Adhesive compositions, adhesive structures, and belts

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 Art

[0002] Reinforcement of rubber products such as belts is carried out using 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, cord fabrics, canvas, and the like.

[0003] However, these reinforcing materials have poor adhesion to rubber, and attempts have been made to improve the adhesion by applying a treatment agent composed of a resorcin-formalin condensate and rubber latex to the surface of the reinforcing material. In the adhesion between these synthetic fibers and rubber, the adhesion between rubber and synthetic fibers has been improved using various adhesive compositions.

[0004] In recent years, from the perspective of the environment and the like, there has been a demand for a method of adhering rubber and fibers without using formalin or components derived from formalin in the production of rubber products. So far, adhesive compositions for adhering rubber and fibers without using resorcin-formalin condensates have been proposed.

[0005] However, when the conventional adhesive compositions are used for adhering fibers and rubber in the production of belts, particularly transmission belts, problems may occur where the rubber and fibers peel off during the production or use of the belt due to the adhesive force and actions such as tension at normal temperature and high temperature. Also, the adhesive force is not satisfactory, and it has been difficult to achieve both de-formalinization and high adhesive force in the production of rubber products.

[0006] Patent Documents 1 and 2 describe adhesive compositions for adhering rubber and fibers, which contain a polymer containing a 2-oxazoline group and rubber latex. However, this adhesive composition contains a condensate of resorcinol and formalin. Furthermore, it does not mention the inclusion of resorcinol or the use of rubber containing an olefin compound with a carboxyl group as the rubber.

[0007] Patent Document 3 describes an adhesive composition for bonding rubber and fibers, which includes a polymer containing a 2-oxazoline group. However, this adhesive composition does not mention the incorporation of resorcinol or rubber latex, nor does it mention the use of rubber containing an olefin compound having a carboxyl group as the rubber.

[0008] Patent Document 4 describes an adhesive composition for bonding rubber and fibers, comprising a polymer containing a 2-oxazoline group and rubber latex. However, this adhesive composition does not mention the inclusion of resorcinol or the use of rubber containing an olefin compound with a carboxyl group as the rubber component. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 5-339552 [Patent Document 2] Japanese Patent Publication No. 2000-248254 [Patent Document 3] Japanese Patent Publication No. 2001-98245 [Patent Document 4] Japanese Patent Publication No. 2013-64037 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to provide an adhesive composition for bonding fibers and rubber that exhibits excellent adhesion even without containing formalin or formalin-derived components. Furthermore, the present invention aims to obtain an adhesive structure with excellent adhesion between fibers and rubber, and a belt containing the adhesive structure, by using such an adhesive composition. [Means for solving the problem]

[0011] The inventors of the present invention conducted diligent research to solve the above problems and, as a result, found that the above problems can be solved by the following adhesive composition, adhesive structure, and belt, and thus completed the present invention. Specifically, the invention is as follows. [1] An adhesive composition for bonding rubber and fibers, comprising resorcinol and / or a salt thereof, a polyoxazoline compound, and an aqueous polymer dispersion. [2] An adhesive composition for bonding rubber and fibers, 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 polymer 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 described in any of [1] to [3], and a rubber layer. A belt containing the adhesive structure described in [5] and [4]. [Effects of the Invention]

[0012] According to the present invention, an adhesive composition for bonding fibers and rubber can be obtained that exhibits excellent adhesion even without containing formalin or formalin-derived components. Furthermore, by using such an adhesive composition, the present invention can provide an adhesive structure with excellent adhesion between fibers and rubber, and a belt containing the adhesive structure. [Modes for carrying out the invention]

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

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

[0015] [Chemical formula]

[0016] The salt of resorcinol may be any salt used to constitute the adhesive composition for bonding rubber and fiber. 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, organic amines such as ammonium, triethylamine, and triethanolamine, and basic amino acids such as lysine and arginine can be mentioned. In the present invention, one or more selected from the group consisting of resorcinol and / or its salt can be used.

[0017] Resorcinol and / or its salt (R) may be present in the adhesive composition in an unreacted state, and at least a part of it may react with the polyoxazoline compound (O) and be present in the state of an initial condensate (RO). In the present invention, it is preferable that it is contained in the adhesive composition as an aqueous solution of the initial condensate (RO).

[0018] <Polyoxazoline compound> Polyoxazoline compounds are compounds having two or more oxazoline groups in their molecule. For example, one or more compounds selected from the group consisting of bisoxazoline compounds having two oxazoline groups, trisoxazoline compounds having three oxazoline groups, and polymer compounds having 2-oxazoline groups in the side chains and / or terminals of the polymer are included. Polyoxazoline compounds may be synthesized or commercially available.

[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), and 2,2'-bis(4-hexyl-2-oxazoline). Oxazoline), 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,One or more substances selected from the group consisting of 2'-hexamethylenebis(4-methyl-2-oxazoline), 2,2'-hexamethylenebis(5-methyl-2-oxazoline), 2,2'-hexamethylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-hexamethylenebis(5,5'-dimethyl-2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis(2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), 2,2'-diphenylenebis(2-oxazoline), 1,4-bis[2-(5-phenyloxazolyl)]benzene, bis(2-oxazolinylcyclohexane)sulfide, etc. , Examples of trisoxazoline compounds having three oxazoline groups include 2,2',2”-(1,3,5-phenylene)-tris(2-oxazoline).

[0020] Examples of polymer compounds having a 2-oxazoline group in the side chain and / or terminal of the polymer include one or more 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 with 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 ethylenically unsaturated monomers containing a 2-oxazoline group 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-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 One or more substances selected from the group consisting of nyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline, 2-isopropenyl-4,4-diethyl-2-oxazoline, 2-isopropenyl-4,5-dimethyl-2-oxazoline, 2-isopropenyl-4,5-diethyl-2-oxazoline, etc.

[0022] There are no particular restrictions on the ethylenically unsaturated monomers copolymerizable with the 2-oxazoline group-containing ethylenically unsaturated monomer, as long as they do not react with the oxazoline group. For example, one or more monomers selected from the group consisting of (meth)acrylic acid esters such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; unsaturated nitriles such as (meth)acrylonitrile; unsaturated amides such as (meth)acrylamide and N-methylol(meth)acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogenated vinyls such as vinyl chloride, vilinidene chloride, and fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene.

[0023] Homopolymers of 2-oxazoline group-containing ethylenically unsaturated monomers, and copolymers obtained by copolymerizing a 2-oxazoline group-containing ethylenically unsaturated monomer with an ethylenically unsaturated monomer copolymerizable therewith, can be produced by various conventionally known polymerization methods, such as suspension polymerization, solution polymerization, emulsion polymerization, and the like. Various conventionally known graft polymerization methods can be used as methods for graft polymerization of 2-oxazoline group-containing ethylenically unsaturated monomers onto a polymer main chain. The polymer to be graft polymerized is not particularly limited. For example, one or more types selected from the group consisting of acrylic resins, polyester resins, polyether resins, polyamide resins, polyurethane resins, etc.

[0024] The number-average molecular weight of a polymer compound having an oxazoline group is not particularly limited, but for example, it is 500 to 2,000,000, preferably 1,000 to 1,000,000, and more preferably 10,000 to 100,000. Furthermore, the oxazoline group equivalent (g solid / eq) of a polymer compound having an oxazoline group is 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 even more preferably 750 or less, from the viewpoint of storage stability and adhesiveness. Note that the oxazoline group equivalent refers to the weight of the compound per oxazoline group, that is, the value obtained from the following formula. Oxazoline group equivalent = Molecular weight / Number of oxazoline groups per molecule

[0025] Examples of commercially available polymer compounds having 2-oxazoline groups in the side chains and / or terminals include one or more selected from the group consisting of, for example, 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] Polyoxazoline compounds are used in various states, such as aqueous solutions, organic solvent solutions, aqueous dispersions, liquids, and molten states. In the present invention, it is preferable to use them in the form of aqueous solutions or aqueous dispersions, from the viewpoint of environmental impact and compatibility with latex.

[0027] In the present invention, the polyoxazoline compound is preferably a polymer compound whose main chain consists of an acrylic skeleton polymer, a styrene-acrylic skeleton polymer, etc., and which has 2-oxazoline groups in its side chains and / or terminals. For example, it is preferable to use the following products from Nippon Shokubai Co., Ltd.: "Epocross WS-300", "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", and "Epocross K-2030E".

[0028] <Aqueous polymer dispersion> As the aqueous polymer dispersion, a material generally referred to as latex (L) can be used. While (L) is not particularly limited, examples include 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, and the like. Of these, vinylpyridine-styrene-butadiene copolymer rubber (VP-SBR) is preferred.

[0029] <Content of each ingredient> In an adhesive composition for bonding rubber and fibers, comprising resorcinol 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) blended per 1 part by mass of resorcinol 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. If the polyoxazoline compound content is less than 0.01 parts by mass, the adhesiveness may decrease. Also, if the polyoxazoline compound content exceeds 500 parts by mass, the adhesiveness to certain rubbers may decrease. Furthermore, for example, the amount of aqueous polymer dispersion (solid content) blended per 1 part by mass of polyoxazoline compound (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. If the amount of aqueous polymer dispersion is less than 0.1 parts by mass, the adhesive properties may decrease. Also, if the amount of aqueous polymer dispersion exceeds 50 parts by mass, the heat-adhesive properties may decrease.

[0030] An adhesive composition for bonding rubber and fibers, comprising 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 is not particularly limited. For example, the amount of aqueous polymer dispersion (solids) blended per 1 part by mass of polyoxazoline compound (solids) 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. If the amount of aqueous polymer dispersion is less than 0.1 parts by mass, the adhesive properties may decrease. Also, if the amount of aqueous polymer dispersion exceeds 50 parts by mass, the heat-adhesive properties may decrease.

[0031] <Other additives> The adhesive composition of the present invention may optionally contain one or more other additives that can be added to the adhesive composition. Examples of other additives include one or more selected from the following: auxiliary agents, crosslinking agents, crosslinking auxiliary agents / cocrosslinking agents, bulking agents, colorants, reinforcing agents, antioxidants, surfactants, softeners, plasticizers, compatibilizers, stabilizers, flame retardants, flame retardant auxiliary agents, tackifiers, etc.

[0032] Examples of auxiliary agents include one or more selected from metal soaps, fatty acid amides, etc. Examples of crosslinking agents include one or more selected from sulfur, thiram compounds, benzotriazole compounds, disulfide compounds, peroxides, polyols, polyisocyanates, etc. Of these, one or more selected from sulfur, peroxides, etc., are preferred. Examples of crosslinking aids and co-crosslinking agents include polyfunctional monomers (unsaturated carboxylate metal salts (e.g., zinc (meth)acrylate, magnesium (meth)acrylate, etc.), dimaleimide compounds (phenylenedimaleimide, etc.), tri(meth)acrylate compounds (trimethylolpropanetri(meth)acrylate, etc.), trialyl compounds (trialyl isocyanurate, etc.), etc.), zinc oxide, polybutadiene, oximes, guanidines, etc.). Of these, one or more selected from unsaturated carboxylate metal salts, dimaleimide compounds, zinc oxide, etc., are preferred. Examples of fillers, colorants, and reinforcing materials include one or more selected from carbon black, zinc oxide, silica, and coloring pigments. Examples of softening agents include paraffin-based process oils. The amount of each of these "other additives" can be any amount within a range that does not adversely affect the properties of the adhesive composition of the present invention. For example, per 100 parts by mass of the adhesive composition, the amount of crosslinking agent can be adjusted to 0.1 to 10.0 parts by mass, the amount of organic peroxide as a crosslinking agent to 0.5 to 8.0 parts by mass, the amount of co-crosslinking agent to 0.5 to 15 parts by mass, and the amount of surfactant softener to 1.5 to 50 parts by mass.

[0033] <Method for manufacturing adhesive composition> The method for producing the adhesive composition is not particularly limited, and any known method for producing adhesive compositions can be used. For example, the product can be manufactured by placing all the ingredients into a container and mixing them using a mixer or other device. Alternatively, it may be manufactured by mixing some of the ingredients first and then adding the remaining ingredients.

[0034] The method for producing an adhesive composition containing resorcinol and / or a salt thereof, a polyoxazoline compound, and an aqueous polymer dispersion is not particularly limited, but for example, one method involves adding resorcinol to an aqueous solution or aqueous dispersion of a polyoxazoline compound while stirring, stirring at room temperature to form an initial condensate, then mixing with an aqueous polymer dispersion (latex), adding water as needed, and stirring at room temperature. Alternatively, an adhesive composition containing a polyoxazoline compound and an aqueous polymer dispersion can be obtained using a salt of resorcinol 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 for example, it involves mixing an aqueous solution or aqueous dispersion of the polyoxazoline compound with an aqueous polymer dispersion (latex), adding water as needed, and stirring at room temperature. The solid content concentration of the adhesive composition of this application is not particularly limited. For example, it can be 1 to 50% by mass, preferably 5 to 30% by mass, and more preferably 5 to 25% by mass.

[0035] <How to use adhesive compositions> The adhesive composition is used to bond rubber and / or fibers by applying it to the bonding surfaces of the rubber and / or fibers, bringing them into contact, preferably by applying pressure and heating. The method of application to rubber and / or fibers is not particularly limited, and known methods can be used. In the present invention, it is preferable to apply the adhesive composition to the fibers by a single-bath treatment method and a two-bath treatment method.

[0036] In the case of a single-bath treatment method, each component is mixed to form an adhesive composition containing 5 to 25% by mass of the active ingredient. This composition is then attached to fibers by methods such as immersion, spraying, or application with a cloth, and then heat-treated to bond it to rubber. Finally, it is heated and pressurized to form rubber products such as belts. In the two-bath processing method, the fibers are treated in the first bath at 70-240°C for 1 second to 10 minutes, then treated in the second bath, followed by further heat treatment, bonding with rubber, and then heated and pressurized to form rubber products such as belts. For example, the first and second baths are: (1) First bath: Resorcinol and / or a salt thereof, and an initial condensate of a polyoxazoline compound Second bath: Aqueous polymer dispersion (latex) (2) First bath: A mixture of resorcinol and / or a salt thereof and a polyoxazoline compound. Second bath: Aqueous polymer dispersion (latex) (3) First bath: Resorcinol and / or a salt thereof, and an 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) These are some examples.

[0037] In the present invention, methods of immersing the fibers in an adhesive composition or applying the adhesive composition to the fibers with a cloth or the like are preferred. The immersion time of the fibers in the adhesive composition can be 10 seconds or less, for example, 0.5 to 5 seconds, and after immersion, the fibers can be treated at 150 to 270°C for 15 to 600 seconds. When the adhesive composition is attached to the fibers, the amount of adhesive composition attached 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 meter of fiber.

[0038] <rubber> The rubber bonded to the fibers by the adhesive composition of the present invention is not particularly limited as long as it is composed of a rubber composition containing a rubber component and a rubber compounding agent. The rubber may be either vulcanized or unvulcanized. However, vulcanized rubber is preferred because it exhibits superior adhesion to vulcanized rubber.

[0039] The rubber component of the rubber composition may be either synthetic rubber or / or natural rubber. As the synthetic rubber, one or more types of diene rubber having carbon-carbon double bonds in the polymer main chain, non-diene rubber not having carbon-carbon double bonds in the polymer main chain, or modified versions of these rubbers can be used.

[0040] In the present invention, the synthetic rubber can be one or more selected from, for example, 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-ethylidene norbornene rubber (EPDM), ethylene-octene copolymer, and ethylene-butene copolymer; silicone rubber; urethane rubber; and more. Furthermore, modified products obtained by, for example, hydrogenation or modification by introducing various functional groups into these rubbers, such as one or more selected from 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 carboxyl groups, reinforcing agents, oils, processing aids, vulcanization accelerators, crosslinking agents, co-crosslinking agents, vulcanization accelerators, and antioxidants. In particular, when using an adhesive composition containing a polyoxazoline compound and an aqueous polymer dispersion, but free of resorcinol, to bond rubber and fibers, the rubber must contain an olefin compound having a carboxyl group.

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

[0043] Examples of carboxylic acid compounds having a (meth)acryloyloxy group include one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, citraconic acid, dimethyl maleic acid, 2-ethyl-3-methyl maleic acid, 2-acryloyloxyethyl succinic acid (light acrylate HOA-MS(N)), 2-acryloyloxyethyl hexahydrophthalic 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 carboxylic acid compounds having a (meth)acryloyloxy group include one or more selected from the group consisting of acrylic anhydride, methacrylic anhydride, maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, 2-ethyl-3-methyl maleic anhydride, and the like.

[0045] Examples of carboxylic acid compound salts having a (meth)acryloyloxy group include one or more selected from the group consisting of various metal salts of the aforementioned carboxylic acid compound having a (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, petroseric acid, oleic acid, elaidic acid, ricinoleic acid, linoleic acid, linoleidic acid, linolenic acid, arachidonic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, docosatetraenoic acid, vaccenic acid, pauric acid, erucic acid, nervonic acid, and sapienic acid. Furthermore, one or more substances 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 acid anhydride, octenylsuccinic acid anhydride, (2-methyl-2-propenyl)succinic acid anhydride, and nonenylsuccinic acid anhydride may be used.

[0047] In the present invention, one or more selected from the group consisting of carboxylic acids having a (meth)acryloyloxy group, carboxylic acid anhydrides having a (meth)acryloyloxy group, unsaturated fatty acids, and saturated fatty acids is preferred. For example, one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl succinic acid, metal acrylate salts, metal methacrylate salts, etc., is more preferred.

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

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

[0050] Furthermore, carbon black can be used as a reinforcing material, and 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 added 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] Examples of oils include one or more selected from the group consisting of 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, fall oil, wood wax, rosin, and pine oil. The oil content is, for example, 1.5 to 50 parts by mass per 100 parts by mass of the rubber component of the rubber composition.

[0052] Examples of vulcanization accelerators include one or more selected from the group consisting of metal oxides such as zinc oxide (zinc oxide) and magnesium oxide, metal carbonates, fatty acids and their derivatives. The amount of vulcanization accelerator is, for example, 5 to 15 parts by mass per 100 parts by mass of the rubber component of the rubber composition.

[0053] Examples of crosslinking agents include one or more selected from the group consisting of sulfur and organic peroxides. Examples of organic peroxides include one or more selected from the group consisting of dialkyl peroxides such as dicumyl peroxide, peroxyesters such as t-butyl peroxyacetate, and ketone peroxides such as dicyclohexanone peroxide. The amount of sulfur added 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 amount of organic peroxide added 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 cocrosslinking agents include one or more selected from the group consisting of 1,2-polybutadiene, oximes, guanidine, and (meth)acrylate compounds (TAIC, maleimides, trimethylolpropane trimethacrylate, acrylates, etc.). The co-crosslinking agent content is, for example, 0.5 to 40 parts by mass per 100 parts by mass of rubber component.

[0055] <Textiles> The fibers bonded to the rubber by the adhesive composition of the present invention are not particularly limited. 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, braids, and combinations of one or more of these. In the present invention, core wires, fabrics (e.g., canvas), and nonwoven fabrics composed of monofilaments and / or twisted yarns are preferably used.

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

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

[0058] [Adhesive structure] The adhesive structure of the present invention comprises one or more fiber layers, one or more layers of adhesive composition, and one or more layers of rubber. The fibrous layers constituting the adhesive structure are not particularly limited as long as they are layers made of fibers. For example, a layer made of fibers that is bonded to rubber by the adhesive composition of the present invention can be included. If there are multiple fibrous layers, each fibrous layer may be the same or different. The adhesive composition layers constituting the adhesive structure may be such that at least one layer of the adhesive composition layers that bond the fiber layer and the rubber layer is composed of the adhesive composition of the present invention. The rubber layers constituting the adhesive structure are not particularly limited as long as they are made of rubber. For example, a layer made of a rubber composition that is bonded to the fibers by the adhesive composition of the present invention may be included. If there are multiple rubber layers, each rubber layer may be the same or different.

[0059] Between the fiber layer and the adhesive composition layer, and between the adhesive composition layer and the rubber layer, an optional intermediate layer such as a primer layer containing epoxy resin or isocyanate resin, a surface treatment layer, or a rubber adhesive layer may be provided as needed. In the present invention, since the adhesive properties of the adhesive composition layer are good, the adhesive structure can be formed by directly laminating without providing the aforementioned intermediate layer. Since the adhesive structure of the present invention aims to be formaldehyde-free, it is preferable that it does not contain a resorcinol-formaldehyde(-latex) layer (RF(L) layer). In some cases, the RF(L) layer may be provided on top of the fiber layer.

[0060] The adhesive structure of the present invention has a layered structure comprising at least a rubber layer / adhesive composition layer / fiber layer. Furthermore, the fiber layer may be embedded within the adhesive composition layer, resulting in a structure of rubber layer / adhesive composition layer / fiber layer / adhesive composition layer / rubber layer. The fiber layer may also be provided on the front surface of the adhesive structure, or only on a portion of it. If the adhesive structure of the present invention has multiple fiber layers and / or rubber layers, these layers can be arranged in any order. For example, the following layer structure is possible. (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. Furthermore, one or more of the adhesive composition layers A to C may be the adhesive composition of the present invention. Furthermore, the fiber layer may be embedded within the adhesive composition layer, resulting in a structure such as, for example, rubber layer A / adhesive composition layer / fiber layer / adhesive composition layer / rubber layer B.

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

[0062] [belt] The belt of the present invention includes the adhesive structure of the present invention and is wrapped around a pulley to transmit power. It may be a V-belt, round belt, toothed belt, flat belt, or V-ribbed belt. For example, the belt has, in this order, an inner rubber layer constituting the pulley contact portion on the inner circumference 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 circumference side of the belt. The fiber layer can be made up of, for example, a core wire to which the adhesive composition is provided so as to form a spiral having a pitch in the belt width direction. Alternatively, 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 from a rubber composition in which an uncrosslinked rubber composition, which is kneaded with various rubber compounding agents mixed with rubber components, is heated and pressurized to crosslink with a crosslinking agent. The rubber compositions forming the compression rubber layer and the back rubber layer may be the same or different.

[0064] Examples of rubber compositions that form the inner rubber layer and the back rubber layer include the rubber components and rubber compounding agents listed as constituting the adhesive structure of the present invention. In the present invention, the rubber components forming the inner rubber layer and the back rubber layer can be the same.

[0065] Examples of methods for forming the belt include the following: (i) A rubber sleeve is placed over a cylindrical drum with a smooth surface, and an uncrosslinked rubber sheet for the back rubber layer and an uncrosslinked rubber sheet for the adhesive composition are sequentially wrapped around its outer circumference to form a laminated molded body. A fiber layer having a layer of adhesive composition is then spirally wrapped around a cylindrical inner mold, and an uncrosslinked rubber sheet for the adhesive composition and an uncrosslinked rubber sheet for the inner rubber layer are then sequentially wrapped around it to form a laminated molded body.

[0066] (ii) Remove the rubber sleeve with the laminated molded body attached from the cylindrical drum, set the laminated molded body in a fitted state on the inner circumferential surface side of the outer mold, and then position the inner mold inside the rubber sleeve set on the outer mold and seal it.

[0067] (iii) The outer mold is heated, and high-pressure air or the like is injected into the sealed interior of the inner mold to pressurize it. 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 progresses, and the fiber layer having the adhesive composition layer is composited and integrated, and finally a cylindrical belt slab is formed. 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 inside of the inner mold is depressurized to release the seal, the belt slab formed between the inner and outer molds via a rubber sleeve is removed, the belt slab is cut into slices of a predetermined width, and the front and back sides are turned inside out to manufacture the belt. [Examples]

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

[0070] [Adhesive composition] <Example 1-1> Adhesive composition A-1 was prepared by mixing 1.3 parts of resorcinol, 15.5 parts of a polyoxazoline compound, 100 parts of an aqueous polymer dispersion, and 613.4 parts of water and stirring. In the obtained adhesive composition A-1, the molar ratio of resorcinol (R) to polyoxazoline compound (O) was R / O = 0.1, and the mass ratio of latex (L) to resorcinol / 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 prepared by blending and stirring each component according to the composition shown in Table 1. In the obtained adhesive composition A-2, the mass ratio of latex (L) to polyoxazoline compound (O) was L / O = 6. The adhesive composition RFL according to Comparative Example 1-1 was prepared by blending and stirring each component according to the composition shown in Table 1.

[0072] [Table 1]

[0073] Polyoxazoline compound 1: Manufactured by Nippon Shokubai Co., Ltd., product name "Epocross WS-300" Polyoxazoline compound 2: Manufactured by Nippon Shokubai Co., Ltd., product name "Epocross WS-500" Polyoxazoline compound 3: Manufactured by Nippon Shokubai Co., Ltd., product name "Epocross WS-700" RF: A 3.04 part solids RF solution was obtained by mixing and reacting 41.69 parts water, 0.21 parts sodium hydroxide, 2.03 parts resorcinol, and 2.15 parts formaldehyde. Aqueous polymer dispersion: Styrene-butadiene-vinylpyridine copolymer latex (solids content 41.5 wt%) Note that the amounts of polyoxazoline compounds 1-3, RF, and aqueous polymer dispersions in Table 1 represent the solid content. Furthermore, the amount of water in Table 1 includes the amount of water contained in each of the polyoxazoline compounds 1-3 (Epocross WS-300, WS-500, or WS-700), RF, and aqueous polymer dispersions.

[0074] [Adhesive structure] <Preparation of rubber> Rubbers R-1 to R-5 were produced by blending and kneading each component according to the composition shown in Table 2.

[0075] [Table 2]

[0076] <Preparation of core wires> A polyethylene terephthalate cord (PET core wire) was prepared, and the PET core wire was fixed to the frame. The adhesive compositions A-1 to A-7 were applied to the PET core wire by passing a cloth soaked in each composition back and forth across the front and back of the PET core wire. The wire was then dried at 195°C for 1 minute and baked at 230°C for 1 minute. For the PET core wire that had undergone the baking treatment, a cloth soaked in adhesive compositions A-1 to A-7 was again applied to the PET core wire by passing it back and forth once on both the front and back of the PET core wire. The 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 obtained processed PET core wires were arranged at equal intervals, sandwiched between the rubber shown in Table 3 or Table 4, and pressed at 160°C for 45 minutes to prepare test specimens for adhesion strength testing. Using the obtained test specimens for adhesion strength testing, the adhesion strength at room temperature, the adhesion strength at room temperature, the adhesion strength at 120°C, and the adhesion strength at 120°C were measured. The results are shown in Table 3 or Table 4.

[0078] [Table 3]

[0079] [Table 4]

[0080] The evaluation and measurement of various characteristics in the above examples and comparative examples were carried out as follows.

[0081] <Room temperature adhesive strength> The test specimens for adhesion strength testing were left undisturbed at room temperature (23°C) for more than 24 hours. The rubber portion and three PET core wires coated with the adhesive composition were fixed to each other, and a peel test was performed at a constant speed of 100 mm / min at 23°C so that the rubber portion and the cords separated vertically, and the room temperature adhesion strength was measured.

[0082] <Heat adhesive strength> Test specimens for adhesion strength testing were left to stand for 30 minutes in a constant temperature bath at the heating temperature listed in Table 3 or Table 4. Using a tensile testing machine, the rubber portion and three PET core wires coated with the adhesive composition were fixed to each other, and a peel test was performed at a constant speed of 100 mm / min at the heating temperature listed in Table 3 or Table 4, so that the rubber portion and the cord separated vertically. The heat adhesion strength at the heating temperature listed in Table 3 or Table 4 was then measured.

Claims

1. An adhesive composition for bonding rubber and fibers, comprising a polyoxazoline compound and an aqueous polymer dispersion, The aqueous polymer dispersion is 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, and hydrogenated acrylonitrile butadiene methacrylic acid terpolymer (X-NBR) latex. The rubber includes rubber containing an olefin compound having a carboxyl group. The adhesive composition.

2. The adhesive composition according to claim 1, wherein the polyoxazoline compound is a polymer compound having two or more 2-oxazoline groups, and the rubber is an olefin-based rubber containing an olefin compound having a carboxyl group.

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

4. A belt comprising the adhesive structure described in claim 3.

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