Water-based adhesives, reinforcing fibers using them, and elastomer products using reinforcing fibers.

Abstract

The present invention provides a water-based adhesive, a reinforcing fiber using the same, and an elastomer article using the reinforcing fiber. The water-based adhesive is a water-based adhesive that does not contain resorcinol and formaldehyde, which makes the adhesion between the fiber and the elastomer excellent, and at the same time can suppress the contamination of the reinforcing fiber manufacturing process. A water-based adhesive for bonding fibers and elastomers, characterized in that it comprises: an oil droplet emulsion (A) containing a liquid conjugated diene rubber and a surfactant, and an aqueous solution or aqueous dispersion (B) of a crosslinking agent.

Description

Technical Field

[0001] This invention relates to a water-based adhesive for bonding fibers and elastomers, reinforcing fibers using the adhesive, and elastomer articles using the reinforcing fibers. Prior Technology

[0002] Generally, industrial rubber products such as tires, conveyor belts, and hoses (e.g., automotive brake hoses) are reinforced with synthetic fibers such as vinylon and rayon, or natural fibers such as cotton. In these products, to fully utilize the excellent physical properties of rubber (e.g., high strength and high modulus of elasticity), it is essential to firmly bond the fibers to the rubber. Conventionally, a method using an adhesive called RFL (Resorcinol-Formaldehyde Resin and Rubber Latex) as the main components is widely known (Patent Documents 1 and 2). However, due to concerns about the carcinogenicity of formaldehyde and the endocrine disruptors of resorcinol, there is a desire to develop alternative materials. As an alternative material, Patent Document 3 proposes a reinforcing fiber that uses a liquid conjugated diene rubber with hydrogen-bonding functional groups, without using resorcinol or formaldehyde, and exhibits excellent adhesion to rubber. Furthermore, Patent Document 4 provides a method for bonding fibers to rubber using a thermosetting resin containing unsaturated carbon bonds. [Previous Technical Documents] [Patent Literature]

[0003] Patent Document 1: Japanese Patent Application Publication No. 54-4976 Patent Document 2: Japanese Patent Application Publication No. 58-2370 Patent Document 3: International Publication No. 2019 / 230700 Patent Document 4: Japanese Patent Application Publication No. 2016-502610 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] While the method described in Patent Document 3 has a certain degree of adhesion, further improvements are desired. Furthermore, since there is an adhesive liquid on the reinforcing fibers, there is a possibility of contaminating the production line when processing woven or knitted fabrics. On the other hand, Patent Document 4 provides a method for manufacturing reinforcing fibers by hardening an isocyanate compound or epoxy compound with unsaturated bonds onto fibers. However, since this method uses organic solvents, it has the problem of a high load on the working environment. Furthermore, the operation system for forming the adhesive layer is complicated and the processing time is long, making it a method with poor productivity. Therefore, a reinforcing fiber with the same level of adhesion as the previous RFL method, less contamination during processing, and excellent production efficiency is required.

[0006] The present invention addresses the aforementioned problems by providing a water-based adhesive, a reinforcing fiber using the same, and an elastomer article using the reinforcing fiber. The water-based adhesive is a water-based adhesive that does not contain resorcinol or formaldehyde, which in particular improves the adhesion between the fiber and the elastomer and also suppresses contamination during the manufacturing process of the reinforcing fiber. [Methods used to solve problems]

[0007] The inventors diligently investigated to solve the aforementioned problems and discovered that by using liquid conjugated diene rubber and a crosslinking agent together, the liquid conjugated diene rubber is not easily absorbed by the elastomer of the bonding object, even at the high temperatures during vulcanization, exhibiting excellent adhesion. However, if the liquid conjugated diene rubber is mixed with crosslinking agents such as epoxy resin, a reaction will occur, making long-term storage difficult, and furthermore, there is a problem of reduced adhesion. Therefore, further investigation revealed that by making the liquid conjugated diene rubber into an oil droplet emulsion in water, and mixing it with an aqueous solution or aqueous dispersion of a crosslinking agent, a water-based adhesive that can be stored for a long time and exhibits excellent adhesion can be obtained. Furthermore, it can suppress step contamination during the manufacture of reinforcing fibers, thus completing the present invention.

[0008] That is, the present invention relates to the following [1]~

[11] . [1] An aqueous adhesive for bonding fibers and elastomers, characterized in that it comprises: an aqueous oil droplet emulsion (A) containing a liquid conjugated diene rubber and a surfactant, and an aqueous solution or aqueous dispersion (B) of a crosslinking agent. [2] As described above [2], the water-based adhesive, wherein the melt viscosity of the aforementioned liquid conjugated diene rubber is less than 4,000 Pa·s when measured at 38°C. [3] As described in [1] or [2] above, the water-based adhesive further includes an oil with a vapor pressure of less than 10 Pa at 20°C. [4] As described in [3] above, the water-based adhesive contains the oil-based oil droplet emulsion (A) in the water. [5] The water-based adhesive described in any of [1] to [4] above, wherein the crosslinking agent is selected from at least one of epoxy resin and isocyanate resin. [6] The water-based adhesive described in any of [1] to [5] above, wherein the content of organic solvent in the aforementioned water-based adhesive is less than 1.0% by mass. [7] A reinforcing fiber, which is formed by attaching a water-based adhesive as described in any of the above [1] to [6] to the fiber. [8] The reinforcing fiber described above in [7], wherein the aforementioned fiber is selected from at least one fiber of polyamide fiber, polyvinyl alcohol fiber, polyester fiber and regenerated cellulose fiber. [9] As described in [7] or [8] above, the amount of the aforementioned aqueous adhesive attached to the aforementioned fiber is 0.01 to 10 parts by weight relative to 100 parts by weight of the fiber used as raw material.

[10] An elastomer article which uses the reinforcing fiber described in any of the above [7] to [9].

[11] The elastomeric articles described above in

[10] are tires, belts or hoses. [Effects of the Invention]

[0009] According to the present invention, a water-based adhesive, a reinforcing fiber using the same, and an elastomer article using the reinforcing fiber are provided. The water-based adhesive is a water-based adhesive that does not contain resorcinol and formaldehyde, which makes the adhesion between the fiber and the elastomer excellent, and at the same time can suppress the contamination of the reinforcing fiber manufacturing process. Simple Explanation of the Diagram

[0010] none. Implementation

[0011] [The form in which the invention is carried out]

[0012] [Water-based adhesive] The water-based adhesive of the present invention is a water-based adhesive used for bonding fibers and elastomers, characterized in that it comprises: an oil droplet emulsion (A) containing liquid conjugated diene rubber and surfactant in water, and an aqueous solution or aqueous dispersion (B) of a crosslinking agent. According to the present invention, the water-based adhesive exhibits excellent adhesion because it combines an oil-droplet emulsion (A) containing liquid conjugated diene rubber with a crosslinking agent. Even at high temperatures during vulcanization, the liquid conjugated diene rubber is not easily absorbed by the elastomer of the bonded object. Furthermore, since the liquid conjugated diene rubber exists in an emulsion state, it can be stored for a long time even when coexisting with a crosslinking agent. Moreover, since the liquid conjugated diene rubber and crosslinking agent can be used in a single-liquid formulation, the environmental impact is low, and space-saving design of manufacturing equipment is possible. Furthermore, compared to adhesives containing only liquid conjugated diene rubber, the reduced adhesion to the fiber surface results in less contamination during the manufacturing of reinforcing fibers, thus improving production efficiency. The present invention will now be described in detail.

[0013] <Water-based oil droplet emulsion (A)> The oil droplet emulsion (A) in this invention comprises liquid conjugated diene rubber and surfactant. [Liquid conjugated diene rubber] The liquid conjugated diene rubber system used in this invention contains at least one monomer unit (hereinafter also referred to as "conjugated diene unit") derived from a conjugated diene in its molecule. Specifically, the amount of monomer units derived from a conjugated diene in all monomer units of the conjugated diene rubber is preferably 50 mol% or more, and more preferably 65 mol% or more. In this specification, "liquid" in the context of liquid conjugated diene rubber refers to a melt viscosity of 4,000 Pa·s or less, measured at 38°C. From the viewpoint of improving adhesion, this melt viscosity is preferably 0.1 Pa·s or more, more preferably 1 Pa·s or more, particularly preferably 10 Pa·s or more, even more preferably 30 Pa·s or more, and even more preferably 50 Pa·s or more. From the viewpoint of operability, it is preferably 2,500 Pa·s or less, and more preferably 2,100 Pa·s or less. If the aforementioned melt viscosity is within the aforementioned range, both the adhesion of the liquid conjugated diene rubber and its operability can be improved. Furthermore, the melt viscosity of liquid conjugated diene rubber refers to the viscosity measured at 38°C using a Brookfield viscometer (Type B viscometer).

[0014] Examples of the aforementioned 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-octtriene, chloropine, β-chlorophenene (hereinafter also referred to as "chlorophenene"), geraniol, etc. These conjugated dienes can be used alone or in combination of two or more. The liquid conjugated diene rubber used in this invention, from the viewpoint of reactivity during vulcanization, is preferably having one or more monomer units derived from butadiene, isoprene, chloropinene and chlorophyllin.

[0015] The liquid conjugated diene rubber used in this invention may also contain units derived from monomers other than the aforementioned conjugated diene monomers, provided that such units do not impede adhesion. Examples of other monomers include copolymerizable vinyl unsaturated monomers or aromatic vinyl compounds. Examples of the aforementioned ethylene-unsaturated monomers include olefins such as ethylene, 1-butene, isobutene, and acrylonitrile. Examples of the aforementioned aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-tributylstyrene, 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. One of these compounds may be used alone, or two or more may be used in combination. Among these, from the viewpoint of improving the polarity of liquid conjugated diene rubber and enhancing its compatibility with fibers, it is preferable to have monomer units derived from acrylonitrile.

[0016] When liquid conjugated diene rubber contains monomer units derived from monomers other than conjugated diene monomers, the content of such monomers is preferably 1 to 50 mol%, more preferably 10 to 40 mol%, and even more preferably 15 to 35 mol%.

[0017] The liquid conjugated diene rubber used in this invention is preferably a modified liquid conjugated diene rubber having hydrogen-bonded functional groups in a portion of the liquid conjugated diene rubber, and more preferably a modified liquid conjugated diene rubber containing conjugated diene units in at least a portion of the polymer chain and having hydrogen-bonded functional groups in the side chains or at the ends of the polymer chain. When the aforementioned modified liquid conjugated diene rubber is used as the liquid conjugated diene rubber, adhesion can be achieved through the interaction between the modified liquid conjugated diene rubber and the elastomer or rubber and fiber of the adhesive. When the modified liquid conjugated diene rubber and the rubber to be bonded are vulcanized to form covalent bonds, the adhesion is improved due to the strong cohesive force. Furthermore, it is believed that adhesion can be improved by forming hydrogen bonds between the hydrogen-bonding functional groups contained in the modified liquid conjugated diene rubber and the surface of the fiber.

[0018] Furthermore, the term "hydrogen bond" in this specification refers to the bonding interaction formed between a hydrogen atom (donor) that is electrically polarized to positive (donor) and an electronegative atom (acceptor) that has a lone pair of electrons.

[0019] In this invention, the term "hydrogen-bonded functional group" refers to a functional group that can function as both a donor and acceptor in the aforementioned hydrogen bond. Specifically, examples include hydroxyl, epoxy, ether, mercapto, carbonyl, carboxyl, aldehyde, amino, imino, imidazole, carbamate, amide, urea, isocyanate, silyl, and their derivatives. As derivatives of the carboxyl group, examples include its salts, esters, amides, and anhydrides. Furthermore, examples of carboxyl groups include groups derived from monocarboxylic acids and groups derived from dicarboxylic acids. As derivatives of the aldehyde group, examples include its acetal form. As derivatives of the silyl group, examples include its ester form. Among these, it is preferred to select one or more from hydroxyl, epoxy, mercapto, carbonyl, carboxyl, carboxyl salts, carboxyl esters, carboxyl anhydrides, aldehydes, aldehyde acetals, silyl groups, silyl esters, amines, and imidazoles.

[0020] Among these hydrogen-bonding functional groups, from the viewpoint of improving adhesion and the ease of manufacturing liquid conjugated diene rubber, it is preferable to select one or more from hydroxyl, carbonyl, carboxyl, carboxyl salts, carboxyl esters, and carboxyl anhydrides; more preferably, it is preferable to select one or more from carboxyl, carboxyl esters, and carboxyl anhydrides; and even more preferably, it is preferable to select esters derived from maleic anhydride and functional groups derived from maleic anhydride.

[0021] From the viewpoint of obtaining reinforcing fibers with excellent rubber adhesion, the average number of hydrogen-bonding functional groups in modified liquid conjugated diene rubber is preferably 1 or more per molecule, more preferably 1.5 or more, and even more preferably 2 or more. Furthermore, from the viewpoint of controlling the viscosity of modified liquid conjugated diene rubber within an appropriate range and improving workability, the aforementioned number of hydrogen-bonding functional groups is preferably 80 or less per molecule, more preferably 40 or less, even more preferably 25 or less, and even more preferably 15 or less.

[0022] The average number of hydrogen-bonded functional groups per molecule of modified liquid conjugated diene rubber is calculated using the following formula, based on the equivalent (g / eq) of the hydrogen-bonded functional groups of the modified liquid conjugated diene rubber and the quantity average molecular weight Mn converted from styrene. The equivalent of the hydrogen-bonded functional groups in the modified liquid conjugated diene rubber refers to the mass of the conjugated diene bonded to each hydrogen-bonded functional group, plus any other monomers other than the conjugated diene that may be present as needed. Average number of hydrogen-bonded 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 conjugated diene as needed)] / (equivalent number of hydrogen-bonded functional groups) Furthermore, the method for calculating the equivalent of hydrogen-bonded functional groups can be appropriately selected according to the type of hydrogen-bonded functional group.

[0023] Methods for obtaining modified liquid conjugated diene rubber include, for example, a method by attaching a modifying compound to a polymer of conjugated diene monomers (hereinafter also referred to as "manufacturing method (1)"), or a method by oxidizing the conjugated diene polymer (hereinafter also referred to as "manufacturing method (2)"), a method by copolymerizing the conjugated diene monomer with a free radical polymerizable compound having hydrogen-bonding functional groups (hereinafter also referred to as "manufacturing method (3)"), and a method by adding a modifying compound that can react with the polymeric active end of an unmodified conjugated diene monomer before adding a polymerization stopper (hereinafter also referred to as "manufacturing method (4)"). From a productive point of view, it is preferable to manufacture by manufacturing method (1), (2), or (3), more preferably by manufacturing method (1) or (3), and especially preferably by manufacturing method (1).

[0024] Manufacturing method (1) is a method of attaching a polymer of conjugated diene monomer, i.e., unmodified liquid conjugated diene rubber (hereinafter also referred to as "unmodified liquid conjugated diene rubber"), to a modified compound. Unmodified liquid conjugated diene rubber systems can be obtained by polymerizing conjugated dienes and other monomers other than conjugated dienes as needed, such as by emulsion polymerization or solution polymerization.

[0025] As for the aforementioned solution polymerization method, well-known or well-known methods can be employed. For example, in a solvent, using a Ziegler catalyst, a metallocene catalyst, an anionic polymerizable active metal or active metal compound, a monomer containing a specified amount of conjugated diene can be polymerized in the presence of a polar compound, as required. Examples of solvents include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0026] Examples of anionic polymerizable active metals include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; and lanthanide rare earth metals such as lanthanum and neodymium. Among these anionic polymerizable active metals, alkali metals and alkaline earth metals are preferred, and alkali metals are even more preferred. As anionic polymerizable active metal compounds, organoalkali metal compounds are preferred. Examples of organoalkali metal compounds include, for instance, monolithium organometallic compounds such as methyllithium, ethyllithium, n-butyllithium, dibutyllithium, tert-butyllithium, hexyllithium, phenyllithium, and stilbene; polyfunctional organolithium compounds such as dilithiummethane, dilithium naphthalene, 1,4-dilithiumbutane, 1,4-dilithium-2-ethylcyclohexane, and 1,3,5-trilithiumbenzene; and sodium naphthalene and potassium naphthalene. Among these organoalkali metal compounds, organolithium compounds are preferred, and monolithium organometallic compounds are even more preferred.

[0027] The amount of the aforementioned organoalkali metal compound used can be appropriately set according to the melt viscosity, molecular weight, etc. of the unmodified liquid conjugated diene rubber and the modified liquid conjugated diene rubber for the purpose. However, it is usually used in an amount of 0.01 to 3 parts by mass relative to 100 parts by mass of all monomers containing conjugated diene. The aforementioned organoalkali metal compounds can also react with secondary amines such as dibutylamine, dihexylamine, and dibenzylamine to be used as organoalkali metal amides.

[0028] In anionic polymerization, polar compounds typically do not deactivate the reaction and are used to adjust the microstructure of the conjugated diene site. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, ethylene glycol diethyl ether, and 2,2-di(2-tetrahydrofuranyl)propane; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides; and phosphine compounds. Polar compounds are typically used in amounts ranging from 0.01 to 1000 moles, relative to organoalkali metal compounds.

[0029] The solution polymerization temperature is typically in the range of -80 to 150°C, preferably in the range of 0 to 100°C, and even more preferably in the range of 10 to 90°C. The polymerization process can be either batch or continuous. The polymerization reaction can be stopped by adding a polymerization stopper. Examples of polymerization stoppers include alcohols such as methanol and isopropanol. The resulting polymerization reaction solution can be injected into a poor solvent such as methanol to precipitate the polymer, or the polymerization reaction solution can be washed with water, separated, dried, and the unmodified liquid conjugated diene rubber can be separated. Of the aforementioned methods for manufacturing unmodified liquid conjugated diene rubber, solution polymerization is preferred.

[0030] As for the aforementioned emulsion polymerization method, well-known or well-known methods can be employed. For example, a specified amount of monomer containing a conjugated diene is emulsified and dispersed in the presence of an emulsifier, and emulsion polymerization is carried out by a free radical polymerization initiator. Examples of emulsifiers include long-chain fatty acid salts with more than 10 carbon atoms and rosin acid salts. Examples of long-chain fatty acid salts include potassium or sodium salts of fatty acids such as decanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid. Water is typically used as a dispersion solvent, but water-soluble organic solvents such as methanol and ethanol may also be included, provided that the stability during polymerization is not compromised. Examples of free radical polymerization initiators include persulfates such as ammonium persulfate or potassium persulfate, organic peroxides, and hydrogen peroxide. To adjust the molecular weight of the resulting unmodified liquid conjugated diene rubber, chain transfer agents can be used. Examples of chain transfer agents include thiols such as tert-dodecylthiol and n-dodecylthiol; carbon tetrachloride; mercaptoacetic acid; diterpenes; terpinene; γ-terpinene; and α-methylstyrene dimers.

[0031] The temperature for emulsion polymerization can be appropriately set according to the type of free radical polymerization initiator used, but it is usually in the range of 0~100℃, preferably in the range of 0~60℃. The polymerization mode can be either continuous polymerization or batch polymerization.

[0032] Polymerization reactions can be stopped by adding polymerization stoppers. Examples of polymerization stoppers include amine compounds such as isopropyl hydroxylamine, diethyl hydroxylamine, and hydroxylamine; quinone compounds such as hydroquinone or benzoquinone; and sodium nitrite.

[0033] After the polymerization reaction stops, an anti-aging agent may be added as needed. After the polymerization reaction stops, unreacted monomers are removed from the obtained latex as needed. Then, salts such as sodium chloride, calcium chloride, and potassium chloride are used as coagulants, and acids such as nitric acid and sulfuric acid are added as needed. While adjusting the pH of the coagulation system to a specified value, the polymer is coagulated, and the dispersion solvent is separated to recover the polymer. After washing and dehydration, it is dried to obtain unmodified liquid conjugated diene rubber. Furthermore, during coagulation, the latex can be pre-mixed with filling oil to form an emulsion dispersion as needed, and the oil-filled unmodified liquid conjugated diene rubber can be recovered.

[0034] There are no particular limitations on the modified compound used in manufacturing method (1), but from the viewpoint of improving the adhesion of the reinforcing fiber, it is preferable to use one with hydrogen-bonding functional groups. Examples of hydrogen-bonding functional groups are those similar to those mentioned above. Among them, from the viewpoint of the strength of hydrogen bonding, amino, imidazole, urea, hydroxyl, epoxy, mercapto, silyl, aldehyde, carboxyl, and their derivatives are preferred. As derivatives of the carboxyl group, their salts, esters, amides, or anhydrides are preferred. One modified compound with such hydrogen-bonding functional groups may be used alone, or two or more may be used in combination.

[0035] Examples of the aforementioned modified compounds include unsaturated carboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itconic acid; unsaturated carboxylic anhydrides such as maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, and itconic anhydride; unsaturated carboxylic esters such as maleate ester, fumarate ester, citracate ester, and itconate ester; unsaturated carboxylic amides such as maleate amide, fumarate amide, citracate amide, and itconate amide; unsaturated carboxylic amides such as maleate amide, fumarate amide, citracate amide, and itconate amide; and vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and mercapto-methyl Silane compounds such as methylmethyldiethoxysilane, mercaptomethyltriethoxysilane, 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.

[0036] The amount of the aforementioned modifying compound used is preferably 0.1 to 100 parts by weight, more preferably 0.5 to 50 parts by weight, and even more preferably 1 to 30 parts by weight, relative to 100 parts by weight of unmodified liquid conjugated diene rubber. The reaction temperature is usually preferably in the range of 0~200℃, and more preferably in the range of 50~200℃. Alternatively, the aforementioned modified compounds can be grafted onto unmodified liquid conjugated diene rubber and hydrogen-bonding functional groups can be introduced. Then, modified compounds that can react with these functional groups can be added to introduce other hydrogen-bonding functional groups into the polymer. Specifically, for example, a method can be used to graft maleic anhydride onto unmodified liquid conjugated diene rubber obtained by living anionic polymerization, followed by reaction with compounds containing hydroxyl groups such as 2-hydroxyethyl methacrylate or methanol, or water.

[0037] The additional amount of modifying compound in modified liquid conjugated diene rubber is preferably 0.5 to 40 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 1.5 to 20 parts by mass, relative to 100 parts by mass of unmodified liquid conjugated diene rubber. Furthermore, the amount of modifying compound added to the modified liquid conjugated diene rubber can be calculated based on the acid value of the modifying compound, or it can be determined using various analytical instruments such as infrared spectroscopy and nuclear magnetic resonance spectroscopy.

[0038] There are no particular limitations on the method of adding the aforementioned modified compound to unmodified liquid conjugated diene rubber. For example, a method can be described by adding unmodified liquid conjugated diene rubber, one or more modified compounds selected from unsaturated carboxylic acids, unsaturated carboxylic acid derivatives, and silane compounds, and a free radical generator as needed, and heating in the presence or absence of an organic solvent. There are no particular limitations on the free radical generator used; commercially available organic peroxides, azo compounds, hydrogen peroxide, etc., can be used. Organic solvents used in the aforementioned methods can generally be categorized as hydrocarbon solvents or halogenated hydrocarbon solvents. Among these organic solvents, hydrocarbon solvents such as n-butane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and xylene are preferred.

[0039] Furthermore, when reacting with the aforementioned modified compound, from the viewpoint of suppressing side reactions, an anti-aging agent can also be added. Examples of anti-aging agents include 2,6-dibutyl-4-methylphenol (BHT), 2,2'-methylenebis(4-methyl-6-tertiary butylphenol), 4,4'-thiobis(3-methyl-6-tertiary butylphenol), 4,4'-butylenebis(3-methyl-6-tertiary butylphenol) (AO-40), 3,9-bis[1,1-dimethyl-2-[3-(3-tertiary butyl-4-hydroxy-5-methylphenyl)propoxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (AO-80), 2,4-bis(octylthiomethyl)- Phenolic anti-aging agents such as 6-methylphenol (Irganox 1520L), 2,4-bis[(dodecylthio)methyl]-6-methylphenol (Irganox 1726), 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]4,6-dipentylphenyl acrylate (Sumilizer GM), hydroquinone, and p-methoxyphenol; phosphoric acid anti-aging agents such as phosphite (2,4-di-tert-butylphenyl) (Irganox 168); and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (Nocrac Amine-based anti-aging agents such as bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (LA-77Y), N,N-bis(octadecylhydroxyamine) (IrgastabFS042), and bis(4-tert-octylphenyl)amine (Irganox5057); bis(octadecyl-3,3'-dithiodipropionate, bis(dodecyl-3,3'-thiodipropionate) (IrganoxPS800), and bis[3-(dodecylthio)propionate-2,2-bis[3- Sulfur-based anti-aging agents such as (dodecylthio)-1-yloxypropoxy]methyl]-1,3-propanediyl (MumilizerTP-D); and compound anti-aging agents such as phenolic and phosphoric acid-based anti-aging agents such as 6-tert-butyl-[3-(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yloxy)propyl]-methylphenol (SumilizerGP). Anti-aging agents can be used alone or in combination of two or more. Among these, 2,6-dibutyl-4-methylphenol and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (Nocrac 6C) are more suitable in terms of efficacy and versatility.

[0040] The amount of anti-aging agent added is preferably 0.01 to 10 parts by weight, and more preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of unmodified liquid conjugated diene rubber. If the amount of anti-aging agent added is within the aforementioned range, side reactions can be suppressed, and modified liquid conjugated diene rubber can be obtained in good yield.

[0041] [Physical Properties of Liquid Conjugated Diene Rubber] There are no particular limitations on the weight average molecular weight (Mw) of liquid conjugated diene rubber, but from the viewpoint of improving adhesion, it is preferable to have a molecular weight greater than 1,000, more preferably greater than 2,000, especially more preferably greater than 3,000, even more preferably greater than 5,000, and even more preferably greater than 20,000. From the viewpoint of operability, it is preferable to have a molecular weight less than 120,000, more preferably less than 100,000, even more preferably less than 75,000, and even more preferably less than 55,000.

[0042] There are no particular limitations on the number average molecular weight (Mn) of liquid conjugated diene rubber, but from the viewpoint of improving adhesion, it is preferable to have a value of more than 1,000, more preferably more than 2,000, especially more than 3,000, even more preferably more than 5,000, and even more preferably more than 20,000. Moreover, from the viewpoint of operability, it is preferable to have a value of less than 120,000, more preferably less than 75,000, even more preferably less than 50,000, and even more preferably less than 47,000. The Mw and Mn of the liquid conjugated diene rubber are the weight-average molecular weight and number-average molecular weight of polystyrene obtained by gel permeation chromatography (GPC), which can be determined by the methods described in the examples.

[0043] The molecular weight distribution (Mw / Mn) of the liquid conjugated diene rubber is preferably 1.00~5.00, more preferably 1.00~3.00, even more preferably 1.00~2.00, even more preferably 1.00~1.50, and particularly preferably 1.00~1.30. If the Mw / Mn is within the aforementioned range, the viscosity deviation of the liquid 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) of standard polystyrene, determined by GPC measurement.

[0044] The glass transition temperature (Tg) of liquid conjugated diene rubber can vary depending on the vinyl content of the conjugated diene units, the type of conjugated diene, and the content of units derived from monomers other than the conjugated diene. However, it is preferably -100 to 10°C, more preferably -100 to 0°C, and even more preferably -100 to -10°C. If the Tg is within the aforementioned range, high viscosity can be suppressed, and operation becomes easier. The glass transition temperature (Tg) of liquid conjugated diene rubber refers to the value calculated from the peak value of the DDSC thermal analysis curve determined by differential scanning calorimetry (DSC). Specifically, it can be determined by the method described in the examples.

[0045] The vinyl content of the liquid conjugated diene rubber is preferably 80 moles or less, more preferably 50 moles or less, and even more preferably 30 moles or less. If the vinyl content is within the aforementioned range, the adhesion is improved. The term "vinyl content" in this specification refers to the total moles of conjugated diene units (those bonded by bonds other than 1,4- bonds) out of a total of 100 moles of conjugated diene units contained in the modified liquid diene rubber. Vinyl content can be calculated using 1H-NMR by the integral ratio of the signal originating from conjugated diene units bonded by 1,2- or 3,4- bonds to the signal originating from conjugated diene units bonded by 1,4- bonds.

[0046] From the viewpoint of improving emulsion stability and adhesion, the content of liquid conjugated diene rubber in the oil-drop emulsion (A) is preferably 1% by mass or more, more preferably 5% by mass or more, particularly preferably 8% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less, relative to the total amount of oil-drop emulsion (A). If the content of liquid conjugated diene rubber in the oil-drop emulsion (A) is within the aforementioned range, the stability of the emulsion during manufacturing can be improved while preventing the emulsion viscosity from becoming extremely high, thereby increasing production efficiency.

[0047] Furthermore, from the viewpoint of improving adhesion, the content of liquid conjugated diene rubber in the aqueous adhesive of the present invention is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total amount of the aqueous adhesive. If the content of liquid conjugated diene rubber in the aqueous adhesive is within the aforementioned range, the stability of the emulsion during manufacturing can be improved while preventing the viscosity of the emulsion composition from becoming extremely high, thereby improving production efficiency.

[0048] <surfactants> The surfactant used in the water-based oil droplet emulsion (A) is not particularly limited, and examples include cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants. From the viewpoint of the compatibility between the aqueous adhesive and the rubber, nonionic surfactants are preferred. One type of surfactant may be used alone, or two or more may be used in combination. In this invention, by using surfactants to formulate the water-based oil droplet emulsion (A) containing liquid conjugated diene rubber, the aqueous adhesive can be stably preserved for a long period even in the presence of a crosslinking agent.

[0049] Examples of nonionic surfactants include polyoxyethylene-type nonionic surfactants such as higher alcohol epoxide adducts, alkylphenol epoxide adducts, styrene-modified phenol epoxide adducts, fatty acid epoxide adducts, polyol aliphatic ester epoxide adducts, higher alkylamine epoxide adducts, and fatty acid amide epoxide adducts; and polyol-type nonionic surfactants such as alkyl glycosides and sucrose fatty acid esters. These nonionic surfactants can be used alone, or in combination of two or more as needed. Commercially available nonionic surfactants include ADEKA's "Adeka Tol TN100", "Adeka Tol PC-6", "Adeka Tol PC-8", "Adeka Tol PC-10", and "Adeka Tol SO-80".

[0050] Examples of cationic surfactants include alkylammonium acetates, alkyl dimethyl benzylammonium salts, alkyl trimethylammonium salts, dialkyl dimethylammonium salts, alkylpyridinium salts, alkyl oxyalkylamines, and polyoxyalkylamines. These cationic surfactants can be used alone, or in combination of two or more as needed.

[0051] Examples of anionic surfactants include carboxylates of fatty acid soaps, sulfates of higher alcohols, sulfates of higher alkyl polyalkylene glycol ethers, sulfates of styrene-modified phenol-epoxide adducts, sulfates of alkylphenol-epoxide adducts, sulfates of sulfated oils, sulfated fatty acid esters, sulfated fatty acids, sulfated alkenes, formaldehyde condensates of alkylbenzene sulfonates, alkylnaphthalene sulfonates, naphthalene sulfonates, and naphthalene sulfonic acids, sulfonates of α-olefin sulfonates, paraffin sulfonates, sulfosuccinate diesters, and higher alcohol phosphates. These anionic surfactants can be used alone, or in combination of two or more as needed. Furthermore, nonionic surfactants and anionic surfactants can be combined as needed.

[0052] Examples of zwitterionic surfactants include alkyl carboxybetaines.

[0053] The HLB (Hydrophilic-Lipophilic Balance) value of the nonionic surfactant is preferably 6 to 17. If the HLB value is within the aforementioned range, the liquid conjugated diene rubber exhibits good compatibility with the oil described later, resulting in reinforcing fibers with good adhesion to the rubber. Furthermore, from the viewpoint of safety and operability in the usage environment, the adhesive component is preferably coated onto the fiber as an oil droplet emulsion in water. From the viewpoint of storage stability in water, the lower limit of the HLB value is preferably 8 or higher, and more preferably 10 or higher. From the viewpoint of compatibility and adhesion to the rubber, the upper limit of the HLB value is preferably 16 or lower, and more preferably 14 or lower. Furthermore, the HLB value is an indicator of the balance between hydrophilicity and lipophilicity, expressed in values ​​from 0 to 20. For example, it can be calculated using the Griffin method by the following formula (I). HLB value = 20 × total formula weight of hydrophilic portion / molecular weight (I) The identification of nonionic surfactants is performed using mass spectrometry to detect and determine the molecular weight and constituent units, and using 1H and 13C-NMR to detect and determine the structure. Based on this, the structure can be identified, and the HLB value can be calculated using equation (I) based on the identified information. Furthermore, as a method for separating nonionic surfactants from adsorbents, reversed-phase liquid chromatography can be used for fractionation.

[0054] From the viewpoint of improving the stability of the emulsion, the content of surfactant in the oil droplet emulsion (A) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of conjugated diene rubber in the oil droplet emulsion (A).

[0055] <Manufacturing Method of Oil Droplet Emulsion (A) in Water> There are no particular restrictions on the manufacturing method of the oil droplet emulsion (A) in water. It is preferred to prepare the emulsion by mechanical or chemical methods and use it at a specified concentration by dilution. As mechanical methods, examples include the use of homogenizers, homogenizers, dispersion mixers, rubber mills, pipeline mixers, high-pressure homogenizers, ultrasonic emulsifiers, etc., which can be used individually or in combination. As a chemical method, various methods can be cited, such as reverse emulsification, D-phase emulsification, HLB temperature emulsification, gel emulsification, and liquid crystal emulsification. From the viewpoint of easily obtaining emulsions with fine particle sizes, reverse emulsification is preferred. Furthermore, in order to obtain emulsions with fine particle sizes, it is also preferable to perform the process while heating at an appropriate temperature (e.g., 30~80°C) with the aim of reducing the viscosity of the liquid-modified conjugated diene rubber.

[0056] In this invention, to improve the stability of the emulsion, alkaline substances such as sodium hydroxide, potassium hydroxide, and amines may be added as needed to adjust the pH before use.

[0057] When using an alkaline substance, the amount of alkaline substance relative to 100 parts by mass of the conjugated diene rubber in the oil droplet emulsion (A) in water is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, especially preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, especially preferably 3 parts by mass or less, from the viewpoint of improving the stability of the emulsion.

[0058] <Aqueous solution or dispersion of crosslinking agent (B)> [Cross-linking agent] The water-based adhesive of this invention uses an aqueous solution or aqueous dispersion of a crosslinking agent (B). By using a crosslinking agent, even at high temperatures during vulcanization, the aforementioned liquid conjugated diene rubber is difficult for the elastomer of the bonded object to absorb, thus exhibiting sufficient adhesion. There are no particular limitations on the crosslinking agent used in this invention. Any compound capable of forming a covalent bond with both liquid conjugated diene rubber and fiber is acceptable. Examples include epoxy resin, isocyanate resin, and other crosslinking agents. Among resins containing azoline groups, carbodiimide groups, amino resins, carboxyl groups, carboxyl anhydrides, polyester resins, carbamate resins, phenolic resins, aldehyde resins, etc., when using polyvinyl alcohol-based fibers as fibers, it is preferable to select at least one of epoxy resins and isocyanate resins; when using polyester-based fibers, it is preferable to select those containing... At least one of azoline-based resin and a carbodiimide-containing resin.

[0059] From the viewpoint of improving adhesion by inhibiting the absorption of the liquid conjugated diene rubber into the elastomer through reaction with the liquid conjugated diene rubber, the content of the crosslinking agent in the aqueous solution or aqueous dispersion (B) is preferably 0.6% by mass or more, more preferably 0.8% by mass or more, and particularly preferably 1.0% by mass or more, relative to the total amount of the crosslinking agent in the aqueous solution or aqueous dispersion (B). Furthermore, from the viewpoint of preventing the loss of softness of the reinforcing fiber and the reduction of fiber properties, it is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[0060] Furthermore, from the perspective of improving adhesion by inhibiting the absorption of liquid conjugated diene rubber into the elastomer through reaction with liquid conjugated diene rubber, the content of crosslinking agent in the water-based adhesive is preferably 10 to 1,000 parts by weight, and more preferably 30 to 800 parts by weight, relative to 100 parts by weight of liquid conjugated diene rubber. More specifically, relative to the total amount of the aqueous adhesive, it is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, particularly preferably 0.9% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. If the content of the crosslinking agent in the aqueous adhesive is above the aforementioned lower limit, the crosslinking agent can react with the liquid conjugated diene rubber, thereby inhibiting the absorption of the liquid conjugated diene rubber into the elastomer. On the other hand, if the content of the crosslinking agent in the aqueous adhesive is below the aforementioned upper limit, the excessive increase of the adhesion strength of the adhesive layer can be prevented.

[0061] [Method for manufacturing aqueous solution or aqueous dispersion of crosslinking agent (B)] There are no particular restrictions on the method of manufacturing the aqueous solution or aqueous dispersion (B) of the crosslinking agent, which can be manufactured by mixing the aforementioned crosslinking agent with water.

[0062] <Other Ingredients> [Oil] In this invention, oil can be used as a component of the adhesive layer. By using oil, uneven coating of the adhesive component is less likely to occur, resulting in improved adhesion. Furthermore, the improved throughput of manufacturing equipment during manufacturing reduces equipment contamination and increases production efficiency. When using oil in this invention, from the viewpoint of stabilizing the emulsion, the oil is preferably contained in the oil droplet emulsion (A) in water. By containing oil in the oil droplet emulsion (A) in water, the viscosity is reduced, thus improving workability. Furthermore, by allowing the oil to adhere to the fibers, the smoothness of the aqueous adhesive layer (adhesive layer) is increased, and the processability is improved.

[0063] The oil used in this invention is preferably a non-volatile oil with a vapor pressure of 10 Pa or less at 20°C. If the vapor pressure of the oil at 20°C exceeds 10 Pa, the oil will evaporate after the adhesive component is coated onto the surface of the fiber, potentially causing wear and tear on the reinforcing fiber. Furthermore, uneven coating of the adhesive component is likely to occur, reducing its adhesion and potentially further contaminating the manufacturing equipment. Based on this viewpoint, the vapor pressure of the oil at 20°C is preferably 5 Pa or less, more preferably 1 Pa or less, particularly preferably 1.0 × 10⁻¹ Pa or less, even more preferably 1.0 × 10⁻² Pa or less, and even more preferably 1.0 × 10⁻⁵ Pa or less. Furthermore, the vapor pressure of oil at 20°C in this invention refers to the value calculated by applying the Antoine formula to the optimal curve obtained from the measured values ​​determined by the gas flow method.

[0064] As for the aforementioned oils with a vapor pressure of less than 10 Pa at 20°C, there are no particular limitations as long as they are compatible with liquid conjugated diene rubbers; examples include natural oils and synthetic oils. Examples of natural oils include mineral oils and vegetable oils. Examples of mineral oils include paraffinic mineral oils, aromatic mineral oils, and cycloalkanes obtained through common refining methods such as solvent refining and hydrogenation refining; waxes (gas-to-liquid waxes) manufactured through processes such as the Fischer-Tropsch process; and mineral oils manufactured by isomerizing waxes. Commercially available paraffin-based mineral oils include the "Diana Process Oil" series produced by Kuang Hsing Corporation and the "Super Oil" series produced by JX Energy Corporation. Examples of vegetable oils include flaxseed oil, camellia oil, macadamia oil, corn oil, mink oil, olive oil, avocado oil, tea plum oil, castor oil, safflower oil, jojoba oil, sunflower seed oil, almond oil, rapeseed oil, sesame oil, soybean oil, peanut oil, cottonseed oil, coconut oil, palm kernel oil, and rice bran oil. Examples of synthetic oils include hydrocarbon-based synthetic oils, ester-based synthetic oils, and ether-based synthetic oils. Examples of hydrocarbon-based synthetic oils include polybutene, polyisobutylene, 1-octene oligomers, 1-decene oligomers, and α-olefin oligomers or their hydrogenates, alkylbenzenes, and alkylnaphthalenes, etc. Examples of ester-based synthetic oils include triglyceride fatty acid esters, diglyceride fatty acid esters, monoglyceride fatty acid esters, monohydric alcohol fatty acid esters, polyhydric alcohol fatty acid esters, phthalates, adipates, and epoxy polymers, etc. Examples of ether-based synthetic oils include polyoxyethylene glycol and polyphenylene ether, etc. Furthermore, in the case of natural oils, suitable examples may include fatty acid ester oils containing at least one of the following: triglycerides, diglycerides, monoglycerides, monohydric alcohols, polyhydric alcohols, phthalates, adipates, epoxy polymers, etc. Commercially available synthetic oils include the "Linealene" series manufactured by Kuang Hsing Corporation, "FGC32", "FGC46", and "FGC68" manufactured by ANDEROL, "Exceparl TGO" manufactured by Kao Corporation, and "ADK Cizer PN-7160" manufactured by ADEKA Corporation.

[0065] From the viewpoint of reducing uneven coating of the adhesive component and improving adhesion, triglycerides, phthalates, and adipates are preferred, and 2-ethylhexanoate triglycerides and adipates are even more preferred.

[0066] When using water-based adhesives in oil, from the viewpoint of stabilizing the emulsion, it is preferable to use oil as a component of the oil droplet emulsion (A) in water, that is, the oil is preferably contained in the oil droplet emulsion (A) in water. The oil content in the oil droplet emulsion (A) in water is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 100 parts by mass or more, relative to 100 parts by mass of conjugated diene rubber. From the point of view of adhesion, it is preferably 900 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 300 parts by mass or less, and even more preferably 200 parts by mass or less.

[0067] [Other ingredients besides oil] Other components besides oil include other polymers (such as unmodified liquid conjugated diene rubber), acids, alkalis, antioxidants, hardeners, dispersants, pigments, dyes, adhesives, carbon black, etc. When the aqueous adhesive contains components other than oil, the content of these components relative to 100 parts by weight of liquid conjugated diene rubber is preferably 10,000 parts by weight or less, more preferably 1,000 parts by weight or less, particularly preferably 100 parts by weight or less, and even more preferably 50 parts by weight or less.

[0068] The water-based adhesive of the present invention is preferably free of organic solvents. The specific content of organic solvents in the water-based adhesive is preferably less than 1.0% by mass, more preferably less than 0.9% by mass, even more preferably less than 0.7% by mass, and even more preferably less than 0.5% by mass. If the content of organic solvents in the water-based adhesive is less than the aforementioned upper limit, the load on the working environment can be reduced, and the operation for forming the adhesive layer can be simplified, thereby improving productivity. Furthermore, the content of organic solvents in water-based adhesives refers to the value determined by gas chromatography, specifically by the method described in the examples.

[0069] <Manufacturing Method of Water-Based Adhesives> The manufacturing method of the water-based adhesive of the present invention is not particularly limited, and can be obtained by mixing an aqueous solution or aqueous dispersion (B) of an oil droplet emulsion (A) and a crosslinking agent in water.

[0070] <Viscosity of Water-Based Adhesives> The viscosity of the water-based adhesive of the present invention at 25°C is preferably 0.1~30.0 mPa·s, more preferably 1.0~15.0 mPa·s, and even more preferably 3.0~12.0 mPa·s. If the viscosity of the water-based adhesive of the present invention at 25°C is within the aforementioned range, then due to its moderate viscosity, the adhesive component can adhere to the fiber more uniformly and efficiently. Furthermore, since the adhesive component does not easily adhere to the manufacturing equipment, contamination of the manufacturing equipment can be suppressed. Furthermore, the viscosity of water-based adhesives refers to the viscosity measured using a Brookfield viscometer (Type B viscometer) at 20°C. The rotor and rotational speed should be appropriately set close to full scale during the measurement.

[0071] [Reinforcing Fibers] The reinforcing fiber of the present invention is attached with the water-based adhesive of the present invention, specifically having an adhesive layer formed by the aforementioned water-based adhesive on at least a portion of the fiber surface. According to the present invention, since at least a portion of the fiber surface is provided with an adhesive layer made of the aforementioned water-based adhesive, the liquid rubber is not absorbed by the elastomer of the bonded object due to heating during vulcanization, and the fiber and the elastomer can be firmly bonded. Furthermore, the phrase "having an adhesive layer on at least a portion of the fiber surface" in this invention means that although the entire fiber can be covered by the adhesive layer, it is sufficient for at least a portion to be covered by the adhesive layer. For example, the adhesive component can exist as a film or layer.

[0072] In this invention, even without formaldehyde or formaldehyde-based resins, which are harmful to the human body, reinforcing fibers with excellent adhesion to rubber can be obtained. In this invention, if the aforementioned adhesive layer contains formaldehyde-based resin, examples of such resins include resorcinol / formaldehyde resin, phenol / formaldehyde resin, melamine / formaldehyde resin, and their derivatives. When the aforementioned adhesive layer contains formaldehyde, its content relative to 100 parts by weight of the aforementioned liquid conjugated diene rubber is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, particularly preferably 3 parts by weight or less, even more preferably 1 part by weight or less, and especially preferably substantially free. The formaldehyde content can be determined by extracting the adhesive layer from the reinforcing fiber using a solvent such as toluene and then performing an HPLC analysis.

[0073] <fiber> There are no particular limitations on the fiber system used in the reinforcing fiber of this invention; hydrophilic or hydrophobic fibers can be used. Furthermore, the term "fiber" in this invention refers not only to short or long fibers, but also to forms such as nonwoven fabrics, woven fabrics, knitted fabrics, felts, and sponges.

[0074] Examples of hydrophilic synthetic fibers include those made of thermoplastic resins having hydrophilic functional groups such as hydroxyl, carboxyl, sulfonic acid, and amine groups, and / or hydrophilic bonds such as amide bonds. 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, and polyamide 9C (a polyamide formed from nonadiamine and cyclohexanedicarboxylic acid); semi-aromatic polyamides such as polyamide 9T (a polyamide formed from nonadiamine and terephthalic acid) synthesized from aromatic dicarboxylic acids and aliphatic diamines; and fully aromatic polyamides such as poly(phenylene terephthalamide) synthesized from aromatic dicarboxylic acids and aromatic diamines], and polyacrylamide resins, etc. Among these, polyvinyl alcohol-based resins and polyamide-based resins are preferred. The hydrophilic synthetic fibers may use one type alone or in combination of two or more types. Furthermore, to further enhance the hydrophilicity of these hydrophilic synthetic fibers, a hydrophilization treatment described later may be applied.

[0075] Examples of hydrophilic natural fibers include wood pulp such as kraft paper pulp and non-wood pulp such as cotton pulp and straw pulp. Examples of hydrophilic regenerated fibers include rayon, lyocell, cupro, and polynosic cellulose fibers. These natural fibers and regenerated fibers can be used individually or in combination of two or more. Furthermore, these hydrophilic natural fibers and regenerated fibers may undergo further hydrophilization treatment as described later to further enhance their hydrophilicity.

[0076] Hydrophilic fibers only require that at least their surface is hydrophilic. Examples include fibers obtained by hydrophilizing the surface of a hydrophobic resin, or core-sheath type composite fibers where the core is a hydrophobic resin and the sheath is a hydrophilic resin. Regarding examples of hydrophilic resins constituting the sheath, descriptions of hydrophilic synthetic fibers are cited. Examples of hydrophobic fibers made from hydrophobic resins include the hydrophobic fibers described later.

[0077] Hydrophilic treatment is any treatment that chemically or physically imparts hydrophilic functional groups to the fiber surface, and there are no particular limitations. For example, it can be carried out by modifying hydrophobic fibers made of hydrophobic resins (described later) with compounds or their derivatives containing hydrophilic functional groups such as isocyanate groups, epoxy groups, hydroxyl groups, amino groups, ether groups, aldehyde groups, carbonyl groups, carboxyl groups, and carbamate groups, or by modifying the surface by electron beam irradiation.

[0078] Hydrophobic fibers can also be used in this invention. Hydrophobic fibers generally do not have polar functional groups on their surface, making it difficult to bond firmly with rubber. However, as in this invention, by providing an adhesive layer on the fiber surface, even hydrophobic fibers can be firmly bonded to rubber.

[0079] Examples of hydrophobic fibers that can be used in this invention include polyolefin fibers such as polyethylene and polypropylene, polyester fibers such as polyethylene terephthalate, and fully aromatic polyester fibers. Among these, polyester fibers are preferred in terms of superior manufacturing cost, strength, heat resistance, and durability.

[0080] In this invention, the aforementioned fibers are preferably synthetic fibers and regenerated fibers, and more preferably one or more fibers selected from polyamide fibers, polyvinyl alcohol fibers, polyester fibers and regenerated cellulose fibers. Furthermore, in this invention, one type of fiber may be used alone, or two or more types may be used together.

[0081] <Reinforcing the physical properties of fibers> The aforementioned reinforcing fiber system preferably has a single yarn fineness of 0.1 dtex or more and 30 dtex or less. While the single yarn fineness can also be less than 0.1 dtex, it is preferred to be 0.1 dtex or more due to industrial manufacturing difficulties. Furthermore, if the single yarn fineness is 30 dtex or less, the surface area of ​​the fiber increases when it becomes a reinforcing fiber, thus improving its adhesion to rubber. Based on this viewpoint, the reinforcing fiber system of the present invention preferably has a single yarn fineness of 0.3 dtex or more, particularly 0.5 dtex or more, even more preferably 1 dtex or more, and even more preferably 20 dtex or less, particularly preferably 15 dtex or less, and even more preferably 10 dtex or less. In the present invention, the reinforcing fiber is preferably a multifilament, and particularly preferably a multifilament that meets the aforementioned single yarn fineness range.

[0082] The rubber adhesion strength of the reinforcing fiber of the present invention is preferably 20 N / 25.4 mm or more, more preferably 30 N / 25.4 mm or more, particularly preferably 35 N / 25.4 mm or more, even more preferably 40 N / 25.4 mm or more, and typically 200 N / 25.4 mm or less. If the rubber adhesion strength of the reinforcing fiber is above the aforementioned lower limit, woven fabrics, knitted fabrics, and elastomer products with excellent reinforcing strength can be obtained. Furthermore, the rubber adhesion of the reinforcing fibers can be determined by the method described in the examples.

[0083] The reinforcing fiber of this invention can be used in any shape, but it is preferably used in the form of fiber cords, woven fabrics, knitted fabrics, etc., in which at least a portion of the reinforcing fiber is included. More preferably, it is used as a woven or knitted fabric in which at least a portion of the reinforcing fiber is included. For example, as described later, it can be used as a knitted fabric bonded to rubber. Also, it can be used as a reinforcing fiber embedded in resin or cement.

[0084] [Manufacturing Method of Reinforcing Fibers] The method for manufacturing the reinforcing fiber of the present invention is not particularly limited. For example, it is preferred to manufacture it by sequentially performing the following steps I-1 and I-2. <Step I-1: The step of adhering the water-based adhesive to the surface of the fiber> In step I-1, there are no particular limitations on the method of attaching the water-based adhesive of the present invention to the fiber. For example, it can be carried out by one or more methods selected from impregnation, roller coating, oiling roller, oiling guide, nozzle (spray) coating and brush coating.

[0085] From the viewpoint of improving the adhesion between the reinforcing fiber and the rubber, the amount of the aforementioned water-based adhesive is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the fiber used as a raw material. Moreover, from the viewpoint of balancing manufacturing cost and effect, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less. Furthermore, the amount of the aforementioned water-based adhesive can be determined using the method described in the examples.

[0086] <Step I-2: The step of heat-treating the fibers with the aforementioned water-based adhesive obtained in Step I-1> The heat treatment in step I-2 is preferably performed at a treatment temperature of 100-200°C for a treatment time of 0.1 seconds to 2 minutes. Since the liquid conjugated diene rubber contained in the aqueous adhesive has reactive multiple bonds, heat treatment in the presence of oxygen is preferably performed at a temperature below 240°C, and more preferably below 200°C. If the heat treatment temperature is within the aforementioned range, the amount of reactive multiple bonds in the liquid conjugated diene rubber will not decrease, thus improving adhesion. Furthermore, it also inhibits fiber deterioration and improves coloring and other quality aspects.

[0087] [Elastomer Products] The elastomeric articles of the present invention are not particularly limited as long as they use the aforementioned reinforcing fibers. Among them, considering the excellent adhesion of the aforementioned reinforcing fibers to rubber, elastomeric articles having the aforementioned reinforcing fibers and a rubber layer are particularly preferred. From the viewpoint of maintaining the shape of the rubber, the reinforcing fibers used in the aforementioned elastomeric articles are preferably used as woven or knitted fabrics containing at least a portion of the reinforcing fibers, and more preferably as laminates consisting of a reinforcing layer and a rubber layer made of woven or knitted fabrics containing at least a portion of the reinforcing fibers.

[0088] The aforementioned elastomer products can be used, for example, as components of rubber products such as tires for automobiles, belts for conveyor belts, timing belts, hoses, and vibration damping rubber, and are more preferably used as tires, belts, or hoses. As for the aforementioned automobile tires, they can be used in various components made of composite materials of reinforcing fibers and rubber layers, such as belts, tire cords, buffer layers, and bead inner bands. As described above, the hose can be used for conveying various fluids in various applications, such as a fluid conveying hose suitable for automobiles, and particularly preferably a liquid fuel hose for automobiles, a brake fluid hose for automobiles, a hydraulic hose for construction machinery or agricultural machinery, an oil delivery hose and a refrigerant hose, and even more preferably a brake fluid hose for automobiles.

[0089] The aforementioned elastomer product is preferably formed using a rubber composition containing the aforementioned reinforcing fibers and admixtures commonly used in the rubber industry. There are no particular limitations on rubber components, and examples include NR (natural rubber), IR (polyisoprene rubber), BR (polybutadiene rubber), SBR (styrene-butadiene rubber), NBR (nitrile rubber), EPM (ethylene-propylene copolymer rubber), EPDM (ethylene-propylene-non-conjugated diene copolymer rubber), IIR (butyl rubber), halogenated butyl rubber, CR (chloropine rubber), CSM (chlorosulfonated polyethylene), and CPE (chlorinated polyethylene rubber). Among these, EPDM rubber, NR, SBR, and NBR are more suitable. One of these rubber components can be used alone, or two or more can be used in combination. For hose applications, EPDM rubber or NBR is more suitable.

[0090] In addition to the aforementioned rubber components, the aforementioned rubber composition may further contain fillers. Examples of such fillers include inorganic fillers such as carbon black, silica, clay, mica, calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, titanium dioxide, glass fiber, fibrous fillers, and glass balloons; and organic fillers such as resin particles, wood flour, and cork flour. By including such fillers in the rubber composition, physical properties such as mechanical strength, heat resistance, and weather resistance can be improved, hardness can be adjusted, and the rubber volume can be increased. From the perspective of improving physical properties such as mechanical strength, carbon black and silica are preferred among the aforementioned fillers.

[0091] Examples of carbon blacks mentioned above include furnace black, channel black, thermal black, acetylene black, and Ketjen black. From the viewpoint of improving crosslinking speed or mechanical strength, furnace black is preferred among these carbon blacks. The average particle size of the aforementioned carbon black is preferably 5-100 nm, more preferably 5-80 nm, and even more preferably 5-70 nm. Furthermore, the average particle size of the aforementioned carbon black can be obtained by measuring the diameter of the particles using a transmission electron microscope and calculating its average value.

[0092] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these silicas, wet silica is preferred. The average particle size of the aforementioned silica is preferably 0.5~200nm, more preferably 5~150nm, and even more preferably 10~100nm. Furthermore, the average particle size of the aforementioned silica can be obtained by measuring the diameter of the particles using a transmission electron microscope and calculating its average value.

[0093] In the aforementioned rubber composition, the content of the aforementioned filler is preferably 20 to 150 parts by mass, more preferably 25 to 130 parts by mass, and even more preferably 25 to 110 parts by mass, relative to 100 parts by mass of the aforementioned rubber component. Furthermore, when using fillers other than silica and carbon black as the aforementioned fillers, their content relative to 100 parts by weight of the aforementioned rubber component is preferably 20 to 120 parts by weight, more preferably 20 to 90 parts by weight, and even more preferably 20 to 80 parts by weight. These fillers can be used alone or in combination with two or more types.

[0094] The aforementioned rubber composition may further contain a crosslinking agent for crosslinking the aforementioned rubber components. 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. One such crosslinking agent may be used alone, or two or more may be used in combination. From the viewpoint of the mechanical properties of the crosslinked product, the aforementioned crosslinking agent is typically contained in amounts of 0.1 to 10 parts by mass relative to 100 parts by mass of the aforementioned rubber components, preferably 0.5 to 10 parts by mass, and more preferably 0.8 to 5 parts by mass.

[0095] When the aforementioned rubber composition contains sulfur or sulfur compounds as a crosslinking agent for crosslinking (vulcanizing) the aforementioned rubber composition, it may further contain a vulcanization accelerator. Examples of such vulcanization accelerators include guanidine compounds, sulfenamide compounds, thiazole compounds, thiuram compounds, thiourea compounds, dithiocarbamate compounds, aldehyde-amine compounds, aldehyde-amine compounds, imidazoline compounds, and xanthate compounds. One of these vulcanization accelerators may be used alone, or two or more may be used in combination. Relative to 100 parts by weight of the aforementioned rubber composition, the aforementioned vulcanization accelerator is typically contained in 0.1 to 15 parts by weight, preferably 0.1 to 10 parts by weight.

[0096] When the aforementioned rubber composition contains sulfur or sulfur compounds as a crosslinking agent for crosslinking (vulcanizing) the aforementioned rubber composition, it may further contain a vulcanizing aid. Examples of such vulcanizing aids include fatty acids such as stearic acid, metal oxides such as zinc oxide, and fatty acid metal salts such as zinc stearate. One such vulcanizing aid may be used alone, or two or more may be used in combination. Relative to 100 parts by weight of the aforementioned rubber composition, the aforementioned vulcanizing aid typically comprises 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight.

[0097] When the aforementioned rubber composition contains silica as a filler, it is preferable to further contain a silane coupling agent. Examples of such silane coupling agents include thioether compounds, mercapto compounds, ethylene compounds, amino compounds, epoxypropoxy compounds, nitro compounds, and chlorine compounds. These silane coupling agents can be used alone or in combination of two or more. The aforementioned silane coupling agent preferably contains 0.1 to 30 parts by weight relative to 100 parts by weight of silica, more preferably 0.5 to 20 parts by weight, and even more preferably 1 to 15 parts by weight. If the content of the silane coupling agent is within the aforementioned range, the dispersibility, coupling effect, and reinforcing properties are improved.

[0098] The aforementioned rubber composition, without impairing the effects of the present invention, aims to improve processability, flowability, etc., and may, as needed, contain silicone oil, aromatic oil, TDAE (treated distilled aromatic extracts), MES (mild extracted solvents), RAE (residual aromatic extracts), paraffin oil, cycloalkanes, and other processing oils, as well as aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, C9 resins, rosin resins, coumarone-indene resins, phenolic resins, and other resin components as softeners. When the aforementioned rubber composition contains the above-mentioned processing oil as a softener, its content is preferably less than 50 parts by weight relative to 100 parts by weight of the aforementioned rubber composition.

[0099] The aforementioned rubber composition, without impairing the effects of the present invention, aims to improve weather resistance, heat resistance, and oxidation resistance. As needed, it may also contain additives such as anti-aging agents, waxes, antioxidants, lubricants, light stabilizers, scorch inhibitors, processing aids, pigments or colorants, flame retardants, antistatic agents, matting agents, anti-blocking agents, ultraviolet absorbers, release agents, foaming agents, antibacterial agents, mildew inhibitors, and fragrances. Examples of antioxidants include hindered phenolic compounds, phosphorus compounds, lactone compounds, and hydroxyl compounds. Examples of anti-aging agents include amine-ketone compounds, imidazole compounds, amine compounds, phenolic compounds, sulfur compounds, and phosphorus compounds. These additives may be used individually or in combination of two or more.

[0100] As a method for manufacturing the aforementioned elastomer product, for example, the aforementioned reinforcing fiber can be embedded in the aforementioned unvulcanized rubber composition, and the rubber composition can be vulcanized to allow the fiber and rubber components to be bonded together through the aforementioned bonding component, thereby obtaining the elastomer product.

[0101] For example, a brake fluid hose for automobiles may have an inner rubber component and an outer rubber component, with a reinforcing layer made of one or two layers of the aforementioned reinforcing fibers between the inner and outer rubber components. Examples of rubber components constituting the inner and outer rubber components include those mentioned above. Examples of rubber components constituting the inner rubber component include EPDM and SBR, while examples of rubber components constituting the outer rubber component include EPDM and CR. The aforementioned reinforcing layer system can be formed by weaving reinforcing fibers. As a method for manufacturing the aforementioned brake fluid hose, a reinforcing layer (first reinforcing layer) woven with the aforementioned reinforcing fibers is formed on the outer surface of the inner rubber component. When forming two reinforcing layers, an intermediate rubber layer can be formed on the outer surface of the first reinforcing layer, and a reinforcing layer (second reinforcing layer) woven with the aforementioned reinforcing fibers can be formed on the outer surface of the intermediate rubber component. Furthermore, it can be manufactured by forming an outer rubber component on the outer surface of the reinforcing layer (first reinforcing layer or second reinforcing layer) and then vulcanizing it. The vulcanization temperature can be appropriately selected according to the type of materials used in each layer of the brake fluid hose. However, from the perspective of inhibiting the deterioration of rubber and reinforcing fibers and improving the adhesion between rubber and reinforcing fibers, it is preferable to be below 200°C. [Example]

[0102] The present invention will now be described in more detail by way of examples, etc., but the present invention is not limited to these examples.

[0103] For liquid acrylonitrile-butadiene rubber (1) (hereinafter also referred to as "liquid NBR (1)"; trade name "Hypro 1300X18 CTBNX", with a monomer content of approximately 21 mol% derived from acrylonitrile, manufactured by HUNTSMAN), liquid acrylonitrile-butadiene rubber (2) (hereinafter also referred to as "liquid NBR (2)"; trade name "Hypro 1300X16 ATBN", with a monomer content of approximately 18 mol% derived from acrylonitrile, manufactured by HUNTSMAN), and liquid polyisoprene rubber (hereinafter also referred to as "liquid IR"; trade name "LIR-410", manufactured by KURARAY), the following physical properties were measured. The results are shown in Table 1.

[0104] <Methods for determining weight-average molecular weight, number-average molecular weight, and molecular weight distribution> The Mw, Mn, and Mw / Mn ratios of liquid conjugated diene rubbers were determined using GPC (gel permeation chromatography) as conversion values ​​to standard polystyrene. The apparatus and conditions for the determination are as follows. • Device: Tosoh Corporation's GPC device "GPC8020" • Separation string: Tosoh Corporation "TSKgel G4000HXL" • Detector: Tosoh Corporation "RI-8020" • Eluent: Tetrahydrofuran • Eluent flow rate: 1.0 ml / min • Sample concentration: 5 mg / 10 ml • Column temperature: 40℃

[0105] <Methods for determining melt viscosity> The melt viscosity of liquid conjugated diene rubber at 38°C was determined using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

[0106] <Methods for Determining Glass Transfer Temperature> 10 mg of liquid conjugated diene rubber was collected in an aluminum pan and the thermal analysis chromatogram was determined by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min. The peak value of the DDSC was taken as the glass transition temperature.

[0107] <Average number of hydrogen-bonded functional groups per molecule> The average number of hydrogen-bonded functional groups per molecule of liquid conjugated diene rubber is calculated from the equivalent (g / eq) of hydrogen-bonded functional groups of modified liquid conjugated diene rubber and the number average molecular weight Mn converted from styrene, using the following formula. Average number of hydrogen-bonded 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 conjugated diene as needed)] / (equivalent number of hydrogen-bonded functional groups) Furthermore, the method for calculating the equivalent of hydrogen-bonded functional groups can be appropriately selected according to the type of hydrogen-bonded functional group.

[0108] The average number of hydrogen-bonded functional groups per molecule of maleic monomethyl ester modified liquid conjugated diene rubber is calculated by determining the acid value of the maleic monomethyl ester modified liquid conjugated diene rubber and then calculating the equivalent number (g / eq) of hydrogen-bonded functional groups from the acid value. After washing the modified sample four times with methanol (5 mL for 1 g of sample), removing impurities such as antioxidants, the sample was dried under reduced pressure at 80 °C for 12 hours. 180 mL of toluene and 20 mL of ethanol were added to and dissolved in 3 g of the modified sample. The solution was then neutralized and titrated with a 0.1 N potassium hydroxide ethanol solution. The acid value was determined using the following formula. Acid value (mgKOH / g) = (AB) × F × 5.611 / S A: The volume (mL) of 0.1N potassium hydroxide ethanol solution required for neutralization. B: Volume (mL) of 0.1N potassium hydroxide ethanol solution dropped into the blank sample (without the sample). F: Valence of 0.1N potassium hydroxide in ethanol solution S: Mass of the sample after weighing (g)

[0109] Based on the acid value, the mass of hydrogen-bonded functional groups per 1g of maleic monomethyl ester-modified liquid conjugated diene rubber is calculated using the following formula. Furthermore, the mass of the polymer backbone (excluding functional groups) per 1g of maleic monomethyl ester-modified liquid conjugated diene rubber is calculated. Then, the equivalent amount (g / eq) of the hydrogen-bonded functional groups is calculated using the following formula. [Mass of hydrogen-bonded functional groups per 1g] = [Acid value] / [56.11] × [Molecular weight of hydrogen-bonded functional groups] / 1000 [Mass of polymer backbone per 1g] = 1 - [Mass of hydrogen-bonded functional groups per 1g] [Equivalent weight of hydrogen-bonded functional groups] = [Mass of polymer backbone per 1g] / ([Mass of hydrogen-bonded functional groups per 1g] / [Molecular weight of hydrogen-bonded functional groups]) Furthermore, the average number of hydrogen-bonded functional groups per molecule of liquid NBR (1) and liquid NBR (2) was not determined as described above, but was based on the catalog value.

[0110] [Table 1] liquid conjugation Diene series rubber Mw (×10 3) Mn (×10 3) molecular weight distributed Mw / Mn At 38℃ melt viscosity (Pa·s) Glass Transfer temperature (°C) hydrogen bonding Functional groups Each molecule Average hydrogen bonding Functional cardinality (number) Liquid NBR(1) 4.6 3.4 1.4 250 -46 carboxyl 2.4 Liquid NBR(2) 4.9 3.8 1.3 145 -51 amino 1.8 Liquid IR 32.4 28.0 1.2 430 -59 Monomethyl maleate 10.0 NBR stands for "acrylonitrile-butadiene rubber", and IR stands for "isoprene rubber".

[0111] <Emulsion Preparation> Modification Example 1: Modification of emulsion (A-1) of liquid NBR (1) For 75g of liquid NBR (1), add 75g of adipate as oil (trade name "ADK Cizer PN-7160", vapor pressure = 1×10⁻⁷ Pa or less, ADEKA (stock)) and stir until evenly mixed. Add 9g of nonionic surfactant (HLB value = 13.8, trade name "Adeka Tol TN100", ADEKA Corporation), and stir for 5 minutes. Next, while stirring, 341g of 0.06mol / L sodium hydroxide aqueous solution was added little by little to obtain an emulsion (A-1) of liquid NBR and oil mixture.

[0112] Modification Example 2: Modification of emulsion (A-2) of liquid NBR (2) For 75g of liquid NBR (2), add 75g of adipate as oil (trade name "ADK Cizer PN-7160", vapor pressure = 1×10⁻⁷ Pa or less, ADEKA (stock)) and stir until evenly mixed. Add 9g of nonionic surfactant (HLB value = 13.8, trade name "Adeka Tol TN100", ADEKA Corporation), and stir for 5 minutes. Next, while stirring, 341g of 0.06mol / L sodium hydroxide aqueous solution was added little by little to obtain an emulsion (A-2) of liquid NBR and oil mixture.

[0113] Modulation Example 3: Modulation of liquid IR emulsion (A-3) For 50g of liquid IR, add 100g of 2-ethylhexanoic acid triglyceride (trade name "Exceparl TGO", vapor pressure = 1×10⁻⁷ Pa or less, manufactured by Kao Corporation) as oil, and stir until evenly mixed. Add 9g of nonionic surfactant (HLB value = 12.4, trade name "Adeka Tol PC-8", ADEKA Corporation), and stir for 5 minutes. Next, 341g of 0.06mol / L sodium hydroxide aqueous solution was added little by little while stirring, and an emulsion (A-3) of a mixture of liquid NBR and oil was obtained.

[0114] Preparation Example 4: Preparation of emulsion (A-4) of liquid IR For 150 g of liquid IR, 9 g of nonionic surfactant (HLB value = 12.4, trade name “Adeka Tol PC-8”, ADEKA (stock)) was added and stirred for 5 min. Next, 341g of 0.06mol / L sodium hydroxide aqueous solution was added little by little while stirring, and an emulsion (A-4) of a mixture of liquid NBR and oil was obtained.

[0115] <Example 1> The crosslinker (B) was prepared in such a manner as to become the composition described in Table 2. The aqueous linker was prepared by mixing it with the emulsion (A-1) prepared by the previous method. Secondly, after impregnating the polyvinyl alcohol (PVA) fibers (trade name “Kuralon 1239”, total fiber 1330dtex, single yarn fiber 6.65dtex, KURARAY (strand)) in the obtained aqueous binder), the liquid was squeezed by roller. Then, by drying the resulting fibers at 115°C for 30 seconds and further heat-treating at 150°C for 30 seconds, the PVA fibers having an adjoining layer constituted with an aqueous adhesive were prepared (PVA fibers with an adjoining layer on the surface of the fiber) were prepared at a number of 80 T / m.

[0116] “Mekanate SU-268A” made by Mingsei Chemical Industries (shares) was used as the isocyanate resin and “Denacol EX-512” made by Nagase chemteX (shares) was used as the epoxy resin.

[0117] For the aqueous sequestrant obtained in Example 1, the content of the organic solvent and the viscosity at 25°C were determined by the following method. Also, the assays were similarly performed for the aqueous sequestrants obtained in the latter embodiments 2, 3, 5, 7, 8 and comparative examples 1 and 2 . The results are shown in Table 2 .

[0118] [Content of organic solvent in aqueous binder] The organic solvent content in the water-based adhesive was analyzed by gas chromatography (Shimadzu Corporation, GC-14B; column: Chemical Inspection Association, G-100).

[0119] [Viscosity of water-based adhesives at 25°C] The viscosity of the resulting water-based adhesive at 25°C was measured using a Brookfield viscometer (Type B viscometer). The rotor and rotational speed were set close to full scale during the measurement. The results are shown in Table 2.

[0120] <Examples 2-6 and Comparative Examples 1-3> Except for changing the composition of the water-based adhesive as described in Table 2, the reinforcing fibers were made in the same manner as in Example 1. Furthermore, Comparative Example 3 was prepared without the use of surfactants (without preparing an oil droplet emulsion (A) in water) to form an aqueous adhesive in the manner described in Table 2.

[0121] <Examples 7 and 8> The reinforcing fibers were prepared in the same manner as in Example 4, except that nylon 6 fibers (total fineness 1400 dtex, single yarn fineness 6.86 dtex) or PET fibers (fineness 1440 dtex, single yarn fineness 7.20 dtex) were used instead of PVA fibers.

[0122] [Table 2] Blending of water-based adhesives (parts by weight) At 25℃ Water-based adhesives viscosity [mPa·s] Organic solvent content [quality%] Oil droplet emulsion in water (A) Aqueous solution or aqueous dispersion of crosslinking agent (B) Oil droplets in water Emulsion (A) Types water Liquid conjugated diene rubber Oil surfactants Liquid NBR Liquid IR adipic acid ester 2-Ethylhexanoic acid triethylhexanoate Glycerides Nonionic interface Surfactant water Isocyanates resin Epoxy resin Example 1 A-1 6.18 1.25 - 1.25 - 0.15 88.68 1.79 0.70 9.1 0.60 2 A-1 9.89 2.00 - 2.00 - 0.24 84.87 0.72 0.28 13.5 0.24 3 A-1 2.47 0.50 - 0.50 - 0.06 92.48 2.87 1.12 8.9 0.96 4 A-2 6.18 1.25 - 1.25 - 0.15 88.68 1.79 0.70 - 0.60 5 A-3 11.39 - 1.33 - 2.67 0.24 83.38 0.72 0.28 11.3 0.24 6 A-4 11.39 - 4.00 - - 0.24 83.38 0.72 0.28 - 0.24 7 A-3 11.39 - 1.33 - 2.67 0.24 83.38 0.72 0.28 11.3 0.24 8 A-3 11.39 - 1.33 - 2.67 0.24 83.38 0.72 0.28 11.3 0.24 Comparative example 1 A-1 12.37 2.50 - 2.50 - 0.30 82.33 - - 16.4 0.00 2 A-3 12.37 - 1.67 - 3.33 0.30 82.33 - - 12.8 0.00 3 - 2.53 0.50 - 0.50 - 0.00 92.48 2.87 1.12 - 0.96

[0123] <Amount of water-based adhesive attached to 100 parts by weight of fiber (parts by weight)> Before applying the water-based adhesive, the fibers were sampled at a predetermined length, and their mass was measured after being treated at 105°C for 4 hours. Secondly, the fibers treated with the water-based adhesive were sampled at the same length and their mass was measured after being treated at 105°C for 4 hours. The amount of water-based adhesive adhering to 100 parts by weight of fiber is calculated as [mass after treatment – ​​mass before treatment] × 100 / [mass before treatment]. Furthermore, in Table 2, the content (mass %) of each component in the water-based adhesive is calculated from the mass ratio of the solid components in the adhesive.

[0124] <Determination of Rubber Adhesion> For the reinforcing fibers obtained in Examples 1-8 and Comparative Examples 1-3, evaluation sheets were prepared using the following method, and then the force (N / 25.4 mm) required to peel the reinforcing fiber from the rubber T-shaped adhesive was measured as an evaluation of the rubber adhesion. The results are shown in Table 3. The higher the value of the rubber adhesion evaluation result, the greater the adhesion between the reinforcing fiber and the rubber. Furthermore, the evaluation sheet is prepared as follows.

[0125] • Evaluation of the production of thin films The reinforcing fibers prepared in Examples 1-3, 6 and Comparative Examples 1, 3 were fixed side-by-side on a masking tape in a bamboo curtain-like manner, with the reinforcing fibers not overlapping each other. These fibers were then overlapped with an uncured rubber composition (hereinafter also referred to as "NBR uncured rubber") prepared using NBR (manufactured by JSR Corporation, "JSR N230S") according to the following blending composition (width 25.4 mm, length 240 mm) (the overlap length between the reinforcing fibers and the NBR uncured rubber is 190 mm). Next, evaluation sheets were prepared by pressure vulcanization for 30 minutes at 150°C and a pressure of 20 kg / cm². Furthermore, Examples 4, 5, 7, 8 and Comparative Example 2 were prepared using the same method as in Example 1, except that NR / SBR uncured rubber was used instead of NBR uncured rubber.

[0126] (The blending composition of uncured NBR rubber) NBR: 100 parts by weight Filler (carbon black): 70 parts by weight Plasticizer (adipate ether ester based): 20 parts by weight Crosslinking agent (sulfur powder): 0.7 parts by weight Vulcanizing aids (zinc oxide, stearic acid): 5 parts by weight Vulcanization accelerator (sulfinamide-based, thiazole-based): 3.0 parts by weight Inorganic additives (kaolin clay, calcium carbonate): 21 parts by weight

[0127] (Blending composition of NR / SBR uncured rubber) NR: 50 parts by weight SBR: 50 parts by weight Filler (carbon black): 45 parts by weight Softener (paraffin-based processing oil): 5 parts by weight Crosslinking agent (sulfur powder): 2.4 parts by weight Vulcanizing aids (two types of zinc oxide, stearic acid): 7 parts by weight Vulcanization accelerator (thiazole-based, thiuram-based): 2.0 parts by weight

[0128] <Step-by-step contamination> In Examples 1-8 and Comparative Examples 1-3, the mixture was applied to each fiber as described in each example. After winding 5 kg of reinforcing fiber, the degree of contamination (gum-up) of the retaining roller through which the reinforcing fiber passed was determined using the following evaluation criteria. Benchmark G (good): There is little or no roller contamination caused by sticking, and there are no problems with yarn making operability. N (normal): Although roller contamination caused by sticking is observed, there are no major problems with yarn-making operability. B (bad): The roller contamination caused by sticking is significant, resulting in single yarns falling off and curling during yarn making, which causes problems with yarn making operability.

[0129] [Table 3] Characteristics of water-based adhesives Fiber type Water-based adhesives Adhesion amount [Quantity] (*1) Rubber type evaluate Oil droplet emulsion in water (A) Types interface Surfactant Crosslinking agent Then force [N / 25.4mm] Step-by-step contamination Example 1 A-1 contain contain PVA 2.0 NBR 36 G 2 A-1 PVA 2.1 NBR 33 G 3 A-1 PVA 1.9 NBR 36 N 4 A-2 PVA 2.1 NR / SBR 40 G 5 A-3 PVA 2.3 NR / SBR 48 N 6 A-4 PVA 2.0 NBR 36 G 7 A-3 Nylon 6 2.2 NR / SBR 50 G 8 A-3 PET 2.1 NR / SBR 31 G Comparative example 1 A-1 contain Does not contain PVA 2.0 NBR 14 G 2 A-3 PVA 1.9 NR / SBR 9 G 3 - Does not contain contain PVA 3.7 NBR 16 B *1: The amount of water-based adhesive adhering to 100 parts by weight of fiber [parts by weight]

[0130] As can be clearly seen from the results of the examples and comparative examples, a water-based adhesive with excellent adhesion to fibers and rubber can be obtained according to the present invention. Furthermore, particularly according to the present invention, fibers and rubber can be firmly bonded even without the use of resorcinol or formaldehyde.

[0131] none

Claims

1. A water-based adhesive for bonding fibers and elastomers, characterized in that it comprises: an oil droplet emulsion (A) containing a liquid conjugated diene rubber and a surfactant, an aqueous solution or aqueous dispersion (B) of a crosslinking agent, and an oil having a vapor pressure of less than 10 Pa at 20°C.

2. The water-based adhesive of claim 1, wherein the melt viscosity of the liquid conjugated diene rubber measured at 38°C is less than 4,000 Pa·s.

3. The water-based adhesive as claimed in claim 1 or 2, wherein the oil-based adhesive is contained in the oil droplet emulsion (A) in the water.

4. The water-based adhesive as claimed in claim 1 or 2, wherein the crosslinking agent is selected from at least one of epoxy resin and isocyanate resin.

5. The water-based adhesive as requested in item 1 or 2, wherein the content of organic solvent in the water-based adhesive is less than 1.0% by mass.

6. A reinforcing fiber formed by attaching an aqueous adhesive of any one of claims 1 to 5 to the fiber.

7. The reinforcing fiber of claim 6, wherein the fiber is selected from at least one fiber selected from polyamide fibers, polyvinyl alcohol fibers, polyester fibers and regenerated cellulose fibers.

8. The reinforcing fiber as claimed in claim 6 or 7, wherein the amount of the aqueous adhesive attached to the fiber is 0.01 to 10 parts by weight relative to 100 parts by weight of the fiber used as raw material.

9. An elastomer article which uses the reinforcing fiber of any one of claims 6 to 8.

10. The elastomeric article of claim 9, wherein the elastomeric article is a tire, belt or hose.