JP2010159391A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for producing tires having excellent low heat-generating performances and capable of achieving the low fuel costs of vehicles. <P>SOLUTION: This rubber composition for base treads comprises 100 pts.mass of a rubber component, silica and a silane coupling agent, wherein the silane coupling agent is a block copolymer or random copolymer comprising binding units A represented by general formula (1) and binding units B represented by general formula (2) and is contained in an amount of 2 to 20 pts.mass per 100 pts.mass of the silica. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition for a tire.

  Conventionally, rolling resistance of tires has been reduced (improvement of rolling resistance performance), and vehicle fuel efficiency has been reduced. In recent years, there has been a strong demand for low fuel consumption, and excellent low heat build-up is required for rubber compositions for producing treads having a high occupation ratio among tire members.

  As a method of reducing the heat generation of the rubber composition, a method of reducing the blending amount of the reinforcing filler is known. However, if the blending amount of the reinforcing filler is reduced, the hardness of the rubber composition decreases. There is a problem that the tire is softened and the steering stability of the vehicle and the wet skid performance of the tire are lowered. In order to solve these problems, silica or the like is generally used as a filler, and at the same time, a silane coupling agent is also used (Patent Document 1). As the silane coupling agent, polysulfide silane such as bis- (3-triethoxysilylpropyl) tetrasulfide is used, but there is a problem that viscosity increase occurs during processing.

  On the other hand, since silica absorbs the vulcanization accelerator and consequently delays the vulcanization speed, there is a problem in the vulcanization system.

JP 2002-363346 A

  An object of the invention is to provide a rubber composition for producing a tire having excellent low heat generation performance and capable of achieving low fuel consumption of a vehicle.

  The present invention includes 15 to 150 parts by mass of silica and 100 parts by mass of a rubber component, and the silane coupling agent includes a bonding unit A represented by the following general formula (1) and the following general formula. A binding unit B represented by the formula (2)

(Wherein, x and y are each an integer of 1 or more. R ₁ is hydrogen, a halogen atom, a branched or unbranched carbon 1-30 alkyl group, a branched or unbranched carbon 2-30 alkenyl group, Alternatively, the terminal of the alkyl group or the alkenyl group may be substituted with a hydroxyl group or a carboxyl group, R ₂ represents hydrogen, a branched or unbranched carbon group having 1 to 30 carbon atoms, or a branched or unbranched carbon group 2 to 2; in the .R ₁ and R ₂ showing a 30 alkenyl groups may form a cyclic structure.)
It is a block copolymer or a random copolymer obtained by copolymerizing the bond unit B at a ratio of 1 mol% to 70 mol% with respect to the total amount of the bond unit A and the bond unit B, and 100 parts by mass of silica. It is the rubber composition for base treads contained 2-20 mass parts with respect to this.

  The present invention is a pneumatic tire using the base tread rubber composition in a base tread portion.

  According to the rubber composition of the present invention, it is possible to provide a pneumatic tire that has excellent low heat generation performance and can achieve low fuel consumption of a vehicle.

It is sectional drawing of the right half of the pneumatic tire which concerns on this invention. It is an expanded sectional view of the tread part of the pneumatic tire concerning the present invention.

<Pneumatic tire structure>
The tread portion of the pneumatic tire according to the present invention has a double structure including a cap portion and a base portion.

  FIG. 1 is a cross-sectional view showing the right half of an embodiment of a pneumatic tire according to the present invention. The tire 1 has a tread portion 2, a sidewall portion 3, and a bead portion 4. Further, a bead core 5 is embedded in the bead portion 4. Further, a carcass 6 provided from one bead portion 4 to the other bead portion and folded back at both ends to lock the bead core 5 and a belt layer 7 composed of two plies outside the crown portion of the carcass 6 are arranged. Has been. The tread portion 2 is composed of two layers: a cap portion 2A on the ground surface side and a base portion 2B on the side adjacent to the belt layer. A bead apex 8 extending in the sidewall direction from the upper end of the bead core 5 is disposed in a region surrounded by the carcass 6 and the folded portion thereof.

  FIG. 2 is an enlarged view of the tread portion 2 in the pneumatic tire 1 according to the present invention. The rubber composition for a base tread according to the present invention is used for the base portion 2.

<Rubber composition>
The rubber composition of the present invention contains 15 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component, and 2 to 20 parts by mass of a specific silane coupling agent with respect to 100 parts by mass of silica.

<Rubber component>
The rubber component used in the present invention is natural rubber (NR) and / or a diene synthetic rubber. Diene-based synthetic rubbers include styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), butadiene rubber (BR), isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR ), Butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR) and the like, and may be contained in one or more kinds in the rubber component used in the present invention. Of these, NR and BR are preferable.

<Silica>
The silica used in the present invention is not particularly limited, and examples thereof include dry method silica and wet method silica, and wet method silica is preferable.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 100 to 300 m ² / g. If the N ₂ SA of silica is less than 100 m ² / g, the reinforcing effect is small, and if it exceeds 300 m ² / g, the dispersibility decreases and the heat generation of the rubber composition increases. The lower limit of N ₂ SA of silica is preferably 13
0 m ² / g, more preferably 150 m ² / g. The upper limit is preferably 280 m ^2.
/ G, more preferably 250m ² / g.

  The compounding quantity of a silica is 15-150 mass parts with respect to 100 mass parts of said rubber components. If the blending amount of silica is less than 15 parts by mass, the rubber strength is lowered, and if it exceeds 150 parts by mass, it becomes difficult to disperse the silica into the rubber and the processability is lowered. From the viewpoint of low heat build-up and workability, the upper limit of the amount of silica is preferably 120 parts by mass, and the lower limit is more preferably 45 parts by mass.

<Silane coupling agent>
The silane coupling agent used in the present invention comprises a binding unit A represented by the following general formula (1) and a binding unit B represented by the following general formula (2).

(Wherein, x and y are each an integer of 1 or more. R ₁ is hydrogen, a halogen atom, a branched or unbranched carbon 1-30 alkyl group, a branched or unbranched carbon 2-30 alkenyl group, Alternatively, the terminal of the alkyl group or the alkenyl group may be substituted with a hydroxyl group or a carboxyl group, R ₂ represents hydrogen, a branched or unbranched carbon group having 1 to 30 carbon atoms, or a branched or unbranched carbon group 2 to 2; in the .R ₁ and R ₂ showing a 30 alkenyl groups may form a cyclic structure.)
A block copolymer or a random copolymer obtained by copolymerizing the bonding unit B at a ratio of 1 mol% to 70 mol% with respect to the total amount of the bonding unit A and the bonding unit B.

  When the molar ratio of the bond unit A and the bond unit B satisfies the above conditions, an increase in viscosity during processing is suppressed as compared with polysulfide silanes such as bis- (3-triethoxysilylpropyl) tetrasulfide. This is presumably because the increase in Mooney viscosity is small because the sulfide portion of the bond unit A is a C—S—C bond and is thermally stable compared to tetrasulfide or disulfide.

Further, when the molar ratio of the bond unit A and the bond unit B satisfies the above condition, shortening of the scorch is suppressed as compared with mercaptosilane such as 3-mercaptopropyltrimethoxysilane. This is unit B has a mercaptosilane structure, probably because the polymer and reaction difficult scorch to cover the -SH group -C ₇ H ₁₅ portion of the coupling unit A is unit B is hardly increased It is done.

  In the silane coupling agent used in the present invention, the total repeating number (x + y) of the repeating number (x) of the bonding unit A and the repeating number (y) of the bonding unit B is set in the range of 3 to 300. Is preferred.

  As the silane coupling agent, only one type of the silane coupling agent which is a copolymer of the binding unit A and the binding unit B may be used, or two or more types may be used in combination.

  The compounding quantity of a silane coupling agent is 2-20 mass parts with respect to 100 mass parts of silica. If the amount of silica is less than 2 parts by mass, the rolling resistance tends to increase, and if it exceeds 20 parts by mass, the performance improvement effect is small and uneconomical. The upper limit of the amount of the silane coupling agent is preferably 16 parts by mass, and the lower limit is preferably 4 parts by mass.

<Softener>
Softeners include petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt and petroleum jelly, and fatty oil-based softeners such as soybean oil, palm oil, castor oil, linseed oil, rapeseed oil and coconut oil. Agents, waxes such as tall oil, sub, beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid. The blending amount of the softening agent is preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component. In this case, there is a risk of reducing wet grip performance when the rubber composition is used in a tire. Less is.

<Anti-aging agent>
As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

<Vulcanization aid>
As the vulcanization aid, stearic acid, zinc oxide (zinc white) or the like can be used.

<Vulcanizing agent>
As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene or the like can be used. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

<Vulcanization accelerator>
Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

<Other ingredients>
In addition to the above-mentioned various components, the rubber composition according to the present invention may contain compounding agents that are conventionally used in the rubber industry, such as crosslinking agents and fillers.

<Method for producing rubber composition for base tread>
The method for producing a rubber composition for a base tread according to the present invention is obtained by kneading a rubber component, silica, a silane coupling agent, and, if necessary, other fillers and compounding agents using, for example, a Banbury mixer. The kneaded product is obtained by kneading a vulcanizing agent and a vulcanization accelerator with, for example, an open roll and further vulcanizing.

<Pneumatic tire manufacturing method>
The pneumatic tire using the base tread rubber composition according to the present invention in the base tread portion is obtained by kneading the components of the base tread rubber composition at 130 ° C. or higher and 160 ° C. or lower with a Banbury mixer or a kneader, for example. It can be produced by preparing an unvulcanized product of a rubber composition for a tire tread and applying the unvulcanized product to a base tread portion of a pneumatic tire for vulcanization molding.

<Examples 1-5, Comparative Examples 1-4>
[Adjustment of rubber composition for unvulcanized base tread]
In accordance with the formulation shown in Table 1 below, NR, BR, silica, silane coupling agent, aroma oil, zinc oxide, stearic acid, antioxidant, and wax were kneaded for 3 minutes with a Banbury mixer. Into the obtained rubber composition, sulfur and a vulcanization accelerator were kneaded with a roll to obtain a rubber composition for an unvulcanized base tread. The following tests were conducted on the rubber composition for the unvulcanized base tread.

(Mooney viscosity index)
In accordance with JIS K 6300 “Unvulcanized rubber—Physical properties—Part 1: Determination of viscosity and scorch time using Mooney viscometer”, heated at 130 ° C. by preheating for 1 minute using a Mooney viscosity tester. The Mooney viscosity (ML _{1 +} 4/130 ° C.) of the unvulcanized rubber composition after 4 minutes was measured by rotating a small rotor under the temperature conditions of, and the Mooney viscosity index of Comparative Example 1 was 100. The Mooney viscosity of each formulation was indicated by an index according to the following formula. In addition, it shows that Mooney viscosity is reduced and processability is excellent as the Mooney viscosity index is small.
(Mooney viscosity index) = (Mooney viscosity of each formulation) ÷ (Mooney viscosity of Comparative Example 1) × 100
(Vulcanization rate index)
In accordance with JIS K 6300 "Unvulcanized rubber-Physical properties-Part 1: Determination of viscosity and scorch time using Mooney viscometer", the time to reach 95% vulcanization at 160 ° C (T95) was measured. The vulcanization rate index of Comparative Example 1 was set to 100, and the vulcanization rate of each formulation was indicated by an index according to the following formula. In addition, it shows that it is excellent in workability, so that a vulcanization rate index | exponent is large.
(Vulcanization rate index) = (Vulcanization rate of each compound) ÷ (Vulcanization rate of Comparative Example 1) × 100
[Manufacture of pneumatic tires]
The unvulcanized rubber composition is molded into the shape of a tread base portion 2B and bonded to other tire members (cap portion 2A, belt layer 7, sidewall portion 3 etc.) under the conditions of 175 ° C. and 20 kgf. By vulcanizing for 12 minutes, the pneumatic tire (tire size: 195 / 65R15) shown in FIG. 1 was produced, and the following measurements were performed.

(Rolling resistance index)
Using a rolling resistance tester, the rolling resistance when the tire was run under the conditions of rim: 15 × 6JJ, internal pressure: 230 kPa, load: 3.43 kN, speed: 80 km / h was measured. The resistance index was set to 100, and the rolling resistance of each formulation was indicated by an index according to the following formula. A larger rolling resistance index indicates a smaller rolling resistance and better fuel efficiency.
(Rolling resistance index) = (Rolling resistance of Comparative Example 1) ÷ (Rolling resistance of each formulation) × 100
(Handling performance)
The test tires were mounted on all wheels of a vehicle (domestic FF car 2000cc), and the vehicle was run on the test course. The handling performance was evaluated by sensory evaluation of the driver. Evaluation was made relative with 10 points being the perfect score and Comparative Example 1 being 6 points. The higher the score, the better.

NR: TSR20
BR: BR50 manufactured by Ube Industries, Ltd.
Silica: Ultrasil VN3 manufactured by Degussa (primary particle size 15 nm)
Tetrasulfide silane: Si69 (bis- (3-triethoxysilylpropyl) -tetrasulfide) manufactured by Degussa
Mercaptosilane: A1891 (3-mercaptopropyltrimethoxysilane) manufactured by Momentive
Silane coupling agent A: Copolymer of bond unit A and bond unit B (bond unit A: 85 mol%, bond unit B: 15 mol%)
Silane coupling agent B: NXT-Z30 manufactured by Momentive Performance Materials (copolymer of bond unit A and bond unit B, bond unit A: 70 mol%, bond unit B: 30 mol%)
Silane coupling agent C: Copolymer of bond unit A and bond unit B (bond unit A: 20 mol%, bond unit B: 80 mol%)
Aroma oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator CZ manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Chemical
Vulcanization accelerator DPG: NOCELLER D manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Evaluation results)
In Examples 1, 3, and 5, 45 parts by mass of silica and 3.6 parts by mass of the silane coupling agent A (bonding unit B: 15 mol%) were each 3.6 parts by mass (with respect to 100 parts by mass of silica). 8 parts by mass), 4.5 parts by mass (10 parts by mass with respect to 100 parts by mass of silica), and 9.0 parts by mass (20 parts by mass with respect to 100 parts by mass of silica). Compared to Comparative Example 1 containing 3.6 parts by mass of tetrasulfide silane as the silane coupling agent, the processability was improved, and the fuel efficiency was improved while maintaining the handling performance.

  In Examples 2 and 4, 45 parts by mass of silica and 3.6 parts by mass of the silane coupling agent B (bonding unit B: 30 mol%) were each 8 parts by mass with respect to 100 parts by mass of silica (100 parts by mass of silica). Parts by mass), 4.5 parts by mass (20 parts by mass with respect to 100 parts by mass of silica). Compared to Comparative Example 1, the processability was improved, and the fuel efficiency was greatly improved while maintaining the handling performance.

  Comparative Example 2 contains 45 parts by mass of silica and 3.6 parts by mass of mercaptosilane as a silane coupling agent with respect to 100 parts by mass of the rubber component. Compared with the comparative example 1, workability was bad and handling performance was also deteriorated.

  Comparative Example 3 is 3.6 parts by mass of 45 parts by mass of silica and silane coupling agent C (bonding unit B: 80 mol%) (8 parts by mass with respect to 100 parts by mass of silica) with respect to 100 parts by mass of the rubber component. Including. Compared to Comparative Example 1, the processability was improved, and the fuel efficiency was improved while maintaining the handling performance.

  In Comparative Example 4, 45 parts by mass of silica and 0.5 parts by mass of silane coupling agent A (bonding unit B: 15 mol%) with respect to 100 parts by mass of the rubber component (1.1 parts by mass with respect to 100 parts by mass of silica) Part) including. Compared with the comparative example 1, workability was bad and handling performance was also deteriorated.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Pneumatic tire, 2 tread part, 2A cap part, 2B base part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex.

Claims (2)

It contains 15 to 150 parts by mass of silica and 100 parts by mass of a rubber component, and the silane coupling agent includes a binding unit A represented by the following general formula (1) and the following general formula (2). A bond unit B represented by

(Wherein, x and y are each an integer of 1 or more. R ₁ is hydrogen, a halogen atom, a branched or unbranched carbon 1-30 alkyl group, a branched or unbranched carbon 2-30 alkenyl group, Alternatively, the terminal of the alkyl group or the alkenyl group may be substituted with a hydroxyl group or a carboxyl group, R ₂ represents hydrogen, a branched or unbranched carbon group having 1 to 30 carbon atoms, or a branched or unbranched carbon group 2 to 2; in the .R ₁ and R ₂ showing a 30 alkenyl groups may form a cyclic structure.)
A block copolymer or a random copolymer obtained by copolymerizing the bond unit B at a ratio of 1 mol% to 70 mol% with respect to the total amount of the bond unit A and the bond unit B, and 100 parts by mass of silica. 2 to 20 parts by mass with respect to
Rubber composition for base tread.   A pneumatic tire using the base tread rubber composition in a base tread portion.

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