JP2009029883A - Method for producing unvulcanized rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an unvulcanized rubbeer composition for tire, improved in the processability during the process ranging from compounding to vulcanization. <P>SOLUTION: The method for producing the unvulcanized rubber composition for a tire is provided, wherein the composition comprises 100 pts.wt. of a rubber component comprising one or more diene rubbers selected from natural rubber and synthetic polyisoprene rubber, 5-30 pts.wt. of silica, 3-15 wt.%, based on the whole amount of the silica, of a silane coupling agent, 0.1-5.0 pt.wt. of a quinone-based radical scavenger, and a vulcanization-based compounding agent. Specifically, this method comprises the first blending step of forming a first blend by blending together at 110-160°C 50 pts.wt. or more of the whole amount of the rubber component, the whole amount of the silica, the whole amount of the silane coupling agent and the whole amount of the quinone-based radical scavenger, the second blending step of forming a second blend by blending at 130-160°C by adding the balance of the rubber component to the first blend, and the third blending step of blending by adding the vulcanization-based compounding agent to the second blend. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing an unvulcanized rubber composition for tires, and more specifically, an unvulcanized rubber composition for tires with improved processability from compounding to vulcanization by suppressing an increase in viscosity. And a tire unvulcanized rubber composition obtained thereby.

  Conventionally, a technique for improving wet performance and reducing rolling resistance by blending silica in a tire rubber composition is known. However, silica generally has a low affinity for rubber molecules, and because it has high cohesiveness due to hydrogen bonding due to silanol groups present on the surface of the silica particles, the dispersibility of the silica particles is low and the processability is poor. There are drawbacks. As a method for improving the processability by reducing the viscosity of unvulcanized rubber, for example, in Patent Document 1 below, first, a rubber component such as natural rubber, a part of a reinforcing filler, and a vulcanization compound In addition to the compounding agent except the agent, an amine compound such as stearylamine, laurylamine, caprylamine, and distearylamine and a parabenzoquinone diimine compound are blended, and then the remaining reinforcing filler and vulcanizing agent It has been proposed to reduce the viscosity from rubber mastication to mixing after blending the reinforcing filler by blending the compounding agent. However, in the method described in Patent Document 1, there is an improvement effect of lowering the viscosity immediately after mixing. However, when silica is blended, it is added to the rubber component than when carbon black is blended. Since the viscosity at the initial stage of mixing is high and the viscosity further increases as the time from the end of mixing to processing or molding becomes longer, the viscosity from the time of compounding of the rubber composition containing silica to vulcanization is increased. There is a need to improve processability during compounding and after vulcanization by suppressing the increase.

JP 2001-192506 A

  Accordingly, an object of the present invention is to provide a method for producing an unvulcanized rubber composition for a silica-containing tire, which has improved processability from blending to vulcanization.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have formulated a masterbatch by blending silica with a diene rubber component in a method for producing an unvulcanized rubber composition for tires containing silica as a reinforcing filler. When adding various compounding agents such as carbon black other than the compounding agent for vulcanization to this masterbatch, and then adding the compounding agent for vulcanization, a specific process together with silica in the step of forming the masterbatch When a quinone radical scavenger is added, the increase in viscosity between the addition of silica to the diene rubber and the vulcanization is suppressed. Has been found to be improved, and the present invention has been completed.

That is, the method for producing an unvulcanized rubber composition for tires of the present invention includes:
(A) 100 parts by weight of rubber comprising at least one diene rubber selected from natural rubber and synthetic polyisoprene rubber, (B-1) 5 to 30 parts by weight of silica, and (C) the total amount of silica 3 to 15% by weight of silane coupling agent, 0.1 to 5.0 parts by weight of (D) quinone radical scavenger, and (E) vulcanized compounding agent, A method for producing a rubber composition, comprising:
(1) (A-1) 50 parts by weight or more of the total amount of the rubber component (A), the total amount of silica (B-1), the total amount of the silane coupling agent (C), and the quinone radical scavenger (D A first mixing step in which a first mixture is formed at a temperature of 110 to 160 ° C. to form a first mixture;
(2) a second mixing step of adding the remaining amount of (A-2) rubber component (A) to the first mixture and mixing at a temperature of 130 to 160 ° C. to form a second mixture;
(3) a third mixing step of adding and mixing the vulcanizing compound (E) to the second mixture;
It is characterized by including.

  In the first mixing step in the method for producing an unvulcanized rubber composition for tires of the present invention, 50 parts by weight or more (A-1) of the total amount of the rubber component (A) blended in the method, silica (B- The total amount of 1), the total amount of the silane coupling agent (C) and the total amount of the quinone radical scavenger (D) are mixed at a temperature of 110 ° C to 160 ° C, preferably 130 ° C to 160 ° C. 1 mixture is formed. The first mixture is generally referred to as a silica blend masterbatch. In the first mixing step, it is desirable that a predetermined amount of the diene rubber component, silica as the reinforcing filler, silane coupling agent, and quinone radical scavenger are mixed as uniformly as possible. Moreover, it is preferable to perform mixing for 0.5 to 3 minutes depending on the mixing ability of the mixer. The first mixing step is preferably performed using a closed mixer. After the first mixture is formed, the first mixture is discharged from the closed mixer, and then the second mixing step is performed.

  After obtaining the first mixture by the first mixing step, in the second mixing step, the remaining amount (A-2) of the rubber component (A) is added to the first mixture and mixed at a temperature of 130 ° C. to 160 ° C. . The second mixing step is preferably performed at a temperature within the above range for 0.5 to 3 minutes. In the second mixing step, carbon black (B-2) of more than 0 parts by weight and 50 parts by weight or less can be added as a reinforcing filler to 100 parts by weight of rubber (A). Addition improves properties such as wear resistance.

  The second mixture obtained in the second mixing step is then subjected to a third mixing step in which a vulcanization accelerator and a vulcanizing compound such as sulfur are added and mixed. A 3rd mixing process can be implemented using apparatuses, such as an open roll conventionally used in order to mix | blend a vulcanization | cure type | system | group compounding agent.

  The rubber component (A) used in the method for producing an unvulcanized rubber composition for tires of the present invention comprises one or more diene rubbers selected from natural rubber and synthetic polyisoprene rubber. It is preferable that 50% by weight or less of the rubber part (A), that is, more than 0 part by weight and 50 parts by weight or less of 100 parts by weight of the rubber part (A) is composed of butadiene rubber. When two or more kinds of rubbers are used as the rubber part (A), as long as the predetermined amount of rubber part is blended in each of the first and second mixing steps, the two or more kinds of rubbers are respectively Even if it mix | blends in either process of a 1st and 2nd mixing process, it may divide | segment and mix | blend in both processes.

The silica (component (B-1)) used in the first mixing step of the method for producing the unvulcanized rubber composition for tires of the present invention is appropriately selected from those generally used in the rubber industry. Although the production method is not particularly limited, the silica preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 100 to 300 m ² / g. When N ₂ SA is less than 100 m ² / g, the filling amount can be increased, but the reinforcing effect is poor. Silica with N ₂ SA exceeding 300 m ² / g is difficult to disperse in the rubber component because of its high cohesiveness. In the description of the present specification, “nitrogen adsorption specific surface area (N ₂ SA)” means a specific surface area (unit m ² / g) measured according to ATSM D3037. The amount of silica (B-1) is 5 to 30 parts by weight, preferably 5 to 25 parts by weight per 100 parts by weight of the diene rubber component (A). When the compounding amount of silica is less than 5 parts by weight with respect to 100 parts by weight of the diene rubber (A), the degree of improvement in fuel efficiency is insufficient, and when it exceeds 30 parts by weight, the wear resistance decreases.

  The silane coupling agent (component (C)) blended in the first mixing step is used to bind the diene rubber component and silica (B-1) and to promote dispersion. A compounding quantity is 3 to 15 weight% on the basis of the total amount of a silica (B-1). As the silane coupling agent (C), it is preferable to use a silane coupling agent containing sulfur in the molecule. Silane coupling agents containing sulfur in the molecule are known, such as those commercially available under the trade name Si69 from Degussa (chemical name: bis (3-triethoxysilylpropyl) tetrasulfide). It is available.

  Specific examples of the quinone radical scavenger (component (D)) blended in the first mixing step include 2,5-tert-butyl-hydroquinone and N- (1,3-dimethylbutyl) -N′-phenyl. -P-quinone diimine is listed, and these are sold under the trade names of Non-Flex Alba and Seiko Chemical Co., Ltd. and Q-Flex QDI from Flexis, respectively. The compounding amount of the quinone radical scavenger (D) is 0.1 to 5.0 parts by weight per 100 parts by weight of the total amount of the rubber component (A). If the amount of the quinone radical scavenger (D) is less than 0.1 parts by weight per 100 parts by weight of the total amount of rubber (A), the change in viscosity from the addition of silica (B-1) to vulcanization Is insufficient, and when the amount exceeds 5.0 parts by weight, the change in viscosity from the addition of silica (B-1) to vulcanization is small, but the hardness after vulcanization also decreases. This is not preferable. In the first mixing step, by adding a quinone-based radical scavenger, the rubber composition by radical recombination between the mixing of silica and vulcanization in the first mixing step, which was remarkable in the conventional method, was performed. An increase in viscosity can be suppressed. The suppression of this increase in viscosity is due to the fact that the molecular chain of the diene rubber cleaved by mastication or kneading is recombined by the radical recombination reaction by the quinone radical scavenger suppressing by the radical scavenging action. Conceivable.

  The amount of carbon black (B-2) blended in the first mixture in the second mixing step is 30 to 80 per 100 parts by weight of the total amount of rubber (A), with the total amount of silica (B-1). What is necessary is just the quantity used as a weight part. If the total amount of silica (B-1) and carbon black (B-2) is less than 30 parts by weight per 100 parts by weight of the total amount of rubber (A), the strength of the rubber obtained after vulcanization becomes insufficient, If it exceeds 80 parts by weight, the heat generation will deteriorate and the durability of the tire will be insufficient. When a tire tread is formed using the unvulcanized rubber composition of the present invention, examples of carbon black include those of SAF, ISAF, and HAF grades that are usually used in rubber compositions for tire treads. It is done.

  In the method for producing an unvulcanized rubber composition for tires of the present invention, talc, clay, calcium carbonate, aluminum hydroxide, magnesium carbonate, etc. may be blended as necessary in addition to silica and carbon black as a filler. it can.

  In the method for producing an unvulcanized rubber composition for tires of the present invention, in addition to the above compounding agents, if necessary, any compounding agent generally used in the art, for example, a vulcanization accelerator Vulcanization accelerating aids, vulcanizing agents, processing aids, anti-aging agents, and the like can be appropriately added in general compounding amounts. In the second mixing step, it is preferable to add a conventional compounding agent other than the vulcanizing compounding agent, if necessary, in addition to the carbon black.

  The unvulcanized rubber composition for tires of the present invention is particularly useful as a rubber for treads that requires high workability as well as improved wet performance and reduced rolling resistance. From the unvulcanized rubber composition for tires of the present invention, a tire tread can be formed by a general pressure molding method.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited by these examples.

Preparation of unvulcanized rubber compositions of Comparative Examples 1 to 5 and Examples 1 to 6 In accordance with the composition of Table 1 below, using a 1.7 liter closed Banbury mixer, in the first mixing step, natural rubber and butadiene Rubber, silica, silane coupling agent, peptizer, radical scavenger 1 or 2 in the case of Examples 1 to 6, 80 ° C. in the case of Comparative Example 4, and Comparative Example 5 Was mixed for about 2 minutes at a temperature of 180 ° C., and in other cases 150 ° C. to form a first mixture and cooled to room temperature. Next, using the same mixer as used in the first mixing step as the second mixing step, carbon black, zinc oxide, stearic acid, an anti-aging agent, and an anti-aging agent as necessary. Add butadiene rubber and mix for about 2 minutes at a temperature of 80 ° C. for Comparative Example 4, 180 ° C. for Comparative Example 5 and 150 ° C. for the other examples. And the second mixture was cooled to room temperature. Then, the vulcanization accelerator and sulfur were mixed for about 2 minutes using the open roll, and each unvulcanized rubber composition of Comparative Examples 1-5 and Examples 1-6 was obtained.

Table 1 footnotes:
(1): STR20
(2): Nipol 1220 manufactured by Nippon Zeon Co., Ltd. (non-oil exhibition)
(3): Tosoh Silica Co., Ltd. nip seal AQ
(4): Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
(5): Nouchitizer SD (chemical name: o, o'-dibenzamide diphenyl disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(6): Seiko Chemical Co., Ltd. non-flex alba (chemical name: 2,5-di-tert-butylhydroquinone)
(7): Q-Flex QDI (chemical name: N- (1,3-dimethylbutyl) -N'-phenyl-p-quinonediimine) manufactured by Flexis
(8): Show Black N234 from Cabot Japan
(9): Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.
(10): Bead stearic acid manufactured by NOF Corporation
(11): Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (chemical name: N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine)
(12): SANTOCURE TBBS manufactured by Flexis (chemical name: N-tert-butyl-2-benzothiazolesulfenamide)
(13): Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd.

Test Methods The performance of the unvulcanized rubber compositions obtained by the following examples and comparative examples was determined by the following test methods. The results of each test are as shown in Table 1.
(1) Mooney viscosity The unvulcanized rubber compositions of Comparative Examples 1 to 5 and Examples 1 to 6 prepared as described above were left in a room maintained at a temperature of 23 ° C. and a relative humidity of 50%. Samples were taken from the unvulcanized rubber composition 1 hour, 1 day, 3 days, and 7 days after the end of the mixing step (third mixing step), and each sample was subjected to an L-shaped rotor in accordance with JIS K6300. (Testing machine: SMV300J manufactured by Shimadzu Corporation) was used to measure Mooney viscosity at a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a temperature of 100 ° C. The measured Mooney viscosity was expressed as an index with the Mooney viscosity determined for a sample taken from the unvulcanized rubber composition of Comparative Example 1 as 1 hour after the end of the mixing step. The Mooney viscosity is an index of processability before vulcanization of the rubber composition, and a small Mooney viscosity value means that the viscosity before vulcanization is low and the processability is excellent.
(2) Hardness The unvulcanized rubber compositions of Comparative Examples 1-5 and Examples 1-6 prepared as described above were press vulcanized at 150 ° C. for 30 minutes to obtain a length of 15 cm, a width of 15 cm, and a thickness of 2 mm. A vulcanized rubber sheet was prepared, and the hardness was determined at a temperature of 23 ° C. according to a JIS K6253 type A durometer hardness test. The hardness calculated for Comparative Example 1 was taken as 100, and the hardnesses of other Comparative Examples and Examples were expressed as indices. It shows that hardness is so high that this value is large.

  As is clear from the results in Table 1 above, the unvulcanized rubber compositions of Examples 1 to 6 are superior in processability to the unvulcanized rubber compositions of Comparative Examples 1 to 5, and are almost equivalent after vulcanization. It can be seen that the hardness is shown.

Claims (7)

(A) 100 parts by weight of rubber comprising at least one diene rubber selected from natural rubber and synthetic polyisoprene rubber, (B-1) 5 to 30 parts by weight of silica, and (C) the total amount of silica 3 to 15% by weight of silane coupling agent, 0.1 to 5.0 parts by weight of (D) quinone radical scavenger, and (E) vulcanized compounding agent, A method for producing a rubber composition, comprising:
(1) (A-1) 50 parts by weight or more of the total amount of the rubber component (A), the total amount of silica (B-1), the total amount of the silane coupling agent (C), and the quinone radical scavenger (D A first mixing step in which a first mixture is formed at a temperature of 110 to 160 ° C. to form a first mixture;
(2) a second mixing step of adding the remaining amount of (A-2) rubber component (A) to the first mixture and mixing at a temperature of 130 to 160 ° C. to form a second mixture;
(3) a third mixing step of adding and mixing the vulcanizing compound (E) to the second mixture;
The manufacturing method of the unvulcanized rubber composition for tires characterized by including this.   The method for producing an unvulcanized rubber composition for a tire according to claim 1, wherein the rubber component (A) includes a butadiene rubber having a content of more than 0 parts by weight and 50 parts by weight or less.   The unvulcanized rubber composition for tires further contains (B-2) more than 0 part by weight and 50 parts by weight or less of carbon black, and this carbon black (B-2) is converted into the first mixture in the second mixing step. The method for producing an unvulcanized rubber composition for tires according to claim 1 or 2, wherein the rubber composition is added.   The unvulcanized rubber composition for tire according to any one of claims 1 to 3, wherein the quinone radical scavenger (D) is selected from a hydroquinone radical scavenger and a quinonediimine radical scavenger. Manufacturing method.   The method for producing an unvulcanized rubber composition for tire according to claim 4, wherein the hydroquinone-based radical scavenger is 2,5-di-tert-butyl-hydroquinone.   The method for producing an unvulcanized rubber composition for a tire according to claim 4, wherein the quinonediimine-based radical scavenger is N- (1,3-dimethylbutyl) -N'-phenyl-p-quinonediimine. .   An unvulcanized rubber composition for tires produced by the method according to claim 1.