JP7160668B2 - Method for producing rubber composition for tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a rubber composition for tires.

Pneumatic tires are required not only to have excellent fuel efficiency but also to have excellent grip performance on wet road surfaces, that is, wet grip performance. However, since these characteristics are contradictory characteristics, it is not easy to improve them at the same time.

Patent Document 1 describes a tire capable of improving the rolling resistance (fuel efficiency) of a tire tread without impairing other properties, particularly wet grip properties, wherein the tread comprises at least one diene elastomer, A tire is disclosed comprising a rubber composition comprising at least one reinforcing filler and greater than 10 phr of a hydrogenated styrene thermoplastic ("TPS") elastomer.

Further, Patent Document 2 discloses a rubber composition in which a rubber component is blended with a solid resin and a plasticizer such as a phosphate ester for the purpose of improving grip performance and wear resistance.

However, Patent Document 1 does not describe fuel efficiency and wet grip performance, nor does it describe the specific gravity of the thermoplastic elastomer to be blended, leaving room for further improvement in fuel efficiency and wet grip performance.

Japanese Patent Publication No. 2013-510939 JP 2016-204503 A JP 2014-189698 A JP 2015-110703 A JP 2015-110704 A

As a result of extensive studies, the present inventors have found that a rubber composition containing a thermoplastic elastomer having a functional group that reacts with or interacts with the surface functional group of an inorganic filler and having a specific gravity of 1.00 or less, It was conceived that fuel efficiency and wet grip performance could be improved.

However, it has been found that the timing of blending the thermoplastic elastomer affects the wear resistance and flex crack resistance of the resulting rubber composition. There was room for improvement in terms of gender balance.

In view of the above points, the present invention can improve flex crack resistance while suppressing deterioration of wear resistance, and has an excellent balance between fuel efficiency, wet grip performance, wear resistance, and flex crack resistance. , an object of the present invention is to provide a manufacturing method by which a rubber composition for tires can be obtained.

Incidentally, Patent Documents 3 to 5 disclose a rubber composition containing a hydrogenated thermoplastic elastomer for the purpose of improving grip performance, but there is no description of fuel efficiency.

In order to solve the above problems, the method for producing a rubber composition for tires according to the present invention is the first non-pro-kneading, in which an inorganic filler in an amount of 50% by mass or more of the inorganic filler is added to the rubber component and mixed. and adding a thermoplastic elastomer having a functional group that reacts or interacts with the surface functional group of the inorganic filler and having a specific gravity of 1.00 or less to the mixture obtained in the first non-pro-kneading step. a second non-professional kneading step of mixing; and a pro-kneading step of adding and mixing a vulcanization compounding agent to the mixture obtained in the second non-professional kneading step, wherein the rubber component is a styrene-butadiene rubber (SBR) and butadiene rubber (BR) or natural rubber (NR), and the thermoplastic elastomer is a modified polystyrene-hydrogenated butadiene/isoprene copolymer-polystyrene triblock copolymer. (modified SEEPS), modified polystyrene-hydrogenated polybutadiene-polystyrene (modified SEBS), and modified polystyrene-styrene butadiene copolymer-polystyrene (modified S-SB-S). and

The amount of the thermoplastic elastomer compounded can be 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

According to the method for producing a rubber composition for tires of the present invention, it is possible to improve flex crack resistance while suppressing deterioration of wear resistance, fuel economy, wet grip performance, wear resistance, and flex crack resistance. It is possible to obtain a rubber composition having an excellent balance of

Matters related to the implementation of the present invention will be described in detail below.

The method for producing a rubber composition for tires according to the present embodiment includes a first non-process kneading step of adding and mixing an inorganic filler in an amount of 50% by mass or more of the inorganic filler compounded amount to a rubber component, and the first non-process kneading step. A second non-professional kneading step in which a thermoplastic elastomer having a functional group that reacts or interacts with the surface functional group of the inorganic filler and having a specific gravity of 1.00 or less is added to the mixture obtained in the kneading step and mixed. and a professional kneading step of adding and mixing a vulcanization compounding agent to the mixture obtained in the second non-professional kneading step.

Although the rubber component according to the present embodiment is not particularly limited, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene -isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and the like. These diene rubbers may be used singly or in combination of two or more.

Specific examples of the diene rubbers listed above include at least one group selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, an alkoxy group, an alkoxysilyl group, and an epoxy group at the molecular terminal or in the molecular chain. Modified diene-based rubbers modified by the functional groups introduced by the introduction of the functional groups of the species are also included. As the modified diene rubber, modified SBR and/or modified BR are preferable. In this embodiment, the diene-based rubber may be an unmodified diene-based rubber alone, a modified diene-based rubber alone, or a blend of a modified diene-based rubber and an unmodified diene-based rubber. In one embodiment, 10 parts by mass or more of modified SBR may be included in 100 parts by mass of diene rubber, and 10 to 80 parts by mass of modified SBR and unmodified diene rubber (e.g., selected from SBR, BR and NR at least one) may be contained in an amount of 90 to 20 parts by mass.

The thermoplastic elastomer according to the present embodiment is not particularly limited as long as it has a functional group that reacts with or interacts with the surface functional group of the inorganic filler. Examples include those having at least one selected from the group consisting of silanol groups, alkoxysilyl groups, epoxy groups, glycidyl groups, polyether groups, polysiloxane groups, and functional groups derived from maleic anhydride. Here, the term "interaction" as used herein means to attract electrically. Further, "polyether group" means a group having two or more ether bonds, and "polysiloxane group" means a group having two or more siloxane bonds.

Further, the specific gravity of the thermoplastic elastomer according to the present embodiment is not particularly limited as long as it is 1.00 or less, but it is preferably 0.80 to 0.95, and more preferably 0.85 to 0.95. more preferred. In this specification, the specific gravity is a value determined according to ISO 1183.

Commercially available products can also be used as such thermoplastic elastomers. Specific examples include "Septon HG-252" manufactured by Kuraray Co., Ltd., "Tuftec MP10" and "Tuftec M1911" manufactured by Asahi Kasei Corporation. By melt-kneading a thermoplastic elastomer having a functional group that reacts with or interacts with the surface functional group of the inorganic filler with the rubber component, a sea-island structure can be obtained with the rubber component as the continuous phase and the thermoplastic elastomer as the dispersed phase. . The uniformly dispersed thermoplastic elastomer functions as a substitute for the inorganic filler, making it easier to obtain excellent wet grip performance. In addition, the inorganic filler reacts with or interacts with the dispersed thermoplastic elastomer, thereby improving the dispersibility of the inorganic filler and making it easier to obtain excellent fuel efficiency.

The thermoplastic elastomer is preferably a styrene-based thermoplastic elastomer having polystyrene as a hard segment, and is selected from the group consisting of hydrogenated butadiene/isoprene copolymers, hydrogenated polybutadiene, and styrene/butadiene copolymers. It is more preferable to use a styrenic thermoplastic elastomer having at least one kind of styrene-based thermoplastic elastomer in a soft segment. Specifically, thermoplastic elastomers include polystyrene-hydrogenated butadiene/isoprene copolymer-polystyrene triblock copolymer (hereinafter also referred to as SEEPS), polystyrene-hydrogenated polybutadiene-polystyrene triblock copolymer (hereinafter SEBS and polystyrene-styrene-butadiene copolymer-polystyrene (hereinafter also referred to as S-SB-S).

The amount of the thermoplastic elastomer compounded is not particularly limited, but it is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and 5 to 15 parts by mass with respect to 100 parts by mass of the rubber component. is more preferable.

In the rubber composition according to the present embodiment, reinforcing fillers such as carbon black and silica can be used as inorganic fillers. That is, the inorganic filler may be carbon black alone, silica alone, or a combination of carbon black and silica. A combination of carbon black and silica is preferred. The amount of the inorganic filler compounded is not particularly limited. 80 parts by mass.

Carbon black is not particularly limited, and various known varieties can be used. The amount of carbon black compounded is preferably 1 to 70 parts by mass, more preferably 1 to 30 parts by mass, per 100 parts by mass of the rubber component.

Silica is also not particularly limited, but wet silica such as wet sedimentation silica and wet gel silica is preferably used. When silica is blended, the blending amount is preferably 10 to 100 parts by mass, more preferably 15 to 70 parts by mass, based on 100 parts by mass of the rubber component from the viewpoint of tan δ balance and reinforcing properties of the rubber. Department.

When silica is blended, a silane coupling agent such as sulfide silane or mercaptosilane may be further blended. When a silane coupling agent is blended, the blending amount is preferably 2 to 20 parts by mass with respect to 100 parts by mass of silica.

In the production method according to the present embodiment, the non-professional kneading step is a first non-professional kneading step in which an inorganic filler of 50% by mass or more of the inorganic filler compounded amount is added to the rubber component and mixed, and a first non-professional kneading step. It is divided into at least two steps, the second non-pro-kneading step in which the thermoplastic elastomer is added to the resulting mixture and mixed. The non-professional kneading step may be further divided into a plurality of steps, and the inorganic filler may be blended in a plurality of steps. That is, in the second non-professional kneading step, the thermoplastic elastomer may be added to the mixture containing the inorganic filler in an amount of 50% by mass or more of the inorganic filler. Addition of a thermoplastic elastomer to a mixture containing 50% by mass or more of an inorganic filler based on the amount of the inorganic filler compounded improves flex crack resistance while suppressing deterioration of wear resistance. be able to. Although the mechanism is not clear, by blending the thermoplastic elastomer into a mixture in which the inorganic filler is already uniformly dispersed, the functional group of the thermoplastic elastomer reacts or interacts with the surface functional group of the inorganic filler. , It is thought that the dispersibility of the thermoplastic elastomer is improved, or the dispersibility of the thermoplastic elastomer is improved by reducing the amount of inorganic filler blended with the thermoplastic elastomer and applying strong shear (shear). be done.

In the production method according to the present embodiment, in addition to the above-described components, additives such as process oil, zinc oxide, stearic acid, softeners, plasticizers, waxes, anti-aging agents, etc., which are commonly used in the rubber industry , vulcanizing agents, vulcanization accelerators, and other vulcanization compounding agents can be appropriately blended within the usual range. Additives other than these vulcanization compounding agents are preferably blended in the non-professional kneading process, may be blended in the first non-professional kneading process of the non-professional kneading process, or may be blended in the second non-professional kneading process. may be

Vulcanizing agents include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Also, the amount of the vulcanizing agent compounded is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component. Also, the amount of the vulcanization accelerator compounded is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

The manufacturing method according to the present embodiment can be carried out using a commonly used mixer such as a Banbury mixer, kneader, or roll.

The rubber composition obtained by such a production method can be used as a tire, such as a tread portion and a sidewall portion of pneumatic tires for various purposes and sizes, such as passenger cars, large tires for trucks and buses. It can be applied to each part. The rubber composition is molded into a predetermined shape by, for example, extrusion processing, combined with other parts, and vulcanized at 140 to 180° C., for example, to produce a pneumatic tire. can.

The type of the pneumatic tire according to the present embodiment is not particularly limited, and as described above, various types of tires such as tires for passenger cars and tires for heavy loads used for trucks and buses can be used.

Examples of the present invention are shown below, but the present invention is not limited to these examples.

<Synthesis example 1 of thermoplastic elastomer>
800 g of cyclohexane, 38 g of dehydrated styrene, and 7.7 g of a cyclohexane solution of sec-butyllithium (10 mass %) were added to a pressure vessel equipped with a stirrer, and a polymerization reaction was carried out at 50° C. for 1 hour. 127 g of a mixture of styrene and butadiene (molar ratio styrene:butadiene = 3:4) was added and polymerized for 1 hour, and 38 g of styrene was further added and polymerized for 1 hour. After that, 2.5 g of chlorotriethoxysilane was added and finally methanol was added to stop the reaction. The reaction solution was distilled under reduced pressure to remove the solvent, and a thermoplastic elastomer 4, which is a styrene-(styrene/butadiene)-styrene type block copolymer having an ethoxysilyl group at one end, was obtained. The obtained thermoplastic elastomer 4 had a number average molecular weight of 163,000 and a styrene content of 74% by mass. The number average molecular weight and styrene content were measured using GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation, using tetrahydrofuran as a solvent, and using standard polystyrene conversion.

<Synthesis example 2 of thermoplastic elastomer>
800 g of cyclohexane, 38 g of dehydrated styrene, and 7.7 g of a cyclohexane solution of sec-butyllithium (10 mass %) were added to a pressure vessel equipped with a stirrer, and a polymerization reaction was carried out at 50° C. for 1 hour. 127 g of a mixture of styrene and butadiene (molar ratio styrene:butadiene = 3:4) was added and polymerized for 1 hour, and 38 g of styrene was further added and polymerized for 1 hour. After that, 1.2 g of epichlorohydrin was added, and finally methanol was added to stop the reaction. The reaction solution was distilled under reduced pressure to remove the solvent, and thermoplastic elastomer 5, which is a styrene-(styrene/butadiene)-styrene type block copolymer having an epoxy group at one end, was obtained. The obtained thermoplastic elastomer 5 had a number average molecular weight of 161000 and a styrene content of 74% by mass. The number average molecular weight and styrene content were measured in the same manner as in Synthesis Example 1 above.

<Examples and Comparative Examples>
Using a Banbury mixer, according to the formulation (parts by mass) shown in Table 1 below, first, in the non-professional kneading step, components other than the vulcanization accelerator and sulfur are divided into the first non-professional kneading step and the second non-professional kneading step. They were added and mixed, kneaded for 4 minutes in the first non-professional kneading step, and kneaded for 3 minutes in the second non-professional kneading step. A rubber composition was prepared by adding and mixing a vulcanization accelerator and sulfur to the resulting mixture (exhaust temperature = 90°C) in a professional kneading step. However, in Comparative Example 5, the kneading time of the first non-professional kneading step was 8 minutes, and the second non-professional kneading step was kneaded for 3 minutes without adding anything.

Details of each component in Table 1 are as follows.

・ SBR1: "VSL5025-0HM" manufactured by Lanxess Co., Ltd.
・SBR2: Solution-polymerized styrene-butadiene rubber modified with amino group and alkoxy group ends, "HPR350" manufactured by JSR Corporation
・NR: RSS#3
・ BR: “BR150B” manufactured by Ube Industries, Ltd.
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
・Carbon black: “N339 SEAST KH” manufactured by Tokai Carbon Co., Ltd.
・ Silane coupling agent: “Si69” manufactured by Evonik
・ Oil: “Process NC140” manufactured by JX Energy Co., Ltd.
・ Zinc oxide: Mitsui Kinzoku Mining Co., Ltd. “Zinc oxide type 2”
・ Anti-aging agent: "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd.
・Thermoplastic elastomer 1: "Septon HG-252" manufactured by Kuraray Co., Ltd. (Hydroxy group terminal modified SEEPS copolymer, styrene content: 28% by mass, specific gravity: 0.90)
- Thermoplastic elastomer 2: Asahi Kasei Co., Ltd. "Tuftec MP10" (amino group terminal modified SEBS copolymer, styrene content: 30% by mass, specific gravity: 0.91)
- Thermoplastic elastomer 3: Asahi Kasei Co., Ltd. "Tuftec M1911" (maleic anhydride-modified SEBS copolymer, styrene content: 30% by mass, specific gravity: 0.91)
- Thermoplastic elastomer 4: The thermoplastic elastomer obtained in Synthesis Example 1 (alkoxysilyl group terminal-modified S-SB-S copolymer, styrene content: 74% by mass, specific gravity: 0.92)
- Thermoplastic elastomer 5: The thermoplastic elastomer obtained in Synthesis Example 2 (epoxy group terminal-modified S-SB-S copolymer, styrene content: 74% by mass, specific gravity: 0.91)
・ Sulfur: “5% oil-containing fine powder sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd.
・ Vulcanization accelerator 1: "Sokushinol CZ" manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator 2: "Noccellar D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

The specific gravity of the thermoplastic elastomer is a value determined according to ISO 1183.

Wet grip performance, fuel efficiency, wear resistance, and flex crack resistance were evaluated for each of the obtained rubber compositions. The evaluation method is as follows.

・Wet grip performance: Using a test piece of a predetermined shape obtained by vulcanizing the obtained rubber composition at 160 ° C. for 30 minutes, using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd., loss factor according to JIS K6394 It is a value obtained by measuring tan δ. The measurement conditions were a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 1%, and a temperature of 0°C. The results are shown as an index with the value of Comparative Example 1 set to 100. A larger index means better wet grip performance.

Low fuel consumption: Using a test piece of a predetermined shape obtained by vulcanizing the obtained rubber composition at 160 ° C. for 30 minutes, using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd., loss factor according to JIS K6394 It is a value obtained by measuring tan δ. The measurement conditions were a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 1%, and a temperature of 60°C. The results are shown as an index with the value of Comparative Example 1 set to 100. A smaller index means better fuel efficiency.

· Abrasion resistance: In accordance with JIS K6264, using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., the wear loss was measured under the conditions of a load of 40 N and a slip ratio of 30%. expressed as the reciprocal of the exponent.

· Flex crack resistance: Based on JIS K6260, using a De Mattia tester, the number of flexures at breakage was measured at an elongation rate of 100%, and shown as an index with the value of Comparative Example 1 set to 100.

The results are as shown in Table 1. From the comparison of Comparative Examples 1 to 5 and Examples 1 to 13, the second thermoplastic elastomer having a functional group that reacts with or interacts with the surface functional group of the inorganic filler. By blending in the non-professional kneading process, it is possible to improve flex crack resistance while suppressing deterioration of wear resistance, and to achieve a balance between wet grip performance, fuel efficiency, wear resistance, and flex crack resistance. It turns out to be excellent.

Comparative Examples 3 and 4 are examples in which the thermoplastic elastomer was blended in the first non-professional kneading step. , fuel efficiency, wear resistance, and flex crack resistance were poorly balanced.

Comparative Example 5 is an example in which the thermoplastic elastomer was blended in the first non-professional kneading step and the kneading time was lengthened. , wet grip performance, fuel efficiency, wear resistance, and flex crack resistance were poorly balanced. From this result, it can be seen that the effects of the present invention cannot be obtained simply by prolonging the kneading time.

The rubber composition for tires obtained by the production method of the present invention can be used for various tires of passenger cars, light trucks and buses.

Claims (2)

A first non-professional kneading step of adding and mixing an inorganic filler of 50% by mass or more based on the amount of the inorganic filler to the rubber component;
A thermoplastic elastomer having a functional group that reacts or interacts with the surface functional group of the inorganic filler and having a specific gravity of 1.00 or less is added to the mixture obtained in the first non-process kneading step and mixed. a second non-professional kneading step;
a professional kneading step of adding and mixing a vulcanization compounding agent to the mixture obtained in the second non-professional kneading step ;
The rubber component comprises a combination of styrene-butadiene rubber (SBR) and butadiene rubber (BR) or natural rubber (NR),
The thermoplastic elastomers include modified polystyrene-hydrogenated butadiene/isoprene copolymer-polystyrene triblock copolymer (modified SEEPS), modified polystyrene-hydrogenated polybutadiene-polystyrene (modified SEBS), and modified polystyrene-styrene butadiene copolymer. A method for producing a rubber composition for tires , which is at least one selected from the group consisting of polymer-polystyrene (modified S-SB-S) . 2. The method for producing a rubber composition for tires according to claim 1, wherein the amount of said thermoplastic elastomer compounded is 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.