Rubber composition for tires, and winter tires

Abstract

To provide a rubber composition for a tire which exhibits excellent modulus, elongation at break and on-ice performance and to provide a tire produced by using the rubber composition for a tire.SOLUTION: There is provided a rubber composition for a tire which comprises 100 pts.mass of a diene-based rubber having a glass transition temperature of -50°C or less, 30 to 100 pts.mass of a specific filler and 0.1 to 30 pts.mass of polyurethane foam particulates, wherein the polyurethane foam particulates is produced by a production method which comprises a dispersion step of dispersing water, a specific polyol in a liquid to obtain a dispersion system and a polymerization step of polymerizing a polyol and a polyisocyanate by mixing the polyisocyanate with the dispersion system so that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0 and generating carbon dioxide to obtain polyurethane foam particulates having an apparent density of 1.00 g / cm3 or less dispersed in the liquid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a rubber composition for tires and winter tires. [Background technology]

[0002] From the perspective of improving tire performance, various compounding agents to be added to tire rubber compositions are being investigated. For example, Patent Document 1 proposes adding crosslinked polyurethane beads to a tire rubber composition from the viewpoint of improving ice performance and wet performance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6883060 [Overview of the project] [Problems that the invention aims to solve]

[0004] Recently, from a safety perspective, there has been a demand for further improvements in the modulus (especially 100% modulus) and elongation at break after vulcanization, as well as in the ice performance of the tire when it is made into a tire, for rubber compositions used in tires. In this context, when the present inventors examined the tire rubber composition described in Patent Document 1, it became clear that, considering future requirements, further improvements in modulus and elongation at break after vulcanization, as well as ice performance when made into a tire, are desirable.

[0005] Therefore, in view of the above circumstances, the object of the present invention is to provide a tire rubber composition that exhibits excellent modulus and elongation at break after vulcanization, and excellent ice performance when made into a tire, as well as a tire manufactured using the above tire rubber composition. [Means for solving the problem]

[0006] As a result of diligent research into the above-mentioned problems, the inventors of this invention discovered that these problems could be solved by incorporating polyurethane foamed microparticles manufactured by a specific method, leading to the present invention. In other words, the inventors have found that the above problem can be solved by the following configuration.

[0007] (1) A tire rubber composition comprising 100 parts by mass of a diene rubber having a glass transition temperature of -50°C or lower, 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 foamed fine particles, The above polyurethane foamed fine particles A dispersion step is performed by dispersing water and a polyol with a hydroxyl value of 40-350 mgKOH / g in a liquid to obtain a dispersion system. By mixing polyisocyanate into the above dispersion system such that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0, the polyol and polyisocyanate are polymerized, and carbon dioxide is generated, resulting in an apparent density of 1.00 g / cm³ dispersed in the liquid. 3 A rubber composition for tires, comprising polyurethane foamed fine particles obtained by a method for producing polyurethane foamed fine particles, which includes a polymerization step to obtain the following polyurethane foamed fine particles. (2) The tire rubber composition according to (1) above, wherein the average particle size of the polyurethane foamed fine particles is 1 to 300 μm. (3) The tire rubber composition according to (1) or (2) above, wherein the polyol is a plant-derived polyol. (4) The tire rubber composition according to any one of (1) to (3) above, wherein in the dispersion step above, a chain extender is further dispersed in the liquid. (5) The tire rubber composition according to any one of (1) to (4) above, wherein in the dispersion step above, a tertiary amine having a hydroxyl group is further dispersed in the liquid as a catalyst. (6) The rubber composition for a tire according to any one of (3) to (5) above, wherein the plant-derived polyol contains at least one of castor oil-based polyol and sebacic acid-based polyester polyol. (7) A winter tire manufactured using the rubber composition for a tire according to any one of (1) to (6) above. [Effects of the Invention]

[0008] As shown below, according to the present invention, there can be provided a rubber composition for a tire that exhibits excellent modulus and elongation at break after vulcanization and excellent ice performance when formed into a tire, and a tire manufactured using the rubber composition for a tire. [Brief Description of the Drawings]

[0009] [Figure 1] It is a schematic partial cross-sectional view showing an example of an embodiment of the tire of the present invention. [Modes for Carrying Out the Invention]

[0010] Hereinafter, the rubber composition for a tire of the present invention and the tire of the present invention will be described. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. Also, each component may be used alone or in combination of two or more. Here, when two or more of each component are used in combination, the content of that component refers to the total content unless otherwise specified. Also, for the rubber composition for a tire, the 100% modulus after vulcanization is also simply referred to as "100% modulus" or "M100", the elongation at break after vulcanization is also simply referred to as "elongation at break", and the ice performance when formed into a tire is also simply referred to as "ice performance". Also, the fact that M100 is excellent (M10 is large), the elongation at break is excellent (the elongation at break is large), and the ice performance is excellent are collectively also referred to as "the effects of the present invention are excellent". Furthermore, in this specification, the hydroxyl group of water is not included in the active hydrogen group.

[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 This is a rubber composition for tires containing 100 parts by mass of a diene rubber having a glass transition temperature of -50°C or lower, 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 foamed fine particles. Here, the polyurethane foamed microparticles are A dispersion step involves dispersing water and a polyol with a hydroxyl value of 40-350 mgKOH / g (hereinafter also referred to as "specific polyol") in a liquid to obtain a dispersion system. By mixing polyisocyanate into the above dispersion system such that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0, the polyol and polyisocyanate are polymerized, and carbon dioxide is generated, resulting in an apparent density of 1.00 g / cm³ dispersed in the liquid. 3 The polyurethane foamed fine particles (hereinafter also referred to as "the fine particles of the present invention") are obtained by a method for producing polyurethane foamed fine particles (hereinafter also referred to as "the method for producing the present invention") which comprises a polymerization step to obtain the following polyurethane foamed fine particles.

[0012] The composition of the present invention is thought to be able to solve the above-mentioned problems by adopting such a configuration. The reason for this is not clear, but it is thought to be roughly as follows. The composition of the present invention contains polyurethane foamed fine particles (fine particles of the present invention) manufactured by a specific method (manufacturing method of the present invention). In the manufacturing method of the present invention, during the polymerization step, the hydroxyl group of the polyol reacts with the isocyanate group of the polyisocyanate to form a urethane bond (-NH-COO-). Furthermore, since the dispersion obtained in the dispersion step contains water, the water reacts with the isocyanate group to generate an amino group. Carbon dioxide is generated at this time. In addition, the generated amino group reacts with the isocyanate group to form a urea bond (-NH-CO-NH-). As a result, in the polymerization process described above, the polyol and polyisocyanate polymerize to produce polyurethane having urethane and urea bonds. At this time, the polymerization proceeds in a dispersion system dispersed in a liquid, and as mentioned above, carbon dioxide is generated, so the resulting polyurethane becomes fine particles (polyurethane foamed fine particles) with a cavity structure. Here, the hydroxyl group content of the polyol is 40-350 mg KOH / g, and the molar ratio of isocyanate groups to active hydrogen groups is 1.5-6.0. Therefore, the apparent density of the resulting polyurethane foamed microparticles is 1.00 g / cm³. 3 It is thought that the following will occur. When such fine particles of the present invention are incorporated into a tire rubber composition, the resulting tire will have a cavity structure derived from the fine particles of the present invention. This is thought to form irregularities on the tire surface, improving friction and water absorption, and leading to excellent performance on ice. Furthermore, as described above, the fine particles of the present invention have urethane bonds and urea bonds. When such fine particles of the present invention are incorporated into a tire rubber composition, it is believed that a tough three-dimensional structure is formed by hydrogen bonding of the urethane bonds and urea bonds, resulting in excellent M100 and elongation at break.

[0013] The components contained in the composition of the present invention will be described below.

[0014] [Diene-based rubber] The diene rubber contained in the composition of the present invention is not particularly limited as long as it is a diene rubber having a glass transition temperature of -50°C or lower. The diene rubber is in solid form. The composition of the present invention may contain one type of diene rubber or two or more types of diene rubber.

[0015] [Specific examples] 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), and chloroprene rubber (CR). Examples of aromatic vinyl-conjugated diene copolymer rubbers include styrene-butadiene rubber (SBR) and styrene-isoprene copolymer rubber. The diene rubber preferably contains at least one selected from the group consisting of butadiene rubber, isoprene rubber, and natural rubber, and more preferably contains butadiene rubber and natural rubber, for the reasons that the effects of the present invention are superior.

[0016] When the above-mentioned diene rubber includes at least one selected from the group consisting of butadiene rubber and natural rubber, the total content of butadiene rubber and natural rubber relative to the total diene rubber is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, for the reasons that the effects of the present invention are superior. There is no particular upper limit, and it is 100% by mass.

[0017] [Molecular weight] The number-average molecular weight (Mn) of the diene rubber is not particularly limited, but for reasons that the effects of the present invention are superior, 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 above diene rubber is not particularly limited, but for the reasons that the effects of the present invention are superior, 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 standard polystyrene equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions. • Solvent: tetrahydrofuran • Detector: RI detector

[0019] [Glass transition temperature] The glass transition temperature (Tg) of diene rubbers is -50°C or lower. In this specification, the glass transition temperature of diene rubber refers to the glass transition temperature (Tg) of a diene rubber if the tire rubber composition contains one type of diene rubber, and the weighted average of the glass transition temperatures obtained by multiplying the glass transition temperature (Tg) of each diene rubber by its mass fraction if the tire rubber composition contains two or more types of diene rubber. For example, in Example 1 described later, the tire rubber composition contains 50 parts by mass of natural rubber (Tg: -65°C) and 50 parts by mass of butadiene rubber (Tg: -110°C), so the Tg of the diene rubber is -87.5°C (= (-65°C) × (50 / (50 + 50)) + (-110°C) × (50 / (50 + 50)).

[0020] The Tg of the diene rubber is preferably -60°C or lower, more preferably -70°C or lower, and even more preferably -80°C or lower, for the sake of superior effects of the present invention. The upper limit of the above Tg is not particularly limited, but it is preferably -150°C or higher, and more preferably -100°C or higher, for the sake of superior effects of the present invention.

[0021] When the composition of the present invention contains two or more types of diene rubber, it is preferable that the Tg of all diene rubbers be -50°C or lower, for which the effects of the present invention are superior.

[0022] [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 more preferably contains both carbon black and a white filler (particularly silica) for superior effects of the present invention.

[0023] [Carbon Black] The carbon black mentioned above 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 described above is not particularly limited, but for the reason that the effects of the present invention are superior, it is 50 to 200 m². 2 It is preferable that the value be / g, and 70-150m 2 It is more preferable that it be / g. Here, the nitrogen adsorption specific surface area (N2SA) is the value obtained by measuring the amount of nitrogen adsorbed onto the carbon black surface according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0024] [White filler] The above-mentioned white filler is not particularly limited, but examples include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium dioxide, calcium sulfate, etc. Among these, silica is preferred because it exhibits superior effects compared to the present invention.

[0025] The silica mentioned above is not particularly limited, but examples include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it provides superior effects in the present invention.

[0026] The specific surface area of ​​the above silica for cetyltrimethylammonium bromide (CTAB) adsorption is not particularly limited, but for superior effects of the present invention, 100 to 400 m² is preferred. 2It is preferable that the amount be / g, and 150-300m 2 It is more preferable that it be / g. Here, the CTAB adsorption specific surface area is the value obtained by measuring the amount of CTAB adsorbed onto the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0027] [Content] In the composition of the present invention, the content of the filler is 30 to 100 parts by mass per 100 parts by mass of the diene rubber described above. In the composition of the present invention, the content of the filler is preferably 40 to 90 parts by mass, and more preferably 50 to 80 parts by mass, per 100 parts by mass of the diene rubber described above, for the reason that the effects of the present invention are superior.

[0028] If the composition of the present invention contains carbon black, the carbon black content is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of the diene rubber described above, for the reason that the effects of the present invention are superior.

[0029] When the composition of the present invention contains a white filler (particularly silica), the amount of the white filler is preferably 1 to 100 parts by mass, more preferably 10 to 90 parts by mass, even more preferably 20 to 80 parts by mass, and particularly preferably 30 to 70 parts by mass, per 100 parts by mass of the diene rubber described above, for the reason that the effects of the present invention are superior.

[0030] [Polyurethane foam microparticles] The polyurethane foamed fine particles of the present invention (fine particles of the present invention) are polyurethane foamed fine particles obtained by a method for producing polyurethane foamed fine particles of the present invention (manufacturing method of the present invention), which comprises the following dispersion step and the following polymerization step. (1) Dispersion process A process to obtain a dispersion by dispersing water and a polyol with a hydroxyl value of 40-350 mgKOH / g in a liquid. (2) Polymerization process By mixing polyisocyanate into the above dispersion system such that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0, the polyol and polyisocyanate are polymerized, and carbon dioxide is generated, resulting in an apparent density of 1.00 g / cm³ dispersed in the liquid. 3 The following process for obtaining polyurethane foamed microparticles

[0031] Furthermore, with respect to the fine particles of the present invention, there are circumstances that make it impossible or practically impractical to directly identify the substance by its structure or characteristics at the time of filing the application, as described below.

[0032] [Impossible / Practical Circumstances] In the polymerization step of the manufacturing method of the present invention, the reaction between the hydroxyl group of the polyol and the isocyanate group of the polyisocyanate (formation of urethane bonds), the reaction between the isocyanate group of the polyisocyanate and water (generation of amino groups), and the reaction between the amino groups generated by the reaction with water and the isocyanate group of the polyisocyanate (formation of urea bonds) are all in competition. That is, in the polymerization step described above, the polyisocyanate consists of a mixture of polyisocyanates that have reacted with water to form some amino groups, polyisocyanates where all isocyanate groups have reacted with water to form amino groups, and polyisocyanates where all isocyanate groups remain unchanged without reacting with water. These then react with the polyol or polyisocyanate. As a result, the structure of the fine particles of the present invention is extremely complex and cannot be represented by a general formula. This is common technical knowledge for those skilled in the art. Furthermore, if the structure is not specified, the properties of the substance determined accordingly cannot be easily determined, and when reacting multiple different monomers, the properties of the resulting polyurethane foam fine particles change significantly if their mixing ratio and reaction conditions are changed, making it impossible to describe them in terms of properties. In other words, the fine particles of the present invention cannot be directly identified by their structure or properties, and can only be identified through the process for obtaining polyurethane foamed fine particles.

[0033] The following describes each step.

[0034] [Dispersion process] The dispersion process involves dispersing water and a polyol (specific polyol) with a hydroxyl value of 40-350 mgKOH / g in an unmodified liquid diene polymer or liquid substance to obtain a dispersion system.

[0035] The following describes each component used in the dispersion process.

[0036] <Liquid> The liquid is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferable that the liquid (hereinafter also referred to as "specific liquid") contains at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil. The specified liquid substance may include liquid substances other than unmodified liquid diene polymers, mineral oils, and vegetable oils, but for reasons that the effects of the present invention are superior, it is preferable to include at least one selected from the group consisting of unmodified liquid diene polymers, mineral oils, and vegetable oils in an amount of 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferable to include 100% by mass (i.e., consisting of at least one selected from the group consisting of unmodified liquid diene polymers, mineral oils, and vegetable oils).

[0037] The specific liquid substance is preferably a liquid substance containing an unmodified liquid diene polymer, for which the effects of the present invention are superior.

[0038] (Unmodified liquid diene polymer) The unmodified liquid diene polymer is not particularly limited, and specific examples include liquid butadiene polymer, liquid aromatic vinyl-conjugated diene copolymer (e.g., liquid styrene-butadiene polymer), and liquid isoprene polymer. Among these, liquid isoprene polymer is preferred because it exhibits superior effects compared to the present invention.

[0039] The number-average molecular weight (Mn) of the unmodified liquid diene polymer is preferably 1,000 to 100,000, more preferably 10,000 or more and less than 50,000, and even more preferably 20,000 to 40,000, for the reasons that the effects of the present invention are superior.

[0040] (Mineral oil) Mineral oils are not particularly restricted, and specific examples include paraffinic, naphthenic, and aromatic oils.

[0041] (vegetable oil) The vegetable oil is not particularly limited, and specific examples include soybean oil, rapeseed oil, coconut oil, and linseed oil. Among these, soybean oil is preferred because it provides superior effects for the present invention.

[0042] (Amount used) The amount of the specific liquid used in the dispersion process is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 100 to 1000 parts by mass, more preferably 200 to 800 parts by mass, and even more preferably 300 to 600 parts by mass, per 100 parts by mass of the specific polyol described later.

[0043] <Water> As described above, the dispersion process involves dispersing water in a liquid.

[0044] (Amount used) The amount of water used in the dispersion process is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 7 to 13 parts by mass per 100 parts by mass of the specific polyol described later.

[0045] (Water / Isocyanate group) The molar ratio of water to isocyanate groups in the polyisocyanate described later (hereinafter also referred to as "water / isocyanate group") is preferably 0.1 to 0.6, and more preferably 0.2 to 0.5, for the reasons that the effects of the present invention are superior.

[0046] <Specific foam stabilizers> In the dispersion step, it is preferable to further disperse at least one of a nonionic surfactant and a silicone-based foam stabilizer (specific foam stabilizer) in the liquid for better effects of the present invention.

[0047] (Nonionic surfactants) The nonionic surfactant is not particularly limited, and conventionally known surfactants can be used. Specific examples include fatty acid sorbitan esters, polyoxyethylene fatty acid sorbitan, polyoxyethylene higher alcohol ethers, polyoxyethylene-propylene higher alcohol ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkylphenols, polyoxyethylene aliphatic hydrocarbon amines (e.g., polyoxyethylene alkylamines, polyoxyethylene alkyleneamines), polyoxyethylene aliphatic hydrocarbon amides (e.g., polyoxyethylene alkylamides, polyoxyethylene alkyleneamides), polyoxyethylene-polyoxypropylene block polymers, and polyoxyethylene sorbitan fatty acid esters. Among these, polyoxyethylene sorbitan fatty acid esters are preferred because they exhibit superior effects compared to the present invention.

[0048] (Silicone-based foam stabilizer) There are no particular restrictions on silicone-based foam stabilizers, and conventionally known ones can be used. The silicone-based foam stabilizer preferably has polysiloxane chains and polyoxyalkylene chains, and the polyoxyalkylene chains are modified from the polysiloxane chain, which is the main chain. The polysiloxane chain described above is preferably an organopolysiloxane chain. A specific example of an organopolysiloxane chain is a polydimethylsiloxane chain. Examples of the polyoxyalkylene chains mentioned above 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.

[0049] (Amount used) The amount of the specific foam stabilizer used in the dispersion process is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 7 to 13 parts by mass per 100 parts by mass of the specific polyol described later.

[0050] <Specific polyols> The polyol used in the dispersion process is a polyol with a hydroxyl value of 40 to 350 mgKOH / g. Here, a polyol is a compound having two or more hydroxyl groups.

[0051] Examples of polyols include polyether polyols; castor oil-based polyols such as castor oil, dehydrated castor oil, hydrogenated castor oil (a hydrogenated product of castor oil), and 5-50 molar alkylene oxide adducts of castor oil; polyester polyols (especially sebaci acid-based polyester polyols); polymer polyols having carbon-carbon bonds in their main chain structure, such as acrylic polyols, polybutadiene diols, and hydrogenated polybutadiene polyols; low molecular weight polyhydric alcohols; and mixed polyols of these. Among these, plant-derived polyols are preferred for the superior effects of the present invention, and castor oil-based polyols and sebaci acid-based polyester polyols (polyols obtained by the esterification reaction of sebaci acid and polyols) are more preferred. For superior effects of the present invention, the polyol preferably contains at least one of a castor oil-based polyol and a sebaciate-based polyester polyol.

[0052] (Hydroxyl value) As mentioned above, the hydroxyl value of polyols is 40-350 mgKOH / g. The hydroxyl value of the polyol is preferably 50-300 mgKOH / g, more preferably 100-250 mgKOH / g, and even more preferably 150-200 mgKOH / g, for reasons that the effects of the present invention are superior. The hydroxyl value is the hydroxyl value specified in JIS K 1557-1:2007, and represents the number of hydroxyl groups per gram of sample and the equivalent amount of potassium hydroxide in milligrams.

[0053] (Percentage of the total number of active hydrogen groups) The ratio (molar ratio) of hydroxyl groups of the polyol to the total number of 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 better effects of the present invention.

[0054] <Catalyst> In the dispersion step, it is preferable to further disperse the catalyst in a liquid for better performance of the present invention. The catalyst is not particularly limited as long as it is a catalyst that promotes the reaction between the polyol and the polyisocyanate, or the reaction between the polyisocyanate and water. The catalyst is preferably an amine or a compound having a hydroxyl group, more preferably an amine having a hydroxyl group (particularly a tertiary amine having a hydroxyl group), even more preferably a tertiary amine having three alcohol groups (-ROH, R: alkylene group), and particularly preferably triethanolamine.

[0055] (Amount used) The amount of catalyst used in the dispersion process is not particularly limited, but for the reasons that the effects of the present invention are superior, it is preferably 0.01 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the specified polyol described above.

[0056] (Percentage of the total number of active hydrogen groups) The ratio (molar ratio) of the active hydrogen groups (amino groups, hydroxyl groups) of the catalyst to the total number of active hydrogen groups is preferably 0.1 to 0.8, more preferably 0.2 to 0.6, and even more preferably 0.3 to 0.5, for better performance of the present invention.

[0057] <Chain extender> In the dispersion step, it is preferable to further disperse the chain extender in the liquid for better performance of the present invention. The chain extender is preferably a compound (polyamine) having two or more amino groups (-NH2) for the reason that the effects of the present invention are superior. When polyamines are used as chain extenders, they react with polyisocyanates, as described later, to form urea bonds.

[0058] Specific examples of polyamines include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, trimethylhexamethylenediamine, 1,2-propanediamine, iminobispropylamine, methyliminobispropylamine, and 1,5-diamino-2-methylpentane (MPMD, manufactured by DuPont Japan); metaphenylenediamine, orthophenylenediamine, paraphenylenediamine, m-xylylenediamine (MXDA), diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiethyldiphenylmethane, diethylmethylbenzenediamine, dimethylthiotoluenediamine (HeartCure 30, manufactured by Kumiai Chemical Co., Ltd.), 4,4'-methylenebis(2-chloroaniline), and 4,4'-methylenebis(3-chloro-2,6-diethylaniline). Aromatic polyamines such as limethylenebis(4-aminobenzoate) and bis(4-amino-2,3-dichlorophenyl)methane; N-aminoethylpiperazine; diamines with a polyether skeleton, exemplified by Jeffermin EDR148 manufactured by Sun Techno Chemical; isophorone diamine, 1,3-bisaminomethylcyclohexane (1,3BAC, manufactured by Mitsubishi Gas Chemical Co., Ltd.), 1-cyclohexylamino-3-aminopropane, 3-aminomethyl-3,3,5-trimethylcyclohexyl Examples include alicyclic polyamines such as liamine; diamines with a norbornane skeleton such as norbornanediamine (NBDA, manufactured by Mitsui Chemicals, Inc.); polyamidoamines having an amino group at the molecular terminus of the polyamide; and 2,5-dimethyl-2,5-hexamethylenediamine, mensendiamine, 1,4-bis(2-amino-2-methylpropyl)piperazine, and Jeffermin D230 and Jeffermin D400 manufactured by Sun Techno Chemical Co., Ltd., which have a polypropylene glycol (PPG) skeleton.

[0059] The polyamine is more preferably a compound having two amino groups (diamine), even more preferably an aromatic compound having two amino groups (aromatic diamine), and particularly preferably dimethylthiotoluenediamine.

[0060] (Usage amount) The amount of the chain extender used in the dispersion step is not particularly limited. However, for reasons of more excellent effects of the present invention, it is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 7 to 13 parts by mass with respect to 100 parts by mass of the above-mentioned specific polyol.

[0061] (Ratio to the total number of active hydrogen groups) When the chain extender is a polyamine, the ratio (molar ratio) of the amino group of the polyamine to the total number of active hydrogen groups is preferably 0 to 0.3, and more preferably 0.1 to 0.2 for reasons of more excellent effects of the present invention.

[0062] <Procedure of the dispersion step> Examples of the procedure of the dispersion step include a method of mixing the above-mentioned respective components and then stirring with a stirrer or the like.

[0063] <Dispersion system> By the dispersion step, a mixture (dispersion system) in which the above-mentioned respective components are dispersed in a liquid material is obtained.

[0064] 〔Polymerization step〕 In the polymerization step, polyisocyanate is mixed with the dispersion system obtained by the dispersion step so that the molar ratio of the isocyanate group to the active hydrogen group is 1.5 to 6.0, thereby polymerizing the polyol contained in the dispersion system and the above polyisocyanate and generating carbon dioxide, and obtaining polyurethane foam fine particles having an apparent density of 1.00 g / cm 3 in the following step. When the dispersion system obtained by the dispersion step contains a chain extender (such as diamine), in the polymerization step, the chain extender can also react with the polyisocyanate.

[0065] <Polyisocyanate> The polyisocyanates used in the manufacture of specific oligomers are not particularly limited as long as they are compounds having two or more isocyanate groups (-NCO). 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), tetramethyl xylylene diisocyanate (TMXDI), tollidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and triphenylmethane triisocyanate; Hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanate-methyl)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H 12 Aliphatic polyisocyanates (including alicyclic polyisocyanates), such as MDI; These carbodiimide-modified polyisocyanates; These are examples of isocyanurate-modified polyisocyanates.

[0066] For the sake of superior effects of the present invention, aromatic polyisocyanates are preferred, and MDI is even more preferred. Examples of the above-mentioned MDIs include monomeric MDI, polymeric MDI, and modified MDI (for example, carbodiimide-modified MDI). Among these, polymeric MDI is preferred because it exhibits superior effects compared to the present invention.

[0067] (Average number of functional groups) The average number of functional groups in 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, for better effects of the present invention. While there is no particular upper limit to the average number of functional groups in polyisocyanate, it is preferably 10 or less, more preferably 5 or less, and even more preferably 4 or less, for reasons that the effects of the present invention are superior. The average number of functional groups represents the average number of isocyanate groups present in the polyisocyanate.

[0068] (NCO increase) The NCO% of the polyisocyanate is preferably 5-80%, more preferably 10-50%, and even more preferably 20-40%, for better effects of the present invention. Note that NCO% represents the percentage (by mass) of isocyanate groups relative to the total polyisocyanate.

[0069] <Isocyanate group / active hydrogen group> As described above, in the polymerization step, polyisocyanate is mixed into the dispersion system obtained in the dispersion step so that the molar ratio of isocyanate groups to active hydrogen groups (hereinafter also referred to as "isocyanate group / active hydrogen group") is 1.5 to 6.0. Here, the active hydrogen group refers to the hydroxyl group of a specific polyol contained in the dispersion system. If the dispersion system contains a polyamine, which is a chain extender, it refers to the amino group of the polyamine in addition to the hydroxyl group of the specific polyol. If the dispersion system contains an amine or a compound having a hydroxyl group, which is a catalyst, it refers to the amino group of the amine or the hydroxyl group of the compound having a hydroxyl group in addition to the hydroxyl group of the specific polyol. The isocyanate group / active hydrogen group ratio is preferably 1.6 to 5.0, more preferably 1.7 to 4.0, and even more preferably 1.8 to 3.0, for better effects of the present invention.

[0070] <Procedure for the polymerization process> One possible procedure for the polymerization process is to mix the polyisocyanate with the dispersion obtained in the dispersion process, and then stir it with a stirrer or the like.

[0071] <Polyurethane foam microparticles> During the polymerization process, the apparent density of the dispersed material in the liquid is 1.00 g / cm³. 3 The following polyurethane foamed fine particles (fine particles of the present invention) are obtained.

[0072] (Apparent density) As mentioned above, the apparent density of polyurethane foamed microparticles is 1.00 g / cm³. 3 The following is the case: As mentioned above, polyurethane foam microparticles have a cavity structure due to the generation of carbon dioxide. Therefore, their apparent density is low. The apparent density of the polyurethane foamed fine particles obtained by the manufacturing method of the present invention is 1.00 g / cm³. 3 The following applies. The apparent density of polyurethane foamed microparticles is set to 0.95 g / cm³ for better performance in this invention. 3 Preferably, it is 0.90 g / cm³. 3 It is more preferable that the following is the case: 0.85 g / cm³ 3 The following is even more preferable: While there is no particular lower limit to the apparent density of polyurethane foamed fine particles, 0.50 g / cm³ is preferred for better performance in the present invention. 3 Preferably, it is 0.60 g / cm³ or more. 3 It is more preferable that the above conditions are met. In this specification, the apparent density of polyurethane foamed fine particles shall be determined by the water displacement method in accordance with JIS K7112.

[0073] (Average particle size) The average particle size of the polyurethane foamed fine particles is preferably 1 to 300 μm, more preferably 3 to 200 μm, even more preferably 5 to 100 μm, particularly preferably 7 to 50 μm, and most preferably 9 to 30 μm, for better effects of the present invention. In this specification, the average particle diameter of polyurethane foamed microparticles is the volume-average diameter measured using a laser diffraction particle size distribution analyzer.

[0074] (Content of fine particles in the dispersion) As described above, polyurethane foamed fine particles (the fine particles of the present invention) dispersed in a liquid are obtained by the polymerization process. Hereinafter, the liquid substance and the fine particles dispersed in the liquid substance will be collectively referred to as a "dispersion," and the liquid substance and the fine particles of the present invention dispersed in the liquid substance will be collectively referred to as the "dispersion of the present invention." The content of polyurethane foamed fine particles in the dispersion (the proportion of polyurethane foamed fine particles to the entire dispersion) (hereinafter also referred to as "content of fine particles in the dispersion") is preferably 10 to 60% by mass for the reasons that the effects of the present invention are superior.

[0075] [Content] In the composition of the present invention, the content of the fine particles of the present invention is 0.1 to 30 parts by mass per 100 parts by mass of the diene rubber described above. In the composition of the present invention, the content of the fine particles of the present invention is preferably 1 to 30 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the diene rubber described above, for the reason that the effects of the present invention are superior. Hereinafter, the content (parts by mass) of polyurethane foamed fine particles per 100 parts by mass of diene rubber will also be referred to as the "amount of fine particles".

[0076] In the composition of the present invention, the content of the dispersion of the present invention is preferably 2 to 60 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the diene rubber described above, for the reason that the effects of the present invention are superior.

[0077] [Optional ingredients] The composition of the present invention may optionally contain other components (optional components) as long as they do not impair its effects or purpose. Examples of the optional components mentioned above include silane coupling agents, terpene resins (e.g., aromatically modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc oxide), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), and various other additives commonly used in rubber compositions.

[0078] [Silane coupling agent] The composition of the present invention preferably contains a silane coupling agent for superior effects. 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 above hydrolyzable group is not particularly limited, but examples include alkoxy groups, phenoxy groups, carboxyl groups, and alkenyloxy groups. Among these, an alkoxy group is preferred because it provides superior effects of the present invention. 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, for superior effects of the present invention. Examples of alkoxy groups with 1 to 4 carbon atoms include methoxy groups, ethoxy groups, and propoxy groups.

[0079] The above organic functional groups are not particularly limited, but are preferably groups that can form chemical bonds with organic compounds, for example, epoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, amino groups, sulfide groups (especially polysulfide groups (-S) n Examples include (n is an integer of 2 or more), mercapto groups, blocked mercapto groups (protected mercapto groups) (e.g., octanoylthio groups), and among these, sulfide groups (especially disulfide groups, tetrasulfide groups), mercapto groups, and blocked mercapto groups are preferred because they provide superior effects for the present invention. Silane coupling agents may be used individually or in combination of two or more types.

[0080] The silane coupling agent described above is preferably a sulfur-containing silane coupling agent because it provides superior effects in the present invention.

[0081] Specific examples of the silane coupling agents mentioned above include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazoletetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, and 3-octanoylthio-1-propyltriethoxysilane. One of these may be used alone, or two or more may be used in combination.

[0082] In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but for reasons in which the effects of the present invention are superior, it is preferably 2 to 20% by mass, and more preferably 5 to 15% by mass, relative to the content of the filler (especially silica) mentioned above.

[0083] [Method for manufacturing rubber composition for tires] The method for producing the composition of the present invention is not particularly limited, and specific examples include, for example, a method of kneading each of the above-mentioned components using known methods and equipment (e.g., Banbury mixer, kneader, roll, etc.). If the composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 155°C), cool them, and then mix in the sulfur or vulcanization accelerator. Furthermore, the compositions of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0084] [2] 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, and other gases. In particular, it is preferable that the composition of the present invention is used (placed) in the tire tread (cap tread). The tire of the present invention is suitable for winter use because it has excellent performance on ice. Figure 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention, but the tire of the present invention is not limited to the embodiment shown in Figure 1.

[0085] In Figure 1, reference numeral 1 represents the bead portion, reference numeral 2 represents the sidewall portion, and reference numeral 3 represents the tire tread portion. Furthermore, a carcass layer 4 with embedded fiber cords is installed between the pair of left and right bead sections 1, 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. Furthermore, in the tire tread section 3, a belt layer 7 is arranged around the entire circumference of the tire, on the outside of the carcass layer 4. Furthermore, a rim cushion 8 is positioned in the bead portion 1 where it contacts the rim. The tire tread portion 3 is formed from the composition of the present invention as described above.

[0086] The tire of the present invention can be manufactured, for example, by conventionally known methods. In addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas to fill the tire. [Examples]

[0087] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0088] [Manufacturing of microparticles] The following types of microparticles were manufactured. Note that particles 1 to 8 correspond to the particles of the present invention as described above, while comparative particles 2 to 3 do not correspond to the particles of the present invention as described above.

[0089] [Fine particles 1]

[0090] <Dispersion process> 100 g of castor oil polyol (URIC AC-009, manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 223 mg KOH / g), 10 g of water, and 345 g of liquid isoprene polymer (LIR-30, manufactured by Kuraray Co., Ltd., with a number average molecular weight of 28,000) were stirred for 3 minutes in a rotary-orbiting stirrer in the presence of 10 g of dimethylthiotoluenediamine (HeartCure 30, manufactured by Kumiai Chemical Co., Ltd.), 15 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 10 g of silicone-based foam stabilizer (Niax silicone L-5111, manufactured by Momentive Performance Materials Inc.). In this way, a dispersion system was obtained by dispersing water, a silicone-based foam stabilizer, castor oil polyol (specific polyol), triethanolamine (catalyst), and dimethylthiotoluenediamine (chain extender) in the liquid isoprene polymer (specific liquid substance).

[0091] <Polymerization process> 200 g of polymeric MDI (Millionate MR-400, manufactured by Tosoh Corporation, with an NCO content of 30% and an average number of functional groups of 3.0) was added to the obtained dispersion and stirred for 3 minutes. This polymerized the castor oil polyol, polymeric MDI, and dimethylthiotoluenediamine, generating carbon dioxide and yielding polyurethane foamed microparticles dispersed in a liquid isoprene polymer (specific liquid). The obtained polyurethane foamed microparticles are also referred to as microparticle 1, and the dispersion of the liquid and microparticles 1 dispersed in the liquid is also referred to as microparticle dispersion 1.

[0092] When the obtained fine particles 1 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 2 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to be 0.89 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0093] [Fine particles 2] Polyurethane foamed microparticles were obtained by following the same procedure as for microparticle 1, except that a sebaciate-based polyester polyol (manufactured by Ito Oil Co., Ltd., URIC SE-2013C, with a hydroxyl value of 55.3 mg KOH / g) was used instead of the above-mentioned URIC AC-009, a nonionic surfactant (polyoxyethylene sorbitan trioleate, manufactured by Kao Corporation, TW-O320V) was used instead of the above-mentioned silicone-based foam stabilizer, the amount of the above-mentioned liquid isoprene polymer was changed to 445 g, and the amount of the above-mentioned polymeric MDI was changed to 300 g. The obtained polyurethane foamed microparticles are also called microparticles 2, and the dispersion of the liquid and microparticles 2 dispersed in the liquid is also called microparticle dispersion 2.

[0094] When the obtained fine particles 2 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 30 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 0.70 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0095] [Fine particles 3] Polyurethane foamed microparticles were obtained following the same procedure as for microparticle 1, except that castor oil polyol (URIC H-30, manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 160.0 mgKOH / g) was used instead of URIC AC-009. The obtained polyurethane foamed microparticles are also called microparticles 3, and the dispersion of the liquid and the microparticles 3 dispersed in the liquid is also called microparticle dispersion 3.

[0096] When the obtained fine particles 3 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 10 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 0.82 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0097] [Fine particles 4] Polyurethane foamed microparticles were obtained following the same procedure as for microparticle 1, except that castor oil polyol (URIC H-30, manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 160.0 mg KOH / g) was used instead of URIC AC-009, dimethylthiotoluenediamine was not used, and N-methyldiethanolamine was used instead of triethanolamine. The obtained polyurethane foamed microparticles are also called microparticles 4, and the dispersion of the liquid and microparticles 4 dispersed in the liquid is also called microparticle dispersion 4.

[0098] When the obtained fine particles 4 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 100 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 0.75 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0099] [Fine particles 5] Polyurethane foamed fine particles were obtained following the same procedure as for fine particles 1, except that mineral oil (Showa Shell Sekiyu Extract No. 4 S) was used instead of the liquid isoprene polymer mentioned above. The obtained polyurethane foamed fine particles are also referred to as fine particles 5, and the dispersion of the liquid and the fine particles 5 dispersed in the liquid is also referred to as fine particle dispersion 5.

[0100] When the obtained fine particles 5 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle size of 5 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to be 0.95 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0101] [Fine particles 6] Polyurethane foamed microparticles were obtained following the same procedure as for microparticle 1, except that vegetable oil (soybean oil manufactured by Riken Agricultural Chemicals Co., Ltd.) was used instead of the liquid isoprene polymer mentioned above. The obtained polyurethane foamed microparticles are also referred to as microparticles 6, and the dispersion of the liquid substance and the microparticles 6 dispersed in the liquid isoprene polymer is also referred to as microparticle dispersion 6.

[0102] When the obtained fine particles 6 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 7 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 0.94 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0103] [Fine particles 7] Polyurethane foamed microparticles were obtained by following the same procedure as for microparticle 1, except that the amount of the above liquid isoprene polymer was changed to 330 g and the above triethanolamine 15 g was replaced with DABCO (1,4-diazabicyclo[2.2.2]octantriethylenediamine, manufactured by Tokyo Chemical Industry Co., Ltd.) 0.05 g. The obtained polyurethane foamed microparticles are also called microparticles 7, and the dispersion of the liquid and the microparticles 7 dispersed in the liquid is also called microparticle dispersion 7.

[0104] When the obtained fine particles 7 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 2 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to be 0.97 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0105] [Fine particles 8] Polyurethane foamed microparticles were obtained following the same procedure as for microparticle 1, except that the polymeric MDI was replaced with monomeric MDI (Millionate MT, manufactured by Tosoh Corporation, with an NCO% of 33% and an average number of functional groups of 2.0). The obtained polyurethane foamed microparticles are also referred to as microparticles 8, and the dispersion of the liquid and the microparticles 8 dispersed in the liquid is also referred to as microparticle dispersion 8.

[0106] When the obtained fine particles 8 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 5 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 0.98 g / cm³. 3Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0107] [Comparative Particles 2]

[0108] <Dispersion process> 100 g of castor oil polyol (URIC AC-009, manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 223 mg KOH / g) and 375 g of liquid isoprene polymer (LIR-30, manufactured by Kuraray Co., Ltd., with a number-average molecular weight of 28,000) were stirred for 3 minutes in a rotary-orbiting stirrer in the presence of 50 g of dimethylthiotoluenediamine (HeartCure 30, manufactured by Kumiai Chemical Co., Ltd.), 15 g of triethanolamine, and 10 g of silicone-based foam stabilizer (Niax silicone L-5111, manufactured by Momentive Performance Materials Inc.). No water was added. In this way, a dispersion system was obtained by dispersing the silicone-based foam stabilizer, castor oil polyol (specific polyol), triethanolamine (catalyst), and dimethylthiotoluenediamine (chain extender) in the liquid isoprene polymer (specific liquid substance).

[0109] <Polymerization process> 200g of polymeric MDI (Millionate MR-400, manufactured by Tosoh Corporation, with an NCO content of 30% and an average number of functional groups of 3.0) was added to the obtained dispersion and stirred for 3 minutes to polymerize the castor oil polyol, polymeric MDI, and dimethylthiotoluenediamine, thereby obtaining polyurethane fine particles dispersed in a liquid isoprene polymer (specific liquid). Since no water was added in the dispersion process, no carbon dioxide was generated. The obtained polyurethane fine particles are also called comparative fine particles 2, and the dispersion of the liquid and comparative fine particles 2 dispersed in the liquid is also called comparative fine particle dispersion 2.

[0110] When the obtained comparative fine particles 2 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle diameter of 1 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to be 1.18 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0111] [Comparative Particles 3] Polyurethane foamed microparticles were obtained following the same procedure as for microparticle 1, except that the amount of liquid isoprene polymer was changed to 295 g and the amount of polymeric MDI was changed to 150 g. The obtained polyurethane foamed microparticles are also called comparative microparticles 3, and the dispersion of the liquid and comparative microparticles 3 dispersed in the liquid is also called comparative microparticle dispersion 3.

[0112] When the obtained comparative fine particles 3 were measured using a laser diffraction particle size distribution analyzer, it was confirmed that particles with an average particle size of 2 μm were generated. The apparent density of the fine particles was calculated using the water displacement method to 1.04 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0113] [Preparation of rubber compositions for tires] The components shown in Table 1 below were blended in the proportions (parts by mass) shown in the table. Specifically, first, the components excluding sulfur and vulcanization accelerator were kneaded in a 1.7-liter sealed mixer for 5 minutes, and released when the temperature reached 150°C to obtain a masterbatch. Next, sulfur and vulcanization accelerator were kneaded into the obtained masterbatch in an open roll to obtain a rubber composition for tires.

[0114] [evaluation] The following evaluations were performed on the obtained tire rubber compositions.

[0115] [M100 and elongation at break] The obtained tire rubber composition was vulcanized at 170°C for 15 minutes using a mold of a predetermined shape (internal dimensions: length 150 mm, width 150 mm, thickness 2 mm) to produce a vulcanized rubber sheet. For the obtained vulcanized rubber sheet, a JIS No. 3 dumbbell-shaped test specimen (2 mm thick) was punched out in accordance with JIS K6251:2017, and the stress (100% modulus) (M100) at 100% elongation (at a temperature of 23°C and a tensile speed of 500 mm / min) and elongation at break were measured. The results are shown in Table 1. The results are expressed as an index with Standard Example 1 set to 100. A higher index indicates superior toughness. An index greater than 100 is preferable.

[0116] [Ice performance] The obtained tire rubber composition was press-vulcanized in a predetermined mold at 170°C for 10 minutes to produce vulcanized rubber test specimens. The obtained vulcanized rubber test specimens were attached to a flattened cylindrical rubber base and tested on an inside drum type ice friction tester at a temperature of -1.5°C and a load of 5.5 kg / cm². 3 The coefficient of friction on ice was measured under the condition of a drum rotation speed of 25 km / hour. The results are shown in Table 1. The results are expressed as an index with standard example 1 set to 100. A higher index indicates greater friction between the rubber and ice, resulting in superior ice performance when used in tires. An index greater than 100 is preferable.

[0117] [Table 1]

[0118] The details of each component shown in Table 1 are as follows. • NR: Natural rubber (STR20, glass transition temperature: -65℃, manufactured by Bombandit). • BR: Polybutadiene rubber (Nipol BR1220, glass transition temperature: -110℃, manufactured by Nippon Zeon Co., Ltd.) • Silica: ULTRASIL VN3 (manufactured by Evonik DeGussa) • Carbon Black: Show Black N339 (manufactured by Cabot Japan Co., Ltd.) • Silane coupling agent: Silane coupling agent (Si69, manufactured by Evonik Degussa) • Zinc oxide: Three types of zinc oxide (manufactured by Seido Chemical Co., Ltd.) • Stearic acid: Beads Stearic Acid YR (manufactured by Nippon Oil & Fats Co., Ltd.) • Anti-aging agent: Amine-based anti-aging agent (Santoflex 6PPD, manufactured by Flexis) • Wax: Paraffin wax (manufactured by Ouchi Shinko Chemical Co., Ltd.) • Oil: Aroma oil (Extract No. 4S, manufactured by Showa Shell Sekiyu Co., Ltd.) • Sulfur: Oil-treated sulfur (manufactured by Hosoi Chemical Co., Ltd.) • Vulcanization accelerator: Sulfenamide-based vulcanization accelerator (Sunceller CM-G, manufactured by Sanshin Chemical Co., Ltd.) • Particulate dispersions 1-8: Particulate dispersions 1-8 manufactured as described above. • Comparative particle 1: Art Pearl C-80T (urethane beads, apparent density: 1.16 g / cm³) manufactured by Negami Kogyo Co., Ltd. 3 , average particle size: 75μm) • Comparative particulate dispersions 2-3: Comparative particulate dispersions 2-3 manufactured as described above. • Liquid isoprene polymer: LIR-30 manufactured by Kuraray Co., Ltd., number average molecular weight 28,000

[0119] In Table 1, "amount of fine particles" refers to the net amount (parts by mass) of fine particles in the fine particle dispersion, excluding liquid particles. Furthermore, in Table 1, "Isocyanate group / active hydrogen group," "Water / isocyanate group," "Apparent density," "Average particle size," and "Content of fine particles in the dispersion" represent the isocyanate group / active hydrogen group, water / isocyanate group, apparent density, average particle size, and content of fine particles in the dispersion of the fine particles used in each example, respectively.

[0120] Table 2 summarizes the formulations of the fine particles used in the examples. In Table 2, the numerical values ​​represent the amount (parts by mass) of each component used.

[0121] [Table 2]

[0122] As can be seen from Table 1, Examples 1 to 11, which are tire rubber compositions containing the fine particles of the present invention, showed excellent M100, elongation at break, and ice performance.

[0123] A comparison of Examples 2-8 (comparison of embodiments where the amount of fine particles is 10 parts by mass and the polyisocyanate is polymeric MDI) shows that for the fine particles of the present invention, Examples 2-4 and 6-7, in which a tertiary amine having a hydroxyl group as a catalyst and a chain extender were further dispersed in the liquid during the dispersion process, showed superior M100. Among these, Examples 2-4, in which the liquid was an unmodified diene polymer, showed even superior M100. Among these, Examples 3-4, in which the hydroxyl value of the polyol was 200 mgKOH / g or less, showed even superior M100. Among these, Example 4, in which the polyol was a castor oil-based polyol, showed even superior M100.

[0124] Furthermore, a comparison between Examples 1-2 and Examples 10 and 11 (comparison of embodiments differing only in the amount of fine particles) showed that Examples 1-2 and 11, which have an amount of fine particles of 1 part by mass or more, exhibited superior M100 and ice performance. Among these, Examples 2 and 11, which have an amount of fine particles of 7 parts by mass or more, showed even superior M100 and ice performance. Among these, Example 2, which has an amount of fine particles of 13 parts by mass or less, showed even superior elongation at break.

[0125] On the other hand, Standard Example 1, which does not contain the fine particles of the present invention, and Comparative Examples 1 to 3, which contain fine particles other than the fine particles of the present invention instead of the fine particles of the present invention, were insufficient in at least one of the following: M100, elongation at break, and ice performance. [Explanation of Symbols]

[0126] 1. Bead section 2 Sidewall section 3. Tire tread section 4. Carcass layer 5 Bead core 6. Bead Filler 7 Belt layer 8 Rim Cushion

Claims

1. A tire rubber composition comprising 100 parts by mass of a diene rubber having a glass transition temperature of -50°C or lower, 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 foamed fine particles, The aforementioned polyurethane foamed fine particles A dispersion step is performed to obtain a dispersion system by dispersing water and a polyol with a hydroxyl value of 40 to 350 mg KOH / g in a liquid. By mixing polyisocyanate into the dispersion system such that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0, the polyol and polyisocyanate are polymerized, and carbon dioxide is generated, resulting in an apparent density of 1.00 g / cm³ dispersed in the liquid. ３ A rubber composition for tires, comprising polyurethane foamed fine particles obtained by a method for producing polyurethane foamed fine particles, which includes a polymerization step to obtain the following polyurethane foamed fine particles.

2. The rubber composition for tires according to claim 1, wherein the average particle size of the polyurethane foamed fine particles is 1 to 300 μm.

3. The tire rubber composition according to claim 1, wherein the polyol is a plant-derived polyol.

4. The tire rubber composition according to claim 1, wherein in the dispersion step, a chain extender is further dispersed in the liquid.

5. The tire rubber composition according to claim 1, wherein in the dispersion step, a tertiary amine having a hydroxyl group is further dispersed in the liquid as a catalyst.

6. The tire rubber composition according to claim 3, wherein the plant-derived polyol comprises at least one of a castor oil-based polyol and a sebaciate-based polyester polyol.

7. A winter tire manufactured using the tire rubber composition described in any one of claims 1 to 6.

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