WO2019065662A1 - Copolymer rubber, method of producing same, and crosslinked rubber composition - Google Patents

Abstract

Provided are a copolymer rubber that is workable, strong, and homogeneous, and is suitable as a resin modifier or the like; a crosslinked rubber composition having excellent mechanical strength, wear resistance, etc.; and a polyfunctional vinyl aromatic copolymer that is a superior raw material for the above. Polymer rubber obtained by copolymerizing raw materials including a polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B), and an aromatic vinyl compound (C), the rubber being characterized in that: the polyfunctional vinyl aromatic copolymer (A) comprises a structural unit (a) originating from a divinyl aromatic compound, a structural unit (b) originating from a monovinyl aromatic compound, and a structural unit (c) originating from a tertiary amino group, including at least 2 mol% of structural unit (a), and at least some of structural unit (a) being present in the form of a vinyl-group-containing structural unit (a1); and the number-average molecular weight of the rubber is 300 to 100,000.

Description

Copolymer rubber, method for producing the same, and crosslinked rubber composition

The present invention relates to a copolymer rubber which is excellent in processability and excellent in tensile strength and abrasion resistance, and a crosslinked rubber product obtained by crosslinking the same.

Conjugated diene rubbers such as SBR (styrene-butadiene rubber), BR (butadiene rubber) and IR (isoprene rubber) styrene-isoprene rubber are excellent in abrasion resistance, elasticity and water resistance, and they can be used as molding materials, resin modifiers, etc. It is used in various applications.

One of the main applications of this conjugated diene rubber is a tire for automobile. The properties required of the tire include mechanical strength, abrasion resistance, wet grip property and the like (hereinafter also referred to as strength and the like). Furthermore, in recent years, development of a tire (eco-tire) excellent in energy saving performance, that is, fuel efficiency, has been actively conducted. This eco-tire is required to have low rolling resistance in addition to high strength.

Although it is known to add a filler (reinforcing filler) such as carbon black or silica to conjugated diene rubber in order to secure the strength etc. of the tire, it is possible to further improve the strength of the tire and to achieve excellent rolling resistance. As a material for imparting (1), terminally modified solution-polymerized SBR (terminally modified S-SBR) has attracted attention. The terminal-modified S-SBR has a functional group at the molecular terminal of the SBR, and the functional group at the molecular terminal interacts with the filler. This interaction improves the dispersibility of the filler in the SBR, and at the same time, the molecular ends of the SBR are constrained to lower the mobility. As a result, hysteresis loss (internal friction) of the tire is reduced and rolling resistance is reduced. Taking advantage of this characteristic, eco-tires have been developed that have both strength and low rolling resistance.

For example, in Patent Document 1, a block copolymer composed of an α-methylstyrene block and a butadiene block is synthesized by living anion polymerization using an organolithium compound as an initiator in a nonpolar solvent, and further, as required, a polyfunctional By reacting the coupling agent, S-SBR having high temperature characteristics and rubbery properties is obtained.
Patent Document 2 discloses a star-block interpolymer having a random copolymer block of a conjugated diene and a monovinyl aromatic monomer, a polyconjugated diene block, and a functional group derived from a multifunctional lithium-based initiator. It is disclosed that it can be widely used as a rubber in the manufacture of tire treads with excellent properties such as reduced rolling resistance and improved traction characteristics.
The techniques of Patent Documents 1 and 2 are considered to have the effect of securing the processability of rubber by introducing a branched structure into the rubber component. However, with regard to the interaction with the filler for securing the strength, there is no special device, and the contribution to the strength is not sufficient.

In Patent Document 3, a rubber composition in which a predetermined amount of carbon black is blended in a blend rubber containing a plurality of diene-based rubbers, has a functional group having an interaction with carbon black at the molecular chain terminal, and a diene There is disclosed a rubber composition comprising a low molecular weight functional group-containing polymer having a polymer structure similar to the rubber component of a rubber system. The rubber composition can control the amount of carbon black distributed in each diene rubber component by blending a low molecular weight polymer having an interaction with carbon black. Therefore, the characteristics of each rubber component can be effectively expressed, and for example, it is possible to achieve both the rolling characteristics and the contradictory rubber characteristics such as the wet characteristics. However, this technique is not sufficient as a contribution to strength because it blends low molecular weight polymers.

Further, Patent Document 4 discloses a crosslinked rubber particle including a conjugated diene monomer unit, an aromatic vinyl monomer unit and a monomer unit having at least two polymerizable unsaturated groups, and a specific bonding structure. Disclosed is a rubber composition containing a conjugated diene / aromatic vinyl copolymer rubber containing conjugated diene monomer units, and the crosslinked rubber particle is a monomer unit having a carboxylic acid group, a hydroxyl group and / or an epoxy group. And may be included. This technology has an appropriate interaction with an inorganic filler (filler) such as silica, and is thus excellent in the dispersibility and the processability of the inorganic filler. However, any substance disclosed as a monomer unit having at least two polymerizable unsaturated groups, or a monomer unit having a carboxylic acid group, a hydroxyl group and / or an epoxy group is a low molecule. . Therefore, the reactivity is excessively high, and there is a possibility that gelation may progress in the crosslinked rubber particles and the rubber composition. In addition, it is essential to synthesize a crosslinked rubber separately from the conjugated diene / aromatic vinyl copolymer rubber and to blend the crosslinked rubber with the conjugated diene / aromatic vinyl copolymer rubber in this technology, which simplifies the process. Improvement is necessary in terms of gender.
Patent Document 5 discloses a soluble polyfunctional vinyl aromatic copolymer, but it does not teach its use for producing a copolymer rubber.

JP 2003-73434 A Japanese Patent Publication No. 2004-517202 JP 2005-213381 A WO 2002/000779 JP, 2004-123873, A

An object of the present invention is to solve such problems and to provide a material having processability, strength and homogeneity.

The inventors of the present invention conducted intensive studies, and as a result, by using a specific polyfunctional vinyl aromatic copolymer compound having both a branched structure and an interaction function with a filler as a constituent unit of a conjugated diene rubber, the above-mentioned The inventors have found that they solve the problems, and completed the present invention.

 
　式中、Ｒ^１は炭素数６～３０の芳香族炭化水素基を示す。
　構造単位（ｃ）の少なくとも一部は多官能ビニル芳香族共重合体の末端に存在する末端基（ｃ１）であり、１分子当たりの平均の末端基（ｃ１）の数は１．０以上であり、構造単位（ａ）、（ｂ）及び（ｃ）の総和に対するビニル基含有構造単位（ａ１）のモル分率は０．０２～０．８の範囲であることを特徴とする多官能ビニル芳香族共重合体である。 The present invention provides a polyfunctional vinyl aromatic containing a structural unit (a) derived from a divinyl aromatic compound, a structural unit (b) derived from a monovinyl aromatic compound, and a structural unit (c) having a tertiary amino group A copolymer,
The structural unit (a) is contained in an amount of 2 mol% to less than 95 mol%, and at least a part of the structural unit (a) is a vinyl group-containing structural unit (a1) represented by the following formula (1)

In the formula, R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.
At least a part of the structural unit (c) is an end group (c1) present at the end of the polyfunctional vinyl aromatic copolymer, and the average number of end groups (c1) per molecule is 1.0 or more And the mole fraction of the vinyl group-containing structural unit (a1) to the total of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8. It is an aromatic copolymer.

The polyfunctional vinyl aromatic copolymer of the present invention has a number average molecular weight Mn of 300 to 100,000, and a molecular weight distribution (Mw / Mn) represented by the ratio of weight average molecular weight Mw to number average molecular weight Mn is 100. It is good that it is less than or equal to .0.

 
　式中、ｍは１～１２の繰り返し単位数を示す。Ｚ^１及びＺ^２は、それぞれ独立に、炭素数１～３のアルキル基を示す。Ｙ^１～Ｙ^４は、それぞれ独立に、水素原子又は炭素数１～３のアルキル基を示す。 In the polyfunctional vinyl aromatic copolymer of the present invention, the structural unit (c) is preferably a structural unit represented by the following formula (2).

In the formula, m represents 1 to 12 repeating units. Z ¹ and Z ² each independently represent an alkyl group having 1 to 3 carbon atoms. Y ¹ to Y ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

The present invention also relates to a copolymer rubber produced by copolymerizing a raw material containing the above-mentioned polyfunctional vinyl aromatic copolymer (A) and a conjugated diene compound (B). Manufacturing method.

Moreover, the method for producing a copolymer rubber according to the present invention comprises copolymerizing and copolymerizing a raw material containing a polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B) and an aromatic vinyl compound (C) It is preferred to produce a united rubber. Moreover, it is preferable to copolymerize by anionic polymerization.

Further, the present invention is a crosslinked rubber composition characterized in that a filler is blended with the copolymer rubber obtained by the method for producing a copolymer rubber, and crosslinking is carried out by vulcanization to obtain a rubber composition. It is a manufacturing method.

In the present invention, a structural unit (A1) of a polyfunctional vinyl aromatic copolymer, a structural unit (B1) of a conjugated diene compound or a structural unit (B1) of a conjugated diene compound, and a structural unit of an aromatic vinyl compound A copolymer rubber containing C1), wherein 0.001 to 6% by weight of the structural unit (A1), 29 to 99.999% by weight of the structural unit (B1) and 0 to 70 of the structural unit (C1) It is a copolymer rubber containing% by weight.

Further, the present invention is a crosslinked rubber composition comprising the copolymer rubber and a filler, wherein the copolymer rubber has a crosslinked structure.

The polyfunctional vinyl aromatic copolymer of the present invention comprises a structural unit (a) derived from a divinyl aromatic compound, a structural unit (b) derived from a monovinyl aromatic compound, and a structural unit (c) having a tertiary amino group Containing).
The structural unit (a) is contained in an amount of 2 mol% to less than 95 mol%, and at least a part of the structural unit (a) is a vinyl group-containing structural unit (a1) represented by the above formula (1). In the formula (1), R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.
At least a part of the structural unit (c) is an end group (c1) present at the end of the polyfunctional vinyl aromatic copolymer, and the average number of end groups (c1) per molecule is 1.0 or more The mole fraction of the vinyl group-containing structural unit (a1) to the total of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8.

The polyfunctional vinyl aromatic copolymer is obtained by copolymerizing a divinyl aromatic compound and a monovinyl aromatic compound, and one having a solubility in a relatively wide range of organic solvents is preferable.
The polyfunctional vinyl aromatic copolymer has an Mn of 300 to 100,000, preferably 500 to 5,000, and more preferably 1 from the viewpoint of processability in producing the copolymer rubber or the crosslinked rubber composition. And 3,000 to 3,000. The molecular weight distribution is 100.0 or less, preferably 1 to 50, more preferably 3 to 20, and still more preferably 5 to 10, from the viewpoint of processability.

The structural unit (a) derived from the divinyl aromatic compound contains a vinyl group as a crosslinking component for developing heat resistance, abrasion resistance and the like. In addition, the structural unit (b) derived from the monovinyl aromatic compound does not have a vinyl group involved in the curing reaction, and therefore imparts flexibility, solubility, and the like. The structural unit (c) having a tertiary amino group interacts with an inorganic filler (filler) such as silica to improve the dispersibility of the filler when it is made into a crosslinked rubber composition. Therefore, the structure and composition of the structural units (a), (b) and (c) are as follows: multifunctional vinyl aromatic copolymer (A), copolymer rubber containing it, and crosslinked rubber composition containing it It greatly affects the physical properties of things.

Examples of the divinyl aromatic compound preferably include, but are not limited to, divinyl benzene (including each isomer), divinyl naphthalene (including each isomer), and divinyl biphenyl (including each isomer). It is not a thing. Moreover, these can be used individually or in combination of 2 or more types. From the viewpoint of moldability, divinylbenzene (m-isomer, p-isomer or a mixture of isomers thereof) is more preferable.

Examples of the monovinyl aromatic compound include vinyl aromatic compounds such as styrene, vinyl naphthalene and vinyl biphenyl, o-methylstyrene, m-methylstyrene, p-methylstyrene, o, p-dimethylstyrene, o-ethyl vinyl Examples thereof include nuclear alkyl substituted vinyl aromatic compounds such as benzene, m-ethylvinylbenzene, p-ethylvinylbenzene and the like, and styrene, vinylnaphthalene, vinylbiphenyl and ethylvinylbenzene (including respective isomers) are preferable.

The multifunctional vinyl aromatic copolymer (A) has a terminal structural unit (d). The terminal structural unit (d) may be composed of the structural unit (a) and part of the structural unit (b), or may be an end group (c1) consisting of the structural unit (c). Monomers other than divinyl aromatic compounds and mono vinyl aromatic compounds (G) may be used as monomers, and part or all of the structural units derived therefrom may be part of terminal structural units.

The structural unit (c) is not limited as long as it has a tertiary amino group, but is preferably a structural unit represented by the above formula (2).
In the above formula (2), m represents the number of repeating units of 1 to 12, but it is more preferably 1 to 6 and still more preferably 2 to 4 from the viewpoint of availability of raw materials and economy. Z ¹ and Z ² each independently represent an alkyl group having 1 to 3 carbon atoms, but from the same viewpoint, preferably both Z ¹ and Z ² are methyl groups. Y ¹ to Y ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, but from the same viewpoint, a hydrogen atom or a methyl group is preferable.

As mentioned above, the divinylaromatic compound gives the structural unit (a) and the monovinylaromatic compound gives the structural unit (b). The divinyl aromatic compound is crosslinked because it has a plurality of vinyl groups to give a branched structure, but the degree of crosslinking is controlled to a degree showing solubility. The structural unit having an unreacted vinyl group is the above structural unit (a1), the structural unit at the end (d1) or the like, and gives a polyfunctional structure having a plurality of vinyl groups.

The method for producing the polyfunctional vinyl aromatic copolymer is not particularly limited, but the method described below is preferable from the viewpoint of easiness of control of the copolymerization composition.
A polyfunctional vinyl aromatic co-polymer comprising a structural unit (a), a structural unit (b) and a structural unit (c ') having a phenolic hydroxyl group by copolymerizing a divinyl aromatic compound, a monovinyl aromatic compound and a phenol compound A polymer precursor (A ') is obtained. The polyfunctional vinyl aromatic copolymer (A) is obtained by reacting the phenolic hydroxyl group in the precursor (A ′) with the halogen compound having a tertiary amino group represented by the following formula (3).

The phenol compound is not limited as long as it is a compound having a phenolic hydroxyl group, but from the viewpoint of ease of copolymerization, ease of control of composition and molecular weight, alkylphenol and phenol are preferable, and cresols are more preferable And xylilenols. Examples of cresols and xylenols include 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 3,4-xylenol, 3,5-xylenol, 2,6-xylenol, ortho-cresol, meta Examples include cresol and paracresol.

 
　式（３）において、ｍ、Ｚ^１及びＺ^２は、式（２）と同じであることが好ましい。Ｘはハロゲンを示すが、反応制御のしやすさの観点から、Ｉ、Ｂｒ、Ｃｌが好ましく、より好ましくはＣｌである。

In Formula (3), m, Z ¹ and Z ² are preferably the same as Formula (2). X represents a halogen, but in terms of ease of reaction control, I, Br and Cl are preferable, and more preferably Cl.

The polyfunctional vinyl aromatic copolymer contains 2% by mole or more and less than 95% by mole of the structural unit (a). It is preferably contained in an amount of 5 to 80 mol%, more preferably 10 to 70 mol%, particularly preferably 15 to 65 mol%.
And, at least a part of the structural unit (a) contains 2 to 80 mol%, preferably 5 to 70 mol%, more preferably 10 to 60 mol%, still more preferably 2 to 80 mol% of the above structural unit (a1) 15 to 50 mol%.

In addition, at least a part of the structural unit (c) is contained as an end group (c1) in the structural unit (d) constituting an end, and the average number per molecule is 1.0 or more, Preferably, it is 1.5 or more.

The mole fraction of the vinyl group-containing structural unit (a1) to the total of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8, preferably 0.05 to 0. It is in the range of 75, more preferably in the range of 0.1 to 0.7, and particularly preferably in the range of 0.15 to 0.50.
In the calculation of mole fraction or mole%, the structural unit (a) includes the structural unit (a1) and the structural unit (d1). The same applies to other structural units that can be terminal structural units.
The terminal structural unit (d) may have 2.1 or more, preferably 2.5 or more, and more preferably 3 or more per molecule.

The polyfunctional vinyl aromatic copolymer may contain 5 mol% or more and less than 98 mol% of the structural unit (b). Preferably, 20 to 95 mol%, more preferably 30 to 90 mol%, particularly preferably 36 to 85 mol% is included. Part of the structural unit (b) may be a terminal structural unit (d2).

The structural unit (d) at the end contains 1.0 or more of the terminal group (c1) as an average number per molecule, except that it is a part of the structural unit (a) and the structural unit (b) The structural units (d1) and (d2) may be used, and divinyl aromatic compounds and other known vinyl monomers (G) other than mono vinyl aromatic compounds may be used as monomers, and structural units derived therefrom may be used. A part or all of the terminal structural units (d3) may be used.

The polyfunctional vinyl aromatic copolymer contains structural unit (c), and a part is present as a terminal group (c1). The structural unit (c) may be contained in an amount of 5 to 90% by mole, preferably 10 to 50% by mole, in the polyfunctional vinyl aromatic copolymer.

A polyfunctional vinyl aromatic copolymer or its precursor can be obtained by the method as described in patent document 5 grade | etc.,. For example, it can be obtained by polymerizing a monomer containing a divinyl aromatic compound, a monovinyl aromatic compound or a phenol compound in a homogeneous solution dissolved in a solvent at a temperature of 20 to 120.degree. The method described above can be adopted as a method of converting the precursor into a polyfunctional vinyl aromatic copolymer.

When manufacturing a polyfunctional vinyl aromatic copolymer or its precursor, the other monomers (G) used by necessity can be used. Other monomers include divinyl aromatic compounds, monomers copolymerizable with mono vinyl aromatic compounds, terminal modifiers and chain transfer agents giving desired end groups, and the like.

An acid catalyst or a Lewis acid catalyst is suitable as a catalyst for copolymerizing the above monomers.
As the acid catalyst, sulfonic acid catalysts such as alkylsulfonic acid and toluenesulfonic acid can be used. The amount used is 0.1 to 10 moles based on 100 moles in total of all the monomer components.

As a Lewis acid catalyst, a compound consisting of a metal ion (acid) and a ligand (base), which can receive an electron pair, can be used without particular limitation. Among the Lewis acid catalysts, metal fluorides or complexes thereof are preferred from the viewpoint of the thermal decomposition resistance of the obtained copolymer, and in particular, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Ti, Preferred are divalent to hexavalent metal fluorides such as W, Zn, Fe and V, or complexes thereof. These catalysts can be used alone or in combination of two or more. From the viewpoint of control of the molecular weight and molecular weight distribution of the obtained copolymer and the polymerization activity, an ether complex of boron trifluoride is most preferably used. Here, examples of the ether of the ether complex include diethyl ether, dimethyl ether and the like.
The Lewis acid catalyst is preferably used in the range of 0.001 to 100 moles, more preferably 0.01 to 50 moles, per 100 moles in total of all the monomer components. Most preferably, it is 0.1 to 10 moles.
Also, if desired, one or more Lewis base compounds can be used as co-catalyst. Specific examples of Lewis base compounds include ester compounds such as ethyl acetate, thioester compounds such as methyl mercaptopropionic acid, ketone compounds such as methyl ethyl ketone, amine compounds such as methyl amine, ether compounds of diethyl ether, diethyl Thioether compounds such as sulfides, and phosphine compounds such as tripropylphosphine and tributylphosphine.

The polymerization reaction is carried out, for example, at 20 to 120 ° C., preferably 40 to 100 ° C., in a homogeneous solvent in which the above-mentioned monomer and acid catalyst or Lewis acid catalyst are dissolved in an organic solvent having a dielectric constant of 2.0 to 15.0. The method of cationic copolymerization is suitable.
As the organic solvent, toluene, xylene, n-hexane, cyclohexane, methylcyclohexane or ethylcyclohexane is particularly preferable from the viewpoint of the balance of polymerization activity and solubility.

The method for recovering the polyfunctional vinyl aromatic copolymer after the termination of the polymerization reaction is not particularly limited. For example, a commonly used method such as a heat concentration method, a steam stripping method, or precipitation with a poor solvent may be used.

The polyfunctional vinyl aromatic copolymer obtained as described above has more than one polymerizable vinyl group, preferably 1.5 or more per molecule, more preferably 2.0 or more per molecule on average. Excellent as a raw material for heavy rubber.
The polyfunctional vinyl aromatic copolymer of the present invention as a raw material of copolymer rubber is also referred to as polyfunctional vinyl aromatic copolymer (A) or copolymer (A).

A copolymer rubber is produced by copolymerizing a raw material containing the polyfunctional vinyl aromatic copolymer (A), the conjugated diene compound (B) and, if necessary, the aromatic vinyl compound (C). When the aromatic vinyl compound (C) is not used, a diene rubber such as butadiene rubber or isoprene rubber can be obtained, and by using the aromatic vinyl compound (C), a copolymer rubber such as SBR is obtained. You can get it.

The method for producing a copolymer rubber by copolymerizing a conjugated diene compound (B) or a raw material containing the same with an aromatic vinyl compound (C) is prepared by using a polyfunctional vinyl aromatic copolymer (A) as a raw material Other than using as, the methods described in, for example, Patent Documents 1 to 4 can be adopted.

As the conjugated diene compound (B), 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene Among them, 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene are preferable, though they may be used alone or in combination of two or more.

The aromatic vinyl compound (C) may be a monovinyl compound or a polyvinyl compound, preferably styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, Ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, tert-butoxydimethylsilylstyrene, isopropoxydimethylsilylstyrene, etc., which may be used alone or in combination of two or more Among these, styrene is preferred.

When 1,3-butadiene is used as the conjugated diene compound (B) and styrene is used as the aromatic vinyl compound (C), styrene-butadiene rubber (SBR) is obtained. When styrene is not used as the aromatic vinyl compound (C), 1,3-butadiene or butadiene rubber (BR) or isoprene rubber (IR) is used as the conjugated diene compound (B). ). Among them, when it has the SBR structure, it is excellent in abrasion resistance, heat resistance and aging resistance.

The method for producing a copolymer rubber by copolymerizing raw materials containing these is not limited, but anionic polymerization in a hydrocarbon solvent is preferable.
For example, in a hydrocarbon solvent, using a compound of an organic alkali metal as an initiator, a polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B), or these and an aromatic vinyl compound (C) are living. Anion polymerization method or multi-step reaction method in which the conjugated diene compound (B) and the aromatic vinyl compound (C) are living anion polymerized and then the reaction is performed by adding the polyfunctional vinyl aromatic copolymer (A) is there. Also, if necessary, the terminal may be terminally modified with a polymerization terminator having a functional group.

Specific examples of the hydrocarbon solvent used in the above method are propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2- Butene, cis-2-butene, 1-pentyne, 2-pentyne, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2- Examples include pentene and cyclohexene.

Moreover, as an organic alkali metal used as an initiator, methyllithium, ethyllithium, n-propyllithium, iso-propyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium, phenyl Lithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, reaction products of diisopropenylbenzene and butyllithium, and the like can be mentioned.

There is no particular limitation on the method of using the polyfunctional vinyl aromatic copolymer (A) in the polymerization, for example, a method of starting the polymerization in coexistence with the conjugated diene compound (B) and optionally the aromatic vinyl compound (C) A method of adding the conjugated diene compound (B) and optionally the aromatic vinyl compound (C) after reacting the copolymer (A) with the polymerization initiator, the conjugated diene compound (B) and optionally aromatic The copolymer (A) is added during polymerization of the vinyl compound (C) to make the rubber molecule have a branched structure, the copolymerization of the conjugated diene compound (B) and, if necessary, the aromatic vinyl compound (C) The method of adding a polymer (A) and coupling a rubber molecule etc. is mentioned.

The weight average molecular weight Mw of the copolymer rubber may be in the range of 100,000 to 500,000. The reaction can be terminated by adding an alkanol, or the like, and the solvent can be removed to obtain a copolymer rubber.

It is preferable to make the use ratio with respect to all the monomers of the said polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B), and an aromatic vinyl compound (C) into the following range.
The polyfunctional vinyl aromatic copolymer (A) is 0.001 to 6% by weight, preferably 0.005 to 3% by weight, more preferably 0.01 to 2% by weight, and the conjugated diene compound (B) Is 94 to 99.999% by weight, and the amount of the aromatic vinyl compound (C) is 0 to 70% by weight.
When the aromatic vinyl compound (C) is used, the polyfunctional vinyl aromatic copolymer (A) is in the same range as above, and the conjugated diene compound (B) is 50 to 97% by weight, preferably 55 The amount of the aromatic vinyl compound (C) is from 2 to 50% by weight, preferably from 5 to 45% by weight.
More preferably, the content of the polyfunctional vinyl aromatic copolymer (A) is 0.01 to 23% by weight, more preferably 0.1 to 1% by weight. The content of the conjugated diene compound (B) is 50 to 97% by weight, more preferably 55 to 90% by weight. The amount of the aromatic vinyl compound (C) is preferably in the range of 2 to 49% by weight, more preferably 5 to 44% by weight.

The content ratio of the structural unit (A1) of the polyfunctional vinyl aromatic copolymer, the structural unit (B1) of the conjugated diene compound, and the structural unit (C1) of the aromatic vinyl compound in the copolymer rubber of the present invention is the structure The composition contains 0.001 to 6% by weight of the unit (A1), 29 to 99.999% by weight of the structural unit (B1) and 0 to 70% by weight of the structural unit (C1). It is preferable that the preferable range be the same ratio as the use ratio of the raw material.

The crosslinked rubber composition of the present invention can be obtained by blending a filler and a crosslinking agent with the above copolymer rubber to obtain a rubber composition and crosslinking the rubber composition by vulcanization. Examples of the filler include carbon black and silica. In particular, the interaction with carbon black is excellent.

As carbon black contained as a filler, carbon black of each grade, such as SRF, GPF, FEF, HAF, ISAF, and SAF, can be used. Among these, HAF, ISAF, and SAF are preferable because a rubber elastic body having excellent abrasion resistance can be obtained.
The silica may be in the form of particles generally used as a filler, but preferably has a primary particle size of 50 nm or less. Specific examples of such silica include hydrous silicic acid, anhydrous silicic acid, calcium silicate, aluminum silicate and the like.

The content of the filler is preferably 10 to 120 parts by weight with respect to 100 parts by weight of the total rubber component including the copolymer rubber, and 55 to 100 parts by weight from the viewpoint of the reinforcing property and the improvement effect of various physical properties thereby. More preferably, it is a part.

The crosslinking agent contained in the rubber composition is not particularly limited as to crosslinking by sulfur, crosslinking by peroxide, etc., but sulfur is usually used. The content of the crosslinking agent is preferably 0.1 to 5 parts by weight, and more preferably 1 to 3 parts by weight with respect to 100 parts by weight of the entire rubber component.

In the above rubber composition, in addition to the above components, if necessary, rubber compounding oils such as silane coupling agents, paraffinic oils, naphthenic oils and aromatic oils, waxes, antioxidants, stearic acid Sulfur aids and processing aids), zinc oxide, vulcanization accelerators, etc. may be contained.

The rubber composition can be prepared by kneading the components using, for example, a kneader such as a plastmill, a Banbury mixer, a roll, an internal mixer and the like. Specifically, among the above-mentioned components, components other than the crosslinking agent and the vulcanization accelerator may be kneaded, and then the obtained kneaded product may be further kneaded by adding the crosslinking agent and the vulcanization accelerator. preferable.

Since the rubber composition of the present invention is excellent in mechanical strength and abrasion resistance, it is suitable as a rubber composition for obtaining a tread of a fuel-efficient tire, a large-sized tire, a high-performance tire, etc. or a sidewall member. . Moreover, it can be suitably used also for rubber belts, rubber hoses, footwear materials and the like.

The crosslinked rubber composition of the present invention is obtained by crosslinking the above rubber composition. For example, in a tire, a tread is manufactured by extruding the above rubber composition according to the shape of the tire (specifically, the shape of a tread), molding it, and heating and pressing it in a vulcanizer. By assembling the tread with other parts, a target tire can be manufactured.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In each of the examples, unless otherwise specified, all parts are by weight, and each physical property was evaluated by the method shown below.

1) Molecular weight and molecular weight distribution Molecular weight and molecular weight distribution are measured using GPC (manufactured by Tosoh Corporation, HLC-8220GPC), tetrahydrofuran (THF) as solvent, flow rate 1.0 ml / min, column temperature 38 ° C., monodispersed polystyrene It carried out using a calibration curve.

2) Structure of Multifunctional Vinyl-Aromatic Copolymer Determined by ¹³ C-NMR and ¹ H-NMR analysis, using JNM-LA600 nuclear magnetic resonance spectrometer manufactured by JEOL. Chloroform-d ₁ was used as a solvent, and a resonance line of tetramethylsilane was used as an internal standard.

3) Analysis of terminal group Calculation of the terminal group is the terminal group with respect to the total amount of monomers obtained from the number average molecular weight obtained by the above GPC measurement, ¹³ C-NMR, ¹ H-NMR measurement and gas chromatography (GC) analysis. The number of terminal groups contained in one molecule of the polyfunctional vinyl aromatic copolymer was calculated from the amount of derivative used to introduce. In Synthesis Example 1, the terminal group is derived from a divinyl aromatic compound or a monovinyl aromatic compound. The calculation of the end group is a specific structural unit introduced at the end from the data on the total amount of each structural unit introduced into the copolymer obtained from GC analysis in addition to the results of 13 C-NMR and 1 H-NMR. The specific amount contained in one molecule of the polyfunctional vinyl aromatic copolymer is calculated from the introduction amount of the specific structural unit introduced at this end and the number average molecular weight obtained by the above-mentioned GPC measurement. The terminal number of structural units was calculated.

4) Mooney viscosity (ML (1 + 4) 100 ° C)
According to JIS K6300-1, L-shaped rotor, preheating 1 minute, rotor operating time 4 minutes, and temperature 100 ° C.

5) Confirmation of gel-like substance The copolymer rubber was dissolved in 5-fold weight of cyclohexane, the solution was filtered, and the presence or absence of the residue on the filter was visually confirmed. If any residue was present, it was judged to be gel-like.

6) Tensile strength The 300% modulus was measured by the tensile test method of JIS K6251, and the measured value of the crosslinked rubber obtained in Comparative Example 1 was indexed to be 100 and indexed. The larger the index value, the better the tensile strength.

7) Wear resistance A wear amount having a slip ratio of 30% was measured using a method using a Lambourd-type wear tester in accordance with JIS K6264, and the measured value of the crosslinked rubber obtained in Comparative Example 1 was 100. Indexed. The larger the index value, the better the wear resistance.

Synthesis Example 1 DVB-810 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., content of divinylbenzene component: 81.0 wt%) 175.8 g (1.09 mol of divinylbenzene component, 0.25 mol of ethylvinylbenzene component), 2, 6- 72.6 g of a solution of xylenol in toluene (0.48 mol of 2,6-xylenol) and 417.3 g of toluene were charged into a 1.0 L reactor, and a solution of 4 mmol of methanesulfonic acid dissolved in 2 mL of toluene was added And reacted at 45 ° C. for 2.5 hours. After terminating the polymerization solution with calcium hydroxide, filtration was performed using activated alumina as a filter aid. Then, under reduced pressure at 60 ° C., 199.7 g of a soluble polyfunctional vinyl aromatic copolymer precursor (precursor X1) having a xylenol skeleton was obtained.
Next, 20.0 g of precursor X1, 12.3 g of potassium carbonate, 197.5 g of acetone, and 54.0 g of 3- (dimethylamino) propyl chloride were charged into a 1.0 L reactor, and the reaction was performed for 72 hours while refluxing. Thereafter, the alkali and chloride were removed under acidic conditions, and then returned to neutrality to obtain a soluble polyfunctional vinyl aromatic copolymer (copolymer X) in which the hydroxyl group of the xylenol skeleton was aminoether-modified.

（＊は、共重合体Ｘの主鎖との結合部分である。）
　また、共重合体Ｘはジビニルベンゼン由来の構造単位（ａ）を６２モル％有し、一分子あたりの平均の（ｘｃ１）の数は２．７個であった。また、全構造に対する（ｘａ１）のモル分率は０．２５であった。
　また、共重合体Ｘは、トルエン、キシレン、アセトン、ＴＨＦ、ジクロロメタン、ジクロロエタン、クロロホルムに可溶であり、ゲルの生成は認められなかった。 Mn of the obtained copolymer X was 1360, Mw was 12900, and Mw / Mn was 9.5. According to GC analysis, GPC measurement, FT-IR, 13C-NMR and 1H-NMR analysis, the copolymer X has the following vinyl group-containing structural unit (xa1) and tertiary amino acid derived from the divinyl aromatic compound (a) It was confirmed to have an end group (xc1) having a group.

(* Is a bonding portion to the main chain of copolymer X.)
Further, the copolymer X had 62 mol% of a structural unit (a) derived from divinylbenzene, and the average number of (xc1) per molecule was 2.7. In addition, the molar fraction of (xa1) to the entire structure was 0.25.
Moreover, the copolymer X was soluble in toluene, xylene, acetone, THF, dichloromethane, dichloroethane, chloroform, and no gel formation was observed.

 　また、共重合体Ｙはジビニルベンゼン由来の構造単位（ａ）を６２モル％有し、一分子あたりの平均の（ｙｃ１）の数は２．０個であった。また、全構造に対する（ｘａ１）のモル分率は０．２０であった。
　また、共重合体Ｙは、トルエン、キシレン、アセトン、ＴＨＦ、ジクロロメタン、ジクロロエタン、クロロホルムに可溶であり、ゲルの生成は認められなかった。 Synthesis example 2
175.8 g of DVB-810 (same as in Synthesis Example 1) (1.09 mol of divinylbenzene component, 0.25 mol of ethylvinylbenzene component), 59.2 g of phenol in toluene (0.48 mol of phenol), toluene 417. 3 g was charged into a 1.0 L reactor, and a solution of 2.5 mmol of methanesulfonic acid dissolved in 2 mL of toluene was added and reacted at 45 ° C. for 6 hours. After terminating the polymerization solution with calcium hydroxide, filtration was performed using activated alumina as a filter aid. Then, the solution was evaporated under reduced pressure at 60 ° C. to obtain 190.4 g of a soluble polyfunctional vinyl aromatic copolymer precursor (precursor Y1) having a phenol skeleton.
Next, 20.0 g of precursor Y1, 12.3 g of potassium carbonate, 197.5 g of acetone, and 54.0 g of 3- (dimethylamino) propyl chloride were charged into a 1.0 L reactor, and the reaction was performed for 72 hours while refluxing. Thereafter, the alkali and chloride were removed under acidic conditions, and then returned to neutrality to obtain a soluble polyfunctional vinyl aromatic copolymer (copolymer Y) in which the hydroxyl group of the phenol skeleton was aminoether modified.
Mn of the obtained copolymer Y was 650, Mw was 2580, and Mw / Mn was 4.0. According to GC analysis, GPC measurement, FT-IR, 13C-NMR and 1H-NMR analysis, the copolymer X is a vinyl group-containing structural unit (xa1) derived from a divinyl aromatic compound (a) and a tertiary amino group It was confirmed to have an end group (yc1) having

Further, the copolymer Y had 62 mol% of a structural unit (a) derived from divinylbenzene, and the average number of (yc1) per molecule was 2.0. Moreover, the molar fraction of (xa1) with respect to the whole structure was 0.20.
Moreover, the copolymer Y was soluble in toluene, xylene, acetone, THF, dichloromethane, dichloroethane, chloroform, and no gel formation was observed.

　また、共重合体Ｚはジビニルベンゼン由来の構造単位（ａ）を６２モル％有し、一分子あたりの平均の（ｚｃ１）の数は２．７個であった。また、全構造に対する（ｘａ１）のモル分率は０．２５であった。
　また、共重合体Ｚは、トルエン、キシレン、ＴＨＦ、アセトン、ジクロロメタン、ジクロロエタン、クロロホルムに可溶であり、ゲルの生成は認められなかった。 Synthesis example 3
Reaction of 20.0 g of precursor X1, 12.3 g of potassium carbonate, 197.5 g of acetone, 54.0 g of 2- (dimethylamino) ethyl chloride in 1.0 L using precursor X1 obtained in Synthesis Example 1 , And after reaction for 72 hours while refluxing, a soluble polyfunctional vinyl aromatic copolymer in which the alkali and chloride are removed under acidic conditions and then returned to neutral and the hydroxyl group of xylenol skeleton is aminoether modified (Copolymer Z) was obtained.
Mn of the obtained copolymer Z was 1340, Mw was 12900, and Mw / Mn was 9.6. According to GC analysis, GPC measurement, FT-IR, 13C-NMR and 1H-NMR analysis, the copolymer Z has the following vinyl group-containing structural unit (xa1) derived from the divinyl aromatic compound (a) and tertiary amino acid It was confirmed to have an end group (zc1) having a group.

Moreover, the copolymer Z had 62 mol% of structural units (a) derived from divinylbenzene, and the average number of (zc1) per molecule was 2.7. In addition, the molar fraction of (xa1) to the entire structure was 0.25.
Moreover, the copolymer Z was soluble in toluene, xylene, THF, acetone, dichloromethane, dichloroethane, chloroform, and no gel formation was observed.

Synthesis example 4
253.2 g of DVB-810 (the same as in Synthesis Example 1), 874.6 g of toluene, and 93.3 g of anisole are charged into a 1.0 L reactor, and 10 mmol of methanesulfonic acid is dissolved in 2 ml of toluene at 50 ° C. The solution was added and allowed to react for 4 hours. After terminating the polymerization solution with calcium hydroxide, filtration was performed using activated alumina as a filter aid. Then, under reduced pressure at 60 ° C., 241.2 g of a soluble polyfunctional vinyl aromatic copolymer (copolymer R) having an anisole skeleton was obtained.
Mn of the obtained copolymer R was 1000, Mw was 18800, and Mw / Mn was 18.8. Moreover, the copolymer R had 64 mol% of structural units (a) derived from divinylbenzene, and contained an average of 2.0 terminal structural groups (rc1) derived from anisole per one molecule. In addition, the molar fraction of (rc1) to the entire structure was 0.12.
The copolymer R was soluble in toluene, xylene, THF, dichloromethane, dichloroethane, chloroform, and no formation of gel was observed.

Example 1
Into a nitrogen-substituted autoclave reactor having an internal volume of 0.5 liter, 245 g of cyclohexane, 2.5 g of THF, 10 g of styrene, 40 g of 1,3-butadiene, and 0.015 g of the copolymer X obtained in Synthesis Example 1 were added. At 25 ° C., 5 g of a cyclohexane solution containing 50 mg of sec-butyllithium was added to initiate polymerization. The heat of polymerization raised the temperature of the reaction solution, and the maximum temperature reached 85 ° C.
After confirming that the polymerization conversion reached 99%, 50 mg of isopropanol was added to terminate the polymerization, and 2,6-di-tert-butyl-p-cresol (BHT) was added to the reaction solution. Subsequently, the solvent was removed by steam stripping to obtain a copolymer rubber A. Physical properties of the obtained copolymer rubber A are shown in Table 1.

Copolymer rubber A, process oil, carbon black, zinc oxide, stearic acid and anti-aging agent were kneaded using a Labo Plastomill at 155 ° C. and 60 rpm for 4 minutes.
Sulfur and a vulcanization accelerator were added to the kneaded product obtained by the above kneading, and the mixture was kneaded for 1 minute at 70 ° C. and 60 rpm using a laboplast mill, and vulcanized to obtain a crosslinked rubber A. The blend ratio of each additive is shown in Table 2. The physical properties of the crosslinked rubber A are shown in Table 3.

Comparative Example 1
A copolymer rubber B was obtained in the same manner as in Example 1, except that, in Example 1, DVB-810 was used instead of the copolymer X and 0.005 g of divinylbenzene equivalent was used. Physical properties of the obtained copolymer rubber B are shown in Table 1.
Furthermore, using the copolymer rubber B, a crosslinked rubber B was obtained in the same manner as in Example 1. Physical properties of the crosslinked rubber B are shown in Table 3.

Example 2
A copolymer rubber C was obtained in the same manner as in Example 1, except that the copolymer Y polymerized in Synthesis Example 2 was used instead of the copolymer X used in Synthesis Example 1. Physical properties of the obtained copolymer rubber C are shown in Table 1.
Furthermore, the copolymer rubber C was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber C. Physical properties of the crosslinked rubber C are shown in Table 3.

Example 3
A copolymer rubber D was obtained in the same manner as in Example 1, except that the copolymer Z polymerized in Synthesis Example 3 was used instead of the copolymer X used in Synthesis Example 1. Physical properties of the obtained copolymer rubber D are shown in Table 1.
Furthermore, the copolymer rubber D was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber D. Physical properties of the crosslinked rubber D are shown in Table 3.

Comparative example 2
A copolymer rubber E was obtained in the same manner as in Example 1, except that the copolymer R polymerized in Synthesis Example 4 was used instead of the copolymer X used in Synthesis Example 1. The physical properties of the resulting copolymer rubber E are shown in Table 1.
Furthermore, the copolymer rubber E was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber E. Physical properties of the crosslinked rubber E are shown in Table 3.

In addition, in Table 2, the used additive is as follows.
Rubber compounding oil: Dyna Process Oil AC-12 manufactured by Idemitsu Kosan
Sulfur: manufactured by Tsurumi Chemical Industry Co., Ltd. Powdered sulfur zinc oxide: manufactured by Mitsui Mining & Smelting Co., Ltd. Zinc White No. 1 stearic acid: manufactured by NOF Corporation Carbon black: manufactured by Nippon Oil Carbon Co., Ltd. Niteron # 300
Vulcanization accelerator: N-tert-butylbenzothiazole-2-sulfenamide anti-aging agent: Ouchi Shinko Chemical Co., Ltd. Noccellar NS

From Tables 1 and 3, it can be seen that the crosslinked rubber composition of the present invention is superior in tensile strength and abrasion resistance to a crosslinked rubber composition obtained using divinylbenzene which is a known branching agent. Moreover, the processability was also excellent.

The polyfunctional vinyl aromatic copolymer of the present invention is excellent as a raw material of copolymer rubber. The copolymer rubber of the present invention has both the processability and the strength because it has a structural unit of a polyfunctional vinyl aromatic copolymer having both a branched structure and an interaction function with the filler. Furthermore, it becomes difficult to form a gel-like substance, becomes homogeneous, and can be applied to molding materials, modifiers of resins, and the like.
Furthermore, a crosslinked rubber composition obtained by compounding and crosslinking a filler with the copolymer rubber is excellent in the dispersibility of the filler, and hence is excellent in mechanical strength and abrasion resistance. Therefore, it can be applied to tires (particularly tire treads), rubber for seismic isolation, rubber hoses, rubber rollers, footwear materials and the like.

Claims (9)

A polyfunctional vinyl aromatic copolymer comprising a structural unit (a) derived from a divinyl aromatic compound, a structural unit (b) derived from a monovinyl aromatic compound, and a structural unit (c) having a tertiary amino group There,
The structural unit (a) is contained in an amount of 2 mol% to less than 95 mol%, and at least a part of the structural unit (a) is a vinyl group-containing structural unit (a1) represented by the following formula (1)

In the formula, R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.
At least a part of the structural unit (c) is an end group (c1) present at the end of the polyfunctional vinyl aromatic copolymer, and the average number of end groups (c1) per molecule is 1.0 or more And the mole fraction of the structural unit (a1) to the total of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8. Polymer. The polyfunctional according to claim 1, wherein the number average molecular weight Mn is 300 to 100,000, and the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is 100.0 or less. Vinyl aromatic copolymer. The polyfunctional vinyl aromatic copolymer according to claim 1 or 2, wherein the structural unit (c) is a structural unit represented by the following formula (2).

In the formula, m represents 1 to 12 repeating units. Z ¹ and Z ² each independently represent an alkyl group having 1 to 3 carbon atoms. Y ¹ to Y ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. A process for producing a copolymer rubber comprising copolymerizing a raw material containing the polyfunctional vinyl aromatic copolymer (A) according to any one of claims 1 to 3 and a conjugated diene compound (B). The method for producing a copolymer rubber according to claim 4, wherein a raw material containing a polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B) and an aromatic vinyl compound (C) is copolymerized. The method for producing a copolymer rubber according to claim 4 or 5, wherein the copolymer is copolymerized by anionic polymerization. A method for producing a crosslinked rubber composition, comprising adding a filler to the copolymer rubber obtained by the method for producing a copolymer rubber according to any one of claims 4 to 6, and crosslinking the mixture by vulcanization. . The structural unit (A1) of the polyfunctional vinyl aromatic copolymer according to any one of claims 1 to 3 and the structural unit (B1) of a conjugated diene compound or the structural unit (B1) of a conjugated diene compound and an aromatic vinyl A copolymer rubber containing the structural unit (C1) of the compound, comprising 0.001 to 6% by weight of the structural unit (A1), 29 to 99.999% by weight of the structural unit (B1) and the structural unit (C1) And 0 to 70% by weight of the copolymer rubber. A crosslinked rubber composition comprising the copolymer rubber according to claim 8 and a filler, wherein the copolymer rubber has a crosslinked structure.