JP2016222757A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance on-ice brake performance while suppressing reduction of abrasion resistance.SOLUTION: There is provided a rubber composition for a tire tread containing 0.1 to 30 pts.mass of alginate powder without carbonization to 100 pts.mass of a diene rubber. There is also provided a pneumatic tire having a tread using the rubber composition.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition used for a tire tread, and also relates to a pneumatic tire using the rubber composition.

  The snowy and snowy road surface is significantly slippery and slippery compared to the general road surface. Therefore, in the tread rubber of winter tires (winter tires) such as studless tires and snow tires, in order to increase the friction force on ice and improve the braking performance on ice, a method of forming the tread rubber with foam rubber, hollow particles, Various methods for blending hard materials such as glass fiber and aluminum whiskers have been proposed.

  For example, Patent Document 1 discloses that by adding calcium alginate particles to a diene rubber, the effect of removing a water film on the road surface on ice is exhibited and the braking performance on ice is improved. However, it has been found that when calcium alginate particles are blended, it is not always easy to achieve both braking performance on ice and wear resistance. Therefore, it is required to improve the braking performance on ice while suppressing a decrease in wear resistance.

  Patent Document 2 discloses a rubber composition containing mesoporous carbon obtained by carbonizing a polysaccharide having a hydroxyl group such as alginic acid. However, it is used for the purpose of maintaining the anti-aging effect, and the braking performance on ice is not disclosed.

JP 2006-225447 A JP2013-124346A

  In view of the above, an object of the present invention is to provide a rubber composition for a tire tread that can improve braking performance on ice while suppressing a decrease in wear resistance, and a pneumatic tire using the same. To do.

  The rubber composition for a tire tread according to the present invention contains 0.1 to 30 parts by mass of non-carbonized alginic acid powder with respect to 100 parts by mass of the diene rubber. The pneumatic tire according to the present invention includes a tread made using the rubber composition.

  According to the present invention, on-ice braking performance can be improved while blending non-carbonized alginic acid powder while suppressing a decrease in wear resistance.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition according to this embodiment is obtained by blending alginic acid powder that has not been carbonized with diene rubber.

  Examples of the diene rubber used as the rubber component in the rubber composition include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and styrene-isoprene copolymer. Examples thereof include rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. These diene rubbers can be used alone or in a blend of two or more. The rubber component is preferably natural rubber, butadiene rubber, styrene butadiene rubber, or a blend of two or more thereof.

  As the diene rubber, it is preferable to use a blend of natural rubber and another diene rubber, and it is particularly preferable to use a blend rubber of natural rubber (NR) and butadiene rubber (BR). In that case, if the ratio of BR is too small, it is difficult to obtain low temperature characteristics of the rubber composition. Conversely, if the ratio is too large, the processability tends to deteriorate and the tear resistance tends to decrease, so the ratio of NR / BR is The mass ratio is preferably about 30/70 to 80/20, more preferably about 40/60 to 70/30.

  The alginic acid powder blended in the rubber composition according to this embodiment is not carbonized. That is, mesoporous carbon obtained by carbonizing alginic acid as described in Patent Document 2 is not included. Here, alginic acid is a linear polymeric polysaccharide obtained by extraction from brown algae plants such as kombu, wakame and kajime, and is a heteropolymer composed of D-mannuronic acid and L-guluronic acid. In the present embodiment, as the alginic acid powder, a powder made of a free acid type alginic acid is used instead of a powder made of an alginic acid metal salt such as a sodium salt or a calcium salt. Alginic acid powder made of such natural polysaccharides has excellent water absorption, and apparent viscosity increases when water is absorbed, so that it is effective to remove water film and improve braking performance on ice by containing it in the rubber composition. Can do. In addition, as shown in the examples below, compared to the case of using alginate metal salt powder, it is possible to improve the braking performance on ice while suppressing a decrease in wear resistance performance, and further, wet braking performance. This is advantageous because an improvement effect is also obtained.

  The average particle diameter of the non-carbonized alginic acid powder is not particularly limited, and may be, for example, 1 to 200 μm or 5 to 100 μm. Here, in this specification, the average particle diameter is a value measured by a laser diffraction / scattering method. For example, a laser diffraction particle size distribution measuring apparatus manufactured by Shimadzu Corporation using a red semiconductor laser (wavelength 680 nm) as a light source. It is a 50% particle diameter (median diameter) of the particle size distribution (volume basis) measured by “SALD-2200”. Such a non-carbonized alginic acid powder is commercially available from Kimika Co., Ltd. under the trade name Kimika Acid and can be used.

  The blending amount of the non-carbonized alginic acid powder is 0.1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. When the blending amount is 0.1 parts by mass or more, a water absorption effect is exhibited, and when it is 30 parts by mass or less, the wear resistance performance can be maintained or improved. The blending amount of the alginic acid powder may be 3 to 25 parts by mass, 5 to 20 parts by mass, or 10 to 20 parts by mass.

  In the rubber composition according to the present embodiment, a reinforcing filler may be blended together with the non-carbonized alginic acid powder.

  As the reinforcing filler, it is preferable to use carbon black and / or silica. That is, the reinforcing filler may be carbon black alone, silica alone, or a combination of carbon black and silica. Preferably, carbon black or a combination of carbon black and silica is used. The compounding amount of the reinforcing filler is not particularly limited. For example, the reinforcing filler is preferably 10 to 150 parts by mass, more preferably 20 to 100 parts by mass, and still more preferably 100 parts by mass of the diene rubber. 30 to 80 parts by mass.

The carbon black is not particularly limited, and various known varieties can be used. For example, when it is used for a tread portion of a winter tire such as a studless tire, a nitrogen adsorption specific surface area (N ₂ SA) (JIS K6217-2) from the viewpoints of low temperature performance, wear resistance performance, rubber reinforcement and the like of the rubber composition. Of 70 to 150 m ² / g and DBP oil absorption (JIS K6217-4) of 100 to 150 ml / 100 g is preferably used. Specifically, SAF grade, ISAF grade, and HAF grade carbon black are exemplified. As a compounding quantity of carbon black, the range of about 10-80 mass parts is preferable with respect to 100 mass parts of diene rubbers, More preferably, it is 15-50 mass parts.

The silica is not particularly limited, but wet silica such as wet precipitation silica or wet gel silica is preferably used. BET specific surface area of the silica (measured according to BET method according to JIS K6430) is not particularly limited, is preferably 90~250m ² / g, more preferably 150~220m ² / g. The blending amount is preferably 10 to 50 parts by mass, more preferably 15 to 50 parts by mass with respect to 100 parts by mass of the diene rubber from the viewpoint of the balance of tan δ of the rubber and reinforcement.

  When silica is blended, a silane coupling agent such as sulfide silane or mercaptosilane is preferably used in combination, and the blending amount is preferably 2 to 20% by mass with respect to the silica blending amount.

  In addition to the above-described components, the rubber composition according to the present embodiment includes process oil, zinc white, stearic acid, softener, plasticizer, wax, anti-aging agent (amine-amine) used in the normal rubber industry. Ketones, aromatic secondary amines, phenols, imidazoles, etc.), vulcanizing agents, vulcanization accelerators (guanidines, thiazoles, sulfenamides, thiurams, etc.) It can mix | blend suitably within the range. In addition, it has braking performance on ice such as plant granules (ground products of seed shells, fruit nuclei, etc.), pulverized products of porous carbides (charcoal, bamboo charcoal, etc.), and polymer gels that are crosslinked diene polymer particles. It is also possible to add known ingredients to improve.

  Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of diene rubber. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-5 mass parts, More preferably, it is 1-3 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 0.5-5 mass parts.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, in the first mixing stage (non-pro kneading process), other additives except for the vulcanizing agent and the vulcanization accelerator are added to the diene rubber together with the reinforcing filler and the non-carbonized alginic acid powder. Then, a rubber composition can be prepared by adding and kneading a vulcanizing agent and a vulcanization accelerator to the obtained mixture in the final mixing stage (pro kneading process).

  The rubber composition thus obtained is used as a tread rubber constituting a ground contact surface of a pneumatic tire, and more preferably as a rubber composition for a tread of a winter tire such as a studless tire or a snow tire. The tread can be formed by vulcanization molding at 140 to 180 ° C., for example, according to a conventional method. There are two types of tread rubber for pneumatic tires: a cap rubber and a base rubber, and a single-layer structure in which both are integrated. In the case of a structure, the tread rubber is composed of the rubber composition, and in the case of a two-layer structure, the cap rubber is composed of the rubber composition.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed (discharge temperature = 160 ° C.), and then obtained. In the final mixing stage, sulfur and a vulcanization accelerator were added to and mixed with the resulting mixture (discharge temperature = 90 ° C.) to prepare a tire tread rubber composition. The details of each component in Table 1 are as follows.

・ Natural rubber: RSS # 3
・ Butadiene rubber: “BR150B” manufactured by Ube Industries, Ltd.
Carbon black: HAF, “N339 Seast KH” manufactured by Tokai Carbon Co., Ltd. (N ₂ SA = 93 m ² / g, DBP = 119 ml / 100 g)
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET = 205 m ² / g)
Paraffin oil: “Process P200” manufactured by JX Nippon Oil & Energy Corporation
・ Silane coupling agent: “Si69” manufactured by Evonik Degussa Japan Co., Ltd.
・ Alginic acid powder not carbonized: “Kimika Acid SA” manufactured by Kimika Co., Ltd.
Carbonized alginate powder: Carbonized “Kimika Acid SA” manufactured by Kimika Co., Ltd. (heated at 100 ° C. to 450 ° C. in vacuum)
・ Calcium alginate: “Flavica Fine” manufactured by Nisshinbo Chemical Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Zinc flower: “Zinc flower No. 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Wax: Nippon Seiki ≡ "OZOACE0355"
・ Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator: “Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

  Studless tires were produced using the obtained rubber compositions. The tire size was 195 / 65R15, and each rubber composition was applied to the tread, and a tire was manufactured by vulcanization molding according to a conventional method. Each of the obtained tires was evaluated for wear resistance performance, on-ice braking performance, wet braking performance, and rolling resistance performance (the rim used was 15 × 5.5 JJ). Each measurement and evaluation method is as follows.

-Wear resistance performance: The above four tires are mounted on a 2000 cc 4WD vehicle, run on a general dry road surface by 10,000 km while rotating left and right every 2500 km, and the average value of the four remaining tread groove depths after running, Comparative example 1 is shown as an index with 100 as the index. The higher the value, the better the wear resistance.

-On-ice braking performance: The above four tires are mounted on a 2000 cc 4WD vehicle, and the braking distance is measured by running ABS from 40 km / h on an icy road (temperature -3 ± 3 ° C) (n = 10) The average value) and the reciprocal of the braking distance are shown as an index with the value of Comparative Example 1 being 100. The larger the index, the shorter the braking distance and the better the braking performance on the road surface on ice.

・ Wet braking performance: The above four tires are mounted on a 2000 cc 4WD, and the braking distance at the time of deceleration to 20 km / h is measured by running ABS on a wet road from 90 km / h (average value of n = 10) ), The reciprocal of the braking distance is expressed as an index with the value of Comparative Example 1 being 100. The larger the index, the shorter the braking distance and the better the braking performance on wet road surfaces.
Rolling resistance performance: The rolling resistance when running at a speed of 80 km / h was set at a room temperature of 23 ° C. with a uniaxial drum tester for measuring rolling resistance at an air pressure of 230 kPa and a load of 4.4 kPa. The result was expressed as an index with respect to the reciprocal of the rolling resistance, with the value of Comparative Example 1 being 100. The larger the index, the smaller the rolling resistance and the better the rolling resistance performance (low fuel consumption).

  The results are as shown in Table 1, and in each example in which 0.1 to 30 parts by mass of non-carbonized alginic acid powder was blended with respect to 100 parts by mass of the diene rubber, Comparative Example 1 as a control. On the other hand, on-ice braking performance and wet braking performance could be improved while maintaining or improving the wear resistance performance and rolling resistance performance. On the other hand, in Comparative Example 2 using the carbonized alginic acid powder, the wear resistance performance, on-ice braking performance, and wet braking performance decreased. Further, in Comparative Example 3 using calcium alginate, the wear resistance performance was greatly reduced while the braking performance on ice was improved. Moreover, in comparative example 4, there were too many alginate powders which were not carbonized, and abrasion resistance performance and rolling resistance performance fell.

  The rubber composition of the present invention can be used for various tires such as passenger cars, light trucks and buses.

Claims (2)

  A rubber composition for tire treads containing 0.1 to 30 parts by mass of non-carbonized alginic acid powder with respect to 100 parts by mass of diene rubber.   A pneumatic tire provided with a tread using the rubber composition according to claim 1.