WO2014104283A1

WO2014104283A1 - Rubber composition for tire tread for winter

Info

Publication number: WO2014104283A1
Application number: PCT/JP2013/085070
Authority: WO
Inventors: 伯勇薛; パガノ　サルヴァトーレ
Original assignee: コンパニーゼネラールデエタブリッスマンミシュラン; ミシュランルシェルシュエテクニークソシエテアノニム
Priority date: 2012-12-28
Filing date: 2013-12-27
Publication date: 2014-07-03

Abstract

A rubber composition which is useful as the tread of a tire for use in winter and which has high gripping performance on ice not only at temperatures lower than -5ºC but also at temperatures between -5ºC and 0ºC. The rubber composition comprises 25-75 phr of polybutadiene or a butadiene copolymer, 25-75 phr of natural rubber or synthetic isoprene, more than 40 phr of a liquid plasticizer, 70-120 phr of a reinforcing filler such as silica and/or carbon black, and 10-50 phr of silicon carbide microparticles having a median particle size (weight average) of 10-300 μm. The present invention further relates to a use of the rubber composition in the production of the tread of a tire for use in winter, and to the tread and the tire.

Description

Rubber composition for winter tire tread

The present invention is for a “winter tire” (also known as a studless tire) that can rotate on a road covered with ice or black ice without the need for a stud. The present invention relates to a rubber composition that can be used particularly as a tread.

The present invention more particularly relates to a tread for a winter tire that is particularly suitable for spinning under “melting ice” conditions encountered in the temperature range typically between −5 ° C. and 0 ° C. It is important to note that within such a range, the pressure of the tires while passing through the vehicle causes ice surface melting, which is covered by a thin film of water (water film layer) that is detrimental to the grip performance of these tires. It is to be.

In order to avoid the detrimental effects of the studs, in particular the strong wear action of the studs on the surface pavement of the road surface itself and the road performance on dry road surfaces, the tire manufacturers etc. Various solutions are provided, including modifying the formulation.

Therefore, first of all, a proposal has been made to mix solid particles having high hardness such as silicon carbide (see, for example, Patent Document 1), and a considerable number of these solid particles are worn by the tread. As it reaches the tread surface, it comes into contact with ice. Such particles can actually act as microstuds on hard ice by an action well known as the scratch effect, and are relatively attackable against the road surface. Furthermore, such particles are not well suited for grip performance on melted ice.

As another proposed solution, there is a solution that improves grip performance on melted ice by mixing a water-soluble powder in the rubber composition of the tread. Such powder dissolves more or less when in contact with snow or melted ice, on the one hand it forms pores on the tire tread surface which can improve the grip performance of the tread on the road surface, and on the other hand, between the tire and the road surface. It is possible to form a groove that acts as a passage for discharging the liquid film formed on the substrate. In all these examples, the very low temperature and very short solubility of the powder used is an essential factor in the satisfactory operation of the tread. If the powder does not dissolve under the use conditions of the tire, the above functions (formation of micropores and passages for drainage) are not performed, and grip performance is not improved. Another known drawback of these solutions is that they are against the reinforcing properties of the rubber composition (and thus its wear resistance) or against the hysteresis of the rubber composition (and therefore its It can be very detrimental to the rolling resistance.

Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5 filed by the present applicant generate effective fine surface roughness by specific water-soluble microparticles (magnesium sulfate, potassium sulfate or hollow microparticles). Specific rubber compositions that can improve the grip performance on ice under ice melting conditions of treads and tires containing these microparticles and that do not detrimentally affect the reinforcement and hysteresis properties It is described.

First, these water-soluble microparticles protrude on the tread surface and perform the above-described scratching effect without fear of scraping the road surface. And after that, the part from which the fine particles are gradually excluded from the rubber composition forms a microcavity that functions as a storage volume and a passage for discharging the water film layer on the ice surface; Underneath, contact between the tread surface and ice is no longer lubricated by removing the water film layer, thus improving the coefficient of friction.

U.S. Pat.No. 3,878,147 International Publication No. 2010/009850 Pamphlet International Publication No. 2011/073188 Pamphlet International Publication No. 2012/085063 Pamphlet International Publication No. 2011/073186 Pamphlet

However, if the fine cavities are formed after the fine particles are gradually excluded from the rubber composition, the substantial contact area between the tread and the ice road surface is reduced as compared with the initial tread state. The grip performance on ice of the tread and the tire decreases at a temperature lower than −5 ° C.

As a result of extensive research, the present inventor is able to generate a micro scratch effect (micro spike effect) with specific microparticles and not only between −5 ° C. and 0 ° C. but also between −5 ° C. and 0 ° C. The present inventors have found a novel and specific rubber composition that makes it possible to improve the grip performance on ice of a tire containing this specific rubber composition as a tread even in the temperature range of.

Thus, the first subject of the present invention is
-Polybutadiene or butadiene copolymer between 25 phr and 75 phr;
-Natural rubber or synthetic polyisoprene between 25 phr and 75 phr;
-More than 40phr liquid plasticizer;
-Reinforcing filler between 70 phr and 120 phr;
-Silicon carbide microparticles with a median particle size (median size) (weight average) between 10 and 50 phr with a content between 10 and 50 phr;
Is a rubber composition containing at least

Another subject of the present invention is the use of such rubber compositions in the manufacture of treads for winter tires (intended for either new tires or re-treading of worn tires).
Another subject of the present invention is these treads and these tires themselves when comprising the rubber composition according to the present invention.

The tires according to the invention are in particular passenger cars, including 4 × 4 (four-wheel drive) vehicles and SUV (sports multipurpose vehicles) vehicles; two-wheel vehicles (especially motorcycles); and more particularly vans and heavy vehicles (ie It is intended to be mounted on industrial vehicles selected from subways, buses, heavy road transport vehicles (trucks, tractors, trailers), or off-road vehicles such as agricultural vehicles or earthmovers.

Furthermore, the following aspects may be sufficient as this invention.
[1] A rubber composition,
-Polybutadiene or butadiene copolymer between 25 phr and 75 phr;
-Natural rubber or synthetic polyisoprene between 25 phr and 75 phr;
-More than 40phr liquid plasticizer;
-Reinforcing filler between 70 phr and 120 phr;
-Silicon carbide microparticles with a median particle size (weight average) between 10 and 300 μm with a content between 10 and 50 phr;
A rubber composition comprising at least
[2] The rubber composition according to [1], wherein the silicon carbide microparticles have a median particle size (weight average) between 50 μm and 150 μm.
[3] The rubber composition according to [1] or [2], wherein the content of the silicon carbide fine particles is between 10 phr and 30 phr.
[4] The rubber composition according to any one of [1] to [3], wherein the polybutadiene has a cis-1,4 bond content of more than 90%.
[5] The rubber composition according to [4], comprising more than 50 phr of the natural rubber or the synthetic polyisoprene.
[6] The rubber composition according to [4], comprising more than 50 phr of the polybutadiene having a cis-1,4 bond content of more than 90%.
[7] The rubber composition according to any one of [1] to [6], wherein the reinforcing filler is selected from an inorganic filler, carbon black, and a mixture of an inorganic filler and carbon black.
[8] The rubber composition according to [7], wherein the inorganic filler is silica.
[9] The rubber composition according to any one of [1] to [8], wherein the content of the reinforcing filler is between 75 phr and 115 phr.
[10] The rubber composition according to [9], wherein the reinforcing filler content is between 80 phr and 110 phr.
[11] The liquid plasticizer is polyolefin oil, naphthene oil, paraffin oil, DAE oil, MES oil, TDAE oil, RAE oil, TRAE oil, SRAE oil, mineral oil, vegetable oil, ether plasticizer, ester The rubber composition according to any one of [1] to [10], which is selected from the group consisting of a plasticizer, a phosphate plasticizer, a sulfonate plasticizer, and a mixture of these compounds.
[12] The rubber composition according to [11], wherein the content of the liquid plasticizer is more than 50 phr.
[13] The rubber composition according to [12], wherein the content of the liquid plasticizer is between 50 phr and 100 phr.
[14] The rubber composition according to any one of [1] to [13], wherein the rubber composition further contains a hydrocarbon resin having a Tg higher than 20 ° C. as a solid plasticizer.
[15] The hydrocarbon resin is a homopolymer or copolymer resins of cyclopentadiene, homopolymer or copolymer resins of dicyclopentadiene, terpene homopolymer or copolymer resins, C ₅ fraction homopolymer or copolymer resins, C ₉ fraction [14] The rubber composition according to [14], which is selected from the group consisting of a homopolymer or copolymer resin of a minute, and a mixture of these resins.
[16] The rubber composition according to [14] or [15], wherein the content of the hydrocarbon resin is between 3 phr and 60 phr.
[17] The rubber composition according to any one of [1] to [16], wherein the content of the entire plasticizer is between 50 phr and 100 phr.
[18] The rubber composition according to [17], wherein the content of the whole plasticizer is between 60 phr and 80 phr.
[19] The rubber composition according to [17] or [18], wherein the ratio of the content of the liquid plasticizer to the content of the hydrocarbon resin is between 3 and 5.
[20] The rubber composition according to [19], wherein a ratio of the content of the liquid plasticizer to the content of the hydrocarbon resin is between 3.5 and 4.5.
[21] Use of the rubber composition according to any one of [1] to [20] for production of a tread for a winter tire.
[22] A tread for a winter tire comprising the rubber composition according to any one of [1] to [20].
[23] A winter tire including the tread according to [22].

I. Measurements and Test Methods Used The treads described in this specification and examples and the constituent rubber compositions of these treads are characterized before and after curing as shown below.

I-1. Mooney Plasticity Use an oscillating consistency meter as described in French standard NF T 43-005 (November 1980). The Mooney plasticity measurement is performed according to the following principle: A rubber composition in a raw state (ie, before curing) is molded in a cylindrical chamber heated to 100 ° C. After 1 minute preheating, the rotor rotates at 2 revolutions / minute in the test specimen, and the work torque to maintain this movement is measured after 4 minutes of rotation. The Mooney plasticity (ML 1 + 4) is expressed in “Mooney units” (MU, 1MU = 0.83 Newton.meters).

I-2. Scorch time measurement is carried out at 130 ° C according to the French standard NF T 43-005. The change in consistencyometric index as a function of time is evaluated against the above standard by the parameter T5 in minutes (in the case of large rotors) and measured on the consistency measuring index (in MU) It makes it possible to determine the scorch time of a rubber composition, defined as the time required to obtain a consistency measurement index increase of 5 units higher than.

I-3. Flowability measurement The measurement is carried out at 150 ° C with a vibrating disc rheometer according to the standard DIN 53529: Part 3 (June 1983). The change in the stiffness of the rubber composition as a result of the vulcanization reaction is explained by the change in the measured fluidity torque as a function of time. Process the measured values according to standard DIN 53529: Part 2 (March 1983): Ti is the induction time, ie the time required to initiate the vulcanization reaction; Tα (eg T90) is α %, Ie the time required to achieve a conversion of α% (eg 90%) of the difference between the lowest torque and the highest torque.

I-4. Tensile tests These tensile tests make it possible to measure elastic stresses and properties at break. Unless otherwise noted, these tests are conducted in accordance with the French standard NF T 46-002 of September 1988. Nominal secant modulus (i.e. apparent stress in MPa) at 10% elongation (denoted as M10), 100% elongation (denoted as M100) and 300% elongation (denoted as M300) at the second elongation (i.e. Measure after the adaptation cycle to the degree of elongation expected in the measurement itself. The breaking stress (MPa) and elongation at break (%) are also measured. All these tensile measurements are carried out according to the French standard NF T 40-101 (December 1979) under standard conditions of temperature (23 ± 2 ° C.) and humidity (50 ± 5% relative humidity).

I-5. Shore A Hardness The Shore A hardness of the cured rubber composition is evaluated according to the standard ASTM D 2240-86.

II. Detailed Description of the Invention The rubber composition of the present invention comprises at least a blend of two specific diene elastomers, a plasticizing system, a reinforcing filler and silicon carbide microparticles, the components of which are detailed below. To do.

In this description, unless otherwise specified, all percentages (%) shown are weight%. “Weight” may be read as “mass”. Furthermore, the interval of values indicated by the expression “between a and b” both indicate a range of values greater than a and less than b (ie, excluding limit values a and b), Any interval of values indicated by the expression “a to b” means a range of values from a to b (ie, including strict limit values a and b).

II-1. Diene Elastomers “Diene” elastomers or rubbers, as is known, are derived at least in part from diene monomers (monomers bearing two carbon-carbon double bonds, which may or may not be conjugated). It should be understood here as meaning elastomers (ie homopolymers or copolymers).

The essential features of the rubber composition of the present invention are natural rubber (NR) between 25 and 75 phr based on diene elastomer (Note; “phr” means parts per 100 parts by weight of elastomer) Or synthetic polyisoprene (IR) between 25 phr and 75 phr of polybutadiene (BR) or butadiene copolymer, or combinations thereof, more preferably between 30 phr and 50 phr of natural rubber or synthetic polyisoprene of 50 phr and 70 phr. In combination with polybutadiene (BR) or butadiene copolymer. The two-component blend base may preferably contain a third elastomer with a content lower than 30 phr, particularly preferably lower than 20 phr (three-component blend) or not.

According to a preferred embodiment, the synthetic polyisoprene is of the cis-1,4 type; among these synthetic polyisoprenes, preferably more than 90%, even more preferably more than 98% It is suitable to use polyisoprene having a cis-1,4 bond content (mol%).

Polybutadienes include in particular polybutadienes having a 1,2-unit content (mol%) of between 4% and 80% or polybutadienes having a cis-1,4-unit content greater than 80%. It is done. Preferably, the polybutadiene has a cis-1,4 bond content (mol%) greater than 90%.

The butadiene copolymer is more preferably selected from the group consisting of butadiene / styrene copolymers (SBRs), isoprene / butadiene copolymers (BIRs), isoprene / butadiene / styrene copolymers (SBIRs) and mixtures of such copolymers. .

Suitable butadiene monomers are in particular 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C ₁ -C ₅ alkyl) -1,3-butadienes, for example 2,3 as an example. -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 and aryl- 1,3-butadiene. Suitable styrene monomers are in particular styrene, methylstyrenes, para- (tert-butyl) styrene, methoxystyrenes and chlorostyrenes.

SBR copolymers especially have a styrene content between 5% and 50% by weight, more preferably between 20% and 40% by weight, a butadiene component 1,2-bond content between 4% and 65%. (Mole%) and trans-1,4-bond content (mol%) between 20% and 80%, butadiene / isoprene copolymers in particular contain between 5% and 90% by weight isoprene. Butadiene / styrene / isoprene copolymers, in particular 5% and 50% by weight, with a glass transition temperature (“Tg”, measured according to ASTM D3418 (1999), described below) Styrene content between 10% and 40%, especially between 15% and 60%, especially between 20% and 50% isoprene, 5% and 50% Butadiene content between 20% and 40% by weight, especially 1,2-unit content of butadiene component between 4% and 85 %% (mol%) Between 6% and 80% butadiene component trans-1,4-unit content (mol%), between 5% and 70% isoprene component 1,2- + 3,4-unit content (mol%) and Any butadiene / isopropylene component having a trans-1,4-unit content (mol%) of between 10% and 50%, and more generally having a Tg between −20 ° C. and −70 ° C. Styrene / isoprene copolymers may be particularly suitable.

According to a particularly preferred embodiment of the invention, the polybutadiene or butadiene copolymer comprises polybutadienes having a content (mol%) of cis-1,4 bonds of more than 90% (more preferably more than 98%), Selected from the group consisting of butadiene / styrene copolymers and mixtures of these elastomers.

According to another preferred embodiment, the rubber composition according to the invention comprises more than 50 phr of natural rubber or synthetic polyisoprene.

According to another preferred embodiment, the rubber composition of the present invention comprises more than 50 phr of polybutadiene having a cis-1,4 bond content (mol%) of more than 90%.

Synthetic elastomers other than diene elastomers, in fact, polymers other than elastomers, such as thermoplastic polymers, in small amounts (generally less than 40 phr, preferably less than 25 phr) with the diene elastomer of the rubber composition of the present invention. In combination).

II-2. Plasticizing system The rubber composition of the present invention has, as another essential characteristic, a characteristic that it contains a plasticizer that is liquid (at 23 ° C.) more than 40 phr, and the role of this plasticizer is Diluting the elastomer and reinforcing filler to soften the rubber composition; by definition, its Tg is lower than −20 ° C., preferably lower than −40 ° C.

Any extender oil, either aromatic or non-aromatic, can be used, ie any liquid plasticizer known for its plasticizing properties on diene elastomers. At ambient temperature (20 ° C.), these plasticizers or these oils are more or less viscous, especially liquids (i.e., in contrast to plasticizing hydrocarbon resins that are inherently solid at ambient temperatures). Annotation is a substance that has the ability to eventually take the shape of its container).

Polyolefin oil, naphthenic oil (low or high viscosity, especially hydrogenated or other), paraffinic oil, DAE (Distillate Aromatic Extracts) oil, MES (Medium Extracted Solvates) oil, TDAE (Treated Distillate Aromatic Extracts) oil , RAE (Residual Aromatic Extracts) oil, TRAE (Treated Residual Aromatic Extracts) oil, SRAE (Safety Residual Aromatic Extracts) oil, mineral oil, vegetable oil, ether plasticizer, ester plasticizer, phosphate plasticizer, sulfonate plasticizer Particularly suitable are liquid plasticizers selected from the group consisting of agents and mixtures of these compounds.

Examples of phosphate plasticizers include phosphate plasticizers containing between 12 and 30 carbon atoms, such as trioctyl phosphate. Examples of ester plasticizers include compounds selected from the group consisting of trimellitate, pyromellitate, phthalate, 1,2-cyclohexanedicarboxylate, adipate, azelate, sebacate, triester of glycerin, and mixtures of these compounds. be able to. Among the triesters mentioned above, unsaturated fatty acids selected from the group consisting of unsaturated _C18 fatty acids, i.e. oleic acid, linoleic acid, linolenic acid and mixtures of these acids (mainly more than 50% by weight and more Mention may be made of glycerin triesters, preferably at more than 80% by weight. More preferably, the fatty acid used is greater than 50% by weight, even more preferably 80% by weight of olein, whether synthetic or natural (in this case, for example, sunflower or rapeseed vegetable oil). Made of acid. Such triesters (trioleates) with a high content of oleic acid are well known; for example, such triesters are described in WO 02/088238 as plasticizers in tire treads. Explained.

The content of the liquid plasticizer in the rubber composition of the present invention is preferably more than 50 phr, more preferably between 50 phr and 100 phr, and even more preferably within the range of 60 to 100 phr.

According to another preferred embodiment, the rubber composition of the present invention is used as a solid plasticizer (at 23 ° C.), for example, International Publication No. 2005/087859, International Publication No. 2006/061064 and International Publication No. Hydrocarbon resins exhibiting a Tg higher than + 20 ° C., preferably higher than + 30 ° C., as described in publication 2007/017060, may also be included.

Hydrocarbon resins are polymers well known to those skilled in the art and are inherently miscible in a diene elastomer composition when additionally described as being carbon and hydrogen based and thus “plasticizing”. It is sex. Hydrocarbon resins are described, for example, in the work entitled “Hydrocarbon Resins” by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-2817-9). Chapter 5 is dedicated to the use of hydrocarbon resins, especially in the field of tire rubber (5.5.5.5 “RubberubbTires and Mechanical Goods”). The hydrocarbon resin can also be aliphatic or aromatic or of the aliphatic / aromatic type, i.e. it can be based on aliphatic and / or aromatic monomers. The hydrocarbon resin may be natural or synthetic and may or may not be oil-based (in which case it is also known by the name of the petroleum resin). The hydrocarbon resin is preferably exclusively hydrocarbon, ie the hydrocarbon resin contains only carbon and hydrogen atoms.

Preferably, the plasticizing hydrocarbon resin exhibits at least one of the following characteristics, more preferably all:
A Tg higher than 20 ° C. (more preferably between 40 ° C. and 100 ° C.);
A number average molecular weight (Mn) between 400 g / mol and 2000 g / mol (more preferably between 500 g / mol and 1500 g / mol);
A polydispersity index (PI) lower than 3, more preferably lower than 2 (Note: PI = Mw / Mn; Mw is the weight average molecular weight).

Tg is measured by a known method using DSC (Suggested scanning calorimetry) according to the standard ASTM D3418 (1999). The macro structure (Mw, Mn and PI) of the above hydrocarbon resin was determined by size exclusion chromatography (SEC) 次 under the following conditions: solvent tetrahydrofuran; temperature 35 ° C; concentration 1 g / l; flow rate 1 ml / min; 0.45 before injection Solution filtered through a filter with a pore size of μm; Moore calibration with polystyrene standards; three in series “Waters” column set (“Styragel” HR4E, HR1 and HR0.5); differential refractometer (“Waters 2410 ") and its associated operating software (" Waters Empower ").

According to a particularly preferred embodiment, the plasticizing hydrocarbon resin comprises a cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resin, a dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resin, a terpene selected homopolymer or copolymer resins, C ₅ fraction homopolymer or copolymer resins, C ₉ fraction homopolymer or copolymer resins, from the group consisting of homopolymer or copolymer resins and these resins α- methylstyrene . More preferably, among the above copolymer resins, (D) CPD / vinyl aromatic copolymer resin, (D) CPD / terpene copolymer resin, (D) CPD / C _five- fraction copolymer resin, (D) CPD / C ₉ fraction copolymer resin, made of terpene / vinylaromatic copolymer resins, terpene / phenol copolymer resins, C ₅ fraction / vinylaromatic copolymer resins, C ₉ fraction / vinylaromatic copolymer resins, and mixtures of these resins A copolymer resin selected from the group is used.

“Terpenes” in this case include, as is known, α-pinene monomers, β-pinene monomers and limonene monomers; preferably, limonene monomers are used; It exists in the form of possible isomers: L-limonene (a levorotatory enantiomer), D-limonene (a dextrorotatory enantiomer) or dipentene, ie, a racemic dextrorotatory and levorotatory enantiomer. Styrene; α-methylstyrene; ortho-, meta- or para-methylstyrene; vinyl toluene; para- (tert-butyl) styrene; methoxystyrenes; chlorostyrenes; hydroxylstyrenes; vinyl mesitylene; divinylbenzene; Or any vinyl aromatic monomer derived from the C ₉ fraction (or more generally the C ₈ to C ₁₀ fraction) is suitable as, for example, a vinyl aromatic monomer. Preferably, the vinyl aromatic compound is a vinyl aromatic monomer derived from styrene or a C ₉ cut (or more generally a C ₈ to C ₁₀ cut). Preferably, the vinyl aromatic compound is a small amount of monomer expressed as a molar fraction in the copolymer.

The content of hydrocarbon resin is preferably between 3 phr and 60 phr, more preferably between 3 phr and 40 phr, especially between 5 phr and 30 phr.

The content of the entire plasticizer (ie liquid plasticizer + hydrocarbon resin having a Tg higher than the above 20 ° C. if necessary) is preferably between 50 phr and 100 phr, more preferably 60-80 phr. Include within range.

The ratio (β / α) of the liquid plasticizer content (βphr) to the hydrocarbon resin content (αphr) is preferably between 3 and 5, more preferably between 3.5 and 4.5.

II-3. Reinforcing fillers Any type of reinforcing filler known for its ability to reinforce rubber compositions that can be used in the manufacture of tires, for example organic fillers such as carbon black, Reinforcing inorganic fillers such as silica that are combined together in a known manner with coupling agents can be used.

Such reinforcing fillers typically consist of nanoparticles and their mean particle size (mean particle size) (mean particle size) (by weight) (e.g., standard ISO-13320 (Particle particle size analysis) Laser dispersion method methods). ))) Is lower than 500 nm, generally between 20 nm and 200 nm, particularly preferably between 20 nm and 150 nm.

カーボン All carbon blacks commonly used in tire treads, especially HAF, ISAF or SAF type blacks (“tire grade” blacks) are suitable as carbon blacks. More specifically, among the latter, for example, 100, 200 or 300 series reinforcing carbon blacks (ASTM grade) such as N115, N134, N234, N326, N330, N339, N347 or N375 blacks. It is done. Carbon black may already be incorporated into the isoprene elastomer, for example in the form of a masterbatch (see, for example, WO 97/36724 or WO 99/16600).

Examples of organic fillers other than carbon black are described in International Publication No. 2006/069792, International Publication No. 2006/069793, International Publication No. 2008/003434, and International Publication No. 2008/003435. And functionalized polyvinyl aromatic organic fillers.

“Reinforcing inorganic fillers”, in this case, also known as “white fillers” or “transparent fillers” in contrast to carbon black, are themselves by means other than intermediate coupling agents Can reinforce the rubber composition intended for the manufacture of the tire, in other words, it can be replaced in the normal tire grade carbon black and its reinforcing role, regardless of its color and its origin (natural or synthetic) It should be understood to mean any inorganic or mineral filler; such fillers are generally characterized by the presence of hydroxyl (—OH) groups on their surface, as is known .

Siliceous type mineral fillers, in particular silica (SiO ₂ ), or alumina type mineral fillers, in particular alumina (Al ₂ O ₃ ), are particularly suitable as reinforcing inorganic fillers. The silica used can be any reinforcing silica known to the person skilled in the art, in particular a BET surface area of both less than 450 m ² / g, preferably between 30 and 400 m ² / g, in particular between 60 m ² / g and 300 m ² / g. And any precipitated or calcined silica exhibiting a CTAB specific surface area. High dispersibility (“HD precipitated silica”) includes, for example, “Ultrasil” 7000 and “Ultrasil” 7005 silicas from Evonik; “Zeosil” 1165MP, 1135MP and 1115MP silicas from Rhodia; “Hi-Sil” EZ150G silica; “Zeopol” 8715, 8745 or 8755 silica from Huber. Examples of reinforcing aluminas include “Baikalox A125” or “Baikalox CR125” aluminas from Baikowski, “APA-100RDX” alumina from Condea, “Aluminoxid C” alumina from Degussa or Sumitomo Chemicals "AKP-G015" alumina.

Preferably, the content of the entire reinforcing filler (carbon black and / or reinforcing inorganic filler) is, for example, between 70 phr and 120 phr, preferably between 75 phr and 115 phr, in particular between 80 phr and 110 phr.

According to a particular embodiment, the reinforcing filler mainly comprises carbon black; in such cases, the carbon black is preferably combined with or without a small amount of reinforcing inorganic filler such as silica. Is present in a content greater than 75 phr.

According to another particular embodiment, the reinforcing filler mainly comprises an inorganic filler, in particular silica; in such a case, the inorganic filler, in particular silica, is combined with a small amount of carbon black or In combination, preferably present in a content greater than 80 phr; carbon black, if present, preferably is less than 20 phr, more preferably less than 10 phr (eg between 0.1 phr and 10 phr) Use in quantity.

Apart from the first aspect of the present invention, ie the search for optimization of grip performance on ice in temperatures below -5 ° C and in the temperature range between -5 ° C and 0 ° C, such as silica The use of major amounts of reinforcing inorganic fillers is also beneficial in terms of grip performance on rainy or snowy road surfaces.

According to another possible embodiment of the invention, the reinforcing filler comprises a blend of carbon black and a reinforcing inorganic filler such as silica in similar amounts; in such cases, inorganic The content of fillers, in particular silica and carbon black, is preferably between 25 and 75 phr, respectively, in particular between 30 and 50 phr, respectively.

In order to couple the reinforcing inorganic filler to the diene elastomer, as is well known, it is necessary to provide a satisfactory bond of chemical and / or physical properties between the inorganic filler (the particle surface) and the diene elastomer. The intended at least bifunctional coupling agent (or binder) is used. In particular, bifunctional organosilanes or polyorganosiloxanes are used.

In particular, for example, in WO 03/002648 pamphlet (or US Patent Application Publication No. 2005/016651) and WO 03/002649 pamphlet (or US Patent Application Publication No. 2005/016650). Silane polysulfides referred to as “symmetric” or “asymmetric” depending on their particular structure, as described.

“Symmetric” silane polysulfides corresponding to the general formula (I) below are particularly suitable without being limited to the following definitions:
(I) Z-A-Sx-A-Z
[Wherein x is an integer of 2 to 8 (preferably 2 to 5);
A is a divalent hydrocarbon group (preferably a C ₁ -C ₁₈ alkylene group or a C ₆ -C ₁₂ arylene group, especially a C ₁ -C ₁₀ , especially a C ₁ -C ₄ alkylene group, especially propylene);
Z corresponds to one of the following formulas:

Wherein the R ¹ groups are unsubstituted or substituted and are the same or different from each other and are C ₁ -C ₁₈ alkyl, C ₅ -C ₁₈ cycloalkyl or C ₆ -C ₁₈ An aryl group (preferably a C ₁ -C ₆ alkyl, cyclohexyl or phenyl group, especially a C ₁ -C ₄ alkyl group, especially methyl and / or ethyl);
R ² groups are unsubstituted or substituted and are the same or different from each other, and are C ₁ -C ₁₈ alkoxyl or C ₅ -C ₁₈ cycloalkoxyl groups (preferably C ₁ -C ₈ A group selected from alkoxyl and C ₅ -C ₈ cycloalkoxyl groups, more preferably a group selected from C ₁ -C ₄ alkoxyl groups, in particular methoxyl and ethoxyl))]. In the case of mixtures of polysulfide alkoxysilanes corresponding to the above formula (I), in particular in the case of ordinary commercially available mixtures, the average value of “x” is preferably between 2 and 5, more preferably 4 The value is close to. However, the invention can also be advantageously carried out with, for example, disulfide alkoxysilanes (x = 2).

Examples of polysulfide silanes that may be mentioned include, more particularly, polysulfides of bis (alkoxy (C ₁ -C ₄ ) alkyl (C ₁ -C ₄ ) silyl (C ₁ -C ₄ )) alkyl (especially disulfides, There are trisulfides or tetrasulfides, such as bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfide, among these compounds, in particular the formula [(C ₂ H ₅ O) ₃ Bi (3-triethoxysilylpropyl) tetrasulfide abbreviated as TESPT with Si (CH ₂ ) ₃ S ₂ ] ₂ or the formula [(C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ S] ₂ Bis (triethoxysilylpropyl) disulfide, abbreviated as TESPD, is used, and preferred examples include those described in the above-mentioned patent application WO 02/083782 (or US 7 217 751). Bis ((C ₁ -C ₄ ) monoalkoxy ( C ₁ -C ₄ ) dialkylsilylpropyl) polysulfides (especially disulfides, trisulfides or tetrasulfides), more preferably bis- (monoethoxydimethylsilylpropyl) tetrasulfide.

Coupling agents other than alkoxysilane polysulfides include, inter alia, WO 02/30939 pamphlet (or US Pat. No. 6,774,255) and WO 02/31041 pamphlet (or US patent application publication no. Bifunctional POS (polyorganosiloxane) or hydroxysilane polysulfide (in the above formula (I), R ² = OH) as described in US 2004/051210) or, for example, Examples include silanes or POSs carrying an azodicarbonyl functional group, as described in the 2006/125532 pamphlet, the WO 2006/125533 pamphlet and the WO 2006/125534 pamphlet.

In the rubber composition according to the present invention, the content of the coupling agent is preferably between 2 phr and 12 phr, more preferably between 3 phr and 8 phr.

A person skilled in the art would add a reinforcing filler having another property, in particular organic, to the surface where the reinforcing filler is coated with an inorganic layer such as silica, or on its surface with functional sites, in particular hydroxyl. And can be used as a filler equivalent to the reinforcing inorganic filler described in this section, provided that it requires the use of a coupling agent to form a bond between the filler and the elastomer. I want you to understand.

II-4. Silicon Carbide Microparticles The rubber composition of the present invention contains silicon carbide microparticles having a median particle size (weight average) between 10 μm and 300 μm with a content between 10 phr and 50 phr. Have

The silicon carbide microparticles in the specific rubber composition of the present invention protrude on the tread surface, and the microspike effect on ice not only in the temperature range lower than −5 ° C. but also in the temperature range between −5 ° C. and 0 ° C. Fulfill.

Microparticles are to be understood by definition and in general to mean micrometer-sized particles, ie, for microparticles, the average particle size and the median particle size (weight average) (both by weight Is between 1 μm and 1 mm.

If it is higher than the above-mentioned minimum value (1 μm), the target technical effect (that is, the generation of an appropriate micro-spike effect) will appear appropriately, while if it is lower than the above-mentioned maximum value (1 mm), it will be particularly rubber. Various benefits emerge when the composition is used as a tread: aesthetics are maintained and wrinkles (no obvious particles are present on the tread surface), and even relatively large tread pattern elements are adhesive during rotation. It has been found that it does not lose and does not impair grip performance on ice within a temperature range between -5 ° C and 0 ° C.

For all these reasons, it is more preferred that the microparticles have a median particle size (weight average) included in the range between 50 μm and 150 μm. This particularly preferred particle size range appears to correspond to an optimal compromise between the desired surface roughness on the one hand and good contact between the rubber composition and ice on the other hand.

Furthermore, for the same reason as above, the content of the microparticles is preferably between 10 phr and 30 phr, more preferably between 12 phr and 25 phr.

For analysis of particle size (or average particle size) and calculation of median particle size (weight average) of fine particles (or average diameter of fine particles assuming substantially spherical), for example, laser diffraction Various known methods according to can be applied (see for example standard ISO-8130-13 or standard JIS K5600-9-3).

Particle size analysis by mechanical sieving can also be used easily and preferably; the operation is to operate a defined amount of sample (eg 200 g) on a vibrating table with various sieve diameters (eg equal to 1.26) According to progressive ratio, consisting of 1000, 800, 630, 500, 400, ... 100, 80 and 63 μm mesh), consisting of sieving for 30 minutes; the excess size collected in each sieve is weighed with a precision balance; The percentage of excess size at each mesh diameter relative to the total weight is estimated from its weight; finally, the median particle size (weight average) (or median diameter) or average particle size (or average diameter) is known from the histogram of the particle size distribution Calculate by the method.

II-5. Various Additives The rubber composition of the present invention comprises, for example, a protective agent such as an antiozonation wax, a chemical antiozonant, an antioxidant; a reinforcing resin; a methylene acceptor (eg, a phenol novolac resin). ) Or methylene donors (eg HMT or H3M); sulfur or sulfur donors and / or peroxides and / or bismaleimide based crosslinking systems; such as vulcanization accelerators or vulcanization activators, Contains all or part of the usual additives commonly used in elastomeric compositions intended for the manufacture of treads for tires, in particular winter tires.

These rubber compositions can be used as coupling activators when using coupling agents, agents for coating inorganic fillers, or improved dispersibility of fillers in rubber compositions and viscosity of rubber compositions. May also contain more general processing aids that, as is known, can improve the processing properties of the composition in the raw state; these agents may contain hydrous acids such as, for example, alkylalkoxysilanes. Degradable silanes; polyols; polyethers; amines; or hydroxylated or hydrolyzable polyorganosiloxanes.

II-6. Manufacture of rubber composition and tread The rubber composition of the present invention is prepared in a suitable mixer in two successive production stages according to the general procedure well known to those skilled in the art, ie between 130 ° C and 200 ° C. A first stage (also referred to as a “non-production” stage), preferably thermomechanically processed or kneaded at high temperatures up to a maximum temperature of between 145 ° C. and 185 ° C., as well as typically below 120 ° C. Manufactured using a second stage (also referred to as a “production” stage) that is machined at a low temperature, for example, between 60 ° C. and 100 ° C., in which the crosslinking or vulcanization system is incorporated.

A process that can be used for the production of such a rubber composition, for example, preferably comprises the following steps:
-In a mixer, between 25 phr and 75 phr polybutadiene or butadiene copolymer and 25 phr and 75 phr natural rubber or synthetic polyisoprene for more than 40 phr liquid plasticizer, for reinforcement between 70 phr and 120 phr Filler, mixed with silicon carbide microparticles with a median particle size (weight average) between 10 μm and 300 μm with a content between 10 phr and 50 phr, all at least once between 130 ° C. and 200 ° C. Kneading thermomechanically until the maximum temperature is reached;
-Cooling the combined mixture to a temperature below 100 ° C;
-Subsequently incorporating a crosslinking system;
-Kneading everything to a maximum temperature below 120 ° C;
-The process of extruding or calendering the rubber composition so obtained, in particular in the form of a tire tread.

For example, the first (non-production) stage is carried out in a single thermomechanical stage during which all essential components, additional coatings or optional processing aids as optional components and various other systems except for the crosslinking system. Additives are introduced into a suitable mixer, such as a conventional closed mixer. After cooling the mixture so obtained in the first non-production stage, the crosslinking system is introduced at low temperature, typically in an open mixer, such as an open mill; For example, mix for 5-15 minutes (production stage).

Suitable crosslinking systems are preferably based on sulfur and primary vulcanization accelerators, especially sulfenamide type accelerators. To this vulcanization system, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (particularly diphenylguanidine), etc. are added, during the first non-production stage and / or It is mixed during the production stage. The sulfur content is preferably between 0.5 phr and 3.0 phr, and the primary accelerator content is between 0.5 phr and 5.0 phr.

Accelerator (primary or secondary) can be any compound that can act as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole type and its derivatives, thiuram type accelerators, or dithiocarbamines. Zinc acid can be used. These accelerators are more preferably 2-mercaptobenzothiazyl disulfide (abbreviated “MBTS”), N-cyclohexyl-2-benzothiazole sulfenamide (abbreviated “CBS”), N, N— Dicyclohexyl-2-benzothiazole sulfenamide (“DCBS”), N-tert-butyl-2-benzothiazole sulfenamide (“TBBS”), N-tert-butyl-2-benzothiazole sulfenimide (“TBSI”) "), Zinc dibenzyldithiocarbamate (" ZBEC "), tetrabenzylthiuram disulfide (" TBZTD) "and mixtures of these compounds.

The final rubber composition thus obtained is then calendered, for example in the form of sheets or plaques, in particular for laboratory characterization, or used directly, for example as a winter tire tread. Extrude into the shape of the resulting rubber-shaped element.

Vulcanization (ie curing) is a known method, generally at temperatures between 130 ° C and 200 ° C, especially depending on the curing temperature, the vulcanization system used and the vulcanization rate of the composition under consideration. For example, it is carried out for a sufficient time that can vary between 5 and 90 minutes.

The rubber composition according to the present invention may constitute all or only a part of the tread according to the present invention in the case of a composite-type tread formed from several rubber compositions having various formulations.

The present invention relates to the rubber composition and tread described above both in the raw state (ie, before curing) and in the cured state (ie, after crosslinking or vulcanization). The rubber composition according to the invention can be used in the production of tires, in particular treads for winter tires. A well-known usage method can be used as a manufacturing method of a tread. The present invention further relates to a winter tire comprising the rubber composition according to the present invention, and a tread for a winter tire. Here, the winter tire is also called a winter tire or a studless tire, and means a tire having improved tire performance on snow and ice in winter.

When specific fine particles are added to the rubber composition according to the present invention, the temperature of the tire containing the rubber composition as a tread is not only lower than −5 ° C. but also within the temperature range between −5 ° C. and 0 ° C. It is possible to improve the grip performance in

III. Examples of the Invention Unless otherwise specified, the measurement methods and test methods for the properties of the rubber composition shown in Table 2 are the same as those described in the above-mentioned “I. Measurement and Test Methods to be Used”.
III-1. Production of Rubber Composition and Tread The following test was carried out by the following method. That is, a reinforcing filler (in this example, the reinforcing inorganic silica, its associated coupling agent, and a small amount of carbon black), a liquid plasticizer, magnesium sulfate microparticles, a diene elastomer (or a blend of diene elastomers). ) And various other components except the vulcanization system (Table 1) were continuously charged into a closed mixer having an initial vessel temperature of about 60 ° C. The mixer was thus filled approximately 70% (volume%). The thermomechanical processing (non-production stage) was then performed in one step by heating the mixer for a total of about 3-4 minutes until a maximum “fall” temperature of 165 ° C. was reached. The mixture so obtained is recovered and cooled, after which sulfur and sulfenamide type accelerators are mixed in an open mixer (homo finisher) at 30 ° C. and all are allowed to run for an appropriate time (e.g. 5 Mixed (production stage) for ~ 12 minutes.

The rubber composition thus obtained is then calendered into rubber plaque (2-3 mm thick) or thin sheet form for the measurement of its physical or mechanical properties, or in the winter of passenger cars Extruded into a tire tread shape.

III-2. Rubber Test In this test, two rubber compositions based on a diene elastomer (a blend of NR and BR with a cis-1,4 bond content (mol%) greater than 95%). (Denoted as C-1 and C-2) were compared. These rubber compositions are reinforced with a blend of silica and carbon black, with or without a silicon carbide microparticle fraction (15 phr).

Tables 1 and 2 below show the properties of these rubber compositions before and after the blending of the above two rubber compositions (Table 1: Content of various components expressed in phr) and curing (at 150 ° C for 30 minutes). ing. The vulcanization system consists of sulfur and sulfenamide.

First of all, to verify the various results in Table 2, there is no significant deterioration in the rubber properties of the rubber composition (C-2) of the present invention despite the presence of high content silicon carbide microparticles. This already constitutes unexpected results for those skilled in the art:
-Raw formability (Mooney plasticity) is almost equal;
-The rheometry (curing) properties have not changed substantially and the scorch time (T5) has increased by 1 minute;
The modulus in Shore A hardness and elongation remains constant after curing, which is favorable for the mechanical behavior of the tread and thus the tire performance;
-The drop in fracture stress is very slight;

III-3. Friction test A test was conducted to compare the following rubber composition C-1 and rubber composition C-2. :
-Rubber composition C-1: Control rubber composition (without silicon carbide fine particles)
-Rubber composition C-2: rubber composition according to the invention, comprising 15 phr of silicon carbide microparticles (median particle size (weight average) of approximately 100 μm);

The above median particle size (weight average) was all measured by mechanical sieving as shown in Section II-4 above. Therefore, only the rubber composition C-2 containing silicon carbide fine particles was in accordance with the present invention.

These two rubber compositions were subjected to a laboratory test consisting of measuring the friction coefficient of these rubber compositions on ice. The principle is based on a block of a rubber composition that slides on an ice path at an applied load (3 kg / cm ^{2 in the} example) at a predetermined speed of 5 km / h. Measure the force (Fx) generated in the moving direction of the block and the force (Fz) generated perpendicular to the moving direction. The Fx / Fz ratio determines the coefficient of friction of the test specimen on ice. The temperature during measurement is set to -2 ° C and -10 ° C. The surface of the rubber composition according to the present invention, which is in contact with ice before the friction test, was cut to a thickness of about 0.5 mm in order to expose the silicon carbide microparticles on the surface.

This test, i.e. a principle well known to those skilled in the art (see, for example, EP 1-052 270A1 and EP 1505-112A1), is the same as the tread described above. Typical grip performance on ice in temperatures below -5 ° C and in the temperature range between -5 ° C and 0 ° C that would be obtained after running tests in vehicles fitted with tires of each rubber composition Allows evaluation under conditions.

The results are shown in Table 3 below. A value higher than the value of the control (rubber composition C-1) arbitrarily set to 100 indicates an improved result, ie a shorter braking distance capability. In Table 3, the rubber composition C-2 according to the invention has a very clear increase (17%) in the coefficient of friction on ice at -2 ° C. relative to the control rubber composition C-1. It is observed.

Also, in Table 3, rubber composition C-2 according to the present invention has a clear increase (5%) in coefficient of friction on ice at -10 ° C. relative to control rubber composition C-1. Observed.

In conclusion, the rubber composition according to the present invention containing silicon carbide microparticles is significantly improved on the above tread not only on the temperature condition below -5 ° C but also in the temperature range between -5 ° C and 0 ° C. Has given the grip performance.

(1) 0.3% 1,2-; 2.7% trans, 97% BR containing cis-1,4- (Tg = -104 ° C);
(2) Natural rubber (decoagulated product);
(3) Silica “Zeosil 1165MP“ HDS ”type (BET: 165 m / s ² , CTAB: 160 m / s ² )” from Rhodia;
(4) Coupling agent TESPT (“Si69” from Degussa);
(5) “SICF 900” (Akzo Nobel; median particle size (weight average): about 100 μm);
(6) ASTM class N234 (Cabot);
(7) MES oil (“Catenex SNR” from Shell);
(8) Escorez 2173 resin from Exxon Mobile;
(9) Diphenylguanidine (Perkacit DPG from Flexsys);
(10) N- (1,3-dimethylbutyl) -N-phenyl-para-phenylenediamine (“Santoflex 6-PPD” from Flexsys);
(11) N-dicyclohexyl-2-benzothiazole sulfenamide (“Santocure CBS” from Flexsys).

Claims

A rubber composition comprising:
-Polybutadiene or butadiene copolymer between 25 phr and 75 phr;
-Natural rubber or synthetic polyisoprene between 25 phr and 75 phr;
-More than 40phr liquid plasticizer;
-Reinforcing filler between 70 phr and 120 phr;
-Silicon carbide microparticles with a median particle size (weight average) between 10 and 300 μm with a content between 10 and 50 phr;
A rubber composition comprising at least
The rubber composition of claim 1, wherein the silicon carbide microparticles have a median particle size (weight average) between 50 μm and 150 μm.
The rubber composition according to claim 1 or 2, wherein the content of the silicon carbide fine particles is between 10 phr and 30 phr.
4. The rubber composition according to claim 1, wherein the polybutadiene has a cis-1,4 bond content of more than 90%.
5. A rubber composition according to claim 4, comprising more than 50 phr of said natural rubber or said synthetic polyisoprene.
The rubber composition of claim 4 comprising more than 50 phr of said polybutadiene having a cis-1,4 bond content greater than 90%.
The rubber composition according to any one of claims 1 to 6, wherein the reinforcing filler is selected from an inorganic filler, carbon black, and a mixture of an inorganic filler and carbon black.
The rubber composition according to claim 7, wherein the inorganic filler is silica.
The rubber composition according to any one of claims 1 to 8, wherein a content of the reinforcing filler is between 75 phr and 115 phr.
The rubber composition according to claim 9, wherein the reinforcing filler content is between 80 phr and 110 phr.
The liquid plasticizer is polyolefin oil, naphthene oil, paraffin oil, DAE oil, MES oil, TDAE oil, RAE oil, TRAE oil, SRAE oil, mineral oil, vegetable oil, ether plasticizer, ester plasticizer The rubber composition according to any one of claims 1 to 10, which is selected from the group consisting of a phosphate plasticizer, a sulfonate plasticizer, and a mixture of these compounds.
The rubber composition according to claim 11, wherein the content of the liquid plasticizer is more than 50 phr.
The rubber composition according to claim 12, wherein the content of the liquid plasticizer is between 50 phr and 100 phr.
The rubber composition according to any one of claims 1 to 13, wherein the rubber composition further comprises a hydrocarbon resin having a Tg higher than 20 ° C as a solid plasticizer.
The hydrocarbon resin is a homopolymer or copolymer resins of cyclopentadiene, homopolymer or copolymer resins of dicyclopentadiene, terpene homopolymer or copolymer resins, C 5 fraction homopolymer or copolymer resins, C 9 fraction homopolymer 15. A rubber composition according to claim 14, selected from the group consisting of polymer or copolymer resins and mixtures of these resins.
The rubber composition according to claim 14 or 15, wherein the content of the hydrocarbon resin is between 3 phr and 60 phr.
The rubber composition according to any one of claims 1 to 16, wherein the content of the whole plasticizer is between 50 phr and 100 phr.
The rubber composition according to claim 17, wherein the content of the whole plasticizer is between 60 phr and 80 phr.
The rubber composition according to claim 17 or 18, wherein a ratio of the content of the liquid plasticizer to the content of the hydrocarbon resin is between 3 and 5.
The rubber composition according to claim 19, wherein a ratio of the content of the liquid plasticizer to the content of the hydrocarbon resin is between 3.5 and 4.5.
Use of the rubber composition according to any one of claims 1 to 20 for the production of a tread for a winter tire.
A tread for a winter tire comprising the rubber composition according to any one of claims 1 to 20.
23. A winter tire comprising the tread according to claim 22.