Petroleum resins, rubber additives, uncrosslinked rubber compositions and crosslinked rubbers

Abstract

To provide a petroleum resin that can impart excellent cut resistance and chipping resistance to isoprene-based rubber.SOLUTION: Provided is a petroleum resin, which is a polymerization product of a raw material component containing aromatic olefin-containing C9 fraction and dicyclopentadiene, and in the raw material component, the ratio C2 / C1 (mass ratio) of the content C2 of the aromatic olefin to the content C1 of the dicyclopentadiene is 0.35 or more and 0.5 or less, and the softening point is 150°C or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a petroleum resin, a rubber additive, an uncrosslinked rubber composition, and a crosslinked rubber. [Background technology]

[0002] Rubber additives have been used to impart various properties to rubber materials. For example, Patent Document 1 discloses a tire tread composition containing at least one elastomer and a specific hydrocarbon polymer additive based on dicyclopentadiene, cyclopentadiene, and methylcyclopentadiene. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2015-523430 Summary of the Invention [Problem to be solved by the invention]

[0004] One of the main applications of rubber materials is tires. Properties required of rubber materials for tires include, for example, cut resistance and chipping resistance for large tires.

[0005] The present invention aims to provide a petroleum resin capable of imparting excellent cut resistance and chipping resistance to isoprene-based rubber. Another object of the present invention is to provide a rubber additive, an uncrosslinked rubber composition, and a crosslinked rubber containing the petroleum resin. Another object of the present invention is to provide a method for producing the petroleum resin. A further object of the present invention is to provide an additive for tread rubber capable of imparting excellent cut resistance and chipping resistance to isoprene-based rubber, an uncrosslinked rubber composition for forming tread rubber containing the additive, and a tread rubber obtained by crosslinking the uncrosslinked rubber composition. [Means for solving the problem]

[0006] One aspect of the present invention relates to a petroleum resin which is a polymer of a feed component containing a C9 fraction containing an aromatic olefin and dicyclopentadiene, in which the ratio C2 / C1 (mass ratio) of the aromatic olefin content C2 to the dicyclopentadiene content C1 in the feed component is 0.35 or more and 0.5 or less, and the softening point is 150°C or more.

[0007] Another aspect of the present invention relates to a rubber additive containing the above petroleum resin.

[0008] The rubber additive according to one embodiment may be an isoprene-based rubber additive.

[0009] The rubber additive according to one embodiment may be a natural rubber additive.

[0010] Yet another aspect of the present invention relates to an uncrosslinked rubber composition containing a rubber component containing an isoprene-based rubber, a crosslinking agent for rubber, and the above petroleum resin.

[0011] Yet another aspect of the present invention relates to a crosslinked rubber obtained by crosslinking the uncrosslinked rubber composition.

[0012] Yet another aspect of the present invention relates to a method for producing a petroleum resin, comprising a first step of thermally polymerizing a raw material component containing a C9 fraction containing an aromatic olefin and dicyclopentadiene to obtain a thermal polymer having a softening point lower than that of the petroleum resin, and a second step of heating the thermal polymer to obtain a petroleum resin. In this production method, the ratio C2 / C1 (mass ratio) of the content C2 of the aromatic olefin to the content C1 of the dicyclopentadiene in the raw material component may be 0.35 or more and 0.5 or less, and the softening point of the petroleum resin may be 150°C or more.

[0013] Yet another aspect of the present invention relates to an additive for tread rubber containing a petroleum resin, the petroleum resin being a thermal polymer of raw material components containing a C9 fraction containing an aromatic olefin and dicyclopentadiene, and the softening point of the petroleum resin is 150°C or higher.

[0014] The tread rubber additive according to one embodiment may be a tread rubber additive for large tires.

[0015] Yet another aspect of the present invention relates to an uncrosslinked rubber composition for forming tread rubber, which contains a rubber component containing an isoprene-based rubber, a crosslinking agent for rubber, and the above-mentioned additive for tread rubber.

[0016] Yet another aspect of the present invention relates to a tread rubber obtained by crosslinking the uncrosslinked rubber composition for a tread. Effect of the Invention

[0017] According to the present invention, there is provided a petroleum resin capable of imparting excellent cut resistance and chipping resistance to isoprene-based rubber. According to the present invention, there are also provided a rubber additive, an uncrosslinked rubber composition, and a crosslinked rubber containing the petroleum resin. According to the present invention, there is also provided a method for producing the petroleum resin. Furthermore, according to the present invention, there are provided an additive for tread rubber capable of imparting excellent cut resistance and chipping resistance to isoprene-based rubber, an uncrosslinked rubber composition for forming tread rubber containing the additive, and a tread rubber obtained by crosslinking the uncrosslinked rubber composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Preferred embodiments of the present invention will now be described in detail.

[0019] (Petroleum resin) The petroleum resin of this embodiment is a polymer of raw material components including a C9 fraction containing aromatic olefins and dicyclopentadiene. The softening point of the petroleum resin of this embodiment is 150° C. or higher. The polymerization method of the raw material components is not particularly limited, and may be, for example, thermal polymerization, cationic polymerization, etc., among which thermal polymerization is particularly preferred.

[0020] In a preferred embodiment, the ratio C2 / C1 (mass ratio) of the aromatic olefin content C2 to the dicyclopentadiene content C1 in the raw material components is 0.35 or more and 0.5 or less.

[0021] The petroleum resin of the present embodiment can impart excellent cut resistance and chipping resistance to isoprene-based rubber, and therefore the petroleum resin of the present embodiment can be suitably used as an additive for rubber, particularly as an additive for isoprene-based rubber.

[0022] The cut resistance and chipping resistance are evaluated by the tear strength of the crosslinked rubber, and the higher the tear strength, the better the cut resistance and chipping resistance. In other words, the petroleum resin of the present embodiment can be said to be a rubber additive that can form a crosslinked rubber having excellent tear strength by blending with an isoprene-based rubber.

[0023] Cut resistance and chipping resistance are important performances for rubber (tread rubber) used in the tread portion of tires. Cut resistance and chipping resistance are particularly important performances for tires used in agricultural vehicles, heavy-load vehicles, and construction vehicles used in harsh environments, as well as large vehicles (e.g., trucks, buses, etc.) that are subject to high loads, i.e., large tires. For this reason, the petroleum resin of this embodiment can be suitably used as an additive for tread rubber, particularly as an additive for tread rubber for large tires.

[0024] Generally, petroleum resins with high softening points have a wide molecular weight distribution, which tends to lead to a high iodine value. The petroleum resin of the present embodiment can achieve both a low iodine value and a high softening point by setting the ratio C2 / C1 within a specific range. Such petroleum resins tend to impart superior cut resistance and chipping resistance to isoprene-based rubber.

[0025] The iodine value of the petroleum resin of the present embodiment may be, for example, 180 or less, preferably 175 or less, and more preferably 160 or less. This tends to allow an appropriate formation of a crosslinked structure with the rubber component during vulcanization of the uncrosslinked rubber composition, making it easier to obtain a crosslinked rubber having properties more suitable for tire applications.

[0026] The lower limit of the iodine value of the petroleum resin of the present embodiment is not particularly limited. The iodine value of the petroleum resin of the present embodiment may be, for example, 50 or more, preferably 100 or more, and more preferably 125 or more. This makes it easier to form a crosslinked structure with the rubber component during vulcanization of the uncrosslinked rubber composition, and tends to make it easier to obtain a crosslinked rubber having properties more suitable for tire applications.

[0027] In this specification, the iodine value of the petroleum resin is a value measured in accordance with JIS K 0070:1992.

[0028] The softening point of the petroleum resin of the present embodiment is 150° C. or higher, preferably 155° C. or higher, more preferably 160° C. or higher, and may be 165° C. or higher. When the petroleum resin has a high softening point, it tends to impart better cut resistance and chipping resistance to the isoprene-based rubber.

[0029] The upper limit of the softening point of the petroleum resin of the present embodiment is not particularly limited. The softening point of the petroleum resin of the present embodiment may be, for example, 220° C. or lower, preferably 200° C. or lower, and more preferably 190° C. or lower. This tends to make it easier to knead with the rubber component.

[0030] In this specification, the softening point of the petroleum resin is a value measured using a DP70 manufactured by Mettler Toledo Co., Ltd. according to a method in accordance with ASTM D6090.

[0031] The number average molecular weight (Mn) of the petroleum resin of this embodiment is not particularly limited, but may be, for example, 500 or more, and preferably 600 or more. The number average molecular weight (Mn) of the petroleum resin of this embodiment is, for example, 1000 or less, and more preferably 900 or less.

[0032] The weight average molecular weight (Mw) of the petroleum resin of this embodiment is not particularly limited, and may be, for example, 1500 or more, and preferably 1800 or more. The weight average molecular weight (Mw) of the petroleum resin of this embodiment is, for example, 2500 or less, more preferably 2300 or less, and even more preferably 2000 or less.

[0033] The molecular weight distribution (Mw / Mn) of the petroleum resin of this embodiment is not particularly limited, but may be, for example, 2.5 or more, and preferably 2.7 or more. This makes it easier for the iodine value to be equal to or higher than the above-mentioned preferable lower limit. The molecular weight distribution (Mw / Mn) of the petroleum resin of this embodiment is, for example, 3.2 or less, and more preferably 3.0 or less. This makes it easier for the iodine value to be equal to or lower than the above-mentioned preferable upper limit.

[0034] In this specification, the number average molecular weight, weight average molecular weight, Z average molecular weight and molecular weight distribution of the petroleum resin are values ​​measured by GPC (gel permeation chromatography) and calculated as standard polystyrene.

[0035] The petroleum resin of the present embodiment may be obtained by, for example, additional polymerization of a thermal polymer of the raw material components (for example, the thermal polymer (A) described below). In this case, the petroleum resin of the present embodiment can also be said to be an additional polymerization product of the thermal polymer of the raw material components.

[0036] The feedstock component contains a C9 fraction containing aromatic olefins and dicyclopentadiene, and in the feedstock component, the ratio C2 / C1 of the aromatic olefin content C2 to the dicyclopentadiene content C1 is preferably 0.35 or more and 0.5 or less in mass ratio.

[0037] The C9 fraction may be, for example, a C9 fraction obtained by thermal cracking of a petroleum-derived raw oil (for example, petroleum naphtha). The C9 fraction is generally a fraction having a boiling point range of about 100° C. to 280° C., and mainly contains compounds having 8 to 10 carbon atoms.

[0038] The C9 fraction contains aromatic olefins, such as vinyltoluene, methylstyrene, indene, styrene, and methylindene.

[0039] The C9 fraction may further contain components other than aromatic olefins, for example, alkylbenzenes such as propylbenzene, methylethylbenzene, and indane, and saturated hydrocarbons such as naphthenes and paraffins.

[0040] The proportion of aromatic olefins in the C9 fraction is not particularly limited. The proportion of aromatic olefins in the C9 fraction may be, for example, 40% by mass or more, preferably 50% by mass or more, and more preferably 65% ​​by mass or more.

[0041] Components other than aromatic olefins in the C9 fraction function as, for example, a diluent in thermal polymerization. The proportion of aromatic olefins in the C9 fraction may be, for example, 40 mass% or less, 30 mass% or less, 20 mass% or less, or 10 mass% or less.

[0042] The ratio C2 / C1 is preferably 0.35 or more, more preferably 0.37 or more, and even more preferably 0.40 or more, which tends to impart excellent cut resistance and chipping resistance to the isoprene-based rubber while maintaining a lower iodine value.

[0043] The ratio C2 / C1 is preferably 0.5 or less, more preferably 0.48 or less, and even more preferably 0.46 or less, which further improves the reactivity during polymerization and makes it easier to obtain a petroleum resin in a suitable embodiment.

[0044] Dicyclopentadiene can be obtained, for example, by dimerizing cyclopentadiene contained in a C5 fraction obtained by thermal cracking of petroleum-derived feedstock oil (e.g., petroleum naphtha) to form dicyclopentadiene, and then separating the dicyclopentadiene from other components in the C5 fraction. The C5 fraction is generally a fraction having a boiling point range of about 20 to 110°C, and mainly contains compounds having 4 to 5 carbon atoms.

[0045] The raw material components may include dicyclopentadiene (a cyclopentadiene dimer) as well as its alkyl-substituted derivatives (for example, methyldicyclopentadiene), cyclopentadiene polymers (for example, tricyclopentadiene), and the like.

[0046] The petroleum resin of the present embodiment can be produced, for example, by the following production method.

[0047] A method for producing a petroleum resin according to one embodiment includes a first step of thermally polymerizing a raw material component to obtain a thermally polymerized product having a softening point lower than that of the petroleum resin, and a second step of heating the thermally polymerized product to obtain a petroleum resin.

[0048] In the first step, the method of thermal polymerization is not particularly limited, and may be carried out, for example, by heating the raw material components to a predetermined reaction temperature or higher.

[0049] The reaction temperature of the thermal polymerization is not particularly limited and may be, for example, 250° C. or higher, preferably 260° C. or higher, and more preferably 270° C. or higher. The reaction temperature of the thermal polymerization may be, for example, 300° C. or lower, and preferably 290° C. or lower.

[0050] The reaction time of the thermal polymerization (the time during which the reaction system is maintained at the reaction temperature) is not particularly limited, and may be, for example, 100 minutes or more, 130 minutes or more, or 160 minutes or more. The reaction time of the thermal polymerization may be, for example, 300 minutes or less, 250 minutes or less, or 200 minutes or less.

[0051] The reaction system of the thermal polymerization may further contain other components than the raw material components. For example, the reaction system of the thermal polymerization may further contain a solvent. As the solvent, for example, saturated hydrocarbons (alkanes, cycloalkanes, etc.), aromatic hydrocarbons (benzene, toluene, etc.), etc. can be used.

[0052] In the first step, for example, unreacted components (for example, components other than aromatic olefins in the C9 fraction, unreacted aromatic olefins, solvents, etc.) may be removed from the reaction product obtained by thermal polymerization to obtain a thermal polymer. The removal of the unreacted components may be carried out, for example, by distillation.

[0053] The thermal polymer obtained in the first step (hereinafter referred to as thermal polymer (A)) has a softening point lower than that of the above-mentioned petroleum resin.

[0054] The softening point of the thermal polymer (A) may be lower than the softening point of the petroleum resin, for example, lower than 165°C, lower than 160°C, lower than 155°C, or lower than 150°C, or may be 145°C or lower.

[0055] The lower limit of the softening point of the thermal polymer (A) is not particularly limited, but from the viewpoint of easily obtaining a petroleum resin having the above-mentioned preferable softening point, the softening point of the thermal polymer (A) may be, for example, 120°C or higher, preferably 140°C or higher, and more preferably 150°C or higher.

[0056] In the present specification, the softening point of the thermal polymer (A) is a value measured by a method in accordance with ASTM D6090 using a DP70 manufactured by Mettler Toledo.

[0057] The iodine value of the thermal polymer (A) may be, for example, not more than 180, preferably not more than 175, and more preferably not more than 160. This makes it easier to obtain a petroleum resin having the above-mentioned suitable iodine value.

[0058] The iodine value of the thermal polymer (A) may be, for example, not less than 50, preferably not less than 100, and more preferably not less than 125. This makes it easier to obtain a petroleum resin having the above-mentioned suitable iodine value.

[0059] In the present specification, the iodine value of the thermally polymerized product (A) is a value measured in accordance with JIS K 0070:1992.

[0060] The number average molecular weight (Mn) of the thermal polymer (A) is not particularly limited, but may be, for example, 400 or more, and preferably 500 or more. The number average molecular weight (Mn) of the thermal polymer (A) is, for example, 1000 or less, and more preferably 900 or less. This makes it easier to obtain a petroleum resin having the above-mentioned suitable number average molecular weight (Mn).

[0061] The weight average molecular weight (Mw) of the thermal polymer (A) is not particularly limited, but may be, for example, 1000 or more, and preferably 1200 or more. The weight average molecular weight (Mw) of the thermal polymer (A) is, for example, 1800 or less, and more preferably 1600 or less. This makes it easier to obtain a petroleum resin having the above-mentioned suitable weight average molecular weight (Mw).

[0062] The number average molecular weight (Mn) of the petroleum resin of this embodiment is not particularly limited, but may be, for example, 500 or more, and preferably 600 or more. The number average molecular weight (Mn) of the petroleum resin of this embodiment is, for example, 1000 or less, and more preferably 900 or less.

[0063] The weight average molecular weight (Mw) of the petroleum resin of this embodiment is not particularly limited, and may be, for example, 1500 or more, and preferably 1800 or more. The weight average molecular weight (Mw) of the petroleum resin of this embodiment is, for example, 2500 or less, more preferably 2300 or less, and even more preferably 2000 or less.

[0064] The molecular weight distribution (Mw / Mn) of the thermal polymer (A) is not particularly limited, but may be, for example, 1.8 or more, and preferably 2.0 or more. The molecular weight distribution (Mw / Mn) of the thermal polymer (A) is, for example, 3.0 or less, and more preferably 2.8 or less. This makes it easier to obtain a petroleum resin having the above-mentioned suitable molecular weight distribution (Mw / Mn).

[0065] In this specification, the number average molecular weight, weight average molecular weight, Z average molecular weight and molecular weight distribution of the thermal polymer (A) are values ​​measured by GPC (gel permeation chromatography) and calculated as standard polystyrene.

[0066] The second step is a step of heating the thermally polymerized product (A) to carry out additional polymerization to obtain a petroleum resin.

[0067] In the second step, the method of additional polymerization is not particularly limited, and may be carried out, for example, by heating the raw material components to a predetermined reaction temperature or higher.

[0068] The reaction temperature of the additional polymerization is not particularly limited, and may be, for example, 220° C. or higher, preferably 230° C. or higher, and more preferably 240° C. or higher. The reaction temperature of the additional polymerization may be, for example, 280° C. or lower, preferably 270° C. or lower, and more preferably 260° C. or lower.

[0069] The reaction time of the additional polymerization (the time during which the reaction system is maintained at the reaction temperature) is not particularly limited, and may be, for example, 3 hours or more, 4 hours or more, or 5 hours or more. The reaction time of the additional polymerization may be, for example, 8 hours or less, 7 hours or less, or 6 hours or less.

[0070] The additional polymerization is preferably carried out in an inert gas atmosphere, for example. The inert gas is not particularly limited, and examples thereof include nitrogen and argon.

[0071] The additional polymerization may be carried out in the presence of a solvent or in the absence of a solvent, but is preferably carried out in the absence of a solvent.

[0072] The additional polymerization may be carried out under atmospheric pressure or in a closed system, or may be carried out under a reduced pressure environment.

[0073] In the second step, a petroleum resin having a higher molecular weight (number average molecular weight and weight average molecular weight) and softening point than the thermal polymer (A) is obtained by additional polymerization. The petroleum resin obtained in the second step also tends to have a higher molecular weight distribution than the thermal polymer (A). The petroleum resin obtained in the second step also tends to have a higher iodine value than the thermal polymer (A). That is, the second step may be a step of obtaining a petroleum resin having a higher softening point, molecular weight (number average molecular weight and weight average molecular weight), molecular weight distribution, and iodine value than the thermal polymer (A).

[0074] (rubber additives) The rubber additive of the present embodiment contains the petroleum resin described above. The rubber additive of the present embodiment can impart excellent cut resistance and chipping resistance to rubber materials (particularly isoprene-based rubber).

[0075] The rubber additive of the present embodiment may be an additive consisting of only petroleum resin, or may be an additive containing petroleum resin and other components. As the other components, any components known as rubber additives can be used without particular limitation. As the other components, for example, each component that may be contained in the uncrosslinked rubber composition described later can be mentioned.

[0076] The amount of the rubber additive of this embodiment added to the rubber component is not particularly limited as long as the amount of the petroleum resin added per 100 parts by mass of the rubber component falls within the preferred range described below.

[0077] The amount of the petroleum resin added may be, for example, 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass, based on 100 parts by mass of the rubber component. This makes the above-mentioned effects more pronounced. From the viewpoint of the rubber elasticity of the crosslinked rubber, the amount of the petroleum resin added may be, for example, 40 parts by mass or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component.

[0078] The rubber additive of the present embodiment can be suitably used as an additive for tread rubber, and can be particularly suitably used as an additive for tread rubber for large tires.

[0079] (Uncrosslinked rubber composition) The uncrosslinked rubber composition of the present embodiment contains a rubber component containing an isoprene-based rubber, a crosslinking agent for rubber, and the above-mentioned petroleum resin. The crosslinked rubber obtained by crosslinking this uncrosslinked rubber composition has excellent cut resistance and chipping resistance, and can be suitably used as a rubber material for tires (especially a rubber material for large tires such as truck tires), and can be particularly suitably used as a rubber material for tire treads (especially a rubber material for large tires).

[0080] Examples of isoprene-based rubber include natural rubber, deproteinized natural rubber, and synthetic rubber. Here, deproteinized natural rubber is natural rubber that has been subjected to a deproteinization treatment. Examples of natural rubber include natural rubber latex, technically graded rubber (TSR), smoked sheet (RSS), gutta percha, Eucommia-derived natural rubber, guayule-derived natural rubber, Russian dandelion-derived natural rubber, and plant-based fermented rubber. Modified natural rubbers obtained by modifying these natural rubbers, such as epoxidized natural rubber, methacrylic acid-modified natural rubber, styrene-modified natural rubber, sulfonic acid-modified natural rubber, and zinc sulfonate-modified natural rubber, are also included in natural rubber. Examples of synthetic rubber include isoprene rubber, isoprene-butadiene rubber, halogenated isoprene rubber, and styrene-isoprene-butadiene rubber.

[0081] The rubber component may further contain a rubber other than the isoprene-based rubber, such as butadiene rubber (BR), nitrile rubber, silicone rubber, styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber, halogenated butyl rubber, halogenated isobutylene copolymer, chloroprene rubber (CR), butyl rubber, and halogenated isobutylene-p-methylstyrene rubber.

[0082] The proportion of the isoprene-based rubber in the rubber component may be, for example, 50% by mass or more, and from the viewpoint of obtaining the above-mentioned effects more significantly, it is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 95% by mass or more, or may be 100% by mass.

[0083] As the crosslinking agent for rubber, those generally used for crosslinking rubber can be used without any particular limitation. As the crosslinking agent for rubber, for example, sulfur crosslinking agents such as sulfur, morpholine disulfide, alkylphenol disulfide, etc.; organic peroxide crosslinking agents such as cyclohexanone peroxide, methyl acetoacetate peroxide, tert-butyl peroxy isobutyrate, tert-butyl peroxy benzoate, benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 1,3-bis(tert-butylperoxy isopropyl)benzene, etc. may be used alone or in combination of two or more kinds.

[0084] The content of the rubber crosslinking agent may be, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, based on 100 parts by mass of the rubber component. The content of the rubber crosslinking agent may be, for example, 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the rubber component.

[0085] The uncrosslinked rubber composition of the present embodiment may further contain various reinforcing agents, fillers, rubber extender oils, softeners, vulcanization accelerators, vulcanization aids, etc., which are used in the rubber industry. Each of these components may be used alone or in combination of two or more.

[0086] Examples of the reinforcing agent include carbon black and silica.

[0087] Carbon black is preferably used as a reinforcing agent since it has effects such as improving the wear resistance and rolling resistance properties of crosslinked rubber, preventing cracks and crazes caused by ultraviolet rays (preventing ultraviolet deterioration), etc. The type of carbon black is not particularly limited, and conventionally known carbon blacks such as furnace black, acetylene black, thermal black, channel black, graphite, etc. can be used.

[0088] Furthermore, the physical properties of the carbon black, such as particle size, pore volume, and specific surface area, are not particularly limited, and various types of carbon black conventionally used in the rubber industry, such as SAF, ISAF, HAF, FEF, GPF, and SRF (all of which are abbreviations for carbon black classified according to the U.S. ASTM standard D-1765-82a), can be used as appropriate.

[0089] When the uncrosslinked rubber composition of the present embodiment contains carbon black, the amount of carbon black may be, for example, 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component. The amount of carbon black may be, for example, 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the rubber component.

[0090] As the silica, any silica that has been used as a reinforcing agent for rubber can be used without any particular limitation. Examples of the silica include dry process white carbon, wet process white carbon, synthetic silicate white carbon, colloidal silica, precipitated silica, etc. There is no particular limitation on the specific surface area of ​​the silica, but it is usually 40 to 600 m 2 / g, preferably 70 to 300m 2 / g, and the primary particle diameter can be 10 to 1000 nm.

[0091] When the uncrosslinked rubber composition of the present embodiment contains silica, the content of silica may be, for example, 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of the rubber component. The content of silica may be, for example, 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 60 parts by mass or less, based on 100 parts by mass of the rubber component.

[0092] In addition, when the uncrosslinked rubber composition of the present embodiment contains silica, the uncrosslinked rubber composition may further contain a silane coupling agent. Examples of the silane coupling agent include vinyl trichlorosilane, vinyl triethoxysilane, vinyl tris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyl trimethoxysilane, 3-chloropropyl trimethoxysilane, 3-chloropropyl triethoxysilane, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl) disulfide, etc. These may be used alone or in combination of two or more.

[0093] When the uncrosslinked rubber composition of the present embodiment contains a silane coupling agent, the content of the silane coupling agent can be appropriately changed depending on the desired amount of silica to be blended, and may be, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. The content of the silane coupling agent may be, for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0094] As the filler, mineral powders such as clay and talc; carbonates such as magnesium carbonate and calcium carbonate; alumina hydrates such as aluminum hydroxide; and the like can be used.

[0095] When the uncrosslinked rubber composition of the present embodiment contains a filler, the content of the filler may be, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, more preferably 3 parts by mass or more, based on 100 parts by mass of the rubber component. The content of the filler may be, for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component.

[0096] As the rubber extending oil, aromatic oils, naphthenic oils, paraffinic oils and the like that have been conventionally used can be used.

[0097] When the uncrosslinked rubber composition of the present embodiment contains a rubber extending oil, the content of the rubber extending oil may be, for example, 0 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component. The content of the rubber extending oil may be, for example, 80 parts by mass or less, preferably 60 parts by mass or less, and more preferably 40 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0098] Examples of softeners include vegetable softeners such as tall oil mainly containing linoleic acid, oleic acid, and abiotic acid, pine tar, rapeseed oil, cottonseed oil, peanut oil, castor oil, palm oil, and factice, paraffinic oils, naphthenic oils, aromatic oils, and phthalic acid derivatives such as dibutyl phthalate.

[0099] When the uncrosslinked rubber composition of the present embodiment contains a softener, the content of the softener may be, for example, 0 part by mass or more, preferably 1 part by mass or more, and more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. The content of the softener may be, for example, 50 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0100] Examples of the vulcanization accelerator include thiuram-based accelerators such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetraethylthiuram disulfide; thiazole-based accelerators such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide; sulfenamide-based accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide and N-oxydiethylene-2-benzothiazolylsulfenamide; guanidine-based accelerators such as diphenylguanidine and diorthotolylguanidine; aldehyde-amine-based accelerators such as n-butylaldehyde-aniline condensation products and butyraldehyde-monobutylamine condensation products; aldehyde-ammonia-based accelerators such as hexamethylenetetramine; and thiourea-based accelerators such as thiocarbanilide.

[0101] When the uncrosslinked rubber composition of the present embodiment contains a vulcanization accelerator, the content of the vulcanization accelerator may be, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. The content of the vulcanization accelerator may be, for example, 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0102] Examples of vulcanization aids include metal oxides such as zinc oxide (zinc oxide) and magnesium oxide; metal hydroxides such as calcium hydroxide; metal carbonates such as zinc carbonate and basic zinc carbonate; fatty acids such as stearic acid and oleic acid; aliphatic metal salts such as zinc stearate and magnesium stearate; amines such as di-n-butylamine and dicyclohexylamine; ethylene dimethacrylate, diallyl phthalate, N,Nm-phenylenedimaleimide, triallyl isocyanurate, and trimethylolpropane trimethacrylate.

[0103] When the uncrosslinked rubber composition of the present embodiment contains a vulcanization aid, the content of the vulcanization aid may be, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. The content of the vulcanization aid may be, for example, 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0104] The uncrosslinked rubber composition of the present embodiment may further contain, as necessary, one or more of various additives used in the rubber industry, such as an antioxidant, a vulcanization retarder, a peptizing agent, a process oil, a plasticizer, etc.

[0105] When the uncrosslinked rubber composition of the present embodiment contains the additive, the content of the additive may be, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. The content of the additive may be, for example, 10 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component.

[0106] The uncrosslinked rubber composition of the present embodiment can be produced by applying a method generally used for producing an uncrosslinked rubber composition, for example, by mixing the above-mentioned components using a kneader such as a Brabender, Banbury mixer, or roll mixer.

[0107] (Crosslinked rubber) The crosslinked rubber of the present embodiment is a crosslinked product obtained by crosslinking the above-mentioned uncrosslinked rubber composition. The crosslinked rubber of the present embodiment has excellent cut resistance and chipping resistance, and is therefore useful as, for example, a rubber material for tires (particularly, a rubber material for large tires), and is particularly useful as a tread rubber (particularly, a tread rubber for large tires).

[0108] The crosslinked rubber of the present embodiment can be produced by crosslinking the uncrosslinked rubber composition in the same manner as in the ordinary crosslinking method for rubber. For example, the uncrosslinked rubber composition can be molded by heating to obtain a crosslinked rubber molded into a desired shape.

[0109] The crosslinked rubber of the present embodiment can be suitably used in various applications. For example, the crosslinked rubber of the present embodiment can be suitably used in applications such as tires, adhesives, films, medical tapes, paints, inks, asphalt binders, fabrics, waterproofing agents, and printer resins, and is particularly suitable for tire applications (particularly large tire applications).

[0110] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. EXAMPLES

[0111] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0112] (Example 1-1) <Production of Thermal Polymer (A-1)> The raw material components shown in Table 1 were mixed in the mass ratio shown in Table 1 to obtain a mixed solution. The resulting mixed solution was then charged into a thermal polymerization apparatus (manufactured by Toyo Koatsu). The mixed solution was then heated to 270°C at a heating rate of 5°C / min and maintained for 180 minutes. It was then quenched with cooling water to obtain a thermally polymerized resin solution. The resulting thermally polymerized resin solution was subjected to light matter removal (distillation) to remove unreacted materials and components with a low degree of polymerization, thereby obtaining a polymer (thermally polymerized product (A-1)).

[0113] <Production of petroleum resin (B-1)> The thermally polymerized product (A-1) was placed in a rotary evaporator (manufactured by AS ONE Co., Ltd.) placed on an oil bath at 250° C., and further polymerization was carried out for 5 hours to obtain a polymer (petroleum resin (B-1)).

[0114] (Example 1-2) <Production of petroleum resin (B-2)> The thermally polymerized product (A-1) was placed in a rotary evaporator (manufactured by AS ONE Co., Ltd.) placed on an oil bath at 250° C., and further polymerization was carried out for 5.5 hours to obtain a polymer (petroleum resin (B-2)).

[0115] (Comparative Example 1-1) <Production of petroleum resin (Y-1)> The raw material components shown in Table 1 were mixed in the mass ratio shown in Table 1 to obtain a mixed solution. The resulting mixed solution was then charged into a thermal polymerization apparatus (manufactured by Toyo Koatsu). The mixed solution was then heated to 270°C at a heating rate of 5°C / min and maintained for 270 minutes. It was then quenched with cooling water to obtain a thermally polymerized resin solution. The resulting thermally polymerized resin solution was subjected to light fraction removal (distillation) to remove unreacted materials and components with a low degree of polymerization, thereby obtaining a polymer (petroleum resin (Y-1)).

[0116] (Comparative Example 1-2) <Production of petroleum resin (Y-2)> The raw material components shown in Table 1 were mixed in the mass ratio shown in Table 1 to obtain a mixed solution. The resulting mixed solution was then charged into a thermal polymerization apparatus (manufactured by Toyo Koatsu). The mixed solution was then heated to 270°C at a heating rate of 5°C / min and maintained for 310 minutes. It was then quenched with cooling water to obtain a thermally polymerized resin solution. The resulting thermally polymerized resin solution was subjected to light matter removal (distillation) to remove unreacted materials and components with a low degree of polymerization, thereby obtaining a polymer (petroleum resin (Y-2)).

[0117] [Table 1]

[0118] In addition, DCPD represents dicyclopentadiene in Table 1. Furthermore, as the diluent in Table 1, Hisol 100 (trade name, manufactured by ENEOS Corporation), which contains a C9 aromatic compound as a main component, was used.

[0119] The thermal polymers and petroleum resins produced in Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 were measured for softening point, iodine value, number average molecular weight, weight average molecular weight, and molecular weight distribution. The results are shown in Tables 2 and 3.

[0120] [Table 2]

[0121] [Table 3]

[0122] (Example 2-1) <Production of Uncrosslinked Rubber Composition (C-1)> The following components were kneaded using a 250 mL kneader (Labo Plastomill, manufactured by Toyo Seiki Seisakusho) to obtain a rubber composition. The details of the kneading operation carried out are as follows (i) to (iii). (i) Mixer kneading: The rubber was put into an internal pressure kneader heated to 130°C, and masticated at 30 rpm for 1 minute, after which 1 / 2 of the mixture of carbon black, zinc oxide, stearic acid and antioxidant was weighed out and the entire amount of petroleum resin (B-1) was put in, and the rotation speed was increased to 50 rpm and kneaded for 1 minute 30 seconds. The remaining 1 / 2 of the mixture of carbon black, zinc oxide, stearic acid and antioxidant was added, and kneading was continued for 1 minute 30 seconds, after which the ram (floating weight) was raised and the powder of the mixture of carbon black, zinc oxide, stearic acid and antioxidant attached to the periphery was put into the kneaded material using a brush, and kneading was continued for another 1 minute, after which the ram was raised again and the powder of the mixture of carbon black, zinc oxide, stearic acid and antioxidant attached to the periphery was put into the kneaded material using a brush, and kneaded for another 3 minutes and then discharged. (ii) Remilling: In order to improve the dispersion of the filler, the kneaded material obtained in (i) above, which had been released and had cooled sufficiently, was further kneaded at 50 rpm for 2 minutes in an internal pressure kneader heated to 120°C, and then released. (iii) Roll mixing (addition of vulcanization system): After the temperature had sufficiently dropped after release, sulfur, a vulcanization accelerator, etc. were added to the above-mentioned kneaded material using two rolls, and the mixture was kneaded to obtain a rubber composition. Rubber (natural rubber, RSS#3): 100 parts by weight Carbon black (manufactured by Tokai Carbon, product name: Seast 7HM): 60 parts by weight Zinc oxide No. 3 (manufactured by Toho Zinc Co., Ltd., product name: Ginrei R): 3 parts by weight Stearic acid (manufactured by Shin Nippon Rika, product name: Stearic Acid 300): 1 part by weight Anti-aging agent (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Nocrac 6C): 1 part by weight ·Petroleum resin (B-1): 5 parts by mass Sulfur (Hosoi Chemicals, 5% oil-treated sulfur): 2 parts by weight Vulcanization accelerator (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccela CZ): 1 part by mass <Production of crosslinked rubber> The obtained uncrosslinked rubber composition (C-1) was placed in a mold (150 mm×150 mm×1 mm) and heated and pressed at 150° C. for 10 minutes to obtain a crosslinked rubber sheet having a thickness of 1 mm.

[0123] (Example 2-2) <Production of Uncrosslinked Rubber Composition (C-2)> Except for using the petroleum resin (B-2) instead of the petroleum resin (B-1), the uncrosslinked rubber composition (C-2) was obtained in the same manner as in Example 2-1 <Production of uncrosslinked rubber composition (C-1)>. <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Example 2-1, except that the uncrosslinked rubber composition (C-2) was used instead of the uncrosslinked rubber composition (C-1).

[0124] (Comparative Example 2-1) <Production of Uncrosslinked Rubber Composition (Z-1)> Except for using the thermal polymer (A-1) instead of the petroleum resin (B-1), the uncrosslinked rubber composition (Z-1) was obtained in the same manner as in Example 2-1 <Preparation of uncrosslinked rubber composition (C-1)>. <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Example 2-1, except that the uncrosslinked rubber composition (C-1) was replaced with the uncrosslinked rubber composition (Z-1).

[0125] (Comparative Example 2-2) <Production of Uncrosslinked Rubber Composition (Z-2)> Except for using extender oil (TDAE) instead of petroleum resin (B-1), the same procedure as in Example 2-1 <Production of uncrosslinked rubber composition (C-1)> was followed to obtain uncrosslinked rubber composition (Z-2). <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Example 2-1, except that the uncrosslinked rubber composition (Z-2) was used instead of the uncrosslinked rubber composition (C-1).

[0126] (Comparative Example 2-3) <Production of Uncrosslinked Rubber Composition (Z-3)> An uncrosslinked rubber composition (Z-3) was obtained in the same manner as in <Production of uncrosslinked rubber composition (C-1)> in Example 2-1, except that the petroleum resin (B-1) was not blended. <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Example 2-1, except that the uncrosslinked rubber composition (C-1) was replaced with the uncrosslinked rubber composition (Z-3).

[0127] The crosslinked rubber sheets obtained in Example 2-1, Example 2-2, Comparative Example 2-1, Comparative Example 2-2, and Comparative Example 2-3 were subjected to a tear test by the following method to determine the tear strength. The results are shown in Table 4.

[0128] (Tear test) Test pieces (angle shapes without notches) were punched out from the crosslinked rubber sheets using a punching die. The punched out samples were then subjected to a tear test at a tensile speed of 500 mm / min in accordance with JIS K6252:2007. The results are shown in Table 4.

[0129] [Table 4]

[0130] (Reference example 1) <Production of Uncrosslinked Rubber Composition (R-1)> The following components were kneaded using a 250 mL kneader (Labo Plastomill, manufactured by Toyo Seiki Seisakusho) to obtain a rubber composition. The details of the kneading operation carried out are as follows (i) to (iii). (i) Mixer kneading: The rubber was put into an internal pressure kneader heated to 135°C, and masticated at 30 rpm for 1 minute, after which 1 / 2 of the mixture of silica, zinc oxide, stearic acid and antioxidant was weighed out and the entire amount of the silane coupling agent and petroleum resin (B-1) was put in, the rotation speed was increased to 50 rpm, and kneading was continued for 1 minute 30 seconds. The remaining 1 / 2 of the mixture of silica, zinc oxide, stearic acid and antioxidant was added, and kneading was continued for 1 minute 30 seconds, after which the ram (floating weight) was raised and the powder of the mixture of silica, zinc oxide, stearic acid and antioxidant attached to the periphery was put into the kneaded material using a brush, and kneading was continued for another 1 minute, after which the ram was raised again and the powder of the mixture of silica, zinc oxide, stearic acid and antioxidant attached to the periphery was put into the kneaded material using a brush, and then kneaded for another 3 minutes and released. (ii) Remilling: In order to improve the dispersion of the filler, the kneaded material obtained in (i) above, which had been released and had cooled sufficiently, was further kneaded at 50 rpm for 2 minutes in an internal pressure kneader heated to 120°C, and then released. (iii) Roll mixing (addition of vulcanization system): After the temperature had sufficiently dropped after release, sulfur, a vulcanization accelerator, etc. were added to the above-mentioned kneaded material using two rolls, and the mixture was kneaded to obtain a rubber composition. Rubber (SBR, 1502): 100 parts by weight Silica (Tosoh Corporation, Nipsil AQ): 40 parts by weight Zinc oxide No. 3 (manufactured by Toho Zinc Co., Ltd., product name: Ginrei R): 3 parts by weight Stearic acid (manufactured by Shin Nippon Rika, product name: Stearic Acid 300): 1 part by weight Anti-aging agent (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Nocrac 6C): 1 part by weight ·Petroleum resin (B-1): 5 parts by mass Silane coupling agent (Osaka Soda Co., Ltd., product name: Kabras 4): 3.2 parts by mass Sulfur (Hosoi Chemicals, 5% oil-treated sulfur): 2 parts by weight Vulcanization accelerator (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccela CZ): 1.5 parts by mass Vulcanization accelerator (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccelaer D): 1.5 parts by mass <Production of crosslinked rubber> The obtained uncrosslinked rubber composition (R-1) was placed in a mold (150 mm×150 mm×1 mm) and heated and pressed at 160° C. for 15 minutes to obtain a crosslinked rubber sheet having a thickness of 1 mm.

[0131] (Reference example 2) <Production of Uncrosslinked Rubber Composition (R-2)> An uncrosslinked rubber composition (R-2) was obtained in the same manner as in <Production of uncrosslinked rubber composition (R-1)> of Reference Example 1, except that the petroleum resin (B-2) was used instead of the petroleum resin (B-1). <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Reference Example 1, except that the uncrosslinked rubber composition (R-2) was used instead of the uncrosslinked rubber composition (R-1).

[0132] (Reference example 3) <Production of Uncrosslinked Rubber Composition (R-3)> An uncrosslinked rubber composition (R-3) was obtained in the same manner as in <Production of uncrosslinked rubber composition (R-1)> of Reference Example 1, except that the thermal polymer (A-1) was used instead of the petroleum resin (B-1). <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Reference Example 1, except that the uncrosslinked rubber composition (R-3) was used instead of the uncrosslinked rubber composition (R-1).

[0133] (Reference example 4) <Production of Uncrosslinked Rubber Composition (R-4)> An uncrosslinked rubber composition (R-4) was obtained in the same manner as in Reference Example 1 <Production of uncrosslinked rubber composition (R-1)>, except that extending oil (TDAE) was used instead of petroleum resin (B-1). <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Reference Example 1, except that the uncrosslinked rubber composition (R-4) was used instead of the uncrosslinked rubber composition (R-1).

[0134] (Reference example 5) <Production of Uncrosslinked Rubber Composition (R-5)> An uncrosslinked rubber composition (R-5) was obtained in the same manner as in <Production of uncrosslinked rubber composition (R-1)> of Reference Example 1, except that the petroleum resin (B-1) was not blended. <Production of crosslinked rubber> A crosslinked rubber sheet was produced in the same manner as in Reference Example 1, except that the uncrosslinked rubber composition (R-5) was used instead of the uncrosslinked rubber composition (C-1).

[0135] The crosslinked rubber sheets obtained in Reference Examples 1 to 5 were subjected to the tear test by the above-mentioned method to determine the tear strength. The results are shown in Table 5.

[0136] [Table 5]

Claims

1. A rubber additive containing a petroleum resin, The petroleum resin is a polymer of a raw material component including a C9 fraction containing an aromatic olefin and dicyclopentadiene, In the raw material components, a ratio C2 / C1 (mass ratio) of a content C2 of the aromatic olefin to a content C1 of the dicyclopentadiene is 0.35 or more and 0.5 or less, The rubber additive, wherein the softening point of the petroleum resin is 155°C or higher.

2. 2. The rubber additive according to claim 1, which is an isoprene-based rubber additive.

3. The rubber additive according to claim 2, which is an additive for natural rubber.

4. The rubber composition contains a rubber component containing an isoprene-based rubber, a rubber cross-linking agent, and a petroleum resin, The petroleum resin is a polymer of a raw material component including a C9 fraction containing an aromatic olefin and dicyclopentadiene, In the raw material components, a ratio C2 / C1 (mass ratio) of a content C2 of the aromatic olefin to a content C1 of the dicyclopentadiene is 0.35 or more and 0.5 or less, The uncrosslinked rubber composition, wherein the petroleum resin has a softening point of 155°C or higher.

5. A crosslinked rubber obtained by crosslinking the uncrosslinked rubber composition according to claim 4.

6. A method for producing a petroleum resin, comprising the steps of: A first step of thermally polymerizing a raw material component including a C9 fraction containing aromatic olefins and dicyclopentadiene to obtain a thermal polymer having a softening point lower than that of the petroleum resin; a second step of heating the thermally polymerized product to obtain a petroleum resin; Including, The content C of the dicyclopentadiene in the raw material component １ The aromatic olefin content C ２ Ratio C ２ / C １ (mass ratio) is 0.35 or more and 0.5 or less, The softening point of the petroleum resin is 155°C or higher. A method for producing petroleum resin.

7. An additive for tread rubber containing a petroleum resin, The petroleum resin is a thermal polymerization product of a raw material component including a C9 fraction containing an aromatic olefin and dicyclopentadiene, The content C of the dicyclopentadiene in the raw material component １ The content C of the aromatic olefin ２ Ratio C ２ / C １ (mass ratio) is 0.35 or more and 0.5 or less, The petroleum resin has a softening point of 155° C. or higher.

8. The tread rubber additive according to claim 7, which is a tread rubber additive for large tires.

9. An uncrosslinked rubber composition for forming a tread rubber, comprising a rubber component containing an isoprene-based rubber, a crosslinking agent for rubber, and the additive for a tread rubber according to claim 7 or 8.

10. A tread rubber obtained by crosslinking the uncrosslinked rubber composition for treads according to claim 9.

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