Rubber composition for tires and tires

Abstract

To provide a rubber composition for a tire and a tire capable of improving overall performance of wet grip performance and low fuel consumption properties when travelling at high speed.SOLUTION: There is provided a rubber composition for a tire which comprises a rubber component containing a styrene butadiene rubber and a butadiene rubber, silica and a resin including an aromatic resin, wherein the content of the styrene butadiene rubber is more than 60 mass% in 100 mass% of the rubber component, the silica has an average particle diameter of 16 nm or less, the content of the silica is more than 80 pts.mass based on 100 pts.mass of the rubber component and the content of the resin>the content of the butadiene rubber>the content of a liquid plasticizer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a rubber composition for a tire and a tire. [Background technology]

[0002] Various methods for improving wet grip performance and fuel economy have been investigated so far (see, for example, Patent Documents 1 and 2). However, in recent years, further improvements in these performances have been demanded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-544936 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-344955 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to solve the above-mentioned problems and provide a rubber composition for a tire and a tire that can improve the overall performance of wet grip performance and fuel economy during high-speed driving. [Means for solving the problem]

[0005] The present disclosure relates to a rubber composition for tires, which contains a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a resin containing an aromatic resin, wherein the content of the styrene-butadiene rubber exceeds 60% by mass in 100% by mass of the rubber component, the average particle size of the silica is 16 nm or less, the content of the silica exceeds 80 parts by mass per 100 parts by mass of the rubber component, and the ratio of the resin content > the butadiene rubber content > the liquid plasticizer content is satisfied. [Effects of the Invention]

[0006] The present disclosure provides a rubber composition for tires that contains a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a resin containing an aromatic resin, wherein the content of the styrene-butadiene rubber exceeds 60% by mass in 100% by mass of the rubber component, the average particle size of the silica is 16 nm or less, the content of the silica exceeds 80 parts by mass per 100 parts by mass of the rubber component, and the resin content > the butadiene rubber content > the liquid plasticizer content, thereby achieving good overall wet grip performance and fuel economy during high-speed driving. DETAILED DESCRIPTION OF THE INVENTION

[0007] The rubber composition for a tire of the present disclosure contains a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a resin containing an aromatic resin, wherein the content of the styrene-butadiene rubber exceeds 60% by mass in 100% by mass of the rubber component, the average particle size of the silica is 16 nm or less, the content of the silica exceeds 80 parts by mass per 100 parts by mass of the rubber component, and the content of the resin > the content of the butadiene rubber > the content of a liquid plasticizer satisfies the relationship: (content of the resin)

[0008] The reason why the above-mentioned effects can be obtained with the above rubber composition is presumed to be as follows. Silica having an average particle size of 16 nm or less (fine particle silica) has an excellent reinforcing effect, but it usually tends to be difficult to disperse uniformly in a rubber composition. In contrast, in the rubber composition, the styrene-butadiene rubber content in the rubber component is more than 60% by mass, and an aromatic resin is used as the resin, which allows the rubber component and the resin to be well compatible and the silica to be well dispersed. As a result, even when a large amount of finely divided silica, which is difficult to disperse, is compounded, the finely divided silica can be uniformly dispersed, effectively reinforcing the rubber composition. Furthermore, since the relationship is resin content > butadiene rubber content > liquid plasticizer content, the liquid plasticizer is less likely to be released, and changes in the state of the rubber component due to deterioration are suppressed. It is believed that the above effects improve the overall wet grip performance and fuel economy during high-speed driving.

[0009] In the rubber composition, the acetone extractable amount (AE) is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. When it is within the above range, the effect tends to be more favorable.

[0010] In the rubber composition, the polymer content (PC) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, and 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 ranges, the effect tends to be more favorably obtained.

[0011] In the rubber composition, the carbon black content (BC) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more, and is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0012] In the rubber composition, the ash content (Ash) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 42% by mass or less. When the ash content is within the above range, the effect tends to be more favorable.

[0013] The acetone extractables (AE), polymer content (PC), carbon black content (BC), and ash content (Ash) are measured by the following methods. First, the acetone extractables (AE) of the rubber composition (sample) are measured by the method for measuring acetone extractables in accordance with JIS K 6229:2015 (unit: mass % of the rubber composition (sample)). The polymer content (PC) is calculated from the weight loss (mass) when the organic matter in the sample remaining after the acetone extraction is thermally decomposed and vaporized by heating in nitrogen (from room temperature to 750°C) in accordance with JIS K6226-1:2003 (unit: mass% in the rubber composition (sample)). The carbon black content (BC) is calculated from the weight loss (mass) when the sample after the thermal decomposition and vaporization is oxidatively burned by heating in air (unit: mass % in the rubber composition (sample)). The ash content (Ash) is calculated from the mass of the components (ash content) that do not burn in the oxidative combustion (unit: mass % in the rubber composition (sample)). From the above definitions, the total of AE, PC, BC, and Ash is 100 mass %.

[0014] Methods known to those skilled in the art can be used to adjust AE, PC, BC, and Ash. For example, AE tends to increase as the amount of plasticizer such as oil in the rubber composition increases. PC tends to increase as the amount of rubber component in the rubber composition increases. BC tends to increase as the amount of carbon black in the rubber composition increases. Ash tends to increase as the amount of components that do not burn by oxidative combustion, such as silica, in the rubber composition increases.

[0015] The rubber composition contains a rubber component. Here, the rubber component is a component that contributes to crosslinking, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0016] 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.

[0017] In this specification, the weight average molecular weight (Mw) can be determined in terms of standard polystyrene based on measurements obtained using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0018] The total styrene content in 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, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably less than 30% by mass. Within the above ranges, the effect tends to be more favorably obtained.

[0019] Here, the total styrene amount in the rubber component is the total content of styrene moieties contained in the entire rubber component (unit: mass%) and can be calculated by Σ (content of each rubber component × styrene amount in each rubber component / 100). For example, if 100% by mass of the rubber component contains 85% by mass of SBR with a styrene content of 40% by mass, 5% by mass of SBR with a styrene content of 25% by mass, and 10% by mass of BR with a styrene content of 0% by mass, the total styrene amount in the rubber component is 35.25% by mass (= 85 × 40 / 100 + 5 × 25 / 100 + 10 × 0 / 100).

[0020] The total vinyl content in the rubber component is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 15% by mass or more, and 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 ranges, the effect tends to be more favorably obtained.

[0021] Here, the total vinyl content in the rubber component is the total content (unit: parts by mass) of vinyl bonds in the butadiene moieties of SBR and BR contained in the rubber component, when the total mass of the rubber component is taken as 100, and can be calculated by Σ (content of each rubber component × proportion of vinyl bond content in the butadiene moieties in the rubber component to the total mass of each rubber component [% by mass]). For example, if 100 parts by mass of the rubber component contains 85 parts by mass of SBR with 40% styrene and 30% vinyl, 5 parts by mass of SBR with 20% styrene and 20% vinyl, and 10 parts by mass of BR with 10% vinyl, the total vinyl content in the rubber component is 17.1 parts by mass (= 85 × (100 [% by mass] - 40 [% by mass]) × 30 [% by mass] + 5 × (100 [% by mass] - 20 [% by mass]) × 20 [% by mass] + 10 × 10 [% by mass]).

[0022] The styrene content and vinyl content in each rubber component can be measured by nuclear magnetic resonance (NMR) spectroscopy. In the examples of this specification, the total styrene amount and the total vinyl amount in the rubber component are calculated according to the above-mentioned formula, but they may also be analyzed from the tire using, for example, a pyrolysis gas chromatograph mass spectrometer (Py-GC / MS) or the like.

[0023] The rubber composition contains styrene-butadiene rubber (SBR) as a rubber component. 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. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation.

[0024] The SBR may be an oil-extended rubber or a resin-extended rubber. These may be used alone or in combination of two or more. Resin-extended SBR is preferred. The oil used in the oil-extended rubber and the resin used in the resin-extended rubber are the same as those described below. The oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, but are usually about 5 to 50 parts by mass per 100 parts by mass of rubber solids.

[0025] SBR may be modified to introduce a functional group that interacts with fillers such as silica. Examples of the functional group include a silicon-containing group (-SiR3 (R are the same or different and are hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, or the like), an amino group, an amido 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 imido 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, an epoxy group, or the like. These functional groups may have a substituent. Of these, a silicon-containing group is preferred, and -SiR3 (R are the same or different and are hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)), or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one R is a hydroxyl group) is more preferred.

[0026] Specific examples of compounds (modifiers) that introduce the above-mentioned functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0027] As SBR, hydrogenated SBR to which hydrogen has been added can also be used. When the SBR is hydrogenated SBR, the hydrogenation method and reaction conditions are not particularly limited, and hydrogenation may be performed by a known method and under known conditions. Typically, hydrogenation is performed at 20 to 150°C under a hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other production methods and conditions are also not particularly limited, and the contents of WO 2016 / 039005, for example, can be applied. Hydrogenated SBR has the same structure as a copolymer of ethylene, butadiene, and styrene as a result of hydrogen being added to the butadiene portion of SBR. Therefore, in this specification, hydrogenated SBR includes not only hydrogenated products of copolymers of butadiene and styrene (SBR), but also copolymers of ethylene, butadiene, and styrene.

[0028] The hydrogenation rate of the hydrogenated SBR is preferably 65 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, and is preferably 95 mol% or less, more preferably 92 mol% or less, and even more preferably 90 mol% or less, based on 100 mol% of all butadiene units before hydrogenation. When the hydrogenation rate is within the above range, better effects tend to be obtained. The hydrogenation rate is 1 It can be calculated from the spectral reduction rate of the unsaturated bond portion of the spectrum obtained by measuring H-NMR.

[0029] The styrene content of the SBR is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0030] The vinyl content of the SBR is preferably 15% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more, and is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less. When it is within the above range, the effect tends to be more favorable.

[0031] The styrene content of the SBR mentioned above means the styrene content of the SBR when there is one type of SBR, and means the average styrene content when there are multiple types of SBR. The average styrene amount of SBR can be calculated by {Σ(content of each SBR × styrene amount of each SBR)} / total content of all SBRs. For example, when 100% by mass of the rubber component contains 85% by mass of SBR with a styrene amount of 40% by mass and 5% by mass of SBR with a styrene amount of 25% by mass, the average styrene amount of the SBR is 39.2% by mass (=(85×40+5×25) / (85+5)).

[0032] The vinyl content of the above-mentioned SBR is the proportion of vinyl bonds (unit: mass%) when the total mass of the butadiene parts in the SBR is taken as 100, and is expressed as vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. When there is one type of SBR, it means the vinyl content of that SBR, and when there are multiple types of SBR, it means the average vinyl content. The average vinyl content of the SBR can be calculated by Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%])}. For example, in 100 parts by mass of the rubber component, 75 parts by mass of SBR with a styrene content of 40% by mass and a vinyl content of 30% by mass, 25 parts by mass of styrene, Vinyl content: In the case where 20% by mass of SBR is 15 parts by mass and the remaining 10 parts by mass is a component other than SBR, the average vinyl content of the SBR is 28% by mass (= {75 × (100 [% by mass] - 40 [% by mass]) × 30 [% by mass] + 15 × (100 [% by mass] - 25 [% by mass]) × 20 [% by mass])} / {75 × (100 [% by mass] - 40 [% by mass]) + 15 × (100 [% by mass] - 25 [% by mass])}.

[0033] The content of SBR in 100% by mass of the rubber component is sufficient as long as it is more than 60% by mass, but is preferably 62% by mass or more, more preferably 64% by mass or more, and even more preferably 65% ​​by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. When it is within the above range, the effect tends to be more favorably obtained.

[0034] The rubber composition contains butadiene rubber (BR) as a rubber component. The BR is not particularly limited, and examples thereof include BRs with a high cis content such as BR1220 manufactured by Zeon Corporation, BR150B manufactured by Ube Industries, Ltd., and BR1280 manufactured by LG Chem, BRs containing 1,2-syndiotactic polybutadiene crystals (SPB) such as VCR412 and VCR617 manufactured by Ube Industries, Ltd., and butadiene rubbers synthesized using a rare earth catalyst (rare earth BR), which are commonly used in the tire industry. These may be used alone or in combination of two or more.

[0035] The BR may be an oil-extended rubber or a resin-extended rubber. These may be used alone or in combination of two or more. Of these, resin-extended rubber is preferred. The oil used in the oil-extended rubber and the resin used in the resin-extended rubber are the same as those described below. The oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, but are usually about 5 to 50 parts by mass per 100 parts by mass of rubber solids.

[0036] The BR may be modified to introduce a functional group that interacts with a filler such as silica. Examples of the functional group include a silicon-containing group (-SiR3 (R are the same or different and are hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, or the like), an amino group, an amido 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 imido 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, an epoxy group, or the like. These functional groups may have a substituent. Of these, a silicon-containing group is preferred, and -SiR3 (R are the same or different and are hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)), or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one R is a hydroxyl group) is more preferred.

[0037] Specific examples of compounds (modifiers) that introduce the above-mentioned functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0038] As BR, hydrogenated BR to which hydrogen has been added can also be used. When the BR is hydrogenated BR, the hydrogenation method and reaction conditions are not particularly limited, and hydrogenation may be carried out by a known method and under known conditions. Typically, hydrogenation is carried out at 20 to 150°C under a hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other production methods and conditions are also not particularly limited, and the contents of, for example, WO 2016 / 039005 can be applied. Note that hydrogenated BR has the same structure as an ethylene-butadiene copolymer as a result of hydrogen being added to the butadiene moiety of BR. Therefore, in this specification, hydrogenated BR includes not only hydrogenated BR but also ethylene-butadiene copolymers.

[0039] The hydrogenation rate of the hydrogenated BR is preferably 65 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, and is preferably 95 mol% or less, more preferably 92 mol% or less, and even more preferably 90 mol% or less, based on 100 mol% of all butadiene units before hydrogenation. When the hydrogenation rate is within the above ranges, better effects tend to be obtained. The hydrogenation rate is 1 It can be calculated from the spectral reduction rate of the unsaturated bond portion of the spectrum obtained by measuring H-NMR.

[0040] The cis amount (cis content) of the BR is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. Within the above ranges, the effect tends to be more favorably obtained. The cis content of BR can be measured by infrared absorption spectroscopy.

[0041] The above-mentioned cis content of BR means the cis content of the BR when there is one type of BR, and means the average cis content when there are multiple types of BR. The average cis content of BR can be calculated by {Σ(content of each BR × cis content of each BR)} / total content of all BRs. For example, when 100% by mass of the rubber component contains 20% by mass of BR with a cis content of 90% by mass and 10% by mass of BR with a cis content of 40% by mass, the average cis content of BR is 73.3% by mass (=(20×90+10×40) / (20+10)).

[0042] In 100% by mass of the rubber component, the BR content is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0043] The rubber composition preferably contains an isoprene-based rubber as a rubber component. Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 are commonly used in the tire industry. IRs are not particularly limited, and examples of IRs such as IR2200 are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. NR is preferred.

[0044] The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0045] Other rubber components include diene rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc. These may be used alone or in combination of two or more.

[0046] The other rubber component may be oil-extended rubber or resin-extended rubber. These may be used alone or in combination of two or more. Of these, resin-extended rubber is preferred. The oil used in the oil-extended rubber and the resin used in the resin-extended rubber are the same as those described below. The oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, but are usually about 5 to 50 parts by mass per 100 parts by mass of rubber solids.

[0047] The other rubber components may be modified to introduce functional groups that interact with fillers such as silica. Examples of the functional group include a silicon-containing group (-SiR3 (R may be the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, or the like), an amino group, an amido 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 imido 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, an epoxy group, or the like. These functional groups may have a substituent. Of these, a silicon-containing group is preferred, and -SiR3 (R may be the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)), or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one R is a hydroxyl group) is more preferred.

[0048] Specific examples of compounds (modifiers) that introduce the above-mentioned functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0049] The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum or biomass. Whether a raw material is derived from biomass can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0050] pMC is the modern standard reference 14 of sample against C concentration 14 This is the ratio of the carbon concentration, and this value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value is explained below.

[0051] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14 C is called a radioactive isotope, and its half-life is 5,730 years, and it decreases regularly. It takes 226,000 years for all of it to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when it was first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0052] on the other hand, 14 C is produced continuously by nuclear reactions in the atmosphere caused by cosmic rays, and this balances with the decrease due to radioactive decay. In the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12The value is approximately mol%. Therefore, by using the difference between these values, it is possible to calculate the ratio (biomass ratio) of compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber).

[0053] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14 The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C) is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0054] Therefore, if rubber is made from 100% biomass (natural) derived materials, it will show a value of approximately 110 pMC, although there may be regional differences (currently, under normal conditions, it is often not 100). On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will be approximately 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0055] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0056] The rubber composition may contain a thermoplastic elastomer as an elastomer other than the rubber component. Thermoplastic elastomers are copolymers (block copolymers) composed of hard segments that act as crosslinking points and soft segments that exhibit rubber elasticity, and are usually solid at room temperature (25°C).

[0057] Examples of hard segments include polystyrene, polypropylene, polyester, polyamide, polyvinyl chloride, polyurethane, etc., and examples of soft segments include vinyl-polydiene, polyisoprene, polybutadiene, polyethylene, polychloroprene, poly2,3-dimethylbutadiene, etc. These may be used alone or in combination of two or more types.

[0058] The thermoplastic elastomer may be used alone or in combination of two or more kinds. Commercially available products available from Kuraray Co., Ltd., Asahi Kasei Corporation, etc. may be used. In this specification, the thermoplastic elastomer is not included in the rubber component.

[0059] The thermoplastic elastomer is preferably a thermoplastic elastomer having a styrene block (a styrene-based thermoplastic elastomer). Specific examples of styrene-based thermoplastic elastomers include styrene-vinylisoprene-styrene triblock copolymer (SIS), styrene-isobutylene diblock copolymer (SIB), styrene-butadiene-styrene triblock copolymer (SBS), styrene-ethylene-butylene-styrene triblock copolymer (SEBS), styrene-ethylene-propylene-styrene triblock copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene triblock copolymer (SEEPS), and styrene-butadiene-butylene-styrene triblock copolymer (SBBS). These may be used alone or in combination. Among these, copolymers having styrene blocks at both ends are preferred, with styrene-ethylene-propylene-styrene triblock copolymer (SEPS) being more preferred. The SEPS may be a hydrogenated styrene-vinylisoprene-styrene triblock copolymer (SIS) in which hydrogen is added to SIS.

[0060] The styrene content of the styrene-based thermoplastic elastomer is preferably 5% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above ranges, better effects tend to be obtained.

[0061] The content of the thermoplastic elastomer is preferably 1 to 30 parts by mass based on 100 parts by mass of the rubber component.

[0062] The rubber composition contains silica. Examples of silica include dry-process silica (silicic anhydride) and wet-process silica (hydrated silicic acid), with wet-process silica being preferred due to its high silanol group content. The silica raw material may be water glass (sodium silicate) or a biomass material such as rice husks. Commercially available products include those from Evonik Degussa, Tosoh Silica Co., Ltd., Solvay Japan, and Tokuyama Corporation. These may be used alone or in combination.

[0063] The average particle size of silica may be 16 nm or less, preferably 15 nm or less, more preferably 14 nm or less, and preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more. When the average particle size is within the above range, better effects tend to be obtained.

[0064] In this specification, the average particle size of silica is measured by observation with a transmission electron microscope (TEM). Specifically, silica particles are photographed with a transmission electron microscope, and the particle size is the diameter of the sphere if the particle shape is spherical, the minor axis if the particle shape is needle-like or rod-like, or the average particle diameter from the center if the particle shape is irregular, and the average particle size of 100 fine particles is the average particle size.

[0065] The content of silica per 100 parts by mass of the rubber component may be more than 80 parts by mass, but is preferably at least 82 parts by mass, more preferably at least 85 parts by mass, and even more preferably at least 90 parts by mass, and is preferably at most 140 parts by mass, more preferably at most 130 parts by mass, and even more preferably at most 120 parts by mass. Within the above ranges, the effect tends to be better obtained.

[0066] In the above rubber composition, the silica content / SBR content is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.4 or more, and is preferably 2.5 or less, more preferably 2.2 or less, and even more preferably 2 or less. Within the above range, better effects tend to be obtained. In this relationship, the silica content is the content (unit: parts by mass) relative to 100 parts by mass of the rubber component, and the SBR content is the content (unit: % by mass) in 100% by mass of the rubber component.

[0067] The rubber composition may contain carbon black. Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or may be obtained by recycling tires. Carbon black may be produced by combustion, such as a furnace method, or by hydrothermal carbonization (HTC). Commercially available carbon black products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nipponka Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These carbon blacks may be used alone or in combination.

[0068] The cetyltrimethylammonium bromide (CTAB) specific surface area of ​​the carbon black is preferably 90 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 110m 2 / g or more, and preferably 160m 2 / g or less, more preferably 140m 2 / g or less, more preferably 120m 2 Within the above range, there is a tendency for the effect to be better obtained. The CTAB specific surface area of ​​carbon black is a value measured in accordance with JIS K6217-3:2001.

[0069] The amount of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0070] The rubber composition preferably 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 sulfide-based compounds such as propyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; 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 include those from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more. Of these, mercapto-based products are preferred.

[0071] As the mercapto-based silane coupling agent, in addition to a compound having a mercapto group, a compound having a structure in which the mercapto group is protected by a protecting group (for example, a compound represented by the following formula (S1)) can also be used.

[0072] Particularly suitable mercapto-based silane coupling agents include silane coupling agents represented by the following formula (S1) and silane coupling agents containing a bonding unit A represented by the following formula (I) and a bonding unit B represented by the following formula (II). [ka] (In the formula, R 1001 -Cl, -Br, -OR 1006 , -O(O=)CR 1006 , -ON=CR 1006 R 1007 , -NR 1006 R 1007 and-(OSiR 1006 R 1007 ) h (OSiR 1006 R 1007 R 1008 a monovalent group (R 1006 , R 1007 and R 1008 may be the same or different, and each represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and h has an average value of 1 to 4; 1002 is R 1001 , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, R 1003 is -[O(R 1009 O) j ]-group(R 1009 is an alkylene group having 1 to 18 carbon atoms, and j is an integer of 1 to 4. 1004 is a divalent hydrocarbon group having 1 to 18 carbon atoms, R 1005 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y, and z are numbers that satisfy the relationships: x+y+2z=3, 0≦x≦3, 0≦y≦2, 0≦z≦1. [ka] [ka] (wherein v is an integer of 0 or more, and w is an integer of 1 or more. R 11 R represents hydrogen, halogen, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, or an alkyl group in which the terminal hydrogen atom has been substituted with a hydroxyl group or a carboxyl group. 12 represents a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms. 11 and R 12 may form a ring structure with

[0073] In formula (S1), R 1005 , R 1006 , R 1007 and R 1008 are each independently a group selected from the group consisting of a linear, cyclic or branched alkyl group, an alkenyl group, an aryl group and an aralkyl group having 1 to 18 carbon atoms. 1002 When R is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of a linear, cyclic, or branched alkyl group, an alkenyl group, an aryl group, and an aralkyl group. 1009 R is preferably a linear, cyclic or branched alkylene group, and is particularly preferably a linear one. 1004 Examples of R include alkylene groups having 1 to 18 carbon atoms, alkenylene groups having 2 to 18 carbon atoms, cycloalkylene groups having 5 to 18 carbon atoms, cycloalkylalkylene groups having 6 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and aralkylene groups having 7 to 18 carbon atoms. The alkylene groups and alkenylene groups may be either linear or branched, and the cycloalkylene groups, cycloalkylalkylene groups, arylene groups, and aralkylene groups may have a functional group such as a lower alkyl group on the ring. 1004As the alkylene group, an alkylene group having 1 to 6 carbon atoms is preferred, and a linear alkylene group such as a methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, or hexamethylene group is particularly preferred.

[0074] R in formula (S1) 1002 , R 1005 , R 1006 , R 1007 and R 1008 Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, a phenethyl group, and a naphthylmethyl group. R in formula (S1) 1009 Examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and a hexylene group, and examples of the branched alkylene group include an isopropylene group, an isobutylene group, and a 2-methylpropylene group.

[0075] Specific examples of the silane coupling agent represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, and 2-lauroylthioethyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

[0076] In the silane coupling agent containing the bond unit A represented by formula (I) and the bond unit B represented by formula (II), the content of the bond unit A is preferably 30 mol% or more, more preferably 50 mol% or more, and preferably 99 mol% or less, more preferably 90 mol% or less. The content of the bond unit B is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and preferably 70 mol% or less, more preferably 65 mol% or less, even more preferably 55 mol% or less. The total content of the bond units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, particularly preferably 100 mol%. The content of the bonding units A and B includes the case where the bonding units A and B are located at the terminals of the silane coupling agent. When the bonding units A and B are located at the terminals of the silane coupling agent, the form of the bonding units A and B is not particularly limited, as long as they form units corresponding to the formulas (I) and (II) representing the bonding units A and B.

[0077] R in formulas (I) and (II)11 With respect to the above, examples of halogen include chlorine, bromine, and fluorine. Examples of branched or unbranched alkyl groups having 1 to 30 carbon atoms include methyl and ethyl groups. Examples of branched or unbranched alkenyl groups having 2 to 30 carbon atoms include vinyl and 1-propenyl groups. Examples of branched or unbranched alkynyl groups having 2 to 30 carbon atoms include ethynyl and propynyl groups.

[0078] R in formulas (I) and (II) 12 Regarding the above, examples of branched or unbranched alkylene groups having 1 to 30 carbon atoms include an ethylene group, a propylene group, etc. Examples of branched or unbranched alkenylene groups having 2 to 30 carbon atoms include a vinylene group, a 1-propenylene group, etc. Examples of branched or unbranched alkynylene groups having 2 to 30 carbon atoms include an ethynylene group, a propynylene group, etc.

[0079] In a silane coupling agent containing a bonding unit A represented by formula (I) and a bonding unit B represented by formula (II), the total number of repetitions (v+w) of the bonding unit A (v) and the bonding unit B (w) is preferably in the range of 3 to 300.

[0080] The content of the silane coupling agent is preferably 6 parts by mass or more, more preferably 8 parts by mass or more, even more preferably 10 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 13 parts by mass or less, even more preferably 11 parts by mass or less, relative to 100 parts by mass of silica.Within the above range, the effect tends to be more excellent.

[0081] The rubber composition preferably contains vulcanized rubber particles. The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used alone or in combination of two or more types.

[0082] Commercially available vulcanized rubber particles include products from Lehigh Corporation and Muraoka Rubber Industry Co., Ltd. In this specification, vulcanized rubber particles are not included in the rubber component.

[0083] The average particle size of the vulcanized rubber particles is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 200 μm or more, and is preferably 1000 μm or less, more preferably 900 μm or less, and even more preferably 800 μm or less. The average particle size of the vulcanized rubber particles is an average particle size on a mass basis calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0084] The content of the vulcanized rubber particles is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0085] In the rubber composition, the content of vulcanized rubber particles / total styrene content in the rubber component is preferably 0.10 or more, more preferably 0.13 or more, even more preferably 0.16 or more, and is preferably 0.22 or less, more preferably 0.20 or less, even more preferably 0.18 or less. Within the above ranges, the effect tends to be more favorable. In this relationship, the content of vulcanized rubber particles is the content (unit: parts by mass) relative to 100 parts by mass of the rubber component, and the total amount of styrene in the rubber component is the content (unit: % by mass) in 100% by mass of the rubber component.

[0086] The rubber composition preferably contains water-soluble particles. The water-soluble particles are not particularly limited as long as they are particles that are soluble in water. For example, a material that has a solubility in water at room temperature (20°C) of 1 g / 100 g water or more can be used.

[0087] Examples of water-soluble particles include water-soluble inorganic salts and water-soluble organic substances. Examples of water-soluble inorganic salts include metal sulfates such as magnesium sulfate and potassium sulfate; metal chlorides such as potassium chloride and sodium chloride; metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates such as potassium carbonate and sodium carbonate; and phosphates such as sodium hydrogen phosphate and sodium dihydrogen phosphate. Examples of water-soluble organic substances include lignin derivatives and sugars. These may be used alone or in combination of two or more. Among these, water-soluble inorganic salts are preferred, metal sulfates are more preferred, and magnesium sulfate is even more preferred.

[0088] As commercially available water-soluble particles, products from Mai Chemical Industry Co., Ltd., Tokyo Chemical Industry Co., Ltd., etc. can be used.

[0089] The median particle size (median diameter, D50) of the water-soluble particles is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, and is preferably 800 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. Within the above ranges, better effects tend to be obtained. In this specification, the median particle size can be measured by laser diffraction.

[0090] The content of the water-soluble particles is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0091] In the rubber composition, the content of the water-soluble particles / the total amount of styrene in the rubber component is preferably 0.10 or more, more preferably 0.13 or more, and even more preferably 0.16 or more, and is preferably 0.22 or less, more preferably 0.20 or less, and even more preferably 0.18 or less. Within the above ranges, the effect tends to be more favorable. In this relationship, the content of water-soluble particles is the content (unit: parts by mass) relative to 100 parts by mass of the rubber component, and the total amount of styrene in the rubber component is the content (unit: % by mass) in 100% by mass of the rubber component.

[0092] The rubber composition may contain talc. The average particle size of the talc is preferably 50 μm or less, more preferably 30 μm or less. There is no particular lower limit to the average particle size of the talc, but it is preferably 1 μm or more.

[0093] The content of talc is preferably 1 to 50 parts by mass based on 100 parts by mass of the rubber component.

[0094] The rubber composition may contain aluminum hydroxide. In this specification, aluminum hydroxide refers to Al(OH)3 or Al2O3·3H2O. Commercially available products include those from Sumitomo Chemical Co., Ltd., Showa Denko K.K., Nabaltec, etc. These may be used alone or in combination of two or more.

[0095] The average particle size of the aluminum hydroxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more, and is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. Within the above ranges, better effects tend to be obtained. The average particle size of aluminum hydroxide is a value measured in the same manner as the average particle size of silica.

[0096] The BET specific surface area (nitrogen adsorption specific surface area, N2SA) of the aluminum hydroxide is preferably 5 m 2 / g or more, more preferably 8m 2 / g or more, more preferably 10m 2 / g or more, and preferably 40m 2 / g or less, more preferably 30m 2 / g or less, more preferably 20m 2 / g or less. The BET specific surface area of ​​aluminum hydroxide is a value measured by the BET method in accordance with ASTM D3037-81.

[0097] The content of aluminum hydroxide is preferably 1 to 25 parts by mass based on 100 parts by mass of the rubber component.

[0098] The rubber composition may contain a calcium compound. The calcium compound is a compound containing calcium, and examples thereof include inorganic salts such as calcium oxide, calcium hydroxide, and calcium carbide; and oxoacid salts such as calcium carbonate, calcium nitrate, and calcium sulfate. Oxoacid salts also include fatty acid salts such as calcium acetate and calcium stearate. Examples of calcium compounds include eggshells (main component: calcium carbonate) and WB16 (a mixture of fatty acid calcium, fatty acid amide, and fatty acid amide ester) manufactured by Struktol. These may be used alone or in combination of two or more. Of these, oxoacid salts are preferred, and calcium carbonate is more preferred.

[0099] The content of the calcium compound is preferably 1 to 30 parts by mass based on 100 parts by mass of the rubber component.

[0100] The rubber composition may contain short fibers. Examples of short fibers that can be used include organic short fibers and inorganic short fibers. Specific examples of organic short fibers include nanocelluloses such as cellulose nanofibers (CNF) and cellulose nanocrystals (CNC); biomass nanomaterials such as chitin nanofibers and chitosan nanofibers; and specific examples of inorganic short fibers include metal fibers and glass fibers. Commercially available products include those from Nippon Paper Industries Co., Ltd. and Sugino Machine Ltd. These may be used alone or in combination of two or more. Of these, organic short fibers are preferred, and nanocellulose is more preferred.

[0101] The particle size of nanocellulose is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, particularly preferably 28 nm or more, and preferably 50 nm or less, more preferably 40 nm or less, even more preferably 35 nm or less, particularly preferably 32 nm or less. Within the above range, the effect tends to be better.

[0102] The particle size of nanocellulose is the average fiber diameter measured by image analysis using scanning electron microscope photographs, transmission electron microscope photographs, atomic force microscope photographs, X-ray scattering data analysis, pore electrical resistance method (Coulter principle method), etc. In this specification, the average fiber diameter of nanocellulose (cellulose fiber) is typically the average fiber diameter of an aggregate of cellulose fibers formed by the aggregation of cellulose molecules.

[0103] The content of the short fibers is preferably 1 to 40 parts by mass based on 100 parts by mass of the rubber component.

[0104] The rubber composition contains an aromatic resin as a resin. Aromatic resins are polymers containing aromatic monomers as constituent monomers, and examples thereof include homopolymers obtained by polymerizing one type of aromatic monomer alone, copolymers obtained by copolymerizing two or more types of aromatic monomers, and copolymers of an aromatic monomer and another monomer copolymerizable therewith.

[0105] Examples of aromatic monomers include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; phenol-based monomers such as phenol, alkylphenol, and alkoxyphenol; naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol; coumarone, indene, and the like. These may be used alone or in combination of two or more. Among these, styrene-based monomers are preferred, and styrene and α-methylstyrene are more preferred.

[0106] Examples of other monomers include non-conjugated olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, etc. These may be used alone or in combination of two or more.

[0107] To obtain a better effect, the aromatic resin is preferably an α-methylstyrene resin (such as an α-methylstyrene homopolymer or a copolymer of styrene and α-methylstyrene), and more preferably a styrene α-methylstyrene resin (a copolymer of styrene and α-methylstyrene).

[0108] The content of the aromatic resin is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0109] Examples of resins that can be used other than aromatic resins include C5 resins, C5 / C9 resins, C9 resins, cyclopentadiene resins, terpene resins, etc. These may be used alone or in combination of two or more.

[0110] C5 resins are polymers containing a C5 fraction as a constituent monomer, and examples thereof include polymers obtained by polymerizing a C5 fraction obtained by thermal cracking of naphtha in the petrochemical industry using a Friedel-Crafts catalyst such as AlCl3 or BF3. C5 fractions typically include olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene; diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene; and the like.

[0111] The amount of the C5 resin relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less.

[0112] C5 / C9 resins are polymers containing C5 and C9 fractions as constituent monomers, and examples thereof include polymers obtained by polymerizing petroleum-derived C5 and C9 fractions using a Friedel-Crafts catalyst such as AlCl3 or BF3. Specific examples include copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, or the like as main components. In this specification, C5 / C9 resins are treated as resins different from aromatic resins, C5 resins, and C9 resins.

[0113] The amount of the C5 / C9 resin, relative to 100 parts by mass of the rubber component, is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less.

[0114] C9 resins are polymers containing a C9 fraction as a constituent monomer. Examples include polymers obtained by polymerizing a C9 fraction, which is a by-product of the thermal decomposition of naphtha in the petrochemical industry along with petrochemical base materials such as ethylene and propylene, using a Friedel-Crafts catalyst such as AlCl3 or BF3. Specific examples of C9 fractions include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. C9 resins may also be obtained by copolymerizing a mixture of C8 to C10 fractions, such as styrene, methylindene, 1,3-dimethylstyrene, and naphthalene, vinylnaphthalene, vinylanthracene, and p-tert-butylstyrene, together with the C9 fraction, using a Friedel-Crafts catalyst. In this specification, C9 resins are treated as resins separate from aromatic resins.

[0115] The amount of the C9 resin relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less.

[0116] Terpene resins are polymers containing terpene compounds (terpene monomers) as constituent monomers, and include, for example, homopolymers obtained by polymerizing one type of terpene compound alone, copolymers obtained by copolymerizing two or more types of terpene compounds, and copolymers of a terpene compound and another monomer that can be copolymerized with it.

[0117] Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. These may be used alone or in combination of two or more.

[0118] To obtain a better effect, the terpene resin is preferably a homopolymer of a terpene compound (polyterpene resin) or a copolymer of a terpene compound and a styrene monomer, more preferably a copolymer of a terpene compound and a styrene monomer.Furthermore, the copolymer of a terpene compound and a styrene monomer is preferably a copolymer of a terpene compound and styrene (terpene styrene resin). In this specification, a polymer containing a terpene compound and a styrene-based monomer as constituent monomers, such as a terpene-styrene resin, is treated as a terpene-based resin, not an aromatic resin.

[0119] The amount of the terpene resin, relative to 100 parts by mass of the rubber component, is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less.

[0120] The cyclopentadiene-based resin is a polymer containing a cyclopentadiene-based monomer as a constituent monomer, and examples thereof include a homopolymer obtained by polymerizing one type of cyclopentadiene-based monomer alone, a copolymer obtained by copolymerizing two or more types of cyclopentadiene-based monomers, and a copolymer of a cyclopentadiene-based monomer and another monomer copolymerizable therewith.

[0121] Examples of cyclopentadiene-based monomers include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. These may be used alone or in combination of two or more. Among these, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a polymer (DCPD-based resin) containing dicyclopentadiene (DCPD) as a constituent monomer, and more preferably a hydrogenated DCPD-based resin.

[0122] The amount of the cyclopentadiene resin relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less.

[0123] The resin is also preferably a modified resin into which a functional group has been introduced (functionalized resin). The modified resin can be produced by a known method, for example, by a slurry method, a metathesis method, etc. Specifically, for example, the modified resin can be produced by reacting a polymer that will become the polymer skeleton of the modified resin with a functional compound that can introduce a functional group, by a known method.

[0124] The polymer that forms the polymer backbone is not particularly limited, and may be, for example, the aromatic resins described above or other resins. These may be used alone or in combination of two or more. Among these, aromatic resins are preferred, α-methylstyrene resins are more preferred, and styrene α-methylstyrene resins (copolymers of styrene and α-methylstyrene) are even more preferred.

[0125] The functional group is preferably a functional group containing at least one element selected from the group consisting of oxygen, silicon, and nitrogen, and more preferably a functional group containing silicon.

[0126] The amount of the modified resin is preferably at least 5 parts by mass, more preferably at least 15 parts by mass, and even more preferably at least 25 parts by mass, per 100 parts by mass of the rubber component, and is preferably at most 50 parts by mass, more preferably at most 40 parts by mass, and even more preferably at most 30 parts by mass. Within the above ranges, the effect tends to be better obtained.

[0127] In the above rubber composition, the ratio of the content of modified resin to the total amount of styrene in the rubber component is preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.8 or more, and is preferably 1.1 or less, more preferably 1.0 or less, even more preferably 0.9 or less. Within the above range, better effects tend to be obtained. In this relationship, the content of the modified resin is the content (unit: parts by mass) relative to 100 parts by mass of the rubber component, and the total amount of styrene in the rubber component is the content (unit: % by mass) in 100% by mass of the rubber component.

[0128] Commercially available resins include those manufactured by 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., JXTG Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0129] The amount of the resin is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0130] In the rubber composition, the silica content / resin content is preferably more than 2, more preferably 2.2 or more, and even more preferably 2.4 or more, and is preferably 5.0 or less, more preferably less than 4.0, and even more preferably 3 or less. When it is within the above range, the effect tends to be better obtained. In this relationship, the silica content and the resin content are the contents (unit: parts by mass) relative to 100 parts by mass of the rubber component.

[0131] The rubber composition may contain a liquid plasticizer. The liquid plasticizer is a plasticizer that is in a liquid state at room temperature (25°C), and oil, liquid polymer, ester-based plasticizer, etc. The liquid plasticizer may be used alone or in combination of two or more types.

[0132] 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 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. Waste oil recovered from vegetable oils used as cooking oils or the like may also be used. Examples of commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Nippon Oil & Energy Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kosan Co., Ltd. These may be used alone or in combination of two or more.

[0133] The oil content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. The lower limit is not particularly limited, and may be 0 parts by mass. Within the above range, better effects tend to be obtained.

[0134] The liquid polymer is a (co)polymer that is in a liquid state at room temperature (25°C). For example, at least one (co)polymer selected from the group consisting of butadiene, isoprene, styrene, farnesene, and derivatives thereof can be used. Specific examples include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid farnesene polymer, and liquid farnesene-butadiene copolymer. The liquid polymer may also be modified or hydrogenated. Commercially available products include those from Cray Valley, Kuraray Co., Ltd., and the like. These may be used alone or in combination.

[0135] The weight average molecular weight (Mw) of the liquid polymer is preferably 9000 or less, more preferably 6000 or less, and even more preferably 4500 or less, and is preferably 100 or more, more preferably 1000 or more, and even more preferably 2000 or more. Within the above ranges, better effects tend to be obtained. In this specification, the liquid polymer is not included in the rubber component.

[0136] The content of the liquid polymer is preferably 0.5 to 25 parts by mass based on 100 parts by mass of the rubber component.

[0137] The ester plasticizer is not particularly limited as long as it is a compound having an ester group that is liquid at room temperature (25°C), and examples thereof include phthalic acid derivatives, long-chain fatty acid derivatives, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives. These may be used alone or in combination of two or more. Among these, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives are preferred, and sebacic acid derivatives are more preferred. The phthalic acid derivatives are not particularly limited, but examples thereof include phthalate esters such as di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). The long-chain fatty acid derivatives are not particularly limited, but examples thereof include long-chain fatty acid glycerin esters. The phosphoric acid derivatives are not particularly limited, but examples thereof include phosphoric acid esters such as tris(2-ethylhexyl)phosphate (TOP) and tributyl phosphate (TBP). The sebacic acid derivatives are not particularly limited, but examples thereof include sebacic acid esters such as di(2-ethylhexyl)sebacate (DOS) and diisooctylsebacate (DIOS). The adipic acid derivatives are not particularly limited, but examples thereof include adipic acid esters such as di(2-ethylhexyl)adipate (DOA) and diisooctyladipate (DIOA). Among these, phosphate ester, sebacate ester, and adipate ester are preferred, and sebacate ester is more preferred. Specific compounds are preferably TOP, DOS, and DOA, and more preferably DOS. As the ester-based plasticizer, for example, products manufactured by Daihachi Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

[0138] The glass transition temperature (Tg) of the ester-based plasticizer is preferably −110° C. or higher, more preferably −100° C. or higher, even more preferably −80° C. or higher, and is preferably −20° C. or lower, more preferably −40° C. or lower, even more preferably −55° C. or lower. By keeping the Tg within the above range, the above-mentioned effects tend to be more suitably obtained. In this specification, the glass transition temperature is a value measured in accordance with JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan at a heating rate of 10°C / min.

[0139] The content of the ester plasticizer is preferably 1 to 20 parts by mass based on 100 parts by mass of the rubber component.

[0140] In the rubber composition, the content of the liquid plasticizer (total content of oil, etc.) is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component. The lower limit is not particularly limited, and may be 0 parts by mass. Within the above range, better effects tend to be obtained.

[0141] In the above rubber composition, the relationship is resin content>BR content>liquid plasticizer content. The resin content - BR content is preferably 2 or more, more preferably 5 or more, and even more preferably 30 or more, and is preferably 55 or less, more preferably 50 or less, and even more preferably 45 or less. Within the above ranges, better effects tend to be obtained. The ratio of the BR content to the liquid plasticizer content is preferably at least 1, more preferably at least 2, and even more preferably at least 3, and is preferably at most 25, more preferably at most 20, and even more preferably at most 15. Within the above ranges, better effects tend to be obtained. Furthermore, the ratio of the resin content to the liquid plasticizer content is preferably 5 or more, more preferably 15 or more, and even more preferably 30 or more, and is preferably 55 or less, more preferably 50 or less, and even more preferably 45 or less. Within the above ranges, better effects tend to be obtained. In this relationship, the resin content and the liquid plasticizer content are the contents (unit: parts by mass) relative to 100 parts by mass of the rubber component, and the BR content is the content (unit: % by mass) in 100% by mass of the rubber component.

[0142] The rubber composition may contain a processing aid. Examples of processing aids include metal salts (compounds in which the hydrogen atoms of an acid are substituted with metal ions), fatty acid amides, amide esters, and fatty acid esters. These may be used alone or in combination of two or more. Of these, metal salts and fatty acid amides are preferred, and metal salts are more preferred.

[0143] Examples of metals used in metal salts include alkali metals such as potassium and sodium, and alkaline earth metals such as calcium and barium. Magnesium, zinc, nickel, molybdenum, etc. can also be used. Of these, alkali metals are preferred.

[0144] Examples of acids used in metal salts include fatty acids such as lauric acid, myristic acid, palmitic acid, etc. In addition, boric acid, carbonic acid, hydrochloric acid, nitric acid, sulfuric acid, etc. can also be used.

[0145] As commercially available processing aids, products from Kishida Chemical Co., Ltd., Kenei Pharmaceutical Co., Ltd., Struktol Co., Ltd., Performance Additives Co., Ltd., etc. can be used.

[0146] The content of the processing aid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 8 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0147] The rubber composition may contain a dibenzylamine compound. The dibenzylamine compound is a compound having at least one group (dibenzylamine group) represented by the following formula: [ka]

[0148] Specific examples of dibenzylamine compounds include dibenzylamine, tetrabenzylthiuram disulfide (TBzTD), zinc dibenzyldithiocarbamate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. Commercially available products include those from Sanshin Chemical Industry Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Lanxess, etc. These may be used alone or in combination of two or more. Of these, compounds having two dibenzylamine groups are preferred, and tetrabenzylthiuram disulfide is more preferred.

[0149] The content of the dibenzylamine compound is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and even more preferably 0.2 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 1.0 part by mass or less, more preferably 0.7 part by mass or less, and even more preferably 0.5 part by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0150] The rubber composition may contain an antioxidant. Examples of the antioxidant 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, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine antioxidants such as quinolone; 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. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis. These antioxidants may be used alone or in combination of two or more.

[0151] The content of the antioxidant is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0152] The rubber composition may contain a wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more.

[0153] The amount of wax per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0154] The rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used, and commercially available products that can be used include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These may be used alone or in combination of two or more.

[0155] The content of stearic acid is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, better effects tend to be obtained.

[0156] The rubber composition may contain zinc oxide. As the zinc oxide, conventionally known ones can be used, and commercially available products include those 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. These may be used alone or in combination of two or more.

[0157] The amount of zinc oxide per 100 parts by mass of the rubber component is preferably at least 0.1 part by mass, more preferably at least 0.3 part by mass, and even more preferably at least 0.5 part by mass, and is preferably at most 6 parts by mass, more preferably at most 3 parts by mass, and even more preferably at most 2 parts by mass. Within the above ranges, the effect tends to be more favorably obtained.

[0158] In the rubber composition, (zinc oxide content / silica content) × 100 is preferably 3.5 or less, more preferably less than 2.0, and even more preferably 0.8 or less, and is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.4 or more. When it is within the above range, the effect tends to be more favorable. In this relationship, the zinc oxide content and the silica content are the contents (unit: parts by mass) relative to 100 parts by mass of the rubber component.

[0159] The rubber composition may contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, 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., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

[0160] The sulfur content, based on 100 parts by mass of the rubber component, is preferably at least 0.3 parts by mass, more preferably at least 0.6 parts by mass, and even more preferably at least 1.1 parts by mass, and is preferably at most 3.5 parts by mass, more preferably at most 2.8 parts by mass, and even more preferably at most 2 parts by mass. Within the above ranges, the effect tends to be more favorably obtained.

[0161] In the rubber composition, the ratio of the zinc oxide content to the sulfur content is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.4 or more, and is preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less. When the ratio is within the above ranges, better effects tend to be obtained. In this relationship, the zinc oxide content and sulfur content are the contents (unit: parts by mass) relative to 100 parts by mass of the rubber component.

[0162] The rubber composition may contain an organic crosslinking agent. 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.

[0163] The content of the organic crosslinking agent is preferably 1 to 15 parts by mass based on 100 parts by mass of the rubber component.

[0164] The rubber composition may contain a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. Commercially available products include those from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Industry Co., Ltd. These may be used alone or in combination.

[0165] The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 2.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0166] The rubber composition preferably contains a dialkyldithiophosphate compound. As the dialkyldithiophosphate compound, for example, a salt of dialkyldithiophosphate with a metal such as zinc or molybdenum can be used. Commercially available products include TP-50 manufactured by Rhein Chemie. These may be used alone or in combination of two or more. Of these, the compound represented by the following formula (1) (zinc dialkyldithiophosphate) is preferred. [ka] (In the formula, R 1 ~R 4 each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms.

[0167] In formula (1), R 1 ~R 4 Examples of the linear or branched alkyl group represented by R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a 4-methylpentyl group, a 2-ethylhexyl group, an octyl group, and an octadecyl group, while examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Among these, R is preferred because it is easily dispersed in the rubber composition and is easy to produce. 1 ~R 4 is preferably a linear or branched alkyl group having 2 to 8 carbon atoms, more preferably an n-butyl group, an n-propyl group, an isopropyl group or an n-octyl group, and even more preferably an n-butyl group.

[0168] The amount of the dialkyldithiophosphate compound is, per 100 parts by mass of the rubber component, preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1 part by mass or more, and is preferably 6 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 2 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0169] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, etc. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0170] The rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0171] As for kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0172] The rubber composition can be used (as a rubber composition for tires) for tire components such as tread, sidewall, base tread, undertread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, etc., and side reinforcing layer of run-flat tires, etc. Among these, it is suitable for the tread (particularly the portion (cap tread) that comes into contact with the road surface during driving).

[0173] The tire of the present disclosure is manufactured by a conventional method using the above rubber composition. That is, the rubber composition is extruded in an unvulcanized state to match the shape of the tread, etc., and molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizer to obtain a tire.

[0174] The above-mentioned tires (pneumatic tires, etc.) can be used for passenger car tires; truck and bus tires; motorcycle tires; high-performance tires; winter tires such as studless tires; run-flat tires with side reinforcing layers; tires with sound-absorbing material that have sound-absorbing material such as sponge in the tire cavity; tires with sealing material that have a sealant inside the tire or in the tire cavity that can seal in the event of a puncture; and tires with electronic components that have electronic components such as sensors and wireless tags inside the tire or in the tire cavity, and are suitable for passenger car tires.

[0175] The size of the tire is not particularly limited, and can be appropriately selected, for example, from a tire width in the range of 100 to 400 mm, an aspect ratio in the range of 25 to 85%, and a rim diameter in the range of 10 to 25 inches. Specific examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 135 / 45R21, 145 / 45R21, 155 / 45R18, 165 / 45R22, 175 / 45R23, 185 / 60R20, 195 / 55R14, 205 / 40R16, 215 / 40R16, 225 / 40R17, 235 / 40R17, 245 / 40R16, 255 / 40R17, 265 / 40R17, 275 / 35R18, 285 / 30R19, and 295 / 45R20.

[0176] It is preferable that the tire outer diameter Dt and the tire section width Wt of the tire satisfy the following relational expression.

number

[0177] Specific examples of tires that can satisfy the above formula include 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, and the like.

[0178] A tire satisfying the above formula is preferably applied to a pneumatic tire for a passenger vehicle, because a pneumatic tire for a passenger vehicle satisfying the above formula tends to be more suitable for solving the problem of the present invention. [Example]

[0179] The present disclosure will be specifically described based on examples, but the present disclosure is not limited to these examples.

[0180] The various chemicals used in the examples and comparative examples will be explained below.

[0181] (rubber component) NR:TSR20 SBR1: Modified SBR synthesized in Production Example 1 below (styrene content: 40% by mass, vinyl content: 25% by mass) SBR2: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59% by mass) SBR3: Styrene-α-methylstyrene resin-extended SBR synthesized in Production Example 2 below (styrene content: 40% by mass, vinyl content: 25% by mass, resin content: 30 parts by mass per 100 parts by mass of rubber solids) BR: BR150B manufactured by Ube Industries, Ltd. (vinyl content: 1% by mass, cis content: 97% by mass)

[0182] (Chemicals other than rubber components) Carbon black: N220 (CTAB specific surface area: 111 m 2 / g) Silica 1: Ultrasil VN3 (average particle size: 17 nm) manufactured by Evonik Degussa Silica 2: Zeosil Premium 200MP (average particle size 14 nm) manufactured by Solvay Japan Co., Ltd. Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Silane coupling agent 2: NXT-Z45 (a copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol %, bonding unit B: 45 mol %)) manufactured by Momentive Resin 1: Marucaretz M-845A (dicyclopentadiene resin) manufactured by Maruzen Petrochemical Co., Ltd. Resin 2: SYLVARES SA85 (styrene α-methylstyrene resin (copolymer of styrene and α-methylstyrene)) manufactured by Arizona Chemical Company Resin 3: Modified styrene α-methylstyrene resin produced in Production Example 3 below Oil: Sankyo Yuka Kogyo Co., Ltd. A / O Mix Magnesium sulfate: USN-00 (ultrafine magnesium sulfate, median particle size: 3 μm) manufactured by Mai Chemical Industry Co., Ltd. Vulcanized rubber particles: Lehigh's Ekodyne Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Processing aid 1: ULTRA-FLOW 440 (fatty acid zinc salt) manufactured by Performance Additives Processing aid 2: ULTAR-LUBE 160 (a mixture of fatty acid soap and fatty acid amide) manufactured by Performance Additives Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil by mass) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Dibenzylamine compound: Sancerer TBzTD (tetrabenzylthiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd. Dialkyldithiophosphate compound: TP-50 (a mixture of zinc dithiophosphate and polymer, R of formula (1)) manufactured by Rhein Chemie 1 ~R 4 n-butyl group, active ingredient 50% by mass

[0183] (Production Example 1) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, with the maximum temperature reaching 85°C. When the polymerization conversion reached 99%, 1,3-butadiene was added, and the polymerization was continued for an additional 5 minutes. N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane was then added as a modifier, and the reaction was continued. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. The solvent was then removed by steam stripping, and the mixture was dried on a heated roll heated to 110°C to obtain SBR1.

[0184] (Production Example 2) Styrene α-methylstyrene resin (Resin 2) and SBR1 were added to cyclohexane in a predetermined ratio and stirred at 400 rpm for 2 hours under 0.4 bar nitrogen pressure with heating. The resulting solution was dried to obtain styrene α-methylstyrene resin-extended SBR (SBR3).

[0185] (Production Example 3) Aluminum chloride and toluene were added to a glass flask purged with inert gas, and styrene and α-methylstyrene were added dropwise. The reaction mixture was then added dropwise to an isoprene / toluene solution to which allyltriethoxysilane had been added by the slurry method, and water was added to the reaction mixture to terminate the reaction. After repeating the process of removing the aqueous layer by separation, the organic layer obtained by separation was blown dry to volatilize the toluene, and then dried under reduced pressure to obtain a modified styrene α-methylstyrene resin (Resin 3).

[0186] Examples and Comparative Examples According to the formulations shown in Tables 1 and 2, materials other than sulfur, vulcanization accelerator, and dibenzylamine compound 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, vulcanization accelerator, and dibenzylamine compound 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 molded into a tread shape and laminated with other tire components to form an unvulcanized tire. The tire was press-vulcanized for 12 minutes at 150°C to produce a test tire (size: 175 / 60R18). The obtained test tire was subjected to the following evaluations, and the results are shown in Tables 1 and 2.

[0187] In Tables 1 and 2, the rubber content in the resin-extended rubber is listed in the rubber column, and the resin content in the resin-extended rubber is added to the resin 2 column.

[0188] In the following evaluations, the evaluation criteria for calculating the index are as follows: (Wet grip performance at high speeds) Table 1: Comparative Example 5 Table 2: Examples 9 and 10 are for Comparative Example 7, Example 11 is for Comparative Example 8, and Example 12 is for Comparative Example 9 (low fuel consumption at high speeds) Table 1: Comparative Example 4 Table 2: Examples 9 and 10 are for Comparative Example 7, Example 11 is for Comparative Example 8, and Example 12 is for Comparative Example 9

[0189] (Acetone extractables (AE)) For rubber test pieces (samples) cut out from the tread of the above test tires, the amount of substances contained in the rubber test pieces that could be extracted with acetone was measured according to the method for measuring acetone extractables in accordance with JIS K 6229:2015. Acetone extractable amount (mass%) = (mass of sample before extraction - mass of sample after extraction) / mass of sample before extraction × 100

[0190] (Polymer content (PC)) For the samples after acetone extraction in the above acetone extractables (AE), the organic matter was pyrolyzed and vaporized by heating in nitrogen (from room temperature to 750°C) in accordance with JIS K6226-1:2003, and the weight loss (mass) was measured, and the PC (mass%) was calculated based on the result.

[0191] (Carbon black content (BC)) For the samples after pyrolysis and vaporization at the above polymer content (PC), the weight loss (mass) was measured when they were oxidatively burned by heating in air, and the BC (mass%) was calculated based on this.

[0192] (Ash content (Ash)) The mass of the component (ash content) that did not burn in oxidative combustion in the above carbon black amount (BC) was measured, and Ash (mass %) was calculated based on this.

[0193] (Wet grip performance at high speeds) Each test tire was mounted on a vehicle, and the braking distance from an initial speed of 100 km / h on a wet asphalt road surface was measured and expressed as an index, with the evaluation standard being 100. A higher index indicates a shorter braking distance and better wet grip performance.

[0194] (low fuel consumption at high speeds) Using a rolling resistance tester, the rolling resistance of each test tire was measured when it was run at a speed of 100 km / h, and the result was expressed as an index, with the evaluation standard being 100. The higher the index, the lower the rolling resistance and the better the fuel economy.

[0195] [Table 1]

[0196] [Table 2]

[0197] As can be seen from Tables 1 and 2, the Examples were superior to the Comparative Examples in the overall performance (total of all indexes) of wet grip performance during high-speed driving and fuel economy, which were the objectives.

[0198] The present disclosure (1) is a rubber composition for a tire, which contains a rubber component containing styrene-butadiene rubber and butadiene rubber, silica, and a resin containing an aromatic resin, wherein the content of the styrene-butadiene rubber exceeds 60% by mass in 100% by mass of the rubber component, the average particle size of the silica is 16 nm or less, the content of the silica exceeds 80 parts by mass per 100 parts by mass of the rubber component, and the content of the resin > the content of the butadiene rubber > the content of a liquid plasticizer.

[0199] The present disclosure (2) is a rubber composition for tires according to the present disclosure (1), which contains a mercapto-based silane coupling agent.

[0200] The present disclosure (3) is a rubber composition for tires according to the present disclosure (1) or (2), which contains a dialkyldithiophosphate compound.

[0201] The present disclosure (4) is a rubber composition for tires in any combination with any of the present disclosures (1) to (3), wherein the total amount of styrene in the rubber component is less than 30% by mass.

[0202] The present disclosure (5) is a rubber composition for tires in any combination with any of the present disclosures (1) to (4), wherein the rubber component contains an isoprene-based rubber.

[0203] The present disclosure (6) is a rubber composition for tires in any combination with any of the present disclosures (1) to (5), where (content of zinc oxide / content of said silica)×100<2.

[0204] The present disclosure (7) is a rubber composition for tires in any combination with any of the present disclosures (1) to (6), wherein 2<content of said silica / content of said resin<4.

[0205] The present disclosure (8) is a rubber composition for tires in any combination with any of the present disclosures (1) to (7), wherein the silica content / styrene-butadiene rubber content is 1.4 or more.

[0206] The present disclosure (9) is a rubber composition for tires in any combination with any of the present disclosures (1) to (8), wherein the resin contains a modified resin.

[0207] The present disclosure (10) is a rubber composition for tires in any combination with any of the present disclosures (1) to (9), wherein the rubber component contains a resin-extended rubber.

[0208] The present disclosure (11) is a rubber composition for tires containing water-soluble particles and any combination of the present disclosures (1) to (10).

[0209] The present disclosure (12) is a rubber composition for tires containing vulcanized rubber particles and any combination of the present disclosures (1) to (11).

[0210] The present disclosure (13) is a tire using a rubber composition in any combination with any of the present disclosures (1) to (12).

Claims

1. The rubber composition contains a rubber component including styrene butadiene rubber and butadiene rubber, silica, a resin including an aromatic resin, and a liquid plasticizer, The content of the styrene-butadiene rubber in 100% by mass of the rubber component is 82% by mass or more, The average particle size of the silica is 16 nm or less, the content of the silica is more than 80 parts by mass per 100 parts by mass of the rubber component, the content of the liquid plasticizer is 15 parts by mass or more per 100 parts by mass of the rubber component, A rubber composition for a tire, wherein the content of the resin > the content of the butadiene rubber > the content of the liquid plasticizer.

2. 2. The rubber composition for tires according to claim 1, which contains a mercapto-based silane coupling agent.

3. 3. The rubber composition for a tire according to claim 1, further comprising a dialkyldithiophosphate compound.

4. The rubber composition for a tire according to any one of claims 1 to 3, wherein the total amount of styrene in the rubber component is less than 30% by mass.

5. 5. The rubber composition for a tire according to claim 1, wherein the rubber component contains an isoprene-based rubber.

6. 6. The rubber composition for a tire according to claim 1, wherein (zinc oxide content / said silica content)×100<2.

7. 7. The rubber composition for a tire according to claim 1, wherein 2<content of said silica / content of said resin<4.

8. The rubber composition for tires according to any one of claims 1 to 7, wherein the silica content / styrene-butadiene rubber content is 1.4 or more.

9. A rubber composition for tires according to claim 1, wherein the content of said resin is 35 parts by mass or less per 100 parts by mass of said rubber component.

10. The rubber composition for a tire according to any one of claims 1 to 9, wherein the resin contains a modified resin.

11. The rubber composition for a tire according to any one of claims 1 to 10, wherein the rubber component contains a resin-extended rubber.

12. The rubber composition for a tire according to any one of claims 1 to 11, which contains water-soluble particles.

13. The rubber composition for a tire according to any one of claims 1 to 12, which contains vulcanized rubber particles.

14. A tire using the rubber composition according to any one of claims 1 to 13.

Images