Rubber composition for heavy-duty tires and heavy-duty tire

Abstract

To provide a rubber composition for heavy-duty tires and a heavy-duty tire which can achieve improved crack resistance.SOLUTION: The present invention relates to a rubber composition for heavy-duty tires, which contains: a rubber component comprising isoprene-based rubber, butadiene rubber, and styrene-butadiene rubber; and two or more fillers, wherein the content of the isoprene-based rubber exceeds the content of the fillers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for heavy-duty tires and a heavy-duty tire.

Background Art

[0002] Hitherto, various methods for improving crack resistance performance have been studied (see, for example, Patent Document 1). However, in recent years, further improvement of crack resistance performance has been demanded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a rubber composition for heavy-duty tires and a heavy-duty tire that solve the above problems and can improve crack resistance performance.

Means for Solving the Problems

[0005] The present invention relates to a rubber composition for heavy-duty tires containing a rubber component including isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and two or more kinds of fillers, wherein the content of the isoprene rubber > the content of the fillers.

Effects of the Invention

[0006] Since the present invention is a rubber composition for heavy-duty tires containing a rubber component including isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and two or more kinds of fillers, wherein the content of the isoprene rubber > the content of the fillers, the crack resistance performance is excellent.

Modes for Carrying Out the Invention

[0007] The rubber composition for heavy load tires of the present disclosure contains a rubber component including isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and two or more fillers, and the content of the isoprene rubber > the content of the fillers.

[0008] The reason why the above-described effects can be obtained with the above rubber composition is presumed as follows. As the rubber component, by mixing isoprene rubber, butadiene rubber, and styrene-butadiene rubber, each phase can be microscopically mixed. In addition, by blending two or more fillers, each microphase can take on more diverse hardnesses. In addition, by making the content of the isoprene rubber higher than the content of the fillers, stress is less likely to concentrate around the fillers, and the microphase of the isoprene rubber can relieve the impact and allow the impact to flow through the entire rubber. It is considered that the crack resistance performance is improved by the above actions.

[0009] The above rubber composition contains a rubber component. Here, the rubber component is a component that contributes to crosslinking, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0010] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, still more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, still more preferably 1,000,000 or less. When within the above range, the effects tend to be obtained more favorably.

[0011] In addition, in this specification, the weight average molecular weight (Mw) can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0012] The total styrene content in the rubber component is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0013] Here, the total styrene content in the rubber component is the total content (unit: mass%) of the styrene moieties contained in the total amount of the rubber component, and can be calculated by Σ (content of each rubber component × styrene content in each rubber component / 100). For example, in 100% by mass of the rubber component, when the styrene-butadiene rubber with a styrene content of 40% by mass is 85% by mass, the styrene-butadiene rubber with a styrene content of 25% by mass is 5% by mass, and the butadiene rubber with a styrene content of 0% by mass is 10% by mass, the total styrene content in the rubber component is 35.25% by mass (= 85×40 / 100 + 5×25 / 100 + 10×0 / 100).

[0014] The total vinyl content in the rubber component is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 1.5% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0015] Here, the total vinyl content in the rubber component is the total content (unit: parts by mass) of vinyl bonds in the butadiene moieties of styrene-butadiene rubber and butadiene rubber contained in the rubber component, when the total mass of the rubber component is taken as 100, and can be calculated by Σ (content of each rubber component × ratio of the vinyl bond amount in the butadiene moiety in each rubber component to the total mass of each rubber component [mass%]). For example, in 100 parts by mass of the rubber component, if there are 85 parts by mass of styrene-butadiene rubber with a styrene content of 40 mass% and a vinyl content of 30 mass%, 5 parts by mass of styrene-butadiene rubber with a styrene content of 20 mass% and a vinyl content of 20 mass%, and 10 parts by mass of butadiene rubber with a vinyl content of 10 mass%, the total vinyl content in the rubber component is 17.1 parts by mass (= 85 × (100 [mass%] - 40 [mass%]) × 30 [mass%] + 5 × (100 [mass%] - 20 [mass%]) × 20 [mass%] + 10 × 10 [mass%]).

[0016] Note that the styrene content and vinyl content in each rubber component can be measured by nuclear magnetic resonance (NMR) method. Also, regarding the total styrene content and total vinyl content in the rubber component, in the examples of this specification, they are calculated according to the above calculation formula. However, for example, they may also be analyzed from the tire by a pyrolysis gas chromatography-mass spectrometer (Py-GC / MS) or the like.

[0017] The above rubber composition contains isoprene-based rubber as a rubber component. Examples of isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc. As NR, for example, those commonly used in the tire industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those commonly used in the tire industry such as IR2200, etc. can be used. Examples of modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., examples of denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more. Among them, NR is preferred.

[0018] In 100% by mass of the rubber component, the content of the isoprene rubber is preferably 30% by mass or more, more preferably 45% by mass or more, still more preferably 55% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0019] The above rubber composition contains butadiene rubber (BR) as the rubber component. BR is not particularly limited, and for example, high cis-content BR such as BR1220 manufactured by Nippon Zeon Co., Ltd., BR150B manufactured by Ube Industries, Ltd., BR1280 manufactured by LG Chem, etc., BR containing 1,2-syndiotactic polybutadiene crystal (SPB) such as VCR412, VCR617 manufactured by Ube Industries, Ltd., butadiene rubber synthesized using a rare earth element-based catalyst (rare earth-based BR), etc., those commonly used in the tire industry can be used. These may be used alone or in combination of two or more. Among them, rare earth-based BR is preferred.

[0020] As the rare earth element-based catalyst used for the synthesis of rare earth-based BR, known ones can be used, but lanthanum series rare earth element compounds are preferred, and neodymium-containing compounds (Nd-based catalysts) are more preferred.

[0021] BR may be an oil-extended rubber extended with oil, a resin-extended rubber extended with resin, or an extended rubber extended with other softeners. These may be used alone or in combination of two or more. The softener content in these extended rubbers is not particularly limited, but is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content. The oil used for the oil-extended rubber and the resin used for the resin-extended rubber are the same as those described later. In addition, examples of other softeners include the liquid polymers described later.

[0022] BR may have a functional group introduced therein by modification to interact with a filler such as silica. Examples of the above functional groups include silicon-containing groups (-SiR3, where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, etc.), amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxy groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, etc. Note that these functional groups may have substituents. Among them, silicon-containing groups are preferred, and -SiR3 (where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)) or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is a hydroxyl group) is more preferred.

[0023] Specific examples of the compound (modifying agent) for introducing the above functional group include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, and the like.

[0024] As the BR, hydrogenated BR with hydrogen added can also be used. When the BR is hydrogenated BR, there are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be carried out by known methods and under known conditions. Usually, it is carried out under hydrogen pressure of 20 to 150 °C and 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other methods and conditions related to the production are not particularly limited, and for example, the content described in International Publication No. 2016 / 039005 can be applied. Note that as a result of hydrogen being added to the butadiene part of the BR, the hydrogenated BR has the same structure as the copolymer of ethylene and butadiene. Therefore, in the present specification, the hydrogenated BR shall include not only the hydrogenated product of the BR but also the copolymer of ethylene and butadiene.

[0025] The hydrogenation rate of the hydrogenated BR, with the total butadiene units before hydrogenation being 100 mol%, is preferably 65 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and is preferably 95 mol% or less, more preferably 92 mol% or less, still more preferably 90 mol% or less. When within the above range, the effect tends to be obtained more favorably. Note that the hydrogenation rate can be calculated from the spectral reduction rate of the unsaturated bond part of the spectrum obtained by measuring 1H-NMR. 1 It can be calculated from the spectral reduction rate of the unsaturated bond part of the spectrum obtained by measuring 1H-NMR.

[0026] The cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, still more preferably 97% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the cis content of BR can be measured by infrared absorption spectroscopy.

[0027] In addition, the above-mentioned cis content of BR means the cis content of the BR when there is one type of BR, and means the average cis content when there are multiple types. 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, in 100% by mass of the rubber component, when BR with a cis content of 90% by mass is 20% by mass and BR with a cis content of 40% by mass is 10% by mass, the average cis content of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0028] In 100% by mass of the rubber component, the content of BR is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and is preferably 45% by mass or less, more preferably 35% by mass or less, still more preferably 25% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0029] In the above rubber composition, the value of the content of BR / total styrene amount in the rubber component is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more, particularly preferably 6 or more, and is preferably 20 or less, more preferably 15 or less, still more preferably 12 or less, particularly preferably 9 or less. When within the above range, the effect tends to be obtained more favorably. In this relationship, the content of BR and the total styrene amount in the rubber component are the contents (unit: mass%) in 100% by mass of the rubber component.

[0030] The above rubber composition contains styrene-butadiene rubber (SBR) as the rubber component. The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. Examples of commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc.

[0031] The styrene content of the SBR is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 18% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0032] The vinyl content of the SBR is preferably 2% by mass or more, more preferably 6% by mass or more, still more preferably 10% by mass or more, and is preferably 35% by mass or less, more preferably 25% by mass or less, still more preferably 15% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0033] In addition, the styrene content of the above-mentioned 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. The average styrene content of the SBR can be calculated by {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBRs. For example, in 100% by mass of the rubber component, when the SBR with a styrene content of 40% by mass is 85% by mass and the SBR with a styrene content of 25% by mass is 5% by mass, the average styrene content of the SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0034] Also, the above-mentioned vinyl content of the SBR is the ratio of vinyl bonds when the total mass of the butadiene part in the SBR is 100 (unit: mass%), and vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. When there is one type of SBR, it means the vinyl content of the 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, if there are 75 parts by mass of SBR with a styrene content of 40 mass% and a vinyl content of 30 mass%, 15 parts by mass of SBR with a styrene content of 25 mass% and a vinyl content of 20 mass%, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28 mass% (={75×(100 [mass%]-40 [mass%])×30 [mass%]+15×(100 [mass%]-25 [mass%])×20 [mass%])} / {75×(100 [mass%]-40 [mass%])+15×(100 [mass%]-25 [mass%])}).

[0035] The glass transition temperature (Tg) of SBR is preferably -15°C or lower, more preferably -25°C or lower, and is also preferably -90°C or higher, more preferably -80°C or higher. When within the above range, the effect tends to be obtained more favorably. The glass transition temperature of SBR is a value measured under the condition of a heating rate of 10°C / min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. in accordance with JIS-K7121.

[0036] As SBR, hydrogenated SBR to which hydrogen is added can also be used. When SBR is hydrogenated SBR, there are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be carried out by known methods and under known conditions. Usually, it is carried out under hydrogen pressurization of 20 to 150°C and 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other methods and conditions related to production are not particularly limited either. For example, the content described in the above-mentioned International Publication No. 2016 / 039005 can be applied. Note that as a result of hydrogen being added to the butadiene part of SBR, hydrogenated SBR has the same structure as a copolymer of ethylene, butadiene, and styrene. Therefore, in the present specification, hydrogenated SBR is considered to include not only hydrogenated products of copolymers of butadiene and styrene (SBR), but also copolymers of ethylene, butadiene, and styrene.

[0037] The hydrogenation rate of the hydrogenated SBR, with the total butadiene units before hydrogenation being 100 mol%, is preferably 65 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and is preferably 95 mol% or less, more preferably 92 mol% or less, still more preferably 90 mol% or less. When within the above range, the effect tends to be obtained more favorably. In addition, the hydrogenation rate 1 can be calculated from the spectral reduction rate of the unsaturated bond part of the spectrum obtained by measuring 1H-NMR.

[0038] The SBR may be an oil-extended rubber extended with oil, a resin-extended rubber extended with resin, or an extended rubber extended with other softening agents. These may be used alone or in combination of two or more. The softening agent content in these extended rubbers is not particularly limited, but is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content. The oil used for the oil-extended rubber and the resin used for the resin-extended rubber are the same as those described later. In addition, examples of other softening agents include the liquid polymers described later.

[0039] The SBR may have functional groups introduced therein that interact with fillers such as silica by modification. Examples of the functional group include, for example, a silicon-containing group (-SiR3, where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, etc.), an amino group, an amide group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxy group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have substituents. Among them, a silicon-containing group is preferred, and -SiR3 (where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)) or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is a hydroxyl group) is more preferred.

[0040] Specific examples of the compound (modifying agent) for introducing the above functional group include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc.

[0041] In 100% by mass of the rubber component, the content of SBR is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and is preferably 45% by mass or less, more preferably 35% by mass or less, still more preferably 25% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0042] In the above rubber composition, the value of the content of BR / the content of SBR is preferably 0.2 or more, more preferably 0.4 or more, still more preferably 0.6 or more, and particularly preferably 0.8 or more. Also, it is preferably 3 or less, more preferably 2 or less, still more preferably 1.5 or less, and particularly preferably 1 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the content of BR and the content of SBR are the contents (unit: mass%) in 100% by mass of the rubber component.

[0043] In the above rubber composition, the value of the content of isoprene rubber / (the content of BR + the content of SBR) is preferably 0.6 or more, more preferably 0.8 or more, still more preferably 1 or more, and particularly preferably 1.2 or more. Also, it is preferably 4 or less, more preferably 2.5 or less, still more preferably 2 or less, and particularly preferably 1.5 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the content of isoprene rubber, the content of BR, and the content of SBR are the contents (unit: mass%) in 100% by mass of the rubber component.

[0044] Examples of rubber components other than isoprene rubber, BR, and SBR include diene rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more.

[0045] The rubber components other than isoprene rubber, BR, and SBR may be oil-extended rubbers extended with oil, resin-extended rubbers extended with resin, or extended rubbers extended with other softeners. These may be used alone or in combination of two or more. The softening agent content in these extended rubbers is not particularly limited, but is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content. The oil used in oil-extended rubber and the resin used in resin-extended rubber are the same as those described later. In addition, examples of other softening agents include liquid polymers and the like described later.

[0046] Rubber components other than isoprene-based rubber, BR, and SBR may have functional groups introduced that interact with fillers such as silica by modification. Examples of the above functional groups include silicon-containing groups (-SiR3, where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, etc.), amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxy groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, etc. These functional groups may have substituents. Among them, silicon-containing groups are preferred, and -SiR3 (where R is the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)) or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is a hydroxyl group) is more preferred.

[0047] Specific examples of the compound (modifying agent) for introducing the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, and the like.

[0048] The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum, or may be recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene and recycled aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0049] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0050] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. The method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical of biological conversion, and examples of chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0051] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers 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.

[0052] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10.

[0053] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the modern standard reference, and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value is described below.

[0054] In one mole (6.02×10 23 pieces) of carbon atoms, there are about 6.02×10 11 pieces of 14 C, which is about one trillionth of ordinary carbon atoms. 14 14 14 C is called a radioactive isotope, and its half-life is 5730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 C elements contained in them at the time of fixation have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 C elements at all. Therefore, chemical substances produced from these fossil fuels also do not contain

[0055] On the one hand, 14 C is constantly generated by nuclear reactions of cosmic rays in the atmosphere, and the balance between the continuous generation and the decrease due to radioactive decay results in a constant amount of 14 C in the Earth's atmospheric environment. Therefore, the 14 C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the total

[0056] This 14 C is generally measured as follows. 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. In the measurement, 14 As the modern standard reference for the concentration of 14 C, the 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific standard substance, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific activity of carbon in this oxalic acid (the 13 C radioactive intensity per gram of carbon) is separated for each carbon isotope, and for 14 C, it is corrected to a constant value and the value after decay correction from 1950 AD to the measurement date is used as the standard

[0057] Therefore, if the rubber is made of a 100% biomass (natural-based) material, although there are regional differences, it will show a value of approximately 110 pMC (currently, in the normal state, it often does not reach 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the 14 C concentration, it will show almost 0 pMC (for example, 0.3 pMC). This value corresponds to the biomass ratio of 0% mentioned above.

[0058] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable in terms of environmental protection.

[0059] The above rubber composition may contain a thermoplastic elastomer as an elastomer other than the rubber component. The thermoplastic elastomer is a copolymer (block copolymer) composed of a hard segment that plays the role of crosslinking points and a soft segment that exhibits rubber elasticity, and is usually solid at room temperature (25°C).

[0060] Examples of the hard segment include polystyrene, polypropylene, polyester, polyamide, polyvinyl chloride, polyurethane, etc., and examples of the soft segment include vinyl-polybutadiene, polyisoprene, polybutadiene, polyethylene, polychloroprene, poly-2,3-dimethylbutadiene, etc. These may be of one kind or two or more kinds.

[0061] The thermoplastic elastomer may be used alone or in combination of two or more. As commercially available products, products of Kuraray Co., Ltd., Asahi Kasei Corporation, etc. can be used. In this specification, the thermoplastic elastomer is not included in the rubber component.

[0062] The thermoplastic elastomer is preferably a thermoplastic elastomer having a styrene block (styrene-based thermoplastic elastomer). Specific examples of styrenic thermoplastic elastomers include styrene-vinyl isoprene-styrene triblock copolymer (SIS), styrene-isobutylene diblock copolymer (SIB), styrene-butadiene-styrene triblock copolymer (SBS), styrene-ethylene·butylene-styrene triblock copolymer (SEBS), styrene-ethylene·propylene-styrene triblock copolymer (SEPS), styrene-ethylene·ethylene·propylene-styrene triblock copolymer (SEEPS), styrene-butadiene·butylene-styrene triblock copolymer (SBBS), and the like. These may be used alone or in combination of two or more. Among them, copolymers having styrene blocks at both ends are preferred, and styrene-ethylene·propylene-styrene triblock copolymer (SEPS) is more preferred. Note that SEPS may be hydrogenated SIS obtained by adding hydrogen to styrene-vinyl isoprene-styrene triblock copolymer (SIS).

[0063] The styrene content of the styrenic thermoplastic elastomer is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0064] The content of the thermoplastic elastomer is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

[0065] The above rubber composition contains two or more kinds of fillers. Examples of the filler include silica, carbon black, vulcanized rubber particles, aluminum hydroxide, talc, calcium compounds, short fibers, and the like. Among them, silica and carbon black are preferred. Also, it is preferable to use in combination one or more kinds of silica and one or more kinds of carbon black.

[0066] The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of the silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, or it may be a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more. As commercially available products, products of Evonik, Tosoh Silica Corporation, Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0067] Silica using a biomass material as a raw material can be obtained, for example, by extracting a silicate from rice husk ash obtained by burning rice husk using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0068] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter media such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0069] When silica crystallizes, it is insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0070] Amorphous silica extracted from rice husk can be those commercially available from Wilmar Co., Ltd. and the like.

[0071] The average particle diameter of the silica is preferably 24 nm or less, more preferably 18 nm or less, still more preferably 17 nm or less, and is also preferably 6 nm or more, more preferably 9 nm or more, still more preferably 12 nm or more. When it is within the above range, the effect tends to be obtained more favorably.

[0072] In addition, in this specification, the method for measuring the average particle diameter of silica uses transmission electron microscope (TEM) observation. Specifically, photograph the silica particles with a transmission electron microscope. When the shape of the particles is spherical, the diameter of the sphere is taken as the particle diameter. When the shape is needle-like or rod-like, the minor axis is taken as the particle diameter. When the shape is amorphous, the average particle diameter from the center is taken as the particle diameter, and the average value of the particle diameters of 100 fine particles is taken as the average particle diameter.

[0073] The content of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and is also preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, with respect to 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0074] In the above rubber composition, the value of the content of silica / the total styrene amount in the rubber component is preferably 2 or more, more preferably 5 or more, still more preferably 6 or more, even more preferably 7 or more, particularly preferably 8 or more, and is also preferably 20 or less, more preferably 15 or less, still more preferably 12 or less, even more preferably 10 or less, particularly preferably 9 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the content of silica is the content (unit: part by mass) with respect to 100 parts by mass of the rubber component, and the total styrene amount is the content (unit: mass%) in 100 mass% of the rubber component.

[0075] In the above rubber composition, the value of the content of SBR / the content of silica is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, and particularly preferably 0.8 or more. Also, it is preferably 4 or less, more preferably 2.5 or less, still more preferably 1.5 or less, and particularly preferably 1 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the content of SBR is the content (unit: mass%) in 100 mass% of the rubber component, and the content of silica is the content (unit: mass part) with respect to 100 mass parts of the rubber component.

[0076] The above rubber composition contains carbon black as a filler. The carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by thermally decomposing waste tires. Also, the production method of the carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These may be used alone or in combination of two or more.

[0077] The cetyltrimethylammonium bromide (CTAB) specific surface area of the carbon black is preferably 75 m 2 / g or more, more preferably 110 m 2 / g or more, still more preferably 130 m 2 / g or more, and also preferably 220 m 2 / g or less, more preferably 200 m 2 / g or less, still more preferably 180 m 2 / g or less. The CTAB specific surface area of the carbon black is a value measured in accordance with JIS K6217-3:2001.

[0078] The content of the carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and preferably 65 parts by mass or less, more preferably 45 parts by mass or less, still more preferably 30 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0079] In the above rubber composition, the value of the content of the carbon black / the content of the SBR is preferably 0.6 or more, more preferably 0.9 or more, still more preferably 1.2 or more, and preferably 8 or less, more preferably 4 or less, still more preferably 2 or less. When within the above range, the effect tends to be obtained more favorably. In this relationship, the content of the carbon black is the content (unit: parts by mass) with respect to 100 parts by mass of the rubber component, and the content of the SBR is the content (unit: mass%) in 100 mass% of the rubber component.

[0080] In the above rubber composition, the value of the content of the silica / the carbon black is preferably 0.1 or more, more preferably 0.3 or more, still more preferably 0.5 or more, even more preferably 0.7 or more, particularly preferably 1 or more, and preferably 15 or less, more preferably 10 or less, still more preferably 5 or less, even more preferably 1.5 or less, particularly preferably 1.2 or less. When within the above range, the effect tends to be obtained more favorably. In this relationship, the content of the silica and the content of the carbon black are the contents (unit: parts by mass) with respect to 100 parts by mass of the rubber component.

[0081] The vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. defined in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. These may be used alone or in combination of two or more kinds. The vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles.

[0082] As commercially available products of vulcanized rubber particles, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used. In this specification, the vulcanized rubber particles are not included in the rubber component.

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

[0084] The content of the vulcanized rubber particles is preferably 2 parts by mass or more, more preferably 6 parts by mass or more, still more preferably 10 parts by mass or more, and is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0085] Examples of fillers other than silica include aluminum hydroxide, talc, calcium compounds, short fibers etc. These may be used alone or in combination of two or more kinds. Among them, carbon black is preferable.

[0086] In this specification, aluminum hydroxide means Al(OH)3 or Al2O3·3H2O. As commercially available products, products of Sumitomo Chemical Co., Ltd., Showa Denko K.K., Nabaltec AG, etc. can be used. These may be used alone or in combination of two or more.

[0087] The average particle diameter of aluminum hydroxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, and preferably 5 μm or less, more preferably 3 μm or less, still more preferably 1 μm or less. When within the above range, the effect tends to be obtained more favorably. In this specification, as the method for measuring the average particle diameter of aluminum hydroxide, transmission electron microscope (TEM) observation is used. Specifically, aluminum hydroxide particles are photographed with a transmission electron microscope. When the shape of the particles is spherical, the diameter of the sphere is taken as the particle diameter. When the particles are needle-shaped or rod-shaped, the minor axis is taken as the particle diameter. When the particles are amorphous, the average particle diameter from the center is taken as the particle diameter, and the average value of the particle diameters of 100 fine particles is taken as the average particle diameter.

[0088] The BET specific surface area (nitrogen adsorption specific surface area, N2SA) of aluminum hydroxide is preferably 5 m 2 / g or more, more preferably 8 m 2 / g or more, still more preferably 10 m 2 / g or more, and preferably 40 m 2 / g or less, more preferably 30 m 2 / g or less, still more preferably 20 m 2 / g or less. The BET specific surface area of aluminum hydroxide is a value measured by the BET method in accordance with ASTM D3037-81.

[0089] The content of aluminum hydroxide is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

[0090] The average particle diameter of talc is preferably 50 μm or less, more preferably 30 μm or less. The lower limit of the average particle diameter of talc is not particularly limited, but is preferably 1 μm or more.

[0091] The content of talc is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

[0092] The calcium compound is a compound having calcium, and examples thereof include inorganic salts such as calcium oxide, calcium hydroxide, and calcium carbide; oxoacid salts such as calcium carbonate, calcium nitrate, and calcium sulfate. In addition, examples of those containing a calcium compound include eggshells (main component: calcium carbonate). These may be used alone or in combination of two or more. Among them, oxoacid salts are preferred, and calcium carbonate is more preferred. In the present specification, calcium fatty acid salt is treated as a processing aid described later and is not included in the filler.

[0093] The content of the calcium compound is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

[0094] As the short fibers, for example, organic short fibers, inorganic short fibers, etc. can be used. Specific examples of organic short fibers include nanocellulose such as cellulose nanofiber (CNF) and cellulose nanocrystal (CNC); biomass nanomaterials such as chitin nanofiber and chitosan nanofiber. Specific examples of inorganic short fibers include metal fibers and glass fiber systems. Commercially available products include products of Nippon Paper Industries Co., Ltd. and Sugino Machine Ltd. These may be used alone or in combination of two or more. Among them, organic short fibers are preferred, and nanocellulose is more preferred.

[0095] The particle size of the nanocellulose is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 25 nm or more, particularly preferably 28 nm or more, and is preferably 50 nm or less, more preferably 40 nm or less, still more preferably 35 nm or less, particularly preferably 32 nm or less. When within the above range, the effect tends to be obtained more favorably.

[0096] The particle size of the nanocellulose is the average fiber diameter measured by image analysis using a scanning electron micrograph, image analysis using a transmission electron micrograph, image analysis using an atomic force micrograph, analysis of X-ray scattering data, the pore electrical resistance method (Coulter principle method), or the like. In addition, in this specification, the average fiber diameter of the nanocellulose (cellulose fiber) is typically the average fiber diameter of an aggregate of cellulose fibers formed by an aggregate of cellulose molecules.

[0097] The content of the short fibers is preferably 1 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

[0098] The content of the filler is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and preferably 80 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 60 parts by mass or less with respect to 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0099] In the above rubber composition, the value of the content of the isoprene rubber / the content of the filler is greater than 1. The value of the content of the isoprene rubber / the content of the filler is preferably 1.05 or more, more preferably 1.1 or more, and preferably 2 or less, more preferably 1.5 or less, still more preferably less than 1.2. When within the above range, the effect tends to be obtained more favorably. In this relationship, the content of the isoprene rubber is the content (unit: mass%) in 100 mass% of the rubber component, and the content of the filler is the content (unit: parts by mass) with respect to 100 parts by mass of the rubber component.

[0100] The above rubber composition preferably contains a softening agent. A softening agent is a material that imparts plasticity to the rubber component, and is a concept including both a softening agent that is liquid (liquid state) at room temperature (25 ° C) and a softening agent that is solid at room temperature (25 ° C). Examples of the softening agent include resins, oils, liquid polymers, ester plasticizers, and the like. Among them, resins and oils are preferred. These softening agents may be derived from petroleum, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Further, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires or products containing various components may be used as softening agents. These softening agents may be used alone or in combination of two or more.

[0101] As the resin, for example, resins such as C5-based resins, C5 / C9-based resins, coumarone-indene-based resins, aromatic-based resins, terpene-based resins, cyclopentadiene-based resins, and hydrogenated products thereof can be used. These may be used alone or in combination of two or more. In the present specification, the resin may be solid or liquid at normal temperature (25°C).

[0102] The C5-based resin is a polymer containing a C5 fraction as a constituent monomer. For example, a homopolymer obtained by polymerizing one type of C5 fraction alone, a copolymer obtained by copolymerizing two or more types of C5 fractions, and a copolymer of a C5 fraction and another monomer copolymerizable therewith can also be mentioned. Examples of the C5 fraction include olefinic hydrocarbons such as 1-pentene, 2-pentene, and 2-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, and 1,3-pentadiene. These may be used alone or in combination of two or more. In the present specification, a polymer containing a C5 fraction and an aromatic monomer (C9 fraction) as constituent monomers is treated as a C5 / C9-based resin.

[0103] The content of the C5-based resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0104] The C5 / C9 resin is a polymer containing a C5 fraction and a C9 fraction as constituent monomers. For example, polymers obtained by polymerizing a petroleum-derived C5 fraction and a C9 fraction using a Friedel-Crafts type catalyst such as AlCl3 or BF3 can be mentioned. Specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. can be mentioned. In this specification, the C5 / C9 resin is treated as a resin different from aromatic resins and C5 resins.

[0105] The content of the C5 / C9 resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0106] The coumarone-indene resin is a polymer containing coumarone and indene as constituent monomers. For example, in addition to copolymers of coumarone and indene, copolymers of coumarone and indene with other monomers copolymerizable therewith can also be mentioned.

[0107] The content of the coumarone-indene resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0108] The aromatic resin is a polymer containing an aromatic monomer as a constituent monomer. For example, homopolymers obtained by polymerizing one type of aromatic monomer alone, copolymers obtained by copolymerizing two or more types of aromatic monomers, and copolymers of aromatic monomers and other monomers copolymerizable therewith can also be mentioned.

[0109] Examples of aromatic monomers include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene; phenol monomers such as phenol, alkylphenol, alkoxyphenol; naphthol monomers such as naphthol, alkylnaphthol, alkoxynaphthol; coumarone, indene, and the like. These may be used alone or in combination of two or more. Among them, styrene monomers are preferred, and styrene and α-methylstyrene are more preferred.

[0110] Examples of other monomers include non-conjugated olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene. These may be used alone or in combination of two or more.

[0111] The aromatic resin is preferably an α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of styrene and α-methylstyrene, etc.), and more preferably a styrene-α-methylstyrene resin (copolymer of styrene and α-methylstyrene).

[0112] The content of the aromatic resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0113] The terpene resin is a polymer containing a terpene compound (terpene monomer) as a constituent monomer. Examples include homopolymers obtained by polymerizing one type of terpene compound alone, copolymers obtained by copolymerizing two or more terpene compounds, and copolymers of a terpene compound and other monomers copolymerizable therewith.

[0114] Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives represented by the composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. These may be used alone or in combination of two or more.

[0115] The terpene resin is preferably a homopolymer obtained by polymerizing one kind of terpene compound alone, or a copolymer of a terpene compound and an aromatic monomer. Furthermore, when the terpene resin is a homopolymer formed by polymerizing one type of terpene compound alone, β-pinene is preferred, and when the terpene resin is a copolymer of a terpene compound and an aromatic monomer, a copolymer of a terpene compound and styrene (terpene styrene resin) is preferred. In this specification, a polymer containing a terpene compound and an aromatic monomer as constituent monomers, such as a terpene styrene resin, is treated as a terpene resin rather than an aromatic resin.

[0116] The amount of the terpene resin is preferably at least 1 part by mass, more preferably at least 3 parts by mass, and even more preferably at least 5 parts by mass, and is preferably at most 30 parts by mass, more preferably at most 20 parts by mass, and even more preferably at most 10 parts by mass, based on 100 parts by mass of the rubber component. Within the above ranges, the effect tends to be better obtained.

[0117] Cyclopentadiene-based resins are polymers containing cyclopentadiene-based monomers as constituent monomers. For example, homopolymers obtained by polymerizing one type of cyclopentadiene-based monomer alone, copolymers obtained by copolymerizing two or more types of cyclopentadiene-based monomers, and copolymers of cyclopentadiene-based monomers and other monomers copolymerizable therewith are also included.

[0118] Examples of cyclopentadiene-based monomers include cyclopentadiene, dicyclopentadiene, tricyclopentadiene, etc. These may be used alone or in combination of two or more. Among them, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a polymer (DCPD-based resin) containing dicyclopentadiene (DCPD) as a constituent monomer, and a hydrogenated DCPD-based resin is more preferred.

[0119] The content of the cyclopentadiene-based resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0120] The resin is preferably a modified resin (functionalized resin) into which a functional group has been introduced. The modified resin can be produced by known methods. For example, it can be prepared by a slurry method, a metathesis method, etc. Specifically, for example, it can be produced by reacting a polymer serving as the polymer skeleton of the modified resin with a functional compound capable of introducing a functional group by a known method.

[0121] The polymer serving as the polymer backbone is not particularly limited, and for example, it may be the above-mentioned C5 resin, aromatic resin, terpene resin, or other resins. 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.

[0122] As the functional group, a functional group containing at least one element selected from the group consisting of oxygen, silicon, and nitrogen is preferred, and a functional group containing silicon is more preferred.

[0123] The content of the modified resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0124] Examples of commercially available products of the above-mentioned resins include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc.

[0125] The content of the resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0126] In the above rubber composition, the value of the resin content / silica content is preferably 0.05 or more, more preferably 0.15 or more, still more preferably 0.2 or more, and is preferably 0.5 or less, more preferably 0.35 or less, still more preferably 0.24 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the contents of the resin and silica are the contents (unit: parts by mass) with respect to 100 parts by mass of the rubber component.

[0127] In the above rubber composition, the value of the resin content / total styrene amount in the rubber component is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 1 or more, particularly preferably 1.5 or more, and is preferably 4 or less, more preferably 3 or less, still more preferably 2 or less, particularly preferably 1.8 or less. When it is within the above range, the effect tends to be obtained more favorably. In this relationship, the resin content is the content (unit: parts by mass) with respect to 100 parts by mass of the rubber component, and the total styrene amount in the rubber component is the content (unit: mass%) in 100 mass% of the rubber component.

[0128] The liquid polymer is a (co)polymer in a liquid state at normal temperature (25°C), and examples thereof include liquid rubber and liquid resin. Among them, liquid resin is preferred. In addition, the liquid polymer may be subjected to a modification treatment or a hydrogenation treatment. As commercially available products, products of Cray Valley, Kuraray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0129] The weight average molecular weight (Mw) of the liquid polymer is less than 10,000, preferably 9,000 or less, more preferably 6,000 or less, still more preferably 4,500 or less, and is preferably 100 or more, more preferably 1,000 or more, still more preferably 2,000 or more. When it is within the above range, the effect tends to be obtained more favorably. In the present specification, the liquid polymer is not included in the rubber component.

[0130] As the liquid rubber, at least one diene-based (co)polymer selected from the group consisting of butadiene, isoprene, styrene, farnesene and their derivatives can be used. Specific examples include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid farnesene polymer, liquid farnesene-butadiene copolymer and other liquid diene-based polymers. Among them, liquid BR is preferred.

[0131] The liquid rubber may be modified with a functional group that interacts with silica, and the terminal and / or main chain may be modified with a functional group containing at least one element selected from the group consisting of oxygen, nitrogen, silicon and phosphorus. Also, the liquid rubber may be either unhydrogenated or hydrogenated.

[0132] The content of the liquid rubber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0133] The liquid resin is a resin that is liquid at normal temperature (25°C), and the above-mentioned types of resins can be used. One type of liquid resin may be used alone, or two or more types of liquid resins may be used in combination.

[0134] The content of the liquid resin is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0135] The content of the liquid polymer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0136] Examples of the oil include process oil, vegetable oil, animal oil, etc. Among them, vegetable oil is preferred. Examples of the process oil include paraffinic process oil (mineral oil), naphthenic process oil, aromatic process oil, etc. Specific examples of the process oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, a process oil with a low content of polycyclic aromatic compound (PCA) can be used for environmental measures. Examples of the low-PCA-content process oil include MES, TDAE, heavy naphthenic oil, etc. Also, from the perspective of life cycle assessment, waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a cooking shop may be used.

[0137] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran 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, grape seed oil, wood rosin, and the like. Further, as vegetable oils, there may be mentioned refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, waste edible oils recovered from those used as edible oils, and the like. Note that the vegetable oil may be liquid or solid at normal temperature (25°C). These may be used alone or in combination of two or more kinds.

[0138] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, or the like. Also, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0139] The method for confirming whether the acylglycerol is contained in the rubber composition is not particularly limited, but 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at normal temperature (25°C) for 24 hours. After removing the rubber composition, at room temperature 1When measuring 1H-NMR and setting the signal of tetramethylsilane (TMS) to 0.00 ppm, signals around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm were observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0140] The fatty acid is not particularly limited and may be 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.

[0141] Among them, it is desirable that the fatty acid contains a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, genome editing, etc.

[0142] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0143] The content of the vegetable oil is preferably 1 part or more, more preferably 3 parts or more, still more preferably 5 parts or more, and preferably 30 parts or less, more preferably 20 parts or less, still more preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0144] As commercially available oils, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orysoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0145] The oil content is preferably 1 part or more, more preferably 3 parts or more, still more preferably 5 parts or more, and preferably 30 parts or less, more preferably 20 parts or less, still more preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0146] The ester plasticizer is not particularly limited as long as it is a compound having an ester group in a liquid state at normal temperature (25°C). Examples include phthalic acid derivatives, long-chain fatty acid derivatives, phosphoric acid derivatives, sebacic acid derivatives, adipic acid derivatives, etc. These may be used alone or in combination of two or more. Among them, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives are preferred, and sebacic acid derivatives are more preferred. The phthalic acid derivatives are not particularly limited, and examples include phthalic acid esters such as di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). The long-chain fatty acid derivatives are not particularly limited, and examples include long-chain fatty acid glycerol esters. The phosphoric acid derivatives are not particularly limited, and examples include phosphoric acid esters such as tris(2-ethylhexyl) phosphate (TOP) and tributyl phosphate (TBP). The sebacic acid derivatives are not particularly limited, and examples include sebacic acid esters such as di(2-ethylhexyl) sebacate (DOS) and diisooctyl sebacate (DIOS). The adipic acid derivatives are not particularly limited, and examples include adipic acid esters such as di(2-ethylhexyl) adipate (DOA) and diisooctyl adipate (DIOA). Among them, phosphate esters, sebacic acid esters, and adipic acid esters are preferred, and sebacic acid esters are more preferred. Also, as specific compounds, TOP, DOS, and DOA are preferred, and DOS is more preferred. As the ester plasticizer, for example, products of Daihachi Chemical Industry Co., Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0147] The glass transition temperature (Tg) of the ester plasticizer is preferably -110 °C or higher, more preferably -100 °C or higher, still more preferably -80 °C or higher, and preferably -20 °C or lower, more preferably -40 °C or lower, still more preferably -55 °C or lower. By setting it within the above range, there is a tendency to more suitably obtain the above effects. In this specification, the glass transition temperature of the ester plasticizer is a value measured using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. in accordance with JIS-K7121 under the condition of a heating rate of 10 °C / min.

[0148] The content of the ester plasticizer is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

[0149] The content of the softening agent is preferably 1 part or more, more preferably 3 parts or more, still more preferably 5 parts or more, and preferably 30 parts or less, more preferably 20 parts or less, still more preferably 10 parts or less with respect to 100 parts by mass of the rubber component. When it is within the above range, there is a tendency to obtain better effects.

[0150] In the above rubber composition, the value of the content of the softening agent / the content of the filler is preferably 0.04 or more, more preferably 0.08 or more, still more preferably 0.1 or more, and preferably 1.5 or less, more preferably 1.2 or less, still more preferably 0.7 or less, particularly preferably 0.3 or less. When it is within the above range, there is a tendency to obtain better effects. In this relationship, the contents of the softening agent and the filler are the contents (unit: part by mass) with respect to 100 parts by mass of the rubber component.

[0151] The above rubber composition preferably contains a silane coupling agent. The silane coupling agent is not particularly limited. 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,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide and other sulfide-based ones, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and other mercapto-based ones, vinyltriethoxysilane, vinyltrimethoxysilane and other vinyl-based ones, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane and other amino-based ones, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and other glycidoxy-based ones, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane and other nitro-based ones, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane and other chloro-based ones can be mentioned. As commercially available products, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0152] In addition, as the mercapto-based silane coupling agent, in addition to the compound having a mercapto group, a compound having a structure in which the mercapto group is protected by a protecting group (for example, the compound represented by the following formula (S1)) can also be used.

[0153] Particularly preferred mercapto-based silane coupling agents include a silane coupling agent represented by the following formula (S1), and a silane coupling agent containing a bonding unit A represented by the following formula (I) and a bonding unit B represented by the following formula (II).

Chemical formula

Chemical formula

Chemical formula

[0154] In formula (S1), R 1005 , R 1006 , R 1007 and R 1008 are each independently preferably a group selected from the group consisting of linear, cyclic or branched alkyl groups, alkenyl groups, aryl groups and aralkyl groups having 1 to 18 carbon atoms. Further, when R 1002 is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of linear, cyclic or branched alkyl groups, alkenyl groups, aryl groups and aralkyl groups. R 1009 is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R 1004 may be, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, a cycloalkylalkylene group having 6 to 18 carbon atoms, an arylene group having 6 to 18 carbon atoms, or an aralkylene group having 7 to 18 carbon atoms. The alkylene group and the alkenylene group may be either linear or branched, and the cycloalkylene group, the cycloalkylalkylene group, the arylene group and the aralkylene group may have a functional group such as a lower alkyl group on the ring. This R 1004As for this, an alkylene group having 1 to 6 carbon atoms is preferable, and particularly a linear alkylene group such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group is preferable.

[0155] R in formula (S1) 1002 , R 1005 , R 1006 , R 1007 and R 1008 Specific examples of R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, a phenethyl group, a naphthylmethyl group, and the like. Examples of R in formula (S1) 1009 As the linear alkylene group, a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a hexylene group, etc. can be mentioned, and as the branched alkylene group, an isopropylene group, an isobutylene group, a 2-methylpropylene group, etc. can be mentioned.

[0156] Specific examples of the silane coupling agent represented by the formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, and the like. These may be used alone or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

[0157] In the silane coupling agent containing the bonding unit A represented by the formula (I) and the bonding unit B represented by the formula (II), the content of the bonding unit A is preferably 30 mol% or more, more preferably 50 mol% or more, preferably 99 mol% or less, and more preferably 90 mol% or less. Also, the content of the bonding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, and still more preferably 55 mol% or less. Further, the total content of the bonding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. Note that the contents of the bonding units A and B are amounts including the case where the bonding units A and B are located at the ends of the silane coupling agent. The form when the bonding units A and B are located at the ends of the silane coupling agent is not particularly limited as long as it forms a unit corresponding to the formulas (I) and (II) representing the bonding units A and B.

[0158] R in the formulas (I) and (II)11 Regarding this, examples of the halogen include chlorine, bromine, fluorine, etc. Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms include a methyl group, an ethyl group, etc. Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms include a vinyl group, a 1-propenyl group, etc. Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms include an ethynyl group, a propynyl group, etc.

[0159] R in formulas (I) and (II) 12 Regarding this, examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms include an ethylene group, a propylene group, etc. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include a vinylene group, a 1-propenylene group, etc. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group, a propynylene group, etc.

[0160] In the silane coupling agent containing the bonding unit A represented by formula (I) and the bonding unit B represented by formula (II), the total number of repetitions (v + w) of the number of repetitions (v) of the bonding unit A and the number of repetitions (w) of the bonding unit B is preferably in the range of 3 to 300.

[0161] The content of the silane coupling agent is preferably 4 parts by mass or more, more preferably 8 parts by mass or more, still more preferably 12 parts by mass or more, and preferably 25 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, based on 100 parts by mass of silica. When within the above range, the effect tends to be obtained more favorably.

[0162] The above rubber composition may contain a processing aid. Examples of the processing aid include metal salts (compounds in which the hydrogen atom of an acid is replaced by a metal ion), fatty acid amides, amide esters, fatty acid esters, etc. These may be used alone or in combination of two or more.

[0163] Examples of the metal used in the metal salt include alkali metals such as potassium and sodium, and alkaline earth metals such as calcium and barium. Magnesium, zinc, nickel, molybdenum, etc. can also be used.

[0164] Examples of the acid used in the metal salt include fatty acids such as lauric acid, myristic acid, and palmitic acid. Boric acid, carbonic acid, hydrochloric acid, nitric acid, sulfuric acid, etc. can also be used.

[0165] As commercially available products of the processing aid, products of Kinoshita Chemical Co., Ltd., Ken-ei Pharmaceutical Co., Ltd., Struktol, Performance Additives, etc. can be used.

[0166] The content of the processing aid is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0167] The above rubber composition may contain an antioxidant. The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as 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), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used. These may be used alone or in combination of two or more.

[0168] The content of the anti-aging agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 2.5 parts by mass or more, and preferably 15 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0169] The above rubber composition may contain wax. The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, plant-derived waxes, etc. can be mentioned. Among them, petroleum waxes and plant-derived waxes are preferred, and petroleum waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramoelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0170] The content of the wax is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0171] The above rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used, and as commercially available products, products of NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0172] The content of stearic acid is preferably 1 part by mass or more, more preferably 2.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0173] The above rubber composition may contain zinc oxide. As zinc oxide, conventionally known ones can be used. As commercially available products, products of 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. These may be used alone or in combination of two or more.

[0174] The content of zinc oxide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0175] The above rubber composition may contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used as crosslinking agents in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0176] The content of sulfur is preferably 0.5 part by mass or more, more preferably 0.9 part by mass or more, still more preferably 1.2 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0177] The above rubber composition preferably contains a dibenzylamine compound. The dibenzylamine compound is a compound having at least one group (dibenzylamine group) represented by the following formula.

Chemical formula

[0178] Specific examples of the dibenzylamine compound include dibenzylamine, tetrabenzylthiuram disulfide (TBzTD), zinc dibenzyldithiocarbamate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and the like. As commercially available products, products of Sanshin Chemical Industry Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Rancess Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, a compound having two dibenzylamine groups is preferable, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is more preferable.

[0179] The content of the dibenzylamine compound is preferably 0.4 parts by mass or more, more preferably 0.8 parts by mass or more, still more preferably 1 part by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less with respect to 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained better.

[0180] The above rubber composition may contain a dialkyldithiophosphate compound. As the dialkyldithiophosphate compound, for example, salts of dialkyldithiophosphoric acid with metals such as zinc and molybdenum can be used. As commercially available products, products such as TP-50 manufactured by Rhein Chemie can be used. These may be used alone or in combination of two or more. Among them, the compound represented by the following formula (1) (zinc dialkyldithiophosphate) is preferable.

Chemical formula

[0181] In formula (1), R 1 ~R 4Examples of the linear or branched alkyl group represented by [it] include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a 4-methylpentyl group, a 2-ethylhexyl group, an octyl group, an octadecyl group, etc. On the other hand, examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, etc. Among them, from the viewpoint of easy dispersion in the rubber composition and easy production, R 1 ~R 4 is preferably a linear or branched alkyl group having 2 to 8 carbon atoms, more preferably an n-butyl group, an n-propyl group, an iso-propyl group, or an n-octyl group, and even more preferably an n-butyl group.

[0182] The content of the dialkyldithiophosphate compound is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

[0183] The above rubber composition may contain a vulcanization accelerator. Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyldisulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. As commercially available products, products of Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0184] The content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 1.4 parts by mass or more, and preferably 15 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0185] In addition to the above components, the rubber composition may further contain additives generally used in the tire industry, such as organic peroxides. The content of these additives is preferably 0.1 to 200 parts by mass based on 100 parts by mass of the rubber component.

[0186] In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the above-mentioned blend from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0187] The rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing.

[0188] As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Further, the composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0189] The above rubber composition can be used (as a rubber composition for tires) in tire members such as, for example, treads, sidewalls, undertreads, shoulders, clinches, bead apexes, breaker cushion rubbers, carcass cord coating rubbers, insulations, chafers, inner liners, etc., and side reinforcing layers of run-flat tires. Among them, it is suitable for treads. Further, when the tread has a multilayer structure, it can be used for either the surface layer (cap tread) or the inner layer (base tread), but it is particularly suitable for the cap tread.

[0190] The tire of the present disclosure is manufactured by a normal method using the above rubber composition. That is, the above rubber composition is extruded in a shape such as a tread at the unvulcanized stage, and together with other tire members, it is formed by a normal method on a tire molding machine to form an unvulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

[0191] The above tire (such as a pneumatic tire) can be used for passenger car tires; heavy-duty tires (truck and bus tires); motorcycle tires; high-performance tires; winter tires such as studless tires; run-flat tires having a side reinforcing layer; tires with a sound-absorbing member such as sponge provided in the tire cavity; tires with a sealing member having a sealant that can be sealed when punctured provided inside the tire or in the tire cavity; tires with electronic components such as sensors and wireless tags provided inside the tire or in the tire cavity, etc., and is suitable for heavy-duty tires.

[0192] The size of the above tire is not particularly limited. For example, the tire width can be appropriately selected within the range of 100 to 400 mm, the aspect ratio within the range of 25 to 85%, and the rim diameter within the range of 10 to 25 inches. Specific examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 135 / 45R21, 145 / 45R21, 155 / 45R18, 165 / 45R22, 175 / 45R23, 185 / 60R20, 195 / 55R14, 205 / 40R16, 215 / 40R16, 225 / 40R17, 235 / 40R17, 245 / 40R16, 255 / 40R17, 265 / 40R17, 275 / 35R18, 285 / 30R19, 295 / 45R20, etc.

Example

[0193] Hereinafter, examples (embodiments) considered preferable for implementation are shown, but the scope of the present invention is not limited to the embodiments.

[0194] The various chemicals used in the examples and comparative examples will be described below.

[0195] (Rubber component) NR: TSR20 BR: Buna CB24 manufactured by LANXESS (cis content: 96% by mass, vinyl content: 0.7% by mass) SBR1: JSR1502 manufactured by JSR Corporation (styrene content: 23.5% by mass, vinyl content: 16% by mass, Tg: -56°C) SBR2: SYNTION 1810 manufactured by Synthos (styrene content: 18% by mass, vinyl content: 10% by mass, Tg: -75°C)

[0196] (Chemicals other than rubber components) Carbon black 1: N220 (CTAB specific surface area: 111 m 2 / g) Carbon black 2: N330 (CTAB specific surface area: 78 m 2 / g) Carbon black 3: N134 (CTAB specific surface area: 142 m 2 / g) Silica: Ultrasil VN3 manufactured by Evonik Industries AG (average particle size: 17 nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Industries AG Oil 1: VIVATEC 500 (aromatic process oil) manufactured by H&R Oil 2: Nisshin Soybean Refined Oil manufactured by Nisshin Oillio Group, Ltd. Liquid rubber: Ricon 134 (liquid BR) manufactured by Cray Valley Resin: Sylvatraxx 4401 (styrene α-methylstyrene resin (copolymer of styrene and α-methylstyrene)) manufactured by Arizona Chemical Liquid resin: Ricon 340 (C5 / C9 resin) manufactured by Cray Valley Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Dibenzylamine compound: Vulcuren VP KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Rancess Vulcanization accelerator: Nocceler NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0197] (Examples and Comparative Examples) According to the compounding ingredients shown in Tables 1 to 3, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur, vulcanization accelerator, and dibenzylamine compound were kneaded at 150 °C for 5 minutes to obtain a kneaded product. Next, sulfur, vulcanization accelerator, and dibenzylamine compound were added to the kneaded product, and it was kneaded using an open roll at 80 °C for 5 minutes to obtain an unvulcanized rubber composition. Next, the unvulcanized rubber composition was molded into the shape of a cap tread, laminated together with other tire members to form an unvulcanized tire, and press-vulcanized at 150 °C for 12 minutes to manufacture a test tire (heavy-duty tire, size: 295 / 80R22.5). The test tires manufactured in this way were examined, and the results calculated based on the following evaluation methods are shown in Tables 1 to 3.

[0198] Also, in the following evaluation methods, the evaluation criteria for calculating the index are as follows. Table 1: Comparative Example 1 Table 2: Comparative Example 5 Table 3: Comparative Example 6

[0199] (Crack resistance performance) Each test tire was mounted on all the wheels of a 10-ton loaded truck loaded to the maximum load capacity, driven for a predetermined distance, and then the state (depth, number, length) of the cracks at the groove bottom was evaluated, and the index was displayed with the evaluation criteria as 100. The larger the index, the better the crack resistance performance.

[0200]

Table 1

[0201]

Table 2

[0202]

Table 3

[0203] From Tables 1 to 3, the examples have better crack resistance performance than the comparative examples.

[0204] The rubber composition for heavy-duty tires of the present invention (1) contains a rubber component including isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and two or more fillers. It is a rubber composition for heavy-duty tires in which the content of the isoprene rubber > the content of the filler.

[0205] The rubber composition for heavy-duty tires of the present invention (2) is the rubber composition for heavy-duty tires according to the present invention (1), wherein the filler includes carbon black and silica.

[0206] The rubber composition for heavy-duty tires of the present invention (3) is the rubber composition for heavy-duty tires according to the present invention (1) or (2), wherein the content of silica ≥ the content of carbon black.

[0207] The rubber composition for heavy-duty tires of the present invention (4) is a rubber composition for heavy-duty tires in any combination of the present invention (1) to (3) containing a resin.

[0208] The rubber composition for heavy-duty tires of the present invention (5) is a rubber composition for heavy-duty tires in any combination of the present invention (1) to (4) containing silica with an average particle diameter of 18 nm or less.

[0209] The rubber composition for heavy-duty tires of the present invention (6) is a rubber composition for heavy-duty tires in any combination of the present invention (1) to (5) containing carbon black with a cetyltrimethylammonium bromide specific surface area of 130 m 2 / g or more.

[0210] The rubber composition for heavy-duty tires of the present invention (7) is a rubber composition for heavy-duty tires in any combination of the present invention (1) to (6) containing a dibenzylamine compound.

[0211] The rubber composition for heavy-duty tires of the present invention (8) is a rubber composition for heavy-duty tires in any combination of the present invention (1) to (7) containing vegetable oil.

[0212] The rubber composition for heavy-duty tires of the present invention (9) is a combination of any one of the present inventions (1) to (8) in which the value of the content of the isoprene rubber / the content of the filler is less than 1.2.

[0213] The rubber composition for heavy-duty tires of the present invention (10) is a combination of any one of the present inventions (1) to (9) in which the value of the content of the butadiene rubber / the total styrene amount in the rubber component is 9 or less.

[0214] The rubber composition for heavy-duty tires of the present invention (11) is a combination of any one of the present inventions (1) to (10) in which the content of the isoprene rubber / (the content of the butadiene rubber + the content of the styrene-butadiene rubber) ≤ 1.5.

[0215] The rubber composition for heavy-duty tires of the present invention (12) is a combination of any one of the present inventions (1) to (11) in which the value of the content of the butadiene rubber / the content of the styrene-butadiene rubber is 2 or less.

[0216] The rubber composition for heavy-duty tires of the present invention (13) is a combination of any one of the present inventions (1) to (12) in which the value of the content of carbon black / the content of the styrene-butadiene rubber is 2 or less.

[0217] The rubber composition for heavy-duty tires of the present invention (14) is a combination of any one of the present inventions (1) to (13) in which the value of the content of silica / the total styrene amount in the rubber component is 12 or less.

[0218] The heavy-duty tire of the present invention (15) is a heavy-duty tire using a rubber composition which is a combination of any one of the present inventions (1) to (14).

Claims

1. A rubber composition for heavy-duty tires containing a rubber component including isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and two or more fillers, wherein the content of the isoprene rubber > the content of the filler.

2. The rubber composition for heavy-duty tires according to claim 1, wherein the filler includes carbon black and silica.

3. The rubber composition for heavy-duty tires according to claim 1 or 2, wherein the content of silica ≥ the content of carbon black.

4. The rubber composition for heavy-duty tires according to claim 1 or 2, containing a resin.

5. The rubber composition for heavy-duty tires according to claim 1 or 2, containing silica with an average particle diameter of 18 nm or less.

6. The rubber composition for heavy-duty tires according to claim 1 or 2, containing carbon black with a cetyltrimethylammonium bromide specific surface area of 130 m ２ / g or more.

7. The rubber composition for heavy-duty tires according to claim 1 or 2, containing a dibenzylamine compound.

8. The rubber composition for heavy-duty tires according to claim 1 or 2, containing vegetable oil.

9. The rubber composition for heavy-duty tires according to claim 1 or 2, wherein the value of the content of the isoprene rubber / the content of the filler is less than 1.

2.

10. The rubber composition for heavy-duty tires according to claim 1 or 2, wherein the value of the content of the butadiene rubber / the total styrene amount in the rubber component is 9 or less.

11. The rubber composition for heavy-duty tires according to claim 1 or 2, wherein the content of the isoprene rubber / (the content of the butadiene rubber + the content of the styrene-butadiene rubber) ≤ 1.

5. Claim 12 The rubber composition for a heavy-duty tire according to claim 1 or 2, wherein the value of the content of the butadiene rubber / the content of the styrene-butadiene rubber is 2 or less. Claim 13 The rubber composition for a heavy-duty tire according to claim 1 or 2, wherein the value of the content of carbon black / the content of the styrene-butadiene rubber is 2 or less. Claim 14 The rubber composition for a heavy-duty tire according to claim 1 or 2, wherein the value of the content of silica / the total styrene amount in the rubber component is 12 or less. Claim 15 A heavy-duty tire using the rubber composition according to claim 1 or 2.

Images