阅读说明：本技术 改性丁二烯聚合物及橡胶组合物 (Modified butadiene polymer and rubber composition ) 是由 新家雄 上西和也 于 2018-05-08 设计创作，主要内容包括：本发明的目的是提供在用于含有增强用填充剂的橡胶组合物时显示优异的分散性、加工性、韧性、低发热性和耐磨耗性的配合剂、以及含有上述配合剂的橡胶组合物。本发明的改性丁二烯聚合物在末端具有包含氮原子和硅原子的官能团,重均分子量为1,000以上且15,000以下,分子量分布为2.0以下。(The purpose of the present invention is to provide a compounding agent that exhibits excellent dispersibility, processability, toughness, low heat build-up and abrasion resistance when used in a rubber composition containing a reinforcing filler, and a rubber composition containing the compounding agent. The modified butadiene polymer of the present invention has a functional group containing a nitrogen atom and a silicon atom at the terminal, has a weight average molecular weight of 1,000 or more and 15,000 or less, and has a molecular weight distribution of 2.0 or less.)

1. A modified butadiene polymer having a functional group containing a nitrogen atom and a silicon atom at the terminal,

the modified butadiene polymer has a weight average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less.

2. The modified butadiene polymer according to claim 1, wherein the viscosity of the modified butadiene polymer is 150 to 240% of the viscosity of the butadiene polymer before modification, wherein the viscosity is measured using a cone-and-plate viscometer.

3. The modified butadiene polymer according to claim 1 or 2, which is used in a rubber composition containing: a rubber component having a weight average molecular weight of more than 15,000; and a reinforcing filler containing at least 1 selected from carbon black and silica.

4. A rubber composition comprising: a rubber component having a weight average molecular weight of more than 15,000; a reinforcing filler; and the modified butadiene polymer according to any one of claims 1 to 3,

the content of the reinforcing filler is 50 to 200 parts by mass per 100 parts by mass of the rubber component,

the content of the modified butadiene polymer is 1 to 25 mass% relative to the content of the reinforcing filler.

5. A rubber composition comprising: a rubber component having a weight average molecular weight of more than 15,000; a reinforcing filler containing at least 1 selected from carbon black and silica; and the modified butadiene polymer according to any one of claims 1 to 3.

6. The rubber composition according to claim 4 or 5, wherein the reinforcing filler contains at least 1 selected from the group consisting of carbon black and silica,

the nitrogen adsorption specific surface area of the silicon dioxide is 194m²More than g, and the CTAB adsorption specific surface area is 185m²The ratio of nitrogen adsorption specific surface area to CTAB adsorption specific surface area is 0.9 to 1.4.

7. The rubber composition according to claim 5 or 6, further comprising a silane coupling agent,

the content of the silane coupling agent is 1-20 mass% relative to the content of the silica.

8. The rubber composition according to any one of claims 4 to 7, wherein the glass transition temperature of the rubber component is-60 ℃ or higher.

Technical Field

The present invention relates to a modified butadiene polymer and a rubber composition.

Background

In general, a rubber composition used for a tire or the like contains a reinforcing filler such as carbon black or silica. On the other hand, due to the interaction between the reinforcing fillers, the reinforcing fillers aggregate in the rubber composition and sufficient characteristics (for example, processability, toughness, low heat build-up property, abrasion resistance) may not be obtained.

Among them, for example, patent document 1 discloses a modified low-molecular weight conjugated diene polymer as a compounding agent for a rubber composition containing a reinforcing filler (claims and the like).

Disclosure of Invention

Problems to be solved by the invention

The present inventors have studied using a modified conjugated diene rubber as a compounding agent with reference to examples of patent document 1, and as a result, have found that the dispersibility of a reinforcing filler (hereinafter, the "dispersibility of a reinforcing filler" is also simply referred to as "dispersibility") and the properties of the obtained rubber composition do not necessarily satisfy the level required in recent years.

In view of the above circumstances, an object of the present invention is to provide a compounding agent which exhibits excellent dispersibility, processability, toughness, low heat build-up and abrasion resistance when used in a rubber composition containing a reinforcing filler, and a rubber composition containing the compounding agent.

Means for solving the problems

As described above, it has been found from the results of the studies by the present inventors that the dispersibility of the reinforcing filler is insufficient when the modified conjugated diene rubber used in the examples of patent document 1 is used as a compounding agent. More specifically, it is found that even when a modified butadiene polymer (modified BR) having a weight average molecular weight of 8 ten thousand, which is used in the examples of patent document 1, is blended in a rubber composition containing a reinforcing filler, the dispersibility of the reinforcing filler is insufficient.

The present inventors have made studies focusing on the size of the modified butadiene polymer, and as a result, have found that a significant correlation is observed between the weight average molecular weight and the molecular weight distribution of the modified butadiene polymer and the dispersibility of the reinforcing filler, and that the dispersibility of the reinforcing filler is significantly improved by setting the weight average molecular weight and the molecular weight distribution to specific ranges.

The present invention is based on the above-described knowledge, and its specific configuration is as follows.

(1) A modified butadiene polymer having a functional group containing a nitrogen atom and a silicon atom at the terminal,

the modified butadiene polymer has a weight average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less.

(2) The modified butadiene polymer according to the item (1), wherein the viscosity of the modified butadiene polymer is 150 to 240% of the viscosity of the butadiene polymer before modification. Wherein the viscosity is measured using a cone and plate viscometer.

(3) The modified butadiene polymer according to the above (1) or (2), which is used in a rubber composition containing: a rubber component having a weight average molecular weight of more than 15,000; and a reinforcing filler containing at least 1 selected from carbon black and silica.

(4) A rubber composition comprising: a rubber component having a weight average molecular weight of more than 15,000; a reinforcing filler; and the modified butadiene polymer according to any one of the above (1) to (3),

the content of the reinforcing filler is 50 to 200 parts by mass per 100 parts by mass of the rubber component,

the content of the modified butadiene polymer is 1 to 25% by mass based on the content of the reinforcing filler.

(5) A rubber composition comprising: a rubber component having a weight average molecular weight of more than 15,000; a reinforcing filler containing at least 1 selected from carbon black and silica; and the modified butadiene polymer according to any one of (1) to (3) above.

(6) The rubber composition according to the above (4) or (5), wherein the reinforcing filler contains at least 1 selected from carbon black and silica,

the nitrogen adsorption specific surface area of the silica was 194m²More than g, and the CTAB adsorption specific surface area is 185m²The ratio of nitrogen adsorption specific surface area to CTAB adsorption specific surface area is 0.9 to 1.4.

(7) The rubber composition according to the above (5) or (6), which further comprises a silane coupling agent,

the content of the silane coupling agent is 1 to 20 mass% relative to the content of the silica.

(8) The rubber composition according to any one of the above (4) to (7), wherein the glass transition temperature of the rubber component is-60 ℃ or higher.

ADVANTAGEOUS EFFECTS OF INVENTION

As shown below, according to the present invention, it is possible to provide a compounding agent which exhibits excellent dispersibility, processability, toughness, low heat generation property and wear resistance when used in a rubber composition containing a reinforcing filler, and a rubber composition containing the compounding agent.

Detailed Description

The modified butadiene polymer as a compounding agent of the present invention and a rubber composition containing the modified butadiene polymer will be described below.

In the present specification, the numerical range expressed by the term "to" means a range including the numerical values described before and after the term "to" as the lower limit value and the upper limit value.

[ specific modified BR ]

The modified butadiene polymer as the compounding agent of the present invention is a butadiene polymer (butadiene polymer) having a functional group (hereinafter, also referred to as a "specific functional group") containing a nitrogen atom and a silicon atom at the terminal, a weight average molecular weight of 1,000 or more and 15,000 or less, and a molecular weight distribution of 2.0 or less.

Hereinafter, the modified butadiene polymer as the compounding agent of the present invention is also referred to as "specific modified BR".

By adopting such a constitution, it is considered that the specific modified BR exhibits excellent dispersibility of the reinforcing filler in the rubber composition when used in the rubber composition containing the reinforcing filler.

The reason for this is not specifically understood, but it is considered that aggregation of the reinforcing filler is prevented by interaction between the nitrogen atom and the silicon atom in the specific functional group of the specific modified BR and the reinforcing filler. As described above, the present inventors found that a criticality is observed between the size (weight average molecular weight, molecular weight distribution) of the modified BR and the dispersibility of the reinforcing filler. This is presumably because, when the size (weight average molecular weight, molecular weight distribution) of the modified BR is within the above-described specific range, the modified BR is extremely likely to enter the gaps between aggregates of the reinforcing fillers, and as a result, the dispersibility of the reinforcing filler is greatly improved.

Hereinafter, specific modified BR will be described in detail.

As described above, the specific modified BR is a butadiene polymer (modified butadiene polymer) having a functional group (specific functional group) containing a nitrogen atom and a silicon atom at the end, a weight average molecular weight of 1,000 or more and 15,000 or less, and a molecular weight distribution of 2.0 or less.

[ specific functional group ]

As described above, the specific modified BR has a functional group (specific functional group) containing a nitrogen atom and a silicon atom at the terminal. The specific functional group may have at least 1 terminal.

< preferred embodiment >

The specific functional group is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom, but an amino group (-NR) is preferable from the viewpoint of further improving the effect of the present invention₂: r is a hydrogen atom or a hydrocarbon group) contains a nitrogen atom, preferably in the form ofThe hydrocarbyloxysilyl group (≡ SiOR: R is a hydrocarbon group) contains a silicon atom in its form.

The specific functional group is preferably a group represented by the following formula (M) because the effect of the present invention is more excellent.

In the above formula (M), R₁And R₂Each independently represents a hydrogen atom or a substituent.

In the formula (M), L represents a 2-valent organic group.

The substituent is not particularly limited as long as it is a 1-valent substituent, and examples thereof include a halogen atom, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, a phosphono group, a silyl group, and a hydrocarbon group which may have a hetero atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

Examples of the hetero atom of the hydrocarbon group which may have a hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom and the like.

Examples of the hydrocarbon group which may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a combination thereof.

The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear or branched alkyl group (particularly, having 1 to 30 carbon atoms), a linear or branched alkenyl group (particularly, having 2 to 30 carbon atoms), a linear or branched alkynyl group (particularly, having 2 to 30 carbon atoms), and the like.

Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

In the formula (M), R is R for further improving the effect of the present invention₁Preferably a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), or an alkylsilyl group (preferably having 1 to 10 carbon atoms)1 to 10 carbon atoms), an aromatic hydrocarbon group (preferably 6 to 18 carbon atoms), and more preferably a hydrogen atom.

Plural R₁May be the same or different.

From the reason that the effect of the present invention is more excellent, R₂The alkyl oxy group (-OR group: R is a hydrocarbon group) is preferable, and the alkoxy group (preferably having 1 to 10 carbon atoms) is more preferable.

As described above, in the formula (M), L represents a single bond or a 2-valent organic group.

Examples of the 2-valent organic group include, for example, an aliphatic hydrocarbon group (e.g., an alkylene group, preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (e.g., an arylene group, preferably having 6 to 18 carbon atoms), -O-, -S-, -SO₂-, -N (R) - (R: alkyl), -CO-, -NH-, -COO-, -CONH-, or a group combining them (for example, alkyleneoxy (-C)_mH_2mO-: m is a positive integer), alkyleneoxycarbonyl, alkylenecarbonyloxy, etc.).

L is preferably an alkylene group (preferably having 1 to 10 carbon atoms) because the effect of the present invention is more excellent.

In the formula (M), n represents an integer of 0 to 2.

For the reason that the effect of the present invention is more excellent, n is preferably 2.

In the formula (M), M represents an integer of 1 to 3.

For the reason that the effect of the present invention is more excellent, m is preferably 1.

In the above formula (M), n and M satisfy the relationship that n + M is 3.

In the above formula (M), the symbol represents a binding site.

[ weight average molecular weight ]

As described above, the weight average molecular weight (Mw) of the specific modified BR is 1,000 or more and 15,000 or less. Among them, from the reason that the effect of the present invention is more excellent, it is preferably 5,000 or more and less than 10,000.

[ number average molecular weight ]

The number average molecular weight of the specific modified BR is not particularly limited as long as the weight average molecular weight and the molecular weight distribution of the specific modified BR are within specific ranges, but is preferably 1,000 or more and 15,000 or less, more preferably 5,000 or more and less than 10,000, from the viewpoint of further improving the effects of the present invention.

[ molecular weight distribution ]

As described above, the molecular weight distribution (Mw/Mn) of the specific modified BR is 2.0 or less. Among these, from the viewpoint of further improving the effect of the present invention, it is preferably 1.7 or less, more preferably 1.5 or less, and further preferably 1.3 or less.

The lower limit is not particularly limited, and is usually 1.0 or more.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene converted values obtained by Gel Permeation Chromatography (GPC) measurement under the following conditions.

Solvent: tetrahydrofuran (THF)

The detector: RI detector

[ microstructure ]

< vinyl Structure >

The proportion of the vinyl structure in the specific modified BR is not particularly limited, but is preferably 10 to 50 mol%, more preferably 20 to 40 mol%, from the viewpoint of further improving the effect of the present invention.

Here, the proportion of the vinyl structure refers to the proportion (mol%) of the repeating units having a vinyl structure among the repeating units derived from butadiene.

< 1, 4-trans structure >

In the specific modified BR, the proportion of the 1, 4-trans structure is not particularly limited, but is preferably 10 to 70 mol%, more preferably 30 to 50 mol%, from the viewpoint of further improving the effect of the present invention.

The proportion of the 1, 4-trans structure is the proportion (mol%) of the repeating unit having a 1, 4-trans structure among all the repeating units derived from butadiene.

< 1, 4-cis structure >

In the specific modified BR, the proportion of the 1, 4-cis structure is not particularly limited, but is preferably 10 to 50 mol%, more preferably 20 to 40 mol%, from the viewpoint that the effect of the present invention is more excellent.

The proportion of the 1, 4-cis structure is the proportion (mol%) of the repeating unit having a 1, 4-cis structure among all repeating units derived from butadiene.

Hereinafter, the "proportion (mol%) of vinyl structure, proportion (mol%) of 1, 4-trans structure, and proportion (mol%) of 1, 4-cis structure" are also referred to as "vinyl/trans/cis".

[ glass transition temperature ]

The glass transition temperature (Tg) of the specific modified BR is not particularly limited, but is preferably from-100 to-60 ℃, more preferably from-90 to-70 ℃, and still more preferably from-85 to-75 ℃ from the viewpoint of further improving the effect of the present invention.

In the present specification, the glass transition temperature (Tg) is measured at a temperature increase rate of 10 ℃/min using a Differential Scanning Calorimeter (DSC), and is calculated by the midpoint method.

[ viscosity ]

The viscosity of the specific modified BR is not particularly limited, but is preferably 1,000 to 10,000 mPas, more preferably 3,000 to 6,000 mPas, from the viewpoint of further improving the effect of the present invention.

The viscosity of the butadiene polymer before the modification of the specific modified BR is not particularly limited, but is preferably 500 to 5,000 mPas, more preferably 1,500 to 3,000 mPas, because the effect of the present invention is more excellent.

Further, the viscosity of the specific modified BR is preferably 150 to 240% of the viscosity of the butadiene polymer before modification, from the viewpoint that the effect of the present invention is more excellent. Hereinafter, the viscosity of the modified BR after modification with respect to the specific BR before modification is also referred to as "viscosity (after modification/before modification)".

In the present specification, the viscosity is measured by a cone-plate viscometer in accordance with JIS K5600-2-3.

[ method for producing modified BR ]

The method for producing the specific modified BR is not particularly limited, and conventionally known methods can be used. The method for adjusting the molecular weight and the molecular weight distribution to specific ranges is not particularly limited, and examples thereof include a method of adjusting the amount ratio of the initiator to the monomer to the terminator, the reaction temperature, the rate of addition of the initiator, and the like.

< preferred embodiment >

A preferred embodiment of the method for producing the specific modified BR includes, for example, a method in which butadiene is polymerized using an organolithium compound, and then the polymerization is terminated using an electrophile containing a nitrogen atom and a silicon atom (hereinafter, also referred to as "the method of the present invention"). When the method of the present invention is used, the obtained specific modified BR exhibits more excellent dispersibility, processability, toughness, low heat generation property, and abrasion resistance when used in a rubber composition containing a reinforcing filler.

(organic lithium Compound)

The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; and polyfunctional organic lithium compounds such as 1, 4-dilithiobutane, 1, 5-dilithiopentane, 1, 6-dilithiohexane, 1, 10-dilithiodecane, 1-dilithiodiphenylene, dilithiobutapolybutadiene, dilithiopolypolyisoprene, 1, 4-dilithiobenzene, 1, 2-dilithio-1, 2-diphenylethane, 1, 4-dilithio-2-ethylcyclohexane, 1,3, 5-trilithiobenzene, and 1,3, 5-trilithio-2, 4, 6-triethylbenzene. Among these, the mono-organolithium compounds of n-butyllithium, sec-butyllithium, and tert-butyllithium are preferable because the effects of the present invention are more excellent.

The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol% based on butadiene, from the viewpoint of further improving the effect of the present invention.

(copolymerization of butadiene)

The method for polymerizing butadiene using the organolithium compound is not particularly limited, and examples thereof include a method in which the organolithium compound is added to a solution of butadiene-containing organic solvent, and stirred at a temperature ranging from 0 to 120 ℃ (preferably from 30 to 100 ℃).

(specific electrophiles)

In the method of the present invention, the polymerization of butadiene is terminated using an electrophile containing a nitrogen atom and a silicon atom (hereinafter, also referred to as a "specific electrophile"). By terminating the polymerization with a specific electrophile, a modified butadiene polymer having the above-mentioned specific functional group at the terminal can be obtained.

The specific electrophile is not particularly limited as long as it is a compound containing a nitrogen atom and a silicon atom, but an amino group (-NR) is preferable from the viewpoint of further improving the effect of the present invention₂: r is a hydrogen atom or a hydrocarbon group) contains a nitrogen atom, preferably in the form of a hydrocarbyloxysilyl group (≡ SiOR: r is a hydrocarbon group) contains a silicon atom.

The specific electrophile is preferably a silazane, and more preferably a cyclic silazane, for the reason that the effect of the present invention is more excellent. Here, the silazane refers to a compound having a structure in which a silicon atom is directly bonded to a nitrogen atom (a compound having an Si — N bond).

The cyclic silazane is preferably a compound represented by the following formula (S) because the effect of the present invention is more excellent.

In the above formula (S), R₁～R₃Each independently represents a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituents are the same as those for R in the above-mentioned formula (M)₁And R₂The same is true.

In the formula (S), L represents a 2-valent organic group. Specific examples and preferred embodiments of the 2-valent organic group are the same as those of L in the above formula (M).

In the formula (S), R is R for further improving the effect of the present invention₁Preferably an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably an alkylsilyl group.

In the above formula (S), the inventionThe reason why the effect is more excellent is that R₂And R₃Each independently is preferably a hydrocarbyloxy group (-OR group: R is a hydrocarbyl group), more preferably an alkoxy group (preferably having 1 to 10 carbon atoms).

In the formula (S), L is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and further preferably 3 to 5 carbon atoms) because the effect of the present invention is more excellent.

Examples of the compound represented by the formula (S) include N-N-butyl-1, 1-dimethoxy-2-azasilacyclopentane, N-phenyl-1, 1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1, 1-dimethoxy-2-azasilacyclopentane, and N-trimethylsilyl-1, 1-diethoxy-2-azasilacyclopentane.

In addition, the silicon atom of the cyclic silazane is considered to exhibit electrophilicity.

The amount of the specific electrophile to the organolithium compound is not particularly limited, but is preferably 0.1 to 10, more preferably 1 to 5 in terms of a molar ratio, from the viewpoint of further improving the effect of the present invention.

[ rubber composition ]

The rubber composition of the present invention (hereinafter, also referred to as "the composition of the present invention") is a rubber composition containing a rubber component having a weight average molecular weight of more than 15,000, a reinforcing filler, and the above-mentioned specific modified BR.

[ rubber component ]

The rubber component is not particularly limited as long as it has a weight average molecular weight (Mw) of more than 15,000.

The rubber component is preferably a diene rubber because the effect of the present invention is more excellent. Specific examples of the diene rubber include Natural Rubber (NR), Isoprene Rubber (IR), Butadiene Rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), Chloroprene Rubber (CR), and the like. Among them, SBR and BR are preferable because the effect of the present invention is more excellent.

The content of the styrene unit (repeating unit derived from styrene) in the SBR (styrene unit content) is not particularly limited, but is preferably 5 to 50 mass% from the viewpoint of further improving the effect of the present invention.

The proportion of the vinyl structure of the SBR is not particularly limited, but is preferably 5 to 80%, more preferably 10 to 75%, and still more preferably 20 to 70% from the viewpoint of further improving the effect of the present invention. Here, the proportion of the vinyl structure refers to the proportion (mol%) of the repeating units having a vinyl structure among the repeating units derived from butadiene.

< weight average molecular weight >

As described above, the weight average molecular weight (Mw) of the rubber component exceeds 15,000. The Mw of the rubber component is preferably 100,000 to 10,000,000 for the reason that the effect of the present invention is more excellent.

The weight average molecular weight is measured as described above.

< glass transition temperature >

The glass transition temperature (Tg) of the rubber component is not particularly limited, but is preferably-60 ℃ or higher because the effect of the present invention is more excellent. The upper limit is not particularly limited, but is preferably 0 ℃ or lower, more preferably-20 ℃ or lower, from the viewpoint of further improving the effect of the present invention. The Tg was determined as described above.

In addition, in the case where the rubber component is an oil-extended product, the glass transition temperature of the rubber component is the glass transition temperature in a state where the oil-extended component (oil) is not contained. In addition, in the case where the rubber component contains 2 or more rubber components, the glass transition temperature of the rubber component is the average glass transition temperature. Here, the average glass transition temperature is a product obtained by multiplying the glass transition temperature of each rubber component by the total mass fraction of each rubber component (weighted average of glass transition temperatures), and the total mass fraction of all the rubber components is defined as 1.

[ Filler for reinforcing ]

The reinforcing filler contained in the composition of the present invention is not particularly limited, and is preferably at least 1 selected from silica and carbon black.

The content of the reinforcing filler in the composition of the present invention is not particularly limited, but is preferably 50 to 200 parts by mass, more preferably 60 to 100 parts by mass, based on 100 parts by mass of the rubber component, for the reason that the effect of the present invention is more excellent.

When the composition of the present invention contains 2 or more reinforcing fillers, the content of the reinforcing filler means the total content.

< silica >)

The composition of the present invention preferably contains silica as a reinforcing filler, because the effect of the present invention is more excellent.

The silica is not particularly limited, and any conventionally known silica can be used.

Examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth. The silica may be used alone in 1 kind, or 2 or more kinds may be used in combination.

The cetyl trimethylammonium bromide (CTAB) adsorption specific surface area of the silica (hereinafter, the "CTAB adsorption specific surface area" is also simply referred to as "CTAB") is not particularly limited, but is preferably 100 to 300m from the viewpoint of further excellent effects of the present invention²(iv)/g, more preferably 185m²More than g.

Here, the CTAB adsorption specific surface area is in accordance with JIS K6217-3: 2001 "section 3: the expression "CTAB adsorption method (section 3: the expression め for determining the specific gravity) -which is the expression of specific surface area" is a value obtained by measuring the amount of CTAB adsorbed on the surface of silica.

Nitrogen adsorption specific surface area (N) of the above silica₂SA), but is preferably 100 to 300m from the viewpoint of further improving the effect of the present invention²(iv)/g, more preferably 194m²More than g.

Here, N₂SA is a substitute characteristic of silica for its surface area that can be used for adsorption to rubber molecules, and is measured according to JIS K6217-2: 2001 "section 2: of specific surface areaThe method of determining the amount of nitrogen adsorbed on the surface of silica, nitrogen adsorption method-single-point method (section 2: determination of specific gravity from め method-asphyxiation method- point method)'.

Ratio of nitrogen adsorption specific surface area of silica to CTAB adsorption specific surface area of silica (N)₂SA/CTAB) is not particularly limited, but is preferably 0.9 to 1.4 from the viewpoint of further improving the effect of the present invention.

The content of silica in the composition of the present invention is not particularly limited, but is preferably 10 to 150 parts by mass, more preferably 50 to 100 parts by mass, based on 100 parts by mass of the rubber component, because the effect of the present invention is more excellent.

< carbon Black >

The composition of the present invention preferably contains carbon black as a reinforcing filler, because the effect of the present invention is more excellent. The carbon black may be used alone in 1 kind, or may be used in combination with 2 or more kinds.

The carbon black is not particularly limited, and various grades of carbon black such as SAF-HS, SAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF-LS, FEF, GPF, SRF and the like can be used.

The nitrogen adsorption specific surface area (N) of the carbon black₂SA), but not particularly limited, and is preferably 50 to 200m from the viewpoint of further improving the effect of the present invention²A concentration of 70 to 150m is more preferable²/g。

Here, the nitrogen adsorption specific surface area (N)₂SA) is a value according to JIS K6217-2: 2001 "section 2: the specific surface area determination method, nitrogen adsorption method, single point method (section 2: the specific surface area determination method of め side, asphyxiation method, point method)', was measured for the amount of nitrogen adsorbed on the carbon black surface.

The content of carbon black in the composition of the present invention is not particularly limited, but is preferably 1 to 100 parts by mass, more preferably 2 to 10 parts by mass, per 100 parts by mass of the rubber component, for the reason that the effect of the present invention is more excellent.

[ specific modified BR ]

As described above, the composition of the present invention contains the above-mentioned specific modified BR.

The content of the specific modified BR in the composition of the present invention is not particularly limited, but is preferably 1 to 25% by mass, more preferably 2.0 to 10.0% by mass, based on the content of the reinforcing filler, for the reason that the effect of the present invention is more excellent.

Further, the content of the specific modified BR is preferably 1 part by mass or more and less than 10 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of further improving the effects of the present invention.

[ silane coupling agent ]

The composition of the present invention preferably contains a silane coupling agent because the effect of the present invention is more excellent. The silane coupling agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group.

The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Among them, an alkoxy group is preferable. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16, more preferably 1 to 4. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, and examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a thioether group, a mercapto group, and the like, and among them, a thioether group and a mercapto group are preferable.

The silane coupling agent is preferably a silane coupling agent containing sulfur.

Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate monosulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, and 1 kind or more of these may be used alone or 2 or more kinds may be used in combination.

The content of the silane coupling agent in the composition of the present invention is not particularly limited, but is preferably 1 to 20% by mass, more preferably 5 to 10% by mass, based on the content of the silica, because the effect of the present invention is more excellent.

[ other Components ]

The composition of the present invention may contain, if necessary, components (other components) other than the above components within a range not impairing the effects and the objects thereof.

Examples of such components include various additives generally used in rubber compositions, such as terpene resins (preferably aromatic modified terpene resins), heat-expandable microcapsules, zinc oxide (zinc oxide), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), and vulcanization accelerators.

[ use ]

The composition of the present invention is preferably used for tires, conveyor belts, hoses, vibration-proof materials, rubber rollers, outer tarpaulins for railway vehicles, and the like. Particularly preferably for tires.