JP6193577B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the rubber composition.

It has been conventionally known that physical properties of a rubber composition can be improved by blending a microfibrillated plant fiber such as cellulose fiber as a filler with the rubber composition. However, since the microfibrillated plant fiber has poor compatibility with the rubber component, there may be a case where a sufficient improvement effect cannot be obtained even if it is blended with the rubber composition.

Patent Document 1 proposes a technique for improving the compatibility with a rubber component by chemically treating the surface of cellulose fibers to introduce a hydrophobic group. In recent years, a method has been proposed in which the pulp is chemically treated with a silane coupling agent having an amino group to improve the compatibility with the rubber component. However, since these methods all require a chemical reaction process, a simpler method is required.

JP 2009-84564 A

The present invention solves the above-mentioned problems and improves the compatibility between the microfibrillated plant fiber and the rubber component by a simple method while suppressing the use of petroleum resources as much as possible, resulting in low fuel consumption, fracture characteristics and handling stability. An object is to provide a rubber composition for a tire that can be improved in a well-balanced manner, and a pneumatic tire produced using the rubber composition.

The present invention relates to a rubber composition for a tire containing a rubber component, a microfibrillated plant fiber, and a terpene resin.

The rubber component preferably contains at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber and modified synthetic rubber.

It is preferable that the microfibrillated plant fiber is cellulose microfibril.

The average fiber diameter of the microfibrillated plant fiber is preferably 10 μm or less.

The content of the microfibrillated plant fiber is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

It is preferable that content of the said terpene-type resin is 1-50 mass parts with respect to 100 mass parts of said rubber components.

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

According to the present invention, a tire rubber composition containing a rubber component, a microfibrillated plant fiber and a terpene resin, and a phase between the microfibrillated plant fiber and the rubber component by a simple method of adding a terpene resin. While improving solubility and reducing energy loss, both rigidity and elongation at break can be achieved. Thereby, it is possible to provide a pneumatic tire with improved fuel economy, fracture characteristics, and steering stability in a well-balanced manner. Further, since the microfibrillated plant fiber is a material that does not use petroleum as a raw material, the amount of petroleum resources used can be reduced and the environment can be considered.

The rubber composition of the present invention includes a rubber component, microfibrillated plant fibers, and a terpene resin. By adding the terpene resin, the adhesiveness at the interface between the rubber component and the microfibrillated plant fiber is improved, and the energy loss at the interface is reduced. Moreover, the contact point in which the microfibrillated plant fibers are entangled with each other is reinforced by the terpene resin, and the breaking strength is improved. These effects can achieve both rigidity and elongation at break while reducing energy loss. Therefore, by using the rubber composition in a tire, it is possible to provide a pneumatic tire with improved fuel economy, fracture characteristics, and steering stability in a well-balanced manner.

Moreover, since the microfibrillated plant fiber is a material that does not use petroleum as a raw material (resource other than petroleum), the amount of petroleum resource used can be reduced.

The rubber component preferably contains at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber and modified synthetic rubber. Examples of natural rubber (NR) include those common in the tire industry, such as TSR20 and RSS # 3. Examples of the modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber, and deproteinized natural rubber. Synthetic rubbers include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-styrene-butadiene copolymer rubber. And chloroprene rubber. Examples of the modified synthetic rubber include those obtained by modifying the ends of the synthetic rubber with polar functional groups. From the viewpoint of versatility and cost, and from the viewpoint of good workability when mixed with microfibrillated plant fibers, rubber components include NR, BR, SBR, IR, IIR and ENR. Preferably, NR and ENR, which are materials derived from non-petroleum resources, are more preferable from the viewpoint of reducing the amount of petroleum resources used and considering the environment.

In the rubber composition of the present invention, the content of NR and ENR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 95% by mass or more. The upper limit of content is not specifically limited, 100 mass% may be sufficient.

As the microfibrillated plant fiber, cellulose microfibril is preferable from the viewpoint that good reinforcing properties can be obtained. Examples of cellulose microfibrils include those derived from natural products such as wood, bamboo, hemp, jute, kenaf, crop residue, cloth, recycled pulp, waste paper, bacterial cellulose, and squirt cellulose.

Although it does not specifically limit as a manufacturing method of a microfibrillated plant fiber, For example, after chemically processing the raw material of the said cellulose microfibril with chemicals, such as sodium hydroxide, a refiner, a twin screw kneader (double screw extruder), Examples of the method include mechanical grinding or beating using a twin-screw kneading extruder, a high-pressure homogenizer, a medium stirring mill, a stone mill, a grinder, a vibration mill, a sand grinder, and the like. In this method, since lignin is separated from the raw material by chemical treatment, microfibrillated plant fibers substantially free of lignin are obtained.

The average fiber diameter of the microfibrillated plant fiber is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less, and particularly preferably 0.5 μm or less from the viewpoint of good rubber reinforcing effect. The lower limit of the average fiber diameter of the microfibrillated plant fiber is not particularly limited, but when mixing the aqueous dispersion of the microfibrillated plant fiber and the rubber component, from the viewpoint of suppressing workability deterioration due to deterioration of drainage. It is preferable that it is 4 nm or more.

The average fiber length of the microfibrillated plant fiber is preferably 5 mm or less, more preferably 1 mm or less, and preferably 1 μm or more, more preferably 50 μm or more. When the average fiber length is less than the lower limit or exceeds the upper limit, there is a tendency similar to the average fiber diameter described above.

The average fiber diameter and average fiber length of microfibrillated plant fibers are image analysis of scanning electron micrographs, image analysis of transmission micrographs, analysis of X-ray scattering data, pore electrical resistance method (Coulter principle method), etc. Can be measured by.

The content of the microfibrillated plant fiber is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 100 parts by mass with respect to 100 parts by mass of the rubber component. Part or less, more preferably 20 parts by weight or less. Within the above range, the rubber reinforcing effect is good, and the yield and workability of various materials in the process of compounding with the rubber component are also good.

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 terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, and aromatics using terpene compounds and aromatic compounds as raw materials. 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 1 part by mass or more, preferably 3 parts by mass or more, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of the rubber component. Within the above range, the microfibrillated plant fiber can be dispersed well, and the fuel economy, breaking characteristics and handling stability can be improved in a well-balanced manner.

In addition to the above components, the rubber composition of the present invention is a compounding agent conventionally used in the rubber industry, such as a filler (carbon black, silica, etc.), a silane coupling agent, a vulcanizing agent, stearic acid, vulcanized. Accelerators, vulcanization accelerators, oils, waxes, anti-aging agents, and the like can be appropriately blended as necessary.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method in which the above components are kneaded with a Banbury mixer, a kneader, an open roll or the like and then vulcanized. In addition, since the microfibrillated plant fiber can be easily dispersed in the rubber component, it is manufactured using a masterbatch obtained by mixing an aqueous dispersion of microfibrillated plant fiber and rubber latex. Is preferred.

The rubber composition of the present invention can be used for tire members, and in particular, can be suitably used for treads and sidewalls.

The pneumatic tire of the present invention is produced by a known method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of each member of the tire at an unvulcanized stage and molded by a normal method on a tire molding machine. After forming an unvulcanized tire by heating, the tire can be manufactured by heating and pressing in a vulcanizer.

The pneumatic tire of the present invention can be suitably used for passenger cars, trucks, buses and the like.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples, Comparative Examples and Reference Examples will be described together.
Natural rubber latex: HYTEX HA (natural rubber latex manufactured by Golden Hope Plantations, solid content: 60% by mass, average particle size: 1 μm)
Microfibrillated plant fiber: Selish KY-100G manufactured by Daicel Chemical Industries, Ltd. (average fiber length: 0.5 mm, average fiber diameter: 0.02 μm, solid content: 10% by mass)
Master batches 1-3: prepared in the following production examples Terpene resin: YS resin PX300N (terpene resin having a softening point of 30 ° C.) manufactured by Yasuhara Chemical Co., Ltd.
Anti-aging agent: NOCRACK 6C manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate zinc oxide: Zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Ouchi Shinsei Chemical NOCELLER DM manufactured by Kogyo Co., Ltd.

<Production Example 1: Preparation of Masterbatch 1>
In accordance with the composition shown in Table 1, the microfibrillated plant fiber was stirred and dispersed in water at 24,000 rpm for 1 hour using a high speed homogenizer (IKA's batch homogenizer T65D Ultra Turrax (Ultraturrax T25)). Natural rubber latex was added and the mixture was further stirred and dispersed for 30 minutes. The obtained mixed solution was coagulated with a 5 mass% formic acid aqueous solution, washed with water, and dried in a heating oven at 40 ° C to obtain a master batch 1.

<Production Example 2: Preparation of Masterbatch 2>
According to the composition of Table 1, a master batch 2 was obtained in the same manner as the master batch 1.

<Production Example 3: Preparation of Masterbatch 3>
The natural rubber latex was coagulated as it was with a 5% by mass aqueous formic acid solution, washed with water, and then dried in a heating oven at 40 ° C. to obtain a master batch 3.

<Preparation of vulcanized rubber composition>
Using a 250 cc internal mixer ripened to 135 ° C. in accordance with the composition of Table 2, the vulcanization accelerator and chemicals other than sulfur and various master batches were kneaded for 3 minutes under the condition of 88 rpm, and then kneaded rubber. The vulcanization accelerator and sulfur were added with a 6-inch open roll under the conditions of 60 ° C. and 24 rpm, and kneaded for 5 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-heated at 150 ° C. to obtain vulcanized rubber compositions corresponding to Examples, Comparative Examples and Reference Examples.

<Examples, comparative examples and reference examples>
The following evaluation was performed using the vulcanized rubber composition produced by the above method. Each index in the characteristic data shown in Table 2 was calculated by the following formula using Reference Example 1 as a reference composition.

(Tensile test)
100% tensile stress was measured according to JIS K6251 “vulcanized rubber and mature plastic rubber—determining tensile properties”, and a 100% tensile stress index was calculated according to the following formula. The larger the 100% tensile stress index, the better the vulcanized rubber composition is reinforced, the higher the rigidity of the rubber, and the better the fracture characteristics.
100% tensile stress index = (100% tensile stress of each formulation) / (100% tensile stress of standard formulation) × 100

(Maneuvering stability index and rolling resistance index)
A test specimen for measurement was cut out from a 2 mm rubber slab sheet of the vulcanized rubber composition prepared by the above-described method, and the temperature was 70 ° C. and the initial strain was 10% using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho). Measure the E ^* (complex modulus) and tan δ (loss tangent) of each test specimen under the conditions of 2% dynamic strain and 10 Hz frequency, and calculate the steering stability index and rolling resistance index using the following formulas: Calculated. The larger the steering stability index, the better the steering stability, and the larger the rolling resistance index, the lower the rolling resistance and the better the fuel efficiency.
Steering stability index = (E ^{* of} each formulation) / (E ^{* of} reference formulation) × 100
Rolling resistance index = (tan δ of reference formulation) / (tan δ of each formulation) × 100

From Table 2, it was confirmed that the combined use of the microfibrillated plant fiber and the terpene resin synergistically improved fuel economy, fracture characteristics, and handling stability, and these performances were obtained in a high level and in a well-balanced manner.

Claims (6)

A method for producing a rubber composition for a tire comprising a rubber component, a microfibrillated plant fiber and a terpene resin ,
The microfibrillated plant fiber is a cellulose microfibril having an average fiber diameter of 10 μm or less and an average fiber length of 1 μm to 5 mm,
The manufacturing method of the rubber composition for tires which uses the masterbatch obtained by mixing the dispersion liquid of the said microfibrillated plant fiber, and rubber latex . The method for producing a rubber composition for a tire according to claim 1, wherein the rubber component includes at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber, and modified synthetic rubber. The method for producing a rubber composition for a tire according to claim 1 or 2 , wherein the content of the microfibrillated plant fiber is 1 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The method for producing a tire rubber composition according to any one of claims 1 to 3 , wherein the content of the terpene resin is 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The method for producing a rubber composition for a tire according to any one of claims 1 to 4 , wherein the terpene resin has a softening point of 10 to 80 ° C. The manufacturing method of the pneumatic tire which produces a pneumatic tire using the rubber composition obtained by the manufacturing method in any one of Claims 1-5 .