Rubber / fiber adhesion treating agent and synthetic fiber cord for rubber reinforcement using same

Abstract

The present invention addresses the problem of providing: a rubber / fiber adhesion treating agent which is composed of an adhesion treating agent using starting materials that are favorable for the reduction of environmental load, while containing no resorcinol and no formalin, and which exhibits an initial adhesive force that is equivalent to or higher than the initial adhesive force of conventional RFLs, while being suppressed in adhesion degradation if buried in a rubber for a long period of time in a high temperature environment and being suppressed in strength deterioration if subjected to repeated extension and compression in a rubber; and a synthetic fiber cord for rubber reinforcement. The present invention also addresses the problem of providing: a rubber / fiber adhesion treating agent which has good productivity and good storage stability of an adhesion treating agent, while being capable of suppressing the occurrence of a resin coagulum during a dipping process; and a synthetic fiber cord for rubber reinforcement. The purpose of the present invention is to provide a rubber / fiber adhesion treating agent which contains at least (A) a lignin derivative, (B) a water-soluble or water-dispersible crosslinking agent and (C) a rubber latex, while containing no resorcinol / formaldehyde resin, wherein the lignin derivative (A) has a number average molecular weight of 10,000 to 60,000 and a weight average molecular weight of 80,000 to 130,000.

Description

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

[0001] The present invention relates to a novel adhesive treatment agent that is advantageous in reducing the environmental load, and to a synthetic fiber cord for reinforcing rubber.

[0002] Synthetic fibers such as nylon fibers, polyester fibers, and aromatic polyamide fibers are widely used as reinforcing materials in rubber products such as tires, hoses, and belts. RFL (resorcinol-formalin-latex) adhesives containing resorcinol, formalin, and rubber latex have been widely used as a means for adhering these synthetic fibers to rubber compositions in rubber products. However, both resorcinol and formalin are highly toxic substances that pose a high environmental burden and are harmful to health. Therefore, in recent years, there has been a demand for reducing their release into the atmosphere during use and for reducing their usage.

[0003] On the other hand, adhesive treatment agents for rubber and fiber, such as RFL adhesives, have problems with storage stability, such as changes in viscosity of the adhesive treatment agent liquid over time after preparation, which causes changes in the amount of resin attached and accompanying changes in adhesive strength and physical properties.

[0004] Furthermore, in order to allow the fibers to retain adhesive properties with rubber, it is essential to apply an adhesive such as the above-mentioned RFL to the fiber surface. However, in the adhesive treatment process, agglomerates resulting from the applied adhesive adhere to treatment devices such as the rollers of the dipping machine, which causes a problem of reduced operability.

[0005] Techniques disclosed to address the above problem include prior art techniques such as those disclosed in Patent Documents 1 to 6.

[0006] Patent Document 1 discloses an adhesive composition for organic fiber cords, which contains a urethane resin having a thermally dissociable blocked isocyanate group, an epoxy compound, a polymer having an oxazoline group, a basic catalyst having a number average molecular weight of 1,000 to 75,000, and rubber latex.

[0007] Patent Document 2 discloses a processing method in which a fabric reinforcing member is immersed in a bath containing a polycarboxylic acid, a base, an epoxy compound, a polyisocyanate compound, and VP latex.

[0008] Patent Document 3 discloses an aqueous adhesive composition containing a thermosetting resin having a specific functional group and an unsaturated elastomer latex.

[0009] 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.

[0010] Patent Document 5 discloses an aqueous adhesive composition containing a specific tri- or higher functional blocked isocyanate oligomer, a latex, a polyacrylate or a lignin compound, and an additive.

[0011] Patent Document 6 discloses a method for producing an adhesive composition with good storage stability, which comprises aging a mixture containing resorcinol and formaldehyde in a state without an alkali catalyst, and then adding rubber latex to form a mixed liquid.

[0012] Japanese Patent Application Laid-Open No. 2013-64037 Japanese Patent Application Laid-Open No. 2020-525622 Japanese Patent Application Laid-Open No. 2019-518087 WO2018 / 003572 US Publication No. 2020 / 0024416 Japanese Patent Application Laid-Open No. 2013-10909

[0013] However, according to Patent Documents 1 and 5, although the initial adhesive strength and heat-resistant adhesive strength were comparable to those of conventional RFL, the fatigue resistance in rubber was insufficient. According to Patent Documents 2, 3, and 4, although the initial adhesive strength was comparable to that of conventional RFL, the heat-resistant adhesive strength and fatigue resistance in rubber were insufficient. Furthermore, Patent Documents 1 and 2 used fossil fuel-derived compounds as a substitute for resorcinol and formalin, which was somewhat disadvantageous in reducing the environmental impact. According to Patent Document 6, the storage stability of the adhesive treatment agent was improved, but it used conventional RFL adhesives, which posed a significant environmental burden. Furthermore, all Patent Documents 1 to 6 still suffered from the problem of resin coagulation during the dipping process. In other words, in order to achieve practical durability in rubber products such as tires, hoses, and belts, an adhesive treatment agent that satisfied all the performance requirements for rubber-reinforcing synthetic fiber cords, including initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance, and that also had good storage stability and was advantageous for reducing the environmental impact, had not yet been obtained.

[0014] The present invention has been made as a result of studies aimed at solving the problems in the prior art described above.

[0015] The object of the present invention is to provide a novel adhesive treatment agent that does not contain resorcinol or formalin and uses raw materials that are advantageous in reducing the environmental impact, and a synthetic fiber cord for rubber reinforcement that uses the same, which exhibits an initial adhesive strength equal to or greater than that of conventional RFL, exhibits little adhesion deterioration over long periods of time at high temperatures when embedded in rubber, and suppresses strength deterioration when subjected to repeated stretching and compression in the rubber.Furthermore, the present invention provides an adhesive treatment agent for rubber and fiber and a synthetic fiber cord for rubber reinforcement that have good storage stability, can suppress the generation of resin coagulation during the dipping process, and are highly productive.

[0016] In order to solve the above problems, the present invention employs the following means.

[0017] That is, (1) An adhesive treatment agent for rubber and fiber, which contains at least a lignin derivative (A), a water-soluble or water-dispersible crosslinking agent (B), and a rubber latex (C), and does not contain a resorcinol-formaldehyde resin, wherein the lignin derivative (A) has a number-average molecular weight of 10,000 to 60,000 and a weight-average molecular weight of 80,000 to 130,000.

[0018] (2) The adhesive treatment agent for rubber and fiber according to (1) above, wherein, when the total solid content of the adhesive treatment agent is taken as 100% by weight, the content of the lignin derivative (A) is 5 to 50% by weight, the solid content weight ratio of the lignin derivative (A) to the water-soluble or water-dispersible crosslinking agent (B) is (solid content of A):(solid content of B)=10:1 to 10:20, and when the adhesive treatment agent is formed into a dried film, the dried film has a maximum point strength of 0.2 MPa to 1.6 MPa and a maximum point elongation of 2% to 120%.

[0019] (3) The adhesive treatment agent for rubber and fiber according to (1) or (2) above, wherein the water-soluble or water-dispersible crosslinking agent (B) contains at least one compound selected from the group consisting of oxazoline group-containing compounds, epoxy compounds, and blocked isocyanate compounds.

[0020] (4) The adhesive treating agent for rubber and fiber according to any one of (1) to (3) above, wherein the water-soluble or water-dispersible crosslinking agent (B) is an HDI-based blocked isocyanate or an MDI-based oxime-blocked isocyanate.

[0021] (5) The adhesive treatment agent for rubber and fiber according to any one of (1) to (4) above, wherein the solids weight ratio of the lignin derivative (A), the water-soluble or water-dispersible crosslinking agent (B), and the rubber latex (C) is ((solids content of A) + (solids content of B)):(solids content of C) = 10:90 to 60:40.

[0022] (6) The liquid viscosity (V ０ (mPa·s)) and the liquid viscosity after 30 days (V ３０ (mPa s)) ３０ / V ０ The adhesive treating agent for rubber and fiber according to any one of (1) to (5) above, wherein the ratio is 90 to 120%.

[0023] (7) A synthetic fiber cord for reinforcing rubber, which is obtained by adhering the adhesive treating agent for rubber and fiber according to any one of (1) to (6) above to a synthetic fiber and then heat-treating it.

[0024] According to the present invention, a new adhesive treatment agent and synthetic fiber cord for rubber reinforcement are obtained that are free of resorcinol and formalin and use raw materials that are advantageous in reducing the environmental impact. These adhesive treatment agents exhibit initial adhesive strength equal to or greater than that of conventional RFL, show little adhesion deterioration even when embedded in rubber at high temperatures for long periods of time, and suppress strength deterioration when subjected to repeated extension and compression in the rubber, making them suitable for use in rubber reinforcement applications. Furthermore, the adhesive treatment agent has good storage stability and can suppress the generation of resin coagulation during the dipping process, making it possible to provide an adhesive treatment agent for rubber and fiber and a synthetic fiber cord for rubber reinforcement that are highly productive.

[0025] The present invention will be described in detail below.

[0026] The adhesive treating agent for rubber and fiber of the present invention is capable of exhibiting adhesiveness to rubber when used to treat synthetic fibers, and must contain at least a lignin derivative (A), a water-soluble or water-dispersible crosslinking agent (B), and a rubber latex (C), and must be free of a resorcinol-formaldehyde resin.

[0027] The lignin derivative (A) used in the present invention is a chemically treated lignin present in trees, which are biomass. Examples of such compounds include kraft lignin obtained from kraft pulp waste liquor in the papermaking industry, which uses wood as a raw material, and lignosulfonic acid or lignosulfonate salts obtained from sulfite pulp waste liquor. Lignin sulfonic acid is a compound in which a sulfone group is introduced into the side chain of the phenylpropane structure of lignin. Examples of lignosulfonate salts include sodium lignosulfonate, magnesium lignosulfonate, and calcium lignosulfonate. In the present invention, these compounds can be used alone or in combination, but sodium lignosulfonate is most preferred from the standpoint of adhesive strength.

[0028] The lignin derivative (A) used in the present invention must have a number-average molecular weight of 10,000 to 60,000 and a weight-average molecular weight of 80,000 to 130,000, preferably a number-average molecular weight of 20,000 to 50,000 and a weight-average molecular weight of 90,000 to 120,000. If the number-average molecular weight and weight-average molecular weight exceed the upper limits of these ranges, fatigue resistance may be insufficient, the storage stability of the adhesive treatment agent may deteriorate, and continuous production may become difficult due to the frequent occurrence of coagulation during the dipping process. If the number-average molecular weight and weight-average molecular weight are below the lower limits of these ranges, the initial adhesive strength and fatigue resistance to the rubber may decrease, which is undesirable. Furthermore, the weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio is preferably 2.5 to 5.0, more preferably 2.8 to 4.7. Outside these ranges, adhesive strength and fatigue resistance may be insufficient. The number average molecular weight and weight average molecular weight in the present invention are values ​​measured by the methods described in the Examples section.

[0029] The water-soluble or water-dispersible crosslinking agent (B) used in the present invention is a compound having a functional group capable of reacting with other compounds upon heating, and is water-soluble or emulsion-type water-dispersible. Specifically, it is preferable that the crosslinking agent (B) contains at least one compound selected from the group consisting of oxazoline group-containing compounds, epoxy compounds, and blocked isocyanate compounds.

[0030] Oxazoline group-containing compounds refer to compounds containing an oxazoline group (preferably a 2-oxazoline group) at the end or side chain of a general organic compound or a substance with an organic polymer and / or oligomer as its main skeleton. While one or more oxazoline groups can be present in a single molecule, for improved adhesive performance, it is preferable to have a large number of oxazoline groups, which are reactive functional groups. The main chain skeleton of oxazoline group-containing compounds includes hydrocarbon chains, ethylene glycol chains, bisphenols such as bisphenol A, and prepolymers such as phenolic resins, novolac resins, and resol resins. These molecular skeletons also include substances containing aromatic rings or heterocyclic rings. Furthermore, substances containing oxazoline groups at the end or side chain of the main component monomer and / or polymers or oligomers derived therefrom are also useful. Examples of such monomers include styrene, styrene derivatives, acrylonitrile, methacrylic acid esters, methacrylic acid, ethylene, butadiene, and acrylamide. These are used as homopolymers and / or oligomers, as well as copolymers. Mixtures of these can also be used.

[0031] The oxazoline group-containing compound may be used in the form of a liquid, a melt, a solid, a solution in water or an organic solvent capable of dissolving these, or a suspension dispersed in water (emulsion particles, latex particles, etc.). For example, such a compound may be emulsified or dissolved as it is, or, if necessary, after being dissolved in a small amount of solvent, using a known emulsifier such as sodium alkylbenzenesulfonate, dioctyl sulfosuccinate sodium salt, or nonylphenol ethylene oxide adduct.

[0032] An epoxy compound is one having two or more epoxy groups in one molecule. Examples of compounds having two or more epoxy groups in the molecule include glycidyl ether-type epoxy resins obtained from compounds having a hydroxyl group in the molecule, glycidyl amine-type epoxy resins obtained from compounds having an amino group in the molecule, glycidyl ester-type epoxy resins obtained from compounds having a carboxyl group in the molecule, cycloaliphatic epoxy resins obtained from compounds having an unsaturated bond in the molecule, heterocyclic epoxy resins such as triglycidyl isocyanurate, and epoxy resins in which two or more types selected from these are mixed in the molecule.

[0033] Specific examples of glycidyl ether type epoxy resins include bisphenol A type epoxy resins obtained by reacting bisphenol A with halogen-containing epoxides such as epichlorohydrin, bisphenol F type epoxy resins obtained by reacting bisphenol F with the halogen-containing epoxides, biphenyl type epoxy resins obtained by reacting biphenyl with the halogen-containing epoxides, resorcinol type epoxy resins obtained by reacting resorcinol with the halogen-containing epoxides, bisphenol S type epoxy resins obtained by reacting bisphenol S with the halogen-containing epoxides, polyethylene glycol type epoxy resins, which are reaction products of polyhydric alcohols with the halogen-containing epoxides, polypropylene glycol type epoxy resins, epoxy resins obtained by oxidizing unsaturated bond moieties such as bis-(3,4-epoxy-6-methyl-dicyclohexylmethyl)adipate and 3,4-epoxycyclohexene epoxide, naphthalene type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and halogen- or alkyl-substituted versions of these.

[0034] The blocked isocyanate compound used in the present invention is a compound that can liberate a blocking agent upon heating to generate an active isocyanate compound. Examples of the blocked isocyanate compound include reaction products of polyisocyanate compounds having a skeleton such as tolylene diisocyanate (TDI), metaphenylene diisocyanate (MDI), diphenylmethane diisocyanate (HDI), hexamethylene diisocyanate, or triphenylmethane triisocyanate with blocking agents such as phenols (e.g., phenol, cresol, or resorcinol), lactams (e.g., ε-caprolactam or valerolactam), or oximes (e.g., acetoxime, methyl ethyl ketoxime, or cyclohexane oxime).

[0035] Among these blocked isocyanate compounds, it is most preferable to select from HDI-based blocked isocyanates, which are reaction products of hexamethylene diisocyanate and a blocking agent, or MDI-based oxime-blocked isocyanates, which are reaction products of diphenylmethane diisocyanate and an oxime-type blocking agent, in order to obtain good adhesive strength and fatigue resistance. Diphenylmethane diisocyanate (MDI) can be selected from 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI, but monomeric MDI (4,4'-MDI) is most preferable from the viewpoint of adhesive strength and fatigue resistance. Polymeric MDI with trifunctional isocyanate groups is not preferable, as it may result in reduced adhesive strength and fatigue resistance. Furthermore, the dissociation temperature of the blocking agent for HDI-based blocked isocyanates or MDI-based oxime-blocked isocyanates is preferably 100 to 160°C. A dissociation temperature within this range is preferable because it has good reactivity during heat treatment and can exhibit higher adhesive strength.

[0036] Examples of the rubber latex (C) that can be 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.

[0037] The present invention does not include resorcinol-formaldehyde resin. Resorcinol-formaldehyde resin is a compound formed by the reaction of resorcinol and formaldehyde. For example, by mixing resorcinol and formaldehyde in an alkaline aqueous solution containing an alkaline compound such as sodium hydroxide and allowing the mixture to stand at room temperature for several hours, a condensation reaction between resorcinol and formaldehyde occurs, resulting in the production of resorcinol-formaldehyde resin.

[0038] In addition to the above-mentioned components (A), (B), and (C), the adhesive treatment agent that can be used in the present invention may contain surfactants, antifoaming agents, vulcanization regulators, antioxidants, and pH adjusters, as needed, within limits that do not impair the objects and effects of the present invention.

[0039] In the adhesive treatment agent of the present invention, when the total solid content of the adhesive treatment agent is taken as 100% by weight, the content of the lignin derivative (A) is preferably 5 to 50% by weight, more preferably 7 to 45% by weight, and even more preferably 10 to 40% by weight. If it is less than 5% by weight or exceeds 50% by weight, the adhesive strength and fatigue resistance may be insufficient. Here, the total solid content refers to the components of the adhesive treatment agent excluding the solvent.

[0040] The solids weight ratio of the lignin derivative (A) to the water-soluble or water-dispersible crosslinking agent (B) is preferably (solids content of A):(solids content of B) = 10:1 to 10:20, more preferably 10:5 to 10:20. If the amount of crosslinking agent (B) is small and exceeds this weight ratio, the adhesive strength may be insufficient, whereas if the amount of crosslinking agent (B) is large and exceeds this weight ratio, the cord may become hard and the fatigue resistance in rubber may deteriorate. When the synthetic fiber cord is used to reinforce rubber products such as tires, belts, and hoses, the durability of the product may deteriorate, which is undesirable.

[0041] The solids weight ratio of the lignin derivative (A), the water-soluble or water-dispersible crosslinking agent (B), and the rubber latex (C) is preferably ((solids of A) + (solids of B)):(solids of C) = 10:90 to 60:40, more preferably 20:80 to 50:50. If the ratio is outside this range, the adhesive strength may be insufficient or fatigue resistance may deteriorate.

[0042] When the adhesive treatment agent of the present invention is used to form a dried film, the dried film preferably has a maximum strength of 0.2 MPa to 1.6 MPa, more preferably 0.3 MPa to 1.4 MPa, and even more preferably 0.5 MPa to 1.4 MPa. A maximum strength of less than 0.2 MPa may result in insufficient adhesive strength, while a maximum strength of more than 1.6 MPa may result in poor fatigue resistance. Furthermore, the maximum elongation of the dried film is preferably 2% to 120%, more preferably 4% to 100%, and even more preferably 20% to 100%. A maximum elongation of less than 2% may result in poor fatigue resistance, while a maximum elongation of more than 120% may result in poor adhesive strength. The methods for preparing the dried film and measuring the maximum strength and maximum elongation are as described in the Examples section. However, if it is difficult to use these methods, equivalent methods can be used.

[0043] The maximum strength and maximum elongation of the dried film of the adhesive treatment agent can be adjusted by the type of agent contained in the adhesive treatment agent and the mixing ratio. For example, the maximum strength can be adjusted to be high by increasing the content of the water-soluble or water-dispersible crosslinking agent (B) contained in the adhesive treatment agent. Furthermore, the maximum elongation can be adjusted to be high by increasing the amount of rubber latex (C) mixed.

[0044] The adhesive treatment agent of the present invention has a liquid viscosity (V ０ The viscosity (mPa·s) is preferably 1.0 to 3.0 mPa·s, and more preferably 1.1 to 2.7 mPa·s. If the liquid viscosity is less than 1.0, the amount of adhesive treatment agent attached to the synthetic fibers may be insufficient, resulting in a decrease in adhesive strength, whereas if it exceeds 3.0, the amount of adhesive treatment agent attached to the synthetic fibers may be excessive, resulting in a decrease in adhesive strength, the generation of coagulation during the dipping step, and other problems that may make continuous production difficult.

[0045] Furthermore, in the present invention, the viscosity of the liquid after preparation (V ０ (mPa·s)) and the liquid viscosity after 30 days (V ３０ (mPa s)) ３０ / V ０ is preferably 90 to 120%, and more preferably the rate of change V ３０ / V ０ The viscosity change rate is preferably 92 to 110%, and more preferably 95 to 110%. Specific viscosity measurement methods will be described later, but the viscosity change rate from this test is used in the present invention as a measure of the storage stability of the adhesive treatment agent. If the viscosity change rate is less than 90% or more than 120%, the amount of adhesive treatment agent that adheres to the synthetic fiber during the dipping step will change as the viscosity of the adhesive treatment agent changes, which can result in a decrease in adhesive strength or the generation of coagulation during the dipping step, making continuous production difficult.

[0046] The liquid viscosity of the adhesive treatment agent can be adjusted to fall within the range specified in the present invention by, for example, optimizing the selection of the types and blending ratios of the lignin derivative (A), water-soluble or water-dispersible crosslinking agent (B), and rubber latex (C) used. Furthermore, a surfactant may be added as appropriate. Examples of surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, and alkylbenzene sulfonates.

[0047] The adhesive treatment agent of the present invention is a solution or dispersion of solids in water, and the total solids concentration is preferably 5 to 25 wt %, more preferably 10 to 20 wt %, and even more preferably 12 to 18 wt %. Outside this range, the adhesive strength may decrease. Outside this range, a sufficient amount of solids may not be applied to the fibers, or cohesive failure may occur in the adhesive solids, which may result in a decrease in adhesive strength.

[0048] The synthetic fiber cord for reinforcing rubber of the present invention is suitable for reinforcing rubber and is made by treating synthetic fiber with the adhesive treating agent for rubber and fiber described above.

[0049] The term "treated" refers to a state in which the adhesive treatment agent has been applied to synthetic fibers and then subjected to a drying or heat treatment. During the drying or heat treatment, for example, volatile components contained in the adhesive treatment agent, such as solvents such as water, are removed by evaporation. Furthermore, when a blocked isocyanate compound is used as the crosslinking agent (B), the blocking agent is released, resulting in a reaction via the isocyanate group. In other words, synthetic fibers treated with the adhesive treatment agent have solid components that are attached or bonded to the synthetic fibers without being chemically modified or unmodified. The adhesive treatment agent of the present invention refers to an adhesive treatment agent containing at least a lignin derivative (A), a water-soluble or water-dispersible crosslinking agent (B), and a rubber latex (C) in the same bath (first bath). This does not refer to a so-called two-bath treatment method, which is a well-known adhesive treatment method for polyester fibers, in which the first and second baths contain the components (A), (B), and (C) separately. Furthermore, it is necessary that neither the first-bath adhesive nor the second-bath adhesive contains resorcinol-formaldehyde resin.

[0050] The amount of adhesive treatment agent adhered to the synthetic fibers is preferably 1 to 15 parts by weight, more preferably 1.5 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.

[0051] The synthetic fibers that can be used in the present invention are preferably in the form of multifilaments. Examples of materials constituting the synthetic fibers include nylon fibers, polyester fibers, aramid fibers, and polyvinyl alcohol fibers. From the standpoints of durability and industrial productivity, it is preferable to use at least one fiber selected from polyester fibers, nylon fibers, and aramid fibers. Furthermore, it is preferable that the at least one fiber selected from polyester fibers, nylon fibers, and aramid fibers account for 60% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more, of the total weight of the synthetic fibers taken as 100% by weight.

[0052] The polyester fiber may be a fiber made of polyethylene terephthalate, polyethylene naphthalate, or the like. It is desirable that the polyester fiber be a fiber obtained by melt spinning and drawing a polyester in which terephthalic acid is the main difunctional carboxylic acid and ethylene glycol is the main glycol component. However, it is also possible to use a fiber made of a polyester in which terephthalic acid is partially or entirely replaced with 2,6-naphthalenedicarboxylic acid, 4,4-dicarboxyphenoxyethane, an isocyanate group, or the like, or in which ethylene glycol is partially or entirely replaced with diethylene glycol, propylene glycol, butanediol, or the like.

[0053] The polyester may also be copolymerized with a small amount of a trifunctional compound such as trimesic acid, trimellitic acid, boric acid, phosphoric acid, glycerin, and trimethylolpropane.

[0054] The polyester fiber 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.

[0055] Alternatively, the polyester fiber may be one 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 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; and aromatic polyepoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate, bis(3,4-epoxy-6-methyl-cyclohexylmethyl)adipate, 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, and bisphenol type polyepoxides. Particularly preferred are sorbitol glycidyl ether type and cresol novolac type polyepoxides.

[0056] These polyepoxide 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 with a common emulsifier such as sodium alkylbenzenesulfonate, dioctyl sulfosuccinate sodium salt, or nonylphenol ethylene oxide adduct and used as an emulsion.

[0057] 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 this range, the effects of the polyepoxide compound are fully exerted, and satisfactory adhesion between the synthetic fiber and rubber is obtained. Furthermore, when the amount is within this range, the fiber does not become too hard, and the tenacity is less likely to decrease during the twisting process described below.

[0058] Examples of the nylon fiber include fibers made of nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, etc., and among these, fibers made of high-molecular-weight nylon 66 having a relative viscosity in sulfuric acid of 3.0 or more, more preferably 3.5 or more, are preferred. The nylon fiber may contain copper compounds, as well as conventionally known inorganic and organic copper salts and elemental copper metal. In addition to the copper compounds, the fiber may also contain other heat-resistant additives such as amine compounds, mercapto compounds, phosphorus compounds, and hindered phenol compounds.

[0059] When used as a tire cord, a polymer with a high degree of polymerization is used to obtain a fiber with high strength and toughness, and the fiber preferably has a relative viscosity in sulfuric acid of 3.0 to 5.0.

[0060] The aramid fiber is not particularly limited as long as it has at least one divalent aromatic group, which may be substituted, and at least one amide bond in the repeating unit of the polymer forming the fiber, and may be a known fiber called a wholly aromatic polyamide fiber or an aramid fiber. In the above, the "divalent aromatic group, which may be substituted," means a divalent aromatic group, which may have one or more identical or different substituents.

[0061] Aramid fibers include para-aramid fibers and meta-aramid fibers, but in the present invention, para-aramid fibers, which have excellent tensile strength, are preferably used. Examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (manufactured by DuPont-Toray Co., Ltd., product name "Kevlar" (registered trademark)) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers (manufactured by Teijin Limited, product name "Technora" (registered trademark)).

[0062] The synthetic fibers used in the present invention are not subject to restrictions on fineness, number of filaments, cross-sectional shape, etc., but typically have a total fineness of 200 to 5,000 dtex, 30 to 1,000 filaments, and a circular cross-section yarn, with a total fineness of 250 to 3,000 dtex, 50 to 500 filaments, and a circular cross-section yarn being 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 decrease, and if it exceeds 1,000 filaments, the cord may become too fluffed and its quality may decrease.

[0063] From the viewpoint of improving fatigue resistance, the synthetic fiber cord of the present invention can be obtained by twisting the above synthetic fibers to form a twisted cord, and then dipping and heat-treating the twisted cord in the adhesive treatment agent of the present invention, 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 direction 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 an organic fiber covered with cotton yarn is used as weft yarns, which are woven into a blind to form a green curtain. The green curtain is then dipped and heat-treated in the adhesive treatment agent to obtain a dip cloth.

[0064] On the other hand, in the case of cords for hoses or belts, for example, a twisted cord is formed by first twisting, or two or three of these first twisted cords are combined and then twisted in the opposite direction to the first twist, usually with the same number of second twists, to form a twisted cord, which is then dipped in an adhesive treating agent and heat-treated while still in the twisted cord form to form a dipped cord.

[0065] The synthetic fiber cord treated with the adhesive treatment agent of the present invention includes both the above-mentioned dipped piece and dipped cord.

[0066] Furthermore, the synthetic fiber cord for rubber reinforcement of the present invention may be treated with a precoating agent before the synthetic fiber is treated with the adhesive treatment agent (adhesive treatment agent containing at least component (A), component (B), and component (C)).

[0067] The precoating agent preferably contains at least an epoxy compound, and the total solids concentration in the precoating agent is preferably 0.1 to 6%. More preferably, the precoating agent contains at least an epoxy compound and a blocked isocyanate compound, and the ratio (solids weight of blocked isocyanate compound) / (solids weight of epoxy compound) is 3 or less, and the total solids concentration in the precoating agent is preferably 0.1 to 6%. Outside this range, the adhesive strength may decrease. Furthermore, the amount of precoating agent adhered to the synthetic fiber is preferably 0.1 to 3 parts by weight of solids weight of precoating agent per 100 parts by weight of synthetic fiber. Outside this range, the adhesive strength may decrease.

[0068] The adhesive treatment agent for rubber and fiber of the present invention, characterized as described above, is a new adhesive treatment agent that does not contain resorcinol or formalin and is made from raw materials that are advantageous for reducing the environmental impact. Synthetic fiber cords for rubber reinforcement that use this agent exhibit initial adhesive strength equal to or greater than that of conventional RFL, experience little adhesion deterioration even when embedded in rubber at high temperatures for long periods of time, and suppress strength deterioration when subjected to repeated stretching and compression in the rubber, making them suitable for use in rubber reinforcement applications. Furthermore, the adhesive treatment agent has good storage stability and suppresses the generation of resin coagulation during the dipping process, making it possible to provide an adhesive treatment agent for rubber and fiber and synthetic fiber cords for rubber reinforcement that are highly productive.

[0069] The synthetic fiber cord for rubber reinforcement of the present invention is obtained by adhering the above-mentioned adhesive treatment agent for rubber and fiber to synthetic fiber and then heat-treating it. The synthetic fiber cord for rubber reinforcement of the present invention can be used to reinforce rubber products such as tires, belts, and hoses, and uses an environmentally friendly adhesive that does not use resorcinol or formalin, and can exhibit performance equal to or better than that of conventional cords that use RFL.

[0070] Next, a method for producing the synthetic fiber cord for reinforcing rubber of the present invention will be described.

[0071] An example of a method for producing a synthetic fiber cord for rubber reinforcement according to the present invention is a method in which an adhesive treatment agent containing at least a lignin derivative (A), a water-soluble or water-dispersible crosslinking agent (B), and a rubber latex (C) and not containing a resorcinol-formaldehyde resin is applied to a synthetic fiber in the same bath, followed by a heat treatment. The synthetic fiber may be in the form of a twisted cord or a green cloth. A preferred method involves dipping the twisted cord or green cloth in the adhesive treatment agent in a dip bath, followed by drying the water at a temperature preferably in the range of 100 to 150°C, followed by a heat treatment at 200 to 255°C. The preferred embodiments of the lignin derivative (A), the water-soluble or water-dispersible crosslinking agent (B), and the rubber latex (C) are as described above.

[0072] Here, "dipping" refers to applying an adhesive treatment agent to a twisted yarn cord or a raw curtain reel by running the twisted yarn cord or the raw curtain reel through a dipping tank equipped with rollers and filled with an adhesive treatment agent. "Heat treatment" refers to heating the twisted yarn cord or the raw curtain reel by running the twisted yarn cord or the raw curtain reel through an oven equipped with rollers and capable of being set to a predetermined temperature. Dipping machines for carrying out such dipping and heat treatment are commercially available, for example, from Ritzler. Note that, in addition to dipping, any other method can be used to attach an adhesive treatment agent to synthetic fibers, such as spraying the adhesive treatment agent from a nozzle.

[0073] 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.

[0074] Furthermore, during the mechanical softening process after the above drying and heat treatment, the synthetic fiber cord can be brought into sliding contact with the edge to perform softening treatment to obtain any desired cord stiffness.

[0075] In the method for producing a synthetic fiber cord for rubber reinforcement of the present invention, the adhesive treatment agent (adhesive treatment agent containing at least component (A), component (B), and component (C)) is applied to the synthetic fiber, and before the heat treatment, a precoat agent may be applied to the synthetic fiber, followed by heat treatment.

[0076] The precoating agent preferably contains at least an epoxy compound, and the total solids concentration in the precoating agent is preferably 0.1 to 6%. More preferably, the precoating agent contains at least an epoxy compound and a blocked isocyanate compound, and the ratio (solids weight of blocked isocyanate compound) / (solids weight of epoxy compound) is 3 or less, and the total solids concentration in the precoating agent is preferably 0.1 to 6%. Outside this range, the adhesive strength may decrease. Furthermore, the amount of precoating agent adhered to the synthetic fiber is preferably 0.1 to 3 parts by weight of solids weight of precoating agent per 100 parts by weight of synthetic fiber. Outside this range, the adhesive strength may decrease.

[0077] When applying the precoating agent, the same dipping method as described above can be used. That is, a preferred method is to dip a twisted yarn cord or a raw cloth of synthetic fiber into the precoating agent in a dip bath, followed by drying the water at a temperature of preferably 100 to 150°C, and then subjecting the cloth to a heat treatment at 200 to 255°C. The same methods as described above can be used to control the amount of solids applied and to soften the cloth.

[0078] The adhesive treatment agent for rubber and fiber and synthetic fiber cord for rubber reinforcement obtained in this way are advantageous new adhesive treatment agents that do not contain resorcinol or formalin and use biomass-derived materials to reduce the environmental impact, and they exhibit initial adhesive strength equal to or greater than that of conventional RFL, experience little adhesion deterioration over long periods of time at high temperatures when embedded in rubber, and suppress strength deterioration when subjected to repeated extension and compression in the rubber, making them suitable for use in rubber reinforcement applications.In addition, the adhesive treatment agent has good storage stability and can suppress the generation of resin coagulation during the dipping process, making it possible to provide an adhesive treatment agent for rubber and fiber and synthetic fiber cord for rubber reinforcement that is highly productive.

[0079] The present invention will be explained 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.

[0080] (1) Amount of Adhesive Treatment Agent Adhesion The amount of adhesive adhering to the synthetic fiber cord for rubber reinforcement was determined according to the dip pick-up mass method of JIS L1017 (2002).

[0081] (2) Initial Adhesion Strength and Heat-Resistant Adhesion Strength These indicate the adhesive strength between the synthetic fiber cord and rubber. The initial adhesive strength was measured in accordance with JIS L1017 (2002) Appendix 1, 3.1T Test (Method A), in which the synthetic fiber cord for rubber reinforcement was embedded in unvulcanized rubber and subjected to a test at 150°C for 30 minutes at 50 kg / cm. ２ After press vulcanization, the samples were allowed to cool, and the synthetic fiber cord was pulled out of the rubber block at a speed of 300 mm / min. The weight required for the pullout was determined for each sample, and the arithmetic average value of 10 samples was taken as the initial adhesive strength. The heat-resistant adhesive strength was measured in accordance with JIS L1017 (2002) Appendix 1, 3.1T test (method A), in which the synthetic fiber cord for rubber reinforcement was embedded in unvulcanized rubber and subjected to a test at 170°C for 70 minutes and 50 kg / cm. ２ After press vulcanization, the samples were allowed to cool, and the synthetic fiber cord was pulled out of the rubber block at a speed of 300 mm / min. The load required for the pulling out was determined for each sample, and the arithmetic average value of 10 samples was taken as the heat-resistant adhesive strength.

[0082] (3) Fatigue resistance in rubber (retention rate) This was evaluated in accordance with JIS L1017 (2002) Appendix 1, 2.2.2 Disc fatigue strength (Goodrich method). Two synthetic fiber cords for rubber reinforcement were embedded in unvulcanized rubber, and the rubber was subjected to a test at 150°C for 30 minutes and a load of 50 kg / cm. ２The test specimens were press-vulcanized under the conditions of (1) to prepare a rubber composite. Each test specimen was subjected to a deformation cycle of 6.3% compression and 12.6% elongation at 2600 cycles / min for 12 hours in a 100°C atmosphere. The synthetic fiber cords were then removed from the rubber and the post-fatigue strength was measured. The retention of the breaking strength before and after the fatigue test was determined for each sample, and the arithmetic average of the eight samples was taken as the fatigue resistance (retention) in rubber. Here, the breaking strength before the fatigue test refers to the breaking strength measured by removing the synthetic fiber cords from the rubber before the fatigue test and conducting a tensile test. That is, the fatigue resistance (retention) (%) in rubber was calculated by dividing the breaking strength of the cord removed from the rubber after the fatigue test by the breaking strength of the cord removed from the rubber before the fatigue test. The breaking strength of the cord removed from the rubber before the fatigue test is 100%.

[0083] 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 (#1502, manufactured by JSR Corporation): 30 (parts by weight) HAF 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).

[0084] (4) Measurement of Liquid Viscosity of Adhesive Treatment Agent After preparation, the adhesive treatment agent sample was measured for its liquid viscosity (V) after preparation in an environment of 25°C using a tuning fork vibro viscometer SV-1A manufactured by A&D Co., Ltd., according to the method of JIS Z8803 (2011). ０ The liquid viscosity after preparation here refers to the liquid viscosity obtained by measuring from immediately after preparation to one hour after. The adhesive treatment agent sample was left to stand in a thermostatic chamber at 25±0.5°C, and 30 days after preparation, the liquid viscosity (V ３０ (mPa·s)) and the rate of change V ３０ / V ０ (%) was calculated.

[0085] (5) Occurrence of coagulated material in 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 visually confirmed. A grade was given for no coagulated material deposited. A grade was given for a case in which a small amount of coagulated material deposited but to an extent that was not a problem in practical use. A grade was given for a case in which a large amount of coagulated material deposited and caused a problem in practical use. In the present invention, grades S and A were considered to be passable grades for process passability that could withstand practical use, with grade S being superior in practical use.

[0086] (6) Maximum point strength and maximum point elongation of the dried film of the adhesive treatment agent The adhesive treatment agent was applied to a glass plate so that the thickness of the dried film was 0.5 mm, and after drying at room temperature for 72 hours, a film-like dried film sample was obtained from which the moisture had dried. The sample was peeled from the glass plate, heat-treated in a 120 ° C oven for 15 minutes, and then heat-treated in a 240 ° C oven for 2 minutes. This was punched out using a No. 2 dumbbell (width 1 cm) as specified in JIS K6251 (2017) to obtain a sample for tensile test measurement. Using a Tensilon RTM-100 testing machine manufactured by Orientec Co., Ltd., the test length between the upper and lower chucks was set to 50 mm, and the measurement sample was gripped with this chuck. A tensile test was performed at a crosshead speed of 50 mm / min in an atmosphere of 25 ° C, and the strength and elongation were measured. The strength and elongation at the point where the strength was maximum were determined for each sample, and the arithmetic mean value of the strength for 6 samples was taken as the maximum strength, and the arithmetic mean value of the elongation for 6 samples was taken as the maximum elongation. Here, the maximum elongation (%) was calculated by dividing the elongation (mm) of the sample at the point where the strength was maximum by the initial test length (50 mm) × 100. For example, when the elongation before the tensile test was 0 mm, the elongation was 0%, and when the elongation after the tensile test was 50 mm, the elongation was 100%.

[0087] (7) Measurement of Number-Average Molecular Weight and Weight-Average Molecular Weight of Lignin Derivative The number-average molecular weight and weight-average molecular weight of the lignin derivative were measured by GPC (gel permeation chromatography). A solvent (ammonia buffer / methanol) was added to a lignin derivative sample, and the mixture was stirred at room temperature to dissolve, followed by filtration through a 0.5 μm filter. Then, measurement was performed by GPC, peaks were detected using a UV detector, and the molecular weight was measured as a relative value based on polyethylene oxide and polyethylene glycol. The measurement results are described in the Examples below. The measurement conditions are detailed below. Measurement device: Shimadzu Corporation Column used: TSKgel GMPW ＸＬ 1 G3000PW ＸＬ 1 tube (φ7.8 mm × 30 cm, manufactured by Tosoh Corporation) Solvent: 0.1 M ammonia buffer (pH 11) / methanol (4 / 1, v / v) Standard substance: monodisperse polyethylene oxide and polyethylene glycol manufactured by Tosoh Corporation and Agilent Corporation Detector: UV detector (Shimadzu Corporation SPD-M20A).

[0088] (Examples 1 to 10, Comparative Examples 1 to 6) Glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase ChemteX Corporation), blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industry Co., Ltd.), and rubber latex (Pyratex, manufactured by Nippon A&L Inc.) were mixed in a solids ratio of 20:40:40, and diluted with water to obtain a precoating agent (P) with a total solids content of 4.0% by weight.

[0089] Furthermore, the lignin derivative (A), the water-soluble or water-dispersible crosslinking agent (B), and the rubber latex (C) were mixed with water so that the solid contents thereof were in the ratios shown in Table 1 or Table 2, to obtain adhesive treatment agents with a total solid content concentration of 15% by weight. The maximum strength and maximum elongation of the dried film of the obtained adhesive treatment agents were measured according to the above-mentioned measurement methods. Furthermore, the liquid viscosity (V ０ (mPa·s)), liquid viscosity after 30 days (V ３０ (mPa s)) ３０ / V ０ was measured.

[0090] Two 1670 dtex polyester multifilament yarns (Toray Industries, Inc., "Tetoron" 1670T-360-705M) were twisted together with a first twist of 40 times per 10 cm and a second twist of 40 times per 10 cm to obtain a twisted yarn cord.

[0091] The twisted yarn cord was immersed in the precoating agent (P) 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. Subsequently, the twisted yarn cord was immersed in the adhesive treatment agent containing the components (A), (B), and (C), dried at 120° C. for 2 minutes, and then heat-treated at 240° C. for 1 minute to obtain a synthetic fiber cord.

[0092] The treatment with the adhesive treatment agent containing components (A), (B), and (C) was carried out by running the cord 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 that the cord came into contact with as it ran through an oven at 120°C in the Computreator treatment machine was confirmed, and the state of coagulation was evaluated according to the method described in the Examples.

[0093] The adhesive solid content of the obtained synthetic fiber cord was 1.1 parts by weight of the precoating agent relative to 100 parts by weight of the polyester fiber, and 4.0 parts by weight of the adhesive treatment agent containing (A), (B), and (C) relative to 100 parts by weight of the polyester fiber.

[0094] The components of the adhesive treatment agents shown in Tables 1 and 2 are as follows: (A)-1: Lignin derivative (manufactured by Nippon Paper Industries Co., Ltd., sodium lignosulfonate, "Vanilex" N, number average molecular weight 29,000, weight average molecular weight 105,000) (A)-2: Lignin derivative (manufactured by Nippon Paper Industries Co., Ltd., sodium lignosulfonate, "Vanilex" RN, number average molecular weight 34,000, weight average molecular weight 112,000) (A)-3: Lignin derivative (manufactured by Nippon Paper Industries Co., Ltd., sodium lignosulfonate, "Pearlex" NP, number average molecular weight 97,000, weight average molecular weight 146,000) (A)-4: Lignin derivative (manufactured by Nippon Paper Industries Co., Ltd., sodium lignosulfonate, "Sunex" P252, number average molecular weight 66,000, weight average molecular weight 135,000) (B)-1: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-6400, oxime-blocked diphenylmethane diisocyanate, dissociation temperature 120 to 160°C) (B)-2: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., SU-268A, blocking agent adduct of hexamethylene diisocyanate, dissociation temperature 100 to 130°C) (B)-3: Carbodiimide group-containing polymer (Nisshinbo Chemical Inc., Carbodilite V-02) (B)-4: Oxazoline group-containing compound (Nippon Shokubai Co., Ltd., "Epocross" K-2030E) (B)-5: Epoxy compound (Nagase ChemteX Corporation, "Denacol" EX313) (B)-6: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-3031CONC, lactam-blocked diphenylmethane diisocyanate, dissociation temperature 160 to 180°C) (B)-7: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-7000, lactam-blocked polymeric MDI, dissociation temperature 160 to 180°C) (C)-1: Rubber latex (Nippon A&L Co., Ltd., "Pyratex").

[0095] (Conventional Example) In Example 1, the adhesive treatment agent containing components (A), (B), and (C) was replaced with an RFL adhesive obtained by the following procedure, and the treatment and evaluation were carried out in the same manner as in Example 1. Resorcinol / formalin were mixed in a molar ratio of 1 / 1.5 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 (Pyratex, manufactured by Nippon A&L Co., Ltd.) in 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 with a solids weight of 15%. The adhesive solids adhesion amount of the obtained synthetic fiber cord for rubber reinforcement was 1.1 parts by weight of precoat agent per 100 parts by weight of polyester fiber, and 4.0 parts by weight of RFL adhesive per 100 parts by weight of polyester fiber.

[0096] The rubber-reinforcing 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 2.

[0097] As can be seen from the results in Table 1, in the examples according to the present invention, the adhesive treatment agent does not contain resorcinol or formalin, which is advantageous in reducing the environmental load compared to the conventional example RFL, and also has good adhesion to rubber, heat-resistant adhesion, and good fatigue resistance in a high-temperature atmosphere. It can also be seen that the adhesive treatment agent has good storage stability, and can suppress the generation of resin coagulation during the dipping process, resulting in good productivity of synthetic fiber cords for rubber reinforcement.

[0098]

[0099]

Claims

1. A rubber-fiber adhesive treating agent that contains at least a lignin derivative (A), a water-soluble or water-dispersible crosslinking agent (B), and a rubber latex (C), and does not contain a resorcinol-formaldehyde resin, wherein the number-average molecular weight of the lignin derivative (A) is 10,000 to 60,000 and the weight-average molecular weight is 80,000 to 130,000.

2. When the total solid content of the adhesive treating agent is 100% by weight, the content of the lignin derivative (A) is 5 to 50% by weight, and the solid content weight ratio of the lignin derivative (A) to the water-soluble or water-dispersible crosslinking agent (B) is (solid content of A):(solid content of B) = 10:1 to 10:

20. The maximum point strength of the dry film when the adhesive treating agent is made into a dry film is 0.2 MPa to 1.6 MPa, and the maximum point elongation is 2% to 120%. The rubber-fiber adhesive treating agent according to Claim 1.

3. The water-soluble or water-dispersible crosslinking agent (B) contains at least one compound selected from the group consisting of an oxazoline group-containing compound, an epoxy compound, and a blocked isocyanate compound. The rubber-fiber adhesive treating agent according to Claim 1 or 2.

4. The water-soluble or water-dispersible crosslinking agent (B) is an HDI-based blocked isocyanate or an MDI-based oxime-blocked isocyanate. The rubber-fiber adhesive treating agent according to Claim 1 or 2.

5. In the adhesive treating agent, the solid content weight ratio of the lignin derivative (A), the water-soluble or water-dispersible crosslinking agent (B), and the rubber latex (C) is ((solid content of A) + (solid content of B)):(solid content of C) = 10:90 to 60:

40. The rubber-fiber adhesive treating agent according to Claim 1 or 2.

6. The liquid viscosity (V ０ (mPa·s)) of the adhesive treatment agent after preparing the liquid, compared with the liquid viscosity (V ３０ (mPa·s)) 30 days later, the change rate V ３０ / V ０ is 90 to 120%, the adhesive treatment agent for rubber and fiber according to claim 1 or 2.

7. A synthetic fiber cord for rubber reinforcement obtained by attaching the rubber-fiber adhesive treating agent according to Claim 1 or 2 to a synthetic fiber and performing heat treatment.