Rubber composition for tire and studless tire

Abstract

To provide a rubber composition for tires that has a large breakage elongation and excellent performance on ice, and a tire manufactured using the rubber composition for tires.SOLUTION: A rubber composition for tires includes 100 pts. mass of diene rubber, 30 to 100 pts. mass of at least one type of filler selected from the group consisting of carbon black and white fillers, and 0.1 to 30 pts. mass of polyurethane fine particles with an average particle diameter of 1 to 300 μm. The polyurethane fine particles are derived from a composition containing polyol, polyisocyanate, water, and oil as a dispersing medium, and satisfying at least one of the following conditions (1) and (2). Condition (1): The polyol is a vegetable oil-based polyol. Condition (2): The polyisocyanate is a biomass-based polyisocyanate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for tires and a studless tire. [Background technology]

[0002] From the viewpoint of improving tire performance, rubber compositions for tires containing various additives have been investigated. For example, Patent Document 1 proposes a rubber composition for tires containing specific polyurethane-based fine particles in order to improve performance on ice and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-164378 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, from the viewpoint of safety, etc., there has been a demand for further improvement in the on-ice performance (hereinafter also simply referred to as "on-ice performance") of rubber compositions used in tires (particularly in tread portions) when made into tires. There has also been a demand for further improvement in the breaking elongation (hereinafter also simply referred to as "breaking elongation") after vulcanization. Under these circumstances, the present inventors have studied the rubber composition for tires described in Patent Document 1 and have found that further improvements in breaking elongation and ice performance are desirable when future requirements are taken into consideration.

[0005] In view of the above circumstances, an object of the present invention is to provide a rubber composition for tires that has a large breaking elongation and excellent performance on ice, and a tire manufactured using the rubber composition for tires. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by blending specific polyurethane fine particles, and have arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A rubber composition for tires, comprising 100 parts by mass of a diene rubber, 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers, and 0.1 to 30 parts by mass of polyurethane fine particles having an average particle size of 1 to 300 μm, A rubber composition for tires, wherein the polyurethane microparticles are obtained from a composition containing a polyol, a polyisocyanate, water, and an oil as a dispersion medium, and the composition satisfies at least one of the following conditions (1) and (2): Condition (1): The polyol is a vegetable oil-based polyol. Condition (2): The polyisocyanate is a biomass-based polyisocyanate. (2) The rubber composition for tires according to (1) above, wherein the composition further comprises an amine catalyst, and the amine catalyst comprises a tertiary amine catalyst. (3) The rubber composition for a tire according to (1) or (2) above, wherein the oil comprises an aromatic oil. (4) The rubber composition for a tire according to any one of (1) to (3) above, wherein the composition further contains a surfactant, and the surfactant contains a silicone-based foam stabilizer. (5) The rubber composition for a tire according to any one of (1) to (4) above, wherein the polyol comprises at least one vegetable oil-based polyol selected from the group consisting of castor oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g and soybean oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g. (6) The rubber composition for a tire according to any one of (1) to (5) above, wherein the molar ratio of isocyanate groups to active hydrogen groups in the composition is 0.8 to 6.0. (7) The diene rubber includes natural rubber and butadiene rubber, The rubber composition for a tire according to any one of (1) to (6) above, wherein the proportion of the butadiene rubber relative to the total diene rubber is 30% by mass or more. (8) A studless tire manufactured by using the rubber composition for tires according to any one of (1) to (7) above in the tread portion. [Effects of the Invention]

[0008] As will be described below, the present invention can provide a rubber composition for a tire having a large breaking elongation and excellent performance on ice, and a tire manufactured using the rubber composition for a tire. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a partial cross-sectional schematic view showing an example of an embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The rubber composition for tires and the like of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits. Each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. "High breaking elongation" is also called "excellent breaking elongation." Furthermore, "excellent breaking elongation and performance on ice" is also referred to as "excellent effects of the present invention."

[0011] [1] Rubber composition for tires The rubber composition for tires of the present invention (hereinafter also referred to as "the composition of the present invention") is A rubber composition for tires, comprising: 100 parts by mass of a diene rubber; 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers; and 0.1 to 30 parts by mass of polyurethane fine particles having an average particle size of 1 to 300 μm, The rubber composition for tires is characterized in that the polyurethane microparticles are polyurethane microparticles (hereinafter also referred to as "specific microparticles") obtained from a composition (hereinafter also referred to as "specific composition") that contains a polyol, a polyisocyanate, water, and oil as a dispersion medium, and that satisfies at least one of the following conditions (1) and (2): Condition (1): The polyol is a vegetable oil-based polyol. Condition (2): The polyisocyanate is a biomass-based polyisocyanate.

[0012] As described above, the composition of the present invention contains polyurethane microparticles (specific microparticles) obtained from the specific composition. It is believed that polyurethane microparticles are obtained from the specific composition in the following manner. Specifically, the hydroxyl groups of the polyol contained in the specific composition react with the isocyanate groups of the polyisocyanate contained in the specific composition to form a urethane bond (—NH—COO—). Furthermore, the isocyanate groups react with water contained in the specific composition to generate amino groups. Carbon dioxide is generated during this process. The generated amino groups then react with the isocyanate groups to form urea bonds (—NH—CO—NH—). As a result, polyurethane having urethane and urea bonds is produced. The reaction (polymerization) proceeds in the oil-dispersed dispersion, and carbon dioxide is generated as described above. It is believed that polyurethane microparticles with pores and irregularities on the surface are obtained. These polyurethane microparticles with pores and irregularities on the surface increase friction on ice roads, which is why the composition of the present invention exhibits excellent performance on ice. Furthermore, the specific composition of the present invention is environmentally friendly because it uses a vegetable oil-based polyol or a biomass-based polyisocyanate.

[0013] Each component contained in the composition of the present invention will be described below.

[0014] [Diene rubber] The composition of the present invention contains a diene rubber. The composition of the present invention may contain one diene rubber or two or more diene rubbers.

[0015] [Specific example] Specific examples of diene rubbers include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, etc. The diene rubber preferably contains at least one selected from the group consisting of butadiene rubber, styrene-butadiene rubber, isoprene rubber, and natural rubber, and more preferably contains natural rubber and butadiene rubber, because this provides better effects of the present invention.

[0016] When the diene rubber contains natural rubber, the proportion of the natural rubber relative to the total diene rubber is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less, for reasons of better effects of the present invention. When the diene rubber contains butadiene rubber, the proportion of the butadiene rubber relative to the total diene rubber is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less, for reasons of better effects of the present invention.

[0017] [Molecular weight] The number average molecular weight (Mn) of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 50,000 to 2,500,000, more preferably 100,000 to 1,500,000, and even more preferably 150,000 to 1,000,000. The weight average molecular weight (Mw) of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000.

[0018] In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) are values calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0019] [Filler] The composition of the present invention contains at least one filler selected from the group consisting of carbon black and white fillers. The composition of the present invention preferably contains both carbon black and a white filler (particularly silica) because the effects of the present invention are more excellent.

[0020] [Carbon black] The carbon black is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m2 for the reason that the effect of the present invention is more excellent. 2 / g, and 70 to 150m 2 / g is more preferred. Here, the nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed onto the surface of carbon black measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0021] [White filler] The white filler is not particularly limited, and examples thereof include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, etc. Among these, silica is preferred because it provides better effects of the present invention.

[0022] The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. Among these, wet silica is preferred because it provides better effects of the present invention.

[0023] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of the silica is not particularly limited, but is preferably 100 to 400 m 2 / g, and 150 to 300m 2 / g is more preferred. Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed onto the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0024] [Content] In the composition of the present invention, the content of the filler is 30 to 100 parts by mass, preferably 50 to 90 parts by mass, and more preferably 60 to 80 parts by mass, per 100 parts by mass of the diene rubber.

[0025] When the composition of the present invention contains carbon black, the content of carbon black is preferably 1 to 50 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the diene rubber, because the effects of the present invention are more excellent.

[0026] When the composition of the present invention contains a white filler (particularly, silica), the content of the white filler is preferably 10 to 90 parts by mass, more preferably 30 to 70 parts by mass, per 100 parts by mass of the diene rubber, because this provides better effects of the present invention.

[0027] [Specific fine particles] The composition of the present invention comprises: Polyurethane microparticles having an average particle size of 1 to 300 μm, The composition contains polyurethane microparticles (specific microparticles) obtained from a composition (specific composition) that includes a polyol, a polyisocyanate, water, and oil as a dispersion medium, and that satisfies at least one of the conditions (1) and (2) described below.

[0028] The specific fine particles will be described below, and a method for producing the specific fine particles will be described later.

[0029] [Polyurethane fine particles] The polyurethane fine particles in the specific fine particles refer to fine particles of polyurethane. Here, polyurethane refers to a polymer having a plurality of urethane bonds (-NH-COO-). The polyurethane preferably has a urea bond (-NH-CO-NH-) in addition to a urethane bond, because this provides a better effect of the present invention.

[0030] [Specific composition] As described above, the specific fine particles are polyurethane fine particles obtained from a composition (specific composition) containing polyol, polyisocyanate, water, and oil as a dispersion medium, and satisfying at least one of the conditions (1) and (2) described below.

[0031] Each component contained in the specific composition will be described below.

[0032] <Polyol> As noted above, certain compositions include a polyol. A polyol is a compound having two or more hydroxy groups (hydroxyl groups). The polyol is preferably a liquid at 20° C. and 1 atmosphere.

[0033] (Example) Examples of polyols include polyether polyols; vegetable oil-based polyols such as castor oil, dehydrated castor oil, hydrogenated castor oil, 5-50 mol alkylene oxide adduct of castor oil, castor oil-based polyols such as sebacic acid-based polyester polyols, and soybean oil-based polyols; polyester polyols; polymer polyols having carbon-carbon bonds in the main chain skeleton such as acrylic polyols, polybutadiene diols, and hydrogenated polybutadiene polyols; low-molecular-weight polyhydric alcohols; and mixed polyols thereof. Among these, vegetable oil-based polyols are preferred, and castor oil-based polyols are more preferred, because they provide better effects of the present invention.

[0034] (Hydroxyl value) The hydroxyl value of the polyol is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 1 to 400 mgKOH / g, more preferably 5 to 300 mgKOH / g, even more preferably 10 to 200 mgKOH / g, and particularly preferably 20 to 100 mgKOH / g. The hydroxyl value is the hydroxyl value described in JIS K 1557-1:2007, and is the number of mg of potassium hydroxide equivalent to the hydroxyl groups in 1 g of sample.

[0035] (Preferred embodiment) For reasons of better effects of the present invention, the polyol preferably contains at least one vegetable oil-based polyol selected from the group consisting of castor oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g and soybean oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g, more preferably a castor oil-based polyol having a hydroxyl value of 10 to 200 mgKOH / g, and even more preferably a castor oil-based polyol having a hydroxyl value of 10 to 200 mgKOH / g.

[0036] (Ratio to total active hydrogen groups) In the specific composition, the ratio (molar ratio) of hydroxy groups (hydroxyl groups) of the polyol (or the polyol and the monool when a monool described below is used) to the total active hydrogen groups is preferably 0.1 to 1.0, more preferably 0.2 to 0.8, and even more preferably 0.3 to 0.7, for reasons of better effects of the present invention.

[0037] <Monoall> In addition to the polyol, a particular composition may also contain a monool. A monool is a compound having one hydroxyl group. Specific examples of monools include alcohols (methanol, ethanol, etc.).

[0038] (Content) When the specific composition contains a monool, the content of the monool is preferably 50 parts by mass or less per 100 parts by mass of the above-mentioned polyol, for the reason that the effects of the present invention are more excellent.

[0039] <Polyisocyanate> As noted above, certain compositions include a polyisocyanate. Polyisocyanate is a compound having two or more isocyanate groups (-NCO).

[0040] (Example) Specific examples of polyisocyanates include aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI; e.g., 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and triphenylmethane triisocyanate; Hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H 12 Aliphatic polyisocyanates (including cycloaliphatic polyisocyanates), such as MDI; These carbodiimide-modified polyisocyanates; These include isocyanurates (for example, PDI isocyanurates).

[0041] The polyisocyanate is preferably an aromatic polyisocyanate, more preferably MDI, because the effects of the present invention are more excellent. Examples of the MDI include monomeric MDI, polymeric MDI, and modified MDI (for example, carbodiimide-modified MDI), and among these, polymeric MDI is preferred because it provides a superior effect of the present invention.

[0042] (Average number of functional groups) The average number of functional groups of the polyisocyanate is preferably 2.1 or more, more preferably 2.3 or more, even more preferably 2.5 or more, particularly preferably 2.7 or more, and most preferably 2.9 or more, because this provides better effects of the present invention. There is no particular upper limit on the average number of functional groups of the polyisocyanate, but for reasons of better effects of the present invention, it is preferably 10 or less, more preferably 5 or less, and even more preferably 4 or less. The average functionality represents the average number of isocyanate groups contained in the polyisocyanate.

[0043] (NCO%) The NCO % of the polyisocyanate is preferably 5 to 80%, more preferably 10 to 50%, and even more preferably 20 to 40%, because this provides better effects of the present invention. Here, NCO% represents the proportion (mass%) of isocyanate groups relative to the entire polyisocyanate.

[0044] <Water> As noted above, certain compositions include water.

[0045] (Content) In the specific composition, the content of water is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the polyol, because this provides better effects of the present invention.

[0046] (Water / Isocyanate group) The molar ratio of water to isocyanate groups of the polyisocyanate (hereinafter also referred to as "water / isocyanate groups") is preferably 0.1 to 0.6, more preferably 0.2 to 0.5, for reasons of better effects of the present invention.

[0047] <Catalyst> The specific composition preferably contains a catalyst, since this provides a better effect of the present invention.

[0048] The catalyst is not particularly limited as long as it promotes the reaction between a polyol and a polyisocyanate or the reaction between a polyisocyanate and water. However, a catalyst that promotes the reaction between a polyisocyanate and water is preferred because the effects of the present invention are more excellent. The catalyst is preferably an amine catalyst, more preferably a tertiary amine catalyst, because the effects of the present invention are more excellent.

[0049] The catalyst is preferably a reactive catalyst, since this provides a better effect of the present invention. Here, the reactivity of the reactive catalyst means that it can react with an isocyanate group. The reactive catalyst is preferably an amine or a compound having a hydroxy group, more preferably an amine having a hydroxy group (particularly, a tertiary amine having a hydroxy group), further preferably a tertiary amine having three alcohol groups (-ROH, R: alkylene group), and particularly preferably triethanolamine, because the effects of the present invention are more excellent.

[0050] (Content) In the specific composition, the content of the catalyst is preferably 0.01 to 30 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the polyol, because this provides better effects of the present invention.

[0051] (Ratio to total active hydrogen groups) The ratio (molar ratio) of the active hydrogen groups (amino groups, hydroxy groups) of the catalyst to the total number of active hydrogen groups is preferably 0.05 to 0.8, more preferably 0.1 to 0.5, and even more preferably 0.15 to 0.3, for reasons of better effects of the present invention.

[0052] <Surfactant> The specific composition preferably contains a surfactant, since this provides a better effect of the present invention. The surfactant is preferably a silicone-based foam stabilizer, as this provides a more excellent effect of the present invention.

[0053] (Silicone foam stabilizer) There are no particular restrictions on the silicone-based foam stabilizer, and any conventionally known silicone-based foam stabilizer can be used. The silicone-based foam stabilizer has a polysiloxane chain and a polyoxyalkylene chain, and is preferably one in which the polysiloxane chain, which is the main chain, is modified with the polyoxyalkylene chain. The polysiloxane chain is preferably an organopolysiloxane chain, and a specific example of the organopolysiloxane chain is a polydimethylsiloxane chain. Examples of the polyoxyalkylene chain include polyoxyalkylene chains composed of one type of oxyalkylene group, such as polyoxyethylene chains and polyoxypropylene chains, and polyoxyalkylene chains composed of two or more types of oxyalkylene groups, such as oxyethyleneoxypropylene block chains and oxyethyleneoxypropylene random chains.

[0054] (Content) In the specific composition, the content of the surfactant is preferably 0.1 to 30 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the above-mentioned polyol, because this provides better effects of the present invention.

[0055] <Oil> As noted above, certain compositions include oil as a carrier fluid. The oil is not particularly limited, and specific examples include mineral oil and vegetable oil. Oil does not include liquid rubber.

[0056] (mineral oil) There are no particular limitations on the mineral oil, and specific examples include paraffinic, naphthenic, and aromatic oils.

[0057] (vegetable oil) There is no particular limitation on the vegetable oil, and specific examples include castor oil, soybean oil, rapeseed oil, coconut oil, and linseed oil.

[0058] (Preferred embodiment) The oil is preferably an aromatic oil (aromatic oil) because this provides a better effect of the present invention. An aromatic oil means an oil containing 35% by mass or more of aromatic hydrocarbons. The oil is preferably a process oil, since this provides a better effect of the present invention.

[0059] (Content) In the specific composition, the content of the oil is preferably 100 to 1000 parts by mass, more preferably 200 to 500 parts by mass, per 100 parts by mass of the above-mentioned polyol, because this provides better effects of the present invention.

[0060] <Isocyanate group / active hydrogen group> In the specific composition, the molar ratio of isocyanate groups to active hydrogen groups (hereinafter also referred to as "isocyanate groups / active hydrogen groups") is preferably 0.5 to 8.0, more preferably 0.8 to 6.0, and even more preferably 2.0 to 4.0, for reasons of better effects of the present invention. Here, the active hydrogen group refers to the hydroxy group of the polyol or monool, and when an amine or a compound having a hydroxy group is used as a catalyst, it refers to the hydroxy group of the polyol or monool, as well as the amino group of the amine or the hydroxy group of the compound having a hydroxy group. Note that the hydroxy group (hydroxyl group) of water is not included in the active hydrogen group.

[0061] <Conditions (1) and (2)> As described above, the specific composition satisfies at least one of the following conditions (1) and (2). Condition (1): The polyol is a vegetable oil-based polyol. Condition (2): The polyisocyanate is a biomass-based polyisocyanate.

[0062] (Vegetable oil-based polyol) The vegetable oil-based polyol refers to a polyol that is a vegetable oil or a derivative of a vegetable oil, or a polyol synthesized using a vegetable oil as a raw material. Examples of the vegetable oil include castor oil, soybean oil, rapeseed oil, coconut oil, linseed oil, etc. Among these, castor oil is preferred because it provides a more excellent effect of the present invention.

[0063] (Biomass-based polyisocyanate) The biomass-based polyisocyanate refers to a polyisocyanate obtained from living organisms (animals and plants) through a chemical reaction (including a bioprocess), or a polyisocyanate synthesized using raw materials derived from living organisms (animals and plants). The organism is preferably a plant, such as sugarcane.

[0064] (Preferred embodiment) The specific composition preferably satisfies at least condition (1) because the effects of the present invention are more excellent.

[0065] [Average particle size] As described above, the average particle size of the specific fine particles is 1 to 300 μm. The average particle size is preferably 2 to 100 μm, more preferably 5 to 50 μm, further preferably 10 to 40 μm, and particularly preferably 20 to 30 μm, for reasons of better effects of the present invention. In this specification, the average particle size is a volume average diameter measured with a laser diffraction particle size distribution measuring device.

[0066] [Apparent density] The apparent density of the specific fine particles is not particularly limited, but is preferably 0.10 to 2.00 g / cm because the effect of the present invention is more excellent. 3 and preferably 1.00 g / cm 3 Super 1.50g / cm 3 More preferably, it is: In this specification, the apparent density of polyurethane fine particles is determined by the water displacement method in accordance with JIS K7112.

[0067] [Preferred embodiment] The specific microparticles are preferably polyurethane microparticles produced by Production Method 1 of the present invention described below (hereinafter also referred to as "specific microparticles 1"), and more preferably polyurethane microparticles produced by Production Method 2 of the present invention described below (hereinafter also referred to as "specific microparticles 2"), because they provide better effects of the present invention.

[0068] Regarding Specified Fine Particles 1 and 2, there are circumstances that make it impossible or almost impractical to "directly identify the substance by its structure or properties at the time of filing the application," as follows:

[0069] In the production methods 1 and 2 of the present invention described below, the reactions between the hydroxyl groups of the polyol and the isocyanate groups of the polyisocyanate (forming urethane bonds), the reaction between the isocyanate groups of the polyisocyanate and water (forming amino groups), and the reaction between the amino groups formed by the reaction with water and the isocyanate groups of the polyisocyanate (forming urea bonds) compete with each other. That is, in the polymerization step, polyisocyanates are present in a mixture of those in which some of the isocyanate groups have reacted with water to form amino groups, those in which all of the isocyanate groups have reacted with water to form amino groups, and those in which all of the isocyanate groups have remained intact without reacting with water, and these react with the polyol or polyisocyanate. Therefore, the structures of the specific fine particles 1 and 2 are extremely complex and cannot be expressed by a general formula. This is common technical knowledge among those skilled in the art. Furthermore, unless the structure is specified, the properties of the substance that are determined accordingly cannot be easily understood, and when reacting multiple different monomers, the properties of the resulting polyurethane microparticles change significantly if the compounding ratio and reaction conditions are changed, so it is impossible to express them in terms of properties.In other words, specific microparticles 1 and 2 cannot be directly specified by their structure or properties, and can only be specified by the process.

[0070] [Content] In the composition of the present invention, the content of the specific fine particles is 0.1 to 30 parts by mass relative to 100 parts by mass of the diene rubber. In particular, for the reason that the effects of the present invention are more excellent, the content is preferably 1 to 20 parts by mass, and more preferably 3 to 10 parts by mass.

[0071] [Optional ingredients] The composition of the present invention may further contain other components (optional components) as needed, provided that the effects and purposes of the composition are not impaired. Examples of the optional components include various additives commonly used in rubber compositions, such as fillers other than the above-mentioned fillers, silane coupling agents, terpene resins (e.g., aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), and vulcanization accelerators.

[0072] [Silane coupling agent] The composition of the present invention preferably contains a silane coupling agent, because the effects of the present invention are more excellent. The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferred because the effects of the present invention are more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 to 16, and more preferably 1 to 4, because the effects of the present invention are more excellent. Examples of alkoxy groups having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

[0073] The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, such as an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group (particularly, a polysulfide group (-S n - (n is an integer of 2 or more), a mercapto group, a blocked mercapto group (protected mercapto group) (for example, an octanoylthio group), and the like. Among these, a sulfide group (particularly a disulfide group or a tetrasulfide group), a mercapto group, and a blocked mercapto group are preferred because they provide better effects of the present invention. The silane coupling agents may be used alone or in combination of two or more.

[0074] The silane coupling agent is preferably a sulfur-containing silane coupling agent, since this provides a better effect of the present invention.

[0075] Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, and the like. One of these may be used alone, or two or more may be used in combination.

[0076] <Content> In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 2 to 20 mass % relative to the content of the above-mentioned filler (particularly silica), and more preferably 5 to 15 mass %.

[0077] [Method of manufacturing rubber composition for tires] The method for producing the composition of the present invention is not particularly limited, and specific examples thereof include a method of kneading the above-mentioned components using a known method or apparatus (e.g., a Banbury mixer, a kneader, a roll, etc.) When the composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than the sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 155°C), cool the mixture, and then mix the sulfur or the vulcanization accelerator. The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0078] [2] Manufacturing method for specific fine particles The method for producing the above-mentioned specific fine particles is not particularly limited as long as it is a method for producing using the above-mentioned specific composition, but because the effects of the present invention are better, it is preferable to use a method for obtaining polyurethane fine particles by reacting a polyol, a polyisocyanate, and water in oil (hereinafter also referred to as "production method 1 of the present invention"), and more preferable to use a method comprising the following steps (hereinafter also referred to as "production method 2 of the present invention"). (1) Dispersion process A process for obtaining a dispersion by dispersing water and polyol in oil. (2) Polymerization process A step of mixing polyisocyanate into the dispersion system to polymerize the polyol and the polyisocyanate and generate carbon dioxide, thereby obtaining polyurethane microparticles dispersed in oil.

[0079] The components contained in the specific composition are as described above.

[0080] [Content of fine particles in dispersion] According to the production methods 1 and 2 of the present invention, polyurethane fine particles dispersed in oil can be obtained. The content of polyurethane microparticles in the dispersion (the proportion of polyurethane microparticles in the entire dispersion) (hereinafter also referred to as "microparticle content in the dispersion") is preferably 10 to 60% by mass, because this provides better effects of the present invention.

[0081] [3] Tires The tire of the present invention is a tire manufactured using the composition of the present invention described above. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, or other gases. The tire of the present invention is particularly useful as a studless tire because of its excellent performance on ice.

[0082] 1 shows a partial cross-sectional schematic view of a tire representing one example of an embodiment of the tire of the present invention, although the tire of the present invention is not limited to the embodiment shown in FIG.

[0083] In FIG. 1, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion (tread portion). Between the pair of left and right bead portions 1, a carcass layer 4 with fiber cords embedded therein is mounted, and the ends of this carcass layer 4 are folded back and wrapped around the bead core 5 and bead filler 6 from the inside to the outside of the tire. In the tire tread portion 3, a belt layer 7 is disposed on the outer side of the carcass layer 4 around the entire circumference of the tire. In addition, a rim cushion 8 is disposed in the bead portion 1 at the portion that comes into contact with the rim. At least the tire tread portion 3 is formed from the above-described composition of the present invention.

[0084] The tire of the present invention can be manufactured, for example, by a conventionally known method. The gas to be filled into the tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0086] [Production of fine particles] Each microparticle was produced as follows.

[0087] Here, as described below, microparticles 1 to 4 have an average particle size of 1 to 300 μm and are polyurethane microparticles obtained from a composition containing a polyol, a polyisocyanate, water, and oil as a dispersion medium, where the polyol is a vegetable oil-based polyol (castor oil-based polyol) (i.e., satisfying condition (1)), and therefore correspond to the above-mentioned specific microparticles. Furthermore, as described below, microparticles 5 have an average particle size of 1 to 300 μm and are polyurethane microparticles obtained from a composition containing a polyol, a polyisocyanate, and water, where the polyol is a vegetable oil-based polyol (castor oil-based polyol) and the polyisocyanate is a biomass-based polyisocyanate (i.e., satisfying conditions (1) and (2)), and therefore correspond to the above-mentioned specific microparticles. Furthermore, as described below, the microparticles 6 have an average particle diameter of 1 to 300 μm and are polyurethane microparticles obtained from a composition containing polyol, polyisocyanate, water, and oil as a dispersion medium, in which the polyisocyanate is a biomass-based polyisocyanate (i.e., satisfying condition (1)), and therefore correspond to the above-mentioned specific microparticles.

[0088] On the other hand, as described below, comparative microparticles 1 have an average particle size of 1 to 300 μm, but are polyurethane microparticles obtained from a composition that does not contain water, and therefore do not fall under the category of the above-mentioned specific microparticles. Also, as described below, comparative microparticles 2 have an average particle size of 1 to 300 μm, but are polyurethane microparticles obtained from a composition that does not satisfy either condition (1) or (2), and therefore do not fall under the category of the above-mentioned specific microparticles. Also, as described below, comparative microparticles 3 are polyurethane microparticles obtained from a composition that contains a polyol, a polyisocyanate, water, and an oil as a dispersion medium, in which the polyol is a vegetable oil-based polyol (castor oil-based polyol) (i.e., satisfies condition (1)), but have an average particle size of more than 300 μm, and therefore do not fall under the category of the above-mentioned specific microparticles.

[0089] The apparent density of particles 1 to 6 is 1.00 g / cm 3 Super 1.50g / cm 3 It was as follows.

[0090] [Fine particles 1]

[0091] <Dispersion process> 100 g of castor oil-based polyol (URIC H-52, manufactured by Ito Oil Mills, hydroxyl value 203 mgKOH / g), 10 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 g of silicone foam stabilizer (Niax silicone L-5111, manufactured by Momentive Performance Materials, Inc.), 1 g of water, and 262 g of oil (Extract No. 4S, manufactured by Shell Lubricants Japan) were stirred for 3 minutes using a planetary centrifugal mixer to obtain a dispersion.

[0092] <Polymerization process> 150 g of polymeric MDI (Millionate MR-400 manufactured by Tosoh Corporation, NCO% 30%) was added to the obtained dispersion and stirred for 30 minutes to polymerize the polyol and polyisocyanate while generating carbon dioxide, resulting in polyurethane microparticles dispersed in oil. The microparticle content in the dispersion was 50 mass %. The obtained polyurethane microparticles are also referred to as microparticles 1, and the dispersion of microparticles 1 dispersed in oil is also referred to as microparticle dispersion 1.

[0093] The average particle size of the fine particles 1 was measured using a laser diffraction particle size distribution measuring device and found to be 120 μm.

[0094] [Fine particles 2] Polyurethane microparticles dispersed in oil were obtained following the same procedure as for microparticles 1, except that a castor oil-based polyol (URIC H-1830 manufactured by Ito Oil Mills, hydroxyl value 82 mgKOH / g) was used instead of the URIC H-52, the amount of triethanolamine was changed to 3 g, the amount of polymeric MDI was changed to 200 g, and the amount of oil was changed to 305 g. The microparticle content in the dispersion was 50 mass %. The obtained polyurethane microparticles are also referred to as microparticles 2, and the dispersion of microparticles 2 dispersed in oil is also referred to as microparticle dispersion 2.

[0095] The average particle size of the fine particles 2 was measured using a laser diffraction particle size distribution measuring device and found to be 72 μm.

[0096] [Fine particles 3] Polyurethane microparticles dispersed in oil were obtained by the same procedure as for microparticles 1, except that a castor oil-based polyol (URIC HF-2009 manufactured by Ito Oil Mills, hydroxyl value 43 mgKOH / g) was used instead of the URIC H-52. The microparticle content in the dispersion was 50 mass%. The obtained polyurethane microparticles are also referred to as microparticles 3, and the dispersion of microparticles 3 dispersed in oil is also referred to as microparticle dispersion 3.

[0097] The average particle size of the fine particles 3 was measured using a laser diffraction particle size distribution measuring device and found to be 30 μm.

[0098] [Fine particles 4]

[0099] <Dispersion process> 100 g of castor oil-based polyol (URIC HF-2009, manufactured by Ito Oil Mills, hydroxyl value 43 mgKOH / g), 10 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 g of silicone foam stabilizer (Niax silicone L-5111, manufactured by Momentive Performance Materials, Inc.), 1 g of water, and 297 g of oil (Extract No. 4S, manufactured by Shell Lubricants Japan) were stirred for 3 minutes using a planetary centrifugal mixer to obtain a dispersion.

[0100] <Polymerization process> To the resulting dispersion, 150 g of polymeric MDI (Millionate MR-400 manufactured by Tosoh Corporation, NCO% 30%) was added and stirred for 30 minutes. Next, 40 g of ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred for 10 minutes. In this way, the polyol, polyisocyanate, and ethanol were polymerized while carbon dioxide was generated, yielding polyurethane microparticles dispersed in oil. The microparticle content in the dispersion was 50 mass %. The obtained polyurethane microparticles are also referred to as microparticles 4, and the dispersion of microparticles 4 dispersed in oil is also referred to as microparticle dispersion 4.

[0101] The average particle size of the fine particles 4 was measured using a laser diffraction particle size distribution measuring device and found to be 18 μm.

[0102] [Fine particles 5]

[0103] <Dispersion process> 100 g of castor oil-based polyol (URIC HF-2009, manufactured by Ito Oil Mills, hydroxyl value 43 mgKOH / g), 10 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 1 g of 2-[2-(dimethylamino)ethoxy]ethanol, 2 g of silicone foam stabilizer (Niax silicone L-5111, manufactured by Momentive Performance Materials, Inc.), 10 g of water, and 273 g of oil (Extract No. 4S, manufactured by Shell Lubricants Japan) were stirred for 3 minutes using a planetary centrifugal mixer to obtain a dispersion.

[0104] <Polymerization process> 150 g of biomass-based polyisocyanate (biomass-based PDI isocyanurate) (Stabio D-376N, manufactured by Mitsui Chemicals, Inc., NCO% 24%) was added to the resulting dispersion and stirred for 30 minutes to polymerize the polyol and polyisocyanate while generating carbon dioxide, yielding polyurethane microparticles dispersed in oil. The microparticle content in the dispersion was 50 mass %. The resulting polyurethane microparticles are also referred to as microparticles 5, and the dispersion of microparticles 5 dispersed in oil is also referred to as microparticle dispersion 5.

[0105] The average particle size of the fine particles 5 was measured using a laser diffraction particle size distribution measuring device and was found to be 37 μm.

[0106] [Fine particles 6] Polyurethane microparticles dispersed in oil were obtained by the same procedure as for microparticles 5, except that polypropylene glycol (Sanyo Chemical Industries, Ltd., Sannix, hydroxyl value 53 mgKOH / g) was used instead of the URIC HF-2009. The microparticle content in the dispersion was 50 mass%. The obtained polyurethane microparticles are also referred to as microparticles 6, and the dispersion of microparticles 6 dispersed in oil is also referred to as microparticle dispersion 6.

[0107] The average particle size of the fine particles 6 was measured using a laser diffraction particle size distribution measuring device and found to be 62 μm.

[0108] [Comparative fine particle 1] 55 g of castor oil-based polyol (URIC HF-2009, manufactured by Ito Oil Mills, hydroxyl value 43 mgKOH / g), 14 g of dimethylthiotoluenediamine (Heartcure 30, manufactured by Kumiai Chemical Co., Ltd.), 92 g of liquid isoprene polymer (LIR-30, manufactured by Kuraray Co., Ltd.), and 1 g of sorbitan acid-based surfactant (TW-O320V, manufactured by Kao Corporation) were stirred for 2 minutes using a planetary centrifugal mixer. A dispersion was thus obtained. 11 g of polymeric MDI (Coronate 1331, manufactured by Tosoh Co., Ltd., NCO% 32%) was added to the resulting dispersion and stirred for 2 minutes. Next, 11 g of maleic anhydride-modified polyisoprene (LIR-403, manufactured by Kuraray Co., Ltd.) was added and stirred for 1 hour to polymerize the polyol and polyisocyanate, resulting in polyurethane microparticles dispersed in the liquid isoprene. The microparticle content in the dispersion was 50% by mass. The obtained polyurethane microparticles are also referred to as comparative microparticles 1, and the dispersion of comparative microparticles 1 dispersed in liquid isoprene is also referred to as comparative microparticle dispersion 1.

[0109] The average particle size of the comparative fine particles 1 was measured using a laser diffraction particle size distribution measuring device and found to be 16 μm.

[0110] The comparative particle dispersion 1 is almost the same as the particle dispersion 1 described in paragraph

[0037] of JP-A No. 2022-164378.

[0111] [Comparative fine particle 2] Polyurethane microparticles dispersed in oil were obtained by the same procedure as for microparticles 1, except that polypropylene glycol (Sanyo Chemical Industries, Ltd., hydroxyl value 53 mgKOH / g) was used instead of the URIC H-52. The microparticle content in the dispersion was 50 mass%. The obtained polyurethane microparticles are also referred to as comparative microparticles 2, and the dispersion of comparative microparticles 2 dispersed in oil is also referred to as comparative microparticle dispersion 2.

[0112] The average particle size of the comparative fine particles 2 was measured using a laser diffraction particle size distribution measuring device and found to be 55 μm.

[0113] [Comparative fine particle 3] Polyurethane microparticles dispersed in oil were obtained by the same procedure as for microparticles 1, except that a castor oil-based polyol (URIC H-1830 manufactured by Ito Oil Mills, hydroxyl value 82 mgKOH / g) was used instead of the URIC H-52 and the amount of water was changed to 13 g. The microparticle content in the dispersion was 50 mass %. The obtained polyurethane microparticles are also referred to as comparative microparticles 3, and the dispersion of comparative microparticles 3 dispersed in oil is also referred to as comparative microparticle dispersion 3.

[0114] The average particle size of the comparative fine particles 3 was measured using a laser diffraction particle size distribution measuring device and found to be 341 μm.

[0115] [Production of rubber composition for tires] The components shown in Tables 1 and 2 below were blended in the proportions (parts by mass) shown in the tables. Specifically, first, the components except for the sulfur and vulcanization accelerator were kneaded in a 1.7-liter internal mixer for 5 minutes, and then released when the temperature reached 150°C to obtain a master batch. Next, the sulfur and vulcanization accelerator were kneaded into the obtained master batch using an open roll to obtain a rubber composition for tires. The parts by mass of the oil (aromatic oil) were adjusted so that the total of the oil or liquid isoprene polymer in the microparticle dispersion and the oil (aromatic oil) was 20 parts by mass.

[0116] [evaluation] The resulting rubber compositions for tires were evaluated as follows.

[0117] [Elongation at break] The obtained rubber composition for tires was vulcanized at 170°C for 10 minutes using a mold of a predetermined shape (inner dimensions: length 150 mm, width 150 mm, thickness 2 mm) to prepare a vulcanized rubber test piece. Using the vulcanized rubber test piece, a dumbbell JIS No. 3 test piece was prepared in accordance with JIS K6251, and a tensile test was performed at room temperature (20°C) at a pulling rate of 500 mm / min to measure the tensile elongation at break. The obtained results are shown in Tables 1 and 2 as an index, with the value of Reference Example 1 being 100. A higher index means a higher tensile elongation at break. An index of 106 or more is preferred.

[0118] [Ice performance] The resulting rubber composition for tires was used in the tread portion, and the tire was vulcanized and molded to produce a pneumatic tire (tire size: 215 / 60R16). The pneumatic tire was mounted on a 16x7J rim, inflated to an air pressure of 220 kPa, and mounted on a test vehicle (a domestically produced 2-liter sedan, front-wheel drive). Next, the test vehicle was suddenly braked from an initial speed of 40 km / h on a test course with an ice surface, and the braking distance until the vehicle came to a complete stop was measured. The braking distances measured as described above are shown in Tables 1 and 2 as an index, with the reciprocal of Reference Example 1 set to 100. A higher index indicates better on-ice performance. An index of 106 or higher is preferred.

[0119] [Table 1]

[0120] [Table 2]

[0121] Details of each component in Tables 1 and 2 are as follows. NR: Natural rubber, STR20 (glass transition temperature: -65°C) BR: Butadiene rubber, Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (glass transition temperature: -110°C) Silica: Evonik Degussa ULTRASIL VN3 Carbon black: Cabot Japan Show Black N339 Silane coupling agent: Evonik Degussa Si69 Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Co., Ltd. Stearic acid: Beads of Stearic Acid YR manufactured by NOF Corporation Antioxidant: Amine-based antioxidant, Santoflex 6PPD manufactured by Flexis Wax: Paraffin wax manufactured by Ouchi Shinko Chemical Co., Ltd. Oil: Aroma oil, Shell Lubricants Japan Extract No. 4S Sulfur: 5% oil-treated sulfur manufactured by Hosoi Chemicals Vulcanization accelerator: Sulfenamide vulcanization accelerator, Sancerer CM-G manufactured by Sanshin Chemical Co., Ltd. Fine particle dispersions 1 to 6: Fine particle dispersions 1 to 6 prepared as described above Comparative microparticle dispersions 1 to 3: Comparative microparticle dispersions 1 to 3 prepared as described above

[0122] In addition, "isocyanate group / active hydrogen group" and "average particle size" in Tables 1 and 2 respectively represent the above-mentioned "isocyanate group / active hydrogen group" and "average particle size" of the specific fine particles.

[0123] As can be seen from Tables 1 and 2, Examples 1 to 7, which contained specific fine particles, all exhibited excellent elongation at break and performance on ice. Comparing Examples 1 to 5 and Example 7 (comparison between embodiments in which the content of specific fine particles is 5 parts by mass per 100 parts by mass of diene rubber), Examples 2 to 5 and Example 7, in which the hydroxyl value of the polyol contained in the specific composition is 10 to 200 mgKOH / g, showed better elongation at break. Among them, Examples 3 to 5, in which the ratio of isocyanate groups to active hydrogen groups of the specific composition was 0.8 to 6.0 and the specific composition satisfied at least condition (1), showed better performance on ice. Comparing Examples 5 and 6 (comparison between embodiments differing only in the content of specific fine particles), Example 5, in which the content of specific fine particles per 100 parts by mass of diene rubber was 10 parts by mass or less, showed better elongation at break.

[0124] On the other hand, Comparative Example 1, which used polyurethane microparticles obtained from a composition that did not contain water, Comparative Example 2, which used polyurethane microparticles obtained from a composition that did not satisfy either condition (1) or (2), and Comparative Example 3, which used polyurethane microparticles with an average particle size of more than 300 μm, had insufficient performance on ice. Comparative Examples 1 and 3 also had insufficient elongation at break. [Explanation of symbols]

[0125] 1 Bead section 2 Sidewall 3 Tire tread 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Rim Cushion

Claims

1. A rubber composition for tires comprising 100 parts by mass of a diene rubber, 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers, and 0.1 to 30 parts by mass of polyurethane fine particles having an average particle size of 1 to 300 μm, The rubber composition for tires, wherein the polyurethane microparticles are obtained from a composition containing a polyol, a polyisocyanate, water, and an oil as a dispersion medium, and the composition satisfies at least one of the following conditions (1) and (2): Condition (1): The polyol is a vegetable oil-based polyol. Condition (2): The polyisocyanate is a biomass-based polyisocyanate.

2. The rubber composition for a tire according to claim 1, wherein the composition further comprises an amine catalyst, and the amine catalyst comprises a tertiary amine catalyst.

3. The rubber composition for a tire according to claim 1 , wherein the oil comprises an aromatic oil.

4. The rubber composition for a tire according to claim 1, wherein the composition further comprises a surfactant, and the surfactant comprises a silicone-based foam stabilizer.

5. 2. The rubber composition for a tire according to claim 1, wherein the polyol comprises at least one vegetable oil-based polyol selected from the group consisting of castor oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g and soybean oil-based polyols having a hydroxyl value of 10 to 200 mgKOH / g.

6. 2. The rubber composition for tires according to claim 1, wherein the molar ratio of isocyanate groups to active hydrogen groups in the composition is 0.8 to 6.

0.

7. the diene rubber includes natural rubber and butadiene rubber, The rubber composition for a tire according to claim 1, wherein the proportion of the butadiene rubber relative to the total amount of the diene rubber is 30% by mass or more.

8. A studless tire manufactured by using the rubber composition for tires according to any one of claims 1 to 7 in a tread portion.

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