JP2016196576A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire for improving low heat generation property and mechanical characteristics.SOLUTION: There is provided a rubber composition for a tire obtained by blending 30 to 80 pts.wt. of carbon black having a nitrogen adsorption specific surface area of 20 to less than 90 m/g and 3.0 to 8.0 pts.wt. of a sulfur component in terms of pure sulfur based on 100 pts.wt. of a rubber component which is a rubber component composed of 40 wt.% or more of a natural rubber and/or an isoprene rubber, 20 to 100 wt.% of a masticated rubber masterbatch in which 0.3 to 5.0 wt.% of a terminal amino dicarbonyl unsaturated compound represented by the formula (i) is coexisted with 100 wt.% of a diene-based rubber optionally including a butadiene rubber and a total of 80 to 0 wt.% of a butadiene rubber, a natural rubber and an isoprene rubber and contains a total 20 to 80 wt.% of a natural rubber and an isoprene rubber and a total of 80 to 20 wt.% of a 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 this rubber composition is used to form a crescent-shaped rubber reinforcing layer in the left and right sidewall portions of the run-flat tire, the required level of mechanical properties such as tensile rupture strength, tensile rupture elongation, fatigue resistance, In particular, the tensile elongation at break and fatigue resistance could not be sufficiently ensured, and further improvements were 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.

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 diene rubber containing butadiene rubber. A rubber component comprising 20 to 100% by weight of a kneaded rubber masterbatch in which 0.3 to 5.0% by weight of a compound coexists, and 80 to 0% by weight in total of butadiene rubber, natural rubber and isoprene rubber, the sum of the rubber and isoprene rubber 20 to 80 wt%, and the rubber component 100 parts by weight comprising the total 80 to 20% by weight of butadiene rubber, a nitrogen adsorption specific surface area is less than 20 m ² / g or more 90m ² / g 30 to 80 parts by weight of carbon black and 3.0 to 8.0 parts by weight of a sulfur component in terms of pure sulfur are blended.

（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 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 comprises butadiene for rubber components containing a modified rubber masterbatch obtained by reacting a compound represented by the general formula (i) with a diene rubber containing natural rubber and / or isoprene rubber. Since rubber, specific carbon black, and sulfur components are added, tan δ (60 ° C) of the rubber composition is reduced, and mechanical properties such as tensile strength at break and tensile elongation at break are maintained and improved. Can do. As a result, when a pneumatic tire is used, the handling stability and fatigue resistance can be improved to a level higher than the conventional level while improving the fuel efficiency.

In the compound represented by the general formula (i), R ⁴ may be a hydroxy group.

  The butadiene rubber may contain 20-50% by weight of syndiotactic-1,2-polybutadiene.

  This rubber composition is suitable for constructing a crescent-shaped rubber reinforcement layer on the left and right sidewalls of a run-flat tire, and reduces the rolling resistance of pneumatic tires and improves fuel efficiency while improving steering stability. In addition, the fatigue resistance can be improved over the conventional level.

  The rubber composition for tires of the present invention comprises a kneaded rubber masterbatch, butadiene rubber and a reinforcing filler. The kneaded rubber masterbatch is a natural rubber and / or isoprene rubber, optionally a diene rubber containing a butadiene rubber and a specific compound coexisting therewith. As the natural rubber, isoprene rubber and butadiene rubber, those usually used for tire rubber compositions can be used.

  The kneaded rubber masterbatch includes at least one of natural rubber and isoprene rubber, and optionally includes 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 with 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 butadiene rubber, styrene butadiene rubber, butyl rubber, and ethylene propylene diene rubber. Of these, butadiene rubber is preferred.

  In the present invention, the kneaded rubber masterbatch is obtained by coexisting 0.3 to 5.0% by weight of a compound represented by the following general formula (i) with 100% by weight of a diene rubber.

（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、Ｒ^４はヒドロキシ基または−ＯＮａ、Ｘは−ＮＨ−または−Ｏ−を表す。）

(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 1.0 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. In addition, fatigue resistance 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 butadiene rubber coexist with the compound represented by the general formula (i). When the rubber composition is formulated, 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 contains a reinforcing filler containing 30 to 80 parts by weight of carbon black to 100 parts by weight of the rubber component containing 20 to 100% by weight of the above-mentioned masticated rubber masterbatch, and It contains 3.0 to 8.0 parts by weight of a sulfur component in terms of pure sulfur. The rubber component can optionally contain other diene rubbers in addition to the kneaded rubber masterbatch. The other diene rubber is an unmodified rubber and is selected from butadiene rubber, natural rubber and isoprene rubber.

  In the present invention, 100% by weight of the rubber component comprises 20 to 100% by weight of the masticated rubber masterbatch and 80 to 0% by weight in total of butadiene rubber, natural rubber and isoprene rubber. The content of the kneaded rubber masterbatch is 20 to 100% by weight, preferably 30 to 100% by weight. The total of butadiene rubber, natural rubber and isoprene rubber is 80 to 0% by weight, preferably 70 to 0% by weight. When the content of the kneaded rubber masterbatch is less than 20% by weight, the affinity of the reinforcing filler containing the 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, a total of 20 to 80% by weight, preferably 30 to 70% by weight, of the natural rubber and isoprene rubber added in the rubber component 100% by weight, in the masticated rubber masterbatch and afterwards, is added. By making the total of the natural rubber and isoprene rubber in the rubber component 20% by weight or more, low heat build-up and mechanical properties at the level required for the crescent-shaped rubber reinforcing layer in the left and right sidewall portions of the run-flat tire You can get specific.

  The rubber component always contains butadiene rubber as a masticated rubber masterbatch and other diene rubbers to be added later. Here, the 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 amount of the butadiene rubber as the masticated rubber masterbatch and other diene rubber added later is 80 to 20% by weight, preferably 70 to 30% by weight, based on 100% by weight of the rubber component. If the total amount of butadiene rubber is less than 20% by weight, the fatigue resistance deteriorates. On the other hand, if the total amount of butadiene rubber exceeds 80% by weight, the hardness decreases and steering stability deteriorates.

The tire rubber composition of the present invention, the rubber component 100 parts by weight of the above, 30 to 80 parts by weight of carbon black nitrogen adsorption specific surface area is less than 20 m ² / g or more 90m ² / g, preferably 40 A reinforcing filler containing 70 parts by weight is blended.

  If the blending amount of carbon black is less than 30 parts by weight, the effect of improving the mechanical properties of the rubber composition cannot be obtained sufficiently. If the carbon black exceeds 80 parts by weight, the heat generation 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 20 m ² / g or more 90m less than ² / g, preferably 30~80m ² / g. When the nitrogen adsorption specific surface area of carbon black is less than 20 m ² / g, mechanical properties such as rubber strength and rubber hardness of the rubber composition are lowered. Further, when the nitrogen adsorption specific surface area of carbon black is 90 m ² / g or more, 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 and silica are preferable.

  The blending amount of carbon black is preferably 30% by weight or more, more preferably 40 to 100% by weight in 100% by weight of the reinforcing filler. By making carbon black 30% by weight or more in 100% by weight of the reinforcing filler, the affinity of the kneaded rubber masterbatch and the reinforcing filler can be further increased.

  The rubber composition for tires of the present invention contains 3.0 to 8.0 parts by weight, preferably 4 to 7 parts by weight of a sulfur component in terms of pure sulfur with respect to 100 parts by weight of the rubber component described above. Hardness falls that the compounding quantity of a sulfur component is less than 3.0 weight part. Moreover, when the compounding quantity of a sulfur component exceeds 8.0 weight part, fatigue property will deteriorate. As the sulfur component, general sulfur that can be used in a tire rubber composition can be used.

  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, fatigue resistance, and wear resistance of the pneumatic tire can be improved to a level higher than the conventional level.

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 natural rubber and / or isoprene rubber is added in an amount of 40% by weight or more and optionally a diene rubber containing a butadiene rubber in an amount of 100% by weight, and a compound represented by the following general formula (i) is added in an amount of 0.3 to 5.0% by weight. First mixing step to obtain a kneaded rubber masterbatch by blending and kneading in a state not containing a reinforcing filler,

（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 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) The rubber component comprising 20 to 100% by weight of the kneaded rubber masterbatch and a total of 80 to 0% by weight of butadiene rubber, natural rubber and isoprene rubber, and natural added in and after the masticated rubber masterbatch The nitrogen adsorption specific surface area is 20 m ² with respect to 100 parts by weight of the rubber component containing 20 to 80% by weight of the total of rubber and isoprene rubber and 80 to 20% by weight of the total of butadiene rubber added in the masticated rubber masterbatch and later. Second mixing step of obtaining a rubber kneaded material by blending and kneading 30 to 80 parts by weight of carbon black which is not less than / g and less than 90 m ² / g,
(3) A third mixing step in which the rubber kneaded material is mixed with a vulcanizing compound containing 3.0 to 8.0 parts by weight of a sulfur component in terms of pure sulfur.

  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 contains 100% by weight of a diene rubber containing natural rubber and / or isoprene rubber, and optionally butadiene rubber, and the compound represented by the general formula (i) is 0.3 to 5. It can be produced by blending 0% by weight and kneading in a state not 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. Further, fatigue resistance is reduced.

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 a natural rubber mastication step, the compound represented by the general formula (i) and optionally butadiene rubber are blended and kneaded in 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 150 to 180 ° C, more preferably 160 to 170 ° C. The kneading time is preferably 1 to 5 minutes, more preferably 2 to 3 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 30 to 80 parts by weight of carbon black with respect to 100 parts by weight of the rubber component containing 20 to 100% by weight of the kneaded rubber masterbatch obtained in the first mixing step (1). A rubber kneaded product is obtained by blending and kneading compounding agents other than the filler and vulcanizing compound. Carbon black is blended in an amount of 30 to 80 parts by weight, preferably 40 to 70 parts by weight, based on 100 parts by weight of the rubber component. If the blending amount of carbon black is less than 30 parts by weight, the effect of improving mechanical properties such as tensile breaking strength and rubber hardness of the rubber composition cannot be obtained sufficiently. If the blending amount of carbon black exceeds 80 parts by weight, 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 blending amount of the carbon black is preferably 30% 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 a compounding agent other than the vulcanized compounding agent in addition to the kneaded rubber masterbatch and the reinforcing filler. 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 rubber compound obtained in the second mixing step with a vulcanizing compound containing 3.0 to 8.0 parts by weight of a sulfur component in terms of pure sulfur. is there. The vulcanized compounding agent refers to the compounding agent described above, but contains 3.0 to 8.0 parts by weight, preferably 4 to 7 parts by weight of the sulfur component in terms of pure sulfur. Hardness falls that the compounding quantity of a sulfur component is less than 3.0 weight part. Moreover, when the compounding amount of the sulfur component exceeds 3 parts by weight, the fatigue property is deteriorated.

  In the third mixing step (3), the vulcanizing compounding agent is preferably at a kneading temperature of 90 to 120 ° C., more preferably 95 to 105 ° C., preferably 1 to 5 so as not to cause early vulcanization and crosslinking. The kneading time may be kneaded for 1 minute, more preferably 2 to 3 minutes.

  The tire rubber composition obtained by the production method of the present invention is blended with 30 to 80 parts by weight of carbon black with respect to 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 blended in the second mixing step. Thus, by not adding the reinforcing filler to the first mixing step, the reinforcing filler and the compound represented by the general formula (i) are prevented from agglomerating and the dispersibility of the carbon black is improved. The tan δ (60 ° C.) of the rubber composition 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 constituting a crescent-shaped rubber reinforcing layer in the left and right sidewall portions of a run flat tire. Since the pneumatic tire in which the rubber reinforcing layer is composed of the rubber composition of the present invention has low heat generation during running, it can reduce rolling resistance and improve fuel efficiency. 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, durability and fatigue resistance to the conventional level or higher.

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

  19 types of rubber compositions (Examples 1 to 8, Standard Examples, and Formulas 1 to 8), which are different 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 to 10) 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 (97 ° C.) using a 1.8 L Banbury mixer, add the compound described in the column of “Composition of first mixing step (kneaded rubber MB)” in Tables 1 to 3 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 obtained 19 kinds of rubber compositions were each vulcanized in a mold having a predetermined shape at 170 ° C. for 10 minutes to prepare test pieces. The rubber hardness, tensile properties, dynamic viscosity were determined by the following methods. Elasticity (tan δ at 60 ° C.) and fatigue resistance were evaluated.

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.

Fatigue resistance A test piece of dumbbell shape No. 3 (distance between marked lines 20 mm) was produced from the obtained test piece in accordance with JIS K6270. For fatigue characteristics, 40% strain was repeatedly given to each test piece, and the number of repetitions until the test piece broke (hereinafter referred to as “number of breaks”) was measured. The number of breaks was measured at n = 6, and the 50% residual probability based on the normal probability distribution was determined from the number of breaks. The obtained results are shown in the “Fatigue resistance” column as an index for setting the value of the standard example to 100. A larger index means a longer fatigue life and better fatigue resistance.

In addition, the kind of raw material used in Tables 1-3 is shown below.
-NR: natural rubber, STR20
-BR: Butadiene rubber, NIPOL BR1220 manufactured by Nippon Zeon
-Carbon black: Cabot Japan Show Black N550, nitrogen adsorption specific surface area of 40 m ² / g
-Sulfur: Flexex HS manufactured by Flexis (Sulfur content is about 80% by weight)
-Vulcanization accelerator: Nouchira CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.

-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.
-Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Co., Ltd.-Stearic acid: Stearic acid YR manufactured by NOF Corporation
Anti-aging agent: SANTOFLEX 6PPD manufactured by FLEXSYS

  As is apparent from Tables 2 and 3, the rubber compositions for tires of Examples 1 to 8 are improved in rubber hardness, tensile breaking strength, tensile breaking elongation, tan δ (60 ° C.), and fatigue resistance over conventional levels. Confirmed to do.

  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. Since the rubber composition of Comparative Example 2 contains carbon black without the compound represented by the general formula (i), the kneaded rubber masterbatch produced in the first mixing step contains rubber hardness, tensile breaking strength, And fatigue resistance is deteriorated.

  In the rubber composition of Comparative Example 3, since the kneaded rubber masterbatch produced in the first mixing step contains carbon black, tensile elongation at break and fatigue resistance are deteriorated. In the rubber composition of Comparative Example 4, the kneaded rubber masterbatch produced in the first mixing step contains carbon black in an amount exceeding a predetermined amount (the blending amount is 100 parts by weight). Sex worsens. In the rubber composition of Comparative Example 5, since the kneaded rubber masterbatch produced in the first mixing step does not contain the compound represented by the general formula (i), the rubber hardness, tensile breaking strength and tensile breaking elongation are deteriorated. To do.

As can be seen from Table 2, the rubber composition of Comparative Example 6 is deteriorated in fatigue resistance because the blending amount of butadiene rubber in 100% by weight of the rubber component is less than 20% by weight. In the rubber composition of Comparative Example 7, since the compounding amount of butadiene rubber in 100% by weight of the rubber component exceeds 80% by weight, the hardness is lowered and steering stability is deteriorated.

As is apparent from Table 3, the rubber composition of Comparative Example 8 has a reduced hardness because the amount of sulfur component is less than 3.0 parts by weight. In the rubber composition of Comparative Example 9, since the compounding amount of the sulfur component exceeds 8.0 parts by weight, the fatigue property is deteriorated. Since the rubber composition of Comparative Example 10 contains the compound represented by the general formula (i) in excess of a predetermined amount, the tensile elongation at break and fatigue resistance are deteriorated.

Claims (4)

Natural rubber and / or isoprene rubber in an amount of 40% by weight or more and optionally 100% by weight of a diene rubber containing butadiene rubber coexisting with 0.3 to 5.0% by weight of a compound represented by the following general formula (i) A rubber component composed of 20 to 100% by weight of a kneaded rubber masterbatch and a total of 80 to 0% by weight of butadiene rubber, natural rubber and isoprene rubber, and a total of 20 to 80% by weight of natural rubber and isoprene rubber, and butadiene per 100 parts by weight of the rubber component containing a total 80 to 20 wt% of rubber, 30 to 80 parts by weight of carbon black nitrogen adsorption specific surface area is less than 20 m ² / g or more 90m ² / g, the net sulfur conversion sulfur components A rubber composition for tires, wherein 3.0 to 8.0 parts by weight are blended.

(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.   3. The tire rubber composition according to claim 1, wherein the butadiene rubber contains 20 to 50% by weight of syndiotactic-1,2-polybutadiene. 4.   A run-flat tire characterized in that a rubber reinforcing layer having a crescent-shaped cross section of left and right sidewall portions of the run-flat tire is constituted by the rubber composition for tires according to any one of claims 1 to 3.