Rubber composition for tires, and studless tire

Abstract

To provide a rubber composition for tires which exhibits large elongation at break and excellent on-ice performance, and a tire produced using the rubber composition for tires.SOLUTION: The rubber composition for tires contains 100 pts.mass of a diene rubber, 30-100 pts.mass of at least one filler selected from the group consisting of carbon black and white fillers, and 1-30 pts.mass of polyurethane fine particles having an average particle diameter of 1-300 μm and having pores on the surface.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] From the viewpoint of improving the performance of tires, rubber compositions for tires blended with various additives have been studied. For example, in Patent Document 1, a rubber composition for tires blended with specific polyurethane-based fine particles has been proposed from the viewpoint of improving ice performance and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, from the viewpoint of safety and the like, further improvement in ice performance (hereinafter, also simply referred to as "ice performance") when used as a tire has been demanded for the rubber composition used in tires (especially the tread portion). Further improvement in the elongation at break after vulcanization (hereinafter, also simply referred to as "elongation at break") has also been demanded. Under such circumstances, when the present inventors examined the rubber composition for tires described in Patent Document 1, it became clear that further improvement in elongation at break and ice performance is desirable in consideration of future requirements.

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires having a large elongation at break and excellent ice performance, and a tire manufactured using the rubber composition for tires.

Means for Solving the Problems

[0006] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by blending specific polyurethane particles having pores on the surface, and thus have arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A rubber composition for tires, containing 100 parts by mass of a diene rubber, 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and a white filler, and 1 to 30 parts by mass of polyurethane fine particles having pores on the surface with an average particle diameter of 1 to 300 μm. (2) The rubber composition for tires according to (1) above, wherein the polyurethane fine particles are polyurethane fine particles obtained by reacting a polyol, a polyisocyanate, and water in oil. (3) The rubber composition for tires according to (1) or (2) above, wherein the polyol constituting the polyurethane fine particles contains a castor oil-based polyol having a hydroxyl value of 10 to 200 mgKOH / g. (4) The rubber composition for tires according to any one of (1) to (3) above, wherein the polyisocyanate constituting the polyurethane fine particles contains an aromatic polyisocyanate. (5) The rubber composition for tires according to any one of (1) to (4) above, wherein in the reaction for obtaining the polyurethane fine particles, the molar ratio of the isocyanate group to the active hydrogen group is 0.8 to 4.0. (6) The diene rubber contains natural rubber and butadiene rubber, The rubber composition for tires according to any one of (1) to (5) above, wherein the proportion of the butadiene rubber in the total diene rubber is 30% by mass or more. (7) A studless tire produced by using the rubber composition for tires according to any one of (1) to (6) above in a tread portion.

Advantages of the Invention

[0008] As described below, according to the present invention, it is possible to provide a rubber composition for tires having a large elongation at break and excellent ice performance, and a tire manufactured using the rubber composition for tires.

Brief Description of Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] The rubber composition for tires and the like of the present invention will be described below. In the present 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. 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, "high elongation at break" is also referred to as "excellent elongation at break". Also, "excellent elongation at break and ice performance" is also referred to as "excellent effects of the present invention".

[0011] [1] Rubber composition for tires The rubber composition for tires of the present invention (hereinafter also referred to as "the composition of the present invention") is A rubber composition for tires containing 100 parts by mass of a diene rubber, 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and a white filler, and 1 to 30 parts by mass of polyurethane fine particles having pores on the surface with an average particle diameter of 1 to 300 μm. It is considered that a tire manufactured using the composition of the present invention exhibits excellent ice performance because specific polyurethane particles having pores on the surface enhance the friction against an ice road surface.

[0012] Hereinafter, each component contained in the composition of the present invention will be described.

[0013] [Diene rubber] The composition of the present invention contains a diene rubber. The composition of the present invention may contain one kind of diene rubber or two or more kinds of diene rubbers.

[0014] 〔Specific examples〕 Specific examples of the diene rubber include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, and the like. The diene rubber preferably contains at least one selected from the group consisting of butadiene rubber, styrene-butadiene rubber, isoprene rubber, and natural rubber, and more preferably contains natural rubber and butadiene rubber, because the effects of the present invention are more excellent.

[0015] When the diene rubber contains natural rubber, the proportion of natural rubber in the total diene rubber is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less, because the effects of the present invention are more excellent. When the diene rubber contains butadiene rubber, the proportion of butadiene rubber in the total diene rubber is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less, because the effects of the present invention are more excellent.

[0016] 〔Molecular weight〕 The number average molecular weight (Mn) of the diene rubber is not particularly limited, but for the reason that the effects of the present invention are more excellent, 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 reason that the effects of the present invention are more excellent, 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.

[0017] In this specification, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement.

[0018] [Filler] The composition of the present invention contains a filler including at least one selected from the group consisting of carbon black and a white filler. For the reason that the effects of the present invention are more excellent, it is more preferable that the composition of the present invention contains both carbon black and a white filler (especially silica).

[0019] [Carbon Black] The above carbon black is not particularly limited, and for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF can be used. The nitrogen adsorption specific surface area (N2SA) of the above carbon black is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 50 to 200 m 2 / g, more preferably 70 to 150 m 2 / g. Here, the nitrogen adsorption specific surface area (N2SA) is a value measured according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single-point method" for the amount of nitrogen adsorbed on the carbon black surface.

[0020] 〔White filler〕 The above white filler is not particularly limited, and examples include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, etc. Among them, silica is preferred because the effects of the present invention are more excellent.

[0021] The above silica is not particularly limited, and examples include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. Among them, wet silica is preferably used because the effects of the present invention are more excellent.

[0022] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of the above silica is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 100 to 400 m 2 / g, and more preferably 150 to 300 m 2 / g. Here, the CTAB adsorption specific surface area is a value measured according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method" for the amount of CTAB adsorbed on the silica surface.

[0023] 〔Content〕 In the composition of the present invention, the content of the filler is 30 to 100 parts by mass with respect to 100 parts by mass of the above-mentioned diene rubber. Among them, it is preferably 50 to 90 parts by mass, and more preferably 60 to 80 parts by mass.

[0024] When the composition of the present invention contains carbon black, the content of carbon black is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the above-mentioned diene rubber, and more preferably 10 to 30 parts by mass, for the reason that the effects of the present invention are more excellent.

[0025] When the composition of the present invention contains a white filler (particularly, silica), the content of the white filler is preferably 10 to 90 parts by mass, more preferably 30 to 70 parts by mass, based on 100 parts by mass of the above-described diene rubber, because the effects of the present invention are more excellent.

[0026] [Specific fine particles] The composition of the present invention contains polyurethane fine particles having pores on the surface with an average particle diameter of 1 to 300 μm (hereinafter, also referred to as "specific fine particles"). Hereinafter, the specific fine particles will be described. The method for producing the specific fine particles will be described later.

[0027] [Polyurethane fine particles] The polyurethane fine particles are fine particles of polyurethane. Here, polyurethane refers to a polymer having a plurality of urethane bonds (-NH-COO-). The polyurethane preferably has a urea bond (-NH-CO-NH-) in addition to the urethane bond, because the effects of the present invention are more excellent.

[0028] [Preferred embodiment] The polyurethane is preferably a polymer of a polyol and a polyisocyanate, because the effects of the present invention are more excellent.

[0029] [Polyol] The polyol is a compound having two or more hydroxy groups (hydroxyl groups). The polyol is preferably a liquid at 20°C and 1 atm.

[0030] [Specific examples] Examples of the polyol include polyether polyols; castor oil-based polyols such as castor oil, dehydrated castor oil, castor hardened oil which is a hydrogenated product of castor oil, and an adduct of 5 to 50 moles of alkylene oxide to castor oil; polyester polyols (particularly sebacic acid-based polyester polyols); polymer polyols having a carbon-carbon bond in the main chain skeleton such as acrylic polyols, polybutadiene diols, and hydrogenated polybutadiene polyols; low molecular weight polyhydric alcohols; and mixed polyols thereof. Among these, castor oil-based polyols are preferred because the effects of the present invention are more excellent. The castor oil-based polyol means a polyol that is castor oil or a derivative of castor oil.

[0031] (Hydroxyl value) The hydroxyl value of the polyol is not particularly limited, but is preferably 1 to 400 mgKOH / g, more preferably 5 to 300 mgKOH / g, still more preferably 10 to 200 mgKOH / g, and particularly preferably 20 to 100 mgKOH / g because the effects of the present invention are more excellent. The hydroxyl value is the hydroxyl value described in JIS K 1557-1:2007 and is the number of milligrams of potassium hydroxide equivalent to the hydroxyl groups in 1 g of the sample.

[0032] (Preferred embodiment) The polyol is preferably a castor oil-based polyol having a hydroxyl value of 10 to 200 mgKOH / g because the effects of the present invention are more excellent.

[0033] <Polyisocyanate> The polyisocyanate is a compound having two or more isocyanate groups (-NCO).

[0034] (Specific examples) Specific examples of the polyisocyanate include aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI; for example, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), triphenylmethane triisocyanate; aliphatic polyisocyanates (including alicyclic polyisocyanates) such as hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), trans-cyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H 12 MDI); these carbodiimide-modified polyisocyanates; these isocyanurate-modified polyisocyanates may be mentioned.

[0035] From the reason that the effects of the present invention are more excellent, aromatic polyisocyanates are preferred, and MDI is more preferred. Examples of the above MDI include monomeric MDI, polymeric MDI, modified MDI (for example, carbodiimide-modified MDI), etc. Among them, polymeric MDI is preferred from the reason that the effects of the present invention are more excellent.

[0036] (Average functionality number) The average functionality of the polyisocyanate is preferably 2.1 or more, more preferably 2.3 or more, even more preferably 2.5 or more, particularly preferably 2.7 or more, and most preferably 2.9 or more, because the effects of the present invention are more excellent. The upper limit of the average functionality of the polyisocyanate is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and even more preferably 4 or less, because the effects of the present invention are more excellent. The average functionality represents the average number of isocyanate groups possessed by the polyisocyanate.

[0037] (NCO%) The NCO% of the polyisocyanate is preferably 5 to 80%, more preferably 10 to 50%, and even more preferably 20 to 40%, because the effects of the present invention are more excellent. The NCO% represents the proportion (mass%) of isocyanate groups in the entire polyisocyanate.

[0038] 〔Average particle diameter〕 The average particle diameter of the specific fine particles is 1 to 300 μm. The above average particle diameter is preferably 2 to 100 μm, more preferably 5 to 50 μm, even more preferably 10 to 40 μm, and particularly preferably 20 to 30 μm, because the effects of the present invention are more excellent. In this specification, the average particle diameter is the volume average diameter measured by a laser diffraction particle size distribution analyzer.

[0039] 〔Vacant holes〕 The specific fine particles have vacant holes on the surface. Whether the fine particles have vacant holes on the surface can be determined by observing the surface of the fine particles with a scanning electron microscope (SEM). The "vacant holes" in the specific fine particles refer to those with a diameter (equivalent circle diameter) of 0.01 μm or more in the SEM photograph. Also, in this specification, the "diameter of the vacant hole" refers to the diameter (equivalent circle diameter) in the SEM photograph.

[0040] The diameter (equivalent circle diameter) of the voids is preferably 0.05 to 100 μm, more preferably 0.1 to 10 μm, and even more preferably 0.5 to 5 μm for better effects of the present invention.

[0041] <Average diameter> The average diameter of the voids is preferably 0.1 to 10 μm, more preferably 0.3 to 5 μm, and even more preferably 0.5 to 3 μm for better effects of the present invention. The average diameter of the voids is determined by performing surface observation by SEM on 10 arbitrarily selected fine particles and calculating the arithmetic mean of the diameters (equivalent circle diameters) of the voids (equivalent circle diameter of 0.01 μm or more).

[0042] <Void ratio> The void ratio of the specific fine particles is not particularly limited, but is preferably 1 to 80%, more preferably 2 to 70%, and even more preferably 3 to 40%. The void ratio is determined by performing surface observation by SEM on 10 arbitrarily selected fine particles and calculating the arithmetic mean of the ratio that the voids (equivalent circle diameter of 0.01 μm or more) occupy with respect to the area of the fine particles on the SEM photograph.

[0043] 〔Apparent density〕 The apparent density of the specific fine particles is not particularly limited, but is preferably 0.10 to 2.00 g / cm 3 for better effects of the present invention, and more preferably 3 more than 1.50 g / cm 3 or less. In this specification, the apparent density of the polyurethane fine particles is determined by the water substitution method in accordance with JIS K7112.

[0044] 〔Preferred embodiment〕 The specific microparticles are preferably polyurethane microparticles (hereinafter also referred to as "specific microparticles 1") produced by Production Method 1 of the present invention described later, and more preferably polyurethane microparticles (hereinafter also referred to as "specific microparticles 2") produced by Production Method 2 of the present invention described later, because the effects of the present invention are more excellent.

[0045] Regarding specific microparticles 1 to 2, there are circumstances where it is impossible or approximately impractical to "directly identify the substance by its structure or properties at the time of filing" as follows.

[0046] In Production Methods 1 to 2 of the present invention described later, the reaction between the hydroxy group of the polyol and the isocyanate group of the polyisocyanate (formation of a urethane bond), the reaction between the isocyanate group of the polyisocyanate and water (generation of an amino group), and the reaction between the amino group generated by the reaction with water and the isocyanate group of the polyisocyanate (formation of a urea bond) compete. That is, in the above polymerization step, as the polyisocyanate, those in which some isocyanate groups have become amino groups by reacting with water, those in which all isocyanate groups have become amino groups by reacting with water, and those in which all isocyanate groups remain as they are without reacting with water are mixed, and these react with the polyol or polyisocyanate. Therefore, the structures of specific microparticles 1 to 2 become extremely complex and cannot be expressed by a general formula. This is common technical knowledge for those skilled in the art. And if the structure is not specified, the properties of the substance that are determined accordingly are not easily understood, and when reacting a plurality of different monomers, if their blending ratios and reaction conditions are changed, the properties of the obtained polyurethane microparticles change greatly, so it is impossible to express them by properties either. That is, specific microparticles 1 to 2 cannot be directly specified by their structure or properties, and can only be specified for the first time by the process.

[0047] [Optional component] The composition of the present invention can further contain other components (optional components) as necessary within a range that does not impair its effects and purposes. Examples of the above optional components include fillers other than the fillers described above, silane coupling agents, terpene resins (e.g., aromatic-modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators, and various other additives commonly used in rubber compositions.

[0048] 〔Silane coupling agent〕 The composition of the present invention preferably contains a silane coupling agent because the effects of the present invention are more excellent. The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The above hydrolyzable group is not particularly limited, and examples include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, etc. Among them, an alkoxy group is preferably used because the effects of the present invention are more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16, more preferably 1 to 4, because the effects of the present invention are more excellent. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, etc.

[0049] The above organic functional group is not particularly limited, but it is preferably a group capable of forming a chemical bond with an organic compound. Examples include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group (particularly, a polysulfide group (-S n -: n is an integer of 2 or more)), a mercapto group, a blocked mercapto group (protected mercapto group) (e.g., an octanoylthio group), etc. Among them, a sulfide group (particularly, a disulfide group, a tetrasulfide group), a mercapto group, and a blocked mercapto group are preferably used because the effects of the present invention are more excellent. The silane coupling agent may be used alone or in combination of two or more.

[0050] The above silane coupling agent is preferably a sulfur-containing silane coupling agent because the effects of the present invention are more excellent.

[0051] Specific examples of the above silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, etc. Among these, one kind may be used alone, or two or more kinds may be used in combination.

[0052] In the composition of the present invention, the content of the silane coupling agent is not particularly limited. However, for the reason that the effects of the present invention are more excellent, it is preferably 2 to 20% by mass, and more preferably 5 to 15% by mass, based on the content of the above-mentioned filler (especially silica).

[0053] [Method for producing a rubber composition for tires] The production method of the composition of the present invention is not particularly limited. Specific examples thereof include, for example, a method of kneading the above-mentioned respective components using a known method and apparatus (for example, Banbury mixer, kneader, roll, etc.). When the composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 155°C), cool them, and then mix sulfur or the vulcanization accelerator. Further, the composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0054] [2] Method for producing specific fine particles The method for producing the above-mentioned specific fine particles is not particularly limited. However, for the reason that the effects of the present invention are more excellent, a method of obtaining polyurethane fine particles by reacting a polyol, a polyisocyanate, and water in oil (hereinafter, also referred to as "Production Method 1 of the present invention") is preferable, and a method including the following steps (hereinafter, also referred to as "Production Method 2 of the present invention") is more preferable. (1) Dispersion step A step of obtaining a dispersion system by dispersing water and a polyol in oil (2) Polymerization step A step of mixing a polyisocyanate with the above-mentioned dispersion system to polymerize the above-mentioned polyol and the above-mentioned polyisocyanate and generate carbon dioxide, thereby obtaining polyurethane fine particles dispersed in oil

[0055] In Production Methods 1 to 2 of the present invention (hereinafter, also collectively referred to as "Production Method of the present invention"), the hydroxy group of the polyol reacts with the isocyanate group of the polyisocyanate to form a urethane bond (-NH-COO-). Further, water reacts with the isocyanate group to generate an amino group. At this time, carbon dioxide is generated. Furthermore, the generated amino group reacts with the isocyanate group to form a urea bond (-NH-CO-NH-). As a result, a polyurethane having a urethane bond and a urea bond is produced. At this time, the above-mentioned polymerization proceeds in a dispersion system dispersed in oil, and since carbon dioxide is generated as described above, polyurethane fine particles having pores on the surface are obtained.

[0056] Hereinafter, each component and the like used in the production method of the present invention will be described.

[0057] [Oil] The oil is not particularly limited, and specific examples include mineral oil and vegetable oil. The oil is preferably a process oil for the reason that the effects of the present invention are more excellent.

[0058] [Mineral oil] The mineral oil is not particularly limited, and specific examples thereof include paraffinic, naphthenic, aromatic, etc.

[0059] [Vegetable oil] The vegetable oil is not particularly limited, and specific examples thereof include soybean oil, rapeseed oil, coconut oil, linseed oil, etc.

[0060] [Usage amount] The amount of the oil is not particularly limited, but for reasons of more excellent effects of the present invention, it is preferably 100 to 1000 parts by mass, more preferably 200 to 500 parts by mass, based on 100 parts by mass of the polyol described later.

[0061] [Polyol] The definition, specific examples and preferred embodiments of the polyol are as described above.

[0062] [Ratio to the total of active hydrogen groups] The ratio (molar ratio) of the hydroxy groups (hydroxyl groups) of the polyol (or polyol and monool when using the monool described later) to the total of the active hydrogen groups is preferably 0.1 to 1.0, more preferably 0.2 to 0.8, and even more preferably 0.3 to 0.7, for reasons of more excellent effects of the present invention.

[0063] [Monool] In the production method of the present invention, a monool may be used in addition to the polyol. The monool is a compound having one hydroxy group (hydroxyl group). Specific examples of the monool include alcohols (such as methanol, ethanol, etc.).

[0064] [Usage amount] The usage amount of the monool is preferably 50 parts by mass or less based on 100 parts by mass of the polyol described above.

[0065] [Polyisocyanate] The definition, specific examples, and preferred embodiments of the polyisocyanate are as described above.

[0066] [Water]

[0067] [Usage amount] The amount of water is not particularly limited, but for reasons of more excellent effects of the present invention, it is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 2 parts by mass, based on 100 parts by mass of the above-described polyol.

[0068] [Water / Isocyanate group] The molar ratio of water to the isocyanate group of the above-described polyisocyanate (hereinafter, also referred to as "water / isocyanate group") is preferably 0.1 to 0.6, more preferably 0.2 to 0.5, for reasons of more excellent effects of the present invention.

[0069] [Catalyst] In the production method of the present invention, it is preferable to use a catalyst for reasons of more excellent effects of the present invention.

[0070] 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, but it is preferably a catalyst that promotes the reaction between the polyisocyanate and water.

[0071] The catalyst is preferably a reactive catalyst for reasons of more excellent effects of the present invention. Here, the reactivity of the reactive catalyst means that it can react with the isocyanate group. The reactive catalyst is preferably an amine or a compound having a hydroxy group, more preferably an amine having a hydroxy group (particularly, a tertiary amine having a hydroxy group), even more preferably a tertiary amine having three alcohol groups (-ROH, R: alkylene group), and particularly preferably triethanolamine, for reasons of more excellent effects of the present invention.

[0072] [Usage amount] The amount of the catalyst is not particularly limited, but from the reason that the effects of the present invention are more excellent, it is preferably 0.01 to 30 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the above-described polyol.

[0073] [Ratio to the total active hydrogen groups] The ratio (molar ratio) of the active hydrogen groups (amino group, hydroxy group) of the catalyst to the total active hydrogen groups is preferably 0.05 to 0.8, more preferably 0.1 to 0.5, and even more preferably 0.15 to 0.3, from the reason that the effects of the present invention are more excellent.

[0074] [Foam stabilizer] In the production method of the present invention, it is preferable to use a foam stabilizer from the reason that the effects of the present invention are more excellent. The foam stabilizer is preferably a nonionic surfactant or a silicone-based foam stabilizer from the reason that the effects of the present invention are more excellent.

[0075] [Nonionic surfactant] The nonionic surfactant is not particularly limited, and conventionally known ones can be used. Specific examples include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acids, polyoxyethylene higher alcohol ethers, polyoxyethylene-propylene higher alcohol ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkylphenols, polyoxyethylene aliphatic hydrocarbon amines (for example, polyoxyethylene alkylamines, polyoxyethylene alkyleneamines), polyoxyethylene aliphatic hydrocarbon amides (for example, polyoxyethylene alkylamides, polyoxyethylene alkyleneamides), polyoxyethylene-polyoxypropylene block polymers, polyoxyethylene sorbitan fatty acid esters, etc. Among them, polyoxyethylene sorbitan fatty acid esters are preferable from the reason that the effects of the present invention are more excellent.

[0076] [Silicone-based foam stabilizer] The silicone-based foam stabilizer is not particularly limited, and conventionally known ones can be used. The silicone-based foam stabilizer preferably has a polysiloxane chain and a polyoxyalkylene chain, and the polyoxyalkylene chain is preferably modified on the polysiloxane chain which is the main chain. The above polysiloxane chain is preferably an organopolysiloxane chain. Specific examples of the organopolysiloxane chain include a polydimethylsiloxane chain. Examples of the above polyoxyalkylene chain include a polyoxyalkylene chain composed of one kind of oxyalkylene group such as a polyoxyethylene chain and a polyoxypropylene chain, and a polyoxyalkylene chain composed of two or more kinds of oxyalkylene groups such as an oxyethylene oxypropylene block chain and an oxyethylene oxypropylene random chain.

[0077] 〔Usage amount〕 The amount of the foam stabilizer is not particularly limited, but for reasons of more excellent effects of the present invention, it is preferably 0.1 to 30 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the above-mentioned polyol.

[0078] [Isocyanate group / Active hydrogen group] In the production method of the present invention, the molar ratio of the isocyanate group to the active hydrogen group (hereinafter, also referred to as "isocyanate group / active hydrogen group") is preferably 0.5 to 6.0, more preferably 0.8 to 4.0, and even more preferably 2.0 to 4.0 for reasons of more excellent effects of the present invention. Here, the active hydrogen group refers to the hydroxy groups of the polyol and the monoalcohol. When an amine or a compound having a hydroxy group is used as a catalyst, in addition to the hydroxy groups of the polyol and the monoalcohol, it refers to the amino group of the above amine and the hydroxy group of the compound having the above hydroxy group. Note that the hydroxy group (hydroxyl group) of water is not included in the active hydrogen group.

[0079] [Content of fine particles in the dispersion] By the production method of the present invention, polyurethane fine particles dispersed in oil can be obtained. The content ratio of the polyurethane fine particles in the dispersion (the ratio occupied by the polyurethane fine particles with respect to the whole dispersion) (hereinafter, also referred to as "the content ratio of the fine particles in the dispersion") is preferably 10 to 60% by mass because the effects of the present invention are more excellent.

[0080] [3] Tire 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 an inert gas such as air, nitrogen, or other gases. Since the tire of the present invention has excellent performance on ice, it is particularly useful for studless tires.

[0081] Fig. 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention. However, the tire of the present invention is not limited to the embodiment shown in Fig. 1.

[0082] In Fig. 1, reference numeral 1 represents the bead portion, reference numeral 2 represents the sidewall portion, and reference numeral 3 represents the tire tread portion (tread portion). Also, between the pair of left and right bead portions 1, a carcass layer 4 in which a fiber cord is embedded is mounted, and the end portion of this carcass layer 4 is folded back from the inside of the tire to the outside around the bead core 5 and the bead filler 6 and wound up. Also, in the tire tread portion 3, a belt layer 7 is disposed over the entire circumference of the tire outside the carcass layer 4. Also, in the bead portion 1, a rim cushion 8 is disposed at the portion in contact with the rim. At least the tire tread portion 3 is formed of the composition of the present invention described above.

[0083] The tire of the present invention can be manufactured, for example, according to a conventionally known method. Also, as the gas to be filled in the tire, in addition to normal air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used.

Example

[0084] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0085] [Manufacture of Fine Particles] Each fine particle was manufactured as follows.

[0086] Note that since Fine Particles 1 to 5 are polyurethane particles having pores on the surface with an average particle diameter of 1 to 300 μm as described later, they correspond to the specific fine particles described above. On the other hand, Comparative Fine Particle 1 does not correspond to the specific fine particles described above because it has no pores on the surface as described later. Also, Comparative Fine Particle 2 does not correspond to the specific fine particles described above because, although it has pores on the surface as described later, its average particle diameter exceeds 300 μm.

[0087] Also, for Fine Particles 1 to 5, the average pore diameter was 0.5 to 3 μm, the porosity was 5 to 40%, and the apparent density was 1.00 g / cm 3 greater than 1.50 g / cm 3 as follows.

[0088] [Fine Particle 1]

[0089] [Dispersion Step] 100 g of castor oil-based polyol (URIC AC-009 manufactured by Ito Oil Co., Ltd., hydroxyl value 223 mgKOH / g), 10 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 g of silicone-based foam stabilizer (Niax silicone L-5111 manufactured by Momentive Performance Materials Inc.), 1 g of water, and 262 g of oil (Extract No. 4S manufactured by Shell Lubricants Japan Co., Ltd.) were stirred for 3 minutes with a planetary stirrer. Thus, a dispersion system was obtained.

[0090] [Polymerization Step] 150 g of polymeric MDI (Millionate MR-400 manufactured by Tosoh Corporation, NCO% is 30%) was added to the obtained dispersion system and stirred for 30 minutes to polymerize the polyol and isocyanate and generate carbon dioxide, thereby obtaining polyurethane fine particles dispersed in the oil. The content rate of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as fine particles 1, and the dispersion of fine particles 1 dispersed in the oil is also referred to as fine particle dispersion 1.

[0091] When SEM observation was performed on the obtained fine particles 1, the fine particles 1 were fine particles having pores on the surface with an average particle diameter of 10 μm.

[0092] 〔Fine Particles 2〕 Instead of the above URIC AC-009, a castor oil-based polyol (URIC HF-2009 manufactured by Ito Oil Co., Ltd., hydroxyl value is 43 mgKOH / g) was used, and instead of the above Millionate MR-400, isophorone diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd., NCO% is 38%) was used. The amount of the above triethanolamine was changed to 20 g, and the amount of the above oil was changed to 272 g. Except for this, according to the same procedure as that for fine particles 1, polyurethane fine particles dispersed in the oil were obtained. The content rate of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as fine particles 2, and the dispersion of fine particles 2 dispersed in the oil is also referred to as fine particle dispersion 2.

[0093] When SEM observation was performed on the obtained fine particles 2, the fine particles 2 were fine particles having pores on the surface with an average particle diameter of 36 μm.

[0094] 〔Fine Particles 3〕 Instead of the above URIC AC-009, a castor oil-based polyol (URIC H-1830 manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 82 mgKOH / g) was used. The amount of the above triethanolamine was changed to 5 g, the amount of the above polymeric MDI was changed to 200 g, and the amount of the above oil was changed to 307 g. Polyurethane fine particles dispersed in oil were obtained according to the same procedure as that for Fine Particles 1. The content rate of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as Fine Particles 3, and the dispersion of Fine Particles 3 dispersed in oil is also referred to as Fine Particle Dispersion 3.

[0095] When SEM observation was performed on the obtained Fine Particles 3, Fine Particles 3 were fine particles having pores on the surface with an average particle diameter of 65 μm.

[0096] 〔Fine Particles 4〕 Polyurethane fine particles dispersed in oil were obtained according to the same procedure as that for Fine Particles 1, except that a castor oil-based polyol (URIC HF-2009 manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 43 mgKOH / g) was used instead of the above URIC AC-009. The obtained polyurethane fine particles are also referred to as Fine Particles 4, and the dispersion of Fine Particles 4 dispersed in oil is also referred to as Fine Particle Dispersion 4.

[0097] When SEM observation was performed on the obtained Fine Particles 4, Fine Particles 4 were fine particles having pores on the surface with an average particle diameter of 28 μm. FIG. 2 shows a scanning electron microscope (SEM) photograph of Fine Particles 4.

[0098] 〔Fine Particles 5〕

[0099] 〔Dispersion Step〕 100 g of a castor oil-based polyol (URIC HF-2009 manufactured by Ito Oil Co., Ltd., with a hydroxyl value of 43 mgKOH / g), 10 g of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 2 g of a silicone-based foam stabilizer (Niax silicone L-5111 manufactured by Momentive Performance Materials Inc.), 1 g of water, and 297 g of an oil (Extract No. 4S manufactured by Shell Lubricants Japan Ltd.) were stirred with a revolving and orbiting stirrer for 3 minutes. Thus, a dispersion system was obtained.

[0100] [Polymerization process] 150 g of polymeric MDI (Millionate MR-400 manufactured by Tosoh Corporation, NCO% is 30%) was added to the obtained dispersion system and stirred for 30 minutes. Next, 40 g of ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred for 10 minutes to polymerize the polyol, isocyanate, and ethanol and generate carbon dioxide, thereby obtaining polyurethane fine particles dispersed in oil. The content of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as fine particles 5, and the dispersion of fine particles 5 dispersed in oil is also referred to as fine particle dispersion 5.

[0101] When SEM observation was performed on the obtained fine particles 5, the fine particles 5 were fine particles having pores on the surface with an average particle diameter of 20 μm.

[0102] [Comparative fine particle 1] 55 g of castor oil-based polyol (URIC HF-2009 manufactured by Ito Oil Co., Ltd., hydroxyl value is 43 mgKOH / g), 14 g of dimethylthiotoluenediamine (Heart Cure 30 manufactured by Kumiai Chemical Co., Ltd.), 92 g of liquid isoprene polymer (LIR-30 manufactured by Kuraray Co., Ltd.), and 1 g of sorbitanic acid-based surfactant (TW-O320V manufactured by Kao Corporation) were stirred for 2 minutes with a rotating and revolving stirrer. Thus, a dispersion system was obtained. 11 g of polymeric MDI (Coronate 1331 manufactured by Tosoh Corporation, NCO% is 32%) was added to the obtained dispersion system and stirred for 2 minutes. Next, 11 g of maleic anhydride-modified polyisoprene (LIR-403 manufactured by Kuraray Co., Ltd.) was added and stirred for 1 hour to polymerize the polyol and isocyanate, thereby obtaining polyurethane fine particles dispersed in liquid isoprene. The content of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as comparative fine particle 1, and the dispersion of comparative fine particle 1 dispersed in liquid isoprene is also referred to as comparative fine particle dispersion 1.

[0103] When SEM observation was performed on the obtained comparative fine particle 1, the comparative fine particle 1 was a fine particle having no pores on the surface with an average particle diameter of 12 μm.

[0104] Note that the comparative fine particle dispersion 1 is almost the same as the particle dispersion 1 described in paragraph

[0037] of JP-A-2022-164378.

[0105] 〔Comparative Fine Particle 2〕 Instead of the above URIC AC-009, a castor oil-based polyol (URIC H-1830 manufactured by Ito Seiyu Co., Ltd., hydroxyl value: 82 mgKOH / g) was used. Except for changing the amount of water to 13 g and the amount of oil to 262 g, polyurethane fine particles dispersed in oil were obtained according to the same procedure as for Fine Particle 1. The content rate of the fine particles in the dispersion was 50% by mass. The obtained polyurethane fine particles are also referred to as Comparative Fine Particle 2, and the dispersion of Comparative Fine Particle 2 dispersed in oil is also referred to as Comparative Fine Particle Dispersion 2.

[0106] When SEM observation was performed on the obtained Comparative Fine Particle 2, Comparative Fine Particle 2 was fine particles having pores on the surface with an average particle diameter of 322 μm. The reason why Comparative Fine Particle 2 is larger than other fine particles is not clear, but it is considered that crosslinking (urea bond) between the fine particles proceeded due to water, resulting in larger fine particles.

[0107] [Manufacture of Rubber Composition for Tire] The components shown in Tables 1 to 2 below were blended at the ratios (parts by mass) shown in the same tables. Specifically, first, the components excluding sulfur and vulcanization accelerator were kneaded in a 1.7-liter sealed mixer for 5 minutes, and discharged when the temperature reached 150°C to obtain a masterbatch. Next, sulfur and vulcanization accelerator were kneaded into the obtained masterbatch on an open roll to obtain a rubber composition for tire. Note that the mass part of the oil (aromatic oil) was adjusted so that the total of the oil or liquid isoprene polymer in the fine particle dispersion and the oil (aromatic oil) becomes 20 parts by mass.

[0108] [Evaluation] The following evaluations were performed on the obtained rubber composition for tire.

[0109] 〔Elongation at Break〕 The obtained rubber composition for tires was vulcanized at 170 °C for 10 minutes using a mold of a predetermined shape (inner dimensions: length 150 mm, width 150 mm, thickness 2 mm) to prepare a vulcanized rubber test piece. Using the vulcanized rubber test piece, a dumbbell JIS No. 3 test piece was prepared in accordance with JIS K6251, and a tensile test was conducted at a tensile speed of 500 mm / min at room temperature (20 °C), and the elongation at break at the time of fracture was measured. The obtained results are shown in Tables 1 and 2 as an index with the value of Standard Example 1 being 100. The larger this index, the greater the elongation at break. The index is preferably 106 or more.

[0110] 〔Ice performance〕 The obtained rubber composition for tires was used for the tread part and vulcanization molded to manufacture a pneumatic tire (tire size: 215 / 60R16). The above pneumatic tire was assembled on a 16×7J rim, filled with air pressure (220 [kPa]), and mounted on a test vehicle (domestic 2-liter sedan FF vehicle). Subsequently, the test vehicle was used to brake suddenly from an initial speed of 40 [km / h] on a test course that was an ice road surface, and the braking distance until a complete stop was measured. The results of the braking distance measured as described above are shown in Tables 1 and 2 as an index with the reciprocal of Standard Example 1 being 100. The larger this index, the better the ice performance. The index is preferably 106 or more.

[0111]

Table 1

[0112]

Table 2

[0113] The details of each component in Tables 1 and 2 are as follows. ·NR: Natural rubber, STR20 manufactured by BOMBARDIER (glass transition temperature: -65 °C) ·BR: Butadiene rubber, Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (glass transition temperature: -110 °C) · Silica: ULTRASIL VN3 manufactured by Evonik Degussa · Carbon black: SHOW BLACK N339 manufactured by Cabot Japan · Silane coupling agent: Si69 manufactured by Evonik Degussa · Zinc oxide: Three types of zinc oxide manufactured by Shohdo Chemical · Stearic acid: BEAD STEARIC ACID YR manufactured by NOF Corporation · Antioxidant: Amine-based antioxidant, Santoflex 6PPD manufactured by Flexsys · Wax: Paraffin wax manufactured by Ouchi Shinsei Chemical · Oil: Aroma oil, EXTRACT No. 4S manufactured by Shell Lubricants Japan · Sulfur: 5% oil-treated sulfur manufactured by Hosoi Chemical · Vulcanization accelerator: Sulfenamide-based vulcanization accelerator, Sunceler CM-G manufactured by Sanshin Chemical · Fine particle dispersions 1 to 5: Fine particle dispersions 1 to 5 manufactured as described above · Comparative fine particle dispersions 1 to 2: Comparative fine particle dispersions 1 to 2 manufactured as described above · Comparative fine particle 3: Polyacrylate porous fine particles, Tech Polymer ACP-8C (average particle diameter: 8 μm) manufactured by Sekisui Chemical

[0114] In Tables 1 to 2, "isocyanate group / active hydrogen group" and "average particle diameter" represent the "isocyanate group / active hydrogen group" and "average particle diameter" of the specific fine particles described above, respectively.

[0115] As can be seen from Tables 1 to 2, Examples 1 to 6 containing the specific fine particles all showed excellent elongation at break and ice performance. From the comparison of Examples 1 to 4 and 6 (comparison between the embodiments where the content of the specific fine particles is 5 parts by mass with respect to 100 parts by mass of the diene rubber), Examples 1 to 2, 4, and 6 where the isocyanate group / hydrogen active group of the specific fine particles is 0.8 to 4.0 showed more excellent elongation at break and ice performance. Among them, Examples 2, 4, and 6 where the hydroxyl value of the polyol constituting the specific fine particles is 10 to 200 mgKOH / g showed even more excellent ice performance. Among them, Examples 4 and 6 where the polyisocyanate constituting the specific fine particles is polymeric MDI showed even more excellent elongation at break and ice performance. From the comparison of Examples 4 to 5 (comparison between the embodiments where only the content of the specific fine particles is different), Example 4 where the content of the specific fine particles with respect to 100 parts by mass of the diene rubber is 20 parts by mass or less showed more excellent elongation at break.

[0116] On the other hand, Comparative Example 1 containing fine particles having no pores on the surface, Comparative Example 2 containing fine particles having pores on the surface but with an average particle diameter exceeding 300 μm, and Comparative Example 3 containing polyacrylic acid ester porous fine particles had insufficient elongation at break and ice performance.

Explanation of symbols

[0117] 1 Bead part 2 Sidewall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims

1. A rubber composition for tires, comprising 100 parts by mass of a diene rubber, 30 to 100 parts by mass of at least one filler selected from the group consisting of carbon black and a white filler, and 1 to 30 parts by mass of polyurethane fine particles having pores on the surface with an average particle diameter of 1 to 300 μm.

2. The rubber composition for tires according to claim 1, wherein the polyurethane fine particles are polyurethane fine particles obtained by reacting a polyol, a polyisocyanate, and water in oil.

3. The rubber composition for tires according to claim 1, wherein the polyol constituting the polyurethane fine particles contains a castor oil-based polyol having a hydroxyl value of 10 to 200 mgKOH / g.

4. The rubber composition for tires according to claim 1, wherein the polyisocyanate constituting the polyurethane fine particles contains an aromatic polyisocyanate.

5. The rubber composition for tires according to claim 1, wherein in the reaction for obtaining the polyurethane fine particles, the molar ratio of the isocyanate group to the active hydrogen group is 0.8 to 4.

0.

6. The diene rubber includes natural rubber and butadiene rubber, and the proportion of the butadiene rubber in the total diene rubber is 30% by mass or more. The rubber composition for tires according to claim 1.

7. A studless tire manufactured using the rubber composition for tires according to any one of claims 1 to 6 in a tread portion.

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