JP4517643B2 - Rubber composition for tire - Google Patents

Description

The present invention is equivalent antistatic effect and conductive carbon black-containing rubber composition of the traditional is obtained and excellent in dispersibility of carbon black, about tire tread rubber composition having improved processability.

  Silica is blended for the purpose of improving the heat buildup and wear resistance of rubber compositions, especially tire rubber compositions. A draft has been reported. For example, Patent Document 1 proposes the use of carbon black having a small particle diameter, Patent Document 2 proposes the incorporation of a conductive substance, and Patent Document 3 discloses a high reinforcing property. It has been proposed to use acetylene black showing However, ordinary acetylene black is excellent in conductivity but not sufficient in rubber reinforcement. Also, when carbon black with a small particle size or acetylene black with high reinforcement is used, the processability of the resulting rubber composition is poor (increased viscosity) ) Is not practically preferable.

JP 1997-118780 A JP 1999-049892 A JP 2002-20549 A

Therefore, the present invention solves the above-mentioned problems of low-conductivity rubber compositions with high silica content, particularly rubber compositions for tire treads, for the purpose of improving fuel economy performance and wet braking performance. An object of the present invention is to provide a rubber composition suitable for a tire tread that has an antistatic effect equivalent to that of a conductive carbon black-containing rubber composition, is excellent in dispersibility of carbon black, and has improved processability. .

According to the present invention, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR) and styrene - for one or more diene-based rubber 100 parts by weight selected from butadiene copolymer rubber (SBR) Te, silica 25-100 parts by weight and the nitrogen adsorption specific surface area _(N 2 SA) 80 m ² / g or less, at a DBP oil absorption 150 ml / 100 g or more, compounding the carbon black 10 to 30 parts by weight ΔDst is 150nm or more A rubber composition for a tire tread is provided.

According to the present invention, excellent workability, reinforcement and electrical conductivity can be obtained by blending carbon black having a specific N ₂ SA, DBP oil absorption and ΔDst into the rubber composition.

The rubber composition for a tire tread according to the present invention includes at least one diene selected from natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), and styrene-butadiene copolymer rubber (SBR). In addition to rubber and silica, N ₂ SA is 80 m ² / g or less, preferably 50 to 70 m ² / g, DBP oil absorption is 150 ml / 100 g or more, preferably 160 to 200 ml / 100 g, and ΔDst (aggregate) The carbon black having a distribution half-value width of 150 nm or more, preferably 160 to 200 nm, is blended in an amount of 10 to 30 parts by weight, preferably 10 to 20 parts by weight. Such carbon black is conventionally known, and is used, for example, for preventing static electricity of resin. Specifically, it is commercially available as Niteron # 3350 (manufactured by Nippon Kayaku Co., Ltd.). Can be used.

If the N ₂ SA of the carbon black according to the present invention is more than 80 m ² / g, the processability is deteriorated, which is not preferable, and if the DBP oil absorption is less than 150 ml / 100 g or ΔDst is less than 150 nm, the conductivity decreases. Therefore, it is not preferable. Incidentally, in the present invention _N 2 SA, DBP oil absorption and ΔDst refers to those measured by the following method.

N ₂ SA: Measured according to JIS K 6217-2.
DBP oil absorption: measured according to JIS K 6217-4.
ΔDst: Measured by the following method using Disc Centrefuge (manufactured by Jolce Loebbl, UK). Specifically, carbon black was precisely weighed, a 20 volume% ethanol aqueous solution and a surfactant were added, and the sample was prepared by dispersing with ultrasonic waves so that the carbon black concentration was 5 mg / 100 cc. Next, the rotational speed of the disc centrifugation was set to 8000 rpm, 10 ml of spin solution (distilled water) was added to the disc centrifugation, and then 0.5 ml of buffer solution (20% by volume ethanol aqueous solution) was injected into the sample. 0.5 to 1.0 ml of the solution was added with a syringe, centrifugal sedimentation was started, and an aggregate distribution curve converted to Stokes was prepared by the photoprecipitation method. The distribution value of the aggregates at half the maximum frequency (maximum absorbance) in this histogram was defined as the half width (ΔDst).

  If the blending amount of the carbon black according to the present invention is too small, it is not preferable because good conductivity is lost. Conversely, if it is too much, low fuel consumption, which is an advantage of silica blending, is lost.

As the diene rubber compounded in the tire tread rubber composition according to the present invention, any diene rubber that can be compounded in the rubber composition, particularly the tire rubber composition can be used. natural rubber (NR), polyisoprene rubber (IR), various polybutadiene rubbers (BR), various scan styrene - butadiene copolymer rubber (SBR) can be mentioned.

The silica blended in the tire tread rubber composition according to the present invention can be any silica that can be blended in the rubber composition, in particular the tire rubber composition, specifically the average particle size. Is preferably 10 to 50 nm in terms of dispersibility and wear resistance, and more preferably 12 to 30 nm in terms of low fuel consumption performance and wet braking performance.

The amount of the silica is 25 to 100 parts by weight per the diene rubber 100 parts by weight, preferably 30 to 80 parts by weight. If the amount is too small, the fuel efficiency and wet braking performance are deteriorated, which is not preferable. On the other hand, if the amount is too large, the workability is remarkably deteriorated.

The rubber composition for a tire tread according to the present invention includes a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, various oils, an antioxidant, a plasticizer, and other general tires in addition to the above-described essential components. Various additives generally blended for rubber can be blended, and the blend can be kneaded into a composition by a general method and used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, the conventional general amounts can be used.

  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.

Example 1 and Comparative Examples 1-3
37.5 parts by weight of oil (Desolex No. 3 manufactured by Showa Shell Sekiyu KK), 65 parts by weight of silica (ZEOSIL 165GR manufactured by Rhodia Co., Ltd.), 100 parts by weight of SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd.), Table 15 parts by weight of carbon black shown in I and 4 parts by weight of a silane coupling agent (Si69 manufactured by Degussa) were kneaded for 3 to 5 minutes with a 1.8 liter closed mixer and released when the temperature reached 165 ± 5 ° C. The Mooney viscosity of the obtained unvulcanized rubber was measured at 100 ° C. according to JIS K6300 (ML _{1 + 4} ), and is shown in Table I as an index with the value of Comparative Example 1 being 100.

  Next, sulfur (oil-treated sulfur produced by Hosoi Chemical Co., Ltd.) and a vulcanization accelerator (Noxeller CZ-G produced by Ouchi Shinsei Chemical Co., Ltd.) are added to the unvulcanized rubber and kneaded with an 8-inch open roll. Then, the test piece (rubber sheet) was obtained by vulcanization at 160 ° C. for 20 minutes in a 15 × 15 × 0.2 cm mold, and the following vulcanized physical properties were evaluated. The results are shown in Table I.

300% modulus (M300): Measured according to JIS K 6251, and shown in Table I as an index with the value of Comparative Example 1 taken as 100.
Lambourne wear: Based on JIS K 6264, measurement was performed under conditions of a load of 15 N and a slip rate of 50%. It was shown as an index with Comparative Example 1 as 100. The larger the index, the better the wear resistance.
Electrical resistance: Measured according to JIS K 6911.

  Comparative Example 1 is an example in which normal HAF is blended and has high electrical resistance as shown in Table I, Comparative Example 2 is an example in which acetylene black is blended and has poor reinforcement as shown in Table I, and Comparative Example 3 has high reinforcement. An example of blending acetylene black has a high viscosity as shown in Table I. On the other hand, Example 1 containing a specific carbon black according to the present invention has a Mooney viscosity equivalent to that of Comparative Example 1, and is excellent in reinforcement and electrical conductivity.

  As described above, according to the present invention, the antistatic effect is excellent, the dispersibility of carbon black is excellent, and the processability is also good, so that it is useful as a rubber for tire treads.

Claims (1)

Silica 25-100 with respect to 100 parts by weight of one or more diene rubbers selected from natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR). parts and nitrogen adsorption specific surface area _(N 2 SA) of 80 m ² / g or less, at a DBP oil absorption 150 ml / 100 g or more, for a tire tread obtained by blending carbon black 10 to 30 parts by weight ΔDst is 150nm or more Rubber composition.