JP2007284572A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rolling resistance characteristics with good balance while maintaining processability, abrasion resistance and wet performances in a rubber composition comprising carbon black compounded therein. <P>SOLUTION: The rubber composition comprises the carbon black in an amount of 10-120 pts.wt. based on 100 pts.wt. of a diene-based rubber. In the rubber composition, 0.1-10 pts.wt. of an aminosilane compound is contained. The aminosilane compound is preferably a compound represented by general formula (1) (R<SP>1</SP><SB>3</SB>Si)<SB>2</SB>-NH (wherein, R<SP>1</SP>represents a 1-8C hydrocarbon group) and/or general formula (2) R<SP>2</SP>-NH-R<SP>3</SP>-Si(-OR<SP>4</SP>)(-OR<SP>6</SP>)-OR<SP>5</SP>(wherein, R<SP>2</SP>represents a hydrogen atom or a 1-8C hydrocarbon group which may contain one or more oxygen atoms or nitrogen atoms in the group; R<SP>3</SP>to R<SP>6</SP>represent each a 1-20C hydrocarbon group which may contain one or more oxygen atoms in the group; and R<SP>3</SP>to R<SP>6</SP>may each be same or different). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber composition, and more specifically, a rubber composition containing carbon black with improved rolling resistance characteristics without impairing workability, wear resistance and wet performance, and a pneumatic tire using the same for a tread About.

  Rubber compositions used in treads for pneumatic tires are strongly demanded to reduce rolling resistance due to market needs for low fuel consumption, and braking performance and handling stability (hereinafter referred to as wet) on wet roads in terms of safety. Improvement in performance), and excellent wear resistance in terms of durability and economy.

  By the way, the above-mentioned rolling resistance characteristics and wet performance are characteristics related to the hysteresis loss of rubber, and a rubber composition of silica compounding that is easy to obtain a balance between the rolling resistance characteristics and the wet performance in a trade-off relationship is used for a tire tread. Although silica is used, silica has strong self-aggregation because it is hydrophilic and the surface is covered with highly polar silanol groups. The actual condition is that the processability in the process and the above rubber properties are not fully utilized.

Rolling resistance characteristics and wet performance have been improved by further improving the dispersibility of carbon black even in rubber compositions containing carbon black with good processability and wear resistance, which have been used for reinforcement fillers. For example, it has been proposed to blend carbon black and a silane coupling agent into a blend polymer such as solution-polymerized SBR and natural rubber (Patent Document 1). Further, it is disclosed that a diene polymer is improved by a polymerization method and that a silane coupling agent is used in combination with improved carbon black (Patent Documents 2 and 3). In addition, it has been proposed to use an organosilane compound to improve the silica dispersibility of silica compound (Patent Document 4).
JP-A-5-331319 JP-A-5-209011 JP 2003-335980 A JP 2001-240700 A

  Usually, as a technique for improving the dispersibility of reinforcing fillers such as carbon black and silica, the surface activity of the filler is increased or the modification of the polymer molecule end by solution polymerization is used. It was inferior in versatility due to the disadvantage that it could not be applied to polymers other than deterioration of processability and solution polymerization. Further, the use of a silane coupling agent has little coupling effect with respect to carbon black, and the use of an organic silane compound does not provide a dispersion effect as expected for carbon black.

  The present invention has been made in view of the above points, and in a rubber composition in which carbon black is blended with a diene rubber used in a tire tread or the like, by improving the dispersibility of carbon black, the processability and The object is to improve rolling resistance characteristics in a well-balanced manner while maintaining wear resistance and wet performance.

  As a result of intensive studies to solve the above problems, the present inventors have found that a compound that can interact with the carbon black surface and improve the affinity with a polymer can solve the above problems. The invention has been reached.

  That is, the present invention provides a rubber composition comprising 0.1 to 10 parts by weight of an aminosilane compound in a rubber composition containing 10 to 120 parts by weight of carbon black with respect to 100 parts by weight of a diene rubber. It is a thing.

The aminosilane compound is preferably a compound represented by the following general formula (1) and / or (2).
(R ¹ ₃ Si) ₂ —NH (1)
(Wherein R ¹ represents a hydrocarbon group having 1 to 8 carbon atoms)
R ² OR ⁴
\ |
N—R ³ —Si—OR ⁵ (2)
/ |
H OR ⁶
(In the formula, R ² represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms which may contain one or more oxygen atoms or nitrogen atoms in the group, and R ^{3 to} R ⁶ represent one or more in the group. A hydrocarbon group having 1 to 20 carbon atoms which may contain an oxygen atom, and R ^{3 to} R ⁶ may be the same or different.)

  And the pneumatic tire of this invention exists in using said rubber composition for a tread.

  According to the rubber composition of the present invention, the amino group portion of the aminosilane compound interacts with the polar group on the surface of the carbon black, and at the same time, the hydrocarbon group improves the affinity with the polymer and suppresses the aggregation of the carbon black. The dispersibility can be improved, and it can greatly contribute particularly to reduction of rolling resistance. Thereby, also in the rubber composition containing carbon black, it is possible to provide a pneumatic tire that improves fuel efficiency and is excellent in safety and economy.

  Embodiments of the present invention will be described below.

  In the rubber composition of the present invention, a diene rubber composed of natural rubber (NR) and a diene synthetic rubber is used as a rubber component, and the rubber composition can be used alone or in a blend of two or more. There are no restrictions.

  Examples of the diene synthetic rubber include styrene butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and the like. It is done.

  The diene synthetic rubber is not particularly limited in molecular weight or microstructure. For example, in the case of SBR, it is not limited by the polymerization method, microstructure such as styrene content, vinyl content, molecular weight, or presence / absence of terminal modification by a functional group such as hydroxyl group or amino group. When used for tire tread, it is selected from SBR obtained by solution polymerization or emulsion polymerization used for tread, which is superior in strength, low heat build-up, abrasion resistance, workability, etc., and terminal-modified SBR as appropriate. It is also preferable to use a blend with BR having good low temperature characteristics for studless tires.

The carbon black used in the rubber composition of the present invention is not particularly limited, but the nitrogen adsorption specific surface area (N ₂ SA) is 70 m ² / g or more, and the DBP oil absorption is 90 ml / 100 g or more. Are preferred.

If the N ₂ SA is less than 70 m ² / g, sufficient wear resistance is difficult to obtain, and if the N ₂ SA is too large, the fuel efficiency is deteriorated, and considering the wear resistance and fuel efficiency, N ₂ A preferable range of SA is 80 to 140 m ² / g. Furthermore, if the DBP is less than 90 ml / 100 g, sufficient wear resistance is difficult to obtain, and if it is too large, the elongation at break tends to deteriorate, and the preferred range of DBP is 90 to 140 ml / 100 g. N ₂ SA is a value measured according to ASTM 3037, and DBP is a value measured according to JIS K6221.

  Specific examples of these carbon blacks include SAF, ISAF, and HAF grade carbon blacks, and a mixture of two or more of these may be used.

  The compounding amount of carbon black is 10 to 120 parts by weight, preferably 20 to 120 parts by weight, and more preferably 40 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. If the carbon black is less than 10 parts by weight, the reinforcing property of the rubber composition cannot be ensured, and if it exceeds 160 parts by weight, the rolling resistance characteristics and wear resistance may not be maintained.

  In the rubber composition of the present invention, the aminosilane compound is contained in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the diene rubber component.

  The aminosilane compound can be obtained, for example, by allowing ammonia to act on the organosilane compound. The number of amino groups and molecular weight in the compound can be used without any particular limitation.

  In the present invention, the aminosilane compound is preferably a compound represented by the following general formula (1) and / or (2).

(R ¹ ₃ Si) ₂ —NH (1)
In the formula, R ¹ represents a hydrocarbon group having 1 to 8 carbon atoms. Of these, an alkyl group having 1 to 3 carbon atoms is preferable.

As aminosilanes represented by the formula (1), hexamethyldisilazane “(CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃ ”, hexaethyldisilazane “(C ₂ H ₅ ) ₃ SiNHSi (C ₂ H ₅ ) ₃ ”, Nonamethyltrisilazane, anilitrimethylsilane, bis (dimethylamino) dimethylsilane, bis (diethylamino) dimethylsilane, triethylaminosilane and the like. Of these, silazane compounds such as hexamethyldisilazane and hexaethyldisilazane are preferred.

R ² OR ⁴
\ |
N—R ³ —Si—OR ⁵ (2)
/ |
H OR ⁶
In the formula, R ² represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms which may contain one or more oxygen atoms or nitrogen atoms in the group, and R ^{3 to} R ⁶ represent one or more hydrocarbon groups in the group. The C1-C20 hydrocarbon group which may contain an oxygen atom is shown, and R ^{3 to} R ⁶ may be the same or different. Among these, R ² is a hydrogen atom, and R ^{3 to} R ⁶ are preferably an alkyl group having 1 to 3 carbon atoms.

Examples of the aminosilane compound represented by the formula (2) include N-2 (aminoethyl) 3-aminopropyltriethoxysilane “(C ₂ H ₅ O) ₃ SiC ₃ H ₆ NHC ₂ H ₄ NH ₂ ”, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane “(CH ₃ O) ₃ SiC ₃ H ₆ NHC ₂ H ₄ NH ₂ ”, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane “(CH _{3 O) 2 Si (CH 3} ) C 3 H 6 NHC 2 H 4 NH 2 ", aminopropylethoxysilane" _{(C 2 H 5 O) 3} SiC 3 H 6 NH 2 ", aminopropyltrimethoxysilane" (CH _{3 O) 3 SiC 3 H 6} NH 2 ", N- phenyl-3-aminopropyltrimethoxysilane" _{(CH 3 O) 3 SiC 3} H 6 NHC 6 H 5 Or the like.

  The aminosilane compounds may be used alone or in combination of two or more thereof.

  In addition, aminosilane compounds with a large molecular weight, that is, those having a large number of hydrocarbon groups such as alkyl groups, are advantageous in improving the dispersibility of carbon black by further improving the affinity with the polymer, and the effect of reducing rolling resistance Becomes easier to obtain.

  The compounding quantity of the said aminosilane compound is 0.1-10 weight part with respect to 100 weight part of rubber components. When the blending amount is less than 0.1 part by weight, the interaction between the amino group and the carbon black surface and the affinity between the aminosilane compound and the polymer are insufficient, and the dispersibility of the carbon black is not improved, and the amount exceeds 10 parts by weight. In addition to not being able to obtain low heat build-up and reducing rolling resistance, the volume effect causes the rubber itself to soften and cause wet performance to deteriorate. .

The rubber composition of the present invention may contain silica as a reinforcing filler in combination with carbon black. Silica is not particularly limited and can be appropriately selected from those conventionally used for reinforcing rubber, for example, dry silica, wet silica (hydrous silicic acid), etc. Is preferred. The silica preferably has a nitrogen adsorption specific surface area (BET) in the range of 100 to 300 m ² / g from the viewpoint of wear resistance and fuel efficiency, and the blending amount thereof is the total amount with carbon black. 120 parts by weight or less, and it is preferable to use a silane coupling agent in an amount of 2 to 20% by weight of silica.

  In the rubber composition of the present invention, in addition to the rubber component, carbon black, and aminosilane compound, if necessary, a vulcanizing agent such as sulfur usually used in the rubber industry, a vulcanization accelerator, a process oil, Various compounding agents such as anti-aging agent, zinc white, stearic acid, and vulcanization aid can be appropriately blended and used as necessary within the range not impairing the effects of the present invention.

  The rubber composition of the present invention can be prepared in accordance with a conventional method using various kneading machines such as a Banbury mixer, a roll, a kneader by blending various compounding agents with the raw rubber and the above-described components, including tire treads. Can be used in tire parts such as sidewalls and bead parts, but especially for tire treads by reducing the rolling resistance without impairing wear resistance or wet performance by making the dispersion state of carbon black uniform It is suitably used as rubber. Of course, it is also suitable for studless tires.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Preparation of rubber composition]
As aminosilane compounds, the following four aminosilane compounds A to D were used. Moreover, the following organosilane compound was used for the comparative example.

[Amino, organosilane compounds]
Aminosilane A: Hexamethyldisilazane “(CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃ ”
Aminosilane B: hexaethyldisilazane “(C ₂ H ₅ ) ₃ SiNHSi (C ₂ H ₅ ) ₃ ”
Aminosilane C: N-2 (aminoethyl) 3-aminopropyltriethoxysilane “(C ₂ H ₅ O) ₃ SiC ₃ H ₆ NHC ₂ H ₄ NH ₂ ”
Aminosilane D: aminopropylethoxysilane “(C ₂ H ₅ O) ₃ SiC ₃ H ₆ NH ₂ ”
Organic silane: methyltriethoxysilane “(C ₂ H ₅ O) ₃ SiCH ₃ ”

  Using a sealed banbury mixer with a capacity of 20 liters, a rubber composition was prepared according to the formulation shown in Table 1 below. The rubber components, carbon black, common compounding components and compounding amounts in Table 1 are as follows.

[Rubber component, carbon black]
Rubber component: Styrene butadiene rubber (SBR), Asahi Kasei Kogyo Co., Ltd., TUFDENE 3330 (styrene content = 31%, oil content 37.5%)
Carbon black (N339): Tokai Carbon Co., Ltd., Seast KH

[Common ingredients and amounts]
・ Oil: 37.5 parts by weight of SBR oil fraction ・ Zinc flower: 3 parts by weight; Mitsui Kinzoku Mining Co., Ltd. “Zinc Flower 1”
・ Stearic acid: 1 part by weight; Kao Corporation “Lunac S-20”
・ Wax: 1 part by weight; Ouchi Shinsei Chemical Co., Ltd. “Sannok”
Anti-aging agent 6C: 2 parts by weight; Ouchi Shinsei Chemical Co., Ltd. “NOCRACK 6C”
Anti-aging agent RD: 2 parts by weight; Ouchi Shinsei Chemical Co., Ltd. “NOCRACK 224”
・ Sulfur: 2 parts by weight; Hosoi Chemical Co., Ltd. “Rubber powder sulfur 150 mesh”
・ Vulcanization accelerator CZ: 1.5 parts by weight; Ouchi Shinsei Chemical Co., Ltd. “Noxeller CZ”

[Evaluation]
Each rubber composition obtained was applied to a cap tread of a tire having a tread having a cap / base structure, and a 205 / 65R15 94H pneumatic radial tire was manufactured in accordance with a conventional method, and rolling resistance and wet performance were evaluated. . Each evaluation method is as follows. The results are shown in Table 1.

[Rolling resistance]
The tire was mounted with a rim of 15 × 6.5 JJ, and the rolling resistance was measured when running at 80 km / h at 23 ° C. with a uniaxial drum tester for measuring rolling resistance at an air pressure of 230 kPa and a load of 450 kgf. . It was displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the rolling resistance and thus the better the fuel efficiency.

[Wet performance]
Measure the braking distance when decelerating to 20 km / h by installing four tires on a 2000cc domestic FF car, running on asphalt road surface watered at a depth of 2-3 mm, operating ABS at 90 km / h did. It displays with the index | exponent which set the value of the comparative example 1 to 100, and shows that it is excellent in wet performance, so that an index | exponent is large.

  As shown in Table 1, it can be seen that the examples according to the present invention using the aminosilane compound in the range of 0.1 to 10 parts by weight substantially maintain the wet performance, reduce the rolling resistance, and are excellent in fuel efficiency. . In particular, in the examples using aminosilanes C and D having a large molecular weight, the effect of reducing rolling resistance is significant. However, when the amount exceeds 10 parts by weight (Comparative Example 3), the reduction in wettability increases for the improvement of rolling resistance, and Comparative Example 2 using an organosilane compound does not provide the same effect as the Examples.

The rubber composition of the present invention is excellent in low fuel consumption, safety and durability, and is particularly suitable for tread rubber of pneumatic tires with emphasis on low fuel consumption, from passenger car tires to large tires for trucks and buses, and studless Can be used for tires.

Claims (3)

In a rubber composition comprising 10 to 120 parts by weight of carbon black with respect to 100 parts by weight of diene rubber,
A rubber composition comprising 0.1 to 10 parts by weight of an aminosilane compound. The rubber composition according to claim 1, wherein the aminosilane compound is a compound represented by the following general formula (1) and / or (2).
(R ¹ ₃ Si) ₂ —NH (1)
(Wherein R ¹ represents a hydrocarbon group having 1 to 8 carbon atoms)
R ² OR ⁴
\ |
N—R ³ —Si—OR ⁵ (2)
/ |
H OR ⁶
(In the formula, R ² represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms which may contain one or more oxygen atoms or nitrogen atoms in the group, and R ^{3 to} R ⁶ represent one or more in the group. A hydrocarbon group having 1 to 20 carbon atoms which may contain an oxygen atom, and R ^{3 to} R ⁶ may be the same or different.) A pneumatic tire using the rubber composition according to claim 1 or 2 for a tread.