JP2006036822A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition that keeps balance of rolling resistance, wet skid properties and structure in a high level without impairing processability not only in blending of silica alone but also in blending of silica/carbon black and a pneumatic tire using the same. <P>SOLUTION: The rubber composition comprises a rubber component composed of 40-80 wt.% of diene-based rubber (A) into which an amino group is introduced and 60-20 wt.% of diene-based rubber (B) into which a hydroxy group and/or an epoxy group is introduced, a reinforcing filer composed of silica alone or a blend of silica and carbon black and a silane coupling agent. The rubber composition is suitably useful for tread of a pneumatic tire. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same for a tread.

  As interest in the environment and safety has increased, tires are also strongly required to improve fuel efficiency by reducing rolling resistance and to improve skid performance on wet road surfaces (wet skid performance). However, these properties are generally contradictory, and in order to achieve both, silica is blended as a reinforcing filler instead of carbon black or together with carbon black. Such silica is generally blended with a silane coupling agent that improves its dispersibility, and is particularly suitably used as a rubber composition for silica blends in tire tread rubber. However, the market demand is still great, and further reduction of rolling resistance and improvement of wet skid property are required.

  Further, strength characteristics such as the breaking strength of rubber are important characteristics that affect all characteristics such as wear resistance, skid characteristics with a road surface, and tread chipping, and it is desired to be improved.

  Various diene rubbers modified with a modifier having affinity or binding property to silica have been proposed as diene rubbers to be blended in such a silica-blended rubber composition. For example, in Patent Documents 1 to 3 listed below, modified diene rubbers having amino groups introduced therein, in Patent Document 4 listed below, modified diene rubbers introduced with epoxy groups, and further to Patent Document 5 listed below. Modified diene rubbers into which hydroxyl groups have been introduced have been proposed.

By the way, a rubber composition containing silica alone as a reinforcing filler has a high cost, wear resistance, and further problems such as generation of static electricity due to an increase in electrical resistance. The use should be ensured even in a combination system of silica and carbon black. Therefore, in consideration of a wide range of applications from silica alone to a combination of silica and carbon black, it is preferable to use a diene rubber modified with an amino group that interacts not only with silica but also with carbon black. . However, when a diene rubber modified with amino groups is used, the processability is generally poor, and the state of the rubber surface skin and edges (edges of the extrudate) at the time of extrusion or extrusion after kneading the rubber composition In addition, the performance (such as uniformity) resulting from the tire manufacturing process is also inferior.
JP 2001-214004 A JP 2000-204103 A WO03 / 029299 JP-A-9-136993 WO96 / 23027

  An object of the present invention is to provide a rubber composition capable of balancing rolling resistance, wet skid property and strength at a high level without impairing processability not only in silica alone but also in silica / carbon black compound, and It is in providing the pneumatic tire using this.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be achieved by blending a specific amount of a diene rubber modified with an epoxy group or a hydroxyl group with a diene rubber modified with an amino group. It has been found that the problem is solved and the present invention has been completed.

  That is, the rubber composition according to the present invention comprises 40 to 80% by weight of a diene rubber (A) having an amino group introduced therein and 60 to 20% by weight of a diene rubber (B) having a hydroxyl group and / or an epoxy group introduced thereto. % Rubber component, silica alone or a reinforcing filler composed of a blend of silica and carbon black, and a silane coupling agent.

  The pneumatic tire according to the present invention is characterized by having a tread made of the rubber composition of the present invention described above.

  According to the present invention, the processability which is a defect of the rubber composition of amino group-modified diene rubber, which is effective not only in silica alone but also in silica / carbon black compound, is effective in rolling resistance, wet skid property and strength properties. By blending a diene rubber modified with an epoxy group or a hydroxyl group, the rolling resistance, wet skid properties and strength are improved while exhibiting a synergistic effect.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition of the present invention, the rubber component is obtained by blending an amino group-modified diene rubber (A) and a hydroxyl group and / or epoxy group modified diene rubber (B).

  In these modified diene rubbers (A) and (B), the base polymer is a polymer of a conjugated diene monomer or a copolymer of a conjugated diene monomer and an aromatic vinyl monomer. Polymers are preferred. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, and 1,3-butadiene and isoprene are particularly preferable. Examples of the aromatic vinyl monomer include styrene, o-, m- or p-methylstyrene, p-tert-butylstyrene, vinylnaphthalene and the like, and styrene is particularly preferable. Specifically, polybutadiene and styrene-butadiene copolymer are particularly suitable.

  The amino group-modified diene rubber (A) is a modified diene rubber having an amino group bonded to a polymer chain by being modified with an amino group. In the present invention, the amino group may be any of a primary amino group, a secondary amino group, and a tertiary amino group, preferably a primary or tertiary amino group, particularly preferably a primary amino group. It is a primary amino group.

  The modification method of the amino group-modified diene rubber (A) is not particularly limited. By reacting a polymer having an active end with a compound having an amino group as a modifier, an amino group is added to the end of the polymer. It may be introduced. Moreover, you may introduce | transduce into a polymer chain by copolymerizing with the monomer of a base polymer using the polymerizable monomer which has an amino group.

  Such amino group-modified diene rubber itself is known, and in the present invention, such known amino group-modified diene rubber can be used. Although not particularly limited, for example, as disclosed in WO03 / 029299, a styrene-butadiene copolymer modified with a primary amino group and an alkoxysilyl group, or disclosed in JP-A-9-71687. For example, a styrene-butadiene copolymer modified with a tertiary amino group can be used.

  The modified diene rubber (B) blended with the amino group-modified diene rubber (A) is modified with a hydroxyl group and / or an epoxy group, so that the modified diene system has a hydroxyl group and / or an epoxy group bonded to a polymer chain. The rubber may be a diene rubber modified with a hydroxyl group, a diene rubber modified with an epoxy group, a blend rubber of both, or a diene rubber into which both a hydroxyl group and an epoxy group are introduced.

  The modification method of the modified diene rubber (B) is not particularly limited, and by reacting a polymer having an active end with a compound having a hydroxyl group or an epoxy group as a modifier, these ends can be added to the end of the polymer. A functional group may be introduced. Moreover, you may introduce | transduce into a polymer chain by copolymerizing with the monomer of a base polymer using the polymerizable monomer which has a hydroxyl group or an epoxy group.

  Such hydroxyl group-modified diene rubbers and epoxy group-modified diene rubbers are known, and such known modified diene rubbers can be used in the present invention. Although not particularly limited, for example, a hydroxyl group-containing diene rubber may be a hydroxyl group-containing styrene-butadiene copolymer or butadiene rubber as disclosed in WO 96/23027. As for the epoxy-modified diene rubber, an epoxy group-containing styrene-butadiene obtained by modification with a tetrafunctional compound having two diglycidylamino groups in one molecule as disclosed in JP-A-9-136993. A copolymer or the like can be used.

  In the present invention, the rubber component contains 40 to 80% by weight of the amino group-modified diene rubber (A) and 60 to 20% by weight of the hydroxyl group and / or epoxy group modified diene rubber (B). It is. When the blending amount of the amino-modified diene rubber (A) is less than 40% by weight, particularly in the blending of silica / carbon black, it becomes impossible to balance rolling resistance, wet skid property and strength at a high level. On the other hand, if the amount of the hydroxyl group and / or epoxy group-modified diene rubber (B) is less than 20% by weight, the processability is impaired.

  In the rubber composition of the present invention, the rubber component may be used in combination with other diene rubbers in addition to the above-described modified diene rubber. Examples of such other diene rubbers include natural rubber (NR). ), Polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), and the like.

  The rubber composition of the present invention is compounded with a reinforcing filler made of silica alone or a blend of silica and carbon black. Examples of the silica include wet silica, dry silica, colloidal silica, precipitated silica and the like that are generally used as a reinforcing agent in rubber compounding. It is particularly preferable to use wet silica containing hydrous silicic acid as a main component. Also, carbon black that is generally used as a reinforcing agent in rubber compounding can be used. In addition, other inorganic fillers, such as a talc, clay, an alumina, a calcium carbonate, can also be mix | blended with the rubber composition of this invention with a silica or a silica and carbon black.

  The compounding amount of the reinforcing filler is preferably 20 to 150 parts by weight with respect to 100 parts by weight of the rubber component. When silica and carbon black are used in combination, it is preferable to add 10 parts by weight or more of silica in order to improve the balance between rolling resistance, wet skid property and strength.

  The silane coupling agent blended in the rubber composition of the present invention promotes the bonding between silica and the polymer. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilyl) Propyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-nitropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. It is done. It is preferable that the compounding quantity of a silane coupling agent is 0.5-20 weight part with respect to 100 weight part of silica.

  The rubber composition of the present invention further includes various additives usually used for rubber compositions such as sulfur vulcanizing agents, vulcanization accelerators, anti-aging agents, zinc white, stearic acid, waxes, oils and the like. Can be blended.

  The rubber composition of the present invention can be used for various uses such as tires, automobile parts, and conveyor belts, and is particularly preferably used as a rubber composition for a tread of a pneumatic tire and vulcanized according to a conventional method. A tread can be formed by molding. The pneumatic tire produced in this way is excellent in fuel efficiency due to low rolling resistance, and also excellent in wet skid properties and strength properties, and the rubber composition is processable in the tire manufacturing process. Because of its excellent performance, it also excels in performance resulting from tire manufacturing processes such as uniformity.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Silica alone)
Using a Banbury mixer, rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared according to the composition shown in Table 1 below. The details of each formulation in Table 1 are as follows.

SSBR1: “Nipol NS116R” (solution polymerized styrene-butadiene copolymer rubber modified with a tertiary amine) manufactured by Nippon Zeon Co., Ltd.

SSBR2: Solution polymerized styrene-butadiene copolymer rubber having a primary amino group synthesized by the method described in WO03 / 029299 using N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane as a modifier.

BR1: “BR1250H” (butadiene rubber modified with a tertiary amine) manufactured by Nippon Zeon Co., Ltd.

SSBR3: solution polymerized styrene-butadiene copolymer rubber having an epoxy group synthesized by a method described in JP-A-9-136993 using tetraglycidyl-1,3-bisaminomethylcyclohexane as a modifier.

SSBR4: solution polymerized styrene-butadiene copolymer rubber having a hydroxyl group synthesized by the method described in WO96 / 23027 using propylene oxide as a modifier.

BR2: “Asaprene E40” (Butadiene rubber modified with an epoxy group) manufactured by Asahi Kasei Chemicals Corporation.

・ Silica: “AQ” manufactured by Tosoh Silica Corporation
Silane coupling agent: “Si-69” manufactured by Degussa.

  In each rubber composition, as a common compounding agent, 40 parts by weight of aroma oil ("Process X140" manufactured by Japan Energy Co., Ltd.) and 1 part by weight of wax ("paraffin wax 155" manufactured by Nippon Seiwa Co., Ltd.) 1 part by weight of anti-aging agent 6PPD (“NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.), 2 parts by weight of zinc white (“Zinc Oxide 2” manufactured by Mitsui Mining & Smelting Co., Ltd.), stearic acid (Kao ( "Lunac S-25") 2 parts by weight, vulcanization accelerator DPG ("Noxeller D" by Ouchi Shinsei Chemical Industry Co., Ltd.) 2 parts by weight, vulcanization accelerator CZ (Ouchi Shinsei Chemical Industry ( 1.8 parts by weight of “NOXELLA CZ” manufactured by Co., Ltd. and 2 parts by weight of sulfur (“5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd.) were blended.

  Each rubber composition was evaluated for processability. Each rubber composition was press vulcanized at 160 ° C. for 20 minutes to prepare a test piece having a predetermined shape, and the breaking strength was measured using the obtained test piece. Furthermore, pneumatic tires having a tire size of 205 / 65R15 were produced according to conventional methods using each rubber composition as a tire tread rubber, and the rolling resistance and wet skid property were evaluated. Then, the balance between wet skid property and rolling resistance (WET / RR balance index) and the balance between strength and rolling resistance (strength / RR balance index) were evaluated. Each evaluation / measurement method is as follows.

・ Processability: A comprehensive evaluation of the rubber composition of each rubber composition when kneaded with a Banbury mixer, roll wrapping properties, and the surface skin and edge state of the rubber sheet. Displayed in five levels: good, C ... acceptable, D ... bad, E ... very bad.

-Rolling resistance: Rolling resistance was calculated | required according to American Automobile Engineers Association standard, SAE J1269, and it showed with the index | exponent calculated by the following formula. The smaller the index, the better.
(Each prototype tire rolling resistance) x 100 / (Each control tire rolling resistance)

-Wet skid property: The traction coefficient was calculated | required based on the traction test conditions on the wet asphalt road surface described in UTQGS of USA. The traction coefficient was expressed as an index obtained by substituting it into the following formula. A larger index is preferable.
(Each prototype tire traction coefficient) x 100 / (Each control tire traction coefficient)

WET / RR balance index: The ratio of the index value (β) of wet skid to the index value (α) of the rolling resistance [(β / α) × 100]. The larger this value, the more the rolling resistance and It means that the wet skid balance is excellent.

Break strength: Measured according to JIS K6251. The results are shown as an index with the value of Comparative Example 1 in the blending system (1), the value of Comparative Example 2 in the blending system (2), and the value of Comparative Example 3 in the blending system (3). . The larger the index, the greater the breaking strength and the better the reinforcement.

Strength / RR balance index: The ratio of the index value (β) of the breaking strength to the index value (α) of the above rolling resistance [(β / α) × 100]. The larger this value, the more the rolling resistance and strength. It means that the balance is excellent.

  The results are as shown in Table 1, and in the compounding system (1), in Comparative Example 1 as a control, the rubber component was an amino group-modified SSBR alone, so the processability was inferior. In Example 1 in which SSBR was blended, the improvement effect was recognized in the balance between wet skid property and rolling resistance, and the balance between strength and rolling resistance, and the workability was greatly improved.

  Further, in the blending system (2) using SSBR and BR in combination, in Comparative Example 2 as a control, in Example 2, by using an amino group-modified rubber and an epoxy group-modified rubber in combination, rolling resistance and wetness are increased. The improvement effect was recognized in the balance with skid property and strength, and the workability was greatly improved.

  Further, in the case of the primary amino group-modified SSBR, the processability by itself was poor as shown in Comparative Example 3, whereas as shown in Examples 3 and 4, a predetermined amount of epoxy group-modified. By using SSBR and hydroxyl group-modified SSBR in combination, an improvement effect was recognized in the balance between rolling resistance, wet skid property and strength, and workability was also greatly improved.

(Combination combination of silica and carbon black)
Using a Banbury mixer, rubber compositions of Examples 5 to 8 and Comparative Examples 5 to 10 were prepared according to the composition shown in Table 2 below. Details of each compound in Table 2 and common compounding agents are the same as in the case of the silica compounding described above, and “Show Black N339” manufactured by Showa Cabot Co., Ltd. was used for carbon black.

For each rubber composition, in the same manner as in the case of silica alone, the processability was evaluated, and the breaking strength, rolling resistance, and wet skid property were measured to determine the balance between wet skid property and rolling resistance (WET / RR balance index) and the balance between strength and rolling resistance (strength / RR balance index) were evaluated. Each evaluation / measurement method is as described above. However, for the index display, the value of Comparative Example 5 is used for the blending system (4), the value of Comparative Example 6 is used for the blending system (5), and the blending system (6). Then, the value of the comparative example 7 was set to 100, respectively.

  The results are shown in Table 2. Even in the combined system of silica and carbon black, by blending the amino group-modified rubber and the epoxy group-modified rubber or the hydroxyl group-modified rubber, the balance between wet skid property and rolling resistance, and In addition, an improvement effect was recognized in the balance of the rolling resistance of the strength, and the workability was greatly improved. In addition, as shown in Comparative Examples 8 and 9, when the epoxy group-modified rubber or the hydroxyl group-modified rubber is used alone, the processability is excellent, but in the system using silica and carbon black in combination as the reinforcing filler, the rolling resistance And wet skid property and strength could not be balanced in a high dimension.

  The rubber composition of the present invention can be used for various uses such as tires, automobile parts, and conveyor belts, and can be preferably used as a rubber composition for a tread of a pneumatic tire.

Claims (2)

A rubber component composed of 40 to 80% by weight of a diene rubber (A) having an amino group introduced therein and 60 to 20% by weight of a diene rubber (B) having a hydroxyl group and / or an epoxy group introduced therein;
A reinforcing filler composed of silica alone or a blend of silica and carbon black;
A silane coupling agent;
A rubber composition comprising: A pneumatic tire having a tread made of the rubber composition according to claim 1.