JP2010013553A - Rubber composition for tire sidewall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire sidewall, which allows the tire sidewall to be improved in low heat generation properties while keeping mechanical characteristics thereof without increasing the manufacturing cost thereof drastically. <P>SOLUTION: The rubber composition for the tire sidewall is obtained by blending 30-100 parts weight reinforcing filler containing ≥10 parts weight carbon black having 20-130 m<SP>2</SP>/g nitrogen adsorption specific surface area in 100 parts weight diene rubber and further incorporating 1-20 parts weight oil-extended white clay in the reinforcing filler-blended diene rubber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire sidewall, and more particularly, to a rubber composition for a tire sidewall that is improved in low heat generation while maintaining mechanical properties without causing a significant cost increase. .

  Of the constituent members of the pneumatic tire, the sidewall easily generates heat because of a large amount of deformation applied during traveling. If the amount of generated heat is large, the rolling resistance increases and the fuel consumption rate deteriorates. Further, since the rubber member is thermally deteriorated due to the heat generated from the sidewalls, the fatigue resistance (durability) may be reduced. For this reason, in general, a rubber composition for a tire sidewall is used as a reinforcing carbon black having a large particle diameter and a relatively small nitrogen adsorption specific surface area so as to reduce the heat build-up of the rubber composition. However, there is a problem that mechanical properties such as tensile elongation at break decrease.

Patent Document 1 describes that carbon black having a specific nitrogen adsorption specific surface area and the like is blended with a diene rubber containing a specific butadiene rubber in order to reduce heat generation without impairing the mechanical properties of the tire sidewall. is suggesting. However, since this rubber composition uses a special butadiene rubber, there is a problem that the production cost increases. For this reason, in a rubber composition for a tire sidewall using carbon black alone as a reinforcing filler, it is still a problem to improve low heat generation while maintaining mechanical characteristics.
JP 2006-63284 A

  An object of the present invention is to provide a rubber composition for a tire sidewall that improves low heat buildup while maintaining mechanical characteristics without causing a significant increase in cost.

The rubber composition for a tire sidewall of the present invention that achieves the above object comprises a reinforcing filler containing 10 parts by weight or more of carbon black having a nitrogen adsorption specific surface area of 20 to 130 m ² / g with respect to 100 parts by weight of a diene rubber. A rubber composition containing 30 to 100 parts by weight, characterized in that the reinforcing filler contains 1 to 20 parts by weight of oil-extended white clay.

  The diene rubber is preferably composed of 20 to 80% by weight of natural rubber or isoprene rubber and 80 to 20% by weight of butadiene rubber and / or styrene butadiene rubber.

  The oil-extended clay may contain 20 to 60% by weight of oil.

The rubber composition for a tire sidewall of the present invention is 30 to 100 parts by weight of a reinforcing filler containing 10 parts by weight or more of carbon black having a nitrogen adsorption specific surface area of 20 to 130 m ² / g with respect to 100 parts by weight of a diene rubber. Since 1 to 20 parts by weight of oil-extended clay is contained in the reinforcing filler for the blended rubber composition, the carbon black has a nitrogen adsorption specific surface area of 20 to 130 m ² / By using a material in the range of g, exothermic property is reduced, and by adding the above amount of oil-extended white clay, mechanical properties such as tensile elongation at break can be maintained. Also, oil-extended white clay is waste white clay after it has been used for lubricating oil refining treatment, etc., so it is possible to reduce production costs by effectively using what was conventionally disposed of as industrial waste. .

  The diene rubber used in the rubber composition for a tire sidewall of the present invention may be any rubber that can be blended in a tread rubber compound, such as natural rubber, isoprene rubber, butadiene rubber, various styrene butadiene rubbers, and acrylonitrile butadiene. Examples thereof include rubber and butyl rubber. These diene rubbers may be used alone or in a plurality of types.

  The diene rubber of the present invention is preferably composed of natural rubber or isoprene rubber and butadiene rubber and / or styrene butadiene rubber. The blending amount of natural rubber or isoprene rubber is preferably 20 to 80% by weight, and more preferably 20 to 50% by weight. When the blending amount of natural rubber or isoprene rubber is less than 20% by weight, the strength of the rubber composition cannot be obtained sufficiently. When the blending amount of natural rubber or isoprene rubber exceeds 80% by weight, fatigue resistance is lowered.

  Moreover, any one or both of butadiene rubber and styrene butadiene rubber may be used. The blending amount of butadiene rubber and / or styrene butadiene rubber is preferably 80 to 20% by weight, and more preferably 80 to 50% by weight. When the blending amount of butadiene rubber and / or styrene butadiene rubber is less than 20% by weight, sufficient fatigue resistance cannot be obtained. If the blending amount of butadiene rubber and / or styrene butadiene rubber exceeds 80% by weight, the strength of the rubber composition becomes insufficient.

  The rubber composition for a tire sidewall of the present invention contains 30 to 100 parts by weight, preferably 30 to 80 parts by weight of a reinforcing filler containing at least 10 parts by weight of carbon black with respect to 100 parts by weight of a diene rubber. When the compounding amount of the reinforcing filler is less than 30 parts by weight, the reinforcing effect of the rubber composition becomes insufficient. When the reinforcing filler exceeds 100 parts by weight, heat generation is deteriorated and workability becomes difficult.

  The compounding amount of carbon black is 10 parts by weight or more with respect to 100 parts by weight of the diene rubber, and preferably 30 to 80 parts by weight. Carbon black is the main component of the reinforcing filler, and the blending ratio in the reinforcing filler is preferably 50% by weight or more, more preferably 70 to 100% by weight. When the blending ratio of carbon black is less than 50% by weight, it becomes difficult to ensure the mechanical strength necessary for the rubber composition for sidewalls.

The nitrogen adsorption specific surface area of the carbon black used in the present invention is 20 to 130 m ² / g, preferably 20 to 80 m ² / g. When the nitrogen adsorption specific surface area of carbon black is less than 20 m ² / g, tensile elongation at break is insufficient. When the nitrogen adsorption specific surface area exceeds 130 m ² / g, the exothermic property cannot be sufficiently reduced. In the present invention, the nitrogen adsorption specific surface area of carbon black is measured according to JIS K6217.

  In the present invention, the exothermic property can be improved while maintaining the mechanical characteristics necessary for the tire sidewall by blending the oil-extended clay with the carbon black blended rubber composition. Also, by blending oil-extended clay, rubber processability can be improved because the viscosity of the rubber composition is lowered. This is because the oil contained in the oil-extended white clay improves the plasticity of the rubber composition and improves the dispersibility of the carbon black, and the acid white clay or the activated white clay in the oil-extended white clay improves the physical property balance of the rubber composition. it is conceivable that. Moreover, in order to prevent carbon black from adsorbing an anti-aging agent or the like, the heat resistance of the rubber composition can be improved.

  The amount of oil-extended clay is 1 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the diene rubber in the reinforcing filler. If the oil-extended clay is less than 1 part by weight, the exothermic property cannot be improved while maintaining the mechanical properties. Further, the viscosity of the rubber composition cannot be lowered. If the oil-extended clay exceeds 20 parts by weight, the tensile elongation at break will deteriorate.

  In the present invention, oil-extended clay refers to removal of unnecessary components such as unsaturated hydrocarbons, resins, oxygen, sulfur compounds and water contained in various petroleum products, semi-finished products, petrochemical raw materials, etc. Used acid clay or activated clay used for decolorization. Conventionally, oil-extended clay has been disposed of as industrial waste after being used for petroleum product refining treatment, etc., but by using this effectively, the production cost of rubber compositions for tire sidewalls can be reduced. be able to.

Acid clay is a white clay mainly composed of montmorillonite and containing a small amount of cristobalite. Active clay is adsorbed by acid treatment of acid clay or natural clay (clay) with natural adsorption performance. White clay with increased performance. The chemical components of the acid clay and the activated clay are preferably SiO ₂ of 50% by weight or more, more preferably 75 to 85% by weight. When the SiO ₂ content is less than 50% by weight, the strength of the rubber composition is lowered.

  The oil species contained in the oil-extended clay is not particularly limited, and examples thereof include mineral oil base oil, kerosene, light oil, jet fuel, various chemical products, and solvents. Of these, mineral oil base oils are preferred. The oil content in the oil-extended clay is preferably 20 to 60% by weight, and more preferably 30 to 40% by weight. If the oil content in the oil-extended clay is less than 20% by weight, the processability is lowered. When the oil content exceeds 60% by weight, the white clay content is small and a predetermined effect cannot be obtained.

  The rubber composition for a tire sidewall of the present invention may contain other fillers, and examples thereof include silica, clay, calcium carbonate, talc, mica, aluminum hydroxide, magnesium carbonate and the like. . The blending method and blending amount of these fillers can be the conventional general blending method and blending amount as long as the object of the present invention is not violated.

  In addition, the rubber composition for tire sidewalls may contain various additives generally used in rubber compositions such as a vulcanization or crosslinking agent, an anti-aging agent, a plasticizer, a softening agent, and a processing aid. Can do. Such additives can be kneaded by a general method to form a rubber composition, which can be used for vulcanization or crosslinking. The blending amount of these additives can be a conventional general blending amount as long as the object of the present invention is not violated.

  The rubber composition for a tire sidewall obtained according to the present invention is preferably used for a sidewall of a pneumatic tire, and the pneumatic tire provided with the sidewall made of the rubber composition for a tire sidewall of the present invention, Since the exothermic property can be improved while maintaining the mechanical characteristics, the durability is excellent. Moreover, since it can implement without raising the raw material cost of the rubber composition for tire sidewalls, production cost can be suppressed.

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

  Among 11 types of rubber compositions (Examples 1 to 6, Comparative Examples 1 to 5) comprising the compositions shown in Tables 1 and 2, weighed the ingredients except for sulfur and the vulcanization accelerator, and 1.7 L The mixture was kneaded for 5 minutes in a closed Banbury mixer, and the master batch was discharged at a temperature of 150 ° C. and cooled at room temperature. This master batch was subjected to a 1.7 L hermetic banbury mixer, and sulfur and a vulcanization accelerator were weighed and mixed to obtain each rubber composition. In addition, 11 types of rubber compositions (Examples 1 to 6 and Comparative Examples 1 to 5) have carbon black, the total amount of clay and clay in the oil-extended clay to be 70 parts by weight, and aroma oil, A rubber composition having a common condition that the total amount of the oil in the oil-extended clay is 10 parts by weight was used.

  The obtained 11 kinds of rubber compositions (Examples 1 to 6, Comparative Examples 1 to 5) were subjected to dynamic viscoelasticity, heat aging resistance, and tensile break elongation tests in predetermined molds, respectively. A vulcanized sheet was prepared by vulcanization at 150 ° C. for 30 minutes, and the test was performed by the method shown below.

Dynamic viscoelasticity (tan δ)
The dynamic viscoelasticity of the obtained vulcanized sheet was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, and tan δ at a temperature of 60 ° C. was calculated. . The obtained results are shown in Tables 1 and 2 as an index with the value of Comparative Example 1 as 100. The smaller the index of tan δ (60 ° C.) at a temperature of 60 ° C., the better the exothermic property.

Heat aging resistance As the heat aging resistance, the rate of change in tensile rupture strength before and after heat aging treatment was evaluated. First, a tensile test piece according to JIS K6251 was prepared from the obtained vulcanized sheet, and the test piece was divided into two, one with and without heat aging treatment. The heat aging treatment was performed under conditions of 70 ° C. and 168 hours. In the tensile test, the breaking strength was measured at a pulling speed of 500 mm / min. The rate of change in tensile rupture strength before and after heat aging treatment was calculated as (tensile rupture strength after heat aging treatment / tensile rupture strength before heat aging treatment), and the result obtained is the value of Comparative Example 1 being 100. And is shown in Tables 1 and 2. It means that heat resistance aging property is excellent, so that this index | exponent is large.

Tensile elongation at break A tensile test piece based on JIS K6251 was prepared using the obtained vulcanized sheet. The test piece was subjected to a tensile test at a tensile speed of 500 mm / min in accordance with JIS K6251 to measure elongation at break. The obtained results are shown in Tables 1 and 2 as an index with Comparative Example 1 as 100. It means that the larger the index, the better the tensile elongation at break.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, STR20
BR: butadiene rubber, Nipol BR1220 manufactured by Nippon Zeon
SBR: styrene butadiene rubber, Nipol 1502 manufactured by Nippon Zeon
CB-1: carbon black, show black N330T manufactured by Cabot Japan (nitrogen adsorption specific surface area of 65 m ² / g)
CB-2: Carbon black, HTC # G (Nitrogen adsorption specific surface area 27 m ² / g) manufactured by Nippon Kayaku Carbon
CB-3: carbon black, Toast carbon company's seast 9M (nitrogen adsorption specific surface area 150 m ² / g)
Oil-exposed white clay: Sample made by Sun Oil Co., Ltd.
Clay: T clay aroma oil manufactured by Nippon Talc Co., Ltd .: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Zinc Hana: Zinc Oxide Type 3 manufactured by Shodo Chemical Industry Co., Ltd. Stearic Acid: Beads manufactured by NOF Co., Ltd. Beads Tear Acid Antiaging Agent: SANTOFLEX 6PPD manufactured by Flexis
Paraffin wax: Sannok Sulfur manufactured by Ouchi Shinsei Chemical Co., Ltd .: Fine powder sulfur vulcanization accelerator with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd .: SANTOCURE TBBS manufactured by Flexis

Claims (4)

A rubber composition comprising 30 to 100 parts by weight of a reinforcing filler containing 10 parts by weight or more of carbon black having a nitrogen adsorption specific surface area of 20 to 130 m ² / g with respect to 100 parts by weight of a diene rubber, A rubber composition for a tire sidewall, in which 1 to 20 parts by weight of oil-extended white clay is contained in the agent.   The rubber composition for a tire sidewall according to claim 1, wherein the diene rubber comprises 20 to 80% by weight of natural rubber and 80 to 20% by weight of butadiene rubber and / or styrene butadiene rubber.   The rubber composition for a tire side wall according to claim 1, wherein the diene rubber comprises 20 to 80% by weight of isoprene rubber and 80 to 20% by weight of butadiene rubber and / or styrene butadiene rubber.   The rubber composition for a tire sidewall according to claim 1, 2 or 3, wherein the oil-extended clay contains an oil component in a proportion of 20 to 60% by weight.