JP2006028245A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition in which low heat generating property and wear resistance are made compatible, concerning rubber compositions and pneumatic tires using the composition. <P>SOLUTION: The rubber composition for tire undertreads containing 100 pts.wt. of a rubber component (A) containing at least 70 wt.% of a natural rubber and/or a polyisoprene rubber; 5-20 pts.wt. of silica (B) surface-treated with at least one kind of a silane coupling agent X expressed by formula (I) Y<SB>3</SB>SiC<SB>3</SB>H<SB>6</SB>SC(=O)R, in which Y indicates independently a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy group, or an acetoxy group; R indicates a 1-18C hydrocarbon group selected from the group consisting of a cyclic or branched alkyl group, alkenyl group, aryl group, and aralkyl group; and 30-45 pts.wt. of carbon black (C) of which the nitrogen-adsorbing specific surface area N<SB>2</SB>SA is 110 m<SP>2</SP>/g or larger; provided that, the total amount of the above-mentioned surface-treated silica and the carbon black is 45-60 pts.wt., and the pneumatic tire using the rubber composition, are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more particularly to a rubber composition having both low heat buildup and wear resistance and a pneumatic tire using the rubber composition in an undertread portion.

  In recent years, there has been a strong demand for improvement in tire life, and as a result, a low heat generation tire with a structure with an increased base capacity has been developed by developing a rubber composition with low heat generation and high reinforcement as rubber for tire treads. The adoption of is urgent. Conventionally, in order to reduce heat generation in the base tread portion of the tire, silica is blended, and bis-3-triethoxylpropyl-tetrasulfide (for example, Si69 manufactured by Dexsa) or the like has been used as a silane coupling agent. . However, since this silane coupling agent has two triethoxysilyl groups, which are reaction sites with silica, in the molecule, the reaction between the silane coupling agents occurs when the treatment amount is increased, and the silica aggregates. As a result, there is a problem that desired low heat build-up cannot be obtained (see Patent Document 1).

Japanese Patent Laid-Open No. 9-328631

  Accordingly, an object of the present invention is to provide a rubber composition excellent in both low heat buildup and wear resistance and a pneumatic tire using the rubber composition in an under tread portion.

According to the invention, (A) 100 parts by weight of a rubber component containing at least 70% by weight of natural rubber and / or polyisoprene rubber, (B) Formula (I):
Y ₃ SiC ₃ H ₆ SC (═O) R (I)
Wherein Y independently represents a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or acetoxy group, and R represents a C ₁ to C group selected from a cyclic or branched alkyl group, an alkenyl group, an aryl group and an aralkyl group. C _{18 represents} a hydrocarbon group)
5 to 20 parts by weight of silica surface-treated with at least one silane coupling agent X represented by the formula: (C) 30 to 45 parts by weight of carbon black having a nitrogen adsorption specific surface area N ₂ SA of 110 m ² / g or more (provided that The total amount of the surface-treated silica and carbon black is 45 to 60 parts by weight).

  According to the present invention, there is also provided the rubber composition for tire undertread, wherein the bulk density retention of silica surface-treated with the silane coupling agent X is 50 to 150%.

According to the present invention, the surface treatment amount of the silica with the silane coupling agent X is 1 ≦ (weight of the silane coupling agent X / weight of silica before the treatment) × 100 ≦ 25.
A pneumatic tire using the rubber composition for a tire undertread that further satisfies the above relationship at a ratio of 20 to 80% with respect to the total tread volume is provided.

  According to the present invention, both the heat resistance and the wear resistance of the rubber composition can be achieved, and the tire life can be extended by using this rubber composition in the tire undertread portion. Even if the undertread of the present invention is exposed, it is possible to prevent problems such as poor appearance of wear and cracks at the groove bottom due to its high rubber reinforcement.

  In order to solve the above-mentioned problems, the inventors surface-treated 3-octanoylthio-propyltriethoxysilane having only one alkoxysilyl group as a silane coupling agent using 1 to 25% by weight of silica. It has been found that by adding silica, the silica is sufficiently dispersed, and a desired low heat build-up can be obtained by a sufficient reaction of the silica-silane coupling agent. In addition, when a di- or monosulfide type silane coupling agent is used, the reinforcing property of the rubber is lower than that of tetrasulfide type Si69. However, in the case of 3-octanoylthio-propyltriethoxysilane surface-treated silica, Si69 It has been found that it has the same reinforcing properties and can secure wear resistance.

  As the rubber component blended in the rubber composition according to the present invention, any diene rubber that can be used for tires and others, for example, various natural rubbers (NR), various polyisoprene rubbers (IR), various styrenes. -Butadiene copolymer rubber (SBR), various polybutadiene rubbers (BR), various acrylonitrile-butadiene copolymer rubbers (NBR), etc. can be mentioned, These can be used individually or as arbitrary blends. In the rubber composition according to the present invention, the rubber component contains 70% by weight or more, more preferably 90% by weight or more of natural rubber (NR) and / or polyisoprene rubber (IR), and other optional diene series. By blending rubber as necessary, it is possible to obtain a rubber composition having low heat buildup and excellent high reinforcement.

The silica used in the present invention can be any silica that can be used for tires, such as natural silica, synthetic silica, more specifically precipitated silica, dry silica, and wet silica. According to the present invention, this silica is used after being uniformly mixed and surface-treated with the silane coupling agent X represented by the formula (I). This surface treatment is by chemical or physical bonding such as reaction between silica and the trialkoxysilyl group (—SiT ₃ ) of the silane coupling agent X of the formula (I). The silane coupling agent X may be subjected to surface treatment on silica after pretreatment such as hydrolysis and condensation. In order to complete the reaction between the silica and the silane coupling agent, a method in which the silane coupling agent is hydrolyzed and condensed in advance and then reacted with silica, a method of heat aging, a catalyst (for example, acid, alkali, tin / aluminum) A method of adding a reaction accelerator such as an organometallic catalyst) can also be used.

  The silane coupling agent X used in the present invention can be synthesized by a known method. Specifically, using the method disclosed in JP-A No. 2001-505225 (filler-containing rubber), by the reaction of the corresponding mercaptosilane and acid anhydride or acid chloride or the transesterification of the corresponding mercaptosilane and thioester. Obtainable. In addition, 3-octanoylthiopropyltriethoxysilane is marketed as NXT silane from Nippon Unicar Co., Ltd.

  In the present invention, the silica particles can be surface-treated using a known method. Specific examples include a dry reaction method and a wet reaction method. The dry reaction method is a method in which silica particles are charged in an apparatus capable of high-speed stirring such as a Henschel mixer, and the silane coupling agent X or a hydrolyzate of the silane coupling agent X is added while stirring. As a method of adding, a method capable of uniformly reacting the silane coupling agent X is desirable, and a known method can be used. For example, a method of gradually dropping, a method of spraying in a mist, and a method of introducing gaseous silane are known. The wet reaction method is a method in which silica particles are reacted in a state dispersed in a solution of a silane coupling agent, and then dried if necessary. As the melting material to be used, water, alcohol or a mixture thereof is preferable. In any of the dry reaction method and the wet reaction method, a known method for increasing the reactivity of the hydroxyl group on the surface of the silane coupling agent and the silica particles can be used. For example, a method of post-heat treatment, a method of using a condensation catalyst such as an acid, an alkali or an organic metal (for example, those based on tin or aluminum) can be mentioned.

  In the present invention, the bulk density retention rate of the silica surface-treated with the silane coupling agent X is preferably 50 to 150%, more preferably 60 to 140%. Here, the bulk density retention rate (%) is a numerical value derived from the following formula (II). The silane coupling agent treatment rate (%) is the ratio of the silane coupling agent used to treat the silica surface, (weight of silane coupling agent / weight of silica before treatment) × 100. A numerical value derived from an expression.

  If the bulk density retention is too small, a sufficient amount of surface treatment cannot be obtained, so that a desired effect is difficult to obtain. On the other hand, if it is too large, the surface treatment is not uniformly performed, and dispersibility in rubber and processability are sufficient This is not preferable because there is a risk that it will disappear. The bulk density was measured according to JIS K 5101 and evaluated with three test samples randomly sampled from surface-treated silica.

  The silica surface-treated with the silane coupling agent X used in the present invention is blended in an amount of 5 to 20 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of the rubber component. If the blending amount is too small, the low heat build-up may be deteriorated, which is not preferable. Conversely, if the blending amount is too large, the dispersibility of silica may be deteriorated and the wear resistance may be decreased. The silane coupling agent treatment rate of silica and silane coupling agent X according to the present invention is not particularly limited, but is preferably 1 to 25%, and more preferably 4 to 25%.

The rubber composition according to the present invention further nitrogen adsorption specific surface area (N ₂ SA) (ASTM D3037 measured according to) is 110m ² / g or more, preferably carbon black 120~165m ² / g, rubber 30 to 45 parts by weight, preferably 35 to 45 parts by weight per 100 parts by weight of the component, and the total amount with the surface-treated silica is 5 to 60 parts by weight, preferably 40 to 55 parts by weight. If the value of N ₂ SA is too low, the wear resistance may be insufficient. Further, if the blending amount of carbon black is too small, it is not preferable because the wear resistance may be deteriorated. Conversely, if the blending amount is too large, heat generation may be increased, which is not preferable. Further, if the total amount of the surface-treated silica and carbon black is too small, it is not preferable because the wear resistance may be lowered. On the other hand, if the amount is too large, the exothermic property may be increased.

  In addition to the essential components described above, the rubber composition according to the present invention is used for tires such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, antioxidants, plasticizers, and other general rubbers. Various additives that are generally blended can be blended, and such additives can be kneaded and vulcanized by a general method to obtain a composition, which can be used for vulcanization or crosslinking. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

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

Standard Example 1, Examples 1-4 and Comparative Examples 1-2
Sample preparation In the formulation shown in Table I, the components other than the vulcanization accelerator and sulfur were kneaded in a 3 liter closed mixer for 5 minutes and released when the temperature reached 165 ± 5 ° C to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this master batch with an open roll to obtain a rubber composition.

  Next, the obtained rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 148 ° C. for 30 minutes to produce a vulcanized rubber sheet. The physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Vulcanized rubber property evaluation test method tan δ (60 ° C.): Measured according to JIS K 6394.
M300 / M100: 300% modulus (M300) and 100% modulus (M100) were measured according to JIS K-6251. In addition, it shows that it is excellent in the reinforcement property, so that the value of M300 / M100 is large.
Abrasion resistance: Measured according to JIS K 6264.
In all cases, the value of standard example 1 was set to 100 and displayed as an index. The result shows that a larger index is better.

Table I Footnote natural rubber: RSS # 3
Silica: Nipsil AQ (silica) manufactured by Nippon Silica Industry Co., Ltd.
A-1289: Nippon Unicar Co., Ltd. bis (3-triethoxysilylpropyl) tetrasulfide NXT: Nihon Unicar Co., Ltd. NXT silane

  A-1289 surface-treated silica: NUC A-1289 manufactured by Nippon Unicar Co., Ltd. was slowly added to Nipsil AQ (Nippon Silica Industry) under stirring with a Henschel mixer to prepare dry-reacted silica particles. The silane coupling agent-reacted silica particles were obtained by drying in an explosion-proof furnace set at 150 ° C. for 1 hour.

  NXT-treated silica: 3-octanoylthiopropyltriethoxysilane NXT was slowly added to Nipsil AQ (Nippon Silica Kogyo Co., Ltd.) being stirred with a Henschel mixer to prepare dry-reacted silica particles. The silane coupling agent-reacted silica particles were obtained by drying for 1 hour in an exposure furnace set at 150 ° C. The numbers in parentheses in Table I are the bulk density retention values obtained as described above.

Carbon Black (SAF): Carbon Black (Show Black N200) manufactured by Showa Cabot Corporation
Anti-aging agent: Anti-aging agent 6PPD manufactured by Flexis
Vulcanization accelerator: Nouchira NS manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Hosei Chemical Industry Co., Ltd. oil-treated sulfur (oil content 5%)

Standard Example 1 is a conventional typical composition, and the physical property evaluation results are shown as indexes with the value of Standard Example 1 being 100. In Comparative Example 1, tan δ (60 ° C.) decreases (improves), but M300 and wear resistance deteriorate. In Comparative Example 2, tan δ (60 ° C.) decreases (improves) and M300 also improves, but wear resistance deteriorates.
On the other hand, in Examples 1 to 4, tan δ (60 ° C.) decreases (improves), M300 / M100, and wear is also improved.

  As described above, according to the present invention, a rubber composition having low heat build-up and good wear resistance can be obtained, so that it is suitable for use as a tire tread, particularly an undertread rubber.

Claims (3)

(A) 100 parts by weight of a rubber component containing at least 70% by weight of natural rubber and / or polyisoprene rubber, (B) Formula (I):
Y ₃ SiC ₃ H ₆ SC (═O) R (I)
Wherein Y independently represents a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or acetoxy group, and R represents a C ₁ to C group selected from a cyclic or branched alkyl group, an alkenyl group, an aryl group and an aralkyl group. C _{18 represents} a hydrocarbon group)
5 to 20 parts by weight of silica surface-treated with at least one silane coupling agent X represented by the formula: (C) 30 to 45 parts by weight of carbon black having a nitrogen adsorption specific surface area N ₂ SA of 110 m ² / g or more (provided that The rubber composition for a tire undertread comprising a total amount of the surface-treated silica and carbon black of 45 to 60 parts by weight.   The rubber composition for a tire undertread according to claim 1, wherein a bulk density retention rate of silica surface-treated with the silane coupling agent X is 50 to 150%. The surface treatment amount of the silica with the silane coupling agent X is 1 ≦ (weight of silane coupling agent X / weight of silica before treatment) × 100 ≦ 25
The pneumatic tire which used the rubber composition for tire under-treads of Claim 1 or 2 which satisfy | fills these relationships in the ratio of 20 to 80% with respect to the total tread volume.