JP2009102614A - Rubber composition for tire and pneumatic tire using the same - Google Patents

Abstract

The present invention provides a rubber composition for tires that enhances the interaction between rubber and filler, has low heat build-up, and can increase the vulcanization speed.
SOLUTION: (A) 100 parts by weight of a sulfur vulcanizable diene rubber, (B) 0.1 to 1 part by weight of 4,4′-oxybis (benzenesulfonyl azide), and (C) a vulcanizing compounding agent. A tire rubber composition comprising the components (A) and (B) mixed during the primary mixing before the addition of the component (C).
[Selection figure] None

Description

  The present invention relates to a rubber composition for tires, and more particularly relates to a rubber composition for tires that enhances the interaction between rubber and filler, has low heat build-up, and can increase the vulcanization speed.

  In recent years, the performance required for tires has been increased by various methods. As an example, there is a strong demand for reducing tire rolling resistance due to market needs for low fuel consumption. As a technique for reducing such rolling resistance, there is a technique for improving the fuel efficiency by modifying the end of the rubber molecule with various functional groups to improve the dispersibility of the filler in the rubber. However, in order to modify the ends of the rubber molecules and obtain the maximum effect, it is necessary to modify many of the end groups, resulting in a decrease in the molecular weight of the rubber. When using a low molecular weight end-modified rubber, especially when silica is used as the filler, long reaction time is required for sufficient reaction and dispersion of the filler, but in this case, the rubber molecules are rapidly cut and the viscosity is lowered. There is also a problem that leads to.

  In order to solve these problems, if the main chain of the rubber can be modified during mixing, the interaction between the rubber and the filler can be increased without causing a decrease in molecular weight, and the required tire performance is satisfied. The rubber composition to be obtained can be obtained. Therefore, in the present invention, by using a specific compounding agent (4,4′-oxybis (benzenesulfonyl azide)) as the main chain modifier, the interaction between the rubber and the filler is enhanced and the fuel efficiency is excellent. It has succeeded in obtaining a tire rubber composition.

  Conventionally, by using the 4,4′-oxybis (benzenesulfonyl azide) as a curing agent, an elastomer composition excellent in ozone resistance or the like is obtained (for example, see Patent Documents 1 and 2), and this is foamed. It has been proposed to obtain a sponge rubber composition for molding a mold that does not cause fogging or contamination of the contact body by using it as an agent / crosslinking agent (see, for example, Patent Document 3). However, there is no known document that suggests that a rubber composition for tires excellent in fuel efficiency can be obtained by using this as a main chain modifier of rubber as in the present invention.

Japanese Examined Patent Publication No. 6-11815 Japanese Patent Publication No. 7-5798 JP-A-8-134248

  In the present invention, a specific main chain modifier is used to react with the main chain of the rubber during mixing, thereby enhancing the interaction between the rubber and the filler, low exothermicity, and increasing the vulcanization rate. An object of the present invention is to provide a rubber composition for a tire that can be used.

  According to the present invention, (A) 100 parts by weight of diene rubber capable of sulfur vulcanization, (B) 0.1 to 1 part by weight of 4,4′-oxybis (benzenesulfonyl azide), and (C) vulcanization system compounding There is provided a rubber composition for a tire comprising an agent, wherein the components (A) and (B) are mixed during the primary mixing before the addition of the component (C).

  The present inventors added 4,4′-oxybis (benzenesulfonyl azide) (OBSA) (B) in the diene rubber (A) during the primary mixing before the addition of the vulcanizing compounding agent (C). When blended as a main chain modifier and heated and kneaded at 160 to 170 ° C., the OBSA reacts with the main chain of the diene rubber (A) to restrain the movement of rubber molecules, so that the breaking hardness is not impaired. The present inventors have found that it becomes low exothermic and can increase the vulcanization rate.

  Examples of the diene rubber (A) used in the tire rubber composition of the present invention include natural rubber (NR), isoprene rubber (IR), various butadiene rubbers (BR), and various styrene-butadiene copolymer rubbers ( SBR), acrylonitrile-butadiene copolymer rubber (NBR), styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, or a blend of two or more. Can be used as rubber.

4,4′-oxybis (benzenesulfonyl azide) (OBSA) to be blended as a main chain modifier in the tire rubber composition of the present invention is an azide compound represented by the following formula (I), Due to the heat during mixing and heating with the rubber, nitrogen gas (N ₂ ) is generated from the azide groups at both ends by the reaction mechanism shown below, and the residual nitrogen radical reacts with the main chain of the diene rubber. The effect of the present invention is exhibited by crosslinking with a part of the diene rubber. OBSA is a known compound, and a commercially available product can be used.

  The 4,4'-oxybis (benzenesulfonyl azide) (OBSA) main chain modifier, which is the compounding agent of the present invention, is 0.1 to 1 part by weight, preferably 0. 1 part by weight based on 100 parts by weight of the diene rubber. Used in an amount of 2 to 0.6 parts by weight. If the amount is too small, the desired effect cannot be exhibited. On the other hand, if the amount is too large, the scorch becomes too fast and the workability deteriorates (the rubber becomes shattered), which is not preferable.

  In the present invention, since the main chain modifier is required to sufficiently proceed with the reaction by the reaction mechanism described above, this is compared with the diene rubber containing the filler before the addition of the vulcanizing compounding agent. For example, it is important to blend and knead in advance using a Banbury mixer or the like under a heating condition of 160 to 170 ° C. During such kneading, the nitrogen gas generated from the main chain modifier is discharged out of the system, so it does not remain in the rubber and the kneaded rubber does not become foamed rubber. In addition, when this main chain modifier is added in the final mixing stage in which the vulcanizing compounding agent is added, the generated nitrogen gas remains in the rubber system, so that it becomes foamed rubber and is not suitable for tire use.

  In the tire rubber composition of the present invention, general carbon black or silica, or a combination thereof, can be blended in a normal predetermined range as a filler. Although there is no restriction | limiting in particular in the mixing | blending time of this filler, It is preferable from a viewpoint of the dispersibility of a filler to add at the time of the said primary mixing.

  Examples of the vulcanizing compound used as the component (C) in the present invention include a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, a vulcanization acceleration aid, and the like. Any compounded in the product can be used.

  In the tire rubber composition of the present invention, various compounding agents blended in the tire rubber composition such as an anti-aging agent and a silane coupling agent can be further blended. At any time, the rubber composition can be kneaded by a general method to be vulcanized or crosslinked. The compounding amounts of these compounding agents can be set to conventional general compounding amounts as long as the object of the present invention is not adversely affected.

  Hereinafter, although an example and a comparative example explain the present invention further, it cannot be overemphasized that the scope of the present invention is not limited to these examples.

Examples 1-12 and Comparative Examples 1-8
Sample preparation In accordance with the formulation (parts by weight) shown in Table I and Table II, each compounding component such as rubber, OBSA, and carbon black excluding sulfur and vulcanization accelerator was loaded into a 1.7 liter B-type Banbury mixer. Mix for 5 to 6 minutes and mix with sulfur and a vulcanization accelerator in a master batch obtained when the temperature reaches 165 ° C. and knead with an open roll to obtain a rubber composition, part of which is This was subjected to a vulcanization rate test. Next, the remaining rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a test sample (rubber sheet), which was subjected to the following rolling resistance and tensile tests. The results are shown in Table I and Table II.

Test method 1) Vulcanization rate: Measured according to JIS K6300. Using a vibration disk vulcanization tester, the time (minutes) required to reach a 30% vulcanization degree was measured under the conditions of an amplitude of 1 degree and 160 ° C.
2) Rolling resistance: In accordance with JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under the conditions of initial strain = 10%, amplitude = ± 2%, frequency = 20 Hz, 60 ° C) was measured, and the rolling resistance was evaluated with this value. The results are shown as an index with the values of Comparative Examples 1, 2, 5, and 7 as 100. The smaller this index, the better the rolling resistance.
3) Breaking strength: Based on JIS K6251, the tensile strength at break (T _B ) was measured using a JIS No. 3 dumbbell-shaped sample. The results are shown as an index with the values of Comparative Examples 1, 2, 5, and 7 as 100. It shows that breaking strength is so large that this index | exponent is large.
4) Scorch: The time for the viscosity to rise by 5 Mooney units at a temperature of 125 ° C. was measured according to JIS K6300. The results are shown as an index with the values of Comparative Examples 1, 2, 5 and 7 as 100. The smaller the index, the faster the scorch and the worse the workability.

  According to the results of Table I and Table II, it can be seen that the rubber composition according to the present invention has improved rolling resistance and increased vulcanization speed without impairing the breaking strength.

  As described above, the rubber composition containing the OBSA of the present invention at the time of the primary mixing improves rolling resistance without impairing the breaking strength, so that it can be used for pneumatic tires, particularly tire treads. Is extremely useful.

Claims (2)

  (A) 100 parts by weight of a sulfur vulcanizable diene rubber, (B) 0.1 to 1 part by weight of 4,4′-oxybis (benzenesulfonyl azide), and (C) a vulcanizing compound. A tire rubber composition obtained by mixing components (A) and (B) during primary mixing before addition of component (C).   A pneumatic tire using the rubber composition according to claim 1.