JP7081222B2 - Manufacturing method of microfibrillated plant fiber / rubber complex - Google Patents

Description

The present invention relates to a method for producing a microfibrillated plant fiber / rubber composite.

By blending microfibrillated plant fibers such as cellulose fibers into the rubber composition as a filler, the rubber composition can be reinforced and the modulus (complex elastic modulus) can be improved. However, microfibrillated plant fibers have strong self-cohesive power and poor compatibility with rubber components.

Further, when a master batch was prepared by mixing rubber latex and microfibrillated plant fibers, agglomerates of microfibrillated plant fibers tended to be easily generated in the master batch. Therefore, when the above masterbatch is used for tires, the generated agglomerates may cause premature wear, cracking, chipping, and interlayer separation, and may also lead to air leakage and loss of steering stability. there were.

As described above, when the microfibrillated plant fiber is blended, although the modulus is improved, the required performance of the tire is lowered, and there is room for improvement in that the functional merit as a tire may be lost.

On the other hand, a method for improving the compatibility between the rubber component and the microfibrillated plant fiber by chemically modifying the microfibrillated plant fiber is disclosed (see, for example, Patent Document 1). Further, a cellulose fiber having an average fiber diameter of 1 to 200 nm and having a carboxy group in the constituent cellulose and a fine cellulose fiber having a carboxy group having an average fiber diameter of 0.1 to 200 nm are treated with a hydrophobic modification having a hydrocarbon group. A method for improving the dispersibility of cellulose fibers in rubber by blending finely modified cellulose fibers obtained by treating with an agent into rubber is disclosed (see, for example, Patent Documents 2 and 3). Furthermore, there is also a method of improving the affinity and dispersibility for rubber components by using a composite cellulose fiber obtained by graft-polymerizing a monomer or a polymer with cellulose nanofibers having an average fiber diameter of nano-order as a reinforcing material for rubber. It is disclosed (see, for example, Patent Document 4).

Japanese Patent No. 4581116 Japanese Unexamined Patent Publication No. 2013-18918 Japanese Unexamined Patent Publication No. 2014-125607 Japanese Unexamined Patent Publication No. 2009-263417

As described above, various methods for improving the dispersibility and compatibility of microfibrillated plant fibers in rubber have been studied. For example, even if the methods disclosed in Patent Documents 1 to 4 are used. , It was not enough in terms of comprehensively improving the above-mentioned performance.

The present invention solves the above-mentioned problems and manufactures a microfibrillated plant fiber / rubber composite capable of improving the required performance of a tire in a well-balanced manner by finely dispersing the microfibrillated plant fiber in rubber and blending it in a rubber composition. The purpose is to provide a method of doing so.

The present invention is a method for producing a microfibrillated plant fiber / rubber composite, in which the anionic surfactant and a microfibrillated plant fiber dispersion are mixed to prepare a mixed solution. A step and a step of mixing the mixed solution with rubber are included, the anionic surfactant has a hydrophobic group and a hydrophilic group, and the microfibrillated plant fiber has an average fiber diameter of 4. The present invention relates to a method for producing a microfibrillated plant fiber / rubber composite, which is characterized by having a diameter of about 100 nm.

The hydrophobic group is preferably a hydrocarbon group.

The hydrophilic group is preferably at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphoric acid group.

The microfibrillated plant fiber dispersion is preferably a chemically modified microfibrillated plant fiber dispersion.

The rubber is preferably a rubber latex or a liquid polymer.

The average fiber diameter of the microfibrillated plant fiber is preferably 10 to 90 nm.

The present invention also relates to a microfibrillated plant fiber / rubber composite obtained by the above-mentioned production method.

The present invention also relates to a rubber composition containing the microfibrillated plant fiber / rubber composite.

The present invention is also a rubber composition containing a rubber component and microfibrillated plant fibers, wherein the average fiber diameter of the microfibrillated plant fibers in the rubber composition is 4 to 100 nm, which is the maximum fiber diameter. It relates to a rubber composition characterized by a frequency value of 10 to 70 nm.

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

The present invention includes a step of mixing an anionic surfactant and a microfibrillated plant fiber dispersion to prepare a mixed solution, and a step of mixing the mixed solution with rubber, and the above-mentioned anionic interface. Since the activator has a hydrophobic group and a hydrophilic group and the average fiber diameter of the microfibrillated plant fiber is 4 to 100 nm, it is a method for producing a microfibrillated plant fiber / rubber composite. It is possible to obtain a microfibrillated plant fiber / rubber composite in which fibrillated plant fibers are finely dispersed. By using such a microfibrillated plant fiber / rubber composite, it is possible to obtain a rubber composition and a pneumatic tire in which the durability, steering stability, and fuel efficiency required for the tire are improved in a well-balanced manner. can.

6 is an electron micrograph of the microfibrillated plant fiber / natural rubber composite obtained in Example 11 observed with an electron microscope. 6 is an electron micrograph of the chemically modified microfibrillated plant fiber / natural rubber composite obtained in Example 20 observed with an electron microscope. 6 is an electron micrograph of the microfibrillated plant fiber / natural rubber composite obtained in Comparative Example 11 observed with an electron microscope.

[Manufacturing method of microfibrillated plant fiber / rubber complex]
The method for producing a microfibrillated plant fiber / rubber composite of the present invention comprises a step of mixing an anionic surfactant and a microfibrillated plant fiber dispersion to prepare a mixed solution (step (1)). , The step of mixing the mixed solution and the rubber (step (2)) is included. The production method of the present invention may include other steps as long as the above steps are included, and the above steps may be performed once or repeated a plurality of times, respectively.

Even if rubber and microfibrillated plant fibers are mixed, the compatibility is poor and it is difficult to sufficiently disperse the microfibrillated plant fibers, whereas the present inventors have hydrophobic and hydrophilic groups. By mixing an anionic surfactant having a It has been found that the separation of plant fibers and rubber and the aggregation of microfibrillated plant fibers can be suppressed, and the generation of agglomerates can be suppressed. Furthermore, since good coagulation is also obtained, a complex in which microfibrillated plant fibers are sufficiently finely dispersed can be prepared, and by preparing the complex in the presence of the above-mentioned surfactant, microfibrillation can be obtained. It was also found that the loss of plant fiber and rubber components can be suppressed.

(Step (1))
In the present invention, first, a step (step (1)) of mixing an anionic surfactant and a microfibrillated plant fiber dispersion to prepare a mixed solution is performed.

The anionic surfactant has a hydrophobic group and a hydrophilic group. By using such a surfactant, the hydrophobic group and the hydrophobic group of rubber form a hydrophobic-hydrophobic bond to show affinity, and the hydrophilic group and the hydroxyl group of the microfibrillated plant fiber are formed. In order to show affinity by adsorbing with hydrogen bonds, it is possible to enhance the dispersibility of microfibrillated plant fibers, suppress the aggregation of microfibrillated plant fibers in rubber, and suppress the generation of aggregates. It is presumed that it can be done. As the anionic surfactant, one type may be used, or two or more types may be used in combination.

The hydrophobic group may be any hydrophobic functional group, but a hydrocarbon group is preferable. The hydrocarbon group may be linear, branched or cyclic, and examples thereof include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group. Of these, aliphatic hydrocarbon groups and aromatic hydrocarbon groups are preferable. The hydrocarbon group preferably has 4 to 20, more preferably 4 to 15, and even more preferably 4 to 12.

The aliphatic hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 6 carbon atoms. Preferred examples include the above-mentioned alkyl group having a carbon number of carbons, and specifically, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-. Examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group and an octadecyl group. In addition, the above-mentioned alkenyl group and alkynyl group having a carbon number are also mentioned. The group is mentioned. Among them, the isobutylene group is preferable from the viewpoint that the effect of the present invention can be obtained more preferably.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms, and specifically, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopropenyl group, and the like. Examples thereof include a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a cyclooctenyl group and the like.

The aromatic hydrocarbon group preferably has 6 to 12 carbon atoms, and specific examples thereof include a phenyl group, a benzyl group, a phenethyl group, a tolyl group, a xylyl group, and a naphthyl group. Be done. Among them, a phenyl group, a benzyl group and a phenyl group are preferable, a phenyl group and a benzyl group are more preferable, and a phenyl group is particularly preferable, from the viewpoint that the effect of the present invention can be obtained more preferably. The substitution position of the methyl group on the benzene ring in the tolyl group and the xylyl group may be any of the ortho-position, the meta-position and the para-position.

The hydrophilic group is preferably at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphoric acid group. Among them, the carboxyl group is particularly preferable from the viewpoint that the effect of the present invention can be obtained more preferably.

Among the above-mentioned anionic surfactants, an anion having a phenyl group or an isobutylene group as a hydrophobic group and a carboxyl group as a hydrophilic group from the viewpoint that the effect of the present invention can be more preferably obtained. Sexual surfactants are particularly preferred.

As the anionic surfactant, those having a functional group as described above are preferable, and specific examples thereof include carboxylic acid type, sulfonic acid type, sulfuric acid ester type and phosphoric acid ester type. It can be classified as a surfactant.

Examples of the carboxylic acid-based surfactant include fatty acid salts having 6 to 30 carbon atoms, polyvalent carboxylates, rosinates, dimerates, polymer acid salts, tall oil fatty acid salts, and polycarboxylic acid types. Examples thereof include a polymer surfactant, preferably a carboxylate having 10 to 20 carbon atoms, a polycarboxylate, and a polycarboxylic acid type polymer surfactant, and particularly preferably a polycarboxylic acid type polymer surfactant. It is an agent.
Examples of the sulfonic acid-based surfactant include alkylbenzene sulfonates, alkyl sulfonates, alkylnaphthalene sulfonates, naphthalene sulfonates, diphenylether sulfonates and the like.
Examples of the sulfate ester-based surfactant include an alkyl sulfate ester salt, a polyoxyalkylene alkyl sulfate ester salt, a polyoxyalkylene alkylphenyl ether sulfate salt, a tristyrene phenol sulfate ester salt, and a distyreneized phenol sulfate. Examples thereof include an ester salt, an α-olefin sulfate ester salt, an alkyl succinic acid sulfate ester salt, a polyoxyalkylene tristylated phenol sulfate ester salt, and a polyoxyalkylene distyreneized phenol sulfate ester salt.
Examples of the phosphoric acid ester-based surfactant include an alkyl phosphate ester salt, a polyoxyalkylene phosphate ester salt and the like.
Examples of the salt of these compounds include metal salts (Na, k, Ca, Mg, Zn, etc.), ammonium salts, amine salts (triethanolamine salts, etc.) and the like.

Examples of the alkyl group in the above-mentioned surfactant include an alkyl group having 4 to 30 carbon atoms. Examples of the polyoxyalkylene group include those having an alkylene group having 2 to 4 carbon atoms, and for example, those having an addition mole number of ethylene oxide of about 1 to 50 mol can be used.

The anionic surfactant preferably has a weight average molecular weight (Mw) of 500 or more, and more preferably 1000 or more. Further, it is preferably 50,000 or less, and more preferably 30,000 or less. When the weight average molecular weight of the anionic surfactant is in such a range, the effect of the present invention can be obtained more preferably.
In the present specification, Mw is gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). It can be obtained by standard polystyrene conversion based on the measured value according to.

As the anionic surfactant, for example, products of Elementis, Kao Corporation, Dai-ichi Kogyo Seiyaku Co., Ltd., Sanyo Chemical Industries, Ltd. and the like can be used.

The microfibrillated plant fiber dispersion liquid is a dispersion liquid (slurry) in which microfibrillated plant fibers are dispersed in a solvent, and the solvent is not particularly limited, and examples thereof include water.

As the microfibrillated plant fiber contained in the dispersion liquid, cellulose microfibrils are preferable from the viewpoint of obtaining good reinforcing properties. Cellulose microfibrils are not particularly limited as long as they are derived from natural products, and for example, resource biomass such as fruits, grains and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp obtained from these as raw materials. Paper, cloth, agricultural waste, waste biomass such as food waste and sewage sludge, unused biomass such as rice straw, straw, and thinned wood, as well as those derived from cellulose produced by squirrels, acetic acid bacteria, etc. Be done. These microfibrillated plant fibers may be used alone or in combination of two or more.

In the present specification, the cellulose microfibrils are typically cellulose fibers having an average fiber diameter within the range of 10 μm or less, and more typically, an average fiber diameter formed by an assembly of cellulose molecules. It means a cellulose fiber having a microstructure of 500 nm or less. Note that typical cellulose microfibrils can be formed, for example, as an aggregate of cellulose fibers having an average fiber diameter as described above.

The method for producing the microfibrillated plant fiber is not particularly limited, but for example, after chemically treating the raw material of the cellulose microfibril with an alkali such as sodium hydroxide as necessary, a refiner and a twin-screw kneader (biaxial). Extruder), twin-screw kneading extruder, high-pressure homogenizer, medium stirring mill, stone mill, grinder, vibration mill, sand grinder, etc. can be used for mechanical grinding or beating. In these methods, lignin is separated from the raw material by chemical treatment, so that microfibrillated plant fiber containing substantially no lignin can be obtained. Further, as another method, a method of treating the raw material of the cellulose microfibrils with ultra-high pressure can be mentioned.

As the microfibrillated plant fiber, for example, a product such as Sugino Machine Limited can be used.

The microfibrillated plant fiber contained in the dispersion may be obtained by the above-mentioned production method and further subjected to oxidation treatment or various chemical modification treatments, or may be derived from the above-mentioned cellulose microfibrils. Natural products (for example, wood, pulp, bamboo, hemp, jute, kenaf, agricultural waste, cloth, paper, squirrel cellulose, etc.) are used as cellulose raw materials, and oxidation treatment and various chemical modification treatments are performed, and then necessary. It is also possible to use one which has been subjected to defibration treatment according to the above, or one which has been further subjected to oxidation treatment or various chemical modification treatments in the state of a microfibrillated plant fiber dispersion. That is, it is also one of the preferred embodiments of the present invention that the microfibrillated plant fiber dispersion is a chemically modified microfibrillated plant fiber dispersion.

Examples of the mode of chemical denaturation of the microfibrillated plant fiber include esterification treatment, etherification treatment, acetalization treatment and the like. More specifically, acylation such as acetylation, cyanoethylation, amination, sulfone esterification, phosphoric acid esterification, alkyl esterification, alkyl etherification, composite esterification, β-ketoesterification, alkylation such as butylation. Esterification, chlorination, etc. are preferably exemplified. Further, alkyl carbamate formation and aryl carbamate formation can also be exemplified.

That is, the microfibrillated plant fiber is a chemically modified microfibrillated plant fiber, and the chemical modification in the chemically modified microfibrillated plant fiber is acetylation, amination, sulfone esterification, alkyl esterification, or composite esterification. , Β-ketoesteration, alkylcarbamation, and arylcarbamation, preferably at least one selected from the group. All of the chemical modification treatments are treatments for making microfibrillated plant fibers hydrophobic, and by using the microfibrillated plant fibers subjected to such chemical modification treatment, the dispersibility of the microfibrillated plant fibers Can be further improved, and the effect of the present invention can be made more suitable.

The chemically modified microfibrillated plant fiber is preferably chemically modified so that the degree of substitution is in the range of 0.2 to 2.5. Here, the degree of substitution means the average number of hydroxyl groups substituted with other functional groups by chemical modification among the hydroxyl groups of cellulose per glucose ring unit, and the theoretical maximum value is 3. When the degree of substitution is 0.2 or more, the dispersibility of the chemically modified microfibrillated plant fiber is particularly good, and when the degree of substitution is 2.5 or less, the chemically modified microfibrillated plant fiber is particularly dispersible. It is excellent and particularly excellent in flexibility, and the effect of the present invention can be obtained more preferably. The degree of substitution is more preferably in the range of 0.3 to 2.5, further preferably in the range of 0.4 to 2.3, and in the range of 0.4 to 2.0. It is particularly preferable to have.

When the chemically modified microfibrillated plant fiber is composed of two or more kinds, the degree of substitution is calculated as an average of all the chemically modified microfibrillated plant fibers.

The degree of substitution in the chemically modified microfibrillated plant fiber can be confirmed, for example, by a titration method using 0.5N-NaOH and 0.2N-HCl, NMR, infrared absorption spectrum and the like.

When the chemically modified microfibrillated plant fiber is an acetylated microfibrillated plant fiber, the degree of substitution is 0.3 to 2.5, and when the chemical-modified microfibrillated plant fiber is an ainated microfibrillated plant fiber, the degree of substitution is 0.3. ~ 2.5, the degree of substitution is 0.3 to 1.8 in the case of sulfone-esterified microfibrillated plant fiber, and the degree of substitution is 0.3 to 1.8 in the case of alkyl esterified microfibrillated cellulose. , The degree of substitution is 0.4 to 1.8 in the case of composite esterified microfibril cellulose, the degree of substitution is 0.3 to 1.8 in the case of β-ketoesterized microfibril cellulose, and the degree of substitution is 0.3 to 1.8. In the case of fibril cellulose, the degree of substitution is preferably in the range of 0.3 to 1.8, and in the case of arylcarbamate-modified microfibril cellulose, the degree of substitution is preferably in the range of 0.3 to 1.8.

The acetylation can be carried out, for example, by adding acetic acid, concentrated sulfuric acid or acetic anhydride to microfibrillated plant fibers and reacting them. More specifically, for example, in the presence of a sulfuric acid catalyst in a mixed solvent of acetic acid and toluene, the microfibrillated plant fiber and acetic anhydride are reacted to proceed with the acetylation reaction, and then the solvent is replaced with water. It can be carried out by a conventionally known method such as a method.

The amination can be carried out by a known method such as a method of reacting with an alkylamine in an alcohol after tosyl esterification and causing a parent nucleus substitution reaction.

The above-mentioned sulfone esterification can be carried out by a simple operation of, for example, dissolving microfibrillated plant fiber in sulfuric acid and putting it in water. In addition, it can be treated by anhydrous sulfuric acid gas treatment, treatment with chlorosulfuric acid and pyridine, or the like.

The phosphoric acid esterification can be carried out, for example, by a method of treating microfibrillated plant fibers treated with dimethylamine or the like with phosphoric acid and urea.

The alkyl esterification can be carried out, for example, by the Schotten-Baumann method (Schotten-Baumann method) in which microfibrillated plant fibers are reacted with a carboxylic acid chloride under basic conditions, and the alkyl etherification can be carried out. , Microfibrillated plant fibers can be reacted with alkyl halides under basic conditions by the Williamson method or the like.

The chlorination can be carried out, for example, by adding thionyl chloride in DMF (dimethylformamide) and heating.

The composite esterification can be carried out, for example, by reacting microfibrillated plant fibers with two or more kinds of carboxylic acid anhydrides or carboxylic acid chlorides under basic conditions.

The β-ketoesterization can be carried out, for example, by reacting the microfibrillated plant fiber with diketene or an alkyl ketene dimer, or by an ester exchange reaction between the microfibrillated plant fiber and a β-ketoester compound such as an alkyl acetoacetate. can.

The alkylcarbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with an alkylisocyanate in the presence of a basic catalyst or a tin catalyst.

The arylcarbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with arylisocyanate in the presence of a basic catalyst or a tin catalyst.

Examples of the mode of the oxidation treatment of the microfibrillated plant fiber include an oxidation treatment using an N-oxyl compound.
The oxidation treatment using the N-oxyl compound can be carried out, for example, by a method in which the N-oxyl compound is used as an oxidation catalyst in water and an copolymer is allowed to act on the microfibrillated plant fibers.

Examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives.
Examples of the copolymerizer include sodium hypochlorite and the like.

The average fiber diameter of the microfibrillated plant fiber is 4 to 100 nm. When the average fiber diameter of the microfibrillated plant fiber is in such a range, the dispersibility of the microfibrillated plant fiber can be sufficiently improved, and the effect of the present invention can be obtained. In addition, damage to microfibrillated plant fibers during processing can be suppressed. The average fiber diameter is preferably 90 nm or less, more preferably 50 nm or less, from the viewpoint that the effects of the present invention can be obtained more preferably. Further, it is preferably 10 nm or more, and more preferably 20 nm or more, because the microfibrillated plant fibers are difficult to be entangled and dispersed.

The average fiber length of the microfibrillated plant fiber is preferably 100 nm or more. It is more preferably 300 nm or more, still more preferably 500 nm or more. Further, 5 mm or less is preferable, 1 mm or less is more preferable, 50 μm or less is further preferable, 3 μm or less is particularly preferable, and 2 μm or less is most preferable. When the average fiber length is less than the lower limit or exceeds the upper limit, there is a tendency similar to the above-mentioned average fiber diameter.

When the microfibrillated plant fiber is composed of two or more kinds, the average fiber diameter and the average fiber length are calculated as the average of all the microfibrillated plant fibers.

In the present specification, the average fiber diameter and the average fiber length of the microfibrillated plant fibers are determined by image analysis by scanning electron micrograph, image analysis by transmission electron micrograph, image analysis by interatomic force micrograph, and X-ray. It can be measured by analysis of scattering data, pore electron resistance method (Coulter principle method), and the like.

The microfibrillated plant fiber dispersion can be produced by a known method, and the production method is not particularly limited. For example, a microfibrillated plant fiber using a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, or the like. Can be prepared by dispersing in a solvent such as water. The temperature and time at the time of preparation can also be appropriately set within a range normally used so that the microfibrillated plant fibers are sufficiently dispersed in a solvent such as water.

The content (solid content) of the microfibrillated plant fiber in the microfibrillated plant fiber dispersion is not particularly limited, but is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass. More preferably, it is 0.5 to 3% by mass.

In the above step (1), as a method for preparing a mixed solution by mixing an anionic surfactant and a microfibrillated plant fiber dispersion, for example, a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, etc. Examples thereof include a method of mixing an anionic surfactant and a microfibrillated plant fiber dispersion liquid using a known stirring device of the above, and the anionic surfactant is sufficiently stirred until it is sufficiently dispersed. And a mixed solution of microfibrillated plant fiber dispersion can be obtained. The temperature and time for preparing the mixed solution can be appropriately set within a range normally used until the anionic surfactant and the microfibrillated plant fiber dispersion are sufficiently dispersed. For example, It is preferably 10 to 40 ° C. for 3 to 120 minutes, more preferably 15 to 30 ° C. for 5 to 90 minutes.

In the step (1), the amount of the anionic surfactant added is 8 to 50 parts by mass with respect to 100 parts by mass of the microfibrillated plant fiber (solid content) contained in the microfibrillated plant fiber dispersion. Is preferable. When the amount of the anionic surfactant added is in such a range, the effect of the present invention can be more preferably obtained. The addition amount is more preferably 9 parts by mass or more, further preferably 10 parts by mass or more. Further, 25 parts by mass or less is more preferable, and 20 parts by mass or less is further preferable.

(Step (2))
In the present invention, next, a step (step (2)) of mixing the mixed liquid obtained in the step (1) and the rubber is performed.

The rubber is preferably a rubber latex or a liquid polymer. Examples of the rubber latex include natural rubber latex, modified natural rubber latex (kenned natural rubber latex, epoxidized natural rubber latex, etc.), synthetic diene rubber latex (butadiene rubber (BR), styrene butadiene rubber (SBR)). , Styrene isoprene butadiene rubber (SIBR), isoprene rubber, acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinylpyridine rubber, latex such as butyl rubber) and the like can be preferably used. As described above, it is also one of the preferred embodiments of the present invention that the rubber latex is a diene-based rubber latex. These rubber latexes may be used alone or in combination of two or more. Of these, natural rubber latex, SBR latex, BR latex, and isoprene rubber latex are more preferable, and natural rubber latex is particularly preferable, from the viewpoint that the effects of the present invention can be obtained more preferably.

Natural rubber latex is collected as the sap of natural rubber trees such as Hevea, and contains water, proteins, lipids, inorganic salts, etc. in addition to rubber components, and the gel content in rubber is based on the complex presence of various impurities. It is believed to be. In the present invention, as natural rubber latex, raw latex (field latex) produced by tapping heavywood, concentrated latex concentrated by centrifugation or creaming method (purified latex, high ammonia latex to which ammonia is added by a conventional method). , LATZ latex stabilized by zinc flower, TMTD and ammonia) and the like can be used.

Natural rubber latex has honeycomb-like cells consisting of proteins and phospholipids, which tend to inhibit the uptake of microfibrillated plant fibers into natural rubber, resulting in natural rubber latex and micro. When mixing with fibrillated plant fiber, it was necessary to take measures such as removing cells in the natural rubber latex in advance by saponification treatment, but in the present invention, the above-mentioned anionic surfactant is used. By doing so, even when a natural rubber latex that has not undergone the saponification treatment is used, the microfibrillated plant fibers can be sufficiently dispersed.

Here, the pH of the rubber latex is preferably 8.5 or higher, more preferably 9.5 or higher. When the pH is 8.5 or more, the rubber latex is less likely to become unstable and tends to be less likely to coagulate. The pH of the rubber latex is preferably 12 or less, more preferably 11 or less. When the pH is 12 or less, the rubber latex tends to be less likely to deteriorate.

The rubber latex can be prepared by a conventionally known manufacturing method, and various commercially available products can also be used. As the rubber latex, it is preferable to use one having a rubber solid content of 10 to 80% by mass. More preferably, it is 20% by mass or more and 60% by mass or less.

Examples of the liquid polymer include liquid diene-based polymers.
The liquid diene polymer is a diene polymer in a liquid state at room temperature (25 ° C.). The liquid diene polymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0 × ^{10 3} to 2.0 × 105. It is more preferably 3.0 × 10 ³ to 5.0 × 10 ⁴ .

Examples of the liquid diene polymer include a liquid styrene-butadiene polymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), and a liquid styrene isoprene copolymer (liquid SIR). Can be mentioned. These may be used alone or in combination of two or more. Among them, liquid SBR and liquid IR are preferable, and liquid IR is more preferable, from the viewpoint that the effect of the present invention can be obtained more preferably.

The amount of styrene in the liquid SBR is preferably 10% by mass or more, more preferably 20% by mass or more. The amount of styrene is preferably 60% by mass or less, more preferably 50% by mass or less. Within the above numerical range, the effect of the present invention can be obtained more preferably.
The amount of styrene in the liquid SBR is calculated by H1 ^- NMR measurement.

As the liquid polymer, for example, products such as Kuraray Co., Ltd. and Clay Valley Co., Ltd. can be used.

In the above step (2), as a method of mixing the mixture obtained in the step (1) with the rubber, for example, a rubber is used in a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, or a blender mill. A method of dropping the mixture obtained in the step (1) while stirring the mixture, and a method of dropping rubber onto the mixture while stirring the mixture obtained in the step (1) can be mentioned. By sufficiently stirring until the mixture is sufficiently dispersed, a mixture (blended latex) of the mixture obtained in the step (1) and the rubber can be obtained. The temperature and time for producing the mixture can be appropriately set within a range normally used until the mixture obtained in step (1) and the rubber are sufficiently dispersed, and are, for example, 10 to 40. The temperature is preferably 3 to 120 minutes, more preferably 15 to 30 ° C. for 5 to 90 minutes.

The pH of the mixture (blended latex) obtained in the above step (2) is preferably 9.0 or higher, more preferably 9.5 or higher. Further, 12 or less is preferable, and 11.5 or less is more preferable. When the pH of the mixture (blended latex) of the mixture obtained in the above step (1) and the rubber is in such a range, deterioration can be suppressed and stable.

In the above step (2), the mixed solution obtained in the step (1) is mixed so that the microfibrillated plant fiber (solid content) is 2 to 45 parts by mass with respect to 100 parts by mass of the solid content of the rubber. It is preferable to do so. When the blending amount of the microfibrillated plant fiber is in such a range, the effect of the present invention can be obtained more preferably. The content of the microfibrillated plant fiber (solid content) is more preferably 5 parts by mass or more, further preferably 10 parts by mass or more. Further, 40 parts by mass or less is more preferable, and 35 parts by mass or less is further preferable.

The mixture (blended latex) obtained in the above step (2) is coagulated as necessary, and the coagulated product (aggregate containing agglomerated rubber and microfibrillated plant fibers) is filtered and dried by a known method, and further. After drying, rubber kneading is performed with a biaxial roll, Banbury or the like to obtain a composite in which microfibrillated plant fibers are sufficiently dispersed in a rubber matrix (microfibrillated plant fibers / rubber composite). The microfibrillated plant fiber / rubber composite obtained by the production method of the present invention is also one of the present inventions, but the microfibrillated plant fiber / rubber composite inhibits the effect of the present invention. Other components may be contained as long as they do not.

The coagulation is usually carried out by adding an acid to the mixture (blended latex) obtained in the step (2). Examples of the acid for coagulation include sulfuric acid, hydrochloric acid, formic acid, acetic acid and the like. The temperature at the time of solidification is preferably 10 to 40 ° C.

At the time of the solidification, it is preferable to adjust the pH of the mixture (blended latex) obtained in the above step (2) to 3 to 5, and more preferably to 3 to 4. By adjusting the pH of the mixture obtained in the above step (2) to such a range, the effect of the present invention can be more preferably obtained.

Further, a flocculant may be added for the purpose of controlling the state of coagulation (size of coagulated particles). As the flocculant, a cationic polymer or the like can be used.

[Rubber composition]
The rubber composition contains the microfibrillated plant fiber / rubber complex. The microfibrillated plant fiber / rubber complex can be used as a masterbatch. In the above-mentioned microfibrillated plant fiber / rubber composite, the microfibrillated plant fiber is sufficiently dispersed in the rubber, and the microfibrillated plant fiber can be sufficiently dispersed even in the rubber composition mixed with other components. Therefore, effective reinforcing properties can be exhibited, and durability (breaking strength), steering stability, and fuel efficiency can be improved in a well-balanced manner.

The rubber composition may contain a rubber component other than the rubber (rubber component) used in the microfibrillated plant fiber / rubber composite.
As the other rubber component, for example, a diene-based rubber can be used.
Examples of the diene rubber include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber ( NBR) and the like. Examples of the rubber component other than the above include butyl rubber and fluorine rubber. These may be used alone or in combination of two or more. As the rubber component, SBR, BR, and isoprene-based rubber are preferable, and SBR is more preferable.

Here, the other rubber component preferably has a weight average molecular weight (Mw) of 200,000 or more, and more preferably 350,000 or more. The upper limit of Mw is not particularly limited, but is preferably 4 million or less, more preferably 3 million or less.

In the present specification, Mw and number average molecular weight (Mn) are gel permeation chromatography (GPC) (GPC-8000 series manufactured by Toso Co., Ltd., detector: differential refractometer, column: manufactured by Toso Co., Ltd.). It can be obtained by standard polystyrene conversion based on the measured value by TSKGEL SUPERMULTIPORE HZ-M).

The other rubber component may be a non-modified diene-based rubber or a modified diene-based rubber.
The modified diene rubber may be any diene rubber having a functional group that interacts with a filler such as silica. For example, at least one end of the diene rubber is a compound (modifier) having the above functional group. End-modified diene rubber modified with (terminal modified diene rubber having the above functional group at the end), main chain modified diene rubber having the above functional group in the main chain, and the above functional group at the main chain and the end. Main chain terminal modified diene rubber (for example, main chain terminal modified diene rubber having the above functional group in the main chain and having at least one end modified with the above modifier), or two or more in the molecule. Examples thereof include end-modified diene rubber which has been modified (coupled) by a polyfunctional compound having an epoxy group and introduced with a hydroxyl group or an epoxy group.

Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group and a disulfide. Examples thereof include a group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group and an epoxy group. .. In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is replaced with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxy group having 1 to 6 carbon atoms). An alkoxysilyl group having 1 to 6 carbon atoms) is preferable.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR) and the like can be used. These may be used alone or in combination of two or more.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less. When it is within the above range, the above effect can be obtained more preferably.
In the present specification, the styrene content of SBR is calculated by H1 ^- NMR measurement.

As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Zeon Corporation, etc. can be used.

The SBR may be a non-modified SBR or a modified SBR. Examples of the modified SBR include modified SBR into which a functional group similar to that of modified diene rubber is introduced.

When SBR is contained, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and may be 100% by mass. Within the above range, good wet grip performance tends to be obtained.

The BR is not particularly limited, and for example, a high cis BR having a high cis content, a BR containing syndiotactic polybutadiene crystals, a BR synthesized using a rare earth catalyst, and the like can be used. These may be used alone or in combination of two or more. Among them, a high cis BR having a cis content of 90% by mass or more is preferable because the wear resistance is improved.

Further, the BR may be a non-modified BR or a modified BR. Examples of the modified BR include modified BR into which a functional group similar to that of the modified diene rubber is introduced.

As the BR, for example, products such as Ube Kosan Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., and Nippon Zeon Co., Ltd. can be used.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. As the NR, for example, SIR20, RSS # 3, TSR20 and the like, which are common in the rubber industry, can be used. The IR is not particularly limited, and for example, IR2200 or the like, which is common in the rubber industry, can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., and modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

In the above rubber composition, the content (solid content) of the microfibrillated plant fiber is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. preferable. Further, 45 parts by mass or less is preferable, 40 parts by mass or less is more preferable, 35 parts by mass or less is further preferable, and 30 parts by mass or less is further preferable. When the content of the microfibrillated plant fiber in the rubber composition is in such a range, the above-mentioned effect is more preferably obtained.

The average fiber diameter of microfibrillated plant fibers in the rubber composition is 4 to 100 nm. When the average fiber diameter of the microfibrillated plant fiber is in such a range, the dispersibility of the microfibrillated plant fiber in the rubber composition can be sufficiently good, and the effect of the present invention can be obtained. can get. In addition, damage to microfibrillated plant fibers during processing can be suppressed. The average fiber diameter is preferably 90 nm or less from the viewpoint that the effects of the present invention can be obtained more preferably. Further, it is preferably 10 nm or more, and more preferably 20 nm or more, because the microfibrillated plant fibers are difficult to be entangled and dispersed.

The average fiber length of the microfibrillated plant fibers in the rubber composition is preferably 100 nm or more. It is more preferably 300 nm or more, still more preferably 500 nm or more. Further, 5 mm or less is preferable, 1 mm or less is more preferable, 50 μm or less is further preferable, 3 μm or less is particularly preferable, and 2 μm or less is most preferable. When the average fiber length is less than the lower limit or exceeds the upper limit, there is a tendency similar to the above-mentioned average fiber diameter.

The mode of the fiber diameter of the microfibrillated plant fiber in the rubber composition is 10 to 70 nm. When the most frequent value of the fiber diameter of the microfibrillated plant fiber is in such a range, the dispersibility of the microfibrillated plant fiber in the rubber composition can be sufficiently good, and the present invention can be made. The effect of is obtained. The mode of the fiber diameter is preferably 15 nm or more, more preferably 18 nm or more, from the viewpoint that the effect of the present invention can be more preferably obtained. Further, 65 nm or less is preferable, and 60 nm or less is more preferable.

In the present specification, the most frequent value of the fiber diameter of the microfibrillated plant fiber is a value obtained from the distribution obtained by observing with a transmission electron microscope and taking an image and measuring the diameter of 100 fibers. Is.

As described above, in a rubber composition containing a rubber component and microfibrillated plant fibers, the average fiber diameter of the microfibrillated plant fibers in the rubber composition is 4 to 100 nm, and the fiber diameter is the most frequent. A rubber composition having a value of 10 to 70 nm is also one of the present inventions. Such a rubber composition can be produced by blending the above-mentioned microfibrillated plant fiber / rubber complex or the like.
Examples of the rubber component include the above-mentioned rubber and other rubber components. Examples of the microfibrillated plant fiber include the same as the above-mentioned microfibrillated plant fiber.

From the viewpoint of the performance balance, the rubber composition preferably contains silica as a filler. Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Of these, wet silica is preferable because it has a large number of silanol groups. As commercially available products, products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., and Tokuyama Corporation can be used. These may be used alone or in combination of two or more.

The content of silica is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, good wet grip performance and steering stability tend to be obtained. The upper limit of the content is not particularly limited, but is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, further preferably 170 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 80 parts by mass or less. be. By setting it below the upper limit, good dispersibility tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 70 m ² / g or more, more preferably 140 m ² / g or more, and further preferably 160 m ² / g or more. By setting it above the lower limit, good wet grip performance and breaking strength tend to be obtained. The upper limit of N ₂ SA of silica is not particularly limited, but is preferably 500 m ² / g or less, more preferably 300 m ² / g or less, and further preferably 250 m ² / g or less. By setting it below the upper limit, good dispersibility tends to be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

(Silane coupling agent)
When the rubber composition contains silica, it is preferable to further contain a silane coupling agent.
The silane coupling agent is not particularly limited, and for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, and the like. Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-Triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) ) Disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide type such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, Mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyl triethoxysilane, vinyl tri Vinyl-based such as methoxysilane, amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro-based systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro-based systems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products such as Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. and the like can be used. These may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more, and more preferably 6 parts by mass or more with respect to 100 parts by mass of silica. When it is 3 parts by mass or more, good fracture strength and the like tend to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it is 20 parts by mass or less, an effect commensurate with the blending amount tends to be obtained.

From the viewpoint of the performance balance, the rubber composition preferably contains carbon black as a filler. The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. As commercial products, products such as Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd. are used. can. These may be used alone or in combination of two or more.

The content of carbon black is preferably 1 part by mass or more, and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, good wear resistance, grip performance, etc. tend to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. By setting the content to the upper limit or less, good processability of the rubber composition tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 80 m ² / g or more, and even more preferably 100 m ² / g or more. By setting it above the lower limit, good wear resistance and grip performance tend to be obtained. The N ₂ SA is preferably 200 m ² / g or less, more preferably 150 m ² / g or less, and even more preferably 130 m ² / g or less. By setting it below the upper limit, good dispersion of carbon black tends to be obtained.
The nitrogen adsorption specific surface area of carbon black is determined by JIS K6217-2: 2001.

The rubber composition may contain a filler other than silica and carbon black. Other fillers include, but are not limited to, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica and the like.

The rubber composition may contain a plasticizer. The plasticizer is not particularly limited, and examples thereof include oil and liquid resin. One type of these plasticizers may be used, or two or more types may be used in combination.

The above oils are not particularly limited, and are paraffin-based process oils, aroma-based process oils, naphthen-based process oils and other process oils, low PCA (polycyclic aromatic) process oils such as TDAE and MES, vegetable oils and fats, and oils and fats. Conventionally known oils such as these mixtures can be used. Of these, aroma-based process oils are preferable in terms of wear resistance and fracture properties. Specific examples of the aroma-based process oil include Diana process oil AH series manufactured by Idemitsu Kosan Co., Ltd.

The liquid resin is not particularly limited, and examples thereof include a liquid aromatic vinyl polymer, a kumaron indene resin, an indene resin, a terpene resin, a rosin resin, and hydrogenated products thereof.

The liquid aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and / or styrene, and is a homopolymer of styrene, a homopolymer of α-methylstyrene, α-methylstyrene and styrene. Examples thereof include liquid resins such as copolymers.

The liquid kumaron inden resin is a resin containing kumaron and inden as a main monomer component constituting the skeleton (main chain) of the resin, and as a monomer component that may be contained in the skeleton other than kumaron and inden. , Styrene, α-methylstyrene, methylindene, vinyltoluene and other liquid resins.

The liquid indene resin is a liquid resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

The liquid terpene resin is a liquid typified by a resin obtained by polymerizing a terpene compound such as α-pinene, β-pinene, kanfel, and zipene, and a terpene phenol which is a resin obtained by using a terpene compound and a phenolic compound as raw materials. It is a terpene-based resin.

The liquid rosin resin is a liquid rosin-based resin typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, or hydrogenated additives thereof.

A solid resin (a polymer in a solid state at room temperature (25 ° C.)) may be blended with the rubber composition.

When the solid resin is contained, the content thereof is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less. Within the above range, good wet grip performance tends to be obtained.

The solid resin is not particularly limited, but for example, a solid styrene resin, a Kumaron inden resin, a terpene resin, a pt-butylphenol acetylene resin, an acrylic resin, and a dicyclopentadiene resin (DCPD resin). , C5 series petroleum resin, C9 series petroleum resin, C5C9 series petroleum resin and the like. These may be used alone or in combination of two or more.

The solid styrene resin is a solid polymer using a styrene monomer as a constituent monomer, and examples thereof include a polymer obtained by polymerizing a styrene monomer as a main component (50% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-Chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) are individually polymerized, and in addition to copolymers obtained by copolymerizing two or more styrene-based monomers, styrene-based monomers And other monomer copolymers that can be copolymerized with this.

Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene and butadiene. Examples thereof include dienes such as isoprene, olefins such as 1-butene and 1-pentene; α, β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof;

Of these, solid α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is preferable.

Examples of the solid Kumaron inden resin include solid resins having the same structural units as the above-mentioned liquid Kumaron inden resin.

Examples of the solid terpene resin include polyterpenes, terpenephenols, aromatic-modified terpene resins and the like.
Polyterpene is a resin obtained by polymerizing a terpene compound and a hydrogenated additive thereof. The _terpene compound is a hydrocarbon having a composition of _{( C 5 H 8} ) _n and an oxygen _- containing derivative _thereof . ) Etc., which are compounds having a terpene as a basic skeleton. , 1,8-Cineol, 1,4-Cineol, α-terpineol, β-terpineol, γ-terpineol and the like.

Examples of the solid polyterpene include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin made from the above-mentioned terpene compound, and hydrogenation to the terpene resin. Also mentioned are solid resins such as treated hydrogenated terpene resins.

Examples of the solid terpene phenol include a solid resin obtained by copolymerizing the terpene compound and a phenolic compound, and a solid resin obtained by hydrogenating the resin. Examples thereof include solid resins in which formalin is condensed. Examples of the phenolic compound include phenol, bisphenol A, cresol, xylenol and the like.

Examples of the solid aromatic-modified terpene resin include a solid resin obtained by modifying a terpene resin with an aromatic compound, and a solid resin obtained by hydrogenating the resin. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and for example, phenol compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, and the like. Naftor compounds such as unsaturated hydrocarbon group-containing naphthols; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, unsaturated hydrocarbon group-containing styrene; kumaron, inden and the like can be mentioned.

Examples of the solid pt-butylphenol acetylene resin include a solid resin obtained by conducting a condensation reaction between pt-butylphenol and acetylene.

The solid acrylic resin is not particularly limited, but a solvent-free acrylic solid resin can be preferably used from the viewpoint that a resin having few impurities and a sharp molecular weight distribution can be obtained.

The solid solvent-free acrylic resin is a high-temperature continuous polymerization method (high-temperature continuous lump polymerization method) (US Pat. No. 4,414) without using polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials as much as possible. , 370, JP-A-59-6207, JP-A-5-58805, JP-A 1-313522, US Pat. No. 5,010,166, Toa Synthetic Research Annual Report TREND2000 No. 3 Examples thereof include (meth) acrylic resins (polymers) synthesized by the method described in No. p42-45 and the like. In addition, in this specification, (meth) acrylic means methacrylic and acrylic.

It is preferable that the solid acrylic resin does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent and the like, which are auxiliary raw materials. Further, the acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As described above, the solid acrylic resin preferably contains no polymerization initiator, chain transfer agent, organic solvent, etc., which are auxiliary raw materials, that is, a resin having high purity. The purity of the solid acrylic resin (ratio of the resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of the monomer component constituting the solid acrylic resin include (meth) acrylic acid, (meth) acrylic acid ester (alkyl ester, aryl ester, aralkyl ester, etc.), (meth) acrylamide, and (meth). Examples thereof include (meth) acrylic acid derivatives such as acrylamide derivatives.

In addition, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinyl, together with (meth) acrylic acid and (meth) acrylic acid derivatives, are used as monomer components constituting the solid acrylic resin. Aromatic vinyl such as naphthalene may be used.

The solid acrylic resin may be a resin composed of only a (meth) acrylic component or a resin having a component other than the (meth) acrylic component as a component.
Further, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

Examples of plasticizers and solid resins include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., Arizona Chemical Co., Ltd., and Nikko Chemical Co., Ltd. , Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

The rubber composition preferably contains an antiaging agent from the viewpoint of crack resistance, ozone resistance and the like.

The antiaging agent is not particularly limited, but is a naphthylamine-based antiaging agent such as phenyl-α-naphthylamine; a diphenylamine-based antiaging agent such as octylated diphenylamine and 4,4'-bis (α, α'-dimethylbenzyl) diphenylamine. N-isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylene P-phenylenediamine-based antioxidants such as diamine; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methyl Monophenolic antioxidants such as phenols and styrenated phenols; tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] bis, tris, polyphenols such as methane Examples include anti-aging agents. Of these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1 are preferable. , 2-Dihydroquinoline polymers are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis Co., Ltd. and the like can be used.

The content of the anti-aging agent is preferably 0.2 parts by mass or more, and more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, sufficient ozone resistance tends to be obtained. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. By setting it below the upper limit, a good appearance tends to be obtained.

The rubber composition preferably contains stearic acid. From the viewpoint of the performance balance, the content of stearic acid is preferably 0.5 to 10 parts by mass or more, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

As the stearic acid, conventionally known ones can be used, and for example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. can be used. ..

The rubber composition preferably contains zinc oxide. From the viewpoint of the performance balance, the zinc oxide content is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

As the zinc oxide, conventionally known zinc oxide can be used, for example, Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Products can be used.

Wax may be added to the rubber composition. The wax is not particularly limited, and examples thereof include petroleum wax, natural wax, and synthetic wax obtained by purifying or chemically treating a plurality of waxes. These waxes may be used alone or in combination of two or more.

Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. The natural wax is not particularly limited as long as it is a wax derived from non-petroleum resources, and is, for example, a plant wax such as candelilla wax, carnauba wax, wood wax, rice wax, jojoba wax; Animal waxes; mineral waxes such as ozokerite, selecin, petroleum, etc .; and purified products thereof. As commercially available products, for example, products such as Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Kagaku Co., Ltd. can be used. The wax content may be appropriately set from the viewpoint of ozone resistance and cost.

It is preferable to add sulfur to the rubber composition in terms of forming an appropriate crosslinked chain in the polymer chain and imparting a good performance balance.

The sulfur content is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further preferably 0.7 part by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and further preferably 3.0 parts by mass or less. Within the above range, a good balance of performance tends to be obtained.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur commonly used in the rubber industry. As commercial products, products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Industry Co., Ltd., Flexis Co., Ltd., Nippon Inui Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The rubber composition preferably contains a vulcanization accelerator.
The content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslinking density, but is usually 0.3 to 10 parts by mass with respect to 100 parts by mass of the rubber component. It is preferably 0.5 to 7 parts by mass.

The type of vulcanization accelerator is not particularly limited, and a commonly used one can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyltiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based vulcanization accelerator; guanidine-based vulcanization accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilviguanidine can be mentioned. These may be used alone or in combination of two or more. Among them, a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator are preferable from the viewpoint of the performance balance.

In addition to the above components, the rubber composition may appropriately contain ordinary additives used for their use according to application fields such as mold release agents and pigments.

As a method for producing the rubber composition, a known method can be used. For example, each of the above components can be kneaded using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanized. ..

As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30. Seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C. Further, the composition in which the vulcanizing agent and the vulcanization accelerator are kneaded is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The rubber composition can be used for tires, sole rubber, floor material rubber, anti-vibration rubber, seismic isolation rubber, butyl frame rubber, belts, hoses, packings, chemical stoppers, and other rubber industrial products. In particular, it is preferable to use it as a rubber composition for tires because it can improve durability (breaking strength), steering stability, and fuel efficiency in a well-balanced manner.

The rubber composition can be suitably used for pneumatic tires. The pneumatic tire is manufactured by a usual method using the rubber composition. That is, a rubber composition containing various materials as needed is extruded according to the shape of the tire member at the unvulcanized stage, and molded together with other tire members by a normal method on a tire molding machine. By doing so, after forming an unvulcanized tire, the tire can be manufactured by heating and pressurizing in a vulcanizer.

The present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
Natural rubber latex: Field latex obtained from Muhibbah LATEKS is used. Liquid polymer: Liquid isoprene rubber manufactured by Kuraray Co., Ltd. Kuraprene LIR-410 (Mw: 30000)
Microfibrillated plant fiber: Biomass nanofiber manufactured by Sugino Machine Co., Ltd. (Product name "BiNFi-s Cellulose", average fiber length: about 2 μm, average fiber diameter: about 0.02 μm, solid content: 2% by mass)
Surfactant 1: NUOSPERSE FX 600 manufactured by Elementis (anionic surfactant, polycarboxylic acid amine salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group), Mw: 2000)
Surfactant 2: NUOSPERSE FX 605 manufactured by Elementis (anionic surfactant, sodium polycarboxylic acid salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group), Mw: 6000)
Surfactant 3: Demol EP manufactured by Kao Co., Ltd. (anionic surfactant, sodium polycarboxylic acid salt (containing isobutylene group as hydrophobic group, carboxyl group as hydrophilic group), Mw: 20000)
Surfactant 4: DKS Discoat N-14 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (anionic surfactant, polycarboxylic acid ammonium salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group)) , Mw: 7000)
Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Zinc oxide: Zinc oxide type 2 stearic acid manufactured by Mitsui Metal Mining Co., Ltd .: Tsubaki sulfur manufactured by Nichiyu Co., Ltd .: Powdered sulfur vulfurous accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Ouchi Shinko Chemical Industry Co., Ltd. ) Noxera-NS (N-tert-butyl-2-benzothiazolyl sulfenamide)

(Preparation of microfibrillated plant fiber dispersion)
150 g of pure water was added to 50 g of microfibrillated plant fiber (2% by weight) to prepare a 0.5% by mass (solid content concentration) suspension of microfibrillated plant fiber, which was stirred and ultrasonically treated. After 10 minutes, a microfibrillated plant fiber dispersion was obtained.

<Examples 1 to 8>
(Preparation of microfibrillated plant fiber / natural rubber complex)
A predetermined amount of a surfactant is added to the prepared microfibrillated plant fiber dispersion according to the formulation shown in Table 1, and the mixture is stirred at room temperature (20 to 30 ° C.) for 5 minutes using a high-speed homogenizer to microfibrillate the plant fiber. A mixture (mixture) of a dispersion and a surfactant was obtained. The obtained mixture was added to a predetermined amount of natural rubber latex according to the formulation in Table 1 and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a pH 10.2 compounded latex. Then, a 2 mass% formic acid aqueous solution was added at room temperature to adjust the pH to 3 to 4, and a coagulated product was obtained. The obtained coagulated product was filtered and dried to obtain a microfibrillated plant fiber / natural rubber composite.

<Example 9>
(Preparation of microfibrillated plant fiber / rubber complex)
A predetermined amount of surfactant is added to the microfibrillated plant fiber dispersion prepared to 0.5% by mass according to the formulation in Table 1, and the mixture is stirred at room temperature (20 to 30 ° C.) for 5 minutes using a high-speed homogenizer. , A mixture (mixture) of a microfibrillated plant fiber dispersion and a surfactant was obtained. The obtained mixture was added to a predetermined amount of the liquid polymer according to the formulation in Table 1 and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a compounded latex. The obtained compounded latex was dried to obtain a microfibrillated plant fiber / rubber complex.

<Example 10>
(Preparation of chemically modified microfibrillated plant fiber / natural rubber composite)
The microfibrillated plant fiber dispersion adjusted to 0.5% by mass was replaced with N-methylpyrrolidone to prepare a microfibrillated plant fiber adjusting solution having a solid content concentration of 1% by mass. To the obtained microfibrillated plant fiber adjusting solution, pyridine was added at a ratio of 1.5 mol to 1 mol of glucose unit of the microfibrillated plant fiber, and further, oleoyl chloride was added to the glucose unit of the microfibrillated plant fiber. It was added at a ratio of 1 mol to 1 mol and reacted at 30 ° C. After completion of the reaction, the obtained product was thoroughly washed with ethanol to obtain a chemically modified microfibrillated plant fiber dispersion. A predetermined amount of the surfactant is added thereto according to the formulation in Table 1, and the mixture is stirred at room temperature (20 to 30 ° C.) for 5 minutes using a high-speed homogenizer to obtain a chemically modified microfibrillated plant fiber dispersion and a surfactant. A mixture (mixture) of the above was obtained. The obtained mixture was added to a predetermined amount of natural rubber latex according to the formulation in Table 1 and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a pH 10 compounded latex. Then, a 2 mass% formic acid aqueous solution was added at room temperature to adjust the pH to 3 to 4, and a coagulated product was obtained. The obtained coagulated product was filtered and dried to obtain a chemically modified microfibrillated plant fiber / natural rubber composite.
The degree of substitution of chemically modified microfibrillated plant fibers in the above chemically modified microfibrillated plant fiber dispersion was determined by FT-IR analysis from the ratio of the peak intensity of the hydroxyl group to the substituent modified by oleoyl chloride. When asked, it was 0.4. The FT-IR analysis was performed by the ATR method (attenuated total reflection method) using a Spectrum 100 manufactured by PerkinElmer.

<Comparative Example 1>
(Preparation of microfibrillated plant fiber / natural rubber complex)
A predetermined amount of natural rubber latex was added to the microfibrillated plant fiber dispersion prepared to 0.5% by mass according to the formulation in Table 1, and the mixture was stirred at room temperature for 5 minutes using a high-speed homogenizer to pH 10.2. Formulated latex was obtained. Then, a 2 mass% formic acid aqueous solution was added at room temperature to adjust the pH to 3 to 4, and a coagulated product was obtained. The obtained coagulated product was filtered and dried to obtain a microfibrillated plant fiber / natural rubber composite.

<Examples 11 to 20 and Comparative Example 11>
According to the formulation shown in Table 2, chemicals other than sulfur and the vulcanization accelerator were kneaded at 130 ° C. for 4 minutes using a 1.7 L Banbury mixer. Next, using a roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded at 80 ° C. for 4 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized product.
The obtained vulcanized product was observed with an electron microscope. The electron micrograph of Example 11 is shown in FIG. From FIG. 1, it can be seen that in Example 11, microfibrillated plant fibers are finely dispersed in the rubber composition. Further, in Examples 12 to 19, microfibrillated plant fibers were finely dispersed in the rubber composition to the same extent as in Example 11. Further, in Example 20, the obtained vulcanized product was also observed with an electron microscope. An electron micrograph is shown in FIG. From FIG. 2, it can be seen that in Example 20, chemically modified microfibrillated plant fibers are finely dispersed in the rubber composition. On the other hand, when the sulfide obtained in Comparative Example 11 was observed with an electron microscope (electron micrograph is shown in FIG. 3), in Comparative Example 11, agglomerates of microfibrillated plant fibers were formed, and rubber was formed. It can be seen that the microfibrillated plant fibers are not finely dispersed in the composition.

The obtained vulcanized product was evaluated as follows, and the results are shown in Table 2.

(Mode of fiber diameter of microfibrillated plant fiber)
The obtained vulture was observed with a transmission electron microscope and an image was taken, and the diameter of 100 microfibrillated plant fibers was measured to determine the most frequent value of the fiber diameter from the distribution obtained.

(Average fiber diameter of microfibrillated plant fiber)
The obtained vulture is observed with a transmission electron microscope and an image is taken, and the diameter of 100 microfibrillated plant fibers is measured to obtain the average value (average fiber diameter) of the fiber diameter from the distribution obtained. rice field.

(Breaking strength)
A No. 3 dumbbell type rubber test piece was prepared using a vulcanized product, and a tensile test was performed according to JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties", and the breaking strength (TB) was measured. .. The TB index of the rubber test piece (reference test piece) of Comparative Example 11 was set to 100, and the TB of each formulation was expressed as an index by the following formula. The larger the TB index, the larger the breaking strength and the better the reinforcing property and durability.
(TB index) = (TB of each formulation) / (TB of reference test piece) × 100

(Maneuvering stability)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the complex elastic modulus E * of each formulation (vulcanized product) under the conditions of temperature 50 ° C., initial strain 10%, dynamic strain 2%, and frequency 10 Hz. Was measured, and the E * of the rubber test piece (reference test piece) of Comparative Example 11 was set to 100, and the index was displayed by the following formula (elastic modulus index). The larger the index, the better the steering stability.
(Elastic modulus index) = (E * of each formulation) / (E * of reference test piece) x 100

(Rolling resistance)
Using the viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the tan δ of each formulation (vulcanized product) was measured under the conditions of temperature 50 ° C., initial strain 10%, dynamic strain 2%, and frequency 10 Hz. The tan δ of the rubber test piece (reference test piece) of Comparative Example 11 was set to 100, and the index was expressed by the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics (fuel efficiency).
(Rolling resistance index) = (tanδ of reference test piece) / (tanδ of each formulation) × 100

(Balance index of tire performance)
Based on each of the above performances, the balance index was calculated by the following formula. The larger the index, the better the balance between durability, steering stability, and fuel efficiency.
(Balance index) = (TB index x elastic modulus index x rolling resistance index) / 10000

From Table 2, a step of mixing a predetermined anionic surfactant and a microfibrillated plant fiber dispersion containing a predetermined microfibrillated plant fiber to prepare a mixed solution, and the obtained mixed solution and rubber. In Examples 11 to 20 using the microfibrillated plant fiber / rubber composite obtained by the manufacturing method including the step of mixing with, the durability required for the tire (reference comparative example) is higher than that of Comparative Example 11 (reference comparative example). Breaking strength), steering stability, and low fuel consumption were obtained in a well-balanced manner.

Claims (5)

A method for producing a microfibrillated plant fiber / rubber complex.
The production method comprises a step (1) of mixing an anionic surfactant and a microfibrillated plant fiber dispersion to prepare a mixed solution, and a step (2) of mixing the mixed solution with rubber. Including,
The anionic surfactant has a hydrophobic group and a hydrophilic group, and the anionic surfactant has a hydrophobic group and a hydrophilic group.
The microfibrillated plant fiber has an average fiber diameter of 4 to 100 nm.
In the step (1), the amount of the anionic surfactant added is 8 to 50 parts by mass with respect to 100 parts by mass of the microfibrillated plant fiber (solid content) contained in the microfibrillated plant fiber dispersion liquid. And
A method for producing a microfibrillated plant fiber / rubber composite, wherein the rubber contains at least one selected from the group consisting of a diene-based rubber latex and a liquid diene-based polymer. The method for producing a microfibrillated plant fiber / rubber composite according to claim 1, wherein the hydrophobic group is a hydrocarbon group. The microfibrillated plant fiber / rubber composite according to claim 1 or 2, wherein the hydrophilic group is at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphoric acid group. Production method. Any of claims 1 to 3, wherein the microfibrillated plant fiber dispersion is a chemically modified microfibrillated plant fiber dispersion containing a chemically modified microfibrillated plant fiber subjected to a treatment for making the microfibrillated plant fiber hydrophobic. A method for producing a microfibrillated plant fiber / rubber composite described in Crab. The method for producing a microfibrillated plant fiber-rubber composite according to any one of claims 1 to 4, wherein the average fiber diameter of the microfibrillated plant fiber is 10 to 90 nm.

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