WO2020158694A1 - An article - Google Patents

Abstract

An article comprises a laminate comprising at least two superposed portions intended to come into contact with the ground during the service life of the article; the superposed portions comprising a first portion being made of a first rubber composition (FC) and a second portion being made of a second rubber composition (SC); wherein each of the rubber compositions is based on at least: an elastomer matrix; a reinforcing filler; and a crosslinking system based on at least one of sulfur or a sulfur-based vulcanization accelerator; wherein the amount in phr of sulfur in the first rubber composition (FC) is higher than that in the second rubber composition (SC), and wherein the amount in phr of sulfur-based vulcanization accelerator in the first rubber composition (FC) is lower than that in the second rubber composition (SC).

Description

AN ARTICLE

The field of the invention is that of laminates with rubber compositions for articles, for example, tires, shoes or caterpillar tracks, in particular for tires, in more particular for tire treads for snow tires or winter tires capable of rolling over ground surfaces covered with snow.

The ability of rubber compositions to be tacky before curing is an important property to the rubber article (for example, a tire, a shoe or a caterpillar track) building. Indeed, for making the rubber articles, it is necessary to be able to apply the different layers of the article on each other and that these layers stick to each other before curing of the article, curing which will associate for crosslinking the layers to others. This property of tack of the composition before curing (vulcanization), is also called “tackiness” or “uncured tack” or “unvulcanized tack” or “green tack”.

A constant objective of manufacturers of the articles is improvement of tack of rubber compositions of the articles before curing.

During their research, the inventor has discovered that a specific laminate with rubber compositions for a rubber article, for example, a tire tread, a shoe sole and a caterpillar track tread, which allows an unexpectedly improved the tack of the rubber compositions of the laminate.

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).

As a tire has a geometry of revolution about an axis of rotation, the geometry of the tire is generally described in a meridian plane containing the axis of rotation of the tire, and the following definitions of directions of the tire are understood in the present application:
- A radial direction is a direction perpendicular to the axis of rotation of the tire;
- An axial direction is a direction parallel to the axis of rotation of the tire;
- A circumferential direction is a direction perpendicular to the meridian plane.

A plane being perpendicular to the axis of rotation of the tire and passing through the middle of a tread surface of the tire is referred to as an equatorial plane of the tire.

In what follows, expressions “radially”, “axially” and “circumferentially” respectively mean “in the radial direction”, “in the axial direction” and “in the circumferential direction”. Expressions “radially on the inside (radially inner or radially internal), or respectively radially on the outside (radially outer or radially external)” mean “closer or, respectively, further away, from the axis of rotation of the tire, in the radial direction, than”. Expressions “axially on the inside (axially inner or axially interior) or respectively axially on the outside (axially outer or axially exterior)” mean “closer or, respectively further away, from the equatorial plane, in the axial direction, than”. Respective dimensions of a given element in the radial, axial and circumferential directions will also be denoted “radial thickness or height”, “axial width” and “circumferential length” of this element. Expression “laterally” means “in the circumferential or axial direction”.

A first aspect of the invention is an article comprising a laminate comprising at least two superposed portions intended to come into contact with the ground during the service life of the article; the superposed portions comprising a first portion being made of a first rubber composition (FC) and a second portion being made of a second rubber composition (SC); wherein each of the rubber compositions is based on at least: an elastomer matrix; a reinforcing filler; and a crosslinking system based on at least one of sulfur (sulphur) or a sulfur-based vulcanization accelerator; wherein the amount in phr of sulfur in the first rubber composition (FC) is higher than that in the second rubber composition (SC), and wherein the amount in phr of sulfur-based vulcanization accelerator in the first rubber composition (FC) is lower than that in the second rubber composition (SC).

The amount in phr of sulfur is to say the amount of vulcanization sulfur content in phr. The vulcanization sulfur may be sulfur, sulfur derived from a sulfur-donating agent or combinations thereof.

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

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).

The specific laminate allows unexpectedly improved the tack of the rubber compositions of the laminate.

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.

Each of the rubber compositions (FC and SC) of the laminate of the article according to the invention is based on each 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 rubbers 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 article according to the first aspect, wherein the each of the rubber compositions (FC and SC), which are the first rubber composition (FC) and the second rubber composition (SC), is such that the elastomer matrix comprises at least a diene elastomer selected from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers and combinations thereof.

According to a preferred embodiment of the second aspect, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, the copolymers are 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, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, the elastomer matrix comprises more than 50 phr and up to 100 phr, preferably 55 to 95 phr, more preferably 60 to 90 phr, still more preferably 65 to 85 phr, particularly 70 to 80 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 5 to 45 phr, more preferably 10 to 40 phr, still more preferably 15 to 35 phr, particularly 20 to 30 phr, of a second diene elastomer which is different from the first diene elastomer.

According to a still more preferred embodiment of the above more preferred embodiment, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, 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 above more preferred embodiment or the above still more preferred embodiment, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, 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 above more preferred embodiment, the above still more preferred embodiment or the above particular embodiment, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, 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.

Each of the rubber compositions (FC and SC) of the laminate of the article according to the invention is based on a reinforcing filler.

A third aspect of the invention is the article according to the first aspect or the second aspect, wherein each of the rubber compositions (FC and SC) is such that the amount of the reinforcing filler is more than 0 phr and up to 250 phr, preferably 10 to 240 phr, more preferably 20 to 230 phr, still more preferably 30 to 220 phr, particularly 40 to 210 phr, more particularly 50 to 200 phr, still more particularly 60 to 190 phr, advantageously 70 to 180 phr, more advantageously 80 to 170 phr, still more advantageously 90 to 160 phr, still more advantageously 100 to 150 phr, especially 110 to 140 phr, especially 120 to 130 phr.

The reinforcing filler may comprise a reinforcing organic filler (for example, carbon black), a reinforcing inorganic filler (for instance, silica) or combinations thereof.

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

A fourth aspect of the invention is the article according to any one of the first to the third aspects, wherein each of the rubber compositions (FC and SC) is such that the reinforcing filler predominately comprises a reinforcing inorganic filler, that is, the reinforcing filler comprises more than 50% by weight of the reinforcing inorganic filler per 100% by weight of the reinforcing filler, preferably the reinforcing filler comprises 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 tires, in other words capable of replacing, in its reinforcing role, a conventional tire-grade carbon black; such a filler is generally characterized, in a known manner, by the presence of hydroxyl (-OH) groups at its surface.

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

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

A fifth aspect of the invention is the article according to the fourth aspect, wherein each of the rubber compositions (FC and SC) is such that the reinforcing inorganic filler predominately comprises silica, that is, the reinforcing inorganic filler comprises more than 50% by weight of silica per 100% by weight of the reinforcing inorganic filler, preferably the reinforcing inorganic filler comprises more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, more particularly 100%, by weight of silica per 100% by weight of the reinforcing inorganic filler.

The silica may be 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 50 to 350 m²/g, still more preferably 100 to 300 m²/g, particularly between 150 and 250 m²/g, wherein 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). Such silica may be covered or not. Mention will be made, as low specific surface silica, of Sidistar R300 from Elkem Silicon Materials. Mention will be made, as highly dispersible precipitated silicas (“HDSs”), for example, of “Ultrasil 7000” and “Ultrasil 7005” from Evonik, “Zeosil 1165 MP”, “Zeosil 1135 MP” and “Zeosil 1115 MP” from Rhodia, “Hi-Sil EZ150G” from PPG, “Zeopol 8715”, “Zeopol 8745” and “Zeopol 8755” from Huber or the silicas with a high specific surface area as described in a patent application WO 03/016387. Mention will be made, as pyrogenic silicas, for example, of “CAB-O-SIL S-17D” from Cabot, “HDK T40” from Wacker, “Aeroperl 300/30”, “Aerosil 380”, “Aerosil 150” or “Aerosil 90” from Evonik. Such silica may be covered, for example, “CAB-O-SIL TS-530” covered with hexamethyldiasilazene or “CAB-O-SIL TS-622” covered with dimethyldichlorosilane from Cabot.

A person skilled in the art will understand that a reinforcing filler of another nature, in particular organic nature, such as carbon black, might be used as filler equivalent to the reinforcing inorganic filler described in the present section, provided that this reinforcing filler is covered with an inorganic layer, such as silica, or else comprises, at its surface, functional sites, in particular hydroxyls, requiring the use of a coupling agent in order to form the connection between the filler and the elastomer. By way of example, mention may be made of carbon blacks for tires, such as described in patent applications WO 96/37547 and WO 99/28380.

According to a preferred embodiment of the invention, in the first rubber composition (FC), the second rubber composition (SC) or the both rubber compositions, preferably the both rubber compositions, the reinforcing filler comprises more than 0 and up to 240 phr, preferably between 10 and 230 phr, more preferably between 20 and 220 phr, still more preferably between 30 and 210 phr, particularly between 40 and 200 phr, more particularly between 50 and 190 phr, still more particularly preferably between 60 and 180 phr, advantageously between 70 and 170 phr, more advantageously between 80 and 160 phr, still more advantageously between 90 and 150 phr, especially between 100 and 140 phr, more especially between 110 and 130 phr, still more especially between 115 and 125 phr, of a reinforcing inorganic filler (for example, silica).

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 mixtures, the mean value of the "x" indices is a fractional number preferably of between 2 and 5, more preferably of approximately 4. However, the 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 mixtures 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 may be from 0.5 to 15% by weight per 100% by weight of the reinforcing inorganic filler, preferably silica if each rubber composition is based on the reinforcing inorganic filler, preferably silica.

According to a preferred embodiment of the invention, the amount of coupling agent is less than 30 phr (for example, between 0.1 and 30 phr), preferably less than 25 phr (for example, between 0.5 and 25 phr), more preferably less than 20 phr (for example, between 1 and 20 phr), still more preferably less than 15 phr (for example, between 1.5 and 15 phr) if each rubber composition is based on the reinforcing inorganic filler, preferably silica.

A sixth aspect of the invention is the article according to any one of the first to the fifth aspects, wherein each of the rubber compositions (FC and SC) is such that the reinforcing filler comprises less than 40 phr (for example, between 0 and 40 phr), preferably less than 30 phr (for example, between 0.5 and 30 phr), more preferably less than 20 phr (for example, between 1 and 20 phr), still more preferably less than 15 phr (for example, between 1.5 and 15 phr), particularly less than 10 phr (for example, between 2 and 10 phr), of carbon black.

Within each of the aforementioned ranges of content of carbon black in the rubber compositions (FC and SC), 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 high grip on snowy ground, low hysteresis loss or both.

As carbon blacks, all carbon blacks conventionally used in tires (“tire-grade” blacks) are suitable, such as for example reinforcing carbon blacks of the 100, 200 or 300 series in ASTM grades (such as for example, the N115, N134, N234, N326, N330, N339, N347 or N375 blacks), or carbon blacks higher series, the 500, 600, 700 or 800 series in ASTM grades (such as for example the N550, N660, N683, N772, N774 blacks). The carbon blacks might for example be already incorporated in an elastomer matrix, for instance, a diene elastomer, in the form of a masterbatch (see for example applications WO 97/36724 or WO 99/16600).

Each of the rubber compositions (FC and SC) of the laminate of the article according to the invention is based on each crosslinking (or vulcanization) system based on sulfur and a sulfur-based vulcanization accelerator, wherein the amount in phr of sulfur in the first rubber composition (FC) is higher than that in the second rubber composition (SC), and wherein the amount in phr of sulfur-based vulcanization accelerator in the first rubber composition (FC) is lower than that in the second rubber composition (SC).

The crosslinking system may be further based on per oxide, bismaleimides, a vulcanization activator, a vulcanization accelerator other than sulfur-based vulcanization accelerator or combinations thereof. The vulcanization activator may be based on zinc (pure zinc, zinc derivatives (for example, zinc fatty acid salt) or combination thereof), fatty acid (in particular, stearic acid), or combinations thereof. The vulcanization accelerator other than sulfur-based vulcanization accelerator may be based on guanidine derivatives (in particular diphenylguanidine), or combination thereof.

A seventh aspect of the invention is the article according to any one of the first to the sixth aspects, wherein the first rubber composition (FC) is such that the amount of sulfur is more than 1.5 phr (for example, between 1.5 and 15 phr), preferably more than 2.0 phr (for example, between 2.0 and 10 phr), more preferably more than 2.5 phr (for example, between 2.5 and 5 phr).

According to a preferred embodiment of the seventh aspect, the amount of sulfur in the second rubber composition (SC) is at most 1.5 phr (for example, more than 0 phr and up to 1.5 phr), preferably at most 1.0 phr (for example, more than 0 phr and up to 1.0 phr).

An eighth aspect of the invention is the article according to any one of the first to the seventh aspects, wherein the second rubber composition (SC) is such that the amount of sulfur-based vulcanization accelerator is more than 1.5 phr (for example, between 1.5 and 15 phr), preferably more than 2.0 phr (for example, between 2.0 and 10 phr), more preferably more than 2.5 phr (for example, between 2.5 and 5 phr).

According to a preferred embodiment of the eighth aspect, the amount of sulfur-based vulcanization accelerator in the first rubber composition (FC) is at most 1.5 phr (for example, more than 0 phr and up to 1.5 phr), preferably at most 1.0 phr (for example, more than 0 phr and up to 1.0 phr).

A ninth aspect of the invention is the article according to any one of the first to the eighth aspects, wherein each of the rubber compositions (FC and SC) is such that the sulfur-based vulcanization accelerator is selected from the group consisting of sulfenamide type sulfur-based vulcanization accelerators (for example, N-cyclohexyl-2-benzothiazole sulfenamide (abbreviated to “CBS”), N,N-dicyclohexyl-2 benzothiazolesulfenamide (“DCBS”), N-tert-butyl-2-benzothiazolesulfenamide (“TBBS”), N-tert-butyl-2 benzothiazolesulfenimide (“TBSI”)), thiazole type sulfur-based vulcanization accelerators (for example, 2-mercaptobenzothiazyl disulfide (abbreviated to “MBTS”)), thiuram type accelerators (for example, tetrabenzylthiuram disulfide (“TBZTD”)), zinc dithiocarbamate type sulfur-based vulcanization accelerators (for example, zinc dibenzyldithiocarbamate (“ZBEC”)) and combinations thereof.

A tenth aspect of the invention is the article according to the ninth aspect, wherein each of the rubber compositions (FC and SC) is such that the sulfur-based vulcanization accelerator predominately comprises a sulfenamide type sulfur-based vulcanization accelerator, that is, the sulfur-based vulcanization accelerator comprises more than 50% by weight of the sulfenamide type sulfur-based vulcanization accelerator per 100% by weight of the sulfur-based vulcanization accelerator, preferably the sulfur-based vulcanization accelerator comprises more than 60%, more preferably more than 70%, still more preferably more than 80%, particularly more than 90%, more particularly 100%, by weight of the sulfenamide type sulfur-based vulcanization accelerator per 100% by weight of the sulfur-based vulcanization accelerator.

The rubber compositions (FC and SC) of the laminates of the articles 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 articles (for example, tires, shoes 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, plasticizing agent, tackifying resins, methylene acceptors (for example, phenolic novolak resin) or methylene donors (for example, hexamethylenetetramine (HMT) or hexamethoxymethylmelamine (H3M)).

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

An eleventh aspect of the invention is the article according to any one of the first to the tenth aspects, wherein at least one of the first rubber composition (FC) or the second rubber composition (SC), preferably each of the rubber compositions, is further based on a plasticizing agent in order to soften the matrix by diluting the elastomer and the reinforcing filler.

According to a preferred embodiment of the eleventh aspect, in at least one of the first rubber composition (FC) or the second rubber composition (SC), preferably in each of the rubber compositions, the amount of the plasticizing agent is more than 30 phr, preferably more than 40 phr (for example, between 40 and 120 phr), more preferably more than 50 phr (for example, between 50 and 110 phr), still more preferably more than 60 phr (for example, between 60 and 100 phr), particularly between more than 70 phr (for example, between 70 and 90 phr).

A twelfth aspect of the invention is the article according to the eleventh aspect, wherein the plasticizing agent comprises a liquid plasticizer(s), a hydrocarbon resin(s) or combinations thereof, preferably comprise a liquid plasticizer(s) and a hydrocarbon resin(s).

Any extending oil, whether of aromatic or non-aromatic nature, any liquid plasticizing agent known for its plasticizing properties with regard to elastomer matrix(es) (for instance, diene elastomer), can be used as the liquid plasticizer. At ambient temperature (20℃) under atmospheric pressure, these plasticizers or these oils, which are more or less viscous, are liquids (that is to say, as a reminder, substances that have the ability to eventually take on the shape of their container), as opposite to plasticizing hydrocarbon resin(s) which are by nature solid at ambient temperature (20℃) under atmospheric pressure.

According to a more preferred embodiment of the twelfth aspect, in at least one of the first rubber composition (FC) or the second rubber composition (SC), preferably in each of the rubber compositions, the plasticizing agent comprises no liquid plasticizer or comprises at most 100 phr, preferably at most 90 phr, more preferably at most 80 phr, still more preferably at most 70 phr, particularly at most 60 phr, more particularly 10 to 60 phr, of a liquid plasticizer(s).

A thirteenth aspect of the invention is the article according to the twelfth aspect, wherein the plasticizing agent comprises a liquid plasticizer(s) selected from the group consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, Distillate Aromatic Extracts (DAE) oils, Medium Extracted Solvates (MES) oils, Treated Distillate Aromatic Extracts (TDAE) oils, Residual Aromatic Extracts (RAE) oils, Treated Residual Aromatic Extracts (TRAE) oils, Safety Residual Aromatic Extracts (SRAE) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and combinations thereof, preferably selected from the group consisting of MES oils, TDAE oils, naphthenic oils, vegetable oils and combinations thereof, more preferably selected from the group consisting of MES oils, vegetable oils and combinations thereof, still more preferably selected from the group consisting of vegetable oils and combinations thereof. The vegetable oil(s) may be made of an oil selected from the group consisting of linseed, safflower, soybean, corn, cottonseed, turnip seed, castor, tung, pine, sunflower, palm, olive, coconut, groundnut and grapeseed oils and combinations thereof, particularly sunflower oil(s), more particularly sunflower oil(s) containing more than 60%, still more particularly more than 70%, especially more than 80%, more especially more than 90%, still more especially 100%, by weight of oleic acid.

While, in a manner known to a person skilled in the art, the designation “resin” is reserved in the present application, by definition, for a compound which is solid at ambient temperature (20℃ under atmosphere pressure), in contrast to a liquid plasticizing compound, such as an oil.

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

According to a more preferred embodiment of the above preferred embodiment, in at least one of the first rubber composition (FC) or the second rubber composition (SC), preferably in each of the rubber compositions, the plasticizing agent comprises no hydrocarbon resin or comprises at most 100 phr, preferably at most 90 phr, more preferably at most 80 phr, still more preferably at most 70 phr, particularly at most 60 phr, more particularly 10 to 60 phr, of a hydrocarbon resin(s).

Preferably, the hydrocarbon resin(s) as being “plasticizing” exhibits at least one, more preferably all, of the following characteristics:
- a Tg_DSC of more than 20℃(for example, between 20℃ and 100℃), preferably more than 30℃ (for example, between 30℃ and 100℃), more preferably more than 40℃ (for example, between 40℃ and 100℃);
- a number-average molecular weight (Mn) of between 400 and 2000 g/mol (more preferably between 500 and 1500 g/mol);
- 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(s) 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”).

A fourteenth aspect of the invention is the article according to the twelfth aspect, wherein the plasticizing agent comprises a hydrocarbon resin(s) 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.

The preferred resins above are well known to a person skilled in the art and are commercially available, for example:
- polylimonene resins: by DRT under the name “Dercolyte L120” (Mn=625 g/mol; Mw=1010 g/mol; PI=1.6; Tg_DSC=72℃) or by Arizona Chemical Company under the name “Sylvagum TR7125C” (Mn=630 g/mol; Mw=950 g/mol; PI=1.5; Tg_DSC=70℃);
- C₅ fraction/vinylaromatic, notably C₅ fraction/styrene or C₅ fraction/C₉ fraction, copolymer resins: by Neville Chemical Company under the names “Super Nevtac 78”, “Super Nevtac 85” or “Super Nevtac 99”, by Goodyear Chemicals under the name “Wingtack Extra”, by Kolon under the names “Hikorez T1095” and “Hikorez T1100”, or by Exxon under the names “Escorez 2101” and “ECR 373”;
- limonene/styrene copolymer resins: by DRT under the name “Dercolyte TS 105” or by Arizona Chemical Company under the names “ZT115LT” and “ZT5100”.

Mention may also be made, as examples of other preferred resins, of phenol-modifiedα-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, for example sold by Arizona Chemical Company under the names “Sylvares SA 100” (Mn=660 g/mol; PI=1.5; Tg_DSC=53℃); “Sylvares SA 120” (Mn=1030 g/mol; PI=1.9; Tg_DSC=64℃); “Sylvares 540” (Mn=620 g/mol; PI=1.3; Tg_DSC=36℃; hydroxyl number=56 mg KOH/g); and “Sylvares 600” (Mn=850 g/mol; PI=1.4; Tg_DSC=50℃; hydroxyl number=31 mg KOH/g).

Each of the rubber compositions (FC and SC) of the laminates of the articles 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 sulfur and the sulfur-based vulcanization accelerator in the crosslinking system are incorporated.

A process which can be used for the manufacture of each of such compositions (FC and SC) 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, 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), sulfur and the sulfur-based 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 sulfur and the sulfur-based 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, sulfur and the sulfur-based 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 calendered, for example in the form of a sheet or of a plaque, in particular for laboratory characterization, or else extruded in the form of a rubber profiled element which can be used directly as a laminate or an article, for example, a tire tread, a shoe sole and a caterpillar track tread.

As for making the laminate of the article according to the invention, 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 of the article.

A fifteenth aspect of the invention is the article according to any one of the first to the fourteenth aspects, wherein the first portion is adjacent to the second portion.

A sixteenth aspect of the invention is the article according to any one of the first to the fifteenth aspects, wherein the first portion is arranged nearer to the ground than the second portion.

A seventeenth aspect of the invention is the article according to any one of the first to the fifteenth aspects, wherein the second portion is arranged nearer to the ground than the first portion.

An eighteenth aspect of the invention is the article according to any one of the first to the seventeenth aspects, wherein the article is a tire, a shoe or a caterpillar track.

A nineteenth aspect of the invention is the article according to the eighteenth aspect, wherein the article is a tire.

According to a preferred embodiment of the above aspect, 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)).

A twentieth aspect of the invention is the article according to the nineteenth aspect, wherein the tire is a snow tire.

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, structures or both 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.

A twenty first aspect of the invention is the article according to the nineteenth aspect or the twentieth aspect, wherein the laminate is comprised in a tread of a tire.

A twenty second aspect of the invention is the article according to the twenty first aspect, wherein the superposed portions are radially superposed portions.

A twenty third aspect of the invention is the article according to the twenty second aspect, wherein the first portion is radially exterior to the second portion, that is, the second portion is radially internal to the first portion. For example, the first portion may be a first layer of a homogeneous rubber composition, as the first rubber composition (FC), and the second portion may be a second layer of another homogeneous rubber composition, as the second rubber composition (SC). Preferably, the first layer is located to be intended to come into contact with the ground in the new state of the tire.

A twenty fourth aspect of the invention is the article according to the twenty third aspect, wherein the second portion is radially external to the first portion, that is, the first portion is radially internal to the second portion. For example, the second portion may be a second layer of a homogeneous rubber composition, as the second rubber composition (SC), and the first portion may be a first layer of another homogeneous rubber composition, as the first rubber composition (FC). Preferably, the second layer is located to be intended to come into contact with the ground in the new state of the tire.

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, three rubber compositions (C-1, C-2 and C-3) were used. The three rubber compositions are based on a diene elastomer (SBR and BR) reinforced with a blend of silica (as a reinforcing inorganic filler) and carbon black, and a crosslinking system based on sulfur and N-dicyclohexyl-2-benzothiazolesulfenamide (as a sulfur-based vulcanization accelerator). The formulations of the three 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 elastomer matrix and the various other ingredients, with the exception of sulfur and a sulfenamide type sulfur-based vulcanization accelerator (as a sulfur-based 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 sulfur and the sulfenamide type sulfur-based vulcanization accelerator were 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.

In order to confirm the effect of the invention, two laminates (L-1: a reference, and L-2: an example according to the invention) comprising the first portion made of the first rubber compositions and the second rubber portions made of the second rubber compositions by superposition of the sheets of the rubber compositions (C-1, C-2 and C-3), as shown in Table 2, are compared.

As the measurement of tack, a test device based on the probe tack tester (ASTM D2979-95) was used. An Instron tensile test machine comprising a fixed metallic jaw and a mobile metallic jaw was used. A first test specimen was stuck on the fixed metallic jaw. A second test specimen was stuck to the mobile jaw. The test specimens were cut into circular plates with a 45 mm diameter punch. The test specimens were made of mixing films on which plastic films were put in order to reinforce the mixing films. The mixing films were obtained by calendaring the unvulcanized mixtures with a thickness of 2 mm.

The principle of the measurement consisted in bringing the two mixing films into contact for 5 seconds by applying a compression force of 20 N. After this contact phase, the two mixing films were separated by driving the cross-member of the tensile test machine. The speed of displacement of the cross-member in this peeling phase was 1 mm/s. The displacement of the cross-member and the force were measured continuously as a function of time from the contact phase to the peeling phase. After the measurement of displacement of the cross-member and the force, each weight of mixing films adhering to each plastic film was measured. Each value of the heavier weight of mixing films adhering to the plastic film is reported in the table 2, in base 100 of the total weight of the mixing films to the both plastic films. The higher the value is, the higher better the tack is.

The measurements of tack were done with two laminates (L-1: a reference, L-2: an example according to the invention). The reference laminate (L-1) was such that the mixing films in the first test specimen and the second test specimen were made of C-1 as the first rubber composition (FC) and the second rubber composition (SC). The example laminate according to the invention (L-2) was such that the mixing film in the first test specimen was made of C-2 as the first rubber composition (FC), and the mixing film in the second test specimen was made of C-3 as the second rubber composition (SC).

Moreover, two tire comprising treads comprising the above laminates (T-1: a reference tire comprising a tread comprising the reference laminate (L-1), T-2: an example tire comprising a tread comprising the example laminate (L-2) according to the invention) were conventionally manufactured and in all respects identical apart from the rubber compositions of treads. These tires are radial carcass passenger vehicle tires and the size of them is 205/55R16.

As snow braking test, a 1,400 cc passenger car provided on all of the four wheels with the same kind of these tires (in the new state) 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.

Furthermore, all of the 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 above 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 as the second portions being made of each second rubber composition at least partially appeared on each tread surface and could at least partially contact with the ground.

The results of the braking tests on snow road are expressed in relative units, the base 100 being selected for the reference tire (T-1), and then the values of the example according to the invention (T-2) are 100 (the new state) and 101 (the worn state) (it should be remembered that a value of greater than 100 indicates an improved performance), which demonstrate that the test tire (T-2) according to the invention has equivalent values of the grip performance on snow to that of the reference tire (T-1) in the new state and the worn state.

In conclusion, the specific laminate with rubber compositions intended in particular for a rubber article, for example, a tire tread, a shoe sole and a caterpillar track tread, which allows an unexpectedly improved the tack of the rubber compositions of the laminate while maintaining the snow grip performance in the new state and the worn state.

(1) BR with 0.3% of 1,2 vinyl; 2.7% of trans; 97% of cis-1,4 (Tg_DSC = -105℃);
(2) Solution SBR with 16% of styrene unit (Tg_DSC = -65℃);
(3) Carbon black (ASTM grade N234 from Cabot);
(4) Silica (“Zeosil 1165MP” from Rhodia (CTAB, BET: 160 m²/g));
(5) Coupling agent TESPT (“Si69” from Evonik);
(6) Oleic sunflower oil (“Agripure 80” from Cargill, Weight percent oleic acid: 100%);
(7) Hydrocarbon resin C₅/C₉ type (“Escorez ECR-373” from Exxon, Tg_DSC= 44℃);
(8) Mixture of 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) Diphenylguanidine (“Perkacit DPG” from Flexsys);
(10) N-dicyclohexyl-2-benzothiazolesulfenamide (“Santocure CBS” from Flexsys).

Claims (24)

1. An article comprising a laminate comprising at least two superposed portions intended to come into contact with the ground during the service life of the article;
   the superposed portions comprising a first portion being made of a first rubber composition (FC) and a second portion being made of a second rubber composition (SC);
   
   wherein each of the rubber compositions is based on at least:
   - an elastomer matrix;
   - a reinforcing filler; and
   - a crosslinking system based on at least one of sulfur or a sulfur-based vulcanization accelerator;
   
   wherein the amount in phr of sulfur in the first rubber composition (FC) is higher than that in the second rubber composition (SC), and wherein the amount in phr of sulfur-based vulcanization accelerator in the first rubber composition (FC) is lower than that in the second rubber composition (SC).
2. The article according to Claim 1, wherein each of the rubber compositions is such that the elastomer matrix comprises at least a diene elastomer selected from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and combinations thereof.
3. The article according to Claim 1 or Claim 2, wherein each of the rubber compositions is such that the amount of the reinforcing filler is more than 0 phr and up to 250 phr.
4. The article according to any one of Claims 1 to 3, wherein each of the rubber compositions is such that the reinforcing filler predominately comprises a reinforcing inorganic filler.
5. The article according to Claim 4, wherein each of the rubber compositions is such that the reinforcing inorganic filler predominately comprises silica.
6. The article according to any one of Claims 1 to 5, wherein each of the rubber compositions is such that the reinforcing filler comprises less than 40 phr of carbon black.
7. The article according to any one of Claims 1 to 6, wherein the first rubber composition (FC) is such that the amount of sulfur is more than 1.5 phr.
8. The article according to any one of Claims 1 to 7, wherein the second rubber composition (SC) is such that the amount of sulfur-based vulcanization accelerator is more than 1.5 phr.
9. The article according to any one of Claims 1 to 8, wherein each of the rubber compositions is such that the sulfur-based vulcanization accelerator is selected from the group consisting of sulfenamide type sulfur-based vulcanization accelerators, thiuram type accelerators, zinc dithiocarbamate type sulfur-based vulcanization accelerators and combinations thereof.
10. The article according to Claim 9, wherein each of the rubber compositions is such that the sulfur-based vulcanization accelerator predominately comprises a sulfenamide type sulfur-based vulcanization accelerator.
11. The article according to any one of Claims 1 to 10, wherein at least one of the first rubber composition (FC) or the second rubber composition (SC) is further based on a plasticizing agent.
12. The article according to Claim 11, wherein the plasticizing agent comprises a liquid plasticizer(s), a hydrocarbon resin(s) or combinations thereof.
13. The article according to Claim 12, wherein the liquid plasticizer(s) are selected from the group consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, Distillate Aromatic Extracts (DAE) oils, Medium Extracted Solvates (MES) oils, Treated Distillate Aromatic Extracts (TDAE) oils, Residual Aromatic Extracts (RAE) oils, Treated Residual Aromatic Extracts (TRAE) oils, Safety Residual Aromatic Extracts (SRAE) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and combinations thereof.
14. The article according to Claims 12, wherein the hydrocarbon resin(s) are selected from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene 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.
15. The article according to any one of Claims 1 to 14, wherein the first portion is adjacent to the second portion.
16. The article according to any one of Claims 1 to 15, wherein the first portion is arranged nearer to the ground than the second portion.
17. The article according to any one of Claims 1 to 15, wherein the second portion is arranged nearer to the ground than the first portion.
18. The article according to any one of Claims 1 to 17, wherein the article is a tire, a shoe or a caterpillar track.
19. The article according to Claim 18, wherein the article is a tire.
20. The article according to Claim 19, wherein the tire is a snow tire.
21. The article according to Claim 19 or Claim 20, wherein the laminate is comprised in a tread of a tire.
22. The article according to Claim 21, wherein the superposed portions are radially superposed portions.
23. The article according to Claim 22, wherein the first portion is radially exterior to the second position.
24. The article according to Claim 23, wherein the second portion is radially exterior to the first position.