JP2014205748A - Rubber composition for sidewall and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for sidewalls which can improve resistance to crack initiation, ozone resistance and durability in a balanced manner while reducing an amount of use of components derived from oil resources, and a pneumatic tire having a sidewall prepared using the rubber composition.SOLUTION: This invention relates to a rubber composition for sidewalls comprising rubber components, vegetable oil and terpene-based resin. Preferably, the oleic acid content in fatty acid 100 mass% constituting the vegetable oil is 85 mass% or more.

Description

The present invention relates to a rubber composition for a sidewall, and a pneumatic tire having a sidewall produced using the rubber composition.

As a plasticizer or softener for rubber, aromatic oils excellent in compounding properties are generally used. However, aromatic oils contain a polycyclic aromatic component and have a carcinogenic problem. In addition, there are problems of fossil resource depletion in the future and a heavy load on the environment.

Then, the example which mix | blended vegetable oil is proposed as a substitute of aromatic oil (refer patent document 1). However, there is room for improvement in that it does not show the same or better blending properties as aromatic oils.

JP 2005-263156 A

The present invention solves the above-mentioned problems, and reduces the amount of components derived from petroleum resources, while improving the crack resistance, ozone resistance and durability in a balanced manner, and the rubber It aims at providing the pneumatic tire which has a side wall produced using the composition.

The present invention relates to a rubber composition for a sidewall containing a rubber component, a vegetable oil and a terpene resin.

The content of oleic acid in 100% by mass of the constituent fatty acid of the vegetable oil is preferably 85% by mass or more.

The vegetable oil is preferably produced by a genetically modified plant.

The vegetable oil is preferably derived from a plant in which the action of at least one enzyme selected from the group consisting of Δ12-desaturase and Δ6-desaturase encoded by Fad2 is suppressed.

The content of the terpene resin with respect to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more.

The present invention also relates to a pneumatic tire having a sidewall produced using the rubber composition.

According to the present invention, since it is a rubber composition for a sidewall containing a rubber component, a vegetable oil, and a terpene resin, crack resistance is reduced while reducing the amount of aromatic oil that is a component derived from petroleum resources. It is possible to provide a pneumatic tire in which the generation property, ozone resistance and durability are improved in a well-balanced manner.

The rubber composition of the present invention contains a rubber component, a vegetable oil, and a terpene resin. By using vegetable oil and terpene resin in combination, crack resistance and durability can be synergistically improved while maintaining good ozone resistance. In addition, since vegetable oil and terpene resin are both materials derived from non-petroleum resources, the use of these as softeners reduces the amount of aromatic oils that are components derived from petroleum resources. can do.

(Rubber component)
Although it does not specifically limit as a rubber component, Rubber | gum derived from resources other than petroleum, such as natural rubber (NR) and epoxidized natural rubber (ENR), can be used conveniently.

When the rubber composition of the present invention contains NR, the content of NR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 80% by mass or less. More preferably, it is 70 mass% or less. Within the above range, crack resistance, ozone resistance and durability can be obtained in a high level and in a well-balanced manner.

The epoxidation rate of ENR is preferably 5 mol% or more, more preferably 10 mol% or more. If it is less than 5 mol%, the modification effect on the rubber composition tends to be small. The epoxidation rate of ENR is preferably 80 mol% or less, more preferably 60 mol% or less. If it exceeds 80 mol%, the polymer component tends to gel easily.
The epoxidation rate means an average value of the ratio of the number of epoxidized out of the total number of carbon-carbon double bonds in the natural rubber component before epoxidation. For example, titration analysis or nuclear magnetic resonance (NMR) ) Required by analysis.

When the rubber composition of the present invention contains ENR, the content of ENR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 80% by mass or less. More preferably, it is 70 mass% or less. Within the above range, crack resistance, ozone resistance and durability can be obtained in a high level and in a well-balanced manner.

If desired, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR Synthetic rubber such as) can also be used. From the reason that good crack resistance, ozone resistance and durability are obtained, it is preferable to use BR as the synthetic rubber.

When the synthetic rubber is used, it is preferable to use a synthetic rubber produced using a renewable bio-derived raw material as a monomer in consideration of future oil depletion and environmental considerations. For example, in the case of BR, a synthetic rubber produced from such a bio-derived raw material can be obtained by a method in which a catalyst is allowed to act on bioethanol to obtain butadiene, which is then polymerized.

When the rubber composition of the present invention contains BR, the content of BR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 80% by mass or less. More preferably, it is 70 mass% or less. Within the above range, crack resistance, ozone resistance and durability can be obtained in a high level and in a well-balanced manner.

(Vegetable oil)
The vegetable oil is not particularly limited, and those commonly used in the tire industry such as canola oil, castor oil, cottonseed oil, linseed oil, and rapeseed oil can be used. Among these, it is preferable to use canola oil.

Vegetable oils are basically composed of triacylglycerol (TAG) molecules, which are composed of three fatty acid chains esterified to the glycerol skeleton. Vegetable oils are mainly used as edible oils, and those rich in oleic acid are required for the purpose of reducing highly unsaturated fatty acids due to nutritional requirements. Thus, studies have been conducted on metabolic pathways for oleic acid synthesis in plants and genes encoding enzymes for these pathways. As a result, it was observed in some plants that the content of oleic acid was increased by suppressing the action of Δ12-desaturase encoded by the gene Fad2. Based on this result, sunflower oil and soybean oil containing oleic acid at a high content have been developed by genetically modified plants and are already on the market.

Thus, a vegetable oil produced from a genetically modified plant (hereinafter also referred to as a genetically modified vegetable oil) has different characteristics from a vegetable oil obtained from a normal plant. By blending the genetically modified vegetable oil, the effect of improving crack resistance, ozone resistance and durability can be enhanced.

For gene modification, a known transformation method used when a gene is introduced into a cell can be employed. For example, Agrobacterium into which a vector such as a plasmid containing a DNA constituting a target gene (target gene) is introduced A method of introducing a gene by infecting a genus fungus into a plant cell (Agrobacterium method), a method of shooting a gold particle carrying a DNA constituting a target gene into a cell by a particle gun (particle gun method), a target gene Examples include a method (electroporation method) in which a hole is made in a cell membrane by a voltage in a solution containing a vector into which is incorporated, and the vector is introduced therefrom.

The type of plant for modifying the gene is not particularly limited, but rapeseed (canola), corn, soybean, sunflower and cotton are preferable, and canola is more preferable because of high productivity.

There are no particular restrictions on the gene modification sites in the plant, but Δ12-desaturase and Δ6-desaturase encoded by Fad2 can be used because the content of oleic acid is high and the content of linoleic acid and linolenic acid can be reduced. It is preferable that the action of at least one enzyme selected from the group consisting of is suppressed.

The content of oleic acid in 100% by mass of the constituent fatty acids of the vegetable oil is preferably 85% by mass or more. If it is less than 85% by mass, the effect of improving crack resistance, ozone resistance and durability tends to be low. The content of oleic acid is preferably 95% by mass or less, more preferably 90% by mass or less. When it exceeds 95% by mass, the reversion resistance is liable to deteriorate.

The content of linoleic acid in 100% by mass of the constituent fatty acid of the vegetable oil is preferably 15% by mass or less, more preferably 8% by mass or less. When it exceeds 15 mass%, there exists a tendency for workability and vulcanization-resistant return property to deteriorate. Although the minimum of content of linoleic acid is not specifically limited, Preferably it is 1 mass% or more.

The content of linolenic acid in 100% by mass of the constituent fatty acid of the vegetable oil is preferably 10% by mass or less, more preferably 5% by mass or less. If it exceeds 10% by mass, the workability and vulcanization resistance tend to deteriorate. Although the minimum of content of linolenic acid is not specifically limited, Preferably it is 1 mass% or more.

The fatty acid composition (contents of oleic acid, linoleic acid, and linolenic acid) can be measured by GLC (gas-liquid chromatography).

The content of the vegetable oil is preferably 5 to 40 parts by mass, more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, a sufficient softening effect tends not to be obtained, and if it exceeds 40 parts by mass, the workability tends to deteriorate.

Since the rubber composition of the present invention uses vegetable oil, the amount of oil derived from petroleum resources such as aromatic oils can be reduced while ensuring good compounding properties. The content of vegetable oil in 100% by mass of total oil is preferably 95% by mass or more, more preferably 99% by mass or more, and still more preferably 100% by mass. The content of oil derived from petroleum resources is preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0% by mass (substantially not contained) in 100% by mass of total oil. .

(Terpene resin)
The terpene resin is a resin polymerized using a terpene compound as a main monomer. Terpene compounds are generally polymers of isoprene (C ₅ H ₈ ), and terpenes classified as monoterpenes (C ₁₀ H ₁₆ ), sesquiterpenes (C ₁₅ H ₂₄ ), diterpenes (C ₂₀ H ₃₂ ), and the like. A compound having a basic skeleton, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-ferrandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1 , 4-cineole, α-terpineol, β-terpineol, γ-terpineol, camphene, tricyclene, sabinene, paramentadienes, and carenes.

As a method for obtaining a terpene compound, in addition to obtaining directly from plant essential oils obtained from leaves, trees, roots and the like of plants, a case where the terpene compound is produced by a genetically modified microorganism incorporating a gene encoding a terpene compound synthase is also included.

Examples of the terpene resin include aromatic terpene compounds and aromatic compounds in addition to terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, and the like. Modified terpene resins, terpene phenol resins using terpene compounds and phenolic compounds as raw materials, hydrogenated terpene resins obtained by hydrogenating terpene resins, and the like can be used. Here, as an aromatic compound used as the raw material of the aromatic modified terpene resin, for example, styrene, α-methylstyrene, vinyl toluene, divinyl toluene and the like can be mentioned, and as a phenol compound used as a raw material of the terpene phenol resin, Examples include phenol, bisphenol A, cresol, xylenol and the like.

The terpene resin is preferably a terpene resin, more preferably an α-pinene resin and a β-pinene resin, from the viewpoint that the effects of the present invention can be obtained satisfactorily.

The softening point of the terpene resin is preferably 80 ° C. or lower, more preferably 60 ° C. or lower, and still more preferably 40 ° C. or lower. If it exceeds 80 ° C., it tends to be difficult to disperse during kneading. The softening point of the terpene resin is preferably 10 ° C. or higher, more preferably 20 ° C. or higher. If it is less than 10 ° C., the working efficiency tends to deteriorate.
In the present invention, the softening point is 1.96 MPa with a plunger while heating 1 g of resin as a sample at a heating rate of 6 ° C./min using a flow tester (manufactured by Shimadzu Corporation, CFT-500D). A load was applied, the nozzle was extruded from a nozzle having a diameter of 1 mm and a length of 1 mm, and the amount of plunger drop of the flow tester was plotted against the temperature.

The content of the terpene resin is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, a synergistic improvement effect due to the combined use with the vegetable oil may not be obtained, and the tackiness of the rubber composition may be lowered, and the processability may be deteriorated. Although the upper limit of the content of the terpene resin is not particularly limited, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less.

(Filler)
The rubber composition of the present invention may further contain a reinforcing agent (filler). The filler is not particularly limited, and silica, carbon black and the like can be used. Especially, it is preferable to use a silica from the point that the effect of this invention is exhibited notably. A rubber composition containing silica (hereinafter also referred to as silica compounding system) is usually more resistant to cracking and durability than a rubber composition containing carbon black (hereinafter also referred to as carbon black compounding system). However, by using a vegetable oil and a terpene resin in combination, the crack resistance and durability of the silica compounding system can be made equivalent to those of the carbon black compounding system.

Specific examples of silica include those prepared by a wet method or a dry method. Specific examples of carbon black include HAF, ISAF, and SAF.

When the rubber composition of the present invention contains silica, the content of silica is preferably 15 parts by mass or more, more preferably 30 parts by mass or more, and preferably 150 parts by mass with respect to 100 parts by mass of the rubber component. It is 100 parts by mass or less, more preferably 100 parts by mass or less. Within the above range, crack resistance, ozone resistance and durability can be obtained in a high level and in a well-balanced manner.

When the rubber composition of the present invention contains carbon black, the carbon black content is preferably at least 15 parts by mass, more preferably at least 30 parts by mass, and preferably at least 100 parts by mass of the rubber component. Is 150 parts by mass or less, more preferably 100 parts by mass or less. Within the above range, crack resistance, ozone resistance and durability can be obtained in a high level and in a well-balanced manner.

Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited as long as it is conventionally used in the tire field. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) Examples thereof include tetrasulfide, bis (2-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltriethoxysilane, and 2-mercaptoethyltrimethoxysilane, and these can be used alone or in any combination. . Among these, bis (3-triethoxysilylpropyl) disulfide, bis (3-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltrimethyl are preferred because the reinforcing effect and processability of the silane coupling agent are good. It is preferable to use ethoxysilane, and it is more preferable to use bis (3-triethoxysilylpropyl) disulfide from the viewpoint that processability is particularly good.
The content of the silane coupling agent is preferably 4 to 12 parts by mass with respect to 100 parts by mass of silica.

(Other materials)
In addition to the above components, the rubber composition of the present invention may contain compounding agents conventionally used in the tire industry, such as waxes, anti-aging agents, sulfur, vulcanization accelerators, zinc oxide, stearic acid and the like as necessary. Can be appropriately blended.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, kneader, open roll or the like and then vulcanizing.

The rubber composition of the present invention is used for tire sidewalls.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as required is extruded according to the shape of the sidewall of the tire at an unvulcanized stage, and molded by a normal method on a tire molding machine, Bonding together with other tire members forms an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce the pneumatic tire of the present invention.

The pneumatic tire of the present invention can be suitably used as a tire for passenger cars.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described.
NR: SIR20
ENR: ENR50 (epoxidation rate: 50 mol%) manufactured by Kungpu Langurs
BR: BR150B manufactured by Ube Industries, Ltd.
Wax: Ozoace 0355 manufactured by Nippon Seiki Co., Ltd.
Carbon black: N220 manufactured by Cabot Japan
Silica: Ultrasil VN3 manufactured by Degussa
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Vegetable oil 1: Natreon canola oil manufactured by Dow AgroSciences (genetically modified vegetable oil, oleic acid content: 70 mass%, linoleic acid content: 18 mass%, linolenic acid content: 7 mass%)
Vegetable oil 2: Natreon canola oil manufactured by Dow AgroSciences (genetically modified vegetable oil, oleic acid content: 85 mass%, linoleic acid content: 8 mass%, linolenic acid content: 4 mass%)
Terpene resin: YS resin PX300N (terpene resin having a softening point of 30 ° C.) manufactured by Yasuhara Chemical Co., Ltd.
Process oil: Aroma oil manufactured by JX Nippon Oil & Energy Co., Ltd. Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Sulfur manufactured by Nippon Oil Co., Ltd. Powdered sulfur vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfanamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.

<Examples and Comparative Examples>
Using a 1.7-L Banbury mixer manufactured by Kobe Steel, Inc., out of the chemicals in the blending amounts shown in Table 1, other than sulfur and vulcanization accelerator were charged so that the filling rate was 58%. The mixture was kneaded for 3 to 8 minutes under the condition of a rotational speed of 80 rpm until the indicated temperature of the kneader reached 140 ° C. Silica was added in two portions. Sulfur and a vulcanization accelerator were added to this mixture and kneaded for 3 minutes at 50 ° C. using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was molded into a size necessary for the following evaluation, and press vulcanized at 160 ° C. for 20 minutes to obtain vulcanized rubber compositions of Examples and Comparative Examples.
Moreover, the tire for a test was obtained by shape | molding the obtained unvulcanized rubber composition in the shape of a side wall, bonding with another tire member, and vulcanizing at 160 degreeC for 20 minute (s).

(Constant stretch fatigue test (measurement of crack resistance))
Using a No. 3 dumbbell (vulcanized rubber composition) composed of the obtained vulcanized rubber composition, a constant strain repeated extension test was performed under the conditions of a maximum strain of 50% and a frequency of 5 Hz without introducing an initial crack. It was. This was repeated 10 million times, and the broken piece was marked with ×, the cracked or scratched mark was marked with Δ, and the broken piece was marked with ○.

(Measurement of ozone resistance)
The obtained vulcanized rubber composition was subjected to a dynamic ozone deterioration test based on JIS K6259 “Vulcanized rubber and thermoplastic rubber—How to obtain ozone resistance”, and the frequency of reciprocating motion was 0.5 ± 0.025 Hz. The ozone resistance was evaluated by observing the state of cracks after testing for 48 hours under conditions of an ozone concentration of 50 ± 5 pphm, a test temperature of 40 ° C., and a tensile strain of 20 ± 2%. The evaluation method represented the number and size of cracks according to the method described in JIS. Note that the alphabet (A, B, and C) indicates that A indicates that the number of cracks is small and C indicates that the number of cracks is large, and the larger the number, the larger the size of the crack.

(Durability measurement)
Using a drum (outer diameter: 1.7 m), the manufactured test tire was subjected to rim (15 × 6.00 JJ), load (6.96 kN), internal pressure (150 kPa), speed (80 km / h). The load was applied, and the vehicle was continuously run from the sidewall portion until a crack occurred in the tread portion, and the distance when the crack occurred (crack generation distance) was measured. Then, the crack generation distance of each formulation was indicated by an index according to the following calculation formula. It shows that it is excellent in durability, so that an index | exponent is large.
(Durability Index) = (Crack generation distance of each formulation) / (Crack generation distance of Comparative Example 2) × 100

From Table 1, the Example which mix | blended vegetable oil and the terpene series resin compared with the comparative example containing only any of vegetable oil and the terpene series resin, while maintaining favorable ozone resistance, crack generation resistance and durability Sexually improved. In addition, Examples 2, 4, 6, and 8 in which the vegetable oil 2 was blended exhibited performance superior to those in Examples 1, 3, 5, and 7 in which the vegetable oil 1 was blended.

Claims (6)

A rubber composition for a side wall comprising a rubber component, a vegetable oil and a terpene resin. The rubber composition for a sidewall according to claim 1, wherein the content of oleic acid in 100% by mass of the constituent fatty acid of the vegetable oil is 85% by mass or more. The rubber composition for a sidewall according to claim 1 or 2, wherein the vegetable oil is produced by a genetically modified plant. The sidewall according to any one of claims 1 to 3, wherein the vegetable oil is derived from a plant in which the action of at least one enzyme selected from the group consisting of Δ12-desaturase and Δ6-desaturase encoded by Fad2 is suppressed. Rubber composition. The rubber composition for a sidewall according to any one of claims 1 to 4, wherein a content of the terpene-based resin with respect to 100 parts by mass of the rubber component is 0.5 parts by mass or more. The pneumatic tire which has a side wall produced using the rubber composition in any one of Claims 1-5.