JP2010132864A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire, which reduces the curing accompanying aging without badly influencing the appearance. <P>SOLUTION: The rubber composition is prepared by compounding 2-30 pts.wt. of a vegetable oil-and-fat into 100 pts.wt. of a diene rubber. The vegetable oil and fat includes at least 0.9×10<SP>-3</SP>wt.% of a naturally derived polyphenol. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for tires, and more particularly relates to a rubber composition for tires that reduces curing due to aging without adversely affecting the appearance.

  In the tread portion of a pneumatic tire, a rubber composition designed to optimize the rubber hardness in accordance with the purpose / application and use environment of the tire is used. However, even if the rubber hardness is optimal at the start of use of the tire, the rubber is cured due to aging when used for a long period of time, so that there is a problem that noise generated by the tire and riding comfort deteriorate. In addition, in the studless tire, there is a problem that the frictional force on ice is reduced when the rubber is hardened due to aging.

  As such an anti-aging measure, it is conceivable to increase the amount of the anti-aging agent blended in the tire rubber composition. However, as the amount of the anti-aging agent increases, the anti-aging agent moves to the surface of the tire and precipitates. Therefore, there is a problem that the tire surface changes to brown and the appearance is impaired.

  As a countermeasure, Patent Document 1 proposes a rubber composition for tires that is blended as a granular material in which an anti-aging agent and a resin are mixed. However, with this rubber composition, although it is possible to prevent the appearance of the tire surface from being deteriorated, the rubber composition has an effect of suppressing the curing of the rubber composition with aging compared to the case where an anti-aging agent is directly blended. Lowering was inevitable and there was room for improvement.

JP 2001-348463 A

  An object of the present invention is to provide a rubber composition for a tire that reduces the curing due to aging without adversely affecting the appearance.

The rubber composition for tires of the present invention that achieves the above object is a rubber composition in which 1 to 30 parts by weight of vegetable oils and fats are blended with 100 parts by weight of diene rubber. It is characterized by containing 9 × 10 ⁻³ wt% or more.

  For treads of studless tires, 0.5 to 20 parts by weight of thermally expandable microcapsules can be blended with 100 parts by weight of the diene rubber.

  Grape seed oil may be used as the vegetable oil. The tire rubber composition can be applied to a tread portion or a sidewall portion.

In the tire rubber composition of the present invention, 1 to 30 parts by weight of a vegetable oil containing 0.9 to ^10-3 % by weight of polyphenol is added to 100 parts by weight of the diene rubber. In order to prevent the rubber component from aging due to the oxidizing action, curing due to aging can be suppressed. Moreover, since an anti-aging agent is not blended in a large amount, the appearance is not adversely affected.

  Further, when 0.5 to 20 parts by weight of the heat-expandable microcapsule is blended with 100 parts by weight of the diene rubber, a water film is formed as described later along with the suppression of curing due to the aging of the rubber component described above. As a result, the frictional force on ice can be further increased, which is useful as a studless tire.

  In the tire rubber composition of the present invention, a diene rubber is used as the rubber component. The diene rubber is not particularly limited, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. Of these, natural rubber, butadiene rubber, and styrene-butadiene rubber are preferable. These diene rubbers can be used alone or as any blend.

  The rubber composition of the present invention prevents the rubber component from aging due to the antioxidant action of polyphenol by blending vegetable oil containing a large amount of polyphenol as a naturally derived component. For this reason, it can suppress that a rubber component ages and hardens | cures. Moreover, let the polyphenol which vegetable oil contains contain a natural origin component. That is, the vegetable oil used in the present invention does not contain a polyphenol antioxidant that is naturally or chemically synthesized by an artificial operation.

In the present invention, the content of polyphenol in the vegetable oil is 0.9 × 10 ⁻³ wt% or more, preferably 1.0 × 10 ⁻³ wt% or more. When the polyphenol content in the vegetable oil is less than 0.9 × 10 ⁻³ wt%, the antioxidant action cannot be sufficiently obtained and the rubber component cannot be inhibited from curing. In the present invention, the content of polyphenol in the vegetable oil was determined by the foreign-thiocult method. The foreign-thiocult method uses a foreign-thiocult reagent that develops a blue color under strong alkali against a reducing substance. Polyphenols in a sample (vegetable oil) are collectively collected by a colorimetric method (660 nm). It was measured as the amount of polyphenol. In addition, (+)-catechin was used as a standard sample, and the amount of polyphenol was determined from the calibration curve.

  The amount of vegetable oil is 1 to 30 parts by weight, preferably 2 to 30 parts by weight, and more preferably 2 to 25 parts by weight with respect to 100 parts by weight of the diene rubber. When the amount of vegetable oil is less than 1 part by weight, the antioxidant effect cannot be sufficiently obtained and the rubber component cannot be prevented from curing. Moreover, when the compounding quantity of vegetable oil exceeds 30 weight part, when an rubber component is mixed, an oil slip etc. will occur and workability will deteriorate.

The vegetable oil used in the present invention is not particularly limited as long as it contains 0.9 × 10 ⁻³ wt% or more of a naturally-derived polyphenol, and examples thereof include grape seed oil. Grape seed oil is produced all over the world, especially Chilean grape seed oil. In addition to the Chilean grape seed oil, the same effect is expected as long as it is a vegetable oil containing 0.9 × 10 ⁻³ wt% or more of polyphenols by improving the variety.

  Grape seed oil contains a large amount of naturally occurring polyphenols and also contains a lot of vitamin E. Since vitamin E has an antioxidant effect, it prevents aging of the rubber composition and suppresses hardening together with polyphenol.

  As described above, the tire rubber composition of the present invention having an excellent anti-aging effect can be cured with the aging of the rubber component when applied to a tread rubber for a studless tire containing a thermally expandable microcapsule. In addition to suppression (suppression of a decrease in frictional force on ice), an effect of maintaining a high frictional force on ice based on the thermally expandable microcapsules over a long period of time can be obtained. Here, the thermally expandable microcapsule is a resin-coated bubble formed at the time of vulcanization that improves the frictional force on ice between the tread and the icy road surface by absorbing the water film on the icy road surface. .

  In this case, the amount of the thermally expandable microcapsule is 0.5 to 20 parts by weight, preferably 1.0 to 15 parts by weight, based on 100 parts by weight of the diene rubber. When the blending amount of the microcapsules is less than 0.5 parts by weight, the volume of the resin-coated bubbles in the tread rubber is insufficient and the friction force on ice cannot be obtained sufficiently. On the other hand, when the blending amount exceeds 20 parts by weight, the wear resistance of the tread rubber is deteriorated.

  The thermally expandable microcapsule that can be used in the present invention has a structure in which a thermally expandable substance is encapsulated in a shell material formed of a thermoplastic resin. For this reason, when the microcapsules in the rubber composition are heated during vulcanization of the unvulcanized tire, the thermally expansible material contained in the shell material expands to increase the particle size of the shell material, and in the tread rubber A large number of resin-coated bubbles are formed. As a result, the water film generated on the ice surface is efficiently absorbed and removed, and a micro edge effect is obtained, so that the frictional force on ice is increased. Examples of such thermally expandable microcapsules include trade name “EXPANCEL 091DU-80” or “EXPANEL 092DU-120” manufactured by Expancel, Sweden, or trade name “Microsphere” manufactured by Matsumoto Yushi Seiyaku Co., Ltd. F-85 "or" Microsphere F-100 "can be used.

  Furthermore, carbon black may be added to the tire rubber composition of the present invention. By blending carbon black, the strength of the rubber composition can be increased and the wear resistance can be improved. The compounding amount of carbon black is preferably 10 to 100 parts by weight, more preferably 20 to 90 parts by weight, based on 100 parts by weight of the diene rubber. When the compounding amount of the carbon black is less than 10 parts by weight, the rubber composition cannot be sufficiently reinforced and hardened and the wear resistance is insufficient. Moreover, when the compounding quantity of carbon black exceeds 100 weight part, the viscosity of a rubber composition will become high and molding processability will deteriorate.

The carbon black used in the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of preferably 30 to 200 m ² / g, more preferably 60 to 170 m ² / g. When the nitrogen adsorption specific surface area is less than 30 m ² / g, the wear resistance is insufficient. When exceeding 200 m < ² > / g, the workability at the time of mixing deteriorates. The nitrogen adsorption specific surface area shall be measured according to JIS K6217-2.

  In addition to carbon black, an inorganic filler can be blended in the tire rubber composition of the present invention. As the inorganic filler, for example, silica, clay, calcium carbonate, talc, mica, aluminum hydroxide, magnesium carbonate and the like can be blended as necessary. Of these, silica is preferable as the inorganic filler.

  When silica is blended, the wet braking performance and low rolling resistance of the rubber composition can be compatible. The amount of silica is preferably 5 to 100 parts by weight, more preferably 10 to 90 parts by weight, with respect to 100 parts by weight of the diene rubber. When the blending amount of silica is less than 5 parts by weight, the effect of achieving both wet braking performance and low rolling resistance cannot be obtained sufficiently. Moreover, when the compounding quantity of a silica exceeds 100 weight part, the workability at the time of mixing will deteriorate. The kind of silica is not particularly limited, and those usually blended in a rubber composition can be used. Examples thereof include wet method silica, dry method silica, and surface-treated silica.

  When silica is blended in the rubber composition of the present invention, the silane coupling agent may be blended in an amount of 3 to 20% by weight, more preferably 3 to 15% by weight, based on the amount of silica in the rubber composition. % May be added. By compounding a silane coupling agent, the dispersibility of silica can be improved and the reinforcement with rubber can be enhanced. When the silane coupling agent is less than 3% by weight of the silica content, silica dispersion is deteriorated. Moreover, when a silane coupling agent exceeds 20 weight% of a silica compounding quantity, silane coupling agents will superpose | polymerize and a desired effect cannot be acquired.

  The type of the silane coupling agent is not particularly limited as long as it can be used for the rubber composition containing silica. For example, bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3- Examples thereof include sulfur-containing silane coupling agents such as (triethoxysilylpropyl) disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane. .

  In the tire rubber composition of the present invention, various additives generally used in tire rubber compositions such as a vulcanization or crosslinking agent, a vulcanization accelerator, a processing aid, an anti-aging agent, and a plasticizer are contained. These additives can be compounded and kneaded by a general method to form a rubber composition, which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

  The rubber composition for tires of the present invention can be produced by mixing the above components using a known rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

  The rubber composition of the present invention having excellent anti-aging performance described above is suitable for constituting a tread portion or a sidewall portion of a pneumatic tire. The tread portion and the sidewall portion thus configured can prevent the compound from leaching to the surface and adversely affecting the appearance, and can prevent the rubber component constituting each from curing due to aging. Moreover, durability, such as the fatigue property of a pneumatic tire, can be improved.

  In the rubber composition of the present invention, a rubber composition containing thermally expandable microcapsules is suitable for constituting a tread portion of a studless tire. Studless tires that use this rubber composition in the tread part can maintain the flexibility of the tread rubber at low temperatures and adhere to the road surface on ice in order to suppress the effects of rubber with aging even after long-term use. It is possible to maintain the frictional force on ice by maintaining the above, and it is possible to obtain a higher frictional force on ice based on the thermally expandable microcapsule.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

Examples 1-3
Six kinds of rubber compositions (Examples 1 to 3 and Comparative Examples 1 to 3) having the composition shown in Table 1 were weighed for the composition components except for the vulcanization accelerator and sulfur, respectively, and a 1.7 L sealed Banbury mixer was used. The mixture was kneaded for 5 minutes, and the master batch was discharged at a temperature of 150 ° C and cooled to room temperature. Thereafter, this master batch was subjected to a 1.7 L hermetic Banbury mixer, and a vulcanization accelerator and sulfur were added and mixed for 2 minutes to prepare a tire rubber composition.

  Using the obtained six types of rubber compositions, the rubber hardness increase rate (aging hardness increase rate) before and after the heat aging test was measured by the following method. Moreover, the workability (oil slip) at the time of mixing of the rubber composition except a vulcanization accelerator and sulfur was measured by the following method.

Aging hardness increase rate Using the obtained tire rubber composition, a test piece vulcanized into a shape of a Rupke sample (a cylindrical shape having a thickness of 12.5 mm and a diameter of 29 mm) was prepared. Each test piece was divided into two groups, and one of them was subjected to air heat aging treatment at 80 ° C. for 120 hours. Using the test specimens before and after the aging treatment, the rubber hardness at a temperature of 20 ° C. was measured by a durometer type A in accordance with JIS K6253. Was used to calculate the rate of increase in rubber hardness (%) accompanying heat aging. The obtained results are shown in Table 1 as an increase in aging hardness with the value of Comparative Example 1 as 100. A smaller index means that the curing of the rubber composition accompanying heat aging is suppressed.

Processability (oil slip)
When blending the ingredients except the vulcanization accelerator, sulfur, aroma oil, grape seed oil and sunflower oil from the rubber composition having the composition shown in Table 1 with a 1.7 L hermetic banbury mixer, aroma oil, grape The processability (oil slip) was evaluated by observing the state of torque increase after adding seed oil and / or sunflower oil. The obtained results were judged according to the following judgment criteria, and the results are shown in Table 1.
A: Torque immediately rises faster than Comparative Example 1.
○: Torque rises as in Comparative Example 1.
△: Compared with Comparative Example 1, it takes a long time for the torque to rise, but there is no problem.
X: Compared with Comparative Example 1, it took time for the torque to rise, and oil slip occurred.

Examples 4-6
Four kinds of rubber compositions (Examples 4 to 6 and Comparative Example 4) having the composition shown in Table 2 were weighed, except for the vulcanization accelerator, sulfur, and thermally expandable microcapsules, respectively. The mixture was kneaded with a 7 L hermetic Banbury mixer for 5 minutes, and the master batch was discharged at a temperature of 150 ° C. and cooled at room temperature. Thereafter, this master batch was subjected to a 1.7 L hermetic Banbury mixer, and a vulcanization accelerator, sulfur, and thermally expandable microcapsules were added and mixed for 2 minutes to prepare a tire rubber composition.

  Using the four types of rubber compositions obtained and the rubber composition of Comparative Example 1, the frictional force on ice was measured by the method described below. The rubber hardness increase rate (aging hardness increase rate) before and after the heat aging test and the processability (oil slip) when mixing the rubber composition excluding the vulcanization accelerator and sulfur were measured by the same method as described above. The results are shown in Table 2.

Friction force on ice A sheet-like rubber piece obtained by vulcanizing each compound was attached to a flat cylindrical base rubber, and the friction coefficient on ice at -1.5 ° C was applied to 5.5 kg / cm with an inside drum type on-ice friction tester. ^3, was measured under the conditions of a drum rotation speed of 25km / h. The obtained results were indexed with the value of Comparative Example 1 being 100, and are shown in Table 2 as the frictional force on ice. The larger this index, the better the frictional force on ice.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, RSS # 3
BR: butadiene rubber, Nipol BR1220 manufactured by Nippon Zeon
Carbon black: Toast carbon carbon seast 6
Silica: Nippon Sil AQ manufactured by Nippon Silica Industry Co., Ltd.
Coupling agent: Silane coupling agent, SI69 manufactured by Degussa
Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. Stearic acid: Beads manufactured by NOF Co., Ltd. Bead stearic acid anti-aging agent: SANTOFLEX 6PPD manufactured by Flexis
Aroma oil: Showa Shell Sekiyu Extract 4 S
Grapeseed oil: Chilean grapeseed oil, edible grape oil manufactured by Catac Planners, natural polyphenol content of 1.3 × 10 ⁻³ wt% (polyphenol content measured by the method described above)
Sunflower oil: Edible sunflower oil manufactured by Showa Sangyo Co., Ltd., heat-expandable microcapsules with a naturally derived polyphenol content of 0.17 × 10 ⁻³ wt%: Microsphere F100 manufactured by Matsumoto Yushi Seiyaku Co., Ltd.
Sulfur: Fine powder sulfur vulcanization accelerator with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd .: Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.

Claims (5)

A rubber composition for tires, comprising 1 to 30 parts by weight of vegetable oil and fat in 100 parts by weight of diene rubber, wherein the vegetable oil and fat contains 0.9 × 10 ⁻³ wt% or more of polyphenol derived from nature.   The tire rubber composition according to claim 1, wherein the vegetable oil is grape seed oil.   The tire rubber composition according to claim 1 or 2, wherein 0.5 to 20 parts by weight of thermally expandable microcapsules is blended with 100 parts by weight of the diene rubber.   A pneumatic tire having a tread portion or a sidewall portion formed of the rubber composition according to claim 1.   A pneumatic tire having a tread portion formed of the rubber composition according to claim 3.