JP2013514398A - Winter tires with improved grip on ice - Google Patents

Abstract

  Winter tires with improved grip on melting ice have treads with at least one diene elastomer such as natural rubber and / or polybutadiene, more than 30 phr liquid plasticizer, between 50 and 150 phr silica and / or Or a reinforcing filler such as carbon black, composition comprising between 35 and 50 phr of hollow fine particles of at least one metal oxide such as aluminosilicate having a median size based on a mass between 2 and 500 μm Including things.

Description

1. FIELD OF THE INVENTION The present invention relates to vehicle tires, particularly “winter” tires (also known as studless tires) that can run on ice or black ice-covered ground surfaces without studs. It is related with the rubber composition used as a tread of (known).
More particularly, the present invention relates to a winter tire tread that is particularly suitable for running under “melting ice” conditions that typically occur within a temperature range between −5 ° C. and 0 ° C. Within this range, it is clearly noted that the tire pressure during vehicle travel causes ice surface melting and the ice is covered with a thin film of water that is detrimental to the grip of these tires. Should.

2. State of the art Tire manufacturers build up their tire treads in order to avoid the harmful effects of studs, in particular their strong wear action on the surface material itself of the ground surface, and considerably poorer road behavior on dry ground surfaces. Various solutions are provided which consist of changing the formulation of the rubber composition.
As an example, first of all, hard solid particles such as silicon carbide (see, for example, US Pat. No. 3,878,147) (some of these appear on the surface of the tread as the tread is worn away, so they come into contact with ice) ) Was proposed. Such particles can actually act as micro-studs on hard ice, thanks to the well-known “claw” effect, but are still relatively aggressive with respect to the ground surface. They are not perfectly suitable for running conditions on melted ice.
For this reason, other solutions have been proposed which consist in particular of incorporating water-soluble powders (ie powders that can be dissolved in water) into the composition that makes up the tread. Such powder dissolves more or less in contact with snow or melted ice, so that on the one hand it can create pores on the tire tread surface that can improve the grip of the tread to the ground surface. It is possible to create a groove that acts as a channel for removing the film of liquid that forms between the tire and the ground surface. Examples of water-soluble powders include, for example, cellulose powder, PVA (polyvinyl alcohol) powder or starch powder, or guar gum powder or xanthan gum powder (for example, patent applications JP-3-159803, JP2002-211203, EP940435, WO2008 / 080750 and WO 2008/080751).
In all these examples, the solubility of the powder used at a very low temperature and in a very short time is an essential factor for the satisfactory functioning of the tread. If the powder does not melt under the conditions of use of the tire, the above functions (generation of micropores and channels for watering) are not performed and the grip is not improved. Another disadvantage known for these solutions is that they are very disadvantageous for the reinforcement of the rubber composition (and therefore for its wear resistance) or for its hysteresis (and therefore its rolling resistance). That's what it means.

3. Brief Description of the Invention Continuing their research, Applicants are able to generate and enhance effective surface micro-roughness thanks to special microparticles. Also, a rubber composition has been found that makes it possible to greatly improve the grip on ice of treads and tires containing them under ice melting conditions without adversely affecting the properties of hysteresis.
Consequently, the present invention provides a tire whose tread includes a rubber composition comprising at least a diene elastomer, a liquid plasticizer of greater than 30 phr, and a reinforcing filler of between 50 and 150 phr, the composition comprising from 2 to The tire further comprises 35-50 phr hollow particles of at least one metal oxide having a median size with a mass between 500 μm.

First of all, these hollow microparticles project from the surface of the tread and perform the function of the claws without the inconvenience of being very wearable with respect to asphalts used as road surfaces. Then, as a result, after being crushed by breaking their hollow structure and being gradually expelled from the rubber matrix, the microparticles act as a holding volume and channel as a film of water on the ice surface. Micropores are generated. Under these conditions, the contact between the tread surface and the ice is no longer lubricated, which improves the coefficient of friction.
The tires of the present invention can be used in passenger cars, motorcycles (especially motorcycles) including 4 × 4 (four-wheel drive) vehicles and SUV (multi-purpose sports vehicles) vehicles, as well as small trucks and large vehicles (ie subways, buses or large vehicles). It is particularly intended to be mounted on industrial vehicles that are specifically selected from road transport vehicles, such as heavy trucks or tow trucks.
The present invention and its advantages will be readily understood in view of the following description and exemplary embodiments.

4). Measurements and Tests Used Treads and the rubber compositions that make up these treads are characterized before and after curing, as shown below.

4.1-Mooney plasticity A vibration consistency meter described in French standard NF T 43-005 (November 1980) is used. Mooney plasticity measurements are made according to the following principle: The raw composition (ie, before curing) is shaped to the shape of a cylindrical chamber heated to 100 ° C. After preheating for 1 minute, the rotor rotates at 2 revolutions / minute in the test sample and the workload torque to maintain this movement is measured after 4 minutes of rotation. Mooney plasticity (ML 1 + 4) is expressed in “Mooney units” (MU, 1MU = 0.83 Newton.meters).
4.2 Scorch time The measurement is carried out at 130 ° C. according to the French standard NF T 43-005. The change in the consistent index as a function of time is evaluated according to the standard by the parameter T5 (in the case of large rotors), expressed in minutes, and indexed by the consistency meter (expressed in MU). Makes it possible to determine the scorch time of the rubber composition, defined as the time required to increase 5 units from the lowest value measured for this index.
4.3 3-Rheometry Measurements are made with a vibrating disc rheometer at 150 ° C. according to the standard DIN 53529-part-3 (June 1983). The change in torque by the rheometer as a function of time represents a change in the composition that hardens as a result of the vulcanization reaction. The measured values are processed according to the standard DIN 53529-part-2 (March 1983). Ti is the induction time, ie, the time required for the vulcanization reaction to start, and T _α (eg, T ₉₀ ) is the conversion of α%, ie, the α% of the difference between the minimum and maximum torque (eg, , 90%).
4.4-Tensile tests These tensile tests make it possible to determine the elastic stress and the properties at break. Unless otherwise stated, they are performed in accordance with the French standard NF T 46-002 of September 1988. Nominal secant modulus (or apparent stress, MPa) is 10% in elongation at the second time (ie, after an accommodation cycle to the expected degree of elongation in the measurement itself). Elongation (represented as M10), 100% elongation (represented as M100), and 300% elongation (represented as M300). The breaking stress (MPa) and breaking elongation (%) 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).
4.5-Shore A Hardness The Shore A hardness of the cured composition is evaluated according to standard ASTM D 2240-86.
4.6-Dynamic Properties Dynamic properties are measured with a viscosity evaluation apparatus (Metraviv VA4000) according to standard ASTM D 5992-96. The response of a vulcanized composition sample (cylindrical test sample having a thickness of 4 mm and a cross-sectional area of 400 mm ² ) subjected to a simple alternating sine shear stress at a frequency of 10 Hz at a temperature of 0 ° C. is recorded. A strain amplitude sweep from 0.1% to 50% (overall cycle) and then from 50% to 1% (return cycle) is performed. The result used is the loss factor tan (δ); the maximum value of tan (δ) observed between values at 0.15% and 50% strain (denoted tan (δ) _max ) (Payne effect) is shown for the return cycle.

5. Detailed Description of the Invention In this description, unless otherwise indicated, all percentages (%) shown are weight percent. The abbreviation “phr” means parts by weight per 100 parts of elastomer (total of these elastomers, if any are present).
Furthermore, any value interval represented by the expression “between a and b” represents a range of values greater than “a” and less than “b” (ie, endpoints a and b are excluded). , Any value interval represented by the expression “a-b” means a range of values ranging from “a” to “b” (ie, including limit points a and b).
The rubber composition of the tread according to the present invention, at least in the tread portion (as a result of which a pattern is formed) that is intended to contact the road during the rotation of the tire, as described above, Based at least on diene elastomers, plasticizing systems, reinforcing fillers, and special hollow particulates, these components are described in detail below.

5.1-Diene Elastomers “Diene” type elastomers (or rubbers, the two terms are synonymous) are at least partially diene monomers (two carbons that may or may not be conjugated). It should be noted that it should be understood to mean an elastomer (ie a homopolymer or copolymer) obtained from a monomer having a carbon double bond).

Diene elastomers can be classified by known methods in two categories: “essentially unsaturated” and “essentially saturated”. Butyl rubber, for example EPDM-based diene and α-olefin copolymers, is included in the class of intrinsically saturated diene elastomers and is low or very low and always has a diene derived unit content of less than 15% (mol%). Have In contrast, an essentially unsaturated diene elastomer is understood to mean a diene elastomer obtained at least in part from a conjugated diene monomer and having a diene (conjugated diene) derived unit content greater than 15% (mol%). Has been. In the category of “essentially unsaturated” diene elastomers, “highly unsaturated” diene elastomers are understood to mean in particular diene elastomers having a diene (conjugated diene) derived unit content of more than 50%.
Selected from the group consisting of at least one highly unsaturated diene elastomer, in particular natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), butadiene copolymer, isoprene copolymer, and mixtures of these elastomers. It is preferable to use a diene elastomer. The above copolymers are more preferably butadiene / styrene copolymers (SBR), isoprene / butadiene copolymers (BIR), isoprene / styrene copolymers (SIR), isoprene / butadiene / styrene copolymers (SBIR), and mixtures of such copolymers. Selected from the group consisting of

The elastomer may be, for example, a block, random, sequential or microsequential elastomer and may be prepared in a dispersion or solution. They may be linked and / or star-branched, or alternatively functionalized with coupling agents and / or star-branching agents, or functionalizing agents. Coupling with carbon black can include, for example, functional groups containing C—Sn bonds, or aminated functional groups such as benzophenone; cups with reinforcing inorganic fillers such as silica. In the ring, for example, a silanol functional group or a polysiloxane functional group having a silanol terminal (for example, as described in US6013718), an alkoxysilane group (for example, as described in US5977238), a carboxyl group (for example, No. 6,815,473 or US 2006/0089445), or polyether groups (eg as described in US Pat. No. 6,503,973). Another example of such a functionalized elastomer may also include an epoxidized type of elastomer (eg, SBR, BR, NR or IR).
The following are preferably suitable: polybutadiene, in particular polybutadiene having a 1,2-unit content of between 4% and 80%, or polybutadiene having a cis-1,4-unit content of more than 80%; Polyisoprene; butadiene / styrene copolymers, in particular between 5% and 50% by weight, more particularly between 20% and 40% styrene content, between 4% and 65% butadiene part, 1,2 bonds Butadiene / styrene copolymer having a content and a trans-1,4-bond content between 20% and 80%; a butadiene / isoprene copolymer, in particular between 5% and 90% by weight, and Butadiene having a glass transition temperature (measured according to “Tg” —ASTM D 3418-82) of −40 ° C. to −80 ° C. Isoprene copolymers; or isoprene / styrene copolymers, in particular a styrene content of between 5% and 50 wt%, and isoprene / styrene copolymer having a Tg of between -50 ° C. from -25 ° C..

  In the case of butadiene / styrene / isoprene copolymers, the styrene content is between 5% and 50% by weight, more particularly between 10% and 40%, more particularly between 15% and 60%, more particularly between 20% and 50%. % Isoprene content, 5% to 50% by weight, more particularly 20% to 40% butadiene content, 4% to 85% 1,2-unit content of butadiene moiety, The trans-1,4-unit content of the butadiene portion between 6% and 80%, the combined content of 1,2- and 3,4-units of isoprene portion between 5% and 70%, and 10 Butadiene / styrene / isoprene copolymers having a trans-1,4-unit content of between 15% and 50% isoprene moieties, more commonly T between −20 ° C. and −70 ° C. Any butadiene / styrene / isoprene copolymers having are particularly suitable.

According to a particularly preferred embodiment of the present invention, the diene elastomer is from natural rubber, synthetic polyisoprene, polybutadiene having a cis-1,4 bond content greater than 90%, butadiene / styrene copolymers, and mixtures of these elastomers. Selected from the group consisting of
According to a more specific and preferred embodiment, the rubber composition comprises 50 to 100 phr natural rubber or synthetic polyisoprene, which natural rubber or synthetic polyisoprene in particular contains more than 90% of cis-1,4 bonds. A quantity of polybutadiene having a quantity can be used as a blend with at most 50 phr.
According to another special and preferred embodiment, the rubber composition comprises 50-100 phr of polybutadiene having a cis-1,4 bond content of more than 90%, which polybutadiene is in particular of natural rubber or synthetic polyisoprene. It can be used as a blend with at most 50 phr.
Synthetic elastomers other than diene elastomers, and more particularly polymers other than elastomers, such as even thermoplastic polymers, can be mixed in small amounts with the diene elastomers of the tread according to the invention.

5.2-Plasticization system The rubber composition of the present invention has, as another essential feature, the characteristic of containing at least 30 phr of a plasticizer that is liquid (at 20 ° C.), the role of which is elastomer and To soften the matrix by diluting the reinforcing filler; by definition, the Tg of the matrix is less than −20 ° C., preferably less than −40 ° C.
Any extending oil, whether aromatic or non-aromatic, can be used with any liquid plasticizer known for its plasticizing properties with respect to diene elastomers. At ambient temperature (20 ° C.), these plasticizers or these oils are more or less viscous and liquid (ie, in contrast to plasticizing hydrocarbon resins that are inherently solid at ambient temperature, in particular. , To be sure, substances that can someday be in the shape of their containers).
Naphthenic oil (low or high viscosity, especially hydrogenated or not), paraffin oil, MES (medium extracted sorbate) oil, TDAE oil (treated, aromatic extraction from distillate) Liquid plasticizers selected from the group consisting of mineral oil, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers, and mixtures of these compounds are particularly suitable. .

As phosphate plasticizers, mention may be made, for example, of those containing between 12 and 30 carbon atoms, for example trioctyl phosphate. Examples of ester plasticizers include trimellitic acid ester, pyromellitic acid ester, phthalic acid ester, 1,2-cyclohexanedicarboxylic acid ester, adipic acid ester, azelaic acid ester, sebacic acid ester, glycerol triester, and Mention may be made of compounds selected from the group consisting of mixtures of these compounds. Among the above triesters, preferably mainly from unsaturated C ₁₈ fatty acids, ie unsaturated fatty acids selected from the group consisting of oleic acid, linoleic acid, linolenic acid, and mixtures of these acids. A glycerol triester can be mentioned which is more than wt%, more preferably more than 80 wt%. More preferably, the fatty acid used, whether synthetic or natural (eg in the case of sunflower or rapeseed vegetable oil), comprises more than 50% by weight, more preferably more than 80% by weight of oleic acid. Such triesters containing high amounts of oleic acid (trioleates) are well known; for example, they are described in publication WO 02/088238 as plasticizers in tire treads.

The content of the liquid plasticizer in the composition of the present invention is preferably more than 40 phr, more preferably in the range of 50 to 100 phr.
According to another preferred embodiment, the composition according to the invention is also a solid (at 20 ° C.) plasticizer, as described, for example, in publications WO 2005/087859, WO 2006/061064 and WO 2007/017060. , Hydrocarbon resins exhibiting a Tg above + 20 ° C, preferably above + 30 ° C.

Hydrocarbon resins are well known to those skilled in the art that are inherently miscible with diene elastomer compositions because they are essentially based on carbon and hydrogen if they are additionally indicated as “plasticize”. Polymer. They are described, for example, in R.I. Mildenberg, M.M. Zander and G. It is described in the work titled “Hydrocarbon Resins” by Collin (New York, VCH, 1997, ISBN 3-527-28617-9), whose chapter 5 is devoted to their use especially in the field of tire rubber. (5.5. “Rubber Tires and Mechanical Goods”). They can be aliphatic or aromatic, or can also be aliphatic / aromatic (ie, based on aliphatic and / or aromatic monomers). They can be natural or synthetic, and may or may not be petroleum-based (in the case of petroleum-based, also known by the name of petroleum resin). They are preferably limited to hydrocarbons only, ie they contain only carbon and hydrogen atoms.
Preferably, the plasticizing hydrocarbon resin exhibits at least one of the following properties, more preferably all.
-Tg above 20 ° C (more preferably between 40 and 100 ° C);
-Number average molecular weight (Mn) between 400 and 2000 g / mol (more preferably between 500 and 1500 g / mol);
A polydispersity index (PI) of less than 3, more preferably less than 2 (note: PI = Mw / Mn, Mw is the weight average molecular weight).

Tg is measured as known by DSC (Differential Scanning Calorimetry) according to the standard ASTM D3418 (1999). The macro structure (Mw, Mn and PI) of the hydrocarbon resin is steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35 ° C .; concentration 1 g / l; flow rate 1 ml / min; Filtered through a 45 μm pore filter; Moore calibration with polystyrene standards; set of three “Waters” columns in series (“Styragel” HR4E, HR1 and HR0.5); differential refractometer (“Warers 2410”) Detected by its operating software ("Waters Empower").
According to a particularly preferred embodiment, the plasticizing hydrocarbon resin is a cyclopentadiene (abbreviated CPD) homopolymer or copolymer resin, a dicyclopentadiene (abbreviated DCPD) homopolymer or copolymer resin, a terpene homopolymer or copolymer resins, C ₅ fraction homopolymer or copolymer resins, C ₉ fraction homopolymer or copolymer resins, and is selected from the group consisting of mixtures of these resins. Among the above copolymer resins, more preferably, (D) CPD / vinyl aromatic copolymer resin, (D) CPD / terpene copolymer resin, (D) CPD / C ₅ cut copolymer resin, (D) CPD / C ₉ fraction copolymer resin, terpene / vinyl aromatic copolymer resin, terpene / phenol aromatic copolymer resin, C ₅ fraction / vinyl aromatic copolymer resin, C ₉ fraction / vinyl aromatic copolymer resin, and mixtures of these resins Those selected from the group are used.

The term “terpene” here combines α-pinene, β-pinene and limonene monomers together, as is known; preferably limonene monomers are used, this compound being known As shown, it exists in the racemic state of three possible isomers (L-limonene (a levorotatory enantiomer), D-limonene (a dextrorotatory enantiomer), otherwise dipentene), a dextrorotatory and a levorotatory enantiomer. To do. Examples of the vinyl aromatic monomer include styrene, α-methylstyrene, ortho-, meta- or para-methylstyrene, vinyltoluene, para- (tert-butyl) styrene, methoxystyrene, chlorostyrene, hydroxystyrene, and vinylmesitylene. Any vinyl aromatic monomer obtained from, divinylbenzene, vinyl naphthalene, or C ₉ fraction (or more generally C ₈ -C ₁₀ fraction) is suitable. Preferably, the vinyl aromatic compounds are styrene, or C ₉ fraction (or, more generally, C ₈ -C ₁₀ fraction) is a vinyl aromatic monomer derived from. Preferably, the vinyl aromatic compound is a minor monomer when expressed in mole fraction in the contemplated copolymer.
The content of the hydrocarbon resin is preferably between 3 and 60 phr, more preferably between 3 and 40 phr, in particular between 5 and 30 phr.
The content of all plasticizers (ie, the combination of liquid plasticizer and solid hydrocarbon resin, if appropriate) is preferably between 40 and 100 phr, more preferably 50-80 phr. Included in range.

5.3-Fillers Any type of reinforcing fillers known for their ability to reinforce rubber compositions that can be used in the manufacture of tires include, for example, organic fillers (eg, carbon black), or reinforcing inorganic fillers ( For example, silica) can also be used, with which coupling agents are combined as is known.
Such reinforcing fillers usually consist of nanoparticles and their average size (by mass) is less than 500 nm, generally between 20 and 200 nm, in particular preferably between 20 and 150 nm. .
All carbon blacks are suitable as carbon blacks, in particular those normally used in tires or tire treads (“tire-grade” black). Among the latter, more particularly, mention may be made of 100, 200 or 300 series (ASTM grade) reinforcing carbon blacks, for example N115, N134, N234, N326, N330, N339, N347 or N375 black. Carbon black may already be incorporated into isoprene elastomers, for example in the form of a masterbatch (see, for example, publications WO 97/36724 or WO 99/16600).
Examples of organic fillers other than carbon black include functionalized polyvinyl organic fillers described in publications WO2006 / 069792, WO2006 / 069793, WO2008 / 003434, and WO2008 / 003435.

  The term “reinforcing inorganic filler” here refers to “white” filler, “transparent” filler or even “non-black”, in contrast to carbon black, whatever its color and its origin (natural or synthetic) Also known as a filler, it can reinforce a rubber composition that is directed to the manufacture of a tire by itself, without means other than an intermediary coupling agent, in other words, in its reinforcing role Should be understood to mean any inorganic or mineral filler that can replace normal tire grade carbon black; such fillers, as is known, have hydroxyl ( Generally characterized by the presence of a —OH) group.

Particularly suitable as reinforcing inorganic fillers are siliceous, in particular silica (SiO ₂ ), or alumina-based, in particular alumina (Al ₂ O ₃ ) mineral fillers. Silica used may be any reinforcing silica known to the person skilled in the art, in particular, less than 450 m ² / g, BET surface area and CTAB ratio of preferably between 30 to 400 m ² / g, especially 60 to 300 meters ² / g It can be any precipitated or thermally generated silica that exhibits both surface areas. Highly dispersible precipitated silicas (“HDS”) include, for example, “Ultrasil” 7000 and “Ultrasil” 7005 silica by Degussa, “Zeosil” 1165MP, 1135MP and 1115MP silica by Rhodia, “Hi-Sil” EZ150G silica by Huber, Huber "Zeopol" 8715, 8745 and 8755 silicas may be mentioned. Examples of alumina for strengthening include “Baikalox A125” or “Baikalox CR125” alumina by Baikowski, “APA-100RDX” alumina by Condea, “Aluminoxid C” alumina by Degussa, or “AKP” by Sumitomo Chemical “01” by 5AK-G alumina. Can do.
Preferably, the content of the total reinforcing filler (carbon black and / or reinforcing inorganic filler) is between 60 and 120 phr, in particular between 70 and 100 phr.
According to certain embodiments, the filler comprises silica, carbon black, or a mixture of carbon black and silica.
According to another particular embodiment, the reinforcing filler mainly comprises carbon black; in such cases, the carbon black is combined with a reinforcing inorganic filler, for example a small amount of silica, or Without reinforcing inorganic filler, it is preferably present in a content exceeding 60 phr.
According to another particular embodiment, the reinforcing filler mainly comprises an inorganic filler, in particular silica. In such cases, the inorganic filler, especially silica, is present in a content preferably exceeding 70 phr, in combination with or without a small amount of carbon black. Carbon black, if present, is preferably used at a content of less than 20 phr, more preferably less than 10 phr (eg between 0.1 and 10 phr).

Independent of the first aspect of the present invention, i.e., the study of the most effective grip on melted ice, the use of reinforcing inorganic fillers, e.g., silica, mainly for wet or snowy ground surfaces There is also an advantage in terms of grip.
According to another possible embodiment of the invention, the reinforcing filler comprises a similar amount of blend of carbon black and a reinforcing inorganic filler such as silica. In such cases, the content of inorganic fillers, especially silica, and carbon black is preferably between 25 and 75 phr, respectively, and more particularly between 30 and 50 phr, respectively.
In order to bind the reinforcing inorganic filler to the diene elastomer, as is well known, it provides a sufficient bond of chemical and / or physical properties between the inorganic filler (the surface of the particle) and the diene elastomer. Intentionally, at least one bifunctional coupling agent (or bonding agent) is used. In particular, bifunctional organosilanes or polyorganosiloxanes are used.
In particular, as described in publications WO 03/002648 (or US 2005/016651) and WO 03/002649 (or US 2005/016650), they are referred to as “symmetric” or “asymmetric” depending on their particular structure. Silane polysulfide is used.

“Symmetric” silane polysulfides corresponding to the following general formula (I):
(I) ZA- _Sx -AZ
{Where,
-X is an integer of 2-8 (preferably 2-5),
- A is a divalent hydrocarbon group (preferably, C ₁ -C ₁₈ alkylene group, or a C ₆ -C ₁₂ arylene group, more especially, C ₁ -C _10, in particular, C ₁ -C ₄ alkylene , In particular propylene),
Z is the following formula:

［式中、
− Ｒ¹基は、無置換であるか若しくは置換されており、互いに同じであるか若しくは異なり、Ｃ₁−Ｃ₁₈アルキル、Ｃ₅−Ｃ₁₈シクロアルキル若しくはＣ₆−Ｃ₁₈アリール基（好ましくは、Ｃ₁−Ｃ₆アルキル、シクロヘキシル若しくはフェニル基、特に、Ｃ₁−Ｃ₄アルキル基、より特別には、メチル及び／又はエチル）を表し、
− Ｒ²基は、無置換であるか若しくは置換されており、互いに同じであるか若しくは異なり、Ｃ₁−Ｃ₁₈アルコキシ若しくはＣ₅−Ｃ₁₈シクロアルコキシ基（好ましくは、Ｃ₁−Ｃ₈アルコキシ及びＣ₅−Ｃ₈シクロアルコキシから選択される基、より一層好ましくは、Ｃ₁−Ｃ₄アルコキシから選択される基、特にメトキシ及びエトキシ）を表す］
の１つに相当する｝
が適切であるが、上の定義は、限定ではない。
より詳細には、シランポリスルフィドの例として、ビス（３−トリメトキシシリルプロピル）若しくはビス（３−トリエトキシシリルプロピル）ポリスルフィドが挙げられ得る。これらの化合物の中で、特に、ビス（３−トリエトキシシリルプロピル）テトラスルフィド（ＴＥＳＰＴと省略される）、又はビス（トリエトキシシリルプロピル）ジスルフィド（ＴＥＳＰＤと省略される）が用いられる。また、好ましい例として、特許公報ＷＯ０２／０８３７８２（又はＵＳ２００４／１３２８８０）に記載されている、ビス（モノ（Ｃ₁−Ｃ₄）アルコキシルジ（Ｃ₁−Ｃ₄）アルキルシリルプロピル）ポリスルフィド（特に、ジスルフィド、トリスルフィド若しくはテトラスルフィド）、より詳細には、ビス（モノエトキシジメチルシリルプロピル）テトラスルフィドが挙げられ得る。

[Where:
-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 aryl groups (preferably C ₁ -C ₆ alkyl, cyclohexyl or phenyl group, in particular C ₁ -C ₄ alkyl group, more particularly methyl and / or ethyl),
The R ² groups are unsubstituted or substituted and are the same or different from each other and are C ₁ -C ₁₈ alkoxy or C ₅ -C ₁₈ cycloalkoxy groups (preferably C ₁ -C ₈ alkoxy And a group selected from C ₅ -C ₈ cycloalkoxy, more preferably a group selected from C ₁ -C ₄ alkoxy, especially methoxy and ethoxy)
Corresponds to one of
Is appropriate, but the above definition is not limiting.
More specifically, examples of silane polysulfides may include bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfides. Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide (abbreviated as TESPT) or bis (triethoxysilylpropyl) disulfide (abbreviated as TESPD) is used. Moreover, as a preferable example, bis (mono (C ₁ -C ₄ ) alkoxyldi (C ₁ -C ₄ ) alkylsilylpropyl) polysulfide (in particular, described in Patent Publication WO 02/083782 (or US 2004/132880), Disulfide, trisulfide or tetrasulfide), more particularly bis (monoethoxydimethylsilylpropyl) tetrasulfide.

As coupling agents other than alkoxysilane polysulfides, in particular bifunctional POS (polyorganosiloxane) as described in patent publications WO 02/30939 (or US 6774255) and WO 02/31041 (or US 2004/051210). Or a hydroxysilane polysulfide (in formula (I) above, R ² = OH) or an azodicarbonyl functional group as described, for example, in patent publications WO 2006/125532, WO 2006/125533 and WO 2006/125534 The silane or POS it has may be mentioned.

In the rubber composition according to the present invention, the content of the coupling agent is preferably between 2 and 12 phr, more preferably between 3 and 8 phr.
One skilled in the art will recognize that another characteristic, particularly organic reinforcing filler, if the reinforcing filler requires the use of a coupling agent to form a bond between the filler and the elastomer, For example, it is understood that if it is coated with silica or otherwise contains functional sites, particularly hydroxyl, on its surface, it can be used as a filler equivalent to the reinforcing inorganic filler described in this section. I will.

5.4 Metal Oxide Hollow Fine Particles The rubber composition according to the present invention has an absolutely necessary feature of containing 35 to 50 phr of hollow fine particles (or microspheres) of at least one metal oxide. The term, of course, includes hydroxides, and these microparticles have a median size with a mass between 2 and 500 μm.
Microparticles are by definition and generally understood to mean micrometer sized particles, ie particles having an average size or median size (both expressed in terms of mass) between 1 μm and 1 mm. .
Below the minimum indicated above, the targeted technical effect (ie producing adequate micro-roughness) may be insufficient, while above the maximum indicated, especially rubber Various disadvantages arise when the composition is used as a tread. Apart from the possible loss of beauty (the particles are too prominent on the surface of the tread) and the risk of reduced cohesion during rotation of the relatively large tread pattern elements, the grip performance on the ice melt may be impaired. Found.
For all these reasons, it is preferred that the hollow microparticles have a median size (by mass) that falls within the range of 5 to 200 μm. This particularly preferred size range appears to correspond on the one hand to the optimum compromise between the desired surface roughness and, on the other hand, good contact between the rubber composition and ice.

According to a preferred embodiment, the metal of the metal oxide is selected from the group consisting of aluminum, silicon, zirconium, transition metals, and mixtures of these metals. Transition metals are understood to mean more particularly metals from the 4th period ranging from scandium to zinc, preferably titanium and zinc. Even more preferably, aluminum, silicon, titanium, zirconium and zinc are suitable.
According to a more preferred embodiment, the metal oxide comprises aluminum oxide and / or hydroxide, silicon oxide and / or hydroxide, aluminum silicon oxide and / or hydroxide, and such oxidation. And / or a mixture of hydroxides. Even more preferably, the metal oxide used is an aluminosilicate.
For example, particle size analysis and median size (or microparticles assumed to be substantially spherical) by laser diffraction (see, for example, standard ISO-8130-13 or standard JIS K5600-9-3) Then, various known methods can be applied to the calculation of the median diameter.
In addition, particle size analysis, preferably by mechanical sieving, can be used. The work consists of placing a certain amount of sample (eg 200 g) on a vibrating table for 30 minutes with various sieve apertures (eg 1000, 800, 630, 500, 400, with increasing ratio equal to 1.26 ... by 100, 80 and 63 μm meshes). The oversized ones collected by each sieve are weighed with a precision balance. Thereby, the percentage of oversize for each mesh caliber relative to the total mass of the product is estimated. Finally, the median size (or median diameter) or average size (or average diameter) is calculated in a known manner from the particle size distribution histogram.

5.5-Various Additives The rubber compositions of the present invention are also commonly used in conventional elastomeric compositions (e.g., protective agents, e.g., protective agents such as tire tires, especially for the production of winter tire treads). Anti-ozone wax, chemical antiozonants, antioxidants, reinforcing resins, methylene acceptors (eg phenol novolac resins) or methylene donors (eg HMT or H3M), sulfur or sulfur donors and / or excess All or part of a crosslinking system based on either oxides and / or bismaleimides, vulcanization accelerators or vulcanization activators).
These compositions are also compositions in the raw state, thanks to coupling activators when coupling agents are used, improving the dispersion of the filler in the rubber matrix and reducing the viscosity of the composition. It may also include an agent for coating the inorganic filler or more generally a processing aid that can improve the processing properties of the material as is known. These agents are, for example, hydrolyzable silanes such as alkyl alkoxysilanes, polyols, polyethers, amines, or hydroxylated or hydrolyzable polyorganosiloxanes.

5.6 Production of Rubber Composition and Tread The rubber composition of the present invention is produced in a suitable mixer using two sequential preparation steps according to the general procedure well known to those skilled in the art: 130 ° C. The first stage of thermomechanical kneading or kneading (sometimes referred to as the “non-productive” stage) at a high temperature up to a maximum temperature between 145 ° C. and 185 ° C., preferably between 145 ° C. and 185 ° C. A subsequent second stage mechanical kneading operation (sometimes referred to as a “productive” stage) at a lower temperature, usually below 120 ° C., for example between 60 ° C. and 100 ° C., crosslinking Or a finishing stage in which a vulcanizing system is incorporated.

Methods that can be used for the production of such compositions are, for example, preferably:
-35 to 35 metal oxide hollow microparticles having a liquid plasticizer above 30 phr, a reinforcing filler between 50 and 150 phr, and a median size (by mass) between 2 and 500 μm in a diene elastomer in a mixer. Incorporating 50 phr, wherein all are thermomechanically kneaded in one or more times until a maximum temperature between 130 ° C. and 200 ° C. is reached;
-Cooling the combined mixture to a temperature below 100 ° C;
-Then incorporating a crosslinking system;
-Kneading everything until a maximum temperature of less than 120 ° C is reached;
-Extruding or calendering the rubber composition thus obtained, in particular in the form of a tire tread.
By way of example, the first (non-pro) stage is carried out as one thermomechanical stage, during which all essential components, optional further coatings or processing aids, and various other additives Are introduced into a suitable mixer, for example a normal internal mixer, except for the crosslinking system. After cooling the mixture thus obtained during the non-pro first stage, the crosslinking system is then introduced at low temperature, usually into an external mixer, for example an open mill; For 15 minutes to mix (pro stage).

Suitable crosslinking systems are preferably based on sulfur and primary vulcanization accelerators, especially sulfenamide accelerators. Added to this vulcanization system are various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (particularly diphenylguanidine), etc. Incorporated during the stage and / or during the pro stage. The sulfur content is preferably between 0.5 and 3.0 phr, and the primary accelerator content is between 0.5 and 5.0 phr.
As accelerators (primary or secondary) any compounds that can act as accelerators for vulcanization of diene elastomers in the presence of sulfur, in particular thiazole and their derivatives accelerators, thiuram accelerators Or zinc dithiocarbamate. 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”), and mixtures of these compounds.
The final composition thus obtained is then extruded, for example, in the form of a sheet or plate, if not for laboratory characterization, or else in the form of a rubber profile element that can be used directly as a winter tire tread. Molded.

Vulcanization (or curing), as is known, is usually at temperatures between 130 ° C. and 200 ° C., in particular the curing temperature, the vulcanization system employed and the vulcanization reaction rate of the considered composition. Depending on the time, for example, sufficient time can vary between 5 and 90 minutes.
In the case of a composite-type tread formed from several rubber compositions with different blends, the rubber composition according to the present invention can be used only for a portion of the tread according to the present invention at least during road rotation of the tire. It can be configured as the part of the tread intended to be brought into contact (resulting in a pattern being formed).
The present invention relates to the tire described above both in the raw state (ie before curing) and in the cured state (ie after crosslinking or vulcanization).

6). Inventive Example 6.1-Preparation of Rubber Compositions The following procedures were used to make these compositions: except for the vulcanization system, reinforcing fillers (carbon black, silica and related couplings). Agent), liquid plasticizer, hollow metal oxide particulates, diene elastomer (or blend of diene elastomers), and various other ingredients, are sequentially introduced into an internal mixer having a container initial temperature of about 60 ° C. Thus the mixer is about 70% (volume%) full. The thermomechanical kneading operation (non-pro stage) is then carried out in one stage, which lasts for a total of about 3-4 minutes until the maximum “dropping” temperature of 165 ° C. is reached. The resulting mixture is collected, cooled, and then incorporated with sulfur and sulfenamide-based accelerators in a 30 ° C. external mixer (homofinisher), all for an appropriate time (eg, between 5 and 12 minutes). ) Mix (pro stage).

6.2-Rubber test and friction test on ice These tests consisted of two compositions based on a diene elastomer (NR and a blend with a cis-1,4 bond content greater than 95%). (Referred to as C-1 and C-2), these compositions are reinforced with a blend of silica and carbon black, with or without mixing 40 phr of hollow aluminosilicate particulates.
The formulation of the two compositions (Table 1—contents of various products are expressed in phr) and their properties before and after curing (150 ° C. for 30 minutes) are given in Tables 1 and 2. The vulcanization system consists of sulfur and sulfenamide.

First of all, when examining the various results in Table 2, the rubber properties of the composition (C-2) of the present invention show any significant degradation despite the presence of high content of metal oxide particulates. This is already unexpected for those skilled in the art.
-The processability in the raw state (Mooney plasticity) is only slightly but actually increased.
The rheometer (curing) properties are substantially unchanged.
-After curing, the tensile modulus remains similar. The shore hardness is surprisingly only slightly increased in terms of the amount of fines used.
-Finally, the hysteresis (tan (δ) _max ) has not increased.
The two compositions are then subjected to a laboratory test consisting of measuring their coefficient of friction on ice. The principle is based on a block of rubber composition applied with a load (e.g. equal to 3 kg / cm < ² >) that slides on an ice track at a predetermined speed (e.g. 5 km / h). Prior to testing, the surface of the test block is prepared by scraping a thickness of 0.5 mm, and then applying the load (eg 3 kg / cm ² ) on the actual dry ground surface (asphalt). A series of frictional motions by sliding repeatedly. The forces generated in the block motion direction (Fx) and in the direction orthogonal to the motion (Fz) are measured. The ratio of Fx / Fz determines the coefficient of friction of the test sample on ice. The temperature during measurement is set to -2 ° C.
This test (the principle of which is well known to those skilled in the art, see for example patent applications EP1052270 and EP1505112) is obtained after a running test in a vehicle in which the tread is fitted with tires made of the same rubber composition. It is possible to evaluate the grip on melted ice under typical conditions.

The results are shown in Table 3. A value exceeding the value of control (Composition C-1) (arbitrarily 100) indicates an improved result, i.e. performance for a shorter braking distance. In the composition C-2 according to the present invention, it can be seen that the coefficient of friction on ice is very clearly increased (23%) compared to the control composition C-1 which does not contain aluminosilicate fine particles.
In conclusion, the compositions according to the invention provide tires and their treads with a considerably improved grip on ice melt.

（１）４．３％の１，２−；２．７％のｔｒａｎｓ；９７％のシス−１，４−を有するＢＲ（Ｔｇ＝−１０４℃）；
（２）天然ゴム（しゃく解された(peptised)）；
（３）シリカ「Ｚｅｏｓｉｌ １１１５ＭＰ」、Ｒｈｏｄｉａ、「ＨＤＳ」タイプ（ＢＥＴ及びＣＴＡＢ：約１２０ｍ²／ｇ）；
（４）カップリング剤ＴＥＳＰＴ（「Ｓｉ６９」、Ｄｅｇｕｓｓａ）；
（５）アルミノケイ酸塩（「Ｆｉｌｌｉｔｅ ２００／７」、Ｊａｐａｎ Ｆｉｌｌｉｔｅ）（粒子の中間値サイズ：約９０μｍ）；
（６）グレード ＡＳＴＭ Ｎ２３４（Ｃａｂｏｔ）；
（７）ＭＥＳオイル（「Ｃａｔｅｎｅｘ ＳＮＲ」、Ｓｈｅｌｌ）；
（８）ジフェニルグアニジン（Ｐｅｒｋａｃｉｔ ＤＰＧ、Ｆｌｅｘｓｙｓ）；
（９）Ｎ−（１，３−ジメチルブチル）−Ｎ−フェニル−パラ−フェニレンジアミン（Ｓａｎｔｏｆｌｅｘ ６−ＰＰＤ、Ｆｌｅｘｓｙｓ）；
（１０）Ｎ−ジシクロヘキシル−２−ベンゾチアゾールスルフェンアミド（「Ｓａｎｔｏｃｕｒｅ ＣＢＳ」、Ｆｌｅｘｓｙｓ）。

(1) 4.3% 1,2-; 2.7% trans; 97% BR with cis-1,4- (Tg = −104 ° C.);
(2) Natural rubber (peptised);
(3) Silica “Zeosil 1115MP”, Rhodia, “HDS” type (BET and CTAB: about 120 m ² / g);
(4) Coupling agent TESPT (“Si69”, Degussa);
(5) Aluminosilicate (“Fillite 200/7”, Japan Fillite) (intermediate particle size: about 90 μm);
(6) Grade ASTM N234 (Cabot);
(7) MES oil (“Catenex SNR”, Shell);
(8) Diphenylguanidine (Perkacit DPG, Flexsys);
(9) N- (1,3-dimethylbutyl) -N-phenyl-para-phenylenediamine (Santoflex 6-PPD, Flexsys);
(10) N-dicyclohexyl-2-benzothiazole sulfenamide (“Santocure CBS”, Flexsys).

Claims (15)

  A tire comprising in its tread a diene elastomer, a liquid plasticizer of more than 30 phr, and a reinforcing filler of between 50 and 150 phr, wherein the composition is centered by a mass between 2 and 500 μm A tire further comprising 35 to 50 phr of hollow fine particles of at least one metal oxide having a value size.   The tire of claim 1 wherein the diene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene copolymer, isoprene copolymer, and mixtures of these elastomers.   The tire of claim 2, wherein the composition comprises 50-100 phr natural rubber or synthetic polyisoprene.   4. Tire according to claim 3, wherein natural rubber or synthetic polyisoprene is used as a blend with at most 50 phr of polybutadiene having a cis-1,4 bond content of more than 90%.   The tire according to claim 2, wherein the composition comprises 50 to 100 phr of polybutadiene having a cis-1,4 bond content of more than 90%.   6. Tire according to claim 5, wherein the polybutadiene is used as a blend with at most 50 phr natural rubber or synthetic polyisoprene.   The tire according to any one of claims 1 to 6, wherein the content of the liquid plasticizer exceeds 40 pr, preferably within the range of 50 to 100 phr.   The liquid plasticizer is selected from the group consisting of naphthenic oil, paraffin oil, MES oil, TDAE oil, mineral oil, vegetable oil, ether plasticizer, ester plasticizer, phosphate plasticizer, sulfonate plasticizer, and mixtures of these compounds. The tire according to any one of claims 1 to 7.   The tire according to any one of claims 1 to 8, wherein the reinforcing filler mainly contains carbon black, and the carbon black content preferably exceeds 60 phr.   The tire according to any one of claims 1 to 8, wherein the reinforcing filler mainly comprises a reinforcing inorganic filler, and the content of the reinforcing inorganic filler preferably exceeds 70 phr.   11. Tire according to any one of claims 1 to 10, wherein the content of the total reinforcing filler is between 60 and 120, preferably between 70 and 100 phr.   The tire according to any one of claims 1 to 11, wherein the metal of the metal oxide is selected from the group consisting of aluminum, silicon, zirconium, transition metals, and mixtures of these metals.   Metal oxides are aluminum oxides and / or hydroxides, silicon oxides and / or hydroxides, aluminum-silicon oxides and / or hydroxides, and such oxides and / or hydroxides 13. Tire according to claim 12, selected from the group consisting of mixtures.   The tire according to claim 13, wherein the metal oxide is an aluminosilicate.   The tire according to any one of claims 1 to 14, wherein the hollow metal oxide fine particles have a median size included in a range of 5 to 200 µm.