Rubber composition, tread rubber, and rubber product

Abstract

The purpose of the present invention is to provide a rubber composition with which it is possible to achieve high-level wet grip performance, fuel efficiency performance, and wear resistance performance, as well as excellent resistance to discoloration and improved ozone resistance.　The present invention is a rubber composition including a rubber component, a filler, and an anti-aging agent, said rubber composition characterized in that the rubber component contains at least two types of styrene-butadiene rubber, the rubber component contains a high-purity natural rubber having a nitrogen content of 0.3 mass% or less, and the anti-aging agent contains a phenylenediamine-based anti-aging agent represented by general formula (1).

Description

Rubber composition, tread rubber and rubber product

[0001] The present invention relates to a rubber composition, a tread rubber, and a rubber product.

[0002] In the technical field of tires, various studies have been conducted to improve braking performance on wet road surfaces (hereinafter referred to as "wet grip performance") from the perspective of improving vehicle safety. For example, Patent Document 1 below discloses that applying a rubber composition to tire tread rubber, which is a rubber component containing 70% by mass or more of natural rubber, a thermoplastic resin, and a filler containing silica, improves the braking performance of the tire on both dry and wet road surfaces. Meanwhile, in connection with the recent global movement toward carbon dioxide emission regulations due to growing interest in environmental issues, there is an increasing demand for improved fuel efficiency in automobiles. To meet such demands, improved fuel efficiency (reduced rolling resistance) is also required in tire performance. However, it was found that the technology described in Patent Document 1 leaves room for improvement in fuel efficiency and wear resistance.

[0003] Therefore, Patent Document 2 discloses a rubber composition containing an emulsion-polymerized styrene-butadiene rubber and a solution-polymerized styrene-butadiene rubber, both of which have a glass transition temperature Tg of −25° C. or higher, a polymer with a low Tg, and further containing a filler and a specific hydrocarbyloxysilane compound, with the aim of achieving both wet grip performance and rolling resistance of a tire.

[0004] Furthermore, rubber products such as tires can deteriorate under the influence of external environments, such as in the presence of ozone, and as this deterioration progresses, cracks and other defects can occur. To address this problem, rubber compositions containing antioxidants are often applied to the various rubber components that make up tires. For example, Patent Document 3 below discloses that cracks and discoloration on the tire surface can be suppressed by applying a rubber composition containing a selected blend of a specific quinoline-based antioxidant and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) to the rubber that makes up the tire surface.

[0005] International Publication No. WO 2015 / 079703 International Publication No. WO 2017 / 188139 International Publication No. WO 2018 / 056384

[0006] However, while the technology described in Patent Document 2 makes it possible to achieve both wet grip performance and rolling resistance of a tire to some extent, there is a problem in that rubber compositions containing hydrocarbyloxysilane compounds having thiol groups or the like are prone to changes in appearance, such as the development of a black luster, over time. Improvements have been desired not only for tires but also for other rubber products (rubber crawlers, seismic isolation rubber, etc.).

[0007] Furthermore, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD) used in Patent Document 3 may have an impact on the environment, and in consideration of the possibility of future restrictions under European regulations, it has been desired to use an antioxidant that has a lower environmental impact and excellent ozone resistance. It should be noted that improvements in ozone resistance have also been desired not only for tires but also for other rubber products (rubber crawlers, seismic isolation rubber, etc.).

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology, to provide a rubber composition that achieves a high level of wet grip performance, fuel economy and abrasion resistance, while also achieving excellent discoloration resistance and improved ozone resistance, and to provide a tread rubber made from such a rubber composition.Another object of the present invention is to provide a rubber product that achieves a high level of wet grip performance, fuel economy and abrasion resistance, while also having excellent discoloration resistance and ozone resistance.

[0009] The gist of the present invention for solving the above problems is as follows: [1] A rubber composition including a rubber component, a filler, and an antioxidant, wherein the rubber component contains at least two types of styrene-butadiene rubber, and the antioxidant is represented by the following general formula (1): [In the formula, R １１ and R １２each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] A rubber composition comprising a triphenylamine-based antioxidant represented by the formula: By having the above-mentioned constitution, wet grip performance, fuel economy, and abrasion resistance can be highly compatible, and excellent discoloration resistance can be achieved, and ozone resistance can also be improved.

[0010] [2] A tread rubber comprising the rubber composition described above. The tread rubber having the above configuration achieves a high level of wet grip performance, fuel economy, and abrasion resistance, and is also excellent in discoloration resistance and ozone resistance.

[0011] [3] At least one rubber product selected from the group consisting of a tire, a rubber crawler, and a seismic isolation rubber, characterized in that the rubber product contains the rubber composition described above. The tread rubber having the above configuration achieves a high level of wet grip performance, fuel efficiency, and abrasion resistance, and is also excellent in discoloration resistance and ozone resistance.

[0012] According to the present invention, it is possible to provide a rubber composition that achieves a high level of wet grip performance, fuel economy, and abrasion resistance while also achieving excellent discoloration resistance and improved ozone resistance, and a tread rubber made from such a rubber composition. Also, according to the present invention, it is possible to provide a rubber product that achieves a high level of wet grip performance, fuel economy, and abrasion resistance while also having excellent discoloration resistance and ozone resistance.

[0013] The rubber composition, tread rubber, and rubber product of the present invention will be described in detail below by way of example based on embodiments thereof.

[0014] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0015] <Rubber Composition for Tire> The rubber composition of the present invention is a rubber composition containing a rubber component, a filler, and an antioxidant. Hereinafter, each component constituting the rubber composition of the present invention will be described.

[0016] (Rubber Component) The rubber component contains at least two types of styrene-butadiene rubber. Each styrene-butadiene rubber contributes to improving the dispersibility of fillers in the rubber composition and wet grip performance when applied to a tire, thereby achieving both wet grip performance, fuel economy, and wear resistance.

[0017] The rubber component preferably contains a styrene-butadiene rubber (A) modified with a modifier containing at least one atom of nitrogen, silicon, and tin and having a glass transition temperature of −50° C. or lower, and an unmodified styrene-butadiene rubber (B) having a glass transition temperature 30° C. or higher than that of the styrene-butadiene rubber (A).

[0018] By including the styrene-butadiene rubber (A) and the styrene-butadiene rubber (B) in the rubber component, wet grip performance can be improved when applied to a tire. In addition, in the present invention, by using the styrene-butadiene rubber (A) modified with a modifier containing at least one atom of nitrogen, silicon, and tin as the rubber component, the dispersibility of fillers such as silica in the rubber composition can be improved. As a result, the rubber composition of the present invention has significantly improved low heat buildup properties and improved filler dispersibility, which can improve reinforcement properties and physical properties such as fuel efficiency and wear resistance when applied to a tire.

[0019] As described above, the styrene-butadiene rubber (A) is preferably a styrene-butadiene rubber modified with a modifier having at least one atom of nitrogen, silicon, and tin and having a glass transition temperature of −50° C. or lower.

[0020] The styrene-butadiene rubber (A) preferably has a glass transition temperature of −50° C. or lower, more preferably −55° C. or lower, and preferably higher than −90° C. When the styrene-butadiene rubber (A) has a glass transition temperature of −50° C. or lower, the fuel economy and wear resistance of a tire using the rubber composition can be sufficiently improved. In addition, styrene-butadiene rubber having a glass transition temperature higher than −90° C. is easy to synthesize.

[0021] The glass transition temperatures of the styrene-butadiene rubber (A) and the styrene-butadiene rubber (B) described below can be measured, for example, as follows: Using each styrene-butadiene rubber as a sample, a DSC curve is recorded using a DSC250 manufactured by TA Instruments, while increasing the temperature from −100° C. at a rate of 20° C. / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve is taken as the glass transition temperature.

[0022] The content ratio of the styrene-butadiene rubber (A) in the rubber component is preferably 15% by mass or more and less than 85% by mass, more preferably 20 to 85% by mass, more preferably 30 to 80% by mass, and even more preferably 40 to 80% by mass. When the content ratio of the styrene-butadiene rubber (A) in the rubber component is 15% by mass or more and less than 85% by mass, the fuel economy and wet grip performance of a tire to which the rubber composition for tires is applied can be further improved.

[0023] Furthermore, the styrene-butadiene rubber (A) preferably has a bound styrene content of less than 15% by mass. The bound styrene content of the styrene-butadiene rubber (A) refers to the proportion of styrene units contained in the styrene-butadiene rubber. If the bound styrene content is less than 15% by mass, the glass transition temperature is likely to be low. From the same viewpoint, the bound styrene content is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. From the viewpoint of the wear resistance of a tire using the rubber composition of the present invention, the bound styrene content is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. The bound styrene content of the styrene-butadiene rubber (A) can be adjusted by the amount of monomers used in the polymerization of the styrene-butadiene rubber, the degree of polymerization, etc.

[0024] As described above, the styrene-butadiene rubber (A) is modified with a modifier having at least one atom of nitrogen, silicon, and tin. From the viewpoint of achieving a higher level of fuel economy, abrasion resistance, and wet grip performance in a tire to which the rubber composition is applied, the styrene-butadiene rubber (A) is preferably modified with a modifier having a nitrogen atom and a silicon atom, and more preferably modified with a modifier having an alkoxy group and a functional group containing a nitrogen atom.

[0025] Here, the "modifier having a nitrogen atom-containing functional group and an alkoxy group" is a general term for modifiers having at least one nitrogen atom-containing functional group and at least one alkoxy group. The nitrogen atom-containing functional group is preferably selected from the following: The monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a linear, branched, alicyclic, or aromatic ring, has a functional group selected from the group consisting of a primary amino group, a primary amino group protected with a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imine group, an imine residue, an amide group, a secondary amino group protected with a hydrolyzable protecting group, a cyclic secondary amino group, an onium salt residue of a cyclic secondary amine, an acyclic secondary amino group, an onium salt residue of an acyclic secondary amine, an isocyanuric acid triester residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a linear, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

[0026] Furthermore, the styrene-butadiene rubber (A) is preferably modified with an aminoalkoxysilane compound, and from the viewpoint of having a high affinity for fillers such as silica, it is more preferable that the terminals are modified with an aminoalkoxysilane compound. When the terminals of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the styrene-butadiene rubber (A) and the filler (particularly silica) becomes particularly strong.

[0027] The modified site of the styrene-butadiene rubber (A) may be the molecular terminal as described above, or may be the main chain. The styrene-butadiene rubber (A) having a modified molecular terminal can be produced, for example, by reacting various modifiers with the terminal of a styrene-butadiene copolymer having an active terminal, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A. In one preferred embodiment, the styrene-butadiene rubber (A) having a modified molecular terminal can be produced, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A, by reacting an aminoalkoxysilane compound with the terminal of a styrene-butadiene copolymer having an active terminal with a cis-1,4 bond content of 75% or more, and then reacting the resulting mixture with a carboxylic acid partial ester of a polyhydric alcohol for stabilization.

[0028] The carboxylic acid partial ester of a polyhydric alcohol refers to an ester of a polyhydric alcohol and a carboxylic acid, which has one or more hydroxyl groups. Specifically, esters of fatty acids with sugars or modified sugars having 4 or more carbon atoms are preferably used. More preferred examples of this ester include (1) fatty acid partial esters of polyhydric alcohols, particularly partial esters (monoesters, diesters, or triesters) of saturated or unsaturated higher fatty acids having 10 to 20 carbon atoms with polyhydric alcohols, and (2) ester compounds in which 1 to 3 partial esters of polycarboxylic acids and higher alcohols are bonded to a polyhydric alcohol. Polyhydric alcohols used as raw materials for the partial esters are preferably sugars (hydrogenated or unhydrogenated) having 5 or 6 carbon atoms and at least three hydroxyl groups, glycols, polyhydroxy compounds, and the like. Furthermore, the raw fatty acids are preferably saturated or unsaturated fatty acids having 10 to 20 carbon atoms, such as stearic acid, lauric acid, and palmitic acid. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specific examples include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

[0029] The aminoalkoxysilane compound is not particularly limited, but is preferably an aminoalkoxysilane compound represented by the following general formula (i): １１ ａ -Si-(OR １２ ) ４－ａ ... (i)

[0030] In general formula (i), R １１ and R １２ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R １１ and R １２ At least one of the groups is substituted with an amino group, a is an integer of 0 to 2, and OR １２If there are multiple, each OR １２ may be the same or different, and the molecule does not contain any active protons.

[0031] The aminoalkoxysilane compound is also preferably an aminoalkoxysilane compound represented by the following general formula (ii):

[0032] In the general formula (ii), n1+n2+n3+n4=4 (where n2 is an integer of 1 to 4, and n1, n3, and n4 are integers of 0 to 3). １ is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. １ may be the same or different, and A １ may be a divalent group that bonds with Si to form a cyclic structure. ２１ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, they may be the same or different. ２２ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, both of which may contain a nitrogen atom and / or a silicon atom. ２２ may be the same or different, or may be joined together to form a ring. ２３ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different. ２４represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when n4 is 2 or greater. As the hydrolyzable group in the primary or secondary amino group having a hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0033] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

[0034] In the general formula (iii), p1+p2+p3=2 (wherein p2 is an integer of 1 to 2, and p1 and p3 are integers of 0 to 1). ２ is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). ２５ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ２６ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and / or a silicon atom. ２６ may be the same or different, or may be joined together to form a ring. ２７ R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. ２８ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. As the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0035] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or (v).

[0036] In the general formula (iv), q1+q2=3 (where q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). ３１ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３２ and R ３３ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３４ are monovalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms or monovalent aromatic hydrocarbon groups having 6 to 18 carbon atoms, and when q1 is 2, they may be the same or different. ３５ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q2 is 2 or more, may be the same or different.

[0037]

[0038] In the general formula (v), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). ３６ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３７ represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different. R ３８represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when r2 is 2. A specific example of the aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0039] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or (vii):

[0040] In general formula (vi), R ４０ is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４１ R is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４２ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, where TMS represents a trimethylsilyl group (the same applies hereinafter).

[0041]

[0042] In general formula (vii), R ４３ and R ４４ are each independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４５ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R ４５ may be the same or different.

[0043] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or the following general formula (ix).

[0044] In general formula (viii), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3). ４６ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４７ and R ４８ are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４７ or R ４８ may be the same or different.

[0045]

[0046] In general formula (ix), X is a halogen atom. ４９ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R ５０ and R ５１ are bonded to form a divalent organic group. ５２ and R ５３ are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ As the hydrolyzable group, a hydrolyzable group is preferred, and as the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0047] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), the following general formula (xi), the following general formula (xii), or the following general formula (xiii).

[0048] In the general formulas (x) to (xiii), the symbols U and V are each an integer of 0 to 2 and satisfy U+V=2. ５４ ~ ９１ may be the same or different and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. α and β in general formula (xiii) are integers of 0 to 5.

[0049] Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred. Among the compounds satisfying general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethanamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethanamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethanamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propan-1-amine are particularly preferred.

[0050] The present invention also provides a method for producing the styrene-butadiene rubber (A) using a modifier containing an aminoalkoxysilane compound represented by the general formula (i). The method for producing the styrene-butadiene rubber (A) specifically includes the steps of: 1) polymerizing styrene-butadiene rubber in a hydrocarbon solvent in the presence of an organic alkali metal compound to produce an activated polymer having an alkali metal bonded to at least one end; and 2) reacting the activated polymer with a modifier containing the aminoalkoxysilane compound represented by the general formula (i).

[0051] Step 1) is a step for preparing an activated polymer having an alkali metal bonded to at least one end thereof, and can be carried out by polymerizing a styrene-based monomer and a butadiene-based monomer in a hydrocarbon solvent in the presence of an organic alkali metal compound.

[0052] The hydrocarbon solvent is not particularly limited, but may be, for example, one or more selected from the group consisting of n-pentane, n-hexane, n-heptane, isooctane, cyclohexane, toluene, benzene, and xylene.

[0053] The organic alkali metal compound can be used in an amount of 0.1 mmol to 1.0 mmol based on 100 g of the total monomers. The organic alkali metal compound is not particularly limited, and examples thereof include at least one selected from the group consisting of methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, s-butyl lithium, t-butyl lithium, hexyl lithium, n-decyl lithium, t-octyl lithium, phenyl lithium, 1-naphthyl lithium, n-eicosyl lithium, 4-butylphenyl lithium, 4-tolyl lithium, cyclohexyl lithium, 3,5-di-n-heptylcyclohexyl lithium, 4-cyclopentyl lithium, naphthyl sodium, naphthyl potassium, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithium sulfonate, sodium sulfonate, potassium sulfonate, lithium amide, sodium amide, potassium amide, and lithium isopropyl amide.

[0054] The polymerization in step 1 may be optionally carried out by further adding a polar additive. The polar additive may be added in an amount of 0.001 to 1.0 part by weight based on 100 parts by weight of the total monomers. Specifically, the polar additive may be added in an amount of 0.005 to 0.5 parts by weight, more specifically, 0.01 to 0.3 parts by weight based on 100 parts by weight of the total monomers. The polar additive may be, for example, at least one selected from the group consisting of tetrahydrofuran, ditetrahydrofurylpropane, diethyl ether, cycloamethyl ether, dipropyl ether, ethylene dimethyl ether, ethylene dimethyl ether, diethyl glycol, dimethyl ether, tert-butoxyethoxyethane, bis(3-dimethylaminoethyl)ether, (dimethylaminoethyl)ethyl ether, trimethylamine, triethylamine, tripropylamine, and tetramethylethylenediamine.

[0055] In the above-mentioned production method, when a conjugated diene monomer and an aromatic vinyl monomer are copolymerized by using the polar additive, the difference in reaction rate between them can be compensated for, thereby guiding the formation of a random copolymer.

[0056] The polymerization in step 1) can be carried out via adiabatic polymerization or isothermal polymerization. Here, the adiabatic polymerization refers to a polymerization method that involves polymerizing the organic alkali metal compound by heat of self-reaction without adding any heat after adding the organic alkali metal compound, while the isothermal polymerization refers to a polymerization method that maintains a constant temperature of the polymer by adding or removing heat after adding the organic alkali metal compound.

[0057] Furthermore, the polymerization may be carried out in a temperature range of 20°C to 200°C, specifically in a temperature range of 0°C to 150°C, more specifically in a temperature range of 10°C to 120°C.

[0058] The step 2) is a modification reaction step in which the activated polymer is reacted with a modifier containing an aminoalkoxysilane compound represented by the general formula (i) to produce styrene-butadiene rubber (A).

[0059] In this case, the modifying agent containing the compound represented by formula (1) may be the same as that described above. The aminoalkoxysilane compound represented by general formula (i) can be used in a ratio of 0.1 to 2.0 moles per mole of the organic alkali metal compound. Furthermore, the reaction in step 2) is a modification reaction for introducing functional groups into the polymer, and each reaction can be carried out at a temperature range of 0°C to 90°C for 1 minute to 5 hours.

[0060]

[0033] The above-described preparation method may further include, after step 2), one or more steps of recovering the solvent and unreacted monomer and drying, if necessary.

[0061] Furthermore, the content of the styrene-butadiene rubber (A) in the rubber component due to the modifier containing the aminoalkoxysilane compound represented by the general formula (i) is not particularly limited, but is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, and more preferably 50% by mass or less. When the content of the styrene-butadiene rubber (A) in the rubber component is 15% by mass or more, fuel economy and wear resistance can be further improved when the rubber composition is applied to a tire. On the other hand, when the content of the styrene-butadiene rubber (A) in the rubber component is 60% by mass or less, a sufficient amount of the styrene-butadiene rubber (B), described below, can be contained, and good wet grip performance can be maintained when the rubber composition is applied to a tire.

[0062] In addition to the styrene-butadiene rubber (A), the rubber component preferably further contains unmodified styrene-butadiene rubber (B) having a glass transition temperature at least 30° C. higher than that of the styrene-butadiene rubber (A). By containing the styrene-butadiene rubber (B) having a high glass transition temperature as the rubber component, wet grip performance can be improved when the rubber composition for tires is applied to tires.

[0063] The styrene-butadiene rubber (B) must have a glass transition temperature that is at least 30° C. higher than that of the styrene-butadiene rubber (A), and preferably at least 35° C. higher, which increases the flexibility of the rubber and can sufficiently improve the fuel economy and wear resistance of a tire using the rubber composition.

[0064] Furthermore, the content of the styrene-butadiene rubber (B) in the rubber component is not particularly limited, but is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably less than 85% by mass, more preferably 80% by mass or less. When the content of the styrene-butadiene rubber (B) in the rubber component is 15% by mass or more, the wet grip performance can be further improved when the rubber composition is applied to a tire. On the other hand, when the content of the styrene-butadiene rubber (B) in the rubber component is less than 85% by mass, the fuel economy and wear resistance can be well maintained when the rubber composition is applied to a tire.

[0065] Furthermore, from the viewpoint of achieving wet grip performance, fuel economy and wear resistance at higher levels when the rubber composition is applied to a tire, it is preferable that the content ratio of the styrene-butadiene rubber (B) is larger than the content ratio of the styrene-butadiene rubber (A) (content ratio of styrene-butadiene rubber (B) / content ratio of styrene-butadiene rubber (A)>1).

[0066] The rubber component may contain a rubber (other rubber) different from the styrene-butadiene rubber (A) and the styrene-butadiene rubber (B) as a rubber component, for the purpose of improving fuel economy, abrasion resistance, etc. when the rubber composition is applied to a tire. The other rubber may be appropriately selected depending on the required performance, and for example, one or more of diene rubbers such as natural rubber (NR), polybutadiene (BR), polyisoprene (IR), ethylene-propylene copolymer rubber, etc., and non-diene rubbers such as butyl rubber may be used.

[0067] However, from the viewpoint of achieving wet grip performance, fuel economy, and abrasion resistance at higher levels when the rubber composition of the present invention is applied to rubber products such as tires, it is preferable that the rubber component consists of only the styrene-butadiene rubber (A) and the styrene-butadiene rubber (B).

[0068]

[0033] (Filler) The rubber composition of the present invention contains a filler in addition to the rubber component described above. By using the filler together with the rubber component containing the styrene-butadiene rubber (A), the dispersibility of the filler is improved, and low fuel consumption performance and wear resistance can be achieved when the rubber composition is applied to a tire.

[0069] Here, the content of the filler is not particularly limited, but is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 120 parts by mass or less. By optimizing the amount of filler, wet grip performance, fuel economy, and wear resistance can be achieved at a higher level. When the filler content is 20 parts by mass or more, sufficient wet grip performance, fuel economy, and wear resistance can be obtained, and when the content is 160 parts by mass or less, deterioration of low heat buildup and processability can be suppressed.

[0070] Silica: From the viewpoints of wet grip performance, fuel economy, and abrasion resistance, it is preferable that the filler contains at least silica. The type of silica contained in the filler is not particularly limited and can be appropriately selected depending on the required performance. For example, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. can be used as the silica, with wet silica being preferred. These silicas may be used alone or in combination of two or more. Precipitated silica can also be used as the wet silica. Precipitated silica is silica obtained by reacting a reaction solution at a relatively high temperature in the neutral to alkaline pH range in the early stages of production to grow primary silica particles, and then adjusting the pH to the acidic side to aggregate the primary particles.

[0071] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is also preferred as the silica. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure a sufficient supply. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs involved in transportation and storage, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned in a biomass boiler using an alkali silicate aqueous solution. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), and then sorted and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by the method described in JP 2019-38728 A, for example.

[0072] The silica preferably has a specific surface area of ​​50 m 2 / g~350m 2 / g. The CTAB specific surface area of ​​silica is 50m 2 / g or more, the abrasion resistance is further improved, and the CTAB specific surface area of ​​the silica is 350 m 2 If it is less than / g, the rolling resistance will be small.

[0073] Furthermore, the silica has a nitrogen adsorption specific surface area (BET method) of 80 m 2 / g or more 330 m 2 The nitrogen adsorption specific surface area (BET method) of silica is preferably less than 80 m 2 When the silica has a nitrogen adsorption specific surface area (BET method) of 330 m / g or more, the tire to which the rubber composition is applied can be sufficiently reinforced, and the fuel efficiency of the tire can be further improved. 2 When the specific surface area of ​​silica by nitrogen adsorption (BET method) is less than 130 m / g, the elastic modulus of the rubber composition does not become too high, and the wet grip performance of a tire using the rubber composition is further improved. 2 / g or more, and 150 m 2 / g or more, and 170 m 2 / g or more, and 180 m 2 / g or more, and 190 m 2 / g or more, and 195 m 2 From the viewpoint of further improving the wet grip performance of the tire, the nitrogen adsorption specific surface area (BET method) of the silica is more preferably 300 m 2 / g or less, and 280 m 2 / g or less is more preferable, and 270m 2 It is more preferable that the tensile strength is not more than 1 / g.

[0074] Furthermore, the content of the silica is preferably 20 parts by mass or more but less than 100 parts by mass per 100 parts by mass of the rubber component. By optimizing the amount of silica, wet grip performance, fuel economy, and abrasion resistance can be simultaneously achieved at higher levels. When the silica content is 20 parts by mass or more, sufficient wet grip performance, fuel economy, and abrasion resistance are obtained, while when the silica content is less than 100 parts by mass, deterioration of low heat buildup and processability can be suppressed. From the same viewpoint, the content of the silica is more preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 62 parts by mass or more, even more preferably 65 parts by mass or more, and particularly preferably 68 parts by mass or more per 100 parts by mass of the rubber component. In addition, the content of the silica is more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and particularly preferably 82 parts by mass or less per 100 parts by mass of the rubber component.

[0075] Carbon Black: Preferably, the filler further contains carbon black in addition to the silica. The carbon black reinforces the rubber composition and improves the abrasion resistance of the rubber composition. As the carbon black, plant-derived carbon black and recycled carbon black (also called "recycled carbon black") are preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Recycled carbon black will be described in detail below.

[0076] From the viewpoint of further improving the abrasion resistance of the rubber composition and a tire using the same, the content of the carbon black (total of recycled carbon black and carbon black other than recycled carbon black) in the rubber composition of the present invention is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of workability of the rubber composition, the content of the carbon black in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of the rubber component.

[0077] As used herein, "recycled carbon black" refers to carbon black recovered from recycled waste materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only waste generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process of scraping the tread portion remaining on the base tire during tire retreading, for example. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0078] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixed grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0079] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residues has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content of the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0080] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0081] The recycled carbon black can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent Publication No. 6,856,781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0082] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0083] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0084] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0085] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0086] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m as measured by the BET method. ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ In this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black measured by the BET method is a statistical thickness specific surface area (STSA) determined in accordance with ASTM D6556.

[0087] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0088] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0089] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0090] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0091] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0092] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0093] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0094] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0095] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of 1.33 for water and a refractive index of 1.75 for the filler.

[0096] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0097] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, the ash content of the recycled carbon black is determined in accordance with ASTM D8474 and D1506.

[0098] The recycled carbon black preferably has a dibutyl phthalate (DBP) absorption of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

[0099] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0100] Commercially available recycled carbon black can be used. For example, Enrestec's product name "PB365" can be mentioned as such a commercially available product. PB365 is a recycled carbon black produced through the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. ２ / g and contains about 17% by mass of ash.

[0101] The amount of recycled carbon black is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, still more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component. When the amount of recycled carbon black is 5 parts by mass or more per 100 parts by mass of the rubber component, the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the amount is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0102] In the filler, the content of silica in the total amount of the silica and the carbon black is preferably 80% by mass or more but less than 100% by mass, more preferably 85% by mass or more but less than 100% by mass, and even more preferably 90% by mass or more but less than 100% by mass. When the content of silica in the total amount of the silica and the carbon black is 80% by mass or more, a decrease in fuel efficiency due to an increase in carbon black can be suppressed, and when the content is less than 100% by mass, the reinforcing effect of carbon black can be reliably secured.

[0103] Other Inorganic Compounds In addition to silica and carbon black, other inorganic compounds represented by the following formula (I) can also be used as the filler: nM.xSiO Ｙ ・zH ２ O ... (I) (In the formula, M is at least one selected from the group consisting of a metal selected from the group consisting of Al, Mg, Ti, Ca and Zr, an oxide or hydroxide of these metals, a hydrate thereof, and a carbonate of these metals; and n, x, y and z are integers of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively.) When the filler contains other inorganic compounds, the content thereof is preferably about 5 to 30 parts by mass per 100 parts by mass of the rubber component.

[0104] The inorganic compound of the above formula (I) includes alumina (Al) such as γ-alumina and α-alumina. ２ O ３ alumina monohydrate (Al) such as boehmite and diaspore; ２ O ３ ・H ２ O); aluminum hydroxides such as gibbsite and bayerite [Al(OH) ３ ]; aluminum carbonate [Al ２ (CO ３ ) ３ ], magnesium hydroxide [Mg(OH) ２ ], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO.4SiO ２ ・H ２ O), attapulgite (5MgO.8SiO２ ・9H ２ O), titanium white (TiO ２ ), titanium black (TiO ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ ], magnesium aluminum oxide (MgO.Al ２ O ３ ), clay (Al ２ O ３ 2SiO ２ ), kaolin (Al ２ O ３ 2SiO ２ ・2H ２ O), pyrophyllite (Al ２ O ３ 4SiO ２ ・H ２ O), bentonite (Al ２ O ３ 4SiO ２ ・2H ２ O), aluminum silicate (Al ２ SiO ５ , Al ４ 3SiO ４ ・5H ２ O, etc.), magnesium silicate (Mg ２ SiO ４ , MgSiO ３ etc.), calcium silicate (Ca ２ SiO ４ etc.), calcium aluminum silicate (Al ２ O ３ CaO 2SiO ２ etc.), magnesium calcium silicate (CaMgSiO ４ ), calcium carbonate (CaCO ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ ・nH ２ O], zirconium carbonate [Zr(CO ３ ) ２ ], crystalline aluminosilicates containing hydrogen, alkali metals or alkaline earth metals to compensate for the charge, such as various zeolites, and the like.

[0105] (Silane Coupling Agent) The rubber composition of the present invention preferably further contains a silane coupling agent in addition to the rubber component and the filler. The inclusion of the silane coupling agent improves the dispersibility of the filler, particularly silica, and contributes to achieving both wet grip performance and fuel economy and wear resistance.

[0106] And, in the present invention, the silane coupling agent preferably contains at least a silane coupling agent (S1) having a thiol group, and more preferably contains a silane coupling agent (S2) having a sulfide bond.The silane coupling agent (S1) having a thiol group can further improve the dispersibility of the silica described above.It should be noted that although the silane coupling agent (S1) having a thiol group can further improve the dispersibility of silica, if the content is too high, it may cause discoloration such as blackening of the tire over time.Therefore, the silane coupling agent further contains a silane coupling agent (S2) having a sulfide bond, and by adjusting the content of these silane coupling agents, it is possible to achieve both wet grip performance, low fuel consumption performance and wear resistance, while suppressing discoloration such as blackening (excellent discoloration resistance).

[0107] Here, the total content of the silane coupling agents is preferably 1 to 15 parts by mass per 100 parts by mass of the silica. When the total content of the silane coupling agents is 1 part by mass or more per 100 parts by mass of the silica, wet grip performance, fuel economy, and abrasion resistance can be sufficiently achieved, and when the total content of the silane coupling agents is 15 parts by mass or less per 100 parts by mass of the silica, discoloration resistance can be sufficiently ensured. From the same viewpoint, the total content of the silane coupling agents is preferably 2 to 14 parts by mass per 100 parts by mass of the silica, more preferably 3 to 13 parts by mass, and even more preferably 5 to 12 parts by mass.

[0108] The content of the silane coupling agent (S1) is 1 to 10 parts by mass per 100 parts by mass of the silica. When the content of the silane coupling agent (S1) is 1 part by mass or more per 100 parts by mass of the silica, wet grip performance, fuel economy, and abrasion resistance can be sufficiently achieved, and when the content of the silane coupling agent (S1) is 10 parts by mass or less per 100 parts by mass of the silica, discoloration resistance can be sufficiently ensured. From the same viewpoint, the content of the silane coupling agent (S1) is preferably 2 to 9.5 parts by mass, more preferably 3 to 9 parts by mass, per 100 parts by mass of the silica.

[0109] Furthermore, from the viewpoint of achieving a good balance between wet grip performance, fuel economy, and abrasion resistance, as well as the effect of discoloration resistance, the mass ratio (B / A) of the content of the silane coupling agent (S2) to the content of the silane coupling agent (S1) is preferably 0.3 or more and less than 3.0. When the content mass ratio (S2 / S1) of the silane coupling agents (S1) and (S2) is 0.3 or more, the effect of discoloration resistance is more reliably obtained, and when the content mass ratio (S2 / S1) of the silane coupling agents (S1) and (S2) is less than 3.0, the wet grip performance, fuel economy, and abrasion resistance are more reliably achieved. From the same viewpoint, the content mass ratio (B / A) of the silane coupling agents (S1) and (S2) is more preferably 0.31 or more and less than 3.0, and even more preferably 0.32 or more and 2.9 or less.

[0110] The silane coupling agent (S1) is not particularly limited as long as it has a thiol group. Examples thereof include 3-(trimethoxysilyl)-1-propanethiol, 3-(triethoxysilyl)-1-propanethiol, 3-(methyldimethoxysilyl)-1-propanethiol, 2-(trimethoxysilyl)-1-ethanethiol, 2-(triethoxysilyl)-1-ethanethiol, 2-(methyldimethoxysilyl)-1-ethanethiol, (trimethoxysilyl)methanethiol, (triethoxysilyl)methanethiol, (methyldimethoxysilyl)methanethiol, 3-[ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol {manufactured by Evonik Degussa, trade name "Si363" and [C １３ H ２７ O (CH ２ CH ２ O) ５ ] ２ (CH ３ CH ２ O)Si(CH ２ ) ３ SH} and the like.

[0111] Furthermore, among the above-mentioned silane coupling agents, the silane coupling agent (S1) preferably has a carbon number of 20 to 75. This is because wet grip performance, fuel economy, and wear resistance can be more reliably achieved at the same time.

[0112] The silane coupling agent (S2) is not particularly limited as long as it has a sulfide bond. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, and the like.

[0113] Bioethanol can also be used as a raw material for silane coupling agents. Bioethanol is produced primarily using sugars and / or cellulose as biological resources, preventing the effective use of other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of a monomer component derived from a biological resource, a monomer component derived from a renewable resource, and a monomer component derived from a fossil resource. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0114] (Antiaging Agent) In addition to the rubber component, the filler, and the silane coupling agent, the rubber composition of the present invention further contains an antioxidant, which has the effect of preventing aging of the rubber composition and rubber products using the same.

[0115] The content of the antioxidant is preferably 0.5 to 10 parts by mass per 100 parts by mass of the rubber component. When the content of the antioxidant is 0.5 parts by mass or more per 100 parts by mass of the rubber component, better ozone resistance is obtained and decreases in the elongation at break (EB) and tensile strength (TB) of the rubber composition after aging can be sufficiently suppressed. When the content of the antioxidant is 10 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties other than ozone resistance (heat buildup, etc.) can be suppressed. From the same viewpoint, the content of the antioxidant is preferably 1 to 8 parts by mass per 100 parts by mass of the rubber component.

[0116] The rubber composition for a tread of the present invention is characterized in that the antioxidant is a triphenylamine-based antioxidant represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] The inclusion of this triphenylamine-based antioxidant can improve the ozone resistance of the rubber composition and suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0117] R in the above general formula (1) １１ and R １２R each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. １１ and R １２ As the alkyl group, a linear or branched alkyl group having 2 to 8 carbon atoms and a cycloalkyl group having 5 to 8 carbon atoms are preferred.

[0118] R in the above general formula (1) １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ R each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. １３ is hydrogen, a linear or branched alkyl group having 1 to 10 carbon atoms, -NH-R １３１ , and -O-R １３２ is preferable. １３１ As R, a linear or branched alkyl group having 2 to 8 carbon atoms and a cycloalkyl group having 5 to 8 carbon atoms are preferred. １３２ As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms is preferred.

[0119] R １１ , R １２ and R １３１ With regard to the above, examples of the linear or branched alkyl group having 2 to 8 carbon atoms include an ethyl group, a propyl group (i.e., an n-propyl group, an isopropyl group), a butyl group (i.e., an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group), a pentyl group, a hexyl group, a heptyl group, and an octyl group.

[0120] R １３ and R １３２With regard to (1), examples of the linear or branched alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group (i.e., an n-propyl group, an isopropyl group), a butyl group (i.e., an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group), a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Among these, a methyl group, an ethyl group, and a propyl group (i.e., an n-propyl group, an isopropyl group) are preferred, a methyl group and an ethyl group are more preferred, and a methyl group is particularly preferred.

[0121] Also, R １１ , R １２ , R １３ , R １３１ and R １３２ Regarding the above, examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0122] The triphenylamine-based antioxidant is a compound represented by the following general formula (1-1): In the above general formula (1-1), a compound represented by R １１１ , R １１２ , R １２１ and R １２２ are each independently an alkyl group, provided that R １１１ and R １１２ The total number of carbon atoms in R is 2 to 11, preferably 2 to 7. １２１ and R １２２ The total number of carbon atoms in R in the general formula (1-1) is 2 to 11, and preferably 2 to 7. １３ represents R in the general formula (1). １３ and is synonymous with hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ are each independently a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.１３ With respect to -NH-R １３１ Examples of the group include —NH—CHR １３１１ R １３１２ is preferred, where R １３１１ and R １３１２ are each independently an alkyl group, provided that R １３１１ and R １３１２ The total number of carbon atoms is 2 to 11, preferably 2 to 7.

[0123] Methods for synthesizing the triphenylamine antioxidant represented by the above general formula (1) are described in French Patent No. 1,354,536 and US Pat. No. 3,277,174. For example, (i) an aromatic amine compound such as aniline, p-toluidine, or p-anisidine is reacted with a halogenated nitrobenzene such as 4-fluoronitrobenzene or 4-chloronitrobenzene to obtain a dinitrotriphenylamine compound such as 4,4'-dinitrotriphenylamine, 4,4'-dinitro-4''-methyltriphenylamine, or 4,4'-dinitro-4''-methoxytriphenylamine, and the dinitrotriphenylamine compound is reduced to obtain a diaminotriphenylamine compound such as 4,4'-diaminotriphenylamine, 4,4'-diamino-4''-methyltriphenylamine, or 4,4'-diamino-4''-methoxytriphenylamine, and the diaminotriphenylamine compound is reacted with a ketone such as acetone, methyl isobutyl ketone, or 2-octanone, or (ii) tris(p-aminophenyl)amine is reacted with a ketone such as acetone, methyl isobutyl ketone, or 2-octanone, The triphenylamine antioxidant represented by the above general formula (1) can be synthesized.

[0124] R in the above general formula (1) １１ and R １２ is preferably an isopropyl group, a 1,3-dimethylbutyl group, a 2-octyl group, or a 1,4-dimethylpentyl group. １１ and R １２A triphenylamine-based antioxidant in which R is an isopropyl group, a 1,3-dimethylbutyl group, a 2-octyl group, or a 1,4-dimethylpentyl group can further improve the ozone resistance of the side rubber and the rubber chafer, and can further suppress the occurrence of cracks in the side rubber and the rubber chafer.

[0125] R in the above general formula (1) １３ is preferably a hydrogen atom, an isopropylamino group, a 1,3-dimethylbutylamino group, a 1,4-dimethylpentylamino group, or a methoxy group. １３ A triphenylamine-based antioxidant in which R is hydrogen, an isopropylamino group, a 1,3-dimethylbutylamino group, a 1,4-dimethylpentylamino group, or a methoxy group can further improve the ozone resistance of the side rubber and the rubber chafer, and can further suppress the occurrence of cracks in the side rubber and the rubber chafer.

[0126] R in the above general formula (1) １１ and R １２ Preferably, R in general formula (1) has 2 to 8 carbon atoms. １１ and R １２ The triphenylamine antioxidant having 2 to 8 carbon atoms can further improve the ozone resistance of the side rubber and the rubber chafer, and can further suppress the occurrence of cracks in the side rubber and the rubber chafer.

[0127] Specific examples of the triphenylamine-based antiaging agent represented by the general formula (1) include 4,4'-bis(isopropylamino)triphenylamine, 4,4'-bis(1,3-dimethylbutylamino)triphenylamine, 4,4'-bis(2-octylamino)triphenylamine, 4,4'-bis(1,4-dimethylpentylamino)triphenylamine, 4,4'-bis(isopropylamino)-4''-methyltriphenylamine, 4,4'-bis(1,3-dimethylbutylamino)-4''-methyltriphenylamine, 4,4'-bis(1,4-dimethylpentylamino)-4''-methyltriphenylamine, 4,4'-bis(2-octylamino)-4''-methyltriphenylamine, Preferred are 4,4',4''-tris(isopropylamino)triphenylamine, 4,4',4''-tris(1,3-dimethylbutylamino)triphenylamine, 4,4',4''-tris(1,4-dimethylpentylamino)triphenylamine, 4,4',4''-tris(2-octylamino)triphenylamine, 4,4'-bis(isopropylamino)-4''-methoxytriphenylamine, 4,4'-bis(1,3-dimethylbutylamino)-4''-methoxytriphenylamine, 4,4'-bis(1,4-dimethylpentylamino)-4''-methoxytriphenylamine, and 4,4'-bis(2-octylamino)-4''-methoxytriphenylamine. These triphenylamine-based antioxidants may be used alone or in combination of two or more.

[0128] The proportion of the triphenylamine-based antioxidant represented by the general formula (1) in the antioxidant (of the total amount of antioxidants) is preferably 10 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 30 to 100 mass%. When the proportion of the triphenylamine-based antioxidant represented by the general formula (1) in the antioxidant is 10 to 100 mass%, the ozone resistance of the side rubber and / or the rubber chafer can be further improved, and the occurrence of cracks in the side rubber and / or the rubber chafer can be further suppressed.

[0129] Quinoline-Based Antiaging Agent: The antiaging agent preferably further contains a quinoline-based antiaging agent. The quinoline-based antiaging agent is an antiaging agent having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety or a tetrahydroquinoline moiety). The quinoline-based antiaging agent has the effect of improving the ozone resistance of the rubber composition, and a rubber composition containing both the triphenylamine-based antiaging agent represented by the general formula (1-1) or (1-2) and the quinoline-based antiaging agent can further suppress the occurrence of cracks in rubber products.

[0130] The quinoline-based antioxidant preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ) and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. The quinoline-based antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). Quinoline-based antioxidants containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline are highly effective in improving the ozone resistance of rubber compositions, and also have the advantage of being less likely to discolor the rubber composition. Therefore, a rubber composition containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline can further suppress the occurrence of cracks in rubber products and is also less susceptible to discoloration. Examples of the polymer of 2,2,4-trimethyl-1,2-dihydroquinoline include a dimer, trimer, and tetramer of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0131] The proportion of the quinoline-based antioxidant in the antioxidant is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass. When the proportion of the quinoline-based antioxidant in the antioxidant is 5 to 50% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0132] Amine-based antioxidant represented by formula (3) The antioxidant may further be an amine-based antioxidant represented by the following general formula (3): [In the formula, R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group. It is preferable to include an amine-based antioxidant represented by the following formula: The amine-based antioxidant represented by formula (3) contains a phenylenediamine moiety, just like the general-purpose antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD), but differs from antioxidant 6PPD in that it does not contain a double bond outside of the phenylenediamine moiety. The amine-based antioxidant represented by formula (3) has the effect of improving the ozone resistance of the rubber composition.

[0133] In the above general formula (3), R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group. ３１ and R ３２ may be the same or different, but from the viewpoint of synthesis, they are preferably the same.

[0134] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, which enhances the anti-aging effect and further improves the ozone resistance of the rubber composition. ３１ and R ３２ From the viewpoint of further improving the ozone resistance of the rubber composition, it is preferable that each of the groups independently represents a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

[0135] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0136] Specific examples of the amine-based antiaging agent represented by the general formula (3) include N,N'-dicyclohexyl-p-phenylenediamine, etc. The amine-based antiaging agents represented by the formula (3) may be used alone or in combination of two or more.

[0137] The proportion of the amine-based antioxidant in the antioxidant is preferably 0.1 to 80% by mass, and more preferably 1 to 70% by mass. When the proportion of the amine-based antioxidant in the antioxidant is 0.1 to 80% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0138] Amine-based antiaging agent of formula (4) Furthermore, the antiaging agent may be an amine-based antiaging agent represented by the following general formula (4): [In the formula, R４１ and R ４２ represents a phenyl group, and m4 represents an integer of 7 or more.]. The amine-based antioxidant represented by the general formula (4) has a higher molecular weight than conventional antioxidants, and as shown in the formula (4), it has a bridge moiety having a unique and relatively long chain length, i.e., "-NH-CH(CH ３ )-(CH ２ ) ｍ４ -CH(CH ３ )-NH-". It is believed that the high molecular weight and the presence of specific bridge moieties of such amine-based antioxidants reduce the diffusion rate in the rubber composition, further suppressing migration to the rubber surface. Furthermore, the amine-based antioxidant (C4) has a moiety composed of "-CH(CH ３ )-(CH ２ ) ｍ４ -CH(CH ３ One hydrogen atom is bonded to each of the two nitrogen atoms present at both ends of "(2-amino-2-methyl-2-methyl-2-propanol)-" (forming a so-called secondary amino group), and the presence of this bond in the structure represented by formula (4) is thought to contribute to the specific effect of improving ozone resistance (weather resistance).

[0139] In the above general formula (4), R ４１ and R ４２ is a phenyl group. ４１ and R ４２ When is a phenyl group, the weather resistance of the rubber composition can be further improved, and discoloration of the rubber composition can be more reliably prevented.

[0140] In the general formula (4), m4 is an integer of 7 or more, and from the viewpoint of improving the weather resistance of the rubber composition and preventing discoloration, it is more preferably an integer of 8 to 16, and even more preferably an integer of 10 to 14.

[0141] Examples of the amine-based antiaging agent of the above formula (4) include N,N'-bis(4-anilinophenyl)dodecane-2,11-diamine, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine, N,N'-bis(4-anilinophenyl)hexadecane-2,15-diamine, N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine, etc. Among these, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine are particularly preferred.

[0142] The proportion of the amine-based antioxidant represented by general formula (4) in the antioxidant is preferably 0.1 to 80 mass%, more preferably 1 to 70 mass%. When the proportion of the amine-based antioxidant represented by general formula (4) in the antioxidant is 0.1 to 80 mass%, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0143] Other Antiaging Agents The rubber composition of the present invention may or may not contain an antioxidant (other antioxidant) other than the triphenylamine-based antioxidant of general formula (1-1) or (1-2), the quinoline-based antioxidant, the amine-based antioxidant of formula (3), and the amine-based antioxidant of formula (4). Examples of other antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and N,N'-diphenyl-p-phenylenediamine (DPPD). However, it is preferable not to include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD). Commercially available antioxidants can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., and Flexis. These antioxidants may be used alone or in combination of two or more. The ratio of other antioxidants in the antioxidants is preferably 0 to 20% by mass, more preferably 0 to 10% by mass.

[0144] (Resin) The rubber composition of the present invention preferably further contains a resin. By further containing a resin, the processability of the rubber composition for tires can be improved, and in addition, the wet grip performance when the rubber composition is used in a tire can be further improved.

[0145] The type of the resin is not particularly limited. ５ based resin, C ５ -C ９ based resin, C ９ These resins may be used alone or in combination of two or more.

[0146] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. ５ Commercially available resins can be used.

[0147] Said C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the above components are contained in an amount of less than 50% by mass, preferably 40% by mass or less. ５ -C ９ Commercially available resins can be used.

[0148] Said C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0149] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated from the blend, and polymerizing the blend using a Friedel-Crafts catalyst. Examples of such resins include β-pinene resin and α-pinene resin. Furthermore, a representative example of a terpene-aromatic compound resin is terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing the terpene with formalin. There are no particular limitations on the terpenes used as raw materials; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. Styrene or the like may also be included in the skeleton.

[0150] The dicyclopentadiene resin is, for example, AlCl ３ or BF ３ This refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as

[0151] Furthermore, it is preferable that the resin is at least partially hydrogenated. By at least partially hydrogenating the resin, the hysteresis loss (tan δ) in the low temperature range can be improved, and therefore the wet grip performance of a tire using the rubber composition is improved. Note that the at least partially hydrogenated resin refers to a resin obtained by reducing and hydrogenating a resin.

[0152] The resin used as the raw material for the hydrogenated resin is, for example, C ５ A resin (C) copolymerized with the fraction and dicyclopentadiene (DCPD) ５ -DCPD-based resin). When the dicyclopentadiene-derived component is 50% by mass or more in the total amount of the resin, C ５ -DCPD-based resins are included in dicyclopentadiene-based resins. When the dicyclopentadiene-derived component is less than 50% by mass in the total amount of resin, C ５ -DCPD resin is C ５The same applies to cases where a small amount of a third component is contained.

[0153] The resin preferably has a softening point higher than 110°C and a polystyrene-equivalent weight-average molecular weight of 200 to 1600 g / mol. Applying a rubber composition containing such a resin to a tire can further improve the tire's wear resistance. When the resin has a softening point higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced, further improving the wear resistance. From the viewpoint of tire wear resistance, the softening point of the resin is preferably 116°C or higher, more preferably 120°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. From the viewpoint of processability, the softening point of the resin is preferably 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, more preferably 141°C or lower, and even more preferably 136°C or lower. The polystyrene-equivalent weight-average molecular weight of the resin can be calculated, for example, by measuring the average molecular weight using gel permeation chromatography (GPC) under the following conditions. Column temperature: 40°C Injection volume: 50 μL Carrier and flow rate: tetrahydrofuran 0.6 mL / min Sample preparation: Approximately 2.5 mg of resin component was dissolved in 10 mL of tetrahydrofuran. The softening point of the resin component can be measured, for example, in accordance with JIS-K2207-1996 (ring and ball method).

[0154] When the polystyrene-equivalent weight-average molecular weight of the resin is 200 g / mol or more, the resin is less likely to precipitate from the tire and the effects of the resin can be fully exerted, and when it is 1600 g / mol or less, the resin is more likely to be compatible with the rubber component.From the viewpoint of suppressing resin precipitation from the tire and suppressing deterioration of the tire appearance, the polystyrene-equivalent weight-average molecular weight of the resin is preferably 500 g / mol or more, more preferably 550 g / mol or more, even more preferably 600 g / mol or more, even more preferably 650 g / mol or more, and still more preferably 700 g / mol or more. Furthermore, from the viewpoint of increasing the compatibility of the resin with the rubber component and further enhancing the effects of the resin, the polystyrene-equivalent weight average molecular weight of the resin is preferably 1350 g / mol or less, more preferably 1330 g / mol or less, more preferably 1300 g / mol or less, more preferably 1200 g / mol or less, more preferably 1100 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less.

[0155] The weight average molecular weight (Mw ＨＲ ) (unit: g / mol) to the softening point (Ts ＨＲ ) (unit: °C) ratio (Ts ＨＲ / Mw ＨＲ ) is preferably 0.07 or more, more preferably 0.083 or more, more preferably 0.095 or more, more preferably 0.104 or more, more preferably 0.125 or more, more preferably 0.135 or more, more preferably 0.14 or more, and even more preferably 0.141 or more. ＨＲ / Mw ＨＲ ) is preferably 0.25 or less, more preferably 0.24 or less, more preferably 0.23 or less, more preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less.

[0156] The content of the resin is preferably 1 to 50 parts by mass per 100 parts by mass of the rubber component. When the content of the resin in the rubber composition is 1 part by mass or more per 100 parts by mass of the rubber component, the effect of the resin is fully exhibited, and when it is 50 parts by mass or less, the resin is less likely to precipitate from the tire, allowing the effect of the resin to be fully exhibited. On the other hand, when the content of the resin exceeds 50 parts by mass per 100 parts by mass of the rubber component, the fuel economy and wear resistance of a tire using the rubber composition deteriorate. From the viewpoint of further enhancing the effect of the resin, the content of the resin in the rubber composition is preferably 5 parts by mass or more per 100 parts by mass of the rubber component, more preferably 7 parts by mass or more, and even more preferably 9 parts by mass or more. From the viewpoint of suppressing resin precipitation from the tire and suppressing deterioration of the tire appearance, the content of the resin in the rubber composition is preferably 45 parts by mass or less per 100 parts by mass of the rubber component, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less.

[0157] (Other Components) In addition to the rubber component, filler, silane coupling agent, antioxidant, and resin component described above, the rubber composition of the present invention may contain, as necessary, various components commonly used in the rubber industry, such as wax, softener, processing aid, stearic acid, zinc oxide (zinc white), vulcanization accelerator, vulcanizing agent, etc., appropriately selected within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding ingredients.

[0158] Examples of the wax include paraffin wax, microcrystalline wax, etc. The content of the wax is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0159] The content of the zinc oxide (zinc white) is not particularly limited, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably less than 4 parts by mass, per 100 parts by mass of the rubber component. If the content of the zinc white is too high (more than 8 parts by mass), it may not disperse and the fracture properties may deteriorate.

[0160] Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, and dithiocarbamate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0161] The vulcanizing agent may be sulfur, etc. The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, more preferably 1 to 4 parts by mass, in terms of sulfur content, per 100 parts by mass of the rubber component.

[0162] (Method for Producing Rubber Composition) The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending various components appropriately selected as necessary with the above-mentioned rubber component, filler, and silane coupling agent, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0163] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0164] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0165] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0166] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0167] <Tread Rubber> The tread rubber of the present invention is characterized by comprising the rubber composition of the present invention. Since the tread rubber of the present invention comprises the rubber composition of the present invention, by applying it to a tire, the tire's wet grip performance, fuel economy and abrasion resistance are well balanced, and in addition to having excellent discoloration resistance, it is also possible to improve ozone resistance. The tread rubber of the present invention may be applied to either a new tire or a retread tire.

[0168] <Rubber Product> The rubber product of the present invention is at least one rubber product selected from the group consisting of a tire, a rubber crawler, and a seismic isolation rubber, and is characterized by containing the rubber composition of the present invention. Such a rubber product of the present invention has a high level of balance between wet grip performance, fuel efficiency, and abrasion resistance, is excellent in discoloration resistance, and further has improved ozone resistance.

[0169] When the rubber composition of the present invention is applied to a tire, it may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. The tire of the present invention is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0170] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0171] Examples 1-1 to 1-7, Comparative Examples 1-1 to 1-4 For Examples 1-1 to 1-7, the components were blended and kneaded according to the formulations shown in Table 1 to prepare sample rubber compositions. The resulting rubber compositions for each Example were then vulcanized to obtain vulcanized rubber test pieces. For Comparative Examples 1-1 to 1-4, vulcanized rubber test pieces were obtained in the same manner as in the above Examples. The blending amounts of the rubber components shown in Table 1 are listed as numerical values ​​including the amount of oil extension, and are rounded to the nearest integer, with the blending amount of each component shown as the amount (parts by mass) per 100 parts by mass of the rubber component.

[0172] The "low Tg modified SBR" in Table 1 was prepared under the following conditions: (Synthesis of low Tg modified SBR (*1)) A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the total weight of 1,3-butadiene and styrene was 67.5 g, respectively. 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were then added, and polymerization was carried out at 50°C for 1.5 hours. At this point, the polymerization conversion rate of the polymerization reaction system reached nearly 100%, and 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50°C for 30 minutes. Thereafter, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to terminate the reaction, and the mixture was dried in a conventional manner to obtain modified SBR. Measurement of the microstructure of the obtained modified SBR revealed that the bound styrene content was 10% by mass, and the glass transition temperature (Tg) was -65°C.

[0173] <Evaluation> (1) Wet Grip Performance For Examples 1-1 to 1-7, the loss tangent (tan δ) of the test specimens was measured using a viscoelasticity measuring device (manufactured by GABO) under conditions of a temperature of -5°C, a strain of 1%, and a frequency of 15Hz. The evaluation results were expressed as an index, with the tan δ of Comparative Example 1-1 set to 100. The larger the index value, the larger the tan δ, and the better the wet grip performance. For Comparative Examples 1-1 to 1-4, measurements were performed in the same manner as in the above examples, and the index was calculated. The evaluation results are shown in Table 1. An index value greater than 100 was assigned an A, greater than 80 and less than 100 was assigned a B, and 80 or less was assigned a C.

[0174] (2) Fuel Efficiency Performance For Examples 1-1 to 1-7, the loss tangent (tan δ) of the test specimens was measured using a viscoelasticity measuring device (manufactured by GABO) under conditions of a temperature of 50°C, a strain of 1%, and a frequency of 15 Hz, and the reciprocal of the measured value was calculated. The evaluation results were expressed as an index, with the reciprocal of tan δ for Comparative Example 1-1 being set to 100. The larger the index value, the smaller the tan δ and the better the fuel efficiency performance. For Comparative Examples 1-1 to 1-4, measurements were performed in the same manner as in the above Examples, and the index was calculated. The evaluation results are shown in Table 1. An index value greater than 120 was assigned an A, greater than 100 but not greater than 120 was assigned a B, and 100 or less was assigned a C.

[0175] (3) Abrasion Resistance Performance For Examples 1-1 to 1-7, test specimens were measured in accordance with JIS K 6264-2:2005 using a Lambourn abrasion tester manufactured by Ueshima Seisakusho, with sandpaper attached to the grinding wheel, at room temperature and a slip ratio of 15%. The evaluation results were indexed using the following formula, with the reciprocal of the abrasion amount for Comparative Example 1-1 set to 100, and the average of the obtained indices was calculated to represent the abrasion resistance index. A larger abrasion resistance index indicates less abrasion and better abrasion resistance. Abrasion Resistance Index = {(Abrasion amount of test specimen for Comparative Example 1) / (Abrasion amount of each test specimen)} × 100. For Comparative Examples 1-1 to 1-4, measurements were performed in the same manner as in the above examples, and the index was calculated. The evaluation results were shown in Table 1, with an abrasion resistance index of over 100 being A, over 85 to 100 being B, and 85 or less being C.

[0176] (4) Discoloration of Appearance For Examples 1-1 to 1-7, the test pieces were stored for 7 days under conditions of 40°C and 50 pphm ozone atmosphere, and then visually inspected for discoloration on the surface. For Comparative Examples 1-1 to 1-4, the test pieces were observed after storage in the same manner as in the above Examples. Evaluation was performed according to the following criteria, and the results are shown in Table 1. ◯: No black gloss occurred ×: Black gloss occurred

[0177] (4) Ozone Resistance For Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-4, test specimens were subjected to a dynamic ozone degradation test (a test in which repeated strain was applied) in accordance with ISO 1431 (JIS K 6259), and the samples were observed at 20x magnification using a microscope. The observed samples were ranked according to the size and depth of cracks and classified according to the following criteria (1 to 5), with the results shown in Table 1. The smaller the criteria value, the better the result. (Ranking by crack size and depth) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Deep and relatively large cracks (less than 1 mm). 4: Deep and large cracks (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to cause breakage.

[0178] * 1 Low Tg modified SBR: Modified SBR obtained by synthesizing the above low Tg modified SBR, equivalent to styrene-butadiene rubber (A) * 2 Medium Tg modified SBR: SBR obtained using butyl lithium as an initiator, with a Tg of -38 ° C. and a styrene-butadiene rubber modified with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propaneamine at the end * 3 High Tg unmodified SBR: Manufactured by ENEOS Material Co., Ltd., product name "HP755B", glass transition temperature -19 ° C., blending amount includes 37.5 parts by mass of oil added to 100 parts by mass of SBR, equivalent to styrene-butadiene rubber (B) * 4 Silica: Manufactured by Tosoh Silica Corporation, product name "Nipsil AQ" * 5 CB: Manufactured by Asahi Carbon Co., Ltd., product name "# 80" * 7 Silane coupling agent (A): Mercapto silane coupling agent, manufactured by EVONIK, product name "Si 363" * 8 Silane coupling agent (B): Sulfide-based silane coupling agent, manufactured by EVONIK, trade name "S 2.5" * 8 Oil: Manufactured by Idemitsu Kosan Co., Ltd., trade name "Diana Process NH-70S" * 9 Hydrogenated C ５ *10 Other components: Total amount of stearic acid, wax, antioxidant, zinc oxide, vulcanization accelerator and sulfur *11 Inorganic filler: Showa Denko K.K.'s "Higilite (registered trademark)" *12 Antiaging agent A: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) *13 Antiaging agent B: 4,4'-bis(2-octylamino)triphenylamine, represented by general formula (1), R １１ and R １２ is a 2-octyl group, and R １３ is hydrogen *14 Antioxidant C: 4,4'-bis(2-octylamino)-4''-methoxytriphenylamine, a compound represented by general formula (1), R １１ and R １２ is a 2-octyl group, and R １３ is a methoxy group *15 Antioxidant D: A triphenylamine-based antioxidant consisting of a compound represented by the following formula

[0179] From Table 1, it can be seen that each sample of the rubber composition for a tread corresponding to the Examples exhibits well-balanced and excellent results in all evaluation items, while each sample of the rubber composition for a tread corresponding to the Comparative Examples is inferior to the Examples in any of the evaluation items.

[0180] According to the present invention, it is possible to provide a rubber composition that achieves a high level of wet grip performance, fuel economy, and abrasion resistance while also achieving excellent discoloration resistance and improved ozone resistance, and a tread rubber made from such a rubber composition. Also, according to the present invention, it is possible to provide a rubber product that achieves a high level of wet grip performance, fuel economy, and abrasion resistance while also having excellent discoloration resistance and ozone resistance.

Claims

1. A rubber composition comprising a rubber component, a filler, and an antioxidant, wherein the rubber component contains at least two types of styrene-butadiene rubber, and the antioxidant is represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.].

2. The rubber composition according to claim 1, characterized in that the rubber component contains styrene-butadiene rubber (A) modified with a modifier containing at least one atom of nitrogen, silicon, and tin and having a glass transition temperature of -50°C or lower, and unmodified styrene-butadiene rubber (B) having a glass transition temperature at least 30°C higher than that of the styrene-butadiene rubber (A).

3. The rubber composition according to claim 2, wherein the styrene-butadiene rubber (A) is modified with a modifier having nitrogen atoms and silicon atoms.

4. The rubber composition according to claim 3, wherein the modifier is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group.

5. The rubber composition according to claim 1 or 2, further comprising a silane coupling agent.

6. The rubber composition according to claim 5, wherein the filler contains at least silica, and the silane coupling agent contains at least a silane coupling agent (S1) having a thiol group.

7. The rubber composition according to claim 6, wherein the total content of the silane coupling agent is 1 to 15 parts by mass per 100 parts by mass of the silica.

8. A rubber composition according to claim 5, characterized in that the silane coupling agent further contains a silane coupling agent (S2) having a sulfide bond, and the mass ratio (S2 / S1) of the content of the silane coupling agent (S2) to the content of the silane coupling agent (S1) is 0.3 or more and less than 3.

9. The rubber composition according to claim 6, wherein the filler further contains carbon black, and the content of the silica in the total amount of the silica and the carbon black is 80 mass % or more but less than 100 mass %.

10. The rubber composition according to claim 2, wherein the ratio of the content of the triphenylamine-based antioxidant to the content of the styrene-butadiene rubber (A) (triphenylamine-based antioxidant / styrene-butadiene rubber (A)) is 0.005 to 0.15 in mass ratio.

11. The rubber composition according to claim 1 or 2, characterized in that the ratio of the content of the triphenylamine-based antioxidant to the content of the silane coupling agent (triphenylamine-based antioxidant / silane coupling agent) is 0.05 to 1 in mass ratio.

12. R in the above general formula (1) １１ , R １２ and R １３ The rubber composition according to claim 1 or 2, wherein is an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, and a 1,4-dimethylpentyl group.

13. R in the above general formula (1) １１ , R １２ and R １３ The rubber composition according to claim 1 or 2, wherein the number of carbon atoms is 2 to 8.

14. The rubber composition according to claim 1 or 2, characterized in that the content of the antioxidant is 0.5 to 10 parts by mass per 100 parts by mass of the rubber component, the antioxidant further contains a quinoline-based antioxidant, and the proportion of the quinoline-based antioxidant in the antioxidant is 5 to 50% by mass.

15. The antioxidant is represented by the following general formula (3): [In the formula, R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group.], and the proportion of the amine-based antioxidant represented by general formula (3) in the antioxidants is 0.1 to 80 mass %.

16. The antioxidant is represented by the following general formula (4): [In the formula, R ４１ and R ４２ represents a phenyl group, and m4 represents an integer of 7 or more. ], and a ratio of the amine-based antioxidant represented by general formula (4) in the antioxidants is 0.1 to 80 mass %.

17. A tread rubber comprising the rubber composition according to claim 1 or 2.

18. At least one rubber product selected from the group consisting of tires, rubber crawlers, and seismic isolation rubber, characterized in that the rubber product contains the rubber composition according to claim 1 or 2.

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