Rubber composition for tire and tire

Abstract

The present invention provides a tire rubber composition capable of changing the performance of a tire in response to a temperature change, and a tire. The present invention relates to a tire rubber composition comprising: a rubber component comprising at least one selected from the group consisting of a polyisoprene rubber, a polybutadiene rubber, and a styrene-butadiene rubber; a cross-linking agent; carbon black; a plasticizer; and a temperature-responsive material A containing a carboxyl group-containing polymer and a metal salt, the amount of the crosslinking agent being more than 0 parts by mass but less than 10 parts by mass, the amount of the carbon black being more than 0 parts by mass but less than 100 parts by mass, and the amount of the plasticizer being more than 5 parts by mass per 100 parts by mass of the rubber component.

Description

Technical Field

[0001] The present invention relates to a tire rubber composition and a tire. Background Art

[0002] Tires need to have a variety of performance. In particular, all-season tires need to cope with large changes in outside temperature and changes in road conditions. Summary of the invention Technical problem to be solved by the invention

[0003] The present invention is directed to solving the above-mentioned problems and provides a tire rubber composition and a tire capable of changing tire performance in response to temperature changes. Solutions to the problem

[0004] The present invention relates to a tire rubber composition, comprising: a rubber component, which comprises at least one selected from polyisoprene rubber, polybutadiene rubber and styrene-butadiene rubber; a crosslinking agent; carbon black; a plasticizer; and a temperature-responsive material A, wherein the temperature-responsive material A contains a carboxyl-containing polymer and a metal salt, and relative to 100 parts by mass of the rubber component, the amount of the crosslinking agent in the tire rubber composition is greater than 0 parts by mass and less than 10 parts by mass, the amount of the carbon black is greater than 0 parts by mass and less than 100 parts by mass, and the amount of the plasticizer is greater than 5 parts by mass. Advantageous Effects of the Invention

[0005] According to the present invention, the structure of the tire has the above-mentioned features. The present invention can provide a tire rubber composition and a tire capable of changing tire performance in response to temperature changes. DETAILED DESCRIPTION

[0006] The present invention relates to a tire rubber composition, comprising a predetermined amount of a rubber component, a crosslinking agent, carbon black, a plasticizer and a temperature-responsive material A, wherein the rubber component comprises at least one selected from polyisoprene rubber, polybutadiene rubber and styrene-butadiene rubber, and the temperature-responsive material A contains a carboxyl-containing polymer and a metal salt.

[0007] To date, the tire industry has not paid much attention to tire performance that changes in response to temperature changes. Conventional technology still has room for improvement in tire performance that changes in response to temperature changes. Specifically, it is necessary to improve the grip performance of the tire on low-temperature ice by reducing the elastic modulus, and it is necessary to improve the handling stability of the tire at high temperatures by improving the elastic modulus. Technology using rubber that is flexible at low temperatures may be a viable solution. However, this technology is disadvantageous for traditional rubber compositions because the use of high-flexibility rubber will reduce handling stability. Another possible technique is to add temperature-responsive materials, such as poly(N-isopropylacrylamide) (PNIPAM). The disadvantage of this material is that it is easily soluble in water at low temperatures and may dissolve in water on rainy days or on ice, thus disappearing from the composition. In contrast, the temperature-responsive material A in the present invention is a material whose elastic modulus increases when the temperature rises from, for example, 0°C to 100°C after absorbing water or whose elastic modulus decreases when the temperature decreases. This material can be used to change tire performance in response to temperature changes.

[0008] The mechanism of this beneficial effect is not completely clear, but is thought to be as follows. After the temperature-responsive material A of the present invention absorbs water, its elastic modulus changes with the change in temperature, thereby changing the elastic modulus of the rubber composition. It is considered that at least one of the water-soluble material B or the water-absorbent material B added as needed can promote water absorption by the temperature-responsive material A. This is probably because at least one of the water-soluble material B or the water-absorbent material B immersed in water dissolves in water or absorbs water, thereby forming voids in the rubber. Therefore, it is believed that the performance of the tire changes in response to temperature changes caused by, for example, flooding.

[0009] The tire rubber composition includes a rubber component, which includes at least one of polyisoprene rubber, polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). In order to better achieve the beneficial effects, the tire rubber composition preferably includes at least one of isoprene rubber and BR, and more preferably includes both isoprene rubber and BR.

[0010] The rubber component that can be used in the rubber composition contributes to crosslinking and is a polymer component that has a weight average molecular weight (Mw) of generally 10,000 or more and is not extracted with acetone. The rubber component is solid at room temperature (25° C.).

[0011] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. When the weight average molecular weight is within the above range, the beneficial effects tend to be better achieved.

[0012] Herein, the weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC) (GPC-8000 series, available from Tosoh Corporation, detector: differential refractometer, column: TSKgel SuperMultipore HZ-M, available from Tosoh Corporation). The obtained value is calibrated with a polystyrene standard.

[0013] Each rubber component such as polyisoprene rubber, BR or SBR may be an unmodified rubber or a modified rubber. The modified rubber may be any rubber having a functional group that interacts with a filler (e.g., silica). Examples of modified rubbers include: a chain end modified rubber obtained by modifying at least one chain end of the rubber with a compound (modifier) ​​having the above functional group (i.e., a chain end modified rubber terminated with the above functional group); a main chain modified rubber having the above functional group in the main chain; a main chain and chain end modified rubber having the above functional group in both the main chain and the chain end (e.g., a main chain and chain end modified rubber having the above functional group in the main chain and at least one chain end modified by the above modifier); and a chain end modified polymer into which a hydroxyl group or an epoxy group is introduced by modification (coupling) with a multifunctional compound having two or more epoxy groups in the molecule.

[0014] Examples of the above functional groups include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazolyl, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfoxyl, thiocarbonyl, ammonium, imido, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy and epoxy. These functional groups may be substituted. Among them, amino (preferably amino in which hydrogen atoms are substituted by C1-C6 alkyl), alkoxy (preferably C1-C6 alkoxy) and alkoxysilyl (preferably C1-C6 alkoxysilyl) are preferred.

[0015] Usable rubbers also include hydrogenated rubbers.

[0016] Examples of isoprene-based rubbers include natural rubber (NR), polyisoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include NR commonly used in the rubber industry, such as SIR20, RSS#3, and TSR20. Any IR can be used, including, for example, IR commonly used in the rubber industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized polyisoprene-based rubber, hydrogenated polyisoprene rubber, and grafted polyisoprene rubber. Modified isoprene-based rubbers having the aforementioned modified rubber functional groups can also be used. Each of them can be used alone or in combination of two or more.

[0017] In the rubber composition, if there is an isoprene-based rubber, the amount of the isoprene-based rubber is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the rubber component. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. When the amount of the isoprene-based rubber is within the above range, the beneficial effects tend to be better achieved.

[0018] Non-limiting examples of BR include high cis BR with high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth catalyzed BR). Each of them can be used alone or in combination of two or more. BR preferably includes high cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more, and even more preferably 98% by mass or more. The upper limit is not limited, preferably 99% by mass or less. The cis content can be determined by infrared absorption spectroscopy.

[0019] BR may be unmodified BR or modified BR. Examples of modified BR include modified BR into which the aforementioned functional groups for modifying rubber have been introduced. BR may include hydrogenated polybutadiene rubber.

[0020] Usable commercially available BR is available from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, and the like.

[0021] In the rubber composition, if BR is present, the amount of BR is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more, based on 100% by mass of the rubber component. The upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less. When the amount of BR is within the above range, the beneficial effects tend to be better achieved.

[0022] Non-limiting examples of SBR include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR), each of which may be used alone or in combination of two or more.

[0023] The styrene content of SBR is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The styrene content is preferably 30% by mass or less, more preferably 23.5% by mass or less, even more preferably 20% by mass or less, and further preferably 15% by mass or less. When the styrene content is within the above range, the beneficial effect tends to be better achieved. In this article, we can 1 The styrene content was calculated by H-NMR analysis.

[0024] The vinyl bond content of SBR is preferably 20% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and particularly preferably 42% by mass or more. The vinyl bond content is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. When the vinyl bond content is within the above range, the beneficial effects tend to be better achieved. Herein, the vinyl bond content (1,2-bonded butadiene unit content) may be measured by infrared absorption spectroscopy.

[0025] The SBR may be an SBR product manufactured or sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, or the like.

[0026] In the rubber composition, if there is SBR, then based on the rubber component as 100% by mass, the amount of SBR is preferably more than 5% by mass, more preferably more than 10% by mass, and more preferably more than 15% by mass. The upper limit is preferably less than 40% by mass, more preferably less than 30% by mass, and more preferably less than 25% by mass. When the amount of SBR is within the above range, it tends to achieve a beneficial effect better.

[0027] Examples of available rubber components other than isoprene-based rubber, BR and SBR include styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR) and acrylonitrile-butadiene rubber (NBR). In addition, examples also include butyl-based rubber and fluororubber. Each of them can be used alone or in combination of two or more.

[0028] The rubber composition contains a cross-linking agent. The crosslinking agent may be any compound capable of crosslinking the rubber component. Examples include crosslinking agents known in the tire industry, such as sulfur, organic crosslinking agents, organic peroxides, and resin crosslinking agents. To better achieve the beneficial effects, sulfur is preferably used.

[0029] In the rubber composition, the amount of the crosslinking agent (total amount of the crosslinking agent) is greater than 0 mass parts and less than 10 mass parts relative to 100 mass parts of the rubber component. The lower limit is preferably 0.6 mass parts or more, more preferably 0.9 mass parts or more, even more preferably 1.2 mass parts or more, and particularly preferably 1.5 mass parts or more. The upper limit is preferably 5.0 mass parts or less, more preferably 3.0 mass parts or less, even more preferably 2.5 mass parts or less, and particularly preferably 2.0 mass parts or less. When the amount of the crosslinking agent is within the above range, it tends to achieve a better beneficial effect.

[0030] Examples of sulfur include sulfur commonly used as a crosslinking agent in the rubber industry, such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Available sulfur may include products commercially available from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexsys, Inc., Nippon Senryu Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. Each of them may be used alone or in combination of two or more.

[0031] In the rubber composition, the amount of sulfur is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, still more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of sulfur is within the above range, the beneficial effects tend to be better achieved.

[0032] Non-limiting examples of the organic crosslinking agent include maleimide compounds, alkylphenol-sulfur chloride condensates, organic peroxides, and amine organic sulfides, each of which may be used alone or in combination of two or more.

[0033] In the rubber composition, the amount of the organic crosslinking agent is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, still more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the organic crosslinking agent is within the above range, the beneficial effects tend to be better achieved.

[0034] Examples of organic peroxides include benzoyl peroxide, diisopropyl peroxide, di-tert-butyl peroxide, tert-butyl isopropyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and 1,3-bis(tert-butylperoxypropyl)benzene. Each of these may be used alone or in combination of two or more.

[0035] In the rubber composition, the amount of the organic peroxide is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, still more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the organic peroxide is within the above range, the beneficial effects tend to be better achieved.

[0036] Non-limiting examples of the resin crosslinking agent include phenol resin, melamine formaldehyde resin, triazine formaldehyde condensate, hexamethoxymethylmelamine resin and alkylphenol-sulfur chloride condensate. Alkylphenol-sulfur chloride condensate is suitable in view of the beneficial effects of the present invention.

[0037] The alkylphenol-sulfur chloride condensate is not limited. In order to obtain low heat generation properties, hardness, etc. and suppress reversion, the alkylphenol-sulfur chloride condensate is preferably a compound represented by formula (II).

[0038] [Chemical formula 1] In the formula, R 101 , R 102 and R 103 are the same as or different from each other and each represents a C5-C12 alkyl group, x and y are the same as or different from each other and each represents an integer of 1 to 3, and k represents an integer of 0 to 250.

[0039] In order to fully disperse the alkylphenol-sulfur chloride condensate in the rubber component, k is preferably an integer of 0-250, and more preferably an integer of 0-100. In order to effectively obtain high hardness, both x and y are preferably 2. In order to fully disperse the alkylphenol-sulfur chloride condensate in the rubber component, R 101 To R 103 Each is preferably a C6-C9 alkyl group.

[0040] The alkylphenol-sulfur chloride condensate can be prepared by a known method, such as a method in which an alkylphenol and sulfur chloride are reacted at a molar ratio of 1:0.9 to 1.25. Examples of the alkylphenol-sulfur chloride condensate include TACKIROL V200 (shown in the following formula (II-1)) available from Taoka Chemical Industry Co., Ltd.

[0041] [Chemical formula 2] In the formula, k represents an integer from 0 to 100.

[0042] In the rubber composition, the amount of the resin crosslinking agent is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, still more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the resin crosslinking agent is within the above range, the beneficial effects tend to be better achieved.

[0043] Usable commercially available crosslinking agents are available from Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexsys, Inc., Nippon Senryu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. Each of these may be used alone or in combination of two or more.

[0044] The rubber composition contains carbon black. Non-limiting examples of carbon black include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550 and N762. Available commercial products can be purchased from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. Each of them can be used alone or in combination of two or more.

[0045] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 30 m 2 / g or more, more preferably 50m 2 / g or more, and more preferably 70m 2 / g or more. N2SA is preferably 200m 2 / g or less, more preferably 150m 2 / g or less, and more preferably 130m / g or less 2 / g or less, particularly preferably 120m 2 / g or less, and the most preferred is 111m 2 When N2SA is within the above range, the beneficial effects tend to be better achieved. The N2SA of carbon black can be measured in accordance with JIS K 6217-2:2001.

[0046] In the rubber composition, the amount of carbon black is greater than 0 mass parts and less than 100 mass parts relative to 100 mass parts of the rubber component. The lower limit is preferably 3 mass parts or more, more preferably 5 mass parts or more, even more preferably 7 mass parts or more, and particularly preferably 10 mass parts or more. The upper limit is preferably 50 mass parts or less, more preferably 30 mass parts or less, even more preferably 25 mass parts or less, and particularly preferably 20 mass parts or less. When the amount of carbon black is within the above range, it tends to achieve better beneficial effects.

[0047] In addition to carbon black, the rubber composition preferably also contains different fillers. Examples of different fillers include inorganic fillers such as silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide and mica. In order to better achieve the beneficial effects, silica is preferred.

[0048] Non-limiting examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet silica is preferred because it contains a large amount of silanol groups.

[0049] The nitrogen adsorption specific surface area (N2SA) of silicon dioxide is preferably 30 m 2 / g or more, more preferably 100m 2 / g or more, and more preferably 125 m 2 / g or more. The N2SA of silica is preferably 300m 2 / g or less, more preferably 250m 2 / g or less, and more preferably 200m / g or less 2 / g or less, particularly preferably 175m 2 When N2SA is within the above range, the beneficial effects tend to be better achieved. The N2SA of silica is measured by the BET method according to ASTM D3037-93.

[0050] Commercially available silica that can be used is available from Evonik Degussa, Rhodia, Tosoh Silicone Chemicals, Solvay Japan Ltd., Tokuyama Corporation, and the like.

[0051] In the rubber composition, the amount of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 55 parts by mass or more, and particularly preferably 60 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit of the amount of silica is not limited, and is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less. When the amount of silica is within the above range, the beneficial effect tends to be better achieved.

[0052] The rubber composition preferably contains a silane coupling agent. Non-limiting examples of usable silane coupling agents include silane coupling agents commonly used with silica in the rubber field, including: sulfide silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, Bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) ) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide and methacrylate 3-triethoxysilylpropyl monosulfide; mercaptosilane coupling agents, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane. Silane; aminosilane coupling agents such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxysilane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitrosilane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorosilane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Available commercial products can be purchased from Evonik Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Dow Corning Toray Co., Ltd., etc. Each of them can be used alone or in combination of two or more.

[0053] In the rubber composition, the amount of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of silica (100 parts by mass of silica constituting the total of the surface-modified silica and silica other than the silica). The upper limit of the amount of the silane coupling agent is preferably 50 parts by mass, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When the amount of the silane coupling agent is within the above range, the beneficial effects tend to be better achieved.

[0054] The rubber composition contains a plasticizer. The term "plasticizer" refers to a material that can impart plasticity to a rubber component. Examples include liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) and resins (resins that are solid at room temperature (25°C)).

[0055] In the rubber composition, the amount of plasticizer (total amount of plasticizer) is greater than 5 parts by mass relative to 100 parts by mass of the rubber component. The lower limit is preferably more than 10 parts by mass, more preferably more than 15 parts by mass, even more preferably more than 20 parts by mass, and particularly preferably more than 25 parts by mass. The upper limit is preferably less than 100 parts by mass, more preferably less than 60 parts by mass, even more preferably less than 50 parts by mass, particularly preferably less than 40 parts by mass, and most preferably less than 35 parts by mass. When the amount of plasticizer is within the above range, it tends to achieve a beneficial effect better.

[0056] Liquid plasticizers (plasticizers that are liquid at room temperature (25° C.)) that can be used in the rubber composition are not limited. It is preferred to use oil or liquid polymers (liquid resins, liquid diene polymers, liquid farnesene polymers, etc.). In order to better achieve the beneficial effects, it is preferred to include oil. Each of them can be used alone or in combination of two or more.

[0057] In the rubber composition, the amount of the liquid plasticizer is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, particularly preferably 40 parts by mass or less, and most preferably 35 parts by mass or less. When the amount of the liquid plasticizer is within the above range, the beneficial effect tends to be better achieved.

[0058] The example of oil includes process oil, vegetable oil and mixture thereof. The example of process oil includes paraffin process oil, aromatic process oil and naphthenic process oil. The example of vegetable oil includes castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower seed oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil and tung oil. Available commercial products can be purchased from Idemitsu Kosan Co., Ltd., Sankyo Oil Chemical Industry Co., Ltd., Inno Shi Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokoku Oil Refining Co., Ltd., Showa Shell Oil Co., Ltd., Fujikosan Co., Ltd., Nissin Olliio Group, etc. Among them, preferred process oil (such as paraffin process oil, aromatic process oil, naphthenic process oil) and vegetable oil.

[0059] In the rubber composition, the amount of oil is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, particularly preferably 40 parts by mass or less, and most preferably 35 parts by mass or less. When the amount of oil is within the above range, the beneficial effect tends to be better achieved. The amount of oil includes the amount of filler oil in the oil-extended rubber.

[0060] Examples of the liquid resin in the liquid polymer include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone-based or indene-based resins), phenolic resins, olefin resins, polyurethane resins, and acrylic resins. Hydrogenates of these resins may also be used.

[0061] Examples of liquid diene polymers in the liquid polymer include liquid styrene-butadiene copolymers (liquid SBR), liquid polybutadiene polymers (liquid BR), liquid polyisoprene polymers (liquid IR), liquid styrene-isoprene copolymers (liquid SIR), liquid styrene-butadiene-styrene block copolymers (liquid SBS block polymers), liquid styrene-isoprene-styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, and liquid farnesene-butadiene copolymers, all of which are liquid at 25° C. The chain ends or main chains of these polymers may be modified with polar groups. Hydrogenates of these polymers may also be used. Usable commercially available liquid diene polymers are available from Sartomer, Kuraray Co., Ltd., and the like.

[0062] In the rubber composition, the amount of the liquid polymer is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. When the amount of the liquid polymer is within the above range, the beneficial effects tend to be better achieved.

[0063] Examples of resins that can be used in rubber compositions (resins that are solid at room temperature (25° C.)) include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenol resins, rosin resins, petroleum resins, terpene resins, and acrylic resins, all of which are solid at room temperature (25° C.). The resins may be hydrogenated. Each of them may be used alone or in combination of two or more. Among them, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0064] In the rubber composition, the amount of the resin is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. When the amount of the resin is within the above range, the beneficial effects tend to be better achieved.

[0065] The softening point of the resin is preferably 50° C. or higher, more preferably 55° C. or higher, still more preferably 60° C. or higher, and further preferably 85° C. or higher. The upper limit is preferably 160° C. or lower, more preferably 150° C. or lower, and still more preferably 145° C. or lower. When the softening point is within the above range, the beneficial effects tend to be better achieved. Here, the softening point of the resin is measured according to JIS K 6220-1:2001 using a ring and ball softening point measuring device, and the temperature when the ball is dropped is defined as the softening temperature.

[0066] The term "aromatic vinyl polymer" refers to a polymer containing an aromatic vinyl monomer as a structural unit. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene. Specific examples include styrene homopolymers (styrene resins), α-methylstyrene homopolymers (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, and copolymers of styrene and other monomers.

[0067] The term "coumarone-indene resin" refers to a resin containing coumarone and indene as main monomer components constituting the resin skeleton (main chain). Examples of monomer components that may be contained in the skeleton in addition to coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0068] The term "coumarone resin" refers to a resin containing coumarone as a main monomer component constituting the resin skeleton (main chain).

[0069] The term "indene resin" refers to a resin containing indene as a main monomer component constituting the resin skeleton (main chain).

[0070] Examples of phenol resins include known polymers obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde or furfural in the presence of an acid or base catalyst. Among them, phenol resins obtained by a reaction in the presence of an acid catalyst, such as novolac phenol resins, are preferred.

[0071] Examples of the rosin resin include rosin resins represented by natural rosin, polymerized rosin, modified rosin, esterified compounds thereof, and hydrogenated products thereof.

[0072] Examples of petroleum resins include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, and hydrogenated products of these resins. Among them, DCPD resin and hydrogenated DCPD resin are preferred.

[0073] The term "terpene resin" refers to a polymer containing terpene as a structural unit. Examples include polyterpene resins made by polymerizing terpene compounds, and aromatic modified terpene resins made by polymerizing terpene compounds and aromatic compounds. Examples of usable aromatic modified terpene resins include terpene-phenol resins made from terpene compounds and phenolic compounds, terpene-styrene resins made from terpene compounds and styrene compounds, and terpene-phenol-styrene resins made from terpene compounds, phenolic compounds, and styrene compounds. Examples of terpene compounds include α-pinene and β-pinene. Examples of phenolic compounds include phenol and bisphenol A. Examples of aromatic compounds include styrene compounds, such as styrene and α-methylstyrene.

[0074] The term "acrylic resin" refers to a polymer containing an acrylic monomer as a structural unit. Examples include styrene acrylic resins, such as styrene acrylic resins containing carboxyl groups and produced by copolymerization of an aromatic vinyl monomer component and an acrylic monomer component. Among them, solvent-free, carboxyl-containing styrene-acrylic resins are suitable for use.

[0075] Usable commercially available resins are available from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Company, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., Innolux Co., Ltd., Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., and the like.

[0076] The rubber composition contains a temperature responsive material A containing a carboxyl group-containing polymer and a metal salt. Poly(N-isopropylacrylamide), or poly(NIPAAm), is a typical temperature-responsive polymer. Poly(NIPAAm) has a lower critical solution temperature (LCST), that is, in an aqueous solution, poly(NIPAAm) is soluble at a temperature below the LCST, and precipitates (phase separation occurs) at a temperature above the LCST. It is well known that poly(N-isopropylacrylamide) hydrogels can cause volume phase changes.

[0077] The temperature responsive material A containing a carboxyl group-containing polymer and a metal salt has the characteristics of a temperature responsive hydrogel. Preferably, the temperature responsive material A has the following properties. (1) Below the LCST, it is transparent; above the LCST, phase separation occurs and turbidity appears. (2) It is soft below the LCST and has high strength and toughness above the LCST. When the temperature rises above the LCST, the elastic modulus and toughness increase. Above a certain temperature, the elastic modulus increases sharply (becoming very hard), while the toughness decreases due to strong phase separation. (3) Almost no volume change is shown near LCST, and no volume phase transition is shown. In the present invention, the characteristic that the hydrogel shows no volume phase transition or almost no volume change means that the ratio V2 / V1 of the volume V2 at a temperature higher than LCST (e.g., T2 ≥ LCST + 5 ° C) to the volume V1 at a temperature lower than LCST (e.g., T1 ≤ LCST - 5 ° C) is in the range of 0.8 to 1.2, preferably 0.85 to 1.15, and more preferably 0.98 to 1.02. (4) The temperature-responsive phase separation is completely reversible.

[0078] The carboxyl-containing polymer may be any carboxyl-containing organic polymer compound. Examples include homopolymers of carboxyl-containing monomers and copolymers of various carboxyl-containing monomers. Each of these may be used alone or in combination of two or more.

[0079] Examples of carboxyl group-containing monomers include α,β-unsaturated carboxylic acids containing one or two or more carboxyl groups in the molecule. Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, aconitic acid, fumaric acid, and crotonic acid.

[0080] Non-limiting examples of homopolymers include polyacrylic acid and polymethacrylic acid.

[0081] The example of copolymer includes the copolymer of various carboxyl-containing monomers and the copolymer of carboxyl-containing monomer and monomer other than carboxyl-containing monomer. Non-limiting examples of monomers other than carboxyl-containing monomer include acrylate monomers (e.g., esters of α, β-vinyl unsaturated carboxylic acids, hydroxyalkyl esters of α, β-vinyl unsaturated carboxylic acids and alkoxyalkyl esters of α, β-vinyl unsaturated carboxylic acids), acrylamide monomers and styrene monomers. Each of them can be used alone or in combination of two or more.

[0082] Non-limiting examples of acrylate monomers include esters of α,β-vinyl unsaturated carboxylic acids, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, lauryl acrylate, and octadecyl acrylate; hydroxyalkyl esters of α,β-vinyl unsaturated carboxylic acids, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 3-hydroxypropyl methacrylate; and alkoxyalkyl esters of α,β-vinyl unsaturated carboxylic acids, such as diethylene glycol methacrylate.

[0083] Non-limiting examples of acrylamide monomers include acrylamide and hydroxymethyl methacrylamide.

[0084] Non-limiting examples of styrene monomers include styrene and alkylstyrenes.

[0085] From the perspective of temperature responsiveness, the content of the structural unit derived from the carboxyl group-containing monomer in the copolymer is ideally 50 mol% or more. This content is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. The upper limit is not limited, for example, 98 mol% or less, more preferably 95 mol% or less.

[0086] From the perspective of temperature responsiveness, the amount of carboxyl groups in the carboxyl-containing polymer is preferably 0.001 mol / g or more, more preferably 0.005 mol / g or more, and even more preferably 0.007 mol / g or more. In addition, it is preferably 0.05 mol / g or less, more preferably 0.03 mol / g or less, and even more preferably 0.014 mol / g or less.

[0087] The carboxyl group-containing polymer may have a cross-linked structure. Examples of the cross-linked structure include a chemical cross-linked structure or a physical cross-linked structure. The chemical cross-linked structure can be formed by initiating cross-linking using a cross-linking agent for forming chemical cross-links during or after the formation of the polymer. In the present invention, a cross-linking agent for forming a chemical cross-link is not included in the cross-linking agent.

[0088] Difunctional or multifunctional monomers can be used as crosslinking agents formed by chemical crosslinking to form a chemical crosslinking structure. Examples of crosslinking agents include N, N'-methylenebisacrylamide (MbAAd), N, N'-ethylenebisacrylamide, diethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and 1-acryloyloxy-3-methacryloyloxy-2-propanol. The amount of the crosslinking agent used to form the chemical crosslink can be determined according to the desired degree of crosslinking, for example, it can be in the range of 0 to 10 mol% relative to the monomer concentration.

[0089] The weight average molecular weight of the carboxyl-containing polymer is not limited. For example, the weight average molecular weight is 1,000,000 or less, preferably 500,000 or less. The lower limit is, for example, more than 5000, preferably more than 10000. In some cases, the weight average molecular weight of the polymer with a cross-linked structure may not be actually measured.

[0090] The physical cross-linked structure is formed by the formation of a salt between two carboxyl groups possessed by the carboxyl group-containing polymer and a divalent metal and / or by polymer entanglement. The physical cross-linked structure formed by the former technology is achieved by forming a salt with a divalent metal in the polymer, and this polymer is formed without using a chemical cross-linking agent. The phenomenon of re-bonding of the physically cut hydrogel after cutting is mainly due to the formation of a salt between the carboxyl group and the divalent metal. However, it is presumed that over a relatively long period of time, polymer entanglement also proceeds and the re-bonding is further strengthened due to the formation of the salt. The hydrogel having a chemical cross-linked structure may also have a physical cross-linked structure due to the formation of a salt between two carboxyl groups possessed by the polymer and a divalent metal, as well as due to the presence of polymer entanglement.

[0091] The polymerization method for preparing the polymer includes free radical polymerization (thermal polymerization) using a thermal initiator and photopolymerization using a photoinitiator. Among them, photopolymerization is preferred. Known initiators can be suitably used as polymerization initiators. Examples of photoinitiators include α-ketoglutaric acid. The amount of the initiator can be, for example, in the range of 0.01 to 10 mol% relative to the monomer concentration.

[0092] There is no limitation on the metal salt as a component constituting the temperature responsive material A. In order to better achieve the beneficial effects, the metal salt is preferably a metal salt of an organic acid, and more preferably a divalent metal salt of an organic acid.

[0093] Non-limiting examples of the organic acid constituting the organic acid divalent metal salt include fatty acids (fatty carboxylic acids), aromatic carboxylic acids, oxycarboxylic acids, and other organic acids.

[0094] Examples of the fatty acid (fatty carboxylic acid) include the following compounds. Formic acid Acetic acid Propionic acid [Propanoic acid] butyric acid [butyric acid] Isobutyric acid Valeric acid Isovaleric acid Caproic acid [hexanoic acid] Enanthic acid (heptylic acid) [heptanoic acid] Caprylic acid (octanoic acid) [octanoic acid] Pelargonic acid [nonanoic acid] Capric acid[Decanoic acid] Lauric acid Myristic acid Pentadecylic acid Palmitic acid (palmitic acid) (cetanoic acid) [hexadecanoic acid] margarinic acid [hexadecanoic acid] Stearic acid Oleic acid Linoleic acid Linolenic acid Tuberculostearic acid [nonadecanoic acid] Arachidic acid Arachidonic acid Eicosapentaenoic acid Behenic acid Docosahexaenoic acid Lignoceric acid Cerotic acid [hexadecanoic acid] Montanic acid Melissic acid

[0095] Examples of the aromatic carboxylic acid include the following compounds. Salicylic acid [Hydroxybenzoic acid] Gallic acid (Trihydroxybenzoic acid) Benzoic acid Phthalic acid Cinnamic acid (β-phenylacrylic acid) Mellitic acid (graphitic acid) [Mellitic acid]

[0096] Examples of the oxycarboxylic acid include the following compounds. Pyruvic acid (pyruvic acid, α-ketopropionic acid, pyropyruvic acid)

[0097] Examples of other organic acids include the following compounds. Oxalic acid Lactic acid (α-hydroxypropionic acid) Tartaric acid Maleic acid Fumaric acid (allomaleic acid, boletic acid, lichenic acid) Malonic acid [propanedioic acid] Succinic acid Malic acid (hydroxysuccinic acid) Citric acid Aconitic acid Glutaric acid Adipic acid Amino acids L-ascorbic acid (Vitamin C)

[0098] Considering the solubility and solubility curve of the salt in the hydrogel in the aqueous solution, formic acid, acetic acid and propionic acid are preferred among the organic acids. For example, in the range of 0°C to 100°C, calcium formate exhibits a relatively moderate positive solubility curve for its relationship with temperature (solubility increases when temperature rises). In contrast, calcium acetate has a negative solubility curve in the range of 0°C to about 60°C and a relatively moderate positive solubility curve in the range of about 50°C to about 85°C. Calcium propionate has a negative solubility curve in the range of 0°C to about 50°C and a positive solubility curve in the range of about 50°C to 100°C.

[0099] The divalent metal constituting the organic acid divalent metal salt is not limited, and is desirably, for example, an alkaline earth metal. Examples of the alkaline earth metal include calcium (Ca), magnesium (Mg), strontium (Sr), and barium (Ba).

[0100] In order to better achieve the beneficial effects, the divalent metal salt of an organic acid is preferably calcium formate, calcium acetate, calcium propionate, magnesium formate, magnesium acetate, magnesium propionate, etc. The LCST of the hydrogel may vary depending on the type of the divalent metal salt of an organic acid used.

[0101] The total metal concentration in the temperature responsive material A can be measured by inductively coupled plasma atomic emission spectroscopy (ICP). The metal ion concentration can be determined by incinerating a known volume of the temperature responsive material A (e.g., at about 1000° C.) to remove organic components, dissolving the residue in a known volume of water, and analyzing the aqueous solution by ICP. In the case where the temperature responsive material A includes a divalent metal salt of an organic acid, the concentration of free metal in the temperature responsive material A that does not form an organic acid salt can be measured using, for example, a metal ion electrode. If metal ions that form an organic acid salt and free metal ions are present in the temperature responsive material A, they can be distinguished from each other using this method.

[0102] In the case where the temperature-responsive material A includes a divalent metal salt of an organic acid, the concentration of the divalent metal salt of the organic acid in the temperature-responsive material A can be appropriately designed according to the physical properties required for the temperature-responsive hydrogel and the amount of carboxyl groups. For example, the concentration of the aqueous metal salt solution in which the polymer is impregnated ranges from 50 mM to saturation concentration, preferably 50 to 500 mM. The term "saturation concentration" refers to the saturated amount (equivalent amount) relative to the number of carboxyl groups in the polymer. The LCST of the hydrogel can be changed by controlling the concentration of the metal salt in the polymer. The metal concentration in the polymer is often higher than the metal concentration in the aqueous metal salt solution in which the polymer is impregnated, and varies with conditions such as the carboxyl concentration in the polymer and the metal salt concentration in the aqueous solution. For example, the concentration of the metal can be about 1.1 to 2.0 times or typically about 1.2 to 1.5 times the metal concentration of the aqueous metal salt solution. In the case where the divalent metal is calcium, the concentration of the divalent metal in the polymer is in the range of about 1 to about 100 mg based on 1 g of the polymer (gel). More typically, the concentration is in the range of about 10 to about 70 mg, and still more typically, in the range of about 15 to about 50 mg.

[0103] The temperature-responsive material A (hydrogel) containing a carboxyl-containing polymer and a metal salt is a gel whose main components are water or an aqueous solution and a polymer. Whether a polymer will form a hydrogel depends mainly on the length of the polymer (in other words, the concentration of the polymerization initiator). When the polymer mass is the same, the higher the concentration of the polymerization initiator, the greater the possibility of gel formation. From this point of view, for example, when the monomer is acrylic acid, when the concentration of the polymerization initiator is 0.1 mol%, gel formation tends to occur at more than 3M, and when the concentration of the polymerization initiator is 0.01 mol%, gel formation tends to occur at more than 2M, which is roughly the same as when the monomer is methacrylic acid. Depending on the type of polymerization initiator and the type of monomer, the concentration of the polymerization initiator can be appropriately selected within the range of hydrogel formation.

[0104] The temperature-responsive material A (hydrogel) has a lower critical solution temperature (LCST). LCST is the lower critical solution temperature at which the hydrogel becomes turbid due to phase separation, and is an indicator of the phase separation temperature. For example, whether there is LCST can be evaluated by measuring the turbidity (light transmittance) using a UV-visible-near infrared spectrophotometer, or measuring the endothermic / exothermic peak using a differential scanning calorimeter, or measuring the temperature dependence of the dynamic elastic modulus using a rheometer (viscoelasticity meter). The LCST of the temperature-responsive material A (hydrogel) varies depending on the composition of the polymer, the type and concentration of the metal salt, etc. For example, the LCST is in the range of 10°C to 80°C, preferably in the range of 25°C to 45°C.

[0105] The temperature-responsive material A (hydrogel) is transparent at a temperature below the LCST and turbid at a temperature above the LCST. In the present invention, the term "transparent" means that the transmittance at a wavelength of 550 nm is 85% or more. The term "turbid" means that the transmittance at a wavelength of 550 nm is 30% or less.

[0106] For example, the temperature responsive material A (hydrogel) can be prepared by immersing a carboxyl group-containing polymer in an aqueous solution of a metal salt. The immersion of the polymer in the aqueous metal salt solution may be performed at room temperature, for example, in the range of 4° C. to 30° C. Considering the LCST of the temperature-responsive hydrogel to be obtained, the immersion may be performed at a temperature above or below the LCST.

[0107] The metal salt concentration of the aqueous metal salt solution can be appropriately determined in consideration of the types of polymer and metal salt and the desired LCST. For example, the metal salt concentration is in the range of 50 mM to saturation concentration. For example, a temperature-responsive hydrogel can be obtained by immersing the polymer in an aqueous metal salt solution having a metal salt concentration of 50 mM to saturation concentration until approximate equilibrium is reached. Regarding the immersion time of the chemically cross-linked gel, approximate equilibrium is reached in approximately 1 to 72 hours. In the case of a physically cross-linked gel, equilibrium is reached in approximately two to seven days. As long as the desired physical properties can be obtained, immersion until equilibrium is reached may be unnecessary.

[0108] In order to better achieve the beneficial effects, the temperature responsive material A is preferably a material that at least partially includes a foamed structure. The temperature responsive material A that at least partially includes a foamed structure may partially or entirely include a foamed structure. When the temperature responsive material A is a material that at least partially includes a foamed structure, it can provide expansion space for the voids where water originally existed. This can prevent the volume increase caused by the expansion of the temperature responsive material A during water absorption, so that the rubber composition can have better hardness when dry.

[0109] By further processing the hydrogel so as to have a foaming structure, a material at least partially including a foaming structure can be obtained. The material is obtained by foaming the hydrogel, and it at least partially includes a foaming structure having a large number of bubbles. The hydrogel can be processed to have a foaming structure by any method that can provide a material at least partially including a foaming structure. The hydrogel can be foamed by a known method. An example of the method includes heating the temperature-responsive material A (hydrogel), then rapidly cooling it with liquid nitrogen or the like (for example, within 1 hour, preferably within 30 minutes, more preferably within 10 minutes, and particularly preferably within 5 minutes), and freeze-drying. The temperature increase may be carried out under any conditions that induce phase separation of the temperature-responsive material A (hydrogel). For example, the temperature increase is preferably 60° C. or higher, more preferably 80° C. or higher, and preferably 120° C. or lower, and more preferably 100° C. or lower. The temperature increase time is preferably 1 minute or longer, preferably 5 minutes or longer, and preferably 24 hours or shorter, more preferably 10 hours or shorter, and even more preferably 1 hour or shorter. The drying time in freeze drying is not limited. For example, the drying time is preferably more than 1 hour, more preferably more than 5 hours, still more preferably more than 10 hours, particularly preferably more than 24 hours, and in addition, preferably less than 72 hours, more preferably less than 48 hours, still more preferably less than 30 hours. Another exemplary method for making the hydrogel have a foaming structure includes foaming the hydrogel by adding an inorganic foaming agent (such as sodium bicarbonate or ammonium carbonate) or an organic foaming agent (such as azodicarbonamide, dinitrosopentamethylenetetramine or p-, p-'-oxybis(benzenesulfonylhydrazide)) to the hydrogel.

[0110] In the rubber composition, the amount of the temperature responsive material A is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. When the amount of the temperature responsive material A is within the above range, the beneficial effect tends to be better achieved. In the present invention, the amount of temperature-responsive material A refers to the amount of temperature-responsive hydrogel (gel whose main components are water or aqueous solution and polymer) containing carboxyl-containing polymer and metal salt. The amount of temperature-responsive material A includes the amount of water contained in the temperature-responsive material (temperature-responsive hydrogel) and the amount of carboxyl-containing polymer and metal salt.

[0111] In order to better achieve the beneficial effects, the rubber composition preferably includes at least one of a water-soluble material B or a water-absorbent material B. In the present invention, at least one of the water-soluble material B or the water-absorbent material B is different from the temperature-responsive material A containing a carboxyl group-containing polymer and a metal salt. Specifically, for example, when the rubber composition contains a temperature-responsive hydrogel including polyacrylic acid and calcium acetate as the temperature-responsive material A and further contains calcium acetate monohydrate as at least one of the water-soluble material B or the water-absorbent material B, the calcium acetate in the temperature-responsive material A does not correspond to at least one of the water-soluble material B or the water-absorbent material B, and the calcium acetate monohydrate added separately corresponds to at least one of the water-soluble material B or the water-absorbent material B.

[0112] The water-soluble material B (hereinafter referred to as the water-soluble material) in at least one of the water-soluble material B or the water-absorbent material B is not limited and may be a known water-soluble material. For example, a material having a solubility in water of 25 g / 100 g of water at 20° C. may be used. In order to better achieve the beneficial effects, a metal salt or a hydrate thereof is preferred, and a divalent metal salt of an organic acid or a hydrate thereof is more preferred. Examples of organic acids and divalent metals constituting the divalent metal salt of an organic acid include the above-mentioned compounds. As the hydrate, a hydrate (e.g., a monohydrate or a dihydrate) capable of forming a metal salt may be suitably used.

[0113] In order to better achieve the beneficial effects, alkaline earth metal salts of organic acids and hydrates thereof are preferred among the water-soluble materials, and calcium formate, calcium acetate, calcium propionate, magnesium formate, magnesium acetate and magnesium propionate and hydrates thereof are more preferred.

[0114] The water-absorbent material B (hereinafter referred to as the water-absorbent material) of at least one of the water-soluble material B and the water-absorbent material B is not limited and may be a known water-absorbent material. For example, a material having a water absorption rate of 5% or more measured by the following method may be used. (Measurement method) The weight was measured before and after immersion in 20°C water for 24 hours, and the water absorption rate was calculated using the following formula. Water absorption (%) = (weight after immersion - weight before immersion) / weight after immersion × 100

[0115] Examples of water-absorbent materials include heteroatom-containing materials (fibers, elastomers, resins). The term "heteroatom" refers to an atom other than a carbon atom and a hydrogen atom, and may be any heteroatom capable of forming a reversible molecular bond with water, such as a hydrogen bond or an ionic bond. The heteroatom is preferably at least one selected from an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, a phosphorus atom and a halogen atom, more preferably an oxygen atom, a nitrogen atom or a silicon atom, and still more preferably an oxygen atom.

[0116] Examples of the structure or group containing an oxygen atom include an ether group, an ester group, a carboxyl group, a carbonyl group, an alkoxy group, and a hydroxyl group. Among them, an ether group is preferred, and an oxyalkylene group is more preferred. Examples of the structure or group containing a nitrogen atom include an amino group (primary amino group, secondary amino group and tertiary amino group), an amide group, a nitrile group and a nitro group. Among them, an amino group is preferred, and a tertiary amino group is more preferred. Examples of the structure or group containing a silicon atom include a silyl group, an alkoxysilyl group, and a silanol group, among which a silyl group is preferred, and an alkoxysilyl group is more preferred. Examples of the structure or group containing a sulfur atom include a thioether group, a sulfate group, a sulfate group, and a sulfone group. Examples of the structure or group containing a phosphorus atom include a phosphate group and a phosphate. Examples of the structure or group containing a halogen atom include halogen groups such as a fluoro group, a chloro group, a bromo group, and an iodo group.

[0117] Examples of water-absorbent fibers include cellulose fibers containing hydroxyl groups. Cellulose microfibers are preferred among the cellulose fibers. Any cellulose microfibers derived from natural materials can be used. For example: resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf, and pulp, paper, or cloth produced from them; waste biomass such as agricultural waste, food residues, and sewage sludge; unused biomass such as rice straw, wheat straw, and thinnings; and cellulose produced by ascidian, acetic acid bacteria, or other organisms. Each of them can be used alone or in combination of two or more.

[0118] Examples of water-absorbing elastomers include oxyalkylene-containing elastomers. Examples of elastomers include epoxide / allyl glycidyl ether copolymers, amine / allyl glycidyl ether copolymers, and silyl / allyl glycidyl ether copolymers. Each of these can be used alone or in combination of two or more.

[0119] Examples of the water-absorbent resin include polyvinyl alcohol, polyurethane, polyvinyl acetate, epoxy resin, cellulose resin, polyethylene glycol, and sodium polyacrylate, each of which may be used alone or in combination of two or more.

[0120] The amount of at least one of the water-soluble material B or the water-absorbing material B in the rubber composition (the total amount of the water-soluble material and the water-absorbing material) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, particularly preferably 40 parts by mass or less, and most preferably 30 parts by mass or less. When the amount is within the above range, the beneficial effect tends to be better achieved. In the case where the rubber composition contains a water-soluble material and / or a water-absorbing material, the amount is preferably within the above range. In the present invention, the amount of at least one of the water-soluble material B or the water-absorbent material B refers to the total amount of the water-soluble material and the water-absorbent material. When both the water-soluble material and the water-absorbent material are hydrates, the total amount includes the amount of the hydrate.

[0121] From the viewpoint of properties such as crack resistance and ozone resistance, the rubber composition preferably contains an antioxidant.

[0122] Non-limiting examples of antioxidants include naphthylamine antioxidants, such as naphthylamine antioxidants, such as phenyl-α-naphthylamine; diphenylamine antioxidants, such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine antioxidants, such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants, such as poly(2,2,4-trimethyl-1,2-dihydroquinoline); monophenol antioxidants, such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; and bisphenol, trisphenol or polyphenol antioxidants, such as tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine or poly(2,2,4-trimethyl-1,2-dihydroquinoline) is more preferred. Available commercial products can be purchased from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexsys Co., Ltd., and the like.

[0123] The amount of the antioxidant in the rubber composition is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

[0124] The rubber composition may contain stearic acid. The amount of stearic acid in the rubber composition is preferably 0.5 to 10 parts by mass or more, more preferably 1.5 to 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0125] The stearic acid may be conventional stearic acid. Available commercial products are available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like.

[0126] The rubber composition may contain zinc oxide. The amount of zinc oxide in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 2 to 6 parts by mass, relative to 100 parts by mass of the rubber component.

[0127] The zinc oxide may be conventional zinc oxide. Available commercial products are available from Mitsui Mining & Smelting Co., Ltd., Toho Asia Lead Co., Ltd., Shiramizu Techno Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., and the like.

[0128] The rubber composition may contain wax. The amount of the wax in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0129] Non-limiting examples of waxes include petroleum waxes and natural waxes, and also include synthetic waxes prepared by purifying or chemically treating a variety of waxes. Each of these waxes may be used alone or in combination of two or more.

[0130] Examples of petroleum waxes include paraffin wax and microcrystalline wax. Natural waxes may be any wax extracted from non-petroleum resources, including vegetable waxes such as candelilla wax, palm wax, Japan wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petroleum grease; and purified products of these waxes. Available commercial products may be purchased from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seira Co., Ltd., Seiko Chemical Co., Ltd., and the like.

[0131] The rubber composition may contain a vulcanization accelerator. The amount of the vulcanization accelerator in the rubber composition is usually 0.3 to 10 parts by mass, preferably 0.5 to 4 parts by mass, relative to 100 parts by mass of the rubber component.

[0132] Any type of vulcanization accelerator can be used, including those commonly used. Examples of vulcanization accelerators include thiazole vulcanization accelerators, such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide; thiuram vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide vulcanization accelerators, such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine vulcanization accelerators, such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. Each of them can be used alone or in combination of two or more. Among them, sulfenamide vulcanization accelerators and guanidine vulcanization accelerators are preferred.

[0133] In addition to the above ingredients, the rubber composition may contain other suitable additives commonly used in the application field, such as a mold release agent or a pigment. The amount of each additive in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0134] In order to better achieve the beneficial effects, in the rubber composition, the ratio of the amount of at least one of the water-soluble material B or the water-absorbent material B to the amount of the crosslinking agent (the amount of at least one of the water-soluble material B or the water-absorbent material B / the amount of the crosslinking agent) is preferably 2.0 to 40.0. The lower limit is preferably 6.7 or more, more preferably 10.0 or more, still more preferably 13.3 or more, particularly preferably 16.7 or more, and most preferably 20.0 or more. The upper limit is preferably 50.0 or less, more preferably 40.0 or less, and still more preferably 30.0 or less.

[0135] The rubber composition can be prepared by known methods. For example, it can be prepared by the following method, kneading the ingredients in a rubber kneading machine such as an open roll mill or a Banbury mixer, and then optionally crosslinking. The kneading conditions include a kneading temperature of generally 50° C. to 200° C., preferably 80° C. to 190° C., and a kneading time of generally 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

[0136] In order to better achieve the beneficial effects, the rubber composition desirably has a dynamic elastic modulus at 0°C when immersed in water (0°C E*w) and a dynamic elastic modulus at 0°C when dry (0°C E*d) satisfying the following formula (1): (1)0℃E*w / 0℃E*d≤0.70. The ratio "0°C E*w / 0°C E*d" is preferably 0.56 or less, more preferably 0.55 or less, still more preferably 0.54 or less, further preferably 0.53 or less, further preferably 0.51 or less, further preferably 0.49 or less, further preferably 0.45 or less, further preferably 0.44 or less, further preferably 0.42 or less, further preferably 0.40 or less, further preferably 0.39 or less, further preferably 0.33 or less, further preferably 0.31 or less, further preferably 0.30 or less, further preferably 0.28 or less, and particularly preferably 0.27 or less. The lower limit is not limited, but is preferably 0.01 or more, more preferably 0.05 or more, and still more preferably 0.10 or more.

[0137] In order to better achieve the beneficial effects, the rubber composition desirably has a dynamic elastic modulus at 0°C when immersed in water (0°C E*w) and a dynamic elastic modulus at 30°C when immersed in water (30°C E*w) that satisfy formula (2): (2)30℃E*w / 0℃E*w≥0.80. The ratio "30°C E*w / 0°C E*w" is preferably 0.83 or more, more preferably 0.85 or more, still more preferably 0.87 or more, further preferably 0.88 or more, further preferably 0.89 or more, further preferably 0.90 or more, further preferably 0.95 or more, further preferably 0.98 or more, further preferably 1.04 or more, further preferably 1.05 or more, further preferably 1.06 or more, further preferably 1.08 or more, particularly preferably 1.10 or more, particularly preferably 1.20 or more, particularly preferably 1.23 or more, particularly preferably 1.24 or more, particularly preferably 1.25 or more, and most preferably 1.29 or more. The upper limit is not limited, but is preferably 3.00 or less, more preferably 2.00 or less, and still more preferably 1.50 or less.

[0138] The mechanism of the beneficial effects of the elastomer composition satisfying the formulae (1) and (2) is not completely clear, but is presumed as follows. The formula "(1) 0℃E*w / 0℃E*d≤0.70" means that the elastic modulus when immersed in water is much lower than the elastic modulus when dried at low temperature. The formula "(2) 30℃E*w / 0℃E*w≥0.80" means that the practical elastic modulus can be maintained even when immersed in water at high temperature compared with the elastic modulus at low temperature. As described above, the rubber composition changes the properties related to the elastic modulus as the temperature changes. Therefore, it can change the tire performance according to the temperature change.

[0139] In this case, the problem (purpose) of changing tire performance in response to temperature changes is solved by a rubber composition, which includes a predetermined amount of a rubber component, a crosslinking agent, carbon black, a plasticizer and a temperature-responsive material A, wherein the rubber component includes at least one selected from polyisoprene rubber, polybutadiene rubber and styrene-butadiene rubber, and the temperature-responsive material A contains a carboxyl-containing polymer and a metal salt, and also satisfies the parameters of formulas (1) and (2). In other words, the parameters cannot define the problem (purpose). The problem in this article is to change tire performance in response to temperature changes. In order to solve this problem, the rubber composition is formulated to contain a predetermined amount of material and satisfy the parameters of formulas (1) and (2).

[0140] In order to better achieve the beneficial effects, the rubber composition desirably has a dynamic elastic modulus (0°C E*w) satisfying the following formula at 0°C when immersed in water: 0℃E*w≤8.0MPa. The value of "0°C E*w" is preferably 5.0 MPa or less, more preferably 4.8 MPa or less, more preferably 4.6 MPa or less, still more preferably 4.5 MPa or less, further preferably 4.2 MPa or less, further preferably 4.0 MPa or less, further preferably 3.8 MPa or less, further preferably 3.7 MPa or less, further preferably 3.5 MPa or less, further preferably 3.3 MPa or less, particularly preferably 3.2 MPa or less, and most preferably 3.1 MPa or less. The lower limit is not limited, but is preferably 1.0 MPa or more, more preferably 1.3 MPa or more, still more preferably 1.5 MPa or more, further preferably 2.7 MPa or more, further preferably 2.8 MPa or more, and further preferably 3.0 MPa or more.

[0141] In order to better achieve the beneficial effects, the rubber composition desirably has a dynamic elastic modulus (30°C E*w) satisfying the following formula at 30°C when immersed in water: 30℃E*w≥3.0MPa. The value of "30°C E*w" is preferably 3.3 MPa or more, more preferably 3.4 MPa or more, still more preferably 3.5 MPa or more, further preferably 3.6 MPa or more, further preferably 3.7 MPa or more, further preferably 3.8 MPa or more, particularly preferably 3.9 MPa or more, further preferably 4.0 MPa or more, further preferably 4.1 MPa or more, further preferably 4.3 MPa or more, and most preferably 4.5 MPa or more. The upper limit is not limited, but is preferably 10.0 MPa or less, more preferably 8.0 MPa or less, still more preferably 7.0 MPa or less, and particularly preferably 6.0 MPa or less.

[0142] In order to better achieve the beneficial effects, the rubber composition desirably has a dynamic elastic modulus (0°C E*d) satisfying the following formula at 0°C when dry: 0℃E*d≥5.0MPa. The value of "0°C E*d" is preferably 6.0 MPa or more, more preferably 6.9 MPa or more, still more preferably 7.0 MPa or more, further preferably 7.8 MPa or more, further preferably 8.0 MPa or more, further preferably 8.2 MPa or more, further preferably 8.3 MPa or more, further preferably 8.4 MPa or more, further preferably 8.5 MPa or more, further preferably 9.0 MPa or more, further preferably 10.0 MPa or more, further preferably 10.5 MPa or more, further preferably 10.7 MPa or more, further preferably 11.0 MPa or more, particularly preferably 11.6 MPa or more, most preferably 12.0 MPa or more, further preferably 12.3 MPa or more. The upper limit is not limited, but is preferably 20.0 MPa or less, more preferably 18.0 MPa or less, still more preferably 16.0 MPa or less, and further preferably 15.0 MPa or less.

[0143] In the present invention, the dynamic elastic modulus E* is measured by the method described in Examples. In the present invention, the dynamic elastic modulus E* of the rubber composition means the dynamic elastic modulus E* of the vulcanized (cross-linked) rubber composition.

[0144] In the present invention, the dynamic elastic modulus E* when dried refers to the dynamic elastic modulus of the vulcanized rubber composition when dried; specifically, the dynamic elastic modulus of the vulcanized rubber composition after drying by the method described in the Examples. In the present invention, the dynamic elastic modulus E* when immersed in water refers to the dynamic elastic modulus of the rubber composition after being immersed in water; specifically, the dynamic elastic modulus of the vulcanized rubber composition after being immersed in water by the method described in the Examples.

[0145] In the present invention, the dynamic elastic modulus E* of the vulcanized rubber composition is determined by measuring the dynamic elastic modulus E* of a test vulcanized rubber sheet at a strain of 2% and a frequency of 10 Hz using ARES (rheometer available from TAinstruments).

[0146] Next, the production criteria satisfying the formulas “(1) 0℃E*w / 0℃E*d≤0.70”, “(2) 30℃E*w / 0℃E*w≥0.80”, “0℃E*w≤8.0MPa”, “30℃E*w≥3.0MPa” and “0℃E*d≥5.0MPa” are explained. The formula "(1) 0℃E*w / 0℃E*d≤0.70" means that the elastic modulus when immersed in water is much lower than the elastic modulus when dried at low temperature. The formula "(2) 30℃E*w / 0℃E*w≥0.80" means that a practical elastic modulus can be maintained even when immersed in water at high temperature compared to the elastic modulus at low temperature. For example, a rubber composition satisfying formulas (1) and (2) can be prepared by adding a temperature-responsive material A containing a carboxyl-containing polymer and a metal salt to the rubber composition. The production of the rubber composition can be facilitated by adding a material that at least partially contains a foaming structure as the temperature-responsive material A or additionally adding at least one of a water-soluble material B or a water-absorbent material B to the rubber composition. The formula "0°C E*w≤8.0MPa" means that the grip performance on icy roads is improved. For example, a rubber composition satisfying this formula can be prepared by adding a temperature-responsive material A to the rubber composition. By adding a material at least partially including a foamed structure as the temperature-responsive material A or additionally adding a material B to the rubber composition, the production of the rubber composition can be facilitated. The formula "0°C E*d≥5.0MPa" means that the grip performance on a dry road surface is improved. For example, a rubber composition satisfying this formula can be prepared by adding a temperature-responsive material A to the rubber composition. By adding a material at least partially containing a foamed structure as the temperature-responsive material A or additionally adding a material B to the rubber composition, the production of the rubber composition can be facilitated.

[0147] The dynamic elastic modulus E* (absolute value) when drying can be controlled by the type and amount of chemicals (especially rubber components, fillers, plasticizers) added to the composition. For example, when the amount of plasticizer increases, the dynamic elastic modulus E* when drying tends to decrease; when the amount of filler increases, the dynamic elastic modulus E* when drying tends to increase; when the amount of sulfur decreases, the dynamic elastic modulus E* when drying tends to decrease. The dynamic elastic modulus E* when drying can also be controlled by changing the amount of sulfur and vulcanization accelerator. Specifically, when the amount of sulfur increases, the dynamic elastic modulus E* when drying tends to increase, and when the amount of vulcanization accelerator increases, the dynamic elastic modulus E* when drying tends to increase.

[0148] Specifically, the formulas "(1) 0℃E*w / 0℃E*d≤0.70", "(2) 30℃E*w / 0℃E*w≥0.80", "0℃E*w≤8.0MPa", "30℃E*w≥3.0MPa", and "0℃E*d≥5.0MPa" can be satisfied by controlling the dynamic elastic modulus E* when dry within the desired range and adding a temperature-responsive material A containing a carboxyl-containing polymer and a metal salt to the rubber composition, while optionally using a material that at least partially contains a foamed structure as the temperature-responsive material A or further adding at least one of a water-soluble material B or a water-absorbent material B to the rubber composition.

[0149] The rubber composition can be used (as a tire rubber composition) in tire components such as tread, sidewall, tread base, lower tread, shoulder, tire clincher, bead apex, cushion rubber, carcass ply rubber, insulation layer, chafer and inner liner, and side reinforcing layer of run-flat tire. The rubber composition is suitable for tread.

[0150] The tire of the present invention can be produced by a conventional method using the rubber composition. For example, a rubber composition containing various materials is extruded and processed into a tread or the like before vulcanization, and then molded together with other tire components on a tire molding machine by a conventional method to form an unvulcanized tire, and the unvulcanized tire is heated and pressurized in the vulcanizer to obtain a tire.

[0151] The tire is suitable for passenger vehicles, large passenger vehicles, large SUVs, trucks and buses or two-wheeled vehicles, or used as a racing tire, winter tire (studless winter tire, snow tire, studded tire), all-season tire, run-flat tire, aircraft tire, mining tire, etc. The tire is suitable for use as a winter tire (studless winter tire, snow tire, studded tire) or an all-season tire, etc. Example

[0152] Hereinafter, examples (embodiments) considered to be preferred for carrying out the present invention will be described. However, the scope of the present invention is not limited to these embodiments.

[0153] Various chemicals used in Examples and Comparative Examples are listed below. NR:TSR20 BR: BR150B (cis content: 98 mass%), purchased from Ube Industries, Ltd. SBR: Nipol SBR1502 (styrene content: 23.5 mass%), purchased from Zeon Corporation Carbon black: Seast N220 (N2SA: 111m 2 / g), purchased from Mitsubishi Chemical Corporation Silicon dioxide: ULTRASIL VN3 (N2SA: 175m 2 / g), purchased from Evonik Degussa Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)tetrasulfide), purchased from Evonik Degussa Oil: Diana Process NH-70S, purchased from Idemitsu Kosan Co., Ltd. Plasticizer A: RICON 150 (liquid polybutadiene polymer), purchased from Sartomer Temperature-responsive material A-1: ​​Production Example 1 (polyacrylic acid / calcium acetate gel) Temperature-responsive material A-2: Production Example 2 (foamed polyacrylic acid / calcium acetate gel) Temperature-responsive material A-3: Production Example 3 (polyacrylic acid / calcium propionate gel) Temperature-responsive material A-4: Production Example 4 (foamed polyacrylic acid / calcium propionate gel) Water-soluble material B: calcium acetate monohydrate (solubility in water at 20°C: 34.7 g / 100 g water), purchased from WAKO Water-absorbent material B: biomass nanofiber (product name "BiNFi-s cellulose", microfibrillated cellulose fiber, water absorption rate: 10%), purchased from SUGINO MACHINE LIMITED Antioxidant: NOCRAC 6C, purchased from Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: stearic acid, purchased from NOF Corporation Zinc oxide: Zinc oxide #2, purchased from Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur purchased from Tsurumi Chemical Industry Co., Ltd. Crosslinking agent A: TACKIROL V200 (alkylphenol-sulfur chloride condensate), purchased from Taoka Chemical Industry Co., Ltd. Vulcanization accelerator CZ: NOCCELER CZ-G, purchased from Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator DPG: NOCCELER D, purchased from Ouchi Shinko Chemical Industry Co., Ltd.

[0154] (Production Example 1) Referring to Advanced Materials 2020, 32, 1905878, temperature-responsive material A-1 was prepared by the following method. The precursor aqueous solution was prepared by dissolving 1.0 M acrylic acid (AAc), 1.0 mol % potassium persulfate (as an initiator) relative to the monomer concentration, and 1.0 mol % N,N′-methylenebisacrylamide (MbAAd) (as a crosslinker) relative to the monomer concentration in ultrapure water. Here, when the concentration of the crosslinking agent is 0 mol%, a physically crosslinked gel can be obtained. When a crosslinking agent is added, a chemically crosslinked gel can be obtained. The solution was poured into a mold of an arbitrarily selected shape and heated in air at 60°C for 6 hours to form a gel. The polymer gel or non-flowable high-viscosity substance is immersed in a sufficient amount of 1000 mM calcium acetate ultrapure aqueous solution until equilibrium is reached, thereby obtaining a temperature-responsive material A-1.

[0155] (Production Example 2) The temperature responsive material A-1 was heated at 80°C for 5 minutes and then frozen in liquid nitrogen. The frozen temperature responsive material A-1 was freeze-dried for 24 hours using a freeze dryer (FDU-2110, purchased from EYELA). Thus, the temperature responsive material A-2 including a foamed structure was obtained.

[0156] (Production Example 3) Referring to Advanced Materials 2020, 32, 1905878, temperature responsive material A-3 was prepared by the following method. The precursor aqueous solution was prepared by dissolving 1.0 M acrylic acid (AAc), 1.0 mol % potassium persulfate (as an initiator) relative to the monomer concentration, and 1.0 mol % N,N′-methylenebisacrylamide (MbAAd) (as a crosslinker) relative to the monomer concentration in ultrapure water. Here, when the concentration of the crosslinking agent is 0 mol%, a physically crosslinked gel can be obtained. When a crosslinking agent is added, a chemically crosslinked gel can be obtained. The solution was poured into a mold of an arbitrarily selected shape and heated in air at 60°C for 6 hours to form a gel. The polymer gel or non-flowable high-viscosity substance was immersed in a sufficient amount of 1000 mM calcium propionate ultrapure aqueous solution until equilibrium was reached, thereby obtaining a temperature-responsive material A-3.

[0157] (Production Example 4) The temperature responsive material A-3 was heated at 80°C for 5 minutes and then frozen in liquid nitrogen. The frozen temperature responsive material A-3 was freeze-dried for 24 hours using a freeze dryer (FDU-2110, purchased from EYELA). Thus, the temperature responsive material A-4 including a foamed structure was obtained.

[0158] <Examples and Comparative Examples> According to the formulation shown in Table 1, chemicals other than sulfur and a vulcanization accelerator were kneaded in a 1.7 L Banbury mixer (Kobe Steel, Ltd.) at 150° C. for 5 minutes to obtain a kneaded mixture. Then, the kneaded mixture was kneaded with sulfur and a vulcanization accelerator at 80° C. for 5 minutes using an open roll mill to obtain an unvulcanized rubber composition. The unvulcanized rubber composition was press-vulcanized at 170° C. for 12 minutes to prepare a 1 mm thick vulcanized rubber composition sheet. In addition, the unvulcanized rubber composition prepared as above was formed into a cap tread shape and assembled with other tire components to form an unvulcanized tire. The unvulcanized tire was vulcanized at 170° C. for 15 minutes to produce a test tire (size: 195 / 65R15).

[0159] The vulcanized rubber composition and the test tire prepared as above were stored in a dark place at room temperature for three months and then subjected to the following evaluations. The results are shown in Table 1.

[0160] (Measurement of dynamic elastic modulus E*) The dynamic elastic modulus E* of a 1 mm thick sheet of the vulcanized rubber composition was measured. Specifically, a 1 mm thick vulcanized rubber composition sheet was maintained at the measuring temperature for 10 minutes, and then the dynamic modulus E* (at 0°C or 30°C) of the vulcanized rubber composition sheet at a strain of 2% and a frequency of 10 Hz was measured using ARES (rheometer, available from TA Instruments). Here, the method of preparing the vulcanized rubber composition sheet used for measurement is as follows. A 1 mm thick vulcanized rubber composition sheet was immersed in water at 25° C. for 10 hours. Then, the sheet was dried to a constant weight under reduced pressure conditions of 80° C. and 1 kPa or less to obtain a dried vulcanized rubber composition sheet. The temperature of the dried vulcanized rubber composition sheet was returned to 25° C., and the obtained sheet was used as a vulcanized rubber composition sheet for measuring the dynamic elastic modulus E* when dried. In addition, the dried vulcanized rubber composition sheet was immersed in water at 25° C. for 10 hours again, and the obtained sheet was used as a vulcanized rubber composition sheet for measuring the dynamic elastic modulus E* when immersed in water.

[0161] (Ice grip performance) A set of test tires were mounted on a 2000cc front-engine rear-wheel drive car made in Japan. The car was driven on ice to evaluate the grip performance on ice. Specifically, the grip performance on ice was evaluated by measuring the stopping distance required for a car traveling on ice at a speed of 30 km / h to stop after applying the locking brake (ice braking stopping distance). The distance was expressed as an index (ice grip performance index) relative to Comparative Example 1 (value 100). A higher index indicates better braking performance on ice (ice grip performance).

[0162] (Dry grip performance) The test tire was mounted on each wheel of a 2000cc front-engine front-wheel drive car made in Japan. The braking distance of the car on a dry asphalt road surface was measured at an initial speed of 100 km / h. The distance was expressed as an index (dry grip performance index) relative to Comparative Example 1 (value 100). A higher index indicates a shorter braking distance and better dry grip performance.

[0163] (Overall Performance) The sum of the ice grip performance (index) and the dry grip performance (index) is defined as the overall performance in terms of ice grip performance and dry grip performance. The overall performance is evaluated. A higher index indicates better overall performance.

[0164]

[0165] The present invention (1) relates to a tire rubber composition comprising: a rubber component comprising at least one selected from the group consisting of polyisoprene rubber, polybutadiene rubber, and styrene-butadiene rubber; Cross-linking agent; Carbon black; Plasticizers; and A temperature-responsive material A comprising a carboxyl group-containing polymer and a metal salt, The tire rubber composition contains a crosslinking agent in an amount greater than 0 and less than 10 parts by mass, carbon black in an amount greater than 0 and less than 100 parts by mass, and a plasticizer in an amount greater than 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0166] The present invention (2) relates to the tire rubber composition according to the present invention (1), further comprising at least one of a water-soluble material B or a water-absorbing material B.

[0167] The present invention (3) relates to the tire rubber composition according to the present invention (2), The ratio of the amount of material B to the amount of the cross-linking agent (the amount of material B / the amount of the cross-linking agent) is 2.0 to 40.0.

[0168] The present invention (4) relates to a tire rubber composition according to any one of the present inventions (1) to (3), The dynamic elastic modulus of the tire rubber composition at 0°C when immersed in water (0°C E*w), the dynamic elastic modulus at 30°C when immersed in water (30°C E*w), and the dynamic elastic modulus at 0°C when dry (0°C E*d) satisfy equations (1) and (2): (1) 0℃E*w / 0℃E*w≤0.70 (2) 30℃E*w / 0℃E*w≥0.80.

[0169] The present invention (5) relates to a tire rubber composition according to any one of the present inventions (1) to (4), The dynamic elastic modulus (0°C E*w) of the tire rubber composition at 0°C when immersed in water satisfies the following formula: 0℃E*w≤8.0MPa.

[0170] The present invention (6) relates to a tire rubber composition according to any one of the present inventions (1) to (5), The dynamic elastic modulus (30°C E*w) of the tire rubber composition at 30°C when immersed in water satisfies the following formula: 30℃E*w≥3.0MPa.

[0171] The present invention (7) relates to a tire rubber composition according to any one of the present inventions (1) to (6), The temperature responsive material A is a material at least partially comprising a foamed structure.

[0172] The present invention (8) relates to a tire having a tread, the tread comprising the rubber composition according to any one of the present inventions (1) to (7).

[0173] The present invention (9) relates to the tire according to the present invention (8), which is a winter tire or an all-season tire.

Claims

1. A tire rubber composition comprising: A rubber component, the rubber component comprising at least one selected from the group consisting of polyisoprene rubber, polybutadiene rubber, and styrene-butadiene rubber; Cross-linking agent; Carbon black; Plasticizers; and A temperature-responsive material A, wherein the temperature-responsive material A comprises a carboxyl-containing polymer and a metal salt, The amount of the crosslinking agent is greater than 0 and less than 10 parts by mass, the amount of the carbon black is greater than 0 and less than 100 parts by mass, and the amount of the plasticizer is greater than 5 parts by mass, relative to 100 parts by mass of the rubber component.

2. The tire rubber composition according to claim 1, wherein The tire rubber composition further includes at least one of a water-soluble material B or a water-absorbent material B.

3. The tire rubber composition according to claim 2, wherein: The ratio of the amount of material B to the amount of the cross-linking agent (amount of material B / amount of cross-linking agent) is 2.0 to 40.

0.

4. The tire rubber composition according to any one of claims 1 to 3, wherein The tire rubber composition has a dynamic elastic modulus at 0°C when immersed in water (0°C E*w), a dynamic elastic modulus at 30°C when immersed in water (30°C E*w), and a dynamic elastic modulus at 0°C when dry (0°C E*d) that satisfy the following formulas (1) and (2): (1) 0℃E*w / 0℃E*d≤0.70 (2)30℃E*w / 0℃E*w≥0.

80.

5. The tire rubber composition according to any one of claims 1 to 4, wherein The dynamic elastic modulus (0°C E*w) of the tire rubber composition at 0°C when immersed in water satisfies the following formula: 0℃E*w≤8.0MPa.

6. The tire rubber composition according to any one of claims 1 to 5, wherein The dynamic elastic modulus (30°C E*w) of the tire rubber composition at 30°C when immersed in water satisfies the following formula: 30℃E*w≥3.0MPa.

7. The tire rubber composition according to any one of claims 1 to 6, wherein The temperature responsive material A is a material at least partially including a foamed structure. 8 . A tire having a tread, the tread comprising the rubber composition according to claim 1 .

9. The tire according to claim 8, wherein: The tires are winter tires or all-season tires.

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