tire

Abstract

The present invention provides a rubber composition for tires and a tire that can improve cut resistance. [Solution] The present invention relates to a tire having a grooved tread, wherein the tread comprises a rubber composition containing a rubber component including natural rubber and an aromatic polyhydric alcohol.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Conventionally, various methods for improving cut resistance performance have been studied (see, for example, Patent Document 1). However, in recent years, further improvement of cut 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 a tire and a tire that can solve the above problems and improve cut resistance performance.

Means for Solving the Problems

[0005] The present invention relates to a tire having a tread in which grooves are formed, wherein the tread contains a rubber composition containing a rubber component containing natural rubber and an aromatic polyhydric alcohol.

Effects of the Invention

[0006] Since the present invention is a tire having a tread in which grooves are formed, and the tread contains a rubber composition containing a rubber component containing natural rubber and an aromatic polyhydric alcohol, the cut resistance performance is excellent.

Modes for Carrying Out the Invention

[0007] The tire of this disclosure is a tire having a tread with grooves formed therein, wherein the tread comprises a rubber composition containing a rubber component including natural rubber and an aromatic polyhydric alcohol.

[0008] The reason why the aforementioned effects can be obtained with the above tires is presumed to be as follows. During the mixing process, the molecular chains of natural rubber are broken, generating radicals. These radicals then chain together, causing the molecular chains of natural rubber to break and the molecular weight to decrease. In the above-mentioned tire, aromatic polyhydric alcohols release protons and act as radical scavengers by trapping the radicals generated in the molecular chains of natural rubber, thereby suppressing the decrease in molecular weight of natural rubber. The above effects are thought to improve the fracture characteristics of the rubber after vulcanization, thereby enhancing its cut resistance.

[0009] The above rubber composition contains rubber components. 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, even more preferably 250,000 or more, and also preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within this range, a better effect tends to be obtained.

[0011] In this specification, the weight-average molecular weight (Mw) can be determined by converting the measured values ​​obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalents.

[0012] The total amount of styrene in the rubber component is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. The lower limit is not particularly limited and may be 0% by mass or 5% by mass or more. When the amount is within the above range, a better effect tends to be obtained.

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

[0014] The total amount of vinyl in the rubber component is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit is not particularly limited and may be 0% by mass or 4% by mass or more. When the amount is within the above range, a better effect tends to be obtained.

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

[0016] The amounts of styrene and vinyl in each rubber component can be measured by nuclear magnetic resonance (NMR) spectroscopy. Furthermore, while the total styrene and total vinyl content in the rubber components are calculated in accordance with the above-described formulas in the examples of this specification, they may also be analyzed from the tire using, for example, a pyrolysis gas chromatograph-mass spectrometer (Py-GC / MS). Unlike physical properties such as the complex modulus of elasticity (E*), the total styrene content and other component amounts have true values ​​that do not depend on the measurement method, so it is preferable to use a measurement method that is as high-precision as possible.

[0017] The above rubber composition contains natural rubber (NR) as a rubber component. Modified NR and grafted NR can also be used. Modified NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber, while grafted NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. For example, SIR20, RSS#3, TSR20, and other types commonly used in the tire industry can be used. These may be used individually or in combination of two or more types.

[0018] The content of NR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass. It is presumed that the cut resistance performance will be improved when the content is within the above range.

[0019] Furthermore, from the viewpoint of aging resistance, the content of NR in 100% by mass of the rubber component is preferably 100% by mass or less, more preferably 70% by mass or less.

[0020] Furthermore, the above rubber composition may also contain isoprene-based rubbers other than NR as rubber components. Other isoprene-based rubbers besides NR include isoprene rubber (IR) and modified IR. The type of IR is not particularly limited; for example, IR2200 and other commonly used rubbers in the tire industry can be used. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used individually or in combination of two or more types.

[0021] The above rubber composition may contain styrene-butadiene rubber (SBR) as a rubber component. SBR is not particularly limited; for example, emulsion polymerized styrene-butadiene rubber (E-SBR) and solution polymerized styrene-butadiene rubber (S-SBR) can be used. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation. SBR may be used alone or in combination of two or more types, but it is preferable to use two or more types in combination.

[0022] The styrene content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 23.5% by mass or more, and also preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, a better effect tends to be obtained.

[0023] The vinyl content of SBR is preferably 8% by mass or more, more preferably 12% by mass or more, even more preferably 16% by mass or more, and also preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0024] The styrene content of SBR mentioned above refers to the styrene content of a single type of SBR if that type is used, and to the average styrene content if there are multiple types of SBR. The average styrene content of SBR can be calculated using the formula {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBR. For example, if 85% of the rubber component is SBR with a styrene content of 40% by mass and 5% is SBR with a styrene content of 25% by mass, the average styrene content of the SBR is 39.2% by mass (=(85 × 40 + 5 × 25) / (85 + 5)).

[0025] Furthermore, the vinyl content of SBR mentioned above is the ratio of vinyl bonds when the total mass of the butadiene portion in the SBR is set to 100 (unit: mass%), and is calculated as: vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. If there is only one type of SBR, it refers to the vinyl content of that SBR; if there are multiple types, it refers to the average vinyl content. The average vinyl content of SBR can be calculated using the formula: 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, if 100 parts by mass of rubber component, 75 parts by mass of SBR contain 40% styrene and 30% vinyl, and 25% styrene, If 15 parts by mass of SBR have a vinyl content of 20% by mass, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28% by 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%])}.

[0026] The glass transition temperature (Tg) of SBR is preferably -20°C or lower, more preferably -40°C or lower, and also preferably -80°C or higher, more preferably -60°C or higher. Within this range, better effects tend to be obtained. The glass transition temperature of SBR was measured in accordance with JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., under a heating rate of 10°C / min.

[0027] Hydrogenated SBRs, which have hydrogen added to them, can also be used as SBRs. When SBR is hydrogenated SBR, there are no particular limitations on the hydrogenation method or reaction conditions; hydrogenation can be carried out using known methods and conditions. Typically, this is done at 20-150°C, under a hydrogen pressure of 0.1-10 MPa, and in the presence of a hydrogenation catalyst. Other manufacturing methods and conditions are also not particularly limited; for example, the contents described in International Publication No. 2016 / 039005 can be applied. Furthermore, hydrogenated SBR has the same structure as a copolymer of ethylene, butadiene, and styrene as a result of hydrogen being added to the butadiene portion of SBR. Therefore, in this specification, hydrogenated SBR includes not only hydrogenated butadiene-styrene copolymers (SBR) but also copolymers of ethylene, butadiene, and styrene.

[0028] The hydrogenation rate of hydrogenated SBR is preferably 65 mol% or more, more preferably 70 mol% or more, and even more preferably 75 mol% or more, with the total butadiene units before hydrogenation being 100 mol%, and also preferably 99 mol% or less, more preferably 97 mol% or less, and even more preferably 95 mol% or less. Within the above range, better effects tend to be obtained. The hydrogenation rate is 1 It can be calculated from the spectral reduction rate of the unsaturated bond region of the spectrum obtained by measuring 1H-NMR.

[0029] SBR may be oil-stretched rubber, resin-stretched rubber, or other plasticizer-stretched rubber. These may be used individually or in combination of two or more types. The plasticizer content in these stretchable rubbers is not particularly limited, but is usually around 5 to 50 parts by mass per 100 parts by mass of rubber solids. The oil used in oil-stretchable rubbers and the resin used in resin-stretchable rubbers are the same as those described later. Other plasticizers include liquid polymers, which will be described later.

[0030] SBR may have functional groups that interact with fillers such as silica introduced through modification. Examples of the above functional groups include silicon-containing groups (-SiR3 (where R is the same or different and can be 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, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, etc. These functional groups may have substituents. Among these, silicon-containing groups are preferred, and -SiR3 (where R is the same or different and can be 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)), with at least one of R being a hydroxyl group) is more preferred.

[0031] Specific examples of compounds (modifiers) that introduce the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0032] The SBR content in 100% by mass of the rubber component is preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less. The lower limit is not particularly limited and may be 0% by mass. When the content is within the above range, a better effect tends to be obtained.

[0033] The above rubber composition may contain butadiene rubber (BR) as a rubber component. The BR is not particularly limited, and can be any BR that is common in the tire industry, such as BR1220 from Nippon Zeon Co., Ltd., BR150B from Ube Industries, Ltd., BR1280 from LG Chem, BR containing 1,2-syndiotactic polybutadiene crystals (SPB) such as VCR412 and VCR617 from Ube Industries, Ltd., or butadiene rubber synthesized using a rare earth element catalyst (rare earth BR). These may be used individually or in combination of two or more. Among these, rare earth BR is preferred.

[0034] While known rare earth element catalysts can be used for the synthesis of rare earth BRs, lanthanum series rare earth element compounds are preferred, and neodymium-containing compounds (Nd-based catalysts) are more preferred.

[0035] BR may be oil-stretched rubber, resin-stretched rubber, or other plasticizer-stretched rubber. These may be used individually or in combination of two or more types. The plasticizer content in these stretchable rubbers is not particularly limited, but is usually around 5 to 50 parts by mass per 100 parts by mass of rubber solids. The oil used in oil-stretchable rubbers and the resin used in resin-stretchable rubbers are the same as those described later. Other plasticizers include liquid polymers, which will be described later.

[0036] BR may have functional groups that interact with packing materials such as silica introduced through modification. Examples of the above functional groups include silicon-containing groups (-SiR3 (where R is the same or different and can be 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, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, etc. These functional groups may have substituents. Among these, silicon-containing groups are preferred, and -SiR3 (where R is the same or different and can be 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)), with at least one of R being a hydroxyl group) is more preferred.

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

[0038] For BR, hydrogenated BR, which has hydrogen added to it, can also be used. When BR is hydrogenated BR, there are no particular limitations on the hydrogenation method or reaction conditions; hydrogenation can be carried out using known methods and conditions. Typically, this is done at 20-150°C, under a hydrogen pressure of 0.1-10 MPa, and in the presence of a hydrogenation catalyst. Other manufacturing methods and conditions are also not particularly limited; for example, the contents described in International Publication No. 2016 / 039005 can be applied. Furthermore, hydrogenated BR has the same structure as an ethylene-butadiene copolymer as a result of hydrogen being added to the butadiene portion of BR. Therefore, in this specification, hydrogenated BR includes not only hydrogenated BR but also an ethylene-butadiene copolymer.

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

[0040] The cis content of BR is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, and also preferably 99.9% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less. When it is within the above range, the effect tends to be better obtained. The cis amount of BR can be measured by infrared absorption spectroscopy.

[0041] The cis amount of BR mentioned above refers to the cis amount of a single type of BR if there is only one type, and to the average cis amount if there are multiple types. The average cis content of BR can be calculated using the formula {Σ(content of each BR × cis content of each BR)} / total BR content. For example, if 20% of BR has a cis content of 90% and 10% has a cis content of 40% out of 100% of rubber components, the average cis content of BR is 73.3% (=(20 × 90 + 10 × 40) / (20 + 10)).

[0042] Other rubber components besides isoprene-based rubber, BR, and SBR include diene-based rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used individually or in combination of two or more types.

[0043] Rubber components other than isoprene-based rubber, BR, and SBR may be oil-stretched rubber, resin-stretched rubber, or other plasticizer-stretched rubber. These may be used individually or in combination of two or more. The plasticizer content in these stretchable rubbers is not particularly limited, but is usually around 5 to 50 parts by mass per 100 parts by mass of rubber solids. The oil used in oil-stretchable rubbers and the resin used in resin-stretchable rubbers are the same as those described later. Other plasticizers include liquid polymers, which will be described later.

[0044] Rubber components other than isoprene-based rubber, BR, and SBR may be modified to introduce functional groups that interact with fillers such as silica. Examples of the above functional groups include silicon-containing groups (-SiR3 (where R is the same or different and can be 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, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, etc. These functional groups may have substituents. Among these, silicon-containing groups are preferred, and -SiR3 (where R is the same or different and can be 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)), with at least one of R being a hydroxyl group) is more preferred.

[0045] Specific examples of compounds (modifiers) that introduce the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0046] The raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or they may be recycled from rubber products such as tires or non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, but examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl. Examples of butadiene include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include styrene, but are not particularly limited. In particular, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0047] The method for producing recycled monomer is not particularly limited, and for example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Furthermore, 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 pressure, decomposed by microwaves, or extracted after mechanical grinding.

[0048] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, but examples include agricultural, forestry, and fishery products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, and biomass naphtha.

[0049] The biomass-derived monomer (biomass monomer) is not particularly limited and includes biomass-derived butadiene and biomass-derived aromatic vinyl. The butadiene is 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited and includes styrene. Furthermore, the method for producing the biomass monomer is not particularly limited and includes, for example, biological and / or chemical and / or physical conversion of plants and animals. A typical biological conversion is fermentation by microorganisms, while chemical and / or physical conversions include those by catalysts, high heat, high pressure, electromagnetic waves, critical liquids, and combinations thereof.

[0050] The polymer synthesized from biomass monomer components (biomass polymer) is not particularly limited, and examples 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.

[0051] Whether the raw materials for a polymer are biomass-derived can be determined by measuring pMC (percent Modern Carbon) in accordance with ASTMD6866-10.

[0052] pMC stands for Modern Standard Reference Carbon. 14 Sample relative to C concentration14 It is the ratio of C concentration and is a value used as an index indicating the biomass ratio of a compound. The significance of this value is described below. In 1 mole (6.02×10 23 atoms) of carbon atoms, there are approximately 6.02×10 11 which is about one trillionth of ordinary carbon atoms. 14 C atoms exist. 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, after carbon dioxide in the atmosphere and the like are taken up and fixed by plants and the like, in fossil fuels such as coal, oil, and natural gas where more than 226,000 years have passed, at the beginning of fixation, 14 all of the C elements have decayed. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 any C elements. Therefore, chemical substances produced from these fossil fuels also do not contain 14 any C elements.

[0053] On the other hand, 14 C is constantly generated by nuclear reactions of cosmic rays in the atmosphere, and the decrease due to radioactive decay is balanced. In the atmospheric environment of the earth, 14 the amount of C is constant. Therefore, the 14 C concentration of substances derived from biomass resources circulating in the current environment is about 1×10 -12 mol% with respect to the entire C atoms as described above. Therefore, by utilizing the difference between these values, the biomass ratio of a certain compound can be calculated.

[0054] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 C / 12 C), 14 the C concentration ( 14 C / 12 C) is measured. In the measurement, 14As a modern standard reference for the concentration of C, the amount of cyclic carbon in nature as of 1950 14 The C concentration will be used. The specific standard material will be the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) will be used. 14 The radioactivity intensity of C is separated by carbon isotope, 13 The standard value is obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date. 14 This value is used as the C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0055] Therefore, if the rubber is made from 100% biomass-derived materials, although there are regional differences, under normal conditions it will often not reach 100, and will show a value of approximately 110 pMC. On the other hand, regarding chemical substances derived from fossil fuels such as petroleum, 14 When the C concentration is measured, it will show a value of around 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% as mentioned above.

[0056] Based on the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in rubber compositions is preferable from an environmental protection standpoint.

[0057] The above rubber composition contains an aromatic polyhydric alcohol. Aromatic polyhydric alcohols are alcohols that contain an aromatic ring and multiple hydroxyl groups within their molecule. Examples of aromatic polyhydric alcohols include lignins, lignans, flavonols, gallic acid, tannic acid, ellagic acid, and chlorogenic acid. These may be used individually or in combination of two or more. The more readily an aromatic polyhydric alcohol releases protons, the easier it is to obtain the desired effect. Therefore, aromatic polyhydric alcohols are preferably phenols, and more preferably polyphenols. Furthermore, aromatic polyhydric alcohols having a COO group are preferred, and at least one selected from the group consisting of gallic acid, ellagic acid, and chlorogenic acid is more preferred.

[0058] In the above rubber composition, the content of aromatic polyhydric alcohol is preferably 0.2 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 1.0 part by mass or more, and preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, the effect tends to be better obtained.

[0059] Furthermore, the content of aromatic polyhydric alcohol is preferably 1.0 part by mass or less per 100 parts by mass of rubber component.

[0060] In the above rubber composition, the content of aromatic polyhydric alcohol is preferably 0.2 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 1.0 part by mass or more, per 100 parts by mass of NR, and also preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and even more preferably 1.3 parts by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0061] The above rubber composition preferably contains silica as a filler. The silica used is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica). The raw material for silica is not particularly limited, and may be a mineral-derived raw material such as quartz, or a biological-derived raw material such as rice husks (for example, silica made from biomass materials such as rice husks), or silica recycled from silica-containing products may be used. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. These silicas may be used individually or in combination of two or more types. Commercially available products from companies such as Evonik, Tosoh Silica Co., Ltd., Solvay Japan Ltd., and Tokuyama Corporation can be used.

[0062] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized.

[0063] The silica recycled from silica-containing products can be, for example, silica recovered from products containing silica such as semiconductors and other electronic components, tires, desiccants, and diatomaceous earth and other filter materials. The recovery method is not particularly limited and can include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from semiconductors and other electronic components or tires is preferred.

[0064] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol.6, pp.216-222, etc.).

[0065] Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0066] The average particle size of silica is preferably 24 nm or less, more preferably 20 nm or less, even more preferably 18 nm or less, and also preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more. Within the above range, a better effect tends to be obtained.

[0067] In this specification, the method for measuring the average particle size of silica is transmission electron microscopy (TEM) observation. Specifically, silica particles are photographed with a transmission electron microscope, and if the particle shape is spherical, the diameter of the sphere is defined as the particle size; if it is needle-shaped or rod-shaped, the shorter axis is defined as the particle size; if it is irregularly shaped, the average particle size from the center is defined as the particle size; and the average particle size of 100 fine particles is defined as the average particle size.

[0068] In the above rubber composition, the silica content is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and preferably 140 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 90 parts by mass or less, per 100 parts by mass of the rubber component. When the silica content is within the above range, the effect tends to be better obtained.

[0069] The above rubber composition preferably contains carbon black as a filler. The carbon black used is not particularly limited and includes N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw materials for carbon black may be biomass materials such as lignin and vegetable oil, or pyrolysis oil obtained by thermal decomposition of waste tires. The manufacturing method for carbon black may be combustion such as the furnace method, hydrothermal carbonization (HTC), or thermal decomposition of methane such as the thermal black method. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Corporation. These may be used individually or in combination of two or more types.

[0070] The specific surface area of ​​cetyltrimethylammonium bromide (CTAB) in carbon black is preferably 70 m². 2 / g or more, more preferably 90m 2 / g or more, more preferably 110m 2 It is 1 / g or more, and preferably 200m 2 / g or less, more preferably 180m 2 / g or less, more preferably 170m 2 It is less than / g. The CTAB specific surface area of ​​carbon black is measured according to JIS K6217-3:2001.

[0071] The carbon black content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 45 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0072] In the above rubber composition, the silica content / carbon black content ratio is preferably 1.5 or higher, more preferably 3.0 or higher, even more preferably 4.5 or higher, and also preferably 9.0 or lower, more preferably 7.0 or lower, and even more preferably 6.0 or lower. When the ratio is within the above range, a better effect tends to be obtained. In this relationship, the silica content and carbon black content are expressed as the content per 100 parts by mass of rubber component (unit: parts by mass).

[0073] Other fillers besides silica and carbon black include vulcanized rubber particles, aluminum hydroxide, talc, calcium compounds, and short fibers. These may be used individually or in combination of two or more.

[0074] Vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the viewpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used individually or in combination of two or more types. The vulcanized rubber particles are not particularly limited and may be either unmodified or modified vulcanized rubber particles.

[0075] Commercially available vulcanized rubber particles can be used, including those from Lehigh, Muraoka Rubber Industries, and others. Note that, in this specification, vulcanized rubber particles are not included in the rubber component.

[0076] The average particle size of the vulcanized rubber particles is preferably 50 μm or more, more preferably 100 μm or more, even more preferably 200 μm or more, and also preferably 1000 μm or less, more preferably 900 μm or less, and even more preferably 800 μm or less. The average particle size of vulcanized rubber particles is the mass-based average particle size calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0077] The content of vulcanized rubber particles is preferably 1 to 30 parts by mass per 100 parts by mass of rubber component.

[0078] In this specification, aluminum hydroxide means Al(OH)3 or Al2O3·3H2O. Commercially available products include those from Sumitomo Chemical Co., Ltd., Showa Denko K.K., Nabaltec, and others. These may be used individually or in combination of two or more types.

[0079] The average particle size of aluminum hydroxide is preferably 0.1 μm or larger, more preferably 0.5 μm or larger, even more preferably 0.8 μm or larger, and also preferably 5 μm or smaller, more preferably 3 μm or smaller, and even more preferably 1 μm or smaller. Within this range, a better effect tends to be obtained. In this specification, the method for measuring the average particle size of aluminum hydroxide is transmission electron microscopy (TEM) observation. Specifically, aluminum hydroxide particles are photographed with a transmission electron microscope, and if the particle shape is spherical, the diameter of the sphere is defined as the particle size; if it is needle-shaped or rod-shaped, the shorter axis is defined as the particle size; if it is irregularly shaped, the average particle size from the center is defined as the particle size; and the average particle size of 100 fine particles is defined as the average particle size.

[0080] The BET specific surface area (nitrogen adsorption specific surface area, N2SA) of aluminum hydroxide is preferably 5 m². 2 / g or more, more preferably 8m 2 / g or more, more preferably 10m 2 It is 1 / g or more, and preferably 40m 2 / g or less, more preferably 30m 2 / g or less, more preferably 20m 2 It is less than / g. The BET specific surface area of ​​aluminum hydroxide is a value measured by the BET method in accordance with ASTM D3037-81.

[0081] The aluminum hydroxide content is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0082] The average particle size of talc is preferably 50 μm or less, more preferably 30 μm or less. The lower limit of the average particle size of talc is not particularly limited, but is preferably 1 μm or more.

[0083] The talc content is preferably 1 to 50 parts by mass per 100 parts by mass of rubber component.

[0084] Calcium compounds are compounds containing calcium, such as inorganic salts of calcium oxide, calcium hydroxide, and calcium carbide; and oxo salts of calcium carbonate, calcium nitrate, and calcium sulfate. Eggshells (main component: calcium carbonate) are another example of substances containing calcium compounds. These may be used individually or in combination of two or more. Among these, oxo salts are preferred, and calcium carbonate is more preferred. In this specification, calcium fatty acid salts are treated as processing aids as described later and are not included in fillers.

[0085] The calcium compound content is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0086] Examples of short fibers that can be used include organic short fibers and inorganic short fibers. Specific examples of organic short fibers include nanocellulose such as cellulose nanofibers (CNF) and cellulose nanocrystals (CNC); biomass nanomaterials such as chitin nanofibers and chitosan nanofibers; and specific examples of inorganic short fibers include metal fibers and glass fiber systems. Commercially available products include those from Nippon Paper Industries Co., Ltd. and Sugino Machine Co., Ltd. These may be used individually or in mixtures of two or more. Among these, organic short fibers are preferred, and nanocellulose is more preferred.

[0087] The particle size of the nanocellulose is preferably 10 nm or larger, more preferably 20 nm or larger, even more preferably 25 nm or larger, and particularly preferably 28 nm or larger. It is also preferably 50 nm or smaller, more preferably 40 nm or smaller, even more preferably 35 nm or smaller, and particularly preferably 32 nm or smaller. When the particle size is within the above range, a better effect tends to be obtained.

[0088] The particle size of nanocellulose is the average fiber diameter measured by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray scattering data analysis, and pore electrical resistance method (Culter principle method). In this specification, the average fiber diameter of nanocellulose (cellulose fiber) is typically the average fiber diameter of an aggregate of cellulose fibers formed by the aggregation of cellulose molecules.

[0089] The short fiber content is preferably 1 to 40 parts by mass per 100 parts by mass of rubber component.

[0090] The filler content is preferably 45 parts by mass or more, more preferably 65 parts by mass or more, even more preferably 85 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 170 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 110 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0091] In the above rubber composition, the silica content / filler content is preferably 0.40 or more, more preferably 0.60 or more, even more preferably 0.70 or more, even more preferably 0.80 or more, and also preferably 0.95 or less, more preferably 0.90 or less, and even more preferably 0.85 or less. It is presumed that the cut resistance performance will improve when the value is within the above range. In this relationship, the silica content and filler content are expressed as the content per 100 parts by mass of rubber component (unit: parts by mass).

[0092] The above rubber composition may contain a silane coupling agent. The silane coupling agent is not particularly limited and includes, 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 Examples include sulfide-based compounds such as ropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, mercapto-based compounds are preferred. Commercially available products include those from companies such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. These can be used individually or in combination of two or more types.

[0093] In addition to compounds containing a mercapto group, compounds in which the mercapto group is protected by a protecting group (for example, compounds represented by the following formula (S1)) can also be used as mercapto-silane coupling agents. It is presumed that the inclusion of a mercapto-silane coupling agent in the above rubber composition improves its cut resistance.

[0094] Particularly suitable mercapto-silane coupling agents include compounds represented by the following formula (S1), compounds represented by the following formula (1), and silane coupling agents comprising a bonding unit A shown in the following formula (2) and a bonding unit B shown in the following formula (3). [ka] (In the formula, R 1001 -Cl, -Br, -OR 1006 -O(O=)CR 1006 , -ON=CR 1006 R 1007 , -NR 1006 R 1007 and -(OSiR 1006 R 1007 ) h (OSiR 1006 R 1007 R 1008 A monovalent group (R) selected from ) 1006 , R 1007 and R 1008 They may be the same or different, and each is a hydrogen atom or a monovalent hydrocarbon group with 1 to 18 carbon atoms, and the average value of h is 1 to 4. 1002 is R 1001 , hydrogen atom or monovalent hydrocarbon group having 1 to 18 carbon atoms, R 1003 is -[O(R 1009 O) j ]-group(R 1009 is an alkylene group with 1 to 18 carbon atoms, and j is an integer from 1 to 4. ), R 1004 R is a divalent hydrocarbon group having 1 to 18 carbon atoms. 1005 (where represents a monovalent hydrocarbon group with 1 to 18 carbon atoms, and x, y, and z are numbers that satisfy the relationships x + y + 2z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, and 0 ≤ z ≤ 1.)

[0095] [ka] In the above equation (1), R 101 , R 102 , and R 103 Each of these is independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) Z -R 112 (z R 111 Each of these is independently a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 R is a group represented as an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms; z represents an integer from 1 to 30; R 104 This represents alkylenes with 1 to 6 carbon atoms.

[0096] [ka] [ka] In equations (2) and (3) above, x represents an integer greater than or equal to 0; y represents an integer greater than or equal to 1; R 201 R represents a C1-C30 alkyl, C2-C30 alkenyl, or C2-C30 alkynyl atom which may be substituted with a hydrogen atom, a halogen atom, a hydroxyl or carboxyl atom; 202 R represents alkylene with 1 to 30 carbon atoms, alkenylene with 2 to 30 carbon atoms, or alkynylene with 2 to 30 carbon atoms; 201 and R 202 They may form a ring structure.

[0097] In equation (S1), R 1005 , R 1006 , R 1007 and R 1008is preferably a group independently selected from the group consisting of linear, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups having 1 to 18 carbon atoms. Also, R 1002 when it is a monovalent hydrocarbon group having 1 to 18 carbon atoms, is preferably a group selected from the group consisting of linear, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups. R 1009 is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R 1004 includes, 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, and an aralkylen 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 aralkylen group may have a functional group such as a lower alkyl group on the ring. This R 1004 is preferably an alkylene group having 1 to 6 carbon atoms, particularly preferably a linear alkylene group, for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group.

[0098] In formula (S1), R 1002 , R 1005 , R 1006 , R 1007 and R 1008 Specific examples of 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, etc. In formula (S1), R 1009Examples of linear alkylene groups include methylene, ethylene, n-propylene, n-butylene, and hexylene groups, while examples of branched alkylene groups include isopropylene, isobutylene, and 2-methylpropylene groups.

[0099] Specific examples of silane coupling agents represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, and 2-lauroylthioethyltrimethoxysilane. These may be used individually or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

[0100] Examples of compounds represented by formula (1) above include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and compounds represented by the following formula (4) (Si363 manufactured by Evonik). Compounds represented by the following formula (4) can be preferably used. These may be used individually or in combination of two or more.

[0101] [ka]

[0102] In a silane coupling agent containing a bonding unit A represented by formula (2) and a bonding unit B represented by formula (3), the content of 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. The content of bonding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 55 mol% or less. The total content of bonding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. The content of bonding units A and B includes the amount when bonding units A and B are located at the ends of the silane coupling agent. The form of bonding units A and B when they are located at the ends of the silane coupling agent is not particularly limited, as long as they form units corresponding to the equations (2) and (3) that represent bonding units A and B.

[0103] R in equations (2) and (3) 201 Examples of halogens include chlorine, bromine, and fluorine. Examples of branched or unbranched alkyl groups with 1 to 30 carbon atoms include methyl and ethyl groups. Examples of branched or unbranched alkenyl groups with 2 to 30 carbon atoms include vinyl and 1-propenyl groups. Examples of branched or unbranched alkynyl groups with 2 to 30 carbon atoms include ethynyl and propynyl groups.

[0104] R in equations (2) and (3) 202 Regarding branched or unbranched alkylene groups with 1 to 30 carbon atoms, examples include ethylene and propylene groups. Regarding branched or unbranched alkenylene groups with 2 to 30 carbon atoms, examples include vinylene and 1-propenylene groups. Regarding branched or unbranched alkylene groups with 2 to 30 carbon atoms, examples include ethynylene and propynylene groups.

[0105] In a silane coupling agent containing a bonding unit A represented by formula (2) and a bonding unit B represented by formula (3), the sum of the number of repeats of bonding unit A (x) and the number of repeats of bonding unit B (y), (x+y), is preferably in the range of 3 to 300.

[0106] The content of the silane coupling agent is preferably 4 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of silica, and also preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0107] The above rubber composition may contain a plasticizer. A plasticizer is a material that imparts plasticity to rubber components, and the concept includes both liquid and solid plasticizers at 25°C. Examples of plasticizers include resins, oils, liquid polymers, and ester-based plasticizers. Among these, oils are preferred. These plasticizers may be derived from mineral resources such as petroleum and natural gas, from biomass, or from naphtha recycled from rubber or non-rubber products. Alternatively, low molecular weight hydrocarbon components obtained by thermal decomposition and extraction of used tires or products containing various components may be used as plasticizers. These plasticizers may be used individually or in combination of two or more.

[0108] Examples of oils include mineral oil, vegetable oil, and animal oil. From a life cycle assessment perspective, waste oil used in rubber mixers and engines, or refined waste cooking oil used in restaurants, may also be used.

[0109] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oil include MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). Furthermore, for environmental reasons, oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of such low-PCA oils include MES, TDAE, and heavy naphthenic oils.

[0110] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax. Furthermore, vegetable oils may also include 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, oxidized polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from use as edible oils. Note that vegetable oils may be liquid or solid at 25°C. These may be used individually or in combination of two or more types.

[0111] 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 hydroxyl 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. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer of three or more. Note that acylglycerols of two or more forms can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be a liquid or a solid at 25°C.

[0112] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, 1 This can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, it is measured at room temperature. 1 When 1H-NMR was measured and the tetramethylsilane (TMS) signal was set to 0.00 ppm, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0113] The aforementioned fatty acids are not particularly limited and may be either unsaturated or saturated fatty acids. 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.

[0114] In particular, it is desirable that the fatty acid contains fatty acids with few double bonds, i.e., saturated fatty acids or monounsaturated fatty acids, and oleic acid is preferred. As a vegetable oil containing such fatty acids, for example, a vegetable oil containing saturated fatty acids or monounsaturated fatty acids may be used, or a vegetable oil that has been modified by transesterification or other means may be used. Furthermore, in order to produce a vegetable oil containing such fatty acids, plants may be improved by breeding, genetic modification, genome editing, etc.

[0115] As for vegetable oils, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0116] The vegetable oil content is preferably 1 to 40 parts by mass per 100 parts by mass of rubber component.

[0117] Commercially available oils that can be used include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., Nisshin Oillio Group Ltd., and others.

[0118] The oil content is preferably 3 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 40 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0119] The resin is not particularly limited, but resins commonly used in the tire industry can be used. Examples include adhesive resins such as C5 resins, C9 resins, C5C9 resins, aromatic vinyl resins, dicyclopentadiene resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenolic resins. These resins may be used individually or in combination of two or more.

[0120] C5 resins refer to resins obtained by polymerizing C5 fractions, and may be hydrogenated or modified versions of these resins. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used individually or in combination of two or more types.

[0121] C9 resins refer to resins obtained by polymerizing a C9 fraction, and may be obtained by polymerizing the C9 fraction alone, or as copolymers obtained by copolymerizing the C9 fraction with other components. They may also be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, and methylindene. These C9 resins may be used individually or in combination of two or more types.

[0122] C5C9 resins refer to resins obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified versions of these resins. As C5C9 petroleum resins, for example, those commercially available from Tosoh Corporation, LUHUA, etc., can be used. These C5C9 resins may be used individually or in combination of two or more types.

[0123] Aromatic vinyl resins refer to resins containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene as the most abundant monomer component, and may also be hydrogenated or modified versions of these compounds. For aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, due to their economical nature, ease of processing, and excellent heat generation properties. Aromatic vinyl resins that can be used are commercially available from companies such as Kraton, Eastman Chemical Company, and Mitsui Chemicals, Inc. These aromatic vinyl resins may be used individually or in combination of two or more types.

[0124] Dicyclopentadiene resins refer to resins containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as monomer components, and may be hydrogenated or modified. Examples of dicyclopentadiene resins include DCPD / C9 resins containing dicyclopentadiene and C9 fraction as monomer components (these DCPD / C9 resins may be hydrogenated or modified), with DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components being preferred, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components being particularly preferred. Dicyclopentadiene resins that are commercially available from companies such as ExxonMobil, ENEOS Corporation, Nippon Zeon Corporation, and Maruzen Petrochemical Co., Ltd. can be used. These dicyclopentadiene resins may be used individually or in combination of two or more types.

[0125] Coumarone-based resins refer to resins containing coumarone as a monomer component, and may be hydrogenated or modified resins. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These coumarone-based resins may be used individually or in combination of two or more types.

[0126] Indene resins refer to resins containing indene as a monomer component, and may be hydrogenated or modified resins. Examples of indene resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These indene resins may be used individually or in combination of two or more types.

[0127] Terpene resins are resins that contain terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the most abundant monomer component, and may be hydrogenated or modified versions of these compounds. Specific examples of terpene resins include, for example, polyterpene resins containing only one or more of the aforementioned terpene compounds as monomer components; aromatically modified terpene resins containing the aforementioned terpene compounds and aromatic compounds as monomer components; and terpene-phenol resins containing the aforementioned terpene compounds and phenolic compounds as monomer components. Examples of aromatic compounds that serve as monomer components in aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components in terpene-phenol resins include phenol, bisphenol A, cresol, and xylenol. These terpene resins may be used individually or in combination of two or more types.

[0128] Rosin-based resins refer to resins containing rosin acid compounds such as abietic acid, neoabietic acid, palastic acid, and isopimal acid, and may be hydrogenated or modified versions of these compounds. Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc. These rosin-based resins may be used individually or in combination of two or more types.

[0129] Phenolic resins are resins that contain phenol compounds such as phenol and cresol as the most abundant monomer component. Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins. These phenolic resins may be used individually or in combination of two or more types.

[0130] The resin may be a modified resin (functionalized resin) into which functional groups have been introduced. Modified resins can be produced by known methods, such as slurry methods and metathesis methods. Specifically, they can be produced, for example, by reacting a polymer that forms the polymer backbone of the modified resin with a functional compound that allows for the introduction of functional groups, using known methods.

[0131] The polymer forming the polymer backbone is not particularly limited and may be, for example, the C5 resin, aromatic resin, or terpene resin mentioned above, or other resins. These may be used alone or in combination of two or more. Among these, aromatic resins are preferred, α-methylstyrene resins are more preferred, and styrene-α-methylstyrene resin (a copolymer of styrene and α-methylstyrene) is even more preferred.

[0132] The functional group is preferably one containing at least one element selected from the group consisting of oxygen, silicon, and nitrogen, and more preferably one containing silicon.

[0133] The modified resin content is preferably 0.5 to 50 parts by mass per 100 parts by mass of the rubber component.

[0134] Commercially available resins from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0135] The resin content is preferably 0.5 to 50 parts by mass per 100 parts by mass of rubber component.

[0136] Liquid polymers are (co)polymers that are in a liquid state at 25°C, and examples include liquid rubber and liquid resin. Furthermore, the liquid polymer may have undergone modification or hydrogenation treatment. Commercially available products include those from Cray Valley, Kuraray Co., Ltd., etc. These may be used individually or in combination of two or more types.

[0137] The weight-average molecular weight (Mw) of the liquid polymer is less than 120,000, preferably 50,000 or less, more preferably 20,000 or less, even more preferably 8,000 or less, and also preferably 100 or more, more preferably 1,000 or more, and even more preferably 2,000 or more. Within the above range, better effects tend to be obtained. In this specification, liquid polymers are not included in the rubber component.

[0138] 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 diene polymers such as liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid farnesene polymer, and liquid farnesene-butadiene copolymer. Among these, branched conjugated diene polymers such as liquid farnesene polymer and liquid farnesene-butadiene copolymer are preferred.

[0139] The liquid rubber may be modified with functional groups that interact with silica, or its terminals and / or main chain may be modified with functional groups containing at least one element selected from the group consisting of oxygen, nitrogen, silicon, and phosphorus. The liquid rubber may also be unhydrogenated or hydrogenated.

[0140] The liquid rubber content is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0141] The liquid resin is a resin that is liquid at 25°C, and any of 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.

[0142] The liquid resin content is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0143] The liquid polymer content is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0144] The ester-based plasticizer is not particularly limited as long as it is a compound having an ester group that is in a liquid state at 25°C, but examples include phthalic acid derivatives, long-chain fatty acid derivatives, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives. These may be used individually or in combination of two or more. Among these, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives are preferred, with sebacic acid derivatives being more preferred. The above phthalic acid derivatives are not particularly limited, but examples include phthalic acid esters such as di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). The above long-chain fatty acid derivatives are not particularly limited, but examples include long-chain fatty acid glycerol esters. The above phosphate derivatives are not particularly limited, but examples include phosphate esters such as tris(2-ethylhexyl) phosphate (TOP) and tributyl phosphate (TBP). The above sebaciate derivatives are not particularly limited, but examples include sebaciate esters such as di(2-ethylhexyl) sebacate (DOS) and diisooctyl sebacate (DIOS). The above adipic acid derivatives are not particularly limited, but examples include adipic acid esters such as di(2-ethylhexyl) adipate (DOA) and diisooctyl adipate (DIOA). Among these, phosphate esters, sebacate esters, and adipic esters are preferred, with sebacate esters being more preferred. Furthermore, as for specific compounds, TOP, DOS, and DOA are preferred, with DOS being more preferred. As ester-based plasticizers, products from companies such as Daihachi Chemical Industry Co., Ltd. and Taoka Chemical Industry Co., Ltd. can be used.

[0145] The glass transition temperature (Tg) of the ester-based plasticizer is preferably -110°C or higher, more preferably -100°C or higher, even more preferably -80°C or higher, preferably -20°C or lower, more preferably -40°C or lower, and even more preferably -55°C or lower. The aforementioned effects tend to be more favorably obtained within this range. In this specification, the glass transition temperature of ester-based plasticizers is the value measured in accordance with JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., under a heating rate of 10°C / min.

[0146] The content of the ester-based plasticizer is preferably 1 to 20 parts by mass per 100 parts by mass of the rubber component.

[0147] The plasticizer content is preferably 3 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 40 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0148] In the above rubber composition, the value of (SBR content + plasticizer content) / silica content is preferably 0.05 or higher, more preferably 0.10 or higher, even more preferably 0.14 or higher, and also preferably 1.0 or lower, more preferably 0.60 or lower, and even more preferably 0.20 or lower. When the value is within the above range, a better effect tends to be obtained. In this relationship, the SBR content is the content per 100% by mass of the rubber component (unit: mass%), while the plasticizer content and silica content are the content per 100 parts by mass of the rubber component (unit: parts by mass).

[0149] In the above rubber composition, the ratio of plasticizer content to filler content is preferably 0.04 or higher, more preferably 0.08 or higher, even more preferably 0.11 or higher, and also preferably 0.25 or lower, more preferably 0.20 or lower, and even more preferably 0.15 or lower. When the ratio is within the above range, a better effect tends to be obtained. In this relationship, the plasticizer content and filler content are expressed as the content per 100 parts by mass of rubber component (unit: parts by mass).

[0150] The above rubber composition preferably contains a surfactant. The inclusion of a surfactant improves the dispersibility of aromatic polyhydric alcohols in the rubber composition, which tends to further suppress the reduction in molecular weight of the aforementioned NR. Therefore, it is presumed that the cut resistance performance will be further improved.

[0151] The surfactant is not particularly limited and includes known anionic surfactants such as polyoxyethylene alkyl ether sulfate salts, nonionic surfactants, and amphoteric surfactants. Among these, nonionic surfactants are preferred. As nonionic surfactants, nonionic surfactants with long carbon chains are preferred, such as ether-type nonionic surfactants, ester-type nonionic surfactants, and ether-ester-type nonionic surfactants. Among these, polyethylene glycol and beef tallow monoamine are preferred.

[0152] In the above rubber composition, the amount of surfactant per 100 parts by weight of the rubber component is preferably 1 part by weight or more, more preferably 2 parts by weight or more, even more preferably 3 parts by weight or more, and also preferably 12 parts by weight or less, more preferably 8 parts by weight or less, and even more preferably 5 parts by weight or less. When the amount is within the above range, a better effect tends to be obtained.

[0153] In the above rubber composition, the ratio of surfactant content to aromatic polyhydric alcohol content is preferably 1.0 or higher, more preferably 2.0 or higher, even more preferably 3.0 or higher, and also preferably 10 or lower, more preferably 7.0 or lower, and even more preferably 5.0 or lower. Within this range, a better effect tends to be obtained. In this relationship, the surfactant content and aromatic polyhydric alcohol content are expressed as the content per 100 parts by mass of rubber component (unit: parts by mass).

[0154] The above rubber composition may contain processing aids. Examples of processing aids include metal salts (compounds in which the hydrogen atoms of an acid are replaced by metal ions), fatty acid amides, amide esters, and fatty acid esters. These may be used individually or in combination of two or more.

[0155] Examples of metals used in metal salts include alkali metals such as potassium and sodium, and alkaline earth metals such as calcium and barium. Magnesium, zinc, nickel, and molybdenum can also be used.

[0156] Acids used in metal salts include fatty acids such as lauric acid, myristic acid, and palmitic acid. Boric acid, carbonic acid, hydrochloric acid, nitric acid, and sulfuric acid can also be used.

[0157] Commercially available processing aids include products from companies such as Kishida Chemical Co., Ltd., Ken-ei Pharmaceutical Co., Ltd., Structol, and Performance Additives.

[0158] The content of the processing aid is preferably 0.1 to 10 parts by mass per 100 parts by mass of the rubber component.

[0159] The above rubber composition may contain an anti-aging agent. While not particularly limited, examples of anti-aging agents 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; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditril-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as methyl amine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis. These may be used individually or in combination of two or more.

[0160] The amount of anti-aging agent is preferably 1 to 10 parts by mass per 100 parts by mass of rubber component.

[0161] The above rubber composition may contain wax. The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. These waxes may be used individually or in combination of two or more types.

[0162] The wax is preferably obtained as a by-product of Fischer-Tropsch synthesis derived from natural gas. The raw materials for Fischer-Tropsch synthesis may also be recycled methane (such as methane obtained by thermal decomposition of tires) or biomass-derived methane (such as methane obtained from carbon dioxide through a methanation process).

[0163] The wax content is preferably 1 to 10 parts by mass per 100 parts by mass of rubber component.

[0164] The above rubber composition may contain stearic acid. Conventional known stearic acid can be used, and commercially available products from companies such as NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries Ltd., and Chiba Fatty Acid Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0165] The stearic acid content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 8 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component. Within this range, a better effect tends to be obtained.

[0166] The above rubber composition may contain zinc oxide. Conventional known zinc oxides can be used, and commercially available products from companies such as Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0167] The zinc oxide content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component. Within this range, a better effect tends to be obtained.

[0168] The above rubber composition may contain sulfur. Examples of sulfur commonly used as a crosslinking agent in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products from companies such as Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0169] The sulfur content is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component. Within this range, a better effect tends to be obtained.

[0170] The above rubber composition may contain a vulcanization accelerator. Examples of vulcanization accelerators include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiram-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-benzothiadylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N′-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotolylguanidine, and orthotolylbiguanidine. Commercially available products from companies such as Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Co., Ltd. can be used. These may be used individually or in combination of two or more.

[0171] The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0172] In addition to the above components, the above rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0173] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the above formulations from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0174] The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing it.

[0175] Regarding the mixing conditions, in the base mixing step where additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish mixing step where the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition mixed with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0176] The tread of this disclosure comprises the above-mentioned rubber composition. When the tread has a multi-layer structure, the above rubber composition can be used for either the surface layer (cap tread) or the inner layer (base tread), but is particularly suitable for the cap tread.

[0177] The above tread is a tread with grooves formed in it. In this specification, "groove" refers to a groove within the contact surface that is at least 2 mm wide and at least 7 mm deep. The shape of the groove is not particularly limited, and shapes commonly used in this field may be adopted.

[0178] In the above-mentioned tire, the thickness Tc of the cap tread is preferably 3.0 mm or more, more preferably 6.0 mm or more, even more preferably 8.0 mm or more, and particularly preferably 10.0 mm or more. The upper limit is not particularly limited, but is preferably 20.0 mm or less, more preferably 18.0 mm or less, and even more preferably 15.0 mm or less. Within the above range, the effect tends to be favorably obtained.

[0179] In this specification, the term "cap tread" refers to the outermost component of the tread in the radial direction of the tire that makes contact with the road surface. If the tread has a single-layer structure, that single layer corresponds to the cap tread; if the tread has a two-layer structure consisting of a cap layer and a base layer, the cap layer corresponds to the cap tread; and if the tread has a structure of three or more layers, the outermost layer that makes contact with the road surface corresponds to the cap tread (cap layer).

[0180] The cap tread thickness Tc refers to the thickness of the cap tread on the tire's equatorial plane in the tire's radial cross-section. Specifically, the cap tread thickness Tc refers to the thickness of the outermost rubber layer (cap tread) among the rubber layers that make up the tread portion of the tire in its radial cross-section, and is the straight-line distance from the tread surface (cap tread surface) to the inner radial surface of the cap tread.

[0181] The thickness of the cap tread on the tire's equatorial plane is the value measured along the tire's equatorial plane from the outermost surface of the cap tread on the tire's equatorial plane. If a conductive element is present on the tire's equatorial plane, the value is measured along the tire's equatorial plane from a straight line connecting the ends of the interface obstructed by the conductive element. If grooves exist on the tire's equatorial plane, the thickness is measured at the center of the tire's width direction on the land portion closest to the tire's equatorial plane, and is the thickness measured in the direction normal to the cap tread surface.

[0182] In this specification, the thickness of the cap tread is measured with the tire bead aligned to the standard rim width. During measurement, the tire is cut in the radial direction, and the bead ends on both sides of the sample are fixed in place, aligned to the standard rim width.

[0183] "Regular internal pressure" refers to the air pressure specified for each tire by the aforementioned standards. For JATMA, it is the maximum air pressure; for ETRTO, it is "INFLATION PRESSURE"; and for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Similar to the case of "regular rim," refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. In the case of tires not specified in the standards, it refers to the regular internal pressure (but 250 kPa or higher) of another tire size (specified in the standards) that uses the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0184] In the above-mentioned tire, the width W of the grooves formed in the tread is preferably 15.0 mm or less, more preferably 10.0 mm or less. W is preferably 2.0 mm or more, more preferably 3.0 mm or more, and even more preferably 5.0 mm or more. When it is within the above range, a better effect tends to be obtained.

[0185] In the above-mentioned tire, the groove depth D of the grooves formed in the tread is preferably 18.0 mm or less, more preferably 15.0 mm or less, even more preferably 13.0 mm or less, and particularly preferably 12.0 mm or less. D is preferably 3.0 mm or more, more preferably 4.0 mm or more, even more preferably 5.0 mm or more, and particularly preferably 8.0 mm or more. When it is within the above range, a better effect tends to be obtained.

[0186] In this specification, the groove depth D of the circumferential groove is measured along the normal to the plane extended from the surface forming the contact surface of the outermost tread surface, and means the distance from the extended surface forming the contact surface to the deepest groove bottom, and refers to the maximum distance among the groove depths of the provided circumferential grooves.

[0187] The tire of this disclosure is manufactured by conventional means using the above rubber composition. Specifically, the rubber composition is extruded to match the shape of a tread or the like at the unvulcanized stage, and then molded together with other tire components in a conventional manner on a tire molding machine to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to obtain a tire.

[0188] The above-mentioned tires (pneumatic tires, etc.) can be used for passenger car tires; truck and bus tires; motorcycle tires; high-performance tires; winter tires such as studless tires; run-flat tires with side reinforcement layers; tires with sound-absorbing materials such as sponges inside the tire cavity; tires with sealing materials that can be sealed in the event of a puncture inside the tire or tire cavity; and tires with electronic components that have electronic components such as sensors and wireless tags inside the tire or tire cavity, and are particularly suitable for passenger car tires.

[0189] The tire sizes mentioned above are not particularly limited; for example, tire widths can be selected within the range of 100-400mm, aspect ratios within the range of 25-85%, and rim diameters within the range of 10-25 inches, as appropriate. 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.

[0190] The above-mentioned tire preferably satisfies the following relationship between the tire outer diameter Dt and the tire section width Wt.

number

[0191] Examples of tires that can satisfy the above formula include 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, etc.

[0192] Tires that satisfy the above formula are preferably applied to pneumatic tires for passenger cars. This is because pneumatic tires for passenger cars that satisfy the above formula tend to be more suitable for solving the problems of this invention. [Examples]

[0193] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

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

[0195] (Rubber component) NR:TSR20 SBR: JSR1502 manufactured by JSR Corporation (styrene content: 23.5% by mass, vinyl content: 16% by mass, Tg: -56℃)

[0196] (Chemicals other than rubber components) Carbon Black: N220 (CTAB specific surface area: 111 m²) 2 / g) Silica: ULTRASIL VN3 from Evonik (average particle size: 18nm) Silane coupling agent: Si363 (3-[ethoxybis(3,6,9,12,15-pentaoxacosan-1-yloxy)silyl]-1-propanethol) manufactured by Evonik. Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd. Aromatic polyhydric alcohol 1: Gallic acid manufactured by Tokyo Chemical Industry Co., Ltd. Aromatic polyhydric alcohol 2: Ellagic acid manufactured by Fujifilm Corporation Aromatic polyhydric alcohol 3: Chlorogenic acid manufactured by Fujifilm Corporation Surfactant: PEG #4000 manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Sulfur: HK-200-5 (5% by mass oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0197] (Examples and Comparative Examples) According to the formulation shown in Table 1, the materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a mixture. Next, sulfur and vulcanization accelerator were added to the mixture and kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. Next, the unvulcanized rubber composition is molded into the shape of a cap tread with grooves, bonded together with other tire components to form an unvulcanized tire, and then press-vulcanized at 150°C for 12 minutes to produce a test tire (size: 175 / 60R18). The test tires manufactured in this manner were examined, and the results calculated based on the evaluation method described below are shown in Table 1.

[0198] (Cut resistance) Each test tire is mounted on a vehicle and driven on rough terrain. The number of cuts (0.5 mm or deeper, 0.5 mm or longer) that occur on the tread contact surface after driving is counted. This value is expressed as an index, with Comparative Example 1 set to 100, and the index increases as the number of cuts decreases. A higher index indicates better cut resistance.

[0199] [Table 1]

[0200] The present invention (1) is a tire having a tread with grooves formed therein, The tread is a tire comprising a rubber composition containing a rubber component including natural rubber and an aromatic polyhydric alcohol.

[0201] The present invention (2) is the tire according to the present invention (1), wherein the rubber composition contains silica, and the value of the silica content / filler content is 0.60 or more and 0.90 or less.

[0202] The present invention (3) is the tire according to the present invention (1) or (2), wherein the content of natural rubber in the rubber component is 30% by mass or more.

[0203] The present invention (4) is a tire according to any one of the present inventions (1) to (3), wherein the rubber composition contains a mercapto-silane coupling agent.

[0204] The present invention (5) is a tire according to any one of the present inventions (1) to (4), wherein the rubber composition contains a surfactant.

[0205] The present invention (6) is a tire according to any one of the present inventions (1) to (5), wherein the content of the aromatic polyhydric alcohol per 100 parts by mass of the rubber component is 0.6 parts by mass or more and 3.0 parts by mass or less.

[0206] The present invention (7) is a tire according to any one of the present inventions (1) to (6), wherein the content of the aromatic polyhydric alcohol per 100 parts by mass of the natural rubber is 0.6 parts by mass or more and 3.0 parts by mass or less.

[0207] The present invention (8) is a tire according to any one of the present inventions (1) to (7), wherein the rubber composition contains carbon black.

[0208] The present invention (9) is a tire according to any one of the present inventions (1) to (8), wherein the rubber composition contains a filler, and the value of the plasticizer content / filler content is 0.08 or more and 0.20 or less.

[0209] The present invention (10) is a tire according to any one of the present inventions (1) to (9), wherein the rubber composition contains silica, and the value of (styrene-butadiene rubber content + plasticizer content) / silica content is 0.10 or more and 0.60 or less.

Claims

1. A tire having a tread with grooves formed therein, The tread comprises a rubber composition containing a rubber component including natural rubber and an aromatic polyhydric alcohol.

2. The tire according to claim 1, wherein the rubber composition contains silica, and the value of the silica content / filler content is 0.60 or more and 0.90 or less.

3. The tire according to claim 1 or 2, wherein the content of natural rubber in the rubber component is 30% by mass or more.

4. The tire according to claim 1 or 2, wherein the rubber composition contains a mercapto-silane coupling agent.

5. The tire according to claim 1 or 2, wherein the rubber composition contains a surfactant.

6. The tire according to claim 1 or 2, wherein the content of the aromatic polyhydric alcohol per 100 parts by mass of the rubber component is 0.6 parts by mass or more and 3.0 parts by mass or less.

7. The tire according to claim 1 or 2, wherein the content of the aromatic polyhydric alcohol per 100 parts by mass of the natural rubber is 0.6 parts by mass or more and 3.0 parts by mass or less.

8. The tire according to claim 1 or 2, wherein the rubber composition contains carbon black.

9. The tire according to claim 1 or 2, wherein the rubber composition contains a filler, and the ratio of the plasticizer content to the filler content is 0.08 or more and 0.20 or less.

10. The tire according to claim 1 or 2, wherein the rubber composition contains silica, and the value of (styrene-butadiene rubber content + plasticizer content) / silica content is 0.10 or more and 0.60 or less.

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