preferred embodiment, the more preferred embodiment or the still more preferred embodiment, the amount of liquid plasticizer is more than 0 phr, preferably more than 5 phr, more preferably more than 10 phr, still more preferably more than 15 phr, particularly more than 20 phr.

According to a still more particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the more particular embodiment, the amount of liquid plasticizer is less than 50 phr, preferably less than 45 phr, more preferably less than 40 phr, still more preferably less than 35 phr, particularly less than 30 phr.

The hydrocarbon resin is solid at ambient temperature (for example, 20℃) under atmospheric pressure. The hydrocarbon resin is polymer well known by a person skilled in the art, which is essentially based on carbon and hydrogen, and thus miscible by nature in a rubber composition, for instance, an elastomer matrix, for a specific instance, a diene elastomer composition. The hydrocarbon resin can be aliphatic or aromatic or also of the aliphatic/aromatic type, that is to say based on aliphatic, aromatic or both monomers. The hydrocarbon resin 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 resin). The hydrocarbon resin is preferably exclusively hydrocarbon, that is to say, that the hydrocarbon resin comprises only carbon and hydrogen atoms.

According to a more preferred embodiment of the preferred embodiment, the hydrocarbon resin has a Tg_DSC of preferably more than 20℃, more preferably more than 30℃, still more preferably more than 40℃, and also less than 100℃.

According to a still more preferred embodiment of the preferred embodiment or the more preferred embodiment, the hydrocarbon resin has a number-average molecular weight (Mn) of between 400 and 2000 g/mol (more preferably between 500 and 1500 g/mol).

According to a particular embodiment of the preferred embodiment, the more preferred embodiment or the still more preferred embodiment, wherein the hydrocarbon resin has a polydispersity index (PI) of less than 3, more preferably less than 2 (reminder: PI = Mw/Mn with Mw the weight-average molecular weight).

The macrostructure (Mw, Mn and PI) of the hydrocarbon resin is determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35℃; concentration 1 g/l; flow rate 1 ml/min; solution filtered through a filter with a porosity of 0.45μm before injection; Moore calibration with polystyrene standards; set of 3 “Waters” columns in series (“Styragel” HR4E, HR1 and HR0.5); detection by differential refractometer (“Waters 2410”) and its associated operating software (“Waters Empower”).

According to a more particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment or the particular embodiment, 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, C₅ fraction homopolymer or copolymer resins, C₉ fraction homopolymer or copolymer resins, alpha-methyl styrene homopolymer or copolymer resins and 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/C₅ fraction copolymer resins, (D)CPD/C₉ fraction copolymer resins, terpene/vinylaromatic copolymer resins, terpene/phenol copolymer resins, C₅ fraction/vinyl-aromatic copolymer resins, C₉ fraction/vinylaromatic copolymer resins and 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 C₉ fraction (or more generally from a C₈ to C₁₀ fraction) are suitable, for example, as vinylaromatic monomer. Preferably, the vinylaromatic compound is styrene or a vinylaromatic monomer resulting from a C₉ fraction (or more generally from a C₈ to C₁₀ 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 4326 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.

According to a still more particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the particular embodiment, or the more particular embodiment, the amount in phr of hydrocarbon resin is higher than that of the liquid plasticizer, preferably higher than twice of the amount in phr of liquid plasticizer.

According to an advantageously embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the particular embodiment, the more particular embodiment or the still more particular embodiment, the amount of hydrocarbon resin is more than 10 phr, preferably more than 20 phr, more preferably more than 30 phr, still more preferably more than 40 phr, particularly more than 50 phr.

According to a more advantageously embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the particular embodiment, the more particular embodiment, the still more particular embodiment or the advantageously embodiment, the amount of hydrocarbon resin is less than 100 phr, preferably less than 90 phr, more preferably less than 80 phr, still more preferably less than 70 phr, particularly less than 60 phr.

A thirteenth aspect of the invention is the rubber composition according to any one of the first to the twelfth aspect, wherein the rubber composition is free of any epoxy hardener, or the rubber composition is further based on an epoxy hardener of which the amount in phr is lower than that of the epoxy, preferably wherein the amount of epoxy hardener is less than 30 phr, more preferably less than 25 phr, still more preferably less than 20 phr, still preferably less than 15 phr, particularly less than 10 phr, more particularly less than 5 phr, still more particularly less than 1 phr.

The epoxy hardener may comprise at least one compound selected from the group consisting of amine compound(s) (for example, polyamidoamine(s), aliphatic amine(s), alicyclic amine(s), aromatic amine(s), fatty aromatic amine(s), amine(s) having ether bond(s), amine(s) having hydroxyl group(s), polyoxypropylene amine(s), modified amine(s) (for example, epoxy modified amine(s), Mannich modified amine(s), amine(s) modified by Michael addition(s), amine salt compound(s) (for example, boron trifluoride amine complex compound(s))), amide compound(s) (for example, polyamide obtained by reacting polyamine), isocyanate compound(s), aromatic diazonium salt compound(s), guanidino compound(s), thiol compound(s) (for example, polythiol), aromatic sulfonium salt compound(s), phenol compound(s), acid anhydride compound(s), basic active hydrogen compound(s) and combinations thereof.

According to a preferred embodiment of the thirteenth aspect, the rubber composition is free of any epoxy hardener.

The rubber composition according to the invention may be based on all or a portion(s) of the usual additives generally used in the elastomer composition(s) intended in particular for laminates, in more particular for articles (for example, tires, shoes, conveyors or caterpillar tracks), in more particular for tires, in still more particular for snow tires or winter tires, such as, for example, protection agents, such as antiozone waxes, chemical antiozonants, antioxidants, tackifying resins.

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 other than the polyethylene glycol, 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 110℃ and 190℃, preferably between 130℃ and 180℃, followed by a second phase of mechanical working (referred to as “productive” phase) at a lower temperature, typically of less than 110℃, for example between 40℃ and 100℃, finishing phase during which at least one of the peroxide or a combination of sulfur with the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the crosslinking system are incorporated.

A process which can be used for the manufacture of such composition comprises, for example and preferably, the following steps:
- incorporating in the elastomer matrix(es), for instance, the diene elastomer(s), in a mixer, the reinforcing filler, the polyethylene glycol, the epoxy, during a first stage (referred to as a “non-productive” stage) everything being kneaded thermomechanically (for example in one or more steps) until a maximum temperature of between 110℃ and 190℃ is reached;
- cooling the combined mixture to a temperature of less than 100℃;
- subsequently incorporating, during a second stage (referred to as a “productive” stage), at least one of the peroxide or a combination of sulfur with the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the crosslinking system; and
- kneading everything up to a maximum temperature of less than 110℃.

By way of example, the first (non-productive) phase is carried out in a single thermomechanical stage during which all the necessary constituents are introduced into an appropriate mixer, such as a standard internal mixer, followed, in a second step, for example after kneading for 1 to 2 minutes, by the other additives, optional additional filler-covering agents or processing aids, with the exception of at least one of the peroxide or the combinations of sulfur with the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the crosslinking system. The total kneading time, in this non-productive phase, is preferably between 1 and 15 min.

After cooling the mixture thus obtained, the peroxide or the combination of sulfur with the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator in the crosslinking system are then incorporated at low temperature (for example, between 40℃ and 100℃), 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 2 and 15 min.

The final composition thus obtained is subsequently extruded or 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, a conveyor belt and a caterpillar track tread.

A fourteenth aspect of the invention is a laminate comprising at least two superposed portions comprising a first portion being made of a first rubber composition (FC) based on an elastomer matrix, a reinforcing filler and at least one of an epoxy or epoxy hardener, and a second portion being made of a second rubber composition (SC) different from the first rubber composition (FC), and the second rubber composition (SC) being a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the amount in phr of epoxy in the first rubber composition (FC) is lower than that in the second rubber composition (SC).

As for making the laminate according to the fourteenth aspect, it is possible to build a first layer of a homogeneous rubber composition, as the first rubber composition (FC), and a second layer of a homogeneous rubber composition, as the second rubber composition (SC), then to superpose the first layer onto the second layer or then to superpose the second layer onto the first layer, or to sandwich the other layer(s) or portion(s) between the first layer and the second layer, to get the laminate.

According to a preferred embodiment of the fourteenth aspect, the first portion is adjacent to the second portion.

A preferred embodiment of the invention is an article comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably the article comprises a laminate according to the fourteenth aspect.

According to a more preferred embodiment of the preferred embodiment, the article is intended to contact with the ground, preferably the article comprises a laminate according to the fourteenth aspect, and at least one of the first portion or the second portion, more preferably each of the portions, is intended to contact with the ground during the service life of the article.

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

According to a still preferred embodiment of the more preferred embodiment, the article comprises a laminate according to the fourteenth aspect, and the first portion is arranged nearer to the ground than the second portion. In case of that the article is a tire, the superposed portions which are the first portion and the second portion are radially superposed portions, that is, the first portion is radially exterior to the second portion.

According to another still preferred embodiment of the more preferred embodiment, the article comprises a laminate according to the fourteenth aspect, and the second portion is arranged nearer to the ground than the first portion. In case of that the article is a tire, the superposed portions which are the second portion and the first portion are radially superposed portions, that is, the second portion is radially exterior to the first portion.

The “radially” means “in the radial direction” which is a direction perpendicular to the axis of the rotation of a tire.

According to a particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment or the other still more preferred embodiment, the article is a tire (for example, a tire tread), a shoe (for example, a shoe sole), a conveyor (for example, a conveyor belt) or a caterpillar track (for example, a caterpillar track tread), preferably a tire, a shoe or a caterpillar track, more preferably a tire tread, a shoe sole or a caterpillar track tread, still more preferably a tire tread.

According to a more particular embodiment of the preferred embodiment, the more preferred embodiment, the still more preferred embodiment, the other still more preferred embodiment or the particular embodiment, the article is a tire comprising several tire parts which are a tread intended to at least partially contact with the ground, two sidewalls intended to contact with the outside air, but not to contact with the ground, two beads, a crown prolonged by two sidewalls ended by two beads, a carcass reinforcement formed at least one ply reinforced by radial textile cards, the carcass reinforcement passing into the crown and the sidewalls and the carcass reinforcement anchored in the two beads, preferably further comprising crown reinforcement placed between carcass reinforcement and the tread, more preferably further comprising an inner liner intended to protect the carcass reinforcement from diffusion of air coming from a space inside the tire, and the inner liner placed radially inner than carcass reinforcement.

According to a still more particular of the embodiment of the more particular embodiment, a portion made of the rubber composition according to any one of the first to the thirteenth aspects, preferably the laminate according to the fourteenth aspect, is placed in at least one of the above tire parts, between two of the above tire parts, radially outer than one of the above tire parts, radially inner than one of the above tire parts or combinations thereof.

A fifteenth aspect of the invention is a tire comprising a rubber composition according to any one of the first to the thirteenth aspects, preferably wherein the tire comprises a laminate according to the fourteenth aspect, more preferably wherein the tire comprising a tread comprising a laminate according to the fourteenth aspect.

According to a preferred embodiment of the fifteenth aspect, the tire is a snow tire.

According to a more preferred embodiment of the fifteenth aspect or the preferred embodiment, the tires are particularly intended to equip passenger motor vehicles, including 4×4 (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)).

The vulcanization (or curing) is carried out in a known way at a temperature generally of between 110℃ and 190℃ for a sufficient time which can vary, for example, between 5 and 90 min depending in particular on the curing temperature, the vulcanization system adopted and the vulcanization kinetics of the composition(s) under consideration.

The invention relates to the rubber composition(s), to the laminate(s), to the article(s), to the tire(s) and the tire tread(s) described above, both in the raw state (i.e., before curing) and in the cured state (i.e., after crosslinking or vulcanization).

The invention is further illustrated by the following non-limiting examples.

Example

In the test, six rubber compositions (C-1, C-2 and C-6: examples according to the invention, C-3, C-4 and C-5: comparative examples or a reference) were used. The rubber compositions are based on a diene elastomer (a blend of SBR and BR) reinforced with a blend of a silica (as a reinforcing inorganic filler) and a carbon black, an epoxy comprising an epoxy resin and a crosslinking system based on 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (as a peroxide) or a combination of sulfur with zinc dibenzyl dithiocarbamate (as a sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator) or N-dicyclohexyl-2-benzothiazolesulfenamide (as a sulfenamide type vulcanization accelerator) with or without a polyethylene glycol. The formulations of the rubber compositions are given at Table 1 with the content of the various products expressed in phr.

Each rubber composition was produced as follows: The reinforcing filler, the polyethylene glycol (in case of C-1, C-2, C-4 and C-6), the epoxy, the elastomer matrix and the various other ingredients, with the exception of the peroxide or the combination of sulfur with the vulcanization accelerator in the crosslinking system, were successively introduced into an internal mixer having an initial vessel temperature of approximately 60℃; the mixer was thus approximately 70% full (% by volume). Thermomechanical working (non-productive phase) was then carried out in one stage, which lasts in total approximately 3 to 4 minutes, until a maximum “dropping” temperature of 165℃ was reached. The mixture thus obtained was recovered and cooled and then the peroxide or the combination of sulfur with the vulcanization accelerator was incorporated on an external mixer (homofinisher) at 20 to 30℃, everything being mixed (productive phase) for an appropriate time (for example, between 5 and 12 min).

The rubber compositions thus obtained were subsequently calendered, either in the form of sheets (thickness of 2 to 3 mm) 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, assembling or both to the desired dimensions, for example as tire semi-finished products, in particular as tire treads.

As the measurement of tear strength, test samples were cut from a cured plaque with a thickness of about 2.5 mm. Notches (perpendicular to the test direction) were created in the samples prior to testing. The force and the elongation at break were measured using an Instron 5565 Uniaxial Testing System. The cross-head speed was 500 mm/min. Samples were tested at 23℃. The results are expressed in base 100, that is to say that the value 100 is arbitrarily assigned to the tear strength index being equal to force at rupture (MPa) of the reference (C-5), and the values of the rubber compositions are shown in Table 1. The higher the value is, the less susceptible is the material to tearing, which is to say that the higher durability is.

Further, two tires (T-0: a reference, T-1, T-2 and T-6: examples according to the invention) comprising treads comprising four rubber compositions (C-0, C-1, C-2 and C-6) respectively are compared. The C-0 has a formulation same as that of the C-5 except that the C-0 is based on 30 phr of an epoxy hardener (polyamidoamine type epoxy hardener, “AP-032 1500 hardener” from Cemedine, viscosity at 25℃: 55000 mPa・s, polyamidoamine: 100%, Triethylenetetramine: 1.4%, Tetraethylenepentamine: 6.4%) instead of the epoxy, which means the C-0 is not based on the epoxy. Each of the treads comprises a laminate comprising two radially superposed portions which are a radially external portion and a radially internal portion adjacent to the radially external portion, the laminate being produced by superposition of the sheets of the rubber compositions (C-0, C-1, C-2 and C-6) respectively. In T-0, the radially internal and the radially external portions are made of C-0. In T-1, T-2 and T-6, the radially internal portion is made of C-1, C-2 and C-6 respectively, and the radially external portions is made of C-0.

These tires, as snow tires having treads comprising grooves circumferentially, axially or both extending, were conventionally manufactured and in all respects identical apart from the rubber compositions and the laminates of the tire treads. These tires are radial carcass passenger vehicle tires and the size of them is 205/55R16.

All of the test tires were fitted to the front and rear axles of motor vehicles, under nominal tire inflation pressure, and were subjected to rolling on a circuit in order to reproduce the tires in the worn state. Then, the below snow braking test was done with the worn tires. Each of the worn tires was still in the service life, and in each of them, each radially internal portion made of C-1, C-2 and C-6 respectively at least partially appeared on each tread surface and could at least partially contact with the ground.

Furthermore, as snow braking test, a 1,400 cc passenger car provided on all of the four wheels with the same kind of the worn tires under 220 kPa of tire inflation pressure mounted onto 6.5Jx16 rim was run on a snow covered road at a temperature of -10 ℃, the deceleration from 50 to 5 km/h during sudden longitudinal braking while anti-lock braking system (ABS) activated was measured. The above snow tests were conducted on a hard pack snow with a CTI penetrometer reading of about 90 in accordance with Standard ASTM F1805.

The result of the above test shows each of the examples T-1, T-2 and T-6 according to the invention has the better grip performance on snow than that of the reference T-0.

In conclusion, the rubber composition according to the invention allows an improved grip performance on snowy ground with the unexpectedly improved durability performance.

(1) Solution SBR with 16% of styrene unit and 24% of unit 1,2 of the butadiene part (Tg_DSC = -65℃);
(2) BR with 0.3% of 1,2 vinyl; 2.7% of trans; 97% of cis-1,4 (Tg_DSC = -105℃);
(3) Carbon black (ASTM grade N234 from Cabot);
(4) Silica (“Zeosil 1165MP” from Rhodia (CTAB, BET: about 160 m²/g));
(5) Coupling agent TESPT (“Si69” from Evonik);
(6) Polyethylene glycol (“Polyethylene Glycol 400” from Tokyo Chemical Industry Co., ltd, weight-average molecular weight (Mw): 380 ~ 400 (mol/g));
(7) Tris(4-hydroxyphenyl)methane triglycidyl ether (from Sigma-Aldrich, viscosity at 150℃: 43 mPa・s, epoxy equivalent weight: 160 g/eq);
(8) Oleic sunflower oil (“Agripure 80” from Cargill, Weight percent oleic acid: 100%);
(9) Hydrocarbon resin C₅/C₉ type (“Escorez ECR-373” from Exxon, Tg_DSC= 44℃);
(10) Zinc dibenzyldithiocarbamate (“Nocceler ZTC [ZDBzC]” from Ouchi Shinko Chemical Industrial);
(11) N-dicyclohexyl-2-benzothiazolesulfenamide (“Santocure CBS” from Flexsys);
(12) 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (“PERHEXA 25B” from Nihon Yushi).

Claims

A rubber composition based on at least:
- an elastomer matrix;
- a reinforcing filler predominately comprising a reinforcing inorganic filler;
- a polyethylene glycol;
- an epoxy; and
- a crosslinking system based on at least one of a peroxide or a sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator.
The rubber composition according to Claim 1, wherein the elastomer matrix comprises at least one diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and combinations thereof.
The rubber composition according to Claim 1 or Claim 2, wherein the amount of reinforcing filler is more than 80 phr.
The rubber composition according to any one of Claims 1 to 3, wherein the amount of reinforcing inorganic filler is more than 50 phr.
The rubber composition according to any one of Claims 1 to 4, wherein the reinforcing inorganic filler predominately comprises a silica.
The rubber composition according to any one of Claims 1 to 5, wherein the reinforcing filler further comprises a carbon black, and wherein the amount of carbon black is less than 45 phr.
The rubber composition according to any one of Claims 1 to 6, wherein the amount of polyethylene glycol is more than 1 phr.
The rubber composition according to any one of Claims 1 to 7, wherein the amount of epoxy is at least 1 phr.
The rubber composition according to any one of Claims 1 to 8, wherein the epoxy comprises at least one epoxy resin comprising at least two epoxide functional groups in a molecule.
The rubber composition according to any one of Claims 1 to 9, wherein the crosslinking system is such that the peroxide is present.
The rubber composition according to any one of Claims 1 to 10, the crosslinking system is such that the sulfur-based vulcanization accelerator other than sulfenamide type vulcanization accelerator is present.
The rubber composition according to any one of Claims 1 to 11, wherein the rubber composition is further based on a plasticizing agent, preferably wherein the amount of plasticizing agent is more than 50 phr.
The rubber composition according to any one of Claims 1 to 12, wherein the rubber composition is free of any epoxy hardener, or the rubber composition is further based on an epoxy hardener of which the amount in phr is lower than that of the epoxy.
A laminate comprising at least two superposed portions comprising a first portion being made of a first rubber composition (FC) based on an elastomer matrix, a reinforcing filler and at least one of an epoxy or epoxy hardener, and a second portion being made of a second rubber composition (SC) different from the first rubber composition (FC), and the second rubber composition (SC) being a rubber composition according to any one of Claims 1 to 13, preferably wherein the amount in phr of epoxy in the first rubber composition (FC) is lower than that in the second rubber composition (SC).
A tire comprising a rubber composition according to any one of Claims 1 to 13, preferably wherein the tire comprises a laminate according to Claim 14, more preferably wherein the tire comprising a tread comprising a laminate according to Claim 14.