Adhesive composition, adhesive structure, and belt

Abstract

To provide an adhesive composition that has excellent adhesion, or specifically, an adhesive composition that has excellent adhesion at room temperature and at high temperatures in adhering a variety of surface-treated fibers to rubber and also has excellent tensile and tear characteristics, and provide an adhesion structure and a belt having excellent interlayer adhesion by using such an adhesive composition.SOLUTION: An adhesive composition contains synthetic rubber, an acid component, and carbodiimide. An adhesion structure has a layer of the adhesive composition and a layer formed from RF or RFL. A belt includes the adhesion 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] Rubber products such as belts are reinforced 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, etc.

[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, various adhesive compositions have been used to improve the adhesion between rubber and synthetic fibers.

[0004] However, when the conventional adhesives are used for the adhesion between fibers and rubber to manufacture belts, particularly transmission belts, problems may occur in that the rubber and fibers peel off during the manufacture or use of the belts due to the adhesive force at normal temperature and high temperature and the action of tension, etc. Also, it has been difficult to achieve both high hardness of the adhesive rubber and high peel adhesive force.

[0005] Patent Document 1 describes an adhesive obtained by reacting a polyolefin (A) having a group that reacts with a carbodiimide group and a carbodiimide group-containing compound (B) in the presence of an unmodified polyolefin (C), and a tackifier (E) is blended in the adhesive. And EPDM is exemplified as the unmodified polyolefin (C). However, it does not describe blending an acid component.

[0006] Patent Document 2 describes an adhesive composition containing (A) an acrylic polymer and (C) a carbodiimide crosslinking agent, and may further contain a polymer component other than the (A) component. As the polymer component other than the (A) component, EPDM is exemplified. However, there is no description about blending an acid component.

[0007] Patent Document 3 describes an adhesive composition containing (A) a crystalline acid-modified polyolefin, (B) an amorphous polyolefin, and (C) a carbodiimide resin. However, there is no description about blending a synthetic rubber or an acid component.

[0008] Patent Document 4 describes an adhesive containing a hydrolysis resistance-imparting agent. As the hydrolysis resistance-imparting agent, carbodiimide compounds such as diisopropylcarbodiimide and dicyclohexylcarbodiimide are listed, but there is no description about blending a synthetic rubber or an acid component.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to obtain an adhesive composition having excellent adhesiveness, particularly an adhesive composition that is excellent in adhesiveness at normal temperature and high temperature and excellent in tensile properties and tear properties when adhering various surface-treated fibers to rubber, and to achieve both high hardness and high peel adhesive strength. In addition, an object of the present invention is to obtain an adhesive structure and a belt having excellent interlayer adhesiveness by using such an adhesive composition.

Means for Solving the Problems

[0011] As a result of intensive studies to solve 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 completed the present invention. Specifically, it is as follows. [1] An adhesive composition containing a synthetic rubber, an acid component, and carbodiimide. [2] An adhesive structure including a layer of the adhesive composition according to [1] and a layer formed from RF or RFL. [3] An adhesive structure including a layer of the adhesive composition according to [1] and a fiber layer having a layer formed from RF or RFL on the surface. [4] A belt including the adhesive structure according to [2] or [3]. [5] A belt including the adhesive structure according to [3], wherein the fiber layer is a core wire made of a twisted yarn.

Effects of the Invention

[0012] According to the present invention, an adhesive composition showing excellent adhesiveness can be obtained, particularly an adhesive composition excellent in adhesiveness at normal temperature and high temperature and excellent in tensile properties and tear properties when adhering various surface-treated fibers to rubber. In addition, according to the present invention, an adhesive structure and a belt having excellent interlayer adhesiveness can be obtained by using such an adhesive composition.

Embodiments for Carrying Out the Invention

[0013] [Adhesive Composition] [Synthetic Rubber]< As the synthetic rubber, one or more of a diene rubber having a carbon-carbon double bond in the polymer main chain, a non-diene rubber having no carbon-carbon double bond in the polymer main chain, or a modified product of these rubbers can be used.

[0014] In the present invention, examples of the synthetic rubber include one or more selected from butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), styrene-butadiene-styrene rubber, ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer, ethylene-butene copolymer, silicone rubber, urethane rubber, and the like. Further, with respect to these rubbers, for example, modified products obtained by hydrogenation (hydrogenation) or modification such as introducing various functional groups, for example, one or more selected from hydrogenated SBR, hydrogenated BR, hydrogenated acrylonitrile-butadiene rubber (H-NBR), chlorosulfonated polyethylene rubber (CSM), and the like can be used.

[0015] In the present invention, olefin-based rubbers are preferred, and one or more selected from ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer, and ethylene-butene copolymer are more preferred. Among ethylene-propylene-diene terpolymers (EPDM), the diene component is not particularly limited, but those having an ethylenenorbornene structure or those having a dicyclopentadiene structure are more preferred.

[0016] The content of the synthetic rubber in the adhesive composition is not particularly limited. For example, it is 25 to 75% by mass, preferably 30 to 70% by mass, more preferably 35 to 65% by mass, and still more preferably 40 to 60% by mass in the total solid content of the adhesive composition. When the content of the synthetic rubber exceeds 75% by mass, the strength of the adhesive is significantly reduced, and the adhesive force may decrease. On the other hand, when it is less than 25% by mass, the formation of the adhesive layer at the interface may not be carried out well, and the adhesive force may decrease.

[0017] <Acid component> As the acid component, it is preferable to use one or more organic acids, for example, one or more selected from the group consisting of carboxylic acid compounds, sulfonic acid compounds, or their anhydrides. A carboxylic acid compound is a compound having one or more carboxyl groups in the molecule, and examples thereof include one or more selected from the group consisting of carboxylic acids having a (meth)acryloyloxy group, unsaturated fatty acids, saturated fatty acids, or anhydrides thereof.

[0018] Examples of the carboxylic acid compound having a (meth)acryloyloxy group include acrylic acid, methacrylic acid, maleic acid, citraconic acid, dimethylmaleic acid, 2-ethyl-3-methylmaleic acid, 1-cyclohexene-1,2-dicarboxylic acid, 1-cyclohexene-1,2-dicarboxylic acid, dodecenyl succinic acid, octenyl succinic acid, (2-methyl-2-propenyl)succinic acid, nonenyl succinic 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)), 2-methacryloyloxyethyl succinic acid (Light ester HO-MS(N)), and the like, and one or more selected from the group consisting thereof can be mentioned.

[0019] Examples of the carboxylic acid compound anhydride having a (meth)acryloyloxy group include acrylic anhydride, methacrylic anhydride, maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, 2-ethyl-3-methyl maleic anhydride, 1-cyclohexene-1,2-dicarboxylic acid anhydride, 1-cyclohexene-1,2-dicarboxylic acid anhydride, dodecenyl succinic anhydride, octenyl succinic anhydride, (2-methyl-2-propenyl)succinic anhydride, and nonenyl succinic anhydride, and one or more selected from the group consisting thereof can be mentioned.

[0020] 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, linolenic acid, arachidonic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, docosatetraenoic acid, vaccenic acid, paullinic acid, erucic acid, nervonic acid, sapienic acid, and the like.

[0021] Examples of saturated fatty acids include one or more selected from the group consisting of valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, and metal salts thereof.

[0022] In the present invention, as carboxylic acid compounds other than the above, for example, one or more selected from the group consisting of citric acid, malonic acid, oxalic acid, benzoic acid, phthalic acid, glutaric acid, lactic acid, glycolic acid, malic acid, tartaric acid, salicylic acid, hydroxybenzoic acid, succinic acid, adipic acid, gallic acid, lauric acid, and acid anhydrides thereof can also be used.

[0023] As the sulfonic acid compound, one or more selected from the group consisting of benzenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, propenesulfonic acid, and the like can be used.

[0024] The organic acid may be a polymer having a carboxyl group and / or a sulfonic acid group. Examples of such polymers include one or more selected from the group consisting of olefin polymers having a carboxyl group and / or a sulfonic acid group, styrene polymers having a carboxyl group and / or a sulfonic acid group, acrylic polymers having a carboxyl group and / or a sulfonic acid group, and the like.

[0025] 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 are more preferable. For example, it is more preferable to use one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, stearic acid, oleic acid, and the like.

[0026] The content of the acid component in the adhesive composition is not particularly limited. For example, in the total solid content of the adhesive composition, it is 0.006 to 18.750% by mass, preferably 0.015 to 14.000% by mass, more preferably 0.026 to 9.750% by mass, and still more preferably 0.060 to 6.000% by mass. When the content of the acid component exceeds 18.750% by mass or is less than 0.006% by mass, an adhesive layer may not be formed well, and the adhesive strength may decrease.

[0027] <carbodiimide> Carbodiimide is a compound having at least one carbodiimide group (-N=C=N-) in the molecule. In the present invention, one or more selected from carbodiimide having one carbodiimide group in the molecule and / or carbodiimide having two or more carbodiimide groups in the molecule are used. The carbodiimide compound can be produced, for example, by subjecting an isocyanate compound having at least one isocyanate group in the molecule to a decarboxylation condensation reaction (carbodiimidization reaction) in the presence of a carbodiimidization catalyst.

[0028] Examples of the carbodiimide having one carbodiimide group in the molecule include, but are not limited to, diisopropylcarbodiimide (MW = 126), dicyclohexylcarbodiimide, dicyclohexylmethanecarbodiimide (MW = 206), tetramethylxylylene carbodiimide, bis(2,6-diisopropylphenyl)-carbodiimide (manufactured by Rhein Chemie, trade name "Stabaxol I"), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (MW = 191), N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide, N,N'-di-p-tolylcarbodiimide, and the like. One or more selected from the group consisting of these compounds can be used.

[0029] Examples of the carbodiimide having two or more carbodiimide groups in the molecule include, but are not limited to, polycarbodiimides obtained by synthesizing polyisocyanate compounds such as hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and tolylene diisocyanate by the above method. The number average molecular weight of the polycarbodiimide is preferably from 400 to 500,000, more preferably from 1,000 to 100,000, and even more preferably about 2,000 to 40,000. Also, commercially available polycarbodiimides such as the "Carbodilite" series (manufactured by Nisshinbo Chemicals) and "Stabaxol" (manufactured by Rhein Chemie), for example, Stabaxol P, Carbodilite LA-1, Carbodilite HMV-15CA, and the like, one or more selected from the group consisting of these compounds can be used.

[0030] In the present invention, it is preferable to use a carbodiimide having a molecular weight exceeding 350, and more preferably one or more selected from the group consisting of bis(2,6-diisopropylphenyl)-carbodiimide, polycarbodiimide (for example, Stabaxol P, Carbodilite LA-1, Carbodilite HMV-15CA, etc.). In the present invention, in consideration of the decomposition of the carbodiimide contained in the adhesive composition, it is preferable not to use an aliphatic carbodiimide compound having a molecular weight of 350 or less.

[0031] The content of carbodiimide in the adhesive composition is not particularly limited. For example, in the total solid content of the adhesive composition, it is 0.006 to 18.750% by mass, preferably 0.015 to 14.000% by mass, more preferably 0.026 to 9.750% by mass, and still more preferably 0.060 to 6.000% by mass. When the content of carbodiimide exceeds 18.750% by mass or is less than 0.006% by mass, it may not be possible to successfully form an adhesive layer, and the adhesive strength may decrease.

[0032] <Other Additives> The adhesive composition of the present invention may contain one or more other additives that can be added to the rubber composition and / or the adhesive composition as necessary. Examples of other additives include processing aids, crosslinking agents, crosslinking aids / cocrosslinking agents, extenders, colorants, reinforcing materials, antioxidants, surfactants, softeners, plasticizers, compatibilizers, stabilizers, flame retardants, flame retardant aids, etc. One or more selected from these can be mentioned.

[0033] Examples of the processing aid include one or more selected from metal soaps, fatty acid amides, etc. Examples of the crosslinking agent include 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 preferable. Examples of the crosslinking aid / cocrosslinking agent include polyfunctional monomers (unsaturated carboxylic acid metal salts (for example, zinc (meth)acrylate, magnesium (meth)acrylate, etc.), dimaleimide compounds (phenylenedimaleimide, etc.), tri(meth)acrylate compounds (trimethylolpropane tri(meth)acrylate, etc.), triallyl compounds (triallyl isocyanurate, etc.), etc.), zinc oxide, polybutadiene, oximes, guanidines, etc. Among these, one or more selected from unsaturated carboxylic acid metal salts, dimaleimide compounds, zinc oxide, etc. are preferable. Examples of the extender / colorant / reinforcing material include one or more selected from carbon black, zinc oxide, silica, etc. Examples of the softening agent include paraffinic process oils and the like. The compounding amount of each of these "other additives" can be an arbitrary amount as long as it does not adversely affect the properties of the adhesive composition of the present invention. For example, with respect to 100 parts by mass of the synthetic rubber in the adhesive composition, the compounding amount of sulfur as a crosslinking agent is 0.1 to 4.0 parts by mass, the compounding amount of the organic peroxide as a crosslinking agent is 0.5 to 8.0 parts by mass, the compounding amount of the co-crosslinking agent is 0.5 to 15 parts by mass, and the compounding amount of the softening agent is 1.5 to 50 parts by mass, respectively, which can be adjusted.

[0034] <Manufacturing method> The manufacturing method of the adhesive composition of the present invention is not particularly limited, and any method can be used as long as it is a known method as a manufacturing method of an adhesive composition. For example, all the components can be put into a container and manufactured by mixing and kneading with a device such as a kneader, a kneader, a roll mill, a mixer, an extruder, etc. Also, it may be manufactured by blending the remaining components after mixing and kneading some of the components.

[0035] <Usage method> The adherend adhered by the adhesive composition of the present invention is not particularly limited. For example, one or more selected from the group consisting of metals, rubbers, and various plastics can be mentioned. Among these, the adhesive composition of the present invention is useful for the adhesion between rubber and various fibers. When the adhesive composition of the present invention is used for the adhesion between rubber and fiber, the rubber as the adherend may be either vulcanized rubber or unvulcanized rubber. Since it has excellent adhesive strength to vulcanized rubber, it is preferably vulcanized rubber. Also, the fiber is not particularly limited, but organic fibers, carbon fibers, glass fibers, etc. are preferred, and fibers having an RFL layer formed on the surface are particularly preferred. Examples of the organic fiber include polyester fiber, polyamide fiber, aramid fiber, etc. Also, examples of the shape of the fiber include fiber structures such as twisted yarn, woven fabric, non-woven fabric, cord, and net.

[0036] [Adhesive structure] The adhesive structure of the present invention includes a layer of the adhesive composition of the present invention (adhesive layer) and a layer formed from RF or RFL (RF(L) layer). An optional intermediate layer such as a primer layer containing an epoxy resin, an isocyanate resin, etc. may be provided between the adhesive layer and the RF(L) layer, if necessary. In the present invention, since the adhesiveness between the adhesive layer and the RF(L) layer is good, it may be directly laminated without providing the intermediate layer to form an adhesive structure.

[0037] In the adhesive structure of the present invention, the RF(L) layer may be provided on the fiber layer. In this case, it is preferable that the adhesive layer, the RF(L) layer, and the fiber layer are in this order. The mode in which the RF(L) layer is provided on the fiber layer includes that the fiber layer has the RF(L) layer on its surface. This includes, for example, that the fiber layer is constituted by fibers having an RFL layer formed on the surface as described above. Further, the fiber layer having the RF(L) layer on its surface may be embedded in the adhesive layer, and may have a structure of adhesive layer / RF(L) layer / fiber layer / RF(L) layer / adhesive layer. An optional intermediate layer such as a primer layer containing an epoxy resin, an isocyanate resin, etc. may be provided between the RF(L) layer and the fiber layer, if necessary.

[0038] The adhesive structure of the present invention may further have one or more rubber layers in addition to the fiber layer. In this case, it is preferable that the rubber layer, the adhesive layer, the RF(L) layer, and the fiber layer are in this order, and it is preferable that the rubber layer, the adhesive layer, and the fiber layer having the RF(L) layer on its surface are in this order. The rubber layer may be an adherend of the adhesive composition. Further, the fiber layer having the RF(L) layer on its surface may be embedded in the adhesive layer, and may have a structure such as rubber layer A / adhesive layer / RF(L) layer / fiber layer / RF(L) layer / adhesive layer / rubber layer B, for example. The components of rubber layer A and rubber layer B may be the same or different, and rubber layer B may not be provided if necessary. Between the RF(L) layer and the fiber layer and between the rubber layer and the adhesive layer, an optional layer such as an undercoat layer, a primer layer containing an epoxy resin or an isocyanate resin, or a rubber paste layer may be provided as necessary.

[0039] <Adhesive composition layer> The adhesive composition layer (adhesive layer) in the adhesive structure of the present invention is composed of the adhesive composition of the present invention, and its thickness is not particularly limited and can be set to any thickness according to the use and the like. For example, it can be 0.001 to 3.0 mm, preferably 0.01 to 2.5 mm.

[0040] <RF(L) layer> The layer formed from RF in the adhesive structure of the present invention is composed of an aqueous solution of an initial condensate (RF) of resorcinol (R) and formalin (F). Further, the layer formed from RFL is composed of an aqueous RFL solution obtained by mixing latex (L) with the RF aqueous solution. The initial condensate in the RF aqueous solution is obtained by reacting resorcinol (R) and formalin (F) in an arbitrary molar ratio, and the molar ratio can be, for example, R / F = 1 / 0.8 to 1 / 4, preferably 1 / 1.3 to 1 / 3. The solid content concentration of the RF aqueous solution or the RFL aqueous solution is not particularly limited, but can be, for example, 3.0 to 30% by mass, preferably 5 to 25% by mass. The solid content mass ratio of the initial condensate (RF) to the latex (L) in the RFL aqueous solution is not particularly limited, but for example, with respect to 1 part by mass of RF, L can be more than 0 part by mass and 30 parts by mass or less, preferably 1.5 to 20 parts by mass.

[0041] The latex (L) is not particularly limited, and examples thereof include one or more selected from the group consisting of vinyl pyridine-styrene-butadiene copolymer rubber (VP-SBR) 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. Among these, vinyl pyridine-styrene-butadiene copolymer rubber (VP-SBR) is preferred.

[0042] The method for preparing the RF aqueous solution is not particularly limited, and examples thereof include a method in which resorcin is added to an aqueous sodium hydroxide solution while stirring, and then formalin is added and stirred at room temperature. Also, the method for preparing the RFL aqueous solution is not particularly limited, and examples thereof include a method in which an RF solution is gradually added to the latex while stirring, water is added as necessary, and the mixture is stirred at room temperature.

[0043] The method for forming the RF(L) layer is not particularly limited, and examples thereof include (i) a method of applying an RF(L) aqueous solution to the adhesive layer, (ii) a method of integrating an RF(L) film formed from the RF(L) aqueous solution and the adhesive layer, (iii) a method of applying and drying an RF(L) aqueous solution on a fiber layer or the like to form an RF(L) film and then integrating it with the adhesive layer, and the like.

[0044] In the present invention, the method (iii) is preferably used. By using the method (iii), a fiber layer having an RF(L) layer on the surface can be formed. In the method (iii), as a method for forming the RF(L) film, for example, there is a method in which a core wire made of fiber is immersed in an RF(L) aqueous solution, coated, and then heated and dried. At this time, the immersion time of the core wire in the RF(L) aqueous solution can be 10 seconds or less, for example, 0.5 to 5 seconds, the heating temperature (heating furnace set temperature) after immersion can be 270°C or less, for example, 150 to 260°C, and the drying temperature can be 360 seconds or less, for example, 15 to 300 seconds. The treatment of the core wire with the RF(L) aqueous solution can be performed one or more times, and the adhesion amount of the RF(L) layer is an amount such that the RF(L) layer is 20 parts by mass or less, for example, 0.5 to 15 parts by mass with respect to 100 parts by mass of the core wire.

[0045] <Fiber layer> The fiber layer that the adhesive structure of the present invention may have is composed of one or more selected from the group consisting of single fibers, woven fabrics, knitted fabrics, non-woven fabrics, twisted yarns, nets, curtains, braided cords, combinations of one or more of these, etc. In the present invention, a core wire composed of single fibers and / or twisted yarns, a cloth (for example, canvas), and a non-woven fabric are preferably used as the fiber layer.

[0046] Examples of the material constituting the fiber layer include polyamide fibers (such as 6 nylon fibers, 66 nylon fibers, 46 nylon fibers, etc.), polyester fibers (such as polyethylene terephthalate (PET) fibers, polyethylene naphthalate (PEN) fibers, etc.), aramid fibers (such as para-aramid fibers, meta-aramid fibers, etc.), vinylon fibers, glass fibers, carbon fibers, metal fibers (steel cords), etc.

[0047] When a belt is configured using the adhesive structure of the present invention, as the fiber layer, it is preferable to use, for example, a core wire composed of a twisted yarn or a braided cord. As the fibers constituting the twisted yarn, one or more 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 dimension between the centers of adjacent core wires in the belt cross section is, for example, 0.05 to 0.20 mm.

[0048] [Belt] The belt of the present invention is a belt including the adhesive structure of the present invention, and is, for example, a transmission belt or a conveyor belt that is wound around a pulley to transmit power. As the transmission belt, any of a V-belt, a round belt, a toothed belt, a flat belt, and a V-ribbed belt may be used. For example, it has an inner rubber layer constituting the pulley contact portion on the inner peripheral side of the belt, a layer of the adhesive composition of the present invention (adhesive layer), a layer formed from RF or RFL (RF(L) layer), a fiber layer, an RF(L) layer, an adhesive layer, and a back rubber layer on the outer peripheral side of the belt in this order. It can also be said that it has an inner rubber layer, an adhesive layer, a fiber layer having an RF(L) layer on the surface, an adhesive layer, and a back rubber layer in this order. The RF(L) layer and the fiber layer can be configured such that, for example, the core wire provided with the RF(L) layer on the surface forms a helix having a pitch in the belt width direction and is sandwiched by the adhesive layer. Further, a back reinforcing cloth may be provided instead of the back rubber layer.

[0049] The inner rubber layer and the back rubber layer are formed of a rubber composition obtained by heating and pressurizing an unvulcanized rubber composition in which various rubber compounding agents are compounded in a rubber component and crosslinking with a crosslinking agent. The rubber compositions forming the compression rubber layer and the back rubber layer may be the same or different.

[0050] Examples of the rubber component of the rubber composition forming the inner rubber layer and the back rubber layer include one or more selected from the group consisting of olefin elastomers such as ethylene-propylene copolymer (EPR), ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer, and ethylene-butene copolymer; chloroprene rubber (CR); chlorosulfonated polyethylene rubber (CSM); hydrogenated acrylonitrile rubber (H-NBR); and the like. In the present invention, the rubber components forming the inner rubber layer, the adhesive layer, and the back rubber layer can be the same.

[0051] Examples of the rubber compounding agents include reinforcing materials, oils, processing aids, vulcanization accelerator aids, crosslinking agents, co-crosslinking agents, vulcanization accelerators, and the like.

[0052] Examples of the reinforcing material include short fibers, and one or more selected from the group consisting of cellulose 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, and the like can be mentioned. The diameter of the short fibers is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less. The compounding amount of the short fibers is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component of the rubber composition, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less.

[0053] Examples of the reinforcing material also include carbon black, and one or more 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, and the like can be mentioned. The compounding amount of carbon black 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, based on 100 parts by mass of the rubber component of the rubber composition.

[0054] Examples of the oil include one or more selected from the group consisting of petroleum softeners, mineral oil-based oils such as paraffin wax, and vegetable oil-based oils such as castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, tall oil, wood rosin, rosin, and pine oil. The content of the oil is, for example, 1.5 to 50 parts by mass based on 100 parts by mass of the rubber component of the rubber composition.

[0055] Examples of the vulcanization accelerator assistant include 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 their derivatives. The content of the vulcanization accelerator assistant is, for example, 5 to 15 parts by mass based on 100 parts by mass of the rubber component of the rubber composition.

[0056] Examples of the crosslinking agent include one or more selected from the group consisting of sulfur and organic peroxides. Examples of the organic peroxides include 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 based on 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 based on 100 parts by mass of the rubber component of the rubber composition.

[0057] 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, acrylate salts, etc.). 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.

[0058] Examples of the method for forming the belt include the following methods. (i) Wrap a rubber sleeve on a cylindrical drum with a smooth surface, and sequentially wind and laminate an uncrosslinked rubber sheet for the back rubber layer and an uncrosslinked sheet for the adhesive layer on its outer periphery. Then, wind a fiber layer having an RF(L) layer spirally around a cylindrical inner mold from above, and further wind and laminate an uncrosslinked rubber sheet for the adhesive layer and an uncrosslinked rubber sheet for the inner rubber layer in order from above to form a laminated molded body.

[0059] (ii) Remove the rubber sleeve provided with the laminated molded body from the cylindrical drum. After setting the laminated molded body in a fitted state on the inner peripheral surface side of the outer mold, position and seal the inner mold inside the rubber sleeve set in the outer mold.

[0060] (iii) Heat the outer mold and inject high-pressure air or the like into the sealed interior of the inner mold to apply pressure. 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. At the same time, the fiber layer having an RF(L) layer is integrally combined. 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.

[0061] (iv) Depressurize the interior of the inner mold to release the seal, take out the belt slab molded through the rubber sleeve between the inner mold and the outer mold, cut the belt slab into a predetermined width, and turn it inside out to manufacture the belt.

Examples

[0062] Hereinafter, examples and comparative examples will be given to explain the present invention in more detail. Note that the present invention is not limited to the following examples. Unless otherwise specified below, “%” means “mass%” and “part” means part by mass.

[0063] [Examples 1 to 4, Comparative Examples 1 to 4] <Preparation of Unvulcanized Sheet of Adhesive Composition> The components shown in Table 1 were mixed in the amounts (parts by mass) shown in Table 1 respectively to obtain an unvulcanized sheet of the adhesive composition. Specifically, after mixing the components other than the crosslinking agent with a Banbury mixer to form a masterbatch, the crosslinking agent was mixed, kneaded using two rolls, turned over, rounded, and rolled to obtain an unvulcanized sheet. For the obtained unvulcanized sheet, the vulcanization characteristics were measured and described in Table 1. Also, test pieces were prepared as follows using the obtained unvulcanized sheet, and the normal temperature adhesive strength, 120 °C adhesive strength, tensile properties, tear strength, and hardness were measured and described in Table 1.

[0064]

Table 1

[0065] <Constituent Components of Adhesive Composition> The constituent components of the adhesive composition in Table 1 are as follows. EPDM: Mitsui TPE 1045 (Trade name of Mitsui Chemicals, ethylene-propylene-diene terpolymer) Carbodiimide compound: bis(2,6-diisopropylphenyl)-carbodiimide Carbon black: FEF carbon (a type of furnace black) Silica: Ultrasil VN3GR (trade name of Evonik Japan) Peroxide: Peroximon F40 (trade name of NOF Corporation)

[0066] In the above Examples and Comparative Examples, the evaluation and measurement of various properties and the like were carried out as follows. <Preparation of Test Pieces> (Preparation of RFL Aqueous Solution) After adding 0.2 g of sodium hydroxide to 41.7 g of soft water while stirring, 2.0 g of resorcinol was added while stirring. 2.15 ml of formalin with a concentration of 37% by mass was added while stirring, and stirring was continued at 23 °C for 1 hour. Soft water was added so that the RF solid content became 3.0% by mass to prepare an RF aqueous solution. After mixing 7.3 g of styrene-butadiene rubber latex (trade name "J9049" manufactured by Nippon A & L Co., Ltd.) and 35.7 g of vinylpyridine-styrene-butadiene rubber latex (trade name "PYRATEX" manufactured by Nippon A & L Co., Ltd.), the RF aqueous solution obtained above was gradually added while stirring, and stirring was continued at 23 °C for 12 hours. Soft water was added while stirring so that the RFL solid content concentration became 16% by mass to prepare an RFL aqueous solution.

[0067] (Preparation of a core wire having an RFL layer) A polyethylene terephthalate cord was prepared, and by passing it through a first tank of crude MDI (trade name, "Sumidule 44V-20" manufactured by Sumitomo Chemical Covestro Urethane Co., Ltd.) (16% by mass toluene solution), a second tank and a third tank of the above RFL aqueous solution, and a fourth tank of adhesive rubber, a core wire having an isocyanate resin layer, an RFL layer, an RFL layer, and an adhesive rubber layer was prepared on the core wire.

[0068] (Preparation of test pieces for adhesion test) Seven of the above core wires were installed in a metal frame at approximately equal intervals so that tension was generated. An unvulcanized rubber sheet of the above adhesive composition was laminated on the recessed part of the mold to form an unvulcanized rubber piece sample with a total thickness of 6.6 mm of a rubber block (6.6 mm × 40 mm × 170 mm), and the metal frame with tension on the core wire and the mold were bonded together. With the cord surface pressed against the rubber side, it was sandwiched between upper and lower vulcanizing hot plates heated to 160 °C and held under the conditions of 160 °C, 4 MPa, and T90 + 5 minutes for crosslinking reaction to prepare test pieces for adhesion test.

[0069] (Preparation of test pieces for other tests) The rubber block was made into a rubber block with a thickness of 2 mm (2 mm × 150 mm × 150 mm), and other test specimens were prepared in the same manner as the test specimens for the adhesion test, except that the vulcanization reaction time was set to T90 + 10 minutes.

[0070] <Vulcanization characteristics> In accordance with JIS K 6300-2 (2001) "Unvulcanized Rubber - Physical Properties - Part 2: Method for Determining Vibration Characteristics by Vibration Type Vulcanization Tester", the vulcanization curve was measured under the following conditions using a rheometer. Temperature: 160 °C Vibration angle: ±1 deg Vibration frequency: 100 cpm From the obtained vulcanization curve, the maximum torque MH (mNm), minimum torque ML (mNm), time T10 (min) until reaching 10% vulcanization, and time T90 (min) until reaching 90% vulcanization were determined.

[0071] <Tensile properties> The measurement was carried out using a tensile testing machine in accordance with JIS K 6251 (2004) "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Properties". The test specimen was a JIS No. 3 test specimen with a thickness of 2.0 mm. M5 represents the tensile stress (MPa) at 5% elongation, TB represents the tensile strength (MPa), and EB represents the elongation at break (%).

[0072] <Tear strength> The measurement was carried out using a tensile testing machine in accordance with JIS K 6252 (2001) "Vulcanized Rubber and Plastic Rubber - Method for Determining Tear Strength". The test specimen was a crescent-shaped test specimen with a thickness of 2.0 mm. The tear strength (TR) was determined by the following formula. TR = F / t TR: Tear strength [N / mm] F: Maximum tear force [N] t: Thickness of the test specimen [mm]

[0073] <Durometer hardness> Using a Type A durometer specified in JIS K 6253, the hardness (instantaneous value) at 23°C was measured.

[0074] <Adhesive strength> Test pieces left standing at 23°C for 24 hours or more were prepared. Using an Instron 5659 tensile testing machine, the rubber part and three cords were each fixed, and a peel test was carried out at a constant speed of 100 mm / min at 23°C so that the rubber part and the cords were separated vertically, and the room temperature adhesive strength was measured. Also, using an adhesive sample left standing in a constant temperature bath at 120°C for 30 minutes, a peel test was carried out in the same manner as above, and the 120°C adhesive strength was measured.

Claims

1. An adhesive composition comprising a synthetic rubber, an acid component, and a carbodiimide, wherein the content of the synthetic rubber is 25 to 75% by mass in the total solid content of the adhesive composition, the content of the acid component is 0.006 to 18.750% by mass in the total solid content of the adhesive composition, the content of the carbodiimide is 0.006 to 18.750% by mass in the total solid content of the adhesive composition, the adhesive composition.

2. An adhesive structure comprising a layer of the adhesive composition according to Claim 1 and a layer formed from RF or RFL.

3. An adhesive structure comprising a layer of the adhesive composition according to Claim 1 and a fiber layer having a layer formed from RF or RFL on the surface.

4. A adherend adhered with the adhesive composition according to Claim 1, wherein the adherend is one or more selected from the group consisting of metal, rubber, plastic, and fiber.

5. A belt comprising the adhesive structure according to Claim 2 or 3.

6. A belt comprising the adhesive structure according to Claim 2 or 3, wherein the fiber layer is a core wire made of a twisted yarn.

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