Rubber composition for tire treads, tire treads, and tires

Abstract

To provide a rubber composition for tire tread having an improved balanced performance of abrasion resistance and chipping resistance, a tire tread composed of the rubber composition, and a tire comprising the tire tread.SOLUTION: The rubber composition for tire tread comprises a diene-based rubber component comprising a styrene-butadiene rubber and an isoprene-based rubber, a filler comprising carbon black, an aromatic ring-containing resin, and a polyhydric alcohol.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for tire treads, a tire tread made of the rubber composition, and a tire equipped with the tire tread. [Background technology]

[0002] Chipping refers to the phenomenon where a portion of the rubber forming the surface layer of the tire tread peels off in a scale-like pattern. When a vehicle equipped with tires drives, the surface of the tread comes into contact with the road surface. This contact between the tread and the road surface causes damage (initial cracks) to a portion of the rubber on the tread surface. During cornering and sudden braking, shear deformation from the road surface concentrates stress on these damages. Cracks then propagate from the tip of these damages, resulting in chipping.

[0003] Patent Document 1 describes a tread rubber composition comprising a rubber component, 20 to 80 parts by mass of carbon black, 10 to 80 parts by mass of silica, 0.2 to 5 parts by mass of a silane coupling agent, and 0.1 to 5 parts by mass of a predetermined alkoxy group-containing compound per 100 parts by mass of the rubber component, which can be used to produce tires with excellent processability before vulcanization, low rolling resistance, and high chipping resistance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-96919 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a rubber composition for tire treads that improves the balance between wear resistance and chipping resistance, a tire tread made of the rubber composition, and a tire equipped with the tire tread. [Means for solving the problem]

[0006] The inventors of the present invention diligently studied to solve the above problems and found that the above problems can be solved by compounding a rubber component containing styrene-butadiene rubber and isoprene-based rubber with a filler containing carbon black, an aromatic ring-containing resin, and a polyhydric alcohol to form a rubber composition. Further studies led to the completion of the present invention.

[0007] In other words, the present invention is [1] A diene rubber component containing styrene-butadiene rubber and isoprene rubber, A filler containing carbon black, Aromatic ring-containing resin, A rubber composition for tire treads containing a polyhydric alcohol, [2] The tire tread rubber composition according to [1] above, wherein the content of styrene-butadiene rubber in the diene-based rubber component is 10 to 50% by mass, preferably 15 to 50% by mass, more preferably 20 to 50% by mass, more preferably 25 to 45% by mass, more preferably 30 to 45% by mass, more preferably 30 to 40% by mass, more preferably 30 to 35% by mass, [3] The styrene content of the styrene-butadiene rubber is 15% or more, preferably 15-50%, more preferably 15-40%, more preferably 15-30%, more preferably 15-25%, or preferably 18% or more, preferably 18-50%, more preferably 18-40%, more preferably 18-30%, more preferably 18-25%, or preferably 20% or more, preferably 20-50%, more preferably 20-40%, more preferably 20-30%, more preferably 20-25%, or preferably 22% or more, preferably 22-50%, more preferably 22-40%, more preferably 22-30%, more preferably 22-25%, the tire tread rubber composition according to [1] or [2] above. [4] The rubber composition for tire treads according to any one of [1] to [3] above, wherein the polyhydric alcohol has 6 or more carbon atoms, preferably 6 to 10, more preferably 6 to 9, and more preferably 6 to 8. [5] The rubber composition for tire treads according to any one of [1] to [4] above, wherein the aromatic ring-containing resin is a homopolymer or copolymer of monomers containing an aromatic ring-containing monomer, and the aromatic ring-containing monomer has at least one hydroxyl group. [6] A rubber composition for tire treads according to any one of [1] to [5] above, further comprising at least one selected from recycled rubber and powdered rubber. [7] The diene rubber component has an average glass transition temperature (Tg) of -50°C or lower, preferably -85 to -50°C, more preferably -80 to -55°C, more preferably -80 to -60°C, more preferably -75 to -60°C, more preferably -75 to -65°C, the tire tread rubber composition according to any one of [1] to [6] above. [8] The rubber composition for tire treads according to any one of [1] to [7] above, wherein the polyhydric alcohol comprises a linear polyhydric alcohol. [9] A rubber composition for tire treads according to any of [1] to [8] above, wherein the content of the isoprene-based rubber in the diene-based rubber component is 30% by mass or more, preferably 30 to 90% by mass, more preferably 30 to 80% by mass, more preferably 30 to 60% by mass, more preferably 30 to 50% by mass, or preferably 35% by mass or more, more preferably 35 to 90% by mass, more preferably 40 to 90% by mass, more preferably 40 to 80% by mass, more preferably 40 to 60% by mass, more preferably 45 to 60% by mass, more preferably 45 to 50% by mass,

[10] A rubber composition for tire treads according to any of [1] to [9] above, wherein the polyhydric alcohol satisfies the following formula (A), (A) α / β≦0.5 (preferably 0.2≦α / β≦0.5, or preferably α / β≦0.4, more preferably 0.2≦α / β≦0.4, or preferably α / β≦0.3, more preferably 0.2≦α / β≦0.3) α: Number of hydroxyl groups in one molecule of polyhydric alcohol β: Number of carbon atoms of the polyhydric alcohol

[11] The melting point of the polyhydric alcohol is less than 50°C, preferably -20°C or higher and less than 50°C, more preferably -20 to 49°C, more preferably -15 to 47°C, more preferably -15 to 45°C, and the rubber composition for tire tread according to any one of [1] to

[10] above,

[12] The content of the carbon black with respect to 100 parts by mass of the diene rubber component is 40 parts by mass or more, preferably 40 to 150 parts by mass, more preferably 41 to 100 parts by mass, more preferably 43 to 100 parts by mass, more preferably 45 to 100 parts by mass, more preferably 45 to 60 parts by mass, and the rubber composition for tire tread according to any one of [1] to

[11] above,

[13] The content of the carbon black in the filler is 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 99% by mass or more, more preferably 100% by mass, and the rubber composition for tire tread according to any one of [1] to

[12] above,

[14] A tire tread made of the rubber composition for tire tread according to any one of [1] to

[13] above,

[15] A tire provided with the tire tread according to

[14] above,

[16] The tire according to

[15] above, which is a heavy-duty tire,

[17] The tire according to

[16] above, which is a heavy-duty tire for trucks and buses, Relates to.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a rubber composition for tire tread with improved balance between abrasion resistance and chipping resistance, a tire tread made of the rubber composition, and a tire provided with the tire tread.

Brief Description of the Drawings

[0009] [[ID=E30]] [Figure 1] An example of a cross-sectional view of a tire. [Modes for carrying out the invention]

[0010] One aspect of the present disclosure is a rubber composition for tire treads comprising a diene rubber component containing styrene-butadiene rubber and isoprene-based rubber, a filler containing carbon black, an aromatic ring-containing resin, and a polyhydric alcohol.

[0011] While we do not intend to be bound by theory, the following is a possible mechanism by which the above effects are achieved. Specifically, aromatic ring-containing resin and styrene-butadiene rubber (SBR) are compatible because their SP values ​​are similar, and the hydroxyl groups (OH) on the carbon black surface can interact with the benzene rings of the aromatic ring-containing resin, thus creating a pseudo-link between SBR, aromatic ring-containing resin, and carbon black. On the other hand, polyhydric alcohols are compatible with isoprene-based rubber, and the hydroxyl groups on the carbon black surface can interact with the hydroxyl groups of polyhydric alcohols, thus creating a pseudo-link between isoprene-based rubber, polyhydric alcohol, and carbon black. It is thought that these "pseudo-links between SBR, aromatic ring-containing resin, and carbon black" and "pseudo-links between isoprene-based rubber, polyhydric alcohol, and carbon black" work together throughout the entire rubber composition, resulting in an improved balance between abrasion resistance and chipping resistance.

[0012] The content of styrene-butadiene rubber in the diene-based rubber component is preferably 10 to 50% by mass. When the content is 10% by mass or more, the chipping resistance improvement effect of SBR is easily exhibited, and the "pseudo-connection between SBR-aromatic ring-containing resin-carbon black" increases, so it is considered that the effect of improving the balance between abrasion resistance and chipping resistance is suitably exhibited. Furthermore, when the content is 50% by mass or less, it is considered that the effect of improving the balance between abrasion resistance and chipping resistance is suitably exhibited. In addition, it is possible to suppress heat generation and ensure low fuel consumption. The content is more preferably 15% by mass or more, more preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. Furthermore, the content is more preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. When using oil-expandable type SBR as the SBR, the content of SBR itself as solid content contained in the oil-expandable type SBR is considered to be the content of SBR in the diene-based rubber component.

[0013] The styrene content of the styrene-butadiene rubber is preferably 15% or more. A styrene content of 15% or more ensures sufficient styrene content, making it easier to obtain the effects of SBR, and increasing the number of "pseudo-connections between SBR, aromatic ring-containing resin, and carbon black," which is considered to favorably improve the balance between abrasion resistance and chipping resistance. The styrene content is more preferably 18% or more, more preferably 20% or more, and even more preferably 22% or more. Furthermore, from the viewpoint of abrasion resistance and low fuel consumption, the styrene content is preferably 50% or less, more preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less. Note that the styrene content in this specification is as follows: 1 This value is calculated by 1H-NMR measurement.

[0014] The carbon number of the polyhydric alcohol is preferably 6 or more. When the carbon number is 6 or more, the compatibility between the polyhydric alcohol and the isoprene-based rubber is better, which makes it easier for the "pseudo-bond between isoprene-based rubber, polyhydric alcohol, and carbon black" to be effectively expressed, and it is thought that the effects of this disclosure are well exhibited. The carbon number may also be 7 or more. Furthermore, from the viewpoint of easily exhibiting the effects of this disclosure, the upper limit of the carbon number is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less.

[0015] The aromatic ring-containing resin is a homopolymer or copolymer of monomers containing an aromatic ring-containing monomer, and it is preferable that the aromatic ring-containing monomer has at least one hydroxyl group. Having at least one hydroxyl group in the aromatic ring-containing monomer increases the proportion of hydroxyl groups in one molecule of the aromatic ring-containing resin. As a result, the hydroxyl groups on the carbon black surface and the hydroxyl groups in the molecules of the aromatic ring-containing resin can interact, which strengthens the interaction between the aromatic ring-containing resin and carbon black, and is considered to effectively improve the balance between abrasion resistance and chipping resistance. Furthermore, since the hydroxyl groups in the molecules of the aromatic ring-containing resin interact with the hydroxyl groups of the polyhydric alcohol, it is considered that the "pseudo-link between SBR-aromatic ring-containing resin-carbon black" and the "pseudo-link between isoprene-based rubber-polyhydric alcohol-carbon black" cooperate throughout the rubber composition to effectively exert their effects. Furthermore, while it is preferable that the aromatic ring-containing monomer has one hydroxyl group, as this is sufficient to achieve the effects of this disclosure, it may also have two, three, or four hydroxyl groups.

[0016] The rubber composition for tire treads preferably further comprises at least one selected from recycled rubber and powdered rubber. Normally, rubber compositions compounded with recycled rubber or powdered rubber have the problem of being prone to deterioration in terms of elongation at break, but the rubber composition of this disclosure is a rubber composition comprising a diene rubber component containing styrene-butadiene rubber and isoprene-based rubber, a filler containing carbon black, an aromatic ring-containing resin, and a polyhydric alcohol. Therefore, even when recycled rubber or powdered rubber is compounded, it is believed that the balance between abrasion resistance and chipping resistance is improved by the above mechanism. The at least one selected from recycled rubber and powdered rubber may be recycled rubber only, powdered rubber only, or a combination of recycled rubber and powdered rubber, but recycled rubber only is preferred.

[0017] The diene-based rubber component preferably has an average glass transition temperature (Tg) of -50°C or lower. A Tg of -50°C or lower allows for a lower overall Tg of the rubber composition, improving abrasion resistance, thus effectively enhancing the balance between abrasion resistance and chipping resistance. The average Tg is more preferably -55°C or lower, more preferably -60°C or lower, and even more preferably -65°C or lower. Furthermore, the average Tg is preferably -85°C or higher, more preferably -80°C or higher, and even more preferably -75°C or higher. Here, the average glass transition temperature (Tg) of the diene-based rubber component in this specification can be determined by Σ(Tg of each diene-based rubber component × mass fraction of each diene-based rubber component in the total diene-based rubber component). Note that the Tg in this specification is measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., under a heating rate of 10°C / min.

[0018] The polyhydric alcohol preferably includes a linear polyhydric alcohol. Including a linear polyhydric alcohol improves the compatibility between the polyhydric alcohol and the isoprene-based rubber, which makes it easier for the "pseudo-linkage between isoprene-based rubber, polyhydric alcohol, and carbon black" to be effectively expressed, and thus the effects of this disclosure are likely to be well exhibited. In addition to linear polyhydric alcohols, the polyhydric alcohol may also include branched polyhydric alcohols and cyclic polyhydric alcohols, but from the viewpoint of easily exhibiting the effects of this disclosure, it is more preferable to use only linear polyhydric alcohols.

[0019] The content of the isoprene-based rubber in the diene-based rubber component is preferably 30% by mass or more. A content of 30% by mass or more is considered to be advantageous because it increases the "pseudo-bonding between isoprene-based rubber, polyhydric alcohol, and carbon black," thereby improving the balance between abrasion resistance and chipping resistance. The content is more preferably 35% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more. Furthermore, the content is preferably 90% by mass or less, more preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0020] The polyhydric alcohol preferably satisfies the following formula (A). When the following formula (A) is satisfied, both the "pseudo-linkage between SBR, aromatic ring-containing resin, and carbon black" and the "pseudo-linkage between isoprene-based rubber, polyhydric alcohol, and carbon black" are more easily expressed effectively, and it is thought that the effects of this disclosure are well exhibited. The α / β value is preferably 0.4 or less, and more preferably 0.3 or less. Furthermore, the lower limit of the α / β value is preferably 0.2 or more. (A) α / β ≤ 0.5 α: Number of hydroxyl groups in one molecule of polyhydric alcohol β: Number of carbon atoms in polyhydric alcohols

[0021] The melting point of the polyhydric alcohol is preferably less than 50°C. A melting point below 50°C allows the polyhydric alcohol to disperse more uniformly within the diene-based rubber component, thus effectively facilitating the manifestation of the "pseudo-bond between isoprene-based rubber, polyhydric alcohol, and carbon black," and thus enabling the effects of this disclosure to be fully realized. The melting point is more preferably 49°C or lower, more preferably 47°C or lower, and even more preferably 45°C or lower. Furthermore, the lower limit of the melting point is not particularly limited, but for example, it may be -20°C or higher, or -15°C or higher.

[0022] The content of carbon black relative to 100 parts by mass of the diene-based rubber component is preferably 40 parts by mass or more. When the content is 40 parts by mass or more, the "pseudo-bonds between SBR-aromatic ring-containing resin-carbon black" and the "pseudo-bonds between isoprene-based rubber-polyhydric alcohol-carbon black" increase, and it is thought that the effects of this disclosure are well exhibited. The content is more preferably 41 parts by mass or more, more preferably 43 parts by mass or more, and even more preferably 45 parts by mass or more. Furthermore, from the viewpoint of obtaining good dispersibility in rubber and easily exhibiting the effects of this disclosure, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 60 parts by mass or less.

[0023] The carbon black content in the filler is preferably 80% by mass or more. When the content is 80% by mass or more, both the "pseudo-bond between SBR-aromatic ring-containing resin-carbon black" and the "pseudo-bond between isoprene-based rubber-polyhydric alcohol-carbon black" are more easily expressed, and it is thought that the effects of this disclosure are well exhibited.

[0024] Another aspect of this disclosure is a tire tread comprising the above-mentioned rubber composition for tire treads.

[0025] Another aspect of this disclosure is a tire having the tire tread described above.

[0026] The aforementioned tire is preferably a heavy-duty tire. It is believed that the effects of this disclosure will be better realized if the tire is a heavy-duty tire.

[0027] The aforementioned heavy-duty tire is preferably for use in trucks and buses. It is believed that the effects of this disclosure are particularly well demonstrated when the tire is a heavy-duty tire for trucks and buses.

[0028] In this specification, when "~" is used to indicate a numerical range, it includes the values ​​at both ends of the range unless otherwise specified.

[0029] <Diene-based rubber components> The diene-based rubber component of this disclosure includes styrene-butadiene rubber and isoprene-based rubber.

[0030] Other diene rubber components besides styrene-butadiene rubber and isoprene rubber can be any of those conventionally used in the rubber industry, such as butadiene rubber (BR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). These other diene rubber components can be used individually or in combination of two or more. Among these, BR is preferred because it allows for better performance of the effects of this disclosure. Specifically, the diene rubber component may more preferably include SBR, isoprene rubber, and BR, or it may consist only of SBR, isoprene rubber, and BR. Alternatively, the diene rubber component may consist only of SBR and isoprene rubber. Furthermore, rubber components can be divided into diene rubber components and non-diene rubber components, but the rubber component of this disclosure is preferably composed of diene rubber components.

[0031] (Styrene-butadiene rubber) Styrene-butadiene rubber (SBR) is not particularly limited and can include, for example, unmodified emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR), as well as modified SBRs such as modified emulsion-polymerized styrene-butadiene rubber (modified E-SBR) and modified solution-polymerized styrene-butadiene rubber (modified S-SBR). Modified SBRs include modified SBRs in which the terminals and / or main chain are modified, and modified SBRs coupled with tin, silicon compounds, etc. (such as those having condensates or branched structures). Furthermore, SBRs can be of the oil-expandable type, in which flexibility is adjusted by adding an expanding oil, or of the non-oil-expandable type, in which no expanding oil is added, and both types can be used. SBRs can be used from manufacturers and distributors such as JSR Corporation, Asahi Kasei Chemicals Corporation, Nippon Zeon Corporation, and ZS Elastomer Co., Ltd. In particular, from the viewpoint of improving the balance between wear resistance and chipping resistance, it is preferable to use at least one of E-SBR, S-SBR, and modified S-SBR, more preferably at least one of E-SBR and modified S-SBR, and it may also be E-SBR alone or modified S-SBR alone. Among the modified S-SBRs, tin-coupled S-SBR can be suitably used because it can improve rubber properties by enhancing the interaction with carbon black. SBR can be used one type or in combination of two or more types.

[0032] The vinyl content (amount of 1,2-bonded butadiene units) of SBR is not particularly limited, but is preferably 10.0 to 80.0%. From the viewpoint of rubber strength and grip performance, the vinyl content is more preferably 13.0% or more, more preferably 20.0% or more, and even more preferably 40.0% or more. On the other hand, from the viewpoint of abrasion resistance and low fuel consumption, the vinyl content is more preferably 70.0% or less, more preferably 60.0% or less, more preferably 40.0% or less, and even more preferably 20.0% or less. Note that the vinyl content in this specification is a value measured by infrared absorption spectroscopy.

[0033] The glass transition temperature (Tg) of SBR is preferably -90°C or higher, more preferably -80°C or higher, and even more preferably -70°C or higher. Furthermore, from the viewpoint of wear resistance, the Tg is preferably -10°C or lower, more preferably -30°C or lower, and even more preferably -45°C or lower. When the Tg of SBR is within the above range, the effects of this disclosure tend to be more favorably obtained.

[0034] (Isoprene rubber) Examples of isoprene-based rubbers include natural rubber (NR), modified NR, altered NR, isoprene rubber (IR), and altered IR. Examples of NR include SIR20, RSS#3, and TSR20, which are common in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber, while examples of altered NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. IR is not particularly limited and isoprene-based rubbers are common in the tire industry. Examples of altered IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. In particular, for better performance of the effects of this disclosure, it is preferable that the isoprene-based rubber includes at least one selected from NR, modified NR, and altered NR, more preferably includes NR, and even more preferably uses only NR. Isoprene-based rubbers can be used individually or in combination of two or more types.

[0035] The glass transition temperature (Tg) of isoprene-based rubber is not particularly limited as long as the effects of this disclosure are not impaired, but is typically around -80 to -60°C or -75 to -65°C.

[0036] (Butadiene rubber) The butadiene rubber (BR) is not particularly limited, and any commonly used in this field can be suitably used. For example, various types of BR can be used, such as low-cis polybutadiene rubber (low-cis BR), high-cis polybutadiene rubber (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), and modified butadiene rubber (modified BR). Among these, high-cis BR is preferred. BR can be those manufactured and sold by companies such as Ube Industries, Ltd., Nippon Zeon Corporation, JSR Corporation, and Lanxess. BR can be used individually or in combination of two or more types.

[0037] High-cis BR refers to butadiene rubber with a cis content (cis-1,4 bond content) of 90% or more. Among these, those with a cis-1,4 bond content of 95% or more are preferred, those with 96% or more are more preferred, and those with 97% or more are even more preferred. The inclusion of high-cis BR can improve low heat generation, tensile strength, elongation at break, and abrasion resistance, and tends to better exhibit the effects of this disclosure. Note that the cis content in this specification is a value measured by infrared absorption spectroscopy.

[0038] As for rare earth-based BR, it is preferably synthesized using a rare earth element catalyst, and has a vinyl content (amount of 1,2-bonded butadiene units) of preferably 1.8% or less, more preferably 1.0% or less, and even more preferably 0.8% or less, and a cis content (cis-1,4 bond content) of preferably 90% or more, more preferably 95% or more, more preferably 96% or more, and even more preferably 97% or more. By having the vinyl content and cis content within the above ranges, the resulting rubber composition exhibits excellent elongation at break and abrasion resistance.

[0039] Known rare earth element catalysts can be used for the synthesis of rare earth BRs, including, for example, lanthanum series rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and catalysts containing Lewis bases as needed.

[0040] SPB-containing BR includes cases where 1,2-syndiotactic polybutadiene crystals are not simply dispersed in the BR, but are chemically bonded to the BR and then dispersed. Because the crystals are chemically bonded to the rubber component and dispersed, the complex modulus tends to improve.

[0041] Modified BRs include modified BRs in which the terminals and / or main chain are modified, modified BRs coupled with tin, silicon compounds, etc. (such as condensates and those with branched structures), modified BRs in which the terminals and / or main chain are modified by functional groups that interact with silica, and in particular, modified BRs having at least one selected from the group consisting of silyl groups, amino groups, amide groups, hydroxyl groups, and epoxy groups. By using modified BRs, the interaction with the filler is strengthened, resulting in improved fuel efficiency.

[0042] The glass transition temperature (Tg) of BR is preferably -150°C or higher, more preferably -130°C or higher, and even more preferably -120°C or higher. Furthermore, from the viewpoint of wear resistance, the Tg is preferably -70°C or lower, more preferably -80°C or lower, even more preferably -90°C or lower, and even more preferably -100°C or lower. When the Tg of BR is within the above range, the effects of this disclosure tend to be well exhibited.

[0043] When BR is included, its content in the diene-based rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of abrasion resistance. Furthermore, the content is preferably 60% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less. When the BR content is within the above range, the effects of this disclosure tend to be exhibited more favorably.

[0044] <Other rubber components> The rubber composition may further contain a non-diene rubber component (other rubber components). Such other rubber components are not particularly limited, and examples thereof include butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. The other rubber components can be used alone or in combination of two or more.

[0045] <Filler> The filler of the present disclosure contains carbon black. Among them, the filler of the present disclosure is preferably composed of carbon black because the effects of the present disclosure can be exhibited well.

[0046] (Carbon black) Carbon black is not particularly limited, and common ones in the rubber industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. Carbon black can be used, for example, those manufactured and sold by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. Carbon black can be used alone or in combination of two or more.

[0047] The nitrogen adsorption specific surface area (N2SA) of carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcing property and the effects of the present disclosure being easily exhibited well, it is preferably 50 m 2 / g or more, more preferably 70 m 2 / g or more, still more preferably 90 m 2 / g or more, and even more preferably 111 m 2 / g or more. Also, from the viewpoint of excellent dispersibility and low heat generation, the N2SA is preferably 500 m 2 / g or less, more preferably 450 m 2 / g or less, still more preferably 300 m 2 / g or less, and even more preferably 250 m 2Less than / g is more preferable, 200m 2 / g or less is more preferable, 180m 2 More preferably less than / g, 160m 2 A value of less than or equal to / g is even more preferable. When the N2SA of carbon black is within the above range, the effects of this disclosure tend to be better realized. The N2SA of carbon black as used herein is a value measured in accordance with JIS K 6217-2:2001.

[0048] The amount of dibutyl phthalate (DBP) absorbed by carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcement and easily exhibiting the effects of this disclosure, it is preferably 50 ml / 100g or more, more preferably 70 ml / 100g or more, more preferably 90 ml / 100g or more, and even more preferably 111 ml / 100g or more. Furthermore, from the viewpoint of low fuel consumption, the DBP absorbed amount is preferably 220 ml / 100g or less, more preferably 180 ml / 100g or less, and even more preferably 130 ml / 100g or less. When the DBP absorbed amount of carbon black is within the above range, the effects of this disclosure tend to be exhibited more favorably. Note that the DBP absorbed amount of carbon black in this specification is a value measured in accordance with JIS K 6217-4:2008.

[0049] The carbon black content in the filler is preferably 80% by mass or more, more preferably 85% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 99% by mass or more, and particularly preferably 100% by mass.

[0050] (Other fillers) In addition to carbon black, other fillers may be used as fillers. Such fillers are not particularly limited, and any filler commonly used in this field, such as silica, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc, or clay, can be used. These fillers can be used individually or in combination of two or more. When using a filler other than carbon black, silica is preferred from the viewpoint of fuel efficiency, wet grip performance, and reinforcing effect.

[0051] The silica used is not particularly limited; for example, silica prepared by the dry method (anhydrous silicic acid) and silica prepared by the wet method (hydrated silicic acid) can be used. Among these, silica prepared by the wet method is preferred because it has many silanol groups on its surface and therefore many reaction sites with silane coupling agents. Silica can be used from manufacturers and distributors such as Evonik Degussa, Solvay, Tosoh Silica Co., Ltd., and Tokuyama Corporation. Silica can be used individually or in combination of two or more types.

[0052] Silica N2SA is, without any particular limitations, intended to ensure low fuel consumption and sufficient reinforcement, 80m 2 Preferably 110m / g or more. 2 More preferably 140m / g or more. 2 More preferably 170m / g or more. 2 A concentration of 500m or more is even more preferable. Furthermore, from the viewpoint of silica dispersibility and processability, the N2SA is 500m 2 Preferably less than / g, 400m 2 / g or less is more preferable, 300m 2 Less than / g is more preferable, 200m 2 A value of less than or equal to / g is even more preferable. The N2SA of silica as used herein is the value measured by the BET method in accordance with ASTM D3037-81.

[0053] The silica content per 100 parts by mass of the diene-based rubber component is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more. Furthermore, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 60 parts by mass or less. When the silica content is within the above range, sufficient reinforcing properties and good dispersion in the rubber are obtained, and the effects of this disclosure tend to be exhibited more favorably.

[0054] <Silane coupling agent> When silica is included, it is preferable to use it in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the rubber industry can be used. Examples of such silane coupling agents include silane coupling agents having a sulfide group such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide (sulfide type); silane coupling agents having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane (mercapto type); and silane coupling agents having a thioester group such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples of silane coupling agents include: silane coupling agents having vinyl groups such as vinyltriethoxysilane and vinyltrimethoxysilane; silane coupling agents having amino groups such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based and mercapto-based silane coupling agents are preferred because they have strong bonding affinity with silica and excellent fuel efficiency. Furthermore, the use of mercapto-based silane coupling agents is also preferred because they can suitably improve fuel efficiency and wear resistance. Examples of such silane coupling agents include those manufactured and sold by companies such as Momentive and Evonik Degussa. These silane coupling agents can be used individually or in combination of two or more types.

[0055] The content of the silane coupling agent relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, even more preferably 4.0 parts by mass or more, and still more preferably 6.0 parts by mass or more, for the reason that a sufficient silica dispersion effect can be obtained. Furthermore, the content is preferably 20.0 parts by mass or less, more preferably 18.0 parts by mass or less, and still more preferably 15.0 parts by mass or less, for the reason that a sufficient coupling effect and silica dispersion effect can be efficiently obtained and reinforcement can be ensured.

[0056] <Aromatic ring-containing resin> In this disclosure, "aromatic ring-containing resin" means a resin that contains an aromatic ring in its structure. Specifically, the aromatic ring-containing resin is a homopolymer or copolymer of monomers containing an aromatic ring-containing monomer, and it is preferable that the aromatic ring-containing resin is an aromatic ring-containing resin in which the aromatic ring-containing monomer has at least one hydroxyl group. The aromatic ring-containing resin is not particularly limited as long as it is a resin used in this art that contains an aromatic ring. Examples of such resins include C9 petroleum resins, C5C9 petroleum resins, alkylphenol resins, coumarone resins, aromatically modified terpene resins, terpene phenol resins, and so on. Among these, it is preferable to include at least one of C9 petroleum resins and terpene phenol resins, and it is even more preferable to include at least one of C9 petroleum resins and terpene phenol resins, for the reason that it has better compatibility with SBR. The aromatic ring-containing resin may consist only of C9 petroleum resins or only of terpene phenol resins. Furthermore, as the resin having at least one hydroxyl group in the aromatic ring-containing monomer, at least one of alkylphenol resins and terpene phenol resins is preferred, with terpene phenol resins being more preferred. The aromatic ring-containing resin can be used individually or in combination of two or more types.

[0057] (C9 petroleum resin) Examples of C9-based petroleum resins include resins obtained by cationic polymerization of monomers such as styrene, vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fractions) with 8 to 10 carbon atoms. C9-based petroleum resins can be those manufactured and sold by companies such as JXTG Energy Corporation. A specific example of a C9-based petroleum resin is styrene-based resin. While there are no particular limitations on styrene-based resins, α-methylstyrene-based resin (AMS) is preferably used. Examples of α-methylstyrene-based resins include homopolymers of α-methylstyrene (poly-α-methylstyrene) and copolymers of α-methylstyrene with other compounds including aromatic compounds and phenolic compounds. Other compounds that can constitute this copolymer include styrene, methylstyrene, methoxystyrene, and divinylbenzene. As for α-methylstyrene-based resins, those manufactured by Arizona Chemical Corporation are preferably used.

[0058] (C5C9 petroleum resin) C5C9 petroleum resin is a resin obtained by copolymerizing a C5 fraction and a C9 fraction, and is also called an aliphatic / aromatic copolymer petroleum resin. Alternatively, hydrogenated petroleum resins may be used. The C5 fraction can be obtained, for example, by the thermal decomposition of naphtha, and components of the C5 fraction include olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene (isoprene), 1,2-pentadiene, 1,3-pentadiene (piperylene), and 3-methyl-1,2-butadiene. The C9 fraction is the same as the C9 fraction of the C9 petroleum resin described above. Examples of C5C9 petroleum resins include copolymers mainly composed of indene, styrene, vinyltoluene, isoprene, and piperine. C5C9 petroleum resins can be used from those manufactured and sold by companies such as LUHUA, Qilong, and Tosoh Corporation.

[0059] (Alkylphenol resin) Examples of alkylphenol resins include alkylphenol aldehyde condensation resins obtained by reacting alkylphenols with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst; alkylphenol alkyne condensation resins obtained by reacting alkylphenols with alkynes such as acetylene; and modified alkylphenol resins obtained by modifying these resins with compounds such as cashew nut oil, tall oil, linseed oil, various animal and vegetable oils, unsaturated fatty acids, rosin, alkylbenzene resins, aniline, and melamine. Examples of alkylphenols that make up alkylphenol resins include cresol, xylenol, tert-butylphenol, octylphenol, and nonylphenol. Alkylphenol resins can be those manufactured and sold by companies such as Taoka Chemical Industries, Ltd.

[0060] (Coumaron resin) Coumaron-based resins are resins whose main component is coumaron. Examples include coumaron resin, coumaron-indene resin, and copolymer resins whose main components are coumaron, indene, and styrene. Coumaron-based resins can be used, for example, those manufactured and sold by companies such as Nippon Paint Chemical Co., Ltd.

[0061] (Aromatic-modified terpene resin) Aromatically modified terpene resins are resins obtained by copolymerizing terpene compounds as monomers with aromatic compounds. Terpene compounds are polymers of isoprene (C5H8) and monoterpenes (C5H8). 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpene (C 20 H 32These are compounds whose basic skeleton is a terpene, classified as such. More specifically, examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allo-cimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, camphene, tricyclene, sabinene, paramentadienes, and karenes. Examples of aromatic compounds include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Aromatic modified terpene resins can be used, for example, those manufactured and sold by companies such as Yasuhara Chemical Co., Ltd.

[0062] (Terpene phenol resin) Terpene phenol resins are resins obtained by copolymerizing a terpene compound as a monomer with a phenolic compound. Terpene phenol resins may or may not be hydrogenated. The terpene compound is the same as the terpene compound used for the aromatically modified terpene resin described above. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol, with phenol being preferred. Terpene phenol resins can be those manufactured and sold by companies such as Yasuhara Chemical Co., Ltd.

[0063] (Mw of aromatic ring-containing resin) The weight-average molecular weight (Mw) of the aromatic ring-containing resin is preferably 300 or higher, more preferably 400 or higher, and even more preferably 500 or higher, as it is less volatile and has good grip performance. Furthermore, the Mw is preferably 10,000 or lower, more preferably 2,500 or lower, even more preferably 1,500 or lower, and even more preferably 1,200 or lower. The weight-average molecular weight (Mw) in this specification can be determined by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0064] (Softening point of aromatic ring-containing resins) The softening point of the aromatic ring-containing resin is preferably 160°C or lower, more preferably 145°C or lower, and even more preferably 130°C or lower. Furthermore, the softening point is preferably 20°C or higher, more preferably 35°C or higher, and even more preferably 50°C or higher. When the softening point of the aromatic ring-containing resin is within the above range, the effects of this disclosure tend to be exhibited more favorably. In this specification, the softening point is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2001 is measured using a ring-spherical softening point measuring device.

[0065] (SP value of aromatic ring-containing resin) The SP value of the aromatic ring-containing resin is preferably 8.00 or higher, more preferably 8.50 or higher, and even more preferably 8.80 or higher. Furthermore, the SP value is preferably 11.00 or lower, more preferably 10.00 or lower, and even more preferably 9.50 or lower. When the SP value of the aromatic ring-containing resin is within the above range, the compatibility with SBR is improved, and the "pseudo-connection between SBR, aromatic ring-containing resin, and carbon black" is more easily and effectively expressed, which tends to allow the effects of this disclosure to be exhibited more favorably. In this specification, the SP value of the aromatic ring-containing resin refers to the solubility parameter calculated by the Hoy method based on the structure of the compound, and the smaller the difference in SP values ​​between the two components, the better the compatibility. The Hoy method is a calculation method described, for example, KL Hoy, "Table of Solubility Parameters", Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. (1985).

[0066] (Content of aromatic ring-containing resins) The content of aromatic ring-containing resin relative to 100 parts by mass of diene rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, and still more preferably 2.0 parts by mass or more, because this allows the "pseudo-bond between SBR, aromatic ring-containing resin, and carbon black" to be effectively expressed. Furthermore, the content is preferably 30.0 parts by mass or less, more preferably 20.0 parts by mass or less, even more preferably 10.0 parts by mass or less, and still more preferably 5.0 parts by mass or less. When the content of aromatic ring-containing resin is within the above range, the effects of this disclosure tend to be exhibited more favorably.

[0067] <Polyhydric alcohols> The polyhydric alcohol is not particularly limited, and for example, linear polyhydric alcohols, branched polyhydric alcohols, and cyclic polyhydric alcohols can be used. Examples of linear polyhydric alcohols include glycols and sugar alcohols. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, isoprene glycol, 1,3-butylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, 1,2-decanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol. Examples of sugar alcohols include tetriols such as erythritol and treitol; pentitols such as arabitol, xylitol, and ribitol; hexitols such as sorbitol, mannitol, and galactitol; heptitols such as boremitol; octitols such as D-erythro-D-galactooctitol; nonitols; and desitols. There are no restrictions on the stereochemistry of these sugar alcohols; they may be D-isomers, L-isomers, or DL-isomers having D-isomers and L-isomers in any ratio. Examples of branched polyhydric alcohols include 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2-ethyl-1,3-hexanediol. Examples of cyclic polyhydric alcohols include glucose, xylose, fructose, maltose, and kebrachitol.

[0068] In particular, the polyhydric alcohol preferably contains at least one of a linear polyhydric alcohol and a cyclic polyhydric alcohol, more preferably contains a linear polyhydric alcohol, and even more preferably contains only a linear polyhydric alcohol.

[0069] The linear polyhydric alcohol preferably contains at least one of glycols and sugar alcohols, more preferably at least one of glycols and sugar alcohols, and may contain only glycols or only sugar alcohols. It is more preferable to contain only glycols for the reason that the effects of this disclosure can be better exhibited. The glycols preferably contain at least one of ethylene glycol and 1,2-hexanediol, and more preferably contain 1,2-hexanediol. The glycols may also consist of only ethylene glycol or only 1,2-hexanediol, and it is more preferable to contain only 1,2-hexanediol for the reason that the effects of this disclosure can be better exhibited. The sugar alcohols preferably include mannitol, galactitol, xylitol and sorbitol, more preferably xylitol and sorbitol, and even more preferably sorbitol.

[0070] Polyhydric alcohols can be those manufactured and sold by companies such as Tokyo Chemical Industries, Ltd., Kanto Chemical Co., Ltd., and Fujifilm Wako Pure Chemical Industries, Ltd. Polyhydric alcohols can be used individually or in combination of two or more types.

[0071] If the number of hydroxyl groups in one molecule of a polyhydric alcohol is two or more, the hydroxyl groups on the carbon black surface and the hydroxyl groups of the polyhydric alcohol can interact, and the effects of this disclosure can be fully realized. The number of hydroxyl groups may be three or more or four or more. Furthermore, from the viewpoint of easily realizing the effects of this disclosure, the upper limit of the number of hydroxyl groups is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less.

[0072] The content of polyhydric alcohol per 100 parts by mass of diene rubber component is preferably 0.3 parts by mass or more, more preferably 0.6 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more, because this allows the "pseudo-bond between isoprene rubber, polyhydric alcohol, and carbon black" to be effectively expressed. Furthermore, the content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less. When the polyhydric alcohol content is within the above range, the effects of this disclosure tend to be exhibited more favorably.

[0073] <At least one selected from recycled rubber and powdered rubber> (Recycled rubber) In this disclosure, "recycled rubber" refers to recycled rubber from used automobile tires, tubes, and other rubber products as defined in JIS K 6313-2012, as well as rubber having equivalent properties. Powdered rubber is excluded. Furthermore, the recycled rubber is subjected to desulfurization treatment.

[0074] The recycled rubber can be any type of recycled rubber, such as recycled tube rubber, recycled tire rubber, or other types, and multiple types can be combined. Among these, recycled tire rubber is preferred.

[0075] Recycled rubber can be obtained by known manufacturing methods, including the most common pan process (oil process), as well as methods using a Banbury mixer and twin-screw reaction extruder, microwave methods, ultrasonic methods, and electron beam irradiation methods, but any method of production is acceptable. Commercially available recycled rubber may also be used. One specific example of manufacturing recycled rubber is to put vulcanized rubber powder into a closed mixer or extruder, heat it to 100-250°C, and treat it for 5-50 minutes while applying mechanical shear force to desulfurize and regenerate it. Commercially available products include those manufactured and sold by companies such as Muraoka Rubber Industries Co., Ltd. and Asahi Recycled Rubber Co., Ltd.

[0076] The rubber component in recycled rubber preferably has a natural rubber content of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. When the natural rubber content is within the above range, excellent elongation at break tends to be obtained. In this specification, the natural rubber content of the rubber component in recycled rubber refers to the value determined by measurement using pyrolysis gas chromatography (PyGC).

[0077] Recycled rubber can be used in one or more combinations.

[0078] When recycled rubber is included, the content of the diene-based rubber component per 100 parts by mass is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of environmental considerations. Furthermore, from the viewpoint of easily exhibiting the effects of this disclosure, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0079] (powdered rubber) In this disclosure, "powdered rubber" refers to vulcanized powdered rubber recycled from waste rubber products. From the standpoint of environmental considerations and cost, it is preferable to use crushed tread rubber from used tires, spew burrs from harvesting, etc. (crushed waste tires) as the raw material for the powdered rubber. Furthermore, the type of waste rubber is not particularly limited, and examples include diene-based rubbers such as NR, SBR, BR, and IR. In addition, powdered rubber can be made from products that have passed 30 mesh or 40 mesh in Tyler Mesh.

[0080] The average particle size of the rubber powder is preferably 70 μm or more, and more preferably 100 μm or more. The average particle size is preferably 1 mm or less, and more preferably 750 μm or less. In this specification, the average particle size of the rubber powder is the mass-based average particle size calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0081] The rubber component in the powdered rubber preferably has a natural rubber content of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. When the natural rubber content is within the above range, excellent elongation at break tends to be obtained. In this specification, the natural rubber content of the rubber component in the powdered rubber refers to the value determined by measurement using pyrolysis gas chromatography (PyGC).

[0082] Powdered rubber can be used, for example, those manufactured and sold by companies such as Muraoka Rubber Industries Co., Ltd., Asahi Recycled Rubber Co., Ltd., and Lehigh Technologies. Powdered rubber can be used individually or in combination of two or more types.

[0083] When powdered rubber is included, the content of the diene-based rubber component per 100 parts by mass is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of environmental considerations. Furthermore, from the viewpoint of easily exhibiting the effects of this disclosure, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0084] (Total content of recycled rubber and powdered rubber) When at least one selected from recycled rubber and powdered rubber is included, the total content of recycled rubber and powdered rubber is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the diene-based rubber component, from the viewpoint of environmental considerations. Furthermore, from the viewpoint of easily exhibiting the effects of this disclosure, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0085] <Other ingredients> In addition to the components described above, the rubber composition of this disclosure may appropriately contain other components commonly used in the manufacture of rubber compositions, such as oils, liquid polymers, resins other than the aromatic ring-containing resins described above, stearic acid, zinc oxide, antioxidants, waxes, processing aids, vulcanizing agents, vulcanization accelerators, and the like.

[0086] (oil) The oil is not particularly limited, and any oil commonly used in the rubber industry can be suitably used, such as paraffinic, aromatic, and naphthenic process oils. Furthermore, process oils with a low content of polycyclic aromatic compounds (PCA) are preferred for environmental reasons. Examples of low-PCA process oils include treated distillate aromatic extract (TDAE) obtained by re-extracting aromatic process oil, aroma substitute oils which are mixtures of asphalt and naphthenic oil, mild extraction solvates (MES), and heavy naphthenic oils. Among these, aromatic process oils are preferred, and TDAE oils are more preferred. Oils manufactured and sold by companies such as H&R, JXTG Energy Corporation, Idemitsu Kosan Co., Ltd., and Sankyo Yuka Kogyo Co., Ltd. can be used. One or more types of oils can be used in combination.

[0087] When oil is included, the amount of oil per 100 parts by mass of the diene-based rubber component is not particularly limited, but is more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. Furthermore, the amount is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. When the oil content is within the above range, the effects of this disclosure tend to be exhibited more favorably. Note that the oil content includes the amount of oil used in oil spreading or oil treatment.

[0088] (Liquid polymer) The liquid polymer is not particularly limited and can be any liquid diene polymer such as liquid butadiene polymer (liquid BR), liquid styrene butadiene copolymer (liquid SBR), liquid isoprene polymer (liquid IR), or liquid styrene isoprene copolymer (liquid SIR). Liquid polymers can be those manufactured and sold by companies such as Kuraray Co., Ltd., Nippon Soda Co., Ltd., Cray Valley, Noveon, etc. One or more liquid polymers can be used.

[0089] When a liquid polymer is included, its content relative to 100 parts by mass of the diene-based rubber component is not particularly limited, but is more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. Furthermore, the content is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. When the liquid polymer content is within the above range, the effects of this disclosure tend to be exhibited more favorably.

[0090] (Resins other than the aromatic ring-containing resins mentioned above) Examples of resins other than the above-mentioned aromatic ring-containing resin include aliphatic petroleum resins (e.g., C5 petroleum resins), terpene resins, rosin resins, etc. These can be used individually or in combination of two or more. When resins other than the above-mentioned aromatic ring-containing resin are included, the content per 100 parts by mass of the diene rubber component is the same as the content for the above-mentioned aromatic ring-containing resin. From the viewpoint of better exhibiting the effects of this disclosure due to the inclusion of the above-mentioned aromatic ring-containing resin, it is preferable not to include resins other than the above-mentioned aromatic ring-containing resin.

[0091] (Stearic acid) When stearic acid is included, its content per 100 parts by mass of the diene rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, the content is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0092] (Zinc oxide) When zinc oxide is included, the content of zinc oxide per 100 parts by mass of the diene rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of abrasion resistance, the content is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0093] (Anti-aging agent) The antioxidant is not particularly limited, and any commonly used in the rubber industry can be suitably used. Examples include quinoline-based antioxidants, quinone-based antioxidants, phenol-based antioxidants, phenylenediamine-based antioxidants, and metal carbamate salts. Antioxidants manufactured and sold by companies such as Ouchi Shinko Chemical Co., Ltd., Kawaguchi Chemical Co., Ltd., and Sumitomo Chemical Co., Ltd. can be used. One or more antioxidants can be used in combination.

[0094] When an anti-aging agent is included, its content per 100 parts by mass of the diene-based rubber component is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more. Furthermore, the content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. When the content of the anti-aging agent is within the above range, it tends to be possible to obtain a sufficient anti-aging effect and suppress discoloration caused by the precipitation of the anti-aging agent on the tire surface.

[0095] (wax) The wax is not particularly limited, and any wax commonly used in the rubber industry can be suitably used, such as petroleum-based waxes, mineral-based waxes, and synthetic waxes. Among these, petroleum-based waxes are preferred. Examples of petroleum-based waxes include paraffin wax, microcrystalline wax, and selected specialty waxes thereof. Waxes manufactured and sold by companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. can be used. One type of wax or a combination of two or more types can be used.

[0096] When wax is included, the content of the diene-based rubber component per 100 parts by mass is preferably 0.3 parts by mass or more, more preferably 0.7 parts by mass or more, and even more preferably 0.8 parts by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, the content is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0097] (Processing aid) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Among these, fatty acid metal salts are preferred. Processing aids such as those manufactured by Structol can be used. Processing aids can be used individually or in combination of two or more types.

[0098] When processing aids are included, the content of the processing aid per 100 parts by mass of the diene rubber component is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more. Furthermore, the content of the processing aid is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. When the content of the processing aid is within the above range, the effects of this disclosure tend to be exhibited more favorably.

[0099] (Vulcanizing agent) The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used, such as organic peroxides such as dicumyl peroxide, sulfur-based vulcanizing agents, resin vulcanizing agents, and metal oxides such as magnesium oxide. Among these, sulfur-based vulcanizing agents are preferred. As sulfur-based vulcanizing agents, for example, sulfur, sulfur donors such as morpholine disulfide can be used. Among these, the use of sulfur is preferred. The vulcanizing agent can be used one or in combination of two or more types.

[0100] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with dispersants, masterbatch-type sulfur, etc.), and insoluble sulfur (oil-treated insoluble sulfur, etc.), all of which can be suitably used. Sulfur can be used from, for example, products manufactured and sold by Tsurumi Chemical Industries, Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals, Ltd., Flexis Co., Ltd., Nippon Dry Distillation Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0101] When a vulcanizing agent is included, its content per 100 parts by mass of the diene-based rubber component is preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, and even more preferably 0.9 parts by mass or more. Furthermore, the content is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. When the content of the vulcanizing agent is within the above range, an appropriate reinforcing effect tends to be obtained, and the effects of this disclosure tend to be exhibited more favorably. Note that when sulfur is used as the vulcanizing agent, the sulfur content refers to the content of the sulfur component itself contained in oil-treated sulfur or other components that are not sulfur.

[0102] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, and known vulcanization accelerators can be used, such as sulfenamide, thiazole, thiram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Among these, at least one of sulfenamide, guanidine, and thiram is preferred, with sulfenamide being more preferred. Vulcanization accelerators manufactured and sold by companies such as Ouchi Shinko Chemical Industry Co., Ltd. and Sanshin Chemical Industry Co., Ltd. can be used. One or more vulcanization accelerators can be used in combination.

[0103] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N'-dicyclohexyl-2-benzothiazolyl sulfenamide (DZ). Among these, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS) is preferred because it exhibits the effects of this disclosure more effectively.

[0104] Examples of thiram-based vulcanization accelerators include tetramethylthiram monosulfide, tetramethylthiram disulfide, and tetrabenzylthiram disulfide (TBzTD).

[0105] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), diorthotolylguanidine, and orthotolylbiguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred because it exhibits the effects of this disclosure more effectively.

[0106] The content of the vulcanization accelerator per 100 parts by mass of the diene rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more. Furthermore, the content is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. When the content of the vulcanization accelerator is within the above range, fracture strength and elongation tend to be ensured, and the effects of this disclosure tend to be exhibited more favorably.

[0107] <Rubber composition for tire treads, tire treads, and tires> The rubber composition for tire treads disclosed herein is used in tire treads because it offers an improved balance between wear resistance and chipping resistance.

[0108] Rubber compositions for tire treads can be manufactured by conventional methods. For example, they can be manufactured by mixing the components other than the vulcanizing agent and vulcanization accelerator in a closed-type kneader such as a Banbury mixer or kneader, or in a known kneader commonly used in the rubber industry such as an open roll (base mixing step), then adding the vulcanizing agent and vulcanization accelerator and mixing further (finishing step), and finally vulcanizing. Remilling (re-mixing step) may be performed between each step.

[0109] Tire treads and tires can be manufactured by conventional methods using the above-mentioned rubber composition for tire treads. Specifically, an unvulcanized tire can be formed by extruding a rubber composition containing the above components to match the shape of a tire tread in an unvulcanized stage, bonding it together with other tire components on a tire molding machine, and molding it in a conventional method. A tire equipped with a tire tread can then be manufactured by pressurizing and vulcanizing this unvulcanized tire in a vulcanizing machine.

[0110] There are no particular limitations on the mixing conditions, but for example, in the base mixing process, mixing is performed at a discharge temperature of 120-170°C for 1-15 minutes; in the remixing process, mixing is performed at a discharge temperature of 120-170°C for 1-15 minutes; and in the finish mixing process, mixing is performed at 70-110°C for 1-10 minutes. There are no particular limitations on the vulcanization conditions, but for example, vulcanization is performed at 150-200°C for 10-30 minutes.

[0111] The tires disclosed herein may be pneumatic or non-pneumatic, but pneumatic tires are preferred. Furthermore, the tires disclosed herein can be used for various applications, including passenger car tires, heavy-duty tires for trucks, buses, and construction vehicles, motorcycle tires, high-performance tires such as racing tires, winter tires, and run-flat tires, and are particularly suitable for use as passenger car tires and heavy-duty tires. In particular, the tires disclosed herein offer an improved balance of wear resistance and chipping resistance, making them especially suitable for use as heavy-duty tires. For heavy-duty applications, they are preferably for trucks and buses. [Examples]

[0112] This disclosure will be specifically described based on examples. This disclosure is not limited to these examples.

[0113] <Rating> Tables 1 and 2 show the results calculated based on the evaluation method below, assuming that the rubber composition obtained by changing the formulation according to Tables 1 and 2 using the various chemicals listed below will be used for the tread of a tire (a tire with the structure shown in Figure 1 (12R22.5)). Note that Comparative Example 1 is the standard comparative example in Table 1, and Comparative Example 6 is the standard comparative example in Table 2.

[0114] (Various chemicals) NR:RSS#3 (Tg:-60℃) SBR1:SL553 (Tin coupling S-SBR, vinyl content: 42%, styrene content: 10%, Tg: -64℃, available from JSR Corporation) SBR2: JSR1502 (E-SBR, vinyl content: 18%, styrene content: 23.5%, Tg: -51℃, available from JSR Corporation) SBR3:Nipol NS616 (S-SBR, styrene content: 21%, vinyl content: 66%, Tg: -23℃, available from ZS Elastomer Co., Ltd.) BR: Ubepol BR150B (High-cis BR, cis content: 97%, trans content: 2%, vinyl content: 1%, Tg: -114℃, available from Ube Industries, Ltd.) Recycled rubber: Recycled rubber with a natural rubber content of 73% by mass (available from Muraoka Rubber Industry Co., Ltd.) Powdered rubber: Powdered rubber W2-A (available from Asahi Recycled Rubber Co., Ltd.) Carbon Black: N220 (N2SA: 114m 2 ( / g, DBP oil absorption: 114ml / 100g, available from Mitsubishi Chemical Corporation) Silica: UltraSil VN3 (N2SA: 175m 2 (Available from Evonik Degussa) Aromatic ring-containing resin 1: Nippon Oil Neopolymer L90 (C9-based petroleum resin polymerized from C9 fraction (without hydroxyl groups), softening point: 90-100°C, Mw: 1000, SP value: 9.10, available from JXTG Energy Corporation) Aromatic ring-containing resin 2: YS Polystar T115 (Terpene phenol resin copolymerized with terpene compounds and phenol (containing one hydroxyl group), softening point: 110~120℃, Mw: 500~1050, SP value: 8.81, available from Yasuhara Chemical Co., Ltd.) Polyhydric alcohol 1: Ethylene glycol (number of carbon atoms: 2, number of hydroxyl groups: 2, α / β ratio: 1, melting point: -13°C, available from Tokyo Chemical Industry Co., Ltd.) Polyhydric alcohol 2:1,2-hexanediol (number of carbon atoms: 6, number of hydroxyl groups: 2, α / β ratio: 0.3, melting point: 45°C, available from Tokyo Chemical Industry Co., Ltd.) Polyhydric alcohol 3: Sorbitol (Number of carbon atoms: 6, Number of hydroxyl groups: 6, α / β ratio: 1, Melting point: 95°C, Available from Kanto Chemical Co., Ltd.) Silane coupling agent: Si266 (sulfide-based, bis(3-triethoxysilylpropyl) disulfide, available from Evonik Degussa) Zinc oxide: Two types of zinc oxide (available from Mitsui Mining & Smelting Co., Ltd.) Stearic acid: Beads of stearic acid (available from NOF Corporation) Sulfur: Powdered sulfur (5% oil content, available from Tsurumi Chemical Industries, Ltd.) Vulcanization accelerator: Noxellar NS (N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), available from Ouchi Shinko Chemical Co., Ltd.)

[0115] (Test tires) According to the formulations shown in Tables 1 and 2, the chemicals other than sulfur and vulcanization accelerator are mixed for 5 minutes at a discharge temperature of 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. Next, sulfur and vulcanization accelerator are added to the resulting mixture and kneaded in an open roll for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition.

[0116] The resulting unvulcanized rubber composition is molded into the shape of a tread, bonded together with other tire components to produce an unvulcanized tire, and then press-vulcanized at 170°C for 20 minutes to obtain a test tire.

[0117] (Abrasion resistance) Each test tire is mounted on all wheels of a vehicle (truck), driven on an asphalt course, and the groove depth of the tire tread is measured after 8000 km of driving. The distance traveled when the tire groove depth decreases by 1 mm is then determined. The results are shown as an index calculated using the following formula, with the distance traveled when the tire groove depth of the standard comparison tire decreases by 1 mm set to 100. A higher index indicates better wear resistance. (Wear resistance index) = (Distance traveled when the tire tread of each compound decreases by 1 mm) / (Distance traveled when the tire tread of the standard comparison example decreases by 1 mm) × 100

[0118] (Chipping resistance) Each test tire was mounted on all wheels of a vehicle (truck), and the vehicle was driven 10 times around a rough terrain test course simulating rocky terrain. The size of each chip in the tread rubber was totaled, and the result was expressed as an index using the following formula, with the reference comparison set to 100. A higher index indicates better chipping resistance. (Chipping resistance index) = (Amount of chipping in the standard comparative example) / (Amount of chipping in each formulation) × 100

[0119] (Performance balance) The sum of the wear resistance index and chipping resistance index values ​​is shown as the "performance balance." A higher performance balance value indicates a better balance between wear resistance and chipping resistance.

[0120] [Table 1]

[0121] [Table 2]

[0122] The results above show that the rubber composition for tire treads disclosed herein improves the balance between wear resistance and chipping resistance. [Explanation of Symbols]

[0123] 10 tires 11 Tread section 12 Sidewall section 13 Bead section 14 Bead core 15 Carcass 16 Steel Belt 18 vertical grooves 30 rim

Claims

1. A diene rubber component containing styrene-butadiene rubber and isoprene-based rubber, A filler containing carbon black, Aromatic ring-containing resin, A rubber composition for tire treads, comprising a polyhydric alcohol, A rubber composition for tire treads, wherein the polyhydric alcohol satisfies the following formula (A). (A) α / β ≤ 0.5 α: The number of hydroxyl groups in one molecule of polyhydric alcohol. β: Number of carbon atoms in polyhydric alcohols

2. A diene rubber component containing styrene-butadiene rubber and isoprene-based rubber, A filler containing carbon black, Aromatic ring-containing resin, A rubber composition for tire treads, comprising a polyhydric alcohol, A rubber composition for tire treads, wherein the melting point of the polyhydric alcohol is less than 50°C.

3. The rubber composition for tire treads according to claim 1 or 2, wherein the content of the styrene-butadiene rubber in the diene-based rubber component is 10 to 50% by mass.

4. The rubber composition for tire treads according to claim 1, 2, or 3, wherein the styrene content of the styrene-butadiene rubber is 15% or more.

5. The rubber composition for tire treads according to any one of claims 1 to 4, wherein the polyhydric alcohol has 6 or more carbon atoms.

6. The rubber composition for tire treads according to any one of claims 1 to 5, wherein the aromatic ring-containing resin is a homopolymer or copolymer of monomers containing an aromatic ring-containing monomer, and the aromatic ring-containing monomer has at least one hydroxyl group.

7. A rubber composition for tire treads according to any one of claims 1 to 6, further comprising at least one selected from recycled rubber and powdered rubber.

8. The rubber composition for tire treads according to any one of claims 1 to 7, wherein the diene-based rubber component has an average glass transition temperature (Tg) of -50°C or lower.

9. The rubber composition for tire treads according to any one of claims 1 to 8, wherein the polyhydric alcohol comprises a linear polyhydric alcohol.

10. The rubber composition for tire treads according to any one of claims 1 to 9, wherein the content of the isoprene-based rubber in the diene-based rubber component is 30% by mass or more.

11. The rubber composition for tire treads according to any one of claims 2 to 10, wherein the polyhydric alcohol satisfies the following formula (A). (A) α / β ≤ 0.5 α: The number of hydroxyl groups in one molecule of polyhydric alcohol. β: Number of carbon atoms in polyhydric alcohols

12. The rubber composition for tire treads according to any one of claims 1 and 3 to 11, wherein the melting point of the polyhydric alcohol is less than 50°C.

13. The tire tread rubber composition according to any one of claims 1 to 12, wherein the content of carbon black relative to 100 parts by mass of the diene-based rubber component is 40 parts by mass or more.

14. The rubber composition for tire treads according to any one of claims 1 to 13, wherein the content of carbon black in the filler is 80% by mass or more.

15. A tire tread comprising the rubber composition for tire treads described in any one of claims 1 to 14.

16. A tire having the tire tread described in claim 15.

17. The tire according to claim 16, which is a heavy-duty tire.

18. The tire according to claim 17, which is a heavy-duty tire for trucks and buses.

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