Tyre comprising a tread
阅读说明：本技术 包括胎面的轮胎 (Tyre comprising a tread ) 是由 森山昌彦 于 2018-06-29 设计创作，主要内容包括：一种轮胎包括胎面，所述胎面包括多个由切口(3、4)界定的胎面花纹元件(1)，所述胎面花纹元件各自包括至少一个侧面(13、14、15、16)、以及在至少一个侧面(13、14、15、16)上至少部分地覆盖有第二橡胶组合物(SC)的层的第一橡胶组合物(FC)，所述第二橡胶组合物(SC)基于：弹性体基质，其包含大于55phr且至多100phr的第一二烯弹性体、以及0至小于45phr的第二二烯弹性体，所述第一二烯弹性体具有小于?25℃的玻璃化转变温度；增强填料，其包含大于100phr的增强无机填料；以及大于45phr的增塑剂，其主要包含至少一种烃类树脂，所述烃类树脂具有大于20℃的玻璃化转变温度。(A tyre comprising a tread comprising a plurality of tread pattern elements (1) delimited by incisions (3, 4), the tread pattern elements each comprising at least one side face (13, 14, 15, 16), and a first rubber composition (FC) at least partially covered on at least one side face (13, 14, 15, 16) with a layer of a second rubber composition (SC) based on: an elastomeric matrix comprising greater than 55phr and up to 100phr of a first diene elastomer having a glass transition temperature of less than-25 ℃, and from 0 to less than 45phr of a second diene elastomer; a reinforcing filler comprising greater than 100phr of a reinforcing inorganic filler; and more than 45phr of a plasticizer comprising essentially at least one hydrocarbon resin having a glass transition temperature of greater than 20 ℃.)
1. A tyre comprising a tread comprising a plurality of tread pattern elements (1) delimited by incisions (3, 4);
said tread pattern elements (1) each comprising at least one side face (13, 14, 15, 16) and a contact surface (2) intended to be in contact with the ground during rolling;
the tread pattern elements (1) each comprise a first rubber composition (FC) at least partially covered on at least one side (13, 14, 15, 16) with a layer of a second rubber composition (SC) different from the first rubber composition (FC), the tyre being characterized in that the second rubber composition (SC) is based on:
-an elastomeric matrix comprising more than 55phr and at most 100phr of a first diene elastomer having a glass transition temperature of less than-25 ℃, and from 0 to less than 45phr of a second diene elastomer;
-a reinforcing filler comprising more than 100phr of a reinforcing inorganic filler; and
-more than 45phr of a plasticizer essentially comprising at least one hydrocarbon resin having a glass transition temperature of more than 20 ℃.
2. Tyre according to claim 1, wherein said second rubber composition (SC) is such that said first diene elastomer is a styrene-butadiene copolymer.
3. Tyre according to claim 2, wherein said second rubber composition (SC) is such that the styrene-butadiene copolymer has less than 28% by weight of styrene units per 100% by weight of styrene-butadiene copolymer.
4. Tyre according to any one of claims 1 to 3, wherein said second rubber composition (SC) is such that said first diene elastomer has a glass transition temperature of less than-35 ℃.
5. Tyre according to any one of claims 1 to 4, wherein said second rubber composition (SC) is such that said elastomeric matrix comprises from 60 to 100phr of a first diene elastomer and from 0 to less than 40phr of a second diene elastomer.
6. Tyre according to any one of claims 1 to 5, wherein said second rubber composition (SC) is such that said reinforcing filler comprises at least 110phr of a reinforcing inorganic filler.
7. Tyre according to any one of claims 1 to 6, wherein said second rubber composition (SC) is such that said reinforcing inorganic filler mainly comprises silica.
8. Tyre according to any one of claims 1 to 7, wherein said second rubber composition (SC) is such that said reinforcing filler comprises from 0 to less than 40phr of carbon black.
9. Tyre according to any one of claims 1 to 8, wherein said second rubber composition (SC) is based on more than 50phr of plasticizer.
10. Tyre according to any one of claims 1 to 9, wherein said second rubber composition (SC) is such that said plasticizer comprises more than 55% by weight of hydrocarbon resin per 100% by weight of plasticizer.
11. Tyre according to any one of claims 1 to 10, wherein said second rubber composition (SC) is such that said plasticizer comprises more than 25phr of hydrocarbon resin.
12. Tyre according to any one of claims 1 to 11, wherein said second rubber composition (SC) is such that said hydrocarbon resin is selected from the group consisting of cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5Fraction homopolymer or copolymer resin, C9A distillate homopolymer or copolymer resin, α -methylstyrene homopolymer or copolymer resin, and mixtures thereof.
13. Tyre according to any one of claims 1 to 12, wherein said second rubber composition (SC) is such that said plasticizer comprises less than 45phr of at least one liquid plasticizer.
14. The tire of claim 13, wherein the second rubber composition (SC) is such that the liquid plasticizer is selected from the group consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffinic oils, Distilled Aromatic Extract (DAE) oils, Medium Extraction Solvate (MES) oils, Treated Distilled Aromatic Extract (TDAE) oils, Residual Aromatic Extract (RAE) oils, Treated Residual Aromatic Extract (TRAE) oils, Safety Residual Aromatic Extract (SRAE) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers, and mixtures thereof.
15. Tyre according to any one of claims 1 to 14, wherein the layer of the second rubber composition (SC) has a thickness (E1) greater than 0.1 mm.
Technical Field
Background
In order to obtain satisfactory driving performances, in particular on wet, snow-covered (snowy) or icy roads, it is known practice to provide a tyre comprising a tread comprising tread pattern elements delimited by incisions, for example obtained by moulding, grooves having an average width greater than or equal to 2mm and/or sipes (incisions) having an average width less than 2 mm. The tread pattern elements comprise contact surfaces intended to come into contact with the ground during rolling, lateral surfaces and defined incisions (in particular sipes); each intersection of a respective side with the contact surface forms an edge corner that facilitates contact between the tire and the ground.
There are generally two types of tread pattern elements. One type is known as a "block," which is bounded by circumferential or axial grooves, with the axial grooves opening on either side of the circumferential groove. The other is called a "rib" which is bounded by a circumferential groove (and optionally an axial groove) and the axial groove is not open to both sides of the circumferential groove. Further, the tread pattern element may include one or more sipes to form additional edge corners.
List of reference files
Patent document
PTL 1：WO2013/087878
In general, it is well known that the rubber composition of the tread (particularly the edge corners) of a tire has a significant effect on the grip performance of the tire on ground, particularly on wet, snowy and/or icy ground. The patent application filed by the applicant (patent document 1) therefore discloses a winter tyre particularly suitable for running on snowy roads and in which the tread pattern elements each comprise at least one side and a contact surface intended to come into contact with the ground during rolling, wherein the tread pattern elements comprise a base rubber composition (FC: first rubber composition) at least partially covered on at least one side with a layer of a covering composition (SC: second rubber composition) different from the first rubber composition and comprising a specific formulation of a covering layer capable of providing a very rigid after vulcanization of the tyre (for example, a composition having a high glass transition temperature, or comprising a high filler content or comprising a high sulphur content), these tread pattern elements being arranged so as to favour grip on the snowy ground.
However, it is always desirable for those skilled in the art to improve grip on wet ground and maintain or improve grip on snow and ice.
Disclosure of Invention
Technical problem
During its research, the inventors have found that a specific covering composition makes it possible to unexpectedly improve the grip on wet ground and at the same time to maintain or improve the grip on snow and ice ground.
In the present specification, all percentages (%) shown are weight percentages (wt.%), unless explicitly stated otherwise.
The expression "elastomer matrix" is understood to mean all the elastomers present in the rubber composition in a given composition.
The abbreviation "phr" denotes parts by weight per 100 parts by weight of elastomeric matrix in the rubber composition under consideration.
In this specification, each Tg, unless explicitly stated otherwiseDSC(glass transition temperatures) are measured in a known manner by DSC (differential scanning calorimetry) according to the standard ASTM D3418-08.
Any interval of values denoted by the expression "between a and b" represents a range of values greater than "a" and less than "b" (i.e. excluding the extremes a and b), while any interval of values denoted by the expression "from a to b" means a range of values from "a" to "b" (i.e. including the strict extremes a and b).
The expression "based on" is understood in the present application to mean that the composition comprises a mixture and/or reaction product of the various components used, some of which are capable of or intended to react together, at least in part, during the various preparation stages of the composition, in particular during vulcanization (curing).
Since a tyre has a geometry of rotation about an axis of rotation, which is generally described in a meridian plane including the axis of rotation of the tyre, the following definitions of tyre directions are understood in the present application:
-the radial direction is a direction perpendicular to the rotation axis of the tyre;
-the axial direction is a direction parallel to the rotation axis of the tyre;
the circumferential direction is a direction perpendicular to the meridian plane.
A plane perpendicular to the axis of rotation of the tire and passing through the middle of the tread surface of the tire is referred to as the equatorial plane of the tire.
Hereinafter, the expressions "in the radial direction", "in the axial direction" and "in the circumferential direction" mean "in the radial direction", "in the axial direction" and "in the circumferential direction", respectively. The expression "radially on the inside (radially inside or radially inside) or radially on the outside (radially outside or radially outside)" means "closer to the axis of rotation of the tire in the radial direction or further from the axis of rotation of the tire". The expression "axially on the inside (axially inside or axially inside) or axially on the outside (axially outside or axially outside)" means "closer to or further from the equatorial plane in the axial direction". The various dimensions of a given element in the radial, axial, and circumferential directions will also be referred to as the "radial thickness or height", "axial width", and "circumferential length" of the element. The expression "laterally" means "in the circumferential or axial direction".
Solution to the problem
A first aspect of the invention is a tyre comprising a tread comprising a plurality of tread pattern elements (1) delimited by incisions (3, 4);
the tread pattern elements (1) each comprise at least one side (13, 14, 15, 16) and a contact surface (2) intended to be in contact with the ground during rolling;
the tread pattern elements (1) each comprise a first rubber composition (FC) at least partially covered on at least one side (13, 14, 15, 16) with a layer of a second rubber composition (SC) different from the first rubber composition (FC), the tyre being characterized in that the second rubber composition (SC) is based on:
-an elastomeric matrix comprising more than 55phr and up to 100phr of a first diene elastomer having a glass transition temperature (Tg) of less than-25 ℃ (for example between-125 ℃ and-25 ℃), preferably less than-30 ℃ (for example between-120 ℃ and-30 ℃), and from 0 to less than 45phr of a second diene elastomerDSC)；
-a reinforcing filler comprising more than 100phr, for example between 100 and 200phr, preferably between 100 and 190phr, more preferably between 100 and 180phr, still more preferably between 100 and 170phr, in particular between 100 and 160phr, more in particular between 100 and 150phr, still more in particular between 100 and 140phr, of a reinforcing inorganic filler; and
-more than 45phr of a plasticizer, mainly comprising at least one hydrocarbon resin having a temperature 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 ℃) still more preferably more than 45 ℃ (for example between 45 ℃ and 100 ℃), in particular at least 50 ℃(e.g., at least 50 ℃ and less than 100 ℃) of a glass transition temperature (TgDSC)。
The tyre of the invention is particularly intended for fitting passenger motor vehicles, including 4 × 4 (four wheel drive) vehicles and SUV (sport utility vehicle) vehicles, and in particular industrial vehicles selected from vans and heavy vehicles, i.e. buses or heavy road transport vehicles (trucks, tractors, trailers).
Advantageous effects of the invention
The particular covering composition makes it possible to unexpectedly improve the grip performance of the tire on wet ground and at the same time to maintain or improve the grip on snow and ice ground.
Each preferred range and/or material encompassed by each of the following aspects, embodiments and variations may apply to any of the other aspects, embodiments and other variations of the invention unless explicitly stated otherwise.
Drawings
Further features and advantages of the invention emerge from the description that follows, with reference to the accompanying drawings, which schematically show (in particular not to a specific scale) embodiments that are non-limiting examples of the objects of the invention.
In these figures:
FIG. 1 shows a partial plan view of a block as tread pattern element (1) of a tire tread according to the present invention;
figure 2 shows the block of figure 1 in a cross section on section line II-II.
Detailed Description
FIG. 1 shows a partial plan view of four rectangular blocks as a plurality of tread pattern elements (1) of a tire tread according to the present invention. Each block is delimited by a cut (3, 4). The cuts are circumferentially extending grooves (3) and axially extending other grooves (4). Each block comprises four lateral faces (13, 14, 15, 16), and a contact surface (2) intended to be in contact with the ground during rolling of the tyre. Each block has a Length (LI) in the circumferential direction of the tire and a width (L2) in the axial direction of the tire. The intersection of the side faces (13, 14, 15, 16) with the contact surface (2) forms four edge corners (23, 24, 25, 26), which edge corners (23, 24, 25, 26) play an important role in driving in particular on slippery road surfaces, in particular by the presence of water, snow or ice.
Figure 2 shows two blocks in a cross section taken along section line II-II of figure 1. The cross-section is perpendicular to the axial direction of the tire.
In these figures, each block comprises a first rubber composition (FC: mixture of base materials), in this case completely covered with a layer of a second rubber composition (SC: covering material or mixture of covering compositions) on four lateral faces (13, 14, 15, 16), said four lateral faces (13, 14, 15, 16) forming the boundaries of a groove (3, 4) extending in the circumferential (3) or axial (3, 4) direction. The second rubber composition (SC) is different from the first rubber composition (FC). The layer of the second rubber composition (SC) has a substantially constant thickness (E1) (over the entire height (Hr) of the covering, in this case equal to the depth (H) of the groove). Thus, the depth (H) of the groove is equal to the height of the block.
According to a preferred embodiment of the present invention, the side face (14, 16, 24, 26) has an orientation perpendicular to the tire circumferential direction, and preferably, a layer of the second rubber composition (SC) is overlaid on the side face (14, 16, 24, 26) having an orientation perpendicular to the tire circumferential direction, so that grip on wet ground, snowy ground and icy ground is excellent.
According to a preferred embodiment of the invention, the second rubber composition (SC) extends in the new state of the tire up to an edge corner (23, 24, 25, 26), said edge corner (23, 24, 25, 26) being formed by the boundary between the contact surface (2) and the side face (13, 14, 15, 16) of the tread pattern element (1).
The first rubber composition (FC) may be a conventional rubber composition, which may be based on at least one diene elastomer (generally from 50 to 100phr of a diene elastomer selected from natural rubber, synthetic polyisoprene, polybutadiene, butadiene copolymers, isoprene copolymers and mixtures thereof, and from 0 to 50phr of another diene elastomer), between 50 and 200phr of a reinforcing filler (for example silica and/or carbon black), more than 30phr of a plasticizer (for example a liquid plasticizer, a hydrocarbon resin or mixtures thereof) and a crosslinking system (not counting other usual additives).
The second rubber composition (SC) is different from the first rubber composition (FC), and is a specific rubber composition which will be described in detail below.
The second rubber composition (SC) is based on an elastomeric matrix comprising: greater than 55phr and up to 100phr of a first diene elastomer having a glass transition temperature of less than-25 ℃; and 0 to less than 45phr of a second diene elastomer different from the first diene elastomer, meaning that the elastomeric matrix contains no second diene elastomer or less than 45phr of the second diene elastomer.
"diene" -type elastomer (or broadly "rubber", these two terms being considered synonymous) is understood in a known manner to be an elastomer (meaning one or more) derived at least in part (i.e. a homopolymer or a copolymer) from diene monomers (monomers bearing two conjugated or non-conjugated carbon-carbon double bonds).
These diene elastomers may be classified into two categories, "substantially unsaturated" or "substantially saturated". generally, the expression "substantially unsaturated" is understood to mean a diene elastomer resulting at least in part from conjugated diene monomers and having a content of units of diene origin (conjugated dienes) which is greater than 15% (mol%), so that diene elastomers such as, for example, diene/α -olefin copolymers of the butyl rubber or EPDM type do not fall within the preceding definition, but may be particularly referred to as "substantially saturated" diene elastomers (low or very low content of units of diene origin, always less than 15%). in the category of "substantially unsaturated" diene elastomers, the expression "highly unsaturated" 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 the present invention is applicable to any type of diene elastomer, those skilled in the art of tires will appreciate that the present invention preferably uses essentially unsaturated diene elastomers.
In view of these definitions, the expression diene elastomer capable of being used in the composition according to 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 each other or with one or more vinyl aromatic compounds preferably having 8 to 20 carbon atoms.
The following are particularly suitable as conjugated dienes: 1, 3-butadiene, 2-methyl-1, 3-butadiene, 2, 3-di (C)i-C5Alkyl) -1, 3-butadiene (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), aryl-1, 3-butadiene, 1, 3-pentadiene or 2, 4-hexadiene. The following are suitable, for example, as vinylaromatic compounds: styrene, (o-, m-or p-) methylstyrene, "vinyltoluene" commercial mixtures, p- (tert-butyl) styrene, methoxystyrene, chlorostyrene, vinylmesitylene, divinylbenzene or vinylnaphthalene.
The first diene elastomer may be selected from the group consisting of polybutadiene (BR), synthetic polyisoprene (IR), Natural Rubber (NR), butadiene copolymers, isoprene copolymers and mixtures thereof; such copolymers are more preferably selected from butadiene-styrene copolymers (SBR) and mixtures thereof.
The first diene elastomer may have any microstructure depending on the polymerization conditions used, in particular on the presence or absence of the modifying and/or randomizing agent and on the amount of modifying and/or randomizing agent used. The elastomer may be, for example, a block, random, sequential or microsequential elastomer, and may be prepared in dispersion or in solution. The elastomer may be coupled and/or star-branched or functionalized by coupling agents and/or star branching agents or functionalizing agents.
A second aspect of the present invention is the tire according to the first aspect, wherein the second rubber composition (SC) is such that the first diene elastomer is a styrene-butadiene copolymer (SBR), preferably a solution process styrene-butadiene copolymer, which is a copolymer of butadiene and styrene prepared in solution.
A third aspect of the present invention is the tire according to the second aspect, wherein the second rubber composition (SC) is such that the styrene-butadiene copolymer has less than 28 wt% (e.g. between 5 and 28 wt%), preferably less than 20 wt% (e.g. between 10 and 20 wt%) of styrene units per 100 wt% of the styrene-butadiene copolymer. Styrene units may be passed according to ISO 215611H NMR method was determined.
A fourth aspect of the present invention is the tire according to any one of the first to third aspects, wherein the second rubber composition (SC) is such that the first diene elastomer has a glass transition temperature (Tg)DSC) Less than-35 ℃ (e.g., between-115 ℃ and-35 ℃), preferably less than-40 ℃ (e.g., between-110 ℃ and-40 ℃), more preferably less than-45 ℃ (e.g., between-105 ℃ and-45 ℃), still more preferably less than-50 ℃ (e.g., between-100 ℃ and-50 ℃), particularly less than-55 ℃ (e.g., between-95 ℃ and-55 ℃), more particularly up to-60 ℃ (e.g., between-90 ℃ and-60 ℃).
A fifth aspect of the present invention is the tire according to any one of the first to fourth aspects, wherein the second rubber composition (SC) is such that the elastomer matrix comprises: from 60 to 100phr, preferably from 70 to 100phr, more preferably from 80 to 100phr, still more preferably from 90 to 100phr, in particular 100phr, of the first diene elastomer; and 0 to 40phr, preferably 0 to 30phr, more preferably 0 to 20phr, still more preferably 0 to 10phr, of a second diene elastomer, which means that the elastomeric matrix is free of second diene elastomer or comprises at most 40phr, preferably at most 30phr, more preferably at most 20phr, still more preferably 10phr of a second diene elastomer.
According to a preferred embodiment of the invention, in the second rubber composition (SC), the second diene elastomer may be chosen from butadiene copolymers and mixtures thereof, preferably from styrene-butadiene copolymers (SBR), butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR), styrene-butadiene-isoprene copolymers (SBIR) and mixtures thereof, more preferably from styrene-butadiene copolymers (SBR) and mixtures thereof.
The second rubber composition (SC) is based on a reinforcing filler comprising more than 100phr of a reinforcing inorganic filler.
The reinforcing filler is capable of reinforcing the rubber composition, and may further comprise a reinforcing organic filler (e.g., carbon black).
According to a preferred embodiment of the invention, the reinforcing filler comprises mainly a reinforcing inorganic filler, which means that the reinforcing filler may comprise more than 50% by weight of reinforcing inorganic filler per 100% by weight of the total reinforcing filler. More preferably, the content of reinforcing inorganic filler is greater than 60% by weight, still more preferably greater than 70% by weight, in particular greater than 80% by weight, more in particular greater than 90% by weight per 100% of the total reinforcing filler.
A sixth aspect of the invention is a tyre according to any one of the first to fifth aspects, wherein the second rubber composition (SC) is such that the reinforcing filler comprises more than 110phr, for example between 110 and 200phr, preferably between 110 and 190phr, more preferably between 110 and 180phr, still more preferably between 110 and 170phr, in particular between 110 and 160phr, more particularly between 110 and 150phr, still more particularly between 110 and 140phr, advantageously between 110 and 130phr, more advantageously between 115 and 125phr, of reinforcing inorganic filler.
The expression "reinforcing inorganic filler" is understood herein to mean any inorganic or mineral filler, whatever its colour and its origin (natural or synthetic), also known as "white filler", "clear filler" or even "non-black filler" with respect to carbon black, which is capable of reinforcing alone, without means other than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words which is capable of replacing, in its reinforcing role, a conventional tire-grade carbon black; such fillers are generally characterized in a known manner by the presence of hydroxyl (-OH) groups on their surface.
It does not matter in which physical state the filler is present, whether it be in the form of a powder, microbeads, granules, beads or any other suitable densified form. Of course, reinforcing inorganic fillers are also described below, i.e. mixtures of various reinforcing inorganic fillers, preferably mixtures of highly dispersible siliceous and/or aluminous fillers.
Mineral fillers of siliceous type (preferably Silica (SiO)2) Mineral fillers of the aluminium and/or aluminium type, preferably alumina (Al)2O3) Are particularly suitable as reinforcing inorganic fillers.
A seventh aspect of the present invention is the tire according to any one of the first to sixth aspects, wherein the second rubber composition (SC) is such that the reinforcing inorganic filler mainly contains silica, that is, the reinforcing inorganic filler contains more than 50% by weight of silica per 100% by weight of the reinforcing inorganic filler. Preferably, the reinforcing inorganic filler may comprise 100% by weight of silica per 100% by weight of the reinforcing inorganic filler. The reinforcing inorganic filler of the reinforcing filler in the second rubber composition (SC) may comprise one silica or a blend of several silicas. The silica used may be any reinforcing silica known to the person skilled in the art, in particular having a BET surface area and a CTAB specific surface area both of which are less than 450m2A/g, preferably from 20 to 400m2(ii) any precipitated silica or fumed silica per gram. This silica may be covered or uncovered. As low specific surface silica there will be mentioned Sidetar R300 from Elkem Silicon Materials. As highly dispersible precipitated silicas ("HDS") mention may be made, for example, of "Ultrasil 7000" and "Ultrasil 7005" from Evonik, "Zeosil 1165 MP", "Zeosil 1135 MP" and "Zeosil 1115 MP" from Rhodia, "Hi-sil ez 150G" from PPG, "Zeopol 8715", "Zeopol 8745" and "Zeopol 8755" from Huber, or silicas with a high specific surface area as described in patent application WO 03/016387. As fumed silica, mention may be made, 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. This silica can be coated, for example, "CAB-O-SIL TS-530" from Cabot coated with hexamethyldisilazane or coated with dimethyldichlorosilane "CAB-O-SIL TS-622”。
The reinforcing inorganic filler used, in particular in the case where it is silica, has a BET surface area and a CTAB specific surface area advantageously ranging from 50 to 350m2G, more advantageously from 100 to 300m2In g, even more preferably in the range from 150 to 250m2Between/g.
The BET surface area is determined according to known methods, i.e.by gas adsorption using The method Brunauer-Emmett-Teller described in "The Journal of The American chemical Society", Vol.60, p.309,
The person skilled in the art will understand that reinforcing fillers of another nature, in particular organic, such as carbon black, can be used as fillers equivalent to the reinforcing inorganic fillers described in this section, provided that they are covered with an inorganic layer, such as silica, or comprise, on their surface, functional sites, in particular hydroxyl groups, which require the use of coupling agents to form a connection between the filler and the elastomer. By way of example, mention may be made of carbon blacks for tires, such as those described in patent applications WO 96/37547 and WO 99/28380.
An eighth aspect of the present invention is a tire according to any one of the first to seventh aspects, wherein the second rubber composition (SC) is such that the reinforcing filler comprises from 0 to less than 40phr, preferably from 0 to less than 30phr, more preferably from 0 to less than 20phr, still more preferably from 0 to less than 10phr, in particular from 0 to less than 5phr, more in particular from 0 to 3phr, still more in particular 0phr of carbon black, which means that the reinforcing filler is free of carbon black or comprises less than 40phr, preferably less than 30phr, more preferably less than 20phr, still more preferably less than 10phr, in particular less than 5phr, more in particular at most 3phr of carbon black.
Within the stated range, there are benefits in terms of the colouring properties (black colorant) and the resistance to ultraviolet rays of the carbon black, without adversely affecting the usual properties provided by the reinforcing inorganic filler, namely the high grip on wet, snowy and icy ground.
According to a preferred embodiment of the present invention, in the second rubber composition (SC), the reinforcing filler may be free of carbon black.
In order to couple the reinforcing inorganic filler to the elastomeric matrix (for example a diene elastomer), it is possible, in a known manner, to use a coupling agent (or bonding agent) intended to provide satisfactory chemical and/or physical connection between the reinforcing inorganic filler (the surface of its particles) and the elastomeric matrix (for example a diene elastomer). The coupling agent is at least bifunctional. In particular, at least bifunctional organosilanes or polyorganosiloxanes can be used.
Silane polysulfides may be used in particular, referred to as "symmetrical" or "asymmetrical" according to their specific 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, wherein:
-x is an integer from 2 to 8 (preferably from 2 to 5);
a is a divalent hydrocarbon group (preferably C)i-C18Alkylene or C6-Ci2Arylene radicals, more particularly CpCi0In particular Ci-C4Alkylene, especially propylene);
-Z corresponds to one of the following formulae:
[ chemical formula 1]
Wherein:
-R1the radicals being unsubstituted or substituted and identical or different from one another and representing C1-Ci8Alkyl radical, C5-Ci8Cycloalkyl or C6-Ci8Aryl (preferably C)1-C6Alkyl, cyclohexyl or phenyl, especially C1-C4Alkyl, more particularly methyl and/or an ethyl group),
-R2the radicals being unsubstituted or substituted and identical or different from one another, represent C1-Ci8Alkoxy or C5-Ci8Cycloalkoxy (preferably selected from C)1-C8Alkoxy and C5-C8A group of cycloalkoxy, more preferably C1-C4The group of alkoxy groups, in particular methoxy and ethoxy), which are particularly suitable but not restricted to the above-mentioned limitations.
In the case of mixtures of alkoxysilane polysulphides corresponding to formula (I) above, in particular commercially available standard mixtures, the average value of the "x" index is a fraction preferably between 2 and 5, more preferably a fraction of approximately 4. However, the invention can also be advantageously carried out using, for example, alkoxysilane disulfide (x ═ 2).
As examples of silane polysulfides, mention will more particularly be made of bis ((C)i-C4) Alkoxy (C)i-C4) Alkylsilyl (C)i-C4) Alkyl) polysulfides (in particular disulfides, trisulfides or tetrasulfides), for example bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides. Among these compounds, the formula [ (C) abbreviated to TESPT is used in particular2H5O)3Si(CH2)3S2]2Bis (3-triethoxysilylpropyl) tetrasulfide of formula (II), or abbreviated to TESPD2HSO)3Si(CH2)3S]2Bis (3-triethoxysilylpropyl) disulfide. As a preferred example, mention will also be made of bis (mono (C)1-C4) Alkoxy di (C)i-C4) Alkylsilylpropyl) polysulfides (in particular disulfides, trisulfides or tetrasulfides), more particularly bis (monoethoxydimethylsilylpropyl) tetrasulfide, as described in patent application WO 02/083782 (or US 7217751).
As coupling agents other than alkoxysilane polysulphides, mention will be made in particular of difunctional POSs (polyorganosiloxanes), or as in the case ofThe hydroxysilane polysulfides described in the applications WO 02/30939 (or US 6774255) and WO 02/31041 (or US 2004/051210) (R in the above formula (I))2OH) or silanes or POS bearing an azodicarbonyl function 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 silanes bearing at least one thiol (-SH) functional group (known as mercaptosilane) and/or at least one thiol group masking functional group, as described, for example, in patents or patent applications US 6849754, WO 99/09036, WO 2006/023815, WO 2007/098080, WO 2008/055986 and WO 2010/072685.
It is, of course, also possible to use mixtures of the abovementioned coupling agents, as described in particular in the abovementioned patent application WO 2006/125534.
According to a preferred embodiment of the invention, the content of coupling agent may be between 0.5 and 15% by weight per 100% by weight of reinforcing inorganic filler (in particular silica).
According to a preferred embodiment of the invention, the second rubber composition (SC) may be based on less than 30phr (for example between 0.1 and 30 phr), preferably less than 25phr (for example between 0.5 and 25 phr), more preferably less than 20phr (for example between 1 and 20 phr) and still more preferably less than 15phr (for example between 1.5 and 15 phr) of coupling agent.
The second rubber composition (SC) is based on more than 45phr (for example between 45 and 105 phr) of plasticizer.
The plasticizer may comprise a hydrocarbon resin, a liquid plasticizer, or a mixture thereof.
A ninth aspect of the present invention is a tire according to any one of the first to eighth aspects, wherein the second rubber composition (SC) is based on more than 50phr (for example between 50 and 100 phr), preferably more than 55phr (for example between 55 and 95 phr), more preferably more than 60phr (for example between 60 and 90 phr), still more than 65phr (for example between 65 and 85 phr), in particular at least 70phr (for example 70 to 80phr) of a plasticizer.
In the second rubber composition (SC), the plasticizer mainly comprises at least one hydrocarbon resin having a glass transition temperature greater than 20 ℃, i.e. the plasticizer comprises more than 50% by weight (e.g. more than 50% by weight and up to 100% by weight) of hydrocarbon resin per 100% by weight of plasticizer.
A tenth aspect of the present invention is the tire according to any one of the first to ninth aspects, wherein the second rubber composition (SC) is such that the plasticizer contains more than 55 wt% (e.g., between 55 wt% and 100 wt%), preferably more than 60 wt% (e.g., between 60 wt% and 95 wt%), more preferably more than 65 wt% (e.g., between 65 wt% and 90 wt%), and still preferably at least 70 wt% (e.g., 70 wt% to 85 wt%) of hydrocarbon resin per 100 wt% of the plasticizer.
An eleventh aspect of the present invention is the tire according to any one of the first to tenth aspects, wherein the second rubber composition (SC) is such that the plasticizer comprises more than 25phr (e.g. between 25 and 85 phr), preferably more than 30phr (e.g. between 30 and 80phr), more preferably more than 35phr (e.g. between 35 and 75 phr), still more preferably more than 40phr (e.g. between 40 and 70 phr), in particular at least 45phr (e.g. 45 to 65phr), more in particular at least 50phr (e.g. 50 to 60phr) of the hydrocarbon resin.
In a manner known to those skilled in the art, the term "resin" is retained in this application by definition as a compound that is solid at ambient temperature (20 ℃ at atmospheric pressure) as opposed to a liquid plasticizing compound (e.g., an oil).
Hydrocarbon resins are polymers well known to those skilled in the art which are essentially based on carbon and hydrogen and are thus naturally miscible in rubber compositions (e.g., diene elastomer compositions). They may be of the aliphatic or aromatic or aliphatic/aromatic type, i.e. based on aliphatic and/or aromatic monomers. They may be natural or synthetic, and may or may not be petroleum-based (in the case of petroleum-based, they are also known as petroleum resins). They are preferably only hydrocarbons, i.e. they contain only carbon and hydrogen atoms.
Preferably, the "plasticized" hydrocarbon resin exhibits at least one, more preferably all, of the following characteristics:
-TgDSCmore than 20 deg.C (e.g. between 20 deg.C and 100 deg.C), preferably more than 30 deg.C (e.g. atBetween 30 ℃ and 100 ℃), more preferably more than 40 ℃ (for example between 40 ℃ and 100 ℃) and still more preferably more than 45 ℃ (for example between 45 ℃ and 100 ℃), in particular at least 50 ℃ (for example at least 50 ℃ and less than 100 ℃);
-a number average molecular weight (Mn) between 400 and 2000g/mol (more preferably between 500 and 1500 g/mol);
polydispersity Index (PI) less than 3, more preferably less than 2 (reminder: PI ═ Mw/Mn, where Mw is the weight average molecular weight).
The macrostructure (Mw, Mn and PI) of the hydrocarbon resin was determined by Size Exclusion Chromatography (SEC): tetrahydrofuran as a solvent; the temperature is 35 ℃; the concentration is 1 g/l; flow rate 1 ml/min; before injection, the solution was filtered through a filter with a porosity of 0.45 μm; performing molar calibration with polystyrene standards; a set of 3 "Waters" columns in series ("Styragel" HR4E, HR1 and HR 0.5); detection was performed by differential refractometer ("Waters 2410") and its associated operating software ("Waters Empower").
A twelfth aspect of the present invention is the tire according to any one of the first to eleventh aspects, wherein the hydrocarbon resin is selected from the group consisting of a cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resin, a dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resin, a terpene homopolymer or copolymer resin, C5Fraction homopolymer or copolymer resin, C9Among the above copolymer resins, it is more preferable to use a resin selected from the group consisting of (D) CPD/vinyl aromatic copolymer resin, (D) CPD/terpene copolymer resin, (D) CPD/C5A distillate copolymer resin, (D) CPD/C9Fractional copolymer resin, terpene/vinyl aromatic copolymer resin, terpene/phenol copolymer resin, C5Fraction/vinyl aromatic copolymer resin, C9Distillate/vinyl aromatic copolymer resins and mixtures thereof.
The term "terpene" is used herein in a known manner to combine α -pinene, β -pinene and limonene monomers, with preference being given to the use of limonene monomers, which compounds are present in a known manner in the form of three possible isomersSuitable as vinylaromatic monomers are, for example, styrene, α -methylstyrene, (o-, m-or p-) methylstyrene, vinyltoluene, p- (tert-butyl) styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene or from C9Fraction (or more generally from C)8To Ci0Fractions) of any vinyl aromatic monomer. Preferably, the vinylaromatic compound is styrene or is derived from C9Fraction (or more generally from C)8To Ci0Fraction) of vinyl aromatic monomers. Preferably, the vinylaromatic compound is the minor monomer (in mole fraction) in the copolymer under consideration.
Preferred resins as above are well known to those skilled in the art and are commercially available, for example:
-a poly-limonene resin: from DRT under the name "Dercolyte L120" (Mn 625 g/mol; Mw 1010 g/mol; PI 1.6; TgDSC72 deg.c) or by Arizona Chemical Company under the designation "Sylvagum TR 7125C" (Mn 630 g/mol; mw is 950 g/mol; PI is 1.5; tg ofDSC＝70℃)；
-C5Distillate/vinyl aromatic copolymer resins, especially C5Fraction/styrene or C5fraction/CgFraction copolymer resin: by the name "Super Nevtac 78", "Super Nevtac 85" or "Super Nevtac 99" by Neville Chemical Company, by the name "Wingtack Extra" by Goodyear Chemicals, by the names "Hikorez T1095" and "Hikorez T1100" by Kolon, or by the names "Escorez 2101" and "ECR 373" by Exxon;
-limonene/styrene copolymer resin: by DRT under the name "Dercolyte TS 105", or by Arizona chemical Company under the names "ZT 115 LT" and "ZT 5100".
As another preferred resin, there may be mentioned, for example, a phenol-modified α -methylstyrene resinThe known manner uses the value known as the "hydroxyl number" (measured according to standard ISO 4326 and expressed in mg KOH/g) α -methylstyrene resins, in particular those α -methylstyrene resins modified with phenol, are known to the person skilled in the art and are commercially available, for example under the name "Sylvares SA 100" (Mn 660 g/mol; PI 1.5; Tg) from Arizona Chemical CompanyDSC＝53℃)、“Sylvares SA 120”(Mn＝1030g/mol；PI＝1.9；TgDSC＝64℃)、“Sylvares 540”(Mn＝620g/mol；PI＝1.3；TgDSCThe temperature is 36 ℃; hydroxyl number 56mg KOH/g), and "Sylvares 600" (Mn 850 g/mol; PI is 1.4; tg ofDSCThe temperature is 50 ℃; hydroxyl number 31mg KOH/g).
A thirteenth aspect of the present invention is a tyre according to any one of the first to twelfth aspects, wherein the second rubber composition (SC) is such that the plasticizer comprises less than 45phr (for example between 1 and 45 phr), preferably less than 35phr (for example between 2 and 35 phr), more preferably less than 30phr (for example between 3 and 30 phr), still more preferably less than 25phr (for example between 5 and 25 phr), in particular between 10 and 25phr, of at least one liquid plasticizer.
Liquid plasticizers are by definition liquid at 20 ℃ (at atmospheric pressure), their function being to soften the matrix by diluting the elastomer and the reinforcing filler; by definition, their TgDSCLess than-20 ℃ (e.g. between-120 and-30 ℃), preferably less than-30 ℃ (e.g. between-100 and-30 ℃), more preferably less than-40 ℃ (e.g. between-80 and-40 ℃), even more preferably less than-50 ℃ (e.g. between-70 and-50 ℃), in particular up to-55 ℃ (e.g. between-55 and-65 ℃).
Any extender oil (whether aromatic or non-aromatic), any liquid plasticizer known to have plasticizing properties for elastomer substrates (e.g., diene elastomers) may be used. At ambient temperature (20 ℃), these plasticizers or these oils (more or less viscous) are liquids (to be reminded here, i.e. substances having the ability to finally assume the shape of their container), in particular in contrast to plasticized hydrocarbon resins which are naturally solid at ambient temperature.
A fourteenth aspect of the present invention is the tire according to the thirteenth aspect, wherein the second rubber composition (SC) is such that the liquid plasticizer is selected from the group consisting of liquid diene polymers, polyolefin oils, naphthenic oils, paraffin oils, Distilled Aromatic Extract (DAE) oils, Medium Extraction Solvate (MES) oils, Treated Distilled Aromatic Extract (TDAE) oils, Residual Aromatic Extract (RAE) oils, Treated Residual Aromatic Extract (TRAE) oils, Safety Residual Aromatic Extract (SRAE) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures thereof.
As phosphate ester plasticizers, mention may be made, for example, of those comprising between 12 and 30 carbon atoms, such as trioctyl phosphate. As examples of ester plasticizers, mention may in particular be made of compounds selected from trimellitate, pyromellitate, phthalate, 1, 2-cyclohexanedicarboxylate, adipate, azelate, sebacate, triglyceride and mixtures thereof. Among the above triesters, mention may be made of preferably predominantly (more than 50% by weight, more preferably more than 80% by weight) unsaturated C18Triglycerides of fatty acids (i.e., unsaturated fatty acids selected from the group consisting of oleic acid, linoleic acid, linolenic acid, and mixtures thereof). More preferably, the fatty acids used, whether of synthetic or natural origin (in this case, for example, sunflower or rapeseed plant oil), consist of more than 50% by weight, still more preferably 80% by weight, of oleic acid. Such triesters (trioleate) containing high levels of oleic acid are well known; they have been described, for example, in application WO 02/088238 as liquid plasticizers in tire treads.
If the liquid plasticizer used comprises petroleum, the petroleum is preferably a non-aromatic petroleum. Liquid plasticizers are described as non-aromatic when the content of polycyclic aromatic compounds based on the total weight of the plasticizer, as determined by the IP 346 method with extracts in DMSO, is less than 3 weight percent. Thus, it is possible to use liquid plasticizers chosen from MES oils, TDAE oils, naphthenic oils (low or high viscosity, in particular hydrogenated or non-hydrogenated), paraffinic oils and mixtures thereof. Also suitable as petroleum are RAE, TRAE and SRAE oils or mixtures thereof containing low levels of polycyclic compounds.
The second rubber composition (SC) according to the invention may be based on all or part of the usual additives usually used in elastomeric compositions intended for the manufacture of tyre treads, such as pigments, protective agents (for example antiozone waxes, chemical antiozonants, antioxidants), antifatigue agents, reinforcing resins (for example methylene acceptors (for example novolac resin) or methylene donors (for example HMT or H3M)), crosslinking systems based on sulfur or on sulfur donors and/or peroxides and/or bismaleimides, vulcanization accelerators, or vulcanization activators.
The second rubber composition (SC) can also be based on coupling activators (when coupling agents are used), agents for covering the reinforcing inorganic filler or, more generally, processing aids capable of improving the processability in the raw state in a known manner, thanks to an improved dispersion of the filler in the rubber matrix and to a reduction in the viscosity of the second rubber composition (SC); these agents are, for example, hydrolyzable silanes such as alkylalkoxysilanes, polyols, polyethers, amines, or hydroxylated or hydrolyzable polyorganosiloxanes.
The second rubber composition (SC) according to the invention is prepared in a suitable mixer using two successive preparation stages according to the general procedure known to the person skilled in the art: a first stage of thermomechanical working or kneading at high temperature (up to a maximum temperature between 110 ℃ and 190 ℃, preferably between 130 ℃ and 180 ℃) (called "non-preparation" stage), followed by a second stage of mechanical working at a lower temperature, generally less than 110 ℃, for example between 40 ℃ and 100 ℃ ("preparation" stage), during which a crosslinking or vulcanization system is introduced.
The process which can be used for preparing the second rubber composition (SC) comprises, for example, preferably the following steps:
-introducing reinforcing fillers, plasticizers into an elastomeric matrix (for example a diene elastomer) in a mixer, thermomechanically kneading all the substances in one or more portions during a first phase (the "non-preparation" phase) until a maximum temperature between 110 ℃ and 190 ℃ is reached;
-cooling the combined mixture to a temperature of less than 100 ℃;
-the subsequent introduction of the crosslinking system during the second stage (the "preparation" stage);
-kneading all the mass up to a maximum temperature of less than 110 ℃.
For example, the first (non-preparation) stage is carried out in a single thermomechanical stage, in which all the necessary components are introduced into a suitable mixer (such as a standard internal mixer), followed by the introduction of further additives, optionally additional filler-covering agents or processing aids, in addition to the crosslinking system, in a second step, for example after kneading for 1 to 2 minutes. The total kneading time in this non-preparation phase is preferably between 1 and 15 minutes.
After cooling the mixture thus obtained, the crosslinking system is then introduced, generally at low temperature (for example between 40 ℃ and 100 ℃), into an open mixer (for example an open mill); the combined mixture (second (preparation) stage) is then mixed for several minutes, for example between 2 and 15 minutes.
The crosslinking system is preferably based on sulfur and a primary vulcanization accelerator, in particular on an accelerator of the sulfenamide type. Added to the vulcanization system are various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine), etc., which are introduced during the first non-preparative stage and/or during the preparative stage.
The sulphur content is preferably between 0.5 and 5.0phr, the primary accelerator content is preferably between 0.5 and 8.0 phr.
As (primary or secondary) accelerator, any compound capable of acting as a vulcanization accelerator for the elastomer matrix (for example a diene elastomer) in the presence of sulfur may be used, in particular thiazole-type accelerators and their derivatives, thiuram-type accelerators or zinc dithiocarbamates. These accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazole disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazolesulfenamide (abbreviated as "CBS"), N-dicyclohexyl-2-benzothiazolesulfenamide ("DCBS"), N-tert-butyl-2-benzothiazolesulfenamide ("TBBS"), N-tert-butyl-2-benzothiazolesulfenimide ("TBSI"), zinc dibenzyldithiocarbamate ("ZBEC"), tetrabenzylthiuramed disulfide ("TBZTD"), and mixtures thereof.
The second rubber composition (SC) thus obtained is then calendered, for example in the form of a sheet or plate, in particular for laboratory characterization, or extruded in the form of a rubber profiled element that can be used directly as a covering layer, which is part of the tread pattern element (1) of the tire tread according to the invention.
The vulcanization (or curing) is carried out in a known manner at a temperature generally between 110 ℃ and 190 ℃ for a sufficient time, which may vary, for example, between 5 and 90 minutes, depending in particular on the curing temperature, on the vulcanization system employed and on the vulcanization kinetics of the second rubber composition (SC) under consideration.
The first step in the preparation of the tire tread according to the invention is to cover the first rubber composition (FC) with a layer of the second rubber composition (SC).
For example, the first step can be carried out with the method described in the above-mentioned application WO2013/087878, i.e. by impregnating a two-dimensional assembly of fibers (for example a fabric or a nonwoven) or a three-dimensional assembly of fibers (in the form of a felt) previously arranged in suitable dimensions with a second rubber composition (SC). The impregnation can be carried out, for example, by hot calendering, by compression moulding or by injection under pressure.
The presence of the fibrous component impregnated with the second rubber composition (SC) allows to obtain, before the vulcanization of the tyre, a good cohesion of the layer of second rubber composition (SC), thus assisting the layer of second rubber composition (SC) to be arranged on the first rubber composition (FC) during the moulding of the tyre.
Of course, tools other than fiber assemblies may also be used to improve the cohesion and arrangement of the layer of the second rubber composition (SC) in the untreated state, such as rigid metal sheets, cellulose fibers (e.g. paper, cardboard) or another polymer.
Of course, if such a fiber assembly, strip or other tool is used to assist in laying the second rubber composition (SC) for disposition on the first rubber composition (FC) during preparation of a tire according to the present invention, the second rubber composition (SC) may include the fiber assembly, strip or other tool unless the fiber assembly, strip or other tool is removed prior to curing of the tire.
Preferably, the fibres used are long fibres, the longest dimension of which is greater than 30mm, more preferably greater than 50 mm.
Any type of fiber, preferably selected from textile fibers, mineral fibers and mixtures thereof, may be used for the layer of the second rubber composition (SC) having a sufficient tensile stiffness to facilitate the arrangement of the layer of the second rubber composition (SC) during the molding of the tire.
The textile fibers may be selected from natural source fibers, synthetic fibers, and mixtures thereof. The natural source fibers may be made of organic materials selected from silk, cotton, bamboo, cellulose, wool and mixtures thereof, preferably cotton, cellulose, wood and mixtures thereof. The synthetic fibers may be made of synthetic materials selected from the group consisting of polyester, polyamide, carbon, aramid, polyethylene, polypropylene, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, polyurethane, polyvinyl alcohol, and mixtures thereof.
The mineral fibers may be selected from glass fibers, basalt fibers, and mixtures thereof.
One way of obtaining such a tread pattern is then to cover the tread, including the whole green form of the first rubber composition (FC), with a layer of a second rubber composition (SC) of suitable thickness, for example before moulding the tread and the incisions (3, 4). After moulding, the second rubber composition (SC) on the contact surface (2) can be left in place or removed by mechanical means, in particular by grinding.
Another way of industrially producing the tread of the tire according to the invention may consist in applying a thin strip of the second rubber composition (SC) to the tire in green uncured form provided with a tread made of the first rubber composition (FC), as described in patent EP 0510550 (the thin strip may be applied to the tread in the circumferential and/or axial direction). Another way may consist in preparing the tread by co-extruding two (or more) compounds when extruding the tread. It is still possible to operate as described in fig. 5 to 6 and in paragraph IV-B of WO 2013/087878.
After the tyre of the invention has been vulcanized, the layer of the above-mentioned specific second rubber composition (SC) has the advantage of providing the edges (23, 24, 25, 26) formed by the intersection of the contact surface (2) and the sides (13, 14, 15, 16) of suitable stiffness with a very suitable rigidity, which is particularly advantageous for the performance of the tyre on snow, while being imparted to the tyre thanks to the presence of the specific second rubber composition, which is capable of improving the grip performance of the tyre on wet ground, while maintaining or improving the grip performance on snow and ice.
A fifteenth aspect of the present invention is the tire according to any one of the first to fourteenth aspects, wherein the layer of the second rubber composition (SC) has a thickness (E1) of more than 0.1mm (for example, between 0.1 and 5.0 mm), preferably more than 0.2mm (between 0.2 and 4.5 mm), in order to obtain good grip on snow. More preferably, the thickness is between 0.2 and 4.0mm, still more preferably between 0.3 and 1.0mm, in order to maintain good performance on snowy ground and at the same time limit the extent to which grip on icy ground is not favoured.
The invention is further illustrated by the following non-limiting examples.
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