JP2020132730A - Rubber composition for studless tire and studless tire including the same - Google Patents

Abstract

To solve the problem in which: conventionally, many measures have been proposed to improve on-ice performance of a studless tire, including the techniques of blending thermally-expandable microcapsules; but the conventional art has the problem of reduced wet performance; and to provide a novel rubber composition for a studless tire that can improve on-ice performance and wet performance more than the conventional art.SOLUTION: A rubber composition contains, based on 100 pts.mass of diene rubber, silica of 10 pts.mass or more, polyethylene glycol bis(2-ethylhexanoate) of 1-40 pts.mass, and thermally-expandable microcapsules of 0.1-20 pts.mass.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for a studless tire and a studless tire using the same. Specifically, the present invention relates to a rubber composition for a studless tire capable of improving on-ice performance and wet performance as compared with the prior art, and a studless tire using the same. It is about.

The studless compound is designed to have a low glass transition temperature (Tg) of the compound in order to ensure flexibility at low temperatures, and tan δ (0 ° C) has a high correlation with braking performance (wet performance) on wet road surfaces. ) Must be low.
To compensate for this, it is known that silica is also used in studless compounds. However, natural rubber, which is mainly used in studless compounds, tends to inhibit the reactivity of the silane coupling agent with silica, and the natural rubber itself does not have a functional group capable of interacting with silica. Therefore, there is a problem that the dispersibility of silica is not improved and the effect of the silica compounding on the wet performance is not fully exhibited.

On the other hand, in order to improve the performance on ice (friction force on icy road surface), it is effective to increase the surface roughness of the tread rubber, and as a method, use heat-expandable microcapsules (hollow polymer). Alternatively, a technique is known that contains a crosslinkable oligomer or polymer having a reactive functional group that is incompatible with diene rubber and three-dimensionally crosslinked fine particles having an average particle size of 1 to 200 μm (for example, Patent Documents). (Refer to 1), this technique does not contribute to the improvement of wet performance, but rather, the compound strength is lowered, so that the wet performance may be lowered.

Japanese Unexamined Patent Publication No. 2014-62168

Therefore, an object of the present invention is to provide a rubber composition for a studless tire capable of enhancing on-ice performance and wet performance as compared with the prior art, and a studless tire using the same.

As a result of diligent research, the present inventors have been able to solve the above problems by blending a specific amount of silica with a diene rubber, and further blending a specific plasticizer and a heat-expandable microcapsule in a specific amount. We were able to complete the present invention.
That is, the present invention is as follows.

1. 1. 10 parts by mass or more of silica, 1 to 40 parts by mass of polyethylene glycol bis (2-ethylhexanoate), and 0.1 to 20 parts by mass of heat-expandable microcapsules are blended with respect to 100 parts by mass of diene rubber. A rubber composition for studless tires, which is characterized by becoming.
2. 2. Three-dimensionally crosslinked fine particles of 0.3 to 30 parts by mass of a crosslinkable oligomer or polymer incompatible with the diene rubber and an average particle size of 0.5 to 50 μm with respect to 100 parts by mass of the diene rubber. The rubber composition for a studless tire according to 1 above, which comprises 0.1 to 12 parts by mass of.
3. 3. A studless tire using the rubber composition according to 1 or 2 for a tread.

The rubber composition of the present invention has 10 parts by mass or more of silica, 1 to 40 parts by mass of polyethylene glycol bis (2-ethylhexanoate), which is a specific plasticizer, and thermal expansion with respect to 100 parts by mass of diene rubber. Since 0.1 to 20 parts by mass of the sex microcapsules are blended, it is possible to provide a rubber composition for a studless tire capable of enhancing on-ice performance and wet performance as compared with the prior art, and a studless tire using the same.

Hereinafter, the present invention will be described in more detail.

(Diene rubber)
The diene rubber used in the present invention includes, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and acrylonitrile-butadiene copolymer rubber (BR). NBR), ethylene-propylene-dienter polymer (EPDM) and the like. These may be used alone or in combination of two or more. Further, its molecular weight and microstructure are not particularly limited, and may be terminal-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.
Of these, from the viewpoint of improving on-ice performance and wet performance, it is preferable to use NR and BR, and out of 100 parts by mass of diene rubber, 30 to 75 parts by mass of NR and 25 to 70 parts by mass of BR are used. preferable.

(silica)
The silica used in the present invention can be any silica conventionally known to be used in rubber compositions, such as dry silica, wet silica, and colloidal silica, which can be used alone or in combination of two or more.
From the viewpoint of further enhancing the on-ice performance and the wet performance, the nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 150 to 250 m ² / g.
The nitrogen adsorption specific surface area (N ₂ SA) shall be determined in accordance with JIS K6217-2.

The blending amount of silica is 10 parts by mass or more, preferably 20 to 120 parts by mass, and more preferably 25 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.

(Specific plasticizer)
In the present invention, polyethylene glycol bis (2-ethylhexanoate) is used as a specific plasticizer.
It is presumed that polyethylene glycol bis (2-ethylhexanoate) has an effect of improving the dispersion of silica by preventing the aggregation of silica in addition to the effect as a plasticizer.

In polyethylene glycol bis (2-ethylhexanoate), the number of repetitions of the polyoxyethylene unit is, for example, 6 to 12, preferably 8 to 10.

As the polyethylene glycol bis (2-ethylhexanoate), a commercially available product can be used, and examples thereof include Lionon DEH-40 manufactured by Lion Specialty Chemicals Co., Ltd.

The blending amount of polyethylene glycol bis (2-ethylhexanoate) is 1 to 40 parts by mass, preferably 2 to 25 parts by mass, based on 100 parts by mass of the diene rubber.
If the blending amount of polyethylene glycol bis (2-ethylhexanoate) is less than 1 part by mass, the blending amount is too small to achieve the effect of the present invention, and if it exceeds 40 parts by mass, the wet performance deteriorates.

(Thermal expandable microcapsules)
The rubber composition in the present invention contains heat-expandable microcapsules from the viewpoint of enhancing the performance on ice.
In the present invention, the heat-expandable microcapsules have a structure in which a heat-expandable substance is encapsulated in a shell material formed of a thermoplastic resin. The shell material of the heat-expandable microcapsules can be formed of a nitrile polymer.
Further, the heat-expandable substance contained in the shell material of the microcapsules has a property of vaporizing or expanding by heat, and for example, at least one kind selected from the group consisting of hydrocarbons such as isoalkane and normal alkane is exemplified. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, 2,2,4-trimethylpentane, and examples of normal alkanes include n-butane, n-propane, n-hexane, and the like. Examples thereof include n-heptane and n-octane. These hydrocarbons may be used alone or in combination of two or more. As a preferable form of the thermally expandable substance, a hydrocarbon obtained by dissolving a gaseous hydrocarbon at room temperature in a liquid hydrocarbon at room temperature is preferable. By using such a mixture of hydrocarbons, a sufficient expansion force can be obtained from a low temperature region to a high temperature region in the vulcanization molding temperature range (150 ° C. to 190 ° C.) of the unvulcanized tire.
Examples of such heat-expandable microcapsules include the trade name "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" manufactured by Expandel, Sweden, or the trade name "Matsumoto Micros" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. "Fair F-85D" or "Matsumoto Microsphere F-100D" or the like can be used.

The blending ratio of the heat-expandable microcapsules is 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, based on 100 parts by mass of the diene rubber.

Here, in the present invention, in order to further improve the performance on ice, the crosslinkable oligomer or polymer incompatible with the diene rubber has 0.3 to 30 parts by mass and the average particle size with respect to 100 parts by mass of the diene rubber. It is preferable to blend 0.1 to 12 parts by mass of three-dimensionally crosslinked fine particles of 0.5 to 50 μm. These components are disclosed and known in Patent Document 1 (Japanese Unexamined Patent Publication No. 2014-62168), and will be described below.

As the crosslinkable oligomer or polymer, one that is incompatible with the (A) diene rubber is used.
"Incompatible with the diene-based rubber" does not mean that it is incompatible with all the rubber components contained in the diene-based rubber, but each used for the diene-based rubber and the crosslinkable oligomer or polymer. It means that the specific components are incompatible with each other.

Examples of the crosslinkable oligomer or polymer include polyether-based, polyester-based, polyolefin-based, polycarbonate-based, aliphatic, saturated hydrocarbon-based, acrylic-based, plant-derived or siloxane-based polymers or copolymers. Can be mentioned.

Of these, from the viewpoint of improving the ice performance and abrasion resistance of the studless tire, the crosslinkable oligomer or polymer is a polyether-based, polycarbonate-based, acrylic-based or siloxane-based polymer or copolymer. It is preferable to have it.

Here, examples of the above-mentioned polyether-based polymer or copolymer include polyethylene glycol, polypropylene glycol (PPG), polypropylene triol, ethylene oxide / propylene oxide copolymer, polytetramethylene ether glycol (PTMEG), and sorbitol. Examples include system polyols.
Further, as the polycarbonate-based polymer or copolymer, for example, an ester of a polyol compound (for example, 1,6-hexanediol, 1,4-butanediol, 1,5-pentanediol, etc.) and a dialkyl carbonate. Examples thereof include those obtained by an exchange reaction.
Further, as the acrylic polymer or copolymer, for example, an acrylic polyol; a single polymer of an acrylate such as an acrylate, a methyl acrylate, an ethyl acrylate, a butyl acrylate, or a 2-ethylhexyl acrylate; or a combination of two or more of these acrylates. Acrylate copolymer; and the like.
The siloxane-based polymer or copolymer is not particularly limited as long as it is a compound having an organopolysiloxane as a main chain, and specific examples thereof include polydimethylsiloxane, methylhydrogenpolysiloxane, and methylphenylpoly. Examples thereof include siloxane and diphenylpolysiloxane.

In the present invention, the crosslinkable oligomer or polymer has a hydroxyl group, a silane functional group, an isocyanate group, a (meth) acryloyl group, and an allyl because the crosslinking between the molecules improves the ice performance of the studless tire. It preferably has at least one reactive functional group selected from the group consisting of groups, carboxy groups, acid anhydride groups and epoxy groups.
Here, the silane functional group is also called a so-called crosslinkable silyl group, and specific examples thereof include a hydrolyzable silyl group; a silanol group; a silanol group as an acetoxy group derivative, an enoxy group derivative, an oxime group derivative, and an amine derivative. Functional groups substituted with such as; etc.
Of these functional groups, the silane functional group and the isocyanate group are for the reason that the crosslinkable oligomer or polymer is appropriately crosslinked during rubber processing, the ice performance of the studless tire is further improved, and the abrasion resistance is also improved. , It is preferable to have an acid anhydride group or an epoxy group, and more preferably it has a silane functional group (particularly a hydrolyzable silyl group, a silanol group) and / or an isocyanate group.

Here, as the hydrolyzable silyl group, specific examples thereof include an alkoxysilyl group, an alkenyloxysilyl group, an asyloxysilyl group, an aminosilyl group, an aminooxysilyl group, an oximesilyl group, an amidesilyl group and the like. Be done.
Of these, an alkoxysilyl group is preferable, and specifically, a methoxysilyl group and an ethoxysilyl group are preferable, because the balance between hydrolyzability and storage stability is good.

Further, the isocyanate group is an isocyanate group that remains when the hydroxyl group of a polyol compound (for example, a polycarbonate-based polyol or the like) is reacted with the isocyanate group of a polyisocyanate compound.
The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule, and specific examples thereof include TDI (for example, 2,4-tolylene diisocyanate (2,4-TDI)). ), 2,6-tolylene diisocyanate (2,6-TDI)), MDI (eg, 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4') -MDI)), 1,4-phenylenediocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), trizine diisocyanate (TODI), 1,5-naphthalenedi isocyanate (NDI), Aromatic polyisocyanates such as triphenylmethane triisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornan diisocyanate (NBDI); transcyclohexane-1,4-diisocyanate , Isophorone diisocyanate (IPDI), bis (isocyanatemethyl) cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H12MDI) and other alicyclic polyisocyanates; these carbodiimide-modified polyisocyanates; these isocyanurate-modified polyisocyanates; etc. ..

In the present invention, when a crosslinkable oligomer or polymer having a hydroxyl group is used as the reactive functional group, a part or all of the crosslinkable oligomer or polymer is previously prepared with an isocyanate compound or the like before being blended with the diene rubber. It is preferable to carry out cross-linking or to add a cross-linking agent such as an isocyanate compound to the rubber in advance.

In the present invention, the reactive functional group is preferably contained at least at the end of the main chain of the crosslinkable oligomer or polymer, and 1.5 or more when the main chain is linear. It is preferable to have two or more. On the other hand, when the main chain is branched, it is preferable to have three or more.

Further, in the present invention, the weight average molecular weight or the number average molecular weight of the crosslinkable oligomer or polymer improves the dispersibility in the diene rubber and the kneading processability of the rubber composition, and further crosslinks the fine particles described later. It is preferably 300 to 30,000, more preferably 500 to 25,000, for the reason that the particle size and shape can be easily adjusted when prepared in the sex oligomer or polymer.
Here, both the weight average molecular weight and the number average molecular weight shall be measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

Further, in the present invention, the content of the crosslinkable oligomer or polymer is 0.3 to 30 parts by mass, preferably 1 to 15 parts by mass with respect to 100 parts by mass of the diene rubber.

The fine particles used in the present invention are three-dimensionally crosslinked fine particles having an average particle diameter of 0.5 to 50 μm formed by using a thermoplastic elastomer.
The average particle size of the fine particles is preferably 1 to 50 μm, more preferably 5 to 40 μm, because the surface of the studless tire is appropriately roughened and the performance on ice is improved. ..
Here, the average particle size means an average value of the equivalent circle diameter measured using a laser microscope. For example, a laser diffraction / scattering type particle size distribution measuring device LA-300 (manufactured by HORIBA, Ltd.), a laser microscope VK- It can be measured with 8710 (manufactured by Keyence) or the like.

In the present invention, the content of the fine particles is 0.1 to 12 parts by mass, preferably 0.3 to 10 parts by mass, and 0.5 to 10 parts by mass with respect to 100 parts by mass of the diene rubber. It is more preferably parts by mass.
The content of the fine particles is 1 to 50% by mass, preferably 3 to 30% by mass, and 5 to 20% by mass, based on the total mass of the crosslinkable oligomer or polymer and the fine particles. Is more preferable.
By containing the above fine particles in a predetermined amount, both the on-ice performance and the wear resistance of the studless tire using the rubber composition for a tire of the present invention for a tire tread are improved.
It is considered that this is because the strain applied locally is dispersed by the elasticity of the fine particles and the stress is also relaxed, so that the performance on ice and the abrasion resistance are improved.

Further, in the present invention, the fine particles have heat that is incompatible with the crosslinkable oligomer or polymer in advance in the crosslinkable oligomer or polymer because the performance on ice and wear resistance of the studless tire are improved. It is preferable that the plastic elastomer is made into fine particles. This is because the crosslinkable oligomer or polymer functions as a solvent for the fine particles, and when a mixture thereof is blended into the rubber composition, the dispersibility and dispersion of the crosslinkable oligomer or polymer and the fine particles in the rubber composition. This is thought to be because the effect of improving sex can be expected.
Here, "incompatible (with the crosslinkable oligomer or polymer)" does not mean that it is incompatible with all the components contained in the crosslinkable oligomer or polymer, but the crosslinkable oligomer or polymer. And each specific component used in the above thermoplastic elastomer is incompatible with each other.

Examples of the thermoplastic elastomer include olefin-based elastomers, styrene-based elastomers, polyvinyl chloride-based elastomers, polyurethane-based elastomers, polyester-based elastomers, and polyamide-based elastomers, and these may be used alone. Two or more types may be used in combination.
Here, specific examples of the olefin-based elastomer include ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and ethylene-butene rubber (EBM).
Specific examples of the styrene-based elastomer include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), and styreneethylene propylene styrene block copolymer (SEPS). , Styrene ethylenebutyrene styrene block copolymer (SEBS, hydrogenated additive of SBS), styrene ethylene ethylene propylene styrene block copolymer (SEEPS) and the like.
Specific examples of the polyvinyl chloride-based elastomer include those obtained by adding a plasticizer to highly polymerizable polyvinyl chloride, those obtained by modifying polyvinyl chloride, and blends of these with other resins. ..
Specific examples of the polyurethane-based elastomer include short-chain glycol diisocyanate as a hard segment and long-chain polyol as a soft segment; mainly hard segments and polyethers rich in urethane and urea bonds. Those consisting of soft segments; etc.
Specific examples of the polyester-based elastomer include those in which polybutylene terephthalate is used as a hard segment and long-chain polyols and polyesters are used as soft segments.
Specific examples of the polyamide-based elastomer include those in which nylon is used as a hard segment and polytetramethylene glycol is used as a soft segment.

Examples of commercially available products of such thermoplastic elastomers include polyamide-based elastomers (TPAE-12, number average molecular weight: 30,000, manufactured by T & K Toka Co., Ltd.), polyamide elastomers (Diamid PAE, manufactured by Degusa Huls), and polyamides. Polyether elastomer (UBESTA® XTA, manufactured by Ube Kosan Co., Ltd.), polyester-based thermoplastic elastomer (Grelax A, manufactured by Dainippon Ink and Chemicals), polyester-based thermoplastic elastomer (Hytrel (registered trademark), Toray Dupont) , Polyether blockamide copolymer (PEBAX (registered trademark), manufactured by Atofina Japan), polyamide elastomer (NOVAMID (registered trademark), manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and the like.

In the present invention, a reactive functional group different from the above-mentioned reactive functional group of the above-mentioned crosslinkable oligomer or polymer is used because only the above-mentioned thermoplastic elastomer can be three-dimensionally crosslinked in the above-mentioned crosslinkable oligomer or polymer. At least one reactive functional group selected from the group consisting of a hydroxyl group, a mercapto group, a silane functional group, an isocyanate group, a (meth) acryloyl group, an allyl group, a carboxy group, an acid anhydride group and an epoxy group. It is preferable to have.
Here, the silane functional group is also called a so-called crosslinkable silyl group, and specific examples thereof are the same as the silane functional group of the crosslinkable oligomer or polymer, for example, a hydrolyzable silyl group; a silanol group; a silanol. Examples thereof include a functional group in which the group is substituted with an acetoxy group derivative, an enoxy group derivative, an oxime group derivative, an amine derivative, or the like.
After the thermoplastic elastomer is three-dimensionally crosslinked, the crosslinkable oligomer or polymer has the same reactive functional groups as the thermoplastic elastomer (for example, carboxy group, hydrolyzable silyl group, etc.). The functional group already possessed may be modified to the same reactive functional group as the thermoplastic elastomer.
Among these functional groups, it is more preferable to have a silane functional group (particularly a hydrolyzable silyl group) or a hydroxyl group because the three-dimensional cross-linking of the thermoplastic elastomer proceeds easily.
Commercially available products of thermoplastic elastomers having such reactive functional groups include, for example, silylated (hydrolyzable silyl group-terminated) amorphous poly-α-olefin polymers (bestplast 206, number average molecular weight: 10600, ebonic). Degusa) and the like.

In the present invention, the reactive functional group is preferably contained at least at the end of the main chain of the thermoplastic elastomer, and 1.5 or more when the main chain is linear. It is preferable to have two or more. On the other hand, when the main chain is branched, it is preferable to have three or more.

Further, in the present invention, the weight average molecular weight or the number average molecular weight of the thermoplastic elastomer is not particularly limited, but the particle size and the cross-linking density of the fine particles are appropriate, and the performance on ice of the studless tire is improved. It is preferably 1000 to 100,000, more preferably 3000 to 60000.
Here, the weight average molecular weight or the number average molecular weight are both measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

Examples of the method of finely dividing the thermoplastic elastomer in the crosslinkable oligomer or polymer to prepare fine particles include a method of three-dimensionally crosslinking using the reactive functional group of the thermoplastic elastomer. ..

As a method for three-dimensional cross-linking using a reactive functional group, specifically, the thermoplastic elastomer having the reactive functional group and a functional group that reacts with water, a catalyst and the reactive functional group are provided. Examples thereof include a method of reacting with at least one component selected from the group consisting of compounds to carry out three-dimensional cross-linking.

Here, the water of the component can be preferably used when the thermoplastic elastomer has a hydrolyzable silyl group, an isocyanate group, and an acid anhydride group as reactive functional groups.

Examples of the catalyst for the above components include a silanol group condensation catalyst (silanol condensation catalyst) and the like.
Specific examples of the silanol condensation catalyst include dibutyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, tetrabutyl titanate, and stannous octanoate.

In addition, examples of the compound having a functional group that reacts with the above-mentioned reactive functional group of the above-mentioned component include a polyisocyanate compound and a silanol compound.

The polyisocyanate compound can be preferably used when the thermoplastic elastomer has a hydroxyl group as a reactive functional group.
Specific examples of the polyisocyanate compound include TDI (for example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI)) and MDI. (For example, 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI)), 1,4-phenylenediisocyanate, polymethylenepolyphenylene polyisocyanate, xylyl Aromatic polyisocyanates such as range isocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), trizine diisocyanate (TODI), 1,5-naphthalenediisocyanate (NDI), triphenylmethane triisocyanate; hexamethylene diisocyanate (HDI), Alibo polyisocyanates such as trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornandiisosocyanatemethyl (NBDI); tris (isocyanatephenyl) thiophosphate, polymethylenepolyphenylisocyanate, polyisocyanate compounds having an isocyanurate ring, etc. Polyisocyanates having 3 or more isocyanate groups; and the like.

The silanol compound can be preferably used when the thermoplastic elastomer has a silane functional group as a reactive functional group.
Specific examples of the silanol compound include tert-butyldimethylsilanol, diphenylmethylsilanol, polydimethylsiloxane having a silanol group, cyclic polysiloxane having a silanol group, and the like.

In the present invention, a solvent may be used, if necessary, when the thermoplastic elastomer is three-dimensionally crosslinked in the crosslinkable oligomer or polymer to prepare fine particles.
Examples of the use of the solvent include a plasticizer, a diluent, and a solvent that serve as a good solvent for the thermoplastic elastomer and are a poor solvent for the crosslinkable oligomer or polymer, and / or the crosslinkable oligomer or Examples thereof include an embodiment in which a plasticizer, a diluent, or a solvent which is a good solvent for the polymer and is a poor solvent for the thermoplastic elastomer is used.
Specific examples of such a solvent include n-pentane, isopentane, neopentane, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane. n-heptane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2,2 , 3-trimethylbutane, n-octane, isooctane and other aliphatic hydrocarbons; cyclopentane, cyclohexane, methylcyclopentane and other alicyclic hydrocarbons; xylene, benzene, toluene and other aromatic hydrocarbons; α-pinene, Examples thereof include terpene-based organic solvents such as β-pinene and limonene.

Further, in the present invention, when the thermoplastic elastomer is three-dimensionally crosslinked in the crosslinkable oligomer or polymer to prepare fine particles, additives such as a surfactant, an emulsifier, a dispersant, and a silane coupling agent are used. It is preferably prepared using.

(Other ingredients)
In addition to the above-mentioned components, the rubber composition in the present invention includes a vulcanization or cross-linking agent; a vulcanization or cross-linking accelerator; various fillers such as zinc oxide, carbon black, clay, talc, and calcium carbonate; a silane cup. Various additives generally blended in rubber compositions such as ring agents; anti-aging agents; plasticizers can be blended, and such additives are kneaded by a general method to form a composition and vulcanized. Or it can be used for cross-linking. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

Further, the rubber composition of the present invention is suitable for producing a pneumatic tire according to a conventional method for producing a pneumatic tire, and is preferably applied to a tread, particularly a cap tread, to be a studless tire.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

Examples 1-5 and Comparative Examples 1-4
Sample preparation In the formulation (parts by mass) shown in Table 1, the vulcanization accelerator and the components excluding sulfur were kneaded in a 1.7 liter sealed Banbury mixer for 5 minutes, and then the kneaded product was released to the outside of the mixer to room temperature. It was cooled. Then, a vulcanization accelerator and sulfur were added in the same Banbury mixer and further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the test method shown below.

Performance on ice: The obtained vulcanized rubber test piece was attached to a flat cylindrical base rubber, and using an inside drum type friction tester on ice, the measurement temperature was -1.5 ° C, the load was 5.5 kg / cm ² , and the drum. The coefficient of friction on ice was measured under the condition of a rotation speed of 25 km / h. The obtained coefficient of friction on ice is shown in the column of "performance on ice" as an index with the value of Comparative Example 1 as 100. The larger the index value, the larger the frictional force on ice and the better the performance on ice.

Wet performance: Using the obtained vulcanized rubber test piece and spraying water on the road surface using an outside friction tester, under the conditions of measurement temperature 25 ° C., surface pressure 180 kPa, and drum rotation speed 30 km / h. The maximum value of the wet friction coefficient was measured. The maximum value of the obtained wet friction coefficient is shown in the column of "wet performance" as an index with the value of Comparative Example 1 as 100. The larger the index value, the better the wet performance.

The results are shown in Table 1.

* 1: NR (RSS # 3)
* 2: BR (Nipol BR1220 manufactured by Zeon Corporation)
* 3: Plasticizer 1 (glycerol monostearate manufactured by Sigma-Aldrich)
* 4: Plasticizer 2 (Lionon DEH-40 manufactured by Lion Specialty Chemicals Co., Ltd., polyethylene glycol bis (2-ethylhexanoate))
* 5: Aroma oil (Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.)
* 6: Carbon black (Show Black N339 manufactured by Cabot Japan)
* 7: Silica (Rhodia 1165MP, nitrogen adsorption specific surface area (N ₂ SA) = 160m ² / g)
* 8: Silane coupling agent 1 (Si69 manufactured by Evonik Degussa)
* 9: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 10: Stearic acid (Industrial stearic acid N manufactured by Chiba Fatty Acid Co., Ltd.)
* 11: Anti-aging agent (Ozonon 6C manufactured by Seiko Chemical Co., Ltd.)
* 12: Thermally expandable microcapsules (Matsumoto Microsphere F100 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)
* 13: Crosslinkable oligomer or polymer that is incompatible with the diene rubber (fine particle-containing crosslinkable polymer prepared according to the method described in paragraph 0074 of JP2014-62168A. The polymer is an isocyanate group-terminated hydroxyl group-terminated. Polyoxypropylene glycol is dispersed in a proportion of 11% by mass of a polyolefin-based polymer having an average particle size of 25 μm crosslinked three-dimensionally by a siloxane bond).
* 14: Sulfur (fine sulfur powder with Jinhua stamp oil manufactured by Tsurumi Chemical Industry Co., Ltd.)
* 15: Vulcanization accelerator 1 (Noxeller CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
* 16: Vulcanization accelerator 2 (PERKACIT DPG manufactured by Flexis)

From the results in Table 1, in the rubber composition of the example, 10 parts by mass or more of silica and polyethylene glycol bis (2-ethylhexanoate), which is a specific plasticizer, were added to 100 parts by mass of diene-based rubber. Since 40 parts by mass and 0.1 to 20 parts by mass of thermally expandable microcapsules are blended, the on-ice performance and wet performance are improved as compared with the composition of Comparative Example 1 having a conventional typical composition. There is.
On the other hand, in Comparative Example 2, since the amount of the plasticizer 1 was simply increased with respect to the rubber composition of Comparative Example 1, the wet performance was deteriorated.
Since Comparative Example 3 simply increased the amount of the heat-expandable microcapsules with respect to the rubber composition of Comparative Example 1, the wet performance was deteriorated.
In Comparative Example 4, since the blending amount of polyethylene glycol bis (2-ethylhexanoate) exceeded the upper limit specified in the present invention, the wet performance deteriorated.

Claims (3)

10 parts by mass or more of silica, 1 to 40 parts by mass of polyethylene glycol bis (2-ethylhexanoate) and 0.1 to 20 parts by mass of heat-expandable microcapsules are blended with respect to 100 parts by mass of diene rubber. A rubber composition for studless tires, which is characterized by becoming. Three-dimensionally crosslinked fine particles of 0.3 to 30 parts by mass of a crosslinkable oligomer or polymer incompatible with the diene rubber and an average particle size of 0.5 to 50 μm with respect to 100 parts by mass of the diene rubber. The rubber composition for a studless tire according to claim 1, wherein 0.1 to 12 parts by mass of is blended. A studless tire using the rubber composition according to claim 1 or 2 for a tread.