JP2015030815A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire rubber composition which can improve low fuel consumption, fracture characteristics, and steering stability in a good balance by improving compatibility of a microfibrillated plant fiber and a rubber component while suppressing consumption of oil resources as much as possible, and to provide a production method of the tire rubber composition and a pneumatic tire manufactured using the tire rubber composition.SOLUTION: A tire rubber composition comprises a rubber component, a microfibrillated plant fiber, and a dry matter of fine algae. It is preferable that the rubber component contains at least one selected from the group consisting of a natural rubber, a modified natural rubber, a synthetic rubber, and a modified synthetic rubber, and it is preferable that the microfibrillated plant fiber is a cellulose microfibril.

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 while suppressing the use of petroleum resources as much as possible, and can improve the fracture characteristics, handling stability and fuel efficiency in a balanced manner. An object is to provide a rubber composition for a tire, a method for producing the same, and a pneumatic tire produced using the rubber composition.

The present invention relates to a rubber composition for tires comprising a rubber component, microfibrillated plant fibers, and a dried product of microalgae.

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.

It is preferable that 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 microalgae is preferably a microalga belonging to the Euglenophycea net.

The microalgae is preferably a microalga belonging to the genus Euglena.

The microalgae are preferably cultured under anaerobic conditions after being cultured under aerobic conditions.

For the tire, comprising the step (I) of mixing the microfibrillated plant fiber and the dried product of the microalgae and the step (II) of further mixing the mixture obtained in the step (I) and the rubber component. The present invention relates to a method for producing a rubber composition.

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

According to the present invention, a rubber composition for a tire containing a rubber component, a microfibrillated plant fiber and a dried product of microalgae, and the microfibrillated plant fiber and the rubber component are added by adding the dried product of microalgae. Since compatibility 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 in terms of fracture characteristics, steering stability, and fuel efficiency. In addition, since the dried microfibrillated plant fibers and microalgae 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 includes a rubber component, microfibrillated plant fibers, and a dried product of microalgae. By adding a dried product of microalgae, adhesion at the interface between the rubber component and the microfibrillated plant fiber 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 dried microalgae, 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.

Moreover, since the microfibrillated plant fiber and the dried product of microalgae are both materials that do not use petroleum as a raw material (non-petroleum resources), 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 it is a method of mixing a rubber component, a microfibrillated plant fiber and a dried product of microalgae. For example, a dried product of microfibrillated plant fiber and microalgae is used. A production method comprising the step (I) of mixing the step (I) and the step (II) of adding a rubber component to the mixture obtained in the step (I) and further mixing is preferable.

(Process (I))
In step (I), the microfibrillated plant fiber and the dried microalgae are mixed. Thus, when the rubber component and the mixture obtained in the step (I) are mixed in the step (II) described later by mixing the microfibrillated plant fiber and the dried product of microalgae in advance, In addition, the microfibrillated plant fiber can be sufficiently dispersed. In the step (I), it is preferable to mix the microfibrillated plant fiber and the dried product of microalgae in a solvent such as water because the dried product of the microfibrillated plant fiber and the dried microalgae 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 dried product of microalga can be mixed uniformly 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.

In the dried microalgae used in step (I), the microalgae is not particularly limited as long as it is algae having a property of converting a part of nutrients in the body into hydrocarbons (aliphatic hydrocarbons), Algae that can assimilate carbon dioxide are preferred.

The aliphatic hydrocarbon is not particularly limited as long as it is an aliphatic hydrocarbon produced by microalgae, for example, a saturated or unsaturated aliphatic hydrocarbon having 15 to 50 carbon atoms such as n-heptadecene; Saturated or unsaturated fatty acid having 15 to 50 carbon atoms such as n-eicosadiene; saturated or unsaturated fatty acid ester having 15 to 50 carbon atoms such as methyl laurate, myristyl myristate and methyl palmitate . Of these, saturated or unsaturated fatty acid esters having 15 to 50 carbon atoms (preferably 15 to 40 carbon atoms) (particularly esters of (higher) fatty acids and (higher) aliphatic alcohols) are preferred.

Specific examples of the microalgae include the microalgae belonging to the Euglenophyceae net, the microalgae belonging to the genus Chlorella, the microalgae belonging to the genus Scededesmus, the microalgae belonging to the genus Desmodesmus, and the genus Spirulina (Spirulina) A microalga belonging to the genus Arthrospira, a microalga belonging to the genus Botryococcus (especially Botryococcus braunii), Pseudocystis (Pseudistiosch) Microalgae belonging to the genus (especially Pseudochoricitis) ellipsiside))) and the like. These microalgae are known to be able to biosynthesize waxes (aliphatic hydrocarbons). Of these, microalgae belonging to the Euglenophycea net are preferred from the viewpoint of wax productivity.

Examples of the microalgae belonging to the Euglenophyceae net include the microalgae belonging to the genus Euglena, Astasia, Kaukinea, Tokurigemushi, Peranema, Puchiwagemushi, Levokincris, and Strombomonas. Of these, microalgae belonging to the genus Euglena are preferred.
This is because microalgae belonging to the genus Euglena are easy to culture, and when cultured under aerobic conditions, paramylon is accumulated in the cells as carbohydrates and then accumulated under anaerobic conditions. It is known that paramylon is decomposed to produce a wax (ester of (higher) fatty acid and (higher) aliphatic alcohol) (Japanese Patent Application Laid-Open No. 59-118090). The effect of the present invention is suitably obtained by drying microalgae containing the wax in the cells and blending it into the tire rubber composition, and blended in the tire rubber composition for the purpose of improving ozone resistance. The dried product can be suitably used as a wax and further as a filler (that is, the dried product is a compounding agent having both filler and wax effects). It is from.

In addition, microalgae belonging to the genus Euglena produce wax (ester of (higher) fatty acid and (higher) aliphatic alcohol) with extremely high production efficiency that reaches 50% by weight of the dry cell mass depending on the culture conditions. (Japanese Patent Laid-Open No. 59-118090) is superior to other naturally-derived waxes in terms of production efficiency.

The microalgae belonging to the genus Euglena are a group of flagellates belonging to the order of Euglena in zoology, Euglenophyceae net in the botany, and Euglena, and can be easily collected and cultured in natural water systems such as ponds and swamps. It is a thing. Representative examples include Euglena Gracilis Z strain, Euglena Gracilis Basilis variant, Euglena Viridis, Astasia Longa, etc., but are not limited thereto, and were treated by a known method. Various mutant strains can also be used.

The microalgae belonging to the genus Euglena may be collected from natural sources or cultured.

In addition, as described above, microalgae belonging to the genus Euglena are naturally present, are easy to culture and produce wax with high efficiency, and the dried algae belonging to the genus Euglena have the effect of filler and wax as they are. It can be used as a compounding agent, and there is no worry of exhaustion, making it possible to manufacture environmentally friendly tires.

For culturing microalgae, known methods for culturing various microorganisms can be applied. Specifically, a medium containing an appropriate amount of a carbon source, a nitrogen source, an inorganic salt, and vitamins may be used, and known media include Koren-Hutner medium (Korren and Hutner, J. Protocol. 14, Supple. 17). (1967)), Hutner medium (Hutner, J. Protocol, 6, 23 (1959)), Kramer-Myers medium, Archer Mikrobiol, 17, 384 (1952)) and the like. Not as long.

Regarding the culture of microalgae, known methods such as Kitaoka et al. ("Eugrena", edited by Shozaburo Kitaoka, Society Publishing Center (1989)), Chemistry and Industry (Michiko Taniguchi, Chemistry and Industry, Volume 52). , Page 262 (1999)) and the like. Among the above-mentioned microalgae, microalgae belonging to the genus Euglena, Chlorella, Spirulina, and Arsulospira have already been cultured on an industrial scale.

As the carbon source, glucose, starch hydrolyzate, molasses, glutamic acid, acetic acid, ethanol and the like are preferable, and two or more kinds may be used in combination.

As the nitrogen source, ammonia, ammonium salt, glutamic acid, aspartic acid and the like are preferable, and two or more kinds may be used in combination. The mass ratio (C / N) of the carbon source and nitrogen source is preferably 4-30.

As the inorganic salt, it is desirable to combine inorganic salts containing calcium, magnesium, manganese, and irons.

As vitamins, vitamin B ₁ , vitamin B ₁₂ , vitamin B _{16 and the} like are preferably added in combination.

The culture temperature is preferably 20 ° C to 35 ° C, more preferably 27 ° C to 33 ° C. Cultivation is possible at temperatures below 20 ° C. and above 35 ° C., but growth tends to be slow and wax production efficiency tends to be poor.

Culture may be performed in the dark or in the light. That is, light irradiation may be performed, and it may be under dark or indoor light.

When culturing in a liquid or suspension, it is desirable to perform appropriate shaking or stirring. In addition, the culture is preferably performed under aerobic conditions, and aeration is desirably 1 to 2 liters of culture solution per minute and 0.4 to 2 liters per minute.

Further, as described in JP-A-59-118090, in order to promote the conversion of paramylon into wax, microalgae belonging to the genus Euglena are cultured for a certain period under aerobic conditions and accumulated in the cells. After that, it is desirable to transfer under anaerobic conditions and culture to produce wax (ester of (higher) fatty acid and (higher) fatty alcohol). In this case, it is desirable to culture under aerobic conditions for 4 days to 7 days, and after reaching the stationary phase of growth, convert to anaerobic conditions and culture for 1 to 3 days. Thereby, a large amount of wax can be efficiently generated in the cells of the microalgae, and better ozone resistance can be obtained.

Examples of the method for conversion to anaerobic conditions include a method in which cells cultured under an aerobic condition are collected by centrifugation and then suspended in a solution such as a phosphate buffer and aerated with nitrogen gas. It is done.

In addition, the wax (ester of (higher) fatty acid and (higher) aliphatic alcohol) tends to exhibit a lower melting point as the number of carbon atoms of the fatty acid and aliphatic alcohol constituting the wax decreases and as the degree of unsaturation increases. Therefore, as described in JP-A-61-254193, the melting point of the generated wax can be controlled according to the purpose by adding a fatty acid during the cultivation of microalgae.

Therefore, apart from the above additives, a fatty acid may be added for the purpose of producing a wax having a specific composition (for example, a wax having a specific carbon number or a wax having a specific number of unsaturated bonds). The timing for adding the fatty acid is not particularly limited. However, when the obtained wax is blended with the rubber composition for tires for the purpose of improving ozone resistance as in the present invention, a microalga belonging to the genus Euglena is a normal medium (medium without added fatty acid). By culturing in (2), a wax (solid fatty acid ester solid at 25 ° C.) with less unsaturated bonds is produced, so it is preferable not to add fatty acid to the culture solution.

The carbon number of the fatty acid is preferably 8 to 40 and more preferably 10 to 20 in consideration of a desirable melting point of the wax to be produced (for example, fatty acid ester).

The fatty acid is not particularly limited, and examples thereof include unsaturated fatty acids such as myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, gadoleic acid, gondoic acid, cetreic acid, and erucic acid; lauric acid And saturated fatty acids such as myristic acid, palmitic acid and stearic acid. These may be used alone or in combination of two or more.

As a method for obtaining a dried product of microalgae from microalgae collected from nature and / or cultured microalgae, any known method may be used. For example, cells may be collected by filtering and / or centrifuging the collected solution and culture solution and dried as they are. In addition, because the effect of improving the ozone resistance is more suitably obtained, it is preferable that the cells are crushed with ultrasonic waves, and then dried, and the cells are crushed with ultrasonic waves, etc., and then centrifuged, etc. It is more preferable to dry after collecting.

Drying can be performed using known means such as reduced pressure drying, hot air drying, drum drying, filter press, hot plate drying, freeze drying and the like. Although drying conditions are not particularly limited, for example, a drying temperature of 0 to 250 ° C., a drying time of 0.5 to 5 days, or freeze drying is preferable.

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.

(Process (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 step (II) preferably contains at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber and modified synthetic rubber. Examples of the rubber component include diene rubbers. Specifically, natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber. (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-styrene-butadiene copolymer rubber, chloroprene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber And modified natural rubbers such as chlorosulfonated polyethylene, epoxidized natural rubber (ENR), hydrogenated natural rubber, and deproteinized natural rubber. Examples of the rubber component other than the diene rubber include ethylene-propylene copolymer rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, and urethane 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, 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 dried microalgae is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, with respect to 100 parts by mass of microfibrillated plant fibers. The amount is preferably 50 parts by mass or less, more preferably 20 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.

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 differences.

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.
Glucose: Nacalai Tesque Co., Ltd. ammonium sulfate: Kanto Chemical Co., Ltd. Corn steep liquor: Oji Corn Starch Co., Ltd. Magnesium sulfate: Kanto Chemical Co., Ltd. monopotassium phosphate: Wako Pure Chemical Industries, Ltd. Sodium acetate: Nacalai Tesque Co., Ltd. Mole salt: Wako Pure Chemical Industries, Ltd. Zinc sulfate: Wako Pure Chemical Industries, Ltd. Manganese sulfate: Kanto Chemical Co., Ltd. Vitamin B ₁ : Vitamins manufactured by Sigma Aldrich B ₁₂ : Natural rubber latex manufactured by Sigma-Aldrich: Natural rubber latex manufactured by HYTEX HA (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)
Dried microalgae: prepared in the following preparation examples Master batches 1-3: prepared in the following manufacturing examples Anti-aging agent: NOCRACK 6C manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate Zinc oxide: Zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Ouchi Shinsei Chemical NOCELLER DM manufactured by Kogyo Co., Ltd.

<Preparation example of dried microalgae>
20 g of glucose, 7 g of ammonium sulfate, 5 g of corn steep liquor, 0.5 g of magnesium sulfate, 0.5 g of monopotassium phosphate, 0.05 g of sodium ethylenediaminetetraacetate, 0.05 g of molle salt, 0.025 g of zinc sulfate, 0.02 g of manganese sulfate 02 g, vitamin B ₁ 5 mg and vitamin B ₁₂ 10 μg were dissolved in 1 L of tap water, charged into a 2 L capacity jar fermenter, and sterilized (120 ° C., 20 minutes) in an autoclave. This was inoculated with 100 ml of Euglena gracilis pre-cultured in the same medium in advance, and cultured with shaking under aerobic conditions of 120 rpm at 28 ° C. for 72 hours under room light. At this time, the pH of the medium was maintained until the end of the culture using a pH controller so that the pH became 3.5 with 2N aqueous sodium hydroxide solution.
Further, the cultured cells were collected by centrifugation, suspended in a phosphate buffer having a pH of 6.8, and cultured with shaking under anaerobic conditions at 120 rpm for 2 days under room light under 20 ml nitrogen gas flow for 1 minute. .
Thereafter, the cells were crushed by sonication, and the crushed material was collected by centrifugation, and then dried at 40 ° C. for 4 days in a vacuum dryer to obtain a dried microalgae.

<Production Example 1: Preparation of Masterbatch 1>
According to the composition in Table 1, using a high-speed homogenizer (IKA's batch homogenizer T65D Ultra Turrax (Ultraturrax T25)), the microfibrillated plant fiber and the dried microalgae were mixed in water at 24,000 rpm. The mixture was stirred and dispersed for a period of time, 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>
Masterbatch 2 was obtained in the same manner as Masterbatch 1 except that the dried microalgae were not blended.

<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 at 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, breaking stress, breaking elongation and breaking energy were measured according to JIS K6251 “Vulcanized rubber and thermoplastic rubber—How to obtain 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 not containing dried microalgae improved tensile stress, tensile strength, fracture energy, and handling stability compared to Reference Example 1. , Elongation at break and low fuel consumption deteriorated. On the other hand, Example 1 containing microfibrillated plant fibers and dried microalgae improved the elongation at break while maintaining the low fuel consumption of Comparative Example 1, and improved tensile stress, tensile strength, fracture energy and handling stability. Improved further.

Claims (10)

A rubber composition for tires comprising a rubber component, microfibrillated plant fibers and a dried product of microalgae. 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 microalga is a microalga belonging to the Euglenophycea net. The tire rubber composition according to any one of claims 1 to 6, wherein the microalga is a microalga belonging to the genus Euglena. The tire rubber composition according to any one of claims 1 to 7, wherein the microalgae are cultured under anaerobic conditions after being cultured under aerobic conditions. 2. A step (I) of mixing the microfibrillated plant fiber and a dried product of the microalgae, and a step (II) of further mixing the mixture obtained in the step (I) and the rubber component. The manufacturing method of the rubber composition for tires in any one of -8. The pneumatic tire produced using the rubber composition for tires in any one of Claims 1-8.