Synthetic fiber cord for rubber reinforcement and its manufacturing method

Abstract

To provide a synthetic fiber cord for rubber reinforcement comprising a novel adhesive treatment agent composed of a raw material being free of resorcin and formalin and suitable for a reduced environmental load, wherein the synthetic fiber cord for rubber reinforcement can suppress generation of resin coagulation in a dipping step, can express initial adhesion comparable to that of the conventional RFL, barely show deterioration of the adhesion even when kept at high temperatures for a long time while being buried in rubber, and is less prone to deterioration of the strength even when subjected to repeated extension and compression in the rubber; and a method for producing the synthetic fiber cord for rubber reinforcement.SOLUTION: A synthetic fiber cord for rubber reinforcement comprises a synthetic fiber treated with an adhesive treatment agent comprising at least lignin (A), a blocked isocyanate compound (B), and rubber latex (C). With total solid content of the adhesive treatment agent being 100 pts.mass, content of the lignin (A) is 5-50 wt.%, and a solid weight ratio between the lignin (A) and the blocked isocyanate compound (B) is expressed as (solid content of A): (solid content of B)=10: 1-10: 20. When the adhesive treatment agent is processed into a dry film, the dry film has maximum-point strength of 0.2 MPa-1.6 MPa and maximum-point elongation of 2%-120%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a synthetic fiber cord for reinforcing rubber, which comprises a novel adhesive treatment agent that is advantageous in reducing environmental impact, and to a method for producing the same. [Background technology]

[0002] Synthetic fibers such as nylon, polyester, and aromatic polyamide fibers are widely used as reinforcing materials in rubber products such as tires, hoses, and belts. Resorcinol, formalin, and rubber latex (RFL) adhesives, which contain resorcinol, formalin, and rubber latex, have traditionally been widely used to bond these synthetic fibers to the rubber composition of rubber products. However, because both resorcinol and formalin are highly toxic substances that pose a significant environmental burden and are harmful to health, there has been a recent demand for reducing their release into the atmosphere during use and for their use in smaller amounts.

[0003] Furthermore, in order to ensure that the fibers adhere to rubber, it is essential to apply an adhesive such as the RFL to the fiber surface. However, during the adhesive application process, aggregates resulting from the adhesive composition applied can adhere to processing equipment such as the rollers of the dipping machine, reducing operability.

[0004] In an attempt to solve the above problem, for example, the following Patent Documents 1 to 6 have been proposed.

[0005] 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.

[0006] Patent Document 2 discloses a processing method in which a fabric reinforcing member is immersed in a bath containing polycarboxylic acid, a base, an epoxy compound, a polyisocyanate compound, and VP latex.

[0007] Patent Document 3 discloses an aqueous adhesive composition containing a thermosetting resin having a specific functional group and an unsaturated elastomer latex.

[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 an aramid fiber cord having an RFL adhesive impregnation degree of 3.5 to 9%.

[0010] Patent Document 6 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. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-64037 [Patent Document 2] Special Publication No. 2020-525622 [Patent Document 3] Special Publication No. 2019-518087 [Patent Document 4] WO2018 / 003572 issue [Patent Document 5] Special Publication No. 2014-530302 [Patent Document 6] U.S. Patent Application Publication No. 2020 / 0024416 Summary of the Invention [Problem to be solved by the invention]

[0012] However, while Patent Documents 1 and 6 demonstrate initial adhesive strength and heat-resistant adhesive strength comparable to conventional RFLs, they lack sufficient fatigue resistance in rubber. Patent Documents 2, 3, and 4 demonstrate initial adhesive strength comparable to conventional RFLs, but lack sufficient heat-resistant adhesive strength and fatigue resistance in rubber. Patent Document 5 improves fatigue resistance, but uses conventional RFL adhesives, resulting in significant environmental impact. Furthermore, Patent Documents 1 and 2 use fossil fuel-derived compounds as a substitute for resorcinol and formalin, which is somewhat disadvantageous in reducing environmental impact. In other words, synthetic fiber cords for rubber reinforcement that meet all of the requirements for achieving practical durability in rubber products such as tires, hoses, and belts—initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance—have not been obtained. Furthermore, Patent Documents 1 to 6 all suffer from the problem of resin coagulation during the dipping process.

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

[0014] An object of the present invention is to provide a synthetic fiber cord for rubber reinforcement, which is made of a new adhesive treatment agent that does not contain resorcinol or formalin and is made from raw materials that are advantageous in reducing the environmental load, and which can suppress the generation of resin coagulation during the dipping process, exhibits initial adhesive strength equal to or greater than that of conventional RFL, shows little adhesion deterioration when exposed to high temperatures for long periods of time while embedded in rubber, and suppresses strength deterioration when subjected to repeated extension and compression in rubber, as well as a method for producing the same. [Means for solving the problem]

[0015] In order to solve the above problems, the present invention employs the following means.

[0016] That is, (1) a synthetic fiber cord for rubber reinforcement, the synthetic fiber being treated with an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C),The lignin (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, the content of lignin (A) is 5 to 50% by weight when the total solid content contained in the adhesive treatment agent is 100 parts by weight, and the solid content weight ratio of the lignin (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:1 to 10:20, a weight ratio of solid contents of the lignin (A), the blocked isocyanate compound (B), and the rubber latex (C) is ((solid content of A)+(solid content of B)):(solid content of C)=10:90 to 60:40, When the adhesive treatment agent is made into a dry film, the dry film has a maximum strength of 0.2 MPa to 1.6 MPa and a maximum elongation of 2% to 120%. The synthetic fiber is treated with a pre-coating agent before being treated with the adhesive treatment agent, and the pre-coating agent contains at least an epoxy compound and a blocked isocyanate compound (solid weight ratio 10:0 to 10:30) and has a concentration of 0.1 to 6%. A synthetic fiber cord for reinforcing rubber, characterized in that

[0017] (2) The synthetic fiber cord for reinforcing rubber according to (1) above, wherein the synthetic fiber is at least one fiber selected from the group consisting of polyester fiber, nylon fiber, and aramid fiber.

[0020] ( 3 ) The above (1), characterized in that the blocked isocyanate compound (B) is an HDI-based blocked isocyanate or an MDI-based oxime-blocked isocyanate. or (2) The synthetic fiber cord for rubber reinforcement according to claim 1.

[0021] ( 4 ) The adhesive treatment agent according to any one of (1) to (3), wherein the pH of the adhesive treatment agent is 8.0 to 10.0. 3 1. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 7.

[0022] ( 5 ) the adhesive treatment agent according to any one of (1) to (3), characterized in that the proportion of coagulated matter in the Maron mechanical stability test is 4.0% or less; 4 1. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 7.

[0024] ( 6 ) The synthetic fiber is a polyester fiber, and the Gurley cord hardness per unit of resin attached to the cord is 30 to 80 mN / % and the rate of change in Gurley cord hardness after heating is 90% to 130%. 5 ) Synthetic fiber cord for rubber reinforcement.

[0025] ( 7 ) The synthetic fiber is a nylon fiber, the Gurley cord hardness per unit of resin attached to the cord is 2 to 35 mN / %, and the rate of change in Gurley cord hardness after heating is 90% to 300%. 5 ) Synthetic fiber cord for rubber reinforcement.

[0026] ( 8 ) A cord having a ply-twist structure with a first twist and a second twist, characterized in that it has at least two or more first twist fiber cords, at least one of which is an aramid fiber. 5 1. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 7.

[0027] ( 9 ) above (1) ~ ( 8 1. A rubber product comprising the synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 8.

[0028] ( 10 ) Adhere an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and rubber latex (C) and having the following properties to synthetic fibers; Before heat treatment, a pre-coating agent is applied to the synthetic fiber, and then heat treatment is performed. The pre-coating agent contains at least an epoxy compound and a blocked isocyanate compound (solid weight ratio 10:0 to 10:30) and has a concentration of 0.1 to 6%. 1. A method for producing a synthetic fiber cord for rubber reinforcement, comprising: (a) The lignin (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, The content of lignin (A) is 5 to 50% by weight when the total solid content in the adhesive treatment agent is 100 parts by weight. The number average molecular weight is 10,000 to 60,000, and the weight average molecular weight is 80,000 to 130,000. (b) The solid weight ratio of the lignin (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:1 to 10:20 The solid weight ratio of the lignin (A), the blocked isocyanate compound (B), and the rubber latex (C) is ((solid content of A) + (solid content of B)): (solid content of C) = 10:90 to 60:40. (c) When the adhesive treatment agent is made into a dry film, the dry film has a maximum strength of 0.2 MPa to 1.6 MPa and a maximum elongation of 2% to 120%

[0030] ( 11) The synthetic fiber is a polyester fiber, and after the adhesive treatment agent is applied, the hot stretch tension in the heat treatment step is 0.2 to 1.0 cN / dtex, and the normalizing tension is 0.05 to 0.5 cN / dtex. 10) A method for producing the synthetic fiber cord for rubber reinforcement according to claim 1.

[0031] ( 12 ) The synthetic fiber is a nylon fiber, and after the adhesive treatment agent is applied, the hot stretch tension in the heat treatment step is 0.4 to 1.3 cN / dtex, and the normalizing tension is 0.4 to 0.9 cN / dtex. 10) A method for producing the synthetic fiber cord for rubber reinforcement according to claim 1. [Effects of the Invention]

[0032] According to the present invention, a synthetic fiber cord for rubber reinforcement can be obtained, which is made from a new adhesive treatment agent that does not contain resorcinol or formalin and is made from raw materials that are advantageous in reducing the environmental load.The synthetic fiber cord can suppress the generation of resin coagulation during the dipping process, exhibits initial adhesive strength equal to or greater than that of conventional RFL, shows little adhesion deterioration when exposed to high temperatures for long periods of time while embedded in rubber, and suppresses strength deterioration when subjected to repeated extension and compression in the rubber, making it suitable for use in rubber reinforcement. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view of a Gurley cord hardness measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below.

[0035] [Synthetic fiber cord for rubber reinforcement] The rubber-reinforcing fiber cord of the present invention is obtained by treating a synthetic fiber with an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C).

[0036] The synthetic fibers used in the present invention are preferably in the form of multifilaments. Materials constituting the synthetic fibers 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 selected from polyester fiber, nylon fiber, and aramid fiber.

[0037] (polyester fiber) 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.

[0038] 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.

[0039] In the present invention, the polyester fiber used in the present invention preferably has the following properties in order to have excellent mechanical properties required for a tire cord, such as high strength, high toughness, high elastic modulus, low shrinkage, and high fatigue resistance, and to suppress deterioration in adhesion and strength even when exposed to high temperatures in rubber for a long period of time. (1) Intrinsic viscosity (IV) = 0.7 to 1.2, preferably 0.8 to 1.1 (2) Carboxyl end group (COOH) = 10 to 30 eq / t, more preferably 12 to 25 eq / t (3) Diethylene glycol (DEG) content: 0.5 to 1.5% by weight, preferably 0.5 to 1.2% by weight (4) Strength (T) = 6.0 to 10.0 cN / dtex, more preferably 7.0 to 9.0 cN / dtex (5) Elongation (E) = 8 to 20%, more preferably 10 to 16% (6) Intermediate elongation (ME) = 4.0 to 6.5%, more preferably 4.5 to 6.0% (7) Dry heat shrinkage (ΔS150°C) = 2.0 to 12.0%, more preferably 3.0 to 10.0%.

[0040] 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.

[0041] 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, 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.

[0042] 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.

[0043] 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.

[0044] (nylon fiber) Examples of the nylon fibers include those made of nylon 6, nylon 66, nylon 46, nylon 610, and nylon 612. Of these, fibers made of high-molecular-weight nylon 66, which has a relative viscosity in sulfuric acid of 3.0 or more, more preferably 3.5 or more, are preferred. The fibers 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 fibers may also contain other heat-resistant additives such as amine compounds, mercapto compounds, phosphorus compounds, and hindered phenol compounds.

[0045] 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.

[0046] (aramid fiber) 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.

[0047] Aramid fibers include para-aramid fibers and meta-aramid fibers, but para-aramid fibers, which have excellent tensile strength, are preferably used in the present invention. Examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (manufactured by DuPont USA and Toray DuPont Co., Ltd., product name "Kevlar" (registered trademark)) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers (manufactured by Teijin Limited, product name "Technora" (registered trademark)).

[0048] (Fiber morphology) 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 handleability may decrease. Furthermore, if it is less than 30 filaments, the cord may become too stiff and handleability may decrease, and if it exceeds 1,000 filaments, the cord may become too fluffed and quality may decrease.

[0049] 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 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 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 in the adhesive treatment agent and heat-treated to obtain a dipped curtain.

[0050] 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 usually the same number of second twists are applied in the opposite direction to the first twists to form a multi-twisted twisted cord, which is then dipped in an adhesive treatment agent and heat-treated while still in the twisted cord form to form a dipped cord.

[0051] The synthetic fiber cord for reinforcing rubber treated with the adhesive treatment agent of the present invention includes both the above-mentioned dipped piece and dipped cord.

[0052] (Treatment agent) The synthetic fiber cord for rubber reinforcement of the present invention is obtained by treating a synthetic fiber with an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C). The term "treated" refers to the state of the adhesive treatment agent after it has been applied to the synthetic fiber 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 distilled off, and the blocking agent of the blocked isocyanate is removed, causing a reaction by the isocyanate group. In other words, in the synthetic fiber treated with the adhesive treatment agent, the solid components in the adhesive treatment agent are attached or bonded to the polyester fiber without being chemically modified or unmodified. The synthetic fiber cord for rubber reinforcement of the present invention is one in which an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C) is applied to the synthetic fiber in the same bath (one bath), rather than the so-called two-bath treatment method known as an adhesive treatment method for polyester fiber, in which (A), (B), and (C) are separately mixed in the first bath and the second bath, respectively. Furthermore, the synthetic fiber cord of the present invention does not contain resorcinol-formaldehyde resin in either the first bath or the second bath adhesive.

[0053] The lignin (A) used in the present invention is an aromatic polymer present in trees and is known as a natural polymeric compound having a phenylpropane skeleton as its basic structure. Lignin (A) includes not only naturally occurring lignin but also chemically treated lignin. Examples of such lignin include kraft lignin obtained from kraft pulp waste liquor and lignosulfonic acid obtained from sulfite pulp waste liquor in the papermaking industry, which uses wood as a raw material. Lignin sulfonic acid is lignin in which a sulfonic acid group has been introduced into the side chain of the phenylpropane structure of lignin. Examples of lignosulfonates include sodium lignosulfonate, magnesium lignosulfonate, and calcium lignosulfonate. In the present invention, these can be used alone or in combination, but sodium lignosulfonate is most preferred from the standpoint of adhesive strength.

[0054] As a result of extensive investigation into the preferred form of the lignin (A) used in the present invention, it was found that the number-average molecular weight is preferably 10,000 to 60,000 and the weight-average molecular weight is preferably 80,000 to 130,000, and more preferably 20,000 to 50,000 and 90,000 to 120,000. If the number-average molecular weight and weight-average molecular weight of the lignin 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 to the rubber and fatigue resistance 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.

[0055] The blocked isocyanate compound (B) used in the present invention is a compound that can liberate a blocking agent upon heating to generate an active isocyanate compound. Examples of blocked isocyanate compounds 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).

[0056] Among these blocked isocyanate compounds, it is most preferable to select from HDI-based blocked isocyanates, which are the reaction product of hexamethylene diisocyanate and a blocking agent, or MDI-based oxime-blocked isocyanates, which are the reaction product of diphenylmethane diisocyanate and an oxime-based 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 standpoint of adhesive strength and fatigue resistance. Polymeric MDI with trifunctional isocyanate groups is not preferred, 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.

[0057] 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.

[0058] In addition to the above (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.

[0059] In the adhesive treatment agent of the present invention, when the total solid content in the adhesive treatment agent is taken as 100% by weight, the content of the lignin derivative (A) must be 5 to 50% by weight, preferably 7 to 45% by weight, and 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.

[0060] Furthermore, the weight ratio of lignin (A) to blocked isocyanate compound (B) (solid content of A):(solid content of B) must be 10:1 to 10:20, preferably 10:5 to 10:20. If the amount of blocked isocyanate compound is too small and exceeds this weight ratio, the adhesive strength may be insufficient. On the other hand, if the amount of blocked isocyanate compound is too large and exceeds this weight ratio, the cord may become hard and its fatigue resistance in rubber may deteriorate. When synthetic fiber cords are used to reinforce rubber products such as tires, belts, and hoses, the durability of the products may deteriorate, which is undesirable.

[0061] Furthermore, the lignin (A), the blocked isocyanate compound (B), and the 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, and more preferably in a weight ratio of ((solid content of A) + (solid content of B)):(solid content of C) of 20:80 to 50:50. Outside this range, the adhesive strength may be insufficient, or fatigue resistance may deteriorate.

[0062] The adhesive treatment agent used in the present invention, when used to form a dried film, must have a maximum strength of 0.2 MPa to 1.6 MPa, preferably 0.3 MPa to 1.4 MPa, and 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. The maximum elongation of the dried film must be 2% to 120%, preferably 4% to 100%, and 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.

[0063] The adhesive treatment agent used in the present invention must contain lignin (A), blocked isocyanate compound (B), and rubber latex (C) in the same treatment agent, and the maximum strength and maximum elongation of the dried film of the adhesive treatment agent must be within the specified ranges. By containing these components in the same treatment agent and ensuring that they fall within the specified ranges of the present invention, the adhesive treatment agent will exhibit excellent adhesion between rubber and fiber, and excellent fatigue resistance of fiber in rubber under high-temperature conditions.

[0064] The maximum point strength and maximum point 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 point strength can be adjusted to a higher value by increasing the amount of blocked isocyanate compound (B) mixed into the adhesive treatment agent. Furthermore, the maximum point elongation can be adjusted to a higher value by, for example, mixing rubber latex into the adhesive treatment agent and increasing the amount of rubber latex mixed into the adhesive treatment agent. On the other hand, adding highly reactive and crosslinkable compounds such as epoxy compounds or oxazoline group-containing substances in addition to (A), (B), and (C) is not recommended because the strength will be higher than the specified range and the elongation will be lower than the specified range, which may lead to a deterioration in fatigue resistance in the rubber.

[0065] The pH of the adhesive treatment agent used in the present invention is preferably 8.0 to 10.0, more preferably 8.5 to 9.8. If the pH is less than 8.0, the adhesive strength may be insufficient, and if it exceeds 10.0, the fatigue resistance in the rubber may deteriorate, which is not preferable.

[0066] Furthermore, in the present invention, it is preferable that the adhesive treatment agent containing at least the three substances (A), (B), and (C) exhibit a coagulation ratio of 4.0% or less in the Maron mechanical stability test. While the specific method of the Maron mechanical stability test will be described later, this test indicates the stability of the adhesive treatment agent when mechanical shear stress is applied to the agent, and is utilized in the present invention as a measure of the degree of coagulation generation during the dipping process in which the adhesive treatment agent is applied to fibers. The coagulation ratio in the Maron mechanical stability test is more preferably 3.5% or less, and even more preferably 3.0% or less. If it exceeds 4.0%, coagulation occurs frequently during the dipping process, making continuous production difficult, and the coagulation generated may adhere to the fiber cord, leading to deterioration of adhesion to the rubber. A coagulation ratio in this test below the specified value of the present invention is preferable because it improves processability during the dipping process.

[0067] There are no particular limitations on the method for keeping the proportion of coagulum in the Maron mechanical stability test below the specified level of the present invention, but it can be adjusted by optimizing the selection of the types and blending ratios of the lignin (A), blocked isocyanate (B), and rubber latex (C) used. Alternatively, a method of adding an additional surfactant is also preferred. Anionic surfactants are preferred as surfactants, and examples thereof include sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, and alkylbenzene sulfonates.

[0068] The adhesive treatment agent used in the present invention is a solids solution or dispersion in water, with a total solids concentration of preferably 5 to 25% by weight, more preferably 10 to 20% by weight, and even more preferably 12 to 18% by weight. 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 the adhesive strength.

[0069] The amount of adhesive treatment agent attached to 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.

[0070] The synthetic fiber cord for rubber reinforcement of the present invention may be treated with a precoat agent before the synthetic fiber is treated with the adhesive treatment agent (adhesive treatment agent containing at least lignin, a blocked isocyanate compound, and rubber latex).

[0071] The precoating agent preferably contains at least an epoxy compound and a blocked isocyanate compound (solids weight ratio of 10:0 to 10:30), with a concentration of 0.1 to 6%. Outside this range, adhesive strength may decrease. Furthermore, the amount of precoating agent adhered to the synthetic fiber is preferably 0.1 to 3 parts by weight in terms of solids weight per 100 parts by weight of synthetic fiber. Outside this range, adhesive strength may decrease.

[0072] (Synthetic fiber cord made of polyester fiber for rubber reinforcement) The strength of the synthetic fiber cord for rubber reinforcement using polyester fiber in the present invention is preferably 5.0 to 7.0 cN / dtex, and more preferably 5.3 to 6.7 cN / dtex. If it is less than 5.0 cN / dtex, it may not be able to bear practical stress in the circumferential direction of a tire when used as a tire cord, for example. If the cord exceeds 7.0 cN / dtex, it is difficult to obtain a practical tire cord in terms of production stability and cost of the raw yarn. Here, cord strength is the value obtained by dividing the cord strength by the standard fineness in the cord configuration (for example, 2200 dtex for two 1100 dtex raw yarns twisted together).

[0073] Furthermore, the synthetic fiber cord for rubber reinforcement using polyester fiber of the present invention preferably has a value of elongation at 2 cN / dtex + dry heat shrinkage (dimensional stability) of 6.0 to 9.0, more preferably 6.5 to 8.5. If the value exceeds 9.0, fatigue resistance in rubber may deteriorate, and tire durability may decrease. A cord with a value of less than 6.0 cannot be used to obtain a practical tire cord in terms of production stability and cost of the raw yarn. The value of elongation at 2 cN / dtex + dry heat shrinkage is an index showing the dimensional stability of the cord. The elongation at 2 cN / dtex corresponds to the elastic modulus of the cord, and a low value indicates a high elastic modulus. In other words, a small sum of the elongation at 2 cN / dtex and dry heat shrinkage (dimensional stability) means that the cord simultaneously possesses high elasticity and low shrinkage. When the value of dimensional stability is within the range specified in the present invention, tire uniformity is maintained during tire molding, leading to improved tire durability. The method for controlling the dimensional stability of the cord is not particularly limited, but examples thereof include adjusting the hot stretch tension and normalizing tension in the dipping process, and selecting a polyester fiber with excellent dimensional stability.

[0074] The synthetic fiber cord for rubber reinforcement using polyester fiber in the present invention preferably has a Gurley cord hardness of 30 to 80 mN / % per unit of resin attached to the cord and a Gurley cord hardness change rate after heating of 90 to 130%. More preferably, the Gurley cord hardness is 35 to 75 mN / % and a Gurley cord hardness change rate after heating of 95% to 120%. By adjusting the Gurley cord hardness within these ranges, the rubber-cord composite can improve its ability to conform to the rubber, resulting in good adhesive strength. There are no particular limitations on the method for adjusting the Gurley cord hardness; for example, reducing the amount of resin attached can reduce the Gurley cord hardness, while increasing the amount of resin attached can improve it. Furthermore, during the heat treatment in the dipping step described below, the Gurley cord hardness can be reduced by reducing the heat treatment temperature and / or heat treatment time, and can be improved by increasing the heat treatment temperature and / or heat treatment time. This can also be achieved by setting the tension in the mechanical softening process after passing through the normalizing zone in the dipping process described below to 0.5 cN to 5.0 cN / dtex.

[0075] (Synthetic fiber cord made of nylon fiber for reinforcing rubber) The strength of the synthetic fiber cord for rubber reinforcement using nylon fiber in the present invention is preferably 6.0 to 10.0 cN / dtex, and more preferably 7.0 to 9.0 cN / dtex. If it is less than 6.0 cN / dtex, it may not be able to bear practical stress in the circumferential direction of a tire when used as a tire cord, for example. If the cord exceeds 9.0 cN / dtex, it is difficult to obtain a practical tire cord in terms of production stability and cost of the raw yarn. Here, cord strength is the value obtained by dividing the cord strength by the standard fineness in the cord configuration (for example, 1880 dtex for two 940 dtex raw yarns twisted together).

[0076] The synthetic fiber cord for rubber reinforcement using nylon fiber in the present invention preferably has a heat strength retention rate of 55 to 85%, more preferably 60 to 80%, at 180°C for 40 hours. This range is preferable because it results in a rubber-reinforced cord that exhibits little loss in strength even when exposed to heat during the vulcanization process or in an actual usage environment, resulting in a rubber-reinforced cord with excellent fatigue resistance. There are no particular restrictions on the method for adjusting the heat strength retention rate. For example, the presence or absence and content of chlorine-containing substances in the adhesive can cause a decrease in heat strength, and this can be adjusted by optimizing the adhesive composition and blending amount.

[0077] In the synthetic fiber cord for rubber reinforcement using nylon fiber according to the present invention, it is preferable that the Gurley cord hardness per unit of resin attached to the cord is 2 to 35 mN / % and the rate of change in Gurley cord hardness after heating is 90% to 300%. More preferably, the Gurley cord hardness is 4 to 30 mN / % and the rate of change in Gurley cord hardness after heating is 140% to 200%. By setting the values ​​within these ranges, the rubber-cord composite can improve the cord's ability to conform to the rubber, resulting in good adhesive strength. There are no particular limitations on the method for adjusting the Gurley cord hardness; for example, the Gurley cord hardness can be reduced by reducing the amount of attached resin, and the Gurley cord hardness can be improved by increasing the amount of attached resin. Furthermore, during the heat treatment in the dipping step described below, the Gurley cord hardness can be reduced by reducing the heat treatment temperature and / or heat treatment time, and the Gurley cord hardness can be improved by increasing the heat treatment temperature and / or heat treatment time. This can also be achieved by setting the tension in the mechanical softening process after passing through the normalizing zone in the dipping process described below to 0.5 cN to 5.0 cN / dtex.

[0078] (Synthetic fiber cord for rubber reinforcement using aramid fiber) The synthetic fiber cord for rubber reinforcement using aramid fiber in the present invention preferably has a ply structure having a first twist and a second twist, with at least two or more first twist fiber cords, at least one of which is an aramid fiber cord. The number of first twist cords is at least two, and is not limited to this number. 2 to 8 cords are preferred, and 2 to 5 cords are more preferred. Of the 2 to 8 first twist cords, 1 to 5 cords are preferably aramid fiber cords, and 1 to 3 cords are more preferred. Fibers other than aramid fiber that can be used as the first twist cord are not particularly limited, but examples include polyester fiber, nylon fiber, rayon fiber, vinylon fiber, and polyurethane fiber. Nylon fiber is preferred from the viewpoint of improving fatigue resistance. Nylon 66 fiber (polyhexamethylene adipamide fiber) is preferred as the nylon fiber from the viewpoint of excellent thermal dimensional stability and heat resistance. Nylon 6 fiber, nylon 46 fiber, etc. may also be used. Nylon 66 fibers are composed of at least 95 mol % or more of hexamethylene adipamide units and may contain up to 5 mol % of copolymer components such as ε-caproamide, tetramethylene adipamide, hexamethylene sebacamide, hexamethylene isophthalamide, tetramethylene terephthalamide, and xylylene phthalamide.

[0079] The twist coefficient (K) of the first twist and the final twist, calculated by the following formula, is preferably 2 to 10 for both the first twist and the final twist, and more preferably in the range of 4 to 8. If the twist coefficient is less than 2, the fatigue resistance of the fiber cord may decrease, and if it exceeds 8, the strength of the fiber cord may decrease, making it insufficient for practical use in rubber reinforcement. By setting the twist coefficient within the preferred range, the cord is endowed with elongation as a structural factor, which alleviates the force applied to the cord when bent and improves fatigue resistance. Twist factor (K) = 0.0033 x T x D 1 / 2 T: Number of twists (T / 10cm) D: Total fiber fineness (dtex) As a twisting method, known twisting machines such as a ring twisting machine, a double twister twisting machine, an aroma twisting machine, etc. The method may involve first twisting the fibers, then winding them, and combining two or more of the resulting first twisted yarns to perform second twisting, or it may involve twisting two or more fiber threads separately, and then twisting the resulting first twisted yarns together without winding them.

[0080] The synthetic fiber cord for rubber reinforcement of the present invention, characterized as described above, is made of a new adhesive treatment agent that does not contain resorcinol or formalin and is made from raw materials that are advantageous in reducing the environmental impact. It can suppress the generation of resin coagulation during the dipping process, exhibits initial adhesive strength equal to or greater than that of conventional RFL, shows little adhesion deterioration when exposed to high temperatures for long periods of time while embedded in rubber, and suppresses strength deterioration when subjected to repeated stretching and compression in the rubber, making it suitable for use in rubber reinforcement.

[0081] Examples of rubber products containing the synthetic fiber cord for rubber reinforcement according to the present invention include tires, belts, and hoses. These environmentally friendly rubber products do not use resorcinol or formalin, yet can exhibit performance equal to or better than that of products using conventional RFL.

[0082] [Method of manufacturing synthetic fiber cord for rubber reinforcement] Next, a method for producing the synthetic fiber cord for reinforcing rubber of the present invention will be described.

[0083] 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 lignin (A), a blocked isocyanate compound (B), and a rubber latex (C) and having the following properties is adhered to a synthetic fiber in the same bath, followed by a heat treatment: (a) The content of lignin (A) is 5 to 50% by weight when the total solid content in the adhesive treatment agent is 100 parts by weight. (b), wherein the solid weight ratio of the lignin (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:1 to 10:20. (c) When the adhesive treatment agent is made into a dry film, the dry film has a maximum strength of 0.2 MPa to 1.6 MPa and a maximum elongation of 2% to 120% If the weight ratio of (solids content of A):(solids content of B) is outside this range and the amount of blocked isocyanate compound is small, the adhesive strength may be insufficient, whereas if the amount of blocked isocyanate compound is large and exceeds this weight ratio, the cord may become hard and its fatigue resistance may deteriorate.

[0084] The synthetic fiber may be in the form of either a twisted cord or a green reel, and a preferred method involves dipping the twisted cord or green reel in an adhesive treatment agent in a dip bath, followed by drying the water at a temperature of preferably 100 to 150° C., and then heat treating the resulting material at 200 to 255° C. The preferred embodiments of the lignin (A), blocked isocyanate compound (B), and rubber latex (C) are those described above.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] Furthermore, in the adhesive treatment agent used in the method for producing a synthetic fiber cord for rubber reinforcement of the present invention, the lignin (A) preferably has a number average molecular weight of 10,000 to 60,000 and a weight average molecular weight of 80,000 to 130,000. If the number average molecular weight and weight average molecular weight of the lignin are outside these ranges, the adhesive strength and fatigue resistance may be insufficient, and therefore it is preferable to select a lignin within these ranges.

[0089] In the method for producing a synthetic fiber cord for rubber reinforcement of the present invention, a precoating agent may be applied to the synthetic fiber and heat-treated before the adhesive treatment agent (adhesive treatment agent containing at least lignin, a blocked isocyanate compound, and rubber latex) is applied to the synthetic fiber and heat-treated. The precoating agent preferably contains at least an epoxy compound and a blocked isocyanate compound (solids weight ratio of 10:0 to 10:30), with a concentration of 0.1 to 6%. Outside this range, adhesive strength may decrease. Furthermore, the amount of precoating agent adhered to the synthetic fiber is preferably 0.1 to 3 parts by weight in terms of solids weight per 100 parts by weight of synthetic fiber. Outside this range, adhesive strength may decrease.

[0090] When applying the pre-coating agent, the same dipping method as described above can be used. That is, a preferred method is to dip a twisted synthetic fiber cord or a raw cloth into the pre-coating 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.

[0091] In the manufacturing method of the present invention, an adhesive treatment agent (containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C) and used in the same bath) is applied to synthetic fibers, and then heat treatment is performed. Preferably, this heat treatment is performed in two stages: hot treatment and normalizing treatment. The heat treatment temperature in both cases is preferably 200 to 255°C. In the case of polyester fibers, the tension during hot treatment (hot stretch tension) is preferably 0.2 to 1.0 cN / dtex, and the tension during normalizing treatment (normalizing tension) is preferably 0.05 to 0.5 cN / dtex, more preferably 0.3 to 0.9 cN / dtex, and 0.1 to 0.4 cN / dtex, and even more preferably 0.4 to 0.8 cN / dtex, and 0.1 to 0.3 cN / dtex. If the tensions are outside these ranges, it may lead to a decrease in strength and fatigue resistance. In the case of polyamide fibers, the tension during hot treatment (hot stretch tension) is preferably 0.4 to 1.3 cN / dtex and the tension during normalizing treatment (normalizing tension) is preferably 0.4 to 0.9 cN / dtex, more preferably 0.5 to 1.1 cN / dtex and 0.5 to 0.8 cN / dtex, and even more preferably 0.4 to 1.0 cN / dtex and 0.5 to 0.7 cN / dtex. A tension outside these ranges may lead to a decrease in strength and fatigue resistance.

[0092] The synthetic fiber cord for rubber reinforcement of the present invention obtained in this manner is made of a new adhesive treatment agent that does not contain resorcinol or formalin and is made from raw materials that are advantageous in reducing the environmental impact. It can suppress the generation of resin coagulation during the dipping process, exhibits initial adhesive strength equal to or greater than that of conventional RFL, shows little adhesion deterioration even when exposed to high temperatures for long periods of time while embedded in rubber, and suppresses strength deterioration when subjected to repeated stretching and compression in the rubber, making it suitable for use in rubber reinforcement. [Example]

[0093] 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.

[0094] (1) Amount of adhesive treatment agent attached The adhesive adhesion was determined according to the dip pick-up mass method of JIS L1017 (2002).

[0095] (2) Initial adhesive strength and heat-resistant adhesive strength This indicates the adhesive strength between the rubber-reinforcing synthetic fiber cord and rubber. The initial adhesive strength was measured in accordance with JIS L-1017 (2002) Appendix 1, 3.1T test (method A), in which the rubber-reinforcing synthetic fiber cord was embedded in unvulcanized rubber, and subjected to a test at 150°C for 30 minutes and 50 kg / cm. 2 After press vulcanization, the samples were allowed to cool, and the synthetic fiber cord for rubber reinforcement was pulled out of the rubber block at a speed of 300 mm / min. The weight required for the pullout was measured for each sample, and the arithmetic average of 10 samples was taken as the initial adhesive strength. The heat-resistant adhesive strength was measured in accordance with the 3.1T test (method A) of JIS L-1017 (2002) Appendix 1, by embedding the synthetic fiber cord for rubber reinforcement in unvulcanized rubber, and if the synthetic fiber was polyester fiber, testing was performed at 170°C for 70 minutes and 50 kg / cm. 2 , 170℃, 24 hours, 50kg / cm for nylon fiber 2 , 170°C, 3 hours, 50 kg / cm for fibers containing aramid fibers 2 After press vulcanization, the rubber was allowed to cool, and the synthetic fiber cord for reinforcing the rubber was pulled out from the rubber block at a speed of 300 mm / min. The load required for the pulling out was measured for each sample, and the arithmetic average value of 10 samples was taken as the heat-resistant adhesive strength.

[0096] (3) Fatigue resistance in rubber (retention rate) The test was conducted 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 test was conducted at 150°C for 30 minutes and 50 kg / cm 2 The test piece was press-vulcanized under the conditions of 1. to 3. prepare a rubber composite. If the synthetic fiber was polyester fiber or nylon fiber, this test piece was subjected to a deformation of 6.3% compression and 12.6% extension per cycle at 2600 cycles / min in a 100°C atmosphere for 12 hours, and if the synthetic fiber was a fiber containing aramid fiber, it was subjected to a deformation of 12% compression and 0% extension per cycle at 1705 cycles / min for 6 hours, after which the synthetic fiber cord for rubber reinforcement was removed from the rubber and the breaking strength after fatigue was measured. The breaking strength retention rate before and after the fatigue test was determined for each sample, and the arithmetic average value of the eight samples was taken as the fatigue resistance (retention rate) of the rubber.

[0097] 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): 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).

[0098] (4) Maximum strength and elongation of the dried film of the adhesive treatment agent The adhesive treatment agent was applied to a glass plate so that the dried film would be 0.5 mm thick, and after drying at room temperature for 72 hours, it was peeled off from the glass plate and heat-treated in an oven at 120°C for 15 minutes, and then in an oven at 240°C for 2 minutes. This was punched out using a No. 2 dumbbell mold and subjected to a tensile test using an Orientec Tensilon RTM-100 testing machine at a crosshead speed of 50 mm / min in an atmosphere of 25°C to measure strength and elongation. 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 point strength, and the arithmetic mean value of the elongation for 6 samples was taken as the maximum point elongation.

[0099] (5) pH measurement of adhesive treatment agents The pH of the adhesive treatment agent sample after preparation was measured using a desktop pH meter (F-72S, manufactured by Horiba, Ltd.) in an environment of 25° C. Here, “after preparation” means that the measurement was performed between immediately after preparation and up to one hour after preparation.

[0100] (6) Maron type mechanical stability test The proportion of coagulated material in the Maron mechanical stability test for adhesive treatment agents was measured using the following method. Using a Maron mechanical stability tester manufactured by Yasuda Seiki Seisakusho, 50 g of adhesive treatment agent was subjected to mechanical shear at a rotor rotation speed of 1,000 rpm, a rotor load of 10 kg, and a rotation time of 3 minutes, and then the sample was filtered through a 100-mesh wire screen. The captured coagulated material was dried and then measured for mass, and the ratio of the amount of coagulated material to the solid mass of the original adhesive treatment agent was calculated in weight percent, and this value was taken as the proportion of coagulated material (%).

[0101] (7) 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.

[0102] (8) Gurley cord hardness per unit of resin attached to the cord A synthetic fiber cord for rubber reinforcement was cut to a length of 1 m, a metal hook was tied to one end, and a 300 g weight was tied to the other end. The cord was then hung vertically in the air for 24 hours in an environment regulated at a temperature of 25°C and a relative humidity of 40%, to obtain a measurement sample.

[0103] This was cut into 38.1 mm (1.5 inches) test pieces, and the Gurley cord hardness was measured using a Gurley's stiffness tester manufactured by Yasuda Seiki Co., Ltd. Figure 1 shows a perspective view of the Gurley's stiffness tester.

[0104] The test specimen mounting and measurement method is as follows: (a) Fix chuck 1 in the desired position according to the length of the specimen, and then mount test specimen 2. (b) At the bottom of rotating rod 3 (below the bearing), there are load setting holes located 25.4 mm (1 inch) (W1 in Figure 1), 50.8 mm (2 inches) (W2 in Figure 1), and 101.6 mm (4 inches) (W3 in Figure 1) from the shaft. The load weight and hole position must be set according to the flexibility of test specimen 2. In this case, the load and hole position must be selected so that needle 5 on scale plate 4 points to numbers 2 through 4. (c) Once the appropriate setting for test specimen 2 is achieved, press the drive button to move the drive shaft left and right, and read the value on scale plate 4 where the needle points to within 0.1 increments. (d) For each test specimen 2, measure once left and right, for a total of 10 test specimens, and calculate the average value for one sample. The calculation method is as follows: The average value of each measurement was calculated using the following formula. Finally, the Gurley cord hardness (mg) was converted to (mN), and the value obtained by dividing it by the amount of resin attached (%) was defined as the Gurley cord hardness per unit of resin attached to the cord (mN / %). Gurley cord hardness (mg) = R x {(W1 x 1) + (W2 x 2) + (W3 x 4)} / 5 x (L - 12.7) 2 / W×19.8 however, R: Average value of the measured values W1: Load applied to the 25.4mm load position (hole) (unit: g) W2: Load applied to the 50.8mm load position (hole) (unit: g) W3: Load applied to the 101.6mm load position (hole) (unit: g) L: Sample length (mm) W: Width of test piece (code gauge) (mm).

[0105] (9) Change in hardness of Gurley cord after heating (change after heating) A synthetic fiber cord for rubber reinforcement was cut to a length of 1 m, a metal hook was tied to one end, a 300 g weight was tied to the other end, and the cord was heated by hanging it vertically in the air for 2 hours in an environment controlled at a temperature of 160°C. Thereafter, the Gurley cord hardness was determined in the same manner as in (8) above. The value in (9) divided by the value in (8) was taken as the rate of change (%) in Gurley cord hardness after heating.

[0106] (9) Measurement of number average molecular weight and weight average molecular weight of lignin The number-average molecular weight and weight-average molecular weight of lignin were measured by GPC (gel permeation chromatography). A solvent (ammonia buffer / methanol) was added to the lignin sample, and the mixture was stirred at room temperature to dissolve, followed by filtration through a 0.5 μm filter. Then, measurement was performed using 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. Detailed measurement conditions are described below. Measuring equipment: Shimadzu Corporation Columns used: 1 TSKgel GMPWXL, 1 G3000PWXL (φ7.8 mm x 30 cm, Tosoh) Solvent: 0.1 M ammonia buffer (pH 11) / methanol (4 / 1, v / v) Standard materials: Monodisperse polyethylene oxide and polyethylene glycol manufactured by Tosoh and Agilent Detector: UV detector (Shimadzu SPD-M20A).

[0107] Example 1 , 2, 5~6, Reference examples 3, 7 , Comparative Examples 1 to 5) Glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase Chemical Industries, Ltd.), blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industries, Ltd.), and rubber latex (Pyratex, manufactured by Nippon A&L Co., Ltd.) were mixed in a solids ratio of 20:40:40, and then diluted with water to obtain a precoat agent (A) with a total solids content of 4.0 wt%.

[0108] Furthermore, lignin (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, to obtain adhesive treatment agents with a total solids concentration of 15% by weight. The pH of the obtained adhesive treatment agents, and the maximum point strength and maximum point elongation of the dried film were measured. Furthermore, the percentage of coagulated material (%) was measured using the method described in the Maron mechanical stability test described above.

[0109] Two 1670 dtex 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.

[0110] The twisted yarn cord was immersed in the precoat agent using a Computreator processor (manufactured by Ritzler Co., Ltd.), then dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute. The cord was then immersed in an adhesive treatment agent containing the components (A), (B), and (C), then dried at 120°C for 2 minutes, then heat-treated at 240°C for 0.5 minutes (hot treatment), and then heat-treated at 240°C for 0.5 minutes (normalization treatment). The tension during the second bath hot treatment (hot stretch tension) and the tension during the second bath normalization treatment (normalizing tension) were the dip tensions shown in Table 1.

[0111] Here, in the treatment with the adhesive treatment agent containing (A), (B), and (C), the cord was run at a running speed of 20 m / min for 1 hour, and 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 treatment machine was confirmed and judged as (coagulated material: much = B>A>S=none).

[0112] The adhesive solid content of the obtained synthetic fiber cord for rubber reinforcement was 1.1 parts by weight of the precoating agent per 100 parts by weight of the synthetic fiber, and 4.0 parts by weight of the adhesive treatment agent containing (A), (B), and (C) per 100 parts by weight of the synthetic fiber.

[0113] The components of the adhesive treatment agent shown in Table 1 are as follows: (A)-1: Lignin (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 (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 (manufactured by Nippon Paper Industries Co., Ltd., sodium lignosulfonate, "Pearlex" NP, number average molecular weight 97,000, weight average molecular weight 146,000) (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, a blocking agent adduct of hexamethylene diisocyanate, dissociation temperature 100 to 130°C) (B)-3: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-3031CONC, lactam-blocked diphenylmethane diisocyanate, dissociation temperature 160-180°C) (B)-4: Blocked isocyanate (Meisei Chemical Industry Co., Ltd., DM-7000, lactam block polymeric MDI, dissociation temperature 160 to 180°C) (C)-1: Rubber latex (Pilatex, manufactured by Nippon A&L Co., Ltd.).

[0114] ( reference Example 4) The precoating agent was changed to precoating agent (A) with a total solids content of 7.0 wt%, obtained by mixing glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase Chemical Industries, Ltd.) and a blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industries, Ltd.) in a solids ratio of 10:35 and diluting with water. Treatment and evaluation were carried out in the same manner as in Example 1. The adhesive solids adhesion weight of the obtained synthetic fiber cord for rubber reinforcement was 1.7 parts by weight per 100 parts by weight of the precoating agent and 3.5 parts by weight per 100 parts by weight of the adhesive treatment agent containing (A), (B), and (C).

[0115] ( reference Example 8) Three 1100 dtex polyester multifilament yarns (Toray Industries, Inc., "Tetoron" 1100T-240-707M) that had been previously treated with a polyepoxide compound (sorbitol polyglycidyl ether) by mixing the polyepoxide compound as a spinning oil during the spinning process 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. This twisted yarn cord was treated and evaluated in the same manner as in Example 1, except that no pre-coating agent was used and an adhesive treatment agent containing (A), (B), and (C) was applied.

[0116] (Conventional Example 1) Treatment and evaluation were performed in the same manner as in Example 1, except that the adhesive treatment agent containing (A), (B), and (C) in Example 1 was replaced with an RFL adhesive obtained by the following procedure. 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. This precondensation product (RF) was then 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 deposition 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 synthetic fiber and 4.0 parts by weight of RFL adhesive per 100 parts by weight of polyester fiber. Example 10 , 11, 14, 15, Reference examples 12, 16 , Comparative Examples 6 to 10) Glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase ChemteX), blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industry Co., Ltd.), and rubber latex (Pyratex, manufactured by Nippon A&L Co., Ltd.) were mixed in a solids ratio of 20:40:40, and then diluted with water to obtain a precoat agent (A) with a total solids content of 4.0 wt%.

[0117] Furthermore, lignin (A), blocked isocyanate compound (B), and rubber latex (C) were mixed with water so that the solid content ratios shown in Table 2 were obtained to obtain adhesive treatment agents with a total solids concentration of 15% by weight. The pH of the obtained adhesive treatment agents, and the maximum point strength and maximum point elongation of the dried film were measured. The proportion (%) of coagulated material was also measured using the method described in the Maron mechanical stability test described above.

[0118] Two 1400 dtex nylon multifilament yarns ("Amilan" 1400T-204-1783, manufactured by Toray Industries, Inc.) 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.

[0119] The twisted yarn cord was immersed in the precoat agent 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. The cord was then immersed in an adhesive treatment agent containing the components (A), (B), and (C), then dried at 120°C for 2 minutes, and subsequently heat-treated at 240°C for 0.5 minutes (hot treatment), and then heat-treated at 240°C for 0.5 minutes (normalization treatment). The tension during the second bath hot treatment (hot stretch tension) and the tension during the second bath normalization treatment (normalizing tension) were the dip tensions shown in Table 2.

[0120] Here, in the treatment with the adhesive treatment agent containing (A), (B), and (C), the cord was run at a running speed of 20 m / min for 1 hour, and 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 treatment machine was confirmed and judged as (coagulated material: much = B>A>S=none).

[0121] The adhesive solid content of the obtained synthetic fiber cord for rubber reinforcement was 1.1 parts by weight of the precoating agent per 100 parts by weight of the synthetic fiber, and 4.0 parts by weight of the adhesive treatment agent containing (A), (B), and (C) per 100 parts by weight of the synthetic fiber.

[0122] The components of the adhesive treatment agent shown in Table 2 are as described above.

[0123] ( reference Example 13) The precoating agent was changed to precoating agent (A) with a total solids content of 7.0 wt%, obtained by mixing glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase ChemteX) and a blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industry) at a solids ratio of 10:35 and diluting with water. Treatment and evaluation were carried out in the same manner as in Example 10. The adhesive solids adhesion weight of the obtained synthetic cord for rubber reinforcement was 1.7 parts by weight for the precoating agent per 100 parts by weight of synthetic fiber, and 3.5 parts by weight for the adhesive treatment agent containing (A), (B), and (C) per 100 parts by weight of synthetic fiber.

[0124] ( reference Example 17) Treatment and evaluation were carried out in the same manner as in Example 10, except that no precoating agent was used and an adhesive treatment agent containing (A), (B), and (C) was used.

[0125] (Conventional example 2) In Example 10, the precoat agent was omitted, and instead the adhesive treatment agent containing (A), (B), and (C) was replaced with an RFL adhesive obtained by the following procedure. The same procedure as in Example 10 was used for treatment and evaluation. 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. This precondensation product (RF) was then 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 resulting synthetic fiber cord for rubber reinforcement was 4.0 parts by weight per 100 parts by weight of synthetic fiber.

[0126] Example 19 , 20, 23, 24, Reference examples 21, 25 , Comparative Examples 11 to 15) Glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase Chemical Industries, Ltd.), blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industry Co., Ltd.), and rubber latex ("Pyratex", manufactured by Nippon A&L Co., Ltd.) were mixed in a solids ratio of 20:40:40, and then diluted with water to obtain a precoat agent (A) with a total solids content of 4.0 wt%.

[0127] Furthermore, lignin (A), blocked isocyanate compound (B), and rubber latex (C) were mixed with water so that the solid content ratios shown in Table 3 were obtained to obtain an adhesive treatment agent with a total solids concentration of 16% by weight. The pH of the obtained adhesive treatment agent, and the maximum point strength and maximum point elongation of the dried film were measured. The proportion (%) of coagulated material was also measured using the method described in the Maron mechanical stability test described above.

[0128] A multifilament yarn of polyparaphenylene terephthalamide (aramid) fiber (trade name Kevlar®, fineness 1670 dtex, filament count 1000) manufactured by DuPont-Toray Co., Ltd. was twisted 40 times / 10 cm in the Z direction to form a first twisted cord. Two of these first twisted cords were aligned and twisted 40 times / 10 cm in the S direction using a ring twister to form a final twist, forming a double-twisted twisted cord.

[0129] The twisted yarn cord was immersed in the precoating agent 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 fiber cord for rubber reinforcement.

[0130] Here, in the treatment with the adhesive treatment agent containing (A), (B), and (C), the cord was run at a running speed of 20 m / min for 1 hour, and 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 treatment machine was confirmed and judged as (coagulated material: much = B>A>S=none).

[0131] The adhesive solid content of the obtained cord was 1.1 parts by weight of the precoating agent per 100 parts by weight of the synthetic fiber, and 5.0 parts by weight of the adhesive treatment agent containing (A), (B), and (C) per 100 parts by weight of the synthetic fiber.

[0132] The components of the adhesive treatment agent shown in Table 3 are as described above.

[0133] ( reference Example 22) The precoating agent was changed to precoating agent (A) with a total solids content of 7.0 wt%, obtained by mixing glycerol polyglycidyl ether ("Denacol" EX313, manufactured by Nagase Chemical Industries, Ltd.) and a blocked isocyanate compound (DM-6400, manufactured by Meisei Chemical Industries, Ltd.) at a solids ratio of 10:35 and diluting with water. Treatment and evaluation were carried out in the same manner as in Example 19. The adhesive solids adhesion weight of the obtained synthetic fiber cord for rubber reinforcement was 1.7 parts by weight per 100 parts by weight of the precoating agent and 4.5 parts by weight per 100 parts by weight of the adhesive treatment agent containing (A), (B), and (C).

[0134] Example 26 A multifilament yarn of aramid fiber (trade name: Kevlar®, fineness: 1670 dtex, filament count: 1000) manufactured by Toray DuPont Co., Ltd. was twisted 40 times / 10 cm in the Z direction to form a first twisted cord. A multifilament yarn of nylon 66 fiber (trade name: Promilan®, fineness: 1400 dtex, filament count: 204) manufactured by Toray Industries, Inc. was twisted 40 times / 10 cm in the Z direction to form a first twisted cord. These two first twisted cords were aligned and twisted 40 times / 10 cm in the S direction using a ring twister to form a final twisted cord. The same procedure as in Example 19 was repeated except for using this two-twisted cord.

[0135] (Conventional example 3) Treatment and evaluation were carried out in the same manner as in Example 19, except that the adhesive treatment agent containing (A), (B), and (C) in Example 19 was changed to an RFL adhesive obtained by the following procedure.

[0136] 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 two hours to obtain a precondensation product of resorcinol and formalin. This precondensation product (RF) was then 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 16%. The adhesive solids deposition 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 synthetic fiber, and 5.0 parts by weight of RFL adhesive per 100 parts by weight of synthetic fiber.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] The synthetic fiber cords for rubber reinforcement obtained as described above were measured for Gurley cord hardness and the rate of change in Gurley cord hardness after heating. Furthermore, after embedding the cords in unvulcanized rubber and vulcanizing them, the initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance in rubber were measured. The results are shown in Tables 1 to 3.

[0141] As can be seen from the results in Tables 1 to 3, in the case of 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, it is possible to suppress the generation of resin coagulation during the dipping process, and it is also clear that the adhesion to rubber and heat-resistant adhesion are good, and furthermore, fatigue resistance in a high-temperature atmosphere is good. [Explanation of symbols]

[0142] 1 chuck 2 test specimens 3 Rotating rod 4 Scale plate 5 needles W1 Load setting hole (25.4 mm (1 inch) from the axis) W2 Load setting hole (50.8 mm (2 inches) from the shaft) W3 Load setting hole (101.6 mm (4 inches) from the shaft)

Claims

1. A synthetic fiber cord for rubber reinforcement, wherein the synthetic fiber is treated with an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C), wherein the lignin (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, and the content of the lignin (A) is 5 to 50% by weight when the total solid content contained in the adhesive treatment agent is taken as 100 parts by weight, and the solid content weight ratio of the lignin (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:1 to 10:20, and the lignin (A) and a weight ratio of the solid contents of a blocked isocyanate compound (B) to a rubber latex (C) of ((solid content of A) + (solid content of B)):(solid content of C) = 10:90 to 60:40; a dried film formed from the adhesive treatment agent has a maximum point strength of 0.2 MPa to 1.6 MPa and a maximum point elongation of 2% to 120%; and a synthetic fiber cord for rubber reinforcement is treated with a precoating agent before being treated with the adhesive treatment agent, the precoating agent containing at least an epoxy compound and a blocked isocyanate compound (solid content weight ratio of 10:0 to 10:30) at a concentration of 0.1 to 6%.

2. 2. The synthetic fiber cord for reinforcing rubber according to claim 1, wherein the synthetic fiber is at least one fiber selected from the group consisting of polyester fiber, nylon fiber, and aramid fiber.

3. 3. The synthetic fiber cord for rubber reinforcement according to claim 1, wherein the blocked isocyanate compound (B) is an HDI-based blocked isocyanate or an MDI-based oxime-blocked isocyanate.

4. 4. The synthetic fiber cord for rubber reinforcement according to claim 1, wherein the pH of the adhesive treatment agent is 8.0 to 10.

0.

5. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 4, characterized in that the adhesive treatment agent has a coagulation rate of 4.0% or less in a Maron mechanical stability test.

6. 6. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 5, wherein the synthetic fiber is a polyester fiber, the Gurley cord hardness per unit of resin attached to the cord is 30 to 80 mN / %, and the rate of change in Gurley cord hardness after heating is 90% to 130%.

7. 6. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 5, wherein the synthetic fiber is a nylon fiber, the Gurley cord hardness per unit of resin attached to the cord is 2 to 35 mN / %, and the rate of change in Gurley cord hardness after heating is 90% to 300%.

8. 6. The synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 5, characterized in that the cord has a ply-twisted structure having a first twist and a second twist, and has at least two or more first twist fiber cords, at least one of which is an aramid fiber.

9. A rubber product comprising the synthetic fiber cord for rubber reinforcement according to any one of claims 1 to 8.

10. A method for producing a synthetic fiber cord for rubber reinforcement, comprising: adhering to a synthetic fiber an adhesive treatment agent containing at least lignin (A), a blocked isocyanate compound (B), and a rubber latex (C) and having the following properties; and before heat-treating the synthetic fiber, adhering a pre-coating agent to the synthetic fiber, and then heat-treating the synthetic fiber; the pre-coating agent containing at least an epoxy compound and a blocked isocyanate compound (solids weight ratio of 10:0 to 10:30) at a concentration of 0.1 to 6%. (a) The number average molecular weight of the lignin (A) is 10,000 to 60,000, and the weight average molecular weight is 80,000 to 130,000, and the content of the lignin (A) is 5 to 50% by weight when the total solid content contained in the adhesive treatment agent is taken as 100 parts by weight. (b) The solid content weight ratio of the lignin (A) to the blocked isocyanate compound (B) is (solid content of A):(solid content of B)=10:1 to 10:20, and the solid content weight ratio of the lignin (A), the blocked isocyanate compound (B) and the rubber latex (C) is ((solid content of A)+(solid content of B)):(solid content of C)=10:90 to 60:

40. (c) When the adhesive treatment agent is made into a dry film, the dry film has a maximum strength of 0.2 MPa to 1.6 MPa and a maximum elongation of 2% to 120%.

11. The method for producing a synthetic fiber cord for rubber reinforcement according to claim 10, characterized in that the synthetic fiber is a polyester fiber, and the hot stretch tension in the heat treatment step after the adhesive treatment agent is applied is 0.2 to 1.0 cN / dtex and the normalizing tension is 0.05 to 0.5 cN / dtex.

12. The method for producing a synthetic fiber cord for rubber reinforcement according to claim 10, characterized in that the synthetic fiber is a nylon fiber, and the hot stretch tension in the heat treatment step after the adhesive treatment agent is applied is 0.4 to 1.3 cN / dtex and the normalizing tension is 0.4 to 0.9 cN / dtex.

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