JP2021001253A - Method for producing rubber-filler composite - Google Patents

Abstract

To provide a method for producing a rubber-filler composite in which the filler used can sufficiently be incorporated into the rubber component.SOLUTION: Provided is a method for producing rubber-filler composite comprising a step of mixing a rubber latex, a filler dispersion and a surfactant, and in which the incorporation ratio of the filler in the rubber-filler composite is 95 mass% or more.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a rubber-filler composite and a rubber-filler composite obtained by the production method.

By blending the rubber composition as a filler (filler) such as silica and microfibrillated plant fibers (cellulose fibers, etc.), the rubber composition can be reinforced and the modulus (complex elastic coefficient) can be improved. However, for example, when a filler is charged into a rubber latex and an attempt is made to mix the rubber component and the filler, there arises a problem that the charged filler is not sufficiently incorporated into the rubber component and remains in the solution.

On the other hand, a method of chemically modifying microfibrillated plant fibers to improve the compatibility between the rubber component and the microfibrillated plant fibers, cellulose fibers having a carboxy group, finely modified cellulose fibers, etc. are blended into the rubber. A method for improving the dispersibility of cellulose fibers in rubber, a method for improving affinity and dispersibility with rubber components by using a composite cellulose fiber obtained by graft-polymerizing a polymer or the like on cellulose nanofibers as a reinforcing material for rubber. Etc. (see Patent Documents 1 to 4).

However, even with the above method, there is a problem that a part of the filler to be used is not sufficiently incorporated into the rubber component, and a desired rubber-filler composite cannot be preferably obtained.

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

An object of the present invention is to solve the above-mentioned problems and to provide a method for producing a rubber-filler composite capable of sufficiently incorporating a filler to be used into a rubber component.

The present invention is a method for producing a rubber-filler composite, which comprises a step of mixing a rubber latex, a filler dispersion, and a surfactant, wherein the filler uptake rate in the rubber-filler composite is 95% by mass or more. The present invention relates to a method for producing a rubber-filler composite.

The filler dispersion is preferably a silica dispersion and / or a microfibrillated plant fiber dispersion.

The surfactant is preferably a nonionic surfactant and / or an anionic surfactant.

The present invention also relates to a rubber-filler composite obtained by the above-mentioned production method.

According to the present invention, it is a method for producing a rubber-filler composite including a step of mixing a rubber latex, a filler dispersion liquid and a surfactant, and the filler uptake rate in the rubber-filler composite is 95% by mass or more. Since it is a method for producing a rubber-filler composite, it is possible to provide a production method capable of sufficiently incorporating the filler to be used into the rubber component.

[Manufacturing method of rubber / filler composite]
The present invention is a method for producing a rubber-filler composite including a step of mixing a rubber latex, a filler dispersion, and a surfactant, and a production method in which the filler uptake rate in the rubber-filler composite is 95% by mass or more. Is. 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.

The mechanism by which the filler uptake rate can be increased to 95% by mass or more is not always clear, but it is presumed as follows.
For example, when a filler is added to a rubber latex and the rubber component and the filler are mixed, the added filler is not sufficiently incorporated into the rubber component and remains in the solution, but the rubber latex is used as the rubber component source and the filler is dispersed as the filler source. By using a liquid and a surfactant at the same time, the hydrophilic groups of the surfactant interact with the functional groups on the filler surface such as silica and microfibrillated plant fibers, and the hydrophobic groups interact with the rubber. , The rubber and the filler are compatible with each other, making it difficult for the filler to come out of the rubber. As a result, it is presumed that most of the filler used in the production of the rubber-filler composite is incorporated into the rubber.

The filler uptake rate in the rubber-filler composite (the proportion (mass) of the filler incorporated (inclusive) in the composite in the total amount of filler used in the production of the rubber-filler composite of 100% by mass) is 95% by mass. The above-mentioned production method is preferably 96% by mass or more, more preferably 98% by mass or more. The upper limit is not particularly limited, and 100% by mass is most preferable.

Here, the filler uptake rate can be adjusted by the type and amount of the rubber latex source, the filler source, and the surfactant. For example, the uptake rate can be adjusted by appropriately selecting the type and amount of the surfactant, and the more the surfactant having a large interaction with the rubber latex type and the filler type used is used, the higher the uptake rate tends to be. .. Further, the uptake rate can be adjusted by appropriately adjusting the concentration of the rubber latex or the filler dispersion liquid.

Specifically, as a method for satisfying a filler uptake rate of 95% by mass or more, (a) a method of using a nonionic surfactant as a surfactant when silica is used as a filler, and (b) microfibrillation as a filler. When plant fibers are used, a method of using an anionic surfactant and / or a nonionic surfactant as a surfactant, (c) a method of adjusting the concentration of rubber latex, and (d) a method of adjusting the concentration of the filler dispersion. Examples thereof include a method of adjusting, (e) first, a method of mixing a surfactant and a filler dispersion, and then a method of mixing rubber latex, and the like alone or in combination as appropriate.

The filler uptake rate (the uptake rate in 100% by mass of the filler charge (the proportion of the filler taken into the rubber)) can be measured by the method described in Examples described later. For example, the dispersion liquid of the rubber-filler composite obtained from the rubber latex, the filler dispersion liquid and the surfactant is solidified, and the produced rubber-filler composite is observed with an electron microscope such as TEM. Next, for the obtained image, the image is binarized using image analysis software such as Image J, a threshold is set, the filler amount is quantitatively analyzed, and the filler uptake rate is calculated based on the filler amount. To do.

In the above-mentioned step of mixing the rubber latex, the filler dispersion and the surfactant, the filler uptake rate in the rubber-filler composite produced by mixing the rubber latex, the filler dispersion and the surfactant is 95% by mass. The process is not particularly limited as long as it is the process adjusted as described above. Among them, the step includes a step of mixing the surfactant and the filler dispersion liquid to prepare a mixed liquid (step (1)) and a step of mixing the mixed liquid and the rubber latex (step (2)). It is preferable that it is a rubber.

(Step (1))
The surfactant has a hydrophobic group and a hydrophilic group, and examples thereof include a nonionic surfactant, an anionic surfactant, and a cationic surfactant. Among them, a nonionic surfactant is preferable when silica is used as the filler from the viewpoint of the filler uptake rate. When microfibrillated plant fibers are used as the filler, nonionic surfactants and anionic surfactants are preferable, and anionic surfactants are more preferable.

The nonionic surfactant is not particularly limited, and is a polyoxyalkylene alkyl ether such as polyoxyethylene alkyl ether, polyoxyethylene polypropylene alkyl ether, polyoxyethylene polybutylene alkyl ether; and poly such as polyoxyethylene alkenyl ether. Conventionally known substances such as oxyalkylene alkenyl ether; polyoxyethylene alkyl phenyl ether; higher fatty acid alkanolamide can be used. Among them, a nonionic surfactant having a polyoxyethylene group as a hydrophilic group and a hydrocarbon group as a hydrophobic group can be preferably used.

As such a nonionic surfactant, compounds represented by the following formulas (I) to (III) can be preferably used. Among them, the compound represented by the following formula (I) is particularly preferably used.

R ^1- O- (EO) _x- H (I)
(In the formula (I), R ¹ represents an alkyl group having 3 to 50 carbon atoms or an alkenyl group having 3 to 50 carbon atoms. EO represents an oxyethylene group. The average number of added moles x is 3 to 100. )

The carbon number of R ¹ is preferably 5 to 30, more preferably 8 to 20. The above x is preferably 5 to 50, more preferably 8 to 30.

R ^2- O- (AO) _y (EO) _z- H (II)
(In formula (II), R ² represents an alkyl group having 3 to 50 carbon atoms or an alkenyl group having 3 to 50 carbon atoms. AO represents an oxypropylene group or an oxybutylene group, and EO represents an oxyethylene group. Average addition. The number of moles y is 3 to 100, and the average number of added moles z is 3 to 100.)

The number of carbon atoms in R ² is preferably 5 to 30, more preferably 8 to 20. The y is preferably 5 to 50, more preferably 8 to 30. The z is preferably 5 to 50, more preferably 8 to 30. The arrangement of EO and AO may be block or random.

In the above formula (III), R ^{3 to} R ⁵ represent the same or different hydrogen atoms, alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 1 to 30 carbon atoms, or alkoxy groups having 1 to 30 carbon atoms. .. R ⁶ represents an alkylene group having 1 to 30 carbon atoms. EO represents an oxyethylene group. The average number of added moles a is 0 to 50, the average number of added moles b is 0 to 50, and the average number of added moles c is 1 to 50.

The carbon number of R ³ and R ⁴ is preferably 1 to 25, and the above R ⁵ is preferably a hydrogen atom or an alkyl group having 1 to 25 carbon atoms. The carbon number of R ⁶ is preferably 3 to 8. The above a and b are preferably 0 to 30, more preferably 5 to 30, and the above c is preferably 1 to 30, more preferably 1 to 10.

As the hydrophobic group of the anionic surfactant, a hydrophobic functional group can be arbitrarily adopted. Of these, 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, and specifically, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, 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. Of these, an isobutylene group is preferable.

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 a cyclobutenyl group. Examples thereof include a 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. .. Among them, a phenyl group, a benzyl group and a phenethyl group are preferable, a phenyl group and a benzyl group are more preferable, and a phenyl group is particularly preferable. The substitution position of the methyl group on the benzene ring in the tolyl group and the xsilyl group may be any of the ortho-position, the meta-position and the para-position.

As the hydrophilic group of the anionic surfactant, at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulfate group and a phosphoric acid group is preferable. Of these, a carboxyl group is particularly preferable.

Specifically, the anionic surfactant can be classified into carboxylic acid-based, sulfonic acid-based, sulfate ester-based, and phosphoric acid ester-based surfactants.

Examples of the carboxylic acid-based surfactant include fatty acid salts having 6 to 30 carbon atoms, polyvalent carboxylates, rosinates, dimerates, polymerates, tall oil fatty acid salts, and polycarboxylic acid types. Examples thereof include a molecular surfactant, preferably a carboxylic acid salt having 10 to 20 carbon atoms, a polycarboxylic acid salt, and a polycarboxylic acid type polymer surfactant, and particularly preferably a polycarboxylic acid type polymer surfactant. Is. 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 alkyl sulfates, polyoxyalkylene alkyl sulfates, polyoxyalkylene alkylphenyl ether sulfates, tristyrene phenol sulfates, and distyrene phenol sulfates. Examples thereof include ester salts, α-olefin sulfate ester salts, alkylsuccinic acid sulfate ester salts, polyoxyalkylene tristyrene phenol sulfate ester salts, and polyoxyalkylene distyrene phenol sulfate ester salts. Examples of the phosphoric acid ester-based surfactant include an alkyl phosphate ester salt and a polyoxyalkylene phosphate ester salt. Examples of salts 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 these surfactants 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 molar number of ethylene oxide of about 1 to 50 mol can be used.

The weight average molecular weight (Mw) of the anionic surfactant is preferably 500 or more, and more preferably 1000 or more. Further, it is preferably 50,000 or less, and more preferably 30,000 or less. 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 cationic surfactant, a quaternary ammonium salt type, that is, a surfactant having a quaternary ammonium group and a hydrocarbon group and represented by the following formula (IV) can be preferably used.

^{[R 7 R 8 R 9 R} 10 N] + X - (IV)
(In formula (IV), R ⁷ and R ⁸ represent the same or different alkyl or alkenyl group having 1 to 22 carbon atoms, and at least one of the R ⁷ and R ⁸ has 4 or more carbon atoms. R ⁹ and R ¹⁰ represent an alkyl group having 1 to 3 carbon atoms. X represents a monovalent anion.)

In the above formula (IV), it is preferable that one of R ⁷ and R ⁸ is a methyl group and the other is an alkyl group having 6 to 18 carbon atoms. R ⁹ and R ¹⁰ are preferably methyl groups. Examples of X include halogen ions such as chloride ion and bromide ion.

Specific examples of the cationic surfactant represented by the above formula (IV) include hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, and hexa. Examples thereof include decyltrimethylammonium chloride, stearyltrimethylammonium chloride, and corresponding alkyltrimethylammonium salts such as bromide. Of these, hexadecyltrimethylammonium bromide is preferable.

As commercially available surfactants, for example, products such as Elementis, Kao Corporation, Dai-ichi Kogyo Seiyaku Co., Ltd., Sanyo Chemical Industries, Ltd., EVONIK-DEGUSSA Co., Ltd., Huntsman Co., Ltd., etc. Can be used.

The filler dispersion is a dispersion (slurry) in which the filler is dispersed in a solvent. The filler is not particularly limited, and examples thereof include carbon black, silica, clay, talc, calcium carbonate, and microfibrillated plant fibers. For example, silica and microfibrillated plant fibers can be preferably used. The solvent is not particularly limited, and examples thereof include water, organic solvents such as alcohol, and water is preferable.

The silica is not particularly limited, and those usually used in the rubber industry can be used, and examples thereof include dry silica (silicic anhydride) and wet silica (silicic anhydride). Among them, wet method silica is preferable, and specific examples thereof include Ultrazil VN3, 7000GR and 9000GR manufactured by Degussa, Nipseal AQ manufactured by Toso Silica, and Zeosil 115GR manufactured by Rhodia Japan. These may be used alone or in combination of two or more.

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, breaking strength, etc. 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.

As the microfibrillated plant fiber, 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. 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 microfibril is typically a cellulose fiber having an average fiber diameter in 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. A typical cellulose microfibril can be formed as, for example, 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. For example, the raw material of the cellulose microfibril is chemically treated with an alkali such as sodium hydroxide as necessary, and then a refiner and a biaxial 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 fibers that are substantially free of 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 fibers include those obtained by the above-mentioned production method and further subjected to oxidation treatment and various chemical modification treatments, and natural products (for example, natural products that can be derived from the above-mentioned cellulose microfibrils). Wood, pulp, bamboo, hemp, jute, kenaf, agricultural waste, cloth, paper, squirrel cellulose, etc.) are used as cellulose raw materials for oxidation treatment and various chemical modification treatments, and then defibration treatment as necessary. , Or a microfibrillated plant fiber dispersion which has been further subjected to oxidation treatment or various chemical modification treatments can also be used.

Examples of the mode of chemical modification 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, phosphate esterification, alkyl esterification, alkyl etherification, composite esterification, β-keto esterification, alkylation such as butylation, etc. Esterification, chlorination, etc. are preferably exemplified. Furthermore, 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-ketoesterification, alkylcarbamate, and arylcarbamate, preferably at least one selected from the group. All of the chemical modification treatments are treatments for hydrophobizing microfibrillated plant fibers, and by using the microfibrillated plant fibers subjected to such chemical modification treatment, the dispersibility of the microfibrillated plant fibers Can be further improved.

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 for 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 dispersibility. Excellent and particularly excellent in flexibility. 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 of combinations, the degree of substitution is calculated as the average of the entire chemically modified microfibrillated plant fiber.

The degree of substitution in the chemically modified microfibrillated plant fiber can be confirmed, for example, by titration 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 substitution degree is 0.3 to 2.5, and when the chemically modified microfibrillated plant fiber is an amination microfibrillated plant fiber, the substitution degree is 0.3. ~ 2.5, Substitutability 0.3-1.8 for sulfone-esterified microfibrillated plant fibers, 0.3-1.8 Substituting for 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-ized 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, microfibrillated plant fibers 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 tosyl esterification and then reaction with an alkylamine in an alcohol to cause a parent nucleus substitution reaction.

The above sulfone esterification can be carried out by a simple operation of, for example, dissolving microfibrillated plant fibers in sulfuric acid and putting them into water. Alternatively, it can be treated by sulfur trioxide gas treatment, treatment with chlorosulfonic acid and pyridine, or the like.

The phosphoric acid esterification can be carried out, for example, by a method of treating microfibrillated plant fibers subjected to dimethylamine treatment 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 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 types 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 transesterifying the microfibrillated plant fiber with a β-ketoester compound such as alkylacetoacetate. it can.

The alkyl carbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with an alkyl isocyanate 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 using the N-oxyl compound as an oxidation catalyst in water and allowing an oxidant to act on the microfibrillated plant fibers.

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

The average fiber diameter of the microfibrillated plant fibers is preferably 4 to 100 nm. The average fiber diameter is preferably 90 nm or less, more preferably 50 nm or less. 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 microfibrillated plant fiber is composed of two or more kinds of combinations, 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 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 filler dispersion can be produced by a known method, and the production method is not particularly limited. For example, the filler is dispersed in a solvent such as water using a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, or the like. Can be prepared by The temperature and time at the time of preparation can also be appropriately set within a range normally used so that the filler is sufficiently dispersed in a solvent such as water.

The content (solid content) of the filler in the filler dispersion is not particularly limited, but is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 0.5 to 7. It is mass%.

In the above step (1), as a method of mixing the surfactant and the filler dispersion liquid to prepare a mixed liquid, for example, a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, or a blender mill is used. Examples thereof include a method of mixing the surfactant and the filler dispersion, and the mixture of the surfactant and the filler dispersion can be obtained by sufficiently stirring the mixture until the surfactant and the filler dispersion are sufficiently dispersed. The temperature and time for preparing the mixed solution can be appropriately set within a range normally used until the surfactant and the filler dispersion are sufficiently dispersed. For example, 3 to 120 minutes at 10 to 40 ° C. is preferable. More preferably, it is at 15 to 30 ° C. for 5 to 90 minutes.

The blending amount of the surfactant is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the rubber latex (solid content of rubber) used for the rubber-filler composite. The addition amount is more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more. Further, 25 parts by mass or less is more preferable, 20 parts by mass or less is further preferable, and 15 parts by mass or less is particularly preferable.

The blending amount of the filler is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the rubber latex (solid content of rubber) used for the rubber-filler composite. The blending amount is more preferably 2 parts by mass or more, further preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. Further, 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 particularly preferable. When microfibrillated plant fiber is used as the filler, the blending amount is preferably in the same range. When silica is used as the filler, the blending amount is preferably 5 to 50 parts by mass, more preferably 7 to 50 parts by mass, still more preferably 7 to 40 parts by mass.

(Step (2))
In the present invention, the step (step (2)) of mixing the mixed solution obtained in the step (1) and the rubber latex is then performed.

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), etc.). Diene rubber latex such as styrene isoprene butadiene rubber (SIBR), isoprene rubber, acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinyl pyridine rubber, butyl rubber and other latex) can be preferably used. As these rubber latexes, they 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.

Natural rubber latex is collected as the sap of natural rubber trees such as Hevea trees, 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 a heavy tree, 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 oxide, TMTD, and ammonia) and the like can be used.

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 is less likely to solidify. 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 production 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.

In the above step (2), as a method of mixing the mixed solution obtained in the step (1) with the rubber latex, for example, a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, or a blender mill can be used. Examples include a method of dropping the mixed solution obtained in the step (1) while adding rubber and stirring, and a method of dropping the rubber latex into the mixed solution obtained in the step (1) while stirring. A mixture (blended latex) of the mixed solution obtained in the step (1) and rubber can be obtained by sufficiently stirring the mixture until the mixture is sufficiently dispersed. 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. 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 latex is in such a range, deterioration can be suppressed and the mixture can be made stable.

The mixture (blended latex) obtained in the above step (2) is coagulated as necessary, and the coagulated product (aggregate containing agglutinated rubber and filler) is filtered and dried by a known method, and after further drying, 2 By kneading rubber with a shaft roll, Banbury, or the like, a composite (rubber-filler composite) in which the filler is sufficiently dispersed in the rubber matrix can be obtained. The rubber-filler composite may contain other components as long as the effect is not impaired.

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, the pH of the mixture (blended latex) obtained in the above step (2) is preferably adjusted to 3 to 5, and more preferably adjusted to 3 to 4.

Further, a coagulant 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.

By such a production method or the like, a rubber-filler composite having a filler uptake rate of 95% by mass or more is produced.

[Rubber composition]
The rubber composition contains the rubber-filler composite. The rubber-filler composite can be used as a masterbatch. In the rubber-filler composite, the filler is sufficiently dispersed in the rubber, and the filler can be sufficiently dispersed even in a rubber composition mixed with other components. Therefore, effective reinforcement can be exhibited, and performance such as durability (breaking strength) and steering stability 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 rubber-filler composite.
As the other rubber component, for example, a diene 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 (CR). NBR) and the like. In addition, examples of rubber components other than the above include butyl rubber and fluororubber. 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 having the above functional group (modifying agent). A terminal-modified diene rubber modified with (a terminal-modified diene rubber having the above functional group at the terminal), a main chain-modified diene rubber having the functional group at the main chain, or the functional group at the main chain and the terminal. 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-based rubbers that have been modified (coupled) with 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 this specification, the styrene content of SBR ^is calculated by H 1 -NMR measurement.

As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., 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 in 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 tire 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 (rare earth BR), 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 a modified BR in which a functional group similar to that of the modified diene rubber is introduced.

As the BR, for example, products such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and ZEON Corporation can be used.

Examples of the isoprene 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, an IR 2200 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 rubber composition, the filler content (solid content) 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. Further, 300 parts by mass or less is preferable, 250 parts by mass or less is more preferable, and 200 parts by mass or less is further preferable.

When the rubber composition contains microfibrillated plant fibers, the content (solid content) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and 10 parts by mass with respect to 100 parts by mass of the rubber component. The above is more 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 particularly preferable. Within the above range, good dispersibility can be obtained and excellent rubber physical characteristics tend to be obtained.

When the rubber composition contains silica, the content thereof 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. 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. is there. Within the above range, good dispersibility can be obtained and excellent rubber physical characteristics tend to be obtained.

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, 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- Sulfates such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercaptos such as Momentive's NXT and NXT-Z, vinyltriethoxysilane, vinyltri Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chlorosystems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. 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 breaking 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.

The rubber composition may contain 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. it 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, a good reinforcing effect tends to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. By setting it below the upper limit, good workability 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, a good reinforcing effect tends to be obtained. Further, the _N 2 SA is preferably 200 meters ² / g or less, more preferably 150 meters ² / g, more preferably not more than 130m ² / g. 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 (filler) other than silica and carbon black. Examples of other fillers include the above-mentioned clay and the like.

The rubber composition may contain a plasticizer. The plasticizer is not particularly limited, and examples thereof include plasticizers that are liquid at room temperature (25 ° C.) such as oil and liquid resin. One type of these plasticizers may be used, or two or more types may be used in combination.

When the plasticizer 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 100 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 30 parts by mass or less. Within the above range, good rubber physical characteristics tend to be obtained.

The oil is not particularly limited, and is limited to 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 these. Conventionally known oils such as a mixture of the above 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 the 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 inden resin, an inden 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 main monomer components 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, vinyl toluene 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, or dipetene, or a terpene phenol which is a resin obtained by using a terpene compound and a phenolic compound as raw materials. It is a terpene resin.

The liquid rosin resin is a liquid rosin-based resin typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, or hydrogen 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, 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, A homopolymer obtained by independently polymerizing o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), a copolymer obtained by copolymerizing two or more styrene-based monomers, and a styrene-based monomer. And other monomer copolymers that can be copolymerized with this.

Examples of the other monomers include acrylonitrile 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, a solid α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is preferable.

Examples of the solid Kumaron indene resin include a solid resin having the same structural unit as the above-mentioned liquid Kumaron indene resin.

Examples of the solid terpene resin include polyterpenes, terpene phenols, and aromatic-modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene _compounds, hydrocarbon and oxygenated derivatives represented by a composition of _{(C 5} H _{8) n,} monoterpenes _(C 10 _{H 16),} sesquiterpene _(C 15 _{H 24),} diterpenes _(C 20 _{H 32} ) Etc., and 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 included 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 phenol-based compound, and a solid resin obtained by hydrogenating the resin. Specifically, the terpene compound, the phenol-based compound, and the like. Examples thereof include a solid resin obtained by condensing formalin. 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 the 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 has an aromatic ring, but 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 naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and 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 subjecting pt-butylphenol and acetylene to a condensation reaction.

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 Patent 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, etc., 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 substantially no polymerization initiator, chain transfer agent, organic solvent, etc., which are auxiliary raw materials, that is, one 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 include (meth) acrylic acid derivatives such as acrylamide derivatives.

In addition, as the monomer component constituting the solid acrylic resin, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinyl are used together with (meth) acrylic acid and (meth) acrylic acid derivative. 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, Arizona Chemical Co., Ltd., and Nikko Chemical Co., Ltd. , Nippon Catalyst Co., Ltd., JXTG Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

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

The anti-aging agent is not particularly limited, but is a naphthylamine-based anti-aging agent such as phenyl-α-naphthylamine; a diphenylamine-based anti-aging 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 anti-aging agents such as diamine; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methyl Monophenolic anti-aging agents such as phenol and styrenated phenol; 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 anti-aging agents and quinoline-based anti-aging agents are preferable, and N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 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. 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 from the viewpoint of the performance balance.

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

The rubber composition preferably contains zinc oxide. The content of zinc oxide 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 from the viewpoint of the performance balance.

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 and natural wax, and synthetic wax obtained by purifying or chemically treating a plurality of waxes can also be used. 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; honey wax, lanolin, whale wax, etc. Animal waxes; mineral waxes such as ozokelite, selecin, petrolactam; 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 from the viewpoint of forming an appropriate crosslinked chain on the polymer chain and imparting good rubber physical characteristics.

The sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 0.7 parts 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.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are generally used in the rubber industry. As commercially available products, products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, 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 crosslink density, but is usually 0.3 to 10 parts by mass with respect to 100 parts by mass of the rubber component. , Preferably 0.5 to 7 parts by mass.

The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of the sulfide accelerator include thiazole-based sulfide-based sulfide accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based sulfide accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based sulfide accelerator; guanidine-based sulfide accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilbiguanidine can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable.

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 final 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 obtained by kneading the vulcanizing agent and the vulcanization accelerator 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 rubbers, floor material rubbers, anti-vibration rubbers, seismic isolation rubbers, butyl frame rubbers, 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 performance such as durability (breaking strength), steering stability, and fuel efficiency.

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 based on 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 Silica: Uratosyl VN3 (N 2 SA172m ² / g) manufactured by Evonik Degussa
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: teric 16A29 (CH ₃ (CH ₂ ) ₁₅ (OC ₂ H ₄ ) _29- OH, nonionic surfactant) manufactured by Huntsman Co., Ltd.)
Surfactant 2: PD-430 (nonionic surfactant, R- (OC ₄ H ₈ ) _p (OC ₂ H ₄ ) _q- OH: R = long-chain alkyl group, p = manufactured by Kao Corporation 3-100, q = 3-100)
Surfactant 3: Si363 manufactured by EVONIK-DEGUSSA (surfactant represented by the following formula, nonionic surfactant)

界面活性剤４：エレメンティス社製のＮＵＯＳＰＥＲＳＥ ＦＸ ６００（陰イオン性界面活性剤、ポリカルボン酸アミン塩（疎水性基としてフェニル基、親水性基としてカルボキシル基を含有）、Ｍｗ２０００）
界面活性剤５：エレメンティス社製のＮＵＯＳＰＥＲＳＥ ＦＸ ６０５（陰イオン性界面活性剤、ポリカルボン酸ナトリウム塩（疎水性基としてフェニル基、親水性基としてカルボキシル基を含有）、Ｍｗ６０００）
界面活性剤６：花王（株）製のデモールＥＰ（陰イオン性界面活性剤、ポリカルボン酸ナトリウム塩（疎水性基としてイソブチレン基、親水性基としてカルボキシル基を含有）、Ｍｗ２００００）
界面活性剤７：第一工業製薬（株）製のＤＫＳディスコート Ｎ−１４（陰イオン性界面活性剤、ポリカルボン酸アンモニウム塩（疎水性基としてフェニル基、親水性基としてカルボキシル基を含有）、Ｍｗ７０００）
老化防止剤：大内新興化学工業（株）製のノクラック６Ｃ（Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン）
酸化亜鉛：三井金属鉱業（株）製の亜鉛華２種
ステアリン酸：日油（株）製の椿
硫黄：鶴見化学工業（株）製の粉末硫黄
加硫促進剤：大内新興化学工業（株）製のノクセラ−ＮＳ（Ｎ−ｔｅｒｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド）

Surfactant 4: NUOSPERSE FX 600 manufactured by Elementtis (anionic surfactant, polycarboxylic acid amine salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group), Mw2000)
Surfactant 5: NUOSPERSE FX 605 manufactured by Elementtis (anionic surfactant, sodium polycarboxylic acid salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group), Mw6000)
Surfactant 6: Demol EP manufactured by Kao Corporation (anionic surfactant, sodium polycarboxylic acid salt (containing isobutylene group as hydrophobic group, carboxyl group as hydrophilic group), Mw20000)
Surfactant 7: DKS Discoat N-14 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (anionic surfactant, ammonium polycarboxylic acid salt (containing phenyl group as hydrophobic group and carboxyl group as hydrophilic group)) , Mw7000)
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 vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Ouchi Shinko Chemical Industry Co., Ltd. ) Noxera-NS (N-tert-butyl-2-benzothiazolyl sulfenamide)

(Preparation of silica dispersion)
190 g of pure water was added to 10 g of silica to prepare a suspension of 5% by mass (solid content concentration) of silica, which was stirred and sonicated for 10 minutes to obtain a silica dispersion.

(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 suspension of 0.5% by mass (solid content concentration) of microfibrillated plant fiber, which was stirred and ultrasonically treated. This was carried out for 10 minutes to obtain a microfibrillated plant fiber dispersion.

<Examples 1-1 to 1-7, 2-1 to 2-11, Comparative Example 1-1>
(Preparation of rubber-filler composite)
A rubber-filler composite was produced according to the formulation formulas shown in Tables 1 and 2.
Specifically, a surfactant is added to the prepared silica dispersion or microfibrillated plant fiber dispersion, and the mixture is stirred at room temperature (20 to 30 ° C.) for 5 minutes using a high-speed homogenizer to obtain the silica dispersion or the microfibrillated plant fiber dispersion. A mixture (mixture) of a microfibrillated plant fiber dispersion and a surfactant was obtained. The obtained mixture was added to natural rubber latex and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a compounded latex having a pH of 10.2. 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 rubber-filler composite.

<Comparative Examples 1-2, 2-1>
(Preparation of rubber-filler composite)
A rubber-filler composite was produced according to the formulation formulas shown in Tables 1 and 2.
Specifically, natural rubber latex is added to a silica dispersion or a microfibrillated plant fiber dispersion prepared to 0.5% by mass, and the mixture is stirred at room temperature for 5 minutes using a high-speed homogenizer to prepare a pH of 10.2. Obtained 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 rubber-filler composite.

The obtained rubber-filler composite was evaluated as follows, and the results are shown in Tables 1 and 2. The reference formulations of hardness (Hs) in Tables 1 and 2 are Examples 1-1 and 2-1 respectively.

(Measurement of filler uptake rate)
For the coagulated product (rubber / filler composite) obtained in each example, TEM measurement was performed to measure the amount of filler incorporated into the composite. Using Image J, the TEM-measured image was binarized, a threshold was set, the filler amount was quantitatively analyzed, and the filler uptake rate was calculated based on the filler amount.

(Hardness (Hs))
The hardness of the obtained rubber-filler composite was measured at 25 ° C. using a type A durometer according to JIS K 6253-1: 2012. The hardness of the standard formulation was set to 100, and the hardness of each formulation was expressed as an index. The larger the index, the higher the hardness.

From Tables 1 and 2, in the rubber-silica composite, a high filler uptake rate was obtained when a nonionic surfactant was used (filter solution: transparent), whereby a high-hardness composite could be produced. .. In the rubber / microfibrillated plant fiber composite, a high filler uptake rate can be obtained when an anionic surfactant and a nonionic surfactant, particularly an anionic surfactant, are used (filter solution: transparent). As a result, a high hardness composite could be produced.

<Making compound rubber>
Chemicals other than sulfur and vulcanization accelerator were kneaded using a 1.7 L Banbury mixer according to the formulations shown in Tables 3-4. Next, using a roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized product.

The obtained vulcanized product was evaluated as follows, and the results are shown in Tables 3-4. The reference formulations in Tables 3 and 4 are comparative formulations 1-2 and 2-1 respectively.

(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 having the reference composition was set to 100, and the TB of each composition 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 standard formulation) x 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 having the standard composition 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.
(Modulus index) = (E * of each formulation) / (E * of reference test piece) x 100

From Tables 3 and 4, in the examples using the rubber-filler composite having a high hardness with a filler uptake rate of 95% by mass or more, the breaking strength and the elongation at break were excellent.

Claims (4)

A method for producing a rubber-filler composite, which comprises a step of mixing a rubber latex, a filler dispersion, and a surfactant.
A method for producing a rubber-filler composite in which the filler uptake rate in the rubber-filler composite is 95% by mass or more. The method for producing a rubber-filler composite according to claim 1, wherein the filler dispersion is a silica dispersion and / or a microfibrillated plant fiber dispersion. The method for producing a rubber-filler composite according to claim 1 or 2, wherein the surfactant is a nonionic surfactant and / or an anionic surfactant. A rubber-filler composite obtained by the production method according to any one of claims 1 to 3.