Rubber composition for tire

Abstract

To provide a rubber composition for a tire excellent in wet grip performance.SOLUTION: A rubber composition for tires, comprising a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, a filler containing an ionic filler, and a plasticizer containing a resin, wherein at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, and an amount of the isoprene-based rubber based on 100% by mass of a rubber component is 20% by mass or more, the styrene-butadiene rubber has a glass transition temperature of - 50 °C. or lower, and a content of the resin per 100 parts by mass of the rubber component is greater than 5 parts by mass.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Rubber compositions for tires used in automobile tires are required to have good wet grip performance from the viewpoint of safety, etc., and various rubber compositions have been proposed, but further improvements are desired (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-131743 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above-mentioned current situation, and has an object to provide a rubber composition for tires that has excellent wet grip performance. [Means for solving the problem]

[0005] The present invention relates to a rubber composition comprising a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber; a filler including an ion-bonding filler; A rubber composition for tires containing a plasticizer including a resin, at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber, and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, The content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, The styrene-butadiene rubber has a glass transition temperature of −50° C. or lower, The present invention relates to a rubber composition for tires, in which the content of the resin per 100 parts by mass of the rubber component is more than 5 parts by mass. [Effects of the Invention]

[0006] The present invention provides a rubber composition for tires, which contains a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, a filler including an ion-bonding filler, and a plasticizer including a resin, wherein at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, and the content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, the glass transition temperature of the styrene-butadiene rubber is −50° C. or less, and the content of the resin in 100 parts by mass of the rubber component is more than 5 parts by mass, thereby making it possible to provide a rubber composition for tires with excellent wet grip performance. DETAILED DESCRIPTION OF THE INVENTION

[0007] The rubber composition for tires contains a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, a filler including an ion-bonding filler, and a plasticizer including a resin, wherein at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, the content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, the glass transition temperature of the styrene-butadiene rubber is -50°C or less, and the content of the resin per 100 parts by mass of the rubber component is more than 5 parts by mass.

[0008] The mechanism by which the above-mentioned effects are obtained is not clear, but is presumed to be as follows. In the above-mentioned rubber composition for tires, the modifying groups in the modified rubber interact with the ionic-bonding filler, so that when the rubber comes into contact with moisture on a wet road surface, the ionic bonds are loosened and the rubber temporarily becomes soft, resulting in improved wet road surface compliance. Furthermore, by containing isoprene-based rubber, resin, and low-Tg SBR with a glass transition temperature of -50°C or less, the rubber composition tends to be soft before the ionic bonds are loosened, making it possible to strongly exert the effect of softening when the ionic bonds are loosened, and it is thought that this significantly improves the ability to follow wet road surfaces. From the above, it is presumed that the above rubber composition for tires significantly improves wet grip performance.

[0009] In this specification, the term "rubber component" refers to a component that contributes to crosslinking, and refers to rubber that is in a solid state (solid rubber) under conditions of 1 atmosphere and 25°C. In other words, rubber that is in a liquid state (liquid rubber) under conditions of 1 atmosphere and 25°C does not qualify as a "rubber component." Here, the rubber component is preferably a polymer having a weight average molecular weight (Mw) of 100,000 or more.

[0010] The weight average molecular weight of the rubber component is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and particularly preferably 270,000 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.

[0011] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) 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).

[0012] Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. As the NR, for example, SIR20, RSS#3, TSR20, and other rubber industry-standard rubbers can be used. As the IR, there are no particular limitations, and for example, IR2200 and other rubber industry-standard rubbers can be used. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0013] The BR is not particularly limited, and examples thereof include high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. Of these, the BR preferably contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0014] The above-mentioned cis amount of BR means the cis amount of the BR when there is one type of BR, and means the average cis amount 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)).

[0015] As the BR, a hydrogenated butadiene polymer (hydrogenated BR) can also be used.

[0016] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0017] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. These may be used alone or in combination of two or more.

[0018] The glass transition temperature (Tg) of the SBR is −50° C. or lower, and from the viewpoint of obtaining better effects, it is preferably −55° C. or lower, more preferably −60° C. or lower. There is no particular limitation on the lower limit of the Tg of the SBR, but it is preferably −75° C. or higher, more preferably −70° C. or higher, and even more preferably −65° C. or higher. The rubber composition for tires may contain at least one SBR having a Tg of -50°C or less, and may, for example, contain an SBR having a Tg of -50°C or less and an SBR having a Tg of more than -50°C.

[0019] When the Tg of SBR is below a certain level, particularly below -50°C, -55°C, or -60°C, the mechanism by which a greater effect is obtained is not clear, but having a Tg below a certain level tends to soften the rubber composition before the ionic bonds are loosened, making it possible to strongly exert the effect of softening when the ionic bonds are loosened, and it is thought that this significantly improves wet road conformability, and therefore wet grip performance is presumably significantly improved.

[0020] In this specification, the glass transition temperature is a value measured by differential scanning calorimetry (DSC) at a temperature rise rate of 10° C. / min in accordance with JIS K7121.

[0021] The total styrene content of the SBR is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, still more preferably 7% by mass or more, and particularly preferably 10% by mass or more, which tends to produce better effects. From the viewpoint of improving fuel economy, the total styrene content of the SBR is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, still more preferably 20% by mass or less, and particularly preferably 10% by mass or less. In this specification, the total styrene content of SBR is determined by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 Unlike physical properties such as the complex modulus (E*), component amounts such as "total styrene content of SBR" have true values ​​that are independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, the term "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis apparatus, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed.

[0022] The total styrene content of SBR 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)).

[0023] The total vinyl 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, still more preferably 20% by mass or more, still more preferably 25% by mass or more, still more preferably 30% by mass or more, still more preferably 35% by mass or more, and particularly preferably 42% by mass or more, which tends to produce better effects. From the viewpoint of improving fuel economy, the total vinyl content of the SBR is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, still more preferably 50% by mass or less, still more preferably 45% by mass or less, and particularly preferably 42% by mass or less. In this specification, the total vinyl content of SBR is measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated by C-NMR.

[0024] The total vinyl content of SBR (amount of 1,2-bonded butadiene units) is the proportion of vinyl bonds (unit: mass%) when the total mass of butadiene parts in SBR is taken as 100, and is calculated 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, it means the average vinyl content. The average vinyl content of 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 and 10 parts by mass of vinyl are used. In the case where 15 parts by mass of SBR with a vinyl content of 20% by mass is used and the remaining 10 parts by mass are 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])}.

[0025] As the SBR, a hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used.

[0026] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. SBR synthesized by a known method can also be used.

[0027] The raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyls. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0028] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0029] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0030] Monomers derived from biomass (biomass monomers) are not particularly limited and include biomass-derived butadiene and biomass-derived aromatic vinyls. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited and includes, for example, biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0031] The polymer synthesized from a biomass monomer component (biomass polymer) is not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymer synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0032] Whether the raw material for a polymer is derived from biomass can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0033] pMC is the modern standard reference 14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0034] 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.

[0035] 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 -12 The value is approximately mol %. Therefore, the biomass ratio of a certain compound can be calculated by using the difference between these values.

[0036] 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. 14The 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.

[0037] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal circumstances, it will usually not reach 100, and will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0038] 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.

[0039] In the rubber composition for tires, the content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, which tends to provide better effects. From the viewpoint of improving steering stability at high speeds, the content is preferably less than 100% by mass, more preferably 90% by mass or less, even more preferably 80% by mass or less, still more preferably 70% by mass or less, still more preferably 60% by mass or less, still more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

[0040] In the rubber composition for tires, the BR content in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, still more preferably 7% by mass or more, and particularly preferably 10% by mass or more, to tend to achieve better effects. From the viewpoint of reducing noise during running, the BR content is preferably less than 80% by mass, more preferably 70% by mass or less, even more preferably 60% by mass or less, still more preferably 50% by mass or less, still more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[0041] In the rubber composition for tires, the content of SBR in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, still more preferably 10% by mass or more, still more preferably 20% by mass or more, still more preferably 25% by mass or more, still more preferably 30% by mass or more, still more preferably 40% by mass or more, and particularly preferably 50% by mass or more, to tend to achieve better effects. Also, from the viewpoint of fuel economy performance, the content is preferably less than 80% by mass, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0042] In addition, when the rubber composition for tires contains a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber, the content of the isoprene-based rubber, the content of the butadiene rubber, and the content of the styrene-butadiene rubber refer to the total amount of the unmodified rubber and the modified rubber. For example, when the content of modified SBR in 100% by mass of the rubber component is 20% by mass and the content of unmodified SBR is 30% by mass, the above-mentioned SBR content is 50% by mass.

[0043] The rubber composition for tires contains isoprene-based rubber, BR, and SBR as rubber components, but may further contain other rubber components. Examples of other usable rubber components include diene-based rubbers other than these. Examples of diene-based rubbers other than isoprene-based rubber, BR, and SBR include styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Other examples of rubber components include butyl-based rubber and fluororubber. The rubber components may be used alone or in combination of two or more. These rubber components may be modified or hydrogenated, and extended rubbers extended with oil, resin, liquid rubber components, or the like may also be used.

[0044] The rubber composition for tires contains modified rubber.

[0045] In this specification, the "modified rubber" may be a rubber in a solid state (solid rubber) or a rubber in a liquid state (liquid rubber) under conditions of 1 atmosphere and 25°C. In the "modified rubber," the term "modified" refers to the inclusion of heteroatoms in the molecule of the diene rubber. When the modified rubber is a rubber in a solid state (modified solid rubber) under conditions of 1 atmosphere and 25°C, the modified rubber corresponds to the rubber component. When the modified rubber is in a liquid state (modified liquid rubber) under conditions of 1 atmosphere and 25°C, the modified rubber does not fall under the category of the rubber component, but falls under the category of a plasticizer described below.

[0046] The heteroatom is not particularly limited, but is preferably at least one selected from the group consisting of oxygen, nitrogen, sulfur, phosphorus, and silicon.

[0047] Specific examples of the modified rubber include rubbers having functional groups that interact with fillers. Examples include terminal-modified rubbers (terminal-modified rubbers having the functional groups at the terminals) in which at least one terminal of the rubber has been modified with a compound (modifier) ​​having the functional group, main-chain-modified rubbers having the functional groups in the main chain, main-chain-terminal-modified rubbers having the functional groups in the main chain and at the terminals (for example, main-chain-terminal-modified rubbers having the functional groups in the main chain and at least one terminal modified with the modifier), and terminal-modified rubbers modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and having hydroxyl groups or epoxy groups introduced therein.

[0048] Examples of the functional group (the functional group containing the heteroatom) include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an 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, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0049] When the modified rubber is a rubber in a solid state under conditions of 1 atmospheric pressure and 25°C (modified solid rubber), that is, when the rubber composition for tires contains a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber, examples of diene-based rubbers that constitute the skeleton of the modified rubber (modified solid rubber) and are in a solid state under conditions of 1 atmospheric pressure and 25°C include the above-mentioned isoprene-based rubber, and diene-based rubbers such as BR, SBR, SIBR, EPDM, CR, and NBR. Of these, BR and SBR are preferred, and SBR is more preferred, from the viewpoint of obtaining better effects.

[0050] When the modified rubber is a rubber in a solid state (modified solid rubber) under conditions of 1 atmosphere and 25°C, the content of the modified rubber (modified solid rubber) in 100% by mass of the rubber component in the rubber composition for tires is preferably 3% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 50% by mass or more, to tend to achieve better effects. Also, from the viewpoint of fuel economy, the content is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0051] When the modified rubber is a rubber in a solid state (modified solid rubber) under conditions of 1 atmosphere and 25°C, the modified solid rubber is preferably modified BR or modified SBR, and more preferably modified SBR, from the viewpoint of obtaining better effects.

[0052] In the rubber composition for tires, the content of the modified SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, to tend to achieve better effects. From the viewpoint of fuel economy performance, the content is preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 50% by mass or less.

[0053] On the other hand, when the modified rubber is a rubber (modified liquid rubber) that is in a liquid state under conditions of 1 atmosphere and 25°C, i.e., when the tire rubber composition contains a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and the tire rubber composition contains a modified rubber (modified liquid rubber) in addition to the rubber component, examples of the diene-based rubber that is in a liquid state under conditions of 1 atmosphere and 25°C and that constitutes the skeleton of the modified rubber (modified liquid rubber) include liquid diene-based rubbers (liquid rubbers) such as liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), and liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer). In particular, the modified liquid rubber is preferably a modified diene rubber that is in a liquid state under conditions of 1 atmospheric pressure and 25°C.

[0054] The liquid diene rubber has a weight average molecular weight (Mw) of 1.0×10 in terms of polystyrene as measured by gel permeation chromatography (GPC). 3 ~5.0×10 4 Preferably, it is 3.0 × 10 3 ~1.5×10 4 The lower or upper limit of Mw of the liquid diene rubber may be 4,500 or 8,500. In this specification, the Mw of the liquid diene rubber is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0055] As the liquid diene rubber, for example, products of Sartomer Co., Ltd., Kuraray Co., Ltd., etc. can be used.

[0056] When the modified rubber is a rubber (modified liquid rubber) in a liquid state under conditions of 1 atmospheric pressure and 25°C, the content of the modified rubber (modified liquid rubber) per 100 parts by mass of the rubber component in the rubber composition for tires is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more, to tend to achieve better effects. Also, from the viewpoint of improving steering stability at high speeds, the content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0057] The rubber composition for tires includes a filler containing an ion-bonding filler.

[0058] In this specification, the term "ionic bonding filler" refers to a filler that has an ionic bonding group or generates an ionic bonding group such that an interaction occurs between the modified group (functional group) of the modified rubber and the ionic bonding group in the filler, such as an ionic crystal or a filler having an ionic functional group. Examples of fillers having an ionic functional group include a reaction product of a filler and an ionic coupling agent. The reaction product of a filler and an ionic coupling agent may be prepared by simultaneously blending the filler and the ionic filler and reacting them during kneading, or by reacting the filler and the ionic filler in advance. For example, in the case of ionic crystals, an interaction occurs between the ionic bond of the ionic crystals and the modifying group of the modified rubber. Furthermore, in the case of a reaction product of a filler and an ionic-bonding coupling agent, in which the filler and the ionic-bonding filler are simultaneously blended and reacted during kneading, the ionic-bonding coupling agent reacts with silica in the rubber composition system, producing silica with ionic-bonding functional groups on the surface, which in turn produces an interaction between the ionic-bonding functional groups and the modifying groups of the modified rubber. In the case of a reaction product of a filler and an ionic-bonding coupling agent, in which the filler and an ionic-bonding filler have been reacted in advance, an interaction similarly occurs between the ionic-bonding functional group and the modifying group of the modified rubber.

[0059] As used herein, the term "ionic coupling agent" refers to a material that reacts with a filler to modify it so that it can form an ionic bond. Preferably, the material reacts with silica to modify it so that it can form an ionic bond.

[0060] The ionic crystal is not particularly limited, and examples thereof include quaternary ammonium salts such as dimethylammonium and triethylammonium; alkali metal salts such as sodium sulfate, potassium sulfate, potassium chloride, sodium chloride, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate; alkaline earth metal salts such as magnesium sulfate, calcium chloride, magnesium chloride, and calcium hydrogencarbonate; and phosphates such as sodium hydrogenphosphate and sodium dihydrogenphosphate.

[0061] In the filler having an ionic functional group, any material that reacts with silica and is modified to form an ionic bond can be used as the ionic coupling agent. Among them, from the viewpoint of obtaining a better effect, it is preferable to include at least one selected from the group consisting of a compound represented by the following formula (1), a hydrolyzate of a compound represented by the following formula (1), and a hydrolysis condensate of a compound represented by the following formula (1).

[0062] [ka]

[0063] In formula (1), R 31 and R 32 R each independently represents a monovalent organic group. 33 and R 34each independently represents an organic group having a group selected from the group consisting of an alkyl group, a vinyl group, an epoxy group, a styryl group, a (meth)acrylic group, an amino group, an isocyanurate group, a ureido group, a mercapto group, a sulfide group, a polyalkyleneoxyalkyl group, a carboxy group, and a quaternary ammonium group, and 34 At least one of them is an organic group having a quaternary ammonium group. Each m independently represents an integer of 0 to 2. n represents an integer. In this specification, the organic group means a group having one or more carbon atoms.

[0064] The hydrolysate of the compound represented by the formula (1) is a compound in which at least a portion of the substituents on the silicon atoms in the compound represented by the formula (1) has been hydrolyzed to form silanol groups. The hydrolysis condensate of the compound represented by the formula (1) is a compound obtained by condensing two or more compounds selected from the group consisting of the compound represented by the formula (1) and hydrolysates of the compound represented by the formula (1).

[0065] In formula (1), m is preferably 1 or 2, and more preferably 2. In formula (1), n ​​is preferably an integer of 2 to 20.

[0066] R in Equation (1) 31 and R 32 The monovalent organic group preferably has 1 to 6 carbon atoms. R 31 and R 32 The organic group having 1 to 6 carbon atoms in the formula (I) may be linear, branched, or have a ring structure. Examples of the organic group having 1 to 6 carbon atoms include alkyl groups and alkenyl groups, with alkyl groups being preferred. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, n-hexyl, and cyclohexyl groups.

[0067] R in Equation (1) 31and R 32 are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0068] R in Equation (1) 33 are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0069] R in Equation (1) 34 is an organic group having at least one quaternary ammonium group. Examples of groups having a quaternary ammonium group include groups represented by the following formula: [ka]

[0070] In the formula, R 35 ~R 37 R each independently represents a monovalent organic group. 38 Y each independently represents a divalent organic group. - represents an anion. k represents an integer.

[0071] R 35 ~R 37 Examples of the monovalent organic group include monovalent hydrocarbon groups, and examples of the monovalent hydrocarbon group include alkyl groups having 1 to 12 carbon atoms and alkenyl groups having 2 to 12 carbon atoms. R 35 ~R 37 The number of carbon atoms is preferably 1 to 12, more preferably 1 to 7, still more preferably 1 to 5, and particularly preferably 1 to 3. R 35 ~R 37 The monovalent organic group is particularly preferably a methyl group or an ethyl group.

[0072] R 38The divalent organic group includes a divalent hydrocarbon group, and examples of the divalent hydrocarbon group include an alkylene group having 1 to 12 carbon atoms and an alkenylene group having 2 to 12 carbon atoms. R 38 The number of carbon atoms is preferably 1 to 12, more preferably 1 to 7, still more preferably 1 to 5, and particularly preferably 1 to 3. R 38 The divalent organic group is particularly preferably a methylene group or an ethylene group.

[0073] k is preferably 0 to 5, more preferably 0 to 3, still more preferably 0 to 1, and particularly preferably 0.

[0074] Y - is not particularly limited, and examples thereof include halide ions (chloride ions, bromide ions, iodide ions, etc.); carboxylate ions (formate ions, acetate ions, trifluoroacetate ions, lactate ions, propionate ions, benzoate ions, oxalate ions, succinate ions, stearate ions, etc.); methyl sulfate ions (alkyl sulfate ions, etc.); sulfonate ions (methanesulfonate ions, benzenesulfonate ions, trifluoromethanesulfonate ions, toluenesulfonate ions, naphthalenesulfonate ions, nitrobenzenesulfonate ions) , dodecylbenzenesulfonate ion, ethanesulfonate ion, etc.); sulfonate imide ions (bis(trifluoromethanesulfonate)imide ion, etc.); borate ions (tetrafluoroborate ion, tetraphenylborate ion, butyltriphenylborate ion, etc.); phosphate ions (hexafluorophosphate ion, etc.); antimonate ions (hexafluoroantimonate ion, etc.); arsenate ions (hexafluoroarsenate ion, etc.); perhalogenate ions (perchlorate ion, periodate ion, etc.); thiocyanate ion, nitrate ion, etc.

[0075] Among the compounds represented by the above formula (1), the hydrolysates of the compounds represented by the above formula (1), and the hydrolysis condensates of the compounds represented by the above formula (1), the compounds represented by the following formula (1-1) are preferred from the viewpoint of obtaining better effects.

[0076] [ka]

[0077] In formula (1-1), R 35 ~R 37 are each independently the R 35 ~R 37 R represents a group similar to 38 are each independently the R 38 represents a group similar to that represented by Y - are each independently the Y - Each k independently represents an integer similar to the above k.

[0078] In formula (1-1), R 35 ~R 37 , R 38 , Y - , and the preferred examples of k are the same as those mentioned above.

[0079] As the ionic bonding coupling agent, for example, a commercially available product such as X-12-1126 manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0080] Among the above ionic-bonding fillers, from the viewpoint that the effect tends to be more favorably obtained, it is preferable to contain at least one selected from the group consisting of quaternary ammonium salts, alkali metal salts, and alkaline earth metal salts. The above rubber composition for tires more preferably contains an alkaline earth metal salt, and further preferably contains magnesium sulfate.

[0081] Although the mechanism by which the effect is enhanced when at least one selected from the group consisting of quaternary ammonium salts, alkali metal salts, and alkaline earth metal salts is not clear, the use of these ionic-bonding fillers enhances the interaction between the modifying groups in the modified rubber and these ionic-bonding fillers, and when the rubber comes into contact with moisture on a wet road surface, the ionic bonds are loosened, effectively softening the rubber temporarily, thereby significantly improving wet road conformability, and it is presumed that this significantly improves wet grip performance.

[0082] In the rubber composition for tires, the content of the ionic-bonding filler is preferably 1 part by mass or more, more preferably 1.3 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, to tend to obtain better effects. From the viewpoint of fuel economy performance, the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 50 parts by mass or less.

[0083] In this specification, the content of the ionic bonding filler refers to the content of ionic crystals when the ionic bonding filler is an ionic crystal. When the ionic filler is a reaction product between a filler and an ionic coupling agent, the content of the reaction product is referred to. When ionic crystals and a reaction product of a filler and an ionic coupling agent are blended, the content is the sum of the contents of each.

[0084] In the rubber composition for tires, the content of the ionic crystals is preferably 1.0 part by mass or more, more preferably 1.3 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, to tend to obtain better effects. From the viewpoint of improving fuel economy, the content is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0085] In the rubber composition for tires, the content of the magnesium sulfate is preferably 1.0 part by mass or more, more preferably 1.3 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, to tend to obtain better effects. From the viewpoint of improving fuel economy performance, the content is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0086] In the rubber composition for tires, the content of the filler having an ionic functional group is preferably 1.0 part by mass or more, more preferably 10 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 130 parts by mass or less, more preferably 125 parts by mass or less, and even more preferably 121 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0087] In the rubber composition for tires, the total content of the compound represented by formula (1), the hydrolyzate of the compound represented by formula (1), and the hydrolysis condensate of the compound represented by formula (1) is preferably at least 1.0 part by mass, more preferably at least 10 parts by mass, and even more preferably at least 21 parts by mass, per 100 parts by mass of the rubber component, and is preferably at most 100 parts by mass, more preferably at most 70 parts by mass, and even more preferably at most 50 parts by mass. Within the above ranges, better effects tend to be obtained.

[0088] The rubber composition for tires preferably contains, as a filler, a filler other than the ionic-bonding filler.

[0089] Fillers other than the ion-bonding filler are not particularly limited, and materials known in the rubber field can be used, including, for example, inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, biochar, poorly dispersible fillers, etc. Among these, carbon black and silica are preferred, and silica is more preferred, from the viewpoint of obtaining better effects.

[0090] Although the mechanism by which silica provides a more effective result is unclear, it is believed that adding silica effectively exposes ionic functional groups on the silica surface, which facilitates interaction with the modified rubber, resulting in a significant improvement in wet grip performance.

[0091] The silica that can be used in the rubber composition for tires is not particularly limited, and can be, for example, silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica), which are commonly used in the tire industry. The raw material for silica is not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from a biomass material such as rice husk), or silica recycled from a silica-containing product. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more types.

[0092] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0093] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0094] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0095] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0096] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 80m 2 / g or more, more preferably 100m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0097] 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, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by pyrolysis of methane, such as in a thermal black process. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. Carbon black may be used alone or in combination.

[0098] The nitrogen adsorption specific surface area (N2SA) of carbon black is 5m 2 / g or more is preferable, and 20m 2 / g or more is more preferable, and 40m 2 / g or more is more preferable. 2 / g or less is preferable, and 130m 2 / g or less is more preferable, and 120m 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.

[0099] Examples of the hardly dispersible filler include microfibrillated plant fibers, short fiber cellulose, gel compounds, etc. Among these, microfibrillated plant fibers are preferred.

[0100] The microfibrillated plant fiber is preferably cellulose microfibrils, as they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf; pulp, paper, and cloth obtained from these raw materials; waste biomass such as agricultural waste, food waste, and sewage sludge; unused biomass such as rice straw, wheat straw, and thinned wood; and cellulose produced by sea squirts, acetic acid bacteria, and the like. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0101] In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, more typically cellulose fibers having a microstructure formed by the aggregation of cellulose molecules and an average fiber diameter of 500 nm or less. Typical cellulose microfibrils are formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0102] In the rubber composition for tires, the content of the filler (total amount of fillers such as ionic filler, carbon black, and silica) is preferably 5 parts by mass or more, more preferably 25 parts by mass or more, and even more 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 120 parts by mass or less, and even more preferably 100 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

[0103] In the rubber composition for tires, the content of silica per 100 parts by mass of the rubber component is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 85 parts by mass or less, to tend to achieve better effects. Also, from the viewpoint of improving steering stability during high-speed running, the content is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, still more preferably 80 parts by mass or more, still more preferably 85 parts by mass or more, and particularly preferably 100 parts by mass or more.

[0104] When the rubber composition for a tire contains carbon black, the effect tends to be better when the content 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. From the viewpoint of improving fuel economy, the content of carbon black is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0105] When the rubber composition for a tire contains silica, it is preferable that it further contains a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N, Examples include sulfide-based compounds such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; 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 Silicones 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.

[0106] In the rubber composition for tires, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of silica. The upper limit of the content is preferably 50 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 range, the effect tends to be more favorably obtained.

[0107] The rubber composition for a tire includes a plasticizer containing a resin. Resin is a material that imparts plasticity to the rubber component, and is a concept that includes both resins that are liquid under conditions of 1 atmosphere and 25°C and resins that are solid under conditions of 1 atmosphere and 25°C. The resins may be used alone or in combination of two or more. In this specification, resin and rubber (rubber component or liquid rubber) are different materials.

[0108] The resin is not particularly limited, but resins commonly used in the tire industry can be used, such as adhesive resins such as C5 resins, C9 resins, C5C9 resins, aromatic vinyl resins, cyclopentadiene resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenol resins. These resins may be used alone or in combination of two or more.

[0109] Among the above resins, petroleum-based resins such as C5 resins, C9 resins, C5C9 resins, aromatic vinyl resins, and cyclopentadiene resins are preferred, as they tend to provide better effects.

[0110] Although the mechanism by which the inclusion of petroleum-based resins provides a greater effect is unclear, it is believed that the inclusion of petroleum-based resins contributes to the improvement of wet grip performance because they are compatible with styrene-butadiene rubber and can increase the energy loss of the rubber composition, thereby significantly improving wet grip performance.

[0111] The C5 resin refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified C5 resin. Examples of the C5 fraction include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used alone or in combination of two or more.

[0112] C9 resin refers to a resin obtained by polymerizing a C9 fraction, and may be a polymer of the C9 fraction alone or a copolymer of the C9 fraction with other components. For example, a resin copolymerized with dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. These resins may also be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used alone or in combination.

[0113] The C5C9 resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. As the C5C9 petroleum resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used. These C5C9 resins may be used alone or in combination of two or more.

[0114] The aromatic vinyl resin refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, or p-chlorostyrene as the monomer component with the largest content, and may be a hydrogenated or modified version of such a compound. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, for example, commercially available products from Kraton, Eastman Chemical Company, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0115] The cyclopentadiene resin refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as a monomer component, and may be hydrogenated or modified. Examples of cyclopentadiene resins include DCPD / C9 resins containing dicyclopentadiene and a C9 fraction as monomer components (the DCPD / C9 resins may be hydrogenated or modified). DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components are particularly preferred. Examples of cyclopentadiene resins that can be used include those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like. These cyclopentadiene resins may be used alone or in combination.

[0116] Coumarone resins refer to resins containing coumarone as a monomer component, and may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These coumarone resins may be used alone or in combination of two or more.

[0117] Indene resins refer to resins containing indene as a monomer component, and may be hydrogenated or modified. Examples of indene resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These indene resins may be used alone or in combination.

[0118] Terpene resins refer to resins containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the most abundant monomer component, and may be hydrogenated or modified. Specific examples of terpene resins include polyterpene resins containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. These terpene resins may be used alone or in combination.

[0119] The rosin-based resin refers to a resin containing a rosin acid compound such as abietic acid, neoabietic acid, palustric acid, or isopimaric acid, and may be a hydrogenated or modified version of such a resin. Examples of the rosin-based resin include, but are not limited to, natural rosin and rosin-modified resins obtained by modifying natural rosin through hydrogenation, disproportionation, dimerization, esterification, or the like. These rosin-based resins may be used singly or in combination of two or more.

[0120] A phenolic resin refers to a resin that contains a phenolic compound such as phenol or cresol as the monomer component with the highest content. Examples of phenolic resins include, but are not limited to, phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins. These phenolic resins may be used alone or in combination of two or more.

[0121] The resin is preferably a modified resin (functionalized resin) into which a functional group has been introduced. 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.

[0122] The polymer that forms the polymer backbone is not particularly limited, and may be, for example, the above-mentioned C5 resin, aromatic resin, terpene resin, or other resin. These may be used alone or in combination of two or more. Among them, 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.

[0123] 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.

[0124] 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.

[0125] When the rubber composition for tires contains the resin, the content of the resin (total amount of the resin in a solid state under conditions of 1 atmospheric pressure and 25°C and the resin in a liquid state under conditions of 1 atmospheric pressure and 25°C) is more than 5 parts by mass, but preferably 7 parts by mass or more, more preferably 8 parts by mass or more, tends to provide better effects. From the viewpoint of improving fuel economy, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less.

[0126] When the rubber composition for a tire contains a solid-state resin under conditions of 1 atmosphere and 25° C., the effect tends to be better when the content of the solid-state resin is preferably more than 5 parts by mass, more preferably 7 parts by mass or more, and even more preferably 8 parts by mass or more. From the viewpoint of improving fuel economy, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less.

[0127] When the rubber composition for a tire contains a resin in a liquid state under conditions of 1 atmosphere and 25°C, the effect tends to be better when the content of the resin in a liquid state is preferably more than 5 parts by mass, more preferably 7 parts by mass or more, and even more preferably 8 parts by mass or more. From the viewpoint of improving fuel economy, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less. The amount of resin contained in the liquid state also includes the amount of resin contained in the resin-extended rubber.

[0128] The rubber composition for a tire may contain a plasticizer other than the resin.

[0129] In this specification, the term "plasticizer" refers to a material that imparts plasticity to a rubber component, and includes both liquid plasticizers at 1 atmosphere and 25°C and solid plasticizers at 1 atmosphere and 25°C. Examples of plasticizers include the above-mentioned resins, oils, liquid rubbers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, biomass-derived plasticizers, or naphtha recycled from rubber and non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as plasticizers. These plasticizers may be used alone or in combination.

[0130] Plasticizers that can be used other than the above resins include, for example, oils, liquid polymers, etc. These may be used alone or in combination of two or more.

[0131] Examples of oils include mineral oil, vegetable oil, animal oil, etc. From the viewpoint of life cycle assessment, waste oils used in rubber mixers or engines, or refined waste cooking oils used in restaurants may also be used.

[0132] As used herein, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral oil include mild extract solvated (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil.

[0133] As used herein, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above-mentioned oils, interesterified oils obtained by interesterifying the above-mentioned oils, hardened oils obtained by hydrogenating the above-mentioned oils, thermally polymerized oils obtained by thermally polymerizing the above-mentioned oils, oxidatively polymerized oils obtained by oxidizing the above-mentioned oils, and waste edible oils recovered from edible oils and the like. Vegetable oils may be liquid or solid at 25°C. These vegetable oils may be used alone or in combination of two or more.

[0134] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. The acylglycerol may be liquid or solid at 25°C.

[0135] The method for confirming whether the acylglycerol is contained in the rubber composition for tires is not particularly limited, but may be any of the following methods: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0136] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0137] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0138] As the oil, for example, commercially available oils from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0139] Examples of the liquid polymer include diene rubbers that are in a liquid state under the above-mentioned conditions of 1 atmosphere and 25° C. (liquid diene rubbers (liquid rubbers)) and liquid farnesene polymers.

[0140] From the viewpoint of sustainability, it is desirable to use the above-mentioned plant-derived plasticizers such as plant-derived oils and farnesene-based polymers as the plasticizer.

[0141] Farnesene polymers are polymers obtained by polymerizing farnesene and contain structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene), but (E)-β-farnesene, which has the following structure, is preferred. [ka]

[0142] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer). These may be used alone or in combination of two or more. Among these, a copolymer of farnesene and a vinyl monomer is preferred.

[0143] Examples of vinyl monomers include aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, 4-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, as well as conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Among these, butadiene is preferred. That is, the farnesene-vinyl monomer copolymer is preferably a copolymer of farnesene and butadiene (farnesene-butadiene copolymer).

[0144] In the farnesene-vinyl monomer copolymer, the copolymerization ratio by mass of farnesene to vinyl monomer (farnesene / vinyl monomer) is preferably 40 / 60 to 90 / 10.

[0145] The farnesene polymer preferably has a weight average molecular weight (Mw) of 3,000 or more and 300,000 or less. The Mw of the farnesene polymer is preferably 8,000 or more, more preferably 10,000 or more, and is preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. Within the above ranges, the effects tend to be more favorably obtained.

[0146] The farnesene-based polymer may be either a liquid or solid at 25° C. Among these, a liquid farnesene-based polymer that is a liquid at 25° C. is preferred.

[0147] In the rubber composition for tires, the content of the plasticizer (total amount of plasticizer) per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 43 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. Within the above ranges, the effect tends to be better obtained. The plasticizer content includes the amount of oil and resin contained in the oil-extended rubber and resin-extended rubber.

[0148] When the rubber composition for a tire contains a solid plasticizer in a solid state under conditions of 1 atmospheric pressure and 25°C, the content of the solid resin is preferably more than 5 parts by mass (greater than 5 parts by mass), more preferably 7 parts by mass or more, even more preferably 8 parts by mass or more, and is preferably 50 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. Within the above ranges, better effects tend to be obtained.

[0149] When the rubber composition for a tire contains a liquid plasticizer that is in a liquid state under conditions of 1 atmospheric pressure and 25°C, the content of the liquid plasticizer is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 35 parts by mass or more, and is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, per 100 parts by mass of the rubber component. Within the above ranges, better effects tend to be obtained. The content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin in the resin-extended rubber extended with the liquid resin.

[0150] When the rubber composition for a tire contains oil in a liquid state under conditions of 1 atmospheric pressure and 25°C, the content of the oil is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 35 parts by mass or more, and is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above ranges, better effects tend to be obtained. The oil content includes the amount of oil contained in the oil-extended rubber.

[0151] The rubber composition for tires preferably contains a fatty acid derivative, as this tends to produce better effects.

[0152] Although the mechanism by which the inclusion of fatty acid derivatives provides a greater effect is unclear, it is believed that the inclusion of fatty acid derivatives facilitates interaction between the ionic filler and modified rubber in the system, which is presumably why wet grip performance is significantly improved.

[0153] Examples of the fatty acid derivatives include fatty acid metal salts, amide esters, fatty acid esters, fatty acid amides, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of fatty acid metal salts, amide esters, and mixtures of fatty acid metal salts and amide esters or fatty acid amides is preferred, and fatty acid metal salts, mixtures of fatty acid metal salts and fatty acid amides, and mixtures of fatty acid metal salts and fatty acid amides are more preferred, and mixtures of fatty acid metal salts and fatty acid amides are even more preferred.

[0154] The fatty acid constituting the fatty acid metal salt is not particularly limited, but examples thereof include saturated or unsaturated fatty acids (preferably saturated or unsaturated fatty acids having 6 to 28 carbon atoms (more preferably 10 to 25 carbon atoms, and even more preferably 14 to 20 carbon atoms)), such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, and nervonic acid. These may be used alone or in combination of two or more. Of these, saturated fatty acids are preferred, and saturated fatty acids having 14 to 20 carbon atoms are more preferred.

[0155] Examples of metals constituting fatty acid metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel, molybdenum, etc. These may be used alone or in combination of two or more. Of these, zinc and calcium are preferred, and calcium is more preferred.

[0156] Examples of the amide ester include fatty acid amide esters containing the above-mentioned saturated or unsaturated fatty acids as constituent components, etc. These may be used alone or in combination of two or more.

[0157] Examples of fatty acid esters include fatty acid esters containing the above-mentioned saturated or unsaturated fatty acids as constituent components, etc. These may be used alone or in combination of two or more.

[0158] The fatty acid amide may be a saturated fatty acid amide or an unsaturated fatty acid amide. These may be used alone or in combination of two or more. Examples of saturated fatty acid amides include N-(1-oxooctadecyl)sarcosinamide, stearic acid amide, and behenic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide.

[0159] A specific example of the mixture of a fatty acid metal salt and an amide ester is Aflux 16 manufactured by Rhein Chemie, which is a mixture of a fatty acid calcium salt and an amide ester.

[0160] A specific example of the mixture of a fatty acid metal salt and a fatty acid amide is WB16 manufactured by Struktol, which is a mixture of fatty acid calcium salt and a fatty acid amide.

[0161] As the fatty acid derivatives, for example, products available from Rhein Chemie, Struktol, etc. can be used.

[0162] The content of the fatty acid derivative is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 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 6 parts by mass or less, and even more preferably 5 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained. On the other hand, from the viewpoint of improving fuel economy performance, the content is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, and is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more.

[0163] The rubber composition for tires preferably contains zinc carboxylate, as this tends to produce better effects.

[0164] Although the mechanism by which zinc carboxylate is used to achieve this effect is unclear, it is believed that the inclusion of zinc carboxylate facilitates interaction between the ionic filler and modified rubber in the system, which is likely to result in a significant improvement in wet grip performance.

[0165] As used herein, zinc carboxylate refers to a zinc salt of a carboxylic acid.

[0166] As the zinc carboxylate, for example, a zinc salt of an aliphatic carboxylic acid, a zinc salt of an aromatic carboxylic acid, or a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid can be suitably used. These may be used alone or in combination of two or more. Among them, a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid is preferred.

[0167] Examples of the aliphatic carboxylic acid in the zinc salt of an aliphatic carboxylic acid include aliphatic carboxylic acids derived from vegetable oils such as coconut oil, palm kernel oil, camellia oil, olive oil, almond oil, canola oil, peanut oil, rice malt oil, cacao butter, palm oil, soybean oil, cottonseed oil, sesame oil, linseed oil, castor oil, and rapeseed oil; aliphatic carboxylic acids derived from animal oils such as beef tallow; and aliphatic carboxylic acids chemically synthesized from petroleum, etc. However, aliphatic carboxylic acids derived from vegetable oils are preferred, as they are environmentally friendly and can prepare for a future decrease in petroleum supply, and furthermore can satisfactorily suppress reversion, and aliphatic carboxylic acids derived from coconut oil, palm kernel oil, or palm oil are more preferred.

[0168] The aliphatic carboxylic acid preferably has 4 or more carbon atoms, more preferably 6 or more carbon atoms, and the aliphatic carboxylic acid preferably has 16 or less carbon atoms, more preferably 14 or less carbon atoms, and even more preferably 12 or less carbon atoms. When the carbon number is within the above range, better effects tend to be obtained.

[0169] The aliphatic group in the aliphatic carboxylic acid may be a chain structure such as an alkyl group or a cyclic structure such as a cycloalkyl group.

[0170] Examples of the aromatic carboxylic acid in the zinc salt of an aromatic carboxylic acid include benzoic acid, phthalic acid, mellitic acid, hemimellitic acid, trimellitic acid, diphenic acid, toluic acid, naphthoic acid, etc. Among these, benzoic acid, phthalic acid, and naphthoic acid are preferred.

[0171] When the zinc carboxylate is a mixture of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid, the content ratio of the zinc salt of aliphatic carboxylic acid to the zinc salt of aromatic carboxylic acid in the mixture (molar ratio, zinc salt of aliphatic carboxylic acid / zinc salt of aromatic carboxylic acid, hereinafter referred to as content ratio) is preferably 1 / 20 or more, more preferably 1 / 15 or more, and even more preferably 1 / 10 or more, and the content ratio is preferably 20 / 1 or less, more preferably 15 / 1 or less, and even more preferably 10 / 1 or less.When it is within the above range, the effect tends to be better obtained.

[0172] The zinc content in the mixture is preferably 3% by mass or more, more preferably 5% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less. Within the above ranges, better effects tend to be obtained.

[0173] The content of the zinc carboxylate (total amount of zinc salts of carboxylic acids) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, still more preferably 2 parts by mass or more, and particularly preferably 2.5 parts by mass or more, per 100 parts by mass of the rubber component, whereby the effect tends to be more favorable. From the viewpoint of improving fuel economy, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

[0174] As the zinc carboxylate, products such as Activator 73A manufactured by Struktol can be used.

[0175] The rubber composition for a tire may contain 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.

[0176] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0177] As commercially available vulcanized rubber particles, for example, products from Lehigh Corporation, Muraoka Rubber Industries Co., Ltd., etc. can be used.

[0178] In the rubber composition for tires, the content of the vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 7 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 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0179] The rubber composition for tires preferably contains an antioxidant from the viewpoints of crack resistance, ozone resistance, and the like.

[0180] The antioxidant is not particularly limited, and examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc.

[0181] In the rubber composition for tires, the content of the antioxidant is preferably 1.0 part by mass or more, more preferably 3.5 parts by mass or more, per 100 parts by mass of the rubber component, and preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less.

[0182] The rubber composition for a tire may contain stearic acid. In the rubber composition for tires, the content of stearic acid is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0183] As the stearic acid, conventionally known products can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0184] The rubber composition preferably contains zinc oxide. In the above rubber composition, the content of zinc oxide is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, per 100 parts by mass of the rubber component.

[0185] As the zinc oxide, conventionally known products can be used, for example, products 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. can be used. Alternatively, two or more of them may be used in combination.

[0186] The rubber composition for a tire may contain short fibers. The amount of the short fibers is preferably 1 part by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less.

[0187] Examples of the short fibers include non-metallic inorganic short fibers such as glass fiber and carbon fiber, and non-metallic organic short fibers such as cellulose fiber, rayon fiber, acrylic fiber, polyester fiber, nylon fiber, aromatic polyamide fiber, urethane fiber, and aramid fiber.

[0188] The rubber composition for tires preferably contains sulfur. In the rubber composition for tires, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.2 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 3.5 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.5 parts by mass or less. Within the above range, the effect tends to be more favorable.

[0189] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0190] The rubber composition for a tire preferably contains a vulcanization accelerator. In the rubber composition for tires, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density, but is preferably 1.0 part by mass or more, more preferably 3.0 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. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0191] The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, 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., Ouchi Shinko Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more. Of these, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0192] In addition to the above components, the rubber composition for tires may also contain compounding agents generally used in the tire industry, such as materials such as a mold release agent, as appropriate.

[0193] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the above-mentioned compound from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0194] From the viewpoint that the effects tend to be more favorable, the rubber composition for tires preferably contains the zinc carboxylate, and the ratio of the content (parts by mass) of the zinc carboxylate to the content (parts by mass) of the modified rubber is preferably 0.02 or more. The ratio of the content (parts by mass) of the zinc carboxylate to the content (parts by mass) of the modified rubber is preferably 0.04 or more, more preferably 0.05 or more, and even more preferably 0.06 or more. The upper limit is not particularly limited, but is preferably 0.20 or less, more preferably 0.15 or less, and even more preferably 0.12 or less. Within the above range, the effects tend to be more favorable.

[0195] Although the mechanism by which a zinc carboxylate content (parts by mass) / modified rubber content (parts by mass) of 0.02 or more provides a more effective result is unclear, it is believed that the inclusion of a certain amount of zinc carboxylate relative to the modified rubber facilitates interaction between the ionic filler and the modified rubber in the system, which is presumably why wet grip performance is significantly improved.

[0196] The rubber composition for tires can be produced, for example, by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0197] Regarding kneading conditions, in the base kneading step in which additives other than the crosslinking agent (vulcanizing agent) and vulcanization accelerator are kneaded, the kneading temperature is preferably 100°C or higher, more preferably 120°C or higher, and preferably 180°C or lower, more preferably 170°C or lower. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is preferably 80°C or higher, and preferably 120°C or lower, more preferably 110°C or lower. 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 preferably 140°C or higher, more preferably 150°C or higher, and preferably 190°C or lower, more preferably 185°C or lower.

[0198] A tire having tire components made of the rubber composition for a tire is manufactured by a conventional method using the rubber composition for a tire. That is, the rubber composition, to which various additives are optionally blended, is extruded in an unvulcanized state to match the shapes of various tire components, molded in a tire building machine by a conventional method, and bonded together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0199] The tire is not particularly limited, and examples thereof include pneumatic tires, solid tires, airless tires, etc. Among these, pneumatic tires are preferred.

[0200] The above tires can be used for passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks and buses, light truck tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc. [Example]

[0201] Below, examples (embodiments) that are considered preferable for implementation will be shown, but the scope of the present invention is not limited to the examples.

[0202] The various chemicals used in the examples and comparative examples will be explained below. NR:TSR20 SBR1: HPR840 manufactured by JSR Corporation (modified SBR, Tg -60°C, styrene content 10% by mass, vinyl content 42% by mass) SBR2: SBR1502 (unmodified SBR, styrene content 23.5% by mass) manufactured by Sumitomo Chemical Co., Ltd. BR: BR150B manufactured by Ube Industries, Ltd. (cis content 95% by mass or more) Carbon black: Diablack I (N220, N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g, DBP 114ml / 100g) Ionic crystal: MN-00 (anhydrous magnesium sulfate, median particle size: 75 μm) manufactured by Mai Chemical Industry Co., Ltd. Silica: Ultrasil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Ionic coupling agent: X-12-1126 (quaternary ammonium salt) manufactured by Shin-Etsu Chemical Liquid rubber: Kuraray LIR-410 (maleic acid modified liquid polyisoprene, Mw 30000) Oil: Sankyo Yuka Kogyo Co., Ltd. A / O Mix Resin: Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene, softening point 85°C) manufactured by Arizona Chemical Co. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 6C: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (6PPD) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant RD: Antage RD (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) manufactured by Kawaguchi Chemical Industry Co., Ltd. Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Fatty acid derivative: WB16 manufactured by Struktol (a mixture of fatty acid metal salts (calcium fatty acids, constituent fatty acids: saturated fatty acids with 14 to 20 carbon atoms) and fatty acid amides) Zinc carboxylate: Activator 73A (a mixture of zinc salts of aliphatic and aromatic carboxylic acids) manufactured by Struktol Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccela D (diphenyl guanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0203] <Examples and Comparative Examples> (Base kneading process) According to the composition shown in Table 1, the materials were charged into a Banbury mixer and kneaded, and after kneading for 2 minutes at a rubber temperature of 160°C, the materials were discharged. Only the mixture (sheet rubber) obtained by discharge was charged into a Banbury mixer and further kneaded (discharge temperature 160°C). (finishing kneading process) The obtained mixture, sulfur, and vulcanization accelerator were charged into a Banbury mixer and kneaded to obtain an unvulcanized rubber composition. Kneading was completed when the rubber temperature reached 100°C. (Vulcanization process) The resulting unvulcanized rubber composition was press-vulcanized at 170°C for 12 minutes to obtain a vulcanized rubber composition.

[0204] The vulcanized rubber composition was evaluated as follows, and the results are shown in Table 1.

[0205] <Measurement of storage modulus G'> (Measurement of G' (MPa) when dry) From the vulcanized rubber composition, circular vulcanized rubber test pieces with a diameter of 12 mm (thickness of 2 mm) were cut out. The storage modulus of each vulcanized rubber test piece was measured using a dynamic viscoelasticity apparatus under the following conditions: deformation mode: shear, measurement temperature: 5°C, frequency: 10 Hz, dynamic strain was changed from 0.25% to 100%. From the measurement results obtained, G' when the stress was about 0.4 MPa was extracted and compared. (Measurement of G' (MPa) when wet) From the vulcanized rubber composition, circular vulcanized rubber test pieces with a diameter of 12 mm (thickness of 2 mm) were cut out. Each vulcanized rubber test piece was immersed in water at 40°C for 72 hours. Then, the storage modulus of each vulcanized rubber test piece was measured using a dynamic viscoelasticity measuring device under the following conditions: deformation mode: shear, measurement temperature: 5°C, frequency: 10 Hz, dynamic strain: changed from 0.25% to 100%. From the measurement results obtained, G' when the stress was about 0.4 MPa was extracted and compared. We measured G' (MPa) in wet conditions and G' (MPa) in dry conditions, and calculated the following rate of change. The higher the rate of change, the better the wet grip performance is considered to be. Change rate (%) = (|Dry G' - Wet G'| / Dry G') x 100

[0206] [Table 1]

[0207] The present invention (1) comprises a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber; a filler including an ion-bonding filler; A rubber composition for tires containing a plasticizer including a resin, at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber, and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, The content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, The styrene-butadiene rubber has a glass transition temperature of −50° C. or lower, The rubber composition for tires has a content of the resin exceeding 5 parts by mass per 100 parts by mass of the rubber component.

[0208] The present invention (2) is the rubber composition for tires according to the present invention (1), wherein the glass transition temperature of the styrene-butadiene is −55° C. or lower.

[0209] The present invention (3) is the rubber composition for tires according to the present invention (1), wherein the glass transition temperature of the styrene butadiene is −60° C. or lower.

[0210] The present invention (4) is a rubber composition for tires containing silica in any combination with any of the present inventions (1) to (3).

[0211] The present invention (5) is a rubber composition for tires, which is any combination with any of the present inventions (1) to (4), in which the ion-bonding filler is at least one selected from the group consisting of quaternary ammonium salts, alkali metal salts, and alkaline earth metal salts.

[0212] The present invention (6) is a rubber composition for tires in any combination with any of the present inventions (1) to (5), in which the resin is a petroleum-based resin.

[0213] The present invention (7) is a rubber composition for tires containing a fatty acid derivative in any combination with any of the present inventions (1) to (6).

[0214] The present invention (8) is a rubber composition for tires containing a zinc carboxylate in any combination with any of the present inventions (1) to (7).

[0215] The present invention (9) contains a zinc carboxylate, The rubber composition for tires is any combination with any of the present inventions (1) to (8), in which the content (parts by mass) of the zinc carboxylate / the content (parts by mass) of the modified rubber is 0.02 or more.

Claims

1. a rubber component including an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber; a filler including an ion-bonding filler; A rubber composition for tires containing a plasticizer including a resin, at least one of the isoprene-based rubber, the butadiene rubber, and the styrene-butadiene rubber is a modified rubber, and / or the rubber composition for tires contains a modified rubber in addition to the rubber component, the content of the isoprene-based rubber in 100% by mass of the rubber component is 20% by mass or more, The styrene-butadiene rubber has a glass transition temperature of −50° C. or lower, The rubber composition for tires has a content of the resin exceeding 5 parts by mass per 100 parts by mass of the rubber component.

2. 2. The rubber composition for tires according to claim 1, wherein the styrene-butadiene has a glass transition temperature of −55° C. or lower.

3. 2. The rubber composition for tires according to claim 1, wherein the styrene-butadiene has a glass transition temperature of −60° C. or lower.

4. The rubber composition for a tire according to claim 1 or 2, which contains silica.

5. 3. The rubber composition for a tire according to claim 1, wherein the ion-bonding filler is at least one selected from the group consisting of quaternary ammonium salts, alkali metal salts, and alkaline earth metal salts.

6. 3. The rubber composition for a tire according to claim 1, wherein the resin is a petroleum-based resin.

7. The rubber composition for a tire according to claim 1 or 2, which contains a fatty acid derivative.

8. The rubber composition for a tire according to claim 1 or 2, which contains a zinc carboxylate.

9. Contains zinc carboxylate, The rubber composition for a tire according to claim 1 or 2, wherein the ratio of the content (parts by mass) of the zinc carboxylate to the content (parts by mass) of the modified rubber is 0.02 or more.

Images