Adhesive composition, bonded structure and belt

Abstract

To obtain an adhesive composition showing excellent adhesiveness, especially an adhesive composition having excellent adhesiveness at room temperature and high temperatures in bonding various surface-treated fibers and rubber and having excellent tensile properties and tear properties and further to obtain a bonded structure and a belt having excellent interlayer adhesiveness by using such an adhesive composition.SOLUTION: There is provided an adhesive composition for bonding rubber and fibers, which contains a polyoxazoline compound and an aqueous polymer dispersion, wherein the rubber includes rubber containing an olefin compound having a carboxyl group. There is provided a bonded structure comprising a fiber layer, a layer of the adhesive composition and a layer of rubber in this order. There is provided a belt including the bonded structure.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an adhesive composition, an adhesive structure, and a belt. [Background technology]

[0002] Rubber products such as belts are reinforced with fibers. For example, polyester fibers such as polyethylene terephthalate fibers and polyamide fibers such as aramid fibers are used as reinforcing materials in the form of filaments, cords, cables, woven cords, canvas, etc.

[0003] However, these reinforcing materials have poor adhesion to rubber, and attempts have been made to improve adhesion by applying a treatment consisting of a resorcinol-formalin condensate and rubber latex to the surface of the reinforcing material. In bonding these synthetic fibers to rubber, various adhesive compositions have been used to improve the adhesion between rubber and synthetic fibers.

[0004] In recent years, from the viewpoint of the environment and the like, there has been a demand for a method for bonding rubber and fibers without using formaldehyde or components derived from formaldehyde in the production of rubber products. Adhesive compositions for bonding rubber and fibers without using a resorcinol-formalin condensate have been proposed so far.

[0005] However, when the adhesive compositions used to date are used to bond fibers and rubber in the manufacture of belts, particularly power transmission belts, there have been problems with the rubber and fibers peeling off during the manufacture and use of the belt due to the adhesive strength at room temperature and high temperature, tensile strength, etc. Furthermore, the adhesive strength is also unsatisfactory, and it has been difficult to achieve both formaldehyde-free and high adhesive strength in the manufacture of rubber products.

[0006] Patent Documents 1 and 2 describe adhesive compositions that contain a polymer containing a 2-oxazoline group and a rubber latex and are used for bonding rubber to fibers. However, this adhesive composition contains a condensate of resorcin and formalin, and there is no mention of blending resorcin or using a rubber containing an olefin compound having a carboxyl group as the rubber.

[0007] Patent Document 3 describes an adhesive composition that contains a polymer containing a 2-oxazoline group and is used for bonding rubber to fibers. However, there is no description of compounding resorcin or rubber latex with this adhesive composition, or of using a rubber containing an olefin compound having a carboxyl group as the rubber.

[0008] Patent Document 4 describes an adhesive composition used for bonding rubber to fibers, which contains a polymer containing a 2-oxazoline group and a rubber latex. However, there is no description of compounding resorcin with this adhesive composition, or of using a rubber containing an olefin compound having a carboxyl group as the rubber. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 5-339552 [Patent Document 2] JP 2000-248254 A [Patent Document 3] JP 2001-98245 A [Patent Document 4] JP 2013-64037 A Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to obtain an adhesive composition for bonding fibers and rubber that exhibits excellent adhesive properties even without containing formalin or a component derived from formalin. Another object of the present invention is to obtain an adhesive structure having excellent adhesion between fiber and rubber, and a belt including the adhesive structure, by using such an adhesive composition. [Means for solving the problem]

[0011] As a result of intensive research aimed at solving the above problems, the present inventors have found that the above problems can be solved by the following adhesive composition, adhesive structure, and belt, and have thus completed the present invention. [1] An adhesive composition for bonding rubber to fibers, comprising resorcinol and / or a salt thereof, a polyoxazoline compound, and an aqueous polymer dispersion. [2] An adhesive composition for bonding rubber to a fiber, comprising a polyoxazoline compound and an aqueous polymer dispersion, wherein the rubber comprises a rubber containing an olefin compound having a carboxyl group. [3] The adhesive composition according to [1] or [2], wherein the polyoxazoline compound is a polymeric compound having two or more 2-oxazoline groups. [4] An adhesive structure comprising, in this order, a fiber layer, a layer of the adhesive composition according to any one of [1] to [3], and a rubber layer. [5] A belt comprising the adhesive structure according to [4]. Effect of the Invention

[0012] According to the present invention, it is possible to obtain an adhesive composition for bonding fibers and rubber that exhibits excellent adhesive properties even without containing formalin or a component derived from formalin. Furthermore, by using such an adhesive composition, the present invention can provide an adhesive structure having excellent adhesion between fiber and rubber, and a belt including the adhesive structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Adhesive composition] The adhesive composition of the present invention is an adhesive composition described below in (1) or (2). (1) An adhesive composition for bonding rubber to fibers, comprising resorcin and / or a salt thereof, a polyoxazoline compound, and an aqueous polymer dispersion. (2) An adhesive composition for bonding rubber to a fiber, comprising a polyoxazoline compound and an aqueous polymer dispersion, wherein the rubber comprises a rubber containing an olefin compound having a carboxyl group.

[0014] <Resorcin and / or its salt> Resorcinol is a compound represented by the following structural formula.

[0015] [ka]

[0016] The resorcin salt may be any salt used in forming an adhesive composition for rubber and fiber, and may be, for example, one or more salts selected from the group consisting of alkali metals such as sodium and potassium, alkaline earth metals such as calcium and magnesium, ammonium, organic amines such as triethylamine and triethanolamine, and basic amino acids such as lysine and arginine. In the present invention, one or more types selected from the group consisting of resorcin and / or salts thereof can be used.

[0017] Resorcin and / or a salt thereof (R) may be present in the adhesive composition in an unreacted state, or at least a portion of it may be reacted with the polyoxazoline compound (O) and present in the state of an initial condensate (RO). In the present invention, the initial condensate (RO) is preferably contained in the adhesive composition as an aqueous solution.

[0018] <Polyoxazoline compounds> The polyoxazoline compound is a compound having two or more oxazoline groups in the molecule. For example, it may be one or more selected from the group consisting of a bisoxazoline compound having two oxazoline groups, a trisoxazoline compound having three oxazoline groups, and a polymer compound having a 2-oxazoline group in the side chain and / or end of the polymer. The polyoxazoline compound may be synthesized and used, or a commercially available one may be used.

[0019] Examples of bisoxazoline compounds having two oxazoline groups include 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(5-methyl-2-oxazoline), 2,2'-bis(4,4'-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline), 2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline), 2,2'-bis(4-hexyl-2-oxazoline), and the like. 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2-oxazoline), 2,2'-p-phenylenebis(5-methyl-2-oxazoline), 2,2'-p-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(4- methyl-2-oxazoline), 2,2'-m-phenylenebis(5-methyl-2-oxazoline), 2,2'-m-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-o-phenylenebis(2-oxazoline), 2,2'-o-phenylenebis(4-methyl-2-oxazoline), 2,2'-o-phenylenebis(5-methyl-2-oxazoline), 2,2'-o-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline) phosphorus), 2,2'-ethylenebis(5-methyl-2-oxazoline), 2,2'-ethylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-tetramethylenebis(4-methyl-2-oxazoline), 2,2'-tetramethylenebis(5-methyl-2-oxazoline), 2,2'-tetramethylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-tetramethylenebis(5,5'-dimethyl-2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,Examples of the oxazoline include one or more selected from the group consisting of 2'-hexamethylene bis(4-methyl-2-oxazoline), 2,2'-hexamethylene bis(5-methyl-2-oxazoline), 2,2'-hexamethylene bis(4,4'-dimethyl-2-oxazoline), 2,2'-hexamethylene bis(5,5'-dimethyl-2-oxazoline), 2,2'-octamethylene bis(2-oxazoline), 2,2'-decamethylene bis(2-oxazoline), 2,2'-9,9'-diphenoxyethane bis(2-oxazoline), 2,2'-cyclohexylene bis(2-oxazoline), 2,2'-diphenylene bis(2-oxazoline), 1,4-bis[2-(5-phenyloxazolyl)]benzene, and bis(2-oxazolinylcyclohexane)sulfide. , An example of a trisoxazoline compound having three oxazoline groups is 2,2',2"-(1,3,5-phenylene)-tris(2-oxazoline).

[0020] Examples of the polymer compound having a 2-oxazoline group at a side chain and / or end of a polymer include one or more types selected from the group consisting of a homopolymer of a 2-oxazoline group-containing ethylenically unsaturated monomer, a copolymer obtained by copolymerizing a 2-oxazoline group-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer copolymerizable therewith, and a polymer obtained by graft polymerization of a 2-oxazoline group-containing ethylenically unsaturated monomer onto a polymer main chain.

[0021] Examples of the 2-oxazoline group-containing ethylenically unsaturated monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2-vinyl-4,4-dimethyl-2-oxazoline, 2-vinyl-4,4-diethyl-2-oxazoline, 2-vinyl-4,5-dimethyl-2-oxazoline, 2-vinyl-4,5-diethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and 2-isopropenyl-2-oxazoline. and 2-isopropenyl-4,4-dimethyl-2-oxazoline, 2-isopropenyl-4,4-diethyl-2-oxazoline, 2-isopropenyl-4,5-dimethyl-2-oxazoline, and 2-isopropenyl-4,5-diethyl-2-oxazoline.

[0022] The ethylenically unsaturated monomer copolymerizable with the 2-oxazoline group-containing ethylenically unsaturated monomer is not particularly limited as long as it does not react with the oxazoline group. For example, one or more selected from the group consisting of (meth)acrylic acid esters such as methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.; unsaturated nitriles such as (meth)acrylonitrile, etc.; unsaturated amides such as (meth)acrylamide, N-methylol (meth)acrylamide, etc.; vinyl esters such as vinyl acetate, vinyl propionate, etc.; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, etc.; α-olefins such as ethylene, propylene, etc.; halogenated vinyls such as vinyl chloride, vinylidene chloride, fluorides, etc.; α,β-unsaturated aromatic monomers such as styrene, α-methylstyrene, etc. may be mentioned.

[0023] A homopolymer of a 2-oxazoline group-containing ethylenically unsaturated monomer and a copolymer obtained by copolymerizing a 2-oxazoline group-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer copolymerizable therewith can be produced by various conventionally known polymerization methods, for example, a suspension polymerization method, a solution polymerization method, an emulsion polymerization method, etc. As a method for graft polymerizing the 2-oxazoline group-containing ethylenically unsaturated monomer to the polymer main chain, various conventionally known graft polymerization methods can be used. The polymer to be graft polymerized is not particularly limited. For example, one or more types selected from the group consisting of acrylic resin, polyester resin, polyether resin, polyamide resin, polyurethane resin, etc. can be mentioned.

[0024] The number average molecular weight of the polymer compound having an oxazoline group is not particularly limited, but is, for example, 500 to 2,000,000, preferably 1,000 to 1,000,000, and more preferably 10,000 to 100,000. Moreover, the oxazoline group equivalent (g solid / eq) of a polymer compound having an oxazoline group is, from the viewpoints of storage stability, adhesiveness, etc., 10 or more, preferably 50 or more, more preferably 100 or more, and 5000 or less, preferably 2000 or less, more preferably 1000 or less, and further preferably 750 or less. The oxazoline group equivalent refers to the weight of the compound per one oxazoline group, that is, the value calculated from the following formula. Oxazoline group equivalent = molecular weight / number of oxazoline groups per molecule

[0025] Examples of commercially available polymer compounds having a 2-oxazoline group at the side chain and / or end of the polymer include one or more types selected from the group consisting of aqueous solutions of 2-oxazoline group-containing polymer compounds such as Nippon Shokubai Co., Ltd.'s product names "Epocross WS-300," "Epocross WS-500," and "Epocross WS-700," and aqueous emulsions of 2-oxazoline group-containing polymer compounds such as Nippon Shokubai Co., Ltd.'s product names "Epocross K-2010E," "Epocross K-2020E," and "Epocross K-2030E."

[0026] The polyoxazoline compound is used in the form of, for example, an aqueous solution, an organic solvent solution, an aqueous dispersion, a liquid, a molten state, etc. In the present invention, it is preferable to use the polyoxazoline compound in the form of an aqueous solution or an aqueous dispersion from the viewpoints of the impact on the environment, compatibility with latex, etc.

[0027] In the present invention, the polyoxazoline compound is preferably a polymer compound having a main chain with an acrylic skeleton, a styrene-acrylic skeleton, or the like, and having a 2-oxazoline group at the side chain and / or at the end. For example, it is preferable to use the product names "Epocross WS-300", "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", and "Epocross K-2030E" of Nippon Shokubai Co., Ltd.

[0028] <Aqueous polymer dispersion> As the aqueous polymer dispersion, generally, what is called latex (L) can be used. (L) is not particularly limited, but for example, one or more selected from the group consisting of vinylpyridine-styrene-butadiene copolymer rubber (VP-SBR) latex, styrene-butadiene copolymer rubber (SBR) latex, polybutadiene rubber (BR) latex, chloroprene rubber (CR) latex, chlorosulfonated polyethylene rubber (CSM) latex, 2,3-dichlorobutadiene copolymer rubber (2,3-DCB) latex, nitrile butadiene rubber (NBR) latex, hydrogenated acrylonitrile butadiene methacrylic acid terpolymer (X-NBR) latex, etc. are listed. Among these, vinylpyridine-styrene-butadiene copolymer rubber (VP-SBR) is preferred.

[0029] <Content of each ingredient> In the adhesive composition for bonding rubber to fibers, which contains resorcin and / or a salt thereof, a polyoxazoline compound, and an aqueous polymer dispersion, the amount of each component is not particularly limited. For example, the amount of polyoxazoline compound (solid content) is 0.01 to 500 parts by mass, preferably 0.05 to 300 parts by mass, and more preferably 0.05 to 150 parts by mass, per part by mass of resorcin. If the content of polyoxazoline compound is less than 0.01 parts by mass, the adhesiveness may decrease. If the content of polyoxazoline compound is more than 500 parts by mass, the adhesiveness to a specific rubber may decrease. For example, the amount of the aqueous polymer dispersion (solid content) is 0.1 to 100 parts by mass, preferably 0.5 to 50 parts by mass, and more preferably 1 to 30 parts by mass, per part by mass of the polyoxazoline compound (solid content). If the amount of the aqueous polymer dispersion is less than 0.1 parts by mass, the adhesiveness may decrease. If the amount of the aqueous polymer dispersion is more than 50 parts by mass, the heat adhesiveness may decrease.

[0030] In an adhesive composition for bonding rubber and fibers, the adhesive composition comprises a polyoxazoline compound and an aqueous polymer dispersion, wherein the rubber comprises a rubber containing an olefin compound having a carboxyl group, and the amount of each component in the adhesive composition is not particularly limited. For example, the amount of the aqueous polymer dispersion (solid content) is 0.1 to 100 parts by mass, preferably 0.5 to 50 parts by mass, and more preferably 1 to 30 parts by mass, per part by mass of the polyoxazoline compound (solid content). If the amount of the aqueous polymer dispersion is less than 0.1 parts by mass, the adhesiveness may decrease. If the amount of the aqueous polymer dispersion is more than 50 parts by mass, the heat adhesiveness may decrease.

[0031] <Other additives> The adhesive composition of the present invention may contain one or more other additives that can be added to the adhesive composition, as necessary, such as one or more selected from the group consisting of auxiliaries, crosslinking agents, crosslinking auxiliaries / co-crosslinking agents, extenders, colorants, reinforcing agents, antioxidants, surfactants, softeners, plasticizers, compatibilizers, stabilizers, flame retardants, flame retardant auxiliaries, and tackifiers.

[0032] The auxiliary may be, for example, one or more selected from metal soaps, fatty acid amides, and the like. The crosslinking agent may be one or more selected from sulfur, thiuram compounds, benzotriazole compounds, disulfide compounds, peroxides, polyols, polyisocyanates, etc. Among these, one or more selected from sulfur, peroxides, etc. are preferred. Examples of the crosslinking auxiliary / co-crosslinking agent include polyfunctional monomers (unsaturated carboxylic acid metal salts (e.g., zinc (meth)acrylate, magnesium (meth)acrylate, etc.), dimaleimide compounds (phenylene dimaleimide, etc.), tri(meth)acrylate compounds (trimethylolpropane tri(meth)acrylate, etc.), triallyl compounds (triallyl isocyanurate, etc.), zinc oxide, polybutadiene, oximes, guanidines, etc. Among these, one or more types selected from unsaturated carboxylic acid metal salts, dimaleimide compounds, zinc oxide, etc. are preferred. The extender, colorant, and reinforcing agent may be one or more selected from carbon black, zinc oxide, silica, color pigments, and the like. The softening agent may be paraffin-based process oil. The amount of each of these "other additives" may be any amount within a range that does not adversely affect the properties of the adhesive composition of the present invention. For example, the amount of the crosslinking agent may be adjusted to 0.1 to 10.0 parts by mass, the amount of the organic peroxide as the crosslinking agent to 0.5 to 8.0 parts by mass, the amount of the co-crosslinking agent to 0.5 to 15 parts by mass, and the amount of the surfactant softener to 1.5 to 50 parts by mass, relative to 100 parts by mass of the adhesive composition.

[0033] <Method of manufacturing adhesive composition> The method for producing the adhesive composition is not particularly limited, and any method can be used as long as it is a method known as a method for producing an adhesive composition. For example, the composition can be produced by putting all the components into a container and mixing them with a device such as a mixer. Alternatively, the composition can be produced by mixing some of the components and then blending the remaining components.

[0034] The method for producing the adhesive composition containing resorcin and / or its salt, polyoxazoline compound, and aqueous polymer dispersion is not particularly limited, but may be, for example, a method in which resorcin is added to an aqueous solution or aqueous dispersion of a polyoxazoline compound while stirring, and then the mixture is stirred at room temperature to form an initial condensate, and then the mixture is mixed with an aqueous polymer dispersion (latex), and water is added as necessary, and the mixture is stirred at room temperature. Also, an adhesive composition containing a polyoxazoline compound and an aqueous polymer dispersion can be obtained by using a salt of resorcin in the same manner. The method for producing an adhesive composition containing a polyoxazoline compound and an aqueous polymer dispersion is not particularly limited, but examples thereof include a method in which an aqueous solution or aqueous dispersion of a polyoxazoline compound is mixed with an aqueous polymer dispersion (latex), water is added as necessary, and the mixture is stirred at room temperature. The solid content concentration of the adhesive composition of the present application is not particularly limited and can be, for example, 1 to 50 mass %, preferably 5 to 30 mass %, and more preferably 5 to 25 mass %.

[0035] <Method of using the adhesive composition> The adhesive composition is used to bond rubber and fibers by applying it to the bonding surfaces of the rubber and / or fibers and bringing them into contact, preferably under pressure and heat. The method for applying the composition to the rubber and / or fibers is not particularly limited, and any known method can be used. In the present invention, it is preferred to apply the adhesive composition to the fibers by a one-bath processing method or a two-bath processing method.

[0036] In the case of the one-bath treatment method, the various components are mixed to prepare an adhesive composition containing 5 to 25 mass % of the active ingredient, which is then attached to fibers by immersion, spraying, coating with a rag or the like, followed by heat treatment, adhesion to rubber, and heating and pressurization to produce a rubber product such as a belt. In the case of the two-bath processing method, the fiber is processed in the first bath and heat-treated at 70 to 240°C for 1 second to 10 minutes, then processed in the second bath, heat-treated, and bonded to rubber, which is then heated and pressurized to form a rubber product such as a belt. The first and second baths are, for example, (1) First bath: Resorcinol and / or its salt and initial condensation product of polyoxazoline compound Second bath: Aqueous polymer dispersion (latex) (2) First bath: A mixture of resorcinol and / or its salt and a polyoxazoline compound. Second bath: Aqueous polymer dispersion (latex) (3) First bath: Resorcinol and / or its salt and aqueous polymer dispersion (latex) Second bath: Polyoxazoline compound (4) First bath: Aqueous polymer dispersion (latex) Second bath: Polyoxazoline compound (5) First bath: Polyoxazoline compound Second bath: Aqueous polymer dispersion (latex) etc.

[0037] In the present invention, preferred are a method of immersing the fiber in the adhesive composition and a method of applying the adhesive composition to the fiber with a cloth, etc. The time for immersing the fiber in the adhesive composition can be 10 seconds or less, for example, 0.5 to 5 seconds, and after immersion, the fiber can be treated at 150 to 270°C for 15 to 600 seconds. When the adhesive composition is applied to the fibers, the amount of the adhesive composition applied is 0.01 to 10 parts by mass, preferably 0.1 to 8 parts by mass, and more preferably 0.5 to 6 parts by mass per 1 m of the fibers.

[0038] <Rubber> The rubber to be bonded to the fibers by the adhesive composition of the present invention is not particularly limited as long as it is made of a rubber composition containing a rubber component and rubber compounding ingredients. The rubber may be either vulcanized or unvulcanized rubber, with vulcanized rubber being preferred since it has excellent adhesive strength to vulcanized rubber.

[0039] The rubber component of the rubber composition may be either synthetic rubber and / or natural rubber. As the synthetic rubber, one or more types of diene rubber having a carbon-carbon double bond in the polymer main chain, non-diene rubber having no carbon-carbon double bond in the polymer main chain, or modified products of these rubbers can be used.

[0040] In the present invention, examples of synthetic rubbers include diene rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and styrene-butadiene-styrene rubber, olefin rubbers such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), ethylene-propylene-dicyclopentadiene rubber, ethylene-propylene-ethylidenenorbornene rubber (EPDM), ethylene-octene copolymer, and ethylene-butene copolymer, silicone rubber, and urethane rubber. In addition, modified products obtained by subjecting these rubbers to hydrogenation (hydrogenation) or modification by introducing various functional groups, for example, hydrogenated SBR, hydrogenated BR, hydrogenated acrylonitrile-butadiene rubber (H-NBR), and chlorosulfonated polyethylene rubber (CSM), can be used.

[0041] Examples of rubber compounding agents include olefin compounds having a carboxyl group, reinforcing materials, oils, processing aids, vulcanization accelerator aids, crosslinking agents, co-crosslinking agents, vulcanization accelerators, and antioxidants. In particular, when an adhesive composition containing a polyoxazoline compound and an aqueous polymer dispersion but not containing resorcin is used to bond rubber to fibers, it is necessary that the rubber contains a rubber containing an olefin compound having a carboxyl group.

[0042] <Olefin compounds having a carboxyl group> In the present invention, examples of the olefin compound having a carboxyl group include one or more compounds selected from the group consisting of a carboxylic acid having a (meth)acryloyloxy group, a carboxylic acid anhydride having a (meth)acryloyloxy group, a carboxylate having a (meth)acryloyloxy group, and an unsaturated fatty acid.

[0043] Examples of the carboxylic acid compound having a (meth)acryloyloxy group include one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, citraconic acid, dimethylmaleic acid, 2-ethyl-3-methylmaleic acid, 2-acryloyloxyethyl-succinic acid (light acrylate HOA-MS(N)), 2-acryloyloxyethylhexahydrophthalic acid (light acrylate HOA-HH(N)), 2-acryloyloxyethyl-phthalic acid (light acrylate HOA-MPL(N)), and 2-methacryloyloxyethyl-succinic acid (light ester HO-MS(N)).

[0044] Examples of the carboxylic acid compound anhydride having a (meth)acryloyloxy group include one or more selected from the group consisting of acrylic anhydride, methacrylic anhydride, maleic anhydride, citraconic anhydride, dimethylmaleic anhydride, 2-ethyl-3-methylmaleic anhydride, and the like.

[0045] Examples of the salt of a carboxylic acid compound having a (meth)acryloyloxy group include one or more types selected from the group consisting of various metal salts of the carboxylic acid compound having the (meth)acryloyloxy group (e.g., Li, Na, K, Mg, Ca, Zn, etc.).

[0046] Examples of unsaturated fatty acids include one or more selected from the group consisting of palmitoleic acid, petroselinic acid, oleic acid, elaidic acid, ricinoleic acid, linoleic acid, linoelaidic acid, linolenic acid, arachidonic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, docosatetraenoic acid, vaccenic acid, paulic acid, erucic acid, nervonic acid, and sapienic acid. Furthermore, one or more selected from the group consisting of (2-methyl-2-propenyl)succinic acid, nonenylsuccinic acid, 1-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, dodecenylsuccinic acid, octenylsuccinic acid, 1-cyclohexene-1,2-dicarboxylic acid anhydride, 4-cyclohexene-1,2-dicarboxylic acid anhydride, dodecenylsuccinic anhydride, octenylsuccinic anhydride, (2-methyl-2-propenyl)succinic anhydride, nonenylsuccinic anhydride, and the like can be used.

[0047] In the present invention, it is preferable to use at least one selected from the group consisting of carboxylic acids having (meth)acryloyloxy groups, carboxylic anhydrides having (meth)acryloyloxy groups, unsaturated fatty acids, and saturated fatty acids. For example, it is more preferable to use at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acryloyloxyethyl-succinic acid, 2-acryloyloxyethylhexahydrophthalic acid, 2-acryloyloxyethyl-phthalic acid, 2-methacryloyloxyethyl succinic acid, metal acrylates, and metal methacrylates.

[0048] The amount of the olefin compound having a carboxyl group is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component of the rubber composition, and is preferably 50 parts by mass or less, more preferably 20 parts by mass or less. When the content of the olefin compound having a carboxyl group exceeds 50 parts by mass or is less than 0.5 parts by mass, it may become difficult to form an adhesive composition layer, and the adhesive strength may decrease.

[0049] The reinforcing material may be short fiber, for example, one or more types selected from the group consisting of cellulose-based fine fiber, 6-nylon fiber, 6,6-nylon fiber, 4,6-nylon fiber, polyethylene terephthalate (PET) fiber, polyethylene naphthalate (PEN) fiber, para-aramid fiber, meta-aramid fiber, polyester fiber, etc. The diameter of the short fibers is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. The amount of the short fibers per 100 parts by mass of the rubber component of the rubber composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less.

[0050] Further, examples of the reinforcing material include carbon black, for example, one or more types selected from the group consisting of channel black, furnace black (SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, N-234, etc.), thermal black (FT, MT, etc.), acetylene black, etc. The amount of carbon black mixed is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 100 parts by mass or less, more preferably 50 parts by mass or less, per 100 parts by mass of the rubber component of the rubber composition.

[0051] The oil may be at least one selected from the group consisting of, for example, petroleum-based softeners, mineral oils such as paraffin wax, and vegetable oils such as castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, Japan wax, rosin, and pine oil. The content of the oil is, for example, 1.5 to 50 parts by mass per 100 parts by mass of the rubber component of the rubber composition.

[0052] The vulcanization accelerator may be, for example, one or more selected from the group consisting of metal oxides such as zinc oxide (zinc white) and magnesium oxide, metal carbonates, fatty acids and derivatives thereof, and the like. The content of the vulcanization accelerator aid is, for example, 5 to 15 parts by mass with respect to 100 parts by mass of the rubber component of the rubber composition.

[0053] The crosslinking agent may be one or more selected from the group consisting of sulfur and organic peroxides. The organic peroxide may be one or more selected from the group consisting of dialkyl peroxides such as dicumyl peroxide, peroxy esters such as t-butyl peroxyacetate, and ketone peroxides such as dicyclohexanone peroxide. The compounding amount of sulfur is, for example, 0.1 to 4.0 parts by mass per 100 parts by mass of the rubber component of the rubber composition, and the compounding amount of the organic peroxide is, for example, 0.5 to 8.0 parts by mass per 100 parts by mass of the rubber component of the rubber composition.

[0054] Examples of the co-crosslinking agent include one or more selected from the group consisting of 1,2-polybutadiene, oximes, guanidine, (meth)acrylate compounds (TAIC, maleimides, trimethylolpropane trimethacrylate, acrylates, etc.), and the like. The content of the co-crosslinking agent is, for example, 0.5 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

[0055] <Textile> There are no particular limitations on the type of fiber that is bonded to rubber by the adhesive composition of the present invention. It is composed of one or more types selected from the group consisting of monofilaments, woven fabrics, knitted fabrics, nonwoven fabrics, twisted yarns, nets, blinds, braided cords, combinations of one or more of these, etc. In the present invention, core wires, cloths (e.g., canvas), and nonwoven fabrics composed of monofilaments and / or twisted yarns are preferably used.

[0056] Examples of materials constituting the fibers include polyamide fibers (such as nylon 6 fibers, nylon 66 fibers, and nylon 46 fibers), polyester fibers (such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers), aramid fibers (such as para-aramid fibers and meta-aramid fibers), vinylon fibers, glass fibers, carbon fibers, and metal fibers (steel cords).

[0057] When a belt is constructed using the adhesive structure of the present invention, it is preferable to use, for example, a core wire made of twisted yarn or braided cord as the fiber layer. As the fiber constituting the twisted yarn, one or more types selected from the group consisting of polyamide fiber, polyester fiber, aramid fiber, vinylon fiber, glass fiber, carbon fiber, metal fiber, etc. are used. The diameter of the core wire is, for example, 0.5 to 2.5 mm, and the dimension between the centers of adjacent core wires in the belt cross section is, for example, 0.05 to 0.20 mm.

[0058] [Adhesive structure] The bonded structure of the present invention includes one or more fiber layers, one or more adhesive composition layers, and one or more rubber layers. The fiber layer constituting the bonded structure is not particularly limited as long as it is a layer composed of fibers. For example, it may be a layer composed of fibers that are bonded to rubber by the adhesive composition of the present invention. When a plurality of fiber layers are included, each fiber layer may be the same or different. Of the adhesive composition layers constituting the bonded structure, at least one adhesive composition layer bonding a fiber layer and a rubber layer needs to be composed of the adhesive composition of the present invention. The rubber layer constituting the bonded structure is not particularly limited as long as it is a layer composed of rubber. For example, it may be a layer composed of a rubber composition that is bonded to a fiber by the adhesive composition of the present invention. When a plurality of rubber layers are included, the rubber layers may be the same or different.

[0059] Between the fiber layer and the layer of the adhesive composition, and between the layer of the adhesive composition and the layer of the rubber, an arbitrary intermediate layer such as a primer layer containing an epoxy resin, an isocyanate resin, etc., a base treatment layer, a rubber paste layer, etc., may be provided as necessary. In the present invention, since the adhesive composition layer has good adhesion, it can be directly laminated to form an adhesive structure without providing the intermediate layer. Since the adhesive structure of the present invention is intended to be formalin-free, it is preferable that it does not contain a resorcinol-formalin (-latex) layer (RF(L) layer). In some cases, the RF(L) layer can be provided on the fiber layer.

[0060] The bonded structure of the present invention has at least a layer structure of rubber layer / adhesive composition layer / fiber layer. In addition, the fiber layer may be embedded in the layer of the adhesive composition to have a structure of rubber layer / adhesive composition layer / fiber layer / adhesive composition layer / rubber layer. In addition, the fiber layer may be provided on the front surface of the bonded structure, or may be provided on a part of the front surface. When the bonded structure of the present invention has a plurality of fiber layers and / or rubber layers, the layers may be provided in any order. For example, the bonded structure may have the following layer structure. (1) Rubber layer A / adhesive composition layer A / fiber layer A / adhesive composition layer B / rubber layer B (2) Rubber layer A / adhesive composition layer A / rubber layer B / adhesive composition layer B / fiber layer A / adhesive composition layer C / rubber layer C (3) Rubber layer A / adhesive composition layer A / fiber layer A / adhesive composition layer B / rubber layer B / adhesive composition layer C / fiber layer B / rubber layer C Here, the rubber layers A to C, the adhesive composition layers A to C, and the fiber layers A to B may be the same or different from each other. Furthermore, at least one of the adhesive composition layers A to C may be the adhesive composition of the present invention. Also, a fiber layer may be embedded in the layer of adhesive composition, for example having a structure of rubber layer A / adhesive composition layer / fiber layer / adhesive composition layer / rubber layer B.

[0061] The thickness of each of the fiber layer, adhesive composition layer, and rubber layer constituting the bonded structure of the present invention is not particularly limited, and can be set to any thickness depending on the application, etc. The thickness of the fiber layer may be, for example, 0.001 to 10.0 mm, and preferably 0.01 to 3.0 mm. The layer thickness of the adhesive composition can be, for example, from 0.001 to 3.0 mm, and preferably from 0.01 to 1.0 mm. The thickness of the rubber layer can be, for example, 0.01 to 500 mm, and preferably 0.05 to 300 mm.

[0062] [belt] The belt of the present invention includes the adhesive structure of the present invention and is wound around a pulley to transmit power. It may be any of a V-belt, a round belt, a toothed belt, a flat belt, and a V-ribbed belt. For example, the belt has an inner rubber layer constituting the pulley contact portion on the inner periphery side of the belt, a layer of the adhesive composition of the present invention (adhesive composition), a fiber layer, a layer of the adhesive composition, and a back rubber layer on the outer periphery side of the belt, in this order. The fiber layer can be composed of a cord on which the adhesive composition is provided so as to form a spiral having a pitch in the belt width direction. Also, a back reinforcing cloth may be provided instead of the back rubber layer.

[0063] The inner rubber layer and the back rubber layer are formed of a rubber composition in which an uncrosslinked rubber composition, which is prepared by mixing a rubber component with various rubber compounding agents, is heated and pressurized to crosslink the uncrosslinked rubber composition with a crosslinking agent. The rubber compositions forming the compressed rubber layer and the back rubber layer may be the same or different.

[0064] Examples of the rubber compositions forming the inner rubber layer and the back rubber layer include the rubber components and rubber compounding agents exemplified as those constituting the bonded structure of the present invention. In the present invention, the inner rubber layer and the back rubber layer may be made of the same rubber component.

[0065] The belt can be formed, for example, by the following method. (i) A rubber sleeve is placed on a cylindrical drum having a smooth surface, and an uncrosslinked rubber sheet for the back rubber layer and an uncrosslinked sheet for the adhesive composition are wound around the outer circumference of the rubber sleeve in that order to form a laminate. On top of that, a fiber layer having a layer of adhesive composition is spirally wound around a cylindrical inner mold, and then an uncrosslinked rubber sheet for the adhesive composition and an uncrosslinked rubber sheet for the inner rubber layer are wound around that in that order to form a laminated molded product.

[0066] (ii) The rubber sleeve with the laminated molded body is removed from the cylindrical drum, and the laminated molded body is set in a fitted state on the inner surface of the outer mold. Then, the inner mold is positioned inside the rubber sleeve set on the outer mold and sealed.

[0067] (iii) The outer mold is heated, and pressurized by injecting high-pressure air or the like into the sealed interior of the inner mold. The inner mold expands, and each uncrosslinked rubber sheet in the laminated molded body is compressed and enters the molding surface of the outer mold, and their crosslinking proceeds, and the fiber layer having the layer of the adhesive composition is integrated into a composite, and finally, a cylindrical belt slab is molded. The molding temperature of the belt slab can be, for example, 100 to 180°C, the molding pressure can be, for example, 0.5 to 2.0 MPa, and the molding time can be, for example, 10 to 60 minutes.

[0068] (iv) The pressure inside the inner mold is reduced to release the seal, and the belt slab molded between the inner mold and the outer mold via the rubber sleeve is removed. The belt slab is then cut into slices of a specified width and turned over to produce the belt. EXAMPLES

[0069] The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is not limited to the following examples. In the following, unless otherwise specified, "%" means "% by mass" and "parts" means parts by mass.

[0070] [Adhesive composition] <Example 1-1> 1.3 parts of resorcin, 15.5 parts of polyoxazoline compound, 100 parts of aqueous polymer dispersion, and 613.4 parts of water were mixed and stirred to produce adhesive composition A-1. In the obtained adhesive composition A-1, the molar ratio of resorcin (R) to polyoxazoline compound (O) was R / O=0.1, and the mass ratio of latex (L) to resorcin-polyoxazoline compound (RO) was L / RO=6.

[0071] <Examples 1-2 to 1-7; Comparative Example 1-1> Adhesive compositions A-2 to A-7 according to Examples 1-2 to 1-7 were produced by mixing and stirring the components according to the compositions shown in Table 1. In the obtained adhesive composition A-2, the mass ratio of the latex (L) to the polyoxazoline compound (O) was L / O=6. The components shown in Table 1 were mixed and stirred to produce an adhesive composition RFL according to Comparative Example 1-1.

[0072] [Table 1]

[0073] Polyoxazoline compound 1: Nippon Shokubai Co., Ltd., product name "Epocross WS-300" Polyoxazoline compound 2: Nippon Shokubai Co., Ltd., product name "Epocross WS-500" Polyoxazoline compound 3: Nippon Shokubai Co., Ltd., product name "Epocross WS-700" RF: RF liquid with a solid content of 3.04 parts obtained by mixing and reacting 41.69 parts of water, 0.21 parts of sodium hydroxide, 2.03 parts of resorcinol, and 2.15 parts of formaldehyde. Aqueous polymer dispersion: Styrene-butadiene-vinylpyridine copolymer latex (solid content 41.5 wt%) The amounts of polyoxazoline compounds 1 to 3, RF, and aqueous polymer dispersion in Table 1 are solid contents. The amount of water in Table 1 includes the amount of water contained in each of polyoxazoline compounds 1 to 3 (Epocross WS-300, WS-500, or WS-700), RF, and aqueous polymer dispersion.

[0074] [Adhesive structure] <Preparation of Rubber> The components were blended and kneaded according to the compositions shown in Table 2 to produce rubbers R-1 to R-5.

[0075] [Table 2]

[0076] <Preparation of the core wire> A polyethylene terephthalate cord (PET cord) was prepared and fixed to a frame. A cloth soaked in adhesive compositions A-1 to A-7 was passed back and forth over the front and back of the PET core wire to apply the adhesive composition to the PET core wire, which was then dried at 195°C for 1 minute and baked at 230°C for 1 minute. The adhesive composition was again applied to the baked PET core wire by passing a cloth soaked in the adhesive composition A-1 to A-7 back and forth over the front and back of the PET core wire, and the PET core wire was then dried at 195°C for 1 minute and baked at 230°C for 1 minute.

[0077] <Examples 2-1 to 2-10, Comparative Examples 2-1 to 2-2> Three of the resulting treated PET cords were arranged at equal intervals, sandwiched between rubbers shown in Table 3 or Table 4, and pressed at 160° C. for 45 minutes to prepare test pieces for adhesion tests. The obtained test pieces for adhesion tests were used to measure adhesion at room temperature, rubber adhesion at room temperature, adhesion at 120° C., and rubber adhesion at 120° C. The results are shown in Table 3 or Table 4.

[0078] [Table 3]

[0079] [Table 4]

[0080] In the above examples and comparative examples, the evaluation and measurement of various properties were carried out as follows.

[0081] <Room temperature adhesive strength> The test piece for the adhesive strength test was left to stand at room temperature (23°C) for 24 hours or more. The rubber part and the three PET core wires coated with the adhesive composition were fixed, and a peel test was performed at 23°C at a constant speed of 100 mm / min so that the rubber part and the cord were separated into upper and lower parts, and the room temperature adhesive strength was measured.

[0082] <Heat adhesive strength> The test pieces for the adhesion test were left to stand for 30 minutes in a thermostatic bath at the heating temperature shown in Table 3 or Table 4. Using a tensile tester, the rubber part and the three PET core wires coated with the adhesive composition were each fixed, and a peel test was performed at the heating temperature shown in Table 3 or Table 4 at a constant speed of 100 mm / min so that the rubber part and the cord were separated into upper and lower parts, and the heat adhesion strength for the heating temperature shown in Table 3 or Table 4 was measured.

Claims

1. An adhesive composition for bonding rubber to a fiber, comprising a polyoxazoline compound and an aqueous polymer dispersion, wherein the rubber comprises a rubber containing an olefin compound having a carboxyl group.

2. 2. The adhesive composition according to claim 1, wherein the polyoxazoline compound is a polymer compound having two or more 2-oxazoline groups.

3. 3. An adhesive structure comprising a fiber layer, a layer of the adhesive composition according to claim 1 or 2, and a rubber layer in this order.

4. A belt comprising the adhesive structure of claim 3.

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