JP7144430B2 - Copolymer rubber, production method thereof, and crosslinked rubber composition - Google Patents

Description

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

Conjugated diene rubbers such as SBR (styrene-butadiene rubber), BR (butadiene rubber), IR (isoprene rubber) styrene-isoprene rubber are excellent in abrasion resistance, elasticity and water resistance, and are used as molding materials, resin modifiers, etc. Used for various purposes.

One of the major uses of this conjugated diene rubber is automobile tires. Characteristics required for tires include mechanical strength, wear resistance, wet grip, and the like (hereinafter also referred to as strength and the like). Furthermore, in recent years, development of tires (eco-tires) with excellent energy-saving performance, ie, low fuel consumption, has been actively carried out. These eco-tires are required to have low rolling resistance in addition to high strength.

It is known to add fillers (reinforcing fillers) such as carbon black and silica to conjugated diene rubber in order to secure the strength of tires. A terminal-modified solution polymerization type SBR (terminal-modified S-SBR) is attracting attention as a material that imparts. Terminal-modified S-SBR has a functional group at the molecular terminal of 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 constrains the molecular ends of the SBR to reduce the mobility. As a result, hysteresis loss (internal friction) of the tire is reduced and rolling resistance is lowered. Taking advantage of this characteristic, eco-tires with both strength and low rolling resistance are being developed.

For example, in Patent Document 1, an organolithium compound is used as an initiator in a nonpolar solvent to synthesize a block copolymer consisting of an α-methylstyrene block and a butadiene block by living anionic polymerization. By reacting with a coupling agent, S-SBR having both high-temperature properties and rubber-like properties is obtained.
Also, Patent Document 2 discloses a star-block interpolymer having random copolymer blocks of conjugated diene and monovinyl aromatic monomers, a polyconjugated diene block, and functional groups derived from a multifunctional lithium-based initiator. , that it can be widely used as a rubber in making tire treads with excellent properties such as reduced rolling resistance and improved traction properties.
The techniques of Patent Documents 1 and 2 are considered to have the effect of ensuring the processability of rubber by introducing a branched structure into the rubber component. However, as for the interaction with the filler for ensuring the strength, there is no special device, and the contribution to the strength is not sufficient.

Further, in Patent Document 3, a rubber composition obtained by blending a predetermined amount of carbon black with a blend rubber containing a plurality of diene rubbers has a functional group that interacts with carbon black at the molecular chain end, and a diene A rubber composition containing a low-molecular-weight functional group-containing polymer having a polymer structure similar to the rubber component of the conventional rubber is disclosed. This rubber composition can control the amount of carbon black distributed in each diene rubber component by blending a low-molecular-weight polymer that interacts with carbon black. Therefore, it is possible to effectively express the characteristics of each rubber component, and to achieve compatibility between rubber characteristics such as rolling characteristics and wet characteristics, which have a trade-off relationship. However, this technique incorporates a low molecular weight polymer, which is not sufficient to contribute to strength.

Further, in Patent Document 4, crosslinked rubber particles containing a conjugated diene monomer unit, an aromatic vinyl monomer unit and a monomer unit having at least two polymerizable unsaturated groups, and a specific bond structure Disclosed is a rubber composition containing a conjugated diene/aromatic vinyl copolymer rubber comprising conjugated diene monomer units having It is disclosed that it may contain This technology has a moderate interaction with inorganic fillers (fillers) such as silica, so it is excellent in dispersibility and workability of inorganic fillers. However, the substances disclosed as monomeric units having at least two polymerizable unsaturated groups and monomeric units having carboxylic acid groups, hydroxyl groups and/or epoxy groups are all low molecular weight. . 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, this technology requires the synthesis of a crosslinked rubber separately from the conjugated diene/aromatic vinyl copolymer rubber, and then blending the crosslinked rubber with the conjugated diene/aromatic vinyl copolymer rubber. In terms of sexuality, improvements are needed.
US Pat. No. 5,300,000 discloses a soluble polyfunctional vinyl aromatic copolymer, but does not teach its use in the preparation of copolymer rubbers.

JP-A-2003-73434 Japanese translation of PCT publication No. 2004-517202 JP 2005-213381 A WO2002/000779 JP 2004-123873 A

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

As a result of extensive studies, the present inventors have found that the above-described polyfunctional vinyl aromatic copolymer compound, which has both a branched structure and a function of interacting with a filler, is used as a structural unit of the conjugated diene rubber. We have found that the problem can be solved, and have 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,
Containing 2 mol% or more and less than 95 mol% of the structural unit (a), at least part of the structural unit (a) being 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 part of the structural units (c) are terminal groups (c1) present at the ends of the polyfunctional vinyl aromatic copolymer, and the average number of terminal groups (c1) per molecule is 1.0 or more. and the molar fraction of the vinyl group-containing structural unit (a1) with respect to the sum 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 the weight average molecular weight Mw to the number average molecular weight Mn of 100. .0 or less.

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。Further, 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 the number of repeating units from 1 to 12. 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.

Further, the present invention is a copolymer rubber characterized in that the copolymer rubber is produced by copolymerizing raw materials containing the polyfunctional vinyl aromatic copolymer (A) and the conjugated diene compound (B). is a manufacturing method.

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

Further, the present invention relates to a crosslinked rubber composition characterized in that a rubber composition is obtained by blending a filler into the copolymer rubber obtained by the above method for producing a copolymer rubber and cross-linking the copolymer rubber by vulcanization. manufacturing method.

Further, the present invention includes a structural unit (A1) of a polyfunctional vinyl aromatic copolymer and 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 ( C1) containing 0.001 to 6% by weight of structural unit (A1), 29 to 99.999% by weight of structural unit (B1) and 0 to 70% by weight of structural unit (C1) It is a copolymer rubber containing % by weight.

The present invention also provides a crosslinked rubber composition comprising the above 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. ).
It contains 2 mol % or more and less than 95 mol % of the structural unit (a), and at least part of the structural unit (a) is the vinyl group-containing structural unit (a1) represented by the above formula (1). In formula (1), R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.
At least part of the structural units (c) are terminal groups (c1) present at the ends of the polyfunctional vinyl aromatic copolymer, and the average number of terminal groups (c1) per molecule is 1.0 or more. and the molar fraction of the vinyl group-containing structural unit (a1) with respect to the sum of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8.

The polyfunctional vinyl aromatic copolymer is preferably obtained by copolymerizing a divinyl aromatic compound and a monovinyl aromatic compound and has solubility in a relatively wide range of organic solvents.
The polyfunctional vinyl aromatic copolymer has an Mn of 300 to 100,000, preferably 500 to 5000, more preferably 1, from the viewpoint of processability during production of the copolymer rubber or crosslinked rubber composition. ,000 to 3,000. Also, the molecular weight distribution is 100.0 or less, preferably 1-50, more preferably 3-20, still more preferably 5-10, from the viewpoint of workability.

The structural unit (a) derived from a divinyl aromatic compound contains a vinyl group as a cross-linking component for exhibiting heat resistance, abrasion resistance, and the like. Also, the structural unit (b) derived from a monovinyl aromatic compound does not have a vinyl group that participates in the curing reaction, and thus imparts flexibility, solubility, and the like. Further, the structural unit (c) having a tertiary amino group interacts with an inorganic filler (filler) such as silica, and improves the dispersibility of the filler when used as a crosslinked rubber composition. Therefore, the structures and compositions of the structural units (a), (b) and (c) are the polyfunctional vinyl aromatic copolymer (A), the copolymer rubber containing it, and the crosslinked rubber composition containing it. It has a great effect on the physical properties of objects.

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

Examples of the monovinyl aromatic compounds include vinyl aromatic compounds such as styrene, vinylnaphthalene, vinylbiphenyl, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylvinyl Examples thereof include nucleus alkyl-substituted vinyl aromatic compounds such as benzene, m-ethylvinylbenzene and p-ethylvinylbenzene, and preferred are styrene, vinylnaphthalene, vinylbiphenyl and ethylvinylbenzene (including their respective isomers).

The polyfunctional vinyl aromatic copolymer (A) has a terminal structural unit (d). The terminal structural unit (d) may consist of part of the structural unit (a) and the structural unit (b), or may be a terminal group (c1) consisting of the structural unit (c). Other monomers (G) than divinyl aromatic compounds and monovinyl aromatic compounds may be used as monomers, and some or all of the structural units generated therefrom may be part of the terminal structural units.

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

As noted above, the divinyl aromatic compound provides structural unit (a) and the monovinyl aromatic compound provides structural unit (b). Since the divinyl aromatic compound has a plurality of vinyl groups, it is crosslinked to give a branched structure, and the degree of crosslinkage is controlled so as to exhibit solubility. A structural unit having an unreacted vinyl group becomes the structural unit (a1) or the terminal structural unit (d1) or the like, giving 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 ease of control of the copolymer composition.
Polyfunctional vinyl aromatic copolymer containing structural unit (a), structural unit (b) and structural unit (c′) having phenolic hydroxyl group by copolymerizing divinyl aromatic compound, monovinyl aromatic compound and phenolic compound A polymer precursor (A') is obtained. A polyfunctional vinyl aromatic copolymer (A) is obtained by reacting a phenolic hydroxyl group in the precursor (A') with a 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 and ease of control of composition and molecular weight, alkylphenols and phenols are preferable, and cresols are more preferable. and xylylenols. 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 para-cresol.

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, Z1 and Z2 are preferably the same as in formula ( ² ). X represents a halogen, preferably I, Br, or Cl, more preferably Cl, from the viewpoint of ease of reaction control.

The polyfunctional vinyl aromatic copolymer contains 2 mol % or more and less than 95 mol % of the structural unit (a). It preferably contains 5 to 80 mol %, more preferably 10 to 70 mol %, particularly preferably 15 to 65 mol %.
At least 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 15 to 50 mol %.

At least part of the structural unit (c) is contained as a terminal group (c1) in the structural unit (d) constituting the terminal, and the average number per molecule is 1.0 or more, or more Preferably, the number is 1.5 or more.

Further, the molar fraction of the vinyl group-containing structural unit (a1) with respect to the sum of the structural units (a), (b) and (c) is in the range of 0.02 to 0.8, preferably 0.05 to 0.05. 75, more preferably 0.1 to 0.7, particularly preferably 0.15 to 0.50.
In calculating the mole fraction or mol %, 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.
In addition, the number of terminal structural units (d) per molecule is 2.1 or more, preferably 2.5 or more, and more preferably 3 or more.

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

The terminal structural unit (d) is part of the structural unit (a) and the structural unit (b), except that the average number of terminal groups (c1) per molecule is 1.0 or more. It may be composed of certain structural units (d1) and (d2), or other known vinyl monomers (G) other than divinyl aromatic compounds and monovinyl aromatic compounds may be used as monomers, and the structural units generated therefrom may be A part or all of it may be used as the terminal structural unit (d3).

The polyfunctional vinyl aromatic copolymer contains structural units (c), some of which are present as terminal groups (c1). Structural unit (c) should be contained in the polyfunctional vinyl aromatic copolymer in an amount of 5 to 90 mol %, preferably 10 to 50 mol %.

A polyfunctional vinyl aromatic copolymer or its precursor can be obtained by the method described in Patent Document 5 or the like. For example, it can be obtained by polymerizing a monomer containing a divinyl aromatic compound, a monovinyl aromatic compound or a phenolic compound in a solvent at a temperature of 20 to 120° C. in a homogeneous solution. The above-mentioned method can be adopted as a method of converting a precursor into a polyfunctional vinyl aromatic copolymer.

Other monomers (G) used as necessary can be used when producing the polyfunctional vinyl aromatic copolymer or its precursor. Examples of other monomers include monomers copolymerizable with divinyl aromatic compounds and monovinyl aromatic compounds, and terminal modifiers and chain transfer agents that provide desired terminal groups.

Acid catalysts or Lewis acid catalysts are suitable as catalysts for copolymerizing the above monomers.
Sulfonic acid catalysts such as alkylsulfonic acid and toluenesulfonic acid can be used as the acid catalyst. The amount used is 0.1 to 10 mol per 100 mol in total of all monomer components.

As the Lewis acid catalyst, any compound composed of a metal ion (acid) and a ligand (base) and capable of accepting an electron pair can be used without particular limitation. Among the Lewis acid catalysts, metal fluorides or complexes thereof are preferable from the viewpoint of thermal decomposition resistance of the obtained copolymer, and particularly B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Ti, Divalent to hexavalent metal fluorides such as W, Zn, Fe and V or complexes thereof are preferred. These catalysts can be used singly or in combination of two or more. An ether complex of boron trifluoride is most preferably used from the viewpoint of control of the molecular weight and molecular weight distribution of the obtained copolymer and polymerization activity. Here, the ether of the ether complex includes diethyl ether, dimethyl ether and the like.
The Lewis acid catalyst is preferably used in an amount of 0.001 to 100 mol, more preferably 0.01 to 50 mol, per 100 mol of all monomer components. Most preferably 0.1 to 10 mol.
One or more Lewis base compounds may also be used as promoters, if desired. Specific examples of Lewis base compounds include ester compounds such as ethyl acetate, thioester compounds such as methylmercaptopropionic acid, ketone compounds such as methyl ethyl ketone, amine compounds such as methylamine, ether compounds such as diethyl ether, diethyl There are thioether compounds such as sulfides and phosphine compounds such as tripropylphosphine and tributylphosphine.

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

After termination of the polymerization reaction, the method for recovering the polyfunctional vinyl aromatic copolymer is not particularly limited.

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

A polyfunctional vinyl aromatic copolymer (A), a conjugated diene compound (B), and, if necessary, raw materials containing an aromatic vinyl compound (C) are copolymerized to produce a copolymer rubber. When the aromatic vinyl compound (C) is not used, diene rubbers such as butadiene rubber and isoprene rubber can be obtained, and copolymer rubbers such as SBR can be obtained by using the aromatic vinyl compound (C). Obtainable.

A method for producing a copolymer rubber by copolymerizing a conjugated diene compound (B) or a raw material containing this and an aromatic vinyl compound (C) comprises using a polyfunctional vinyl aromatic copolymer (A) as one of raw materials. In addition to using as, known methods such as those described in Patent Documents 1 to 4 can be employed.

Conjugated diene compounds (B) include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. etc. can be used alone or in combination of two or more. Among these, 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene are preferred.

The aromatic vinyl compound (C) may be either 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 and the like, 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), a styrene-butadiene rubber (SBR) is obtained. When styrene is not used as the aromatic vinyl compound (C) and 1,3-butadiene or isoprene is used as the conjugated diene compound (B), butadiene rubber (BR) or isoprene rubber (IR ). Above all, if it has an SBR structure, it will be excellent in wear resistance, heat resistance, and aging resistance.

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

Specific examples of hydrocarbon solvents used in the above method include 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- pentene, cyclohexene, and the like.

Examples of organic alkali metals used as initiators include methyllithium, ethyllithium, n-propyllithium, iso-propyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium, phenyl Examples include lithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, and reaction products of diisopropenylbenzene and butyllithium.

The method of using the polyfunctional vinyl aromatic copolymer (A) in polymerization is not particularly limited, and an example is a method of coexisting with the conjugated diene compound (B) and, if necessary, the aromatic vinyl compound (C) to initiate polymerization. , a method of reacting the copolymer (A) with a polymerization initiator and then adding the conjugated diene compound (B) and optionally the aromatic vinyl compound (C), the conjugated diene compound (B) and optionally the aromatic A method of adding the copolymer (A) during the polymerization of the vinyl compound (C) to give the rubber molecule a branched structure, A method of adding the polymer (A) to couple rubber molecules can be used.

The weight average molecular weight Mw of the copolymer rubber is preferably 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 the copolymer rubber.

The proportions of the polyfunctional vinyl aromatic copolymer (A), the conjugated diene compound (B), and the aromatic vinyl compound (C) to the total monomers are preferably within the following ranges.
Polyfunctional vinyl aromatic copolymer (A) is 0.001 to 6 wt%, preferably 0.005 to 3 wt%, more preferably 0.01 to 2 wt%, conjugated diene compound (B) is 94 to 99.999% by weight, and 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% by weight. to 90% by weight, and the aromatic vinyl compound (C) is 2 to 50% by weight, preferably 5 to 45% by weight.
More preferably, the polyfunctional vinyl aromatic copolymer (A) is 0.01 to 23% by weight, more preferably 0.1 to 1% by weight. The conjugated diene compound (B) is 50 to 97% by weight, more preferably 55 to 90% by weight. 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 It contains 0.001 to 6% by weight of units (A1), 29 to 99.999% by weight of structural units (B1) and 0 to 70% by weight of structural units (C1). A preferred range is the same ratio as the ratio of the raw materials used.

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

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

The content of the filler is preferably 10 to 120 parts by weight per 100 parts by weight of the total rubber component including the copolymer rubber. Part is more preferred.

The cross-linking agent contained in the rubber composition is not particularly limited to cross-linking by sulfur, cross-linking by peroxide, etc., but usually sulfur is used. The content of the cross-linking agent is preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of the total rubber component.

In the above rubber composition, in addition to the above components, if necessary, a silane coupling agent, a rubber compounding oil such as paraffin oil, naphthene oil, aromatic oil, wax, anti-aging agent, stearic acid (additive) Vulcanization aids and processing aids), zinc oxide, vulcanization accelerators, and the like may also be included.

The rubber composition can be prepared by kneading each component using a kneader such as a plastomill, a Banbury mixer, a roll, or an internal mixer. Specifically, among the above components, components other than the cross-linking agent and the vulcanization accelerator are kneaded, and then the cross-linking agent and the vulcanization accelerator are added to the resulting kneaded product and further kneaded. preferable.

Since the rubber composition of the present invention is excellent in mechanical strength and wear resistance, it is suitable as a rubber composition for obtaining treads and sidewall members of tires such as fuel-efficient tires, large tires, and high-performance tires. . Moreover, it can be suitably used for rubber belts, rubber hoses, materials for footwear, and the like.

The crosslinked rubber composition of the present invention is obtained by subjecting the above rubber composition to crosslinking treatment. For example, a tire is manufactured by extruding the rubber composition according to the shape of the tire (specifically, the shape of the tread), molding it, and heating and pressurizing it in a vulcanizer to produce a tread. Then, by assembling this tread and other parts, the desired tire can be manufactured.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. The parts in each example are parts by weight unless otherwise specified, and the physical properties were evaluated by the following methods.

1) Molecular weight and molecular weight distribution Measurement of molecular weight and molecular weight distribution is performed using GPC (manufactured by Tosoh Corporation, HLC-8220GPC), tetrahydrofuran (THF) as solvent, flow rate 1.0 ml / min, column temperature 38 ° C., monodisperse polystyrene A calibration curve was used.

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

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

4) Mooney viscosity (ML (1+4) 100°C)
It was determined according to JIS K6300-1 with an L-shaped rotor, 1 minute of preheating, 4 minutes of rotor operating time, and a temperature of 100°C.

5) Confirmation of Gel Matter The copolymer rubber was dissolved in cyclohexane of 5 times its weight, the solution was filtered, and the presence or absence of residue on the filter was visually confirmed. If there was any residue, it was determined that there was a gel-like substance.

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

7) Abrasion resistance Using a method using a Lambourn-type abrasion tester conforming to JIS K6264, the amount of abrasion at a slip rate of 30% was measured, and the measured value of the crosslinked rubber obtained in Comparative Example 1 was taken as 100. indexed. The higher 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 (divinylbenzene component 1.09 mol, ethylvinylbenzene component 0.25 mol), 2,6- 72.6 g of a toluene solution of xylenol (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 the polymerization solution was terminated with calcium hydroxide, it was filtered using activated alumina as a filter aid. Then, the mixture was devolatilized under reduced pressure at 60° C. to obtain 199.7 g of a soluble polyfunctional vinyl aromatic copolymer precursor (precursor X1) having a xylenol skeleton.
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 reacted for 72 hours while refluxing. After that, alkali and chloride were removed under acidic conditions, and then neutralized to obtain a soluble polyfunctional vinyl aromatic copolymer (copolymer X) in which the hydroxyl groups of the xylenol skeleton were modified with amino ether.

（＊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。The obtained copolymer X had Mn of 1360, Mw of 12900 and Mw/Mn of 9.5. According to GC analysis, GPC measurement, FT-IR, 13C-NMR and 1H-NMR analysis, copolymer X has the following vinyl group-containing structural unit structural unit (xa1) derived from divinyl aromatic compound (a) and tertiary amino It was confirmed to have a terminal group (xc1) having a group.

(* is the portion that binds to the main chain of the copolymer X.)
Further, the copolymer X had 62 mol % of structural units (a) derived from divinylbenzene, and the average number of (xc1) per molecule was 2.7. Also, the molar fraction of (xa1) with respect to the entire structure was 0.25.
Copolymer X was soluble in toluene, xylene, acetone, THF, dichloromethane, dichloroethane, and 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
DVB-810 (same as Synthesis Example 1) 175.8 g (divinylbenzene component 1.09 mol, ethylvinylbenzene component 0.25 mol), phenol toluene solution 59.2 g (phenol 0.48 mol), toluene 417. 3 g was charged into a 1.0 L reactor, a solution of 2.5 mmol of methanesulfonic acid dissolved in 2 mL of toluene was added, and the mixture was reacted at 45° C. for 6 hours. After the polymerization solution was terminated with calcium hydroxide, it was filtered using activated alumina as a filter aid. Then, the mixture was devolatilized 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 reacted for 72 hours while refluxing. After that, alkali and chloride were removed under acidic conditions, and then neutralized to obtain a soluble polyfunctional vinyl aromatic copolymer (copolymer Y) in which the hydroxyl groups of the phenol skeleton were modified with amino ether.
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, copolymer X has a vinyl group-containing structural unit structural unit (xa1) derived from a divinyl aromatic compound (a) and a tertiary amino group It was confirmed to have a terminal group (yc1) having

Copolymer Y had 62 mol % of the structural unit (a) derived from divinylbenzene, and the average number of (yc1) per molecule was 2.0. Also, the molar fraction of (xa1) with respect to the entire structure was 0.20.
Copolymer Y was soluble in toluene, xylene, acetone, THF, dichloromethane, dichloroethane, and 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
Using the precursor X1 obtained in Synthesis Example 1, 20.0 g of the precursor X1, 12.3 g of potassium carbonate, 197.5 g of acetone, and 54.0 g of 2-(dimethylamino)ethyl chloride were reacted in 1.0 L. A soluble polyfunctional vinyl aromatic copolymer in which the hydroxyl group of the xylenol skeleton is modified with an amino ether by putting it into a vessel and reacting for 72 hours while refluxing, removing the alkali and chloride under acidic conditions, and then neutralizing it. (Copolymer Z) was obtained.
The obtained copolymer Z had Mn of 1340, Mw of 12900 and Mw/Mn of 9.6. According to GC analysis, GPC measurement, FT-IR, 13C-NMR and 1H-NMR analysis, copolymer Z has the following vinyl group-containing structural unit structural unit (xa1) derived from divinyl aromatic compound (a) and tertiary amino It was confirmed to have a terminal group (zc1) with a group.

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

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

Example 1
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 to a nitrogen-purged autoclave reactor having an internal volume of 0.5 liter. At 25° C., 5 g of a cyclohexane solution containing 50 mg of sec-butyllithium was added to initiate polymerization. The temperature of the reaction solution rose due to the heat of polymerization, reaching a maximum temperature of 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. Then, the solvent was removed by steam stripping, and a copolymer rubber A was obtained. Table 1 shows the physical properties of the obtained copolymer rubber A.

Copolymer rubber A, process oil, carbon black, zinc oxide, stearic acid and antioxidant were kneaded at 155° C. and 60 rpm for 4 minutes using Laboplastomill.
Sulfur and a vulcanization accelerator were added to the kneaded material obtained by the above kneading, and the mixture was kneaded at 70° C. and 60 rpm for 1 minute and vulcanized to obtain a crosslinked rubber A. Table 2 shows the blending ratio of each additive. Table 3 shows the physical properties of the crosslinked rubber A.

Comparative example 1
Copolymer rubber B was obtained in the same manner as in Example 1, except that 0.005 g of DVB-810 was used instead of copolymer X in terms of divinylbenzene. Table 1 shows the physical properties of the obtained copolymer rubber B.
Furthermore, using the copolymer rubber B, a crosslinked rubber B was obtained in the same manner as in Example 1. Table 3 shows the physical properties of the crosslinked rubber B.

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. Table 1 shows the physical properties of the obtained copolymer rubber C.
Furthermore, the copolymer rubber C was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber C. Table 3 shows the physical properties of the crosslinked rubber C.

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. Table 1 shows the physical properties of the obtained copolymer rubber D.
Furthermore, the copolymer rubber D was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber D. Table 3 shows the physical properties of Crosslinked Rubber D.

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. Table 1 shows the physical properties of the obtained copolymer rubber E.
Furthermore, the copolymer rubber E was kneaded and vulcanized in the same manner as in Example 1 to obtain a crosslinked rubber E. Table 3 shows the physical properties of the crosslinked rubber E.

In Table 2, the additives used are as follows.
Rubber compounding oil: Dynaprocess oil AC-12 manufactured by Idemitsu Kosan Co., Ltd.
Sulfur: powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Zinc oxide: Zinc Flower No. 1 manufactured by Mitsui Kinzoku Co., Ltd. Stearic acid: Carbon black manufactured by NOF Corporation: Niteron #300 manufactured by Shin Nikka Carbon Co., Ltd.
Vulcanization accelerator: N-tert-butylbenzothiazole-2-sulfenamide Antioxidant: Noxcellar NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Tables 1 and 3 show that the crosslinked rubber composition of the present invention is superior in tensile strength and abrasion resistance to crosslinked rubber compositions obtained using divinylbenzene, which is a known branching agent. Moreover, workability was also excellent.

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

Claims (8)

A polyfunctional vinyl aromatic copolymer 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 There is
Containing 2 mol% or more and less than 95 mol% of the structural unit (a), at least part of the structural unit (a) being 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.
Structural unit (c) is a structural unit represented by the following formula (2),

In the formula, m represents the number of repeating units from 1 to 12. 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.
At least part of the structural units (c) are terminal groups (c1) present at the ends of the polyfunctional vinyl aromatic copolymer, and the average number of terminal groups (c1) per molecule is 1.0 or more. and the molar fraction of the structural unit (a1) with respect to the sum 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. A method for producing a copolymer rubber, comprising copolymerizing raw materials containing the polyfunctional vinyl aromatic copolymer (A) according to claim 1 and a conjugated diene compound (B). 4. The method for producing a copolymer rubber according to claim 3 , wherein raw materials containing the polyfunctional vinyl aromatic copolymer (A), the conjugated diene compound (B) and the aromatic vinyl compound (C) are copolymerized. 4. The method for producing a copolymer rubber according to claim 3 , wherein the copolymerization is carried out by anionic polymerization. 4. A method for producing a crosslinked rubber composition, comprising blending a filler with the copolymer rubber obtained by the method for producing a copolymer rubber according to claim 3 , and cross-linking the mixture by vulcanization. The structural unit (A1) of the polyfunctional vinyl aromatic copolymer according to claim 1 and the structural unit (B1) of the conjugated diene compound, or the structural unit (B1) of the conjugated diene compound and the structural unit of the aromatic vinyl compound ( C1) containing 0.001 to 6% by weight of structural unit (A1), 29 to 99.999% by weight of structural unit (B1) and 0 to 70% by weight of structural unit (C1) % by weight. A crosslinked rubber composition comprising the copolymer rubber according to claim 7 and a filler, wherein the copolymer rubber has a crosslinked structure.