JP2023077691A - Tire rubber composition and tire - Google Patents

Abstract

To provide a tire rubber composition and a tire which can achieve improvement in overall performance of wear resistance during high-speed traveling and sustained steering stability in repeated traveling.SOLUTION: The present invention relates to a tire rubber composition that comprises a rubber component comprising styrene-butadiene rubber, silica, carbon black, and a plasticizer comprising a liquid polymer. A content of the silica is more than 25 pts.mass relative to 100 pts.mass of the rubber component, with 2.5<the carbon black content/the silica content<5.0, and the liquid polymer content/the silica content>0.25.SELECTED DRAWING: None

Description

The present disclosure relates to rubber compositions for tires and tires.

Various techniques for improving wear resistance and steering stability have been studied so far (see Patent Documents 1 and 2, for example). However, in recent years, there has been a demand for further improvements in these performances.

JP 2017-141405 A JP 2007-186567 A

An object of the present disclosure is to solve the above problems and to provide a tire rubber composition and a tire that can improve the overall performance of wear resistance during high-speed running and steering stability maintenance performance during repeated running. .

The present disclosure contains a rubber component containing styrene-butadiene rubber, silica, carbon black, and a plasticizer containing a liquid polymer, wherein the silica content is greater than 25 parts by mass with respect to 100 parts by mass of the rubber component. 2.5<content of carbon black/content of silica<5.0, and content of liquid polymer/content of silica>0.25.

The present disclosure contains a rubber component containing styrene-butadiene rubber, silica, carbon black, and a plasticizer containing a liquid polymer, wherein the silica content is greater than 25 parts by mass with respect to 100 parts by mass of the rubber component. 2.5<the content of the carbon black/the content of the silica<5.0, and the content of the liquid polymer/the content of the silica>0.25. Therefore, the overall performance of the wear resistance during high-speed running and the steering stability maintenance performance during repeated running is improved.

The rubber composition for tires of the present disclosure contains a rubber component containing styrene-butadiene rubber, silica, carbon black, and a plasticizer containing a liquid polymer, and the content of the silica with respect to 100 parts by mass of the rubber component is more than 25 parts by mass, 2.5<content of the carbon black/content of the silica<5.0, and content of the liquid polymer/content of the silica>0.25.

The reason why the aforementioned effects are obtained with the rubber composition is presumed as follows.
By containing carbon black, heat is generated on the tread surface due to the reinforcing effect of carbon black and the interaction between carbon black and styrene-butadiene rubber, and good grip is obtained even during high-speed running. Furthermore, by containing silica, the styrene-butadiene rubber part bonded with silica has low heat build-up within a minute area, and the phase difference when transmitting force is also small, so the reaction force generated on the tread surface is transmitted inside the tire. It becomes easy and it becomes possible to improve steering stability.
These effects can be obtained by blending more than 25 parts by mass of silica with respect to 100 parts by mass of the rubber component and blending carbon black at a ratio of more than 2.5 times to less than 5.0 times that of silica. It is thought that it will be easier for
In addition, by containing more than 25% of the liquid polymer relative to the content of silica, the dispersibility of silica is improved and silica and polymer are easily bonded. Therefore, it is considered that the reinforcing effect of silica can be easily obtained, and the wear resistance during high-speed running is improved.
In addition, since the liquid polymer has a higher molecular weight than a normal plasticizer and is less likely to flow out of the system, it is considered that the above state can be easily maintained.
It is believed that due to the above effects, the overall performance of the wear resistance during high-speed running and the steering stability maintenance performance during repeated running is improved.

In the rubber composition, the acetone extraction amount (AE) is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and preferably 40% by mass or less, more preferably It is 35% by mass or less, more preferably 30% by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the polymer content (PC) is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and preferably 50% by mass or less, more preferably It is 45% by mass or less, more preferably 40% by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the amount of carbon black (BC) is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and preferably 45% by mass or less, more preferably is 40% by mass or less, more preferably 35% by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the ash content (Ash) is preferably 3% by mass or more, more preferably 6% by mass or more, still more preferably 9% by mass or more, and preferably 25% by mass or less, more preferably It is 20% by mass or less, more preferably 15% by mass or less. Within the above range, the effect tends to be obtained more favorably.

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

As methods for adjusting AE, PC, BC, and Ash, methods known to those skilled in the art can be employed. For example, AE tends to increase as the amount of plasticizer, such as oil, in the rubber composition increases. PC tends to increase as the amount of rubber component in the rubber composition increases. BC tends to increase as the amount of carbon black in the rubber composition increases. Ash tends to increase as the amount of components that do not burn in oxidative combustion, such as silica, increases in the rubber composition.

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

The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, still more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and still more preferably 1,000,000. It is below. Within the above range, the effect tends to be obtained more favorably.

In the present specification, the weight average molecular weight (Mw) is a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL manufactured by Tosoh Corporation. It can be obtained by standard polystyrene conversion based on the measured value by SUPERMULTIPORE HZ-M).

The total styrene content in the rubber component is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably over 35% by mass, and preferably 50% by mass or less, more preferably 45% by mass or less. , more preferably 40% by mass or less. Within the above range, the effect tends to be obtained more favorably.

Here, the total styrene content in the rubber component is the total content (unit: mass %) of the styrene part contained in the total amount of the rubber component, and Σ (content of each rubber component × styrene content in each rubber component /100). For example, in 100% by mass of the rubber component, SBR with a styrene content of 40% by mass is 85% by mass, SBR with a styrene content of 25% by mass is 5% by mass, and BR with a styrene content of 0% by mass is 10% by mass. , the total styrene content in the rubber component is 35.25% by mass (=85×40/100+5×25/100+10×0/100).

The total vinyl content in the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less. , more preferably 20% by mass or less. Within the above range, the effect tends to be obtained more favorably.

Here, the total vinyl content in the rubber component is the total content of vinyl bonds in the butadiene portion of SBR and BR contained in the rubber component (unit: parts by mass) when the total mass of the rubber component is 100. . For example, in 100 parts by mass of the rubber component, 85 parts by mass of SBR containing 40% by mass of styrene and 30% by mass of vinyl, 5 parts by mass of SBR containing 20% by mass of styrene and 20% by mass of vinyl, and 5 parts by mass of vinyl Amount: When 10% by mass of BR is 10 parts by mass, the total amount of vinyl in the rubber component is 17.1 parts by mass (= 85 x (100 [mass%] - 40 [mass%]) x 30 [mass %]+5×(100 [mass %]−20 [mass %])×20 [mass %]+10×10 [mass %]).

The styrene content and vinyl content in each rubber component can be measured by a nuclear magnetic resonance (NMR) method.
Further, the total styrene content and total vinyl content in the rubber component are calculated according to the above-mentioned formulas in the examples of the present specification. MS), etc., may be analyzed from the tire.

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

The SBR may be oil-extended rubber extended with oil or resin-extended rubber extended with resin. These may be used alone or in combination of two or more.
The oil used for the oil-extended rubber and the resin used for the resin-extended rubber are the same as those described later. Although the oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, they are usually about 5 to 50 parts by mass per 100 parts by mass of the rubber solid content.

The 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 (—SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group, alkoxy group, etc.), amino group, amide group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. These functional groups may have substituents, and among these, silicon-containing groups are preferred. —SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group (preferably hydrocarbon group having 1 to 6 carbon atoms (more preferably alkyl group having 1 to 6 carbon atoms)) or alkoxy group (preferably is an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is more preferably a hydroxyl group).

Specific examples of the compound (modifier) that introduces the functional group include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltri ethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like.

Hydrogenated SBR in which hydrogen is added can also be used as SBR.
When the SBR is hydrogenated SBR, the hydrogenation method and reaction conditions are not particularly limited, and hydrogenation may be carried out by a known method under known conditions. Usually, it is carried out at 20 to 150° C. under hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other production methods and conditions are not particularly limited, and, for example, the contents described in International Publication No. 2016/039005 can be applied.
Hydrogenated SBR has the same structure as a copolymer of ethylene, butadiene, and styrene as a result of adding hydrogen to the butadiene portion of SBR. Therefore, in this specification, hydrogenated SBR includes not only a hydrogenated product of a copolymer of butadiene and styrene (SBR), but also a copolymer of ethylene, butadiene, and styrene.

The hydrogenation rate of the hydrogenated SBR is preferably 65 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and preferably 100 mol% of the total butadiene units before hydrogenation. is 95 mol % or less, more preferably 92 mol % or less, still more preferably 90 mol % or less. Within the above range, the effect tends to be obtained more favorably.
The hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond portion of the spectrum obtained by measuring ¹ H-NMR.

The styrene content of SBR is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably is 40% by mass or less. Within the above range, the effect tends to be obtained more favorably.

The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably is 30% by mass or less. Within the above range, the effect tends to be obtained more favorably.

The styrene content of the SBR mentioned above means the styrene content of the SBR when there is one type of SBR, and means the average styrene content when there are multiple types of SBR.
The average styrene content of SBR can be calculated by {Σ (content of each SBR × styrene content of each SBR)}/total content of all SBRs. SBR is 85% by mass, styrene content: When SBR is 5% by mass with 25% by mass, the average styrene content of SBR is 39.2% by mass (= (85 × 40 + 5 × 25) / (85 + 5)) .

In addition, the above-mentioned vinyl content of SBR is the ratio of vinyl bonds when the total mass of the butadiene portion in SBR is 100 (unit: mass%), vinyl content [mass%] + cis content [mass%] + Trans amount [% by mass]=100 [% by mass]. When there is one type of SBR, it means the vinyl content of the SBR, and when there are multiple types, it means the average vinyl content.
The average vinyl content of SBR is Σ {content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ {content of each SBR amount × (100 [mass%] - styrene content [mass%] of each SBR)}. Parts by mass, styrene content: 25 mass%, vinyl content: 20 mass% SBR is 15 mass parts, and the remaining 10 mass parts are other than SBR, the average vinyl content of SBR is 28 mass% (= {75 × ( 100 [mass%]-40 [mass%]) × 30 [mass%] + 15 × (100 [mass%]-25 [mass%]) × 20 [mass%])} / {75 × (100 [mass% ]−40 [mass %])+15×(100 [mass %]−25 [mass %])}.

The SBR content in 100% by mass of the rubber component is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 99% by mass or more. The upper limit is not particularly limited, and may be 100% by mass. Within the above range, the effect tends to be obtained more favorably.

Other rubber components include diene rubbers such as isoprene rubber, butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). is mentioned. These may be used individually by 1 type, and may use 2 or more types together.

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

The content of the isoprene-based rubber is preferably 1 to 30% by mass in 100% by mass of the rubber component.

The BR is not particularly limited, for example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR150B manufactured by Ube Industries, Ltd., BR1280 manufactured by LG Chem, etc. BR containing 1,2-syndiotactic polybutadiene crystals (SPB) such as VCR412 and VCR617, and butadiene rubber (rare earth-based BR) synthesized using a rare earth catalyst, which are commonly used in the tire industry can be used. . These may be used individually by 1 type, and may use 2 or more types together.

BR may be oil-extended rubber extended with oil or resin-extended rubber extended with resin. These may be used alone or in combination of two or more.
The oil used for the oil-extended rubber and the resin used for the resin-extended rubber are the same as those described later. Although the oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, they are usually about 5 to 50 parts by mass per 100 parts by mass of the rubber solid content.

BR may be modified to introduce a functional group that interacts with a filler such as silica.
Examples of the above functional groups include silicon-containing groups (—SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group, alkoxy group, etc.), amino group, amide group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. These functional groups may have substituents, and among these, silicon-containing groups are preferred. —SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group (preferably hydrocarbon group having 1 to 6 carbon atoms (more preferably alkyl group having 1 to 6 carbon atoms)) or alkoxy group (preferably is an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is more preferably a hydroxyl group).

Specific examples of the compound (modifier) that introduces the functional group include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltri ethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like.

Hydrogenated BR to which hydrogen is added can also be used as BR.
When BR is hydrogenated BR, the hydrogenation method and reaction conditions are not particularly limited, and hydrogenation may be performed by a known method under known conditions. Usually, it is carried out at 20 to 150° C. under hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other production methods and conditions are not particularly limited, and, for example, the contents described in International Publication No. 2016/039005 can be applied.
Hydrogenated BR has the same structure as a copolymer of ethylene and butadiene as a result of adding hydrogen to the butadiene portion of BR. Therefore, in this specification, hydrogenated BR includes not only hydrogenated BR but also copolymers of ethylene and butadiene.

The hydrogenation rate of hydrogenated BR is preferably 65 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and preferably 100 mol% of the total butadiene units before hydrogenation. is 95 mol % or less, more preferably 92 mol % or less, still more preferably 90 mol % or less. Within the above range, the effect tends to be obtained more favorably.
The hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond portion of the spectrum obtained by measuring ¹ H-NMR.

The cis amount (cis content) of BR is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass. 97% by mass or less, more preferably 97% by mass or less. Within the above range, the effect tends to be obtained more favorably.
The cis amount of BR can be measured by infrared absorption spectrometry.

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

The content of BR in 100% by mass of the rubber component is preferably 1 to 30% by mass.

Rubber components other than isoprene-based rubber, SBR, and BR may be oil-extended rubber extended with oil or resin-extended rubber extended with resin. These may be used alone or in combination of two or more.
The oil used for the oil-extended rubber and the resin used for the resin-extended rubber are the same as those described later. Although the oil content in the oil-extended rubber and the resin content in the resin-extended rubber are not particularly limited, they are usually about 5 to 50 parts by mass per 100 parts by mass of the rubber solid content.

Rubber components other than isoprene-based rubber, SBR, and BR may be modified to introduce functional groups that interact with fillers such as silica.
Examples of the above-mentioned functional groups include silicon-containing groups (—SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group, alkoxy group, etc.), amino group, amide group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. These functional groups may have substituents, and among these, silicon-containing groups are preferred. —SiR ₃ (R is the same or different, hydrogen, hydroxyl group, hydrocarbon group (preferably hydrocarbon group having 1 to 6 carbon atoms (more preferably alkyl group having 1 to 6 carbon atoms)) or alkoxy group (preferably is an alkoxy group having 1 to 6 carbon atoms)), and at least one of R is more preferably a hydroxyl group).

Specific examples of the compound (modifier) that introduces the functional group include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltri ethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like.

Raw materials (monomers) for synthetic rubbers such as SBR and BR may be petroleum-derived or biomass-derived. Whether or not the raw material is derived from biomass can be determined by pMC (percent modern carbon) measured according to ASTM D6866-10.

The pMC is the ratio of the ¹⁴ C concentration of the sample to ^{the 14} C concentration of the modern standard reference, and this value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value will be described below.

In 1 mol (6.02×10 ²³ ) of carbon atoms, there are about 6.02×10 ^{11 14} C atoms, which is about 1/1 trillion of normal carbon atoms. ¹⁴ C is called a radioactive isotope and its half-life is 5730 years and decreases regularly. It takes 226,000 years for all of these to collapse. Therefore, in fossil fuels such as coal, petroleum, and natural gas, it is thought that more than 226,000 years have passed since carbon dioxide, etc. in the atmosphere was taken in and fixed by plants. All of the ¹⁴ C elements that were also included in the have collapsed. Therefore, at present, which is the 21st century, fossil fuels such as coal, petroleum, and natural gas do not contain ^{the 14} C element at all. Therefore, chemical substances produced using these fossil fuels as raw materials do not contain the ¹⁴ C element at all.

On the other hand, ¹⁴ C is continuously produced by cosmic ray nuclear reactions in the atmosphere, and the amount of 14 C is in balance with the decrease due to radioactive decay, and the amount of ¹⁴ C is constant in the earth's atmospheric environment. Therefore, the ¹⁴ C concentration of biomass resource-derived substances circulating in the current environment is about 1×10 ⁻¹² mol % with respect to all C atoms, as described above. Therefore, using the difference between these values, it is possible to calculate the ratio (biomass ratio) of natural resource-derived compounds (biomass resource-derived compounds) in a certain compound (rubber).

This ¹⁴ C is generally measured as follows. ¹³ C concentration ( ¹³ C/ ¹² C), ¹⁴ C concentration ( ¹⁴ C/ ¹² C) measurements are performed using tandem accelerator-based accelerator mass spectrometry. In the measurement, ^{the 14} C concentration in circulating carbon in nature in 1950 is adopted as a modern standard reference for ^{the 14} C concentration. As a specific standard substance, an oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (the radioactivity intensity of ¹⁴ C per 1 g of carbon) is fractionated for each carbon isotope, corrected to a constant value for ¹³ C, and the decay from 1950 AD to the date of measurement. The corrected value is used as the standard ¹⁴ C concentration value (100%). The pMC value is the ratio of this value to the value of the sample actually measured.

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

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

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

Examples of hard segments include polystyrene, polypropylene, polyester, polyamide, polyvinyl chloride, and polyurethane. Examples of soft segments include vinyl-polydiene, polyisoprene, polybutadiene, polyethylene, polychloroprene, poly-2,3-dimethylbutadiene, and the like. is mentioned. These may be one kind or two or more kinds.

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

The thermoplastic elastomer is preferably a thermoplastic elastomer having a styrene block (styrene-based thermoplastic elastomer).
Specific examples of styrene-based thermoplastic elastomers include styrene-vinylisoprene-styrene triblock copolymer (SIS), styrene-isobutylene diblock copolymer (SIB), styrene-butadiene-styrene triblock copolymer (SBS ), styrene-ethylene/butylene-styrene triblock copolymer (SEBS), styrene-ethylene/propylene-styrene triblock copolymer (SEPS), styrene-ethylene/ethylene/propylene-styrene triblock copolymer (SEEPS ), styrene-butadiene/butylene-styrene triblock copolymer (SBBS), and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, copolymers having styrene blocks at both ends are preferred, and styrene-ethylene/propylene-styrene triblock copolymers (SEPS) are more preferred.
The SEPS may be a hydrogenated SIS obtained by adding hydrogen to a styrene-vinylisoprene-styrene triblock copolymer (SIS).

The styrene content of the styrene-based thermoplastic elastomer is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass. 30% by mass or less, more preferably 30% by mass or less. Within the above range, the effect tends to be obtained more favorably.

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

The rubber composition contains silica.
Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it contains many silanol groups. The raw material of silica may be water glass (sodium silicate) or a biomass material such as rice husks. Commercially available products of Evonik Degussa, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The average particle size of silica is preferably 24 nm or less, more preferably 17 nm or less, still more preferably 16 nm or less, particularly preferably 15 nm or less, and is preferably 6 nm or more, more preferably 9 nm or more, and still more preferably 12 nm or more. is. Within the above range, the effect tends to be obtained more favorably.

In this specification, transmission electron microscope (TEM) observation is used as a method for measuring the average particle size of silica. Specifically, the silica particles are photographed with a transmission electron microscope. In the case of a standard type, the average particle size from the center is taken as the particle size, and the average value of the particle sizes of 100 fine particles is taken as the average particle size.

The content of silica may be more than 25 parts by mass with respect to 100 parts by mass of the rubber component, preferably 26 parts by mass or more, more preferably 27 parts by mass or more, and still more preferably 28 parts by mass or more, Also, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition contains carbon black.
Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material of carbon black may be a biomass material such as lignin or vegetable oil, or may be obtained by recycling tires. Further, the method for producing carbon black may be combustion such as a furnace method, or may be hydrothermal carbonization (HTC). Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These may be used alone or in combination of two or more.

The cetyltrimethylammonium bromide (CTAB) specific surface area of carbon black is preferably 100 m ² /g or more, more preferably 120 m ² /g or more, still more preferably 140 m ² /g or more, and preferably 180 m ² /g. Below, more preferably 160 m ² /g or less, still more preferably 140 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The CTAB specific surface area of carbon black is a value measured according to JIS K6217-3:2001.

The content of carbon black is preferably 70 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, and preferably 120 parts by mass or less, with respect to 100 parts by mass of the rubber component. It is more preferably 110 parts by mass or less, still more preferably 100 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, 2.5<content of carbon black/content of silica<5.0.
The carbon black content/silica content is preferably 2.6 or more, more preferably 2.8 or more, still more preferably 3.0 or more, and preferably 4.5 or less, more preferably 4 0.0 or less, more preferably 3.5 or less. Within the above range, the effect tends to be obtained more favorably.
In this relationship, the content of carbon black and the content of silica are the contents (unit: parts by mass) per 100 parts by mass of the rubber component.

The total content of silica and carbon black is preferably 90 parts by mass or more, more preferably more than 100 parts by mass, still more preferably 110 parts by mass or more, and preferably 140 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 130 parts by mass or less, and even more preferably 120 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- Sulfides such as triethoxysilylpropyl methacrylate monosulfide, mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane, and 3-aminopropyl Amino compounds such as triethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, 3- Examples include nitro-based solvents such as nitropropyltriethoxysilane, and chloro-based solvents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., and the like can be used. These may be used alone or in combination of two or more. Among them, mercapto-based compounds are preferred.

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

（式中、Ｒ^１００１は－Ｃｌ、－Ｂｒ、－ＯＲ^１００６、－Ｏ（Ｏ＝）ＣＲ^１００６、－ＯＮ＝ＣＲ^１００６Ｒ^１００７、－ＮＲ^１００６Ｒ^１００７及び－（ＯＳｉＲ^１００６Ｒ^１００７）_ｈ（ＯＳｉＲ^１００６Ｒ^１００７Ｒ^１００８）から選択される一価の基（Ｒ^１００６、Ｒ^１００７及びＲ^１００８は同一でも異なっていても良く、各々水素原子又は炭素数１～１８の一価の炭化水素基であり、ｈは平均値が１～４である。）であり、Ｒ^１００２はＲ^１００１、水素原子又は炭素数１～１８の一価の炭化水素基、Ｒ^１００３は－［Ｏ（Ｒ^１００９Ｏ）_ｊ］－基（Ｒ^１００９は炭素数１～１８のアルキレン基、ｊは１～４の整数である。）、Ｒ^１００４は炭素数１～１８の二価の炭化水素基、Ｒ^１００５は炭素数１～１８の一価の炭化水素基を示し、ｘ、ｙ及びｚは、ｘ＋ｙ＋２ｚ＝３、０≦ｘ≦３、０≦ｙ≦２、０≦ｚ≦１の関係を満たす数である。）

（式中、ｖは０以上の整数、ｗは１以上の整数である。Ｒ^１１は水素、ハロゲン、分岐若しくは非分岐の炭素数１～３０のアルキル基、分岐若しくは非分岐の炭素数２～３０のアルケニル基、分岐若しくは非分岐の炭素数２～３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを示す。Ｒ^１２は分岐若しくは非分岐の炭素数１～３０のアルキレン基、分岐若しくは非分岐の炭素数２～３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２～３０のアルキニレン基を示す。Ｒ^１１とＲ^１２とで環構造を形成してもよい。） Particularly suitable mercapto-based silane coupling agents include a silane coupling agent represented by the following formula (S1), or a combination of a bonding unit A represented by the following formula (I) and a bonding unit B represented by the following formula (II). silane coupling agents containing.

(wherein R ¹⁰⁰¹ is —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 ) (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ may be the same or different, and each is a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; , h has an average value of 1 to 4.), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, R ¹⁰⁰³ is —[O(R ¹⁰⁰⁹ O) _j ]-group (R ¹⁰⁰⁹ is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4.), R ¹⁰⁰⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰⁵ is 1 carbon atom to 18 monovalent hydrocarbon groups, and x, y and z are numbers satisfying the relationships x+y+2z=3, 0≤x≤3, 0≤y≤2, 0≤z≤1.)

(Wherein, v is an integer of 0 or more, w is an integer of 1 or more, R ¹¹ is hydrogen, halogen, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched C 2 to A 30 alkenyl group, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, or an alkyl group in which the terminal hydrogen is substituted with a hydroxyl group or a carboxyl group, where R ¹² is a branched or unbranched carbon number represents an alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms, wherein R ¹¹ and R ¹² form a ring structure; may be used.)

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

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

Specific examples of the silane coupling agent represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3- Lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoy Luthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthio Ethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane and the like can be mentioned. These may be used alone or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

In the silane coupling agent containing the linking unit A represented by the formula (I) and the linking unit B represented by the formula (II), the content of the linking unit A is preferably 30 mol% or more, more preferably 50 mol. % or more, preferably 99 mol % or less, more preferably 90 mol % or less. The content of the binding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol % or less. Also, the total content of the binding units A and B is preferably 95 mol % or more, more preferably 98 mol % or more, and particularly preferably 100 mol %.
In addition, the content of the bonding units A and B is the amount including the case where the bonding units A and B are positioned at the terminal of the silane coupling agent. When the bonding units A and B are located at the ends of the silane coupling agent, the form is not particularly limited as long as they form units corresponding to the formulas (I) and (II) representing the bonding units A and B. .

Halogen for R ¹¹ in formulas (I) and (II) includes chlorine, bromine, and fluorine. Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms include a methyl group and an ethyl group. Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms include a vinyl group and a 1-propenyl group. Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms include ethynyl group and propynyl group.

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

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

The content of the silane coupling agent is preferably 4 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 20 parts by mass or less with respect to 100 parts by mass of silica. , more preferably 16 parts by mass or less, and still more preferably 12 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains vulcanized rubber particles.
The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder or the like defined in JIS K 6316:2017 can be used. Recycled rubber powder produced from pulverized waste tires or the like is preferable from the viewpoint of environmental consideration and cost. These may be used individually by 1 type, and may use 2 or more types together.

As commercial products of vulcanized rubber particles, products of Lehigh, Muraoka Rubber Industry Co., Ltd., etc. can be used. In this specification, vulcanized rubber particles are not included in the rubber component.

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

The content of the vulcanized rubber particles is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 40 parts by mass with respect to 100 parts by mass of the rubber component. Below, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the total styrene content in the vulcanized rubber particles/rubber component is preferably 0.5 or more, more preferably 1.5 or more, still more preferably 2.5 or more, and preferably 5 below, more preferably 4 or less, still more preferably 3 or less. Within the above range, the effect tends to be obtained more favorably.
In this relationship, the content of vulcanized rubber particles is the content (unit: parts by mass) per 100 parts by mass of the rubber component, and the total styrene content in the rubber component is the content per 100 mass% of the rubber component ( Unit: % by mass).

The rubber composition may contain talc.
The average particle size of talc is preferably 50 μm or less, more preferably 30 μm or less. Although the lower limit of the average particle size of talc is not particularly limited, it is preferably 1 μm or more.

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

The rubber composition may contain aluminum hydroxide.
As used herein, aluminum _hydroxide means Al(OH) ₃ or _{Al2O3.3H2O .} As commercially available products, products of Sumitomo Chemical Co., Ltd., Showa Denko Co., Ltd., Nabaltec, etc. can be used. These may be used alone or in combination of two or more.

The average particle size of aluminum hydroxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, and is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably It is 1 μm or less. Within the above range, the effect tends to be obtained more favorably.
In addition, the average particle size of aluminum hydroxide is a value measured by the same method as the average particle size of silica.

The BET specific surface area (nitrogen adsorption specific surface area, N ₂ SA) of aluminum hydroxide is preferably 5 m ² /g or more, more preferably 8 m ² /g or more, still more preferably 10 m ² /g or more, and preferably is 40 m ² /g or less, more preferably 30 m ² /g or less, still more preferably 20 m ² /g or less.
The BET specific surface area of aluminum hydroxide is a value measured by the BET method according to ASTM D3037-81.

The content of aluminum hydroxide is preferably 1 to 25 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition may contain a calcium compound.
A calcium compound is a compound containing calcium, and examples thereof include inorganic salts such as calcium oxide, calcium hydroxide, and calcium carbide; and oxoacid salts such as calcium carbonate, calcium nitrate, and calcium sulfate. Oxoacid salts also include fatty acid salts such as calcium acetate and calcium stearate. Examples of products containing a calcium compound include eggshell (main component: calcium carbonate) and WB16 (mixture of fatty acid calcium, fatty acid amide and fatty acid amide ester) manufactured by Structol. These may be used individually by 1 type, and may use 2 or more types together. Of these, oxoacid salts are preferred, and calcium carbonate is more preferred.

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

The rubber composition may contain short fibers.
As short fibers, for example, organic short fibers, inorganic short fibers, and the like can be used. Specific examples of organic short fibers include nanocelluloses such as cellulose nanofibers (CNF) and cellulose nanocrystals (CNC); chitin nanofibers; and biomass nanomaterials such as chitosan nanofibers. Examples thereof include metal fiber, glass fiber, and the like. Commercially available products include Nippon Paper Industries Co., Ltd., Sugino Machine Co., Ltd., and the like. These may be used individually by 1 type, and may be used in mixture of 2 or more types. Among them, organic short fibers are preferred, and nanocellulose is more preferred.

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

The particle size of nanocellulose can be determined by image analysis using scanning electron micrographs, image analysis using transmission electron micrographs, image analysis using atomic force micrographs, analysis of X-ray scattering data, pore electric resistance method (Coulter It is the average fiber diameter measured by the principle method). In this specification, the average fiber diameter of nanocellulose (cellulose fibers) is typically the average fiber diameter of aggregates of cellulose fibers formed by aggregation of cellulose molecules.

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

The rubber composition contains a liquid polymer as a plasticizer.
The liquid polymer is a (co)polymer that is in a liquid state at normal temperature (25° C.). Specific examples include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid farnesene polymer, liquid farnesene butadiene copolymer, and the like. Further, the liquid polymer may be subjected to modification treatment or hydrogenation treatment. As commercially available products, products of Cray Valley, Kuraray Co., Ltd., etc. can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, liquid SBR is preferable.

The weight average molecular weight (Mw) of the liquid polymer is preferably 9500 or less, more preferably 9000 or less, still more preferably 8500 or less, and is preferably 100 or more, more preferably 1000 or more, and still more preferably 4000 or more. . Within the above range, the effect tends to be obtained more favorably.
In this specification, the liquid polymer is not included in the rubber component.

The liquid polymer is also preferably a hydrogenated liquid polymer to which hydrogen has been added.
The hydrogenation method and reaction conditions are not particularly limited, and hydrogenation may be carried out by a known method under known conditions. Usually, it is carried out at 20 to 150° C. under hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst.
In the hydrogenated liquid SBR, as a result of adding hydrogen to the butadiene portion of SBR, it has the same structure as a copolymer of ethylene, butadiene and styrene. Therefore, in this specification, the hydrogenated liquid SBR includes not only a hydrogenated product of a copolymer of butadiene and styrene (SBR) but also a copolymer of ethylene, butadiene and styrene.

The hydrogenation rate of the hydrogenated liquid SBR is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, based on 100 mol% of the total butadiene units before hydrogenation, and It is preferably 90 mol % or less, more preferably 80 mol % or less, still more preferably 70 mol % or less. Within the above range, the effect tends to be obtained more favorably.
The hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond portion of the spectrum obtained by measuring 1H-NMR.

The content of the liquid polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and preferably 60 parts by mass or less, based on 100 parts by mass of the rubber component. It is more preferably 50 parts by mass or less, still more preferably 45 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the above rubber composition, the content of liquid polymer/the content of silica>0.25.
The liquid polymer content/silica content is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 1.0 or more, and preferably 3.0 or less, more preferably 2 0.0 or less, more preferably 1.5 or less. Within the above range, the effect tends to be obtained more favorably.
In this relationship, the content of the liquid polymer and the content of silica are the contents (unit: parts by mass) per 100 parts by mass of the rubber component.

The rubber composition preferably contains a resin as a plasticizer.
Examples of resins that can be used include terpene-based resins, aromatic resins, C5-based resins, C5/C9-based resins, C9-based resins, cyclopentadiene-based resins, and the like. Moreover, resin may be used individually by 1 type, and may use 2 or more types together.

A terpene-based resin is a polymer containing a terpene compound (terpene-based monomer) as a constituent monomer. Copolymers, as well as copolymers of terpene compounds and other monomers copolymerizable therewith, are also included.

Terpene compounds are hydrocarbons represented by the composition (C ₅ H ₈ ) _n and their oxygen-containing derivatives, such as monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ), etc., and have a terpene as a basic skeleton. , 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like. These may be used individually by 1 type, and may use 2 or more types together.

In order to obtain better effects, the terpene-based resin is preferably a copolymer of a terpene compound and an aromatic monomer, and more preferably a copolymer of a terpene compound and styrene (terpene-styrene resin).
In this specification, a polymer containing a terpene compound and an aromatic monomer as constituent monomers, such as a terpene styrene resin, is treated as a terpene resin rather than an aromatic resin.

The content of the terpene-based resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Aromatic resin is a polymer containing an aromatic monomer as a constituent monomer, for example, a homopolymer obtained by polymerizing one aromatic monomer alone, two or more aromatic monomers In addition to copolymers obtained by copolymerizing the above, copolymers of aromatic monomers and other monomers copolymerizable therewith may also be used.

Examples of aromatic monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, Styrenic monomers such as o-chlorostyrene, m-chlorostyrene and p-chlorostyrene; Phenolic monomers such as phenol, alkylphenol and alkoxyphenol; Naphthol monomers such as naphthol, alkylnaphthol and alkoxynaphthol ; coumarone, indene, and the like. These may be used individually by 1 type, and may use 2 or more types together.

Other monomers include, for example, non-conjugated olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene. These may be used individually by 1 type, and may use 2 or more types together.

The content of the aromatic resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of the rubber component. Below, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less.

C5-based resins are polymers containing C5 fractions as constituent monomers. For example, C5 fractions obtained by pyrolysis of naphtha in the petrochemical industry are mixed with Friedel-Crafts-type catalysts such as AlCl ₃ and BF ₃ . Examples thereof include polymers obtained by polymerization. The C5 fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene; diolefinic hydrocarbons such as 1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, 3-methyl-1,2-butadiene;

The content of the C5 resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less.

The C5/C9-based resin is a polymer containing a C5 fraction and _a C9 fraction as _constituent monomers. and polymers obtained by polymerization using. Specific examples include copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, and the like.
In this specification, the C5/C9 resin is treated as a resin different from the aromatic resin, the C5 resin, and the C9 resin.

The content of the C5/C9 resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

The C9-based resin is a polymer containing a C9 fraction as _a constituent monomer. Examples thereof include polymers obtained by polymerization using a Friedel-Crafts-type catalyst such as _BF3 . Specific examples of the C9 fraction include vinyl toluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, indene and the like. C9-based resins include, together with the C9 fraction, styrene which is a C8 fraction, methylindene which is a C10 fraction, 1,3-dimethylstyrene, etc., naphthalene, vinylnaphthalene, vinylanthracene, and p-tert-butylstyrene. etc. may also be used as raw materials, and these C8-C10 fractions may be obtained by copolymerizing the mixture as it is, for example, with a Friedel-Crafts type catalyst.
In this specification, the C9 resin is treated as a resin different from the aromatic resin.

The content of the C9 resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less.

A cyclopentadiene-based resin is a polymer containing a cyclopentadiene-based monomer as a constituent monomer. In addition to copolymers obtained by copolymerizing the above, copolymers of cyclopentadiene-based monomers and other monomers copolymerizable therewith can also be used.

Cyclopentadiene-based monomers include, for example, cyclopentadiene, dicyclopentadiene, tricyclopentadiene, and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a polymer (DCPD-based resin) containing dicyclopentadiene (DCPD) as a constituent monomer, and more preferably a hydrogenated DCPD-based resin.

The content of the cyclopentadiene-based resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of the rubber component. Below, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less.

Commercially available products of the above-mentioned resins include, for example, Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Co., Nichinuri Chemical Co., Ltd. ), Nippon Shokubai Co., Ltd., JXTG Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

The content of the resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 15 parts by mass or less, more preferably 10 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the resin content/silica content is preferably 0.05 or more, more preferably 0.10 or more, still more preferably 0.15 or more, and preferably 0.4 or less. , more preferably 0.3 or less, and still more preferably 0.2 or less. Within the above range, the effect tends to be obtained more favorably.
In this relationship, the content of resin and the content of silica are the contents (unit: parts by mass) per 100 parts by mass of the rubber component.

As plasticizers other than liquid polymers and resins, for example, oils (including the oil content in oil-extended rubber), ester-based plasticizers, and the like can be used.
Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, or the like can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. Moreover, it may be a waste oil obtained by recovering vegetable oils and fats as edible oils. Commercial products include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Energy Co., Ltd., Orisoi, H&R, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., etc. products can be used. These may be used individually by 1 type, and may use 2 or more types together.

The content of the oil is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 50 parts by mass or less, and more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. It is preferably 40 parts by mass or less, more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The ester plasticizer is not particularly limited as long as it is a compound having an ester group that is in a liquid state at room temperature (25° C.). derivatives and the like. These may be used alone or in combination of two or more. Among them, phosphoric acid derivatives, sebacic acid derivatives, and adipic acid derivatives are preferred, and sebacic acid derivatives are more preferred.
The phthalic acid derivative is not particularly limited, and examples thereof include phthalate esters such as di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). The long-chain fatty acid derivative is not particularly limited. , For example, long-chain fatty acid glycerol esters can be mentioned, and the phosphoric acid derivative is not particularly limited. , The sebacic acid derivative is not particularly limited, but examples thereof include sebacate esters such as di(2-ethylhexyl) sebacate (DOS) and diisooctyl sebacate (DIOS). Examples include, but are not limited to, adipates such as di(2-ethylhexyl)adipate (DOA) and diisooctyladipate (DIOA).
Among them, phosphate, sebacate and adipate are preferred, and sebacate is more preferred. Moreover, as a specific compound, TOP, DOS, and DOA are preferable, and DOS is more preferable.
As the ester plasticizer, for example, products of Daihachi Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

The glass transition temperature (Tg) of the ester plasticizer is preferably −110° C. or higher, more preferably −100° C. or higher, still more preferably −80° C. or higher, preferably −20° C. or lower, more preferably −40. °C or below, more preferably -55°C or below. By setting it within the above range, there is a tendency that the above effect can be obtained more preferably.
In this specification, the glass transition temperature is measured according to JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan under the condition of a temperature increase rate of 10° C./min. It is a measured value.

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

The content of the plasticizer (total content of liquid polymer, resin, oil, etc.) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass, per 100 parts by mass of the rubber component. It is the above, and is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In the rubber composition, the content of the liquid polymer relative to 100% by mass of the plasticizer is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and preferably 90% by mass. % or less, more preferably 80 mass % or less, and still more preferably 75 mass % or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain processing aids.
Processing aids include metal salts (compounds in which hydrogen atoms of acids are substituted with metal ions), fatty acid amides, amide esters, fatty acid esters, and the like. These may be used alone or in combination of two or more. Among them, metal salts and fatty acid amides are preferred, and metal salts are more preferred.

Examples of metals used in metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as calcium and barium, and the like. Magnesium, zinc, nickel, molybdenum, etc. can also be used. Among them, alkali metals (especially potassium) and zinc are preferred.

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

As commercially available processing aids, products of Kishida Chemical Co., Ltd., Kenei Pharmaceutical Co., Ltd., Structol, Performance Additives, etc. can be used.

The content of the processing aid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 2 parts by mass or more, and preferably 8 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 6 parts by mass or less, and even more preferably 4 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain an antioxidant.
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; -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, Monophenol anti-aging agents such as styrenated phenol; inhibitors and the like. As commercially available products, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The content of the anti-aging agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 4.5 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. As commercially available products, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The wax content is preferably 0.5 parts by mass or more, more preferably 2.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass, relative to 100 parts by mass of the rubber component. It is below the department. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain stearic acid.
As the stearic acid, conventionally known ones can be used, and commercially available products such as NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The stearic acid content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of the rubber component. be. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain zinc oxide.
As zinc oxide, conventionally known ones can be used, and commercially available products are available from Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd. etc. products can be used. These may be used individually by 1 type, and may use 2 or more types together.

The content of zinc oxide is preferably 1 part by mass or more, more preferably 2.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass, relative to 100 parts by mass of the rubber component. It is below. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used as cross-linking agents in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The sulfur content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 1.3 parts by mass or more, and preferably 3.5 parts by mass or more, based on 100 parts by mass of the rubber component. It is 5 parts by mass or less, more preferably 3 parts by mass or less, and still more preferably 2.5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain an organic cross-linking agent.
Examples of the organic cross-linking agent include, but are not limited to, maleimide compounds, alkylphenol/sulfur chloride condensates, organic peroxides, and amine organic sulfides. These may be used alone or in combination of two or more.

The content of the organic cross-linking agent is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition may contain a vulcanization accelerator.
Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; N) and other thiuram-based vulcanization accelerators; N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene- Sulfenamide-based vulcanization accelerators such as 2-benzothiazolesulfenamide and N,N'-diisopropyl-2-benzothiazolesulfenamide; Sulfur accelerators may be mentioned. As commercially available products, products of Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. Below, more preferably 8 parts by mass or less, still more preferably 6 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

（式中、Ｒ^１～Ｒ^４はそれぞれ独立に炭素数１～１８の直鎖若しくは分岐鎖アルキル基、又は炭素数５～１２のシクロアルキル基を表す。） The rubber composition preferably contains a dialkyldithiophosphate compound.
As the dialkyldithiophosphate compound, for example, a salt of a dialkyldithiophosphate and a metal such as zinc or molybdenum can be used. Commercially available products such as TP-50 manufactured by Rhein Chemie can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, a compound represented by the following formula (1) (zinc dialkyldithiophosphate) is preferable.

(In the formula, R ¹ to R ⁴ each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms.)

In formula (1), linear or branched alkyl groups represented by R ¹ to R ⁴ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, 4-methylpentyl group, Examples include 2-ethylhexyl group, octyl group, octadecyl group and the like, while cycloalkyl groups include cyclopentyl group, cyclohexyl group, cyclooctyl group and the like. Among these, R ¹ to R ⁴ are preferably linear or branched alkyl groups having 2 to 8 carbon atoms, and n- A butyl group, an n-propyl group, an iso-propyl group and an n-octyl group are more preferred, and an n-butyl group is even more preferred.

The content of the dialkyldithiophosphate compound is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and still more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. is 6 parts by mass or less, more preferably 4 parts by mass or less, and still more preferably 2 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In addition to the above components, the 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 with respect to 100 parts by mass of the rubber component.

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

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-190°C, preferably 150-185°C. Vulcanization time is usually 5 to 15 minutes.

Examples of the rubber composition include tread, sidewall, base tread, undertread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, runflat It can be used for tire members such as tire side reinforcing layers (as a rubber composition for tires). Among others, it is suitable for the tread (in particular, the portion (cap tread) that comes into contact with the road surface during running).

A tire of the present disclosure is manufactured by a conventional method using the above rubber composition.
That is, the rubber composition is extruded according to the shape of the tread or the like in an unvulcanized stage, and molded together with other tire members on a tire molding machine by a conventional method to obtain an unvulcanized tire. to form A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

Tires for trucks and buses; tires for motorcycles; high-performance tires; winter tires such as studless tires; run-flat tires with side reinforcing layers; A tire with a sound absorbing member provided in the tire cavity; A tire with a sealing member provided with a sealant that can be sealed in the tire interior or in the tire cavity in the event of a puncture; Electronic parts such as sensors and wireless tags provided in the tire interior or the tire cavity It can be used for tires with electronic parts, etc., and is suitable for passenger car tires.

The size of the tire is not particularly limited. For example, the tire width can be selected within the range of 100 to 400 mm, the aspect ratio within the range of 25 to 85%, and the rim diameter within the range of 10 to 25 inches. is. Specific examples of /40R16, 225/40R17, 235/40R17, 245/40R16, 255/40R17, 265/40R17, 275/35R18, 285/30R19, 295/45R20 and the like.

なお、タイヤ外径（Ｄｔ）とは、タイヤを適用リムに装着して内圧２５０ｋＰａ・無負荷とした状態のタイヤの外径である。タイヤ断面幅（Ｗｔ）とは、タイヤを適用リムに装着して内圧２５０ｋＰａ・無負荷とした状態のタイヤ側面の模様又は文字など全てを含むサイドウォール間の直線距離、つまり総幅からタイヤの側面の模様、文字などを除いた幅である。 In the tire described above, the tire outer diameter Dt and the tire cross-sectional width Wt preferably satisfy the following relational expressions.

The tire outer diameter (Dt) is the outer diameter of the tire when the tire is mounted on an applicable rim and the internal pressure is 250 kPa with no load. The tire cross-sectional width (Wt) is the linear distance between the sidewalls including all patterns and letters on the tire side when the tire is mounted on the applicable rim and the internal pressure is 250 kPa and no load, that is, the total width to the tire side. This is the width excluding patterns, characters, etc.

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

A tire that satisfies the above formula is preferably applied to a pneumatic tire for a passenger car. This is because pneumatic tires for passenger cars that satisfy the above formula tend to be more suitable for solving the problems of this case.

The present disclosure will be specifically described based on Examples, but the present disclosure is not limited thereto.

Various chemicals used in Examples and Comparative Examples are described below.

(rubber component)
SBR1: Solution-polymerized SBR synthesized in Production Example 1 below (styrene content: 40% by mass, vinyl content: 24% by mass)
SBR2: Emulsion-polymerized SBR synthesized in Production Example 2 below (styrene content: 40% by mass, vinyl content: 12% by mass, containing 50 parts by mass of oil per 100 parts by mass of rubber solids)
SBR3: JSR1502 manufactured by JSR Corporation (styrene content: 24% by mass, vinyl content: 16% by mass)
SBR4: Resin-extended SBR synthesized in Production Example 3 below (styrene content: 40% by mass, vinyl content: 24% by mass, containing 8 parts by mass of resin per 100 parts by mass of rubber solids)

(Chemicals other than rubber components)
Carbon black 1: N134 (CTAB specific surface area: 142 m ² /g)
Carbon black 2: S185 (CTAB specific surface area: 160 m ² /g)
Silica 1: Zeosil 1115MP manufactured by Solvay Japan Co., Ltd. (average particle size: 24 nm)
Silica 2: Ultrasil 9100GR manufactured by Evonik Degussa (average particle size: 15 nm)
Silane coupling agent 1: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Silane coupling agent 2: Momentive NXT-Z45 (copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%))
Vulcanized rubber particles: Ekodyne manufactured by Lehigh
Resin: YS resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (terpene styrene resin (copolymer of styrene and terpene compound))
Liquid SBR: L-SBR-820 (Mw: 8500) manufactured by Kuraray Co., Ltd.
Hydrogenated liquid SBR: Hydrogenated liquid SBR synthesized in Production Example 4 below (hydrogenation rate: 50 mol%)
Oil: A/O mix extension oil manufactured by Sankyo Yuka Kogyo Co., Ltd. Oil component of oil-extended rubber Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation
Antiaging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Antiaging agent 2: Nocrac RD (poly (2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Processing Aid 1: ULTRA-FLOW 440 (fatty acid zinc) manufactured by Performance Additives
Processing aid 2: Potassium tetraborate manufactured by Kishida Chemical Co., Ltd. Zinc oxide: Zinc white No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Sulfur: HK-200-5 manufactured by Hosoi Chemical Industry Co., Ltd. (5% by mass powdered sulfur in oil)
Vulcanization accelerator 1: Noxceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator 2: Noxceler D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Dialkyldithiophosphate compound: TP-50 manufactured by Rhein Chemie (mixture of zinc dithiophosphate and polymer, R1 to R4 in formula (1) are n-butyl groups, active ingredient 50% by mass)

(Production example 1)
A nitrogen purged autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the contents of the reactor to 20° C., n-butyllithium was added to initiate the polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added and the mixture was further polymerized for 5 minutes, after which N-(3-dimethylaminopropyl)acrylamide was added as a modifier to carry out the reaction. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried with a hot roll adjusted to 110° C. to obtain SBR1.

(Production example 2)
Water, emulsifier (rosin acid soap emulsifier manufactured by Harima Chemicals Co., Ltd. and fatty acid soap manufactured by Wako Pure Chemical Industries, Ltd.), electrolyte (sodium phosphate manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a pressure-resistant reactor equipped with a stirrer. ), styrene, and butadiene. The reactor temperature was set to 5° C., and an aqueous solution in which a radical initiator was dissolved and an aqueous solution in which a catalyst was dissolved were added to the reactor to initiate polymerization. After 5 hours from the initiation of polymerization, a polymerization terminator was added to terminate the reaction to obtain a latex. TDAE is added to the latex and allowed to stand for half a day to allow the latex to absorb oil, then the latex is added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated sodium chloride aqueous solution or formic acid to form a crumb. A polymer was obtained. The polymer was dried in a vacuum dryer at 40° C. to obtain SBR2.

(Production example 3)
The terpene styrene resin and SBR1 were added in the given ratio to cyclohexane and stirred under 0.4 bar nitrogen pressure with heating for 2 hours at a stirring speed of 400 rpm. The resulting solution was dried to obtain modified styrene α-methylstyrene resin extended SBR (SBR4).

(Production example 4)
Liquid SBR, tetrahydrofuran, and 10% palladium carbon were added to a pressure vessel, and after nitrogen substitution, hydrogen substitution was carried out so that the pressure was 5.0 kg/cm ² and the reaction was carried out at 80° C. to obtain hydrogenated liquid SBR.

(Examples and Comparative Examples)
According to the formulations shown in Tables 1 and 2, materials other than sulfur, vulcanization accelerators and dialkyldithiophosphate compounds were mixed at 150° C. for 5 minutes using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. The mixture was kneaded to obtain a kneaded product. Next, sulfur, a vulcanization accelerator and a dialkyldithiophosphate compound were added to the resulting kneaded product, and kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. . The resulting unvulcanized rubber composition was molded into a tread shape, laminated with other tire members to form an unvulcanized tire, press-vulcanized at 150 ° C. for 12 minutes, and a test tire ( Size: 175/60R18) was manufactured. The obtained test tires were used for the following evaluations, and the results are shown in Tables 1 and 2.

In Tables 1 and 2, the rubber content in the oil-extended rubber is described in the rubber column, and the oil content in the oil-extended rubber is described in the extended oil column. In addition, the rubber content in the resin-extended rubber is described in the rubber column, and the resin content in the resin-extended rubber is added to the resin column.

In addition, in the evaluation below, the evaluation criteria for calculating the index are as follows.
(Abrasion resistance during high-speed running)
Table 1: Comparative Example 3
Table 2: Example 10 is Comparative Example 6, Example 11 is Comparative Example 7, and Example 12 is Comparative Example 8
(Steering stability maintenance performance during repeated driving)
Table 1: Comparative Example 5
Table 2: Example 10 is Comparative Example 6, Example 11 is Comparative Example 7, and Example 12 is Comparative Example 8

(Acetone extraction amount (AE))
A rubber test piece (sample) cut out from the tread of the test tire was measured according to the method for measuring the amount of acetone extracted in accordance with JIS K 6229:2015, and the substance extracted by acetone contained in the rubber test piece was measured. amount was measured.
Acetone extraction amount (mass%) = (mass of sample before extraction - mass of sample after extraction) / mass of sample before extraction x 100

(Polymer amount (PC))
Regarding the sample after acetone extraction in the above acetone extraction amount (AE), weight loss when organic matter is thermally decomposed and vaporized by heating in nitrogen (from room temperature to 750 ° C.) according to JIS K6226-1:2003. The minutes (mass) were measured, and PC (mass %) was calculated based thereon.

(Carbon black amount (BC))
For the sample after pyrolysis and vaporization in the above polymer amount (PC), the weight loss (mass) when oxidatively burned by heating in air was measured, and BC (% by mass) was calculated based on it.

(Ash content (Ash))
The mass of the component (ash) that does not burn in oxidative combustion in the carbon black amount (BC) was measured, and Ash (% by mass) was calculated based on the mass.

(Abrasion resistance during high-speed running)
Each test tire was mounted on a vehicle, and the groove depth of the tread portion was measured after running 50,000 km at an average speed of 100 km/h. From the measured values, the wear amount of the tread portion was calculated and expressed as an index based on the evaluation standard of 100. A larger index indicates less wear and better wear resistance.

(Steering stability maintenance performance during repeated driving)
Each test tire was attached to a vehicle, and the stability of the control when the tire was attached to the vehicle and run on a test course was sensory-evaluated on a 5-point scale (out of 5 points). Evaluation was performed by 20 test drivers, and the total score was calculated. The same test was conducted again, and the score of the second time/the score of the first time was calculated. The larger the index, the smaller the difference between the scores of the second and first runs, indicating that the steering stability (dry steering stability) maintenance performance during repeated running is excellent.

From Tables 1 and 2, the examples were superior to the comparative examples in the overall performance (total of each index) of the desired wear resistance during high-speed running and the steering stability maintenance performance during repeated running.

The present disclosure (1) contains a rubber component containing styrene-butadiene rubber, silica, carbon black, and a plasticizer containing a liquid polymer, and the silica content is 25 parts by mass with respect to 100 parts by mass of the rubber component. 2.5<the content of the carbon black/the content of the silica<5.0, and the content of the liquid polymer/the content of the silica>0.25. is.

The present disclosure (2) is the rubber composition for tires according to the present disclosure (1), wherein the total amount of styrene in 100 mass% of the rubber component is more than 35 mass%.

The present disclosure (3) is the rubber composition for tires according to the present disclosure (1) or (2), wherein the plasticizer contains a resin.

The present disclosure (4) is a rubber composition for a tire that is any combination with any one of the present disclosures (1) to (3) wherein the content of silica + the content of carbon black>100.

The present disclosure (5) is a rubber composition for tires in any combination with any one of the present disclosures (1) to (4), wherein the carbon black has a cetyltrimethylammonium bromide specific surface area of 140 m ² /g or more.

The present disclosure (6) is a rubber composition for tires, which is any combination with any one of the present disclosures (1) to (5), wherein the silica has an average particle size of 16 nm or less.

(7) of the present disclosure is a rubber composition for tires which is any combination with any one of (1) to (6) of the present disclosure containing a mercapto-based silane coupling agent.

(8) of the present disclosure is a rubber composition for tires in any combination with any one of (1) to (7) of the present disclosure containing a dialkyldithiophosphate compound.

The present disclosure (9) is a tire rubber composition in any combination with any one of the present disclosures (1) to (8), wherein the content of the liquid polymer is 50% by mass or more in 100% by mass of the plasticizer. be.

The present disclosure (10) is a rubber composition for tires in any combination with any one of the present disclosures (1) to (9), wherein the liquid polymer comprises a hydrogenated liquid polymer.

The present disclosure (11) is a rubber composition for tires in any combination with any one of the present disclosures (1) to (10), wherein the rubber component contains a resin-extended rubber.

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

The present disclosure (13) is a tire using a rubber composition of any combination of the present disclosure (1) to (12).

Claims (13)

Contains a rubber component containing styrene-butadiene rubber, silica, carbon black, and a plasticizer containing a liquid polymer,
The silica content is more than 25 parts by mass with respect to 100 parts by mass of the rubber component,
2.5<the carbon black content/the silica content<5.0,
A rubber composition for a tire wherein the content of the liquid polymer/the content of the silica>0.25. The rubber composition for tires according to claim 1, wherein the total amount of styrene in 100% by mass of said rubber component is more than 35% by mass. The rubber composition for tires according to claim 1 or 2, wherein the plasticizer contains a resin. The rubber composition for a tire according to any one of claims 1 to 3, wherein the content of silica + the content of carbon black>100. The rubber composition for tires according to any one of claims 1 to 4, wherein the carbon black has a cetyltrimethylammonium bromide specific surface area of 140 m ² /g or more. The rubber composition for tires according to any one of claims 1 to 5, wherein the silica has an average particle size of 16 nm or less. The rubber composition for tires according to any one of claims 1 to 6, which contains a mercapto-based silane coupling agent. The rubber composition for tires according to any one of claims 1 to 7, which contains a dialkyldithiophosphate compound. The rubber composition for tires according to any one of claims 1 to 8, wherein the content of the liquid polymer is 50% by mass or more in 100% by mass of the plasticizer. The rubber composition for tires according to any one of claims 1 to 9, wherein the liquid polymer comprises a hydrogenated liquid polymer. The rubber composition for tires according to any one of claims 1 to 10, wherein the rubber component contains a resin-extended rubber. The rubber composition for tires according to any one of claims 1 to 11, which contains vulcanized rubber particles. A tire using the rubber composition according to any one of claims 1 to 12.