Adhesive treatment agent for rubber and fiber and synthetic fiber cord for rubber reinforcement using the same

Abstract

To provide an adhesive treatment agent for rubber and fiber that is less prone to adhesive degradation under long-term high temperatures while embedded in rubber, also resists degradation when receiving repeated extension and compression in the rubber, and achieves improved passability of a dipping process, as well as to provide a synthetic fiber cord for reinforced rubber.SOLUTION: An adhesive treatment agent for rubber and fiber contains phenylpropanoid (A), blocked isocyanate compound (B) and rubber latex (C). In a Maron mechanical stability test, the coagulation content is 4.0% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive treatment agent for fibers that improves the adhesion between rubber and synthetic fibers, a synthetic fiber cord for rubber reinforcement formed by adhering this adhesive treatment agent to synthetic fibers, and a rubber product including this synthetic fiber cord for rubber reinforcement. [Background technology]

[0002] Synthetic fibers, such as nylon fibers, polyester fibers, and aromatic polyamide fibers, have traditionally been widely used as reinforcing materials in rubber products such as tires, hoses, and belts. However, when embedded in rubber products and used as reinforcing materials, they are exposed to high temperatures due to heat generation from the rubber, and are repeatedly stretched, compressed, and flexed, which can cause a decrease in the adhesion between the rubber and the synthetic fibers and a decrease in the strength of the synthetic fibers, leading to failure of the rubber products. In recent years, there has been a growing need to improve the durability of rubber products in order to reduce the frequency of replacement due to failures in order to protect the environment.

[0003] On the other hand, the adhesive applied to the reinforcing material is essential for maintaining adhesion to the rubber, but there was a problem in that agglomerates resulting from the adhesive composition applied in the reinforcing material manufacturing process adhered to processing equipment such as the rollers of the dipping machine, reducing operability.

[0004] Prior art techniques disclosed in Patent Documents 1 to 5, for example, address the above-mentioned problems.

[0005] Patent Document 1 discloses a cord with an RFL adhesive impregnation rate of 3.5 to 9%.

[0006] Patent Document 2 discloses a method for producing a polyester fiber cord for rubber reinforcement, which is coated with a first treating agent containing three compounds: an aliphatic epoxide compound, a blocked polyisocyanate compound, and a vinylpyridine-styrene-butadiene rubber latex having a glass transition point of -30 to 0°C, and further coated with a second treating agent containing resorcinol-formalin-rubber latex (RFL) as an outer layer, and which is treated at a first bath hot stretch tension of 0.05 to 0.40 cN / dtex.

[0007] Patent Document 3 discloses an organic fiber cord in which a ply-twisted cord having a first twist and a second twist, the first twist having a twist multiplier of 1000 to 2500 and the second twist having a twist multiplier of 1500 to 3600, is coated with an adhesive containing resorcinol-formaldehyde-rubber latex (RFL), and the cord compression ratio is 83 to 97%, and the degree of RFL impregnation into the cord is 10 to 50%.

[0008] Patent Document 4 discloses an adhesive for organic fibers that contains at least one component selected from the group consisting of polyphenols, chlorophenol resins, and lignin resins, and at least one component selected from water-soluble polymers other than the above components or water-dispersible polymers other than the above components.

[0009] Patent Document 5 discloses a technology for reducing the rate of coagulation in a Maron mechanical stability test and improving passability in a dipping step by adding a rosin acid soap, an aliphatic soap, and a nonionic surfactant to an adhesive latex obtained by emulsion polymerization of a composition containing an aliphatic conjugated diene monomer, a vinylpyridine monomer, and other monomers copolymerizable with these. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Special Publication No. 2014-530302 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-76186 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-150105 [Patent Document 4] WO2018 / 003572 issue [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-169422 Summary of the Invention [Problem to be solved by the invention]

[0011] However, while Patent Document 1 improves fatigue resistance, its adhesive strength is insufficient. Patent Documents 2 and 3 improve adhesive strength and fatigue resistance compared to conventional products, but do not provide sufficient durability in the face of ever-increasing demands. Patent Document 4 improves initial adhesive strength, but does not provide sufficient heat-resistant adhesive strength or durability. Furthermore, all Patent Documents 1 to 4 still suffer from the problem of resin coagulation during the dipping process.

[0012] On the other hand, according to Patent Document 5, although the occurrence of resin coagulation during the dipping step was reduced, the fatigue resistance and adhesive strength were not sufficient.

[0013] The present invention has been made as a result of studies aimed at solving the problems in the prior art described above.

[0014] The object of the present invention is to provide an adhesive treatment agent for rubber and fiber, and synthetic fiber cord for rubber reinforcement, which exhibits little adhesive deterioration when embedded in rubber of tires, belts, hoses, etc. at high temperatures for long periods of time, suppresses deterioration when subjected to repeated stretching and compression in the rubber, and also suppresses the generation of resin coagulation during the dipping process. [Means for solving the problem]

[0015] In order to solve the above problems, the present invention employs the following means: (1) Phenylpropanoid (A), blocked isocyanate compound (B), and rubber latex (C) , and surfactant (D) An adhesive treatment agent for rubber and fiber comprising: The solid weight ratio of the phenylpropanoid (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:5 to 10:20, , The phenylpropanoid (A) includes lignins, and the blocked isocyanate compound (B) includes an aromatic polyisocyanate compound blocked with methyl ethyl ketoxime or an aromatic compound of diphenylmethane diisocyanate, An adhesive treatment agent for rubber and fiber characterized in that the proportion of coagulated material measured by the Maron mechanical stability test is 4.0% or less.

[0017] ( 2 ) The blocked isocyanate compound (B) is characterized in that the dissociation temperature of the blocking agent is 100 to 160°C. (1) The adhesive treatment agent for rubber and fiber described in

[0020] ( 3 ) The surfactant (D) is an anionic surfactant. (1) or (2) 1. An adhesive treatment agent for rubber and fiber according to any one of the preceding claims.

[0021] ( 4 ) The amount of the solid content of the surfactant (D) added is 1 to 7 parts by weight based on 100 parts by weight of the solid content of the rubber latex (C). 3 ) An adhesive treatment agent for rubber and fiber according to any one of the preceding claims.

[0022] ( 5 )(1)~( 4 1. A synthetic fiber cord for rubber reinforcement, characterized in that the adhesive treatment agent according to any one of the preceding items is adhered to a synthetic fiber and then heat-treated.

[0023] ( 6 ) characterized in that it is further coated with an adhesive treatment agent containing resorcinol-formalin-rubber latex (RFL) ( 5 ) A synthetic fiber cord for rubber reinforcement according to the above.

[0024] ( 7 )( 5 )or( 6 A rubber product comprising the synthetic fiber cord for rubber reinforcement according to claim 1. [Effects of the Invention]

[0025] According to the present invention, a synthetic fiber cord for rubber reinforcement can be obtained that exhibits significantly improved heat-resistant adhesion and fatigue resistance in high-temperature environments when exposed to high temperatures for long periods of time during the rubber vulcanization process or during use of rubber products. Rubber products reinforced with the synthetic fiber cord for rubber reinforcement according to the present invention can withstand harsh conditions for longer periods of time than conventional cords when used in tires, belts, and hoses. Furthermore, the generation of resin coagulation can be suppressed during the dipping process, which is part of the cord manufacturing process. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described in detail below.

[0027] The adhesive treatment agent for rubber and fiber of the present invention is an adhesive treatment agent for rubber and fiber comprising a phenylpropanoid (A), a blocked isocyanate compound (B), and a rubber latex (C), and the proportion of coagulated material determined by the Maron mechanical stability test must be 4.0% or less.

[0028] The phenylpropanoid (A) of the present invention is an aromatic compound having a basic skeleton of a C6-C3 unit in which a linear propane (C3) is bonded to a benzene ring (C6), and derivatives thereof. Examples include coumaric acid, cinnamic acid, caffeic acid, eugenol, anethole, coniferyl alcohol, sinapyl alcohol, sesamin, lignins, and lignans. Among these, from the viewpoint of improving the adhesive strength between rubber and fiber, it is preferable to use a compound containing at least one compound selected from the group consisting of coumaric acid, caffeic acid, lignins, and lignans. Examples of coumaric acid include o-coumaric acid, m-coumaric acid, p-coumaric acid, and ferulic acid. Examples of cinnamic acid include cinnamic acid, methyl cinnamate, ethyl cinnamate, n-butyl cinnamate, and cinnamic anhydride. Examples of caffeic acid include caffeine, methyl caffeate, and caffeic acid phenethyl ester. Examples of lignins include kraft lignin and lignosulfonic acid, and examples of lignosulfonic acid include sodium lignosulfonate, magnesium lignosulfonate, and calcium lignosulfonate. Examples of lignans include pinoresinol, podophyllotoxin, steganacin, lariciresinol, secoisolariciresinol, matairesinol, hydroxymatairesinol, and syringaresinol. In the present invention, these can be used alone or in combination.

[0029] The blocked isocyanate compound (B) used in the present invention is one in which the blocking agent is liberated by heating to produce an active isocyanate compound. Specific examples include reaction products of polyisocyanate compounds such as tolylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and triphenylmethane triisocyanate with blocking agents such as phenols such as phenol, cresol, and resorcinol, lactams such as ε-caprolactam and valerolactam, and oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexane oxime.

[0030] Among these blocked polyisocyanate compounds, aromatic polyisocyanate compounds blocked with methyl ethyl ketoxime and aromatic compounds of diphenylmethane diisocyanate give particularly good results.

[0031] The blocked isocyanate compound (B) preferably has a dissociation temperature of the blocking agent of 100 to 160°C in order to prevent the occurrence of resin coagulation in the dipping step, which is part of the production process of the cord.

[0032] Examples of the rubber latex (C) used in the present invention include natural rubber latex, butadiene rubber latex, styrene-butadiene rubber latex, vinylpyridine-styrene-butadiene rubber latex, nitrile rubber latex, hydrogenated nitrile rubber latex, chloroprene rubber latex, chlorosulfonated rubber latex, and ethylene-propylene-diene rubber latex, and these can be used alone or in combination.

[0033] In the present invention, the weight ratio of the phenylpropanoid (A) solid matter to the blocked isocyanate (B) solid matter is preferably 10:1 to 10:30, and more preferably 10:5 to 10:20. While a large amount of blocked isocyanate compound improves adhesive strength, it can also reduce the cord's flexibility, thereby reducing fatigue resistance in rubber, and can cause aggregates to adhere to processing equipment such as the rollers of a dipping machine in the rubber reinforcement synthetic fiber cord manufacturing process, resulting in reduced operability. By incorporating the phenylpropanoid (A) and blocked isocyanate compound (B) into the same treatment agent and ensuring that their amounts are within the specified ranges of the present invention, an adhesive treatment agent can be obtained that exhibits excellent adhesion between rubber and fiber and excellent fatigue resistance of fiber in rubber under high-temperature conditions.

[0034] In the adhesive treating agent for rubber and fiber of the present invention, the solid content of the phenylpropanoid (A) in 100% by weight of the total solid content is preferably 5 to 50% by weight, more preferably 10 to 40% by weight. If it is less than 5% by weight or exceeds 50% by weight, the adhesive strength may be insufficient.

[0035] In the adhesive treating agent for rubber and fiber of the present invention, the phenylpropanoid (A), blocked isocyanate compound (B), and rubber latex (C) are preferably mixed in a weight ratio of [(solid content of A) + (solid content of B)]:(solid content of C) of 10:90 to 60:40. More preferably, the weight ratio of [(solid content of A) + (solid content of B)]:(solid content of C) is 20:80 to 50:50. Outside this range, the adhesive strength may be insufficient and fatigue resistance may deteriorate.

[0036] Furthermore, in the present invention, the adhesive treatment agent for rubber and fiber containing at least the three substances described above must show a coagulation rate of 4.0% or less in the Maron mechanical stability test. The specific method of the Maron mechanical stability test will be described later, but this test indicates the stability of the adhesive treatment agent when mechanical shear stress is applied to the adhesive treatment agent, and is used in the present invention as a measure of the degree of coagulation that occurs during the dipping process in which the adhesive treatment agent is applied to fibers.

[0037] The adhesive treating agent for rubber and fiber of the present invention must have a coagulation rate of 4.0% or less in the Maron mechanical stability test, preferably 3.5% or less, and more preferably 3.0% or less. If the rate exceeds 4.0%, coagulation occurs frequently during the dipping process, making continuous production difficult, and the coagulation may adhere to the synthetic fiber cord for rubber reinforcement, leading to a deterioration in adhesion to the rubber. If the coagulation rate in the same test is below the specified level of the present invention, the processability during the dipping process is improved, which is preferable.

[0038] Synthetic fiber cords used in rubber products are required to have heat-resistant adhesion and fatigue resistance in rubber, and their production requires good processability in the dipping process, but it has been extremely difficult to achieve both of these with conventionally known techniques. As a result of extensive research into achieving both of these, the present invention has discovered for the first time that by using an adhesive treatment agent comprising a mixture of components (A), (B), and (C), it is possible to achieve both, and that there is a mixing ratio of each component that produces a remarkable effect.

[0039] There are no particular limitations on the method for keeping the coagulum ratio in the Maron mechanical stability test below the specified value of the present invention, but it can be adjusted by optimizing the selection of the phenylpropanoid (A), blocked isocyanate (B), and rubber latex (C) used and their compounding ratios. Another preferred method involves adding a surfactant (D) to the adhesive treatment agent for rubber and fiber. Furthermore, it is more preferable that the surfactant be an anionic surfactant. Examples of anionic surfactants include alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, and alkylbenzene sulfonates.

[0040] Examples of alkyl sulfates include sodium lauryl sulfate, sodium higher alcohol sulfate, triethanolamine lauryl sulfate, and ammonium lauryl sulfate. Examples of polyoxyethylene alkyl ether sulfates include sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene polyoxypropylene alkyl ether sulfate, and ammonium polyoxyethylene distyrenated ether sulfate. Examples of alkyl benzene sulfonates include alkyl benzene sulfonic acid, sodium dodecyl benzene sulfonate, sodium alkyl naphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium alkyl diphenyl ether disulfonate, and sodium alkane sulfonate.

[0041] The amount of the solid content of the surfactant (D) added is preferably 1 to 7 parts by weight, more preferably 2 to 5 parts by weight, based on 100 parts by weight of the solid content of the rubber latex (C). If it is less than 1 part by weight, the effect of inhibiting coagulation may be low, and if it exceeds 7 parts by weight, the adhesive strength may decrease and foaming of the treatment agent may occur in the dipping step, resulting in poor processability.

[0042] The adhesive treating agent for rubber and fiber of the present invention is a solids solution or dispersion in water, and the total solids concentration is preferably 3 to 25% by weight, more preferably 5 to 20% by weight. If the concentration is outside this range, the adhesive strength may decrease.

[0043] The synthetic fiber cord for rubber reinforcement of the present invention comprises a synthetic fiber and the adhesive treatment agent for rubber and fiber of the present invention described above (an adhesive treatment agent for rubber and fiber comprising a phenylpropanoid, a blocked isocyanate compound, and rubber latex, characterized in that the proportion of coagulated material determined by the Maron mechanical stability test is 4.0% or less).

[0044] The amount of adhesive treatment agent adhered to the synthetic fibers is preferably 0.5 to 12 parts by weight, more preferably 1.0 to 10 parts by weight, in terms of solid content, per 100 parts by weight of synthetic fibers. If the amount is outside this range, the adhesive strength may decrease.

[0045] The synthetic fiber used in the synthetic fiber cord for rubber reinforcement of the present invention is preferably in the form of a multifilament. Materials constituting the synthetic fiber include nylon 6, nylon 66, nylon 46, polyethylene terephthalate, polyethylene naphthalate, aramid, and polyvinyl alcohol. From the standpoints of durability and industrial productivity, it is particularly preferable to use at least one fiber selected from nylon fiber, polyester fiber, and aromatic polyamide fiber.

[0046] The polyester fiber is preferably a fiber obtained by melt spinning and drawing a polyester having terephthalic acid as the main difunctional carboxylic acid and ethylene glycol as the main glycol component, but fibers made of polyester in which terephthalic acid is partially or completely replaced with 2,6-naphthalenedicarboxylic acid, 4,4-dicarboxyphenoxyethane, isocyanate groups, etc., or in which ethylene glycol is partially or completely replaced with diethylene glycol, propylene glycol, butanediol, etc., can also be used.

[0047] The polyester may also be a copolymer of a small amount of a trifunctional compound such as trimesic acid, trimellitic acid, boric acid, phosphoric acid, glycerin, and trimethylolpropane.

[0048] The polyester fibers may also be modified with various modifiers, for example, terminal carboxyl group blocking agents such as carbodiimide compounds, epoxy compounds, isocyanate compounds, and oxazoline compounds.

[0049] As the aromatic polyamide fibers, those made from poly-p-phenylene terephthalamide, poly-p-phenylene-3,4'-diphenyl ether terephthalamide, and copolymers mainly made of these are preferably used.

[0050] The synthetic fibers used in the present invention may be those to which a polyepoxide compound has been added in advance during the spinning process. The polyepoxide compound may be a compound containing at least two epoxy groups in one molecule in an amount of 0.1 g equivalent or more per 100 g of the compound. Specific examples include reaction products of polyhydric alcohols such as pentaerythritol, ethylene glycol, polyethylene glycol, propylene glycol, glycerol, and sorbitol with halogen-containing epoxides such as epichlorohydrin; polyepoxide compounds obtained by oxidizing unsaturated compounds with peroxide or hydrogen peroxide, such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate, bis(3,4-epoxy-6-methyl-cyclohexylmethyl)adipate, and aromatic polyepoxides such as phenol novolac, hydroquinone, biphenyl, bisphenol S, brominated novolac, xylene-modified novolac, phenol glyoxal, trisoxyphenylmethane, trisphenol PA, and bisphenol polyepoxides. Particularly preferred are sorbitol glycidyl ether and cresol novolac polyepoxides.

[0051] These compounds are usually used as an emulsion or solution, i.e., the compound is dissolved in a solvent and used as a solution, or emulsified using a common emulsifier such as sodium alkylbenzenesulfonate, dioctyl sulfosuccinate sodium salt, or nonylphenol ethylene oxide adduct and used as an emulsion.

[0052] The polyepoxide compound is applied together with a spinning oil during the synthetic fiber spinning process. The amount of the polyepoxide compound attached is preferably in the range of 0.1 to 5% by weight. When the amount of the polyepoxide compound attached is within the above range, the effect of the polyepoxide compound is fully exerted, and satisfactory adhesion between the synthetic fiber and rubber is obtained. Furthermore, when the amount is within the above range, the fiber does not become too hard, and the tenacity is less likely to decrease during the twisting process described below.

[0053] The synthetic fibers used in the present invention are not subject to any restrictions on fineness, number of filaments, cross-sectional shape, etc., but typically have a total fineness of 200 to 5,000 dtex and preferably 30 to 1,000 filaments, with 250 to 3,000 dtex and 50 to 500 filaments being particularly preferred. If the total fineness is less than 200 dtex, the cord strength may be insufficient, and if it exceeds 5,000 dtex, the cord may become too thick and its handleability may decrease. Furthermore, if it is less than 30 filaments, the cord may become too stiff and its handleability may deteriorate, and if it exceeds 500 filaments, the cord may become too fluffed and its quality may deteriorate.

[0054] From the viewpoint of improving fatigue resistance, the synthetic fiber cord for rubber reinforcement of the present invention can be obtained by twisting the above synthetic fibers to form a twisted cord, and then dipping the twisted cord in the adhesive treatment agent of the present invention and heat-treating it either as is or after weaving it into a blind. For example, twisted cords used for carcass tire cords can be made by first twisting in the S or Z direction, and then combining two or three first-twist cords and twisting them together, usually with the same number of second twists in the opposite direction to the first twist, to form a multi-twisted twisted cord. The twisted cords are used as warp yarns, and cotton yarn or synthetic fiber covered with cotton yarn is used as weft yarns, and the weft is woven into a blind to form a green curtain. The green curtain is then dipped in the adhesive treatment agent and heat-treated to obtain a dipped curtain.

[0055] On the other hand, in the case of hose cords, for example, one strand or two strands are aligned and first twisted to form a single-twist twisted cord, and in the case of belt cords, two or three single-twist cords are put together and then twisted in the opposite direction to the first twist, usually with the same number of second twists, to form a multi-twist twisted cord, which is then dipped in an adhesive treatment agent and heat-treated while still in the twisted cord form to obtain a dipped cord.

[0056] The synthetic fiber cord for reinforcing rubber to which the adhesive treatment agent of the present invention is applied refers to both the above-mentioned dipped cloth and dipped cord.

[0057] The synthetic fiber cord for rubber reinforcement of the present invention may be subjected to a dip treatment and heat treatment in a primer treatment agent containing an epoxy compound, so that the primer treatment agent adheres to the synthetic fiber, before the twisted cord is dipped and heat treated in the adhesive treatment agent for rubber and fiber of the present invention described above (an adhesive treatment agent for rubber and fiber comprising a phenylpropanoid, a blocked isocyanate compound, and rubber latex, which is characterized in that the proportion of coagulated material measured by the Maron mechanical stability test is 4.0% or less).

[0058] The epoxy compound that can be used in the primer treatment agent can be a compound that contains at least two or more epoxy groups in one molecule, and the compound contains 0.1g equivalent or more per 100g of the compound.Specifically, it can be mentioned the reaction product of polyhydric alcohols such as pentaerythritol, ethylene glycol, polyethylene glycol, propylene glycol, glycerol, sorbitol, etc. with halogen-containing epoxides such as epichlorohydrin, polyepoxide compounds obtained by oxidizing unsaturated compounds with peroxide or hydrogen peroxide, for example, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate, bis(3,4-epoxy-6-methyl-cyclohexylmethyl)adipate, aromatic polyepoxides such as phenol novolac type, hydroquinone type, biphenyl type, bisphenol S type, brominated novolac type, xylene-modified novolac type, phenol glyoxal type, trisoxyphenylmethane type, trisphenol PA type, bisphenol type polyepoxide, etc. Particularly preferred are sorbitol glycidyl ether type and cresol novolac type polyepoxides.

[0059] These compounds are usually used as an emulsion or solution, i.e., the compound is dissolved in a solvent and used as a solution, or emulsified using a common emulsifier such as sodium alkylbenzenesulfonate, dioctyl sulfosuccinate sodium salt, or nonylphenol ethylene oxide adduct and used as an emulsion.

[0060] Here, the primer treatment agent containing an epoxy compound preferably has a solids concentration of 1 to 10% by weight, and the resin adhesion amount of the primer treatment agent is preferably in the range of 0.2 to 6 parts by weight per 100 parts by weight of synthetic fiber from the viewpoint of adhesion and fatigue resistance.

[0061] Furthermore, the synthetic fiber cord for rubber reinforcement of the present invention may be prepared by dipping and heat-treating a twisted cord in the adhesive treatment agent for rubber and fiber of the present invention described above (an adhesive treatment agent for rubber and fiber comprising a phenylpropanoid, a blocked isocyanate compound, and rubber latex, characterized in that the proportion of coagulated material measured by the Maron mechanical stability test is 4.00% or less), and then dipping and heat-treating the twisted cord in an adhesive treatment agent containing resorcinol-formalin-rubber latex (RFL) to adhere the RFL.

[0062] Resorcinol-formalin-rubber latex (RFL) is a mixture of resorcinol-formaldehyde precondensate and rubber latex. It is preferably prepared using resorcinol-formaldehyde precondensate obtained by precondensation under an alkaline catalyst. For example, resorcinol and formaldehyde are mixed in an alkaline aqueous solution containing an alkaline compound such as sodium hydroxide, and the mixture is left at room temperature for several hours to allow the resorcinol and formaldehyde to precondense. After this, rubber latex is added to form a mixed emulsion.

[0063] The resorcinol-formaldehyde precondensate preferably has a molar ratio of resorcinol to formaldehyde of 1:0.3 to 1:5, preferably 1:0.75 to 1:2.0. If the molar ratio of formaldehyde is lower than this range, the dipped cord may become tacky, which may lead to soiling of the dipping machine. On the other hand, if the molar ratio of formaldehyde is higher than this range, the adhesive strength may decrease.

[0064] Examples of rubber latexes that can be used to prepare resorcinol-formalin-rubber latex include natural rubber latex, butadiene rubber latex, styrene-butadiene rubber latex, vinylpyridine-styrene-butadiene rubber latex, nitrile rubber latex, hydrogenated nitrile rubber latex, chloroprene rubber latex, chlorosulfonated rubber latex, and ethylene-propylene-diene rubber latex, and these can be used alone or in combination.

[0065] For resorcinol-formaldehyde-rubber latex, the preferred compounding ratio of resorcinol-formaldehyde precondensate to rubber latex is 2 / 1 to 1 / 12 by solid weight. Outside this range, adhesive strength may decrease.

[0066] The solid content concentration of the adhesive treatment agent containing RFL is preferably 3 to 20% by weight.

[0067] The amount of adhesive treatment agent containing RFL adhered to synthetic fibers is preferably in the range of 0.5 to 10 parts by weight of solid content of the adhesive treatment agent containing RFL per 100 parts by weight of synthetic fibers from the viewpoint of adhesion and fatigue resistance. If it exceeds 10 parts by weight, it may cause contamination of the dip treatment machine described below. The synthetic fiber cord for rubber reinforcement of the present invention characterized as described above exhibits significantly improved fatigue resistance during the rubber vulcanization process and during use of rubber products, and suppresses the generation of resin coagulation during the dipping process. Rubber products reinforced with the synthetic fiber cord for rubber reinforcement of the present invention can withstand longer-term, harsh use than conventional products when used in tires, belts, and hoses, and are therefore extremely useful for rubber reinforcement.

[0068] Next, a method for producing the synthetic fiber cord for reinforcing rubber of the present invention will be described.

[0069] An example of a method for producing the synthetic fiber cord for rubber reinforcement of the present invention is a method in which a twisted synthetic fiber cord is dipped into the adhesive treatment agent for fiber and rubber of the present invention, followed by drying to remove water at a temperature preferably in the range of 100 to 150°C, and then heat treatment at 200 to 255°C.

[0070] Here, "dipping" refers to applying an adhesive treatment agent to a twisted cord by running the twisted cord through a dipping tank equipped with rollers and filled with the adhesive treatment agent. "Heat treatment" refers to heating the twisted cord by running the twisted cord through an oven equipped with rollers and capable of being set to a predetermined temperature. Dip treatment machines for carrying out such dipping and heat treatment are commercially available, for example, from Ritzler. Note that any other method can be used to attach the adhesive treatment agent to synthetic fibers, such as spraying the adhesive treatment agent from a nozzle.

[0071] In order to control the amount of solids of the adhesive treatment agent attached to the synthetic fibers, means such as squeezing with a pressure roller, scraping with a scraper, blowing with air, and suction may be used.

[0072] Furthermore, after the above drying and heat treatment, the synthetic fiber cord can be softened by sliding it against an edge to obtain any desired cord stiffness.

[0073] Furthermore, when an adhesive treatment agent containing an RFL is subsequently applied, the same dipping method as above can be employed. That is, the synthetic fiber cord for rubber reinforcement obtained above is dipped in an adhesive treatment agent containing an RFL, and the water is dried preferably at a temperature of 100 to 150°C, followed by heat treatment at 200 to 255°C. The same methods as above can be employed for controlling the amount of solids applied and for softening treatment.

[0074] The synthetic fiber cord for rubber reinforcement of the present invention thus obtained has significantly improved heat-resistant adhesion and fatigue resistance when exposed to high temperatures for long periods during the rubber vulcanization process and during use in rubber products. Rubber products reinforced with the synthetic fiber cord for rubber reinforcement of the present invention can withstand longer periods of severe use when used in tires, belts, and hoses, and are therefore extremely useful for rubber reinforcement. [Example]

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples specifically described below, the measured values ​​were determined by the following methods.

[0076] (1) Maron type mechanical stability test The percentage of coagulated material in a rubber and fiber adhesive treatment agent was measured using the Maron mechanical stability tester. Using a Yasuda Seiki Seisakusho Maron mechanical stability tester, 50 g of adhesive treatment agent was subjected to mechanical shear at a rotor speed of 1,000 rpm, a rotor load of 10 kg, and a rotation time of 3 minutes. The sample was then filtered through a 100-mesh wire screen. The captured coagulated material was dried and its mass was measured. The percentage by weight of the coagulated material relative to the solid mass of the original rubber and fiber adhesive treatment agent was calculated, and this value was taken as the percentage of coagulated material (%).

[0077] (2) Formation of aggregates during the dipping process In the dipping and heat treatment process using a Ritzler Computreator treatment machine, a twisted yarn cord was immersed in the adhesive treatment agent of the present invention and run for 1 hour at a cord running speed of 20 m / min. After that, the amount of coagulated material deposited on the turn roll with which the cord came into contact as it ran through an oven at 120°C was checked and rated (coagulated material: much = B>A>S=none). In the present invention, S and A were set as pass marks for process passability that could withstand practical use, with S being superior in practical use.

[0078] (3) Amount of adhesive treatment agent attached The weight of the twisted yarn cord per certain length was measured in advance, and the weight of the synthetic fiber cord of the same length after the adhesive was applied was measured, and the amount of adhesive applied was calculated as the difference.

[0079] (4) Initial adhesive strength and heat-resistant adhesive strength This indicates the adhesive strength between synthetic fiber cord and rubber. In accordance with JIS L-1017 (2002) Appendix 1, 3.1T test (A method), a synthetic fiber cord is embedded in unvulcanized rubber, and the initial adhesive strength is measured at 150°C for 30 minutes at 50 kg / cm. 2 , heat-resistant adhesive strength is 170℃, 70 minutes, 50lg / cm 2 After cooling, the synthetic fiber cord was pulled out from the rubber block at a speed of 300 mm / min, and the load required for the pull-out was expressed in N / cm. The average value of 10 measurements was taken as the adhesive strength value.

[0080] (5) Fatigue resistance in rubber (retention rate) Evaluation was performed in accordance with 2.2.2 Disc Fatigue Strength (Goodrich Method) of JIS-L1017 (2002) Appendix 1. Two synthetic fiber cords were embedded in unvulcanized rubber and vulcanized at 150°C for 30 minutes to create a rubber composite. This test specimen was subjected to a deformation cycle of 6.3% compression and 12.6% elongation at 2600 cycles / min in a 100°C atmosphere for 12 hours, after which the synthetic fiber cords were removed from the rubber and the post-fatigue breaking strength was measured, and the result was expressed as a retention rate before and after the fatigue test. The retention rate was the average value of 8 measurements.

[0081] The composition of the unvulcanized rubber compound used in measuring the initial adhesive strength, heat resistant adhesive strength and fatigue resistance in rubber is as follows. Natural rubber (RSS#1): 70 (parts by weight) SBR (JSR1501): 30 (weight parts) RF carbon black: 40 (parts by weight) Stearic acid: 2 (parts by weight) Sulfur: 2 (parts by weight) Zinc oxide: 5 (parts by weight) 2,2'-Dithiobenzothiazole: 3 (parts by weight) Naphthenic acid process oil: 3 (parts by weight).

[0082] (Examples 1 to 5, Comparative Examples 1 and 2) Phenylpropanoid (A), blocked isocyanate compound (B), and rubber latex (C) were mixed with water so that the solid content ratios were as shown in Table 1. For adhesive treatment agents containing surfactant (D), the solid content of surfactant (D) was mixed in the ratio shown in Table 1 relative to 100% by weight of the solid content of rubber latex (C), yielding an adhesive treatment agent with a total solids concentration of 15% by weight. The percentage of coagulated material (%) of this adhesive treatment agent was measured using the method described in (1) Maron's mechanical stability test above. Water was added to the 15% by weight adhesive treatment agent, resulting in an adhesive treatment agent with a total solids concentration of 10% by weight, which was then used in the dip treatment described below.

[0083] In addition, a resorcinol / formalin molar ratio of 1 / 1.4 was mixed in the presence of caustic soda, adjusted to a solids concentration of 10%, and aged for 2 hours to obtain a precondensation product of resorcinol and formalin. Next, this precondensation product (RF) was mixed with rubber latex (Nippol 2518FS, manufactured by Nippon Zeon Co., Ltd.) at a ratio of RF / L = 1 / 5 (solids weight ratio) and aged for 24 hours. This mixture was diluted with water to obtain an RFL adhesive treatment agent with a solids weight of 15%.

[0084] Separately, two 1670 dtex circular cross-section polyester multifilament yarns (Toray Industries, Inc., "Tetoron" 1670T-360-705M) were twisted with a twist number of 40 turns / 10 cm for the first twist and 40 turns / 10 cm for the second twist to obtain a twisted yarn cord.

[0085] The twisted yarn cord was immersed in an adhesive treatment agent containing the above-mentioned components (A), (B), (C), and (D) using a Computreator processor (manufactured by Ritzler Co., Ltd.), then dried at 120°C for 2 minutes and subsequently heat-treated at 245°C for 1 minute to obtain a synthetic fiber cord. The cord was then run at a speed of 20 m / min for 1 hour. After the treatment was completed, the amount of coagulated material deposited on the turn roll with which the cord came into contact as it ran through the 120°C oven of the Computreator processor was confirmed and evaluated (coagulated material: large = B>A>S = none).

[0086] Next, the cord was immersed in the RFL adhesive treatment agent, dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute to obtain a synthetic fiber cord.

[0087] The solid adhesive content of the resulting synthetic fiber cord was 3.5 parts by weight of the adhesive containing (A), (B), (C), and (D) per 100 parts by weight of synthetic fiber, and 4 parts by weight of the adhesive containing RFL per 100 parts by weight of synthetic fiber.

[0088] The synthetic fiber cord thus obtained was embedded in unvulcanized rubber and vulcanized, after which the initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance in rubber were measured. The results are shown in Table 1.

[0089] (Examples 6 to 9, Comparative Examples 3 to 4) Glycerol polyglycidyl ether ("Denacol" EX313 (manufactured by Nagase Chemicals Co., Ltd.)) was diluted with water to obtain a primer treatment agent with a total solids content of 6.0% by weight.

[0090] Furthermore, the phenylpropanoid (A), blocked isocyanate compound (B), and rubber latex (C) were mixed with water so that the solid contents thereof were in the ratios shown in Table 1, and in the case of adhesive treatment agents containing surfactant (D), the solid content of surfactant (D) relative to 100% by weight of the solid content of rubber latex (C) was mixed in the ratio shown in Table 1 to obtain adhesive treatment agents with a total solid content concentration of 15% by weight. The proportion (%) of coagulated material in this adhesive treatment agent was measured using the method described in (1) Maron's mechanical stability test above.

[0091] Two 1670 dtex circular cross-section polyester multifilament yarns (Toray Industries, Inc., "Tetoron" 1670T-360-705M) were twisted with a twist number of 40 turns / 10 cm for the first twist and 40 turns / 10 cm for the second twist to obtain a twisted yarn cord.

[0092] The twisted cord was immersed in the primer treatment agent using a Computreator treatment machine (manufactured by Ritzler Co., Ltd.), then dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute to obtain a synthetic fiber cord.

[0093] Next, the cord was immersed in an adhesive treatment agent containing the above-mentioned components (A), (B), (C), and (D) using a Computreator processor (manufactured by Ritzler Co., Ltd.), dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute to obtain a synthetic fiber cord. The cord was then run at a speed of 20 m / min for 1 hour. After the treatment was completed, the amount of coagulated material deposited on the turn roll with which the cord came into contact as it ran through the 120°C oven of the Computreator processor was confirmed and evaluated (coagulated material: abundant = B>A>S = none).

[0094] The solid adhesive content of the resulting synthetic fiber cord was 1.2 parts by weight of the primer treatment agent per 100 parts by weight of the synthetic fiber, and 4.0 parts by weight of the adhesive containing (A), (B), (C), and (D) per 100 parts by weight of the synthetic fiber.

[0095] The components of the adhesive treatment agent shown in Table 1 are as follows: (A)-1: Lignin (manufactured by Tokyo Chemical Industry Co., Ltd., sodium lignosulfonate) (A)-2: Caffeic acid (Tokyo Chemical Industry Co., Ltd., caffeic acid) (A)-3: Cinnamic acid (Tokyo Chemical Industry Co., Ltd., trans-cinnamic acid) (A)-4: Coumaric acid (Tokyo Chemical Industry Co., Ltd., trans-p-coumaric acid) (A)-5: Lignans (Kanto Chemical Co., Ltd., pinoresinol) (B)-1: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-6400, dissociation temperature 120 to 160°C) (B)-2: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-3031CONC, dissociation temperature 160-180°C) (C)-1: Rubber latex (Pilatex, manufactured by Nippon A&L Co., Ltd.) (D)-1: Anionic surfactant (Emeral 20C, manufactured by Kao Corporation) (D)-2: Anionic surfactant (Pelex NB-L, manufactured by Kao Corporation) The synthetic fiber cord thus obtained was embedded in unvulcanized rubber and vulcanized, after which the initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance in rubber were measured. The results are shown in Table 1.

[0096] As can be seen from the results in Table 1, in the case of Examples 1 to 9 according to the present invention, the adhesion to rubber and heat-resistant adhesion were good, and further, fatigue resistance in a high-temperature atmosphere was significantly improved, and the processability in the dipping step was also good.

[0097] [Table 1]

Claims

1. 1. An adhesive treatment agent for rubber and fiber comprising a phenylpropanoid (A), a blocked isocyanate compound (B), a rubber latex (C), and further a surfactant (D), wherein the solids weight ratio of the phenylpropanoid (A) to the blocked isocyanate compound (B) is (solids content of A):(solids content of B)=10:5 to 10:20, the phenylpropanoid (A) is a lignin, and the blocked isocyanate compound (B) contains an aromatic polyisocyanate compound blocked with methyl ethyl ketoxime or an aromatic compound of diphenylmethane diisocyanate, and the proportion of coagulated material in a Maron mechanical stability test is 4.0% or less.

2. 2. The adhesive treating agent for rubber and fiber according to claim 1, wherein the blocked isocyanate compound (B) has a dissociation temperature of the blocking agent of 100 to 160°C.

3. 3. The adhesive treating agent for rubber and fiber according to claim 1, wherein the surfactant (D) is an anionic surfactant.

4. The adhesive treatment agent for rubber and fiber according to any one of claims 1 to 3, characterized in that the amount of solid content of the surfactant (D) added is 1 to 7 parts by weight based on 100 parts by weight of solid content of the rubber latex (C).

5. A synthetic fiber cord for reinforcing rubber, characterized in that the adhesive treatment agent according to any one of claims 1 to 4 is adhered to a synthetic fiber and then heat-treated.

6. 6. The synthetic fiber cord for reinforcing rubber according to claim 5, further comprising an adhesive treatment agent containing resorcinol-formalin-rubber latex (RFL) attached thereto.

7. A rubber product comprising the synthetic fiber cord for rubber reinforcement according to claim 5 or 6.

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