JPWO2011096393A1 - Rubber composition and method for producing the same - Google Patents

Abstract

The present invention relates to (A) a rubber component, (B) a microfibrillated plant fiber obtained by mechanically defibrating pulp, and (C) a rubber composition containing a resole resin and a method for producing the same.

Description

  The present invention relates to a rubber composition containing a microfibrillated plant fiber and a resole resin.

  In rubber compositions, it has been conventionally known to improve physical properties of rubber by containing cellulose fibers as a filler blended in a rubber component (see, for example, Patent Document 1). Patent Literature 1 discloses a master batch obtained by stirring and mixing an aqueous dispersion of cellulose short fibers and rubber latex, and removing water from the mixed solution. However, cellulose fibers have poor compatibility with rubber, and when blended as a rubber composition, sufficient effects cannot be obtained in terms of breaking characteristics and energy loss at the interface, and these characteristics must be improved. It is difficult to put it into practical use for various purposes. Therefore, in order to improve the compatibility between cellulose fibers and rubber components, it has been proposed to use cellulose short fibers that have been subjected to surface treatment such as acetylation, but this surface modification requires reaction in a solvent. There are many processes for surface treatment. In addition, the compatibility between the cellulose fiber and the rubber component is improved by such a surface treatment, but since a chemical bond at the interface between the cellulose fiber and the rubber component does not occur, a sufficient reinforcing effect is obtained. There was a problem in that it was not.

JP 2006-206864 A

  An object of the present invention is to provide a rubber composition in which microfibrillated plant fibers are well dispersed in a rubber component, and a method for producing the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that, in a rubber composition containing microfibrillated plant fibers, by further containing a resol resin, the microfibrillated plant fibers and the rubber component It has been found that the interaction at the interface can be improved, and that such treatment can be easily carried out in an aqueous system. Moreover, the rubber composition which can improve physical characteristics, such as breaking strength, was improved by improving the dispersibility of the fiber in a rubber composition.

  The present invention has been completed based on such findings.

Item 1. (A) rubber component,
(B) A rubber composition containing microfibrillated plant fibers obtained by mechanically defibrating pulp, and (C) a resole resin.

  Item 2. Item 2. The rubber composition according to Item 1, wherein the resol resin (C) is obtained by polymerization of benzene having at least one hydroxyl group and formaldehyde.

  Item 3. Item 3. The rubber composition according to Item 2, wherein the benzene having at least one hydroxyl group is resorcin.

  Item 4. Item 4. The rubber composition according to any one of Items 1 to 3, wherein the content of the microfibrillated plant fiber (B) is 1 to 50 parts by weight with respect to 100 parts by weight of the rubber component (A).

  Item 5. Item 5. The rubber composition according to any one of Items 1 to 4, wherein the content of the resole resin (C) is 0.01 to 5 parts by weight with respect to 100 parts by weight of the rubber component (A).

  Item 6. Item 6. The rubber composition according to any one of Items 1 to 5, wherein the mechanical fibrillation treatment in the microfibrillated plant fiber (B) is a grinding treatment.

  Item 7. Item 7. The rubber composition according to any one of Items 1 to 6, wherein the microfibrillated plant fiber (B) has an average fiber diameter of 10 μm or less.

  Item 8. Item 8. The rubber composition according to any one of Items 1 to 7, which is used for tires.

Item 9. A step of blending a rubber latex containing 1 to 60% by weight of a rubber component with respect to the whole rubber latex component and a solution containing benzene and formaldehyde having at least one hydroxyl group to obtain a resole resin-rubber dispersion ( a1),
Step (b1) of obtaining resole resin-rubber dispersion-containing microfibrillated plant fiber by mechanically defibrating after mixing the resole resin-rubber dispersion obtained in step (a1) and pulp.
A step of mixing a resol resin-rubber dispersion-containing microfibrillated plant fiber obtained by the step (b1) and a rubber latex containing 1 to 60% by weight of a rubber component with respect to the entire rubber latex component to obtain a dispersion. Item 9. The method for producing a rubber composition according to any one of Items 1 to 8, further comprising a step (d1) of solidifying the dispersion obtained by the step (c1) and the step (c1) and then drying to obtain a master batch.

Item 10. A step of blending a rubber latex containing 1 to 60% by weight of a rubber component with respect to the whole rubber latex component and a solution containing benzene and formaldehyde having at least one hydroxyl group to obtain a resole resin-rubber dispersion ( a1),
After the pulp is mechanically defibrated to obtain microfibrillated plant fibers, the microfibrillated plant fibers and the resole resin-rubber dispersion obtained in the step (a1) are mixed, and the resole resin-rubber dispersion is contained. Obtaining a microfibrillated plant fiber (b2),
The resole resin-rubber dispersion-containing microfibrillated plant fiber obtained in the step (b2) and the rubber latex containing 1 to 60% by weight of the rubber component with respect to the entire rubber latex component are mixed to obtain a dispersion. Item 9. The method for producing a rubber composition according to any one of Items 1 to 8, comprising a step (c1) and a step (d1) in which the dispersion obtained in the step (c1) is solidified and then dried to obtain a master batch.

  Item 11. Item 10. The method for producing a rubber composition according to Item 9, wherein the mechanical defibrating treatment in the step (b1) is grinding treatment.

  Item 12. Item 11. The method for producing a rubber composition according to Item 10, wherein the mechanical defibrating treatment in the step (b2) is grinding treatment.

  Item 13. Item 15. A pneumatic tire using the rubber composition according to any one of Items 1 to 8.

  Hereinafter, the present invention will be described in detail.

  The rubber composition of the present invention contains (A) a rubber component, (B) microfibrillated plant fiber obtained by mechanically defibrating pulp, and (C) a resole resin.

  Examples of the rubber component (A) include diene rubber components. 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 Examples thereof include polymer rubber, chlorosulfonated polyethylene, modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber, deproteinized natural rubber, and the like. Examples of the rubber component other than the diene rubber component 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.

  The lignin contained in the microfibrillated plant fiber (B) may be chemically removed or not removed.

  If the lignin is not completely removed chemically, it is presumed that the matrix portion composed of lignin and hemicellulose filling the space between the microfibrillated cellulose is broken and microfibrillated (microfibrillated). Therefore, the microfibrillated plant fiber (B) obtained by mechanical fibrillation treatment is composed of cellulose, hemicellulose and protolignin (lignin in a state existing in the plant tissue) inherent in the plant material. It is presumed that this structure is retained. A structure in which hemicellulose and / or lignin is coated partly or entirely around cellulose microfibrils and / or cellulose microfibril bundles, in particular, hemicellulose covers cellulose microfibrils and / or cellulose microfibril bundles, It is presumed to have a structure covered with lignin. However, it is presumed that there will also be a portion where hemicellulose and / or lignin is removed and the hemicellulose or cellulose fiber length is exposed on the surface.

  The average fiber diameter of the microfibrillated plant fibers (hereinafter also referred to as average fiber diameter) is preferably 10 μm or less, more preferably 4 nm to 1 μm, further preferably 4 nm to 200 nm, further preferably 4 nm to 100 nm. Is more preferable. Microfibrillated plant fibers are intricately intertwined. Regarding the relationship between the lignin content and the cellulose content in the microfibrillated plant fiber, the lignin is 2 to 70% by weight, preferably 5 to 60% by weight, more preferably 10 to 50% by weight, based on the weight of cellulose. Moreover, when lignin is contained in the microfibrillated plant fiber, the content of lignin is preferably 1 to 40% by weight, more preferably 3 to 35% by weight, and still more preferably 5 to 35% by weight. In the microfibrillated plant fiber (B), when the lignin in the pulp as a raw material is not removed, the lignin content in the pulp and the lignin content in the microfibrillated plant fiber are almost the same. Similarly, the relationship between the cellulose content and the lignin content in the pulp and the relationship between the cellulose content and the lignin content in the microfibrillated plant fiber are almost the same.

  In JP 2001-342353 A, an acetone solution of a phenol derivative is added to a defatted wood powder obtained by degreasing wood powder (ethanol: benzene = 1: 2 solution) to sorb the phenol derivative, and phosphoric acid is added. Although a composition obtained by treatment is described, this composition is different from the microfibrillated plant fiber (B) used in the present invention in that it is not microfibrillated.

  The pulp used in producing the microfibrillated plant fiber (B) may be any pulp that has been used in the production of conventional microfibrillated cellulose, and lignin is not removed or partly removed. It may be.

  As a plant raw material for supplying pulp used in producing the microfibrillated plant fiber (B), a wide variety of plant raw materials for supplying pulp used in the production of conventional microfibrillated cellulose are used. For example, wood, bamboo, hemp, jute, kenaf, crop waste, cloth, recycled pulp, and waste paper. Preferred are wood, bamboo, hemp, jute, kenaf, and crop residue.

  The method for pulping the plant material is not particularly limited, and is performed by a conventional method. For example, a mechanical pulping method for mechanically pulping plant materials can be applied. Examples of the mechanical pulp (MP) obtained by the mechanical pulping method include groundwood pulp (GP), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP).

  Moreover, chemical pulp (CP) obtained by pulverizing plant raw materials chemically or chemically and mechanically by chlorination, alkali treatment, oxygen oxidation treatment, sodium hypochlorite treatment, sulfite treatment, etc. (Craft pulp (KP), sulfite pulp (SP), etc.), semi-chemical pulp (SCP), chemiground pulp (CGP), chemimechanical pulp (CMP) can also be used. Further, the pulp may be subjected to chemical modification treatment commonly used in the pulp field as necessary, for example, esterification treatment, etherification treatment, acetalization treatment, pulp treated with an aromatic ring of lignin, etc. The applied pulp is illustrated. The esterification treatment, etherification treatment, and acetalization treatment mainly include esterification, etherification, and acetalization treatment of hydroxyl groups present in cellulose, hemicellulose, and lignin. Further, the treatment of the lignin aromatic ring includes introducing a desired substituent into the lignin aromatic ring.

  From the viewpoint that the content of the microfibrillated plant fiber (B) can maintain a good balance between the reinforcing property and the fracture property without deteriorating the dispersibility of the microfibrillated plant fiber (B) in the rubber. The amount of the rubber component (A) is preferably in the range of 1 to 50 parts by weight, more preferably in the range of 2 to 35 parts by weight, and still more preferably in the range of 3 to 20 parts by weight.

  The resole resin (C) is obtained by polymerizing benzene having at least one hydroxyl group and formaldehyde. Examples of benzene having at least one hydroxyl group include phenol, resorcin, cresol, modified resorcin, modified phenol, catechol and the like. These may be used singly or in combination. Resorcinol, phenol and cresol are preferred from the viewpoint of good production efficiency of resole resin by reaction with formaldehyde. An alkali is used as a catalyst when benzene having at least one hydroxyl group and formaldehyde are polymerized. Examples of the alkali include sodium hydroxide and potassium hydroxide, but are not particularly limited.

  The content of the resole resin (C) is 100 parts by weight of the rubber component (A) from the viewpoint of expressing the interaction at the interface between the microfibrillated plant fiber and the rubber and having good physical properties such as breaking strength. Is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, and still more preferably 0.1 parts by weight or more. In addition, the content of the resole resin (C) does not deteriorate the dispersion of the microfibrillated plant fiber, and the physical properties such as breaking strength are good, with respect to 100 parts by weight of the rubber component (A). 5 parts by weight or less is preferable, 3 parts by weight or less is more preferable, and 2 parts by weight or less is more preferable.

  The resole resin (C) contained in the rubber composition of the present invention is partially chemically bonded to the rubber component (A) and partially chemically bonded to the microfibrillated plant fiber (B). Presumed to be. Therefore, the separation at the interface between the rubber component (A) and the microfibrillated plant fiber (B) in the rubber composition can be suppressed, and the microfibrillated plant fiber (B) is excellent in the rubber component (A). Can be dispersed.

  The rubber composition of the present invention is obtained by the steps (a1) and (a1) of blending a rubber latex with a solution containing benzene having at least one hydroxyl group and formaldehyde to obtain a resol resin-rubber dispersion. Steps (b1) and (b1) obtained by mixing the resol resin-rubber dispersion and the pulp and then mechanically performing a defibrating process to obtain the resole resin-rubber dispersion-containing microfibrillated plant fiber. -By mixing the rubber dispersion-containing microfibrillated plant fiber and rubber latex, obtaining a dispersion (c1), and drying the dispersion obtained by the step (c1) to obtain a master batch (d1) It can manufacture (henceforth the manufacturing method 1).

  In the production method 1, the resol resin-rubber dispersion and the pulp are mixed and then mechanically defibrated, and the resol resin-rubber dispersion obtained by the production method 1 is contained. Since the surface of the microfibrillated plant fiber is treated relatively uniformly, the effect of further increasing the dispersibility of the fiber in the rubber composition can be obtained.

  Further, as a production method different from the production method 1, the rubber composition of the present invention comprises a rubber latex and a solution containing benzene having at least one hydroxyl group and formaldehyde, and a resole resin-rubber dispersion is obtained. Step (a1), after the pulp is mechanically defibrated to obtain microfibrillated plant fibers, the microfibrillated plant fibers and the resole resin-rubber dispersion obtained in step (a1) are mixed, and resole Step (b2) of obtaining resin-rubber dispersion-containing microfibrillated plant fiber, resole resin-rubber dispersion-containing microfibrillated plant fiber obtained by step (b2) and rubber latex are mixed to obtain a dispersion. The dispersion obtained by the step (c1) and the step (c1) is dried and manufactured by the step (d1) of obtaining a master batch. It may (hereinafter also referred to as the production method 2).

  In the production method 2, the pulp is mechanically defibrated to produce microfibrillated plant fibers, and then mixed with a resol resin-rubber dispersion. Since the mixing operation of the pulp before the defibrating treatment and the resol resin-rubber dispersion can be eliminated, the process until obtaining the master batch can be simplified.

  The rubber component in the rubber latex used in the step (a1) in the production methods 1 and 2 may be the same or different from the rubber component in the rubber latex compounded in the step (c1). From the viewpoint that the microfibrillated plant fiber can be dispersed well, it is preferable to use the same kind of rubber component.

  In the rubber composition, the rubber component contained in the rubber latex in the step (a1) in the production methods 1 and 2 is excellent in the adhesion and dispersibility of the microfibrillated plant fiber in the rubber composition. It is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and further preferably 0.3% by weight or more based on the total rubber component contained. Moreover, the rubber component contained in the rubber latex in the step (a1) in the production methods 1 and 2 increases the adhesion of the microfibrillated plant fibers in the rubber composition and avoids the aggregation of the microfibrillated plant fibers. From the viewpoint of being good, the content is preferably 10% by weight or less, more preferably 5% by weight or less, and still more preferably 2% by weight or less based on the entire rubber component contained in the rubber composition. Specific examples of the rubber component may be those listed above.

  The remaining rubber component is blended as a rubber component in the rubber latex blended in the step (c1) in the production methods 1 and 2. That is, the blending amount of the rubber component in the step (c1) is preferably 90 to 99.9% by weight, more preferably 95 to 99.8% by weight, and 98 to 99.7% by weight with respect to the entire rubber component contained in the rubber composition. Further preferred.

  In the step (a1) in the production steps 1 and 2, by mixing a rubber latex with a solution containing benzene having at least one hydroxyl group and formaldehyde, the benzene having at least one hydroxyl group and formaldehyde are polymerized to form a resole A resin is formed and dispersed in the rubber latex. As benzene having at least one hydroxyl group, the same ones as mentioned above can be used. Further, an alkali may be blended as a catalyst in the polymerization of benzene having at least one hydroxyl group and formaldehyde. Specific examples of the alkali can be the same as those mentioned above.

  What is necessary is just to mix | blend suitably each compounding quantity of benzene which has at least 1 hydroxyl group, and formaldehyde so that it may become content of the resole resin contained in the said rubber composition.

  A mechanical defibrating method after mixing the resole resin-rubber dispersion and the pulp in the step (b1) of the manufacturing method 1 and the pulp in the step (b2) of the manufacturing method 2 are mechanically defibrated. As a method, it is mechanically ground or beaten by a refiner, twin screw kneader (double screw extruder), twin screw kneader, high pressure homogenizer, medium stirring mill, stone mill, grinder, vibration mill, sand grinder, etc. The method of doing is mentioned. By these methods, the pulp is defibrated or refined into microfibrillated plant fibers. A preferable temperature in the defibrating treatment is 0 to 99 ° C, more preferably 0 to 90 ° C. It is desirable that the pulp that is the raw material for the defibrating process has a shape (for example, a powder form) suitable for the defibrating process. In addition, it is advantageous in terms of reducing the defibrating energy when the pulp is steamed with steam (for example, heated in a pressure cooker in the presence of moisture) prior to the defibrating treatment.

  A preferable defibrating method is grinding treatment, and it is preferable to use a stone mill type grinding machine or a twin screw kneading extruder. The grinding may be performed until the fiber diameter reaches a desired size.

  The dispersion obtained in step (c1) of production methods 1 and 2 is solidified with an acid and then dried.

  Examples of the acid for solidifying the solid content in the dispersion include formic acid, acetic acid, hydrochloric acid, and sulfuric acid.

  The rubber composition (masterbatch) obtained by the above method further comprises reinforcing fillers such as carbon black and silica; silane compounds such as silane coupling agents; process oils; waxes; anti-aging agents; sulfur and vulcanization. Vulcanizing agents such as accelerators; vulcanizing aids such as zinc oxide and stearic acid can be appropriately blended.

  In the rubber composition of the present invention, the microfibrillated plant fiber (B) is well dispersed in the rubber component (A) through the resol resin (C). Therefore, the fracture characteristics and rigidity are improved. Therefore, it is suitably used for tires, and when used for tires, it is possible to improve steering stability without deteriorating low fuel consumption characteristics.

  When the rubber composition of the present invention is used for tires, rubber containing the rubber component (A), microfibrillated plant fiber (B), and resole resin (C) prepared as described above with a Banbury mixer, kneader, open roll or the like A rubber composition can be produced by further kneading a desired additive into the composition and then vulcanizing it.

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

  A pneumatic tire is manufactured by a normal method using the rubber composition of the present invention. That is, the rubber composition of the present invention is further mixed with a desired compounding agent and kneaded, and the resulting kneaded product is extruded in accordance with the shape of various members of the tire at an unvulcanized stage. An unvulcanized tire is formed by molding in the usual manner. A tire can be obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

  Since the rubber composition of the present invention contains a resole resin and microfibrillated plant fibers, the interface between the rubber component and cellulose is partially chemically bonded through the resole resin. Interfacial interaction with plant fibers is improved, and the dispersibility of the microfibrillated plant fibers in the rubber component is improved. Therefore, the breaking characteristics of the rubber composition are improved. When such a rubber composition is used for a pneumatic tire, it is possible to improve steering stability by improving rigidity without reducing fuel efficiency.

[Example]
The present invention will be described more specifically with reference to the following examples and comparative examples. In addition, this invention is not limited to the following embodiment.

<Preparation of Resole Resin-Rubber Dispersion 1>
Dissolve 0.5 g of sodium hydroxide in 242.2 g of water, and then add 16.2 g of formalin (concentration: 37% by weight formaldehyde aqueous solution) and 11.0 g of resorcin, homogenize, and aged at 30 ° C for 5 hours to liquid A Got. Next, 80.0 g of Liquid A, 64.8 g of natural rubber latex (Golden Hope Plantations, HYTEX-HA, solid content 60% by weight) and 63.8 g of water were mixed with stirring and aged for 1 hour at 30 ° C. A resin-rubber dispersion 1 was obtained.

<Preparation of resole resin-rubber dispersion 2>
Dissolve 1.0g of sodium hydroxide in 368.5g of water, add 26.5g of formalin (formaldehyde aqueous solution with a concentration of 37% by weight) and 17.0g of resorcin, homogenize it, and age for 8 hours at 25 ° C Got. Next, the total amount of solution A, 259.7 g of modified styrene butadiene rubber latex (manufactured by Nippon A & L Co., Ltd., PYRATEX, solid content 41 wt%), 114.1 g of styrene butadiene rubber latex (JSR Corp., JSR 2108, solid content 40 wt%) and water 213.2 g was stirred and mixed, and aged at 25 ° C. for 1 hour to obtain a resole resin-rubber dispersion 2.

<Preparation of microfibrillated plant fiber>
Pulp (unbleached kraft pulp derived from conifers (lignin 5-7 wt%)), or a mixture of the pulp and resole resin-rubber dispersion 1, or a mixture of the pulp and resole resin-rubber dispersion 2 with a solid content of 30 wt% Then, microfibrillated plant fibers 1, 2 and 3 were prepared by processing with a twin-screw kneading extruder under the operating conditions of 400 rpm and 0 ° C. Table 1 shows the blending amounts of microfibrillated plant fibers 1 and 2. In addition, the content ratio of the resole resin in the resole resin-rubber dispersion in the microfibrillated plant fiber 2 is 1.0% by weight, the content ratio of the natural rubber is 8.1% by weight, and in the microfibrillated plant fiber 3 The content of resole resin in the resole resin-rubber dispersion was 1.6% by weight, and the content of synthetic rubber was 8.9% by weight.

<Preparation of master batch>
・Preparation of masterbatch 1
50 g of microfibrillated plant fiber 1 (solid content: 30% by weight) was stirred and dispersed in 1450 g of water using a high-speed homogenizer (IKA batch homogenizer T65D Ultra Turrax (Ultraturrax T25)) for 1 hour. Then, 250 g of natural rubber latex (Golden Hope Plantations, HYTEX-HA, solid content concentration: 60% by weight) was added, and the mixture was further stirred and dispersed at 24,000 rpm for 30 minutes to prepare a dispersion. The obtained dispersion was coagulated with a 5 wt% formic acid aqueous solution, washed with water, and then dried in a heating oven at 40 ° C. to obtain a master batch 1.

Preparation of masterbatch 2 A dispersion is prepared using microfibrillated plant fiber 2 containing resole resin-rubber dispersion 1. The resulting dispersion is coagulated with 5% by weight aqueous formic acid, washed with water, It was prepared in the same manner as Masterbatch 1 except that it was dried in a heating oven at 0 ° C.

-Preparation of masterbatch 3 A dispersion was prepared using microfibrillated plant fiber 3 containing resole resin-rubber dispersion 2, and the resulting dispersion was coagulated with a 5 wt% aqueous formic acid solution, washed with water, It was prepared in the same manner as Masterbatch 1 except that it was dried in a heating oven at 0 ° C.

・Preparation of masterbatch 4 Without using microfibrillated plant fibers, solid rubber concentration: 60% natural rubber latex (HYTEX-HA, manufactured by Golden Hope Plantations, Inc.) was coagulated with 5% by weight aqueous formic acid solution. After washing with water, drying in a heating oven at 40 ° C. gave a master batch 4.

・Preparation of masterbatch 5
25 g of microfibrillated plant fiber 1 (solid content: 30% by weight) was stirred and dispersed in 725 g of water using a high-speed homogenizer (IKA batch homogenizer T65D Ultra Turrax (Ultraturrax T25)) for 1 hour. Then, 250 g of natural rubber latex (Golden Hope Plantations, HYTEX-HA, solid content concentration: 60% by weight) was added, and the mixture was further stirred and dispersed at 24,000 rpm for 30 minutes to prepare a dispersion. The obtained dispersion was coagulated with a 5 wt% aqueous formic acid solution, washed with water, and then dried in a heating oven at 40 ° C. to obtain a master batch 5.

-Preparation of masterbatch 6 A dispersion was prepared using microfibrillated plant fiber 2 containing resole resin-rubber dispersion 1, and the resulting dispersion was coagulated with a 5 wt% aqueous formic acid solution, washed with water, It was prepared in the same manner as Masterbatch 5 except that it was dried in a heating oven at 0 ° C.

・Preparation of Masterbatch 7 A dispersion was prepared using microfibrillated plant fiber 3 containing resole resin-rubber dispersion 2, and the resulting dispersion was coagulated with a 5 wt% aqueous formic acid solution, washed with water, It was prepared in the same manner as Masterbatch 5 except that it was dried in a heating oven at 0 ° C.

・Preparation of masterbatch 8
50 g of microfibrillated plant fiber 1 (solid content: 30% by weight) and 7.1 g of resole resin-rubber dispersion 1 in 1450 g of water in a high speed homogenizer (IKA batch homogenizer T65D Ultra Turrax (Ultraturrax T25)) 24,000 rpm for 1 hour with stirring, and then 250 g of natural rubber latex (Golden Hope Plantations, HYTEX-HA, solid content: 60% by weight) is added, and further 24,000 rpm, 30 minutes A dispersion was prepared by stirring and dispersing. The obtained dispersion was coagulated with a 5 wt% formic acid aqueous solution, washed with water, and then dried in a heating oven at 40 ° C. to obtain a master batch 1.

・Preparation of masterbatch 9
It was prepared in the same manner as Masterbatch 8 except that 8.3 g of resole resin-rubber dispersion 2 was used.

-Preparation of masterbatch 10
High-speed homogenizer (IKA batch homogenizer T65D Ultra Turrax (Ultraturrax T25)) in 25 g of water with 25 g of microfibrillated plant fiber 1 (solid content: 30% by weight) and 3.6 g of resole resin-rubber dispersion 1 24,000 rpm for 1 hour with stirring, and then 250 g of natural rubber latex (Golden Hope Plantations, HYTEX-HA, solid content: 60% by weight) is added, and further 24,000 rpm, 30 minutes A dispersion was prepared by stirring and dispersing. The obtained dispersion was coagulated with a 5 wt% aqueous formic acid solution, washed with water, and then dried in a heating oven at 40 ° C. to obtain a master batch 5.

-Preparation of masterbatch 11
It was prepared in the same manner as Masterbatch 8 except that 4.2 g of resole resin-rubber dispersion 2 was used.

<Preparation of vulcanized rubber composition>
Various master batches and compounding agents were kneaded for 5 minutes with a 6-inch open roll at 60 ° C. and 24 rpm, and then press heated at 150 ° C. to correspond to Comparative Examples 1 and 2, Examples 1 to 8 and Reference Example 1. A vulcanized rubber composition was obtained. Tables 2 and 3 show the mixing ratios of various master batches and compounding agents. In addition, the compounding amount of natural rubber in Examples 1, 3, 5, and 7 represents the total amount of natural rubber in rubber latex and natural rubber in microfibrillated plant fiber 2, and in microfibrillated plant fiber 2 These natural rubbers contain 0.9% by weight (Examples 1 and 5) and 0.4% by weight (Examples 3 and 7) in the total amount of natural rubber. Similarly, the compounding amount of the synthetic rubber in Examples 2, 4, 6, and 8 represents the total amount of the synthetic rubber in the rubber latex and the synthetic rubber in the microfibrillated plant fiber 3, and the microfibrillated plant fiber 3 This synthetic rubber contains 1.0% by weight (Examples 2 and 6) and 0.5% by weight (Examples 4 and 8) in the total amount of natural rubber and synthetic rubber.

The detail of each compounding component in Table 2 and Table 3 is shown below.

Anti-aging agent: NOCRACK 6C (Ouchi Shinsei Chemical Co., Ltd.)
Stearic acid: Bead stearic acid Tsubaki (manufactured by NOF Corporation)
Zinc oxide: 2 types of zinc oxide (Mitsui Metal Mining Co., Ltd.)
Sulfur: Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)
Vulcanization accelerator: Noxeller DM (Ouchi Shinsei Chemical Co., Ltd.)

<Examples 1-8, Comparative Examples 1-2, and Reference Example 1>
The following evaluation was performed using the vulcanized rubber composition produced by the above method. The tensile strength index, breaking elongation index, fracture energy index, steering stability index, and rolling resistance index in the characteristic data shown in Table 4 and Table 5 are based on Reference Example 1 and the following formula: Calculated.

(Tensile test)
Tensile strength and elongation at break were measured according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The following formula:
Tensile strength index = (breaking stress of each compound) ÷ (breaking stress of standard compound) × 100
Breaking elongation index = (breaking elongation of each compound) ÷ (breaking elongation of the standard compound) × 100
Tensile strength index, breaking elongation index, and breaking energy index were calculated according to the following formula: Fracture energy index = (Breaking stress of each formulation × Breaking elongation ÷ 2) ÷ (Breaking stress of reference blend × Breaking elongation ÷ 2) × 100. 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, 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). 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 * for each formulation) ÷ (E * for standard formulation) x 100
Rolling resistance index = (tan δ of each formulation) ÷ (tan δ of standard 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 when used as a pneumatic tire.

Claims (13)

(A) rubber component,
(B) A rubber composition containing microfibrillated plant fibers obtained by mechanically defibrating pulp, and (C) a resole resin. The rubber composition according to claim 1, wherein the resol resin (C) is obtained by polymerization of benzene having at least one hydroxyl group and formaldehyde. The rubber composition according to claim 2, wherein the benzene having at least one hydroxyl group is resorcin. The rubber composition according to any one of claims 1 to 3, wherein the content of the microfibrillated plant fiber (B) is 1 to 50 parts by weight with respect to 100 parts by weight of the rubber component (A). The rubber composition according to any one of claims 1 to 4, wherein the content of the resol resin (C) is 0.01 to 5 parts by weight with respect to 100 parts by weight of the rubber component (A). The rubber composition according to any one of claims 1 to 5, wherein the mechanical fibrillation treatment in the microfibrillated plant fiber (B) is a grinding treatment. The rubber composition according to any one of claims 1 to 6, wherein the average fiber diameter of the microfibrillated plant fiber (B) is 10 µm or less. The rubber composition according to any one of claims 1 to 7, which is used for tires. A step of blending a rubber latex containing 1 to 60% by weight of a rubber component with respect to the whole rubber latex component and a solution containing benzene and formaldehyde having at least one hydroxyl group to obtain a resole resin-rubber dispersion ( a1),
Step (b1) of obtaining resole resin-rubber dispersion-containing microfibrillated plant fiber by mechanically defibrating after mixing the resole resin-rubber dispersion obtained in step (a1) and pulp.
A step of mixing a resol resin-rubber dispersion-containing microfibrillated plant fiber obtained by the step (b1) and a rubber latex containing 1 to 60% by weight of a rubber component with respect to the entire rubber latex component to obtain a dispersion. The manufacturing method of the rubber composition in any one of Claims 1-8 including the process (d1) which solidifies the dispersion liquid obtained by (c1) and a process (c1), and is made to dry and obtains a masterbatch. A step of blending a rubber latex containing 1 to 60% by weight of a rubber component with respect to the whole rubber latex component and a solution containing benzene and formaldehyde having at least one hydroxyl group to obtain a resole resin-rubber dispersion ( a1),
After the pulp is mechanically defibrated to obtain microfibrillated plant fibers, the microfibrillated plant fibers and the resole resin-rubber dispersion obtained in the step (a1) are mixed, and the resole resin-rubber dispersion is contained. Obtaining a microfibrillated plant fiber (b2),
The resole resin-rubber dispersion-containing microfibrillated plant fiber obtained in the step (b2) and the rubber latex containing 1 to 60% by weight of the rubber component with respect to the entire rubber latex component are mixed to obtain a dispersion. The method for producing a rubber composition according to any one of claims 1 to 8, comprising a step (d1) of solidifying the dispersion obtained by the step (c1) and the step (c1) and then drying to obtain a master batch. . The method for producing a rubber composition according to claim 9, wherein the mechanical defibrating process in the step (b1) is a grinding process. The method for producing a rubber composition according to claim 10, wherein the mechanical defibrating process in the step (b2) is a grinding process. A pneumatic tire using the rubber composition according to claim 1.