Rubber composition for tires and pneumatic tires

Abstract

To provide a rubber composition for tires excellent in steering stability, and a pneumatic tire using the same.SOLUTION: The rubber composition for tires contains a rubber component, silica, and a compound represented by the following formula (I), and the acetone extraction amount of the rubber composition is less than 16.0 mass%. (In the formula (I), R1 represents a hydrocarbon group; R2 and R3 are the same or different and each represent a hydrogen atom, a hydrocarbon group, or an -(AO)n-H group (n represents an integer of 1 or more, each n of R2 and R3 may be the same or different, and AO is the same or different and represents a C2 or higher oxyalkylene group); and at least one of R2 and R3 is an -(AO)n-H group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a rubber composition for tires and a pneumatic tire using the same. [Background technology]

[0002] In recent years, there has been a demand for improving the driving stability of automobile tires from the viewpoint of safety, etc. In addition, since driving stability and fuel economy are generally contradictory performances, there has also been a demand for improving these performances in a well-balanced manner. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present disclosure is to solve the above problems and to provide a rubber composition for tires that is excellent in steering stability, and a pneumatic tire using the same. [Means for solving the problem]

[0004] The present disclosure provides a rubber composition comprising a rubber component, silica, and a compound represented by the following formula (I): The rubber composition for tires has an acetone extractable amount of less than 16.0% by mass. [ka] (In formula (I), R 1 represents a hydrocarbon group. 2 , R 3 are the same or different and represent a hydrogen atom, a hydrocarbon group, or -(AO) n -H group (n is an integer of 1 or more, R 2 , R 3 Each n may be the same or different; AO may be the same or different and represent an oxyalkylene group having 2 or more carbon atoms; 2 , R 3 At least one of the following is -(AO) n -H group.) [Effects of the Invention]

[0005] According to the present disclosure, the rubber composition for tires contains a rubber component, silica, and a compound represented by formula (I) and has an acetone extractable amount of less than 16.0 mass %, thereby improving steering stability. DETAILED DESCRIPTION OF THE INVENTION

[0006] The rubber composition for a tire of the present disclosure contains a rubber component, silica, and the compound represented by formula (I), and has an acetone extractable amount of less than 16.0% by mass.

[0007] The reason why the above-mentioned effects can be obtained with the above rubber composition is presumed to be as follows. By setting the acetone extractable amount (AE amount) to less than 16.0% by mass, it is possible to suppress viscosity reduction during mixing while increasing contact between the compound of formula (I) and silica. As a result, the alkyloxirane group of formula (I) reacts with the hydroxyl group on the silica surface, making the silica more hydrophobic, allowing for efficient transmission of shear deformation and improving dispersibility within the system. This is thought to improve handling stability, as it improves the ability to follow small deformations while also increasing strength (M100) at large deformations. It is believed that the above effects contribute to improved steering stability.

[0008] In the rubber composition, the acetone extractables (AE) are less than 16.0% by mass, preferably 14.0% by mass or less, more preferably 13.0% by mass or less, even more preferably 12.0% by mass or less, and particularly preferably 11.0% by mass or less. There is no particular lower limit, but it is preferably 5.0% by mass or more, more preferably 7.0% by mass or more, even more preferably 8.0% by mass or more, and particularly preferably 9.0% by mass or more. Within the above range, the effect tends to be more favorably obtained. The acetone extractables (AE) are measured for a rubber composition (sample) after vulcanization by a method for measuring acetone extractables in accordance with JIS K 6229:2015 (unit: mass % of the rubber composition (sample) after vulcanization).

[0009] The AE can be adjusted by any method known to those skilled in the art. For example, the AE tends to increase as the amount of plasticizer such as oil in the rubber composition increases.

[0010] The rubber composition includes a rubber component. In the rubber composition, the rubber component is a component that contributes to crosslinking, and is generally a polymer with a weight average molecular weight (Mw) of 10,000 or more.

[0011] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above ranges, the effect tends to be more favorably obtained.

[0012] In this specification, the weight average molecular weight (Mw) can be determined in terms of standard polystyrene based on 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).

[0013] The rubber component is not particularly limited, and any rubber known in the tire field can be used. Examples include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Among these, isoprene rubber, BR, and SBR are preferred from the viewpoint of obtaining better effects, and it is more preferred to contain at least isoprene rubber.

[0014] 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.

[0015] When the rubber composition contains an isoprene-based rubber, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 40% by mass or more, particularly preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, particularly preferably 60% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0016] The reason why the above-mentioned effects are obtained by including isoprene-based rubber is presumed to be as follows. When isoprene-based rubber is included, the strength of the rubber increases the strength (M100) at large deformation, which is thought to result in improved handling stability.

[0017] 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.

[0018] 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.

[0019] When the rubber composition contains BR, the BR content, based on 100% by mass of the rubber component, is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 40% by mass or more, particularly preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, particularly preferably 60% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0020] 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.

[0021] The styrene content of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20% by mass or more, and most preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. Within the above range, the effect tends to be more favorable. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0022] When the rubber composition contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, particularly preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less. When the content is within the above range, better effects tend to be obtained.

[0023] The 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, oil-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 explained for the plasticizers 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 10 to 50 parts by mass per 100 parts by mass of rubber solids.

[0024] The rubber component 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 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.

[0025] 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.

[0026] The rubber composition contains silica as a filler. 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.

[0027] The average primary particle size of silica is preferably 25 nm or less, more preferably 20 nm or less, even more preferably 16 nm or less, and particularly preferably 14 nm or less.The lower limit of the average primary particle size is not particularly limited, but is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more.Within the above range, handling stability and fuel efficiency tend to be favorably obtained. The average primary particle size of silica can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of silica observed within the field of view, and averaging the measurements.

[0028] The reason why such an effect is obtained is presumed to be as follows. By reducing the average primary particle size of silica, especially by using silica with a fine particle size of 16 nm or less, the reinforcing properties are enhanced, which is thought to improve responsiveness and therefore significantly improve handling stability.

[0029] The content of silica is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 40 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 70 parts by mass or less, particularly preferably 60 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0030] The reason why such an effect can be obtained by reducing the silica content to a predetermined amount or less is presumed to be as follows. In particular, it is believed that adjusting the silica content to 60 parts by mass or less improves the dispersibility of silica, thereby improving fuel economy.

[0031] Examples of fillers that can be used other than silica include inorganic fillers other than silica and carbon black. Examples of inorganic fillers other than silica include clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide. These may be used alone or in combination of two or more. Of these, carbon black is preferred.

[0032] The 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. Furthermore, carbon black may be produced by combustion, such as in a furnace, or by hydrothermal carbonization (HTC). Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination.

[0033] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m 2 / g or more is preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 Within the above range, the effect tends to be better. The nitrogen adsorption specific surface area of ​​carbon black can be determined according to JIS K6217-2:2001.

[0034] 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 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0035] The amount of filler (total amount of silica, carbon black, etc.) is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 40 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 70 parts by mass or less, particularly preferably 60 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0036] In the present disclosure, a compound represented by the following formula (I) is used: The compound represented by formula (I) may be used alone or in combination of two or more kinds. [ka] (In formula (I), R 1 represents a hydrocarbon group. 2 , R 3 are the same or different and represent a hydrogen atom (-H), a hydrocarbon group, or -(AO) n -H group (n represents an integer of 1 or more, R 2 , R 3 Each n may be the same or different; AO may be the same or different and represent an oxyalkylene group having 2 or more carbon atoms; 2 , R 3 At least one of the following is -(AO) n -H group.)

[0037] R 1 ~R 3The hydrocarbon group may be linear, branched, or cyclic, and examples thereof include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. Of these, aliphatic hydrocarbon groups are preferred. The number of carbon atoms in the hydrocarbon group is preferably 1 or more, more preferably 5 or more, even more preferably 8 or more, and particularly preferably 12 or more, and is preferably 30 or less, more preferably 25 or less, even more preferably 22 or less, and particularly preferably 20 or less. Within the above ranges, the effects tend to be more favorably obtained.

[0038] Examples of the aliphatic hydrocarbon group include an alkyl group, an alkylene group, an alkenyl group, an alkenylene group, an alkynyl group, and an alkynylene group. Among these, an alkyl group having the above-mentioned number of carbon atoms is preferable. 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, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, and an octadecyl group.

[0039] The alicyclic hydrocarbon group is preferably one having 3 to 8 carbon atoms, and specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group.

[0040] The aromatic hydrocarbon group preferably has 6 to 10 carbon atoms, and specific examples thereof include a phenyl group, a benzyl group, a phenethyl group, a tolyl group, a xylyl group, a naphthyl group, etc. In the tolyl group and the xylyl group, the substitution position of the methyl group on the benzene ring may be any of the ortho, meta, and para positions.

[0041] R 2 , R 3 No-(AO) n -H group (n is an integer of 1 or more, R2 , R 3 Each n may be the same or different. AO may be the same or different and represent an oxyalkylene group having 2 or more carbon atoms. The number of carbon atoms is preferably 3 or more, and although there is no particular upper limit, it is preferably 7 or less, more preferably 6 or less, and even more preferably 5 or less. When it is within the above range, the effect tends to be more suitably obtained.

[0042] The alkylene group A in the oxyalkylene group AO may be either linear or branched. The AO is an oxyalkylene group having 2 to 3 carbon atoms (oxyethylene group (EO), oxypropylene group (PO)) with a branched chain R 4 (R 4 represents a hydrocarbon group. n The -H group is more preferably a group represented by the following formula (A) or (B), and even more preferably a group represented by the following formula (A). 4 is preferably bonded to the carbon atom adjacent to the oxygen atom. [ka] (In formulas (A) and (B), R 4 represents a hydrocarbon group. n is -(AO) n The n is the same as that of the -H group.)

[0043] R 4 The hydrocarbon group of R 1 ~R 3 Examples include the same groups as the hydrocarbon groups in the above. Among them, an aliphatic hydrocarbon group is preferred, and an alkyl group is more preferred. The number of carbon atoms in the hydrocarbon group (preferably an aliphatic hydrocarbon group, more preferably an alkyl group) is preferably 1 or more, more preferably 2 or more, and preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, and particularly preferably 3 or less. When the number is within the above range, the effect tends to be more suitably obtained.

[0044] (AO) nWhen contains two or more kinds of oxyalkylene groups, the arrangement of the oxyalkylene groups may be block or random.

[0045] n represents the number of moles of AO added. n is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 16 or less, even more preferably 10 or less, particularly preferably 5 or less, and most preferably 3 or less. When n is within the above range, the effect tends to be more suitably obtained.

[0046] In formula (I), R 2 , R 3 At least one of the following is -(AO) n -H group, but R 2 , R 3 All of -(AO) n It is more preferably a -H group. That is, the compound represented by the above formula (I) is more preferably a compound represented by the following formula (I-1). This tends to provide a more suitable effect. [ka] (In formula (I-1), n1 and n2 are integers of 1 or more (the same integer as n), and are the same as formula (I).)

[0047] In formula (I) and formula (I-1), the total number of moles of AO added (n1+n2) is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and is preferably 40 or less, more preferably 32 or less, even more preferably 20 or less, particularly preferably 10 or less, and most preferably 6 or less. Within the above ranges, the effect tends to be more suitably obtained.

[0048] Specific examples of the compound represented by formula (I) include liponols (in formula (I), R 2 :-(CH2CH2)xH,R 3 :-(CH2CH2)yH), etc. These may be used alone or in combination of two or more.

[0049] Specific examples of the compound represented by the formula (I-1) include POE (2) octylamine, POE (4) decylamine, POE (2) dodecylamine, POE (5) dodecylamine, POE (15) dodecylamine, POE (2) tetradecylamine, POE (2) hexadecylamine, POE (2) octadecylamine, POE (20) octadecylamine, and POE (2) octadecenylamine. POE (m) indicates that an average of mmol of polyoxyethylene is added. Commercially available products of these compounds include Amit 102 (POE (2) dodecylamine), Amit 105 (POE (5) dodecylamine), Amit 302 (POE (2) octadecylamine), and Amit 320 (POE (20) octadecylamine), all manufactured by Kao Corporation.

[0050] The compound represented by formula (I) may be the above-mentioned commercially available product, etc., or may be one produced separately from these commercially available products, etc. As a production method, for example, a method of reacting an alkylene oxide with a polyvalent amine compound in the presence or absence of a catalyst can be considered, but the production method is not limited to this method.

[0051] The content of the compound represented by formula (I) (the total content when two or more types are used in combination) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, even more preferably 1.0 part by mass or more, and particularly preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, the content is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 6.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content of the compound represented by formula (I) is within the above range, the effects can be more suitably obtained.

[0052] The rubber composition preferably contains a silane coupling agent in order to obtain better effects. 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 that can be used include those from Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZMAX Corporation, and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more. Of these, mercapto-based silane coupling agents and amino-based silane coupling agents are preferred from the viewpoint of obtaining good handling stability and fuel economy.

[0053] The reason why such an effect is obtained is presumed to be as follows. By using mercapto- and amino-based silane coupling agents, the coupling reaction with silica proceeds efficiently, making it easier to achieve silica dispersion. This improves the ability to follow small deformations while also increasing strength (M100) during large deformations, which is thought to improve handling stability and fuel economy through the coupling reaction.

[0054] 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.

[0055] 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(R1009 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

[0056] 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. 1004Examples 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. 1004 As 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of silica, and is preferably 16 parts by mass or less, more preferably 14 parts by mass or less, and even more preferably 12 parts by mass or less. Within the above range, the effect tends to be more favorable.

[0064] From the viewpoint of obtaining better effects, the rubber composition preferably contains a resin as a plasticizer. The resin is preferably at least one resin selected from the group consisting of C5 resins, C5 / C9 resins, C9 resins, coumarone-indene resins, styrene resins, terpene resins, cyclopentadiene resins, and hydrogenated versions thereof.

[0065] 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.

[0066] 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, the C5 / C9 resin is treated as a resin different from the styrene resin, the C5 resin, and the C9 resin.

[0067] 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 styrene resins.

[0068] The coumarone-indene resin is a polymer containing coumarone and indene as constituent monomers, and examples thereof include copolymers of coumarone and indene, as well as copolymers of coumarone and indene with other monomers copolymerizable therewith.

[0069] Styrenic resins are polymers containing a styrene monomer as a constituent monomer, and examples thereof include homopolymers obtained by polymerizing one type of styrene monomer alone, copolymers obtained by copolymerizing two or more types of styrene monomers, and copolymers of a styrene monomer and another monomer copolymerizable therewith.

[0070] Examples of styrene-based monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. These may be used alone or in combination of two or more. Among these, styrene and α-methylstyrene are more preferred.

[0071] To obtain a better effect, the styrene-based resin is preferably an α-methylstyrene-based 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).

[0072] 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.

[0073] Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H16 ), 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.

[0074] 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 as a styrene-based resin.

[0075] 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.

[0076] 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.

[0077] From the viewpoint of handling stability and fuel economy, the resin preferably contains a styrene-based resin or a terpene-based resin.

[0078] The reason why such an effect is obtained is presumed to be as follows. The use of resins, particularly styrene-based resins and terpene-based resins, provides the rigidity of rubber and improves responsiveness, which is believed to result in a well-balanced improvement in handling stability and fuel economy.

[0079] The resin content (total amount) is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 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 13 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0080] The amount of the styrene resin is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 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 13 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0081] The amount of the terpene resin is preferably at least 5 parts by mass, more preferably at least 8 parts by mass, and even more preferably at least 10 parts by mass, per 100 parts by mass of the rubber component, and is preferably at most 20 parts by mass, more preferably at most 15 parts by mass, and even more preferably at most 13 parts by mass. Within the above ranges, better effects tend to be obtained.

[0082] The resin may be a solid resin that is solid at room temperature (25° C.) or a liquid resin that is liquid at room temperature (25° C.). To obtain better effects, the resin preferably contains at least a solid resin.

[0083] The softening point of the resin is preferably 50°C or higher, more preferably 80°C or higher, and is preferably 180°C or lower, more preferably 130°C or lower. In the present disclosure, the softening point of a resin is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0084] The amount of the solid resin is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 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 13 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0085] The content of the liquid resin per 100 parts by mass of the rubber component is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, and may be 0 part by mass. When the content is within the above range, better effects tend to be obtained.

[0086] 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., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0087] As plasticizers other than resins, for example, liquid polymers, oils (including oil in oil-extended rubber), etc. can be used. These may be used alone or in combination of two or more. Of these, oils are preferred.

[0088] 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. In addition to these, from the perspective of life cycle assessment, oils used as lubricants in rubber processing mixers and engines, etc., and oils obtained by refining waste cooking oil used in restaurants may also be used. Commercially available products that can be used include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Corporation, 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.

[0089] The amount of oil per 100 parts by mass of the rubber component is preferably 20 parts by mass or less, more preferably 14 parts by mass or less, and even more preferably 10 parts by mass or less, and may be 0 part by mass. When the amount is within the above range, better effects tend to be obtained.

[0090] The reason why such an effect can be obtained by using a small amount of oil, for example, 10 parts by mass or less, is presumed to be as follows. By reducing the amount of oil, the viscosity decrease during mixing is suppressed and the probability of contact between the compound represented by formula (I) and silica is increased, so that shear deformation is efficiently transmitted and the silica dispersion effect of the compound represented by formula (I) is easily obtained. Therefore, it is presumed that the handling stability is improved because the strength (M100) at large deformation is increased while the ability to follow small deformation is improved.

[0091] The content of the plasticizer (total content of resin, oil, etc.) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 8 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0092] 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.

[0093] In the rubber composition, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more, and is preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 4.0 parts by mass or less, per 100 parts by mass of the rubber component. Within the above ranges, the effect tends to be more favorable.

[0094] 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.

[0095] In the rubber composition, the content of the 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 6 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0096] 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.

[0097] In the rubber composition, the content of stearic acid is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

[0098] 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.

[0099] In the rubber composition, the content of zinc oxide is preferably 1.0 part by mass or more, more preferably 2.5 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

[0100] 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.

[0101] In the rubber composition, the sulfur content is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 3.5 parts by mass or less, more preferably 2.8 parts by mass or less, and even more preferably 2.5 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0102] 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.

[0103] In the rubber composition, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more, and is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 7.0 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] In order to obtain better effects in the rubber composition, it is desirable that the acetone extractable amount (AE) and the content (parts by mass) of silica per 100 parts by mass of the rubber component satisfy the following formula. AE / silica content≦0.22 The upper limit of the AE / silica content is preferably 0.20 or less, more preferably 0.19 or less, even more preferably 0.18 or less, and particularly preferably 0.17 or less. The lower limit is preferably 0.10 or more, more preferably 0.12 or more, and even more preferably 0.13 or more. Within the above range, the effect tends to be more favorable.

[0108] The reason why such an effect is obtained is presumed to be as follows. By setting the AE amount / silica content at a predetermined level or less, it is thought that the compound of formula (I) is more easily dissolved in the acetone extractable components, disperses in the system during mixing, and comes into contact with the silica more easily. This improves the ability to follow small deformations while also increasing the strength (M100) during large deformations, which is thought to improve handling stability.

[0109] In order to obtain better effects in the above rubber composition, it is desirable that the acetone extractable amount (AE) and the content (parts by mass) of the compound represented by formula (I) per 100 parts by mass of the rubber component satisfy the following formula: AE / content of the compound represented by formula (I)≧1.2 The lower limit of the content of AE / compound represented by formula (I) is preferably 1.8 or more, more preferably 2.0 or more, even more preferably 2.2 or more, and particularly preferably 2.3 or more. The upper limit is preferably 3.2 or less, more preferably 2.9 or less, even more preferably 2.7 or less, and particularly preferably 2.6 or less. Within the above range, the effect tends to be more favorable.

[0110] The reason why such an effect is obtained is presumed to be as follows. By setting the content of AE / compound represented by formula (I) to a predetermined level or more, flexibility of the rubber is obtained, resulting in good conformability. This is thought to result in good steering stability because the strength (M100) at large deformation is maintained high due to the small amount of AE while the conformability to small deformation is good.

[0111] In order to obtain better effects in the above rubber composition, it is desirable that the content (parts by mass) of the resin per 100 parts by mass of the rubber component and the content (parts by mass) of the silica per 100 parts by mass of the rubber component satisfy the following formula: Resin content / silica content ≥ 0.13 The lower limit of the resin content / silica content is preferably 0.15 or more, more preferably 0.17 or more, even more preferably 0.20 or more, and particularly preferably 0.22 or more. The upper limit is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.27 or less, and particularly preferably 0.25 or less. Within the above range, the effect tends to be more favorable.

[0112] The reason why such an effect is obtained is presumed to be as follows. By setting the resin content / silica content ratio to a predetermined value or less, the silica is covered with the resin component after contact with the compound represented by formula (I), which is thought to facilitate dispersion of the silica in the rubber component and further enhance dispersibility. This is thought to improve the ability to follow small deformations while also increasing the strength (M100) at large deformations, thereby improving handling stability.

[0113] In order to obtain better effects in the rubber composition, it is desirable that the content (parts by mass) of the resin per 100 parts by mass of the rubber component and the content (parts by mass) of the compound represented by formula (I) per 100 parts by mass of the rubber component satisfy the following formula: Resin content / compound content represented by formula (I)≧1.20 The lower limit of the resin content / compound content represented by formula (I) is preferably 1.80 or more, more preferably 2.00 or more, even more preferably 2.50 or more, and particularly preferably 2.70 or more. The upper limit is preferably 4.50 or less, more preferably 4.00 or less, even more preferably 3.75 or less, and particularly preferably 3.50 or less. Within the above range, better effects tend to be obtained.

[0114] The reason why such an effect is obtained is presumed to be as follows. By setting the resin content / compound content represented by formula (I) to a predetermined value or less, it is believed that the resin component is present in sufficient amount relative to the compound of formula (I), and that the silica is coated with the resin after reaction with the silica, making it easier to disperse. This is believed to improve the ability to follow small deformations while also increasing the strength (M100) at large deformations, thereby improving handling stability.

[0115] The rubber composition can be used (as a rubber composition for tires) in tire components such as treads, sidewalls, base treads, undertreads, shoulders, clinches, bead apexes, breaker cushion rubbers, carcass cord coating rubbers, insulation, chafers, inner liners, and side reinforcing layers of run-flat tires. It is particularly suitable for treads (particularly the portion (cap tread) that comes into contact with the road surface during running). When used as a tread (cap tread), a rubber layer (such as a base tread) disposed on the radially inner side of the tire may contain the compound represented by formula (I). It is preferable to satisfy the relationship: the content of the compound represented by formula (I) in the tread (cap tread) is greater than the content of the compound represented by formula (I) in the rubber layer disposed on the radially inner side of the tread (cap tread).

[0116] 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.

[0117] 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. [Example]

[0118] The present disclosure will be specifically described based on examples, but the present disclosure is not limited to these examples.

[0119] The various chemicals used in the examples and comparative examples will be explained below.

[0120] NR:TSR20 SBR: HPR850 manufactured by JSR Corporation (styrene content 27.5% by mass, vinyl bond content 59.0% by mass) BR: BR150B manufactured by Ube Industries, Ltd. (vinyl content 1% by mass, cis content 97% by mass) Carbon black: Show Black N220 (N2SA114m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica 1: Ultrasil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Silica 2: 9000GR (N2SA235m) manufactured by Evonik Degussa 2 / g) 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 Silane coupling agent 3: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa Compound 1: Liponol HT / 14 (compound represented by the above formula (I-1)) manufactured by Lion Specialty Chemicals Co., Ltd. Compound 2: Liponol T / 15 (compound represented by the above formula (I-1)) manufactured by Lion Specialty Chemicals Co., Ltd. Compound 3: Liponol C / 15 (a compound represented by formula (I) (formula (I-1))) manufactured by Lion Specialty Chemicals Co., Ltd. Compound 4: Amit 102 (POE(2) dodecylamine, a compound represented by the above formula (I-1)) manufactured by Kao Corporation Resin 1: SYLVARES SA85 (α-methylstyrene-based resin (copolymer of α-methylstyrene and styrene), softening point 85°C) manufactured by Arizona Chemical Co. Resin 2: Sylvatraxx 4150 manufactured by Arizona Chemical Company (β-pinene resin, β-pinene content 98% by mass or more, Mw 2350, Mn 830) Resin 3: YS Resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (aromatic modified terpene resin, softening point 125°C) Oil: Sankyo Yuka Kogyo Co., Ltd. A / O Mix Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (N,N'-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0121] Examples and Comparative Examples According to the formulations shown in Tables 1 to 6, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape and laminated together 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 to 6.

[0122] In the following evaluations, the evaluation criteria for calculating the index are as follows: Tables 1 and 2: Comparative Example 1-1 Tables 3 and 4: Comparative Example 2-1 Tables 5 and 6: Comparative Example 3-1

[0123] <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. Acetone extractable amount (mass%) = (mass of sample before extraction - mass of sample after extraction) / mass of sample before extraction × 100

[0124] <Low fuel consumption performance> Using a rolling resistance tester, the rolling resistance was measured when the test tire was run on a rim (15x6JJ), with an internal pressure (230kPa), a load (3.43kN), and at a speed (80km / h), and the result was expressed as an index, with the reference comparative example being set at 100. The higher the index, the better the fuel economy performance.

[0125] <Handling stability> The test tires were fitted to all wheels of a vehicle (domestic FF 2000cc) and the vehicle was driven on a test course, and the handling stability was evaluated by a sensory evaluation by the driver while driving in a meandering manner. The results were expressed as an index, with the reference comparative example being set at 100. The higher the index, the better the handling stability.

[0126] [Table 1]

[0127] [Table 2]

[0128] [Table 3]

[0129] [Table 4]

[0130] [Table 5]

[0131] [Table 6]

[0132] As can be seen from each table, the Examples had better handling stability than the Comparative Examples, and also had better overall performance (total of all indexes) of handling stability and fuel economy.

[0133] The present disclosure (1) includes a rubber component, silica, and a compound represented by the following formula (I): The rubber composition for tires has an acetone extractable amount of less than 16.0% by mass. [ka] (In formula (I), R 1 represents a hydrocarbon group. 2 , R 3 are the same or different and represent a hydrogen atom, a hydrocarbon group, or -(AO) n -H group (n represents an integer of 1 or more, R 2 , R 3 Each n may be the same or different; AO may be the same or different and represent an oxyalkylene group having 2 or more carbon atoms; 2 , R 3 At least one of the following is -(AO) n -H group.)

[0134] The present disclosure (2) is the rubber composition for tires according to the present disclosure (1), wherein the average primary particle size of the silica is 16 nm or less.

[0135] The present disclosure (3) is the rubber composition for a tire according to the present disclosure (1) or (2), wherein the content of the silica per 100 parts by mass of the rubber component is 60 parts by mass or less.

[0136] The present disclosure (4) is a rubber composition for a tire according to any one of the present disclosures (1) to (3), which contains at least one selected from the group consisting of a mercapto-based silane coupling agent and an amine-based silane coupling agent.

[0137] The present disclosure (5) is a rubber composition for a tire according to any one of the present disclosures (1) to (4), which contains at least one resin selected from the group consisting of a styrene-based resin and a terpene-based resin.

[0138] The present disclosure (6) is the rubber composition for a tire according to any one of the present disclosures (1) to (5), wherein the rubber component contains an isoprene-based rubber.

[0139] The present disclosure (7) is the rubber composition for a tire according to any one of the present disclosures (1) to (6), wherein the content of oil per 100 parts by mass of the rubber component is 10 parts by mass or less.

[0140] The present disclosure (8) is the rubber composition for a tire according to any one of the present disclosures (1) to (7), in which the acetone extractable amount (AE) and the content (parts by mass) of the silica relative to 100 parts by mass of the rubber component satisfy the following formula: AE / silica content≦0.18

[0141] The present disclosure (9) is a rubber composition for a tire according to any one of the present disclosures (1) to (8), in which the acetone extractable amount (AE) and the content (parts by mass) of the compound represented by formula (I) relative to 100 parts by mass of the rubber component satisfy the following formula: AE / content of the compound represented by formula (I)≧2.0

[0142] The present disclosure (10) is a rubber composition for a tire according to any one of the present disclosures (1) to (9), in which the content (parts by mass) of the resin and the content (parts by mass) of the silica relative to 100 parts by mass of the rubber component satisfy the following formula: Resin content / silica content ≥ 0.13

[0143] The present disclosure (11) is a rubber composition for a tire according to any one of the present disclosures (1) to (10), in which the content (parts by mass) of the resin and the content (parts by mass) of the compound represented by formula (I) relative to 100 parts by mass of the rubber component satisfy the following formula: Resin content / compound content represented by formula (I)≧1.20

[0144] The present disclosure (12) is a pneumatic tire having a tire component made using the rubber composition according to any one of the present disclosures (1) to (11).

[0145] The present disclosure (13) is a pneumatic tire according to the present disclosure (12), wherein the tire component is a tread.

Claims

1. The rubber composition includes a rubber component, silica, and a compound represented by the following formula (I): The amount of acetone extractables is less than 16.0% by mass, the acetone extractable amount (AE) and the content (parts by mass) of the silica relative to 100 parts by mass of the rubber component satisfy a relationship of AE / content of silica≦0.18, The rubber composition for tires, wherein the resin content (parts by mass) and the silica content (parts by mass) per 100 parts by mass of the rubber component satisfy the relationship resin content / silica content ≥ 0.

13. 【Chemical 1】 (In formula (I), R １ represents a hydrocarbon group. ２ , R ３ are the same or different and represent a hydrogen atom, a hydrocarbon group, or -(AO) ｎ -H group (n represents an integer of 1 or more, R ２ , R ３ Each n may be the same or different; AO may be the same or different and represent an oxyalkylene group having 2 or more carbon atoms; ２ , R ３ At least one of the groups is -(AO) ｎ -H group.)

2. 2. The rubber composition for a tire according to claim 1, wherein the silica has an average primary particle size of 16 nm or less.

3. 3. The rubber composition for a tire according to claim 1, wherein the content of the silica per 100 parts by mass of the rubber component is 60 parts by mass or less.

4. 4. The rubber composition for a tire according to claim 1, further comprising at least one selected from the group consisting of a mercapto-based silane coupling agent and an amine-based silane coupling agent.

5. 5. The rubber composition for a tire according to claim 1, which contains at least one resin selected from the group consisting of a styrene-based resin and a terpene-based resin.

6. The rubber composition for a tire according to any one of claims 1 to 5, wherein the rubber component contains an isoprene-based rubber.

7. 7. The rubber composition for a tire according to claim 1, wherein the content of oil per 100 parts by mass of the rubber component is 10 parts by mass or less.

8. The rubber composition for a tire according to any one of claims 1 to 7, wherein the acetone extractable amount (AE) and the content (parts by mass) of the compound represented by formula (I) relative to 100 parts by mass of the rubber component satisfy the following formula: AE / content of the compound represented by formula (I)≧2.0

9. The rubber composition for a tire according to any one of claims 1 to 8, wherein the content (parts by mass) of the resin and the content (parts by mass) of the compound represented by formula (I) relative to 100 parts by mass of the rubber component satisfy the following formula: Resin content / compound content represented by formula (I)≧1.20

10. A pneumatic tire having a tire component made using the rubber composition according to any one of claims 1 to 9.

11. The pneumatic tire of claim 10, wherein the tire component is a tread.

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