Rubber-reinforced composite cord and method for manufacturing the same

Abstract

To provide a composite cord for reinforcing rubber that has high cord elastic modulus and can hold high elastic modulus even after being subjected to heat treatment during rubber molding.SOLUTION: A composite cord for reinforcing rubber includes high strength and high elastic modulus fibers and low strength and low elastic modulus fibers. The high strength and high elastic modulus fiber has higher strength and elastic modulus than the low strength and low elastic modulus fiber in the composite cord for reinforcing rubber. The composite cord for reinforcing rubber is a dip cord containing resin adhesive including latex at least in a portion of a surface and the inside of a raw cord formed by primarily twisting the high strength and high elastic modulus fibers and the low strength and low elastic modulus fibers individually, and combining the primarily twisted yarns with each other and finally twisting the combined yarn in a direction opposite to the primary twisting direction. When the final twisting of the dip cord is released, length (A) of the primarily twisted yarn of the high strength and high elastic modulus fibers is shorter than length (B) of the primarily twisted yarn of the low strength and low elastic modulus fibers. The length ratio (A) / (B) is 0.950 or more and 0.995 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composite cord for rubber reinforcement and a method for manufacturing the same, and more particularly to a composite cord for rubber reinforcement used for reinforcing rubber products such as tires and a method for manufacturing the same.

Background Art

[0002] In order to improve the strength and durability of rubber moldings such as rubber tires and rubber belts, it is generally practiced to embed reinforcing fibers in the rubber of the rubber molding. Conventionally, as this reinforcing fiber, glass fiber, polyvinyl alcohol fiber typified by vinylon fiber, polyester fiber, nylon, polyamide fiber such as aramid (aromatic polyamide), carbon fiber, and polyphenylene benzoxazole fiber have been widely used.

[0003] And in order to increase the rigidity during use of the rubber molding, it has been considered to use high-strength and high-modulus fibers such as aromatic polyamide fibers, carbon fibers, and polyphenylene benzoxazole fibers as the reinforcing fibers. However, even if simply using high-strength and high-modulus fibers as the reinforcing fibers, it is impossible to simultaneously obtain the rigidity during use of the rubber molding and the retention of strength over a long period of use of the rubber molding.

[0004] Patent Document 1 discloses a technique for obtaining a cord having the rigidity of a rubber molding and the retention of strength over a long time by using a para-type aromatic polyamide fiber as a high-strength and high-modulus fiber and a polyester fiber as a low-strength and low-modulus fiber to form a composite cord. However, in this technique, there is a high possibility that the rigidity during use of the rubber molding is insufficient, and it is difficult to achieve both higher rigidity and longer life in the future. For this purpose, it is necessary to further improve the rigidity of the composite cord, suppress the decrease in the rigidity of the composite cord generated during the heat treatment in the rubber molding process, and also suppress the decrease in strength to form a cord structure.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Special Publication No. 2019-532192 [Patent Document 2] Special Publication No. 2016-500769 [Overview of the project] [Problems that the invention aims to solve]

[0006] The objective of the present invention is to provide a composite cord for rubber reinforcement that has a high cord modulus of elasticity and can maintain a high modulus of elasticity even after heat treatment during rubber molding. [Means for solving the problem]

[0007] The present invention relates to a rubber-reinforced composite cord comprising high-strength, high-modulus fibers and low-strength, low-modulus fibers, wherein the high-strength, high-modulus fibers in the rubber-reinforced composite cord are fibers with higher strength and modulus than the low-strength, low-modulus fibers, and the rubber-reinforced composite cord is a dip cord in which a resin adhesive containing latex is contained in at least a part of the surface and interior of a raw cord formed by under-twisting the high-strength, high-modulus fibers and the low-strength, low-modulus fibers, and then over-twisting the under-twisted threads together in the opposite direction to the under-twisting direction, and when the over-twist of the dip cord is released, the length of the under-twisted thread of the low-strength, low-modulus fibers (A) is longer than the length of the under-twisted thread of the high-strength, high-modulus fibers (B), and the length ratio (A) / (B) is 1.005 or more and 1.100 or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a composite cord for rubber reinforcement that has a high cord modulus of elasticity and can maintain a high modulus of elasticity even after heat treatment during rubber molding. [Modes for carrying out the invention]

[0009] [High-strength, high-modulus fiber] In the present invention, the high-strength, high-modulus fiber is a fiber with higher strength and modulus than the low-strength, low-modulus fiber described later, preferably having a strength of 10 cN / dtex or more and an initial tensile resistance of 300 cN / dtex or more as indicated by the initial tensile resistance of JIS L 1017. If the strength is less than 10 cN / dtex, the strength required for rubber-reinforced composite cords cannot be obtained, which is undesirable, and if the initial tensile resistance is less than 300 cN / dtex, the rigidity required for rubber-reinforced composite cords cannot be obtained, which is also undesirable.

[0010] Examples of high-strength, high-modulus fibers that satisfy the above conditions include glass fibers, aromatic polyamide fibers (aramid fibers), carbon fibers, poly(p-phenylenebenzooxal) fibers, aromatic polyester fibers, and ultra-high molecular weight polyethylene fibers. Aromatic polyamide fibers are preferred, and among them, para-type aromatic polyamide fibers are particularly preferred due to their excellent heat resistance and strength.

[0011] Para-type aromatic polyamide fibers are polyamide fibers in which the chain bonds of the aromatic polyamide are coaxial or parallel and oriented in opposite directions. Specifically, examples include poly-para-phenylene terephthalamide fibers (e.g., "Twaron®" manufactured by Teijin Aramid BV) and copolymerized aromatic polyamide fibers such as co-para-phenylene·3,4'-oxydiphenylene·terephthalamide fibers (e.g., "Technora®" manufactured by Teijin Limited).

[0012] This high-strength, high-modulus fiber has higher strength and modulus than the low-strength, low-modulus fiber described later. Aromatic polyamide fibers with high strength and high modulus of elasticity can be those that are conventionally known and can be manufactured by known methods. For example, they are described in Japanese Patent Publication No. 49-100322, Japanese Patent Publication No. 47-10863, Japanese Patent Publication No. 58-144152, and Japanese Patent Publication No. 4-65513.

[0013] The fineness of the high-strength, high-modulus fibers is preferably between 400 dtex and 2000 dtex. If it is less than 400 dtex, the strength and rigidity required for rubber-reinforced composite cords cannot be obtained. On the other hand, if it exceeds 2000 dtex, not only does the overall diameter of the rubber-reinforced composite cord become thicker, but the entire cord, including the high-modulus fibers, also becomes thicker. As a result, when bent at the same radius of curvature, the strain of the cord increases, reducing bending durability and decreasing strength retention during prolonged use.

[0014] [Low-strength, low-modulus fibers] In the present invention, the low-strength, low-modulus fiber is a fiber with lower strength and modulus than the high-strength, high-modulus fiber described above, preferably with a strength of 9 cN / dtex or less and an initial tensile resistance of 100 cN / dtex or less as indicated by the initial tensile resistance of JIS L 1017. If the strength exceeds 9 cN / dtex or the initial tensile resistance exceeds 100 cN / dtex, the bending durability of the low-strength, low-modulus fiber decreases, which is undesirable, and the bending durability of the entire composite cord for rubber reinforcement decreases, resulting in a decrease in strength retention during long-term use, which is also undesirable.

[0015] Examples of low-strength, low-modulus fibers that satisfy these conditions include polyurethane fibers, aliphatic polyamide fibers known as nylon 6, nylon 66, nylon 46, etc., polyester fibers, polyvinyl alcohol fibers, and rayon fibers, with polyester fibers being preferred. Examples of polyester fibers include polyethylene terephthalate and polytrimethylene terephthalate.

[0016] The fineness of the low-strength, low-modulus fibers is preferably between 400 dtex and 2000 dtex. If it is less than 400 dtex, the overall bending durability of the rubber reinforcement composite cord decreases, resulting in a decrease in strength retention during prolonged use. On the other hand, if it exceeds 2000 dtex, the composite cord becomes thicker, so when bent at the same radius of curvature, the strain of the cord increases, reducing bending durability and strength retention during prolonged use. Furthermore, the moldability during the manufacturing of the reinforcement rubber deteriorates.

[0017] [Dip Code] The composite cord for rubber reinforcement of the present invention is a dip cord in which the above high-strength and high-modulus fibers and low-strength and low-modulus fibers are respectively twisted downwards, and a resin adhesive containing latex is contained in at least a part of the surface and inside of the green cord formed by combining the twisted yarns and twisting them upwards in the direction opposite to the downward twisting direction.

[0018] In the above, the green cord is preferably a multi-twisted yarn obtained by twisting two or more of the downward-twisted yarns in the direction opposite to the twisting direction of the downward-twisted yarns. From the viewpoints of the rigidity of the cord and the retention of strength during long-term use, the twist coefficient of the high-strength and high-modulus fibers is preferably 2.0 to 6.0, and the twist coefficient of the low-strength and low-modulus fibers is preferably 2.0 to 5.0.

[0019] In the downward-twisting process for obtaining the green cord, the tension when twisting the low-strength and low-modulus fibers is higher than the tension when twisting the high-strength and high-modulus fibers, and in the upward-twisting process, it is preferable that the tension applied to the downward-twisted yarn of the low-strength and low-modulus fibers is higher than the tension applied to the downward-twisted yarn of the high-strength and high-modulus fibers.

[0020] This green cord has a twist coefficient of the upward twist represented by the following formula of 3.5 or more and 7.5 or less, preferably 4.0 or more and 7.0 or less. By being in this range, the strength and modulus of the cord required for the rigidity of the rubber molded product during use and the flexural fatigue resistance of the rubber molded product during long-term use can be obtained simultaneously. TM = T×√D / 1055 (However, TM represents the twist coefficient, T represents the number of twists (turns / m), and D represents the total fineness (tex) of the high-strength and high-modulus fibers and the low-strength and low-modulus fibers.)

[0021] In the present invention, when untwisting the S-twist of the dip cord, the length (A) of the Z-twist yarn of the high-strength high-modulus fiber is shorter than the length (B) of the Z-twist yarn of the low-strength low-modulus fiber, and the length ratio (A) / (B) is important to be 0.950 or more and 0.995 or less. By being within this range, the high dimensional stability of the high-strength high-modulus fiber is effectively exhibited. For example, it is possible to suppress a decrease in the elastic modulus of the rubber reinforcing composite cord due to heat treatment during rubber molding or high temperature during use of the rubber molded product.

[0022] From the viewpoints of strength retention during long-term use and weight reduction of the reinforcing rubber, the total fineness of the rubber reinforcing composite cord of the present invention is preferably 3500 dtex or less. From the viewpoints of rigidity during use of the reinforcing rubber and strength retention during long-term use, the elastic modulus of the rubber reinforcing composite cord of the present invention is preferably 150 cN / dtex or more and 300 cN / dtex or less. From the viewpoint of dimensional stability, the heat shrinkage rate of the rubber reinforcing composite cord of the present invention under the heat treatment conditions of 150 °C for 30 minutes is preferably 2.0% or less.

[0023] 〔Adhesive treatment〕 The rubber reinforcing composite cord of the present invention can be produced by an adhesive treatment in which a raw cord is impregnated with a solution of an adhesive. By this adhesive treatment, the rubber reinforcing composite cord of the present invention, which is a dip cord containing an adhesive in at least a part of the surface and the inside of the raw cord, can be obtained.

[0024] In this adhesive treatment, preferably while applying a tension of 0.5 cN / dtex or more, the raw cord is impregnated with a treatment agent containing an adhesive, and preferably heat treatment is performed at a temperature of 220 to 250 °C for preferably 1 to 10 minutes. By doing so, the fibers are sufficiently stretched during the adhesive treatment, and the elastic modulus of the obtained rubber reinforcing composite cord can be increased. When using an aromatic polyamide fiber as the high-strength high-modulus fiber, from the viewpoints of adhesiveness at high temperatures, etc., it is preferable to use a resorcinol formalin latex adhesive as the adhesive.

[0025] [Resorcinol, Formalin, Latex Resin] The amount of adhesive applied to the raw cord by the bonding treatment is preferably 5 to 20% by weight, based on the weight of the rubber-reinforced composite cord of the present invention obtained by the bonding treatment. Furthermore, the concentration of the adhesive solution used in the bonding process is preferably 5 to 20% by weight. A concentration of less than 5% by weight is undesirable because it does not allow for sufficient adhesion, while a concentration exceeding 20% ​​by weight is undesirable because it can easily lead to scum formation and cause problems.

[0026] When using resorcinol-formaldehyde-latex resin as an adhesive, the amount of resorcinol-formaldehyde-latex resin attached after the bonding treatment is preferably 5 to 20% by weight, based on the weight of the rubber-reinforced composite cord. After the bonding treatment, the resorcinol-formaldehyde-latex resin adheres to the surface and interior of the rubber-reinforced composite cord of the present invention. Excellent adhesive strength can be obtained when the amount of resorcinol-formaldehyde-latex resin attached is 5 to 20% by weight, based on the weight of the rubber-reinforced composite cord.

[0027] In resorcinol-formaldehyde-latex resin, the molar ratio of resorcinol to formaldehyde is preferably 1:0.6 to 1:8, and more preferably 1:0.8 to 1:6. If the amount of formaldehyde is less than this range, the crosslinking density of the resorcinol-formaldehyde condensate decreases and the molecular weight decreases, which is undesirable because the cohesive force of the resin layer decreases, leading to reduced adhesion and potentially reduced flexural fatigue resistance. On the other hand, if the amount of formaldehyde is more than this range, the crosslinking density increases, causing the resorcinol-formaldehyde condensate to harden. This tends to inhibit the compatibility of the resorcinol-formaldehyde-latex resin with the rubber during co-vulcanization with the rubber of the adherend, resulting in reduced adhesion, which is undesirable.

[0028] In resorcinol-formaldehyde-latex resin, the mixing ratio of resorcinol-formaldehyde to latex is preferably 1:3 to 1:16, and more preferably 1:4 to 1:10, in terms of solid weight ratio. If the latex ratio is lower than this range, the co-vulcanization component with the rubber is small, which tends to reduce adhesive strength and is undesirable. On the other hand, if the latex ratio is higher than this range, sufficient strength as an adhesive film cannot be obtained, which tends to reduce adhesive strength and durability, and the tackiness of the bonded composite cord becomes significantly higher, which may reduce process passability such as cam-up and handling in the bonding process and belt molding process, and is undesirable.

[0029] As resorcinol, pre-oligomerized resorcinol-formaldehyde initial condensates or polynuclear chlorophenol-based resorcinol-formaldehyde initial condensates obtained by oligomerizing chlorophenol and resorcinol with formalin can be used. These may be used alone or in combination.

[0030] Examples of latex include hydrogenated acrylonitrile-butadiene rubber latex, acrylonitrile-butadiene latex, isoprene rubber latex, urethane rubber latex, styrene-butadiene rubber latex, vinylpyridine-styrene-butadiene rubber latex, chloroprene rubber latex, butadiene rubber latex, and chlorosulfonated polyethylene latex. These may be used individually or in combination.

[0031] When the surface of a single filament of a rubber-reinforced composite cord is surface-treated with an epoxy compound and then bonded with a resorcinol-formaldehyde-latex adhesive, vinylpyridine-styrene-butadiene rubber latex is preferred as the latex because it has high affinity with the surface and can increase the strength of the resin layer.

[0032] A crosslinking agent may be used in combination with the resorcinol-formaldehyde-latex resin. Examples of crosslinking agents include amines, ethylene urea, and blocked isocyanate compounds. Among these, blocked isocyanate compounds are preferred because they have good temporal stability and good interaction with pretreatment agents. Preferred blocked isocyanate compounds include dimethylpyrazole block, methyl ethyl ketone oxime block, and caprolactam block. Two or more of these may be used in combination.

[0033] [Surface treatment with epoxy compounds] High-strength, high-modulus fibers generally have an inert surface and are difficult to bond with other materials. This tendency is particularly strong in aromatic polyamide fibers.

[0034] Therefore, in order to obtain sufficient adhesion, it is preferable to perform a surface treatment in which the surface of the raw cord before the bonding treatment is impregnated with an epoxy compound by immersing it in a solution containing an epoxy compound. This surface treatment can improve the chemical affinity between high-strength, high-modulus fibers, especially aromatic polyamide fibers, and resorcinol-formaldehyde-latex resin.

[0035] The amount of solid epoxy compound adhering to the raw cord is preferably 0.05 to 5.0% by weight, and more preferably 0.2 to 2.0% by weight, based on the weight of the raw cord.

[0036] If the amount of adhesive is less than 0.05% by weight, the epoxy resin layer formed on the surface of the single yarn is insufficient, making it difficult to obtain good adhesion between the high-strength, high-modulus fibers of the raw cord and between the resorcinol, formalin, and latex resin, which is undesirable. On the other hand, if the amount of adhesive is greater than 5.0% by weight, the high-strength, high-modulus fibers of the raw cord are strongly bound together by the epoxy resin, resulting in a hard rubber-reinforced composite cord with poor bending fatigue resistance, which is undesirable.

[0037] Examples of epoxy compounds used for surface treatment include reaction products of polyhydric alcohols such as ethylene glycol, glycerol, sorbitol, pentaerythritol, and polyethylene glycol with halogen-containing epoxides such as epichlorohydrin; reaction products of polyhydric phenols such as resorcinol, bis(4-hydroxyphenyl)dimethylmethane, phenol-formaldehyde resin, and resorcinol-formaldehyde resin with the aforementioned halogen-containing epoxides; and polyepoxide compounds obtained by oxidizing unsaturated compounds with peracetic acid or hydrogen peroxide, namely 3,4-epoxycyclohexene epoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate, and bis(3,4-epoxy-6-methyl-cyclohexylmethyl) adivate.

[0038] Of these, the reaction product of a polyhydric alcohol and epichlorohydrin is preferred, as are compounds produced by a polyepoxide compound, such as a polyglycidyl ether compound of a polyhydric alcohol, and a curing agent. When using polyepoxide compounds, an emulsifier, such as sodium alkylbenzenesulfonate or sodium dioctyl sulfosuccinate, may be used to create an emulsion.

[0039] Polyepoxide compounds may also be used in combination with amine-based or imidazole-based curing agents, blocked polyisocyanates which are addition compounds of polyisocyanates with blocking agents such as oximes, phenols, or caprolactams, or ethyleneurea which is a reaction compound with ethyleneimine.

[0040] [Manufacturing method] The rubber-reinforced composite cord of the present invention can be manufactured by first twisting high-strength, high-modulus fibers and low-strength, low-modulus fibers, then joining the twisted threads together and twisting them in the opposite direction to the twist to form a raw cord, and then incorporating a latex-containing resin adhesive into at least a portion of the surface and interior of the cord.

[0041] To incorporate a latex-containing resin adhesive into at least a portion of the surface and interior of the raw cord obtained as described above, it is preferable to impregnate the raw cord with a treatment agent containing the adhesive while applying a tension of 0.5 cN / dtex or more, and then heat-treat it at a temperature of 230 to 270°C for 1 to 10 minutes.

[0042] With the above manufacturing method, when the upper twist of the dip cord is released, the length of the undertwist yarn (A) of the high-strength, high-modulus fiber is shorter than the length of the undertwist yarn (B) of the low-strength, low-modulus fiber, and the length ratio (A) / (B) can be between 0.950 and 0.995.

[0043] In other words, according to the present invention, a method for manufacturing a rubber-reinforced composite cord containing high-strength, high-modulus fibers and low-strength, low-modulus fibers, wherein in the rubber-reinforced composite cord, the high-strength, high-modulus fibers are fibers with higher strength and modulus than the low-strength, low-modulus fibers, and the rubber-reinforced composite cord is a dip cord in which a resin adhesive containing latex is contained in at least a part of the surface and interior of a raw cord formed by under-twisting the high-strength, high-modulus fibers and the low-strength, low-modulus fibers, and then over-twisting the under-twisted threads together in the opposite direction to the under-twisting direction, and when the over-twist of the dip cord is released, the high-strength, high-modulus fibers A method for manufacturing a composite cord for rubber reinforcement is provided, characterized in that the length of the under-twisted yarn (A) is shorter than the length of the under-twisted yarn (B) of the low-strength, low-modulus fiber, and the length ratio (A) / (B) is 0.950 or more and 0.995 or less, and the manufacturing method includes an adhesive treatment step, in which the adhesive treatment step includes at least a step of under-twisting a high-strength, high-modulus fiber and a low-strength, low-modulus fiber, respectively, and then joining the under-twisted yarns together and over-twisting them in the opposite direction to the under-twisting direction to form a raw cord, which is then impregnated with a treatment agent containing an adhesive while applying a tension of 0.5 cN / dtex or more, and heat-treating it at a temperature of 230 to 270°C for 1 to 10 minutes. [Examples]

[0044] The present invention will be described below with reference to examples. (1) Ratio of under-twisted yarn length when rubber reinforcement cord is untwisted A rubber-reinforced composite cord was subjected to a twist detection machine, and the top twist was untwisted while applying a load equal to 0.045 times the total fineness (dtex). After untwisting, one undertwisted yarn was stretched linearly under the load, and the other undertwisted yarn was loosened. First, the length of the undertwisted yarn that was stretched linearly was measured. Leaving the other loose undertwisted yarn intact, the one stretched linearly was cut, and the other loose undertwisted yarn was stretched linearly and its length was measured. The length of the undertwisted yarn of the low-strength, low-modulus fiber measured above was denoted as (A), and the length of the undertwisted yarn of the high-strength, high-modulus fiber was denoted as (B). The length ratio (A) / (B) was then calculated.

[0045] (2) Fineness, total fineness The fineness (by weight) including the attached resin or the total fineness (by weight) was measured in accordance with JIS L1017.

[0046] (3) Tensile strength of the cord The tensile strength of rubber-reinforced composite cords was measured in accordance with JIS L1017. The tensile strength was calculated by dividing the tensile strength at break by the fineness of the rubber-reinforced composite cord, including the amount of resin adhering to it.

[0047] (4) Adhesion rate of adhesive The adhesive adhesion rate was measured according to the dip pickup (mass method) of JIS L1017.

[0048] (5) Code modulus The initial tensile resistance of the rubber-reinforced composite cord was measured in accordance with JIS L1017, and this was defined as the cord's modulus of elasticity.

[0049] (6) Tensile strength, tensile strength, and modulus of elasticity (M1) of the cord after heat treatment The rubber-reinforced composite cord was heat-treated at 150°C for 30 minutes without load, and thereafter, the cord tensile strength, tensile strength, and cord modulus were measured in the same manner as in (3) and (5) above.

[0050] (7) Thermal shrinkage The heat shrinkage rate was measured according to the dry heat shrinkage rate (Method B) of JIS L1017 and was defined as the heat shrinkage rate. The heating conditions were 150°C for 30 minutes.

[0051] (8) Strong retention rate Rubber reinforcement composite cords were embedded in rubber, and a rubber test specimen was prepared by vulcanizing it at 150°C for 30 minutes. This rubber test specimen was subjected to a disc fatigue tester in accordance with JIS L1017, with elongation and compression of ±10% at 2500 rpm for 6 hours. Tensile tests were performed on the rubber test specimens before and after the fatigue test, and the strength retention rate was calculated using the following formula. Strong retention rate (%) = (Strength of the rubber test specimen after fatigue test) / (Strength of the rubber test specimen before fatigue test) × 100

[0052] (9) Strength and initial tensile resistance The tensile strength and initial tensile resistance of the fibers were measured in accordance with JIS L1017.

[0053] [Example 1] Poly(p-phenylene terephthalamide) fiber (Twaron T1000 1100dtex, manufactured by Teijin Limited, with a strength of 21 cN / dtex and an initial tensile resistance of 540 cN / dtex) was used as the high-strength, high-modulus fiber. The yarn was twisted in the Z direction at a rate of 450 t / m in a ring twisting process to produce the under-twisted yarn.

[0054] Furthermore, polyethylene terephthalate fiber (Tetron BHT 1100T249 P952NL, manufactured by Teijin Limited, which has a strength of 7.1 cN / dtex and an initial tensile resistance of 70 cN / dtex) was used as a low-strength, low-modulus fiber, and a ring twisting process was performed to create a base twist yarn with a twist of 450 t / m in the Z direction.

[0055] One under-twisted yarn of poly(p-phenylene terephthalamide) fiber and one under-twisted yarn of polyethylene terephthalate fiber were used to create a top-twisted yarn by twisting them in the S direction at a rate of 450 t / m (twist coefficient TM = 6.3).

[0056] The following treatment was performed using this top-twisted yarn. For the first bath, 0.5 g of piperazine was dispersed in 978.5 g of water, 1 g of Neocol SW-30 (sodium dioctyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (solid component concentration: 30% by weight) was added, and then 20 g of polyepoxide compound (Denacol EX314, manufactured by Nagase ChemteX Corporation) was dispersed to prepare a treatment solution (solid component 2% by weight).

[0057] The upper twisted yarn was immersed in this first bath treatment solution while applying a tension of 1.5 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 240°C for 2 minutes to obtain the post-bath fiber cord.

[0058] Next, the second treatment solution was prepared. First, resorcinol-formaldehyde initial condensate and Sumikanol S700 (manufactured by Sumitomo Chemical Co., Ltd., 65% by weight aqueous solution) were added to a caustic soda aqueous solution and thoroughly stirred to disperse. Formalin was then added to this solution so that the R / F ratio was 1 / 0.5 (molar ratio) and mixed uniformly, and the mixture was aged at 25°C for 6 hours. Next, a mixture of Nippol 2518FS (manufactured by Nippon Zeon Co., Ltd., vinylpyridine-styrene-butadiene rubber latex) and Nippol LX-111A (manufactured by Nippon Zeon Co., Ltd., polybutadiene rubber latex) (vinylpyridine-styrene-butadiene rubber latex / polybutadiene rubber latex = 75 / 25 (weight ratio)) was mixed with the resorcinol-formaldehyde initial condensate dispersion at a solid content ratio (RF / L ratio) of 1 / 9 by weight (treatment solution concentration 10% by weight), and aged at 25°C for 24 hours. The resulting treatment solution was used as the second treatment solution.

[0059] The fiber cord, after the first bath treatment, was immersed in this second bath solution under a tension of 1.5 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 245°C for 2 minutes to obtain a rubber-reinforced composite cord. The evaluation results are shown in Table 1.

[0060] [Example 2] High-strength, high-modulus fibers were subjected to a ring twisting process, with a twist of 350 t / m in the Z direction to obtain a base twist yarn. Low-strength, low-modulus fibers were subjected to a ring twisting process, with a twist of 350 t / m in the Z direction to obtain a base twist yarn. Otherwise, the same process as in Example 1 was applied to obtain a composite cord for rubber reinforcement. The evaluation results are shown in Table 1.

[0061] [Example 3] High-strength, high-modulus fibers were subjected to a ring twisting process, with a twist of 500 t / m in the Z direction to produce a base twist yarn. Low-strength, low-modulus fibers were subjected to a ring twisting process, with a twist of 500 t / m in the Z direction to produce a base twist yarn. One under-twisted yarn of high-strength, high-modulus fiber and one under-twisted yarn of low-strength, low-modulus fiber were twisted in the S direction at 500 t / m (twist coefficient TM = 7.0) to obtain an upper-twisted yarn. The same processing as in Example 1 was applied to obtain a composite cord for rubber reinforcement. The evaluation results are shown in Table 1.

[0062] [Example 4] The top twisted yarn was immersed under a tension of 0.7 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 245°C for 2 minutes to form a fiber cord after the single-bath treatment. Next, the fiber cord after this one-bath treatment was immersed under a tension of 0.7 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 245°C for 2 minutes. Otherwise, the same treatment as in Example 1 was performed to obtain a rubber-reinforced composite cord. The evaluation results are shown in Table 1.

[0063] [Example 5] The top twisted yarn was immersed under a tension of 1.5 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 240°C for 2 minutes to form a fiber cord after the single-bath treatment. Next, the fiber cord after this one-bath treatment was immersed under a tension of 0.7 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 235°C for 2 minutes. Otherwise, the same treatment as in Example 1 was performed to obtain a rubber-reinforced composite cord. The evaluation results are shown in Table 1.

[0064] [Table 1]

[0065] [Comparative Example 1] The top twisted yarn was immersed under a tension of 0.3 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 240°C for 2 minutes to form a fiber cord after the single-bath treatment. Next, the fiber cord after this one-bath treatment was immersed under a tension of 0.3 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 245°C for 2 minutes. Otherwise, the same treatment as in Example 1 was performed to obtain a rubber-reinforced composite cord. The evaluation results are shown in Table 2.

[0066] [Comparative Example 2] High-strength, high-modulus fibers were subjected to a ring twisting process, with a twist of 250 t / m in the Z direction to produce a base twist yarn. Low-strength, low-modulus fibers were subjected to a ring twisting process, with a twist of 250 t / m in the Z direction to produce a base twist yarn. One under-twisted yarn of high-strength, high-modulus fiber and one under-twisted yarn of low-strength, low-modulus fiber were twisted in the S direction at a rate of 250 t / m (twist coefficient TM = 7.7) to obtain an upper-twisted yarn. The same processing as in Comparative Example 1 was applied to obtain a composite cord for rubber reinforcement. The evaluation results are shown in Table 2.

[0067] [Comparative Example 3] High-strength, high-modulus fibers were subjected to a ring twisting process, with a twist of 550 t / m in the Z direction to produce a base twist yarn. Low-strength, low-modulus fibers were subjected to a ring twisting process, with a twist of 550 t / m in the Z direction to produce a base twist yarn. One under-twisted yarn of high-strength, high-modulus fiber and one under-twisted yarn of low-strength, low-modulus fiber were twisted in the S direction at 50 t / m (twist coefficient TM = 7.7) to obtain an upper-twisted yarn. The same processing as in Comparative Example 1 was performed to obtain a composite cord for rubber reinforcement. The evaluation results are shown in Table 2.

[0068] [Comparative Example 4] The top twisted yarn was immersed under a tension of 1.5 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 220°C for 2 minutes to form a fiber cord after the single-bath treatment. Next, the fiber cord after this one-bath treatment was immersed under a tension of 0.7 cN / dtex, dried at 150°C for 90 seconds, and then heat-treated at 220°C for 2 minutes. Otherwise, the same treatment as in Example 1 was performed to obtain a rubber-reinforced composite cord. The evaluation results are shown in Table 2.

[0069] [Table 2] [Industrial applicability]

[0070] The rubber reinforcing composite cord of the present invention can be used to reinforce rubber, and in particular can be used to reinforce rubber tires. That is, the present invention provides a rubber tire that includes the above-mentioned rubber reinforcing composite cord.

[0071] The rubber reinforcing composite cord of the present invention, when used in rubber tires for reinforcement, makes it possible to obtain rubber tires with superior tire characteristics while having a thinner rubber layer than other rubber reinforcing cords, thereby contributing to improved fuel efficiency.

Claims

1. A composite cord for rubber reinforcement comprising high-strength, high-modulus fibers and low-strength, low-modulus fibers, wherein the high-strength, high-modulus fibers in the composite cord have higher strength and modulus than the low-strength, low-modulus fibers. The high-strength, high-modulus fiber has a strength of 10 cN / dtex or more and an initial tensile resistance of 300 cN / dtex or more, the low-strength, low-modulus fiber has a strength of 9 cN / dtex or less and an initial tensile resistance of 100 cN / dtex or less, the rubber-reinforced composite cord is a raw cord formed by under-twisting the high-strength, high-modulus fiber and the low-strength, low-modulus fiber, and then over-twisting the two under-twisted threads together in the opposite direction to the under-twist, the twist coefficient of the over-twist shown in the following formula is 4.9 or more and 7.0 or less, and the raw cord is a dip cord in which a resin adhesive containing latex is contained in at least a part of the surface and interior of the raw cord. A composite cord for rubber reinforcement, characterized in that when the upper twist of the dip cord is released, the length of the lower twist of the high-strength, high-modulus fiber (A) is shorter than the length of the lower twist of the low-strength, low-modulus fiber (B), and the length ratio (A) / (B) is 0.950 or more and 0.995 or less. TM=T×√D / 1055 (However, TM is the twist coefficient, T is the number of twists (twists / m), and D is the total fineness (tex) of the high-strength, high-modulus fibers and the low-strength, low-modulus fibers.)

2. The rubber-reinforced composite cord according to claim 1, wherein the fineness of the high-strength, high-modulus fiber is 400 dtex or more and 2000 dtex or less, and the fineness of the low-strength, low-modulus fiber is 400 dtex or more and 2000 dtex or less.

3. The rubber-reinforced composite cord according to claim 1, wherein the high-strength, high-modulus fiber is a para-type aromatic polyamide fiber.

4. The rubber-reinforced composite cord according to claim 3, wherein the low-strength, low-modulus fiber is a polyester fiber.

5. The rubber-reinforced composite cord according to claim 2, wherein the total fineness of the rubber-reinforced composite cord is 3500 dtex or less.

6. The rubber-reinforced composite cord according to claim 1, wherein the elastic modulus of the rubber-reinforced composite cord is 150 cN / dtex or more and 300 cN / dtex or less.

7. The rubber-reinforced composite cord according to claim 1, wherein the heat shrinkage rate of the rubber-reinforced composite cord under heat treatment conditions of 150°C for 30 minutes is 2.0% or less.

8. A method for manufacturing a rubber-reinforced composite cord containing high-strength, high-modulus fibers and low-strength, low-modulus fibers, wherein in the rubber-reinforced composite cord, the high-strength, high-modulus fibers are fibers with higher strength and modulus than the low-strength, low-modulus fibers, the high-strength, high-modulus fibers having a strength of 10 cN / dtex or more and an initial tensile resistance of 300 cN / dtex or more, and the low-strength, low-modulus fibers having a strength of 9 cN / dtex or less and an initial tensile resistance of 100 cN / dtex or less, and the rubber-reinforced composite cord is a raw cord formed by under-twisting the high-strength, high-modulus fibers and the low-strength, low-modulus fibers, and then over-twisting the two under-twisted threads together in the opposite direction to the under-twist, wherein the twist coefficient of the over-twist shown in the following formula is 4.9 or more and 7.0 or less, and the surface of the raw cord A dip cord having a latex-containing resin adhesive in at least a portion of its interior, wherein when the upper twist of the dip cord is released, the length of the under-twisted yarn of the high-strength, high-modulus fiber (A) is shorter than the length of the under-twisted yarn of the low-strength, low-modulus fiber (B), and the length ratio (A) / (B) is 0.950 or more and 0.995 or less, and the manufacturing method includes an adhesive treatment step, in which the raw cord formed by under-twisting the high-strength, high-modulus fiber and the low-strength, low-modulus fiber respectively, and then over-twisting the under-twisted yarns together in the opposite direction to the under-twist, is impregnated with a treatment agent containing adhesive while applying a tension of 0.5 cN / dtex or more, and heat-treated at a temperature of 230 to 270°C for 2 to 10 minutes, is a method for manufacturing a composite cord for rubber reinforcement. TM=T×√D / 1055 (However, TM is the twist coefficient, T is the number of twists (twists / m), and D is the total fineness (tex) of the high-strength, high-modulus fibers and the low-strength, low-modulus fibers.)

9. A rubber tire comprising a rubber-reinforced composite cord according to any one of claims 1 to 7.

Images