Rubber composition for tires, and tire

Abstract

The present invention provides: a rubber composition for tires, the composition being capable of changing the tire performance in response to temperature changes; and a tire. The present invention relates to a rubber composition for tires, the composition containing a rubber component that contains at least one rubber selected from the group consisting of an isoprene rubber, a butadiene rubber and a styrene butadiene rubber, a crosslinking agent, carbon black, a plasticizer and a temperature-responsive material A that contains a metal salt and a polymer having a carboxyl group, wherein relative to 100 parts by mass of the rubber component, the content of the crosslinking agent is more than 0 part by mass but less than 10 parts by mass, the content of the carbon black is more than 0 part by mass but less than 100 parts by mass, and the content of the plasticizer is more than 5 parts by mass.

Description

Rubber composition for tires and tires

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

[0002] Tires have traditionally been required to have a variety of performance characteristics. All-season tires, in particular, must be able to handle large changes in outside temperature and road surface conditions.

[0003] An object of the present invention is to solve the above problems and to provide a rubber composition for a tire and a tire that are capable of changing tire performance in response to temperature changes.

[0004] The present invention relates to a rubber composition for tires, which includes a rubber component containing at least one rubber selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber, a crosslinking agent, carbon black, a plasticizer, and a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt, wherein the content of the crosslinking agent is more than 0 parts by mass and less than 10 parts by mass, the content of the carbon black is more than 0 parts by mass and less than 100 parts by mass, and the content of the plasticizer is more than 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0005] According to the present invention, since the tire has the above-mentioned structure, it is possible to provide a rubber composition for a tire and a tire that are capable of changing tire performance in response to temperature changes.

[0006] The present invention provides a rubber composition for tires, which comprises a rubber component including at least one rubber selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber, a crosslinking agent, carbon black, a plasticizer, and a temperature-responsive material A including a polymer having a carboxyl group and a metal salt, in a predetermined blend ratio.

[0007] In the tire industry, little attention has been paid to changing tire performance in response to temperature changes, and conventional technologies have room for improvement in terms of changing tire performance in response to temperature changes. In particular, it is necessary to improve ice grip performance by decreasing the elastic modulus at low temperatures on ice, and to improve steering stability by increasing the elastic modulus at high temperatures. One approach is to use rubber with low-temperature flexibility, but conventional rubber compositions have the problem that increasing the flexibility of the rubber reduces steering stability. Another approach is to incorporate a temperature-responsive material such as poly(N-isopropylacrylamide) (PNIPAM), but this material has the problem of being soluble in water at low temperatures and dissolving in water on rainy days or on ice, resulting in its disappearance from the composition. On the other hand, the temperature-responsive material A in the present invention is a material whose elastic modulus increases upon heating, for example, in the range of 0°C to 100°C, after absorbing water, and whose elastic modulus decreases upon cooling, thereby enabling tire performance to change in response to temperature changes.

[0008] The reason why such an effect is obtained is not entirely clear, but is presumed to be as follows. It is believed that after the temperature-responsive material A of the present invention absorbs water, the elastic modulus changes with temperature changes, thereby changing the elastic modulus of the rubber composition. It is also believed that water absorption into the temperature-responsive material A is promoted by further blending a water-soluble and / or water-absorbent material B as needed. This is believed to be because the water-soluble and / or water-absorbent material B dissolves in water and / or absorbs water when immersed in water, etc., causing voids to form in the rubber. It is therefore presumed that tire performance changes in response to temperature changes, such as when immersed in water.

[0009] The rubber composition for a tire contains a rubber component including at least one rubber selected from the group consisting of isoprene rubber, butadiene rubber (BR), and styrene-butadiene rubber (SBR). Among them, from the viewpoint of obtaining better effects, it is preferable to contain at least one of an isoprene-based rubber and a BR, and it is more preferable to contain both an isoprene-based rubber and a BR.

[0010] The rubber component usable in the rubber composition is a component that contributes to crosslinking, and is generally a polymer component having a weight average molecular weight (Mw) of 10,000 or more and that is not extracted with acetone. The rubber component is in a solid state 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. Within the above ranges, the effect tends to be more favorably obtained.

[0012] In this specification, the weight average molecular weight (Mw) can be determined in terms of standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0013] The rubber components such as isoprene rubber, BR, and SBR may be unmodified or modified. The modified rubber may be any rubber having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified rubber (terminal-modified rubber having the functional group at the terminal) in which at least one terminal of the rubber has been modified with a compound (modifier) ​​having the functional group, main-chain-modified rubber having the functional group in the main chain, main-chain terminal-modified rubber having the functional group in the main chain and at least one terminal (for example, main-chain terminal-modified rubber having the functional group in the main chain and at least one terminal modified with the modifier), and terminal-modified rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein.

[0014] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0015] Furthermore, hydrogenated rubber can also be used as the rubber.

[0016] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NR, for example, SIR20, RSS#3, TSR20, and other commonly used rubbers in the rubber industry, can be used. IR is not particularly limited, and for example, IR2200 and other commonly used rubbers in the rubber industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and the like. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and the like. Modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. Modified isoprene-based rubbers having the same functional groups as the modified rubbers described above can also be used. These may be used alone or in combination of two or more.

[0017] When the rubber composition contains an isoprene-based rubber, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. 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. Within the above range, the effect tends to be more favorably obtained.

[0018] The BR is not particularly limited, and examples thereof include high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. Of these, the BR preferably contains 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 particularly limited, but is preferably 99% by mass or less. The cis content can be measured by infrared absorption spectroscopy.

[0019] The BR may be either unmodified or modified. The modified BR may be modified BR having the same functional group as the modified rubber. The BR may also be hydrogenated butadiene rubber.

[0020] As the BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0021] When the rubber composition contains BR, the content of BR in 100% by mass of the rubber component 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. The upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0022] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. These 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, still more preferably 15% by mass or less, and particularly preferably 10% by mass or less. By setting it within the above range, the effect tends to be more favorably obtained. In this specification, the styrene content is defined as １ It can be measured by H-NMR measurement.

[0024] The vinyl bond content of SBR is preferably 20% by mass or more, more preferably 35% by mass or more, even 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 even more preferably 50% by mass or less. By keeping it within the above range, better effects tend to be obtained. In this specification, the vinyl bond content (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0025] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0026] When the rubber composition contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0027] Usable rubber components other than isoprene rubber, BR, and SBR include styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Other examples include butyl rubber and fluororubber. These may be used alone or in combination of two or more.

[0028] The rubber composition contains a crosslinking agent. The crosslinking agent is not particularly limited as long as it is a compound that has the effect of crosslinking the rubber component, and crosslinking agents known in the tire field, such as sulfur, organic crosslinking agents, organic peroxides, and resin crosslinking agents, can be used. Among these, sulfur is preferred from the viewpoint of obtaining better effects.

[0029] In the rubber composition, the content of the crosslinking agent (total amount of crosslinking agent) is more than 0 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. The lower limit is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, even more preferably 1.2 parts by mass or more, and particularly preferably 1.5 parts by mass or more. The upper limit is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, and particularly preferably 2.0 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0030] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, and the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., and the like. These may be used alone or in combination of two or more.

[0031] In the rubber composition, the sulfur content is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, even more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0032] The organic cross-linking agent is not particularly limited, and examples thereof include maleimide compounds, alkylphenol-sulfur chloride condensates, organic peroxides, amine organic sulfides, etc. These may be used alone or in combination of two or more.

[0033] In the rubber composition, the content of the organic crosslinking agent is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, even more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

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

[0035] In the rubber composition, the content of the organic peroxide is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, even more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0036] The resin crosslinking agent is not particularly limited, and examples thereof include phenolic resins, melamine-formaldehyde resins, triazine-formaldehyde condensates, hexamethoxymethyl-melamine resins, alkylphenol-sulfur chloride condensates, etc. Among these, alkylphenol-sulfur chloride condensates are preferred in terms of the effects of the present invention.

[0037] The alkylphenol-sulfur chloride condensate is not particularly limited, but is preferably a compound represented by the following formula (II) from the viewpoint of low heat buildup, good hardness, and suppression of reversion.

[0038] (In the formula, R １０１ , R １０２ and R １０３ are the same or different and represent an alkyl group having 5 to 12 carbon atoms; x and y are the same or different and represent an integer of 1 to 3; and k represents an integer of 0 to 250.

[0039] In view of the good dispersibility of the alkylphenol-sulfur chloride condensate in the rubber component, k is preferably an integer of 0 to 250, more preferably an integer of 0 to 100. In view of the efficient development of high hardness, x and y are both preferably 2. １０１ ~R １０３ The alkyl group preferably has 6 to 9 carbon atoms, since this allows the alkylphenol-sulfur chloride condensate to be easily dispersed in the rubber component.

[0040] The alkylphenol-sulfur chloride condensate can be prepared by a known method, for example, by reacting an alkylphenol with sulfur chloride at a molar ratio of 1:0.9 to 1.25. A specific example of the alkylphenol-sulfur chloride condensate is Tackirol V200 (formula (II-1) below) manufactured by Taoka Chemical Co., Ltd.

[0041] (In the formula, k represents an integer of 0 to 100.)

[0042] In the rubber composition, the content of the resin crosslinking agent is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass or more, even more preferably 1.2 parts by mass or more, particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, particularly preferably 2.0 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0043] Commercially available crosslinking agents include those manufactured by Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

[0044] The rubber composition contains carbon black. Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These carbon blacks may be used alone or in combination of two or more.

[0045] The nitrogen adsorption specific surface area of ​​carbon black (N ２ SA) is 30m ２ / g or more is preferable, and 50m ２ / g or more is more preferable, and 70m ２ / g or more is more preferable. ２ The SA is 200m ２ / g or less is preferable, and 150m ２ / g or less is more preferable, and 130m ２ / g or less is more preferable, and 120m ２ / g or less is particularly preferred, and 111m ２ Within the above range, the effect tends to be more favorable. ２ SA is determined according to JIS K6217-2:2001.

[0046] In the rubber composition, the content of carbon black is more than 0 parts by mass and less than 100 parts by mass per 100 parts by mass of the rubber component. The lower limit is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0047] The rubber composition preferably contains a filler other than carbon black. Examples of the filler include inorganic fillers such as silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. Among these, silica is preferred from the viewpoint of obtaining better effects.

[0048] The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silica), wet process silica (hydrated silica), etc. Among these, wet process silica is preferred because it has a large number of silanol groups.

[0049] The nitrogen adsorption specific surface area of ​​silica (N ２ SA) is preferably 30 m ２ / g or more, more preferably 100m ２ / g or more, more preferably 125m ２ / g or more. ２ SA is preferably 300m ２ / g or less, more preferably 250m ２ / g or less, more preferably 200m ２ / g or less, particularly preferably 175m ２ Within the above range, the effect can be suitably obtained. ２ SA is a value measured by the BET method in accordance with ASTM D3037-93.

[0050] As silica, for example, products available from Evonik Tegussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0051] In the rubber composition, the content 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, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but 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. Within the above range, the effects can be suitably obtained.

[0052] The rubber composition desirably contains a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include 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, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N , N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, and other sulfide-based compounds; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products that can be used include those manufactured by Evonik Tegussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZMAX Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0053] In the rubber composition, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, per 100 parts by mass of silica (100 parts by mass of the total amount of silica constituting the surface-modified silica and silica contained elsewhere). The upper limit of the content is preferably 50 parts by mass, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0054] The rubber composition contains a plasticizer. Here, the plasticizer is a material that imparts plasticity to the rubber component, and examples of the plasticizer include a liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25°C)) and a resin (a resin that is in a solid state at room temperature (25°C)).

[0055] In the rubber composition, the content of the plasticizer (total amount of plasticizer) exceeds 5 parts by mass per 100 parts by mass of the rubber component. The lower limit 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. 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. Within the above range, the effect tends to be more favorably obtained.

[0056] The liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25°C)) that can be used in the rubber composition is not particularly limited, and it is desirable to use oil, liquid polymer (liquid resin, liquid diene-based polymer, liquid farnesene-based polymer, etc.). Among these, it is preferable to include oil from the viewpoint of obtaining a better effect. These may be used alone or in combination of two or more kinds.

[0057] In the rubber composition, the content 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, per 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. Within the above range, the effect tends to be more favorably obtained.

[0058] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils that can be used include 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 oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Co., Ltd. Of these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

[0059] In the rubber composition, the oil content 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, per 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. Within the above range, the effect tends to be more favorably obtained. The oil content includes the extender oil of the oil-extended rubber.

[0060] Regarding liquid polymers, examples of liquid resins 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 and indene simple resins), phenol resins, olefin resins, polyurethane resins, and acrylic resins. Hydrogenated products of these resins can also be used.

[0061] Regarding liquid polymers, examples of liquid diene-based polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene 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, which are liquid at 25°C. These may be modified at the terminals or main chains with polar groups. Hydrogenated products of these may also be used. Examples of the liquid diene-based polymers that can be used include products from Sartomer Corporation, Kuraray Co., Ltd., and the like.

[0062] In the rubber composition, the content of the liquid polymer 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, per 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, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0063] Examples of the resins (resins in a solid state at room temperature (25°C)) that can be used in the rubber composition include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins that are solid at room temperature (25°C). The resins may also be hydrogenated. These may be used alone or in combination of two or more. Of these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0064] In the rubber composition, the content of the resin 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, per 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, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0065] The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be better obtained. The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K6220-1:2001 is measured using a ring and ball softening point tester.

[0066] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit, and examples thereof include resins obtained by polymerizing α-methylstyrene and / or styrene, such as a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, and a copolymer of styrene and another monomer.

[0067] The coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0068] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0069] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0070] The phenolic resin may be a known polymer obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, or furfural in the presence of an acid or alkali catalyst, among which those obtained by reaction in the presence of an acid catalyst (such as novolac phenolic resin) are preferred.

[0071] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0072] Examples of the petroleum resin include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, and hydrogenated versions of these. Of these, DCPD resin and hydrogenated DCPD resin are preferred.

[0073] The terpene resin is a polymer containing terpene as a structural unit, and examples thereof include polyterpene resins obtained by polymerizing a terpene compound and aromatic-modified terpene resins obtained by polymerizing a terpene compound and an aromatic compound. Examples of aromatic-modified terpene resins that can be used 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, and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0074] The acrylic resin is a polymer containing an acrylic monomer as a constituent unit. For example, a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component can be used. Among them, a solvent-free carboxyl-containing styrene-acrylic resin can be preferably used.

[0075] Examples of resins that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0076] The rubber composition includes a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt. Poly(N-isopropylacrylamide) is known as a representative example of a temperature-responsive polymer, and Poly(NIPAAm) exhibits a lower critical solution temperature (LCST), a phenomenon in which it dissolves at low temperatures in an aqueous solution and precipitates (phase-separates) at high temperatures. Poly(N-isopropylacrylamide) hydrogels are also known to undergo a volume phase transition.

[0077] On the other hand, the temperature-responsive material A containing a polymer having a carboxyl group and a metal salt also has the properties of a temperature-responsive hydrogel, and preferably has the following properties: (1) It is transparent below the LCST, and becomes cloudy due to phase separation above the LCST. (2) It is soft below the LCST, and exhibits high strength and high toughness above the LCST. Above the LCST, the higher the temperature, the better the elastic modulus and toughness, but above a certain temperature, the stronger the phase separation, causing a sudden rise in elastic modulus (becoming extremely hard) and a decrease in toughness. (3) There is almost no change in volume around the LCST, and no volume phase transition is exhibited. In the hydrogel of the present invention, not exhibiting a volume phase transition or substantially not exhibiting a volume change means that it does not exhibit a volume phase transition at a temperature below the LCST (for example, T １ ≦LCST-5°C) １ Temperatures above the LCST (e.g., T ２ ≧LCST + 5°C) ２ The ratio V ２ / V １ is in the range of 0.8 to 1.2, preferably in the range of 0.85 to 1.15, and more preferably in the range of 0.98 to 1.02. (4) The temperature-responsive phase separation is completely reversible.

[0078] The polymer having a carboxyl group is not particularly limited as long as it is an organic polymer compound having a carboxyl group, and examples thereof include a homopolymer of a monomer having a carboxyl group, a copolymer of multiple types of monomers including a monomer having a carboxyl group, etc. These may be used alone or in combination of two or more types.

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

[0080] The homopolymer is not particularly limited, and examples thereof include polyacrylic acid and polymethacrylic acid.

[0081] Examples of the copolymer include copolymers composed of multiple types of monomers having a carboxyl group, and copolymers of a monomer having a carboxyl group and a monomer other than the monomer having a carboxyl group. The monomer other than the monomer having a carboxyl group is not particularly limited, and examples thereof include acrylate monomers (e.g., α,β-ethylenically unsaturated carboxylic acid esters, hydroxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids, alkoxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids), acrylamide monomers, and styrene monomers. These may be used alone or in combination of two or more.

[0082] The acrylate monomer is not particularly limited, but examples thereof include α,β-ethylenically unsaturated carboxylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, lauryl acrylate, and stearyl acrylate; hydroxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 3-hydroxypropyl methacrylate; and alkoxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids such as diethylene glycol methacrylate.

[0083] The acrylamide monomer is not particularly limited, but examples thereof include acrylamide, methylol methacrylamide, and the like.

[0084] The styrene-based monomer is not particularly limited, but examples thereof include styrene and alkylstyrene.

[0085] From the viewpoint of temperature responsiveness, the copolymer preferably has a content of structural units derived from monomers having a carboxyl group of 50 mol% or more. The 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. There is no particular upper limit, but for example, 98 mol% or less is preferred, and 95 mol% or less is more preferred.

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

[0087] The polymer having a carboxyl group may have a crosslinked structure. Examples of the crosslinked structure include a chemically crosslinked structure and a physically crosslinked structure. The chemically crosslinked structure can be formed by crosslinking with a crosslinking agent for chemical crosslink formation during or after polymer formation. In the present invention, the crosslinking agent for chemical crosslink formation is not included in the crosslinking agent.

[0088] As the crosslinking agent for chemical crosslinking used to form the chemical crosslinked structure, a difunctional or higher functional monomer can be used. Examples of the crosslinking agent include N,N'-methylenebisacrylamide (MbAAd), N,N'-ethylenebisacrylamide, diethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1-acryloyloxy-3-methacryloyloxy-2-propanol, etc. The amount of the crosslinking agent for chemical crosslinking can be, for example, in the range of 0 to 10 mol% with respect to the concentration of the monomer, depending on the desired degree of crosslinking.

[0089] The weight-average molecular weight of the polymer having a carboxyl group is not particularly limited, but is, for example, 1,000,000 or less, more preferably 500,000 or less. The lower limit is, for example, 5,000 or more, preferably 10,000 or more. However, it may be practically impossible to measure the average molecular weight of a polymer having a crosslinked structure.

[0090] A physically crosslinked structure is formed, for example, by two carboxyl groups in a polymer having carboxyl groups forming a salt with one divalent metal, and / or by entanglement of the polymer. The former physically crosslinked structure is formed by forming a salt with a divalent metal on a polymer formed without using a crosslinking agent for chemical crosslinking. The phenomenon in which physically cut hydrogels rejoin after cutting is mainly due to salt formation between carboxyl groups and divalent metals. However, it is presumed that polymer entanglement also progresses over a relatively long period of time, further reinforcing the rejoining due to salt formation. Note that a hydrogel having a chemically crosslinked structure also has a physically crosslinked structure, since two carboxyl groups in the polymer form a salt with one divalent metal and the polymers are also entangled.

[0091] Polymerization methods for preparing the polymer include radical polymerization (thermal polymerization) using a thermal initiator and photopolymerization using a photoinitiator. Of these, photopolymerization is preferred. Known initiators can be used as appropriate as the polymerization initiator. Examples of photoinitiators include α-ketoglutaric acid. The initiator concentration can be in the range of 0.01 to 10 mol % relative to the monomer concentration.

[0092] The metal salt that is a component of the temperature-responsive material A is not particularly limited, but from the viewpoint of obtaining better effects, an organic acid metal salt is preferred, and an organic acid divalent metal salt is more preferred.

[0093] The organic acid constituting the organic acid divalent metal salt is not particularly limited, but examples thereof include fatty acids (alicyclic carboxylic acids), aromatic carboxylic acids, oxocarboxylic acids, and other organic acids.

[0094] Examples of fatty acids (aliphatic carboxylic acids) include the following compounds: Formic acid [methanoic acid], Acetic acid [ethanoic acid], Propionic acid [propanoic acid], Butyric acid [butanoic acid], Isobutyric acid, Valeric acid [pentanoic acid], Isovaleric acid, Caproic acid [hexanoic acid], Enanthic acid [heptylic acid] [heptanoic acid], Caprylic acid [octanoic acid], Pelargonic acid [nonanoic acid], Capric acid [decanoic acid], Lauric acid [dodecanoic acid], Myristic acid [tetradecanoic acid], Pentadecylic acid [pentadecanoic acid], Palmitic acid [cetanoic acid] [hexadecanoic acid], Margaric acid [heptadecanoic acid], Stearic acid [octadecanoic acid], Oleic acid, Linoleic acid, Linolenic acid, Tuberculin stearic acid [nonadecanoic acid] Arachidic acid (eicosanoic acid), arachidonic acid, eicosapentaenoic acid, behenic acid (docosanoic acid), docosahexaenoic acid, lignoceric acid (tetracosanoic acid), cerotic acid (hexacosanoic acid), montanic acid (octacosanoic acid), melissic acid (triacontanoic acid).

[0095] Examples of aromatic carboxylic acids include the following compounds: salicylic acid (hydroxybenzoic acid), gallic acid (trihydroxybenzoic acid), benzoic acid (benzenecarboxylic acid), phthalic acid, cinnamic acid (β-phenylacrylic acid), mellitic acid (mellitic acid, graphitic acid) (benzenehexacarboxylic acid).

[0096] Examples of oxocarboxylic acids include the following compounds: pyruvic acid (oxopropionic acid, α-ketopropionic acid, pyruvate)

[0097] Other organic acids include the following compounds: oxalic acid (ethanedioic acid), lactic acid (α-hydroxypropanoic acid), tartaric acid, maleic acid, fumaric acid (fumaric acid, aromamaleic acid, boretic acid, lichenic acid), malonic acid (propanedioic acid), succinic acid, malic acid (hydroxysuccinic acid), citric acid, aconitic acid, glutaric acid, adipic acid (hexanedioic acid), amino acids, L-ascorbic acid (vitamin C).

[0098] Among organic acids, formic acid, acetic acid, and propionic acid are desirable, taking into consideration the solubility and solubility curve of the salt in the aqueous solution in the hydrogel. For example, calcium formate exhibits a relatively small positive solubility curve with respect to temperature in the range of 0 to 100°C (solubility increases as temperature increases). In contrast, calcium acetate exhibits a negative solubility curve with respect to temperature in the range of 0 to about 60°C, and a relatively small positive solubility curve in the range of about 50 to about 85°C. Calcium propionate exhibits a negative solubility curve with respect to temperature in the range of 0 to about 50°C, and a positive solubility curve in the range of about 50 to 100°C.

[0099] The divalent metal constituting the organic acid divalent metal salt is not particularly limited, but is preferably an alkaline earth metal, such as calcium (Ca), magnesium (Mg), strontium (Sr), or barium (Ba).

[0100] Among the organic acid divalent metal salts, calcium formate, calcium acetate, calcium propionate, magnesium formate, magnesium acetate, magnesium propionate, etc. are desirable from the viewpoint of obtaining better effects. The LCST of the hydrogel can be changed depending on the type of organic acid divalent metal salt used.

[0101] The total metal concentration in temperature-responsive material A can be measured, for example, by inductively coupled plasma optical emission spectrometry (ICP). A known volume of temperature-responsive material A is sintered (e.g., at about 1000°C) to remove organic components, the residue is dissolved in a known amount of water, and the resulting aqueous solution is measured by ICP, thereby determining the metal concentration. When temperature-responsive material A contains an organic acid divalent metal salt, the concentration of free metal in temperature-responsive material A that does not form an organic acid salt can be measured, for example, with a metal ion electrode. When temperature-responsive material A contains metal ions that form organic acid salts and free metal ions, it is possible to separate the two using this method.

[0102] When the temperature-responsive material A contains an organic acid divalent metal salt, the concentration of the organic acid divalent metal salt in the temperature-responsive material A can be appropriately determined taking into account the physical properties and the amount of carboxyl groups required for the temperature-responsive hydrogel. The concentration of the metal salt aqueous solution impregnated into the polymer is, for example, in the range of 50 mM to saturation concentration, preferably in the range of 50 to 500 mM. The saturation concentration refers to the saturation amount (equivalent amount) relative to the amount of carboxyl groups in the polymer. The LCST of the hydrogel can be changed by adjusting the concentration of the metal salt relative to the polymer. The metal concentration relative to the polymer tends to be higher than the metal concentration of the metal salt aqueous solution impregnated into the polymer. Although this varies depending on conditions such as the concentration of carboxyl groups in the polymer and the concentration of the metal salt in the aqueous solution, it can be, for example, about 1.1 to 2.0 times, more typically about 1.2 to 1.5 times, higher. When the divalent metal is calcium, the concentration of the divalent metal relative to the polymer is, for example, in the range of about 1 to 100 mg, more typically in the range of about 10 to 70 mg, and even more typically in the range of about 15 to 50 mg, per 1 g of polymer (gel).

[0103] Temperature-responsive material A (hydrogel) containing a polymer with carboxyl groups and a metal salt is a gel whose main components are water or an aqueous solution and a polymer. Whether or not the polymer forms a hydrogel depends primarily on the length of the polymer (in other words, the concentration of the polymerization initiator). Even if the polymer mass is the same, a higher concentration of the polymerization initiator increases the tendency for gelation. From this perspective, for example, when the monomer is acrylic acid, the polymerization initiator tends to gel at 3 M or higher when the concentration is 0.1 mol%, and at 2 M or higher when the concentration is 0.01 mol%. The same is true when the monomer is methacrylic acid. The concentration of the polymerization initiator can be appropriately selected within the range that forms a hydrogel, depending on the type of polymerization initiator and the type of monomer.

[0104] The temperature-responsive material A (hydrogel) has a lower critical solution temperature (LCST). The LCST is the lower critical solution temperature at which the hydrogel becomes cloudy due to phase separation, and serves as an index of the phase separation temperature. The presence of an LCST can be evaluated, for example, by measuring the turbidity (transmittance) using an ultraviolet-visible-near-infrared spectrophotometer. It can also be evaluated by measuring the endothermic / thermal peak using a differential scanning calorimeter or by measuring the temperature dependence of the dynamic elastic modulus using a rheometer (viscoelasticity measuring device). The LCST of the temperature-responsive material A (hydrogel) varies depending on the polymer composition, the type and concentration of the metal salt, etc., but is, for example, in the range of 10 to 80°C, preferably in the range of 25 to 45°C.

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

[0106] The temperature-responsive material A (hydrogel) can be produced, for example, by immersing the polymer having a carboxyl group in an aqueous solution of the metal salt. The immersion of the polymer in the aqueous solution of the metal salt can be carried out at room temperature, for example, at a temperature in the range of 4 to 30° C. However, taking into account the LCST of the resulting temperature-responsive hydrogel, the immersion can be carried out at a temperature higher or lower than the LCST.

[0107] The metal salt concentration in the metal salt aqueous solution can be determined appropriately taking into consideration the type of polymer and metal salt and the desired LCST, but is, for example, in the range of 50 mM to saturation concentration. For example, a temperature-responsive hydrogel can be obtained by immersing the gel in an aqueous solution containing a metal salt ranging from 50 mM to saturation concentration until equilibrium is reached. In the case of a chemically crosslinked gel, equilibrium is reached in, for example, about 1 to 72 hours, while in the case of a physically crosslinked gel, equilibrium is reached in 2 to 7 days. However, if the desired physical properties are obtained, immersion until equilibrium is reached may not be necessary.

[0108] From the viewpoint of obtaining a better effect, the temperature-responsive material A is preferably a material having a foamed structure at least in part. As long as the temperature-responsive material A has a foamed structure at least in part, the temperature-responsive material A may have a partial foamed structure or may have a foamed structure entirely. By making the temperature-responsive material A a material having a foamed structure at least in part, voids where water originally existed can be used as space for swelling, and therefore the temperature-responsive material A can be prevented from swelling and increasing in volume upon water absorption, which is thought to further improve the hardness of the rubber composition when dried.

[0109] The material having at least a partial foamed structure can be obtained by further processing the hydrogel into a foamed structure. The material is formed by foaming the hydrogel, and has at least a partial foamed structure containing numerous bubbles. The method for processing the hydrogel into a foamed structure is not particularly limited as long as it can produce a material having at least a partial foamed structure. Known methods for foaming the hydrogel can be used. For example, a method in which the temperature-responsive material A (hydrogel) is heated, then rapidly cooled (for example, within 1 hour, preferably within 30 minutes, more preferably within 10 minutes, and particularly preferably within 5 minutes) using liquid nitrogen or the like to freeze the material, followed by freeze-drying is included. The heating conditions are not particularly limited as long as the temperature-responsive material A (hydrogel) undergoes phase separation. For example, the heating temperature 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 heating time is preferably 1 minute or longer, more 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 for the freeze-drying is not particularly limited, but is, for example, preferably 1 hour or more, more preferably 5 hours or more, even more preferably 10 hours or more, and particularly preferably 24 hours or more. Also, 72 hours or less is preferable, more preferably 48 hours or less, and even more preferably 30 hours or less. Other methods for processing the hydrogel into a foamed structure include a method of foaming by blending a foaming agent, such as an inorganic foaming agent such as sodium bicarbonate or ammonium carbonate, or an organic foaming agent such as azodicarbonamide, dinitrosopentamethylenetetramine, or p,p'-oxybisbenzenesulfonylhydrazide.

[0110] In the rubber composition, the content of the temperature-responsive material A 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, per 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, and particularly preferably 40 parts by mass or less. Within the above range, better effects tend to be obtained. In the present invention, the content of the temperature-responsive material A refers to the amount of a temperature-responsive hydrogel (a gel whose main components are water or an aqueous solution and a polymer) containing a polymer having a carboxyl group and a metal salt, and means the amount including the water contained in the temperature-responsive material (temperature-responsive hydrogel) in addition to the polymer having a carboxyl group and the metal salt.

[0111] From the viewpoint of obtaining better effects, the rubber composition desirably contains a water-soluble and / or water-absorbent material B. In the present invention, the water-soluble and / or water-absorbent material B means a material that is blended separately from the temperature-responsive material A containing the aforementioned polymer having a carboxyl group and metal salt. That is, for example, when the temperature-responsive material A contains a temperature-responsive hydrogel containing polyacrylic acid and calcium acetate, and the temperature-responsive material B further contains calcium acetate monohydrate, the calcium acetate constituting the temperature-responsive material A does not fall under the category of water-soluble and / or water-absorbent material B, and the separately blended calcium acetate monohydrate falls under the category of water-soluble and / or water-absorbent material B.

[0112] In the water-soluble and / or water-absorbent material B, the water-soluble material B (hereinafter also simply referred to as "water-soluble material") is not particularly limited, and known water-soluble materials can be used. For example, a material having a solubility in water at 20°C of 25 g / 100 g water or more can be used. Among them, from the viewpoint of obtaining better effects, the metal salts and hydrates thereof are preferred, and the organic acid divalent metal salts and hydrates thereof are more preferred. The organic acids and divalent metals constituting the organic acid divalent metal salts can also be the same compounds as those described above. As the hydrate, hydrates that can form metal salts, such as monohydrates and dihydrates, can be used as appropriate.

[0113] Among the water-soluble materials, from the viewpoint of obtaining a better effect, alkaline earth metal salts of organic acids and hydrates thereof are preferred, and calcium formate, calcium acetate, calcium propionate, magnesium formate, magnesium acetate, magnesium propionate, and hydrates thereof are more preferred.

[0114] In the water-soluble and / or water-absorbent material B, the water-absorbent material B (hereinafter also simply referred to as "water-absorbent material") is not particularly limited, and any known water-absorbent material can be used. For example, a material having a water absorption rate of 5% or more calculated by the following measurement method can be used. (Measurement method) After immersion in water at 20°C for 24 hours, the weights before and after immersion are measured, and the water absorption rate is calculated using the following formula: Water absorption rate (%) = (weight after immersion - weight before immersion) / weight after immersion x 100

[0115] Examples of water-absorbing materials include materials (fibers, elastomers, and resins) having heteroatoms. The heteroatom refers to an atom other than carbon and hydrogen atoms, and is not particularly limited as long as it can form a reversible molecular bond with water, such as a hydrogen bond or an ionic bond, but is preferably at least one atom selected from the group consisting of 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 even more preferably an oxygen atom.

[0116] Examples of structures and groups containing oxygen atoms include ether groups, esters, carboxy groups, carbonyl groups, alkoxy groups, and hydroxy groups. Of these, ether groups are preferred, and oxyalkylene groups are more preferred. Examples of structures and groups containing nitrogen atoms include amino groups (primary amino groups, secondary amino groups, and tertiary amino groups), amide groups, nitrile groups, and nitro groups. Of these, amino groups are preferred, and tertiary amino groups are more preferred. Examples of structures and groups containing silicon atoms include silyl groups, alkoxysilyl groups, and silanol groups. Of these, silyl groups are preferred, and alkoxysilyl groups are more preferred. Examples of structures and groups containing sulfur atoms include sulfide groups, sulfate groups, sulfate esters, and sulfo groups. Examples of structures and groups containing phosphorus atoms include phosphate groups and phosphate esters. Examples of structures and groups containing halogen atoms include halogeno groups such as fluoro groups, chloro groups, bromo groups, and iodo groups.

[0117] For example, since cellulose fibers have hydroxyl groups, examples of water-absorbent fibers include cellulose fibers. Preferred cellulose fibers are cellulose microfibrils. Cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf; pulp, paper, cloth, agricultural waste, waste biomass such as food waste and sewage sludge obtained from these raw materials; unused biomass such as rice straw, wheat straw, and thinned wood; and cellulose produced by sea squirts, acetic acid bacteria, and the like. These may be used alone or in combination of two or more.

[0118] Examples of water-absorbent elastomers include elastomers having an oxyalkylene group. Examples of such elastomers include epoxide-allyl glycidyl ether copolymers, amine-allyl glycidyl ether copolymers, and silyl-allyl glycidyl ether copolymers. These may be used alone or in combination of two or more.

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

[0120] In the rubber composition, the content of the water-soluble and / or water-absorbent material B (total content of the water-soluble material and the water-absorbent 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, per 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. Within the above ranges, better effects tend to be obtained. When either the water-soluble material or the water-absorbent material is contained, the amount thereof is preferably within the same range. In the present invention, the content of the water-soluble and / or water-absorbent material B means the total content of the water-soluble material and the water-absorbent material, and if the water-soluble material or the water-absorbent material is a hydrate, the amount includes the hydrate.

[0121] The rubber composition preferably contains an antioxidant from the viewpoint of crack resistance, ozone resistance, and the like.

[0122] The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and the like. Examples of suitable antioxidants include p-phenylenediamine antioxidants such as amines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis.

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

[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, and more preferably 1.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0125] As the stearic acid, conventionally known products can be used, such as products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

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

[0127] As the zinc oxide, conventionally known products can be used, for example, products available from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

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

[0129] The wax is not particularly limited, and examples thereof include petroleum waxes, natural waxes, etc. Synthetic waxes obtained by refining or chemically treating multiple waxes can also be used. These waxes may be used alone or in combination of two or more types.

[0130] Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are derived from resources other than petroleum, and include, for example, plant-based waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and spermaceti; mineral-based waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd.

[0131] The rubber composition may contain a vulcanization accelerator. The content 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, per 100 parts by mass of the rubber component.

[0132] The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may 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 components, the rubber composition may contain appropriate additives typically used in the application of the rubber composition, such as a release agent, a pigment, etc. The content of the additive in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0134] In the rubber composition, the ratio of the water-soluble and / or water-absorbent material B to the crosslinking agent (content of water-soluble and / or water-absorbent material B / content of crosslinking agent) is desirably 2.0 to 40.0 from the viewpoint of obtaining better effects. The lower limit is preferably 6.7 or more, more preferably 10.0 or more, even 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 even more preferably 30.0 or less.

[0135] The rubber composition can be produced by a known method. For example, the rubber composition can be produced by kneading the components using a rubber kneading device such as an open roll or a Banbury mixer, and optionally crosslinking the components. The kneading conditions are as follows: the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

[0136] From the viewpoint of obtaining better effects, it is desirable that the dynamic modulus of elasticity at 0°C when immersed in water (0°C E*w) and the dynamic modulus of elasticity at 0°C when dry (0°C E*d) of the rubber composition satisfy the following formula (1): (1) 0°C E*w / 0°C E*d≦0.70 0°C E*w / 0°C E*d is preferably 0.56 or less, more preferably 0.55 or less, even more preferably 0.54 or less, still more preferably 0.53 or less, still more preferably 0.51 or less, still more preferably 0.49 or less, still more preferably 0.45 or less, still more preferably 0.44 or less, still more preferably 0.42 or less, still more preferably 0.40 or less, still more preferably 0.39 or less, still more preferably 0.33 or less, still more preferably 0.31 or less, still more preferably 0.30 or less, still more preferably 0.28 or less, and particularly preferably 0.27 or less. The lower limit is not particularly limited, but is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more.

[0137] From the viewpoint of obtaining better effects, it is desirable that the dynamic modulus of elasticity at 0°C when immersed in water (0°C E*w) and the dynamic modulus of elasticity at 30°C when immersed in water (30°C E*w) of the rubber composition satisfy the following formula (2): (2) 30°C E*w / 0°C E*w≧0.80 30°C E*w / 0°C E*w is preferably 0.83 or more, more preferably 0.85 or more, even more preferably 0.87 or more, still more preferably 0.88 or more, still more preferably 0.89 or more, still more preferably 0.90 or more, still more preferably 0.95 or more, still more preferably 0.98 or more, still more preferably 1.04 or more, still more preferably 1.05 or more, still more preferably 1.06 or more, still more 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 particularly limited, but is preferably 3.00 or less, more preferably 2.00 or less, and even more preferably 1.50 or less.

[0138] The reason why the above-mentioned effects are obtained by an elastomer composition that satisfies the above formulas (1) and (2) is not entirely clear, but is presumed as follows. Formula (1) "0°C E*w / 0°C E*d≦0.70" means that at low temperatures, the elastic modulus decreases relatively significantly when immersed in water compared to when dry. On the other hand, formula (2) "30°C E*w / 0°C E*w≧0.80" means that when immersed in water, a practical elastic modulus is maintained even at high temperatures compared to low temperatures. In this way, the behavior of the elastic modulus of the above rubber composition changes with temperature, and therefore tire performance can be changed in response to temperature changes.

[0139] In this case, the problem (objective) of changing tire performance in response to temperature changes is solved by configuring a rubber composition that contains a rubber component containing at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber, a crosslinking agent, carbon black, a plasticizer, and a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt in a predetermined blend, and that satisfies the parameters of the above formulas (1) and (2). In other words, the parameters do not define the problem (objective), and the object of the present application is to change tire performance in response to temperature changes, and as a means of solving this, a rubber composition is configured that contains the rubber composition in the above predetermined blend and that satisfies the parameters of the above formulas (1) and (2).

[0140] From the viewpoint of obtaining better effects, it is desirable that the dynamic modulus of elasticity at 0°C when immersed in water (0°C E*w) of the rubber composition satisfies the following formula: 0°C E*w≦8.0 MPa 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, even more preferably 4.5 MPa or less, still more preferably 4.2 MPa or less, still more preferably 4.0 MPa or less, still more preferably 3.8 MPa or less, still more preferably 3.7 MPa or less, still more preferably 3.5 MPa or less, still more 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 particularly limited, but is preferably 1.0 MPa or more, more preferably 1.3 MPa or more, even more preferably 1.5 MPa or more, still more preferably 2.7 MPa or more, still more preferably 2.8 MPa or more, and still more preferably 3.0 MPa or more.

[0141] From the viewpoint of obtaining better effects, it is desirable that the dynamic modulus of elasticity at 30°C when immersed in water (30°C E*w) of the rubber composition satisfies the following formula: 30°C E*w ≥ 3.0 MPa 30°C E*w is preferably 3.3 MPa or more, more preferably 3.4 MPa or more, even more preferably 3.5 MPa or more, still more preferably 3.6 MPa or more, still more preferably 3.7 MPa or more, still more preferably 3.8 MPa or more, and particularly preferably 3.9 MPa or more, and among these, 4.0 MPa or more is preferred, 4.1 MPa or more is more preferred, 4.3 MPa or more is even more preferred, and 4.5 MPa or more is most preferred. The upper limit is not particularly limited, but is preferably 10.0 MPa or less, more preferably 8.0 MPa or less, even more preferably 7.0 MPa or less, and particularly preferably 6.0 MPa or less.

[0142] From the viewpoint of obtaining better effects, it is desirable that the dynamic modulus of elasticity at 0°C in a dry state (0°C E*d) of the rubber composition satisfies the following formula: 0°C E*d ≥ 5.0 MPa 0°C E*d is preferably 6.0 MPa or more, more preferably 6.9 MPa or more, even more preferably 7.0 MPa or more, still more preferably 7.8 MPa or more, still more preferably 8.0 MPa or more, still more preferably 8.2 MPa or more, still more preferably 8.3 MPa or more, still more preferably 8.4 MPa or more, still more preferably 8.5 MPa or more, still more preferably 9.0 MPa or more, still more preferably 10.0 MPa or more, still more preferably 10.5 MPa or more, still more preferably 10.7 MPa or more, still more preferably 11.0 MPa or more, particularly preferably 11.6 MPa or more, most preferably 12.0 MPa or more, and of these, preferably 12.3 MPa or more. The upper limit is not particularly limited, but is preferably 20.0 MPa or less, more preferably 18.0 MPa or less, even more preferably 16.0 MPa or less, and still more preferably 15.0 MPa or less.

[0143] In the present invention, the dynamic modulus of elasticity E* is measured by the method described in the Examples. Note that in the present invention, the dynamic modulus of elasticity E* of a rubber composition means the dynamic modulus of elasticity E* of the rubber composition after vulcanization (crosslinking).

[0144] In the present invention, the dynamic modulus of elasticity E* in a dry state means the dynamic modulus of elasticity of a rubber composition (after vulcanization) in a dry state, specifically, the dynamic modulus of elasticity of a rubber composition (after vulcanization) dried by the method described in the Examples. In the present invention, the dynamic modulus of elasticity E* when immersed in water means the dynamic modulus of elasticity of a rubber composition (after vulcanization) after immersion in water, specifically, the dynamic modulus of elasticity of a rubber composition (after vulcanization) after immersion in water by the method described in the Examples.

[0145] In the present invention, the dynamic modulus E* of the rubber composition (after vulcanization) is measured using an ARES (a rheometer manufactured by TA Instruments) on a test vulcanized rubber sheet under conditions of a strain of 2% and a frequency of 10 Hz.

[0146] Next, we will explain manufacturing guidelines for satisfying the above formulas (1) "0°C E*w / 0°C E*d≦0.70" and (2) "30°C E*w / 0°C E*w≧0.80," "0°C E*w≦8.0 MPa," "30°C E*w≧3.0 MPa," and "0°C E*d≧5.0 MPa." Formula (1) "0°C E*w / 0°C E*d≦0.70" means that at low temperatures, the elastic modulus decreases relatively significantly when immersed in water compared to when dry. On the other hand, formula (2) "30°C E*w / 0°C E*w≧0.80" means that a practical elastic modulus is maintained even at high temperatures when immersed in water compared to low temperatures. A rubber composition satisfying formulas (1) and (2) can be achieved, for example, by including a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt. Furthermore, this can be further achieved by using a material having at least a portion of a foamed structure as temperature-responsive material A or by further including a water-soluble and / or water-absorbent material B. "0°C E*w≦8.0 MPa" means improved grip performance on icy roads. A rubber composition satisfying this formula can be achieved, for example, by including the temperature-responsive material A. This can be further achieved by using a material having at least a portion of a foamed structure as temperature-responsive material A or by further including material B. "30°C E*w≧3.0 MPa" means improved steering stability on wet roads. A rubber composition satisfying this formula can be achieved, for example, by including the temperature-responsive material A. This can be further achieved by using a material having at least a portion of a foamed structure as temperature-responsive material A or by further including material B. "0°C E*d≧5.0 MPa" means improved grip performance on dry roads. A rubber composition satisfying this formula can be achieved, for example, by including the temperature-responsive material A. Furthermore, the achievement of this object can be facilitated by using a material having a foam structure at least in a part of the temperature-responsive material A, or by further including the material B.

[0147] The dynamic modulus of elasticity E* (absolute value) in the dry state can be adjusted by the type and amount of chemicals (particularly, rubber components, fillers, and plasticizers) blended into the composition. For example, increasing the amount of plasticizer tends to decrease the dynamic modulus of elasticity E* in the dry state, increasing the amount of filler tends to increase the dynamic modulus of elasticity E* in the dry state, and decreasing the amount of sulfur tends to decrease the dynamic modulus of elasticity E* in the dry state. The dynamic modulus of elasticity E* in the dry state can also be adjusted by adjusting the blending amounts of sulfur and vulcanization accelerator. More specifically, increasing the amount of sulfur tends to increase the dynamic modulus of elasticity E* in the dry state, and increasing the amount of vulcanization accelerator tends to increase the dynamic modulus of elasticity E* in the dry state.

[0148] More specifically, by adjusting the dynamic elastic modulus E* in a dry state to fall within a desired range, and then including a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt, and, if necessary, by making temperature-responsive material A a material having a foam structure in at least a portion thereof, or by further including a water-soluble and / or water-absorbent material B, it becomes possible to satisfy the above formulas (1) "0°C E*w / 0°C E*d≦0.70", (2) "30°C E*w / 0°C E*w≧0.80", "0°C E*w≦8.0 MPa", "30°C E*w≧3.0 MPa", and "0°C E*d≧5.0 MPa".

[0149] The rubber composition can be used (as a rubber composition for tires) for tire components such as treads, sidewalls, base treads, undertreads, shoulders, clinches, bead apexes, breaker cushion rubbers, carcass cord covering rubbers, insulation, chafers, inner liners, and side reinforcing layers of run-flat tires, among others. Among these, the rubber composition is particularly suitable for treads.

[0150] The tire of the present invention is manufactured by a conventional method using the above-mentioned rubber composition. For example, the rubber composition containing various materials is extruded into a shape such as a tread while still unvulcanized, and molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in the vulcanizer to obtain a tire.

[0151] The above-mentioned tires are suitably used as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc. Among these, they are suitably used as winter tires (studless tires, snow tires, studded tires) and all-season tires.

[0152] Below, examples (embodiments) that are considered preferable for implementation will be shown, but the scope of the present invention is not limited to the examples.

[0153] The various chemicals used in the following Examples and Comparative Examples will be collectively described below. NR: TSR20 BR: BR150B (cis content: 98% by mass) manufactured by Ube Industries, Ltd. SBR: Nipol SBR1502 (styrene content: 23.5% by mass) manufactured by Nippon Zeon Co., Ltd. Carbon black: Seast N220 (N) manufactured by Mitsubishi Chemical Corporation ２ SA: 111m ２ / g) Silica: Ultrasil VN3 (N manufactured by Evonik Tegussa) ２ SA: 175m ２ / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Tegussa Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Plasticizer A: Licon 150 (liquid butadiene polymer) manufactured by 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 manufactured by WAKO (solubility in water at 20°C: 34.7 g / 100 g water) Water-absorbing material B: Biomass nanofiber (product name "BiNFi-s Cellulose", microfibrillated cellulose fiber, water absorption: 10%) manufactured by Sugino Machine Co., Ltd. Antiaging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: manufactured by NOF Corporation Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Crosslinking agent A: Tackirol V200 (alkylphenol-sulfur chloride condensate) manufactured by Taoka Chemical Co., Ltd. Vulcanization accelerator CZ: Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator DPG: Noccela D manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0154] (Production Example 1) With reference to Advanced Materials 2020, 32, 1905878, a temperature-responsive material A-1 was produced by the following production method. A precursor aqueous solution was prepared by dissolving 1.0 M acrylic acid (AAc) in ultrapure water, 1.0 mol% of the initiator potassium peroxodisulfate relative to the monomer concentration, and 1.0 mol% of the crosslinker N,N'-methylenebisacrylamide (MbAAd) relative to the monomer concentration. Here, a physically crosslinked gel was obtained when the crosslinker concentration was 0 mol%, and a chemically crosslinked gel was obtained when a crosslinker was added. This solution was poured into a mold of any shape and heated at 60°C for 6 hours in air to polymerize and form a gel. The polymerized gel or non-fluid, highly viscous material was immersed in a sufficient amount of an aqueous solution prepared by dissolving calcium acetate at a concentration of 1000 mM in ultrapure water until equilibrium was reached, thereby obtaining a temperature-responsive material A-1.

[0155] (Production Example 2) Temperature-responsive material A-1 was heated at 80°C for 5 minutes and then frozen in liquid nitrogen. After freezing, the material was freeze-dried for 24 hours using a freeze dryer (FDU-2110 manufactured by EYELA) to obtain temperature-responsive material A-2 having a foam structure.

[0156] (Production Example 3) With reference to Advanced Materials 2020, 32, 1905878, a temperature-responsive material A-3 was produced by the following production method. A precursor aqueous solution was prepared by dissolving 1.0 M acrylic acid (AAc) in ultrapure water, 1.0 mol% of the initiator potassium peroxodisulfate relative to the monomer concentration, and 1.0 mol% of the crosslinker N,N'-methylenebisacrylamide (MbAAd) relative to the monomer concentration in water. Here, a physically crosslinked gel was obtained when the crosslinker concentration was 0 mol%, and a chemically crosslinked gel was obtained when a crosslinker was added. This solution was poured into a mold of any shape and heated at 60°C for 6 hours in air to polymerize and form a gel. The polymerized gel or non-fluid, highly viscous material was immersed in a sufficient amount of an aqueous solution prepared by dissolving calcium propionate at a concentration of 1000 mM in ultrapure water until equilibrium was reached, thereby obtaining a temperature-responsive material A-3.

[0157] (Production Example 4) Temperature-responsive material A-3 was heated at 80°C for 5 minutes and then frozen in liquid nitrogen. After freezing, the material was freeze-dried for 24 hours using a freeze dryer (FDU-2110 manufactured by EYELA) to obtain temperature-responsive material A-4 having a foam structure.

[0158] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized for 12 minutes at 170°C to obtain a vulcanized rubber composition sheet having a thickness of 1 mm. The obtained unvulcanized rubber composition was molded into the shape of a cap tread and laminated with other tire components to produce an unvulcanized tire. The tire was then vulcanized for 15 minutes at 170°C to obtain a test tire (size: 195 / 65R15).

[0159] The vulcanized rubber composition and test tire obtained were stored in a dark place at room temperature for three months, and then the following evaluations were carried out. The results are shown in Table 1.

[0160] (Measurement of Dynamic Modulus of Elasticity E*) The dynamic modulus of elasticity E* was measured using a 1 mm thick vulcanized rubber composition sheet. Specifically, the 1 mm thick vulcanized rubber composition sheet was kept at the measurement temperature for 10 minutes, and then the dynamic modulus of elasticity E* of the vulcanized rubber composition sheet was measured (0°C, 30°C) using an ARES (a rheometer manufactured by TA Instruments) under conditions of 2% strain and 10 Hz frequency. The vulcanized rubber composition sheet for measurement was prepared as follows. The 1 mm thick vulcanized rubber composition sheet was immersed in water at 25°C for 10 hours, and then dried under reduced pressure at 80°C and 1 kPa or less until it reached a constant weight, thereby obtaining a dried vulcanized rubber composition sheet. The temperature of the obtained dried vulcanized rubber composition sheet was returned to 25°C, and the sheet was used as the vulcanized rubber composition sheet for measuring the dynamic modulus of elasticity E* when dry. The dried vulcanized rubber composition sheet was again immersed in water at 25° C. for 10 hours to prepare a vulcanized rubber composition sheet for measuring the dynamic modulus of elasticity E* when immersed in water.

[0161] (Ice grip performance) The test tires were mounted on a domestically produced 2000cc front-engine, front-wheel drive vehicle, and the vehicle was driven on ice to evaluate ice grip performance. Specifically, the ice grip performance was evaluated by driving the vehicle on ice, applying the lock brakes at 30 km / h, and measuring the stopping distance (ice braking stopping distance) required to stop the vehicle. The result was expressed as an index (ice grip performance index) with Comparative Example 1 set to 100. The higher the index, the better the braking performance on ice (ice grip performance).

[0162] (Dry Grip Performance) The test tires were mounted on all wheels of a vehicle (domestic FF 2000cc), and the braking distance from an initial speed of 100 km / h on a dry asphalt road surface was measured and expressed as an index (dry grip performance index) with Comparative Example 1 set to 100. A larger index indicates a shorter braking distance and better dry grip performance.

[0163] (Overall Performance) The overall performance of ice grip performance and dry grip performance was evaluated as the sum of the ice grip performance (index) and the dry grip performance (index). The higher the index, the better the overall performance.

[0164]

[0165] The present invention (1) is a rubber composition for a tire, comprising: a rubber component containing at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber; a crosslinking agent; carbon black; a plasticizer; and a temperature-responsive material A containing a polymer having a carboxyl group and a metal salt, wherein the content of the crosslinking agent is more than 0 parts by mass and less than 10 parts by mass, the content of the carbon black is more than 0 parts by mass and less than 100 parts by mass, and the content of the plasticizer is more than 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0166] The present invention (2) is the rubber composition for a tire according to the present invention (1), which contains a water-soluble and / or water-absorbent material B.

[0167] The present invention (3) is the rubber composition for tires according to the present invention (2), wherein the ratio of the material B to the crosslinking agent (content of material B / content of crosslinking agent) is 2.0 to 40.0.

[0168] The present invention (4) is a rubber composition for tires according to any one of the present inventions (1) to (3), in which the dynamic modulus of elasticity at 0°C when immersed in water (0°C E*w), the dynamic modulus of elasticity at 30°C when immersed in water (30°C E*w), and the dynamic modulus of elasticity at 0°C when dry (0°C E*d) satisfy the following formulas (1) to (2): (1) 0°C E*w / 0°C E*d≦0.70 (2) 30°C E*w / 0°C E*w≧0.80

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

[0170] The present invention (6) is the rubber composition for tires according to any one of the present inventions (1) to (5), in which the dynamic modulus of elasticity at 30°C when immersed in water (30°C E*w) satisfies the following formula: 30°C E*w≧3.0 MPa

[0171] The present invention (7) is the rubber composition for a tire according to any one of the present inventions (1) to (6), wherein the temperature-responsive material A is a material having a foamed structure at least in part.

[0172] The present invention (8) is a tire using the rubber composition according to any one of the present inventions (1) to (7) in the tread.

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

Claims

1. A rubber component including at least one rubber selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber; A cross-linking agent; Carbon black, A plasticizer; a temperature-responsive material A including a polymer having a carboxyl group and a metal salt; a content of the crosslinking agent relative to 100 parts by mass of the rubber component being more than 0 parts by mass and less than 10 parts by mass, a content of the carbon black being more than 0 parts by mass and less than 100 parts by mass, and a content of the plasticizer being more than 5 parts by mass.

2. 2. The rubber composition for tires according to claim 1, further comprising a water-soluble and / or water-absorbent material B.

3. 3. The rubber composition for tires according to claim 2, wherein a ratio of said material B to said crosslinking agent (content of said material B / content of said crosslinking agent) is 2.0 to 40.

0.

4. The rubber composition for tires according to any one of claims 1 to 3, wherein a dynamic modulus of elasticity at 0°C when immersed in water (0°C E*w), a dynamic modulus of elasticity at 30°C when immersed in water (30°C E*w), and a dynamic modulus of elasticity at 0°C when dry (0°C E*d) 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 rubber composition for tires according to any one of claims 1 to 3, wherein a dynamic modulus of elasticity (0°C E*w) at 0°C when immersed in water satisfies the following formula: 0℃E*w≦8.0MPa

6. The rubber composition for tires according to any one of claims 1 to 3, wherein a dynamic modulus of elasticity (30°C E*w) at 30°C when immersed in water satisfies the following formula: 30℃E*w≧3.0MPa

7. The rubber composition for a tire according to any one of claims 1 to 3, wherein the temperature responsive material A is a material having at least a foamed structure in a part thereof.

8. A tire using the rubber composition according to any one of claims 1 to 3 in the tread.

9. 9. The tire of claim 8, which is a winter tire or an all-season tire.