Rubber composition, rubber composition for tread, and tire

Abstract

Provided is a rubber composition which brings about excellent performances with respect to low rolling resistance, low-temperature characteristics, and steering stability and brings about improvements in high-temperature crack propagation resistance after deterioration, high-temperature tensile strength after deterioration, high-temperature tensile strength after deterioration, and sustainable-material proportion.　This rubber composition comprises a rubber component, resins, and recycled carbon black, and is characterized in that the resins are a rosin-based resin and at least one resin selected from the group consisting of terpene-based resins and terpene / aromatic compound resins and are contained in a total amount larger than 0 parts by mass but not larger than 50 parts by mass per 100 parts by mass of the rubber component and that the recycled carbon black, when examined with a grind gauge, shows three or more lines each having a length of 10 mm or longer and the third largest particle among the particles which have caused the lines each having a length of 10 mm or longer has a particle size of 20 μm or less.

Description

Rubber composition, tread rubber composition, and tire

[0001] The present invention relates to rubber compositions, rubber compositions for treads, and tires.

[0002] From the perspective of improving vehicle safety, various studies have been conducted to improve the braking performance (low-temperature characteristics) and traction of tires not only on normal road surfaces but also in low-temperature environments such as icy and snowy roads. For example, a technology is known in which a rubber composition containing aromatic oils along with rubber components such as natural rubber (NR) and butadiene rubber (BR) is used in the tread rubber to improve performance on wet and icy / snowy roads (Patent Document 1). In addition, to improve grip performance on wet and icy / snowy roads, C is added to 100 parts by mass of a rubber component containing a total of 30% by mass or more of natural rubber and / or polyisoprene rubber. ５ A technique is also known in which a rubber composition containing 5 to 50 parts by mass of a resin is used as tread rubber (Patent Document 2).

[0003] However, the technologies disclosed in Patent Documents 1 and 2 above made it difficult to achieve both improved low-temperature characteristics of tires and reduced rolling resistance (hereinafter referred to as "low rolling resistance") at a high level. Furthermore, the technologies in Patent Documents 1 and 2 were not sufficient in terms of high-temperature crack propagation resistance and high-temperature tensile strength after degradation of the rubber composition, and further improvements were desired.

[0004] On the other hand, apart from the aforementioned wet performance, wear resistance, and low rolling resistance, from the perspective of social sustainability, there is a demand for the use of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and recycled resources, for various components used in tires. The development of technologies to increase the usage rate of sustainable materials (hereinafter sometimes referred to as the "sustainable material ratio") is also desired.

[0005] Here, if conventional recycled carbon black is used as a filler in the tread rubber instead of unused carbon black in order to increase the proportion of sustainable materials in the tire, there is a risk that other tire rubber properties other than wear resistance (e.g., high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation) may deteriorate.

[0006] Japanese Patent Publication No. 5-269884 Japanese Patent Publication No. 2006-241358

[0007] Therefore, the present invention aims to provide a rubber composition that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainable material ratio. Furthermore, the present invention aims to provide a tread rubber composition and tire that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after thermal degradation, high-temperature tensile strength after degradation, and sustainable material ratio.

[0008] The inventors diligently researched rubber compositions containing rubber components and resins to solve the above problems. They found that by including a specific amount of at least one resin selected from the group consisting of terpene resins and terpene-aromatic compound resins, as well as a rosin resin, it is possible to achieve excellent low-temperature characteristics and handling stability even when replacing currently used fossil resource-derived materials with sustainable materials. Furthermore, by limiting the resin content to a specific range, the dispersibility of the filler can be improved, allowing for good maintenance of low fuel consumption, low-temperature characteristics, and handling stability in tires to which the rubber composition is applied. In addition, by using a specific recycled carbon black as the carbon black, it is possible to further improve high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainability ratio while maintaining good low rolling resistance, low-temperature characteristics, and handling stability.

[0009] In other words, the gist of the present invention is as follows: [1] A rubber composition comprising a rubber component, a resin, and recycled carbon black, wherein the resin comprises at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and a rosin resin, in a total of 0 to 50 parts by mass per 100 parts by mass of the rubber component, and the recycled carbon black is characterized in that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less. The rubber composition of the present invention is excellent in low rolling resistance, low temperature characteristics and handling stability, and it is also possible to improve high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation and sustainable material ratio.

[0010] [2] A rubber composition for treads, characterized by comprising the rubber composition of the present invention. The rubber composition for treads of the present invention is excellent in low rolling resistance, low temperature characteristics and handling stability, and can also improve high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation and sustainable material ratio.

[0011] [3] A tire characterized by comprising the rubber composition of the present invention. The tire of the present invention is excellent in low rolling resistance, low temperature characteristics and handling stability, and can also improve high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation and sustainable material ratio.

[0012] According to the present invention, it is possible to provide a rubber composition that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainable material ratio. Furthermore, according to the present invention, it is also possible to provide a tread rubber composition and tire that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainable material ratio.

[0013] This is an explanatory diagram illustrating an example of measurement results using a grind gauge.

[0014] Embodiments of the present invention will be described below. The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0015] In this specification, "sustainable material ratio" refers to the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources in the rubber composition, tread rubber composition, and tire in question.

[0016] In this specification, the term "biomass resources" refers to carbon-neutral organic resources of biological origin, excluding fossil resources (such as petroleum, coal, and natural gas). These biological resources may be edible or inedible, but are preferably inedible, as they do not compete with food resources and are considered to be resources that can be used effectively.

[0017] In this specification, the term "recycled resources" refers to resources obtained by recycling products that have been used, collected without being used, or discarded. For example, recycled resources include resources obtained by recycling used rubber products such as used tires.

[0018] <Rubber composition>

[0019] The composition of the rubber composition of the present invention is described below. The rubber composition of the present invention comprises a rubber component, a resin, and recycled carbon black, wherein the resin comprises at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and a rosin resin, in a total of 0 to 50 parts by mass per 100 parts by mass of the rubber component, and the recycled carbon black is characterized in that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less.

[0020] In the rubber composition of the present invention, by blending a rosin-based resin with at least one resin selected from the group consisting of terpene-based resins and terpene-aromatic compound-based resins, the balance between low rolling resistance, low-temperature characteristics, and handling stability can be improved. However, simply blending the aforementioned resins reduces the fuel efficiency and wear resistance of tires to which the rubber composition is applied, and if the resin content exceeds 50 parts by mass per 100 parts by mass of rubber components, the low rolling resistance of tires to which the rubber composition is applied deteriorates. In contrast, in the tire rubber composition of the present invention, by setting the resin content to 50 parts by mass or less per 100 parts by mass of rubber components, the dispersibility of the filler in the rubber composition can be improved, thereby complementing the balance between low rolling resistance, low-temperature characteristics, and handling stability of the rubber composition. Furthermore, by using a specific recycled carbon black as the carbon black, the sustainability ratio can be further improved while maintaining good low rolling resistance, low-temperature characteristics, and handling stability.

[0021] (Rubber component) The rubber composition of the present invention contains a rubber component, which provides rubber elasticity to the composition. Preferably, the rubber component contains isoprene rubber and styrene-butadiene rubber. ・Isoprene rubber The isoprene rubber is a rubber whose main backbone is isoprene units, and specifically includes natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), modified synthetic isoprene rubber (modified IR), etc. As for natural rubber (NR), for example, RSS#3, TSR20 (e.g., SIR20 or STR20), etc., which are common in the tire industry can be used. By including isoprene rubber in the rubber component, the fracture strength of the rubber composition can be increased. As a result, the rolling resistance of tires to which this rubber composition is applied can be reduced, improving fuel efficiency, and the wear resistance of the tires can also be improved.

[0022] The origin of the aforementioned natural rubber is not particularly limited, and examples include rubber derived from the Para rubber tree, guayule, or Russian dandelion. The natural rubber may be modified or altered, and the synthetic isoprene rubber may also be altered. These isoprene-based rubbers may be used individually or in combination of two or more. Natural rubber is preferred as the isoprene-based rubber.

[0023] The content of the isoprene-based rubber is preferably 1 to 80 parts by mass, and more preferably 1 to 65 parts by mass, per 100 parts by mass of the rubber component. When the content of the isoprene-based rubber is 1 to 65 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and low-temperature performance of the tire to which the rubber composition is applied can be further improved. Furthermore, from the viewpoint of maximizing the compounding effect of the isoprene-based rubber, the content of the isoprene-based rubber is preferably 10 parts by mass or more per 100 parts by mass of the rubber component.

[0024] Furthermore, the isoprene-based rubber preferably has a sustainable ratio of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to keep the sustainable ratio of the isoprene-based rubber within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as monomer components. In addition, mass balance certified synthetic rubber can also be used to keep the sustainable ratio within the above range.

[0025] Styrene-butadiene rubber Examples of the styrene-butadiene rubber include emulsion-polymerized styrene-butadiene rubber and solution-polymerized styrene-butadiene rubber. The styrene-butadiene rubber (SBR) preferably has a glass transition temperature of less than -40°C, more preferably -45°C or lower, even more preferably -50°C or lower, and preferably higher than -90°C. When the glass transition temperature of the styrene-butadiene rubber is less than -40°C, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied can be sufficiently improved. Furthermore, styrene-butadiene rubber with a glass transition temperature higher than -90°C is easier to synthesize.

[0026] The content of the styrene-butadiene rubber is preferably 20 to 99 parts by mass, more preferably 30 to 99 parts by mass, and even more preferably 35 to 99 parts by mass, per 100 parts by mass of the rubber component. When the content of the styrene-butadiene rubber is 60 to 99 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and wet grip performance of the tire to which the tire rubber composition is applied can be further improved.

[0027] The difference in SP values ​​between the isoprene-based rubber and the styrene-butadiene rubber is 0.3 (cal / cm²). ３ ) １／２ Preferably, it is 0.35 (cal / cm³). ３ ) １／２ It is even more preferable that the above conditions are met. The difference in SP values ​​between isoprene-based rubber and styrene-butadiene rubber is 0.3 (cal / cm²). ３ ) １／２ In the above cases, isoprene-based rubber and styrene-butadiene rubber tend to be incompatible.

[0028] The styrene-butadiene rubber preferably has a bound styrene content of less than 15% by mass. The bound styrene content of styrene-butadiene rubber refers to the proportion of styrene units contained in the styrene-butadiene rubber. When the bound styrene content of styrene-butadiene rubber is less than 15% by mass, the glass transition temperature tends to be low. The bound styrene content of styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. Furthermore, from the viewpoint of the wear resistance performance of tires to which the rubber composition is applied, the bound styrene content of styrene-butadiene rubber 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 styrene-butadiene rubber can be adjusted by the amount of monomer used in the polymerization of styrene-butadiene rubber, the degree of polymerization, etc.

[0029] The styrene-butadiene rubber is preferably modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group. When the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group, the balance between the wet grip performance, fuel efficiency, and wear resistance of the tire to which the rubber composition is applied is further improved, and in particular, the fuel efficiency and wear resistance can be further improved. The modifier having a functional group containing a nitrogen atom and an alkoxy group is a general term for modifiers having a functional group containing at least one nitrogen atom and at least one alkoxy group. The functional group containing a nitrogen atom is preferably selected from the following. A monovalent hydrocarbon group having 1 to 30 carbon atoms, including a linear, branched, alicyclic, or aromatic ring, having a functional group selected from the group consisting of a primary amino group, a primary amino group protected by 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 by 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, and which may contain a linear, branched, alicyclic, or aromatic ring, or a monovalent hydrocarbon group having 1 to 30 carbon atoms, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

[0030] - Modified styrene-butadiene rubber of the first preferred embodiment - The styrene-butadiene rubber (SBR) is preferably modified with an aminoalkoxysilane compound, and more preferably the ends are modified with an aminoalkoxysilane compound from the viewpoint of having a high affinity for the filler. When the ends of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (especially silica) becomes particularly large.

[0031] The modified sites in the styrene-butadiene rubber may be at the molecular ends as described above, or they may be on the main chain. Styrene-butadiene rubber with modified molecular ends can be produced, for example, by reacting various modifying agents with the ends of a styrene-butadiene copolymer having active ends, according to the methods described in International Publication No. 2003 / 046020 and Japanese Patent Publication No. 2007-217562. In one preferred embodiment, styrene-butadiene rubber with modified molecular ends can be produced by reacting an aminoalkoxysilane compound with the ends of a styrene-butadiene copolymer having active ends with a cis-1,4 bond content of 75% or more, and then stabilizing it by reacting it with a carboxylic acid partial ester of a polyhydric alcohol, according to the methods described in International Publication No. 2003 / 046020 and Japanese Patent Publication No. 2007-217562.

[0032] The carboxylic acid partial ester of the polyhydric alcohol means an ester of a polyhydric alcohol and a carboxylic acid and a partial ester having one or more hydroxyl groups. Specifically, esters of saccharides or modified saccharides having 4 or more carbon atoms and fatty acids are preferably used. This ester is more preferably (1) a fatty acid partial ester of a polyhydric alcohol, particularly a partial ester (any of monoester, diester, and triester) of a saturated or unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyhydric alcohol, (2) an ester compound in which a partial ester of a polycarboxylic acid and a higher alcohol is bonded to 1 to 3 polyhydric alcohols, and the like. As the polyhydric alcohol used as a raw material for the partial ester, saccharides having 5 or 6 carbon atoms having at least three hydroxyl groups (which may or may not be hydrogenated), glycols, polyhydroxy compounds, and the like are preferably used. Further, as the raw material fatty acid, a saturated or unsaturated fatty acid having 10 to 20 carbon atoms is preferable, and for example, stearic acid, lauric acid, and palmitic acid are used. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferable, and specifically, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, and the like can be mentioned.

[0033] The above aminoalkoxysilane compound is not particularly limited, but an aminoalkoxysilane compound represented by the following general formula (i) is preferable. R １１ ａ [[ID=`6]]-Si-(OR １２ ) ４－ａ ・・・ (i)

[0034] In the 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, at least one of R １１ and R １２ is substituted with an amino group, a is an integer of 0 to 2, and OR １２If there are multiple ORs, each OR １２ These elements may be identical or different from each other, and the molecule does not contain an active proton.

[0035] Among the above aminoalkoxysilane compounds, aminoalkoxysilane compounds represented by the following general formula (ii) are also preferred.

[0036] In general formula (ii), n1 + n2 + n3 + n4 = 4 (where n2 is an integer from 1 to 4, and n1, n3, and n4 are integers from 0 to 3). A １ This is at least one functional group selected from saturated cyclic tertiary amine compound residues, unsaturated cyclic tertiary amine compound residues, ketimine residues, nitrile groups, (thio)isocyanate groups, isocyanuric acid trihydrocarbyl ester groups, pyridine groups, (thio)ketone groups, amide groups, and first or second amino groups having hydrolyzable groups. When n4 is 2 or more, A １ They may be the same or different, A １ R may be a divalent group that bonds with Si to form a cyclic structure. ２１ R 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 may be the same or different when n1 is 2 or more. 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, and may contain a nitrogen atom and / or a silicon atom. When n2 is 2 or more, R ２２ These elements may be identical or different from each other, or they may come together to form a ring. ２３ 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, and may be the same or different if n3 is 2 or more. ２４This 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, and may be the same or different when n4 is 2 or more. The hydrolyzable group in the first or second amino group having a hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and the trimethylsilyl group is particularly preferred.

[0037] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

[0038] In general formula (iii), p1 + p2 + p3 = 2 (where p2 is an integer between 1 and 2, and p1 and p3 are integers between 0 and 1). A ２ R is NRa (where Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). ２５ R 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 This 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, all of which may contain a nitrogen atom and / or a silicon atom. When p2 is 2, R ２６ These elements may be identical or different from each other, or they may come 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 This 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.

[0039] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or the following general formula (v).

[0040] In the general formula (iv), q1 + q2 = 3 (where q1 is an integer from 0 to 2, and q2 is an integer from 1 to 3). ３１ R 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 Each of these is 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 This 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 may be the same or different when q1 is 2. ３５ This 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 may be the same or different if q2 is 2 or more.

[0041]

[0042] In the general formula (v), r1 + r2 = 3 (where r1 is an integer from 1 to 3, and r2 is an integer from 0 to 2). ３６ R 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 R is 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 dimethylsilylaminoethyl 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 may be the same or different when r1 is 2 or more. ３８is 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 when r2 is 2, it may be the same or different. A specific example of an aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propaneamine.

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

[0044] In general formula (vi), R ４０ R 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 This 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. Here, TMS represents a trimethylsilyl group (the same applies hereinafter).

[0045]

[0046] In general formula (vii), R ４３ and R ４４ Each of these is 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 R 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 They may be the same or different.

[0047] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viiii) or the following general formula (ix).

[0048] In the general formula (viiii), s1 + s2 is 3 (where s1 is an integer from 0 to 2, and s2 is an integer from 1 to 3). ４６ R 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 Each of these is 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 They may be the same or different.

[0049]

[0050] In the general formula (ix), X is a halogen atom. ４９ R 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 Each of these is 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 They are bonded together to form a divalent organic group. ５２ and R ５３ Each of these is independently a halogen atom, a hydrocarbyl oxy 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 for the hydrolyzable group, a hydrolyzable group is preferred, and among the hydrolyzable groups, a trimethylsilyl group and a tert-butyldimethylsilyl group are preferred, with a trimethylsilyl group being particularly preferred.

[0051] 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 (xiiiii).

[0052] In general formulas (x) to (xiiii), the symbols U and V are integers from 0 to 2 and satisfying U + V = 2, respectively. ５４ ~ ９２ These 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. In general formula (xiiii), α and β are integers from 0 to 5.

[0053] Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptan-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)heptan-1,7-diamine are particularly preferred. Furthermore, among the compounds satisfying general formula (xiiii), 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)propane-1-amine are particularly preferred.

[0054] - A second preferred embodiment of modified styrene-butadiene rubber - It is also preferable that the styrene-butadiene rubber (SBR) is modified with a coupling agent represented by the following general formula (I). In this case, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied can be further improved.

[0055] In the above general formula (I), R １ , R ２ and R３ Each of these independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. ４ , R ５ , R ６ , R ７ and R ９ Each of these independently represents an alkyl group having 1 to 20 carbon atoms. ８ and R １１ Each of these independently represents an alkylene group having 1 to 20 carbon atoms. １０ R represents an alkyl or trialkylsilyl group having 1 to 20 carbon atoms. m represents an integer from 1 to 3, and p represents 1 or 2. １ ~R １１ m and p are independent of each other if there are multiple. i, j and k each represent an integer from 0 to 6 independently, where (i + j + k) is an integer from 3 to 10. A represents an organic group having 1 to 20 carbon atoms, a hydrocarbon group, or at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and lacking active hydrogen. Here, in general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups lacking active hydrogen include hydroxyl groups (-OH), secondary amino groups (>NH), and primary amino groups (-NH). ２ Examples include functional groups having active hydrogen, such as sulfhydryl groups (-SH), and organic groups that do not have active hydrogen.

[0056] The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) has a weight-average molecular weight (Mw) of 20 × 10 ４ ~300 x 10 ４ The molecular weight is 200 × 10 with respect to the total amount of the modified styrene-butadiene rubber. ４ ~500 x 10 ４ It is preferable that the modified styrene-butadiene rubber contains 0.25 to 30% by mass and has a shrinkage factor (g') of less than 0.64.

[0057] Generally, branched polymers tend to have smaller molecular size compared to linear polymers of the same absolute molecular weight, and the shrinkage factor (g') is an indicator of the ratio of the molecular size to that of a linear polymer of the same assumed absolute molecular weight. That is, the greater the degree of branching of the polymer, the smaller the shrinkage factor (g') tends to be. In this embodiment, intrinsic viscosity is used as an indicator of molecular size, and the intrinsic viscosity of the linear polymer is [η] = -3.883M ０．７７１ The following relationship is assumed to apply. The shrinkage factor (g') is calculated for each absolute molecular weight of modified styrene-butadiene rubber, and the absolute molecular weight is 100 × 10 ４ ~200 x 10 ４The average value of the shrinkage factor (g') at that time is taken as the shrinkage factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to the formation of a polymer by which one polymer is directly or indirectly bonded to another polymer. The "degree of branching" is the number of polymers that are directly or indirectly bonded to each other for one branch. For example, if the five styrene-butadiene copolymer chains described later are indirectly bonded to each other via coupling residues described later, the degree of branching is 5. A coupling residue is a structural unit of the modified styrene-butadiene rubber that is bonded to a styrene-butadiene copolymer chain, and is a structural unit derived from a coupling agent, for example, produced by reacting the styrene-butadiene copolymer described later with the coupling agent. A styrene-butadiene copolymer chain is a structural unit of the modified styrene-butadiene rubber, and is a structural unit derived from the styrene-butadiene copolymer, for example, produced by reacting the styrene-butadiene copolymer described later with the coupling agent. The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, even more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be below the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. By using modified styrene-butadiene rubber with a shrinkage factor (g') within this range, the processability of the rubber composition is improved. Since the shrinkage factor (g') tends to depend on the degree of branching, for example, the shrinkage factor (g') can be controlled using the degree of branching as an indicator. Specifically, when using modified styrene-butadiene rubber with a branching degree of 6, the shrinkage factor (g') tends to be between 0.59 and 0.63, and when using modified styrene-butadiene rubber with a branching degree of 8, the shrinkage factor (g') tends to be between 0.45 and 0.59.

[0058] The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) preferably has branching, with a degree of branching of 5 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bound to the coupling residues, and it is more preferable that the branching includes branches in which five or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber such that the degree of branching is 5 or more, and the branching includes branches in which five or more styrene-butadiene copolymer chains are bound to one coupling residue, the shrinkage factor (g') can be more reliably reduced to less than 0.64. The number of styrene-butadiene copolymer chains bound to one coupling residue can be confirmed from the value of the shrinkage factor (g'). Furthermore, it is more preferable that the modified styrene-butadiene rubber has branching, with a degree of branching of 6 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bound to the coupling residue, and it is even more preferable that the branching includes branches in which six or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber such that the degree of branching is 6 or more, and the branching includes branches in which six or more styrene-butadiene copolymer chains are bound to one coupling residue, the shrinkage factor (g') can be reduced to 0.63 or less. Furthermore, it is even more preferable that the modified styrene-butadiene rubber has branching, with a degree of branching of 7 or more, and even more preferable that the degree of branching is 8 or more. The upper limit of the degree of branching is not particularly limited, but it is preferably 18 or less.Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bound to the coupling residue, and it is even more preferable that the branching includes branches in which seven or more styrene-butadiene copolymer chains are bound to one of the coupling residues, and it is particularly preferable that the branching includes branches in which eight or more styrene-butadiene copolymer chains are bound to one of the coupling residues. By specifying the structure of the modified styrene-butadiene rubber such that the degree of branching is eight or more, and the branching includes branches in which eight or more styrene-butadiene copolymer chains are bound to one of the coupling residues, the shrinkage factor (g') can be reduced to 0.59 or less.

[0059] Preferably, at least one end of the styrene-butadiene copolymer chain is bonded to a silicon atom of a coupling residue. In this case, the ends of multiple styrene-butadiene copolymer chains may be bonded to one silicon atom. Alternatively, the end of a styrene-butadiene copolymer chain may be bonded to a carbon-1 to carbon-20 alkoxy or hydroxyl group, and as a result, that silicon atom may constitute a carbon-1 to carbon-20 alkoxysilyl or silanol group.

[0060] The modified styrene-butadiene rubber can be an oil-applied rubber to which an extensible oil has been added. The modified styrene-butadiene rubber may be oil-applied or non-oil-applied, but from the viewpoint of abrasion resistance, it is preferable that the Mooney viscosity measured at 100°C is 20 or more and 100 or less, and more preferably 30 or more and 80 or less.

[0061] The weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is preferably 20 × 10 ４ 300 x 10 ４ The following is more preferable: 50 × 10 ４ The above is more preferable to 64 × 10 ４ The above is preferable to 80 × 10 ４ That concludes the explanation. Furthermore, the weight-average molecular weight is preferably 250 × 10⁻⁶. ４is as follows, more preferably 180 × 10 ４ is as follows, more preferably 150 × 10 ４ is as follows. When the weight-average molecular weight is 20 × 10 ４ or more, the low-loss property and abrasion resistance of the rubber composition can be sufficiently improved. Further, when the weight-average molecular weight is 300 × 10 ４ or less, the processability of the rubber composition is improved.

[0062] The modified styrene-butadiene rubber preferably contains 0.25% by mass or more and 30% by mass or less of a modified styrene-butadiene rubber having a molecular weight of 200 × 10 ４ or more and 500 × 10 ４ or less (hereinafter also referred to as "specific high molecular weight component") based on the total amount (100% by mass) of the modified styrene-butadiene rubber. When the content of the specific high molecular weight component is 0.25% by mass or more and 30% by mass or less, the low-loss property and abrasion resistance performance of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber preferably contains the specific high molecular weight component at 1.0% by mass or more, more preferably 1.4% by mass or more, still more preferably 1.75% by mass or more, even more preferably 2.0% by mass or more, particularly preferably 2.15% by mass or more, and extremely preferably 2.5% by mass or more. Further, the modified styrene-butadiene rubber preferably contains the specific high molecular weight component at 28% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 18% by mass or less. In the present specification, the "molecular weight" of the rubber component is the molecular weight in terms of standard polystyrene obtained by GPC (gel permeation chromatography). In order to obtain a modified styrene-butadiene rubber in which the content of the specific high molecular weight component is in such a range, it is preferable to control the reaction conditions in the polymerization step and the reaction step described later. For example, in the polymerization step, the amount of the organic monolithium compound used as a polymerization initiator described later may be adjusted. Further, in the polymerization step, in either a continuous or batch polymerization mode, a method having a residence time distribution, that is, a method of broadening the time distribution of the growth reaction, may be used.

[0063] In the modified styrene-butadiene rubber, the molecular weight distribution (Mw / Mn), expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), is preferably 1.6 or more and 3.0 or less. If the molecular weight distribution of the modified styrene-butadiene rubber is within this range, the processability of the rubber composition will be good.

[0064] The method for producing the modified styrene-butadiene rubber is not particularly limited, but it is preferable to have a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting the active end of the styrene-butadiene copolymer with a reactive compound with five or more functions (hereinafter also referred to as a "coupling agent").

[0065] The polymerization step is preferably carried out by a growth reaction using a living anionic polymerization reaction, which allows for the production of a styrene-butadiene copolymer having active ends, and thus a modified styrene-butadiene rubber with a high degree of modification. The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

[0066] The amount of the organic monolithium compound used as a polymerization initiator is preferably determined by the molecular weight of the target styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers such as 1,3-butadiene and styrene used relative to the amount of polymerization initiator is related to the degree of polymerization, that is, to the number average molecular weight and / or weight average molecular weight. Therefore, in order to increase the molecular weight, it is good to adjust the amount of polymerization initiator in the direction of decreasing it, and in order to decrease the molecular weight, it is good to adjust the amount of polymerization initiator in the direction of increasing it. The organic monolithium compound is preferably an alkyllithium compound from the viewpoint of ease of industrial availability and ease of controlling the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation end is obtained. Examples of alkyllithium compounds include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenilithium. As alkyllithium compounds, n-butyllithium and sec-butyllithium are preferred from the viewpoint of ease of industrial availability and ease of controlling the polymerization reaction. These organic monolithium compounds may be used individually or in combination of two or more.

[0067] In the polymerization step, examples of polymerization reaction modes include batch and continuous polymerization reaction modes. In the continuous mode, one or more connected reactors can be used. Continuous reactors include, for example, tank-type or tubular reactors equipped with stirrers. In the continuous mode, monomers, an inert solvent, and a polymerization initiator are preferably fed continuously into the reactor, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is discharged continuously. Batch reactors include, for example, tank-type reactors equipped with stirrers. In the batch mode, monomers, an inert solvent, and a polymerization initiator are preferably fed, monomers are added continuously or intermittently during polymerization as needed, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is discharged after polymerization is complete. In this embodiment, in order to obtain a styrene-butadiene copolymer with a high proportion of active ends, a continuous mode is preferred, as it allows for the continuous discharge of the polymer and enables it to be used for the next reaction in a short time.

[0068] The polymerization step is preferably carried out in an inert solvent. Examples of solvents include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents are not limited to the following, but examples include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; and hydrocarbons consisting of aromatic hydrocarbons such as benzene, toluene, and xylene, and mixtures thereof. Treating impurities such as allenes and acetylenes with organometallic compounds before the polymerization reaction tends to yield styrene-butadiene copolymers with high concentrations of active ends, and is therefore preferable because it tends to yield modified styrene-butadiene rubber with a high degree of modification.

[0069] In the polymerization step, a polar compound may be added. By adding a polar compound, styrene can be randomly copolymerized with 1,3-butadiene, and the polar compound also tends to be used as a vinylizing agent to control the microstructure of the 1,3-butadiene portion. Examples of the polar compound include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium-tert-amylate, potassium-tert-butyrate, sodium-tert-butyrate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used individually or in combination of two or more.

[0070] In the polymerization step, the polymerization temperature is preferably 0°C or higher, more preferably 120°C or lower, and particularly preferably 50°C to 100°C, from the viewpoint of productivity. Within this range, it tends to be possible to ensure a sufficient amount of coupling agent reacting with the active ends after polymerization is complete.

[0071] The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. The amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably more than 0% by mass and 60% by mass or less, and more preferably 20% by mass or more and 45% by mass or less. When the amounts of bound butadiene and bound styrene are within the above ranges, the low loss and abrasion resistance of the rubber composition can be further improved. The amount of bound styrene can be measured by ultraviolet absorption of the phenyl group, and the amount of bound butadiene can also be determined from this.

[0072] In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bond in the butadiene bond unit is not particularly limited, but is preferably 10 mol% to 75 mol%, and more preferably 20 mol% to 65 mol%. When the amount of vinyl bond is within the above range, the low loss and abrasion resistance of the rubber composition can be further improved. For modified styrene-butadiene rubber, the amount of vinyl bond (1,2-bond amount) in the butadiene bond unit can be determined by Hampton's method [R. R. Hampton, Analytical Chemistry, 21, 923 (1949)].

[0073] The alkoxysilyl groups in the coupling agent represented by the general formula (I) above tend to react with the active end of the styrene-butadiene copolymer, for example, to dissociate alkoxylithium and form a bond between the end of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups in the coupling residue is obtained by subtracting the number of SiORs lost due to the reaction from the total number of SiORs in one molecule of the coupling agent. In addition, the azasilyl groups in the coupling agent form >N-Li bonds and bonds between the end of the styrene-butadiene copolymer and the silicon of the coupling residue. Note that the >N-Li bonds tend to readily become >NH and LiOH with water during finishing. Furthermore, unreacted alkoxysilyl groups remaining in the coupling agent tend to readily become silanols (Si-OH groups) with water during finishing.

[0074] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably 0°C to 120°C, and even more preferably 50°C to 100°C. The temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10°C or less, more preferably 5°C or less. The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. The time from the end of the polymerization step to the start of the reaction step is preferably shorter from the viewpoint of coupling rate, but more preferably within 5 minutes. Mixing in the reaction step may be done by mechanical stirring, stirring with a static mixer, etc. If the polymerization step is continuous, it is preferable that the reaction step is also continuous. For example, a tank-type or tubular-type reactor with a stirrer may be used in the reaction step. The coupling agent may be diluted with an inert solvent and continuously supplied to the reactor. If the polymerization step is batch-type, the coupling agent may be added to the polymerization reactor, or it may be transferred to another reactor and the reaction step may be carried out.

[0075] In the general formula (I), A is preferably represented by any one of the following general formulas (II) to (V). By having A represented by any one of the general formulas (II) to (V), a modified styrene-butadiene rubber having more excellent performance can be obtained.

[0076] In the general formula (II), B １ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When there are a plurality of Bs １ they are each independent.

[0077] In the general formula (III), B ２ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, B ３ represents an alkyl group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When there are a plurality of each of Bs ２ and B <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k represents 0. More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a represents an integer from 2 to 10. Even more preferably, in the general formula (I), A is represented by the general formula (II), k represents 0, and in the general formula (II), a represents an integer from 2 to 10. Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakiss[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakiss(3-trimethoxysilylpropyl Examples include tris(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and among these, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane are particularly preferred.

[0082] The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the number of moles of styrene-butadiene copolymer to the number of moles of the coupling agent reacts in a desired stoichiometric ratio, thereby tending to achieve the desired degree of branching. Specifically, the number of moles of the polymerization initiator is preferably 5.0 times or more, more preferably 6.0 times or more, of the number of moles of the coupling agent. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1) × i + p × j + k) is preferably an integer between 5 and 10, and more preferably an integer between 6 and 10.

[0083] To obtain a modified styrene-butadiene rubber having the aforementioned specific polymer component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer is preferably 1.5 to 2.5, more preferably 1.8 to 2.2. Furthermore, it is preferable that the obtained modified styrene-butadiene rubber exhibits a single peak in its molecular weight curve determined by GPC. The peak molecular weight of the modified styrene-butadiene rubber determined by GPC is Mp １ The peak molecular weight of the styrene-butadiene copolymer is Mp ２ In that case, it is preferable that the following equation holds true. (Mp １ / Mp ２ )<1.8×10-12×(Mp ２ -120 x 10 ４ ) ２ +2 MP ２ is 20 x 10 ４ 80 x 10 ４ Below, Mp １ is 30 x 10 ４ The above 150 x 10 ４ The following is preferable: Mp １ and Mp ２ This is determined by the method described in the examples below.

[0084] The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. A modification rate of 30% by mass or more further improves the low loss and abrasion resistance of the rubber composition.

[0085] After the reaction step, an inactivator, neutralizing agent, etc., may be added to the copolymer solution as needed. Examples of inactivators include, but are not limited to, water; and alcohols such as methanol, ethanol, and isopropanol. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture with 9 to 11 carbon atoms, mainly centered around 10); aqueous solutions of inorganic acids; and carbon dioxide. Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propinate and 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

[0086] Known methods can be used to obtain the modified styrene-butadiene rubber from the polymer solution. Examples of such methods include separating the solvent by steam stripping, filtering out the polymer, and then dehydrating and drying it to obtain the polymer; concentrating the solution in a flushing tank and then defoliating it with a vent extruder or the like; and directly defoliating it with a drum dryer or the like.

[0087] A modified styrene-butadiene rubber obtained by reacting a coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is, for example, represented by the following general formula (VI).

[0088] In general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight-average molecular weight of the styrene-butadiene copolymer chain is 10 × 10 ４ ~100 x 10４ It is preferable that this is the case. The styrene-butadiene copolymer chain is a structural unit of modified styrene-butadiene rubber, and is a structural unit derived from the styrene-butadiene copolymer, for example, produced by reacting the styrene-butadiene copolymer with a coupling agent. １２ , R １３ and R １４ Each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. １５ and R １８ Each of these independently represents an alkyl group having 1 to 20 carbon atoms. １６ , R １９ , and R ２０ Each of these independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. １７ and R ２１ Each of these independently represents an alkylene group having 1 to 20 carbon atoms. ２２ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x represent integers from 1 to 3, where x ≤ m; p represents 1 or 2; y represents an integer from 1 to 3, where y ≤ (p + 1); and z represents an integer from 1 to 2. D and R when multiple instances exist. １２ ~R ２２ m, p, x, y, and z are independent of each other and may be the same or different. Also, i represents an integer from 0 to 6, j represents an integer from 0 to 6, k represents an integer from 0 to 6, (i + j + k) is an integer from 3 to 10, and ((x × i) + (y × j) + (z × k)) is an integer from 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and not having active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups not having active hydrogen include hydroxyl groups (-OH), secondary amino groups (>NH), and primary amino groups (-NH). ２ Examples include functional groups having active hydrogen, such as sulfhydryl groups (-SH), and organic groups that do not have active hydrogen.

[0089] In the above general formula (VI), A is preferably represented by any of the above general formulas (II) to (V). By having A represented by any of the above general formulas (II) to (V), the low loss and wear resistance of the rubber composition can be further improved.

[0090] -Third Preferred Embodiment of Modified Styrene-Butadiene Rubber- It is also preferable that the styrene-butadiene rubber (SBR) is modified with a modifying agent containing a compound (alkoxysilane) represented by the following general formula (1) at least one of its ends.

[0091] By using styrene-butadiene rubber modified with a modifier containing an oligosiloxane and a tertiary amino group, which are filler affinity groups, as the rubber component, the dispersibility of fillers such as silica can be improved. As a result, the rubber composition of the present invention has improved filler dispersibility, which greatly improves low loss performance, reduces the rolling resistance of tires to which the rubber composition is applied, and improves fuel efficiency.

[0092] In the above general formula (1), R １ ~R ８ Each of these is an alkyl group having 1 to 20 carbon atoms; L １ and L ２ Each of these is an alkylene group having 1 to 20 carbon atoms; n is an integer from 2 to 4.

[0093] Specifically, in equation (1), R １ ~R ４ Each of these may independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the R １ ~R ４When substitution occurs, each can be independently substituted with one or more substituents selected from the group consisting of C1-C10 alkyl groups, C3-C10 cycloalkyl groups, C1-C10 alkoxy groups, C4-C10 cycloalkoxy groups, C6-C12 aryl groups, C6-C12 aryloxy groups, C2-C12 alkanoyloxy groups (Ra-COO-, where Ra is an alkyl group having C1-C9), C7-C13 aralkyloxy groups, C7-C13 arylalkyl groups, and C7-C13 alkylaryl groups. More specifically, the R １ ~R ４ R may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically, the R １ ~R ４ Each of these may independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0094] Also, in equation (1), R ５ ~R ８ Each of these is independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, more specifically a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and in the case of substitution, R comes first. １ ~R ４ It can be substituted with substituents as described above. ５ ~R ８ If the substituent is not an alkyl group but a hydrolyzable substituent, N-R ５ R ６ and N-R ７ R ８ The bond can be hydrolyzed to N-H in the presence of moisture, which can adversely affect the processability of the polymer.

[0095] More specifically, in the compound represented by formula (1), R １ ~R ４ R is a methyl group or an ethyl group, ５ ~R ８ This can be an alkyl group having 1 to 10 carbon atoms.

[0096] The amino group in the compound represented by formula (1), i.e., N-R５ R ６ and N-R ７ R ８ It is preferable that R is a tertiary amino group. The tertiary amino group provides even better processability when the compound represented by formula (1) is used as a modifying agent. ５ ~R ８ If a protecting group to protect the amino group is bonded, or if hydrogen is bonded, it may be difficult to realize the effect of the compound represented by formula (1). When hydrogen is bonded, the anion reacts with hydrogen during the modification process and loses its reactivity, making the modification reaction itself impossible. When a protecting group is bonded, the modification reaction takes place, but the bonded group remains at the polymer end and is deprotected by hydrolysis during post-processing, becoming a primary or secondary amino group. This deprotected primary or secondary amino group may cause increased viscosity of the compound during subsequent compounding, potentially leading to reduced processability.

[0097] Furthermore, L in the compound represented by formula (1) １ and L ２ Each of these is independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms. More specifically, L １ and L ２ Each of these can be an alkylene group having 1 to 10 carbon atoms, or more specifically, an alkylene group having 1 to 6 carbon atoms, such as a methylene group, an ethylene group, or a propylene group.

[0098] L in the compound represented by formula (1) １ and L ２ Regarding this, the closer the distance between the Si atom and N atom within the molecule, the better the effect. However, when Si is directly bonded to N, there is a risk that the bond between Si and N may break during subsequent processing steps, and the secondary amino group generated at this time is likely to be washed away by water during post-processing. As a result, in the modified styrene-butadiene rubber produced, it becomes difficult for the amino group to bond with fillers such as silica, and consequently, the effect of improving the dispersibility of the filler may decrease. Considering the improvement effect depending on the length of the bond between Si and N, the aforementioned L １ and L ２Each of these is more preferably an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, or a propylene group, and more specifically, it can be a propylene group. １ and L ２ First, R １ ~R ４ It can be substituted with substituents as described above.

[0099] Furthermore, the compound represented by formula (1) is preferably one of the compounds represented by the following structural formulas (1-1) to (1-5), because it is possible to achieve even better low loss performance.

[0100] The compound represented by formula (1) has an alkoxysilane structure that binds to the active end of the styrene-butadiene copolymer, while the Si-O-Si structure and the three or more amino groups attached to the ends exhibit affinity for fillers such as silica. Compared to conventional modifiers containing one amino group in the molecule, this compound can promote the bonding between the filler and the modified styrene-butadiene rubber. Furthermore, the degree of binding to the active end of the styrene-butadiene copolymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant after coupling without becoming significantly larger than before. Therefore, there is no deterioration in the physical properties of the modified styrene-butadiene rubber itself, and aggregation of the filler in the rubber composition is prevented, improving the dispersibility of the filler and thus improving the processability of the rubber composition. These effects, in particular, make it possible to improve fuel efficiency and wet grip performance in a balanced manner when the rubber composition is applied to tires.

[0101] The compound represented by formula (1) can be produced through a condensation reaction represented by the following reaction scheme.

[0102] In the above reaction scheme, R １ ~R ８ , L １ and L ２, and n are the same as those defined in formula (1) above, and R' and R'' are arbitrary substituents that do not affect the condensation reaction. For example, R' and R'' are each independently R １ ~R ４ It can be made identical to any one of the following.

[0103] The reaction in the above reaction scheme proceeds in the presence of an acid, and the acid can be any acid that is commonly used in condensation reactions, without limitation. Those skilled in the art can select the optimal acid according to various process variables such as the type of reactor in which the reaction is carried out, the starting materials, and the reaction temperature.

[0104] Furthermore, the styrene-butadiene rubber modified with a modifying agent containing the compound represented by formula (1) above may have a narrow molecular weight distribution of 1.1 to 3.0 (Mw / Mn, also called the "polydispersion index (PDI)"). If the molecular weight distribution of the modified styrene-butadiene rubber exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may decrease when applied to a rubber composition. Considering the remarkable effect of controlling the molecular weight distribution of the modified styrene-butadiene rubber on improving tensile properties and viscoelasticity, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. Furthermore, by using the modifying agent, the molecular weight distribution of the modified styrene-butadiene rubber becomes similar to that of the styrene-butadiene copolymer before modification.

[0105] The molecular weight distribution of the modified styrene-butadiene rubber can be calculated from the ratio of the weight-average molecular weight (Mw) to the logarithmic-average molecular weight (Mn) (Mw / Mn). In this case, the number-average molecular weight (Mn) is the common average of the individual polymer molecular weights calculated by measuring the molecular weights of n polymer molecules, summing these molecular weights, and dividing by n, while the weight-average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The average of the overall molecular weight can be expressed in grams per mole (g / mol). Furthermore, the weight-average molecular weight and the number-average molecular weight are polystyrene-equivalent molecular weights analyzed by gel permeation chromatography (GPC), respectively.

[0106] Furthermore, the modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution conditions and has a number-average molecular weight (Mn) of 50,000 g / mol to 2,000,000 g / mol, more specifically, 200,000 g / mol to 800,000 g / mol. The modified styrene-butadiene rubber has a weight-average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol, more specifically, 300,000 g / mol to 1,500,000 g / mol. If the weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is less than 100,000 g / mol, or if the number-average molecular weight (Mn) is less than 50,000 g / mol, there is a risk of a decrease in tensile properties when applied to a rubber composition. Furthermore, if the weight-average molecular weight (Mw) exceeds 4,000,000 g / mol or the number-average molecular weight (Mn) exceeds 2,000,000 g / mol, the processability of the modified styrene-butadiene rubber deteriorates, worsening the workability of the rubber composition, making mixing difficult, and making it difficult to sufficiently improve the physical properties of the rubber composition. More specifically, when the modified styrene-butadiene rubber satisfies the conditions of weight-average molecular weight (Mw) and number-average molecular weight (Mn) simultaneously with the molecular weight distribution, it can improve the viscoelasticity and processability of the rubber composition in a well-balanced manner when applied to a rubber composition.

[0107] The modified styrene-butadiene rubber preferably has a vinyl bond content of 5% or more in the butadiene portion, more preferably 10% or more, and more preferably 60% or less. By setting the vinyl bond content of the butadiene portion within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0108] The modified styrene-butadiene rubber may have a Mooney viscosity (MV) of 40 to 140, specifically 60 to 100, at 100°C. Having a Mooney viscosity within this range allows for superior processability. The Mooney viscosity can be measured using a Mooney viscometer, such as the Monsanto MV2000E, at 100°C and a rotor speed of 2 ± 0.02 rpm, using the large rotor. The sample used can be left at room temperature (23 ± 3°C) for at least 30 minutes, then 27 ± 3 g can be taken, placed inside a die cavity, and the platen can be operated for measurement.

[0109] As described above, it is preferable that one end of the modified styrene-butadiene rubber is modified with a modifying agent containing the compound represented by the general formula (1), but it is preferable that the other end is further modified with a modifying agent containing the compound represented by the general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a higher level of both fuel efficiency and wet grip performance can be achieved in the tire to which the rubber composition is applied.

[0110] In the above general formula (2), R ９ ~R １１ These are, independently of each other, hydrogen; a C1-C30 alkyl group; a C2-C30 alkenyl group; a C2-C30 alkynyl group; a C1-C30 heteroalkyl group, a C2-C30 heteroalkenyl group; a C2-C30 heteroalkynyl group; a C5-C30 cycloalkyl group; a C6-C30 aryl group; or a C3-C30 heterocyclic group. Also, in formula (2), R １２ R is a single bond; a substituent-substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituent-substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituent-substituted or unsubstituted arylene group having 5 to 20 carbon atoms, where the substituent is a C1 to C10 alkyl group, a C5 to C10 cycloalkyl group, or a C6 to C20 aryl group. Also, in formula (2), R １３is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or an active group represented by the following general formula (2a) or general formula (2b), where m is an integer from 1 to 5, and R １３ At least one of them is an operator represented by the following general formula (2a) or general formula (2b), and when m is an integer from 2 to 5, multiple R １３ They may be identical or different from one another.

[0111]

[0112] In the above general formula (2a), R １４ R is a substituent-substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituent-substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituent-substituted or unsubstituted arylene group having 6 to 20 carbon atoms, where the substituent is a substituent having 1 to 10 carbon atoms, a substituent having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2a), R １５ and R １６ These are, independently of each other, a C1-C10 alkyl group, a C5-C10 cycloalkyl group, or a C6-C20 aryl group, or an unsubstituted C1-C20 alkylene group. Also, in formula (2a), R １７ R is a hydrogen atom; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms, where X is an N, O, or S atom, provided that when X is O or S, R １７ It does not exist.

[0113]

[0114] In the above general formula (2b), R １８R is a C1-C20 alkylene group substituted or unsubstituted with a substituent; a C5-C20 cycloalkylene group substituted or unsubstituted with a substituent; or a C6-C20 arylene group substituted or unsubstituted with a substituent, where the substituent is a C1-C10 alkyl group, a C5-C10 cycloalkyl group, or a C6-C20 aryl group. Also, in formula (2b), R １９ and R ２０ These are, independently of each other, C1-C30 alkyl groups; C2-C30 alkenyl groups; C2-C30 alkynyl groups; C1-C30 heteroalkyl groups; C2-C30 heteroalkenyl groups; C2-C30 heteroalkynyl groups; C5-C30 cycloalkyl groups; C6-C30 aryl groups; and C3-C30 heterocyclic groups.

[0115] Furthermore, in the compound represented by the above general formula (2), R ９ ~R １１ R is independently of hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms. １２ R is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms. １３ R is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; an alkynyl group having 2 to 10 carbon atoms; or an active group represented by the above general formula (2a) or general formula (2b), wherein in the above general formula (2a), １４ R is an unsubstituted alkylene group having 1 to 10 carbon atoms. １５ and R １６ These are unsubstituted alkylene groups having 1 to 10 carbon atoms, R １７ R is an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms, and in the above general formula (2b), R １８ R is an unsubstituted alkylene group having 1 to 10 carbon atoms. １９ and R ２０ These may be, independently of each other, an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms.

[0116] More specifically, the compound represented by the general formula (2) above can be the compound represented by the following structural formulas (2-1) to (2-3).

[0117] Furthermore, when the styrene-butadiene copolymer is modified with a modifying agent containing the compound represented by the general formula (2), the modifying agent containing the compound represented by formula (2) is used as a modification initiator. Specifically, for example, by polymerizing the butadiene monomer and the styrene monomer in a hydrocarbon solvent in the presence of a modifying agent containing the compound represented by formula (2), a modifying group derived from the compound represented by formula (2) can be imparted to the styrene-butadiene copolymer.

[0118] - Rubber components other than isoprene-based rubber and styrene-butadiene rubber The rubber components may also contain rubber components other than isoprene-based rubber and styrene-butadiene rubber (hereinafter sometimes referred to as "other rubber components").

[0119] Other rubber components include diene-based rubbers, and among these diene-based rubbers, butadiene-based rubbers are preferred. Here, butadiene-based rubber refers to rubber that contains units derived from butadiene as monomer units.

[0120] Examples of the butadiene rubber (BR) include high-cis content butadiene rubber, low-cis content butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available butadiene rubber (BR) can be used, and examples of such commercially available butadiene rubber include products from UBE Elastomer Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation. These butadiene rubbers may be used individually or in combination of two or more types.

[0121] The butadiene-based rubber preferably has a sustainable ratio of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to make the sustainable ratio of the butadiene-based rubber within the above range, for example, butadiene derived from biological resources may be used. Suitable butadiene obtained from biological resources include butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tigric acid).

[0122] Furthermore, as the rubber component, rubber derived from biological resources and rubber derived from recycled resources are preferred. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer component constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%. Also, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer component constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%.

[0123] The aforementioned rubber component is a component that contributes to crosslinking, and typically has a weight-average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 5,000,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) of the rubber component can be determined, for example, by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC).

[0124] The ratio of each monomer unit (for example, units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component can be appropriately adjusted depending on the member to which it is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the isoprene-based rubber and butadiene-based rubber mentioned above. The ratio of cis-bonded units in the butadiene-derived units can also be appropriately adjusted depending on the member to which it is applied. In this specification, "monomer unit" means a constituent unit of a polymer, "unit derived from isoprene" means a constituent unit in a polymer composed of isoprene, which is a monomer (including isoprene units in natural rubber), "unit derived from butadiene" means a constituent unit in a polymer composed of butadiene, which is a monomer, and "unit derived from aromatic vinyl compounds" means a constituent unit in a polymer composed of aromatic vinyl compounds, which are monomers. In this specification, the ratio of each monomer unit is measured by NMR.

[0125] In addition to the isoprene-based rubber, butadiene rubber, and styrene-butadiene copolymer rubber mentioned above, the rubber component may also include diene-based rubbers such as acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, and styrene-isoprene-butadiene copolymer rubber. These rubber components may be used individually or in combination of two or more.

[0126] The rubber component may have functional groups that interact with fillers such as carbon black and silica introduced through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups. These functional groups may also have substituents. These functional groups may be introduced into the rubber component individually or in combination of two or more. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atoms of the amino group are replaced by alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are even more preferred.

[0127] The functional group can be introduced, for example, by reacting a compound having the functional group (modifier) ​​with the rubber component. The compound having the functional group (modifier) ​​is a modifying functional group that interacts with fillers such as silica and carbon black, and can be a nitrogen-containing functional group, a silicon-containing functional group, or an oxygen-containing functional group. Examples of nitrogen-containing functional groups include amino group-containing compounds, examples of silicon-containing functional groups include silicon halides and hydrocarbyloxysilane compounds, and examples of oxygen-containing functional groups include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples include compounds described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used individually or in combination of two or more.

[0128] Furthermore, the rubber derived from the aforementioned sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be manufactured, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and optionally using monomer components derived from fossil resources, in the same manner as conventional methods for manufacturing synthetic rubber derived from fossil resources. For example, the method described in Japanese Patent Application Publication No. 2022-179158 can be used to prepare rubber derived from biological resources.

[0129] (Resin) The rubber composition of the present invention further comprises a resin, wherein the resin comprises at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and a rosin resin. By including a rosin resin as an essential component in addition to at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, low rolling resistance and low-temperature characteristics can be further improved. In addition, as a result of increased compatibility with the rubber components, the dispersibility of carbon black and silica, described later, is improved, and a better balance of low rolling resistance, low-temperature characteristics, and handling stability can be obtained. Furthermore, the use of fossil fuel-derived raw materials in the rubber composition can be reduced, thereby reducing the environmental burden, and the ratio of natural resource-derived raw materials (sustainable material ratio) in the rubber composition can be improved.

[0130] The aforementioned terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or polymer components separated therefrom, using a Friedel-Crafts type catalyst. Examples include β-pinene resin and α-pinene resin.

[0131] Furthermore, typical examples of terpene-aromatic compound resins include terpene-phenol resins and styrene-terpene resins. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensation with formalin. Styrene-terpene resins can be obtained by reacting styrene with terpenes using a Friedel-Crafts type catalyst. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred.

[0132] Examples of rosin-based resins include natural resin rosins such as gum rosin contained in raw pine resin and tall oil, tall oil rosin, and wood rosin. Examples of modified rosins, rosin derivatives, and modified rosin derivatives include polymerized rosin and its partially hydrogenated rosin; glycerol ester rosin and its partially hydrogenated or fully hydrogenated rosin; pentaerythritol ester rosin and its partially hydrogenated or polymerized rosin; and so on.

[0133] Furthermore, in addition to the terpene resins, terpene-aromatic compound resins, and rosin resins mentioned above, the resin also includes C ５ based resin, C ５ -C ９ based resin, C ９ This includes resins such as C10, cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used individually or in combination of two or more. Among these resins, C ５ based resin, C ５ -C ９ based resin, C ９ C resins, cyclopentadiene resins, and aromatic resins are preferred. ５ based resin, C ９ based resin, C ５ -C ９Aromatic resins, such as cyclopentadiene resins, can improve wear resistance and fuel efficiency in a balanced way. Aromatic resins, on the other hand, can improve grip performance, wear resistance, and rubber strength in a balanced way.

[0134] Furthermore, the resin may be hydrogenated, that is, it may be a hydrogenated resin. In addition, the resin may have functional groups that interact with fillers such as carbon black and silica introduced into it through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0135] Said C ５ As for resins, C is obtained by the thermal decomposition of naphtha in the petrochemical industry. ５ Examples include aliphatic petroleum resins obtained by (co)polymerizing the fractions. ５ The fraction typically includes olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, as well as diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0136] Said C ５ -C ９ C resins are C ５ -C ９ This refers to synthetic petroleum resins, C ５ -C ９ Examples of resins include petroleum-derived C ５ -C １１ The fraction is AlCl ３ BF ３Examples include solid polymers obtained by polymerization using Friedel-Crafts catalysts such as [list of catalysts], and more specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. ５ -C ９ As for resin systems, C ９ Resins containing fewer of the above components are preferred from the viewpoint of compatibility with rubber components. Here, "C ９ "The above components are low" means that the total amount of C in the resin is low. ９ This means that the above components are present in an amount of less than 50% by mass, preferably 40% by mass or less.

[0137] Said C ９ C resins are C ９ This refers to synthetic petroleum resins, such as AlCl ３ Ya BF ３ Using Friedelcrafts type catalysts such as C ９ This refers to a solid polymer obtained by polymerizing a fraction. ９ Examples of resin compounds include copolymers mainly composed of indene, α-methylstyrene, vinyltoluene, etc.

[0138] The cyclopentadiene-based resin refers to a resin containing units derived from cyclopentadiene monomers as monomer units. Examples of the cyclopentadiene-based resin include homopolymers of cyclopentadiene monomers, copolymers of two or more cyclopentadiene monomers, and copolymers of cyclopentadiene monomers and other monomers. Examples of cyclopentadiene monomers include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene, among which dicyclopentadiene is preferred, that is, a dicyclopentadiene-based resin is preferred as the cyclopentadiene-based resin. Examples of the dicyclopentadiene-based resin include AlCl ３ Ya BF ３ This refers to resins obtained by polymerizing dicyclopentadiene using Friedel-Crafts type catalysts such as the above. Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C ９Copolymers with fractions (such as vinyltoluene and indene) are examples.

[0139] The aforementioned aromatic resin refers to a resin that contains units derived from aromatic monomers as monomer units. Examples of such aromatic resins include homopolymers of aromatic monomers, copolymers of two or more aromatic monomers, and copolymers of aromatic monomers with other monomers. Examples of aromatic monomers include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenol monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0140] The resin preferably has a softening point of 30°C or higher, more preferably 60°C or higher, more preferably 90°C or higher, more preferably higher than 110°C, and more preferably 120°C or higher. Furthermore, the resin preferably has a softening point of 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, and more preferably 140°C or lower. The softening point of the resin is measured in accordance with JIS-K2207-1996 (ring-sphere method).

[0141] Commercially available resins can be used, and examples of such commercially available resins include those from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Company, Kraton Polymer Company, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Corporation, Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Polymer Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., Taoka Chemical Industries, Ltd., and others.

[0142] Furthermore, the difference in SP value between the resin and the isoprene-based rubber is 0.6 (cal / cm²). ３ ) １／２Preferably, the following conditions are met: The difference in SP value between the resin and the isoprene-based rubber is 0.6 (cal / cm²). ３ ) １／２ The following conditions improve compatibility with isoprene-based rubber, control the mobility of the rubber components, and improve hysteresis loss (tanδ) in the low-temperature range, thereby improving the low-temperature characteristics and workability of tires to which the rubber composition is applied. Furthermore, the difference in SP values ​​between the resin and the isoprene-based rubber is set to 0.59 (cal / cm²) from the viewpoint of further improving compatibility. ３ ) １／２ Preferably, it is 0.58 (cal / cm³). ３ ) １／２ More preferably, the following is 0.57 (cal / cm³) ３ ) １／２ It is even more preferable that the following conditions are met: The difference in SP values ​​between the resin component and the isoprene-based rubber is 0.6 (cal / cm²). ３ ) １／２The following conditions are met: the compatibility between the resin component and the isoprene-based rubber is further improved, and the wet grip performance of the tire to which the rubber composition is applied is further improved. On the other hand, it is also preferable that the weight-average molecular weight of the resin, in terms of polystyrene, is 500 g / mol or more and 1300 g / mol or less. When the weight-average molecular weight of the resin, in terms of polystyrene, is 500 g / mol or more, the resin component is less likely to precipitate from the tire, and the effects of the resin component can be fully expressed. When it is 1300 g / mol or less, the resin component is more compatible with the rubber component. Therefore, from the viewpoint of suppressing the precipitation of resin components from the tire and suppressing the deterioration of the tire appearance, the weight-average molecular weight of the resin, in terms of polystyrene, is preferably 500 g / mol or more, more preferably 550 g / mol or more, more preferably 600 g / mol or more, more preferably 650 g / mol or more, and even more preferably 700 g / mol or more. Furthermore, from the viewpoint of improving the compatibility of the resin component with the rubber component and further enhancing the effects of the resin component, the weight-average molecular weight of the resin component in terms of polystyrene is more preferably 1250 g / mol or less, more preferably 1230 g / mol or less, more preferably 1220 g / mol or less, and even more preferably 1200 g / mol or less.

[0143] Furthermore, it is preferable that the mass ratio of the resin to the isoprene-based rubber [mass ratio of resin component / mass ratio of isoprene-based rubber] is 0.5 or higher. By having the mass ratio of the resin to the isoprene-based rubber within the above range, the wet grip performance of the tire to which the rubber composition is applied can be further improved. The mass ratio of the resin to the isoprene-based rubber [mass ratio of resin component / mass ratio of isoprene-based rubber] is preferably 0.10 or higher, more preferably 0.20 or higher, more preferably 0.25 or higher, preferably 2.0 or lower, more preferably 1.9 or lower, and even more preferably 1.8 or lower.

[0144] Furthermore, the content of at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and rosin resin in the rubber composition of the present invention is greater than 0 to 50 parts by mass per 100 parts by mass of the rubber component. Including at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and rosin resin in the rubber composition (with a total content greater than 0) allows the effects of the resin to be fully expressed, and if the content is 50 parts by mass or less, the resin component is less likely to precipitate from the tire, and the effects of the resin component can be fully expressed. On the other hand, if the content of the resin component exceeds 50 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and wear resistance of the tire to which the rubber composition is applied deteriorate. From the viewpoint of further enhancing the effects of the resin component, the content of the resin component in the rubber composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, even more preferably 9 parts by mass or more, particularly preferably 15 parts by mass or more, and most preferably 17 parts by mass or more, from the viewpoint of suppressing the precipitation of the resin component from the tire and suppressing the deterioration of the tire appearance.

[0145] (Recycled carbon black, carbon black) In addition to the rubber components and resins described above, the tread rubber composition of the present invention contains recycled carbon black. Since the recycled carbon black is a material derived from recycled resources, the inclusion of recycled carbon black improves the proportion of sustainable materials in the side rubber rubber composition. By applying this rubber composition to a tire, the proportion of sustainable materials in the tire can be improved, thereby reducing the environmental impact.

[0146] In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials submitted for recycling. Examples of such waste materials include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only rubber generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is fine rubber generated, for example, in the buffing process of retreading tires, where the tread portion remaining on the base tire is scraped off. Peeling rubber is long pieces of rubber, for example, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by scraping the surface of rubber products such as tires using a U-shaped or V-shaped knife like a peeler. Furthermore, waste rubber includes not only cross-linked rubber but also unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, and rubber parts or components at the manufacturing stage of final products. Used tires may be retreaded, or they may be tires discarded for any reason, such as tires that have reached the end of their lifespan, tires that have been replaced or scrapped, or ELTs (End-of-Life Tires). Waste oil is not limited to that generated when plastics and rubber are decomposed, but also includes used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oil that does not contain any non-organic composition, such as those derived from silicone rubber or polyvinyl chloride, is desirable. Furthermore, waste oil that is mixed with carbon black or rubber containing carbon black is desirable. The aforementioned "recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., carbon black that is not recycled. Note that "used" here includes not only those that have been actually used and then discarded, but also those that were manufactured but discarded without actually being used.

[0147] Furthermore, it is preferable that the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by thermal decomposition of a vulcanized rubber product containing carbon black is readily available because a large amount of vulcanized rubber product containing carbon black exists and it can be easily obtained by thermal decomposition. Moreover, it is preferable that the recycled carbon black is obtained from the solid residue generated by the thermal decomposition of the above-mentioned vulcanized rubber product containing carbon black. When a rubber product containing carbon black is thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from either. When recovering carbon black from volatile components, it is possible to recover oil with a specific gravity suitable for producing carbon black and use it to produce carbon black using an existing carbon black production method (for example, Japanese Patent Publication No. 2015-520259). In this case, unlike carbon black recovered from solid residue, there are advantages such as the absence of impurities and the absence of mixtures of different grades. Furthermore, in the production of environmentally friendly carbon black, there are various options besides the oil obtained by recovering volatile components from the thermal decomposition of rubber mentioned above, such as using vegetable oil or oil derived from waste plastics. However, edible resources such as vegetable oil present challenges in securing sufficient quantities due to other uses such as food, and the environmental impact associated with the expansion of cultivated land must also be considered. Similarly, oil derived from waste plastics is used for other purposes such as horizontal recycling of plastics, so supply issues are also a concern. On the other hand, when using volatile components (oil) produced by the thermal decomposition of vulcanized rubber products, particularly tires, the tire industry has a system for continuing to use existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire manufacturing, thereby contributing to reducing the environmental burden on the industry. The grade of carbon black is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0148] The solid residue obtained by thermally decomposing waste materials such as used rubber and used tires contains ash in addition to carbon black. The ash originates from non-volatile components contained in rubber and tires. Therefore, the recycled carbon black obtained from this solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, a higher carbon content in recycled carbon black is preferable. In the recycled carbon black, the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and still more preferably 89% by mass or more. In the recycled carbon black, the carbon content is preferably 97% by mass or less. Note that the carbon content does not include adsorbed water.

[0149] The aforementioned ash content specifically includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from solid residue obtained by thermal decomposition of waste, a certain amount of ash remains even after various processes to remove it. In this embodiment, the presence of ash in recycled carbon black is permitted. The lower limit of the ash content in the recycled carbon black may be 0.5% by mass.

[0150] Furthermore, the recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

[0004] of Patent No. 6856781 (Comparison of Surface Morphology and Chemistry of Pyrolysis Carbon Black and Commercial Carbon Black, Powder Technology 160 (2005) 190-193).

[0151] The recycled carbon black may lack functional groups on its surface, or it may have been treated to include functional groups on its surface. 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. 3173251, carbon black obtained from a thermal decomposition process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. In addition, in Japanese Patent No. 6856781, carbon black obtained from a thermal decomposition process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black that has been treated to include functional groups on its surface.

[0152] Furthermore, for the thermal decomposition of cross-linked rubber products (vulcanized rubber products) such as used tires, one example is a thermal decomposition method at a temperature of 650°C or higher.

[0153] The cross-linked rubber products used in the aforementioned decomposition may be grouped by the type of rubber component they contain beforehand, and the decomposition process may be carried out for each group separately. Alternatively, they may be grouped by the type of filler they contain beforehand (for example, the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and the decomposition process may be carried out for each group separately. Furthermore, they may be grouped by both the type of rubber component and the type of filler, and the decomposition process may be carried out for each group separately. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again incorporated into the rubber component, a rubber composition with better performance can be obtained.

[0154] Furthermore, if the cross-linked rubber product used in the decomposition is derived from a tire, it may be grouped in advance by tire type (for example, for passenger cars, trucks and buses, heavy vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.) and then the decomposition process may be carried out for each group. Alternatively, it may be grouped in advance by tire component (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.) and then the decomposition process may be carried out for each group. In addition, it may be possible to group by tire type and by tire component and then carry out the decomposition process for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again blended into the rubber component, a rubber composition with better performance can be obtained.

[0155] Furthermore, the recycled carbon black is one in which, when measured with a grind gauge, there are three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that produce such lines is 20 μm or less. By incorporating recycled carbon black into a rubber composition that, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that produce such lines is 20 μm or less, the dispersibility of the recycled carbon black in the rubber is improved, and the high-temperature crack propagation resistance and high-temperature tensile strength after degradation of the rubber composition can be improved while increasing the sustainability ratio. Methods for evaluating the dispersibility of carbon black using a grind gauge are described in JIS K5101 (especially regarding the preparation of paste) and JIS K5400 (especially regarding the method of evaluation by the manner in which linear marks are generated).

[0156] In the evaluation method for recycled carbon black of this embodiment, as described later, from the viewpoint of the durability of the rubber composition, it is important whether the particle size of the third largest particle in the recycled carbon black being measured is 20 μm or less. Therefore, from the viewpoint of accurately measuring particle sizes around 20 μm, and from the viewpoint of ease of measurement, it is preferable to use a grind gauge with a range of 0 to 25 μm. Note that any grind gauge with an upper limit of the range greater than 20 μm can be used, as it is possible to determine whether the particle size of the third largest particle is 20 μm or less. Furthermore, when using it for other purposes (performance other than the durability of the rubber composition containing recycled carbon black), the range of the grind gauge to be used can be appropriately selected according to the purpose. As described above, JIS K5101-1-5 describes a method for preparing a paste of recycled carbon black as a measurement sample in grind gauge measurement, and in the recycled carbon black of this embodiment, the paste of the recycled carbon black is prepared in accordance with JIS K5101-1-5 as a measurement sample for measurement using a grind gauge. By preparing recycled carbon black paste in accordance with JIS K5101-1-5, the evaluation system for recycled carbon black can be further improved.

[0157] In one embodiment, the accuracy of grind gauge measurement can be further improved by appropriately adjusting the viscosity of the paste. In one embodiment, it is preferable to prepare a paste (measurement sample) containing recycled carbon black by blending recycled carbon black and zinc oxide with epoxidized soybean oil. Here, the blending ratio of the paste is not particularly limited, but it is preferable to use about 8 to 12 g of recycled carbon black and about 160 to 200 g of zinc oxide per 100 mL of epoxidized soybean oil.

[0158] Furthermore, when preparing the recycled carbon black paste in accordance with JIS K5101-1-5, it is preferable to apply a load of 0.4 to 0.5 kN and to rotate the glass plate at a speed of 90 to 110 r / min, from the viewpoint of improving evaluation accuracy.

[0159] Figure 1 shows an explanatory diagram of an example of measurement results using a grind gauge. In the measurement using grind gauge 1, several lines attributable to particles in the measurement sample are observed. In this embodiment, in accordance with JIS standards, lines 2 with a length of less than 10 mm are not considered, and lines 3 with a length of 10 mm or more are considered. Furthermore, among the lines 3 with a length of 10 mm or more, line 31 attributable to the largest particle and line 32 attributable to the second largest particle are judged to be abnormal values, and in this embodiment, from the viewpoint of improving measurement accuracy, attention is focused on line 33 attributable to the third largest particle. The scale 4 at the location where line 33 attributable to the third largest particle appears is read, and this reading is taken as the particle size of the third largest particle. If the particle size of the third largest particle is 20 μm or less, the deterioration of the durability of the rubber composition, especially the performance after degradation, can be suppressed even when recycled carbon black is added. In this specification, the measurement of recycled carbon black using a grind gauge is performed by the method described in the examples.

[0160] In this embodiment, recycled carbon black having three or more lines of 10 mm or longer in length, as measured by a grind gauge, and the particle size of the third largest particle among the particles that give rise to these lines of 10 mm or longer being 20 μm or less, can be produced by various methods. For example, recycled carbon black with a particle size of 20 μm or less can be produced by further grinding the recycled carbon black produced by a general method from recycled waste by extending the grinding process for a longer time or increasing the grinding intensity.

[0161] Furthermore, the recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m² obtained by the BET method. ２ It is preferable that the amount be / g, and 50 to 90 m ２ It is more preferable that the amount be / g, and 55 to 75 m ２ It is particularly preferable that the value be / g. Here, in this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black by the BET method is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556.

[0162] The recycled carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, the pH of the recycled carbon black is determined according to ASTM D1512.

[0163] The recycled carbon black preferably has a toluene staining transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, in this specification, the toluene staining transmittance of recycled carbon black is determined according to ASTM D1618.

[0164] The recycled carbon black preferably has a heating loss of 3% by mass or less at 125°C, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Hereinafter, the heating loss of the recycled carbon black at 125°C is determined according to ASTM D1509.

[0165] 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.

[0166] The recycled carbon black preferably has a 35-mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Here, in this specification, the 35-mesh sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0167] The recycled carbon black preferably has a 325-mesh (44 μm) sieve residue of 1,000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. Here, in this specification, the 325-mesh (44 μm) sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0168] 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. Hereinafter, the pellet hardness of the recycled carbon black is determined according to ASTM D5230.

[0169] 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. Hereinafter, the pellet fine powder content of the recycled carbon black is determined according to ASTM D1508.

[0170] The recycled carbon black preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Hereinafter, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size analyzer, with the refractive index of water being 1.33 and the refractive index of the filler being 1.75.

[0171] The recycled carbon black preferably contains 50% or more by volume of particles 5 μm or smaller, more preferably 70% or more by volume, and particularly preferably 80% or more by volume.

[0172] 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 various physical properties of the side rubber to which the rubber composition is applied can be improved. Furthermore, it is preferable that the recycled carbon black has an ash content of 20% by mass or less. Here, in this specification, the ash content of the recycled carbon black is determined according to ASTM D8474 / D1506.

[0173] The recycled carbon black preferably has an oil adsorption capacity (OAN) 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, in this specification, the OAN of the recycled carbon black is determined according to ASTM D2414.

[0174] The recycled carbon black preferably has a compressed oil adsorption amount (COAN) 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, in this specification, the COAN of the recycled carbon black is determined according to ASTM D3493.

[0175] The recycled carbon black preferably contains one or more elements selected from the group consisting of Zn (zinc), Fe (iron), and Cu (copper). Such recycled carbon black can maintain the physical properties of the rubber composition while retaining components that may affect the deterioration of the rubber composition's properties, thus simplifying processing steps such as purification to completely remove components that may affect the deterioration of the rubber composition's properties.

[0176] If the recycled carbon black contains Zn, the Zn content in the recycled carbon black is preferably 2.5% by mass or less. A lower Zn content in the carbon black is preferable, but if the Zn content is 2.5% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Zn content is more preferably 2.0% by mass or less, even more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. The Zn content may also be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate. Methods for adjusting the Zn content in recycled carbon black to within the above range include, for example, pre-analyzing the amount of Zn contained in the raw rubber to be acid-treated and recycled, and applying some or all of the raw rubber with a low Zn content.

[0177] Furthermore, if the recycled carbon black contains Fe, the Fe content in the recycled carbon black is preferably 0% by mass or more and 0.1% by mass or less. A lower Fe content in the recycled carbon black is preferable, but if the Fe content is 0.1% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the physical properties of the rubber composition, the Fe content is more preferably 0.09% by mass or less, even more preferably 0.08% by mass or less, still preferably 0.07% by mass or less, even more preferably 0.06% by mass or less, even more preferably 0.05% by mass or less, particularly preferably 0.04% by mass or less, and most preferably 0.03% by mass or less. The Fe content may also be 0.01% by mass or more, or 0.02% by mass or more. The above upper and lower limits can be combined as appropriate.

[0178] If the recycled carbon black contains Cu, the Cu content in the recycled carbon black is preferably 0% by mass or more and 0.05% by mass or less. A lower Cu content in the recycled carbon black is preferable, but if the Cu content is 0.05% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the physical properties of the rubber composition, the Cu content is more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, and even more preferably 0.01% by mass or less. The Cu content may also be 0.01% by mass or more, or 0.02% by mass or more. The above upper and lower limits can be combined as appropriate.

[0179] Furthermore, the recycled carbon black may contain components other than Zn, Fe, and Cu as described above. "Components other than Zn, Fe, and Cu" refers to components other than Zn, Fe, and Cu in the ash. Examples of components other than Zn, Fe, and Cu in the ash include Si (silicon), S (sulfur), Ca (calcium), K (potassium), Br (bromine), Mg (magnesium), Cl (chlorine), P (phosphorus), Co (cobalt), Na (sodium), and Al (aluminum).

[0180] The recycled carbon black may contain silicon (Si). In that case, the Si content in the recycled carbon black is preferably 0% by mass or more and 1.0% by mass or less. A Si content of 1.0% by mass or less suppresses a decrease in the physical properties of the rubber composition. From a similar viewpoint, the Si content is more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. It is also preferable that the Si content is 0% by mass, i.e., substantially Si-free. On the other hand, the Si content may be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate.

[0181] The recycled carbon black may contain sulfur (S). In that case, the S content in the recycled carbon black is preferably 0.4% by mass or more, and more preferably 0.5% by mass or more. Furthermore, the S content is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The above upper and lower limits can be combined as appropriate.

[0182] The recycled carbon black may contain Ca (calcium). In that case, the Ca content in the recycled carbon black is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and particularly preferably 0.8% by mass or more. Furthermore, the Ca content is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and even more preferably 1.1% by mass or less. The above upper and lower limits can be combined as appropriate.

[0183] Furthermore, the recycled carbon black may contain K, Br, Mg, Cl, P, Co, Na, and Al. In this case, it is preferable that the content of K, Br, Mg, Cl, P, Co, Na, and Al in the recycled carbon black is 0% by mass or more and 0.2% by mass or less, respectively. Moreover, in the recycled carbon black (B), it is even more preferable that the content of P, Co, Na, and Al is 0% by mass, that is, that P, Co, Na, and Al are substantially not contained in the recycled carbon black.

[0184] The recycled carbon black content is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, more preferably 5 to 50 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component. When the recycled carbon black content is 5 parts by mass or more per 100 parts by mass of the rubber component, it has a significant effect in improving the ratio of sustainable materials in the side rubber to which the rubber composition is applied, and when it is 50 parts by mass or less, the crack propagation resistance, high-temperature tensile strength after degradation, and low heat generation properties of the rubber composition can be well maintained.

[0185] Furthermore, the tread rubber composition of the present invention may also contain carbon black other than recycled carbon black. By combining carbon black other than recycled carbon black with recycled carbon black, the crack propagation resistance and high-temperature tensile strength after degradation of the rubber composition can be further improved. Among the carbon black other than recycled carbon black, plant-derived carbon black is particularly preferred. Examples of plant-derived carbon black include those derived from castor oil and pine resin oil.

[0186] Other than the recycled carbon black mentioned above, there are no particular restrictions, but it is preferable to use carbon black of high, medium, or low structure grades such as SAF, ISAF, IISAF, N339, HAF, FEF, GPF, and SRF, and especially SAF, ISAF, IISAF, N339, HAF, and FEF grades. Nitrogen adsorption specific surface area (N ２ (Measured in accordance with SA, JIS K6217-2:2001), 20m ２ Preferably 30 m ２ More preferably 50 m ２ More preferably 70 m ２ More preferably 250m / g or more, and also 250m ２ Preferably less than / g, and 200m ２ More preferably less than / g, and 150m ２ A value of less than / g is even more preferable. This carbon black may be used alone or in combination of two or more types.

[0187] The content of carbon black other than the recycled carbon black is not particularly limited, but is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component (A). Also, it is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0188] The proportion of recycled carbon black in the total amount of recycled carbon black and other carbon black (i.e., the total amount of carbon black) is preferably 1 to 100% by mass, more preferably 5 to 100% by mass, even more preferably 10 to 100% by mass, even more preferably 15 to 100% by mass, and even more preferably 20 to 100% by mass. When the proportion of recycled carbon black in the total amount of carbon black is 1% by mass or more, it has a great effect on improving the ratio of sustainable materials in the rubber composition and the side rubber using it. Furthermore, when the proportion of recycled carbon black in the total amount of carbon black is 100% by mass, it is possible to further improve the reinforcing properties, handling stability, high-temperature crack propagation resistance after degradation, and high-temperature tensile strength after degradation of the rubber composition while improving the ratio of sustainable materials in the rubber composition and the tire using it.

[0189] (Reinforcing Filler) Furthermore, it is preferable that the rubber composition for the present invention further contains a reinforcing filler other than the carbon black described above. This is because it can enhance various properties of the vulcanized rubber composition of the present invention, such as fracture strength, abrasion resistance, low heat generation, and wet performance. Here, the reinforcing filler can be any reinforcing filler commonly used in the rubber field, such as silica, talc, clay, aluminum hydroxide, and titanium oxide.

[0190] The type of silica is not particularly limited. Examples include wet silica, colloidal silica, calcium silicate, and aluminum silicate. Among the above, wet silica is preferred, and precipitated silica is more preferred. These silicas may be used individually or in combination of two or more types.

[0191] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferred. These silicate plants include, for example, mosses, ferns, horsetails, cucurbitaceae, nettleaceae, and grasses. Among these plants, grasses are preferred. Among grasses, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred from the viewpoint of availability. Further examples of silica include silicon wafer scraps used as raw materials for semiconductors, silica recycled from glass bottles, etc., and used in manufacturing.

[0192] The silica is not particularly limited, but for example, if the CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m ２ / g or more, 250m ２ Silica of 0.35 nm or less can be used. The CTAB specific surface area refers to the value measured in accordance with ASTM D3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. ２ The specific surface area (m²) is calculated from the amount of adsorption of CTAB. ２ The CTAB specific surface area is defined as ( / g). The BET specific surface area of ​​the silica is 100 m². ２ / g or more, 250m ２ It can be less than or equal to / g. The BET specific surface area is the specific surface area obtained by the BET method, and in this invention, it can be measured in accordance with ASTM D4820-93.

[0193] The silica content can be adjusted as appropriate depending on, for example, the tire category to be applied, the tire material, the target performance, etc. For example, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. Alternatively, the silica content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the rubber component.

[0194] Furthermore, the proportion of silica in the total content of silica and carbon black is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. It may also be 100% by mass, but is preferably 98% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0195] (Silane Coupling Agent) Furthermore, if the tread rubber composition of the present invention contains silica, it is preferable that the rubber composition contains a silane coupling agent in order to improve the effect of the silica. Examples of the silane coupling agent include 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-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl- Examples include N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. These silane coupling agents may be used individually or in combination of two or more. Bioethanol can also be used as a raw material for the silane coupling agent.

[0196] The content of the silane coupling agent can be adjusted as appropriate depending on, for example, the tire category, tire components, target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of silica.

[0197] (Other Components) In addition to the components described above, the rubber composition of the present invention may further contain various additives used in rubber products, especially tires, such as liquid softeners like oil and liquid polymers, antioxidants, zinc oxide, sulfur, vulcanization accelerators, waxes, stearic acid, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica and other fillers, organic peroxides, cellulose nanofibers, cellulose particles, solid fine particles such as eggshells, rice husks, and walnut powder, and rubber powder obtained by crushing used rubber products.

[0198] <Method for Producing the Rubber Composition> The method for preparing the rubber composition of the present invention is not particularly limited, and known methods can be used. For example, it can be obtained by kneading each component, which includes a predetermined rubber component, carbon black, and a metal-containing cyclic compound, using a kneader such as a Banbury mixer, roll mixer, or internal mixer. Alternatively, components other than the crosslinking accelerator and crosslinking agent may be mixed in a non-production (non-pro) stage, and the crosslinking accelerator and crosslinking agent may be added to the mixture and mixed in a production (pro) stage to prepare the rubber composition. The rubber composition of this embodiment can be crosslinked or vulcanized. The conditions for crosslinking or vulcanizing the rubber composition can be adjusted as appropriate, for example, the temperature can be 120 to 200°C and the heating time can be 1 minute to 900 minutes.

[0199] <Tread Rubber Composition, Tire> The tread rubber composition of the present invention consists of the rubber composition of the present invention described above. The tire of the present invention also contains the rubber composition of the present invention described above. By constructing a tire, particularly a tread, from the rubber composition of the present invention, excellent low rolling resistance, low-temperature characteristics, and handling stability can be achieved, as well as improved workability and sustainable material ratio.

[0200] Herein, the tire of the present invention can be used, for example, as a tire for construction vehicles, a tire for trucks and buses, a tire for aircraft, or a tire for passenger cars. In the tire of the present invention, the rubber composition of the present invention described above must be applied to the tread (base tread, cap tread, under tread), but it can be applied to various other components, for example, cushion rubber, shoulder, sidewall, bead filler, carcass coating rubber, belt coating rubber, insulation, chafer, inner liner, etc., and can also be used as a side reinforcement layer for run-flat tires. Furthermore, the rubber composition of this embodiment can be applied to hoses, rubber tracks, seismic isolation rubber, etc., in addition to tires.

[0201] <Other Products> Furthermore, the rubber composition of the present invention described above can be used, for example, in treads (base tread, cap tread, under tread), cushion rubber, shoulders, sidewalls, clinches, bead fillers, carcass coating rubber, insulation, chafers, inner liners, etc. It can also be used in the side reinforcement layer of run-flat tires, etc. In addition to tires, the rubber composition of the present invention can also be applied to rubber tracks, hoses, etc.

[0202] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the examples described below.

[0203] <Evaluation of Recycled Carbon Black> The physical properties of recycled carbon black 1 and 2 were evaluated using the following method.

[0204] (1) Grind gauge measurement: 3.75 g of zinc oxide, 0.20 g of the test carbon black, and 2.00 mL of epoxidized soybean oil were mixed to obtain a mixture. The obtained mixture was kneaded for 5 to 10 minutes to form a paste, and the sample paste was prepared. In accordance with JIS K5101-1-5, paste was prepared using a Huber Mahler (model: H3) manufactured by Toyo Seiki Co., Ltd. under conditions of a load of 0.4536 kN and a glass plate rotation speed of 100 r / min. In accordance with JIS K5400, each sample paste was placed on a grind gauge and stretched with a scraper. A grind gauge with a range of 0 to 25 μm was used. It was confirmed that three or more continuous lines of 10 mm or more appeared, and the scale at the location where the line caused by the third largest particle among the particles that produced the continuous lines of 10 mm or more appeared was read, and this reading was taken as the particle size of the third largest particle. The average value of the particle size measured four times is shown in Table 1.

[0205] (2) Nitrogen adsorption specific surface area (N ２ SA) In accordance with ASTM D6556, calculate the specific surface area (N) of nitrogen adsorption of the tested carbon black. ２ SA was measured.

[0206] (3) Elemental analysis: The content of zinc (Zn), copper (Cu), and iron (Fe) was confirmed by X-ray fluorescence analysis (XRF).

[0207] (4) Ash content The ash content of the carbon black sample was measured according to ASTM D8474 and D1506.

[0208]

[0209] [Reference Example 1 and Reference Comparative Example 1] Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 2. Other chemicals included antioxidants, oils, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in both the comparative example and the example. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were also the amounts commonly used when preparing rubber compositions.

[0210] <Evaluation> After vulcanization treatment, the following evaluations (1) and (2) were performed on each obtained sample. (1) Sustainable material ratio The total content of materials derived from biological resources (biomass resources) and recycled resources (recycled resources) was measured for the rubber composition of each sample, and the content per 100 parts by mass of rubber component (sustainable material blending portion) and the mass ratio of the rubber composition (sustainable material ratio) were derived. The obtained sustainable material ratios are shown in Table 2. Note that a larger obtained sustainable material blending portion and sustainable material ratio indicates a better sustainability ratio.

[0211] (2) Testing each sample of high-temperature crack-progression tread rubber composition after degradation The rubber composition to be tested was first degraded in a nitrogen atmosphere at 100°C for 24 hours, and strip-shaped test pieces were prepared from the rubber composition with a 0.5 mm hole drilled in the lengthwise direction in the center, and a dc / dc test was performed using the test pieces (using Shimadzu's "Servopulsa" at a frequency of 5 Hz and 80°C, repeated fatigue was applied with a strain of 30-100%, and the tear energy [J / m] at 1950 cycles was measured. ２ The crack propagation rate when the common logarithm of [ ] is 3.9 was calculated, and the high-temperature crack propagation resistance after degradation was measured by taking the reciprocal of the calculated rate. The measured values ​​were indexed, with the measured value of Reference Example 1 set to 100 and the measured value of Reference Comparative Example 1 indexed. The results are shown in Table 2. A larger index value indicates a lower crack propagation rate and superior high-temperature crack propagation resistance after degradation.

[0212] (3) High-temperature tensile strength after degradation For each sample of the rubber composition for treads, the rubber composition to be tested was degraded in advance at 100°C under a nitrogen atmosphere for 48 hours. Tensile tests were performed at 100°C in accordance with JIS K6251:2017 and the tensile strength was measured. The tensile strength of the test piece of Reference Example 1 was set to 100, and the high-temperature tensile strength (fracture resistance) after degradation was expressed as an index using the following formula. The results are shown in Table 2. High-temperature tensile strength index after degradation = (Tensile strength of the test piece / Tensile strength of the test piece of Reference Example 1) × 100 The larger the index of high-temperature tensile strength after degradation, the more difficult the vulcanized rubber is to break, indicating superior post-degradation performance (fracture resistance).

[0213]

[0214] *1 Natural rubber: RSS#3 *2 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *3 New carbon black: Manufactured by Asahi Carbon, N550 *4 Recycled carbon black 1: Same as Table 1 *5 Recycled carbon black 2: Same as Table 1

[0215] Tables 1 and 2 show that even for rubber compositions containing recycled carbon black with the same ash content, the high-temperature crack propagation resistance and high-temperature tensile strength after degradation of the rubber composition vary significantly depending on whether there are three or more lines of 10 mm or longer in length when measured with a grind gauge of the incorporated recycled carbon black, and whether the particle size of the third largest particle among those resulting in lines of 10 mm or longer is 20 μm or less.

[0216] [Reference Examples 2-3, Reference Comparative Example 2] Samples of rubber compositions were prepared by compounding and kneading according to the formulations shown in Table 3 using conventional methods. In Table 3, the amounts of each component are expressed as integers. Other amounts are expressed to one decimal place.

[0217] <Evaluation> (1) For each sample of the low-rolling-resistance rubber composition, tanδ was measured using a viscoelasticity measuring device (manufactured by Ueshima Seisakusho Co., Ltd.) at a temperature of 50°C, a strain of 0.1%, and a frequency of 52 Hz. The tanδ measured in each example was indexed with the tanδ of Comparative Example 1 set to 100. A smaller index value indicates that the vulcanized rubber has lower heat generation and that the tire obtained from the vulcanized rubber has lower rolling resistance (excellent low-rolling-resistance). The evaluation results are shown in Table 3.

[0218] (2) The storage modulus (E') of the handling stability test specimen was measured using a viscoelasticity measuring device (manufactured by Ueshima Seisakusho Co., Ltd.) under the conditions of a temperature of 30°C, a strain of 0.1%, and a frequency of 52 Hz. The evaluation results are expressed as an index, with the E' of Comparative Example 1 set to 100. A larger index value indicates a larger E' and superior dry handling performance. The evaluation results are shown in Table 3.

[0219] (3) The loss modulus of elasticity (E'') of the low-temperature characteristic test specimen was measured using a viscoelasticity measuring device (manufactured by Ueshima Seisakusho Co., Ltd.) under the conditions of a temperature of -20°C, a strain of 0.1%, and a frequency of 52 Hz. The evaluation results are expressed as an index, with E'' of Comparative Example 1 set to 100. A smaller index value indicates a smaller E'' and superior low-temperature characteristics. The evaluation results are shown in Table 3.

[0220] (4) Sustainable Material Ratio For each sample of rubber composition, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources was calculated to determine the sustainable material ratio. The evaluation indicates that a higher numerical value indicates a higher and better use of sustainable materials. The evaluation results are shown in Table 3.

[0221]

[0222] *11 TSR#20, SP value = 8.20 (cal / cm³) ３ ) １／２ *12 Hydrocarbyloxysilane compound-modified styrene-butadiene rubber synthesized by the method described below, Tg = -65°C, SP value = 8.65 (cal / cm²) ３ ) １／２ *13 Styrene-butadiene rubber obtained with butyllithium as an initiator, with a Tg of -38°C and the terminals modified with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine, Tg = -38°C, SP value = 8.95 (cal / cm²) ３ ) １／２ *14 Asahi Carbon Co., Ltd., product name "#80" *15 Tosoh Silica Co., Ltd., product name "Nip Seal AQ" *16 Showa Denko K.K., product name "Hydgley Light H-43M", average particle size = 1.0 μm *17 Evonik, product name "Si75" *18 Nippon Zeon Co., Ltd., product name "Quinton (registered trademark) G100B" *19 Kraton, Inc., product name "SYLVATRAXX8125", SP value = (estimated) 8.76 (cal / cm) ３ ) １／２Weight-average molecular weight (Mw) = 1218 g / mol *20 Clayton Corporation, product name "SYLVATRAXX 2097", SP value = (estimated) 9.97 (cal / cm³) ３ ) １／２ Weight-average molecular weight (Mw) = 1157 g / mol *21 Sigma-Aldrich, product number "307564" *22 Total amount of antioxidant, vulcanization accelerator, and sulfur; the same amount was used in both the reference comparative example and the reference example.

[0223] (Synthesis method for hydrocarbyloxysilane compound-modified styrene-butadiene rubber (*12)) In a dried, nitrogen-purged 800 mL pressure-resistant glass container, cyclohexane solutions of 1,3-butadiene and styrene were added to a total volume of 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-ditetrahydrofurylpropane was added, followed by 0.8 mmol of n-butyllithium, and polymerization was carried out at 50°C for 1.5 hours. To the polymerization reaction system where the polymerization conversion rate was nearly 100%, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifying agent, and the modification reaction was carried out at 50°C for 30 minutes. Subsequently, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the modified SBR was obtained by drying according to a conventional method.

[0224] Table 3 shows that the rubber compositions of Reference Examples 2 and 3 show improved sustainable material ratios compared to the rubber composition of Reference Comparative Example 2. The rubber composition of Reference Example 2 shows improved low rolling resistance and low-temperature characteristics compared to the rubber composition of Reference Comparative Example 1, and the rubber composition of Reference Example 3 shows improved handling stability compared to the rubber composition of Reference Comparative Example 2. Therefore, a formulation containing at least one resin selected from the group consisting of terpene resins and terpene-aromatic compound resins used in the rubber composition of Reference Example 2, and a rosin-based resin used in the rubber composition of Reference Example 3, can achieve a balance between low rolling resistance, low-temperature characteristics, handling stability, and sustainable material ratios.

[0225] [Reference Examples 4-5, Reference Comparative Example 3, Standard Example] In addition, rubber compositions were prepared using a conventional Banbury mixer and the compounding methods shown in Table 4. Each of the obtained rubber compositions was evaluated using the evaluation methods described below.

[0226] (1) The Zn content was measured by Zn-containing X-ray fluorescence analysis.

[0227] (2) Ash Content The ash content of carbon black was measured by thermogravimetric analysis (TGA, RIGAKU Corporation). The sample was heated from room temperature to 550°C under a nitrogen atmosphere, and then heated to maintain 550°C under an air atmosphere, and the loss on heating (mass%) was measured. The loss on heating (mass%) when the sample was heated from room temperature to 550°C under a nitrogen atmosphere was defined as "Loss on Heating 1," and the loss on heating (mass%) when heated to maintain 550°C under an air atmosphere was defined as "Loss on Heating 2." The ash content was calculated using the following formula: Ash content (mass%) = 100 - Loss on Heating 1 - Loss on Heating 2

[0228] (3) Tensile Strength Tensile tests were conducted at room temperature in accordance with JIS K6301-1995, and the tensile strength of each rubber composition was measured. The evaluation results were expressed as an index using the following formula, with the standard example as the control (index value 100): Tensile strength index = (Tensile strength of test specimens other than the standard example / Tensile strength of test specimen of the standard example) × 100 A higher index indicates that the rubber composition is less prone to fracture and has superior tensile strength.

[0229] (4) Viscoelasticity A viscoelasticity test was conducted using "ARES-G2" manufactured by TA Instruments, Inc., under the conditions of a frequency of 15 Hz, shear strain of 10%, and temperature of 50°C, and the storage modulus (G') of the rubber composition was measured. The evaluation results were indexed with the standard example as the control (index value 100). A higher index indicates a higher G', which in turn indicates superior rubber properties when applied to products such as tires.

[0230]

[0231] *23 SBR: Styrene-butadiene rubber, product name "#1500" *24 CB3: Carbon Black 3, recycled carbon black equivalent to N330 *25 CB4: Carbon Black 4, recycled carbon black equivalent to N330 *26 CB5: Carbon Black 5, recycled carbon black equivalent to N330 *27 CB6: Carbon Black 6, new carbon black equivalent to N330

[0232] Table 4 shows that when carbon black with a Zn content and ash content within the range of the present invention is applied, the deterioration of the physical properties of the rubber composition is suppressed.

[0233] [Reference Example 6, Reference Comparative Example 4] Two types of rubber compositions having the compound compositions shown in Table 5 were prepared. The obtained rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The obtained vulcanized rubber test pieces were punched out into JIS-3 dumbbells, and the obtained vulcanized rubber test pieces were subjected to a tensile test at room temperature according to JIS K6251:2004, and the breaking strength (TB) before thermal degradation (initial) and after thermal degradation (100°C × 24 hours) was measured. The results are shown in Table 2. Note that a higher breaking strength value indicates better fracture resistance, i.e., better crack resistance.

[0234]

[0235] *27 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *28 Carbon black: Manufactured by Asahi Carbon, product name "N550", nitrogen adsorption specific surface area (N ２ SA) = 40m ２ / g, OAN = 121 mL / 100 g *29 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *30 Anti-aging agent: Total amount of Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 6C" and Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 224", the same ratio in each rubber composition *31 Oil: ENEOS, product name "A / Omix" *32 Fatty acid: Miyoshi Oil & Fat Co., Ltd., product name "MXST" *33 Other chemicals: Total amount of sulfur, vulcanization accelerator, resin, and wax, the same ratio in each rubber composition

[0236] Table 5 shows that replacing carbon black (virgin carbon black) with commercially available recycled carbon black among the various materials contained in the rubber composition reduces the tensile strength before and after thermal degradation.

[0237] Based on the evaluations in Tables 1, 2, and 3 to 5, the rubber composition and tires obtained by the present invention are expected to improve crack propagation resistance after high-temperature degradation and high-temperature tensile strength after degradation while increasing the proportion of sustainable materials, and are expected to achieve a balance between low rolling resistance, low-temperature characteristics, handling stability, and the proportion of sustainable materials.

[0238] According to the present invention, it is possible to provide a rubber composition that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainable material ratio. Furthermore, according to the present invention, it is also possible to provide a tread rubber composition and tire that is excellent in low rolling resistance, low-temperature characteristics and handling stability, and also improves high-temperature crack propagation resistance after degradation, high-temperature tensile strength after degradation, and sustainable material ratio.

[0239] 1: Grind gauge 2: Line less than 10 mm in length 3: Line 10 mm or longer 31: Line caused by the largest particle 32: Line caused by the second largest particle 33: Line caused by the third largest particle 4: Scale mark at the location where the line caused by the third largest particle appeared

Claims

1. A rubber composition comprising a rubber component, a resin, and recycled carbon black, wherein the resin comprises at least one selected from the group consisting of terpene resins and terpene-aromatic compound resins, and a rosin resin, in a total of 0 to 50 parts by mass per 100 parts by mass of the rubber component, and the recycled carbon black is characterized in that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce the lines with a length of 10 mm or more is 20 μm or less.

2. The rubber composition according to claim 1, characterized in that, in the measurement using the grind gauge, the paste of recycled carbon black is prepared as the measurement sample in accordance with JIS K5101-1-5.

3. The rubber composition according to claim 1, characterized in that, in the measurement using the grind gauge, the applied load is set to 0.4 to 0.5 kN and the rotation speed of the glass plate is set to 90 to 110 r / min in accordance with JIS K5101-1-5, and the paste of the recycled carbon black is adjusted.

4. The rubber composition according to claim 1 or 2, characterized in that the rubber component contains isoprene rubber and styrene-butadiene rubber.

5. The rubber composition according to claim 4, characterized in that the styrene-butadiene rubber has a glass transition temperature of less than -40°C.

6. The rubber composition according to claim 4, characterized in that the isoprene-based rubber content is 1 to 80 parts by mass per 100 parts by mass of the rubber component.

7. The rubber composition according to claim 4, characterized in that the isoprene-based rubber content is 1 to 40 parts by mass per 100 parts by mass of the rubber component.

8. The rubber composition according to claim 4, characterized in that the styrene-butadiene rubber is modified with a modifying agent having a functional group containing a nitrogen atom and an alkoxy group.

9. A rubber composition for treads, characterized by comprising the rubber composition described in claim 1 or 2.

10. A tire characterized by comprising the rubber composition described in claim 1 or 2.

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