Rubber Reinforcement Cord

Abstract

To provide a cord for reinforcing rubber having tensile strength, elongation at low load, high elastic modulus at high load, adhesiveness, and fatigue resistance, and small in dispersion of these physical properties, and high in reliability.SOLUTION: A cord for reinforcing rubber includes a stretch broken yarn, where the average fiber length of the stretch broken yarn is 30-120 cm; the tensile strength of the cord for reinforcing rubber is 8.0 cN / dtex or higher; and the coefficient of variability of the tensile strength CV% is 20% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber reinforcing cord, and more particularly to a rubber reinforcing cord used to reinforce rubber products such as tires. [Background technology]

[0002] Embedding reinforcing fibers into rubber has become a common practice to improve the strength and durability of rubber products such as rubber belts and rubber tires. Conventionally, glass fibers, polyvinyl alcohol fibers such as vinylon fibers, polyester fibers, nylon, polyamide fibers such as aramid (aromatic polyamide), carbon fibers, and polyparaphenylene benzoxal fibers have been widely used as reinforcing fibers. Among these, aromatic polyamide fibers are particularly promising due to their high strength, high elastic modulus, dimensional stability, heat resistance, and chemical resistance.

[0003] However, these reinforcing fibers cannot simultaneously satisfy the moldability when the rubber composition is cured into a molded rubber product and the rigidity of the molded rubber product during use, and therefore various solutions have been proposed.

[0004] For example, Patent Document 1 discloses a technology relating to a cord that has elongation in a low load range and uses a composite cord made of para-aromatic polyamide fiber and aliphatic polyamide (nylon) fiber. In this technology, the proportion of para-aromatic polyamide fiber in the composite cord is not particularly high, and the proportion of low-strength, low-elasticity nylon fiber is high. As a result, not only does the overall cord diameter of the composite cord increase, but the entire cord including the high-elasticity fiber also increases in thickness. This results in greater strain on the cord when bent with the same curvature radius, resulting in a problem of reduced flexural fatigue durability.

[0005] Furthermore, aromatic polyamide fibers often have a relatively inactive surface, and as such, have insufficient adhesion to the matrix rubber, preventing the aromatic polyamide fibers from fully exhibiting their properties.

[0006] As a measure to improve this adhesiveness, for example, Patent Document 2 proposes a method of using stretch-break processed aromatic polyamide fiber yarn to achieve both adhesiveness to rubber and strength. However, this leads to poor uniformity of the reinforcing yarn, which causes variations in physical properties along the length of the reinforcing yarn, resulting in variations in the rubber reinforcing physical properties.

[0007] Large variations in rubber reinforcement properties result in low reliability as a product. For rubber tire applications, where reliability is particularly important, stretch-break processed aromatic polyamide fiber yarns have not yet been actively put to practical use, despite their high strength and high adhesiveness. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-100365 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-180491 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a highly reliable rubber-reinforcing cord that has tensile strength, elongation under low load, high elastic modulus under high load, adhesiveness and fatigue resistance, and exhibits little variation in these physical properties. [Means for solving the problem]

[0010] That is, the present invention relates to a rubber reinforcing cord comprising a stretch-break textured yarn, wherein the stretch-break textured yarn has an average fiber length of 30 to 120 cm, and the rubber reinforcing cord has a tensile strength of 8.0 cN / dtex or more and a tensile strength variation rate CV% of 20% or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a highly reliable rubber-reinforcing cord that has tensile strength, elongation under low load, high elastic modulus under high load, adhesiveness, and fatigue resistance, and exhibits little variation in these physical properties. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a manufacturing device for stretch-breaking textured yarn. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Stretch-break processed yarn] Stretch-break textured yarn is a yarn obtained by stretch-breaking a long fiber bundle and then entangling the resulting fibers. This stretch-break textured yarn has a reinforcing yarn bundle structure with fluff on its surface, and the fluff on the surface acts as an anchor, resulting in high adhesion to rubber. Furthermore, the fluff on the surface allows a large amount of adhesive to be applied to the fiber surface even with a small amount or low adhesive concentration, thereby ensuring high rubber adhesion while contributing to cost reduction and environmental load reduction.

[0014] These effects are particularly effective for aromatic polyamide fibers and polyester fibers, which are difficult to bond to rubber due to their surface chemical structure. In the present invention, by using this as a rubber reinforcing cord, a rubber tire with excellent adhesion to rubber and fatigue resistance can be obtained.

[0015] The stretch-break textured yarn is preferably a stretch-break textured yarn obtained by stretch-breaking a long fiber bundle of aromatic polyamide, and entangling the resulting fibers to bind them. The stretch-break textured yarn used in the present invention can be produced, for example, by the method described in JP-A-2008-163488, that is, by the steps shown in FIG.

[0016] In this process, the continuous filament bundle 1 is stretched between nip rollers 2 and 4 to a breaking elongation or more of the continuous filament bundle, and then the stretch-broken fibers (hereinafter sometimes referred to as stretch-broken fibers) are sucked from the nip rollers 4 by a suction air nozzle 5 and taken up, and then the fibers are entangled and / or bundled by winding the ends of the stretch-broken fibers by a conjugating air nozzle 6, and the fibers are passed through nip rollers 7 and wound up as a stretch-broken yarn 8. The conjugation of the stretch-broken fibers by the conjugating air nozzle 6 may be performed by either entangling the fibers with each other using an interlace type air nozzle or winding the fiber ends using a swirl type air nozzle.

[0017] In the present invention, the average fiber length of the stretch-broken single fibers is 30 to 120 cm. If the average fiber length is less than 30 cm, the fuzz that improves adhesion and the permeability of the adhesive into the fiber bundle are sufficient, but the entanglement between the fibers is insufficient, resulting in a decrease in tensile strength and a decrease in fatigue resistance against repeated vibration. On the other hand, if the average fiber length exceeds 120 cm, the reinforcing yarn bundle structure becomes similar to that of a filament (long fiber), which prevents the adhesive from permeating the fiber bundle and results in insufficient adhesion.

[0018] [Single yarn fineness of stretch-break processed yarn] The single yarn fineness of the stretch-break textured yarn is preferably 1.5 dtex or less, more preferably 1.0 dtex or less. With this single yarn fineness, the number of fibers constituting the fiber bundle is large, and therefore, a decrease in fiber strength due to stretch-breaking can be suppressed.

[0019] [Strength and its variability CV%] The rubber reinforcing cord of the present invention comprises a stretch-break textured yarn produced by a stretch-breaking method, and this stretch-break textured yarn has long single fibers constituting it, and the fibers are more highly aligned than in conventional spun yarns, allowing it to obtain high strength. The rubber reinforcing cord of the present invention has a tensile strength of 8.0 cN / dtex or more. If the tensile strength is less than 8.0 cN / dtex, sufficient strength for rubber products cannot be obtained.

[0020] The rubber-reinforcing cord of the present invention has a tensile strength variation rate (CV%) of 20% or less. If the tensile strength variation rate (CV%) exceeds 20%, the variation rate of the strength of the molded rubber product will be high and the variation rate of the rubber adhesion will also be high, resulting in a rubber product with low reliability.

[0021] [Number of fluffs 1-3mm long] The number of fluffs having a length of 1 to 3 mm observed on the rubber reinforcing coating of the present invention when measured with a fluff detector using a laser beam is preferably 1,000 fluffs / 10 m or less. Satisfying these conditions is preferable because it reduces the rate of variation in rubber adhesion, making it more reliable.

[0022] The number of fluffs is measured using a fluff detector using laser light, such as an F-Index Tester manufactured by Shikibo Co., Ltd. or a Laser Spot manufactured by Keisokuki Kogyo Co., Ltd.

[0023] [Diameter variation CV%] In measurement by a fuzz detector using a laser beam, the diameter variation rate CV% observed for the rubber reinforcing cord of the present invention is preferably 9% or less. When this condition is satisfied, the strength variation rate CV% of the rubber reinforcing cord is particularly low, which is preferable because the strength variation rate as rubber can be kept low.

[0024] [Twisted Yarn] In a preferred embodiment of the rubber reinforcing cord of the present invention, the cord is a plied yarn obtained by second twisting two or more first twisted yarns in the direction opposite to the twist direction of the first twisted yarn, and the twist coefficient TM of the first twisted yarn and the plied yarn, expressed by the following formula, is 3 or more. TM=T×√D / 1055 (where TM is the twist coefficient, T is the number of twists (turns / m), and D is the total fineness (tex) of the stretch-break textured yarn.)

[0025] By setting the twist factor TM to 3 or more, high adhesion to rubber can be achieved due to the unevenness of the surface caused by the twist and the fluff formed from the ends of the single fibers. By twisting in the above manner, the filaments that make up the fluff are tightly bound within the twisted yarn, making them less likely to fall off and reducing the variability of their physical properties. As a result, for example, fluff fall-off can be significantly reduced when the reinforcing cord comes into contact with guides, jigs, etc. at high speed during the processing of rubber tires, resulting in excellent processability and adhesion after processing. Furthermore, elongation under low loads is improved, stress on the filaments can be dispersed, and high fatigue resistance can be achieved.

[0026] [High-strength, high-elasticity fiber] In the present invention, the stretch-break textured yarn is preferably a stretch-break textured yarn made of a high-strength, high-elasticity fiber having a tensile strength of 10 cN / dtex or more and an elastic modulus of 300 cN / dtex or more as measured by the initial tensile resistance according to JIS L 1017.

[0027] Examples of high-strength, high-modulus fibers that satisfy this condition include glass fibers, aromatic polyamide fibers (aramid fibers), carbon fibers, polyparaphenylene benzoxal fibers, aromatic polyester fibers, and ultra-high molecular weight polyethylene fibers. Among these, aromatic polyamide fibers are preferred.

[0028] The aromatic polyamide fibers themselves may be conventionally known and may be produced by known methods, such as those described in JP-A-49-100322, JP-A-47-10863, JP-A-58-144152, and JP-A-4-65513.

[0029] Among aromatic polyamide fibers, para-aromatic polyamide fibers are preferred because of their excellent heat resistance and strength. Para-aromatic polyamide fibers are polyamide fibers in which the extended chain bonds of aromatic polyamides are coaxial or parallel and point in opposite directions. Specific examples include polyparaphenylene terephthalamide fibers (e.g., "Twaron (registered trademark)" manufactured by Teijin Aramid BV) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers, which are copolymerized aromatic polyamide fibers (e.g., "Technora (registered trademark)" manufactured by Teijin Limited).

[0030] In particular, copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide fibers (for example, Technora (registered trademark) manufactured by Teijin Limited), which are copolymer-type aromatic polyamide fibers, are preferred because of their excellent flex fatigue resistance.

[0031] [Low strength, low modulus fiber] The rubber reinforcing cord of the present invention is preferably a plied yarn obtained by twisting two or more first twisted yarns in the opposite direction to the twisting direction of the first twisted yarn. This plied yarn preferably consists of one first twisted yarn and the other first twisted yarn. One of the first twisted yarns constituting this plied yarn is a first twisted yarn obtained by twisting the above-mentioned stretch-break textured yarn. The other first twisted yarn constituting the plied yarn is preferably a twisted yarn made of low-strength, low-elasticity fibers having lower strength and elasticity than the stretch-break textured yarn.

[0032] That is, a preferred embodiment of the present invention is a rubber reinforcement cord comprising a stretch-break processed yarn having an average fiber length of 30 to 120 cm and a twisted yarn of a low-strength, low-elastic modulus fiber having a strength and elastic modulus lower than those of the stretch-break processed yarn, wherein the strength of the rubber reinforcement cord is 8.0 cN / dtex or more and the rate of variation in strength, CV%, is 20% or less.

[0033] Examples of low-strength, low-elastic modulus fibers include polyurethane fibers, aliphatic polyamide fibers such as nylon 6, nylon 66, and nylon 46, polyester fibers such as polyethylene terephthalate and polytrimethylene terephthalate, polyvinyl alcohol fibers known as vinylon, and rayon fibers. Among these, polyurethane fibers and polyethylene terephthalate fibers with a low degree of polymerization are particularly preferred because they have a low elastic modulus and a breaking elongation of 30% or more, particularly 100% or more. Using these fibers as twisted yarns of low-strength, low-elastic modulus fibers allows for easy handling during the twisting process and easy stretchability under low loads.

[0034] [Adhesion treatment] When aromatic polyamide fiber bundles are used as high-strength, high-elasticity fibers for stretch-break processed yarns, it is preferable to use them as rubber reinforcing cords after performing an adhesive treatment by applying a resorcinol-formalin-latex adhesive to the surface of the aromatic polyamide fibers, from the viewpoint of adhesiveness at high temperatures, etc.

[0035] This adhesive treatment may be carried out by impregnating the rubber reinforcing cord of the present invention in a solution of resorcinol-formalin-latex adhesive, or by immersing high-strength, high-modulus stretch-break yarn fibers in a solution of resorcinol-formalin-latex adhesive and then twisting the fibers.

[0036] [Resorcinol, formalin, latex adhesive] The amount of resorcinol-formalin-latex adhesive attached during the adhesive treatment is preferably 5 to 20% by weight based on the weight of the rubber reinforcing cord. After the adhesive treatment, the resorcinol-formalin-latex adhesive is attached to the surface and inside of the rubber reinforcing cord. By having the amount of resorcinol-formalin-latex adhesive attached be 5 to 20% by weight based on the weight of the rubber reinforcing cord, excellent adhesive strength can be obtained.

[0037] To adhere the resorcinol-formalin-latex adhesive to the rubber reinforcing cord, the cord is surface treated with a solution containing resorcinol-formalin-latex resin. The concentration of this solution is preferably 5 to 20% by weight. A concentration of less than 5% by weight is undesirable as sufficient adhesion is not possible, while a concentration of more than 20% by weight is undesirable as scum is likely to form, which can cause problems.

[0038] In the resorcinol-formalin-latex resin, the molar ratio of resorcinol to formaldehyde is preferably 1:0.6 to 1:8, more preferably 1:0.8 to 1:6. If the amount of formaldehyde is less than this range, the crosslink density of the resorcinol-formalin condensate decreases and the molecular weight decreases, which reduces the cohesive strength of the resin layer and leads to reduced adhesion and flex fatigue resistance, which is undesirable. On the other hand, if the amount of formaldehyde is greater than this range, the increased crosslink density hardens the resorcinol-formalin condensate, which inhibits the compatibility of the resorcinol-formalin-latex resin with the rubber during co-vulcanization, tending to reduce adhesion, which is undesirable.

[0039] The blending ratio of resorcinol-formalin to latex in the resorcinol-formalin-latex resin, expressed as a solids weight ratio, is preferably 1:3 to 1:16, more preferably 1:4 to 1:10. If the ratio of latex is less than this range, the amount of co-vulcanized component with rubber is small, which tends to reduce adhesive strength, which is undesirable. On the other hand, if the ratio of latex is greater than this range, the adhesive film cannot be sufficiently strong, which tends to reduce adhesive strength and durability, and the adhesive-treated composite cord becomes significantly tacky, which may reduce processability, such as come-up and handleability, during the adhesive treatment and belt molding processes, which is undesirable.

[0040] Resorcinol may be a precondensate of resorcinol-formalin which has been oligomerized in advance or a polynuclear chlorophenol-based precondensate of resorcinol-formalin which chlorophenol and resorcinol are oligomerized with formalin. These may be used alone or in combination.

[0041] 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 alone or in combination.

[0042] When the surface of a single yarn of a rubber reinforcing cord is 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 a high affinity with the surface and can increase the strength of the resin layer.

[0043] Resorcinol-formalin-latex resin may be used in combination with a crosslinking agent. Examples of crosslinking agents include amines, ethylene urea, and blocked isocyanate compounds. Among these, blocked isocyanate compounds are preferred because of their good stability over time and good interaction with pretreatment agents. Preferred blocked isocyanate compounds are dimethylpyrazole-blocked, methyl ethyl ketone oxime-blocked, and caprolactam-blocked blocked isocyanates. Two or more of these may be used in combination.

[0044] [Surface treatment with epoxy compound] High-strength, high-modulus fibers, including para-aromatic polyamide fibers, generally have an inert surface, making them difficult to bond to other substances. Therefore, to ensure sufficient adhesion, it is preferable to perform a surface treatment on rubber reinforcing cords before the adhesive treatment, in which the cords are immersed in a solution containing an epoxy compound to impregnate the cords with the epoxy compound. This surface treatment improves the chemical affinity between the aromatic polyamide fiber and the resorcinol-formalin-latex resin.

[0045] When aromatic polyamide fibers are used as the high-strength, high-modulus fibers for stretch-breaking rubber reinforcing cords, the solids content of the epoxy compound attached to the aromatic polyamide fiber monofilament is preferably 0.05 to 5.0 wt %, more preferably 0.2 to 2.0 wt %, based on the weight of the monofilament. Amounts less than this range are undesirable because the epoxy resin layer formed on the surface of the monofilament is insufficient, making it difficult to achieve adhesion between the aromatic polyamide fiber monofilaments and between the monofilament and the resorcinol-formaldehyde-latex resin. On the other hand, amounts greater than this range result in the monofilaments being strongly bundled together by the epoxy resin, resulting in a stiffer composite cord and poorer resistance to flex fatigue.

[0046] Specific examples of epoxy compounds used in 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 above-mentioned halogen-containing epoxides; and polyepoxide compounds obtained by oxidizing unsaturated compounds with peracetic acid or hydrogen peroxide, such as 3,4-epoxycyclohexene epoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate, and bis(3,4-epoxy-6-methyl-cyclohexylmethyl)adipate.

[0047] Of these, reaction products of polyhydric alcohols and epichlorohydrin are preferred, and compounds formed from polyepoxide compounds such as polyglycidyl ether compounds of polyhydric alcohols and curing agents are also preferred.

[0048] When a polyepoxide compound is used, an emulsifier such as sodium alkylbenzenesulfonate or dioctyl sulfosuccinate sodium salt may be used to form an emulsion. The polyepoxide compound may be used in combination with an amine-based or imidazole-based curing agent, a blocked polyisocyanate which is an addition compound of a polyisocyanate with a blocking agent such as oxime, phenol, or caprolactam, or ethylene urea which is a reaction compound with ethyleneimine.

[0049] When a polyepoxide compound is used, the weight of the polyepoxide compound is A parts by weight, and the weight of the curing agent, blocked polyisocyanate, and ethylene urea is B parts by weight, and the relationship between the two preferably satisfies the condition 0.05≦A / (A+B)≦0.9. When this range is met, particularly good adhesiveness can be obtained. [Example]

[0050] The present invention will be described below with reference to examples.

[0051] (1) Average fiber length 200 single fibers were randomly extracted from the stretch-break textured yarn without breaking them, and the length of the single fibers was measured in an extended state, and the average value of the 200 fibers was calculated.

[0052] (2) Total fineness The total fineness (weight) including the attached resin was measured in accordance with JIS L1017.

[0053] (3) Tensile strength and its variation rate CV% The reinforcing yarn was subjected to a tensile test 10 times in accordance with JIS L 1017, and the load-elongation curve was calculated. The tensile strength was calculated by dividing the tensile strength at break by the fineness of the rubber reinforcing cord, including the amount of resin attached, and the average value was calculated. The coefficient of variation (CV%) was calculated using the standard deviation and average value of the tensile strength measured 10 times according to the following formula. CV% = 100 x (standard deviation of tensile strength) / (average value of tensile strength)

[0054] (4) Number of fluffs 1 to 3 mm long Using a laser spot fluff detector using laser light manufactured by Keisokuki Kogyo Co., Ltd., the number of fluffs in the rubber reinforcing cords with lengths of 1 to 3 mm was measured three times at a sweep speed of 8 m / min, and the average number was calculated.

[0055] (5) Diameter variation rate CV% Measurements were taken three times at a sweep speed of 8 m / min using a laser spot manufactured by Keisokuki Kogyo Co., Ltd., and the average value was calculated.

[0056] (6) Adhesive adhesion rate Measurements were taken at 20 locations in 5m increments (total length 100m) and the amount of adhesion was calculated using the formula below. The average value per 100m (average value of 20 locations) as well as the maximum and minimum values ​​among the 20 locations were measured. Adhesive adhesion rate = 100 x (weight of dipped yarn treated for rubber adhesion - weight of yarn before treatment) / weight of yarn before treatment

[0057] (7) Rubber adhesion and its variability CV% This shows the adhesive strength between rubber reinforcing cords and rubber. Five cords were embedded near the surface of an unvulcanized rubber sheet with a carcass compound that mainly contains natural rubber, and the test was conducted at 150°C for 30 minutes at 500N / cm 2 The test piece was vulcanized under a press pressure of 1000 psi, and then the force required to peel off the three cords, leaving only the cords at both ends, in a direction 90 degrees to the rubber sheet surface at a speed of 200 mm / min was measured three times, and the average value was calculated. The coefficient of variation (CV%) was calculated using the standard deviation and average value of the rubber adhesion measured three times, according to the following formula: CV% = 100 x (standard deviation of rubber adhesion) / (average rubber adhesion)

[0058] (8) Fatigue resistance and its variability CV% A load of 1.6 cN / dtex was applied to a rubber-reinforced cord containing resorcinol-formaldehyde-latex resin, and the cord was attached to a 10 mm diameter roller and subjected to a reciprocating motion at 100 rpm. After 100,000 repeated flexing cycles, the composite cord was removed and its remaining strength was measured three times. The strength retention rate was calculated from the average value and the strength before the repeated flexing cycles. The coefficient of variation (CV%) was calculated using the standard deviation and average value of the residual strength after repeated bending measured three times according to the following formula. Coefficient of variation CV% = (standard deviation of residual strength after flexural fatigue) / (average value of residual strength after flexural fatigue) x 100

[0059] (9) Elastic modulus indicated by the initial tensile resistance according to JIS L 1017 A tensile test similar to that for tensile strength was conducted, and the load-extension curve was calculated from the slope of the tangent to the maximum point of the load change relative to the extension change (maximum point of the tangent angle) near the origin.

[0060] Example 1 Using a stretch-broken yarn manufacturing device as shown in Figure 1, continuous long fiber bundle 1 was produced, with a total fiber size of 1100 dtex, a single fiber size of 0.8 dtex, a tensile strength of 24 cN / dtex, and a JIS L A single crimp-free para-aramid fiber (Technora, manufactured by Teijin Limited) having an elastic modulus of 530 cN / dtex, as indicated by an initial tensile resistance of 1017, was used, and the continuous long fiber bundle was stretch-broken between nip rollers 2 and 4 at a stretch-break ratio of 6.7 (surface speed of nip roller 4 / surface speed of nip roller 2) and a surface speed of nip roller 4 of 300 m / min. Subsequently, the stretch-broken fiber bundle was taken out from nip roller 4 by suction with suction air nozzle 5, and the fiber bundle was passed through conjugating air nozzle 6 having a swirling flow in a direction to apply a Z twist, thereby entangling the fiber bundle and winding the ends of the stretch-broken fibers, thereby bundling. The fiber bundle then passed through nip roller 7 and was taken up by winding device 9, to obtain a stretch-broken textured yarn 8 having a total fineness of 440 dtex, an average fiber length of 45 cm, and a tensile strength of 22 cN / dtex. At this time, the distance (stretch-break length) between nip roller 2 and nip roller 4 was set to 100 cm. This stretch-break textured yarn was twisted in the Z direction at 550 t / m using a ring twisting machine to form a first twisted yarn.

[0061] Furthermore, polyethylene terephthalate fiber (Tetron (registered trademark) P903BZ 560 dtex manufactured by Teijin Limited) was used as the low-strength, low-elasticity fiber, and was twisted in the Z direction at 550 t / m in a ring twisting process to form a first twisted yarn. Two first twisted yarns of stretch-break textured yarn and one first twisted yarn of polyethylene terephthalate fiber were twisted in the S direction at 550 t / m to form a fiber cord.

[0062] This fiber cord was subjected to the following treatment: For the first bath, 0.5 g of piperazine was dispersed in 978.5 g of water, 1 g of Neocol SW-30 (dioctyl sulfosuccinate sodium salt, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added (solid content: 30 wt%), and then 20 g of a polyepoxide compound (Denacol EX314, manufactured by Nagase ChemteX Corporation) was dispersed in the solution (solid content: 2 wt%) to prepare a treatment solution.

[0063] The fiber cord was immersed in this first-bath treatment solution, dried at 150°C for 2 minutes, and then heat-treated at 240°C for 1 minute to obtain a one-bath-treated fiber cord. The amount of the first-bath treatment agent adhering to the obtained one-bath-treated fiber cord was measured and found to be 0.5% by weight.

[0064] Next, the second bath was prepared. First, resorcinol-formalin precondensate and Sumikanol S700 (Sumitomo Chemical Co., Ltd., 65% by weight aqueous solution) were added to a caustic soda solution and thoroughly stirred to disperse. To this, formalin was added to achieve an R / F ratio of 1 / 0.5 (molar ratio), mixed uniformly, and then aged at 25°C for 6 hours.

[0065] Next, a mixture of Nippol 2518FS (Nippon Zeon Co., Ltd., vinylpyridine-styrene-butadiene rubber latex) and Nippol LX-111A (Nippon Zeon Co., Ltd., polybutadiene rubber latex) (vinylpyridine-styrene-butadiene rubber latex / polybutadiene rubber latex = 75 / 25 (weight ratio)) was mixed with the resorcinol-formalin precondensate dispersion at a solids ratio (RF / L ratio) of 1 / 9 by weight (treatment liquid concentration 10 wt%) and aged at 25°C for 24 hours. The resulting treatment liquid was used as the second bath treatment liquid. After the first bath treatment, the fiber cord was immersed in the second bath treatment solution, dried at 150° C. for 2 minutes, and then heat-treated at 240° C. for 1 minute. The results of the obtained rubber reinforcing cord are shown in Table 1.

[0066] Example 2 For the stretch-break textured yarn of Example 1, the twisted yarn obtained by ring twisting was changed to a twisted yarn in the Z direction at 900 t / m to obtain a first twisted yarn. Two of these first twisted yarns were used to give a twisted yarn in the S direction at 900 t / m to obtain a fiber cord. This fiber cord was used to obtain a rubber reinforcing cord in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0067] Example 3 For the stretch-break textured yarn of Example 1, the twisted yarn obtained by ring twisting was changed to a twisted yarn in the Z direction at 600 t / m to obtain a first twisted yarn. This first twisted yarn was used to twist in the S direction at 600 t / m to obtain a fiber cord. This fiber cord was used to obtain a rubber reinforcing cord in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0068] Comparative Example 1 For the stretch-break textured yarn of Example 1, the twisted yarn obtained by ring twisting was changed to a twisted yarn in the Z direction at 200 t / m to obtain a first twisted yarn. Two of these first twisted yarns were used to obtain a fiber cord by twisting in the S direction at 200 t / m. Using this fiber cord, a rubber reinforcing cord was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0069] Comparative Example 2 A rubber reinforcing cord was obtained in the same manner as in Example 1, except that a single crimp-free para-aramid fiber (Technora) having a total fineness of 440 dtex, a single fiber fineness of 0.8 dtex, and a tenacity of 24 cN / dtex was used and ring twisted without being subjected to stretch-breaking. The evaluation results are shown in Table 1.

[0070] [Table 1]

[0071] The rubber reinforcing cords obtained in the Examples were superior to the rubber reinforcing cords obtained in the Comparative Examples in terms of strength, rubber adhesion, and fatigue resistance, and also had a low CV%. [Industrial Applicability]

[0072] The rubber reinforcing cord of the present invention can be used to reinforce rubber, particularly rubber tires. The rubber reinforcing cord of the present invention allows the thickness of the rubber layer to be thinner than that of other rubber reinforcing cords while maintaining excellent tire properties, thereby contributing to improved fuel economy, etc. [Explanation of symbols]

[0073] 1. Continuous long fiber bundle 2, 4, 7 Nip rollers 3 Guide to prevent disturbance of fiber bundle during stretch breaking 5 Suction air nozzle 6. Conjugated air nozzle 8. Draft-breaking processed yarn 9 Winding device

Claims

1. A rubber reinforcement cord comprising a stretch-breaking yarn, The rubber reinforcing cord is a ply-twisted yarn obtained by second-twisting two or more first-twisted yarns in the direction opposite to the twisting direction of the first-twisted yarns, The twist coefficient TM of the first twisted yarn and the plied yarn, expressed by the following formula, is 3 or more, TM=T×√D / 1055 (where TM is the twist coefficient, T is the number of twists (turns / m), and D is the total fineness (tex) of the stretch-break textured yarn.) One of the first twisted yarns constituting the ply yarn is a first twisted yarn obtained by twisting a stretch-break textured yarn, the other of the first twisted yarns constituting the ply-twisted yarn is a twisted yarn of low-strength, low-elasticity fiber having lower strength and elasticity than the stretch-break textured yarn; The stretch-breaking yarn is an aromatic polyamide fiber, The average fiber length of the stretch-break processed yarn is 30 to 120 cm. The rubber reinforcing cord is characterized in that the tensile strength is 8.0 cN / dtex or more and the tensile strength variation rate CV% is 20% or less.

2. 2. The rubber reinforcing cord according to claim 1, wherein the number of fluffs having a length of 1 to 3 mm observed on the rubber reinforcing cord is 1,000 or less per 10 m when measured with a fluff detector using a laser beam.

3. 2. The rubber reinforcing cord according to claim 1, wherein the diameter variation rate CV% of the rubber reinforcing cord observed in measurement with a fuzz detector using a laser beam is 9% or less.

4. A rubber reinforcing cord comprising the rubber reinforcing cord according to any one of claims 1 to 3 and a resorcin-formalin-latex adhesive adhered thereto, wherein the amount of the resorcin-formalin-latex adhesive adhered is 5 to 20 wt % based on the weight of the rubber reinforcing cord.

5. A method for producing a rubber reinforcing cord, comprising the step of immersing the rubber reinforcing cord according to any one of claims 1 to 3 in a treating agent containing a resorcinol-formalin-latex adhesive at a concentration of 5 to 20% by weight.

6. A rubber tire comprising the rubber reinforcing cord according to claim 1.

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