Manufacturing method of rubber-filler composite

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

[Technical Field]

[0001] The present invention relates to a method for producing a rubber-filler composite, and a rubber-filler composite obtained by the method. [Background Art]

[0002] By blending fillers such as silica and microfibrillated vegetable fibers (cellulose fibers, etc.) into a rubber composition, it is possible to reinforce the rubber composition and improve the modulus (complex elastic modulus). However, for example, when adding a filler to a rubber latex and attempting to mix the rubber component with the filler, a problem occurs in that the added filler is not sufficiently incorporated into the rubber component and remains in the solution.

[0003] In response to this, there have been disclosed a method of chemically modifying microfibrillated plant fibers to improve the compatibility between the rubber component and the microfibrillated plant fibers, a method of blending cellulose fibers having carboxyl groups or finely modified cellulose fibers with rubber to improve the dispersibility of cellulose fibers in rubber, and a method of using composite cellulose fibers obtained by graft-polymerizing polymers onto cellulose nanofibers as a rubber reinforcing material to improve the affinity and dispersibility of the rubber component (see Patent Documents 1 to 4).

[0004] However, even with the above-mentioned methods, there is a problem that a part of the filler used is not sufficiently incorporated into the rubber component, and the desired rubber-filler composite cannot be suitably obtained. [Prior art document] [Patent document]

[0005] [Patent Document 1] Patent No. 4 No. 581116 [Patent Document 2] JP Patent Publication No. 2013-18918 [Patent Document 3] JP Patent Publication No. 2014-125607 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-263417

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to solve the above problems and provide a method for producing a rubber-filler composite capable of sufficiently incorporating a filler to be used into a rubber component, etc.

Means for Solving the Problems

[0007] The present invention relates to a method for producing a rubber-filler composite including a step of mixing a rubber latex, a filler dispersion, and a surfactant, wherein the filler incorporation rate in the rubber-filler composite is 95% by mass or more.

[0008] The filler dispersion is preferably a silica dispersion and / or a microfibrillated plant fiber dispersion.

[0009] The surfactant is preferably a nonionic surfactant and / or an anionic surfactant.

[0010] The present invention also relates to a rubber-filler composite obtained by the above production method.

Effects of the Invention

[0011] According to the present invention, there is provided a method for producing a rubber-filler composite including a step of mixing a rubber latex, a filler dispersion, and a surfactant, wherein the filler incorporation rate in the rubber-filler composite is 95% by mass or more. Therefore, a production method capable of sufficiently incorporating a filler to be used into a rubber component can be provided.

Embodiments for Carrying Out the Invention

[0012] 〔Method for Producing Rubber-Filler Composite〕 The present invention relates to a method for producing a rubber-filler composite including a step of mixing a rubber latex, a filler dispersion, and a surfactant, and the production method is such that the filler incorporation rate in the rubber-filler composite is 95% by mass or more. Note that the production method of the present invention may include other steps as long as the above step is included, and each of the above steps may be performed once or may be repeatedly performed a plurality of times.

[0013] The mechanism by which the filler incorporation rate can be made 95% by mass or more is not necessarily clear, but 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. However, when using a rubber latex as the rubber component source, a filler dispersion as the filler source, and at the same time using a surfactant, the hydrophilic group of the surfactant interacts with the functional groups on the surface of the filler such as silica and microfibrillated plant fibers, and the hydrophobic group interacts with the rubber, so that the rubber and the filler are compatible and it becomes difficult for the filler to escape from 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.

[0014] This is a production method in which the filler incorporation rate in the rubber-filler composite (the ratio (mass) of the filler incorporated (included) in the composite in 100% by mass of the total amount of the filler used in the production of the rubber-filler composite) is 95% by mass or more, 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.

[0015] Here, the filler incorporation rate can be adjusted according to the types and amounts of the rubber latex source, the filler source, and the surfactant. For example, the incorporation rate can be adjusted by appropriately selecting the type and amount of the surfactant. The more the surfactant having a large interaction with the type of rubber latex and filler used is used, the more the incorporation rate tends to increase. Also, the incorporation rate can be adjusted by appropriately adjusting the concentrations of the rubber latex and the filler dispersion.

[0016] Specifically, as methods for satisfying a filler incorporation rate of 95% by mass or more, (a) when using silica as the filler, a method of using a nonionic surfactant as the surfactant, (b) when using microfibrillated plant fiber as the filler, a method of using an anionic surfactant and / or a nonionic surfactant as the surfactant, (c) a method of adjusting the concentration of the rubber latex, (d) a method of adjusting the concentration of the filler dispersion, (e) first, a method of mixing the surfactant and the filler dispersion and then mixing the rubber latex, etc. can be mentioned, which can be used alone or in appropriate combination.

[0017] Note that the measurement of the filler incorporation rate (the incorporation rate in 100% by mass of the charged amount of the filler (the ratio of the filler incorporated into the rubber)) can be measured by the method described in the examples below. For example, the dispersion of the rubber-filler composite obtained from the rubber latex, the filler dispersion, and the surfactant is coagulated, 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 value is set, the filler amount is quantitatively analyzed, and the filler incorporation rate is calculated based on the filler amount.

[0018] The step of mixing the aforementioned rubber latex, filler dispersion, and surfactant is not particularly limited as long as it is a step of mixing the rubber latex, filler dispersion, and surfactant and adjusting the filler incorporation rate in the produced rubber-filler composite to 95% by mass or more. Among them, it is preferable that the step includes a step of mixing the surfactant and the filler dispersion to produce a mixed solution (step (1)) and a step of mixing the mixed solution and the rubber latex (step (2)).

[0019] (Step (1)) Surfactants have a hydrophobic group and a hydrophilic group, and examples thereof include nonionic surfactants, anionic surfactants, and cationic surfactants. Among them, from the viewpoint of the filler incorporation rate, when silica is used as the filler, nonionic surfactants are preferred. When microfibrillated plant fibers are used as the filler, nonionic surfactants and anionic surfactants are preferred, and anionic surfactants are more preferred.

[0020] The nonionic surfactant is not particularly limited, and conventionally known ones such as polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ether, polyoxyethylene polypropylene alkyl ether, and polyoxyethylene polybutylene alkyl ether; polyoxyalkylene alkenyl ethers such as polyoxyethylene alkenyl ether; polyoxyethylene alkyl phenyl ether; and higher fatty acid alkanolamides can be used. Among them, nonionic surfactants having a polyoxyethylene group as the hydrophilic group and a hydrocarbon group as the hydrophobic group can be preferably used.

[0021] As such nonionic surfactants, 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.

[0022] R 1 -O-(EO) x -H (I) (In 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 addition mole number x is 3 to 100.)

[0023] R 1 The number of carbon atoms of is preferably 5 to 30, more preferably 8 to 20. The above x is preferably 5 to 50, more preferably 8 to 30.

[0024] 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. The average number of moles added y is 3 to 100, and the average number of moles added z is 3 to 100.)

[0025] R 2 preferably has 5 to 30 carbon atoms, more preferably 8 to 20 carbon atoms. The above y is preferably 5 to 50, more preferably 8 to 30. The above z is preferably 5 to 50, more preferably 8 to 30. Note that the arrangement of EO and AO may be block or random.)

[0026]

Chemical formula

[0027] In the above formula (III), R 3 ~R 5 are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, or an alkoxy group 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 moles added a is 0 to 50, the average number of moles added b is 0 to 50, and the average number of moles added c is 1 to 50.)

[0028] R 3 and R 4 preferably have 1 to 25 carbon atoms, and the above R 5 is preferably a hydrogen atom or an alkyl group having 1 to 25 carbon atoms. Also, the above R 6 preferably has 3 to 8 carbon atoms. 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.)

[0029] For the hydrophobic group of the anionic surfactant, any hydrophobic functional group can be arbitrarily adopted. Among them, 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. Among them, an aliphatic hydrocarbon group and an aromatic hydrocarbon group are preferable. The number of carbon atoms of the hydrocarbon group is preferably 4 to 20, more preferably 4 to 15, and still more preferably 4 to 12.

[0030] As the aliphatic hydrocarbon group, those having 1 to 20 carbon atoms are preferable, those having 1 to 10 carbon atoms are more preferable, and those having 1 to 6 carbon atoms are still more preferable. Preferable examples include alkyl groups having the above number of carbon atoms. Specifically, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group, etc. are included. In addition, alkenyl groups and alkynyl groups having the above number of carbon atoms are also included. As an example, alkenyl groups such as vinyl group, allyl group, 1-propenyl group, 1-methylethenyl group, isobutylene group, and alkynyl groups such as ethynyl group and propargyl group are included. Among them, isobutylene group is preferable.

[0031] As the alicyclic hydrocarbon group, those having 3 to 8 carbon atoms are preferable, and specifically, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclopropenyl group, cyclobutenyl group, cyclopentenyl group, cyclohexenyl group, cycloheptenyl group, cyclooctenyl group, etc. are included.

[0032] As the aromatic hydrocarbon group, those having 6 to 12 carbon atoms are preferable, and specifically, a phenyl group, a benzyl group, a phenethyl group, a tolyl group, a xylyl group, a naphthyl group, etc. may be mentioned. 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. In addition, 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, meta-position, and para-position.

[0033] 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 sulfuric acid group, and a phosphoric acid group is preferable. Among them, a carboxyl group is particularly preferable.

[0034] Specifically, the anionic surfactant can be classified into surfactants such as carboxylic acid type, sulfonic acid type, sulfuric acid ester type, and phosphoric acid ester type.

[0035] Examples of carboxylic acid surfactants include fatty acid salts with 6 to 30 carbon atoms, polyvalent carboxylate salts, rosin acid salts, dimer acid salts, polymer acid salts, tall oil fatty acid salts, and polycarboxylic acid type polymer surfactants, etc. Preferably, they are carboxylate salts, polycarboxylate salts, and polycarboxylic acid type polymer surfactants with 10 to 20 carbon atoms, and particularly preferably polycarboxylic acid type polymer surfactants. Examples of sulfonic acid surfactants include alkylbenzene sulfonate salts, alkyl sulfonate salts, alkyl naphthalene sulfonate salts, naphthalene sulfonate salts, diphenyl ether sulfonate salts, etc. Examples of the above sulfate ester surfactants include alkyl sulfate ester salts, polyoxyalkylene alkyl sulfate ester salts, polyoxyalkylene alkyl phenyl ether sulfate ester salts, tristyrenated phenol sulfate ester salts, distyrenated phenol sulfate ester salts, α-olefin sulfate ester salts, alkyl succinic acid sulfate ester salts, polyoxyalkylene tristyrenated phenol sulfate ester salts, polyoxyalkylene distyrenated phenol sulfate ester salts, etc. Examples of phosphate ester surfactants include alkyl phosphate ester salts, polyoxyalkylene phosphate ester salts, etc. Examples of salts of these compounds include metal salts (such as Na, K, Ca, Mg, Zn, etc.), ammonium salts, amine salts (such as triethanolamine salts, etc.). In addition, examples of the alkyl group in these surfactants include alkyl groups with 4 to 30 carbon atoms. Also, examples of the polyoxyalkylene group include those having an alkylene group with 2 to 4 carbon atoms, and for example, those with an ethylene oxide addition molar number of about 1 to 50 moles can be used.

[0036] The anionic surfactant preferably has a weight average molecular weight (Mw) of 500 or more, more preferably 1000 or more. Further, it is preferably 50000 or less, more preferably 30000 or less. In the present specification, Mw can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0037] As the cationic surfactant, a quaternary ammonium salt type, that is, a surfactant represented by the following formula (IV) having a quaternary ammonium group and a hydrocarbon group, etc. can be preferably used.

[0038] [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 groups or alkenyl groups 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 alkyl groups having 1 to 3 carbon atoms. X represents a monovalent anion.)

[0039] 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 ions and bromide ions.

[0040] Specific examples of the cationic surfactant represented by the above formula (IV) include, for example, alkyltrimethylammonium salts such as hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, stearyltrimethylammonium chloride, and bromides corresponding thereto. Among them, hexadecyltrimethylammonium bromide is preferred.

[0041] As commercially available products of surfactants, for example, products of Elementis, Kao Corporation, Daiichi Kogyo Seiyaku Co., Ltd., Sanyo Chemical Industries, Ltd., EVONIK-DEGUSSA AG, Huntsman Corporation, etc. can be used.

[0042] 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, microfibrillated vegetable fiber, etc. For example, silica, microfibrillated vegetable fiber, etc. can be preferably used. The solvent is not particularly limited, and examples thereof include water and organic solvents such as alcohol. Among them, water is preferred.

[0043] The silica is not particularly limited, and those usually used in the rubber industry can be used. For example, dry process silica (anhydrous silicic acid), wet process silica (anhydrous silicic acid), etc. can be mentioned. Among them, wet process silica is preferred. Specifically, examples include Ultrasil VN3, 7000GR, 9000GR manufactured by Degussa, Nipsil AQ manufactured by Tosoh Silica Corporation, and Zeosil 115GR manufactured by Rhodia Japan. These may be used alone or in combination of two or more.

[0044] 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, still more preferably 160 m 2is above / g. By setting it above the lower limit, there is a tendency to obtain good wet grip performance, breaking strength, etc. Also, for the N of silica 2 The upper limit of SA is not particularly limited, but preferably 500 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. By setting it below the upper limit, there is a tendency to obtain good dispersibility. Incidentally, the N of silica 2 SA is a value measured by the BET method in accordance with ASTM D3037 - 93.

[0045] As the microfibrillated plant fiber, cellulose microfibrils are preferable from the viewpoint of obtaining good reinforcing properties. The 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, paper, cloth, agricultural crop residues, food waste, and sewage sludge obtained from these as raw materials, waste biomass such as rice straw, wheat straw, and thinned wood, and those derived from cellulose produced by sea squirts, acetic acid bacteria, etc. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0046] Incidentally, in this specification, the cellulose microfibril typically means a cellulose fiber having an average fiber diameter within the range of 10 μm or less, and more typically a cellulose fiber having a micro - structure with an average fiber diameter of 500 nm or less formed by an aggregation of cellulose molecules. Incidentally, typical cellulose microfibrils can be formed as an aggregate of cellulose fibers having the average fiber diameter as described above, for example.

[0047] The method for producing the microfibrillated plant fiber is not particularly limited. For example, after chemically treating the raw material of the cellulose microfibril with an alkali such as sodium hydroxide as needed, it is mechanically ground or beaten using a refiner, a twin-screw kneader (twin-screw extruder), a twin-screw kneading extruder, a high-pressure homogenizer, a medium stirring mill, a stone mortar, a grinder, a vibration mill, a sand grinder, etc. In these methods, since lignin is separated from the raw material by chemical treatment, microfibrillated plant fibers substantially free of lignin can be obtained. Further, as other methods, a method of subjecting the raw material of the cellulose microfibril to ultra-high pressure treatment, etc. may be mentioned.

[0048] As the above microfibrillated plant fiber, for example, products such as those of Sugino Machine Limited can be used.

[0049] Note that as the above microfibrillated plant fiber, those obtained by the above production method and further subjected to oxidation treatment or various chemical modification treatments, or natural products (for example, wood, pulp, bamboo, hemp, jute, kenaf, agricultural crop residues, cloth, paper, sea squirt cellulose, etc.) that can be the source of the above cellulose microfibril are used as cellulose raw materials, subjected to oxidation treatment or various chemical modification treatments, and then defibrated as needed, or those obtained by further subjecting the microfibrillated plant fiber dispersion to oxidation treatment or various chemical modification treatments can also be used.

[0050] Examples of the mode of chemical modification of the above microfibrillated plant fiber include esterification treatment, etherification treatment, acetalization treatment, etc. More specifically, acylation such as acetylation, cyanoethylation, amination, sulfonic esterification, phosphoric esterification, alkyl esterification, alkyl etherification, complex esterification, β-ketoesterification, alkylation such as butylation, chlorination, etc. are preferably exemplified. Further, alkylcarbamation and arylcarbamation can also be exemplified.

[0051] That is, the above-mentioned microfibrillated plant fiber is a chemically modified microfibrillated plant fiber, and the chemical modification in the chemically modified microfibrillated plant fiber is at least one selected from the group consisting of acetylation, amination, sulfonic esterification, alkyl esterification, complex esterification, β-ketoesterification, alkylcarbamation, and arylcarbamation. Any of the above chemical modification treatments is a treatment for hydrophobizing the microfibrillated plant fiber. By using the microfibrillated plant fiber subjected to such a chemical modification treatment, the dispersibility of the microfibrillated plant fiber can be further improved.

[0052] It is preferable that the above-mentioned chemically modified microfibrillated plant fiber is 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 by other functional groups per glucose ring unit of the hydroxyl groups of cellulose, 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. When it is 2.5 or less, the chemically modified microfibrillated plant fiber is particularly excellent in dispersibility and particularly excellent in flexibility. The degree of substitution is more preferably in the range of 0.3 to 2.5, still more preferably in the range of 0.4 to 2.3, and particularly preferably in the range of 0.4 to 2.0.

[0053] In addition, when the above-mentioned chemically modified microfibrillated plant fiber is composed of a combination of two or more kinds, the above degree of substitution is calculated as an average for the whole chemically modified microfibrillated plant fiber.

[0054] The degree of substitution in the above-mentioned chemically modified microfibrillated plant fiber can be confirmed, for example, by a titration method using 0.5N-NaOH and 0.2N-HCl, or by measurements such as NMR and infrared absorption spectrum.

[0055] When the above chemically modified microfibrillated plant fiber is acetylated microfibrillated plant fiber, the degree of substitution is 0.3 to 2.5; when it is aminated microfibrillated plant fiber, the degree of substitution is 0.3 to 2.5; when it is sulfonated esterified microfibrillated plant fiber, the degree of substitution is 0.3 to 1.8; when it is alkyl esterified microfibrillated cellulose, the degree of substitution is 0.3 to 1.8; when it is complex esterified microfibrillated cellulose, the degree of substitution is 0.4 to 1.8; when it is β-keto esterified microfibrillated cellulose, the degree of substitution is 0.3 to 1.8; when it is alkyl carbamate microfibrillated cellulose, the degree of substitution is 0.3 to 1.8; when it is aryl carbamate microfibrillated cellulose, the degree of substitution is preferably in the range of 0.3 to 1.8.

[0056] The above acetylation can be carried out, for example, by a method of adding acetic acid, concentrated sulfuric acid, acetic anhydride to the microfibrillated plant fiber and reacting them. More specifically, for example, in a mixed solvent of acetic acid and toluene, in the presence of a sulfuric acid catalyst, the microfibrillated plant fiber and acetic anhydride are reacted to advance the acetylation reaction, and then the solvent is replaced with water, etc., which can be carried out by a conventionally known method.

[0057] The above amination can be carried out by a known method such as a method of reacting with an alkylamine in alcohol after tosylation and performing a nucleophilic substitution reaction.

[0058] The above sulfonated esterification can be carried out, for example, by a simple operation of dissolving the microfibrillated plant fiber in sulfuric acid and pouring it into water. In addition, it can also be carried out by a method of treating with anhydrous sulfur dioxide gas, treating with chlorosulfonic acid and pyridine, etc.

[0059] The above phosphorylation can be carried out, for example, by a method of treating the microfibrillated plant fiber treated with dimethylamine treatment, etc. with phosphoric acid and urea.

[0060] The above alkyl esterification can be carried out, for example, by the Schotten-Baumann method in which microfibrillated plant fibers are reacted with carboxylic acid chloride under basic conditions, and the above alkyl etherification can be carried out by the Williamson method or the like in which microfibrillated plant fibers are reacted with alkyl halide under basic conditions.

[0061] The above chlorination can be carried out, for example, by a method in which thionyl chloride is added and heated in DMF (dimethylformamide).

[0062] The above complex esterification can be carried out, for example, by a method in which two or more kinds of carboxylic acid anhydrides or carboxylic acid chlorides are reacted with microfibrillated plant fibers under basic conditions.

[0063] The above β-ketoesterification can be carried out, for example, by a method in which diketene or alkyl ketene dimer is reacted with microfibrillated plant fibers, or by a transesterification reaction of microfibrillated plant fibers with a β-ketoester compound such as alkyl acetoacetate.

[0064] The above alkyl carbamation can be carried out, for example, by a method in which alkyl isocyanate is reacted with microfibrillated plant fibers in the presence of a basic catalyst or a tin catalyst.

[0065] The above aryl carbamation can be carried out, for example, by a method in which aryl isocyanate is reacted with microfibrillated plant fibers in the presence of a basic catalyst or a tin catalyst.

[0066] Examples of the mode of oxidation treatment of the above microfibrillated plant fibers include oxidation treatment using an N-oxyl compound. The oxidation treatment using the above 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 a co-oxidant is allowed to act on the microfibrillated plant fibers.

[0067] Examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives. Examples of the co-oxidizing agent include sodium hypochlorite.

[0068] The average fiber diameter of the microfibrillated plant fiber is preferably 4 to 100 nm. As the average fiber diameter, 90 nm or less is preferable, and 50 nm or less is more preferable. Further, for the reason that the entanglement of the microfibrillated plant fiber is difficult to unwind and difficult to disperse, it is preferably 10 nm or more, and more preferably 20 nm or more.

[0069] The average fiber length of the microfibrillated plant fiber is preferably 100 nm or more. More preferably, it is 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 still more preferable, 3 μm or less is particularly preferable, and 2 μm or less is most preferable.

[0070] In addition, when the microfibrillated plant fiber is composed of a combination of two or more kinds, the average fiber diameter and the average fiber length are calculated as the average of the whole microfibrillated plant fiber.

[0071] In this specification, the average fiber diameter and the average fiber length of the microfibrillated plant fiber can be measured by image analysis using a scanning electron micrograph, image analysis using a transmission electron micrograph, image analysis using an atomic force micrograph, analysis of X-ray scattering data, pore electrical resistance method (Coulter principle method), etc.

[0072] The filler dispersion can be produced by a known method, and the production method is not particularly limited. For example, it can be prepared by dispersing a filler in a solvent such as water using a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, etc. The temperature and time during the preparation can also be appropriately set within the range usually carried out so that the filler is sufficiently dispersed in a solvent such as water.

[0073] The content (solid content) of the filler in the above filler dispersion is not particularly limited, but is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably 0.5 to 7% by mass.

[0074] In the above step (1), as a method of mixing the surfactant and the filler dispersion to prepare a mixed solution, for example, a method of mixing the surfactant and the filler dispersion using a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, etc. can be mentioned. By sufficiently stirring until it is sufficiently dispersed, a mixed solution of the surfactant and the filler dispersion can be obtained. The temperature and time for preparing the mixed solution can be appropriately set within the usually performed range until the surfactant and the filler dispersion are sufficiently dispersed. For example, 10 to 40 °C for 3 to 120 minutes is preferable, and 15 to 30 °C for 5 to 90 minutes is more preferable.

[0075] The compounding 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 in the rubber-filler composite. The addition amount is more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more. Also, 25 parts by mass or less is more preferable, 20 parts by mass or less is still more preferable, and 15 parts by mass or less is particularly preferable.

[0076] The compounding 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 in the rubber-filler composite. The compounding amount is more preferably 2 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. Also, 40 parts by mass or less is more preferable, 35 parts by mass or less is still more preferable, and 30 parts by mass or less is particularly preferable. When microfibrillated plant fiber is used as the filler, the compounding amount is preferably in the same range. When silica is used as the filler, the compounding amount is preferably 5 to 50 parts by mass, more preferably 7 to 50 parts by mass, and still more preferably 7 to 40 parts by mass.

[0077] (Step (2)) Next, in the present invention, a step of mixing the mixed solution obtained in step (1) with a rubber latex (step (2)) is performed.

[0078] As the rubber latex, for example, natural rubber latex, modified natural rubber latex (saponified 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, vinyl pyridine rubber, butyl rubber, etc. latex) and other diene rubber latex can be preferably used. These rubber latexes may be used alone or in combination of two or more. Among them, natural rubber latex, SBR latex, BR latex, and isoprene rubber latex are more preferable, and natural rubber latex is particularly preferable.

[0079] Natural rubber latex is collected as the sap of natural rubber trees such as Hevea trees, and contains water, protein, lipid, inorganic salts, etc. in addition to the rubber component. The gel content in the rubber is considered to be based on the complex existence of various impurities. In the present invention, as the natural rubber latex, raw latex (field latex) tapped from Hevea trees, concentrated latex (purified latex, high ammonia latex added with ammonia by a conventional method, LATZ latex stabilized with zinc white, TMTD, and ammonia, etc.) concentrated by a centrifugation method or a creaming method can be used.

[0080] The pH of the rubber latex is preferably 8.5 or more, more preferably 9.5 or more. When the pH is 8.5 or more, the rubber latex is less likely to become unstable and less likely to coagulate. The pH of the above rubber latex is preferably 12 or less, more preferably 11 or less. When the pH is 12 or less, the rubber latex is less likely to deteriorate.

[0081] 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.

[0082] In the above step (2), as a method of mixing the mixed solution obtained in step (1) and the rubber latex, for example, a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, etc. is charged with rubber, and while stirring, the mixed solution obtained in step (1) is dropped, or while stirring the mixed solution obtained in step (1), the rubber latex is dropped into it, etc. can be mentioned. By sufficiently stirring until sufficient dispersion is achieved, a mixture (compounded latex) of the mixed solution obtained in step (1) and the rubber can be obtained. The temperature and time for preparing the mixture can be appropriately set within the range usually carried out until the mixed solution obtained in step (1) and the rubber are sufficiently dispersed. For example, 10 to 40°C for 3 to 120 minutes is preferable, and 15 to 30°C for 5 to 90 minutes is more preferable.

[0083] The pH of the mixture (compounded latex) obtained in the above step (2) is preferably 9.0 or more, more preferably 9.5 or more. Also, it is preferably 12 or less, more preferably 11.5 or less. When the pH of the mixture (compounded latex) of the mixed solution obtained in the above step (1) and the rubber latex is within such a range, deterioration can be suppressed and it can be made stable.

[0084] If the mixture (compounded latex) obtained in the above step (2) is coagulated as necessary, the coagulum (aggregate containing aggregated rubber and filler) is filtered and dried by a known method, and further after drying, rubber kneading is performed with a two-roll mill, Banbury, etc., 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 effects are not inhibited.

[0085] The above-mentioned coagulation is carried out by adding a normal acid to the mixture (compounded latex) obtained in the above step (2). Examples of the acid for coagulation include sulfuric acid, hydrochloric acid, formic acid, acetic acid, etc. The temperature for coagulation is preferably 10 to 40 °C.

[0086] During the above-mentioned coagulation, it is preferable to adjust the pH of the mixture (compounded latex) obtained in the above step (2) to 3 to 5, and more preferably to 3 to 4.

[0087] Also, for the purpose of controlling the coagulation state (the size of the coagulated aggregated particles), a flocculant may be added. As the flocculant, a cationic polymer or the like can be used.

[0088] By such a manufacturing method or the like, a rubber-filler composite with a filler incorporation rate of 95% by mass or more is produced.

[0089] 〔Rubber composition〕 The above rubber composition contains the above rubber-filler composite. The rubber-filler composite can be used as a masterbatch. In the above rubber-filler composite, the filler is sufficiently dispersed in the rubber, and the filler can also be sufficiently dispersed in the rubber composition mixed with other components. Therefore, effective reinforcing properties can be exhibited, and the performance such as durability (tensile strength) and handling stability can be improved in a well-balanced manner.

[0090] Other rubber components other than the rubber (rubber component) used in the above rubber-filler composite can be blended in the above rubber composition. As the above other rubber components, for example, diene-based rubbers 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), acrylonitrile-butadiene rubber (NBR), etc. Examples of rubber components other than those described above include butyl rubber, fluororubber, etc. These may be used alone or in combination of two or more. As the rubber component, SBR, BR, and isoprene rubber are preferred, and SBR is more preferred.

[0091] Here, the other rubber component is preferably a rubber having a weight average molecular weight (Mw) of 200,000 or more, more preferably 350,000 or more. The upper limit of Mw is not particularly limited, but is preferably 4,000,000 or less, more preferably 3,000,000 or less.

[0092] In this specification, Mw and number average molecular weight (Mn) can be determined by standard polystyrene conversion based on the measured values by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0093] The other rubber component may be an unmodified diene rubber or a modified diene rubber. Examples of the modified diene rubber may be a 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 modified with a compound (modifying agent) having the functional group (end-modified diene rubber having the functional group at the end), a main chain-modified diene rubber having the functional group in the main chain, a main chain-end modified diene rubber having the functional group in the main chain and at the end (for example, a main chain-end modified diene rubber having the functional group in the main chain and at least one end modified with the modifying agent), a terminal-modified diene rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein, etc.

[0094] 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, a disulfide 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, an epoxy group, etc. These functional groups may have substituents. Among them, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted 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 alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0095] SBR is not particularly limited. For example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

[0096] The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When it is within the above range, the above effects can be obtained more preferably. In this specification, the styrene content of SBR is 1 calculated by 1H-NMR measurement.

[0097] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0098] SBR may be non-modified SBR or modified SBR. Examples of the modified SBR include modified SBR into which the same functional groups as those of the modified diene rubber are introduced.

[0099] 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. By setting it within the above range, good tire performance tends to be obtained.

[0100] BR is not particularly limited, and for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), etc. can be used. These may be used alone or in combination of two or more. Among them, high-cis BR with a cis content of 90% by mass or more is preferred because of the improved abrasion resistance.

[0101] Also, BR may be non-modified BR or modified BR. Examples of the modified BR include modified BR into which the same functional groups as those of the modified diene rubber are introduced.

[0102] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0103] Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. As NR, for example, those commonly used in the rubber industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those commonly used in the rubber industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0104] In the above rubber composition, the filler content (solid content) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, it is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and still more preferably 200 parts by mass or less.

[0105] When the above rubber composition contains microfibrillated plant fiber, its content (solid content) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, it is preferably 45 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass or less, and particularly preferably 30 parts by mass or less. By setting it within the above range, good dispersibility can be obtained, and there is a tendency to obtain excellent rubber physical properties.

[0106] When the above rubber composition contains silica, its content is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and still more 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 it is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 170 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 80 parts by mass or less. By setting it within the above range, good dispersibility can be obtained, and there is a tendency to obtain excellent rubber physical properties.

[0107] When the above rubber composition contains silica, it is preferably further contained with a silane coupling agent. The silane coupling agent is not particularly limited. 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-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. of the sulfide series, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto series such as NXT and NXT-Z manufactured by Momentive, vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane, amino series such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy series such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro series such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro series such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. can be mentioned. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

[0108] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, based on 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. Further, the above 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.

[0109] The above 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, N762 and the like. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Carbon Co., Ltd., Columbia Carbon Company and the like can be used. These may be used alone or in combination of two or more.

[0110] The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, based on 100 parts by mass of the rubber component. By setting it above the lower limit, a good reinforcing effect tends to be obtained. Further, the above 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 processability tends to be obtained.

[0111] 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, still 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 above N 2 SA is preferably 200 m 2 / g or less, more preferably 150 m 2 / g or less, still 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 according to JIS K6217-2:2001.

[0112] The above rubber composition may be blended with other fillers (reinforcing agents) other than silica and carbon black. Examples of other fillers include the aforementioned clay and the like.

[0113] The above rubber composition may be blended with a plasticizer. The plasticizer is not particularly limited, but examples include plasticizers that are liquid at normal temperature (25°C) such as oils and liquid resins. These plasticizers may be used alone or in combination of two or more.

[0114] When containing a plasticizer, its content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. Also, the above content is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 30 parts by mass or less. When within the above range, there is a tendency to obtain good rubber physical properties.

[0115] The oil is not particularly limited, and conventionally known oils such as paraffinic process oil, aromatic process oil, naphthenic process oil and other process oils, low PCA (polynuclear aromatic) process oils such as TDAE and MES, vegetable oils and fats, and mixtures thereof can be used. Among them, aromatic process oil is preferred in terms of abrasion resistance and fracture properties. Specific examples of the above aromatic process oil include the Diana Process Oil AH series manufactured by Idemitsu Kosan Co., Ltd.

[0116] The liquid resin is not particularly limited, and examples include liquid aromatic vinyl polymers, coumarone-indene resins, indene resins, terpene resins, rosin resins, or hydrogenated products thereof.

[0117] The liquid aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and / or styrene, and examples of the liquid resin include a homopolymer of styrene, a homopolymer of α-methylstyrene, and a copolymer of α-methylstyrene and styrene.

[0118] The liquid coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Examples of the monomer components that may be contained in the skeleton in addition to coumarone and indene include liquid resins such as styrene, α-methylstyrene, methyl indene, and vinyl toluene.

[0119] The liquid indene resin is a liquid resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0120] The liquid terpene resin is a liquid terpene-based resin typified by terpene phenol, which is a resin obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphene, and diterpene, or a resin obtained using a terpene compound and a phenolic compound as raw materials.

[0121] The liquid rosin resin is a liquid rosin-based resin typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, or hydrogenated products thereof.

[0122] A solid resin (a polymer in a solid state at normal temperature (25°C)) may be blended in the rubber composition.

[0123] When the solid resin is contained, its content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. Also, the above content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. When within the above range, good wet grip performance tends to be obtained.

[0124] The solid resin is not particularly limited, and examples thereof include solid styrene resins, coumarone-indene resins, terpene resins, p-t-butylphenol acetylene resins, acrylic resins, dicyclopentadiene resins (DCPD resins), C5 petroleum resins, C9 petroleum resins, C5-C9 petroleum resins, and the like. These may be used alone or in combination of two or more.

[0125] The solid styrene resin is a solid polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers obtained by polymerizing a styrene monomer as a main component (50% by mass or more). Specifically, homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of a styrene monomer and other monomers copolymerizable therewith are also included.

[0126] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; and the like.

[0127] Among them, a solid α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is preferable.

[0128] Examples of the solid coumarone-indene resin include solid resins having the same structural units as the aforementioned liquid coumarone-indene resin.

[0129] Examples of solid terpene resins include polyterpenes, terpene phenols, and aromatic-modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons represented by the composition of (C 5 H 8 ) n and their oxygen-containing derivatives, and are compounds having a terpene classified into monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) etc. as the basic skeleton. Examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-farnesene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc.

[0130] Examples of solid polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, etc. using the above-mentioned terpene compounds as raw materials, and solid resins such as hydrogenated terpene resins obtained by subjecting the terpene resins to hydrogenation treatment.

[0131] Examples of solid terpene phenols include solid resins obtained by copolymerizing the above-mentioned terpene compounds and phenolic compounds, and solid resins obtained by subjecting the resins to hydrogenation treatment. Specifically, examples include solid resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, xylenol, etc.

[0132] 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 subjecting the resin to a hydrogenation treatment. The aromatic compound is not particularly limited as long as it has an aromatic ring. Examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0133] Examples of the solid p-t-butylphenol acetylene resin include a solid resin obtained by subjecting p-t-butylphenol and acetylene to a condensation reaction.

[0134] The solid acrylic resin is not particularly limited, but a solventless acrylic solid resin can be preferably used in that a resin with few impurities and a sharp molecular weight distribution can be obtained.

[0135] The solid solventless acrylic resin is a (meth)acrylic resin (polymer) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (the methods described in U.S. Patent No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Patent No. 5,010,166, TREND2000, No. 3, p42-45, etc. of Toagosei Co., Ltd.) without using a polymerization initiator, a chain transfer agent, an organic solvent, etc. as auxiliary raw materials as much as possible. In this specification, "(meth)acrylic" means methacrylic and acrylic.

[0136] The solid acrylic resin preferably does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, etc. as auxiliary raw materials. Further, the acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

[0137] As described above, as the solid acrylic resin, those that substantially do not contain polymerization initiators, chain transfer agents, organic solvents, etc. that serve as auxiliary raw materials, that is, those with high purity are preferred. The purity of the solid acrylic resin (the proportion of the resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

[0138] Examples of the monomer components constituting the solid acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (such as alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0139] In addition, as the monomer components constituting the solid acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0140] The solid acrylic resin may be a resin composed only of (meth)acrylic components or a resin having components other than (meth)acrylic components as constituent elements. In addition, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, etc.

[0141] Examples of the plasticizer and solid resin that can be used include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Corporation, Arakawa Chemical Industries, Ltd., Tago Chemical Industries, Ltd., etc.

[0142] From the viewpoints of crack resistance, ozone resistance, etc., the above rubber composition preferably contains an antioxidant.

[0143] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used.

[0144] The content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, based on 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.

[0145] The above rubber composition preferably contains stearic acid. From the perspective of the above performance balance, the content of stearic acid is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0146] As for stearic acid, conventionally known ones can be used. For example, products of NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0147] The above rubber composition preferably contains zinc oxide. From the viewpoint of the above performance balance, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0148] As for zinc oxide, conventionally known ones can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shoindo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0149] The above rubber composition may be blended with wax. The wax is not particularly limited, and examples include petroleum waxes and natural waxes. Synthetic waxes 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.

[0150] Examples of petroleum waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are waxes derived from non-petroleum resources. For example, plant waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti wax; mineral waxes such as ozokerite, ceresin, and petrolactam; and purified products thereof. As commercially available products, for example, products of Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used. The content of the wax may be appropriately set from the viewpoints of ozone resistance and cost.

[0151] In the above rubber composition, it is preferable to blend sulfur in terms of forming appropriate cross-linked chains in the polymer chain and imparting good rubber physical properties.

[0152] The sulfur content is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and still more 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 still more preferably 3.0 parts by mass or less.

[0153] Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used in the rubber industry. As commercially available products, products of Tsukimi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys, Nippon Dry Distillation Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0154] The above 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. Usually, it is 0.3 to 10 parts by mass, preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

[0155] The type of vulcanization accelerator is not particularly limited, and those commonly used can be used. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These can be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0156] In addition to the above components, the above rubber composition may be appropriately blended with ordinary additives used in their applications, such as mold release agents and pigments, according to the application field.

[0157] As a method for producing the above rubber composition, a known method can be used. For example, it can be produced by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing.

[0158] As for 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 finishing 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 kneaded with 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.

[0159] The above rubber composition can be used for tires, sole rubbers, floor rubbers, vibration-proof rubbers, seismic isolation rubbers, butyl frame rubbers, belts, hoses, packings, stoppers, and other rubber industrial products. In particular, since it can improve performance such as durability (breaking strength), handling stability, and low fuel consumption, it is preferably used as a rubber composition for tires.

[0160] The above rubber composition can be suitably used for pneumatic tires. The pneumatic tire is manufactured by a usual method using the above rubber composition. That is, a rubber composition blended with various materials as necessary is extruded into the shape of a tire member at the unvulcanized stage, and together with other tire members, it is formed by a usual method on a tire molding machine to form an unvulcanized tire, and then the tire can be manufactured by heating and pressurizing in a vulcanizer.

Examples

[0161] The present invention will be specifically described based on examples, but the present invention is not limited only to these.

[0162] Hereinafter, various chemicals used in the examples and comparative examples will be collectively described. Natural rubber latex: Field latex obtained from Muhibbah LATEKS was used Silica: Ultrasil VN3 (N 2 SA172m 2 / g) manufactured by Evonik Degussa Microfibrillated plant fiber: Biomass nanofiber manufactured by Sugino Machine Ltd. (product name: "BiNFi-s cellulose", average fiber length: approximately 2 μm, average fiber diameter: approximately 0.02 μm, solid content: 2% by mass) Surfactant 1: teric 16A29 manufactured by Huntsman Corporation (CH 3 (CH 2 ) 15 (OC 2 H 4 ) 29 -OH, nonionic surfactant) Surfactant 2: PD-430 manufactured by Kao Corporation (nonionic surfactant, R-(OC 4 H 8 ) p (OC 2 H 4 ) q -OH: R = long-chain alkyl group, p = 3 to 100, q = 3 to 100) Surfactant 3: Si363 manufactured by EVONIK-DEGUSSA (surfactant represented by the following formula, nonionic surfactant)

[0163]

Chemical formula

[0164] (Preparation of silica dispersion) 190 g of pure water was added to 10 g of silica to prepare a 5 mass% (solid content concentration) suspension of silica, and this was stirred and ultrasonically treated for 10 minutes to obtain a silica dispersion.

[0165] (Preparation of microfibrillated plant fiber dispersion) 150 g of pure water was added to 50 g of microfibrillated plant fiber (2 wt%) to prepare a 0.5 mass% (solid content concentration) suspension of microfibrillated plant fiber, and this was stirred and ultrasonically treated for 10 minutes to obtain a microfibrillated plant fiber dispersion.

[0166] (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 in Tables 1 to 2. Specifically, a surfactant was added to the prepared silica dispersion or microfibrillated plant fiber dispersion, and it was stirred at room temperature (20 to 30 °C) for 5 minutes using a high-speed homogenizer to obtain a mixture (mixed solution) of the silica dispersion or microfibrillated plant fiber dispersion and the surfactant. 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 with a pH of 10.2. Then, a 2 mass% aqueous formic acid solution was added at room temperature to adjust the pH to 3 to 4, and a coagulum was obtained. The obtained coagulum was filtered and dried to obtain a rubber-filler composite.

[0167] (Comparative Examples 1-2, 2-1) (Preparation of Rubber-Filler Composite) According to the formulation in Tables 1 - 2, a rubber-filler composite was manufactured. Specifically, natural rubber latex was added to a silica dispersion or microfibrillated plant fiber dispersion prepared to 0.5% by mass, and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a compounded latex with a pH of 10.2. Next, a 2% by mass aqueous formic acid solution was added at room temperature and adjusted to a pH of 3 - 4 to obtain a coagulum. The obtained coagulum was filtered and dried to obtain a rubber-filler composite.

[0168] The obtained rubber-filler composite was evaluated as follows, and the results are shown in Tables 1 - 2. Note that the reference formulations for the hardness (Hs) in Tables 1 and 2 are Examples 1-1 and 2-1, respectively.

[0169] (Measurement of Filler Incorporation Rate) For the coagulum (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 value was set, the filler amount was quantitatively analyzed, and the filler incorporation rate was calculated based on the filler amount.

[0170] (Hardness (Hs)) The hardness of the obtained rubber-filler composite was measured at 25°C using a Type A durometer in accordance with JIS K 6253-1:2012. The hardness of the reference formulation was set to 100, and the hardness of each formulation was expressed as an index. The larger the index, the higher the hardness.

[0171]

Table 1

[0172]

Table 2

[0173] From Tables 1 and 2, in the rubber-silica composite, a high filler incorporation rate was obtained when using a nonionic surfactant (filtrate: transparent), and thus, a composite with high hardness was produced. In the rubber-microfibrillated plant fiber composite, a high filler incorporation rate was obtained when using an anionic surfactant, a nonionic surfactant, particularly when using an anionic surfactant (filtrate: transparent), and thus, a composite with high hardness was produced.

[0174] <Preparation of compounded rubber> According to the formulations shown in Tables 3 to 4, chemicals other than sulfur and vulcanization accelerators were kneaded using a 1.7 L Banbury mixer. Next, sulfur and vulcanization accelerators were added to the obtained kneaded material using rolls 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 vulcanizate.

[0175] The obtained vulcanizates were evaluated as follows, and the results are shown in Tables 3 to 4. The reference formulations in Tables 3 and 4 are Comparative Formulations 1-2 and 2-1, respectively.

[0176] (Tensile strength) Using the vulcanizate, No. 3 dumbbell-shaped rubber test pieces were prepared, and a tensile test was conducted in accordance with JIS K6251 "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Properties" to measure the tensile strength (TB). Taking the TB index of the rubber test piece of the reference formulation as 100, the TB of each formulation was expressed as an index using the following calculation formula. The larger the TB index, the greater the tensile strength, indicating excellent reinforcing properties and durability. (TB index) = (TB of each formulation) / (TB of the reference formulation) × 100

[0177] (Handling stability) Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the complex elastic modulus E* of each formulation (vulcanizate) was measured under the conditions of a temperature of 50 °C, an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. Taking the E* of the rubber test piece of the reference formulation as 100, it was expressed as an index using the following calculation formula (elastic modulus index). The larger the index, the better the handling stability. (Elastic modulus index) = (E* of each formulation) / (E* of the reference test piece) × 100

[0178]

Table 3

[0179]

Table 4

[0180] From Tables 3 and 4, in the examples using a high-hardness rubber-filler composite with a filler incorporation rate of 95% by mass or more, the breaking strength and elongation at break were excellent.

Claims

[Claim 1] A method for producing a rubber-filler composite, comprising the step of mixing a rubber latex, a filler dispersion, and a surfactant, The filler incorporation rate in the rubber-filler composite is 95% by mass or more, The rubber latex is natural rubber latex, The filler dispersion is a microfibrillated plant fiber dispersion, The surfactant is an anionic surfactant, the surfactant is blended in an amount of 1 to 50 parts by mass relative to 100 parts by mass of a rubber solid content of the rubber latex, The mixing step includes a step of mixing the surfactant and the filler dispersion to prepare a mixed liquid, and a step of mixing the mixed liquid with the rubber latex.

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