JP2016194011A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire which has improved low heat generation properties and mechanical characteristics.SOLUTION: There is provided a rubber composition for a tire which is a rubber component formed of 40-100 wt.% of a masticated rubber master batch where 0.3-5.0 wt.% of a specific compound represented by general formula (i) is made to coexist with 100 wt.% of a diene rubber containing 40 wt.% or more of natural rubber and/or isoprene rubber and arbitrarily containing a styrene-butadiene rubber, and 60-0 wt.% of the total of styrene-butadiene rubber and natural rubber; and contains 160-220 pts.wt. of a reinforcing filler containing 80-150 pts.wt. of a carbon black having a nitrogen adsorption specific area of 50 m/g or less and 1-20 pts.wt. of a thermosetting resin with respect to 100 pts.wt. of a rubber component containing 40-100 wt.% of the total of the natural rubber and the isoprene rubber in the rubber component and 60-0 wt.% of the styrene-butadiene rubber.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for tires that is improved in low heat build-up and mechanical properties.

  In recent years, as a required performance for pneumatic tires, it has been demanded that fuel efficiency performance is excellent with increasing interest in global environmental problems. In order to improve fuel efficiency, it is necessary to reduce rolling resistance. For this reason, the rolling resistance of the tire is reduced by suppressing the heat generation of the rubber composition constituting the pneumatic tire. Generally, 60 ° C. tan δ by dynamic viscoelasticity measurement is used as an index of exothermic property of the rubber composition. The smaller the tan δ (60 ° C.) of the rubber composition, the smaller the exothermic property.

  As a method for reducing the tan δ (60 ° C.) of the rubber composition, for example, the amount of carbon black is decreased or the particle size of the carbon black is increased. However, such a method has a problem that mechanical properties such as rubber hardness, tensile breaking strength, and tensile breaking elongation of the rubber composition are lowered, and steering stability and wear resistance are lowered when the tire is formed.

  Patent Document 1 discloses that a rubber composition obtained by kneading a rubber component, (2Z) -4-aminophenylamino-4-oxo-2-butenoic acid, and a filler modifies the viscoelastic characteristics of the tire. It has been proposed to improve fuel economy performance. However, when trying to use this rubber composition for bead insulation of a pneumatic tire, the required level of mechanical properties such as tensile strength at break and tensile elongation at break, in particular, sufficient tensile elongation at break cannot be secured, Moreover, in order to increase the adhesiveness with the bead wire, further improvement has been demanded.

International Publication No. 2012/147984

  An object of the present invention is to provide a rubber composition for tires that is improved in low heat build-up and mechanical properties over conventional levels.

（式中、Ｒ¹は置換基を有してもよい炭素数６〜１２の２価の芳香族炭化水素基、Ｒ²，Ｒ³はそれぞれ独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数６〜１２のアリール基、ヒドロキシ基または炭素数１〜６のアルコキシ基、Ｒ⁴はヒドロキシ基または−ＯＮａ、Ｘは−ＮＨ−または−Ｏ−を表す。） The rubber composition for tires of the present invention that achieves the above object is represented by the following general formula (i) in which 100% by weight of a natural rubber and / or isoprene rubber is 40% by weight or more and optionally a styrene-butadiene rubber is 100% by weight. A rubber component comprising 40 to 100% by weight of a kneaded rubber masterbatch in which 0.3 to 5.0% by weight of a compound coexisting, and 60 to 0% by weight of a total of styrene butadiene rubber and natural rubber, and the rubber The nitrogen adsorption specific surface area is 50 m ² / g or less with respect to 100 parts by weight of the rubber component including 40 to 100% by weight of the natural rubber and isoprene rubber in the component and 60 to 0% by weight of the styrene butadiene rubber. 160 to 220 parts by weight of reinforcing filler containing 80 to 150 parts by weight of carbon black, and 1 to 20 parts by weight of thermosetting resin And wherein the formulated.

(In the formula, R ¹ is an optionally substituted divalent aromatic hydrocarbon group having 6 to 12 carbon atoms, R ² and R ³ are each independently a hydrogen atom, a halogen atom, or 1 to 6 carbon atoms. An alkyl group, a C 6-12 aryl group, a hydroxy group or a C 1-6 alkoxy group, R ⁴ represents a hydroxy group or —ONa, and X represents —NH— or —O—.)

The rubber composition for tires of the present invention is a rubber component containing a kneaded rubber masterbatch in which a compound represented by the above general formula (i) coexists in a diene rubber containing natural rubber and / or isoprene rubber. Since specific carbon black and thermosetting resin are blended, tan δ (60 ° C.) of the rubber composition can be reduced, and mechanical properties such as tensile breaking strength and tensile breaking elongation can be maintained and improved. it can. As a result, when a pneumatic tire is used, the steering stability and the wear resistance can be improved to a level higher than the conventional level while improving the fuel efficiency. Moreover, adhesiveness with a bead wire can be made higher than the conventional level.
In the compound represented by the general formula (i), R ⁴ may be a hydroxy group.

  This rubber composition is suitable for use in bead insulation of pneumatic tires, and improves bead wire adhesion and tire durability while reducing rolling resistance and improving fuel economy performance of pneumatic tires. At the same time, it is possible to improve the handling stability, the wear resistance and the conventional level.

  The rubber composition for tires of the present invention comprises a kneaded rubber master batch and a reinforcing filler. The kneaded rubber masterbatch is obtained by kneading a specific compound with natural rubber and / or isoprene rubber and optionally diene rubber containing styrene butadiene rubber. As the natural rubber, isoprene rubber and styrene butadiene rubber, those usually used in rubber compositions for tires can be used.

  The kneaded rubber masterbatch includes at least one of natural rubber and isoprene rubber, and optionally includes styrene butadiene rubber. If the kneaded rubber masterbatch does not have natural rubber and isoprene rubber, the desired effect of the present invention cannot be achieved.

  The content of natural rubber and isoprene rubber is preferably 40 to 100% by weight, more preferably 50 to 100% by weight, in 100% by weight of the diene rubber constituting the masticated rubber masterbatch. When the content of the natural rubber and isoprene rubber is less than 40% by weight, the compound of the general formula (i) cannot be sufficiently dispersed and mixed in the diene rubber.

  The diene rubber constituting the kneaded rubber masterbatch can optionally contain other diene rubbers other than natural rubber and isoprene rubber. Examples of other diene rubbers include styrene butadiene rubber, butadiene rubber, butyl rubber, and ethylene propylene diene rubber. Of these, styrene butadiene rubber is preferred.

（式中、Ｒ¹は置換基を有してもよい炭素数６〜１２の２価の芳香族炭化水素基、Ｒ²，Ｒ³はそれぞれ独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数６〜１２のアリール基、ヒドロキシ基または炭素数１〜６のアルコキシ基、Ｒ⁴はヒドロキシ基または−ＯＮａ、Ｘは−ＮＨ−または−Ｏ−を表す。） In the present invention, the kneaded rubber masterbatch is obtained by kneading a compound represented by the following general formula (i) in an amount of 0.3 to 5.0% by weight in 100% by weight of a diene rubber.

(In the formula, R ¹ is an optionally substituted divalent aromatic hydrocarbon group having 6 to 12 carbon atoms, R ² and R ³ are each independently a hydrogen atom, a halogen atom, or 1 to 6 carbon atoms. An alkyl group, a C 6-12 aryl group, a hydroxy group or a C 1-6 alkoxy group, R ⁴ represents a hydroxy group or —ONa, and X represents —NH— or —O—.)

In general formula (i), R < ¹ > is a C6-C12 bivalent aromatic hydrocarbon group which may have a substituent. Examples of the divalent aromatic hydrocarbon group having 6 to 12 carbon atoms include a phenylene group, a naphthylene group, and a biphenylene group. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxy group, a nitro group, a cyano group, a sulfo group, and a halogen atom. These substituents can arbitrarily substitute 0 to 4 hydrogen atoms of the aromatic hydrocarbon group. R ¹ is preferably a phenylene group.

R ² and R ³ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, or an alkoxy group having 1 to 6 carbon atoms. Examples of the halogen atom in R ² and R ³ include fluorine, chlorine, bromine and iodine. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and isopentyl. Group, n-hexyl group and the like. As a C6-C12 aryl group, a C6-C12 monocyclic or condensed polycyclic aromatic hydrocarbon is shown, for example, a phenyl group, a naphthyl group, a biphenyl group etc. are mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, and an n-pentoxy group. , Isopentoxy group, n-hexyloxy group and the like.

As R ² and R ^3, R ² is a hydrogen atom, it is preferred that R ³ is an alkyl group having 1 to 6 carbon hydrogen atom or atoms, more preferably R ² and R ³ are hydrogen atoms.
R ⁴ is a hydroxy group or —ONa, preferably a hydroxy group.
X is —NH— or —O—. X is preferably —NH—.

  Examples of the compound represented by the general formula (i) include (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid, (2Z) -4-[(3-amino Phenyl) amino] -4-oxo-2-butenoic acid, (2Z) -4-[(4-aminophenyl) amino] -2-methyl-4-oxo-2-butenoic acid, sodium (2Z) -4- Illustrative examples include [(4-aminophenyl) amino] -4-oxo-2-butenoic acid, sodium (2Z) -4-[(3-aminophenyl) amino] -4-oxo-2-butenoic acid, and the like. it can. Among them, (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid, sodium (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2- Butenoic acid is preferred, and (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid is particularly preferred.

  In the kneaded rubber masterbatch, the content of the compound represented by the general formula (i) is 0.3 to 5.0% by weight, preferably 0.5 to 5.0% by weight based on 100% by weight of the diene rubber. It is. When the content of the compound represented by the general formula (i) is less than 0.3% by weight, the desired effect of the present invention cannot be achieved. On the other hand, if it exceeds 5.0% by weight, the tensile elongation at break of the rubber composition decreases.

  The kneaded rubber masterbatch should be free of reinforcing fillers. When the kneaded rubber masterbatch contains a reinforcing filler, the effects of reducing tan δ (60 ° C.) and improving mechanical properties such as tensile breaking strength, tensile breaking elongation, and rubber hardness are obtained by the present invention. It is inferior to the tire rubber composition obtained.

  In this masticated rubber masterbatch, natural rubber, isoprene rubber and optionally styrene butadiene rubber coexist with the compound represented by the general formula (i) and are dispersed and mixed. Therefore, a reinforcing filler containing carbon black is added later. When the rubber composition is used, the affinity between the diene rubber and the reinforcing filler containing carbon black can be improved.

  The rubber composition for tires of the present invention is obtained by blending a reinforcing filler containing 80 to 150 parts by weight of carbon black with respect to 100 parts by weight of a rubber component containing 40 to 100% by weight of the above-described masticated rubber masterbatch. is there. The rubber component can optionally contain other diene rubbers in addition to the kneaded rubber masterbatch. The other diene rubber is selected from styrene butadiene rubber, natural rubber and isoprene rubber.

  In the present invention, 100% by weight of the rubber component is composed of 40 to 100% by weight of the kneaded rubber masterbatch and 60 to 0% by weight in total of styrene butadiene rubber, natural rubber and isoprene rubber. The content of the kneaded rubber masterbatch is 40 to 100% by weight, preferably 50 to 100% by weight. The total of styrene butadiene rubber, natural rubber and isoprene rubber is 60 to 0% by weight, preferably 50 to 0% by weight. When the content of the kneaded rubber masterbatch is less than 40% by weight, the affinity of the reinforcing filler containing diene rubber and carbon black cannot be sufficiently increased.

  The rubber composition for tires of the present invention specifies the total of the natural rubber and isoprene rubber composing the kneaded rubber masterbatch in the rubber component and other diene rubbers to be added later. That is, in 100% by weight of the rubber component, the total amount of the natural rubber and isoprene rubber added in the masticated rubber masterbatch and after-treatment is 40-100% by weight, preferably 50-100% by weight. By setting the total of the natural rubber and isoprene rubber in the rubber component to 40% by weight or more, the low exothermic property and mechanical specification required for the bead insulation of the pneumatic tire can be obtained.

  The rubber component can contain styrene butadiene rubber as a masticated rubber masterbatch and other diene rubbers to be added later. Here, the styrene-butadiene rubber is another diene rubber that can be added later to the kneaded rubber masterbatch, and is optionally contained in the kneaded rubber masterbatch. The total blending amount of styrene butadiene rubber and styrene butadiene rubber as the raw rubber masterbatch and other diene rubbers to be added later is 60 to 0% by weight, preferably 50 to 0% by weight in 100% by weight of the rubber component. . When the total amount of the styrene butadiene rubber exceeds 60% by weight, the tensile strength at break, the tensile elongation at break and the adhesiveness are lowered.

The rubber composition for tires of the present invention comprises 160 to 220 reinforcing fillers containing 80 to 150 parts by weight of carbon black having a nitrogen adsorption specific surface area of 50 m ² / g or less with respect to 100 parts by weight of the rubber component described above. Mix parts by weight.

  The compounding amount of carbon black is 80 to 150 parts by weight, preferably 80 to 130 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of carbon black is less than 80 parts by weight, the effect of improving the mechanical properties of the rubber composition cannot be obtained sufficiently. If the carbon black exceeds 150 parts by weight, the exothermic property of the rubber composition increases, and the rolling resistance increases when a tire is formed.

The nitrogen adsorption specific surface area of the carbon black 50 m ² / g or less, preferably 30 to 50 m ² / g. When the nitrogen adsorption specific surface area of carbon black exceeds 50 m ² / g, tan δ (60 ° C.) increases. In this specification, the nitrogen adsorption specific surface area of carbon black shall be measured according to JIS K6217-2.

  As the reinforcing filler, other reinforcing fillers other than carbon black can be blended, and examples thereof include silica, clay, aluminum hydroxide, calcium carbonate and the like. As the reinforcing filler, carbon black, clay and silica are preferable.

  The compounding amount of the reinforcing filler containing carbon black is 160 to 220 parts by weight, preferably 160 to 210 parts by weight with respect to 100 parts by weight of the rubber component. If the compounding amount of the reinforcing filler is less than 160 parts by weight, the effect of improving the mechanical properties of the rubber composition cannot be obtained sufficiently. On the other hand, when the reinforcing filler exceeds 220 parts by weight, the exothermic property of the rubber composition increases, and the rolling resistance increases when the tire is formed.

  The proportion of carbon black in 100% by weight of the reinforcing filler is preferably 36% by weight or more, more preferably 50 to 70% by weight. By setting the proportion of carbon black to 36% by weight or more, the affinity between the kneaded rubber masterbatch and the reinforcing filler can be further increased.

  The rubber composition of the present invention improves its mechanical properties by blending a thermosetting resin. The compounding quantity of a thermosetting resin is 1-20 weight part with respect to 100 weight part of rubber components, Preferably it is 2-10 weight part. When the amount of the thermosetting resin is less than 1 part by weight, the effect of improving the mechanical properties of the rubber composition cannot be sufficiently obtained. Moreover, when the compounding quantity of a thermosetting resin exceeds 20 weight part, the exothermic property of a rubber composition will become large.

  As a thermosetting resin mix | blended by this invention, what is normally mix | blended with the rubber composition for tires can be used. For example, a phenol resin, an epoxy resin, a polyester resin, a urethane resin, a urea resin, a melamine resin, etc. can be illustrated. Among these, phenol resins and melamine resins are good in mechanical properties and durability as a rubber composition for tires. A phenol resin is particularly preferable, and a cresol resin, a resorcin resin, an alkylphenol resin, or a modified phenol resin may be used. Examples of the modified phenol resin include cashew modified phenol resin, oil modified phenol resin, epoxy modified phenol resin, aniline modified phenol resin, melamine modified phenol resin and the like.

  The cresol resin is a compound obtained by reacting cresol and formaldehyde, and a compound using m-cresol is particularly preferable. Examples of the cresol resin include Sumicanol 610 manufactured by Sumitomo Chemical Co., Ltd. and SP7000 manufactured by Nippon Shokubai Co., Ltd. Resorcin resin is a compound obtained by reacting resorcin and formaldehyde. For example, Penacolite B-18-S, B-19-S, B-20-S, B-20-S, etc. manufactured by INDSPEC Chemical Corporation, etc. Can be illustrated. Further, as the resorcin resin, a modified resorcin resin may be used, and examples thereof include a resorcin resin modified with alkylphenol and the like, and a resorcin / alkylphenol / formalin copolymer can be exemplified. The cashew-modified phenol resin is a phenol resin modified with cashew oil, such as Sumitomo Bakelite's Sumilite Resin PR-YR-170, PR-150, Dainippon Ink & Chemicals Phenolite A4-1419, etc. Can be illustrated. The phenol resin is an unmodified resin obtained by a reaction between phenol and formaldehyde, and examples thereof include Sumikanol 620 manufactured by Sumitomo Chemical Co., Ltd.

  In this invention, the methylene donor agent which hardens the thermosetting resin mentioned above can be mix | blended. As the methylene donor agent, those usually combined with a thermosetting resin can be used. Examples of methylene donors include hexamethylenetetramine, hexamethoxymethyl melamine, pentamethoxymethyl melamine, hexaethoxymethyl melamine, para-formaldehyde polymer, melamine N-methylol derivative and the like. These methylene donors can be used alone or in any blend.

  Examples of hexamethylenetetramine include Sunseller HT-PO manufactured by Sanshin Chemical Industry Co., Ltd. Examples of hexamethoxymethylmelamine (HMMM) include CYREZ 964RPC manufactured by CYTEC INDUSTRIES. Examples of pentamethoxymethylmelamine (PMMM) include BARA CHEMICAL Co. , LTD. An example is Sumikanol 507A manufactured by the company.

  The compounding amount of these methylene donors is 0.5 to 4 parts by weight, preferably 0.7 to 3 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of the methylene donor is less than 0.5 parts by weight, the effect of increasing the rubber hardness and strength may not be sufficiently obtained. On the other hand, if the blending amount of the methylene donor exceeds 3 parts by weight, the crack growth resistance may be lowered.

  The rubber composition of the present invention reduces the rolling resistance when the tan δ (60 ° C.) is reduced to form a pneumatic tire, and maintains and improves mechanical properties such as tensile breaking strength and tensile breaking elongation. The handling stability and wear resistance of the pneumatic tire can be improved to a level higher than the conventional level. Moreover, the adhesiveness of the bead insulation with respect to a bead wire can be made higher than the conventional level.

（式中、Ｒ¹は置換基を有してもよい炭素数６〜１２の２価の芳香族炭化水素基、Ｒ²，Ｒ³はそれぞれ独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数６〜１２のアリール基、ヒドロキシ基または炭素数１〜６のアルコキシ基、Ｒ⁴はヒドロキシ基または−ＯＮａ、Ｘは−ＮＨ−または−Ｏ−を表す。）
（２）前記素練りゴムマスターバッチ４０〜１００重量％、並びにスチレンブタジエンゴムおよび天然ゴムの合計６０〜０重量％からなるゴム成分であると共に、素練りゴムマスターバッチ中および後添加する天然ゴムおよびイソプレンゴムの合計を４０〜１００重量％、並びにスチレンブタジエンゴムの合計６０〜０重量％を含むゴム成分１００重量部に対し、窒素吸着比表面積が５０ｍ²／ｇ以下であるカーボンブラックを８０〜１５０重量部を含む補強性充填剤を１６０〜２２０重量部、熱硬化性樹脂を１〜２０重量部配合し、混練することによりゴム混練物を得る第二混合工程、
（３）前記ゴム混練物に加硫系配合剤を配合し、混合する第三混合工程。 The tire rubber composition of the present invention can be preferably prepared by a production method including at least the steps described in the following (1) to (3).
(1) A compound represented by the following general formula (i) is added in an amount of 0.3 to 5.0% by weight to 100% by weight of a diene rubber containing 40% by weight or more of natural rubber and / or isoprene rubber and optionally styrene butadiene rubber. 1st mixing process which obtains a kneaded rubber masterbatch by knead | mixing in the state which does not contain a reinforcing filler,

(In the formula, R ¹ is an optionally substituted divalent aromatic hydrocarbon group having 6 to 12 carbon atoms, R ² and R ³ are each independently a hydrogen atom, a halogen atom, or 1 to 6 carbon atoms. An alkyl group, a C 6-12 aryl group, a hydroxy group or a C 1-6 alkoxy group, R ⁴ represents a hydroxy group or —ONa, and X represents —NH— or —O—.)
(2) A rubber component comprising 40 to 100% by weight of the masticated rubber masterbatch and a total of 60 to 0% by weight of styrene butadiene rubber and natural rubber, and a natural rubber to be added in and after the masticated rubber masterbatch and 80 to 150 carbon black having a nitrogen adsorption specific surface area of 50 m ² / g or less with respect to 100 parts by weight of a rubber component containing 40 to 100% by weight of the total isoprene rubber and 60 to 0% by weight of the styrene butadiene rubber. A second mixing step of blending 160 to 220 parts by weight of a reinforcing filler containing parts by weight and 1 to 20 parts by weight of a thermosetting resin and obtaining a rubber kneaded product by kneading,
(3) A third mixing step of mixing and mixing a vulcanizing compounding agent in the rubber kneaded product.

  The rubber composition for tires of the present invention can be manufactured by a manufacturing method including at least three steps including a first mixing step (1), a second mixing step (2), and a third mixing step (3). If necessary, other kneading steps and / or mixing steps can be added. In this specification, mixing refers to the operation of mixing the blended ingredients to bring them into a homogeneous state, and kneading means distributing and dispersing the mixture in a homogeneous state, applying shearing force, and heating as necessary. The operation of kneading. The kneading and mixing can be performed using a commonly used means.

  The first mixing step (1) is a step of preparing a kneaded rubber master batch. The kneaded rubber masterbatch comprises 100% by weight of diene rubber containing natural rubber and / or isoprene rubber, and optionally styrene butadiene rubber, and 0.3 to 5 of the compound represented by the general formula (i) is added thereto. It can be produced by blending 0.0% by weight and kneading without containing a reinforcing filler. When the compounding amount of the compound represented by the general formula (i) is less than 0.3% by weight, the tan δ (60 ° C.) of the rubber composition is reduced, and the mechanical properties such as tensile breaking strength, tensile breaking elongation, rubber hardness, etc. The effect of improving the physical characteristics is not sufficiently obtained. On the other hand, if it exceeds 5.0% by weight, the tensile elongation at break of the rubber composition decreases. Moreover, the adhesiveness with respect to a bead wire falls on the contrary.

In this production method, the kneaded rubber master batch needs to contain no reinforcing filler. If the kneaded rubber masterbatch contains a reinforcing filler, a tire rubber composition having the desired effect cannot be obtained. Moreover, as a compound represented by general formula (i), the compound whose R < ⁴ > is a hydroxy group is preferable.

  In the first mixing step (1), for example, in the natural rubber mastication step, the compound represented by the general formula (i) and optionally the styrene butadiene rubber are mixed and kneaded with natural rubber and / or isoprene rubber. Can be implemented.

  Here, in 100% by weight of the diene rubber, the content of natural rubber and / or isoprene rubber is 40% by weight or more, preferably 50 to 100% by weight. When the content of the natural rubber and isoprene rubber is less than 40% by weight, the compound specified in the diene rubber cannot be sufficiently dispersed and mixed.

  In the first mixing step (1), the diene rubber and the compound represented by the general formula (i) are preferably kneaded at 120 to 180 ° C, more preferably 150 to 170 ° C. The kneading time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes. By setting the kneading temperature and time in the first mixing step (1) within the above ranges, mechanical properties such as tensile breaking strength and tensile breaking elongation, particularly, tensile breaking elongation can be prevented from decreasing.

  In the second mixing step (2), the reinforcement containing 80 to 150 parts by weight of carbon black with respect to 100 parts by weight of the rubber component containing 40 to 100% by weight of the kneaded rubber masterbatch obtained in the first mixing step (1). A rubber kneaded product is obtained by mixing and kneading 160 to 220 parts by weight of a filler and a compounding agent other than a vulcanizing compound. Carbon black is blended in an amount of 80 to 150 parts by weight, preferably 80 to 130 parts by weight, per 100 parts by weight of the rubber component. If the blending amount of the carbon black is less than 80 parts by weight, the effect of improving the mechanical properties such as tensile strength at break and rubber hardness of the rubber composition cannot be obtained sufficiently. When the blending amount of carbon black is 80 parts by weight or more, tan δ (60 ° C.) increases and tensile elongation at break decreases.

  As described above, examples of the reinforcing filler other than carbon black include silica, clay, aluminum hydroxide, and calcium carbonate. Of these, silica is preferable. The proportion of carbon black is preferably 36% by weight or more in 100% by weight of the reinforcing filler.

  In the second mixing step (2), the rubber kneaded material is mixed with 1 to 20 parts by weight, preferably 2 to 10 parts by weight of the thermosetting resin with respect to 100 parts by weight of the rubber component. When the amount of the thermosetting resin is less than 1 part by weight, the effect of improving the mechanical properties of the rubber composition cannot be sufficiently obtained.

  In addition to the kneaded rubber masterbatch, the reinforcing filler containing carbon black, and the thermosetting resin, the rubber kneaded material is mixed with a compounding agent other than the vulcanizing compounding agent. Here, the vulcanizing compound includes a vulcanizing agent and a crosslinking agent, a vulcanization accelerator, a crosslinking accelerator, and a vulcanization retarder. Examples of additives other than vulcanizing additives include, for example, various additives generally used in tire rubber compositions such as zinc oxide, stearic acid, antioxidants, various oils, and plasticizers. Can do.

  In the second mixing step (2), the kneading operation is performed under the normal conditions in which the rubber kneaded material described above is applied to the mixture of the diene rubber and the reinforcing filler. The kneading temperature in the second mixing step is preferably 120 to 190 ° C, more preferably 140 to 180 ° C.

  The third mixing step (3) is a step of blending and mixing a vulcanizing compound with the rubber kneaded material obtained in the second mixing step. A vulcanization system compounding agent means the compounding agent mentioned above. Further, a methylene donor of a thermosetting resin can be blended. In the third mixing step, mixing is performed by determining conditions so that the vulcanizing compound does not cause early vulcanization and crosslinking.

  In the tire rubber composition obtained by the production method of the present invention, 80 to 150 parts by weight of carbon black is blended with 100 parts by weight of the rubber component including the kneaded rubber masterbatch. This carbon black is not blended in the kneaded rubber masterbatch produced in the first mixing step, but needs to be blended in the second mixing step. By not adding carbon black to the first mixing step in this way, the reinforcing filler and the compound represented by the general formula (i) are prevented from agglomerating, thereby improving the dispersibility of the carbon black and the rubber composition. The tan δ (60 ° C.) of the product can be reduced, and the mechanical strength, particularly the tensile elongation at break can be improved.

  The rubber composition for tires of the present invention can be suitably used for bead insulation of pneumatic tires. Since the pneumatic tire using the rubber composition of the present invention for bead insulation has low heat generation during running, rolling resistance can be reduced and fuel efficiency can be improved. At the same time, by improving the mechanical properties of the rubber composition, it is possible to maintain and improve the handling stability, wear resistance, and durability to the conventional level or higher. Furthermore, the adhesion of the bead insulation to the bead wire can be increased and the tire durability can be improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  18 types of rubber compositions (Examples 1 to 8, Standard Examples, etc.) having different formulations as shown in Tables 1 to 3 in the three steps including the first mixing step, the second mixing step, and the third mixing step. Comparative examples 1-9) were prepared. First, kneading is carried out under the conditions described in the column “First kneading condition of the first mixing step” and the following conditions of the first mixing step, with the compounding described in the column “Mixing of the first mixing step (kneaded rubber masterbatch)”. A kneaded rubber masterbatch was prepared. In addition, the compound of the comparative example which does not correspond to the kneaded rubber masterbatch of this invention is also considered as a kneaded rubber masterbatch for convenience. Using the resulting kneaded rubber masterbatch, kneading is carried out under the conditions of the following second mixing step with the formulation described in the column of “blending of the second mixing step (rubber kneaded product)” to prepare a rubber kneaded product did. Using the obtained rubber kneaded material, the rubber composition for tires was prepared by mixing under the conditions of the following third mixing step with the formulation described in the column of “3rd mixing step”.

  In addition, the description of the column of “kneaded rubber masterbatch (amount of rubber component)” in “mixture of second mixing step (rubber kneaded material)” in Tables 1 to 3 is the kneaded rubber master prepared in the first mixing step The amount of the rubber component described in the parenthesis represents the amount of the diene rubber contained therein. The description of “compounding agent (Table 4)” in “compounding of the second mixing step (rubber kneaded material)” in Tables 1 to 3 is the sum of compounding agents other than the vulcanizing compounding agent added in the second mixing step. The compounding agents other than the vulcanizing compounding agents are shown in Table 4 as common prescriptions.The amount of the compounding agent other than the vulcanizing compounding compound described in Table 4 is the tire described in Tables 1-3. Means parts by weight with respect to 100 parts by weight of the rubber component constituting the rubber composition.

<First mixing step>
After pre-mixing natural rubber for 1 minute using a 1.8L Banbury mixer (97 ° C), add the compound listed in the column of "Composition of the first mixing step (kneaded rubber MB)" in Tables 1 and 2 And kneaded. In the table, a compound that does not correspond to the kneaded rubber masterbatch of the present invention is also described in the column of “Composition of the first mixing step (kneaded rubber MB)” for convenience. The total mixing time in the first mixing step was 4 minutes, and the filling rate was 72%. Tables 1 to 3 show the kneading temperature and the time for keeping the kneading temperature.

<Second mixing step>
Using a 1.8 L Banbury mixer, the kneaded rubber masterbatch obtained in the first mixing step and optionally the diene rubber blended in the second mixing step are premixed for 1 minute, and then carbon black or the like “ The compounding agents described in the column “Combination of two mixing steps (rubber kneaded product)” were mixed. In the table, the mixture obtained in the first mixing step that does not correspond to the kneaded rubber masterbatch of the present invention is also described in the column of “kneaded rubber MB (rubber component amount)” for convenience. The total mixing time of the second mixing step is 5 minutes 30 seconds, and the rubber temperature at that time is 162 ° C.

<Third mixing step>
The rubber kneaded material obtained in the second mixing step, the vulcanization accelerator, and sulfur at a temperature of 70 to 90 ° C. in an open roll machine are described in the column of “third mixing step” in Tables 1 to 3. The rubber composition for tires was obtained by blending with the composition.

  The 18 kinds of rubber compositions obtained were each vulcanized in a mold having a predetermined shape at 170 ° C. for 10 minutes to prepare test pieces, and the rubber hardness, tensile properties and dynamic viscosity were determined by the following methods. Elasticity (tan δ at 60 ° C.) was evaluated. Moreover, the adhesiveness (wire adhesiveness) with respect to the bead wire of 18 types of obtained rubber compositions was evaluated by the method shown below.

Rubber hardness Using the obtained test piece, it was measured at a temperature of 20 ° C. with a durometer type A according to JIS K6253. The obtained results are shown in the column of “rubber hardness” with the value of the standard example being 100. The larger the rubber hardness index, the better the steering stability.

Tensile properties From the obtained test pieces, JIS No. 3 dumbbell-type test pieces (thickness 2 mm) were punched out in accordance with JIS K6251 and tested at a tensile rate of 500 mm / min, and the tensile strength at break and tensile elongation at break were measured. . The obtained results are shown in the columns of “breaking strength” and “breaking elongation” as indices with the respective values of the standard examples as 100. The larger the breaking strength index, the better the steering stability and wear resistance. The larger the elongation at break, the better the tire durability.

Dynamic viscoelasticity (tan δ at 60 ° C)
Based on JIS K6394, the obtained test piece was subjected to a loss tangent tan δ at a temperature of 60 ° C. under the conditions of an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. It was measured. The obtained results are shown in the column of “tan δ (60 ° C.)” as an index with the value of the standard example as 100. The smaller the index of tan δ (60 ° C.), the smaller the heat generation, and the smaller the rolling resistance when the tire is made, the better the fuel efficiency.

Bead wire adhesion (wire adhesion)
A plurality of bead wires are arranged in parallel with each other at intervals of 13 mm, and this is embedded in a strip-like sheet (25 mm width of JIS K6256 peeling test) of an unvulcanized tire rubber composition and 10 at 170 ° C. Test samples were prepared by press vulcanization for minutes. Divide the test sample into two groups, one group is used to evaluate the initial bead wire adhesion, and the other group is immersed in warm water at 70 ° C. for 2 weeks to form a test sample for water aging evaluation, and water resistant adhesion Sex was evaluated.

  For initial adhesion and water-resistant adhesion, each test sample was subjected to a bead wire pull-out test in accordance with JIS K6256, the pull-out force during pull-out and the rubber coverage on the bead wire (with rubber [%] ) Was measured visually. The obtained results are shown in the columns “Initial Adhesion” and “Waterproof Adhesion” of “Wire Adhesiveness” in Tables 1 and 2 as indices with the respective values of the standard examples as 100. The larger these indexes, the better the “initial adhesion” and “water resistant adhesion” to the bead wire.

In addition, the kind of raw material used in Tables 1-3 is shown below.
-NR: natural rubber, TSR20
-SBR: styrene butadiene rubber, Nipol 1502 manufactured by Nippon Zeon
-Carbon black: Niteron #G made by Nippon Kayaku Carbon Co., Nitrogen adsorption specific surface area of 30 m ² / g
-Thermosetting resin: Cashew modified phenolic resin, Sumitrite resin PR-NR-1 manufactured by Sumitomo Bakelite Co., Ltd.
-Sulfur: Shikoku Kasei Kogyo Co., Ltd. Mukuron OT-20
-Vulcanization accelerator: Noxeller DZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
-Methylene donor: Sumikanol 508 manufactured by Taoka Chemical Industry Co., Ltd. (partial condensate of hexamethoxymethylolmelamine (HMMM) (component content: 100% by mass))

-Compound (i): (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid, prepared by the following method.
Under a nitrogen atmosphere, a reaction vessel was charged with 25.17 g (0.233 mol) of 1,4-phenylenediamine and 230 ml of tetrahydrofuran. A solution prepared by dissolving 22.84 g (0.233 mol) of maleic anhydride in 50 ml of tetrahydrofuran was added dropwise thereto in about 1 hour under ice cooling, and the mixture was stirred overnight at room temperature. After completion of the reaction, the precipitated crystals were collected by filtration, washed twice with 40 ml of tetrahydrofuran, dried at 40 ° C. for 5 hours, and crude (2Z) -4-[(4-aminophenyl) amino] -4-oxo- 46.92 g of 2-butenoic acid was obtained as an orange powder. 250 ml of methanol was added to 46.92 g of crude (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid, stirred at 50 ° C. for 1 hour, cooled, filtered, and 20 ml of methanol. Washed twice. The obtained crystals were dried to obtain 42.67 g of (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid as a yellow-orange powder. The yield was 88.8%.

In addition, the kind of raw material used in Table 4 is shown below.
-Clay: T clay manufactured by Nippon Talc Co., Ltd.-Zinc oxide: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.-Stearic acid: Stearic acid YR manufactured by NOF Corporation
-Aroma oil: Diana Process NH-60 manufactured by Idemitsu Kosan Co., Ltd.
-Cobalt naphthenate: Cobalt naphthenate manufactured by DIC (Co = 10%)

  As is apparent from Tables 2 and 3, the rubber compositions for tires of Examples 1 to 8 are rubber hardness, tensile breaking strength, tensile breaking elongation, and tan δ (60 ° C.), and bead wire adhesion after initial and water aging resistance. It has been confirmed that the performance is improved to a level higher than the conventional level.

  As is clear from Table 1, the rubber composition of Comparative Example 1 did not perform the first mixing step and did not use the kneaded rubber masterbatch, so that the tensile breaking strength and the tensile breaking elongation deteriorate. In the rubber composition of Comparative Example 2, since the kneaded rubber masterbatch produced in the first mixing step does not contain the compound represented by the general formula (i) but contains carbon black, the rubber hardness and tensile breaking strength are high. Getting worse.

  In the rubber composition of Comparative Example 3, since the kneaded rubber masterbatch produced in the first mixing step contains carbon black, the tensile elongation at break is deteriorated. In the rubber composition of Comparative Example 4, the kneaded rubber masterbatch produced in the first mixing step contains carbon black without containing natural rubber and isoprene rubber (content is less than 40% by weight). The tensile strength at break and the tensile strength at break deteriorate, and tan δ (60 ° C.) cannot be reduced.

  In the rubber composition of Comparative Example 5, since the kneaded rubber masterbatch produced in the first mixing step contains carbon black, the tensile elongation at break deteriorates. In the rubber composition of Comparative Example 6, since the kneaded rubber masterbatch produced in the first mixing step does not contain natural rubber and isoprene rubber (content is less than 40% by weight), rubber hardness and tensile strength at break Deteriorates and tan δ (60 ° C.) cannot be reduced.

  As is clear from Table 2, the rubber composition of Comparative Example 7 is prepared by masticating natural rubber in the first mixing step and styrene-butadiene rubber, carbon black and general formula (i) in the second mixing step. Since the compound was kneaded in a lump and no kneaded rubber masterbatch was used, the rubber hardness, tensile breaking strength and tensile breaking elongation deteriorate. In the rubber composition of Comparative Example 8, the compounding amount of the compound represented by the general formula (i) exceeds 5% by weight in the first mixing step, so that the tensile elongation at break is deteriorated. Also, the bead wire adhesion is deteriorated.

  In the rubber composition of Comparative Example 9, since the styrene butadiene rubber exceeds 60% by weight in 100% by weight of the rubber component, the tensile breaking strength, the tensile breaking elongation, and the bead wire adhesion are deteriorated.

Claims (3)

Natural rubber and / or isoprene rubber is allowed to coexist with 0.3 to 5.0% by weight of a compound represented by the following general formula (i) in 100% by weight of diene rubber containing 40% by weight or more and optionally styrene butadiene rubber. It is a rubber component comprising 40 to 100% by weight of a kneaded rubber masterbatch and a total of 60 to 0% by weight of styrene butadiene rubber and natural rubber, and the total of the natural rubber and isoprene rubber in the rubber component is 40 to 100%. A reinforcing filler containing 80 to 150 parts by weight of carbon black having a nitrogen adsorption specific surface area of 50 m ² / g or less with respect to 100 parts by weight of a rubber component containing 60% by weight and 60% by weight of the styrene butadiene rubber. A rubber composition for tires, comprising 160 to 220 parts by weight and 1 to 20 parts by weight of a thermosetting resin.

(In the formula, R ¹ is an optionally substituted divalent aromatic hydrocarbon group having 6 to 12 carbon atoms, R ² and R ³ are each independently a hydrogen atom, a halogen atom, or 1 to 6 carbon atoms. An alkyl group, a C 6-12 aryl group, a hydroxy group or a C 1-6 alkoxy group, R ⁴ represents a hydroxy group or —ONa, and X represents —NH— or —O—.) The tire rubber composition according to claim 1, wherein in the general formula (i), R ⁴ is a hydroxy group.   A pneumatic tire using the rubber composition for tires according to claim 1 or 2 for bead insulation.