Surface-modified fiber, reinforcing fiber, and molded article using same

Abstract

Provided are a surface-modified fiber, a reinforcing fiber, and a molded article using the reinforcing fiber, with which it is possible to improve adhesion to rubber without using resorcinol or formaldehyde. The surface-modified fiber has a fiber and a surface-modified layer that covers at least a portion of the surface of the fiber, and the solid surface Zeta potential of the surface of the surface-modified layer is-20.0-30.0 mV.

Description

[0001] This application is a divisional application of an application with an application date of November 10, 2020, an application number of 202080082717.9, and an invention title of "Surface-Modified Fibers, Reinforcing Fibers, and Molded Bodies Using the Same". Technical Field

[0002] The present invention relates to surface-modified fibers, reinforcing fibers having excellent adhesiveness to rubber, and molded bodies using the reinforcing fibers. Background Art

[0003] Synthetic organic fibers such as polyethylene terephthalate (PET), nylon 66, vinylon, and rayon are inexpensive, have high strength, excellent heat resistance and durability, and are lightweight. Therefore, they are used as reinforcing fibers for automobile tires and brake hoses. In these products, in order to exhibit the excellent physical properties (for example, high strength and high elastic modulus) of rubber, it is necessary to firmly bond the fibers to the rubber.

[0004] As a method for firmly bonding fibers to rubber, a method using an adhesive called RFL is currently widely known. The RFL has resorcinol-formaldehyde resin and rubber latex as main components (Patent Documents 1 and 2).

[0005] However, formaldehyde contained in RFL is suspected of being carcinogenic, and resorcinol is suspected of being an environmental hormone. Therefore, it is desired to develop alternative materials that do not use these raw materials.

[0006] As an alternative material to RFL, for example, Patent Document 3 proposes a technique using an adhesive containing an adhesive compound having an unsaturated carbon bond and an epoxy group that react with a vulcanizing agent used for rubber vulcanization. In addition, Patent Document 4 proposes a technique for improving the activity of a functional group layer provided by imparting a blocked isocyanate compound and an epoxy compound in the first stage and using an adhesive component having latex as a main component in the second stage.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 54-4976

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 58-2370

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2011-111563

[0012] Patent Document 4: European Patent No. 3258006 Specification Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] Compared with the existing method using RFL, the method using an adhesive described in Patent Document 3 has problems of significantly deteriorated adhesiveness and lack of practicality. In addition, the treatment described in Patent Document 4 requires a process of providing an intermediate layer called a rubber coating and requires heat treatment at high temperatures in two stages. Therefore, the treatment requires a large amount of energy and there is a risk of thermal deterioration of the fibers, and sometimes the reinforcing performance is reduced. It should be noted that Patent Document 4 only describes a technique using an adhesive component mainly composed of latex, and there is no description of using an adhesive component mainly composed of a conjugated diene rubber.

[0015] The present invention has been completed in view of the above-described existing problems, and an object thereof is to provide a surface-modified fiber, a reinforcing fiber, and a molded body using the reinforcing fiber that can improve the adhesiveness to rubber without using resorcinol and formaldehyde.

[0016] Means for Solving the Problems

[0017] The inventors of the present invention conducted intensive studies to solve the above problems, and as a result, found that by attaching a specific compound to the fiber to adjust the Zeta potential of the fiber surface to a specific range, the affinity between the fiber and the adhesive component becomes high. As a result, even without using resorcinol and formaldehyde, the adhesiveness between the fiber and the rubber is improved, and thus the present invention was completed.

[0018] That is, the present invention relates to the following [1] to

[14] .

[0019] [1] A surface-modified fiber having a fiber and a surface-modified layer covering at least a part of the surface of the fiber, wherein the solid surface Zeta potential of the surface of the surface-modified layer is -20.0 to 30.0 mV.

[0020] [2] The surface-modified fiber according to the above [1], wherein

[0021] the above fiber is one or more fibers selected from polyester fibers, polyamide fibers, polyvinyl alcohol fibers, and regenerated cellulose fibers.

[0022] [3] The surface-modified fiber according to the above [1] or [2], wherein

[0023] the above surface-modified layer contains a compound having a nitrogen-containing functional group.

[0024] [4] The surface-modified fiber according to any one of the above [1] to [3], wherein

[0025] the above surface-modified layer contains a compound having a group selected from Oxazolinyl A compound having one or more functional groups selected from oxazolidinonyl, carbodiimide group, ureido group, amino group, and aziridinyl group.

[0026] [5] The surface-modified fiber according to any one of the above [1] to [4], wherein

[0027] The amount of the above surface-modified layer is 0.01 to 5.0 parts by mass relative to 100 parts by mass of the fiber used as a raw material.

[0028] [6] A reinforcing fiber having:

[0029] The surface-modified fiber according to any one of the above [1] to [5], and

[0030] An adhesive layer that covers at least a part of the surface of the above surface-modified fiber and contains a conjugated diene rubber.

[0031] [7] The reinforcing fiber according to the above [6], wherein

[0032] The number-average molecular weight (Mn) of the above conjugated diene rubber exceeds 2000 and is 120000 or less.

[0033] [8] The reinforcing fiber according to the above [6] or [7], wherein

[0034] The above conjugated diene rubber has one or more monomer units selected from butadiene, isoprene, and farnesene in the molecule.

[0035] [9] The reinforcing fiber according to any one of the above [6] to [8], wherein

[0036] The above conjugated diene rubber is a modified conjugated diene rubber having a hydrogen-bonding functional group in a part of the conjugated diene rubber, and the hydrogen-bonding functional group is one or more selected from hydroxyl group, epoxy group, aldehyde group, acetalized body of aldehyde group, carboxyl group, salt of carboxyl group, esterified body of carboxyl group, acid anhydride of carboxyl group, silanol group, esterified body of silanol group, amino group, imidazole group, and mercapto group.

[0037]

[10] The reinforcing fiber according to any one of the above [6] to [9], wherein

[0038] The above adhesive layer further contains an oil having a vapor pressure of 10 Pa or less at 20 °C.

[0039]

[11] A molded article using the reinforcing fiber according to any one of the above [6] to

[10] .

[0040]

[12] The molded article according to

[11] above further has a rubber layer.

[0041]

[13] The molded article according to

[11] or

[12] above, wherein

[0042] the above-mentioned molded article is a tire, a belt or a tube.

[0043]

[14] A molded article having, in sequence, a fiber, a surface modification layer, an adhesive layer, and a rubber layer,

[0044] the adhesive force between the above-mentioned adhesive layer and the above-mentioned rubber layer is 70 N or more per 25.4 mm width on average.

[0045] Effects of the Invention

[0046] The present invention can provide a surface-modified fiber, a reinforcing fiber, and a molded article using the reinforcing fiber, which can improve the adhesiveness to rubber without using resorcinol and formaldehyde. Detailed Embodiments

[0047] [Surface-Modified Fiber]

[0048] The surface-modified fiber of the present invention is characterized in that it has a fiber and a surface modification layer covering at least a part of the surface of the above-mentioned fiber, and the solid surface Zeta potential of the surface of the above-mentioned surface modification layer is -20.0 to 30.0 mV.

[0049] According to the present invention, since the solid surface Zeta potential is adjusted to the above range, a strong affinity is exhibited between the modified conjugated diene rubber contained in the adhesive component and the fiber. Therefore, the fiber, the adhesive component, and the rubber are firmly bonded to each other, and as a result, the adhesiveness between the fiber and the rubber is improved.

[0050] It should be noted that in the present invention, the "surface modification layer covering at least a part of the surface of the fiber" may refer to a manner in which the surface modification layer exists in the form of a film or a layer on at least a part of the surface of the fiber, or a manner in which a component equivalent to the surface modification layer is contained in the raw material of the fiber and a component of the surface modification layer exists on a part of the surface of the fiber itself.

[0051] From the viewpoint of improving the affinity between the fiber and the adhesive component, and as a result, improving the adhesiveness between the fiber and the rubber, the solid surface Zeta potential of the surface of the surface modification layer is preferably -20.0 to 20.0 mV, more preferably -15.0 to 15.0 mV, further preferably -10.0 to 12.0 mV, still further preferably -5.0 to 10.0 mV, even further preferably -5.0 to 9.0 mV, further more preferably -5.0 to 6.0 mV, and still further more preferably -5.0 to 0 mV.

[0052] <Surface modification layer>

[0053] The surface modification layer in the present invention may be composed of a compound capable of adjusting the Zeta potential of the above solid surface to the above range, and there is no particular limitation. For example, it is preferably a layer containing a compound having a nitrogen-containing functional group. Specifically, it is preferably a layer containing a compound having one or more functional groups selected from oxazolinyl, oxazolidinonyl, carbodiimide group, urea group, amino group, and aziridinyl group.

[0054] Examples of the compound having the above functional group include: an oxazolidinonyl compound obtained by reacting a blocked isocyanate compound with an epoxy compound, an oxazolinyl group-introduced acrylic or styrene / acrylic copolymer high molecular main chain-containing oxazolinyl compound, a carbodiimide group-containing compound (polyvalent carbodiimide) having a carbodiimide group introduced into the molecule, a urea group-containing compound such as a urea derivative, an amino group-containing high molecular weight body having an amino group introduced into the molecule, an aziridinyl group-containing compound (2,2-bis(hydroxymethyl)butanol tris[3-(1-aziridinyl)propionate]) having an aziridinyl group introduced at the molecular end, etc. Among these, from the viewpoint of improving the adhesion between the surface-modified fiber and the rubber, an oxazolinyl group-containing compound obtained by reacting a blocked isocyanate compound with an epoxy compound is preferred, and from the viewpoint of reducing the environmental burden, an oxazolinyl group-containing compound is preferred. oxazolinyl group-containing compound.

[0055] From the viewpoint of improving the adhesion to the rubber, the surface modification layer preferably covers the entire surface of the fiber, but it is sufficient to substantially cover at least a part of the surface of the fiber. With respect to 100 parts by mass of the fiber used as a raw material, the specific amount of the surface modification layer covering the surface of the fiber is preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 1.0 parts by mass, and further preferably 0.1 to 0.3 parts by mass.

[0056] <Fiber>

[0057] The fibers used in the surface-modified fibers of the present invention are not particularly limited, and hydrophobic fibers formed of a hydrophobic resin that cannot be firmly bonded to rubber in the prior art can be appropriately used. Since hydrophobic fibers generally do not have polar functional groups on the fiber surface, they lack affinity for the adhesive components described later and cannot be firmly bonded to rubber. However, by providing a surface-modified layer on the fiber surface as in the present invention, even hydrophobic fibers can be firmly bonded to rubber. It should be noted that in the present invention, "fibers" include not only single fibers and long fibers, but also forms such as non-woven fabrics, fabrics, knitted fabrics, felts, and sponges.

[0058] Examples of the hydrophobic fibers that can be used in the present invention include: polyolefin fibers such as polyethylene and polypropylene; polyester fibers such as polyethylene terephthalate; and wholly aromatic polyester fibers. Among these, polyester fibers are preferred because of their excellent manufacturing cost, strength, heat resistance, and durability.

[0059] In the present invention, hydrophilic fibers can be used. Examples of the hydrophilic synthetic fibers include synthetic fibers composed of a thermoplastic resin having hydrophilic functional groups such as hydroxyl groups, carboxyl groups, sulfonic acid groups, and amino groups, and / or hydrophilic bonds such as amide bonds.

[0060] Specific examples of such thermoplastic resins include: polyvinyl alcohol resins; polyamide resins [aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, polyamide 9C (polyamide formed from nonanediamine and cyclohexanedicarboxylic acid), etc.; semi-aromatic polyamides synthesized from aromatic dicarboxylic acids and aliphatic diamines such as polyamide 9T (polyamide formed from nonanediamine and terephthalic acid); wholly aromatic polyamides synthesized from aromatic dicarboxylic acids and aromatic diamines such as poly(p-phenyleneterephthalamide), etc.]; polyacrylamide resins, etc.

[0061] Among these, polyvinyl alcohol resins and polyamide resins are preferred. The hydrophilic synthetic fibers can be used alone or in combination of two or more. In addition, for these hydrophilic synthetic fibers, in order to further improve hydrophilicity, the hydrophilic treatment described later can be further carried out.

[0062] Examples of the hydrophilic natural fibers include: natural cellulose fibers such as wood pulp such as kraft pulp, cotton pulp, and non-wood pulp such as straw pulp.

[0063] Examples of the hydrophilic regenerated fibers include: regenerated cellulose fibers such as rayon, lyocell fiber, cuprammonium fiber, and polynosic fiber.

[0064] These natural fibers and regenerated fibers can be used individually, one type at a time, or in combination of two or more types. Additionally, for these hydrophilic natural fibers and regenerated fibers, in order to further enhance hydrophilicity, a hydrophilization treatment described below can be further implemented.

[0065] The hydrophilic fiber only needs to have hydrophilicity at least on the surface. For example, it can be a fiber obtained by hydrophilizing the surface of a hydrophobic fiber, a core-sheath type composite fiber with a hydrophobic resin as the core and a hydrophilic resin as the sheath, etc. For examples of the hydrophilic resin constituting the sheath, the description of hydrophilic synthetic fibers is cited. As the hydrophobic fiber formed from a hydrophobic resin, for example, the above-mentioned hydrophobic fibers can be cited.

[0066] The hydrophilization treatment only needs to chemically or physically impart hydrophilic functional groups to the fiber surface, and there is no particular limitation. For example, it can be carried out by a method of modifying a hydrophobic fiber formed from the above-mentioned hydrophobic resin with a compound or its derivative containing hydrophilic functional groups such as isocyanate group, epoxy group, hydroxyl group, amino group, ether group, aldehyde group, carbonyl group, carboxyl group, and urethane group, or by a method of modifying the surface by electron beam irradiation.

[0067] As the hydrophilic fiber used in the present invention, from the viewpoint of being used as a reinforcing fiber, synthetic fibers and regenerated fibers are preferred, and among them, one or more fibers selected from polyester fibers, polyamide fibers, polyvinyl alcohol fibers, and regenerated cellulose fibers are preferred.

[0068] It should be noted that in the present invention, the fibers can be used individually, one type at a time, or in combination of two or more types.

[0069] <Manufacturing method of surface-modified fiber>

[0070] The manufacturing method of the surface-modified fiber of the present invention is not particularly limited, and it can be manufactured by preparing a solution of the compound constituting the above-mentioned surface-modified layer using water or an organic solvent, attaching the solution to the above-mentioned fiber, and then drying it by heat treatment or the like.

[0071] The method of attaching the solution of the above-mentioned surface modifier to the fiber is not particularly limited. For example, it is preferably carried out by one or more methods selected from dipping, roll coater, oiling roll, oiling guide, nozzle (spray) coating, and brush coating.

[0072] As the heat treatment for drying the above-mentioned solution, it is preferably carried out at a treatment temperature of 100~250°C and a treatment time of 0.1 second to 2 minutes. It should be noted that the heat treatment can be carried out only once at a specific temperature, and it can also be carried out two or more times by changing the treatment temperature and treatment time.

[0073] The above surface modification layer may contain other components other than the above. Examples of other components include crosslinking agents, acids, bases, inorganic salts, organic salts, pigments, dyes, antioxidants, polymerization initiators, plasticizers, etc.

[0074] When the surface modification layer contains the above other components, from the viewpoint of improving the adhesion to rubber, the content of other components in the surface modification layer is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.

[0075] [Reinforcing fiber]

[0076] The reinforcing fiber of the present invention has the above surface-modified fiber of the present invention and an adhesive layer covering at least a part of the surface of the above surface-modified fiber and containing a conjugated diene rubber. In the present invention, since the above surface-modified fiber has high affinity with the adhesive layer, the fiber, the adhesive layer, and the rubber can be firmly adhered.

[0077] For the reinforcing fiber of the present invention, the entire surface of the surface-modified fiber may be covered with the adhesive layer, or at least a part thereof may be covered with the adhesive layer. For example, it may be a manner in which the adhesive component exists in the form of a film or a layer.

[0078] It should be noted that for the reinforcing fiber of the present invention, even if the adhesive layer does not contain formaldehyde harmful to the human body and resins using formaldehyde as a raw material, a reinforcing fiber with excellent adhesion to rubber can be obtained. In the present invention, when the above adhesive layer contains a resin using formaldehyde as a raw material, examples of the resin include resorcinol / formaldehyde resin, phenol / formaldehyde resin, melamine / formaldehyde resin, and their derivatives. In the above adhesive layer, when the above formaldehyde component is contained, its content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 3 parts by mass or less, still further preferably 1 part by mass or less, and particularly preferably substantially free of the above formaldehyde component with respect to 100 parts by mass of the above conjugated diene rubber. The content of formaldehyde can be measured by HPLC, etc. after extracting the adhesive layer from the reinforcing fiber using a solvent such as toluene.

[0079] <Adhesive layer>

[0080] The adhesive layer in the reinforcing fiber of the present invention is not particularly limited as long as it contains a conjugated diene rubber. For example, it can be formed by attaching an adhesive component to the surface-modified fiber, and the adhesive component includes a solution obtained by dissolving a conjugated diene rubber in oil or an emulsion obtained by dispersing a conjugated diene rubber in water. Hereinafter, the manner of the adhesive layer will be specifically described.

[0081] 〔Conjugated diene rubber〕

[0082] The conjugated diene rubber used in the present invention contains at least monomer units derived from conjugated dienes (hereinafter, also referred to as "conjugated diene units") in the molecule. For example, it is preferably that the monomer units derived from conjugated dienes account for 50 mol% or more of all monomer units in the conjugated diene rubber.

[0083] Examples of the above-mentioned conjugated diene monomers include: butadiene, 2-methyl-1,3-butadiene (hereinafter, also referred to as "isoprene"), 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, β-farnesene (hereinafter, also referred to as "farnesene"), myrcene, and chloroprene, etc. These conjugated dienes can be used alone or in combination of two or more. From the viewpoint of reactivity during vulcanization, the conjugated diene rubber more preferably has monomer units derived from one or more selected from butadiene, isoprene, and farnesene.

[0084] The conjugated diene rubber used in the present invention may contain units of other monomers other than the above-mentioned conjugated diene monomers as long as it does not hinder adhesion. Examples of other monomers include copolymerizable ethylenically unsaturated monomers and aromatic vinyl compounds.

[0085] Examples of the above-mentioned ethylenically unsaturated monomers include: olefins such as ethylene, 1-butene, and isobutene, etc.

[0086] Examples of the above-mentioned aromatic vinyl compounds include: styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-tert-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, and divinylbenzene, etc. These aromatic vinyl compounds can be used alone or in combination of two or more.

[0087] When the conjugated diene rubber contains monomer units of other monomers other than the conjugated diene monomers, its content is preferably 30 mol% or less, more preferably 10 mol% or less, and still more preferably 5 mol% or less.

[0088] The conjugated diene rubber used in the present invention is preferably a modified conjugated diene rubber having a hydrogen-bonding functional group in a part of the conjugated diene rubber, and more preferably a modified conjugated diene rubber in which at least a part of the polymer chain contains a conjugated diene unit and has a hydrogen-bonding functional group in the side chain or at the end of the polymer chain.

[0089] When the above-mentioned modified conjugated diene rubber is used as the conjugated diene rubber, the rubber to be adhered and the surface-modified fiber as the adherends are bonded to each other by the interaction of the modified conjugated diene rubber. When the modified conjugated diene rubber and the rubber to be adhered are vulcanized to form a covalent bond, strong cohesion is generated, and thus the adhesiveness is further improved.

[0090] In addition, it is considered that the adhesiveness is improved by the formation of hydrogen bonds between the hydrogen-bonding functional groups contained in the modified conjugated diene rubber and the surface-modified layer of the surface-modified fiber.

[0091] It should be noted that in this specification, "hydrogen bond" refers to a bonding interaction formed between a hydrogen atom (donor) bonded to an atom with high electronegativity (O, N, S, etc.) and polarized to be positive and an atom with a lone pair of electrons polarized to be negative (acceptor).

[0092] In the present invention, "hydrogen-bonding functional group" refers to a functional group that can function as a donor and an acceptor in the above hydrogen bond. Specifically, examples include: hydroxyl group, epoxy group, ether group, mercapto group, carboxyl group, carbonyl group, aldehyde group, amino group, imino group, imidazole group, urethane group, amide group, urea group, isocyanate group, nitrile group, silanol group and their derivatives. As derivatives of the aldehyde group, its acetalized products can be cited. As derivatives of the carboxyl group, examples include its salts, its esterified products, its amidated products, and its acid anhydrides. As derivatives of the silanol group, its esterified products can be cited. In addition, as the carboxyl group, groups derived from monocarboxylic acids and groups derived from dicarboxylic acids can be cited. Among these, one or more selected from hydroxyl group, epoxy group, aldehyde group, acetalized products of aldehyde group, carboxyl group, salts of carboxyl group, esterified products of carboxyl group, acid anhydrides of carboxyl group, silanol group, esterified products of silanol group, amino group, imidazole group, and mercapto group are preferred.

[0093] Among these, from the viewpoints of improving adhesiveness and ease of manufacture of the conjugated diene rubber, one or more selected from hydroxyl group, carboxyl group, carbonyl group, salts of carboxyl group, esterified products of carboxyl group, and acid anhydrides of carboxyl group are preferred, more preferably one or more selected from carboxyl group, esterified products of carboxyl group, and acid anhydrides of carboxyl group, and further preferably esterified products derived from maleic anhydride and functional groups of maleic anhydride.

[0094] From the viewpoint of obtaining a reinforcing fiber with excellent rubber adhesiveness, the number of hydrogen-bonding functional groups in the modified conjugated diene rubber is preferably 1 or more per molecule on average, more preferably 3 or more, and further preferably 4 or more. In addition, from the viewpoint of controlling the viscosity of the modified conjugated diene rubber within an appropriate range and improving workability, the number of the above hydrogen-bonding functional groups is preferably 80 or less per molecule on average, more preferably 40 or less, further preferably 30 or less, still further preferably 20 or less, and even further preferably 15 or less.

[0095] Regarding the average number of hydrogen-bonding functional groups per molecule of the modified conjugated diene rubber, it is calculated based on the following formula according to the equivalent weight (g / eq) of the hydrogen-bonding functional group of the modified conjugated diene rubber and the number-average molecular weight Mn converted to styrene. The equivalent weight of the hydrogen-bonding functional group of the modified conjugated diene rubber refers to the mass of the conjugated diene bonded to an average of 1 hydrogen-bonding functional group and other monomers other than the conjugated diene as required.

[0096] Average number of hydrogen-bonding functional groups per molecule = [(number-average molecular weight (Mn)) / (molecular weight of styrene unit) × (average molecular weight of conjugated diene and other monomer units other than the conjugated diene as required)] / (equivalent weight of hydrogen-bonding functional group)

[0097] It should be noted that the calculation method of the equivalent weight of the hydrogen-bonding functional group can be appropriately selected according to the type of the hydrogen-bonding functional group.

[0098] As a method for obtaining the modified conjugated diene rubber, for example, a method of adding a modification compound to a polymer of a conjugated diene monomer (hereinafter, also referred to as "production method (1)"), a method of obtaining by oxidizing a conjugated diene polymer (hereinafter, also referred to as "production method (2)"), a method of obtaining by copolymerizing a conjugated diene monomer and a radical polymerizable compound having a hydrogen-bonding functional group (hereinafter, also referred to as "production method (3)"), and a method of adding a modification compound capable of reacting with the polymerization active terminal before adding a polymerization terminator to a polymer of an unmodified conjugated diene monomer having a polymerization active terminal (hereinafter, also referred to as "production method (4)") can be mentioned. Among them, from the viewpoint of productivity, it is preferably produced by production method (1) or (2) or (3), more preferably by production method (1) or (3), and further preferably by production method (1).

[0099] 〔Production method (1) of modified conjugated diene rubber〕

[0100] The production method (1) is a method of adding a modifying compound to a polymer of a conjugated diene monomer, that is, an unmodified conjugated diene rubber (hereinafter, also referred to as "unmodified conjugated diene rubber").

[0101] The unmodified conjugated diene rubber can be obtained by polymerizing a conjugated diene and, if necessary, other monomers other than the conjugated diene by, for example, an emulsion polymerization method or a solution polymerization method.

[0102] As the above solution polymerization method, a known method or a method based on a known method can be applied. For example, in a solvent, a Ziegler-type catalyst, a metallocene-type catalyst, an active metal or an active metal compound capable of anionic polymerization is used, and a monomer containing a given amount of conjugated diene is polymerized in the presence of a polar compound as needed.

[0103] Examples of the solvent include: aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; aromatic hydrocarbons such as benzene, toluene, and xylene, etc.

[0104] Examples of the active metal capable of anionic polymerization include: alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; lanthanide rare earth metals such as lanthanum and neodymium, etc. Among these active metals capable of anionic polymerization, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.

[0105] As the active metal compound capable of anionic polymerization, an organoalkali metal compound is preferred. Examples of the organoalkali metal compound include: organomonolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, hexyllithium, phenyllithium, and stilbenyllithium; polyfunctional organolithium compounds such as dilithium methane, dilithium naphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, potassium naphthalene, etc. Among these organoalkali metal compounds, organolithium compounds are preferred, and organomonolithium compounds are more preferred.

[0106] The amount of the above organoalkali metal compound can be appropriately set according to the melt viscosity, molecular weight, etc. of the target unmodified conjugated diene rubber and modified conjugated diene rubber, and is usually used in an amount of 0.01 to 3 parts by mass relative to 100 parts by mass of all monomers containing a conjugated diene.

[0107] The above organoalkali metal compound can also be reacted with a secondary amine such as dibutylamine, dihexylamine, or dibenzylamine to form an organoalkali metal amide for use.

[0108] Polar compounds are usually used in anionic polymerization to adjust the microstructure of conjugated diene moieties without deactivating the reaction. Examples of polar compounds include: ether compounds such as dibutyl ether, tetrahydrofuran, ethylene glycol diethyl ether, 2,2-bis(2-tetrahydrofuryl)propane; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alcoholates, phosphine compounds, etc. The polar compound is usually used in an amount of 0.01 to 1000 moles relative to the organoalkali metal compound.

[0109] The temperature of solution polymerization is usually in the range of -80 to 150 °C, preferably in the range of 0 to 100 °C, more preferably in the range of 10 to 90 °C. The polymerization method can be either batch or continuous.

[0110] The polymerization reaction can be stopped by adding a polymerization inhibitor. Examples of polymerization inhibitors include: alcohols such as methanol and isopropyl alcohol. The resulting polymerization reaction solution is poured into a poor solvent such as methanol to precipitate the polymer, or the polymerization reaction solution is washed with water, separated, and then dried, whereby the unmodified conjugated diene rubber can be separated.

[0111] As a method for producing the unmodified conjugated diene rubber, among the above methods, solution polymerization is preferably used.

[0112] As the above emulsion polymerization method, a known method or a method based on a known method can be applied. For example, a monomer containing a given amount of conjugated diene is emulsified and dispersed in the presence of an emulsifier, and emulsion polymerization is carried out using a radical polymerization initiator.

[0113] Examples of emulsifiers include long-chain fatty acid salts having 10 or more carbon atoms and citronellates. Examples of long-chain fatty acid salts include potassium salts or sodium salts of fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid.

[0114] As the dispersion solvent, water is usually used, and water-soluble organic solvents such as methanol and ethanol can be included within a range that does not hinder the stability during polymerization.

[0115] Examples of radical polymerization initiators include: persulfates such as ammonium persulfate and potassium persulfate, organic peroxides, hydrogen peroxide, etc.

[0116] To adjust the molecular weight of the obtained unmodified conjugated diene rubber, a chain transfer agent can be suitably used. Examples of chain transfer agents include: thiols such as tert-dodecyl mercaptan and n-dodecyl mercaptan; carbon tetrachloride, mercaptoacetic acid, diterpenes, terpinolene, γ-terpinene, α-methylstyrene dimer, etc.

[0117] The temperature of the emulsion polymerization can be appropriately set according to the type of free radical polymerization initiator to be used, etc., and is usually in the range of 0 to 100 °C, preferably in the range of 0 to 60 °C. The polymerization method can be either continuous polymerization or batch polymerization.

[0118] The polymerization reaction can be stopped by adding a polymerization inhibitor. Examples of the polymerization inhibitor include amine compounds such as isopropylhydroxylamine, diethylhydroxylamine, and hydroxylamine, quinone compounds such as hydroquinone and benzoquinone, and sodium nitrite.

[0119] After the polymerization reaction is stopped, an anti-aging agent can be added as needed. After the polymerization reaction is stopped, unreacted monomers are removed from the obtained latex as needed, and then salts such as sodium chloride, calcium chloride, and potassium chloride are used as a coagulant, and acids such as nitric acid and sulfuric acid are added as needed to adjust the pH of the coagulation system to a given value while coagulating the polymer, and then the dispersion solvent is separated to recover the polymer. Then, after washing with water and dehydration and drying, an unmodified conjugated diene rubber is obtained. It should be noted that during coagulation, the latex and the filler oil made into an emulsified dispersion can be mixed in advance as needed, and recovered as an oil-extended unmodified conjugated diene rubber.

[0120] (Modified compound used in Production Method (1))

[0121] The modified compound used in Production Method (1) is not particularly limited, and from the viewpoint of improving the adhesiveness of the reinforcing fiber, a modified compound having a hydrogen-bonding functional group is preferred. Examples of the hydrogen-bonding functional group include the same functional groups as described above. Among these, from the viewpoint of the strength of the hydrogen bond force, amino group, imidazolyl group, ureido group, hydroxyl group, epoxy group, mercapto group, silanol group, aldehyde group, carboxyl group and its derivatives are preferred. As derivatives of the carboxyl group, its salts, its esterified products, its amidated products, or its acid anhydrides are preferred. These modified compounds having a hydrogen-bonding functional group can be used alone or in combination of two or more.

[0122] Examples of the above-mentioned modified compounds include: unsaturated carboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itaconic acid; unsaturated carboxylic anhydrides such as maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, and itaconic anhydride; unsaturated carboxylic esters such as maleic acid esters, fumaric acid esters, citraconic acid esters, and itaconic acid esters; unsaturated carboxylic acid amides such as maleic acid amides, fumaric acid amides, citraconic acid amides, and itaconic acid amides; unsaturated carboxylic acid imides such as maleic acid imides, fumaric acid imides, citraconic acid imides, and itaconic acid imides; silane compounds such as vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, mercaptomethylmethyldiethoxysilane, mercaptoethyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 2-mercaptoethylmethoxydimethylsilane, 2-mercaptoethylethoxydimethylsilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldiethoxymethylsilane, 3-mercaptopropyldimethoxyethylsilane, 3-mercaptopropyldiethoxyethylsilane, 3-mercaptopropylmethoxydimethylsilane, 3-mercaptopropylethoxydimethylsilane, etc.

[0123] With respect to 100 parts by mass of the unmodified conjugated diene rubber, the amount of the above-mentioned modified compound is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 50 parts by mass, and still more preferably 1 to 30 parts by mass.

[0124] The reaction temperature is generally preferably in the range of 0 to 200 °C, more preferably in the range of 50 to 200 °C.

[0125] In addition, after grafting the above-mentioned modified compound onto the unmodified conjugated diene rubber and introducing a hydrogen-bonding functional group, a modified compound capable of reacting with this functional group can be further added to introduce other hydrogen-bonding functional groups into the polymer. Specifically, for example, a method in which maleic anhydride is grafted onto an unmodified conjugated diene rubber obtained by living anionic polymerization, and then a compound having a hydroxyl group such as 2-hydroxyethyl methacrylate or methanol, or a compound such as water is made to react can be cited.

[0126] With respect to 100 parts by mass of the unmodified conjugated diene rubber, the addition amount of the modified compound in the modified conjugated diene rubber is preferably 0.5 to 40 parts by mass, more preferably 1 to 30 parts by mass, and still more preferably 1.5 to 20 parts by mass. It should be noted that the amount of the modified compound added to the modified conjugated diene rubber can be calculated based on the acid value of the modified compound, and can also be determined by various analytical instruments such as infrared spectroscopy and nuclear magnetic resonance spectroscopy.

[0127] The method of adding the above-mentioned modified compound to the unmodified conjugated diene rubber is not particularly limited. For example, a method can be cited in which a liquid unmodified conjugated diene rubber and one or more modified compounds selected from unsaturated carboxylic acids, unsaturated carboxylic acid derivatives, silane compounds, etc. are added, and a radical generator is further added as needed, and heating is carried out in the presence or absence of an organic solvent. The radical initiator to be used is not particularly limited, and commonly commercially available organic peroxides, azo compounds, hydrogen peroxide, etc. can be used.

[0128] As the organic solvent used in the above method, hydrocarbons solvents and halogenated hydrocarbons solvents are generally cited. Among these organic solvents, hydrocarbons solvents such as n-butane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and xylene are preferred.

[0129] In addition, when reacting to add a modified compound by the above method, an anti-aging agent can be added in view of suppressing side reactions, etc. As the anti-aging agent, commonly commercially available agents can be used, such as butylated hydroxytoluene (BHT), N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (NOCRAC 6C), etc.

[0130] Relative to 100 parts by mass of the unmodified conjugated diene rubber, the addition amount of the anti-aging agent is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass. When the addition amount of the anti-aging agent is within the above range, side reactions can be suppressed, and the modified conjugated diene rubber can be obtained in good yield.

[0131] [Physical properties of conjugated diene rubber]

[0132] The weight-average molecular weight (Mw) of the conjugated diene rubber is not particularly limited. From the viewpoint of improving adhesiveness, it is preferably more than 2000, more preferably 5000 or more, further preferably 10000 or more, still further preferably 15000 or more, even further preferably 20000 or more, and particularly preferably 25000 or more. From the viewpoint of operability, it is preferably 120000 or less, more preferably 100000 or less, further preferably 75000 or less, still further preferably 55000 or less.

[0133] The number-average molecular weight (Mn) of the conjugated diene rubber is not particularly limited. From the viewpoint of improving adhesiveness, it is preferably 2000 or more, more preferably 5000 or more, further preferably 10000 or more, still further preferably 15000 or more, even further preferably 20000 or more, and particularly preferably 25000 or more. Moreover, from the viewpoint of operability, it is preferably 120000 or less, more preferably 75000 or less, further preferably 50000 or less, still further preferably 47000 or less.

[0134] The Mw and Mn of the conjugated diene rubber are the polystyrene-converted weight-average molecular weight and number-average molecular weight determined by gel permeation chromatography (GPC). Specifically, they can be determined by the method described in the examples.

[0135] The molecular weight distribution (Mw / Mn) of the conjugated diene rubber is preferably from 1.00 to 5.00, more preferably from 1.00 to 3.00, further preferably from 1.00 to 2.00, still further preferably from 1.00 to 1.50, and particularly preferably from 1.00 to 1.30. When Mw / Mn is within the above range, the viscosity deviation of the conjugated diene rubber is small and the operation is easy. The molecular weight distribution (Mw / Mn) refers to the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) converted to standard polystyrene determined by GPC measurement.

[0136] In addition, from the viewpoint of the adhesion between the conjugated diene rubber and the fiber, the conjugated diene rubber is preferably liquid.

[0137] In this specification, "liquid" means that the melt viscosity of the conjugated diene rubber measured at 38 °C is 4000 Pa·s or less. From the viewpoint of improving the adhesion, the melt viscosity is preferably 0.1 Pa·s or more, more preferably 1 Pa·s or more, further preferably 10 Pa·s or more, still further preferably 30 Pa·s or more, and even further preferably 50 Pa·s or more. From the viewpoint of operability, it is preferably 2500 Pa·s or less, more preferably 2100 Pa·s or less. When the above melt viscosity is within the above range, the adhesion of the conjugated diene rubber can be improved and the operability can be made good.

[0138] It should be noted that the melt viscosity of the conjugated diene rubber refers to the viscosity measured at 38 °C using a Brookfield viscometer (type B viscometer).

[0139] The glass transition temperature (Tg) of the conjugated diene rubber can vary depending on the vinyl content of the conjugated diene unit, the type of conjugated diene, the content of units from other monomers other than the conjugated diene, etc., and is preferably from -100 to 10 °C, more preferably from -100 to 0 °C, and further preferably from -100 to -10 °C. When Tg is within the above range, high viscosity can be suppressed and the operation becomes easy.

[0140] The vinyl content of the conjugated diene rubber is preferably 80 mol% or less, more preferably 50 mol% or less, and further preferably 30 mol% or less. When the vinyl content is within the above range, the adhesion is improved.

[0141] In this specification, the "vinyl content" means the total mole % of conjugated diene units bonded together in a 1,2-bonded or 3,4-bonded manner (conjugated diene units bonded together in a manner other than 1,4-bonded) in a total of 100 mole % of the conjugated diene units contained in the modified liquid diene rubber. The vinyl content can be determined using 1 1H-NMR, and calculated based on the integral value ratio of the signals from the conjugated diene units bonded together in a 1,2-bonded or 3,4-bonded manner and the signals from the conjugated diene units bonded together in a 1,4-bonded manner.

[0142] 〔Oil〕

[0143] The adhesive layer in the present invention can be formed, for example, by applying an adhesive component containing a solution in which a conjugated diene rubber is dissolved in an oil to the surface-modified fiber.

[0144] In the present invention, for example, a so-called non-volatile oil having a vapor pressure of 10 Pa or less at 20°C is preferably used. By using such an oil, after the adhesive component is applied to the surface of the fiber, the oil does not volatilize for a long time. Therefore, it is not easy to form coating spots of the adhesive component, and the adhesiveness is improved. In addition, contamination of the manufacturing equipment during manufacturing can be suppressed. From these viewpoints, as the oil, the vapor pressure of the oil at 20°C is preferably 8 Pa or less, more preferably 5 Pa or less, further preferably 1 Pa or less, still further preferably 0.1 Pa or less, and even further preferably 0.01 Pa or less.

[0145] It should be noted that in the present invention, the vapor pressure of the oil at 20°C is the value calculated by applying the Antoine equation to the measured value obtained by the gas flow method to obtain the best curve.

[0146] In the present invention, when using an oil, compared with the prior art using RFL, a heating process for resinification is not required. In addition, compared with the prior art using a solvent such as water as a diluent, an evaporation process for removing water or the like is not required. Thus, manufacturing can be carried out efficiently with simple equipment compared to the past, and it is also environmentally friendly.

[0147] As the oil having a vapor pressure of 10 Pa or less at 20°C that can be used in the present invention, any oil that is compatible with the conjugated diene rubber can be used, and there is no particular limitation. For example, natural oils and synthetic oils can be mentioned. As natural oils, for example, mineral oils and vegetable oils can be mentioned.

[0148] Examples of the mineral oil include paraffinic mineral oils, aromatic mineral oils, naphthenic mineral oils obtained by common purification methods such as solvent purification and hydro-purification, waxes (GTL waxes) produced by the Fischer-Tropsch process, and mineral oils produced by isomerizing waxes.

[0149] Examples of commercially available paraffinic mineral oils include the "Diana ProcessOil" series manufactured by Idemitsu Kosan Co., Ltd. and the "Super Oil" series manufactured by JX Nippon Oil & Energy Corporation.

[0150] Examples of vegetable oils include linseed oil, camellia oil, macadamia nut oil, corn oil, mink oil, olive oil, avocado oil, camellia sasanqua oil, castor oil, safflower oil, jojoba oil, sunflower oil, almond oil, rapeseed oil, sesame oil, soybean oil, peanut oil, cottonseed oil, coconut oil, palm kernel oil, rice bran oil, and the like.

[0151] Examples of synthetic oils include hydrocarbon synthetic oils, ester synthetic oils, ether synthetic oils, and the like. Examples of hydrocarbon synthetic oils include α-olefin oligomers such as polybutene, polyisobutene, 1-octene oligomer, 1-decene oligomer, and ethylene-propylene copolymer or their hydrides, alkylbenzenes, and alkylnaphthalenes. Examples of ester synthetic oils include triglyceride fatty acid esters, diglyceride fatty acid esters, monoglyceride fatty acid esters, monohydric alcohol fatty acid esters, and polyhydric alcohol fatty acid esters. Examples of ether synthetic oils include polyalkylene glycol and polyphenyl ether. Examples of commercially available synthetic oils include the "LINEALENE" series manufactured by Idemitsu Kosan Co., Ltd., "FGC32", "FGC46", "FGC68" manufactured by ANDEROL Corporation.

[0152] The oil may be one selected from the above natural oils and synthetic oils, or two or more natural oils, two or more synthetic oils, or one or more of each of natural oils and synthetic oils may be mixed.

[0153] In the present invention, from the viewpoints of making the viscosity of the adhesive component within an appropriate range and improving the workability, a mineral oil is preferred, and at least one selected from paraffinic mineral oils and naphthenic mineral oils is more preferred.

[0154] From the viewpoint of safety, the flash point of the oil used in the present invention is preferably 70°C or higher. From this viewpoint, the flash point of the oil is preferably 100°C or higher, more preferably 130°C or higher, and still more preferably 140°C or higher. The upper limit value of the flash point of the oil is not particularly limited, and is preferably 320°C or lower.

[0155] From the viewpoint of improving the adhesive force to rubber, the content of the conjugated diene rubber in the above-mentioned adhesive component is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, and even more preferably 40% by mass or less. When the content of the conjugated diene rubber in the adhesive component is within the above range, sufficient adhesive force can be obtained, and the viscosity of the adhesive component can be prevented from extremely increasing.

[0156] In addition, the content of the oil in the above-mentioned adhesive component is preferably 20% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and even more preferably 60% by mass or more, and preferably 99% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less.

[0157] The mass ratio of the conjugated diene rubber to the oil [conjugated diene rubber (R)∶oil (O)] in the above-mentioned adhesive component is preferably 0.1∶9.9 to 8∶2, more preferably 0.5∶9.5 to 6∶4, still more preferably 1∶9 to 5∶5, and even more preferably 1∶9 to 4∶6. Generally, it is known that oil deteriorates the adhesiveness of rubber, but when the conjugated diene rubber and the oil are used in combination at the above specific mass ratio, the viscosity can be reduced while maintaining the adhesiveness, the workability of the adhesive component is improved, and the adhesion workability to the surface-modified fiber is also improved.

[0158] It should be noted that in the present invention, an adhesive layer can be formed by attaching the adhesive component to the surface-modified fiber, and the adhesive component includes an emulsion in which the above-mentioned conjugated diene rubber is dispersed in water.

[0159] When the conjugated diene rubber is dispersed in water to prepare an oil-in-water emulsion for use, it is preferable to pre-prepare an emulsion (latex) of the adhesive component by a mechanical method or a chemical method and use it at a given concentration by dilution or the like.

[0160] As the mechanical method, there can be mentioned: methods using a homogenizer, a high-speed stirrer, a dispersion stirrer, a colloid mill, a pipe mixer, a high-pressure homogenizer, an ultrasonic emulsifier, etc., and these can be used alone or in combination.

[0161] As the chemical method, there can be mentioned: various methods such as the reverse phase emulsification method, the D phase emulsification method, the HLB temperature emulsification method, the gel emulsification method, and the liquid crystal emulsification method. From the viewpoint of easily obtaining an emulsion with a small particle size, the reverse phase emulsification method is preferred. In addition, in order to obtain an emulsion with a small particle size, it is sometimes preferable to carry out the operation while heating at an appropriate temperature (for example, 30 to 80°C) in order to reduce the viscosity of the modified conjugated diene rubber.

[0162] From the viewpoint of improving the adhesion to rubber, when the adhesive component is made into an emulsion, the content of conjugated diene rubber in the adhesive component is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 2% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and even more preferably 20% by mass or less. When the content of conjugated diene rubber in the adhesive component is within the above range, sufficient adhesion can be obtained and the viscosity of the adhesive component can be prevented from extremely increasing.

[0163] The above conjugated diene rubber can be used alone or in combination of two or more. In addition, the above oil can also be used alone or in combination of two or more.

[0164] In addition, the adhesive component in the present invention may contain components other than conjugated diene rubber and oil within the range that does not hinder the adhesion to rubber.

[0165] Examples of the above other components include other polymers (such as unmodified conjugated diene rubber), acids, bases, antioxidants, curing agents, dispersants, pigments, dyes, adhesion aids, carbon black, etc.

[0166] When the above adhesive component contains other components, the content is preferably 10000 parts by mass or less, more preferably 1000 parts by mass or less, still more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, further more preferably 25 parts by mass or less, and even further more preferably 10 parts by mass or less, based on 100 parts by mass of the conjugated diene rubber.

[0167] [Method for manufacturing reinforcing fiber]

[0168] The method for manufacturing the reinforcing fiber of the present invention is not particularly limited, and it can be manufactured by a method including the following steps: a step of attaching the above conjugated diene rubber to the fiber in a state of being mixed with the above oil, and a step of attaching the above conjugated diene rubber to the fiber in a state of being dispersed in water.

[0169] In the present invention, from the viewpoint of efficiently attaching the conjugated diene rubber to the surface-modified fiber and from the viewpoint of suppressing the contamination of manufacturing equipment, a method including the step of attaching the above conjugated diene rubber to the fiber in a state of being mixed with the above oil is preferred.

[0170] As a more specific method for manufacturing the reinforcing fiber of the present invention, the following method can be cited.

[0171] [Method (I)]

[0172] As the method (I), any method can be used as long as it forms an adhesive layer containing the above-mentioned adhesive component on the surface of the surface-modified fiber, and there is no particular limitation. From the viewpoint of improving the adhesion to rubber, a method including the following step I-1 is preferred.

[0173] Step I-1: A step of attaching the above-mentioned adhesive component to the surface of the surface-modified fiber

[0174] In step I-1, the method of attaching the above-mentioned adhesive component to the surface-modified fiber is not particularly limited. For example, a method of directly attaching the above-mentioned adhesive component, a method of adding a solvent to the above-mentioned adhesive component as needed and attaching it, etc. can be cited.

[0175] As the method of attaching the above-mentioned adhesive component, it is preferably carried out by one or more selected from dipping, roll coater, oiling roll, oiling guide, nozzle (spray) coating, and brush coating, etc.

[0176] From the viewpoint of improving the adhesion between the reinforcing fiber and rubber, the amount of the above-mentioned adhesive component attached is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, further preferably 1 part by mass or more, relative to 100 parts by mass of the fiber used as the raw material. Moreover, from the viewpoint of the balance between manufacturing cost and effect, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 3 parts by mass or less.

[0177] In the present invention, when a conjugated diene rubber is used in combination with a specific oil, after the adhesive component is attached to the surface-modified fiber, it is fused at room temperature of about 20 °C for about 3 days to 10 days, whereby the reinforcing fiber of the present invention can be obtained. However, depending on the situation, the following step I-2 can also be carried out.

[0178] Step I-2: A step of heat-treating the surface-modified fiber to which the above-mentioned adhesive component obtained in step I-1 is attached

[0179] The heat treatment in step I-2 is preferably carried out at a treatment temperature of 100 to 200 °C for a treatment time of 0.1 second to 2 minutes. Since the conjugated diene rubber contained in the above-mentioned adhesive component has a reactive double bond, the heat treatment in the presence of oxygen is preferably 200 °C or less, more preferably 175 °C or less. When the temperature of the heat treatment is within the above range, the adhesive force can be improved without reducing the amount of reactive double bonds in the conjugated diene rubber, and furthermore, the deterioration of the fiber can be suppressed, and the quality such as coloring can be made good.

[0180] The above-mentioned reinforcing fiber may contain other components other than the above-mentioned surface-modified fiber and the above-mentioned adhesive component. As other components, crosslinking agents, acids, bases, inorganic salts, organic salts, pigments, dyes, antioxidants, polymerization initiators, plasticizers, etc. can be cited.

[0181] From the viewpoints of improving the adhesion to rubber and enhancing strength, the total content of the hydrophilic fiber and the adhesive component in the above-mentioned reinforcing fiber is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[0182] <Physical properties of the reinforcing fiber>

[0183] The above-mentioned reinforcing fiber is preferably a multifilament having a single filament fineness of 0.1 dtex or more and 30 dtex or less. The single filament fineness may be less than 0.1 dtex, and from the viewpoint of the ease of industrial production, it is preferably 0.1 dtex or more. In addition, when the single filament fineness is 30 dtex or less, the surface area of the fiber increases when the reinforcing fiber is formed, so the adhesion to rubber is improved. From this viewpoint, the reinforcing fiber of the present invention is preferably a multifilament having a single filament fineness of more preferably 0.3 dtex or more, still more preferably 0.5 dtex or more, even more preferably 1 dtex or more, and further preferably 20 dtex or less, still more preferably 15 dtex or less, and even more preferably 10 dtex or less.

[0184] The rubber adhesion of the reinforcing fiber of the present invention is preferably 30 N / 25.4 mm or more, more preferably 50 N / 25.4 mm or more, still more preferably 70 N / 25.4 mm or more, even more preferably 80 N / 25.4 mm or more, and usually 200 N / 25.4 mm or less. When the rubber adhesion of the reinforcing fiber is at the above lower limit value or more, a fabric, a knitted fabric, and a molded article having excellent reinforcing strength can be obtained.

[0185] In addition, the rubber adhesion of the reinforcing fiber of the present invention is preferably 30 N / 3 strands or more, more preferably 40 N / 3 strands or more, still more preferably 50 N / 3 strands or more, even more preferably 60 N / 3 strands or more, and usually 200 N / 3 strands or less. When the rubber adhesion of the reinforcing fiber is at the above lower limit value or more, a fabric, a knitted fabric, and a molded article having excellent reinforcing strength can be obtained.

[0186] It should be noted that the rubber adhesion of the reinforcing fiber can be measured by the method described in the examples.

[0187] The reinforcing fiber of the present invention can be used in any shape, preferably in the form of a fiber cord, a fabric, a knitted fabric, etc. that contain the reinforcing fiber in at least a part, and more preferably as a fabric or a knitted fabric that contain the reinforcing fiber in at least a part. For example, it can be used as a knitted fabric adhered to rubber as described later. In addition, it can also be used in the form of a reinforcing fiber embedded in a resin, an adhesive, etc.

[0188] [Molded article]

[0189] The molded article of the present invention is not particularly limited as long as the above reinforcing fibers are used. Among them, from the viewpoint of the excellent adhesiveness of the above reinforcing fibers to rubber, a molded article having the above reinforcing fibers and a rubber layer (hereinafter, also referred to as "rubber molded article") is particularly preferred. From the viewpoint of maintaining the form of rubber, the reinforcing fibers used in the above rubber molded article are preferably used in the form of a fabric or a knitted fabric containing the reinforcing fibers at least in part, and more preferably used in the form of a laminate in which a reinforcing layer and a rubber layer are laminated, the reinforcing layer being formed of a fabric or a knitted fabric containing the reinforcing fibers at least in part.

[0190] As a preferred embodiment of the molded article of the present invention, it sequentially has a fiber, a surface modification layer, an adhesive layer, and a rubber layer. The adhesive force between the above adhesive layer and the above rubber layer is 70 N or more, more preferably 80 N or more, per 25.4 mm width on average. When the adhesive force is 70 N or more, it can be suitably used for various uses described later.

[0191] The above rubber molded article can be used, for example, as a member of a tire such as an automotive tire, a conveyor belt, a timing belt, a hose, and a rubber product such as a vibration-proof rubber. Among them, it is more preferably used as a tire, a belt, or a hose.

[0192] As the above automotive tire, it can be used for various members made of a composite material of reinforcing fibers and a rubber component, such as a belt, a carcass ply, a flap, and a rim strip.

[0193] As the above hose, it can be used for the purpose of transporting various fluids in various applications. For example, it is suitable for a fluid transport hose for automotive use, and is particularly preferably used for a liquid fuel hose for automotive use, a brake oil hose for automotive use, and a refrigerant hose, and more preferably used for a brake oil hose for automotive use.

[0194] The above rubber molded article is preferably molded using the above reinforcing fibers and a rubber composition in which compounding agents commonly used in the rubber field are compounded with a rubber component.

[0195] As the rubber component, there is no particular limitation, and examples thereof include: NR (natural rubber), IR (polyisoprene rubber), BR (polybutadiene rubber), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), EPM (ethylene-propylene copolymer rubber), EPDM (ethylene-propylene-non-conjugated diene copolymer rubber), IIR (butyl rubber), halogenated butyl rubber, CR (chloroprene rubber), etc. Among them, NR, IR, BR, SBR, EPDM, and CR are preferably used, and EPDM is more preferably used. These rubber components can be used alone or in combination of two or more. In tire applications, rubbers commonly used in the tire industry can be used. Among them, it is preferable to use natural rubber alone or in combination with SBR. When natural rubber and SBR are combined, from the viewpoint of suppressing the reduction in physical properties caused by reversion of rubber vulcanization, the mass ratio of natural rubber to SBR (natural rubber / SBR) is preferably in the range of 50 / 50 to 90 / 10.

[0196] Examples of the above natural rubber include: TSR (Technically Specified Rubber) such as SMR (TSR produced in Malaysia), SIR (TSR produced in Indonesia), STR (TSR produced in Thailand), etc., RSS (Ribbed Smoked Sheet) and other natural rubbers commonly used in the tire industry, high-purity natural rubber, epoxidized natural rubber, hydroxylated natural rubber, hydrogenated natural rubber, grafted natural rubber, etc.

[0197] As the above SBR, ordinary SBR used in tire applications can be used. Specifically, SBR with a styrene content of 0.1 to 70% by mass is preferred, more preferably 5 to 50% by mass, and further preferably 15 to 35% by mass. In addition, SBR with a vinyl content of 0.1 to 60% by mass is preferred, more preferably 0.1 to 55% by mass.

[0198] The weight-average molecular weight (Mw) of the above SBR is preferably 100,000 to 2,500,000, more preferably 150,000 to 2,000,000, and further preferably 200,000 to 1,500,000. In the above range, processability and mechanical strength can be taken into account. It should be noted that the weight-average molecular weight of SBR refers to the weight-average molecular weight converted to polystyrene determined by gel permeation chromatography (GPC).

[0199] As the above SBR, as long as it is within the range that does not impair the effects of the present invention, modified SBR into which a functional group has been introduced can be used. Examples of the functional group include: amino group, alkoxysilyl group, hydroxyl group, epoxy group, carboxyl group, etc.

[0200] In addition to the above rubber components, the above rubber composition may further contain a filler. Examples of the filler include: inorganic fillers such as carbon black, silica, clay, mica, calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, titanium oxide, glass fiber, fibrous filler, and glass hollow sphere; and organic fillers such as resin particles, wood powder, and cork powder. By including such a filler in the rubber composition, physical properties such as mechanical strength, heat resistance, or weather resistance can be improved, the hardness can be adjusted, and the rubber can be incremented.

[0201] From the viewpoint of improving physical properties such as enhancing mechanical strength, among the above fillers, carbon black and silica are preferred.

[0202] Examples of the above carbon black include: furnace black, channel black, thermal black, acetylene black, and Ketjen black. From the viewpoint of improving the crosslinking speed and mechanical strength, among these carbon blacks, furnace black is preferred.

[0203] The average particle diameter of the above carbon black is preferably 5 to 100 nm, more preferably 5 to 80 nm, and further preferably 5 to 70 nm. It should be noted that the average particle diameter of the above carbon black can be obtained by measuring the diameter of the particles using a transmission electron microscope and calculating their average value.

[0204] Examples of the above silica include: wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. Among these silicas, wet silica is preferred.

[0205] The average particle diameter of the above silica is preferably 0.5 to 200 nm, more preferably 5 to 150 nm, and further preferably 10 to 100 nm.

[0206] It should be noted that the average particle diameter of the above silica can be obtained by measuring the diameter of the particles using a transmission electron microscope and calculating their average value.

[0207] In the above rubber composition, relative to 100 parts by mass of the above rubber component, the content of the above filler is preferably 20 to 150 parts by mass, more preferably 25 to 130 parts by mass, and further preferably 25 to 110 parts by mass.

[0208] In addition, as the above filler, when using a filler other than silica and carbon black, relative to 100 parts by mass of the above rubber component, its content is preferably 20 to 120 parts by mass, more preferably 20 to 90 parts by mass, and further preferably 20 to 80 parts by mass.

[0209] These fillers can be used alone or in combination of two or more.

[0210] In order to crosslink the above rubber components, the above rubber composition may further contain a crosslinking agent. Examples of such crosslinking agents include sulfur, sulfur compounds, oxygen, organic peroxides, phenolic resins, amino resins, quinones and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides and organometallic halides, and silane compounds. These crosslinking agents can be used alone, or two or more of them can be used in combination. From the viewpoint of the mechanical properties of the crosslinked product, relative to 100 parts by mass of the above rubber components, the above crosslinking agent usually contains 0.1 to 10 parts by mass, preferably contains 0.5 to 10 parts by mass, and more preferably contains 0.8 to 5 parts by mass.

[0211] For the above rubber composition, for example, as a crosslinking agent for crosslinking (vulcanizing) the above rubber components, in the case of containing sulfur, sulfur compounds, etc., a vulcanization accelerator can be further contained. Examples of such vulcanization accelerators include guanidine compounds, sulfenamide compounds, thiazole compounds, thiuram compounds, thiourea compounds, dithiocarbamic acid compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, imidazoline compounds, and xanthate compounds. These vulcanization accelerators can be used alone, or two or more of them can be used in combination. Relative to 100 parts by mass of the above rubber components, the above vulcanization accelerator usually contains 0.1 to 15 parts by mass, preferably contains 0.1 to 10 parts by mass.

[0212] For the above rubber composition, for example, as a crosslinking agent for crosslinking (vulcanizing) the above rubber components, in the case of containing sulfur, sulfur compounds, etc., a vulcanization aid can be further contained. Examples of such vulcanization aids include fatty acids such as stearic acid, metal oxides such as zinc white, and fatty acid metal salts such as zinc stearate. These vulcanization aids can be used alone, or two or more of them can be used in combination. Relative to 100 parts by mass of the above rubber components, the above vulcanization aid usually contains 0.1 to 15 parts by mass, preferably contains 1 to 10 parts by mass.

[0213] When the above rubber composition contains silica as a filler, it is preferably further contained with a silane coupling agent. Examples of such silane coupling agents include sulfide compounds, mercapto compounds, vinyl compounds, amino compounds, glycidyloxy compounds, nitro compounds, chlorine compounds, etc.

[0214] These silane coupling agents can be used alone, or two or more of them can be used in combination. Relative to 100 parts by mass of silica, the above silane coupling agent preferably contains 0.1 to 30 parts by mass, more preferably contains 0.5 to 20 parts by mass, and further preferably contains 1 to 15 parts by mass. When the content of the silane coupling agent is within the above range, the dispersibility, coupling effect, and reinforcement are improved.

[0215] Within the range that does not hinder the effects of the present invention, the above rubber composition may contain, as softening agents, silicone oil, aromatic oil, TDAE (Treated Distilled Aromatic Extracts), MES (Mild Extracted Solvates), RAE (Residual Aromatic Extracts), paraffin oil, naphthenic oil and other processing oils, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, C9 resins, rosin resins, benzofuran-indene resins, phenolic resins and other resin components, as required, for the improvement of processability, fluidity, etc. When the above rubber composition contains the above processing oil as a softening agent, its content is preferably less than 50 parts by mass relative to 100 parts by mass of the above rubber component.

[0216] Within the range that does not hinder the effects of the present invention, the above rubber composition may contain, as required, additives such as anti-aging agents, waxes, antioxidants, lubricants, light stabilizers, anti-scorching agents, processing aids, pigments, colorants such as dyes, flame retardants, antistatic agents, matting agents, anti-blocking agents, ultraviolet absorbers, mold release agents, foaming agents, antibacterial agents, mildew-proof agents, fragrances, etc., to improve weather resistance, heat resistance, oxidation resistance, etc. Examples of antioxidants include hindered phenol compounds, phosphorus compounds, lactone compounds, hydroxy compounds, etc. Examples of anti-aging agents include amine-ketone compounds, imidazole compounds, amine compounds, phenol compounds, sulfur compounds, phosphorus compounds, etc. These additives can be used alone or in combination of two or more.

[0217] As a method for manufacturing the above rubber molded body, for example, a molded body in which the surface-modified fiber and the rubber component are bonded via the above bonding component can be obtained by embedding the above reinforcing fiber in the unvulcanized above rubber composition and vulcanizing the rubber composition.

[0218] As the above brake hose for automobiles, for example, a brake hose having an inner rubber layer and an outer rubber layer and having one or two reinforcing layers formed of the above reinforcing fiber between the inner rubber layer and the outer rubber layer can be cited.

[0219] As the rubber components constituting the inner rubber layer and the outer rubber layer, the above components can be cited. Among them, as the rubber components constituting the inner rubber layer, EPDM, SBR, etc. can be cited, and as the rubber components constituting the outer rubber layer, EPDM, CR, etc. can be cited. The above reinforcing layer can be formed by braiding the reinforcing fiber.

[0220] As a manufacturing method of the above brake oil pipe, a reinforcing layer (first reinforcing layer) formed by braiding the above reinforcing fibers can be formed on the outer surface of the inner rubber layer. In the case of forming two reinforcing layers, an intermediate rubber layer can be further formed on the outer surface of the first reinforcing layer, and a reinforcing layer (second reinforcing layer) formed by braiding the above reinforcing fibers can be formed on the outer surface of the intermediate rubber layer. Therefore, it can be manufactured by forming an outer rubber layer on the outer surface of the reinforcing layer (first reinforcing layer or second reinforcing layer) and vulcanizing.

[0221] The vulcanization temperature can be appropriately selected according to the types of constituent materials of each layer of the brake oil pipe, etc. From the viewpoints of suppressing the deterioration of rubber and reinforcing fibers and improving the adhesion between rubber and reinforcing fibers, it is preferably 200 °C or lower.

[0222] Examples

[0223] Hereinafter, the present invention will be described more specifically by way of examples, etc., but the present invention is not limited by any of the above examples, etc.

[0224] <Manufacture of modified conjugated diene rubber>

[0225] ・Manufacture of modified conjugated diene rubber having monomer units represented by the following formula (1a)

[0226] [Chemical formula 1]

[0227]

[0228] Production Example 1: Production of modified conjugated diene rubber (A-1)

[0229] A 5 L autoclave was fully dried and purged with nitrogen, 756 g of hexane and 122.3 g of n-butyllithium (17 mass% hexane solution) were added. After the temperature was raised to 50 °C, while controlling the polymerization temperature at 50 °C under stirring conditions, 1344 g of butadiene was gradually added and polymerized for 1 hour. Then, methanol was added to stop the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After the stirring was stopped and it was confirmed that separation into a polymer solution phase and an aqueous phase occurred, the water was separated. The washed polymer solution was vacuum dried at 70 °C for 24 hours, whereby unmodified liquid polybutadiene (A'-1) was obtained.

[0230] Next, 600 g of the obtained unmodified liquid polybutadiene (A'-1) was added to an autoclave with a capacity of 1 L that had been purged with nitrogen. 30 g of maleic anhydride and 0.6 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name "NOCRAC 6C", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added, and the reaction was carried out at 170 °C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene (A-1).

[0231] Production Example 2: Production of modified conjugated diene rubber (A-2)

[0232] A 5 L autoclave that had been thoroughly dried was purged with nitrogen. 1260 g of hexane and 36.3 g of n-butyllithium (17 mass% hexane solution) were added. After the temperature was raised to 50 °C, while controlling the polymerization temperature at 50 °C under stirring conditions, 1260 g of butadiene was gradually added, and polymerization was carried out for 1 hour. Then, methanol was added to stop the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution and stirred to wash the polymer solution with water. After stirring was stopped and it was confirmed that separation into a polymer solution phase and an aqueous phase occurred, the water was separated. The polymer solution after washing was vacuum dried at 70 °C for 24 hours to obtain unmodified liquid polybutadiene (A'-2).

[0233] Next, 500 g of the obtained unmodified liquid polybutadiene (A'-2) was added to an autoclave with a capacity of 1 L that had been purged with nitrogen. 25 g of maleic anhydride and 0.5 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name "NOCRAC 6C", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added, and the reaction was carried out at 170 °C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene (A-2).

[0234] Production Example 3: Production of modified conjugated diene rubber (A-3)

[0235] A 5 L autoclave that had been thoroughly dried was purged with nitrogen. 1140 g of hexane and 20.9 g of n-butyllithium (17 mass% hexane solution) were added. After the temperature was raised to 50 °C, while controlling the polymerization temperature at 50 °C under stirring conditions, 1390 g of butadiene was gradually added, and polymerization was carried out for 1 hour. Then, methanol was added to stop the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution and stirred to wash the polymer solution with water. After stirring was stopped and it was confirmed that separation into a polymer solution phase and an aqueous phase occurred, the water was separated. The polymer solution after washing was vacuum dried at 70 °C for 24 hours to obtain unmodified liquid polybutadiene (A'-3).

[0236] Next, 500 g of the obtained unmodified liquid polybutadiene (A'-3) was added to an autoclave with a capacity of 1 L that had been purged with nitrogen. 25 g of maleic anhydride and 0.5 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name "NOCRAC 6C", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added, and the reaction was carried out at 170 °C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene (A-3).

[0237] Production Example 4: Production of Modified Conjugated Diene Rubber (A-4)

[0238] To 525 g of the obtained maleic anhydride-modified liquid polybutadiene (A-3), 9.0 g of methanol was added, and the reaction was carried out at 80 °C for 6 hours to obtain maleic acid monomethyl ester-modified liquid polybutadiene (A-4).

[0239] Production Example 5: Production of Modified Conjugated Diene Rubber (A-5)

[0240] To 525 g of the obtained maleic anhydride-modified liquid polybutadiene (A-2), 8.5 g of methanol was added, and the reaction was carried out at 80 °C for 6 hours to obtain maleic acid monomethyl ester-modified liquid polybutadiene (A-5).

[0241] It should be noted that the measurement methods and calculation methods for the physical properties of the modified conjugated diene rubbers are as described below, and the results are shown in Table 1.

[0242] <Method for Measuring Weight-Average Molecular Weight, Number-Average Molecular Weight, and Molecular Weight Distribution>

[0243] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the modified conjugated diene rubber were determined as conversion values in terms of standard polystyrene using GPC (gel permeation chromatography). The measuring apparatus and conditions are as described below.

[0244] · Apparatus: GPC apparatus "GPC8020" manufactured by Tosoh Corporation

[0245] · Separation column: "TSKgel G4000HXL" manufactured by Tosoh Corporation

[0246] · Detector: "RI-8020" manufactured by Tosoh Corporation

[0247] · Eluent: Tetrahydrofuran

[0248] · Eluent flow rate: 1.0 ml / min

[0249] · Sample concentration: 5 mg / 10 ml

[0250] · Column temperature: 40 °C

[0251] <Method for measuring melt viscosity>

[0252] The melt viscosity of the modified conjugated diene rubber at 38 °C was measured using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

[0253] <Method for measuring glass transition temperature>

[0254] 10 mg of the modified conjugated diene rubber was collected in an aluminum pan, and a thermogram was measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 10 °C / min. The peak value of DDSC was taken as the glass transition temperature.

[0255] <Method for measuring vinyl content>

[0256] Using H-NMR (500 MHz) manufactured by JEOL Ltd., the vinyl content of the modified conjugated diene rubber was measured at a concentration of sample / deuterated chloroform = 50 mg / 1 mL and a cumulative number of 1024 times. The vinyl content was calculated based on the area ratio of the double bond peaks from the vinylated diene compound and the double bond peaks from the non-vinylated diene compound in the obtained spectrum. 1

[0257] <Average number of hydrogen-bonding functional groups per molecule>

[0258] The average number of hydrogen-bonding functional groups per molecule of the modified conjugated diene rubber was calculated using the following formula based on the equivalent weight (g / eq) of the hydrogen-bonding functional group of the modified conjugated diene rubber and the number-average molecular weight Mn in terms of styrene.

[0259] Average number of hydrogen-bonding functional groups per molecule = [(number-average molecular weight (Mn)) / (molecular weight of styrene unit) × (average molecular weight of conjugated diene and other monomer units included as needed in addition to conjugated diene)] / (equivalent weight of hydrogen-bonding functional group)

[0260] It should be noted that the calculation method of the equivalent weight of the hydrogen-bonding functional group can be appropriately selected according to the type of the hydrogen-bonding functional group.

[0261] For the calculation of the average number of hydrogen-bonding functional groups per molecule of maleic anhydride-modified conjugated diene rubber and maleic acid monomethyl ester-modified conjugated diene rubber, the acid value of maleic anhydride-modified conjugated diene rubber and maleic acid monomethyl ester-modified conjugated diene rubber was determined, and the equivalent weight (g / eq) of the hydrogen-bonding functional group was calculated based on this acid value.

[0262] ​The sample after the modification reaction was washed 4 times with methanol (5 mL relative to 1 g of the sample) to remove impurities such as antioxidants, and then the sample was dried under reduced pressure at 80 °C for 12 hours. After dissolving 3 g of the sample after the modification reaction in 180 mL of toluene and 20 mL of ethanol, it was subjected to neutralization titration with an ethanol solution of 0.1 N potassium hydroxide, and the acid value was determined using the following formula.

[0263] Acid value (mgKOH / g) = (A - B) × F × 5.611 / S

[0264] A: The volume of the ethanol solution of 0.1 N potassium hydroxide added for neutralization (mL)

[0265] B: The volume of the ethanol solution of 0.1 N potassium hydroxide added for the blank sample without the sample (mL)

[0266] F: The titration factor of the ethanol solution of 0.1 N potassium hydroxide

[0267] S: The mass of the weighed sample (g)

[0268] Based on the acid value, the mass of the hydrogen-bonding functional groups contained in 1 g of maleic anhydride-modified conjugated diene rubber and maleic acid monomethyl ester-modified conjugated diene rubber was calculated using the following formula, and further, the mass other than the functional groups (polymer main chain mass) contained in 1 g of maleic anhydride-modified conjugated diene rubber and maleic acid monomethyl ester-modified conjugated diene rubber was calculated. Then, the equivalent weight (g / eq) of the hydrogen-bonding functional groups was calculated using the following formula.

[0269] [Mass of hydrogen-bonding functional groups per 1 g] = [Acid value] / [56.11] × [Molecular weight of hydrogen-bonding functional groups] / 1000

[0270] [Mass of polymer main chain per 1 g] = 1 - [Mass of hydrogen-bonding functional groups per 1 g]

[0271] [Equivalent weight of hydrogen-bonding functional groups] = [Mass of polymer main chain per 1 g] / ([Mass of hydrogen-bonding functional groups per 1 g] / [Molecular weight of hydrogen-bonding functional groups])

[0272]

[0273] <Constituent materials of the surface modification layer (surface modifiers)>

[0274] By mixing each component according to the formulation in Table 2, the constituent materials of the surface modification layer (surface modifiers B-1 to B-9) were prepared.

[0275]

[0276] The details of the compounds described in Table 2 are as follows.

[0277] ・ Blocked isocyanate compound

[0278] MEIKANATE DM-3031 CONC (manufactured by Meisei Chemical Industry Co., Ltd., purity 54% by mass)

[0279] ・ Epoxy compound

[0280] DENACOL EX-614B (manufactured by Nagase ChemteX Corporation, purity 100% by mass)

[0281] ・ Containing oxazolinyl compound

[0282] EPOCROS WS-700 (manufactured by Nippon Shokubai Co., Ltd., purity 25% by mass)

[0283] ・ Containing carbodiimide group compound

[0284] CARBODILITE Prototype (manufactured by Nisshinbo Chemical Inc., purity 40% by mass)

[0285] ・ Sodium acrylate compound

[0286] Aqualic DL-453 (manufactured by Nippon Shokubai Co., Ltd., purity 35% by mass)

[0287] ・ Ethyleneimine compound

[0288] EPOMIN SP-200 (manufactured by Nippon Shokubai Co., Ltd., purity 100% by mass)

[0289] ・ Diamide type cationic compound

[0290] ADEKA MINE SF-201 (manufactured by ADEKA Corporation, purity 80% by mass)

[0291] <Dilute solution of conjugated diene rubber>

[0292] A solution was prepared by diluting each of the modified conjugated diene rubbers described in Table 1 with a fatty acid ester or a mineral oil to 25% by mass.

[0293] Note that, as the fatty acid ester, a polyol fatty acid ester (trimethylolpropane trioctanoate) was used, whose vapor pressure at 20 °C was 1.7×10 -7 Pa, flash point was 258 °C, and it had no volatility. In addition, as the mineral oil, a mineral oil with a vapor pressure at 20 °C of 7.0×10 -3 Pa and a flash point of 158 °C and having no volatility was used.

[0294] <Example 1>

[0295] The PET fiber as a polyester fiber (total fineness 1100 dtex, single filament fineness 6.10 dtex) was impregnated in the surface modifier (B-1), and the liquid was extruded with a roller.

[0296] Then, the obtained fiber was dried at 140 °C for 60 seconds and further heat-treated at 240 °C for 60 seconds, thereby producing a surface-modified fiber.

[0297] Next, a diluted solution of the modified conjugated diene rubber was prepared so as to have the composition and adhesion amount shown in Table 3, and then the above diluted solution was applied to the surface-modified fiber using an oiling guide and wound up. Then, after fusing at room temperature (20 °C) for 3 days, it was twisted at a twist of 80 T / m to produce a reinforcing fiber.

[0298] <Examples 2 to 7 and Comparative Examples 1 to 4>

[0299] The surface-modified layer, the adhesive layer, and their adhesion amounts were changed as described in Table 3, and except for this, reinforcing fibers were produced by the same method as in Example 1.

[0300] <Reference Example 1>

[0301] The PET fiber as a polyester fiber (total fineness 1100 dtex, single filament fineness 6.10 dtex) was impregnated in the following pretreatment liquid, and the liquid was extruded with a roller, dried at 140 °C for 60 seconds, and further heat-treated at 240 °C for 60 seconds.

[0302] Next, after applying RFL, it was dried at 140 °C for 60 seconds and further heat-treated at 240 °C for 60 seconds, thereby obtaining a treated yarn. The obtained treated yarn was twisted at a twist of 80 T / m to produce a reinforcing fiber. It should be noted that the pretreatment liquid and RFL liquid used were prepared by the following methods.

[0303] [Preparation of RFL Pretreatment Liquid]

[0304] Water: 96.96 parts by mass

[0305] Blocked isocyanate: 2.29 parts by mass

[0306] Epoxy compound: 0.75 parts by mass

[0307] The pretreatment liquid is prepared using a blocked isocyanate and an epoxy resin. It should be noted that as the blocked isocyanate, "Meikanote DM-3031CONC" manufactured by Meisei Chemical Industry Co., Ltd. was used, and as the epoxy resin, "DENACOL EX-614B" manufactured by Nagase ChemteX Corporation was used.

[0308] [Preparation of RFL Liquid]

[0309] Liquid A

[0310] Water: 524 parts by mass

[0311] Resorcinol: 15 parts by mass

[0312] Formaldehyde (active ingredient 37% by mass): 16 parts by mass

[0313] Sodium hydroxide aqueous solution (active ingredient 10% by mass): 4 parts by mass

[0314] The above Liquid A was aged at a temperature of 25°C for 6 hours.

[0315] Liquid B

[0316] SBR latex (active ingredient 40% by mass): 207 parts by mass

[0317] Vinylpyridine-modified SBR latex (active ingredient 40% by mass): 233 parts by mass

[0318] After mixing the above Liquid B with the aged Liquid A, it was aged at a temperature of 25°C for 16 hours to produce the RFL liquid.

[0319] <Measurement of Zeta Potential>

[0320] Using a Zeta potential / particle size measurement system ELSZ-1000 (manufactured by Otsuka Electronics Co., Ltd.) and a cell for flat plates, the Zeta potential of the fiber surface of the surface-modified fibers obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was measured under the conditions of pH = 7 and a temperature of 25°C.

[0321] Specifically, the fibers were arranged and closely adhered to the cell for flat plates without gaps, and a dispersion obtained by dispersing monitoring particles (polystyrene particles coated with hydroxypropyl cellulose [manufactured by Otsuka Electronics Co., Ltd.]) in a 10 mM sodium chloride (NaCl) solution was injected into the cell for flat plates. Electrophoresis was carried out under the condition of applying a voltage of 80 V.

[0322] <Measurement of Adhesion between Reinforcing Fiber and EPDM Rubber>

[0323] For the reinforcing fibers obtained in Examples 1 to 7, Comparative Examples 1 to 4, and Reference Example 1, evaluation sheets were produced by the following method, and the force (N / 25.4 mm) required for T-peeling the reinforcing fibers from the rubber was measured and evaluated as the rubber adhesion. The results are shown in Table 3.

[0324] The evaluation results of the rubber adhesion indicate that the larger the value, the greater the adhesion between the reinforcing fiber and the rubber. It should be noted that the bonding sheet was produced as follows.

[0325] 〔Production of evaluation sheet〕

[0326] The reinforcing fibers produced in the Examples, Comparative Examples, and Reference Example were arranged in a curtain shape and fixed on masking tape so that the reinforcing fibers did not overlap each other, and then, they were superposed with an unvulcanized rubber composition prepared according to the following compounding composition using EPDM rubber separately. Then, press vulcanization was carried out at 150 °C and a pressure of 20 kg / cm 2 for 30 minutes to produce an evaluation sheet.

[0327] 〔Compounding composition of EPDM unvulcanized rubber〕

[0328] EPDM rubber: 100 parts by mass

[0329] Filler (carbon black): 60 parts by mass

[0330] Softening agent (paraffin processing oil): 20 parts by mass

[0331] Crosslinking agent (sulfur powder): 1.5 parts by mass

[0332] Vulcanization aid (2 kinds of lead white, stearic acid): 6 parts by mass

[0333] Vulcanization accelerator (thiazole type, thiuram type): 1.5 parts by mass

[0334]

[0335] <Examples 8 to 16 and Comparative Examples 5 to 10>

[0336] The fibers, surface modification layers, adhesive layers, and their coating amounts were changed as described in Table 4, and except for this, reinforcing fibers were produced by the same method as in Example 1. It should be noted that in addition to polyester fibers, nylon fibers (total fineness 1100 dtex, monofilament fineness 6.10 dtex) as polyamide fibers and vinylon fibers (total fineness 1330 dtex, monofilament fineness 6.65 dtex, “KURARON 1239” manufactured by Kuraray Co., Ltd.) as polyvinyl alcohol fibers were also used as fiber types.

[0337] <Reference Example 2>

[0338] An reinforcing fiber was produced in the same manner as in Reference Example 1, except that no twisting was finally performed.

[0339] <Measurement of Adhesion between Reinforcing Fiber and NR / SBR Rubber>

[0340] For the reinforcing fibers obtained in Examples 8 to 16, Comparative Examples 5 to 10, and Reference Example 2, an evaluation sheet was produced by the following method, and the force (N / 25.4 mm) required for T-peeling the reinforcing fiber from the rubber was measured and evaluated as the rubber adhesion. The results are shown in Table 4. The evaluation results of the rubber adhesion show that the larger the value, the greater the adhesion between the reinforcing fiber and the rubber. It should be noted that the adhesive sheet was produced as follows.

[0341] <[Production of Evaluation Sheet]>

[0342] The reinforcing fibers produced in the above Examples, Comparative Examples, and Reference Example were arranged in a curtain shape on a masking tape so that the reinforcing fibers did not overlap each other and fixed, and then, it was superposed with an unvulcanized rubber composition prepared separately according to the following formulation. Then, pressure vulcanization was carried out at 150 °C and a pressure of 20 kg / cm 2 for 30 minutes, thereby producing an evaluation sheet.

[0343] <[Formulation of NR / SBR Unvulcanized Rubber]>

[0344] NR rubber: 70 parts by mass

[0345] SBR rubber: 41.25 parts by mass

[0346] Filler (carbon black): 45 parts by mass

[0347] Vulcanizing agent (sulfur powder): 3.5 parts by mass

[0348] Vulcanization aid (lead white, stearic acid): 6 parts by mass

[0349] Vulcanization accelerator (thiazole type): 1 part by mass

[0350]

[0351] <Example 17: Treatment Method of Twisted Cord>

[0352] A cord was produced by applying 470 twists / m in the S direction and 470 twists / m in the Z direction to 2 PET fibers as polyester fibers (total fineness 1100 dtex, single fiber fineness 6.10 dtex), and a twisted fiber cord was produced.

[0353] After impregnating the above-twisted soft wire in the surface modifier (B-1), the liquid was extruded with a roller. The obtained fibrous soft wire was dried at 140 °C for 60 seconds, and further heat-treated at 240 °C for 60 seconds for production. Then, after impregnating in an emulsion composition containing the modified conjugated diene rubber described in Table 5 as the main component, the liquid was extruded with a roller, dried at 140 °C for 60 seconds, and then wound up. It should be noted that the content of the modified conjugated diene rubber in the emulsion composition was 10% by mass.

[0354] <Examples 18 and 19 and Comparative Example 11>

[0355] The surface modification layer, the adhesive layer, and their coating amounts were changed as described in Table 5, and otherwise, the reinforcing fibers were produced in the same manner as in Example 17.

[0356] <Reference Example 3>

[0357] Twisted PET fibrous soft wire was used, and otherwise, the reinforcing fibers were produced in the same manner as in Reference Example 1.

[0358] <Measurement of Rubber Adhesion>

[0359] For the reinforcing fibers obtained in Examples 17 to 19, Comparative Example 11, and Reference Example 3, evaluation specimens were prepared by the following method, and the force (N / 3 pieces) required for T-peeling the reinforcing fibers from the rubber was measured and evaluated as the rubber adhesion. The results are shown in Table 5. The evaluation results of the rubber adhesion indicate that the larger the value, the greater the adhesion between the reinforcing fiber and the rubber. It should be noted that the adhesive specimens were prepared as follows.

[0360] <Preparation of Evaluation Specimens>

[0361] Three reinforcing fibers produced in the above Examples, Comparative Examples, and Reference Examples were arranged at a certain interval in the NR / SBR unvulcanized rubber composition prepared by the above formulation. Then, press vulcanization was carried out at 150 °C and a pressure of 20 kg / cm 2 for 30 minutes to prepare an adhesive specimen.

[0362]

[0363] From the results of the Examples and Comparative Examples, it is clear that according to the present invention, surface-modified fibers and reinforcing fibers having excellent adhesion to rubber can be obtained. In particular, according to the present invention, when using an adhesive containing resorcinol-formaldehyde resin and rubber latex as the main components, the fiber and the rubber can be firmly adhered.

Claims

1. A surface-modified fiber having a fiber and a surface-modified layer covering at least a part of the surface of the fiber, wherein the solid surface Zeta potential of the surface of the surface-modified layer is -20.0 to 30.0 mV, and the fiber is a polyvinyl alcohol-based fiber.

2. The surface-modified fiber according to claim 1, wherein, the surface-modified layer contains a compound having a nitrogen-containing functional group.

3. The surface-modified fiber according to claim 1 or 2, wherein, The surface modification layer contains a compound having one or more functional groups selected from oxazolinyl, oxazolidinonyl, carbodiimide group, urea group, amino group, and aziridinyl group.

4. The surface-modified fiber according to any one of claims 1 to 3, wherein, the amount of the surface-modified layer is 0.01 to 5.0 parts by mass relative to 100 parts by mass of the fiber used as a raw material.

5. A reinforcing fiber having: the surface-modified fiber according to any one of claims 1 to 4, and an adhesive layer covering at least a part of the surface of the surface-modified fiber and containing a conjugated diene rubber.

6. The reinforcing fiber according to claim 5, wherein, the number-average molecular weight (Mn) of the conjugated diene rubber exceeds 2000 and is 120000 or less.

7. The reinforcing fiber according to claim 5 or 6, wherein, the conjugated diene rubber has in the molecule one or more monomer units derived from a monomer selected from butadiene, isoprene, and farnesene.

8. The reinforcing fiber according to any one of claims 5 to 7, wherein, the conjugated diene rubber is a modified conjugated diene rubber having a hydrogen-bonding functional group in a part of the conjugated diene rubber, and the hydrogen-bonding functional group is one or more selected from a hydroxyl group, an epoxy group, an aldehyde group, an acetalized product of an aldehyde group, a carboxyl group, a salt of a carboxyl group, an esterified product of a carboxyl group, an acid anhydride of a carboxyl group, a silanol group, an esterified product of a silanol group, an amino group, an imidazole group, and a mercapto group.

9. The reinforcing fiber according to any one of claims 5 to 8, wherein, the adhesive layer further contains an oil having a vapor pressure of 10 Pa or less at 20 °C.

10. A molded article using the reinforcing fiber according to any one of claims 5 to 9.

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