JP2013194088A - Rubber composition for tire, production method of the same, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, a production method of the composition, and a pneumatic tire manufactured by using the rubber composition, in which compatibility between a microfibril vegetable fiber and a rubber component is improved by a simple process while suppressing use of petroleum resource to the minimum and fracture characteristics, steering stability and low fuel consumption property can be improved in a good balance.SOLUTION: A rubber composition for a tire comprises a rubber component, microfibrilated plant fibers and a bio-based polymer.

Description

The present invention relates to a rubber composition for tires, a method for producing the same, 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, when blended in a rubber composition, the elongation at break tends to decrease or the fuel efficiency tends to decrease due to energy loss at the interface with the rubber component. is there. Therefore, unless these characteristics are improved, it is difficult to apply to various uses, particularly tires that are used for a long time under harsh conditions.

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 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, and has improved fracture characteristics, handling stability and fuel efficiency. It aims at providing the rubber composition for tires which can be improved with good balance, its manufacturing method, and the pneumatic tire produced using this rubber composition.

As a result of studies by the present inventors, by using a bio-based polymer, it is possible to perform surface treatment of microfibrillated plant fibers by a simple method while suppressing the use of petroleum resources as much as possible. It has been found that the compatibility between the plant fiber and the rubber component is improved and the above-mentioned problems can be solved.
That is, this invention relates to the rubber composition for tires containing a rubber component, a microfibrillated vegetable fiber, and a biobase polymer.

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.

The bio-based polymer is preferably a polymer obtained by polymerizing a monomer derived from a living organism or a polymer produced by a microorganism.

The biobase polymer is preferably an aliphatic polyester resin.

The biobase polymer is preferably polylactic acid.

It is preferable that content of the said biobase polymer is 0.05-50 mass parts with respect to 100 mass parts of said microfibrillated plant fibers.

The present invention also includes a step (I) of mixing the microfibrillated plant fiber and the biobase polymer, and a step of adding the rubber component to the mixture obtained in the step (I) and further mixing (II). The manufacturing method of the said rubber composition containing these.

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

According to the present invention, there is provided a rubber composition for a tire comprising a rubber component, a microfibrillated plant fiber, and a biobase polymer. The phase of the microfibrillated plant fiber and the rubber component can be obtained by a simple method of adding the biobase polymer. Since solubility can be improved, both rigidity and elongation at break can be achieved while maintaining good fuel efficiency. Thereby, it is possible to provide a pneumatic tire that is improved in a well-balanced manner with respect to breaking characteristics, steering stability, and low fuel consumption. In addition, since the microfibrillated plant fiber and the bio-based polymer are materials that do 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 comprises a rubber component, a microfibrillated plant fiber and a biobase polymer. By adding a bio-based polymer having a high affinity for microfibrillated plant fibers, adhesion at the interface between the rubber component and the microfibrillated plant fibers is improved, and energy loss at the interface is reduced. In addition, the contact point where the microfibrillated plant fibers are entangled with each other is reinforced by the biobase polymer, and the breaking strength is improved. With these actions, both rigidity and elongation at break can be achieved while suppressing an increase in energy loss. Therefore, by using the rubber composition in a tire, it is possible to provide a pneumatic tire in which fracture characteristics, steering stability and fuel efficiency are improved in a well-balanced manner.

In addition, since the microfibrillated plant fiber and the bio-based polymer are both materials that do not use petroleum as a raw material (resources other than petroleum), the amount of petroleum resources used can be reduced.

The method for producing the rubber composition of the present invention is not particularly limited as long as the rubber component, the microfibrillated plant fiber, and the biobase polymer are mixed. For example, the step of mixing the microfibrillated plant fiber and the biobase polymer. A production method including (I) and step (II) in which a rubber component is added to the mixture obtained in step (I) and further mixed is preferable.

(Process (I))
In step (I), the microfibrillated plant fiber and the biobase polymer are mixed. Thus, by mixing the microfibrillated plant fiber and the biobase polymer in advance, when the rubber component and the mixture obtained in the step (I) are mixed in the step (II) to be described later, The fibrillated plant fiber can be sufficiently dispersed. In the step (I), it is preferable to mix the microfibrillated plant fiber and the biobase polymer in a solvent such as water because the microfibrillated plant fiber and the biobase polymer can be easily mixed.

As the microfibrillated plant fiber used in the step (I), 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, particularly preferably 0.5 μm, from the viewpoint of a good balance between the rubber reinforcing effect and the elongation at break. It is as follows. The lower limit of the average fiber diameter of the microfibrillated plant fiber is not particularly limited, but when a solvent such as water is used in step (I), it is 4 nm or more from the viewpoint of suppressing deterioration of workability due to deterioration of drainage. Preferably there is.

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.

In step (I), an aqueous dispersion of microfibrillated plant fibers is preferably used. Thereby, the microfibrillated plant fiber and the bio-based polymer can be uniformly mixed in a short time. The content (solid content) of microfibrillated plant fibers in the aqueous dispersion of microfibrillated plant fibers is preferably 2 to 40% by mass, more preferably 5 to 30% by mass.

The biobase polymer used in the step (I) is not particularly limited as long as it is a polymer obtained by polymerizing a biological monomer or a polymer produced by a microorganism. In addition, the polymer obtained by polymerizing the monomer derived from a living body may contain a monomer component derived from petroleum resources. Biological monomers include not only monomers such as lactic acid and succinic acid obtained directly from living organisms, but also monomers obtained by chemically treating biological substances such as ethanol and glycerin obtained from living organisms. . In addition, a method for polymerizing a biological monomer is not particularly limited, and examples thereof include a method using a catalyst or an enzyme. In the present specification, the bio-based polymer does not include microfibrillated plant fibers.

Specific examples of the bio-based polymer include polyhydroxyalkanoate (for example, Kaneka PHBH manufactured by Kaneka Corporation), polycaprolactone, polybutylene succinate, polybutylene succinate / adipate, polyethylene succinate, polylactic acid, polymalic acid, Aliphatic polyester resins such as polyglycolic acid, polydioxanone, poly (2-oxetanone), polyhydroxybutyric acid; aliphatic aromatic copolyesters such as polybutylene succinate / terephthalate, polybutylene adipate / terephthalate, polytetramethylene adipate / terephthalate Examples thereof include resins. Of these, aliphatic polyester resins are preferred, and polylactic acid is more preferred because the effects of the present invention are suitably obtained and available in large quantities.

In the step (I), it is preferable to blend each component so as to have a content described later in the rubber composition of the present invention. Thereby, the balance of a rubber reinforcement effect, breaking elongation, and energy loss becomes favorable.

The method of mixing each component in the step (I) is not particularly limited, and for example, a general method such as a propeller type stirring device, a homogenizer, a rotary stirring device, an electromagnetic stirring device, manual stirring, or the like can be used.

(Step II)
In step (II), the rubber component is added to the mixture obtained in step (I) and further mixed. In this step, the microfibrillated plant fiber and the rubber component are combined.

The rubber component used in the step (II) preferably contains at least one selected from the group consisting of natural rubber (NR), modified natural rubber, synthetic rubber and modified synthetic rubber. Examples of the modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber, and deproteinized natural rubber. Examples of the synthetic rubber include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), and acrylonitrile-styrene-butadiene copolymer. Examples thereof include diene rubbers such as polymer rubber, chloroprene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, and chlorosulfonated polyethylene. Examples of synthetic rubbers other than diene rubbers include ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, and urethane rubber. Examples of the modified synthetic rubber include rubber obtained by adding a functional group to the synthetic rubber. These rubber components may be used alone or in combination of two or more. What is necessary is just to mix | blend suitably also in the blend ratio in the case of blending according to various uses. Among them, NR, BR, SBR, IR, IIR and ENR are preferable from the viewpoint of versatility and cost, and good workability when mixed with microfibrillated plant fibers. From the viewpoint that the amount of petroleum resources used can be reduced and the environment can be taken into consideration, NR and ENR, which are materials derived from resources other than petroleum, are more preferable.
Moreover, it is preferable to use the said rubber component in the state of a latex from the point that a microfibril plant fiber and a rubber component can be mixed uniformly in a short time. In rubber latex, content (solid content) of a rubber component becomes like this. Preferably it is 30-80 mass%, More preferably, it is 40-70 mass%.

In the step (II), it is preferable to blend each component so as to have a content described later in the rubber composition of the present invention. Thereby, the balance of the rubber reinforcing effect, elongation at break and energy loss becomes good, and the yield and workability of various materials become good.

The method of mixing each component in step (II) is not particularly limited, and the same method as in step (I) can be used.

By the steps (I) and (II), a master batch in which microfibrillated plant fibers are uniformly dispersed in a rubber matrix can be prepared. In addition, when the mixture obtained by process (II) is a slurry state, after solidifying and drying the said mixture by a well-known method, a masterbatch can be prepared by knead | mixing with a Banbury mixer etc.

The rubber composition of this invention is manufactured by a well-known method using the said masterbatch. For example, it can be produced by a method in which the masterbatch and other components are kneaded with a Banbury mixer, a kneader, an open roll or the like and then vulcanized. Other compounding agents include, for example, reinforcing agents (carbon black, silica, etc.), silane coupling agents, vulcanizing agents, stearic acid, vulcanization accelerators, vulcanization acceleration aids, oils, cured resins, waxes, aging An inhibitor etc. are mentioned.

In the rubber composition of the present invention, the content of the microfibrillated plant fiber is preferably 1 part by mass or more, 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. If it is in the said range, microfibrillated plant fiber will be disperse | distributed favorably and it can improve in a well-balanced destruction characteristic, steering stability, and low fuel consumption.

In the rubber composition of the present invention, the content of the bio-based polymer is preferably 0.05 parts by mass or more, more preferably 1 part by mass or more, and preferably 100 parts by mass of microfibrillated plant fibers. Is 50 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 10 parts by mass or less. If it is in the said range, a microfibrillated plant fiber can be disperse | distributed favorably and a destructive characteristic, steering stability, and low fuel consumption can be improved with good balance.

In the rubber composition of the present invention, the content of NR in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 80% by mass or more, and may be 100% by mass. If it is in the said range, microfibrillated plant fiber will be disperse | distributed favorably and it can improve in a well-balanced destruction characteristic, steering stability, and low fuel consumption.

The content of non-petroleum resources in 100% by mass of the rubber composition is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 97% by mass or more. According to the present invention, since the above-described components are used in combination, even when the content of non-petroleum resources is increased, destruction characteristics, steering stability, and low fuel consumption can be obtained in a well-balanced manner.
The content of non-petroleum resources, the abundance of carbon isotope ^{14 C} in carbon dioxide in the exhaust gas by burning rubber composition was measured, the ^{14 C} of resources other than petroleum derived materials and petroleum-resource-derived material It can be discriminated by a method such as comparing the difference in the abundance.

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, cellulose microfibril)
Polylactic acid: Lacia (Bio-based polymer) manufactured by Mitsui Chemicals, Inc.
Master batches 1 to 3: Prepared in the following production examples 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>
According to the composition of Table 1, microfibrillated plant fibers and polylactic acid were 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)). Then, 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>
Master batch 2 was obtained in the same manner as master batch 1 except that polylactic acid was not used.

<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 Example 1, Comparative Example 1, and Reference Example 1.

<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. In Table 2, the content of non-petroleum resources is the content (mass%) of non-petroleum resources in 100% by mass of the rubber composition.

(Tensile test)
100% tensile stress, 300% tensile stress, tensile strength, elongation at break, and fracture energy were measured according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The following formula:
100% tensile stress index = (100% tensile stress of each formulation) / (100% tensile stress of standard formulation) × 100
300% tensile stress index = (300% tensile stress of each formulation) / (300% tensile stress of standard formulation) × 100
Tensile strength index = (breaking stress of each compound) / (breaking stress of the standard compound) × 100
Breaking elongation index = (breaking elongation of each formulation) / (breaking elongation of the reference formulation) × 100
Fracture energy index = (Fracture energy of each formulation) / (Fracture energy of the reference formulation) × 100
Were used to calculate a 100% tensile stress index, a 300% tensile stress index, a tensile strength index, a breaking elongation index, and a breaking energy index. The larger the index, the better the vulcanized rubber composition is reinforced, and the higher the mechanical strength of the rubber, the better the fracture characteristics.

(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). The E ^* (complex elastic modulus) and tan δ (loss tangent) of each test specimen were measured under the conditions of dynamic strain 2% and frequency 10 Hz. The following formula:
Steering stability index = (E ^{* of} each formulation) / (E ^{* of} reference formulation) × 100
Rolling resistance index = (tan δ of each formulation) / (tan δ of reference formulation) × 100
The steering stability index and rolling resistance index were calculated. The larger the steering stability index, the better the steering stability when used as a pneumatic tire, and the smaller the rolling resistance index, the better the rolling resistance characteristic (low fuel consumption) when used as a pneumatic tire. Indicates to give.

From Table 2, Comparative Example 1 containing microfibrillated plant fibers and no biobase polymer improved the tensile stress and the like compared to Reference Example 1, but deteriorated elongation at break and fuel efficiency. On the other hand, Example 1 containing a microfibrillated plant fiber and a bio-based polymer improved the elongation at break while maintaining low fuel consumption as compared with Comparative Example 1. Other performances were also superior to Comparative Example 1.

Claims (11)

A rubber composition for tires comprising a rubber component, microfibrillated plant fibers and a bio-based polymer. The tire rubber composition 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 rubber composition for tires according to claim 1 or 2, wherein the microfibrillated plant fiber is cellulose microfibril. The rubber composition for a tire according to any one of claims 1 to 3, wherein the microfibrillated plant fiber has an average fiber diameter of 10 µm or less. The rubber composition for a tire according to any one of claims 1 to 4, wherein a 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 tire rubber composition according to any one of claims 1 to 5, wherein the biobase polymer is a polymer obtained by polymerizing a monomer derived from a living organism or a polymer produced by a microorganism. The tire rubber composition according to any one of claims 1 to 6, wherein the bio-based polymer is an aliphatic polyester resin. The rubber composition for tires according to any one of claims 1 to 7, wherein the biobase polymer is polylactic acid. The tire rubber composition according to any one of claims 1 to 8, wherein a content of the biobase polymer is 0.05 to 50 parts by mass with respect to 100 parts by mass of the microfibrillated plant fiber. A step (I) of mixing the microfibrillated plant fiber and the biobase polymer, and a step (II) of adding the rubber component to the mixture obtained in the step (I) and further mixing. The manufacturing method of the rubber composition for tires in any one of 1-9. The pneumatic tire produced using the rubber composition in any one of Claims 1-9.