JP7845124B2 - Polyester fiber cord for rubber reinforcement - Google Patents

Description

This invention relates to a polyester fiber cord for rubber reinforcement, comprising a novel adhesive treatment agent advantageous for reducing environmental impact, and exhibiting significantly improved heat-resistant adhesive strength.

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. RFL (resorcinol-formaldehyde-latex) adhesives, containing resorcinol-formaldehyde resin (consisting of resorcinol and formalin) and rubber latex, have traditionally been widely used to bond these synthetic fibers to rubber compositions. However, both resorcinol and formalin are highly toxic substances, posing a significant environmental burden and health risks. Therefore, in recent years, there has been a growing demand to reduce their release into the atmosphere during use and to minimize their usage.

Furthermore, as mentioned above, while synthetic fibers are widely used as reinforcing materials in rubber products, polyester fibers, in particular, are favored for use in tire applications due to their excellent strength, elastic modulus, and thermal dimensional stability. When polyester fibers are embedded in rubber products as reinforcing materials, they undergo thermal degradation in high-temperature environments. This chemical thermal degradation is influenced by the rubber itself and the various additives incorporated into the rubber. Polyester fibers subjected to high-temperature treatment in rubber containing amine-based antioxidants undergo amine decomposition and hydrolysis primarily due to these amine compounds, low-molecular-weight compounds produced by the oxidative degradation of the rubber itself, water molecules, and moisture contained in the rubber. Such amine-decomposed or hydrolyzed polyester fibers suffer a significant decrease in their initial properties, such as adhesion and strength, rendering them unsuitable for use.

When polyester fibers undergo amine decomposition or hydrolysis, it results in a decrease in strength due to molecular chain severance and a reduction in adhesion between the rubber and the fiber layer. However, despite these drawbacks, polyester fibers, when used as rubber reinforcing fibers, possess high strength, high modulus of elasticity, excellent thermal dimensional stability, and improvements in fatigue resistance and adhesion. Combined with advancements in tire manufacturing technology, they are now used as carcass material in most passenger car radial tires. Nevertheless, due to the aforementioned inherent drawbacks, their use is currently limited to passenger car carcass materials with relatively small tire sizes, where heat generated during high-speed tire operation is less likely to accumulate and chemical degradation is less likely. They are only used to a very limited extent in large tires such as those for trucks and buses. Generally, polyester fiber cords are not used in truck and bus tires, aircraft tires, run-flat tires, or radial tire cap ply materials.

Cap ply materials and run-flat tire reinforcement materials generate significantly more heat and reach higher temperatures than carcass materials. Conventional polyester fiber cords are unsuitable for these applications, and nylon 66 and rayon fibers, which offer superior heat-resistant adhesion, are generally used. While polyester fiber is preferable as a fiber material for tire reinforcement materials due to cost, supply stability, and elastic modulus, a significant improvement in the heat-resistant adhesion of polyester fiber cords is necessary for their application in these specific uses.

Furthermore, in order to give the fibers adhesive properties to rubber, it is essential to treat the fiber surface with an adhesive such as the RFL mentioned above. However, in the adhesive treatment process, resin residue caused by the composition of the applied adhesive adheres to the processing equipment, such as the rolls of the dipping machine, leading to reduced productivity due to the need for cleaning and making continuous production difficult. Additionally, the resin residue accumulated on the rolls can transfer to the surface of the dip cord, leading to quality defects.

As a technology addressing the above problem, for example, there is prior art described in Patent Documents 1 to 6.

Patent Document 1 discloses a method for treating polyester fibers with an aqueous adhesive composition containing a thermosetting resin having specific functional groups and an unsaturated elastomer latex.

Patent Document 2 discloses a method for treating polyester fibers with an organic fiber adhesive containing 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 aforementioned components or water-dispersible polymers other than the aforementioned components.

Patent Document 3 discloses a method for treating polyester fibers with an aqueous adhesive composition comprising a specific blocked isocyanate oligomer with three or more functions, a latex, a polyacrylate or lignin compound, and additives.

Patent Document 4 discloses a method in which polyester fibers are treated with a treatment solution containing a carrier and an aqueous solution of blocked isocyanate, and then treated with RFL containing an epoxy compound.

Patent Document 5 discloses a method in which polyester fibers are treated with a treatment solution containing a thermoplastic polymer, a heat-reactive aqueous urethane, and an epoxy compound, and then treated with RFL (Reactive Fiber Flow).

Patent Document 6 discloses a method in which polyester fibers are treated with a treatment agent containing three types of compounds: a compound containing an oxazoline group, an epoxy compound, and a rubber latex, and then treated with RFL (Rapid Fiber Linear).

Special table 2019-518087 publication WO2018/003572 U.S. Publication No. 2020/0024416 Japanese Patent Publication No. 2006-2327 Japanese Patent Publication No. 2001-19927 Japanese Patent Publication No. 2013-10909

However, while Patent Documents 1-3 achieve adhesive strength comparable to conventional RFL adhesives without using resorcinol-formaldehyde resin, they do not sufficiently improve heat resistance, fatigue resistance in rubber, or contribute to improved tire performance. Patent Documents 4-6, while showing improvement in heat resistance, all use conventional RFL adhesives, posing a significant environmental burden. Furthermore, all of Patent Documents 1-6 still suffer from the production problem of resin residue accumulation during the dipping process.

This invention was developed as a result of investigating the problems in the prior art described above.

The object of the present invention is a rubber-reinforced polyester fiber cord made of a novel adhesive treatment agent that does not contain resorcinol-formaldehyde resin and uses alternative raw materials advantageous for reducing environmental impact. This cord exhibits initial adhesive strength equal to or greater than conventional RFL adhesives, significantly improves heat-resistant adhesive strength when exposed to high temperatures in rubber for extended periods during the rubber vulcanization process and product use, enhances fatigue resistance, and is suitable as a tire reinforcement material. Furthermore, the invention provides a rubber-reinforced polyester fiber cord that can suppress resin residue accumulation during the dipping process and offers good productivity.

To solve these problems, the present invention employs the following means.

In other words,
(1) A polyester fiber cord for rubber reinforcement, wherein the polyester fiber is coated with a first treatment agent comprising at least four types: (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound, and further coated as an outer layer with a second treatment agent comprising at least three types: (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) rubber latex, wherein the first treatment agent comprises, with a total solid content of 100% by weight, ( A) A polyester fiber cord for rubber reinforcement containing 10 to 50% by weight of a compound containing an oxazoline group, 3 to 13% by weight of a blocked isocyanate compound, 20 to 60% by weight of a rubber latex, and 20 to 60% by weight of an epoxy compound, wherein the number average molecular weight of the lignin derivative contained in the second treatment agent is 10,000 to 60,000 and the weight average molecular weight is 80,000 to 130,000, and it does not contain resorcinol-formaldehyde resin.

(2) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate.

(3) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate.

(4) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate, and the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate.

(5) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (C) rubber latex contained in the first treatment agent includes VP latex having a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C.

(6) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (c) rubber latex contained in the second treatment agent includes VP latex having a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C.

(7) The rubber-reinforced polyester fiber cord according to (1) above, characterized in that the (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate, the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate, the (C) rubber latex contained in the first treatment agent contains VP latex with a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C, and the (c) rubber latex contained in the second treatment agent contains VP latex with a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C.

(8) The polyester fiber cord for rubber reinforcement according to any one of (1) to (7) above, characterized in that the (A) oxazoline group-containing compound contained in the first treatment agent has a Tg of 0 to 80°C and an oxazoline group content of 1.0 to 5.0 mmol/g, in solid form.

(9) A polyester fiber cord for rubber reinforcement according to any one of (1) to (7) above, characterized in that the tackiness of the cord surface layer is 2.0 to 10.0 N/ ^cm² .

(10) The second treatment agent, characterized in that, when the total solid content of the treatment agent is 100% by weight, (a) the content of the lignin derivative is 5 to 50% by weight, and the solid content weight ratio of (a) the lignin derivative to (b) the blocked isocyanate compound is (solid content of a):(solid content of b) = 10:1 to 10:20, as described in any of (1) to (7) above, for rubber-reinforced polyester fiber cord.

(11) A polyester fiber cord for rubber reinforcement according to any one of (1) to (7) above, characterized in that the amount of resin adhering to the film by the first treatment agent is 1 to 4% by weight, the amount of resin adhering to the film by the second treatment agent is 1 to 4% by weight, and the total amount of resin adhering to the film by the first treatment agent and the film by the second treatment agent is 2 to 6% by weight.

(12) A tire made using a rubber-reinforced polyester fiber cord as described in any of (1) to (11) above.

According to the present invention, a novel adhesive treatment agent for rubber-reinforced polyester fiber cord, which does not contain resorcinol-formaldehyde resin and uses alternative raw materials advantageous for reducing environmental impact, exhibits initial adhesive strength equal to or greater than that of conventional RFL adhesives, and significantly improves heat-resistant adhesive strength when exposed to high temperatures in rubber for extended periods during the rubber vulcanization process and product use, thereby improving fatigue resistance and making it suitable as a reinforcing material for tires. Furthermore, it is possible to provide a rubber-reinforced polyester fiber cord with good productivity by suppressing resin residue accumulation during the dipping process.

The present invention will be described in detail below.

The present invention provides a rubber-reinforced polyester fiber cord in which polyester fibers are coated with a first treatment agent comprising at least four components: (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound. Furthermore, the outer layer is coated with a second treatment agent comprising at least three components: (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) rubber latex.

The polyester fiber used in this invention is preferably 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, 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.

Furthermore, the above-mentioned polyester may, in small amounts, be a copolymer of trifunctional compounds such as trimesic acid, trimellitic acid, boric acid, phosphoric acid, glycerin, and trimethylolpropane.

The polyester fiber cord for rubber reinforcement of the present invention has excellent mechanical properties such as high strength, high toughness, high modulus of elasticity, low shrinkage, and high fatigue resistance, and suppresses adhesive degradation and strength degradation even when exposed to high temperatures in rubber for a long time. Therefore, the polyester fiber used in the present invention preferably has the following properties.
(1) Intrinsic viscosity (IV) = 0.7 to 1.2, more preferably 0.8 to 1.1
(2) Carboxylate terminal 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, more 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 rate (ΔS 150℃) = 2.0 to 12.0%, more preferably 3.0 to 10.0%.

For the polyester fibers used in the rubber-reinforced polyester fiber cord of the present invention to have particularly high chemical durability, it is advantageous that they have high viscosity, a low number of carboxyl end groups, and a low amount of diethylene glycol.

The polyester fibers used in this invention may be modified using terminal carboxyl group chelating agents such as carbodiimide compounds, epoxy compounds, isocyanate compounds, and oxazoline compounds to reduce the number of carboxyl end groups.

Furthermore, the polyester fibers of the present invention may have polyepoxide compounds applied to them in advance during the yarn manufacturing process. Examples of polyepoxide compounds that can be used in the present invention include compounds containing at least two epoxy groups per molecule, in an amount of 0.1 g equivalent or more per 100 g of the compound. Specifically, 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, and polyepoxide compounds obtained by oxidizing unsaturated compounds with peroxide or hydrogen peroxide. These include aromatic polyepoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carbochylate, 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.

These compounds are typically used as emulsifiers. To create an emulsifier or solution, the compound is used either directly or, if necessary, dissolved in a small amount of solvent, and then emulsified or dissolved using known emulsifiers, such as sodium alkylbenzenesulfonate, sodium dioctyl sulfosuccinate, or nonylphenol ethylene oxide adduct.

The polyepoxide compound is applied along with the spinning oil during the polyester fiber spinning process. The amount of the polyepoxide compound applied is in the range of 0.1 to 5% by weight. If the amount of the polyepoxide compound is less than 0.1% by weight, the effect of the polyepoxide compound may not be fully realized, and satisfactory adhesion between the polyester fiber and the rubber may not be achieved. On the other hand, if the amount of the polyepoxide compound exceeds 5% by weight, the fiber becomes very hard, making it difficult to apply during the spinning process. Furthermore, this is undesirable because it reduces the penetration of treatment agents used in subsequent processes, resulting in decreased adhesive performance.

The polyester fibers used in this invention are not restricted by fineness, filament count, or cross-sectional shape, but typically, a total fineness of 200 to 5000 dtex, 30 to 1000 filaments, and a circular cross-section yarn are used, with a total fineness of 250 to 3000 dtex, 50 to 500 filaments, and a circular cross-section yarn being more preferable. If the total fineness is less than 200 dtex, the cord strength may be insufficient, and if it exceeds 5000 dtex, the cord may become thicker, reducing its handling properties. Furthermore, if the filament count is less than 30, the cord may become stiff, worsening its handling properties, and if it exceeds 500 filaments, the amount of fuzz may increase, reducing its quality.

The polyester fiber cord for rubber reinforcement of the present invention is obtained by twisting the above-mentioned polyester fibers to form a twisted cord, and then either using the twisted cord as is or by weaving it into a raw cloth and then treating it with adhesive. The raw cord used for typical carcass tire cords is obtained by first twisting it in the S or Z direction, then combining two or three of these under-twisted cords and applying typically the same number of top twists in the opposite direction to the under-twist to create a multi-twisted cord. This twisted cord is then treated with adhesive to obtain a dip cord. Alternatively, the twisted cord can be used as the warp, with cotton yarn or synthetic fiber covered with cotton yarn as the weft, and after weaving into a raw cloth, the raw cloth is treated with adhesive to obtain a dip cloth.

The polyester fiber cord for rubber reinforcement in this invention refers to both the dip cord and the dip roll described above.

The present invention provides a rubber-reinforced polyester fiber cord in which polyester fibers are coated with a first treatment agent comprising at least four components: (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound. Furthermore, the outer layer is coated with a second treatment agent comprising at least three components: (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) rubber latex.

The compound containing an oxazoline group (A) used in the first treatment agent of the present invention refers to a compound that contains an oxazoline group (preferably a 2-oxazoline group) at the end or side chain of a substance whose main skeleton is a general organic compound or organic polymer or oligomer. The oxazoline group can be one or more in the skeleton, but it is more preferable to have a large number of oxazoline groups, which are reactive functional groups, in order to improve adhesive performance. As the skeleton of the main chain of the oxazoline group-containing compound, hydrocarbon chains, ethylene glycol chains, bisphenols such as bisphenol A, and initial polymers such as phenol resins, novolac resins, and resol resins can be used, and substances containing aromatic rings or heterocycles in their molecular skeletons can also be used. Furthermore, substances containing an oxazoline group at the end or side chain of the main component monomer and/or polymers or oligomers composed thereof are also useful. Examples of these monomers include styrene, styrene derivatives, acrylonitrile, methacrylic acid esters, methacrylic acid, ethylene, butadiene, and acrylamide, which can be used as individual polymers and/or oligomers, as well as copolymers. These can also be used as mixtures.

The oxazoline group-containing compound can be used in liquid, molten, solid, or dissolved in water or an organic solvent capable of dissolving these substances, or as a suspension dispersed in water or the like (emulsion particles, latex particles, etc.). For example, such a compound may be used as is, or dissolved in a small amount of solvent as needed, and then emulsified or dissolved using a known emulsifier, such as sodium alkylbenzenesulfonate, sodium dioctyl sulfosuccinate, or nonylphenol ethylene oxide adduct.

The oxazoline group-containing compound preferably has a Tg (glass transition temperature) of 0 to 80°C and an oxazoline group content of 1.0 to 5.0 mmol/g, solid. More preferably, it has a Tg (glass transition temperature) of 10 to 70°C and an oxazoline group content of 1.2 to 3.0 mmol/g, solid. Outside this range, the heat-resistant adhesive strength may decrease.

The (B) blocked isocyanate compound used in the first treatment agent in this invention is a compound that, upon heating, releases the blocking agent and generates an active isocyanate compound. Examples of blocked isocyanate compounds include reaction products between polyisocyanate compounds having a skeleton such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and triphenylmethane triisocyanate, and blocking agents such as phenols (phenols such as phenol, cresol, and resorcinol), lactams (ε-caprolactam and valerolactam), and oximes (acetoxime, methyl ethyl ketoxime, and cyclohexane oxime).

Among these blocked isocyanate compounds, bifunctional MDI-based blocked isocyanates, in which diphenylmethane diisocyanate is blocked with a blocking agent, are particularly preferred for obtaining good adhesion and fatigue resistance. Even more preferred are bifunctional MDI-based blocked isocyanates blocked with oximes. Polymeric MDI having three or more isocyanate groups is undesirable because it may result in reduced fatigue resistance.

Examples of rubber latex (C) that can be used in the first treatment agent of 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, ethylene-propylene-diene rubber latex, etc., which can be used alone or in combination. Among these, it is preferable from the viewpoint of adhesive strength and fatigue resistance that the latex contains VP latex with a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C, and more preferably VP latex with a Mooney viscosity (ML1 + 4 at 100°C) of 30 to 80 and a Tg of -60°C to -40°C.

The epoxy compound (D) that can be used in the first treatment agent of the present invention has two or more epoxy groups in one molecule.

Compounds containing two or more epoxy groups in their molecule include, for example, glycidyl ether-type epoxy resins obtained from compounds containing hydroxyl groups, glycidylamine-type epoxy resins obtained from compounds containing amino groups, glycidyl ester-type epoxy resins obtained from compounds containing carboxyl groups, cyclic aliphatic epoxy resins obtained from compounds containing unsaturated bonds, heterocyclic epoxy resins such as triglycidyl isocyanates, or epoxy resins in which two or more types selected from these are present in the molecule.

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

The rubber-reinforced polyester fiber cord of the present invention is coated with a first treatment agent comprising (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound. The first treatment agent must contain 10 to 50% by weight of (A) the compound containing an oxazoline group, 3 to 13% by weight of (B) the blocked isocyanate compound, 20 to 60% by weight of (C) the rubber latex, and 20 to 60% by weight of (D) the epoxy compound, based on the total solids content (dry weight) of the first treatment agent. Preferably, the first treatment agent... The first treatment agent contains, with respect to the total solid content, (A) 12 to 45% by weight of a compound containing an oxazoline group, (B) 4 to 12% by weight of a blocked isocyanate compound, (C) 25 to 55% by weight of a rubber latex, and (D) 25 to 55% by weight of an epoxy compound. More preferably, with respect to the total solid content of the first treatment agent, it contains, with respect to the total solid content, (A) 15 to 40% by weight of a compound containing an oxazoline group, (B) 5 to 11% by weight of a blocked isocyanate compound, (C) 30 to 50% by weight of a rubber latex, and (D) 30 to 50% by weight of an epoxy compound. If the proportion of (A) the compound containing an oxazoline group falls outside this range, the heat-resistant adhesive strength and fatigue resistance may decrease. If the proportion of (B) the blocked isocyanate compound falls outside this range, the initial adhesive strength may decrease. If the proportion of (C) the rubber latex falls outside this range, the initial adhesive strength and fatigue resistance may decrease. (D) If the proportion of epoxy compounds falls outside this range, initial adhesion may decrease, and fatigue resistance may worsen.

Furthermore, in addition to (A), (B), (C), and (D) above, surfactants, defoaming agents, vulcanization modifiers, antioxidants, and pH adjusters may be added to the first treatment agent used in the present invention as needed, within a range that does not hinder the objectives and effects of the present invention.

The lignin derivative (a) used in the second treatment agent of the present invention is a chemically treated form of lignin present in trees, which are biomass. Examples of such derivatives include kraft lignin obtained from kraft pulp wastewater and ligninsulfonic acid obtained from sulfurous acid pulp wastewater in the papermaking process using wood as a raw material. Lignosulfonic acid is formed by introducing a sulfonate group into the side chain of the phenylpropane structure of lignin. Examples of ligninsulfonates include sodium ligninsulfonate, magnesium ligninsulfonate, and calcium ligninsulfonate. In the present invention, these can be used individually or in combination, but sodium ligninsulfonate is most preferably used from the viewpoint of adhesive strength.

The lignin derivative (a) used in this 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 limit of this range, fatigue resistance may be insufficient, the storage stability of the adhesive treatment agent may deteriorate, and resin residue may accumulate in the dipping process, making continuous production difficult. If the number average molecular weight and weight average molecular weight are below the lower limit of this range, the initial adhesion strength to rubber and fatigue resistance will decrease, which is undesirable. Furthermore, the weight average molecular weight (Mw)/number average molecular weight (Mn) is preferably 2.5 to 5.0, and more preferably 2.8 to 4.7. If it falls outside this range, adhesion strength and fatigue resistance may be insufficient. In this invention, the number-average molecular weight and weight-average molecular weight refer to the values measured by the methods described in the Examples section.

The (b) blocked isocyanate compound used in the second treatment agent in this invention is the same as the (B) blocked isocyanate compound used in the first treatment agent, and the preferably used blocked isocyanate compound is also the same.

The (c) rubber latex that can be used in the second treatment agent of the present invention is the same as the (C) rubber latex used in the first treatment agent, and the preferred Mooney viscosity is also the same. Examples 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, ethylene-propylene-diene rubber latex, etc., and these can be used alone or in combination. Among these, it is preferable from the viewpoint of adhesive strength and fatigue resistance to include VP latex with a Mooney viscosity (ML1 + 4 100°C) of 20 to 100 and a Tg of -70°C to -30°C, and more preferably VP latex with a Mooney viscosity (ML1 + 4 100°C) of 30 to 80 and a Tg of -60°C to -40°C.

In the second treatment agent of the present invention, when the total solid content contained in the adhesive treatment agent is taken as 100% by weight, the content of (a) lignin derivative 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 more than 50% by weight, the adhesive strength and fatigue resistance may be insufficient.

Furthermore, the solid content weight ratio of (a) lignin derivative to (b) blocked isocyanate compound is preferably (solid content of a):(solid content of b) = 10:1 to 10:20, and more preferably 10:5 to 10:20. If the amount of (b) is too low beyond this weight ratio, the adhesive strength may be insufficient. If the amount of (b) is too high beyond this weight ratio, the cord may become stiff, and its fatigue resistance in rubber may deteriorate. Using the cord for reinforcing rubber products such as tires, belts, and hoses may worsen the product's durability, which is undesirable.

Furthermore, the solid content weight ratio of (a) lignin derivative, (B) blocked isocyanate compound, and (c) rubber latex is preferably ((solid content of a) + (solid content of b)):(solid content of c) = 10:90 to 60:40, and more preferably 20:80 to 50:50. If the ratio deviates from this range, the adhesive strength may be insufficient or the fatigue resistance may deteriorate.

Furthermore, in addition to (a), (b), and (c) above, the second treatment agent used in the present invention may contain, as necessary, surfactants, defoaming agents, vulcanization modifiers, antioxidants, pH adjusters, carbon black, colorants, etc., within a range that does not hinder the objectives and effects of the present invention.

The first treatment agent of the present invention is a solid component dissolved or dispersed in water, with a total solid component concentration preferably 1 to 15% by weight, more preferably 2 to 13% by weight, and even more preferably 3 to 10% by weight. Exceeding this range may lead to a decrease in initial adhesive strength and heat-resistant adhesive strength.

The second treatment agent of the present invention is a solid component dissolved or dispersed in water, with a total solid content concentration preferably 5 to 25% by weight, more preferably 10 to 20% by weight, and even more preferably 12 to 18% by weight. Exceeding this range may lead to a decrease in initial adhesive strength.

The amount of resin adhering to the film by the first treatment agent of the present invention is 1 to 4% by weight per 100% by weight of polyester fiber, and the amount of resin adhering to the film by the second treatment agent is 1 to 4% by weight per 100% by weight of polyester fiber, and the total amount of resin adhering to the film by the first and second treatment agents is 2 to 6% by weight per 100% by weight of polyester fiber. Preferably, the amount of resin adhering to the film by the first treatment agent is 1.5 to 3.0% by weight per 100% by weight of polyester fiber, the amount of resin adhering to the film by the second treatment agent is 1.5 to 3.0% by weight per 100% by weight of polyester fiber, and the total amount of resin adhering to the film by the first and second treatment agents is 2 to 5% by weight per 100% by weight of polyester fiber. Deviating from this range may lead to a decrease in adhesive strength.

Furthermore, the tackiness of the surface layer of the rubber-reinforced polyester fiber cord of the present invention is preferably 2.0 to 10.0 N/ ^cm² , and more preferably 3.0 to 9.0 N/ ^cm² . The tackiness of the cord surface layer can be measured by the method described later. If the tackiness of the cord surface layer is less than 2.0, the adhesion to the rubber may decrease, and if it exceeds 10.0, resin residue may accumulate during the dipping process, worsening the process passability of the cord. The tackiness of the cord can be adjusted to a preferred range, particularly by optimizing the selection and content of the latex in the second bath treatment agent and the mixing ratio with other compounding agents.

Next, the method for manufacturing the rubber-reinforced polyester fiber cord of the present invention will be described.

An example of the method for producing the rubber-reinforced polyester fiber cord of the present invention is to attach polyester fibers to a first treatment agent containing at least four types: (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound, and then heat-treat the resulting cord. Subsequently, the cord is attached to a second treatment agent containing at least three types: (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) rubber latex, and then heat-treated. The polyester fibers may be in the form of twisted cord or raw bamboo roll. For the heat treatment after attachment of the first and second treatment agents, it is preferable to dry the moisture at a temperature of 100 to 150°C, followed by heat treatment at 200 to 255°C.

One method for applying the first or second treatment agent to polyester fibers is dipping. Dipping involves running a twisted cord or raw yarn through a dipping tank filled with an adhesive treatment agent and equipped with rollers, thereby applying the treatment agent to the twisted cord or raw yarn. Heat treatment involves heating the twisted cord or raw yarn through an oven equipped with rollers and capable of being set to a predetermined temperature. Such dipping and heat treatment machines are commercially available, for example, from Ritzler. In addition to dipping, other methods for applying the treatment agent to polyester fibers include application by spraying the adhesive treatment agent from a nozzle; any method can be employed.

Furthermore, to control the amount of solid material adhering to the polyester fibers, methods such as squeezing with a pressure roller, scraping with a scraper, blowing with air, and suction may be used.

Furthermore, during the mechanical softening process following the drying and heat treatment described above, a softening treatment can be applied to achieve the desired cord stiffness by rubbing the polyester fiber cord against the edge.

The present invention provides a rubber-reinforced polyester fiber cord that, in this manner, does not contain resorcinol-formaldehyde resin and is composed of a novel adhesive treatment agent using alternative raw materials advantageous for reducing environmental impact. This rubber-reinforced polyester fiber cord exhibits initial adhesive strength equivalent to or greater than conventional RFL, and significantly improves heat-resistant adhesive strength when exposed to high temperatures in rubber for extended periods during the rubber vulcanization process and product use, resulting in improved fatigue resistance and making it suitable as a tire reinforcement material. Furthermore, it provides a rubber-reinforced polyester fiber cord with good productivity by suppressing resin residue accumulation during the dipping process.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. In the examples described below, each measurement value was obtained by the following method.

(1) Amount of adhesive treatment agent applied The amount of adhesive applied was determined according to the mass method of dip pickup in JIS L1017 (2002).

(2) Initial Adhesion and Heat-Resistant Adhesion This indicates the adhesion between the polyester fiber cord and the rubber. The initial adhesion was measured in accordance with JIS L1017 (2002) Annex 1, 3.1T test (Method A). The polyester fiber cord was embedded in unvulcanized rubber, vulcanized at 150°C for 30 minutes at 50 kg/ ^cm² press vulcanization, and then allowed to cool. The polyester fiber cord was then pulled out of the rubber block at a speed of 300 mm/min, and the load required for the pull-out was determined for each sample. The arithmetic mean of 10 samples was taken as the initial adhesion. Furthermore, the heat-resistant adhesive strength was measured in accordance with JIS L1017 (2002) Annex 1, 3.1T test (Method A). Polyester fiber cords were embedded in unvulcanized rubber, vulcanized at 150°C for 180 minutes at 50 kg/ ^cm² press vulcanization, and then allowed to cool. The synthetic fiber cords were then pulled out of the rubber block at a speed of 300 mm/min, and the load required for the pull-out was determined for each sample. The arithmetic mean of 10 samples was used as the heat-resistant adhesive strength.

(3) Fatigue resistance (retention rate) in rubber
The fatigue strength of the disc was evaluated in accordance with JIS L1017 (2002), Annex 1, 2.2.2, Goodrich method. Two polyester fiber cords were embedded in unvulcanized rubber and press-vulcanized at 150°C for ³⁰ minutes at 50 kg/cm² to create a rubber composite. This test specimen was subjected to deformation of 6.3% compression and 12.6% elongation per cycle at 2600 cycles/min under a 100°C atmosphere for 12 hours. After that, the polyester fiber cords were removed from the rubber and the fracture strength after fatigue was measured. The retention rate of the fracture strength before and after the fatigue test was determined for each sample, and the arithmetic mean of eight samples was taken as the fatigue resistance (retention rate) in the rubber.

The composition of the unvulcanized rubber compound used for measuring initial adhesion, heat-resistant adhesion, 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 (weight portion)
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.

(4) Passability through the dipping process Two strands of 1670dtex polyester multifilament yarn (manufactured by Toray Industries, Inc., "Tetron" 1670T-360-705M) are twisted with 40 twists/10cm for the undertwist and 40 twists/10cm for the upper twist to obtain a twisted cord. The twisted cord is immersed in a first treatment agent using a computer treater (manufactured by Ritzler Co., Ltd.), dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute. Subsequently, it is immersed in a second treatment agent, dried at 120°C for 2 minutes, and then heat-treated at 240°C for 1 minute to obtain a polyester fiber cord. After 3000m of heat treatment with the second treatment agent has been completed, the amount of resin residue accumulated on the heat treatment furnace turn roll (the roll in contact with the cord) of the computer treater is checked and determined to be (resin residue: a lot = B > A > S = none). In this invention, S and A are considered acceptable levels for process passability that are suitable for practical use, but S is superior in practical terms.

(5) Measurement of number-average molecular weight and weight-average molecular weight of lignin derivatives The number-average molecular weight and weight-average molecular weight of lignin derivatives were measured by GPC (gel permeation chromatography). A solvent (ammonia buffer/methanol) was added to the lignin derivative sample, and it was dissolved by stirring at room temperature. The sample was then filtered through a 0.5 μm filter. After that, it was measured by GPC, and a peak was detected with a UV detector. 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: TSKgel GMPW _XL (1 tube), G3000PW _XL (1 tube) (φ7.8 mm x 30 cm, Tosoh Corporation)
Solvent: 0.1 M ammonia buffer (pH 11) / methanol (4/1, v/v)
Standard material: Monodisperse polyethylene oxide and polyethylene glycol manufactured by Tosoh and Agilent. Detector: UV detector (Shimadzu Corporation SPD-M20A).

(6) Tackiness of the cord surface Unvulcanized rubber (thickness 0.4 mm) was attached to the contact part (1 x 1.5 cm) of the Toyo Seiki Co., Ltd. "Tackiness Checker" HTC-1 using double-sided tape. Meanwhile, polyester fiber cord was wrapped around a flat aluminum plate without any gaps. The tackiness of the polyester fiber cord on the aluminum plate was measured using the "Tackiness Checker" under measurement conditions of a pressing force of 10 N and a pressing time of 6 seconds (unit: N/1.5 ^cm² ). The arithmetic mean of 6 measurements was calculated and the value converted to the unit N/ ^cm² was taken as the tackiness of the cord surface. The composition of the unvulcanized rubber compound was the same as that used in (3) above.

(7) Tire High-Speed Durability Using the polyester fiber cord described above as the carcass ply, a radial tire of size 165-SR13 was manufactured in the same manner as a normal tire. After completing the high-speed durability test specified in JIS D4230 using a drum testing machine, the speed was further increased in 10 km/h increments every 30 minutes, and the distance traveled until the tire failed was measured. The evaluation was shown on an index where the evaluation result of a tire using polyester fiber cord with RFL adhesive as the carcass ply (conventional example) described later was set to 100. A higher index indicates better high-speed durability.

(Examples 1-12, Comparative Examples 1-7)
(A) A compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) a rubber latex, and (D) an epoxy compound were mixed in the proportions shown in Table 1, and diluted with water to obtain a first treatment agent with a total solids content of 6% by weight. In Example 2 only, the total solids content was 2% by weight.

Furthermore, (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) a rubber latex were mixed in the proportions shown in Table 1, and diluted with water to obtain a second treatment agent with a total solid content of 15% by weight. Note that in Example 2 only, the total solid content was 20% by weight.

Two strands of 1670dtex polyester multifilament yarn (Toray Industries, Inc., "Tetron" 1670T-360-705M) were twisted together with 40 twists per 10cm for the under-twist and 40 twists per 10cm for the upper-twist to obtain a twisted cord.

The twisted cord was immersed in a first treatment agent using a computer treater (manufactured by Ritzler Co., Ltd.), dried at 120°C for 2 minutes, and then heat-treated at 245°C for 1 minute. Subsequently, it was immersed in a second treatment agent, dried at 120°C for 2 minutes, and then heat-treated at 240°C for 1 minute to obtain a polyester fiber cord.

The amount of resin adhering to the coating of the obtained polyester fiber cords using the first treatment agent and the amount of resin adhering to the coating of the coating of the second treatment agent are shown in Table 1.

The components of the first bath treatment agent shown in Table 1 are as follows:
(A)-1: Compound containing an oxazoline group (Epocross K-2035E, manufactured by Nippon Shokubai Co., Ltd., oxazoline group-containing acrylic/styrene copolymer, Tg 50°C, oxazoline group amount 1.8 mmol/g, solid)
(A)-2: Compound containing an oxazoline group (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., oxazoline group-containing acrylic copolymer, Tg 50°C, oxazoline group amount 4.5 mmol/g, solid)
(A)-3: Compound containing an oxazoline group (Epocross K-2010E, manufactured by Nippon Shokubai Co., Ltd., oxazoline group-containing acrylic/styrene copolymer, Tg -50℃, oxazoline group amount 1.8 mmol/g, solid)
(A)-4: Compound containing an oxazoline group (Epocross WS-300, manufactured by Nippon Shokubai Co., Ltd., oxazoline group-containing acrylic/styrene copolymer, Tg 90°C, oxazoline group amount 7.7 mmol/g, solid)
(B)-1: Blocked isocyanate (DM-6400, manufactured by Meisei Chemical, oxime-blocked MDI, 2 functional groups)
(B)-2: Blocked isocyanate (DM-3031CONC, manufactured by Meisei Chemical, lactam block MDI, 2 functional groups)
(B)-3: Blocked isocyanate (Elastron BN-27, manufactured by Daiichi Kogyo Seiyaku, lactam block polymeric MDI, 5 functional groups)
(B)-4: Blocked isocyanate (Meikanate TP-10, manufactured by Meisei Chemical, oxime-blocked TDI, 6 functional groups)
(C)-1: Rubber latex (PYRATEX, manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 35, Tg-55℃).
(C)-2: Rubber latex (PYRATEX-HM, manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 90, Tg-55℃).
(C)-3: Rubber latex (PYRATEX-LB manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 120, Tg-25℃).
(D)-1: Epoxy compound (Nagase ChemteX Corporation, "Denacol" EX614B).

The components of the second bath treatment agent shown in Table 1 are as follows:
(a)-1: Lignin derivative ("Vanilex" N manufactured by Nippon Paper Industries Co., Ltd., sodium ligninsulfonate, number average molecular weight 29,000, weight average molecular weight 105,000)
(a)-2: Lignan derivative ("Vanilex" RN manufactured by Nippon Paper Industries Ltd., sodium ligninsulfonate, number average molecular weight 34,000, weight average molecular weight 112,000)
(a)-3: Lignin derivative (Pearllex "NP" manufactured by Nippon Paper Industries Ltd., sodium lignin sulfonate, number average molecular weight 97,000, weight average molecular weight 146,000)
(a)-4: Lignin derivative ("Sun Extract" P252 manufactured by Nippon Paper Industries Co., Ltd., sodium lignin sulfonate, number average molecular weight 66,000, weight average molecular weight 135,000)
(b)-1: Blocked isocyanate (DM-6400, manufactured by Meisei Chemical, oxime-blocked MDI, 2 functional groups)
(b)-2: Blocked isocyanate (DM-3031CONC, manufactured by Meisei Chemical, lactam block MDI, 2 functional groups)
(b)-3: Blocked isocyanate (Elastron BN-27, manufactured by Daiichi Kogyo Seiyaku, lactam block polymeric MDI, 5 functional groups)
(c)-1: Rubber latex (PYRATEX, manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 35, Tg-55℃).
(c)-2: Rubber latex (PYRATEX-HM, manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 90, Tg-55℃).
(c)-3: Rubber latex (PYRATEX-LB manufactured by Nippon A&L Co., Ltd., VP latex, Mooney viscosity (ML1+4 100℃) 120, Tg-25℃).

(Comparative Example 8)
The same treatment as in Example 1 was performed, except that immersion with the first treatment agent and heat treatment were not performed.

(Conventional example)
For the first treatment agent, a treatment agent with the composition shown in Table 1 was used, and for the second treatment agent, a conventional RFL adhesive was used, and the same immersion and heat treatment as in Example 1 was performed. RFL was prepared by mixing resorcinol/formaldehyde in a molar ratio of 1/1.5 in the presence of caustic soda, adjusting the solid content concentration to 10%, and aging for 2 hours to obtain an initial condensate of resorcinol and formalin (RF (resorcinol-formaldehyde resin)). Next, this initial condensate (RF) and rubber latex (Piratex, manufactured by Nippon A&L Co., Ltd.) were mixed at a ratio of RF/L = 1/5 (solid content weight ratio) and aged for 24 hours. This mixture was diluted with water to a solid content of 15% by weight and used.

The polyester fiber cords obtained as described above were embedded in unvulcanized rubber and vulcanized. After vulcanization, the initial adhesive strength, heat-resistant adhesive strength, and fatigue resistance within the rubber were measured. Furthermore, radial tires were fabricated using these polyester fiber tire cords as carcass plies, and high-speed durability tests were conducted. The results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, in the examples according to the present invention, the adhesive treatment agent does not contain resorcinol-formaldehyde resin, which is advantageous in reducing environmental impact compared to conventional RFL adhesives. Furthermore, it exhibits adhesion to rubber as good as RFL adhesives, significantly improved heat resistance, and enhanced fatigue resistance. Additionally, it shows that resin residue accumulation in the dipping process is suppressed, resulting in improved productivity. Moreover, it demonstrates that tire performance exceeding that of tire cords using conventional RFL adhesives can be achieved.

Claims (12)

A polyester fiber cord for rubber reinforcement is provided, wherein the polyester fiber is coated with a first treatment agent comprising at least four types: (A) a compound containing an oxazoline group, (B) a blocked isocyanate compound, (C) rubber latex, and (D) an epoxy compound, and further coated as an outer layer with a second treatment agent comprising at least three types: (a) a lignin derivative, (b) a blocked isocyanate compound, and (c) rubber latex, wherein the first treatment agent comprises (A) with a total solid content of 100% by weight. A polyester fiber cord for rubber reinforcement, characterized by containing 10-50% by weight of a compound containing an oxazoline group, 3-13% by weight of a blocked isocyanate compound, 20-60% by weight of rubber latex, and 20-60% by weight of an epoxy compound, wherein the number-average molecular weight of the lignin derivative contained in the second treatment agent is 10,000-60,000 and the weight-average molecular weight is 80,000-130,000, and it does not contain resorcinol-formaldehyde resin. The polyester fiber cord for rubber reinforcement according to claim 1, characterized in that the (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate. The polyester fiber cord for rubber reinforcement according to claim 1, characterized in that the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate. The rubber-reinforced polyester fiber cord according to claim 1, characterized in that the (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate, and the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate. The rubber-reinforced polyester fiber cord according to claim 1, characterized in that the (C) rubber latex contained in the first treatment agent includes VP latex with a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C. The rubber-reinforced polyester fiber cord according to claim 1, characterized in that the (c) rubber latex contained in the second treatment agent includes VP latex having a Mooney viscosity (ML1 + 4 at 100°C) of 20 to 100 and a Tg of -70°C to -30°C. The (B) blocked isocyanate compound contained in the first treatment agent is a bifunctional MDI-based blocked isocyanate, and the (b) blocked isocyanate compound contained in the second treatment agent is a bifunctional MDI-based blocked isocyanate, and further,
The rubber-reinforced polyester fiber cord according to claim 1, characterized in that the (C) rubber latex contained in the first treatment agent contains VP latex having a Mooney viscosity (ML1 + 4 100°C) of 20 to 100 and a Tg of -70°C to -30°C, and the (c) rubber latex contained in the second treatment agent contains VP latex having a Mooney viscosity (ML1 + 4 100°C) of 20 to 100 and a Tg of -70°C to -30°C. The rubber-reinforced polyester fiber cord according to any one of claims 1 to 7, characterized in that the (A) oxazoline group-containing compound contained in the first treatment agent has a Tg of 0 to 80°C and an oxazoline group content of 1.0 to 5.0 mmol/g, in solid form. A polyester fiber cord for rubber reinforcement according to any one of claims 1 to 7, characterized in that the tackiness of the cord surface layer is 2.0 to 10.0 N/cm². The second treatment agent is characterized in that, when the total solid content of the treatment agent is considered to be 100% by weight, the content of (a) the lignin derivative is 5 to 50% by weight, and the solid content weight ratio of (a) the lignin derivative to (b) the blocked isocyanate compound is (solid content of a):(solid content of b) = 10:1 to 10:20, as described in any one of claims 1 to 7. A polyester fiber cord for rubber reinforcement according to any one of claims 1 to 7, characterized in that the resin adhesion amount of the film coated by the first treatment agent is 1 to 4% by weight, the resin adhesion amount of the film coated by the second treatment agent is 1 to 4% by weight, and the total resin adhesion amount of the film coated by the first treatment agent and the film coated by the second treatment agent is 2 to 6% by weight. A tire made using a rubber-reinforced polyester fiber cord according to any one of claims 1 to 7.