Method for producing polyurethane foamed microparticles, polyurethane foamed microparticles, and rubber composition for tires.

Abstract

To provide a compounding agent which further improves wet grip performance, modulus and elongation at break when used in a rubber composition for a tire and to provide a rubber composition for a tire containing the compounding agent.SOLUTION: There is provided a method for producing polyurethane foam particulates, which comprises: a dispersion step of dispersing water, at least one of a non-ionic surfactant and a silicone-based foam stabilizer, a polyol having a hydroxyl group value of 40 to 350 mgKOH / g and a catalyst in a liquid containing at least one selected from the group consisting of an unmodified liquid diene-based polymer, mineral oil and vegetable oil 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 method for producing polyurethane foamed microparticles, polyurethane foamed microparticles, and a rubber composition for 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 wet grip performance, modulus (especially 100% modulus), and elongation at break of rubber compositions used in tires (particularly treads) when made into tires. In this context, the present inventors investigated the crosslinked polyurethane beads described in Patent Document 1 and found that, considering future requirements, it is desirable that when used in tire rubber compositions, they further improve the wet grip performance, modulus after vulcanization, and elongation at break when made into tires.

[0005] Therefore, in view of the above circumstances, the present invention aims to provide a compounding agent that, when used in a tire rubber composition, further improves the wet grip performance, modulus after vulcanization, and elongation at break when made into a tire, and a tire rubber composition containing the above compounding agent. [Means for solving the problem]

[0006] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that polyurethane foam fine particles dispersed in a liquid can solve the above-mentioned problems by dispersing water, a surfactant, a specific polyol, and a catalyst in a liquid, then mixing in a specific ratio of polyisocyanate, polymerizing the polyol and polyisocyanate, and generating carbon dioxide, thereby obtaining polyurethane foam fine particles dispersed in a liquid. This led 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 dispersion step to obtain a dispersion system by dispersing water, at least one of a nonionic surfactant and a silicone foam stabilizer, a polyol with a hydroxyl value of 40 to 350 mg KOH / g, and a catalyst in a liquid containing at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil. 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 method for producing polyurethane foamed fine particles, comprising a polymerization step for obtaining the following polyurethane foamed fine particles. (2) The average particle size of the polyurethane foamed fine particles is 1 to 300 μm. The content of polyurethane foamed fine particles in the dispersion, which consists of the above liquid and polyurethane foamed fine particles dispersed in the above liquid, is 10 to 60% by mass. A method for producing polyurethane foamed fine particles as described in (1) above, wherein the polyol is a plant-derived polyol. (3) A method for producing polyurethane foamed fine particles according to (1) or (2) above, wherein the catalyst is a tertiary amine having a hydroxyl group. (4) The method for producing polyurethane foam microparticles according to any one of (1) to (3) above, wherein the polyisocyanate contains a polyisocyanate having an average functional group number of 2.1 or more. (5) The method for producing polyurethane foam microparticles according to any one of (1) to (4) above, wherein in the dispersion step, a chain extender is further dispersed in the liquid material. (6) The method for producing polyurethane foam microparticles according to any one of (1) to (5) above, wherein the polyol contains at least one of a castor oil-based polyol and a sebacic acid-based polyester polyol. (7) Polyurethane foam microparticles produced by the production method according to any one of (1) to (6) above. (8) A rubber composition for tires containing the polyurethane foam microparticles according to (7) above and having a hollow structure inside. (9) A rubber composition for tires containing 100 parts by mass of a diene rubber, 1 to 30 parts by mass of the polyurethane foam microparticles according to (7) above, and 3 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and a white filler. [Advantages of the Invention]

[0008] As shown below, according to the present invention, when used in a rubber composition for tires, a compounding agent that further improves the wet grip performance, modulus after vulcanization, and elongation at break when made into a tire, and a rubber composition for tires containing the compounding agent can be provided. [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 method for producing polyurethane foam microparticles of the present invention, the polyurethane foam microparticles of the present invention, the rubber composition for tires of the present invention, and the tire of the present invention will be described. In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Furthermore, 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 each component refers to the total content unless otherwise specified. Furthermore, with respect to polyurethane foamed fine particles, the wet grip performance when used in tire rubber compositions is simply referred to as "wet grip performance," the 100% modulus after vulcanization is simply referred to as "100% modulus" or "M100," and the elongation at break after vulcanization is simply referred to as "elongation at break." Furthermore, the superior wet grip performance, the superior M100 (large M100), and the superior elongation at break (large elongation at break) are collectively referred to as "the superior effects of the present invention." Furthermore, in this specification, the hydroxyl group of water is not included in the active hydrogen group.

[0011] [1] Method for producing polyurethane foamed microparticles The method for producing polyurethane foamed fine particles of the present invention (hereinafter also simply referred to as "the method of production of the present invention") comprises the following dispersion step and the following polymerization step. (1) Dispersion process A process to obtain a dispersion system by dispersing water, at least one of a nonionic surfactant and a silicone foam stabilizer (hereinafter also referred to as a "specific foam stabilizer"), a polyol with a hydroxyl value of 40 to 350 mgKOH / g (hereinafter also referred to as a "specific polyol"), and a catalyst in a liquid (hereinafter also referred to as a "specific liquid") which contains at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil. (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 above liquid (specific liquid). 3The following process for obtaining polyurethane foamed microparticles

[0012] Polyurethane foamed microparticles produced by the manufacturing method of the present invention (hereinafter also referred to as "microparticles of the present invention") are thought to be able to solve the above-mentioned problems due to their structure. The reason for this is not clear, but it is thought to be approximately as follows. 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 has a cavity structure derived from the fine particles of the present invention. This is thought to contribute to heat generation, resulting in excellent wet grip performance. 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 following describes each step.

[0014] [Dispersion process] The dispersion step is a process of obtaining a dispersion system by dispersing water, at least one of a nonionic surfactant and a silicone foam stabilizer (specific foam stabilizer), a polyol with a hydroxyl value of 40 to 350 mgKOH / g (specific polyol), and a catalyst in a liquid (specific liquid) containing at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil.

[0015] The following describes each component used in the dispersion process.

[0016] [Specific liquid substances] The specified liquid substance is a liquid substance containing at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil. The specified liquid may include liquids other than unmodified liquid diene polymers, mineral oils, and vegetable oils, but for reasons that the effects of the present invention are superior with respect to the resulting polyurethane foamed fine particles, 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). Hereinafter, the superior effectiveness of the present invention in the obtained polyurethane foamed fine particles will also be referred to simply as "the superior effectiveness of the present invention."

[0017] 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.

[0018] <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.

[0019] 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.

[0020] 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

[0021] <Mineral oil> Mineral oils are not particularly restricted, and specific examples include paraffinic, naphthenic, and aromatic oils.

[0022] <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.

[0023] <Usage amount> 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.

[0024] 〔water〕 As described above, the dispersion process involves dispersing water in a specific liquid substance.

[0025] <Usage amount> 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.

[0026] <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.

[0027] [Specific foam stabilizers] As described above, in the dispersion step, at least one of a nonionic surfactant and a silicone-based foam stabilizer (the specific foam stabilizer) is dispersed in a specific liquid substance.

[0028] <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.

[0029] <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.

[0030] <Usage amount> 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.

[0031] [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.

[0032] 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.

[0033] <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.

[0034] <Percentage of total 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.

[0035] 〔catalyst〕 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.

[0036] <Usage amount> 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.

[0037] <Percentage of total active hydrogen groups> The ratio (molar ratio) of the catalyst's active hydrogen groups (amino groups, hydroxyl groups) 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.

[0038] [Chain extender] In the manufacturing method of the present invention, it is preferable to further disperse the chain extender in the dispersion step for reasons that the effects of the present invention are superior. 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.

[0039] 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.

[0040] 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.

[0041] <Usage amount> The amount of chain extender 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 specified polyol described above.

[0042] <Percentage of active hydrogen groups> When the chain extender is a polyamine, the ratio (molar ratio) of the amino groups 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 better performance of the present invention.

[0043] [Procedure for distributed processes] One possible procedure for the dispersion process is to mix the aforementioned components and then stir them using a stirrer or similar device.

[0044] [Dispersion system] The dispersion process yields a mixture (dispersion system) in which the above-mentioned components are dispersed in a specific liquid.

[0045] [Polymerization process] The polymerization step involves mixing polyisocyanate into the dispersion obtained in the dispersion step so that the molar ratio of isocyanate groups to active hydrogen groups is 1.5 to 6.0. This polymerizes the polyol contained in the dispersion with the polyisocyanate, generating carbon dioxide and resulting in an apparent density of 1.00 g / cm³ dispersed in a specific liquid. 3 This is the process for obtaining the following polyurethane foamed fine particles. Furthermore, if the dispersion obtained by the dispersion step contains a chain extender (such as a diamine), the chain extender may also react with the polyisocyanate during the polymerization step.

[0046] [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.

[0047] 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.

[0048] <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.

[0049] <NCO%> 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.

[0050] [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.

[0051] Procedure of the polymerization process As the procedure of the polymerization process, for example, a method of mixing a polyisocyanate into the dispersion system obtained by the dispersion process and then stirring with a stirrer or the like can be mentioned.

[0052] 〔Polyurethane foamed fine particles〕 By the polymerization process, the following polyurethane foamed fine particles (the fine particles of the present invention) having an apparent density of 1.00 g / cm dispersed in a specific liquid substance are obtained. 3

[0053] <Apparent density> As described above, the apparent density of the polyurethane foamed fine particles is 1.00 g / cm 3 or less. As described above, the polyurethane foamed fine particles have a cavity structure due to the generation of carbon dioxide. Therefore, the apparent density is small. By manufacturing according to the manufacturing method of the present invention, the apparent density of the obtained polyurethane foamed fine particles is 1.00 g / cm 3 or less. The apparent density of the polyurethane foamed fine particles is preferably 0.95 g / cm or less, more preferably 0.90 g / cm or less, and even more preferably 0.85 g / cm or less, for the reason that the effects of the present invention are more excellent. 3 3 3 The lower limit of the apparent density of the polyurethane foamed fine particles is not particularly limited, but is preferably 0.50 g / cm or more, more preferably 0.60 g / cm or more, for the reason that the effects of the present invention are more excellent. 3 3 In this specification, the apparent density of the polyurethane foamed fine particles is determined by the water substitution method in accordance with JIS K7112.

[0054] <Average particle diameter> ​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.

[0055] <Content of fine particles in the dispersion> As described above, the polymerization process yields polyurethane foamed fine particles (the fine particles of the present invention) dispersed in a specific liquid. Hereinafter, the liquid substance and the fine particles dispersed in the liquid substance will be collectively referred to as a "dispersion," and the specific liquid substance and the fine particles of the present invention dispersed in the specific 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.

[0056] [2] Polyurethane foam microparticles The polyurethane foamed microparticles of the present invention (microparticles of the present invention) are polyurethane foamed microparticles produced by the manufacturing method of the present invention described above. The polyurethane foamed fine particles and the fine particles of the present invention are as described above.

[0057] 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.

[0058] [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.

[0059] [3] 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 that contains a diene rubber and the polyurethane foamed fine particles of the present invention (fine particles of the present invention) described above. Since the composition of the present invention contains the fine particles of the present invention, it typically has a cavity structure inside derived from the fine particles of the present invention.

[0060] The rubber tire composition of the present invention is preferably a rubber tire composition containing 100 parts by mass of diene rubber, 1 to 30 parts by mass of the fine particles of the present invention described above, and 3 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers, for the reason that the effects of the present invention are superior.

[0061] The components contained in the composition of the present invention will be described below.

[0062] [Diene-based rubber] The diene rubber contained in the composition of the present invention is not particularly limited as long as it is a solid diene rubber. The composition of the present invention may contain one type of diene rubber or two or more types of diene rubber.

[0063] [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, styrene-butadiene rubber, isoprene rubber, and natural rubber, and more preferably contains styrene-butadiene rubber, for the reasons that the effects of the present invention are superior.

[0064] When the diene rubber contains SBR, the SBR content 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 better effects of the present invention. There is no particular upper limit, and it is 100% by mass.

[0065] [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 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.

[0066] [Polyurethane foam microparticles] The composition of the present invention contains the polyurethane foamed fine particles (fine particles of the present invention) described above. The fine particles of the present invention are as described above.

[0067] [Content] 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".

[0068] 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.

[0069] [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 fillers, 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.

[0070] [Filler] The composition of the present invention preferably contains a filler because it provides superior effects. The composition of the present invention preferably contains at least one filler selected from the group consisting of carbon black and white fillers, and more preferably contains both carbon black and white fillers (particularly silica), for better effects of the present invention.

[0071] <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".

[0072] <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.

[0073] 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.

[0074] 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. 2 It 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".

[0075] <Content> In the composition of the present invention, the content of the filler is preferably 3 to 200 parts by mass, more preferably 10 to 100 parts by mass, and even more preferably 50 to 90 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.

[0076] If the composition of the present invention contains carbon black, the carbon black content is preferably 1 to 100 parts by mass, and more preferably 5 to 20 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] When the composition of the present invention contains a white filler (particularly silica), the amount of the white filler is preferably 1 to 150 parts by mass, more preferably 10 to 100 parts by mass, and even 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.

[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 that 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] [4] 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). 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 using 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 be 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] [Fine particles 9] Polyurethane foamed microparticles were obtained by following the same procedure as for microparticle 1, except that the amount of water was changed to 5g. The obtained polyurethane foamed microparticles are also called microparticles 9, and the dispersion of the liquid and the microparticles 9 dispersed in the liquid is also called microparticle dispersion 9.

[0108] When the obtained fine particles 9 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 be 0.92 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0109] [Fine particles 10] Polyurethane foamed microparticles were obtained by following the same procedure as for microparticle 1, except that the amount of water was changed to 15g. The obtained polyurethane foamed microparticles are also called microparticles 10, and the dispersion of the liquid and the microparticles 10 dispersed in the liquid is also called microparticle dispersion 10.

[0110] When the obtained fine particles 10 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 0.83 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0111] [Comparative Particles 2]

[0112] <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).

[0113] <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.

[0114] 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.

[0115] [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.

[0116] 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 be 1.04 g / cm³. 3 Furthermore, the content of fine particles in the dispersion was 50% by mass.

[0117] [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. In Table 1, the mass of SBR represents the net amount of rubber (mass) excluding the oil used for spreading.

[0118] [evaluation] The following evaluations were performed on the obtained tire rubber compositions.

[0119] [tanδ(0℃)] 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. The dynamic viscoelasticity of the obtained vulcanized rubber sheet was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., with an initial strain of 10%, amplitude of ±2%, and frequency of 20 Hz, and tanδ at a temperature of 0°C was determined. The results are shown in Table 1. The results are expressed as an index with Comparative Example 1 set to 100. A higher index indicates better wet grip performance when used as a tire.

[0120] [M100 and EB] As described above, a vulcanized rubber sheet was produced. 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) and elongation at break (EB) at 100% elongation were measured under conditions of a temperature of 23°C and a tensile speed of 500 mm / min. 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.

[0121] [Table 1]

[0122] The details of each component shown in Table 1 are as follows. • SBR: Styrene-butadiene rubber, manufactured by Nippon Zeon Corporation, NIPOL1739 (Tg (glass transition temperature): -39℃, Mw: 760,000) • Silica: Rhodia Zeosil 1165MP • Carbon Black: Tokai Carbon Co., Ltd. Seast 6 • Particulate dispersions 1-10: Particulate dispersions 1-10 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 • Silane coupling agent: Bis-(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik, Si69 • Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. • Stearic acid: NOF Corporation's Bead Stearic Acid YR • Anti-aging agent: Flexis Santoflex 6PPD • Sulfur: Finely powdered sulfur containing Kinka oil, manufactured by Tsurumi Chemical Industries Co., Ltd. • Vulcanization accelerator 1: Noxellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd. • Vulcanization accelerator 2: Soccinol DG manufactured by Sumitomo Chemical Co., Ltd.

[0123] In Table 1, "amount of fine particles" refers to the net amount of fine particles (parts by mass) of the fine particle dispersion, excluding the liquid portion. The amount of fine particles in Comparative Example 1 refers to the amount of comparative fine particles 1 (parts by mass). 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, respectively, of the fine particles used in each example.

[0124] Furthermore, the formulations of the fine particles used in the examples are summarized in Table 2. In Table 2, the numerical values ​​represent the amount (parts by mass) used for each component.

[0125] [Table 2]

[0126] As can be seen from Table 1, Examples 1 to 12, which are tire rubber compositions containing the fine particles of the present invention, showed excellent wet grip performance, M100, and elongation at break.

[0127] A comparison of Examples 1-7 (comparing embodiments where the amount of water used in the dispersion step is 10 parts by mass per 100 parts by mass of the specific polyol, the amount of fine particles is 10 parts by mass, and the polyisocyanate is polymeric MDI) showed that Examples 1-3 and 5-7, in which a chain extender was further dispersed in the specific liquid in the dispersion step, showed superior M100. In particular, Examples 1-3 and 7, in which the specific liquid was an unmodified liquid diene polymer, showed even superior M100. Among these, Examples 1-3, in which the catalyst was a tertiary amine having a hydroxyl group, showed superior wet grip performance. Among these, Examples 1 and 3, in which the polyol was a castor oil-based polyol, showed even superior wet grip performance. Among these, Example 3, in which the hydroxyl value of the polyol was 200 mgKOH / g or less, showed even superior M100.

[0128] Furthermore, a comparison between Example 1, Example 9, and Example 10 (comparison of embodiments that differ only in the amount of water used in the dispersion process) showed that Example 1 and Example 10, in which the water / isocyanate group ratio was 0.2 or higher, exhibited superior wet grip performance. In particular, Example 1, in which the water / isocyanate group ratio was 0.5 or lower, showed superior M100 and elongation at break.

[0129] Furthermore, a comparison between Example 1, Example 11, and Example 12 (a comparison of embodiments that differ only in the amount of fine particles) showed that Example 1, with a fine particle amount of 5 to 15 parts by mass, exhibited superior wet grip performance and M100.

[0130] 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: wet grip performance, M100, and elongation at break. [Explanation of Symbols]

[0131] 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 dispersion step is to obtain a dispersion system by dispersing water, at least one of a nonionic surfactant and a silicone foam stabilizer, a polyol with a hydroxyl value of 40 to 350 mg KOH / g, and a catalyst in a liquid containing at least one selected from the group consisting of an unmodified liquid diene polymer, mineral oil, and vegetable oil. 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 method for producing polyurethane foamed fine particles, comprising a polymerization step for obtaining the following polyurethane foamed fine particles.

2. The average particle size of the polyurethane foamed fine particles is 1 to 300 μm. The content of polyurethane foamed fine particles in the dispersion, which consists of the liquid and polyurethane foamed fine particles dispersed in the liquid, is 10 to 60% by mass. The method for producing polyurethane foamed fine particles according to claim 1, wherein the polyol is a plant-derived polyol.

3. The method for producing polyurethane foamed fine particles according to claim 1, wherein the catalyst is a tertiary amine having a hydroxyl group.

4. The method for producing polyurethane foamed fine particles according to claim 1, wherein the polyisocyanate comprises a polyisocyanate with an average number of functional groups of 2.1 or more.

5. A method for producing polyurethane foamed fine particles according to claim 1, wherein in the dispersion step, a chain extender is further dispersed in the liquid.

6. The method for producing polyurethane foamed fine particles according to claim 1, wherein the polyol comprises at least one of a castor oil-based polyol and a sebaciate-based polyester polyol.

7. Polyurethane foamed fine particles produced by the manufacturing method described in any one of claims 1 to 6.

8. A rubber composition for tires containing polyurethane foamed fine particles as described in claim 7, and having a hollow structure inside.

9. A rubber composition for tires comprising 100 parts by mass of diene rubber, 1 to 30 parts by mass of polyurethane foamed fine particles as described in claim 7, and 3 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers.

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