JP2018083890A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition excellent in balance between fuel economy and wet grip performance.SOLUTION: The rubber composition contains, based on 100 pts.mass of a diene rubber, 20-150 pts.mass of silica and 1-100 pts.mass of fine particles comprising a polymer which has a constituent unit represented by general formula (1) and at least one functional group selected from a nitrile group, an amino group, a carboxyl group, an epoxy group, and a hydroxyl group and which does not have a reactive silyl group. A pneumatic tire using the rubber composition is also provided. In the formula (1), Ris a hydrogen atom or a methyl group, and Ris a C4-18 alkyl group.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  For example, rubber compositions used for tires are required to balance the grip performance (wet grip performance) on wet road surfaces and the rolling resistance performance contributing to low fuel consumption at a high level. However, since these are contradictory properties, it is not easy to improve at the same time. Silica is used as a filler in order to achieve both low fuel consumption and wet grip performance. However, with the growing interest in the environment and safety, it is required to improve these characteristics at a higher level. .

  Patent Document 1 discloses that the weight average molecular weight is 5,000 to 1,000,000 and the glass transition point is −70 to 0 ° C. for the purpose of improving wet grip performance while suppressing deterioration of fuel efficiency. ) It is disclosed that an acrylate polymer is blended. However, there is no disclosure of blending fine particles made of a polymer having a specific functional group with a specific (meth) acrylate structural unit.

  Patent Document 2 discloses kneading a modified diene rubber having a hydrocarbyloxysilyl group, crosslinked rubber particles, and silica in order to obtain a rubber elastic body having a small rolling resistance and excellent rebound resilience. Yes. In this document, the balance between rolling resistance performance and wet grip performance is improved, but the crosslinked rubber particles are mainly composed of a diene rubber, and have a specific functional group together with a specific (meth) acrylate structural unit. There is no disclosure of blending fine particles comprising a polymer having the same.

  Patent Document 3 discloses a non-aromatic vinyl polymer (for example, (meth) acrylate) having a reactive silyl group represented by the formula ≡Si-X (wherein X is hydroxyl or a hydrolyzable group). It is disclosed that polymer nanoparticles) are blended into a rubber composition. However, in this document, the nanoparticles are used as a reinforcing filler, and it is essential to have a reactive silyl group in order to exhibit reinforcing properties when used in combination with a coupling agent. There is no disclosure that the balance between low fuel consumption and wet grip performance can be improved by using fine particles made of a specific (meth) acrylate polymer having no reactive silyl group.

WO2015 / 155965A1 WO2012 / 111640A1 Special table 2009-542827

  An object of an embodiment of the present invention is to provide a rubber composition that is excellent in balance between low fuel consumption and wet grip performance when used in tire applications.

  The rubber composition according to the embodiment has 20 to 150 parts by mass of silica and a structural unit represented by the following general formula (1) with respect to 100 parts by mass of the diene rubber, and also includes a nitrile group, an amino group, and a carboxyl group. And 1 to 100 parts by mass of fine particles made of a polymer having at least one functional group selected from the group consisting of an epoxy group and a hydroxyl group and having no reactive silyl group.

式（１）中、Ｒ^１は水素原子又はメチル基であり、同一分子中のＲ^１は同一でも異なっていてもよく、Ｒ^２は炭素数４〜１８のアルキル基であり、同一分子中のＲ^２は同一でも異なっていてもよい。

In Formula (1), R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, and in the same molecule R ² may be the same or different.

  The pneumatic tire according to the embodiment is manufactured using the rubber composition.

  According to the embodiment, it is possible to provide a rubber composition excellent in the balance between low fuel consumption and wet grip performance when used in tire applications.

  The rubber composition according to the present embodiment comprises (A) a diene rubber, (B) silica, (C) a weight having a structural unit represented by the general formula (1) and having a specific functional group. And a fine particle made of a coalescence. According to this embodiment, it is considered that the silica and the specific fine particles are highly dispersed in the diene rubber forming the matrix phase. Therefore, low fuel consumption and wet grip performance when used in a tire are achieved. The balance can be improved.

(A) Diene rubber As the diene rubber as a rubber component, for example, natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), Examples include chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. Two or more types can be used in combination. Among these, at least one selected from the group consisting of NR, BR and SBR is preferable.

  Specific examples of each of the diene rubbers listed above include at least one functional group selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, a silyl group, and a carboxyl group at the molecular end or molecular chain. A modified diene rubber modified with the functional group by introducing a group is also included. As the modified diene rubber, modified SBR is preferably used. Therefore, the diene rubber according to one embodiment includes a styrene butadiene rubber having at least one functional group selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, a silyl group, and a carboxyl group. By using a modified SBR having such a functional group, it is a concept including an interaction (intermolecular force such as hydrogen bond and affinity) between the silanol group on the surface of the silica particle and the ester group of the fine particle. )). Therefore, silica and the above-mentioned fine particles can be highly dispersed in the diene rubber, and it is excellent in balance between low fuel consumption, wet grip performance and tear resistance when used for tires. The diene rubber may be a modified SBR alone or a blend of a modified SBR and an unmodified diene rubber. In one embodiment, the modified SBR may be contained in an amount of 30 parts by mass or more or 50 parts by mass or more in 100 parts by mass of the diene rubber. Further, 100 parts by mass of diene rubber may include 50 to 90 parts by mass of modified SBR and 50 to 10 parts by mass of unmodified diene rubber (for example, BR and / or NR), and 60 to 90 parts by mass of modified SBR. And 40 to 10 parts by mass of unmodified diene rubber.

In these functional groups, the amino group may be not only a primary amino group (—NH ₂ ) but also a secondary amino group or a tertiary amino group. In the case of a secondary or tertiary amino group, the total number of carbon atoms of the hydrocarbon groups as substituents is preferably 15 or less, more preferably 10 or less. In the silyl group, not only a silyl group in a narrow sense represented by —SiH ₃ but also at least one of hydrogen atoms bonded to a silicon atom is substituted with a substituent such as a hydroxyl group, an alkyl group, an alkoxyl group, an alkylene group, or an ether group. It may be a substituted silyl group. For example, as the silyl group, —SiR ⁵ R ⁶ R ⁷ (wherein R ⁵ , R ⁶ , and R ⁷ are each independently a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxyl group, — (R ⁸ —O ) _p -R ^{9, or,} -O- (preferably one having 1 to 5 carbon atoms as a good. alkyl group any R ₁₀ -O) q ^{-R 11,} the alkoxyl group is those having 1 to 4 carbon atoms In the alkyl polyether group represented by — (R ⁸ —O) _p —R ⁹ and —O— (R ¹⁰ —O) _q —R ¹¹ , R ⁸ is an alkylene group having 1 to 4 carbon atoms, R ⁹ is an alkyl group having 1 to 16 carbon atoms, p is 1 to 20, R ¹⁰ is an alkylene group having 1 to 4 carbon atoms, R ¹¹ is an alkyl group having 1 to 16 carbon atoms, and q is 1 to 20 Preferred). Preferably, the silyl group is an alkylsilyl group or an alkoxysilyl group, more preferably an alkoxysilyl group. Examples of the alkoxysilyl group include a trialkoxysilyl group, an alkyl dialkoxysilyl group, and a dialkylalkoxysilyl group, and a trialkoxysilyl group such as a triethoxysilyl group or a trimethoxysilyl group is preferable.

  In one embodiment, the functional group of the modified SBR is preferably at least one selected from the group consisting of an amino group, a hydroxyl group, and a silyl group, and more preferably an amino group and / or an alkoxysilyl group. It is.

  The above functional group may be introduced into at least one end of the styrene butadiene rubber, or may be introduced into the molecular chain. That is, it may be a terminal-modified SBR in which the functional group is introduced into at least one end of the molecular chain of the SBR, or a main-chain modified SBR in which the functional group is introduced into the main chain of the SBR. It may be a main chain terminal-modified SBR having a functional group introduced therein. Modified SBR itself having such a functional group is known, and its production method and the like are not limited. For example, the functional group may be introduced by modifying a styrene butadiene rubber synthesized by anionic polymerization with a modifier.

(B) Silica Silica is not particularly limited, but wet silica such as wet precipitated silica or wet gel silica is preferably used. The BET specific surface area (measured according to the BET method described in JIS K6430) of silica is not particularly limited, and may be, for example, 90 to 250 m ² / g or 150 to 220 m ² / g.

  The compounding amount of silica is not particularly limited and can be appropriately set according to the use. The amount may be 20 to 150 parts by mass or 20 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. -100 mass parts may be sufficient, and 40-90 mass parts may be sufficient.

(C) Fine particles As fine particles, those composed of a (meth) acrylate polymer having an alkyl (meth) acrylate unit represented by the following general formula (1) as a structural unit (also referred to as a repeating unit) are used. It is done.

式（１）中、Ｒ^１は、水素原子又はメチル基であり、同一分子中に存在するＲ^１は同一でも異なってもよい。Ｒ^２は、炭素数４〜１８のアルキル基であり、同一分子中に存在するＲ^２は同一でも異なってもよい。Ｒ^２のアルキル基は直鎖でも分岐していてもよい。Ｒ^２は、炭素数６〜１６のアルキル基であることが好ましく、より好ましくは炭素数８〜１５のアルキル基である。

In Formula (1), R ¹ is a hydrogen atom or a methyl group, and R ¹ present in the same molecule may be the same or different. R ² is an alkyl group having 4 to 18 carbon atoms, and R ² present in the same molecule may be the same or different. The alkyl group for R ² may be linear or branched. R ² is preferably an alkyl group having 6 to 16 carbon atoms, and more preferably an alkyl group having 8 to 15 carbon atoms.

  The (meth) acrylate polymer is obtained by polymerizing a monomer containing one or more alkyl (meth) acrylates. Here, (meth) acrylate means one or both of acrylate and methacrylate. (Meth) acrylic acid means one or both of acrylic acid and methacrylic acid.

  Examples of the alkyl (meth) acrylate include n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-nonyl acrylate, and n-acrylate. Decyl, n-undecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, N-alkyl (meth) acrylates such as n-nonyl methacrylate, n-decyl methacrylate, n-undecyl methacrylate, and n-dodecyl methacrylate; isobutyl acrylate, isopentyl acrylate, isohexyl acrylate, isoheptyl acrylate , Isooctyl acrylate , Isononyl acrylate, isodecyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isotetradecyl acrylate, isobutyl methacrylate, isopentyl methacrylate, isohexyl methacrylate, isoheptyl methacrylate, isooctyl methacrylate, methacrylic acid Isoalkyl (meth) acrylates such as isononyl, isodecyl methacrylate, isoundecyl methacrylate, isododecyl methacrylate, isotridecyl methacrylate, and isotetradecyl methacrylate; 2-methylbutyl acrylate, 2-ethylpentyl acrylate, 2-acrylate Methylhexyl, 2-ethylhexyl acrylate, 2-ethylheptyl acrylate, 2-methylpentyl methacrylate, methacrylate Le acid 2-methylhexyl, 2-ethylhexyl methacrylate, and methacrylic acid 2-ethyl-heptyl and the like. Any of these may be used alone or in combination of two or more.

  Here, isoalkyl refers to an alkyl group having a methyl side chain at the second carbon atom from the end of the alkyl chain. For example, isodecyl means a C10 alkyl group having a methyl side chain at the second carbon atom from the chain end, and includes not only an 8-methylnonyl group but also a 2,4,6-trimethylheptyl group. It is.

  As one embodiment, the (meth) acrylate polymer is preferably a polymer having a structural unit represented by the following general formula (2) as a structural unit represented by the formula (1).

式（２）中、Ｒ^３は、水素原子又はメチル基であり（好ましくはメチル基）、同一分子中のＲ^３は同一でも異なってもよい。Ｚは、炭素数１〜１５のアルキレン基（即ち、アルカンジイル基）であり、同一分子中のＺは同一でも異なってもよい。Ｚは直鎖でも分岐していてもよい。

In Formula (2), R ³ is a hydrogen atom or a methyl group (preferably a methyl group), and R ³ in the same molecule may be the same or different. Z is an alkylene group having 1 to 15 carbon atoms (ie, alkanediyl group), and Z in the same molecule may be the same or different. Z may be linear or branched.

The structural unit of the formula (2) is a case where R ² in the formula (1) is represented by the following general formula (2A). Z in Formula (2A) is the same as Z in Formula (2).

このような構成単位を生じる（メタ）アクリレートとしては、上記の（メタ）アクリル酸イソアルキルが挙げられる。かかるイソアルキル基を有する（メタ）アクリレート（より好ましくは、メタクリレート）を用いることにより、本実施形態による効果を高めることができる。式（２）及び（２Ａ）中のＺは、炭素数５〜１２のアルキレン基であることが好ましく、より好ましくは炭素数６〜１０のアルキレン基である。

Examples of the (meth) acrylate that generates such a structural unit include the above-mentioned isoalkyl (meth) acrylate. By using (meth) acrylate (more preferably methacrylate) having such an isoalkyl group, the effect of this embodiment can be enhanced. Z in the formulas (2) and (2A) is preferably an alkylene group having 5 to 12 carbon atoms, and more preferably an alkylene group having 6 to 10 carbon atoms.

  The (meth) acrylate polymer has at least one functional group selected from the group consisting of nitrile group, amino group, carboxyl group, epoxy group and hydroxyl group. Here, those functional groups that are included as part of the reactive silyl group described later are excluded. By blending the polymer fine particles having these specific functional groups, the fine particles are obtained by the interaction between the fine particles and between the fine particles and silica (a concept including intermolecular forces such as hydrogen bonds and affinity). And the dispersibility of silica can be improved, and the balance between low fuel consumption and wet grip performance when used in tire applications can be improved.

Here, the amino group may be not only a primary amino group (—NH ₂ ) but also a secondary amino group or a tertiary amino group. In the case of a secondary or tertiary amino group, the total number of carbon atoms of the hydrocarbon groups as substituents is preferably 15 or less, more preferably 10 or less. As an epoxy group, a glycidyl group is mentioned, for example.

  The method for introducing these functional groups into the (meth) acrylate polymer is not particularly limited. For example, a vinyl monomer having the functional group (hereinafter referred to as a functional group-containing vinyl monomer) is replaced with the above alkyl (meth) acrylate. It may be copolymerized. Examples of the functional group-containing vinyl monomer include those having a nitrile group such as acrylonitrile and methacrylonitrile, and those having an amino group such as 2- (dimethylamino) ethyl acrylate and 2- (dimethyl methacrylate). Amino) ethyl, 2- (diethylamino) ethyl acrylate, 2- (diethylamino) ethyl methacrylate, 2-aminoethyl acrylate, 2-aminoethyl methacrylate, butylaminoethyl methacrylate, and the like, having a carboxyl group Examples include acrylic acid and methacrylic acid, and those having an epoxy group include glycidyl acrylate, glycidyl methacrylate, acrylic acid [(3,4-epoxycyclohexane) -1-yl] methyl, and methacrylic acid. [( 3,4-epoxycyclohexane) -1-yl] methyl and the like, and those having a hydroxyl group include, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, methacrylic acid Examples include 2-hydroxypropyl, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, and the like. These functional group-containing vinyl monomers may be used alone or in combination of two or more.

  A copolymer using such a functional group-containing vinyl monomer is represented by the following general formula (3) together with the structural unit represented by the formula (1) (preferably the structural unit represented by the formula (2)). Having a structural unit.

式（３）中、Ｒ^４は、水素原子又はメチル基であり（好ましくはメチル基）、同一分子中のＲ^４は同一でも異なってもよい。Ｑ^１は、ニトリル基（−ＣＮ）を含む基、アミノ基を含む基、カルボキシル基（−ＣＯＯＨ）を含む基、エポキシ基を含む基、又はヒドロキシル基（−ＯＨ）を含む基であり、同一分子中のＱ^１は同一でも異なってもよい。一実施形態において、Ｑ^１は、ニトリル基、又は、−ＣＯＯＱ^２でもよく、ここで、Ｑ^２は、水素原子、グリシジル基、エポキシシクロヘキシル基、−Ｑ^３−ＮＱ^４Ｑ^５、又は−Ｑ^６−ＯＨでもよい。Ｑ^３は、炭素数１〜５（好ましくは２〜４）のアルキレン基、Ｑ^４及びＱ^５は、それぞれ独立に水素原子又は炭素数１〜５（好ましくは１〜３）のアルキル基である。Ｑ^６は、炭素数１〜５（好ましくは２〜４）のアルキレン基である。

In formula (3), R ⁴ is a hydrogen atom or a methyl group (preferably a methyl group), and R ⁴ in the same molecule may be the same or different. Q ¹ is a group containing a nitrile group (—CN), a group containing an amino group, a group containing a carboxyl group (—COOH), a group containing an epoxy group, or a group containing a hydroxyl group (—OH). Q ¹ in the molecule may be the same or different. In one embodiment, Q ¹ may be a nitrile group or —COOQ ² , wherein Q ² is a hydrogen atom, a glycidyl group, an epoxycyclohexyl group, —Q ³ —NQ ⁴ Q ⁵ , or —Q ^6. -OH may also be used. Q ³ is an alkylene group having 1 to 5 (preferably 2 to 4) carbon atoms, Q ⁴ and Q ⁵ are each independently a hydrogen atom or an alkyl group having 1 to 5 (preferably 1 to 3) carbon atoms. . Q ⁶ is an alkylene group having 1 to 5 carbon atoms (preferably 2 to 4 carbon atoms).

  The (meth) acrylate polymer constituting the fine particles may be a copolymer of the above alkyl (meth) acrylate and a functional group-containing vinyl monomer, but the alkyl (meth) acrylate and the functional group-containing vinyl monomer are polyfunctional. A polymer having a crosslinked structure formed by crosslinking in the presence of a vinyl monomer may be used. That is, in a preferred embodiment, the (meth) acrylate polymer includes a structural unit derived from a polyfunctional vinyl monomer together with a structural unit represented by the formula (1) and a structural unit represented by the formula (3). And a cross-linked structure having a structural unit derived from the polyfunctional vinyl monomer as a cross-linking point.

  Polyfunctional vinyl monomers include compounds having at least two vinyl groups that can be polymerized by free radical polymerization, such as diols or triols (eg, ethylene glycol, propylene glycol, 1,4-butanediol, 1, Di (meth) acrylate or tri (meth) acrylate of 6-hexanediol, trimethylolpropane, etc .; alkylene di (meth) acrylamide such as methylenebis-acrylamide; at least 2 of diisopropenylbenzene, divinylbenzene, trivinylbenzene, etc. Examples thereof include vinyl aromatic compounds having a single vinyl group, and these can be used alone or in combination of two or more.

  The (meth) acrylate polymer constituting the fine particles preferably contains the structural unit represented by the formula (1) as a main component. Although it does not specifically limit, It is preferable that the molar ratio of the structural unit of Formula (1) with respect to all the structural units (all repeating units) which comprise a (meth) acrylate type polymer is 50 mol% or more, More preferably Is 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less. The molar ratio of the structural unit of the formula (3) to all structural units constituting the (meth) acrylate polymer is preferably 5 mol% or more, more preferably 10 mol% or more, and still more preferably 14 mol%. In addition, it is preferably 40 mol% or less, more preferably 30 mol% or less. The molar ratio of the structural units based on the polyfunctional vinyl monomer may be 0.5 to 20 mol%, 1 to 10 mol%, or 1 to 5 mol%. In addition, this (meth) acrylate type polymer may also contain the structural unit based on vinyl compounds other than the above in the range which does not impair the effect.

  In one embodiment, when the (meth) acrylate polymer is a polymer having a structural unit of the formula (2), the molar ratio of the structural unit of the formula (2) to all the structural units of the polymer is 25 mol%. Preferably, it is 35 mol% or more, more preferably 50 mol% or more, and preferably 90 mol% or less, and may be 80 mol% or less.

  As the (meth) acrylate polymer, a polymer having no reactive silyl group, that is, a polymer having no reactive silyl group in the molecular terminal or molecular chain of the (meth) acrylate polymer constituting the fine particles. Use. This embodiment utilizes the intermolecular interaction between fine particles and fine particles and silica due to the functional groups described above, via a coupling agent between fine particles having reactive silyl groups and a rubber component. It is not intended to provide reinforcement by bonding. Therefore, in this embodiment, the fine particles do not have a reactive silyl group. Here, the reactive silyl group is a functional group represented by the formula ≡Si-X (wherein X is a hydroxyl group or a hydrolyzable group), and 1 to 3 hydroxyl groups or This is a group having a structure in which a hydrolyzable monovalent group is bonded to a tetravalent silicon atom. Examples of X include a hydroxyl group, an alkoxy group, and a halogen atom.

  The glass transition point (Tg) of the fine particles comprising the (meth) acrylate polymer is preferably −70 to 0 ° C. in order to enhance the effect of improving wet grip performance. The glass transition point can be set according to the monomer composition constituting the (meth) acrylate polymer. The glass transition point of the fine particles is preferably −50 to −10 ° C., more preferably −40 to −20 ° C.

  The average particle size of the fine particles is preferably 10 nm or more and less than 100 nm. By adding the (meth) acrylate polymer containing the specific structural unit to the diene rubber as such fine particles, low fuel consumption and wet grip performance can be improved in a balanced manner. The average particle size of the fine particles is more preferably 20 to 90 nm, still more preferably 30 to 80 nm.

  The method for producing the fine particles is not particularly limited, and can be synthesized using, for example, known emulsion polymerization. A preferred example is as follows. That is, an alkyl (meth) acrylate and a functional group-containing vinyl monomer are dispersed in an aqueous medium such as water in which an emulsifier is dissolved together with a polyfunctional vinyl monomer as a crosslinking agent, and a water-soluble radical polymerization initiator is obtained in the obtained emulsion. By adding (for example, a peroxide such as potassium persulfate) and performing radical polymerization, fine particles composed of a (meth) acrylate polymer are generated in the aqueous medium. Fine particles are obtained. As other fine particle production methods, known polymerization methods such as suspension polymerization, dispersion polymerization, precipitation polymerization, miniemulsion polymerization, soap-free emulsion polymerization (non-emulsifier emulsion polymerization), and microemulsion polymerization can be used.

  The blending amount of the fine particles is not particularly limited and can be appropriately set according to the use, and is preferably 1 to 100 parts by mass, more preferably 2 to 50 parts by mass with respect to 100 parts by mass of the diene rubber. Part, more preferably 3 to 30 parts by weight, or 5 to 20 parts by weight.

  In addition to the above components, the rubber composition according to this embodiment includes a silane coupling agent, a reinforcing filler other than silica, oil, zinc white, stearic acid, an anti-aging agent, a wax, a vulcanizing agent, a vulcanizing agent. Various additives generally used in rubber compositions such as a sulfur accelerator can be blended.

  The compounding quantity of a silane coupling agent is not specifically limited, For example, 2-20 mass% of silica mass may be sufficient, and 4-15 mass% may be sufficient.

  Examples of the reinforcing filler other than silica include carbon black. The compounding quantity of a reinforcing filler is not specifically limited, For example, it is 20-150 mass parts with respect to 100 mass parts of diene rubbers, and may be 30-100 mass parts with the total amount containing a silica.

  Sulfur is preferably used as the vulcanizing agent. The compounding quantity of a vulcanizing agent is not specifically limited, For example, 0.1-10 mass parts may be sufficient with respect to 100 mass parts of diene rubbers, and 0.5-5 mass parts may be sufficient. Moreover, as a vulcanization accelerator, various vulcanization accelerators, such as a sulfenamide type | system | group, a thiuram type | system | group, a thiazole type | system | group, and a guanidine type | system | group, are mentioned, for example, any 1 type is used individually or in combination of 2 or more types. Can do. The compounding quantity of a vulcanization accelerator is not specifically limited, For example, 0.1-7 mass parts may be sufficient with respect to 100 mass parts of diene rubbers, and 0.5-5 mass parts may be sufficient.

  The rubber composition according to the present embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, for example, in the first mixing stage, to the diene rubber, together with silica and the above fine particles, other additives excluding the vulcanizing agent and the vulcanization accelerator are added and mixed. In the mixing stage, a rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator.

  The rubber composition thus obtained can be used for various rubber members for tires, vibration-proof rubbers, conveyor belts and the like. Preferably, it is for tires, and includes various uses such as passenger car tires, heavy duty tires for trucks and buses, and pneumatic tires of various sizes. Applicable parts of the tire include each part of the tire such as a tread part and a sidewall part. For a pneumatic tire, according to a conventional method, the rubber composition is molded into a predetermined shape by extrusion or the like and combined with other parts to produce a green tire. Then, for example, the green tire is vulcanized at 140 to 180 ° C. By doing so, it can be manufactured. Among these, it is particularly preferable to use as a tire tread formulation.

  Examples are shown below, but the present invention is not limited to these examples.

[Measurement method of average particle diameter]
The average particle diameter of the fine particles is a particle diameter (50% diameter: D50) at an integrated value of 50% in a particle size distribution measured by a dynamic light scattering method (DLS), and is a dynamic light scattering light intensity manufactured by Otsuka Electronics Co., Ltd. It was measured by a photon correlation method (based on JIS Z8826) using a meter “DLS-8000” (angle of incident light and detector 90 °).

[Method for measuring Tg]
Tg of the fine particles was measured by a differential scanning calorimetry (DSC) method according to JIS K7121 at a heating rate of 20 ° C./minute (measurement temperature range: −150 ° C. to 150 ° C.).

[Synthesis Example 1: Fine Particle 1 (Comparative Example)]
Mix 15.0 g 2,4,6-trimethylheptyl methacrylate (ie isodecyl methacrylate), 0.394 g ethylene glycol dimethacrylate, 1.91 g sodium dodecyl sulfate, 122 g water and 13.0 g ethanol The monomer was emulsified by stirring for 1 hour, 0.179 g of potassium persulfate was added, then nitrogen bubbling was performed for 1 hour, and the solution was kept at 70 ° C. for 8 hours. Fine particles 1 were obtained by coagulation by adding methanol to the obtained solution. The average particle size of the fine particles was 60 nm and Tg was -37 ° C.

The fine particle 1 was analyzed by ¹³ C-NMR for the chemical structure of the polymer. As a result, a structural unit derived from ethylene glycol dimethacrylate (2) and a structural unit derived from ethylene glycol dimethacrylate (2,4,6-trimethylheptyl methacrylate) Hereinafter, the molar ratio of each structural unit was 97 mol% for the structural unit of the formula (2) and 3 mol% for the EGDM structural unit.

[Synthesis Example 2: Fine Particle 2]
Mix 14.0 g 2,4,6-trimethylheptyl methacrylate, 1.36 g methacrylonitrile, 0.504 g ethylene glycol dimethacrylate, 2.44 g sodium dodecyl sulfate, 135 g water and stir for 1 hour The monomer was emulsified, 0.229 g of potassium persulfate was added, nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 2 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 2 was 60 nm, and Tg was −25 ° C. As a result of ¹³ C-NMR analysis for fine particles 2, the structural unit of formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 73 mol%, and the structural unit of formula (3) derived from methacrylonitrile was 24. The mol% and EGDM constitutional units were 3 mol%.

[Synthesis Example 3: Fine Particle 3]
9.50 g 2,4,6-trimethylheptyl methacrylate, 4.80 g n-dodecyl methacrylate, 0.805 g methacrylonitrile, 0.446 g ethylene glycol dimethacrylate, 2.16 g sodium dodecyl sulfate, The monomer was emulsified by mixing 135 g of water and allowed to stir for 1 hour, 0.203 g of potassium persulfate was added, then nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 3 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 3 was 62 nm, and Tg was −39 ° C. As a result of ¹³ C-NMR analysis for fine particles 3, the structural unit of formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 56 mol%, and the structural unit of formula (1) derived from n-dodecyl methacrylate. 25 mol%, methacrylonitrile-derived structural unit of the formula (3) was 16 mol%, and EGDM structural unit was 3 mol%.

[Synthesis Example 4: Fine Particle 4]
11.5 g 2,4,6-trimethylheptyl methacrylate, 3.24 g 2- (dimethylamino) ethyl methacrylate, 0.438 g ethylene glycol dimethacrylate, 2.12 g sodium dodecyl sulfate, 135 g water The monomer was emulsified by mixing and stirring for 1 hour, 0.199 g of potassium persulfate was added, then nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 4 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 4 was 58 nm, and Tg was −25 ° C. As a result of ¹³ C-NMR analysis of the fine particles 4, the structural unit of the formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 69 mol%, and the formula (3 derived from 2- (dimethylamino) ethyl methacrylate (3 ) Was 28 mol% and EGDM structural unit was 3 mol%.

[Synthesis Example 5: Fine particle 5]
Mix 12.5 g 2,4,6-trimethylheptyl methacrylate, 2.30 g glycidyl methacrylate, 0.438 g ethylene glycol dimethacrylate, 2.12 g sodium dodecyl sulfate, 135 g water and let stir for 1 hour After emulsifying the monomer and adding 0.199 g of potassium persulfate, nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 5 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 5 was 63 nm, and Tg was −24 ° C. As a result of ¹³ C-NMR analysis on the fine particles 5, the structural unit of the formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 75 mol%, and the structural unit of the formula (3) derived from glycidyl methacrylate was 22 The mol% and EGDM constitutional units were 3 mol%.

[Synthesis Example 6: Fine particle 6]
5.50 g 2,4,6-trimethylheptyl methacrylate, 7.77 g n-dodecyl methacrylate, 1.78 g glycidyl methacrylate, 0.413 g ethylene glycol dimethacrylate, 2.00 g sodium dodecyl sulfate, 135 g The water was mixed and allowed to stir for 1 hour to emulsify the monomer, 0.188 g of potassium persulfate was added, nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 6 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 6 was 60 nm, and Tg was −39 ° C. As a result of ¹³ C-NMR analysis of the fine particles 6, the structural unit of the formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 35 mol%, and the structural unit of the formula (1) derived from n-dodecyl methacrylate. Was 44 mol%, the glycidyl methacrylate-derived structural unit of the formula (3) was 18 mol%, and the EGDM structural unit was 3 mol%.

[Synthesis Example 7: Fine Particle 7]
The monomer was mixed by mixing 14.0 g 2-ethylhexyl methacrylate, 0.733 g methacrylonitrile, 0.500 g ethylene glycol dimethacrylate, 2.42 g sodium dodecyl sulfate, 135 g water and stirring for 1 hour. After emulsification and addition of 0.227 g potassium persulfate, nitrogen bubbling for 1 hour was performed and the solution was held at 70 ° C. for 8 hours. Fine particles 7 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 7 was 63 nm, and Tg was −2.0 ° C. As a result of ¹³ C-NMR analysis of fine particles 7, the constituent unit of formula (2) derived from 2-ethylhexyl methacrylate was 84 mol%, the constituent unit of formula (3) derived from methacrylonitrile was 13 mol%, and EGDM configuration The unit was 3 mol%.

[Synthesis Example 8: Fine particle 8]
12.0 g 2,4,6-trimethylheptyl methacrylate, 2.94 g 2-hydroxyethyl methacrylate, 0.464 g ethylene glycol dimethacrylate, 2.25 g sodium dodecyl sulfate, 135 g water, The monomer was emulsified by stirring for 1 hour, 0.211 g of potassium persulfate was added, then nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours. Fine particles 8 were obtained by coagulation by adding methanol to the obtained solution. The average particle diameter of the fine particles 8 was 58 nm, and Tg was −20 ° C. As a result of ¹³ C-NMR analysis on the fine particles 8, the constitutional unit of the formula (2) derived from 2,4,6-trimethylheptyl methacrylate was 68 mol% and the constitution of the formula (3) derived from 2-hydroxyethyl methacrylate. The unit was 29 mol%, and the EGDM constitutional unit was 3 mol%.

[Evaluation of rubber composition]
Using a lab mixer, according to the formulation (parts by mass) shown in Table 1 below, first, in the first mixing stage, other compounding agents except for sulfur and vulcanization accelerator were added to the diene rubber component and kneaded ( (Discharge temperature = 160 ° C.). Next, in the final mixing stage, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded (discharge temperature = 90 ° C.) to prepare a rubber composition. The details of each component in Table 1 are as follows.

-Modified SBR: "HPR350" (amino group and alkoxysilyl group-modified SBR) manufactured by JSR Corporation
・ BR: “UBEPOL BR150B” manufactured by Ube Industries, Ltd.
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Corporation
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Sulfur: Hosoi Chemical Co., Ltd. “Powder sulfur for rubber 150 mesh”
・ Vulcanization accelerator: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Secondary vulcanization accelerator: “Noxeller D” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Fine particles 1 to 8: Fine particles obtained by the method described in Synthesis Examples 1 to 8 Crosslinked rubber particles: “Nanoprene BM350H” styrene butadiene rubber gel (Tg: −35 ° C.) manufactured by LANXESS.

  About each obtained rubber composition, the test piece of a predetermined shape is produced by vulcanizing in 160 degreeC x 20 minutes, and the dynamic viscoelasticity test is done using the obtained test piece, and 0 degreeC and 60 degreeC The tan δ was measured. Further, the tear strength was measured. The results are shown in Table 1. The measuring method is as follows.

  0 ° C. tan δ: Using a rheometer E4000 manufactured by UBM, the loss factor tan δ was measured under the conditions of a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 0 ° C. The index was displayed. The larger the index, the larger the tan δ, and the better the wet grip performance.

  -60 ° C. tan δ: The temperature was changed to 60 ° C., and tan δ was measured in the same manner as 0 ° C. tan δ, and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the less heat is generated, and the smaller the rolling resistance in the tire, the better the rolling resistance performance (ie, low fuel consumption).

  -Tear strength: The tear strength of the test piece was measured in accordance with JIS K6252, and displayed as an index with the value of Comparative Example 1 being 100. A larger index indicates better tear resistance.

  As shown in Table 1, in Comparative Example 2 in which fine particles 1 are blended with Comparative Example 1 as a control, wet grip while suppressing deterioration of rolling resistance performance and maintaining or improving tear resistance characteristics The performance could be remarkably improved. In Examples 1 to 7, by blending fine particles 2 to 8 having a predetermined functional group, rolling resistance performance can be further improved with respect to Comparative Example 2, while maintaining or improving tear resistance. The balance between low fuel consumption and wet grip performance could be improved. On the other hand, in Comparative Example 3 in which crosslinked rubber particles were blended, not only the effect of improving wet grip performance was small, but also rolling resistance performance and tear resistance were deteriorated.

Claims (4)

For 100 parts by mass of diene rubber,
20 to 150 parts by mass of silica,
Reactive silyl having a structural unit represented by the following general formula (1) and having at least one functional group selected from the group consisting of nitrile group, amino group, carboxyl group, epoxy group and hydroxyl group 1 to 100 parts by mass of fine particles made of a polymer having no group;
Containing a rubber composition.

(In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, R ² in the same molecule May be the same or different.)   The rubber composition according to claim 1, wherein the glass transition point of the fine particles is -70 to 0 ° C.   The rubber according to claim 1 or 2, wherein the diene rubber includes a styrene butadiene rubber having at least one functional group selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, a silyl group, and a carboxyl group. Composition.   The pneumatic tire produced using the rubber composition of any one of Claims 1-3.