JP7570883B2 - Rubber composition for crosslinking and tire tread - Google Patents

Description

The present invention relates to a rubber composition for crosslinking and a tire tread.

In recent years, in the field of rubber materials for tire treads, sheets, films, and asphalt modification, crosslinkable rubber compositions containing rubber-like polymers having an ethylene structure and incorporating crosslinkable unsaturated groups have been proposed for the purpose of increasing mechanical strength and compression set (see, for example, Patent Documents 1 to 5).

International Publication No. WO 2003/085010 JP 2010-270314 A International Publication No. 2019/151126 International Publication No. 2019/151127 International Publication No. 2019/078083

However, conventionally proposed rubber compositions for crosslinking that have an ethylene structure and contain a rubber-like polymer having a crosslinkable unsaturated group tend to have a high Mooney viscosity, making them difficult to knead and resulting in poor processability of the rubber composition for crosslinking. As a result, the rubber material obtained tends to have low tensile energy and low abrasion resistance.

The present invention aims to provide a crosslinkable rubber composition that contains a rubber-like polymer having an ethylene structure and a crosslinkable unsaturated group, and that exhibits good processability and can give molded articles having sufficient tensile energy and abrasion resistance.

As a result of intensive research and investigation into solving the problems of the conventional techniques described above, the present inventors have found that a crosslinkable rubber composition containing a rubber-like polymer (A) having an iodine value, an ethylene structure, and an amount of vinyl aromatic blocks specified within predetermined numerical ranges, a crosslinking agent (B), and a ring-containing resin (C) having a predetermined softening point can solve the problems of the conventional techniques described above, and have thus completed the present invention.
That is, the present invention is as follows.

[1]
a rubber-like polymer (A) having an iodine value of 10 to 250 (g/100 g), an ethylene structure of 3 mass% or more, a vinyl aromatic monomer unit content of 5 mass% or more and 30 mass% or less, and a vinyl aromatic monomer block having 8 or more chained vinyl aromatic monomer units of less than 10 mass%;
A crosslinking agent (B);
A hydrogenated ring-containing resin (C) having a softening point of less than 140° C.;
A crosslinkable rubber composition comprising:
The rubber-like polymer (A) has a weight average molecular weight of 250,000 or more and 1,000,000 or less,
The rubber-like polymer (A) has a modification rate of 70% by mass or more as measured by a column adsorption GPC method,
the content of the rubber-like polymer (A) relative to the total amount of rubber components in the rubber composition for crosslinking is 20 mass% or more,
the content of the ring-containing resin (C) is 30 parts by mass or less based on 100 parts by mass of the total amount of rubber components in the rubber composition for crosslinking,
The rubber composition for crosslinking further contains silica and oil,
The ratio of the amount of silica (parts by mass)/the amount of oil (parts by mass) relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking is 6 or more.
Crosslinkable rubber composition .
[2]
The rubber composition for crosslinking according to the above [1] , wherein the content of vinyl units and butylene units in the rubber-like polymer (A) is 20 mol % or more.
[3]
The rubber composition for crosslinking according to the above [1] or [2] , wherein the rubber-like polymer (A) contains a nitrogen atom.
[4]
The rubber composition for crosslinking according to any one of [1] to [3] above, wherein the hydrogenated ring-containing resin (C) having a softening point of less than 140° C. has a softening point of 90° C. or higher.
[5]
Relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking,
The rubber composition for crosslinking according to any one of [1] to [4] above, containing 10 to 30 parts by mass of a hydrogenated ring-containing resin (C) having a softening point of less than 140° C.
[6]
the amount (parts by mass) of the hydrogenated ring-containing resin (C) having a softening point of less than 140° C. relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking/the content (ST) (% by mass) of the vinyl aromatic monomer unit in the rubber polymer (A) is
The rubber composition for crosslinking according to any one of [1] to [5] above, wherein the modulus is 0.3 or more.
[7]
The hydrogenated ring-containing resin (C) having a softening point of less than 140° C. is a partially hydrogenated resin and/or
or a hydrogenated terpene resin.
[8]
The rubber composition for crosslinking contains 1 to 8 parts by mass of a plant-derived oil relative to 100 parts by mass of the rubber component.
8. The crosslinkable rubber composition according to any one of [1] to [7] , further comprising:
[9]
The rubber composition for crosslinking according to any one of [1] to [8] , further comprising 10 to 130 parts by mass of silica per 100 parts by mass of the rubber component in the rubber composition for crosslinking.
[10]
A tire tread comprising the rubber composition for crosslinking according to any one of [1] to [9] above.

The present invention provides a crosslinkable rubber composition that has good processability, can be thoroughly kneaded, and can produce molded articles with sufficient tensile energy and abrasion resistance.

Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail.
It should be noted that the following embodiment is merely an example for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be practiced with appropriate modifications within the scope of the gist of the present invention.

[Rubber composition for crosslinking]
The crosslinkable rubber composition of the present invention comprises
A rubber-like polymer (A) having an iodine value of 10 to 250 (g/100 g), an ethylene structure of ≧3 mass %, and a vinyl aromatic monomer block of <10 mass %, and a crosslinking agent (B);
It contains a hydrogenated ring-containing resin (C) having a softening point of less than 140°C.
The above-mentioned constitution provides a rubber composition for crosslinking which has good processability and gives a molded article having sufficient tensile energy and abrasion resistance.

(Rubber Polymer (A))
The rubber-like polymer (A) contained in the crosslinkable rubber composition of the present embodiment has an iodine value of 10 to 250 (g/100 g), an ethylene structure of ≧3 mass%, and a vinyl aromatic monomer block content of <10 mass%.

<Iodine value>
The rubber-like polymer (A) has an iodine value of 10 to 250 (g/100 g).
The iodine value is, from the viewpoints of co-crosslinkability when the rubber-like polymer (A) is used in a rubber composition for crosslinking and flexibility when made into a tire, 10 (g/100 g) or more, preferably 15 (g/100 g) or more, more preferably 30 (g/100 g) or more, and even more preferably 50 (g/100 g) or more.
On the other hand, from the viewpoint of mechanical strength and abrasion resistance when used as a tire material, the molecular weight is set to 250 (g/100g) or less, preferably 200 (g/100g) or less, more preferably 150 (g/100g) or less, even more preferably 100 (g/100g) or less, and even more preferably 70 (g/100g) or less.
The iodine value can be measured according to the method described in "JIS K 0070:1992".
The iodine value is a value that represents the amount of halogen that reacts with 100 g of a target substance converted into the number of grams of iodine, and therefore the unit of the iodine value is "g/100 g".
For example, in the production method of a rubber-like polymer described below, when a conjugated diene monomer and a vinyl aromatic monomer are copolymerized, the iodine value of the rubber-like polymer decreases as the content of the conjugated diene monomer decreases, since the conjugated diene monomer has a double bond. Also, when the conjugated diene monomer is hydrogenated, the iodine value decreases as the hydrogenation rate increases.
The iodine value of the rubber-like polymer (A) can be controlled within the above-mentioned numerical range by adjusting the polymerization conditions such as the amount of the conjugated diene monomer having an unsaturated bond added, the polymerization time, the polymerization temperature, and the amount of hydrogen added in the hydrogenation step, the hydrogenation time, and other conditions.

<Content of ethylene structure>
The rubber-like polymer (A) used in the crosslinking rubber composition of the present embodiment has an ethylene structure of 3 mass % or more (ethylene structure ≧3 mass %).
By having the ethylene structure of 3% by mass or more, the effect of preventing the tensile strength of the crosslinking rubber composition using the rubber-like polymer (A) from decreasing can be obtained. The ethylene structure is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 40% by mass or more.
The ethylene structure is preferably 90% by mass or less, more preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.
When the ethylene structure in the rubber-like polymer (A) is 90% by mass or less, excellent rubber elasticity is obtained.
The ethylene structure in the rubber polymer (A) includes all ethylene structures obtained by copolymerizing ethylene monomers, ethylene structures obtained by polymerizing conjugated diene monomers and then hydrogenating them, etc. For example, when a 1,4-butadiene unit is hydrogenated, two ethylene structures are obtained, and when a 1,4-isoprene unit is hydrogenated, one propylene structure and one ethylene structure are obtained.
The ethylene structure of the rubber-like polymer (A) can be measured by the method described in the Examples below, and can be controlled to be within the above-mentioned numerical range by adjusting the amount of ethylene added, the amount of conjugated diene monomer added, the hydrogenation rate, etc.

<Vinyl aromatic monomer block content>
The rubber-like polymer (A) used in the crosslinkable rubber composition of this embodiment has a vinyl aromatic monomer block content of less than 10 mass % (vinyl aromatic monomer block < 10 mass %).
The rubber-like polymer (A) refers to a block in which eight or more vinyl aromatic monomer units are linked together.
When the vinyl aromatic monomer block content of the rubber-like polymer (A) is less than 10 mass %, fuel economy tends to be improved when the crosslinkable rubber composition of the present embodiment is used as a raw material for tires.
The aromatic vinyl monomer block content of the rubbery polymer (A) is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.
From the viewpoint of flexibility, it is preferred that the vinyl aromatic monomer block has a small number of blocks in which 30 or more vinyl aromatic monomer units are chained, or that there is no such block.
Specifically, when the copolymer is a butadiene-styrene copolymer, the morphology of the vinyl aromatic monomer block can be determined by decomposing the polymer by the Kolthoff method (the method described in I.M. KOLTHOFF, et al., J. Polym. Sci. 1, 429 (1946)) and analyzing the amount of polystyrene insoluble in methanol. As another method, the morphology can be determined by a known method such as measuring the chain of styrene units using NMR, as described in International Publication No. 2014-133097.
The vinyl aromatic monomer block content of the rubbery polymer (A) can be controlled within the above numerical range by adjusting the method of adding the vinyl aromatic monomer, the addition of a polymerization aid, the polymerization temperature, etc.

<Content of Vinyl Aromatic Monomer Units in Rubber Polymer (A)>
The content of vinyl aromatic monomer units in the rubber-like polymer (A) used in the crosslinkable rubber composition of this embodiment is preferably 5 mass % or more, more preferably 10 mass % or more, even more preferably 15 mass % or more, and even more preferably 20 mass % or more, from the viewpoints of deformation resistance during transportation of a molded body and breaking strength and wet skid resistance when used in a tire tread.
On the other hand, from the viewpoints of cuttability during measurement of the sheet-like or block-like molded body, adhesion of the packaging film, and resistance to tearing of the packaging film, and further from the viewpoints of fuel economy and abrasion resistance when used in a tire tread, the content is preferably 45% by mass or less, and further from the viewpoint of compatibility with the hydrogenated resin (C), the content is more preferably 30% by mass or less, and even more preferably 25% by mass or less.
The content of the vinyl aromatic monomer units in the rubber-like polymer (A) can be measured by the method described in the Examples below, and can be controlled within the above-mentioned numerical range by adjusting the amount of the vinyl aromatic monomer added in the polymerization step.

<Vinyl Unit and Butylene Unit Contents of Rubber Polymer (A)>
The rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment preferably has a vinyl unit and butylene unit content of 20 mol % or more.
The content of vinyl units and butylene units is preferably 20 mol % or more, more preferably 25 mol % or more, and even more preferably 30 mol % or more, from the viewpoints of the manufacturability of the rubber polymer (A), the processability of the crosslinkable rubber composition of the present embodiment, and the wet skid resistance when used in a tire tread.
From the viewpoints of heat aging resistance of the rubber polymer (A) and fuel economy when used in a tire tread, it is preferably 60 mol % or less, more preferably 50 mol % or less, and even more preferably 45 mol % or less.
The contents of vinyl units and butylene units in the rubber-like polymer (A) can be measured by ¹ H-NMR measurement in the Examples.
The vinyl unit and butylene unit contents of the rubbery polymer (A) can be controlled within the above numerical ranges by adding a polar compound or adjusting the polymerization temperature during polymerization of the rubbery polymer (A).

<Monomer Units That Allow the Rubber Polymer (A) to Contain an Unsaturated Group>
The rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment preferably contains 2 mass % or more of conjugated diene monomer units or monomer units having an unsaturated group such as myrcene.
From the viewpoints of economy and productivity, the rubber-like polymer (A) more preferably contains a conjugated diene monomer unit.
When the rubber polymer (A) contains a conjugated diene monomer unit or myrcene as a component, the conjugated diene monomer unit or myrcene has a double bond, and therefore the resulting rubber polymer (A) also has a double bond, which becomes a crosslinkable unsaturated group.
The content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene in the rubber polymer (A) is closely related to the above-mentioned iodine value.
The content of the conjugated diene monomer unit or the monomer unit having an unsaturated group such as myrcene is 2% by mass or more, which is excellent in terms of ease of crosslinking. The content of the conjugated diene monomer unit is more preferably 3% by mass or more, and further preferably 6% by mass or more.
The content of the conjugated diene monomer unit or the monomer unit having an unsaturated group such as myrcene is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less, which provides excellent weather resistance and resistance to deterioration over time.
Of the conjugated diene monomer units and monomer units having an unsaturated group such as myrcene, the conjugated diene monomer units are preferred from the viewpoints of economy and productivity.
The content of the conjugated diene monomer units and monomer units having an unsaturated group such as myrcene in the rubber-like polymer (A) can be measured by the method for measuring the "hydrogenation ratio" described in the Examples below, and can be controlled to within the above-mentioned numerical range by adjusting the amount of the conjugated diene monomer units and monomers having an unsaturated group such as myrcene added or the hydrogenation ratio of the conjugated diene monomer, which will be described later.

<Content of α-olefin in rubber polymer (A)>
The content of α-olefin in all monomer units excluding vinyl aromatic monomer units in the rubbery polymer (A) is preferably 13 mass% or more, more preferably 20 mass% or more, and even more preferably 30 mass% or more, from the viewpoint of productivity of the rubbery polymer.
On the other hand, from the viewpoint of mechanical strength when used in a tire, it is preferably 70 mass % or less, more preferably 60 mass % or less, even more preferably 55 mass % or less, and even more preferably 50 mass % or less.
When the rubber polymer (A) is produced by hydrogenating a polymer or copolymer of a conjugated diene monomer, the α-olefin content can be controlled by adjusting the conjugated diene monomer content, the vinyl bond content, or the hydrogenation rate before the hydrogenation reaction.
When 1,2-vinylbutadiene is hydrogenated, it becomes butylene, which has an α-olefin structure.
The α-olefin content of the rubbery polymer (A) can be measured by ¹ H-NMR measurement in the Examples.

<Modification of the rubber-like polymer (A) constituting the crosslinkable rubber composition>
In the crosslinkable rubber composition of this embodiment, from the viewpoints of the peel resistance of the crosslinkable rubber composition from a molded article of the crosslinkable rubber composition and the fuel economy when made into a tire, it is preferable that the rubber-like polymer (A) contains a nitrogen atom or a tin atom, and it is more preferable that it contains a nitrogen atom.

The rubber-like polymer (A) used in the cross-linking rubber composition of this embodiment preferably has a modification rate of 40 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, as measured by a column adsorption GPC method, from the viewpoints of the mechanical strength of the cross-linking rubber composition and dispersibility when produced into a tire using silica or carbon black.
In this specification, the "modification ratio" represents the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the rubber-like polymer (A).
The position at which the nitrogen atom is introduced into the rubber polymer (A) used in the crosslinkable rubber composition of this embodiment may be any of the polymerization initiation terminal, the molecular chain (including the graft product), and the polymerization terminal of the rubber polymer (A).
The modification rate can be controlled within the above-mentioned range by adjusting the amount of the modifier added to the rubber-like polymer and the modification process time.

When the rubber-like polymer (A) used in the crosslinking rubber composition of this embodiment is produced by polymerizing a conjugated diene monomer and then hydrogenating it, it is preferable to adopt a method of introducing tin atoms or nitrogen atoms into the polymer using a coupling agent containing tin atoms or nitrogen atoms, from the viewpoints of polymerization productivity, high modification rate, and wear resistance and fuel economy when made into a tire. In particular, it is more preferable to adopt a method of introducing nitrogen atoms into the polymer using a coupling agent containing nitrogen atoms.

As the nitrogen atom-containing coupling agent, from the viewpoints of polymerization productivity and a high modification rate, an isocyanate compound, an isothiocyanate compound, an isocyanuric acid derivative, a nitrogen group-containing carbonyl compound, a nitrogen group-containing vinyl compound, a nitrogen group-containing epoxy compound, a nitrogen group-containing alkoxysilane compound, and the like are preferred.
Of these nitrogen atom-containing coupling agents, nitrogen group-containing alkoxysilane compounds are more preferred from the viewpoints of polymerization productivity of the rubber polymer (A), high modification rate, and tensile strength when made into a tire.

Examples of nitrogen-containing alkoxysilane compounds include, but are not limited to, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, 2,2-dimethoxy-1-( 2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy,2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy,2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, and 2- Ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, and tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-azacyclopentane, These include N1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N1-methyl-N3-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N3-(3-(trimethoxysilyl)propyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N1-methyl-N3-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N3-(3-(trimethoxysilyl)propyl)-1,3-propanediamine.

When the rubber-like polymer (A) used in the crosslinkable rubber composition of this embodiment is produced by copolymerizing ethylene and a conjugated diene monomer, it preferably contains a tin atom, a nitrogen atom, or a silicon atom from the viewpoints of the breaking strength of the crosslinkable rubber composition and the fuel economy, abrasion resistance, and flexibility when made into a tire.
From the viewpoint of the productivity of the rubber-like polymer (A), it is preferable to employ a method in which, when the conversion rate of the polymerization reaction reaches 100%, a coupling agent containing a tin atom, a nitrogen atom, or a silicon atom is used to introduce these atoms into the polymer.
Examples of coupling agents containing a tin atom, a nitrogen atom, or a silicon atom include tin-containing compounds such as bis(1-octadecyl maleate)dioctyl tin, isocyanate compounds such as 4,4-diphenylmethane diisocyanate, and alkoxysilane compounds such as glycidylpropyltrimethoxysilane.

<Glass Transition Temperature of Rubber Polymer (A)>
The glass transition temperature of the rubber polymer (A) used in the crosslinkable rubber composition of the present embodiment is preferably −90° C. or higher, more preferably −80° C. or higher, and even more preferably −75° C. or higher, from the viewpoint of the tensile strength of the crosslinkable composition.
On the other hand, from the viewpoints of flexibility of the rubber composition to be crosslinked and cut resistance of the sheet during tire production, the temperature is preferably −15° C. or lower, more preferably −30° C. or lower, and further preferably −40° C. or lower.
The glass transition temperature is measured in accordance with ISO 22768:2006 by recording a DSC curve while increasing the temperature within a predetermined temperature range, and the peak top (inflection point) of the DSC differential curve is determined as the glass transition temperature.

<Weight average molecular weight of rubber polymer (A)>
The weight average molecular weight of the rubber-like polymer (A) used in the crosslinkable rubber composition of this embodiment is, from the viewpoints of compatibility with the crosslinkable rubber composition and the tensile elongation of the crosslinkable rubber composition, preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and even more preferably 250,000 or more.
On the other hand, from the viewpoint of processability of the rubber composition for crosslinking, it is preferably 1,000,000 or less, more preferably 700,000 or less, even more preferably 600,000 or less, and even more preferably 500,000 or less.
The molecular weight distribution (= weight average molecular weight/number average molecular weight) of the rubber-like polymer (A) used in the crosslinking rubber composition of this embodiment is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.6 or less, from the viewpoint of compatibility with the crosslinking rubber composition and fuel saving when used in a tire. On the other hand, from the viewpoint of processability of the crosslinking rubber composition, it is preferably 1.05 or more, more preferably 1.2 or more, and even more preferably 1.4 or more.
The weight average molecular weight and the molecular weight distribution can be calculated from the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography).
The weight average molecular weight and molecular weight distribution of the rubber-like polymer (A) can be controlled within the above-mentioned numerical ranges by adjusting various polymerization conditions such as the amount of monomer added in the polymerization step, polymerization time, polymerization temperature, polymerization pressure, etc.

The rubber-like polymer (A) used in the crosslinking rubber composition of this embodiment may have two or more (co)polymer blocks having different composition ratios of vinyl aromatic monomer, ethylene, α-olefin, and conjugated diene monomer from the viewpoint of compatibility with the crosslinking rubber composition, flexibility over a wide range from low to high temperatures, and the like. From the viewpoint of flexibility, the amount of vinyl aromatic monomer in the (co)polymer block is preferably 60 mass% or less, more preferably 50 mass% or less, and even more preferably 40 mass% or less.

(Method for producing rubber polymer (A))
The rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment is preferably produced by polymerizing or copolymerizing at least a conjugated diene monomer and then hydrogenating (adding hydrogen) a part or most of the double bonds, or by copolymerizing at least ethylene and a conjugated diene monomer.

Examples of methods for polymerizing or copolymerizing at least a conjugated diene monomer and then hydrogenating it include methods of polymerizing a conjugated diene monomer by anionic polymerization under various additives and conditions, copolymerizing it with other monomers as necessary, and then hydrogenating it, as described in, for example, WO 96/05250, JP 2000-053706, WO 2003/085010, WO 2019/151126, WO 2019/151127, WO 2002/002663, and WO 2015/006179.

As a method for copolymerizing at least ethylene and a conjugated diene monomer, for example, as described in WO 2019/078083, WO 2019/171679, and WO 2019/142501, there is a method in which ethylene, a conjugated diene monomer, and, if necessary, other monomers are added and copolymerized by coordination polymerization under various additives and conditions.

From the viewpoint of the degree of freedom in the structures that can be produced, it is preferable that the rubber-like polymer (A) is obtained by polymerizing a conjugated diene monomer and then hydrogenating it.

Examples of conjugated diene monomers include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene.
Among these, from the viewpoint of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.
These may be used alone or in combination of two or more.

As the monomer constituting the rubber-like polymer (A), a vinyl aromatic monomer can also be used.
Examples of vinyl aromatic monomers include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene).
Among these, styrene is preferred from the viewpoint of industrial availability.
These may be used alone or in combination of two or more.

In addition to the above-mentioned monomers, other monomers may be used as the rubber polymer (A) if necessary.
Examples of other monomers used as necessary include, but are not limited to, unsaturated carboxylic acid esters, unsaturated carboxylic acids, α,β-unsaturated nitrile compounds, α-olefins (butylene, propylene, butylene, pentene, hexene, etc.), ethylene, myrcene, ethylidene norbornene, isopropylidene norbornene, cyclopentadiene, and divinylbenzene.

When the rubber-like polymer (A) used in the crosslinking rubber composition of the present embodiment is produced by polymerizing or copolymerizing a conjugated diene monomer and then hydrogenating the polymer, the vinyl bond amount of the conjugated diene monomer unit of the conjugated diene-based polymer before hydrogenation is important, and the vinyl bond amount in the conjugated diene monomer unit is preferably 10 mol% or more, more preferably 20 mol% or more, from the viewpoint of productivity of the rubber-like polymer (A) and high wet skid resistance when made into a tire. Also, from the viewpoint of mechanical strength when used in a tire, it is preferably 75 mol% or less, more preferably 60 mol% or less, even more preferably 45 mol% or less, and even more preferably 30 mol% or less.
The vinyl bond content can be measured by the method described in the Examples below.

The above polymerization and hydrogenation steps may each be carried out in a batch or continuous manner.

The hydrogenation rate of the rubber-like polymer (A) and the inter- and intra-molecular distribution of monomers such as ethylene, conjugated diene monomer, myrcene, α-olefin, and vinyl aromatic monomer are not particularly limited, and may be uniform, non-uniform, or distributed.

(Addition of additives to rubber polymer (A))
During the production of the rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment, it is preferable to add various additives to prepare a rubber composition.

<Rubber softener>
For example, in order to improve the productivity of the rubber polymer (A) and the processability when an inorganic filler or the like is blended during tire production, 1 to 30% by mass of a rubber softener may be added. When the molecular weight of the rubber polymer (A) is high, for example when the weight average molecular weight exceeds 1,000,000, the rubber softener is preferably used in an amount of 15 to 30% by mass, while in order to expand the degree of freedom in blending when a composition is formed by blending a filler, it is preferably used in an amount of 1 to 15% by mass.
The content of the rubber softener in the rubber composition containing the rubber-like polymer (A) is more preferably 20 mass % or less, even more preferably 10 mass % or less, and even more preferably 5 mass % or less, from the viewpoint of aging deterioration characteristics when made into a tire.
The rubber softener is not particularly limited, but examples thereof include extender oil, liquid rubber, and resin.
As the rubber softener, an extender oil is preferred from the viewpoints of processability, productivity, and economic efficiency.
The method of adding a rubber softener to a conjugated diene polymer is not limited to the following, but a preferred method is to add a rubber softener to a polymer solution, mix, and remove the solvent from the resulting polymer solution containing the rubber softener.

<Extender oil>
From the viewpoints of processability, productivity and economic efficiency, it is preferable to add an extender oil to the rubber polymer (A).
Preferred examples of the extender oil include aromatic oil, naphthenic oil, and paraffinic oil.
Among these, from the viewpoint of environmental safety, oil bleeding prevention, and wet grip properties, aromatic alternative oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred. Examples of aromatic alternative oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts) shown in Kautschuk Gummi Kunststoffe 52(12)799(1999).

<Rubber stabilizer>
After the polymerization step of the rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment, a rubber stabilizer is preferably added from the viewpoints of preventing gel formation and improving processing stability.
The rubber stabilizer is not limited to the following, and known stabilizers can be used, such as antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

(Physical Properties of Rubber Polymer (A))
<Residual Solvent Amount>
In the rubber composition obtained by adding various additives to the rubber polymer (A) used in the crosslinking rubber composition of this embodiment, the residual solvent of the polymerization solvent used in the polymerization process of the rubber polymer (A) is preferably low from the viewpoint of odor and VOC reduction. It is preferably 5000 ppm or less, more preferably 3000 ppm or less, and even more preferably 1500 ppm or less. In addition, from the viewpoint of economic balance, it is preferably 50 ppm or more, more preferably 150 ppm or more, and even more preferably 300 ppm or more.

<Moisture content>
The water content in the rubber-like polymer (A) used in the crosslinking rubber composition of this embodiment, or in the rubber composition obtained by adding various additives to the rubber-like polymer (A), is preferably 0.05% by mass or more and 1.5% by mass or less. The water content in the rubber composition obtained by adding additives to the rubber-like polymer (A) is preferably 0.05% by mass or more from the viewpoint of gel suppression during drying after solvent removal. 0.1% by mass or more is more preferable, and 0.2% by mass or more is even more preferable. On the other hand, from the viewpoint of condensation suppression and discoloration resistance of the rubber composition, it is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.8% by mass or less.

<Mooney Viscosity>
The Mooney viscosity of the rubber-like polymer (A) used in the crosslinkable rubber composition of the present embodiment and of the rubber composition obtained by adding various additives to the rubber-like polymer (A) is an index including information such as the molecular weight, molecular weight distribution, degree of branching, softener, residual solvent, and water content of the rubber-like polymer (A).
The Mooney viscosity of the rubber polymer (A) and the rubber composition measured at 100° C. is preferably 40 or more, more preferably 50 or more, and even more preferably 55 or more, from the viewpoints of the abrasion resistance of the rubber composition for crosslinking of this embodiment, and the steering stability and breaking strength when made into a tire. On the other hand, from the viewpoints of the productivity of the rubber polymer (A) and the rubber composition, and the processability when made into a composition blended with a filler or the like, it is preferably 170 or less, more preferably 150 or less, even more preferably 130 or less, and even more preferably 110 or less.
The Mooney viscosity can be measured by the method specified in ISO289.

<Mooney relaxation rate>
From the viewpoint of moldability, the Mooney relaxation ratio (MSR) measured at 100°C of the rubber polymer (A) or a mixture of the rubber polymer (A) and at least one selected from the group consisting of a softener, an extender oil, and a stabilizer is preferably 0.80 or less, more preferably 0.7 or less, and even more preferably 0.6 or less.
When the rubber-like polymer (A) is distributed as a single substance, the Mooney relaxation coefficient can be measured as a single substance. When the rubber-like polymer (A) is distributed in a state containing a softener, an extender oil, and a stabilizer, the Mooney relaxation coefficient is measured in the state of a mixture with these, and is preferably 0.80 or less.
The Mooney relaxation rate is an index of molecular entanglement of a conjugated diene copolymer, and the lower the rate, the greater the degree of molecular entanglement. The Mooney relaxation rate can be reduced by increasing the molecular weight of the rubber polymer (A), increasing the branching degree with the above-mentioned coupling agent or a specified branching agent, or reducing the amount of rubber softener added to increase the Mooney viscosity.
The Mooney relaxation rate can be determined by preheating the rubbery polymer (A) or a rubber composition using the rubbery polymer (A) at 100°C for 1 minute, rotating a rotor at 2 rpm, measuring the Mooney viscosity (ML ₍₁₊₄₎ ) from the torque after 4 minutes, and then immediately stopping the rotation of the rotor, recording the torque every 0.1 seconds for 1.6 seconds to 5 seconds after the rotation was stopped in Mooney units, determining the slope of the straight line when the torque vs. time (seconds) is plotted logarithmically, and determining the absolute value of the slope as the Mooney relaxation rate.

(Method for molding rubber composition containing rubber-like polymer (A) and various additives)
The rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment, or a rubber composition containing the rubbery polymer (A), is preferably molded into a sheet or block shape from the viewpoint of handling. A block shape is more preferable, and a block shape (bale) of 1,000 cm3 or ^more is even more preferable. A rectangular parallelepiped bale of 17.5 kg to 35 kg is even more preferable.

(Constituents of rubber composition for crosslinking)
The rubber composition for crosslinking of the present embodiment contains a crosslinking agent (B) and a hydrogenated ring-containing resin (C) having a softening point of less than 140°C, and may further contain other rubber components, fillers, etc. as necessary.

<Other rubber components>
The other rubber components are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include styrene-butadiene rubber (emulsion polymerization tire or solution polymerization type), natural rubber, polyisoprene, butadiene rubber (high-cis polybutadiene, low-cis polybutadiene, syndiotactic 1,2-polybutadiene, acrylonitrile-butadiene rubber (NBR), chloroprene rubber, ethylene-α-olefin copolymer rubber such as ethylene-propylene rubber, ethylene-butene rubber, and ethylene-octene, ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, and urethane rubber.
These may be used alone or in combination of two or more.
The mixing may be carried out by mixing a dry polymer after polymerization, or by mixing in a solution state during polymerization.

<Content of Rubber-Like Polymer (A) in Total Amount of Rubber Component>
The content of the rubber-like polymer (A) relative to the total amount of rubber components in the crosslinkable rubber composition of this embodiment is preferably 20 mass% or more, more preferably 40 mass% or more, even more preferably 60 mass% or more, and even more preferably 80 mass% or more.

<Average iodine value of total rubber component>
The average iodine value of the total amount of rubber components in the rubber composition for crosslinking of this embodiment is preferably 250 (g/100 g) or less from the viewpoints of suppressing uneven crosslinking and achieving high mechanical strength.
It is more preferably 200 (g/100g) or less, even more preferably 130 (g/100g) or less, and even more preferably 70 (g/100g) or less.

<Crosslinking Agent (B)>
The rubber composition for crosslinking of the present embodiment contains a crosslinking agent (B).
Examples of the crosslinking agent (B) include sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, and oxime-nitrosamine-based crosslinking agents, and these may be used in combination.
From the viewpoint of resistance to compression set and minimal deterioration of physical properties over time, sulfur-based crosslinking agents (vulcanizing agents) are preferred, and sulfur is more preferred.

The content of the crosslinking agent (B) in the rubber composition for crosslinking of the present embodiment is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of tensile modulus.
The term "rubber component" includes the above-mentioned rubber-like polymer (A) and other rubber components.
The content of the crosslinking agent (B) per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoints of high tensile strength and high crosslinking rate.
On the other hand, from the viewpoint of suppressing uneven crosslinking and achieving high tensile strength, the amount is preferably 20 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.
The structure and ratio of the rubber polymer (A) and the ring-containing resin (C) described below may affect the preferred amount of the crosslinking agent (B) to be added to some extent, but from the viewpoint of tensile modulus, it may be selected within this range.

When a sulfur-based crosslinking agent (vulcanizing agent) is used as the crosslinking agent (B), it is preferable to use a vulcanization accelerator in combination.
In particular, when the iodine value of the rubber-like polymer (A) is 200 or less, it is preferable to use a vulcanization accelerator in combination.
As the vulcanization accelerator, from the viewpoint of a short crosslinking time of the crosslinking rubber composition and abrasion resistance, compounds such as guanidine, aldehyde amine, aldehyde ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, and xanthate are preferred, and guanidine vulcanization accelerators such as diphenylguanidine, and thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide, and N-t-butyl-2-benzothiazolylsulfenamide are more preferred.
The vulcanization accelerator may be used alone or in combination of two or more kinds.

<Hydrogenated Ring-Containing Resin (C) Having a Softening Point of Less than 140° C.>
The cross-linking rubber composition of the present embodiment contains a hydrogenated ring-containing resin (C) having a softening point of less than 140° C. (hereinafter, may be referred to as ring-containing resin (C)).
By using a hydrogenated ring-containing resin (C) having a softening point of less than 140°C, the processability of the crosslinkable rubber composition of this embodiment is unlikely to decrease, the tensile energy is unlikely to decrease, and the abrasion resistance is unlikely to decrease.
By making the softening point of the ring-containing resin (C) less than 140° C., it is possible to prevent the rubber composition for crosslinking from becoming too viscous or too rigid. In addition, by making the ring-containing resin (C) have a hydrogenated structure, it becomes possible to improve compatibility with the rubber-like polymer (A) having an ethylene structural portion.
In this specification, the term "ring-containing resin (C)" refers to a resin having an aromatic ring and/or an aliphatic ring.
In the rubber composition for crosslinking of tires, a polymer having an aromatic ring and/or an aliphatic ring, a low molecular weight, and in a glassy state at room temperature is generally referred to as a "resin." In this specification, such a resin is also a preferred embodiment of the ring-containing resin (C).
The softening point of the ring-containing resin (C) is determined by various factors, the main factor being the molecular weight. The higher the molecular weight, the higher the softening point, and the smaller the molecular weight, the lower the softening point tends to be. Therefore, by referring to the molecular weight, it is possible to select a ring-containing resin (C) having a preferred softening point.

The molecular weight of the ring-containing resin (C) is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more, from the viewpoint of the high tensile energy of the cross-linking rubber composition of this embodiment, and is preferably 2500 or less, more preferably 2000 or less, and even more preferably 1500 or less, from the viewpoint of the processability of the cross-linking rubber composition.

From the viewpoint of the cut resistance when the crosslinkable rubber composition of this embodiment is made into a sheet, the glass transition temperature of the hydrogenated ring-containing resin (C) is preferably 90°C or lower, more preferably 85°C or lower, and even more preferably 80°C or lower. On the other hand, from the viewpoint of the rigidity of the crosslinkable rubber composition of this embodiment and the handleability during mixing of the crosslinkable rubber composition, the glass transition temperature is preferably 40°C or higher, more preferably 45°C or higher, even more preferably 50°C or higher, and even more preferably 110°C or higher.

The ring-containing resin (C) has a low viscosity due to its cyclic structure, and is assumed to easily function as a physical crosslinking point.
It is presumed that the rubber-like polymer (A) having an iodine value of 10 to 250 (g/100 g) and containing ethylene structures of 3% by mass or more and the hydrogenated ring-containing resin (C) having a softening point of less than 140° C. are easily kneaded together and have high compatibility, resulting in good performance.
It is presumed that a low softening point leads to low cohesive strength, making the rubber composition for cross-linking more flexible, and that flexibility has the effect of making the rubber composition for cross-linking less susceptible to wear when subjected to mechanical impact.

The softening point of the ring-containing resin (C) is preferably less than 140°C, more preferably 135°C or less, and even more preferably 130°C or less, from the viewpoint of cut resistance when the crosslinkable rubber composition of this embodiment is made into a sheet.
On the other hand, from the viewpoint of the rigidity of the rubber composition for crosslinking and the handleability during mixing of the rubber composition for crosslinking, the temperature is preferably 90°C or higher, more preferably 95°C or higher, even more preferably 100°C or higher, and even more preferably 110°C or higher.

The ring-containing resin (C) used in the cross-linking rubber composition of this embodiment is a resin in which the unsaturated bonds in the molecule have been partially or completely hydrogenated.
More specifically, it is a resin in which unsaturated groups of a resin having at least one selected from the group consisting of an aromatic ring such as a benzene ring, cyclopentadiene, dicyclopentadiene, and a terpene structure are partially or completely hydrogenated.
Examples of the hydrogenation method include a method in which a resin having an unsaturated bond in the molecule is hydrogenated under pressurized hydrogen at 1 to 100 atmospheres using a catalyst selected from the group consisting of an organic carboxylate nickel, an organic carboxylate cobalt, and an organometallic compound of Groups 1 to 3; a metal catalyst of nickel, platinum, palladium, ruthenium, or rhodium supported on carbon, silica, diatomaceous earth, or the like; and a cobalt, nickel, rhodium, or ruthenium complex.
The resin before hydrogenation may be a natural resin or a synthetic resin.

As the ring-containing resin (C) used in the crosslinkable rubber composition of the present embodiment, a commercially available product can be suitably used. Specifically, the product names of Idemitsu Kosan Co., Ltd. are DCPD (dicyclopentadiene)/aromatic (C9) copolymer-based hydrogenated petroleum resins, which use C5 fraction as the main raw material, "Imerv P100", "Imerv P125", "Imerv S100", and "Imerv S110", the product names of Arakawa Chemical Industries Co., Ltd. are hydrogenated resins, which use C9 fraction as the main raw material, "Arcon P-90", "Arcon P-100", "Arcon P-115", "Arcon P-125", "Arcon M-90", "Arcon M-100", "Arcon M-115", and "Arcon M-135" (P stands for fully hydrogenated, and M stands for partially hydrogenated), and the product names of DCPD (dicyclopentadiene)/aromatic (C9) copolymer-based hydrogenated petroleum resins, "T-REZ OP501", "T-REZ PR801", and "T-REZ HA125", "T-REZ HB125", and specific examples of terpene-based hydrogenated resins include Yasuhara Chemical's Clearon P105, Yasuhara Chemical's Clearon P115, Yasuhara Chemical's Clearon P125, Yasuhara Chemical's Clearon P135, Yasuhara Chemical's Clearon P150 (product name, softening point 152°C), Yasuhara Chemical's Clearon M105, Yasuhara Chemical's Clearon M115, Yasuhara Chemical's Clearon K100, Yasuhara Chemical's Clearon K110, Yasuhara Chemical's Clearon K4100, Yasuhara Chemical's Clearon K4090, and the like.
These hydrogenated ring-containing resins (C) may be used alone or in combination of two or more.
Among these, from the viewpoint of high tensile strength, partially hydrogenated (partially hydrogenated) and hydrogenated terpene resins are preferred. From the viewpoint of compatibility, partially hydrogenated (partially hydrogenated) C5 fractions and C9 fractions (excluding partial hydrogenation of homopolymers) and hydrogenated terpene resins are more preferred. Partially hydrogenated (partially hydrogenated) C5 fractions and C9 fractions (excluding partial hydrogenation of homopolymers) are even more preferred. In particular, from the viewpoint of compatibility, it is preferred when the content of vinyl aromatic monomer units in the rubbery polymer (A) is less than 30 mass%.
Partial hydrogenation provides co-crosslinking properties and reduces unevenness in crosslink density. In addition, because the fractions are mixtures, they have higher compatibility than homopolymers. Therefore, it is presumed that partially hydrogenated (partially hydrogenated) C5 fractions and C9 fractions (excluding homopolymer partially hydrogenated) will have particularly good mechanical strength.

From the viewpoints of tensile strength and tensile elongation, the rubber composition for crosslinking of the present embodiment preferably contains 10 to 40 parts by mass of the hydrogenated ring-containing resin (C) having a softening point of less than 140° C. per 100 parts by mass of the rubber component in the rubber composition for crosslinking. From the viewpoint of tensile energy, it is more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more.
On the other hand, from the viewpoint of ease in mixing the rubber composition for crosslinking, the amount is more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less.
In particular, from the viewpoints of tensile strength, tensile elongation and tensile energy, when the content of vinyl aromatic monomer units in the rubbery polymer (A) is less than 30 mass %, the above content is preferred.

<Non-hydrogenated resin other than component (C)>
The rubber composition for crosslinking of the present embodiment may contain a non-hydrogenated resin, if necessary, in addition to the component (C).
Non-hydrogenated resins are compounds that are solid at room temperature (23° C.) and are based essentially on carbon and hydrogen (but may also contain other atoms).
The non-hydrogenated resins may be based on aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, aliphatic and aromatic monomers. The resins may be petroleum or non-petroleum based natural or synthetic resins.
Such non-hydrogenated resins include hydrocarbon resins selected from the group consisting of cyclopentadiene (CPD) homopolymer or copolymer resins, dicyclopentadiene (DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5 cut homopolymer or copolymer resins, C9 cut homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and blends of these resins.
Among the above-mentioned copolymer resins, more particularly, copolymers selected from the group consisting of (D) CPD/vinyl aromatic copolymer resins, (D) CPD/terpene copolymer resins, terpene/phenol copolymer resins, (D) CPD/C5 fraction copolymer resins, (D) CPD/C9 fraction copolymer resins, terpene/vinyl aromatic copolymer resins, terpene/phenol copolymer resins, C5 fraction/vinyl aromatic copolymer resins, and blends of these resins are preferred.
The above-mentioned non-hydrogenated resins may be used alone or in combination of two or more kinds.

(Preferable physical properties of the rubber composition for crosslinking)
<(C) Mass parts/(ST) Mass %>
In the rubber composition for crosslinking of this embodiment, from the viewpoint of high tear strength, the amount (parts by mass) of hydrogenated ring-containing resin (C) per 100 parts by mass of the rubber component in the rubber composition for crosslinking/the content (ST) (mass%) of vinyl aromatic monomer units in the rubber-like polymer (A), i.e., C/ST, is preferably 0.3 or more, more preferably 0.6 or more, more preferably 1.2 or more, even more preferably 1.7 or more, and even more preferably 2.2 or more.

<Silica amount (parts by mass)/Oil amount (parts by mass)>
From the viewpoint of rigidity, the rubber composition for crosslinking of this embodiment preferably has a ratio of silica amount (parts by mass)/oil amount (parts by mass) per 100 parts by mass of the rubber component in the rubber composition for crosslinking of 6 or more, more preferably 7 or more, even more preferably 8 or more, and even more preferably 9 or more.
Here, silica refers to precipitated silica.
The oil means an extender oil, such as aromatic oil, naphthenic oil, paraffin oil, vegetable oil, etc.

(Other components of the rubber composition for crosslinking)
<Extender oil>
The rubber composition for crosslinking of the present embodiment preferably contains an extender oil from the viewpoint of ensuring moldability after kneading.
The amount of the extending oil per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more.
By making the content of the extender oil 1 part by mass or more, the processability of the blend is improved.
On the other hand, the content of the extender oil is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less, based on 100 parts by mass of the rubber component. By making the content of the extender oil 80 parts by mass or less, the abrasion resistance of the rubber composition for crosslinking tends to be further improved.

Examples of preferred extender oils include aromatic oils, naphthenic oils, paraffinic oils, etc. Among these, from the viewpoint of environmental safety, prevention of oil bleeding, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred.
Examples of aromatic substitute oils include Treated Distillate Aromatic Extracts (TDAE) and Mild Extraction Solvate (MES) as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as Residual Aromatic Extracts (RAE).

The extender oil may be a vegetable oil. By using a vegetable oil as the extender oil, it is possible to improve the moldability after kneading while achieving environmental friendliness compared to the case where a synthetic oil or a mineral oil is used as the extender oil.
Such vegetable oils are not particularly limited, but include, for example, linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, turnip seed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grape seed oil, etc. Among these, sunflower oil is preferably used. These vegetable oils may be used alone or in combination of two or more.
From the viewpoint of the abrasion resistance of the rubber composition to be crosslinked, oils derived from plants (vegetable oils) are preferred.
In particular, from the viewpoint of ensuring abrasion resistance and moldability after kneading, the rubber composition for crosslinking of this embodiment preferably further contains 1 to 80 parts by mass of a plant-derived oil per 100 parts by mass of the rubber component in the rubber composition for crosslinking, more preferably 5 to 60 parts by mass, and even more preferably 10 to 40 parts by mass.

In addition, the vegetable oil preferably contains fatty acids.
The fatty acid is not particularly limited, but examples thereof include saturated fatty acids such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, and behenic acid; and unsaturated fatty acids such as linoleic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, arachidonic acid, palmitoleic acid, oleic acid, erucic acid, and nervonic acid.
Among these, unsaturated fatty acids are preferred, with oleic acid, linoleic acid, linolenic acid and mixtures thereof being more preferred, and oleic acid being even more preferred. These monounsaturated fatty acids tend to be less susceptible to oxidation and deterioration.
The fatty acids may be used alone or in combination of two or more.
When the vegetable oil contains fatty acids, the content of oleic acid contained in the fatty acids 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, based on the total amount of fatty acids. In particular, sunflower oil containing oleic acid in the above content is preferred.

<Filler>
In the rubber composition for crosslinking of the present embodiment, a filler can be used from the viewpoint of improving reinforcement properties.
The amount of the filler is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of reinforcement, it is preferably more than 30 parts by mass, more preferably more than 50 parts by mass, even more preferably more than 60 parts by mass, and even more preferably more than 70 parts by mass, relative to 100 parts by mass of the rubber component. On the other hand, from the viewpoint of processability of the crosslinkable rubber composition, it is preferably 130 parts by mass or less, more preferably 120 parts by mass or less.
The "rubber component" includes the above-mentioned rubber-like polymer (A) and further other rubber components.

Examples of the filler include, but are not limited to, carbon black, silica, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloons, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, barium sulfate, and the like. Of these, it is preferable to use carbon black.
These may be used alone or in combination of two or more.
The carbon black is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include FEF, GPF, SRF, HAF, N339, IISAF, ISAF, SAF, etc. These may be used alone or in combination of two or more kinds.
The nitrogen adsorption specific surface area (N2SA, measured in accordance with JIS K6217-2:2001) of the carbon black is not particularly limited and can be appropriately selected depending on the purpose.

Among these fillers, silica is preferred, and precipitated silica is more preferred, from the viewpoints of fuel economy and wet skid resistance when the rubber composition for crosslinking of the present embodiment is made into a tire tread.
In addition, the amount of silica added in the rubber composition for crosslinking of this embodiment is preferably 10 to 130 parts by mass, more preferably 40 to 120 parts by mass, even more preferably 50 to 100 parts by mass, and even more preferably 60 to 80 parts by mass, per 100 parts by mass of the rubber component in the rubber composition for crosslinking of this embodiment, from the viewpoints of fuel saving properties and wet skid resistance.

<Silane coupling agent>
The rubber composition for crosslinking of the present embodiment may contain a silane coupling agent from the viewpoints of improving the dispersibility of the filler and improving the tensile strength of the crosslinked product.
The silane coupling agent has the function of strengthening the interaction between the rubber component and the inorganic filler, and has groups that have affinity or binding properties for both the rubber component and the filler. A compound having a sulfur bonding portion and an alkoxysilyl group or silanol group portion in one molecule is preferred.
Such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, S-[3-(triethoxysilyl)-propyl]octanethioate, condensates of S-[3-(triethoxysilyl)-propyl]octanethioate with [(triethoxysilyl)-propyl]thiol, silanes bearing at least one thiol (-SH) functional group (referred to as mercaptosilane) and/or at least one masked thiol group.

The content of the silane coupling agent in the crosslinking rubber composition of this embodiment is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1.0 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the above-mentioned filler. When the content of the silane coupling agent is within the above range, the above-mentioned addition effect of the silane coupling agent tends to be more pronounced.

<Other additives>
In addition to the above, various additives such as other softeners and fillers, heat resistance stabilizers, antistatic agents, weather resistance stabilizers, antioxidants, colorants, and lubricants may be added to the crosslinking rubber composition of this embodiment.
As the other softening agents, known softening agents can be used.
Other fillers include, for example, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate.
As the heat resistance stabilizer, antistatic agent, weather resistance stabilizer, antioxidant, colorant, and lubricant, known materials can be used.

[Method for producing rubber composition for crosslinking]
The crosslinkable rubber composition of the present embodiment is obtained by mixing the rubber-like polymer (A), the crosslinking agent (B), and the hydrogenated ring-containing resin (C). If necessary, additives such as other rubber components, silica-based inorganic fillers, carbon black or other fillers, silane coupling agents, and rubber softeners may be mixed.
The mixing method is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating.
Among these, the melt kneading method using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoints of productivity and good kneading properties.
In addition, it is possible to use either a method in which the rubber component, the other filler, the silane coupling agent, and the additives are kneaded at once, or a method in which they are mixed in several batches.

[Application]
The crosslinkable rubber composition of the present embodiment can be preferably used for tire components, interior and exterior parts of automobiles, anti-vibration rubber, belts, footwear (particularly outsoles and midsoles), foams, various industrial product applications, and the like.
Among these, it is preferably used for tire parts.
As tire components, the present invention can be used in various tire parts such as tire treads, carcasses, sidewalls, and beads of various tires, including fuel-efficient tires, all-season tires, high-performance tires, snow tires, and studless tires.
In particular, as a tire component, since the vulcanizate has an excellent balance of wear resistance, fuel efficiency, wet skid resistance, and snow performance, it is suitably used for fuel-efficient tires, high-performance tires, and tire treads for snow tires.

Conventional methods can be used to manufacture tires. For example, components normally used in tire manufacturing, such as a carcass layer, a belt layer, and a tread layer, each layer being composed of at least one selected from the group consisting of an unvulcanized rubber composition for crosslinking and a cord, are laminated on a tire-building drum in order, and the drum is removed to produce a green tire. The green tire is then heated and vulcanized in the usual manner to manufacture the desired tire (e.g., a pneumatic tire).

Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited in any way by the following examples and comparative examples.
Various physical properties in the examples and comparative examples were measured by the methods shown below.

(Physical Properties 1) Molecular weight and molecular weight distribution)
<Measurement condition 1>:
Using the rubber-like polymers obtained in the polymerization examples described below as samples, chromatograms were measured using a GPC measurement apparatus (manufactured by Tosoh Corporation under the trade name "HLC-8320GPC") having three columns packed with polystyrene gel connected together under the following specific conditions, and an RI detector (manufactured by Tosoh Corporation under the trade name "HLC8020"), and the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) were determined based on a calibration curve obtained using standard polystyrene.

[Specific measurement conditions]
GPC measuring device: Tosoh Corporation product name "HLC-8320GPC"
Eluent: 5 mmol/L triethylamine in THF (tetrahydrofuran)
Guard column: "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation
Column: Three "TSKgel SuperMultiporeHZ-H" columns manufactured by Tosoh Corporation were connected.
Oven temperature: 40°C
Flow rate: 0.35 mL/min. Sample: 10 mg of a sample to be measured was dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into the GPC measurement device.

Among the various samples measured under the above <Measurement Condition 1>, samples whose molecular weight distribution (Mw/Mn) was less than 1.6 were measured again under the following <Measurement Condition 2>, and the results were used as the measured values.
For samples that were measured under the above <Measurement Condition 1> and had a molecular weight distribution value of 1.6 or more, the result measured under <Measurement Condition 1> was used as the measured value.

<Measurement condition 2>:
Using the rubber-like polymers obtained in the polymerization examples described below as samples, chromatograms were measured using a GPC measurement apparatus (manufactured by Tosoh Corporation under the trade name "HLC-8320GPC") having three columns packed with polystyrene gel connected together under the following specific conditions, and an RI detector (manufactured by Tosoh Corporation under the trade name "HLC8020"), and the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) were determined based on a calibration curve using standard polystyrene.

[Specific measurement conditions]
Eluent: THF containing 5 mmol/L triethylamine
Guard column: "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation
Column: Tosoh Corporation's "TSKgel Super H5000", "TSKgel Super H6000", and "TSKgel Super H7000" connected in this order from upstream Oven temperature: 40°C
Flow rate: 0.6 mL/min. Sample: 10 mg of a sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 20 μL of the measurement solution was injected into a GPC measurement device for measurement.

(Physical Property 2) Polymer Mooney Viscosity
The rubber-like polymers obtained in the polymerization examples described later were used as samples, and the Mooney viscosity was measured in accordance with ISO 289 using a Mooney viscometer (manufactured by Ueshima Seisakusho Co., Ltd., trade name "VR1132").
After preheating the sample at 100° C. for 1 minute, the sample was rotated at 2 rpm in an L-type rotor, and the torque after 4 minutes was measured to obtain the Mooney viscosity (ML ₍₁₊₄₎ ).

(Physical Property 3) Modification Rate
The modification ratio of the rubber-like polymer obtained in the polymerization examples described later was measured by column adsorption GPC method as follows.
The rubber-like polymers obtained in the polymerization examples were used as samples, and measurements were carried out by utilizing the adsorption properties of modified basic polymer components in a GPC column packed with silica gel.

The amount of sample adsorption to the silica-based column was measured by subtracting the chromatograms of the sample solution containing the sample and low molecular weight internal standard polystyrene measured on a polystyrene-based column from the chromatograms measured on a silica-based column, and the modification rate was calculated.

The specific measurement conditions are as follows.
In addition, for samples in which the molecular weight distribution of the rubber-like polymer was 1.6 or more as a result of measurement under <Measurement Condition 1> in the above (Physical Property 1), the following <Measurement Condition 3> was used, and for samples in which the molecular weight distribution was less than 1.6, the following <Measurement Condition 4> was used.

<Measurement Condition 3: GPC Measurement Condition Using Polystyrene Column>
GPC measuring device: Tosoh Corporation product name "HLC-8320GPC"
Eluent: THF containing 5 mmol/L triethylamine
Guard column: "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation
Column: Three "TSKgel SuperMultiporeHZ-H" columns manufactured by Tosoh Corporation were connected.
Oven temperature: 40°C
Flow rate: 0.35 mL/min RI detector (Tosoh HLC8020)
Sample: 10 mg of a sample to be measured and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into the GPC measurement device.

<Measurement Condition 4: GPC Measurement Condition Using Polystyrene Column>
GPC measuring device: Tosoh Corporation product name "HLC-8320GPC"
Eluent: THF containing 5 mmol/L triethylamine
Guard column: "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation
Column: Tosoh Corporation's "TSKgel Super H5000", "TSKgel Super H6000", and "TSKgel Super H7000" connected in this order from upstream Oven temperature: 40°C
Flow rate: 0.6 mL/min RI detector (Tosoh HLC8020)
Sample: 10 mg of a sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 20 μL of the measurement solution was injected into a GPC measurement device for measurement.

<GPC measurement conditions using a silica column>
GPC measuring device: Tosoh Corporation product name "HLC-8320GPC"
Eluent: THF
Guard column: "DIOL 4.6 x 12.5 mm 5 micron"
Column: Zorbax PSM-1000S, PSM-300S, and PSM-60S connected in this order from upstream Oven temperature: 40°C
Flow rate: 0.5 mL/min RI detector (Tosoh HLC8020)
Sample: 10 mg of a sample to be measured and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a measurement solution, and 50 μL of the measurement solution was injected into the GPC measurement device.

How to calculate the denaturation rate:
The peak area P1 of the sample and the peak area P2 of the standard polystyrene were calculated by setting the total peak area of the chromatogram using the polystyrene column to 100. Similarly, the peak area P3 of the sample and the peak area P4 of the standard polystyrene were calculated by setting the total peak area of the chromatogram using the silica column to 100. Then, based on the obtained area values, the modification rate (%) was calculated by the following formula.
Denaturation rate (%) = [1 - (P2 x P3) / (P1 x P4)] x 100
(where P1 + P2 = P3 + P4 = 100)

(Physical Property 4) Amount of Bound Styrene (Styrene Content)
A rubber-like polymer obtained in a polymerization example described later was used as a sample. 100 mg of the sample was dissolved in chloroform to make a total volume of 100 mL to prepare a measurement sample.
The amount of bound styrene (mass %) relative to 100 mass % of the rubber-like polymer sample was measured based on the amount of absorption of ultraviolet light at wavelengths (around 254 nm) by the phenyl groups of styrene (measuring device: Shimadzu Corporation spectrophotometer "UV-2450").

(Physical Property 5) Microstructure of Butadiene Moiety (1,2-Vinyl Bond Amount)
The rubber-like polymer obtained in the polymerization example described below was used as a sample, and 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample.
Using a solution cell, an infrared spectrum was measured in the range of 600 to 1000 cm ^-1 , and the microstructure of the butadiene portion, i.e., the amount of 1,2-vinyl bonds (mol%) was determined from the absorbance at a predetermined wave number according to the calculation formula of the Hampton method (the method described in R. R. Hampton, Analytical Chemistry 21, 923 (1949)) (measuring device: Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).
The "content of vinyl units and butylene units" before hydrogenation corresponds to the "amount of 1,2-vinyl bonds" and has the same numerical value.
Therefore, the "content of vinyl units and butylene units" in Table 1 corresponds to the amount of 1,2-vinyl bonds before hydrogenation.

(Physical Property 6) Hydrogenation Ratio of Rubber Polymer, Ethylene Structure, Vinyl Unit and Butylene Unit Content of Rubber Polymer)
Using the rubber-like polymer obtained in the polymerization example described later as a sample, the hydrogenation rate of the rubber-like polymer, the content of the ethylene structure, the vinyl unit and the butylene unit were measured by ¹ H-NMR measurement. The conditions of ¹ H-NMR measurement are described below.
<Measurement conditions>
Measuring equipment: JNM-LA400 (manufactured by JEOL)
Solvent: deuterated chloroform Measurement sample: rubber-like polymer Sample concentration: 50 mg/mL
Observation frequency: 400MHz
Chemical shift reference: TMS (tetramethylsilane)
Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45°
Measurement temperature: 26°C

(Physical Property 7) Amount of Styrene Blocks in Rubber Polymer
A chain in which eight or more styrene structural units are linked together is defined as a styrene block, and the amount of the styrene block was determined as follows.
From the 400 MHz ¹ H-NMR spectrum measured using deuterated chloroform as a solvent, the integral ratio of each chemical shift range of the following (X) was calculated to determine the content of styrene blocks in the rubber polymer.
(X) Aromatic vinyl compound having 8 or more chains: 6.00≦S<6.68

(Physical Property 8) Iodine Value of Rubber Polymer
The iodine value was measured as follows.
After dissolving the sample in cyclohexane, iodine monochloride solution was added and the mixture was left in the dark. Potassium iodide and water were then added, and the mixture was titrated with sodium thiosulfate solution. When the solution turned pale yellow, starch solution was added and titrated until the blue color disappeared, thereby determining the iodine value.

[Production of rubber-like polymer]
(Preparation of hydrogenation catalyst)
In the polymerization examples described later, the hydrogenation catalyst used in preparing the rubber polymer was prepared by the following method.
A nitrogen-purged reaction vessel was charged with 1 liter of dried and purified cyclohexane, and 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. With sufficient stirring, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the mixture was allowed to react at room temperature for about 3 days to obtain a hydrogenation catalyst (TC-1).

(Polymerization of rubber-like polymer)
<(Polymerization Example 1) Rubber-like Polymer 1>
A 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of controlling temperature was used as a reactor. 2,700 g of 1,3-butadiene, 300 g of styrene, 21,000 g of cyclohexane, and 30 mmol of tetrahydrofuran (THF) and 11.6 mmol of 2,2-bis(2-oxolanyl)propane as polar substances, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 43° C.
As a polymerization initiator, 68.0 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization, and the final temperature inside the reactor reached 76°C. Two minutes after this reaction temperature peak was reached, 13.6 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound 1) was added as a modifier to the reactor, and a coupling reaction was carried out for 20 minutes. 13.3 mmol of methanol was added as a reaction terminator to this polymer solution, and a portion of the rubber-like polymer solution before hydrogenation was extracted for analysis and the solvent was removed in a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubber-like polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain a rubber-like polymer 1. The iodine value of the obtained rubber-like polymer 1 was 108 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

<(Polymerization Examples 2 and 3) Rubber-like Polymers 2 and 3>
The hydrogenation reaction was carried out for 60 minutes and 80 minutes, respectively, and the other conditions were the same as in Polymerization Example 1, to obtain Rubber Polymer 2 and Rubber Polymer 3.
The resulting rubber polymer 2 had an iodine value of 65 (g/100 g), and the rubber polymer 3 had an iodine value of 22 (g/100 g).
The analysis results are shown in Table 1.

<(Polymerization Example 4) Rubber-like Polymer 4>
A temperature-controllable autoclave having an internal volume of 40 L, equipped with a stirrer and a jacket, was used as a reactor. 3,000 g of 1,3-butadiene, 21,000 g of cyclohexane, and 90 mmol of tetrahydrofuran (THF) as a polar substance, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 45° C.
As a polymerization initiator, 74.0 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature in the reactor began to rise due to heat generated by the polymerization, and the final temperature in the reactor reached 76° C. Two minutes after the reaction temperature reached its peak, 14.8 mmol of silicon tetrachloride (compound 2) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 14.4 mmol of methanol was added to this polymer solution as a reaction terminator, and a portion of the rubber-like polymer solution before hydrogenation was extracted for analysis and the solvent was removed in a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubber-like polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was carried out for 10 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain rubber-like polymer 4. The iodine value of the obtained rubber-like polymer 4 was 418 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

<(Polymerization Example 5) Rubber-like Polymer 5>
A temperature-controllable autoclave having an internal volume of 40 L, equipped with a stirrer and a jacket, was used as a reactor. 1,000 g of 1,3-butadiene, 1,350 g of styrene, 21,000 g of cyclohexane, and 162 mmol of tetrahydrofuran (THF) as a polar substance, all of which had been previously removed from impurities, were placed in the reactor, and the internal temperature of the reactor was maintained at 48° C.
As a polymerization initiator, 54.0 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature in the reactor began to rise due to heat generated by the polymerization, and when the monomer conversion in the reactor reached 96%, 650 g of butadiene was added in two portions and further reacted. The final temperature in the reactor reached 82°C. Two minutes after the reaction temperature peak was reached, 10.8 mmol of silicon tetrachloride (compound 2) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 10.5 mmol of methanol was added to this polymer solution as a reaction terminator, and a part of the rubber-like polymer solution before hydrogenation was extracted for analysis and desolvated with a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubbery block polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubbery polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain a rubbery polymer 5. The iodine value of the obtained rubbery polymer 5 was 39 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

<(Polymerization Example 6) Rubber-like Polymer 6>
A 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of controlling temperature was used as a reactor. 2,000 g of 1,3-butadiene, 750 g of styrene, 21,000 g of cyclohexane, and 30 mmol of tetrahydrofuran (THF) and 7.8 mmol of 2,2-bis(2-oxolanyl)propane as polar substances, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 43° C.
As a polymerization initiator, 32.3 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature in the reactor began to rise due to heat generated by the polymerization, and when the monomer conversion in the reactor reached 96%, 250 g of butadiene was added and further reacted. The final temperature in the reactor reached 86°C. Two minutes after the reaction temperature reached its peak, 6.5 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound 1) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 5.8 mmol of methanol was added to this polymer solution as a reaction terminator, and a part of the rubber-like polymer solution before hydrogenation was extracted for analysis and the solvent was removed with a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubber-like polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain rubber-like polymer 6. The iodine value of the obtained rubber-like polymer 6 was 54 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

<(Polymerization Example 7) Rubber-like Polymer 7>
A 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of controlling temperature was used as a reactor. 2,000 g of 1,3-butadiene, 240 g of styrene, 21,000 g of cyclohexane, and 158 mmol of tetrahydrofuran (THF) as a polar substance, all of which had previously been removed of impurities, were placed in the reactor, and the internal temperature of the reactor was maintained at 46° C.
As a polymerization initiator, 52.5 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature in the reactor started to rise due to heat generated by the polymerization, and when the monomer conversion in the reactor reached 96%, 760 g of butadiene was added in two portions and further reacted. The final temperature in the reactor reached 80° C. Two minutes after the peak reaction temperature was reached, 10.5 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound 1) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 9.4 mmol of methanol was added to this polymer solution as a reaction terminator, and a part of the rubber-like polymer solution before hydrogenation was extracted for analysis and the solvent was removed with a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubber-like polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was carried out for 60 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain rubber-like polymer 7. The iodine value of the obtained rubber-like polymer 7 was 65 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

<(Polymerization Example 8) Rubber-like Polymer 8>
A 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of controlling temperature was used as a reactor. 2,150 g of 1,3-butadiene, 510 g of styrene, 21,000 g of cyclohexane, and 30 mmol of tetrahydrofuran (THF) and 7.8 mmol of 2,2-bis(2-oxolanyl)propane as polar substances, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 48° C.
As a polymerization initiator, 32.3 mmol of n-butyllithium was fed to the reactor.
After the polymerization reaction started, the temperature in the reactor started to rise due to heat generated by the polymerization, and 5 minutes after the reaction temperature in the reactor reached its peak, 240 g of styrene was added and reacted. Then, 2 minutes after the reaction temperature in the reactor reached its peak, 100 g of butadiene was added and further reacted. The final temperature in the reactor reached 86°C. 2 minutes after the reaction temperature reached its peak, 6.5 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound 1) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 5.8 mmol of methanol was added to this polymer solution as a reaction terminator, and a part of the rubber-like polymer solution before hydrogenation was extracted for analysis and the solvent was removed with a dryer to obtain a rubber-like polymer before hydrogenation.
Thereafter, the hydrogenation catalyst (TC-1) was added to the rubber-like polymer solution before hydrogenation in an amount of 70 ppm based on titanium per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was carried out for 60 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85° C. to obtain a rubber-like polymer 8. The iodine value of the obtained rubber-like polymer 8 was 54 (g/100 g).
To the resulting rubber polymer solution were added 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants, and the mixture was dried.
The analysis results are shown in Table 1.

The types of modifiers in Table 1 are as follows:
Compound 1: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane Compound 2: silicon tetrachloride

(Examples 1 to 8, Reference Examples 9, 10, Reference Examples 11 to 13, Examples 14 to 17, Comparative Examples 1 and 2)
The components shown in Tables 2 to 4 below were mixed to obtain rubber compositions for crosslinking.
A sealed mixer (capacity: 0.3 L) equipped with a temperature control device was used for the first stage of mixing.
Filling rate 65%, rotor rotation speed 30 to 50 rpm, rubber-like polymers 1 to 8 (A),
Other rubber components, reinforcing filler, silane coupling agent, extender oil, zinc oxide, stearic acid, ring-containing resin (C) and wax were kneaded.
At this time, the temperature of the internal mixer was controlled, and each rubber composition (
A compound (compound) was obtained.

Next, in the second mixing step, the mixture obtained above was cooled to room temperature, and then the antioxidant was added and mixed again to improve the dispersion of the reinforcing filler. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.
After cooling, in the third stage of kneading, sulfur (B) and other vulcanization accelerators were added and kneaded using an open roll set at 70° C. to obtain a rubber composition for crosslinking.
Thereafter, the product was molded and vulcanized in a vulcanization press at 160° C. for 20 minutes.
The vulcanized rubber compositions were evaluated by the following methods.
The results are shown in Tables 2 to 4.

(Mixed materials)
<Rubber component>
Polymers 1 to 8: Rubber-like polymers 1 to 8 obtained in polymerization examples
NR: Natural rubber (peptized)
EPDM: Ethylene-propylene rubber ("Esprene 505A" manufactured by Sumitomo Chemical Co., Ltd.)

<Reinforcing filler>
Silica (product name "Ultrasil 7000GR" manufactured by Evonik Degussa, nitrogen adsorption specific surface area 170 m2/g)
Carbon black (product name "Seat KH (N339)" manufactured by Tokai Carbon Co., Ltd.)

<Silane coupling agent>
Silane coupling agent (product name "Si75" manufactured by Evonik Degussa, bis(triethoxysilylpropyl)disulfide)

<Resin>
Hydrogenated resin 1: Arakawa Chemical Industries Co., Ltd. Alcon M-115 (C9 resin, softening point 115°C, partially hydrogenated)
Hydrogenated resin 2: Arakawa Chemical Industries Co., Ltd. Alcon M-135 (C9 resin, softening point 135°C, partially hydrogenated)
Hydrogenated resin 3: Arakawa Chemical Industries Co., Ltd. Alcon M-90 (C9 resin, softening point 90°C, partially hydrogenated)
Hydrogenated terpene: Clearon M125 (terpene resin, softening point 125°C, fully hydrogenated) manufactured by Yasuhara Chemical Co., Ltd.
Non-hydrogenated resin: ENEOS Corporation Neopolymer 150 (C9 resin, softening point 150°C, non-hydrogenated)
Fully hydrogenated resin: Alcon P-140 (C9 resin, fully hydrogenated, softening point 140°C) manufactured by Arakawa Chemical Industries, Ltd. The above hydrogenated resins 1 to 3 and hydrogenated terpene correspond to hydrogenated ring-containing resins (C) having a softening point of less than 140°C.

<Extender oil>
Plant-derived oil: NOVANCE LUBRIROB TOD 1880 (sunflower oil)
Mineral oil: JX Nippon Oil & Energy Corporation Process NC140 (SRAE oil)

<Vulcanizing agent>
sulfur

<Vulcanization accelerator>
Vulcanization accelerator 1: CBS (N-cyclohexyl-2-benzothiazylsulfinamide)
Vulcanization accelerator 2: DPG (diphenyl guanidine)

<Vulcanization aid>
Zinc oxide Stearic acid

＜Other＞
Wax (paraffin wax)
Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)

In the table, "resin/styrene content" indicates "amount (parts by mass) of hydrogenated ring-containing resin (C) relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking/content (ST) (mass%) of vinyl aromatic monomer units in the rubber-like polymer (A)."
"Amount of silica/amount of oil" refers to "the amount of silica (parts by mass)/the amount of oil (parts by mass) relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking."

(Characteristics evaluation)
<(Evaluation 1) Processability>
The compound before the third stage kneading was used as a sample, and the viscosity was measured using a Mooney viscometer in accordance with ISO 289 after preheating at 130°C for 1 minute and rotating the rotor at 2 revolutions per minute for 4 minutes.
The result of Comparative Example 1 was set to 100 and indexed.
A larger index indicates better processability.
Tables 2 to 4 show symbols for the cases where each performance varies within the following ranges with Comparative Example 1 as the standard.
AA: Improved by 20% or more A: Improved by 15% or more but less than 20% B: Improved by 5% or more but less than 15% C: Improved by 0% or more but less than 5% D: Worsened by more than 0% but less than 10% E: Worsened by 10% or more

<(Evaluation 2) Tensile Energy>
The tensile energy of the obtained vulcanized rubber test pieces was evaluated by the test method described below.
The tensile energy results of each example were indexed with the result of Comparative Example 1 set at 100.
The larger the value, the higher the tensile energy and the better the rubber strength.
[Measurement of tensile energy]
A JIS No. 3 dumbbell-shaped test piece was punched out from the obtained vulcanized rubber test piece, and a tensile test was performed at a tensile speed of 500 mm/min in accordance with JIS K6251:2010. The stress was measured by integrating the stress from zero strain to the fracture strain in the obtained stress-strain curve.
In Tables 2 to 4, the symbols are given when each performance property changes within the following ranges with Comparative Example 1 as the standard.
AA: Improved by 20% or more A: Improved by 15% or more but less than 20% B: Improved by 5% or more but less than 15% C: Improved by 0% or more but less than 5% D: Worsened by more than 0% but less than 10% E: Worsened by 10% or more

<(Evaluation 3) Abrasion resistance>
Using an Acron abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the amount of abrasion was measured at a load of 44.4 N and 1000 revolutions in accordance with JIS K6264-2, and the result of Comparative Example 1 was indexed to 100.
A larger index indicates better abrasion resistance.
In Tables 2 to 4, the symbols are given when each performance property changes within the following ranges with Comparative Example 1 as the standard.
AA: Improved by 20% or more A: Improved by 15% or more but less than 20% B: Improved by 5% or more but less than 15% C: Improved by 0% or more but less than 5% D: Worsened by more than 0% but less than 10% E: Worsened by 10% or more

The crosslinkable rubber composition of this embodiment has industrial applicability in fields such as tire components, interior and exterior parts of automobiles, anti-vibration rubber, belts, footwear, foams, and various industrial product applications.

Claims (10)

a rubber-like polymer (A) having an iodine value of 10 to 250 (g/100 g), an ethylene structure of 3 mass% or more, a vinyl aromatic monomer unit content of 5 mass% or more and 30 mass% or less, and a vinyl aromatic monomer block having 8 or more chained vinyl aromatic monomer units of less than 10 mass%;
A crosslinking agent (B);
A hydrogenated ring-containing resin (C) having a softening point of less than 140° C.;
A crosslinkable rubber composition comprising:
The rubber-like polymer (A) has a weight average molecular weight of 250,000 or more and 1,000,000 or less,
The rubber-like polymer (A) has a modification rate of 70% by mass or more as measured by a column adsorption GPC method,
the content of the rubber-like polymer (A) relative to the total amount of rubber components in the rubber composition for crosslinking is 20 mass% or more,
the content of the ring-containing resin (C) is 30 parts by mass or less based on 100 parts by mass of the total amount of rubber components in the rubber composition for crosslinking,
The rubber composition for crosslinking further contains silica and oil,
The ratio of the amount of silica (parts by mass)/the amount of oil (parts by mass) relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking is 6 or more.
Crosslinkable rubber composition . 2. The crosslinkable rubber composition according to claim 1 , wherein the content of vinyl units and butylene units in the rubber-like polymer (A) is 20 mol % or more. The crosslinkable rubber composition according to claim 1 or 2 , wherein the rubber-like polymer (A) contains a nitrogen atom. The hydrogenated ring-containing resin (C) having a softening point of less than 140° C. has a softening point of 90° C. or higher.
The rubber composition for crosslinking according to any one of claims 1 to 3 . Relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking,
The softening point of the hydrogenated ring-containing resin (C) is less than 140 ° C., and the hydrogenated ring-containing resin (C) contains 10 to 30 parts by mass.
The crosslinkable rubber composition according to claim 1 . the amount (parts by mass) of the hydrogenated ring-containing resin (C) having a softening point of less than 140° C. relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking/the content (ST) (% by mass) of the vinyl aromatic monomer unit in the rubber polymer (A) is
The rubber composition for crosslinking according to claim 1 , wherein the modulus is 0.3 or more. The hydrogenated ring-containing resin (C) having a softening point of less than 140° C. is a partially hydrogenated resin and/or a hydrogenated terpene resin.
The rubber composition for crosslinking according to any one of claims 1 to 6 . The rubber composition for crosslinking further contains 1 to 80 parts by mass of a plant-derived oil relative to 100 parts by mass of the rubber component.
The rubber composition for crosslinking according to any one of claims 1 to 7 . Relative to 100 parts by mass of the rubber component in the rubber composition for crosslinking,
Further containing 10 to 130 parts by mass of silica,
The crosslinkable rubber composition according to any one of claims 1 to 8 . A tread for a tire comprising the rubber composition for crosslinking according to any one of claims 1 to 9 .