JP2019049076A - Fiber cord for rubber reinforcement - Google Patents

Abstract

To provide a fiber cord for rubber reinforcement improved in heat-resistant adhesion of fiber with rubber which cannot be achieved by a prior art, and improved in stress relaxation of a rubber-cord composite material.SOLUTION: The fiber cord for rubber reinforcement has a stress relaxation rate of 50% or less by a rubber-cord composite material compression test, preferably a stress relaxation gradient of 27 or less by the rubber-cord composite material compression test, and preferably a maximum stress of 500 N or more by the rubber-cord composite material compression test. Preferably, the ratio (A/B) of a major axis A to a minor axis B in a section of a hose reinforcing fiber is 1.3 times or greater, and the Gurley cord hardness is 12 mN or less.SELECTED DRAWING: None

Description

  The present invention relates to fiber cords used in rubber products such as tires, hoses and belts.

  Fibers such as polyester and aramid are conventionally and widely used as reinforcements for rubber products such as tires, hoses and belts because they have excellent strength, elastic modulus and thermal dimensional stability. However, when embedded in a rubber product as a reinforcing material and used for a long time, the cord is degraded, stress relaxation of the rubber-cord composite occurs, adhesion between the rubber and the cord decreases, and the cord can withstand use. There was a problem that it disappeared.

  The following proposals have been made as methods for solving these problems.

  In Patent Document 1, a polyester fiber is treated with a treating agent containing a polyepoxide compound at the time of spinning or drawing, and then treated as a cord, and then treated with a treating agent containing resorcinol formalin rubber latex (RFL) and a chlorophenol compound. There is disclosed a polyester fiber for rubber reinforcement characterized in that the treated rubber has a Gurley hardness of 300 mg or less by blending and processing a polybutadiene rubber latex to the rubber latex.

Patent Document 2 is a hose reinforcing polyester fiber cord obtained by applying a treatment agent containing resorcin-formalin-rubber latex (RFL) and chloro-modified resorcinol (P) to polyester fiber to which a polyepoxide compound has been applied in advance. Thus, a hose reinforcing polyester fiber cord is disclosed, which is characterized in that the treating agent meets all the following requirements.
(A) R / F = 1 / 0.5 to 1/3 (molar ratio)
(B) RF / L = 1/3 to 1/15 (weight ratio)
(C) P / RFL = 1/1 to 1/5 (weight ratio).
(D) Aging time of RF: 4 to 8 hours (wherein R is the amount of resorcin, F is the amount of formalin, L is the amount of rubber latex, P is the amount of chloromodified resorcin, RF is the amount of resorcin and formalin, and RFL is resorcinol. Indicates the amount of formalin and rubber latex.)
In Patent Document 3, a method of reducing stress relaxation of a rubber hose by adopting a multicomponent copolymer rubber composed of a blend of acrylonitrile-butadiene rubber and a blend mainly composed of acrylic rubber in the inner tube rubber layer. Is disclosed.

JP-A-11-286876 JP, 2008-202182, A Japanese Patent Application Laid-Open No. 62-28395

  However, according to Patent Document 1 and Patent Document 2, although the initial adhesiveness is sufficient, the heat resistant adhesive force is not sufficient. According to Patent Document 3, although the improvement of stress relaxation is obtained by the modification of the rubber, the improvement of stress relaxation by the reinforcing fiber is not obtained, and both the initial adhesion and the heat resistant adhesion are not sufficient. Therefore, the present invention is to provide a rubber reinforcing fiber cord having improved heat-resistant adhesion between fiber and rubber and improved stress relaxation of a rubber-cord composite, which can not be achieved by the above-mentioned prior art. It will be an issue.

The present invention is intended to solve the above problems, and adopts the following means. That is, the rubber-reinforcing fiber cord of the present invention is a rubber-reinforcing fiber cord characterized by having a stress relaxation rate of 50% or less in the rubber-cord composite compression test. In the rubber reinforcing fiber cord of the present invention, the following (1) to (4) are more preferable conditions, and by applying these, further excellent effects can be expected.
(1) In the rubber-cord composite compression test, the slope of stress relaxation is 27 or less (2) In the rubber-cord composite compression test, the maximum stress is 500 N or more (3) Fiber cord for rubber reinforcement The ratio (A / B) of the major axis A to the minor axis B in the cross section of the cross section is 1.3 or more (4) the Gurley cord hardness is 12 mN or less

  According to the present invention, it is for rubber reinforcement having improved heat-resistant adhesion when used in a rubber product which could not be achieved by the conventional rubber reinforcing fiber cord and improved stress relaxation of the rubber-cord composite. A fiber cord is obtained.

It is a perspective view of a measuring device of Gurley cord hardness. It is the schematic which shows the relationship between a cord cross section, and major axis A and minor axis B. It is the schematic of the positional relationship of the code | cord and rubber plate in the sample of a rubber-cord composite compression test.

  Hereinafter, the present invention will be described in detail.

  The rubber reinforcing fiber cord of the present invention (hereinafter sometimes referred to as a cord) is a cord made of organic fibers. The fiber cord for rubber reinforcement of the present invention is preferably used for various rubber members for various uses such as tires, belts, hoses, etc. for automobiles, and durability can be improved.

  The organic fiber used for the rubber reinforcing fiber cord is preferably in the form of multifilament. Also, the material constituting the organic fiber is not particularly limited, but it is versatile to contain at least one selected from polyethylene terephthalate, polyethylene naphthalate, nylon 6, nylon 66, nylon 46, polyvinyl alcohol, rayon and aramid. It is preferable in terms of durability and industrial productivity. Among them, at least one selected from polyethylene terephthalate, nylon 66, and aramid is more preferable in view of versatility, durability, and industrial productivity.

  In addition, the organic fiber used in the present invention may be one to which a polyepoxide compound is given in advance. Examples of the polyepoxide compound that can be used in the present invention include compounds containing 0.1 g equivalent or more of at least two or more epoxy groups in one molecule per 100 g of the compound. Specifically, 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 oxidation of unsaturated compounds with hydrogen peroxide or the like Such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboarylate, bis (3,4-epoxy-6-methyl-cyclohexylmethyl) adipate, phenol novolac type, hydroquinone type Biphenyl type, bisphenol S type, brominated novolak type, xylene modified novolak type, phenolglyoxal type, trisoxyphenylmethane type, trisphenol PA type, bisphenol type Aromatic polyepoxides such as polyepoxides can be mentioned. Particularly preferred are sorbitol glycidyl ether type and cresol novolac type polyepoxides.

  These compounds are usually used as an emulsion or solution and applied to organic fibers. For solution, the compound is used as it is or dissolved in water. In order to make an emulsion, one which is dissolved in a small amount of a solvent is used, as necessary, to emulsify it using a known emulsifier such as sodium alkylbenzene sulfonate, dioctyl sulfosuccinate sodium salt, nonylphenol ethylene oxide adduct and the like.

  The polyepoxide compound may be applied together with a spinning oil in the spinning process of organic fibers. The adhesion amount of the polyepoxide compound at this time is preferably in the range of 0.05 to 5% by weight. By setting the adhesion amount of the polyepoxide compound in the above range, the effect of the polyepoxide compound is sufficiently exerted, the adhesion between the organic fiber and the rubber can be sufficiently obtained, and the flexibility of the cord is maintained. It becomes favorable also about process passability after a process.

  The organic fibers used in the present invention are not restricted by the fineness or the number of filaments, but generally, the total fineness is preferably 200 to 5,000 dtex, 30 to 1,000 filaments are preferable, and the total fineness 250 to 3,000 dtex, 50 to 500 filaments are particularly preferable. If it is less than 20 dtex, the strength of the cord may be insufficient, and if it exceeds 5,000 dtex, the cord may become thick and the handleability may be deteriorated. In addition, if it is less than 30 filaments, the cord becomes hard and there is a possibility that the handleability may be deteriorated. If it exceeds 500 filaments, the fluff may be increased and the quality may be reduced.

  The fiber cord for rubber reinforcement of the present invention is usually obtained by twisting the above-mentioned organic fiber to form a raw cord (twist cord) and thereafter treating with an adhesive.

  When twisting an organic fiber, it is preferable that the twist coefficient K1 is 200 <= K1 <= 2000, More preferably, it is 200 <= K1 <= 1500. By setting the twist coefficient in this range, good fatigue resistance and good cord strength can be obtained.

The twist coefficient K is represented by the following equation.
K = T × D ^1/2
(K: twist coefficient, T: twist number per unit length (times / 10 cm), D: total fineness dTex)
As an RFL adhesive, practical rubber adhesion can be obtained by using an RFL processing agent in which a rubber latex (L) is added to resorcin-formalin initial condensate (RF) which is usually used.

  The RFL adhesive comprises resorcin-formalin-rubber latex (RFL). The resorcin-formalin-rubber latex is a mixture of resorcin-formaldehyde initial condensate and a rubber latex. The resorcin-formalin-rubber latex (RFL) is preferably prepared using a resorcin-formaldehyde initial condensation product obtained by the initial condensation under an alkaline catalyst. For example, resorcinol and formaldehyde are added and mixed in an alkaline aqueous solution containing an alkaline compound such as sodium hydroxide, and allowed to stand at room temperature for several hours to precondensate resorcinol with formaldehyde, and then rubber latex is added to mix the emulsion. It is prepared by the following method.

  The resorcin-formaldehyde precondensate has a molar ratio of resorcin to formaldehyde of 1: 0.30 to 1: 5.0, preferably 1: 0.75 to 1: 2.0. Good adhesion can be obtained by setting the molar ratio of formaldehyde to the above range.

  Examples of rubber latex used for preparation of resorcinol formalin rubber latex 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 and the like can be mentioned, and these can be used alone or in combination.

  Moreover, as for the glass transition temperature of the latex to be used, the thing of -30 degreeC or less is preferable. By using a latex having a glass transition temperature lower than the above temperature, a more flexible adhesive film can be formed, and the adhesion between the rubber and the resin layer is enhanced during vulcanization of compounding the rubber and the cord, and sufficient adhesion is obtained. Can demonstrate.

  The resorcinol-formalin-rubber latex preferably has a blending ratio of resorcin-formaldehyde initial condensate to rubber latex (resorcinol-formaldehyde initial condensate / rubber latex) of 1/8 or less in solid content weight. By setting the compounding ratio in the above range, a flexible adhesive film can be formed, and the adhesion between the rubber and the resin layer can be enhanced at the time of vulcanization of compounding the rubber and the cord, and sufficient adhesive power can be exhibited.

  The rubber-reinforcing fiber cord of the present invention is a rubber-reinforcing fiber cord characterized by having a stress relaxation rate of 50% or less in a rubber-cord composite compression test. If the stress relaxation rate exceeds 50%, the set of the rubber-cord composite becomes large, and for example, the reduction of the crimping pressure in the case of forming a rubber hose is accelerated, and the life as a rubber product is shortened. The method for obtaining a rubber reinforcing fiber cord having a stress relaxation rate of 50% or less is not particularly limited. For example, only latex (L) having a glass transition temperature of -30 ° C or less is used, and resorcinol formaldehyde precondensate and rubber are used. After applying an adhesive that makes the compounding ratio of latex (resorcinol formaldehyde precondensate / rubber latex) 1/8 or less by solid weight, the heat treatment temperature after application of the adhesive is 180 to 220 ° C. Can be achieved by

  The slope of stress relaxation in the rubber-cord composite compression test for the rubber reinforcing fiber cord in the present invention is preferably 27 or less. By setting it to 27 or less, it is possible to suppress the set of the rubber-cord complex, which is preferable. The method for obtaining a rubber reinforcing fiber cord having a stress relaxation slope of 27 or less in the rubber-cord composite compression test is not particularly limited. For example, the heat treatment temperature after application of the adhesive is 180 to 220 ° C. This can be achieved by applying a pressure of not less than 5 MPa and applying pressure using a nip roll.

  The maximum stress in the rubber-cord composite compression test of the rubber reinforcing fiber cord in the present invention is preferably 500 N or more. By setting it as 500 N or more, the initial stress of a rubber-cord complex becomes high, for example, the squeeze pressure at the time of using a rubber hose becomes high, and it can prevent the liquid leak etc. of a rubber hose. The method for obtaining a rubber reinforcing fiber cord having a maximum stress of 500 N or more in the rubber-cord composite compression test is not particularly limited. For example, only latex (L) having a glass transition temperature of -30 ° C or less is used. After applying an adhesive that makes the blending ratio of formaldehyde precondensate to rubber latex (resorcinol formaldehyde precondensate / rubber latex) 1/8 or less by weight of solid content, the cord tension in dry processing is 1. It can be achieved by setting it to 0 to 2.0 cN / dTex.

  The rubber-cord composite compression test will be described later.

  The Gurley cord hardness of the rubber reinforcing fiber cord in the present invention is preferably 12 mN or less. By setting the diameter to 12 mN or less, the followability of the cord to the rubber is improved in the rubber-cord composite, and good adhesion can be obtained. The method for setting the Gurley cord hardness to 12 mN or less is not particularly limited, but after the heat treatment temperature after adhesive application is set to 180 to 220 ° C., the tension at the time of mechanical softening is 0.5 cN to 5.0 cN / dtex It can be achieved by

  In order to apply the adhesive to the organic fiber or the green cord, a method of dipping in a dip of the adhesive is preferable. The solid content concentration of the adhesive in the dip solution is preferably 3 to 30% by weight, more preferably 5 to 25% by weight. By setting the solid content concentration of the adhesive in the dip solution to the above-mentioned range, it is possible to obtain sufficient adhesive strength and maintain the storage stability of the dip solution, and also uniformly deposit the dip solution on the surface of the organic fiber cord The balance on making them The adhesion amount of the adhesive to the rubber reinforcing fiber cord is preferably 0.2 to 5% by weight, more preferably 0.5 to 4% by weight, based on the weight of the rubber reinforcing fiber cord. Good adhesion can be obtained by setting the adhesion amount of the adhesive in the above-described range, and fatigue resistance is improved by maintaining the flexibility of the cord. Furthermore, good operation stability can be obtained by suppressing the gum buildup of solids on the roll during the treatment process.

  In order to control the adhesion amount of the adhesive to the organic fiber or the raw cord, for example, a method such as squeezing with a pressure roller, scraping with a screever, blowing off by compressed air, or suction can be used.

  The organic fiber or green cord to which the adhesive is applied is dried (dry treatment) at 70 to 150 ° C. for 0.5 to 5 minutes, and then heat treated at 180 to 220 ° C. for 0.5 to 5 minutes (hot treatment) Subsequently, in order to control the physical properties of the cord, heat treatment at a temperature of 180 to 220 ° C. for 0.5 to 5 minutes (hereinafter referred to as normalizing treatment) is preferable. In this way, an adhesive coating can be formed on the fiber surface, but in some cases drying can be omitted. The upper limit of the temperature is not limited, but by setting the heat treatment temperature in the above range, a more flexible adhesive film can be formed, and the adhesion between the rubber and resin layer is increased at the time of vulcanization to combine rubber and cord, sufficient adhesion It can exert its power. On the other hand, if the temperature of the hot treatment and the normalizing treatment is less than 180 ° C., adhesion to rubber may be insufficient and it is more preferable to set it to 180 ° C. or more. The cord tension at the time of dry processing is preferably 0.1 to 2.0 cN / dTex. With this range, the strength of the code can be kept good. Furthermore, by setting the cord tension during dry processing to 1.0 to 2.0 cN / dTex, the adhesive can be localized on the cord surface, and the maximum stress in the rubber-cord composite compression test is increased, which is further preferable. .

  The rubber reinforcing fiber cord may be provided with an adhesive, subjected to drying and heat treatment steps, and then subjected to mechanical softening treatment to reduce the cord hardness. Here, the mechanical softening treatment is a treatment for softening the cured resin during the drying heat treatment by bending the cord with the edge blade.

  The angle at which the cord is bent by the edge blade is preferably 100 ° to 130 °, and more preferably 115 ° to 125 °. By setting the bending angle in the above range, the resin can be effectively softened.

  Further, the cord tension at the time of mechanical softening treatment is preferably 0.5 to 5.0 cN / dtex, and more preferably 3.0 to 4.0 cN / dtex. By setting the cord tension in the above range, it is possible to make the cord flexible as long as good cord strength can be maintained.

  The rubber reinforcing fiber cord preferably has a flat shape in which the ratio (A / B) of the major axis A to the minor axis B in the cross section of the cord is 1.3 or more. Here, the major diameter A means the longest diameter in the cross section of the cord, and the minor diameter B means the longest diameter among the diameters orthogonal to the major diameter A. FIG. 2 shows the relationship between the cross section of the cord and the major axis A and the minor axis B. As a method of forming the cross section of the cord into a flat shape, for example, a method of applying an adhesive, drying and heat treatment, winding while pressing with a nip roll or the like, a method of winding while forming through a flat mold, Any method can be used. When pressing with a nip roll, the cord can be flattened by applying a pressure of 0.5 MPa or more as the pressure applied to the cord.

  The rubber reinforcing cord of the present invention can be obtained by the above process.

  According to the present invention, a rubber-reinforcing fiber cord is obtained which has improved heat-resistant adhesion and improved stress relaxation of a rubber-cord composite during a rubber vulcanization process and product use. Therefore, the rubber product containing the rubber reinforcing fiber cord of the present invention has practically sufficient adhesion between the fiber cord and the rubber, and can endure long-term use when used as a tire, a belt and a hose. . Also, by improving the stress relaxation of the rubber-cord composite, the performance improvement of the rubber hose, in particular the reduction of the crimping pressure of the hose, is improved, and it can withstand longer-term use.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited by these examples. In the present invention, the method of measuring the characteristic value of the rubber reinforcing cord and the method of evaluation are as follows.

(1) Treatment agent adhesion amount:
It calculated | required by the mass method of JISL1017 (2002) 8.15 b).

(2) Initial peel adhesion and heat resistant peel adhesion A cord is wound around an aluminum plate without gaps, and an EPDM rubber of the composition shown in Table 1 is attached to one side of the aluminum plate, and the initial peel adhesion is 150 ° C. In 30 minutes, the heat-resistant peeling adhesive strength was subjected to 70 minutes of press vulcanization at 170 ° C. At this time, the thickness of the rubber was 3 mm, and the press pressure was adjusted so that the surface pressure of the rubber and the fiber cord was 3 MPa. Regarding winding of the fiber cord to the aluminum plate, for each level, 200 mm long in the fiber direction and 30 mm wide in the direction perpendicular to the fiber direction, and the tension at the time of winding was 0.5 cN / dtex. After cooling, the rubber side sample to which the cords were adhered was cut and taken out from the aluminum plate, and the sample was further cut into a width of 20 mm while maintaining the length of 200 mm. This sample is maintained at a temperature of 20 ° C. and a humidity of 65% at a speed of 50 mm / min so that the rubber and fiber cords are at an angle of 90 °, and the fiber cords are made of Orientech Co., Ltd. Tensilon RTM-100. The integral value of the peeling force when peeled using a mold tester was indicated by N / 20 mm.

(3) Gurley cord hardness Cut out the treated cord to a length of 1 m, connect a metal hook to one end, connect a 300 g weight to the other end, and adjust the temperature to 25 ° C and the relative humidity to 40%. The sample was suspended in the air for 24 hours and the cord was held vertically to obtain a measurement sample.

This was cut into 38.1 mm (1.5 inches) to obtain a test piece, and Gurley cord hardness was measured with "Gurley's stiffness tester" manufactured by Yasuda Seiki Co., Ltd.
FIG. 2 shows a perspective view of "Gurley's stiffness tester".

(A) Fix the chuck 1 in the set position according to the sample length, and mount the test piece 2. (A) 25.4 mm (one inch) (W1 in Fig. 1), 50.8 mm (2 inch) (W2 in Fig. 1) (2 inches in Fig. 1) at the lower part of the rotary rod 3 (lower than the bearing) And the position of the weight of the load and the position of the hole according to the flexibility of the test piece 2 since it is at a position of 4 inches (W3 in FIG. 1). In this case, the load and the position of the hole must be chosen so that the needle 5 indicates 2 to 4 on the dial 4. (C) When the setting corresponding to the test piece 2 is made, the drive button is pressed, the drive shaft is moved to the left and right, and the numerical value of the scale 4 pointed by the needle is read to 0.1 unit. (D) For one test piece 2, the values of one test sample, 10 test pieces, 20 times in total are obtained, and the average value of one sample is obtained. The calculation method is as follows. The mean value of each measured value was calculated by the following equation.
Gurley cord hardness (mN) = R × {(W1 × 25.4) + (W2 × 50.8) + (W3 × 101.6)} × (L−12.7) 2 / W × 3. 375 × 10-5
However,
R: The load (unit g) applied to the load position (hole) of the average value W1: 25.4 mm of the measured values
W2: Load applied to the load position (hole) of 50.8 mm (unit g)
W3: Load applied to the load position (hole) of 101.6 mm (unit g)
L: Sample length (mm)
W: Width of test piece (cord gauge) (mm)
It is.

(4) Stress relaxation rate in rubber-cord composite compression test As shown in FIG. 3, the EPDM rubber of the composition shown in Table 1 is molded to the same thickness as the cord gauge of the cord to be evaluated, and the upper surface of the rubber plate The cords were arranged under tension so as to be 60000 dtex / inch (25.4 mm), and an EPDM-based rubber plate of the same thickness was attached from the top. The tension at the time of arranging the cords was 0.5 cN / dtex. After two samples were prepared and stacked, EPDM rubber plates having a thickness twice as large as that of a cord gauge were respectively bonded to the upper and lower sides, and press vulcanization was performed at 150 ° C. for 30 minutes. The positional relationship between the cords and the rubber plate is shown in FIG. At this time, the press pressure was adjusted so that the surface pressure of the rubber and the cord was 3 MPa. After cooling, with the longitudinal direction of the cord as a vertical, the sample was cut into horizontal 25.4 mm × vertical 10 mm, and used as a measurement sample. This measurement sample was compressed to a distance of 7 times the cord gauge at a speed of 1 mm / min in an environment with a temperature of 20 ° C. and a humidity of 65% using an indenter with a contact surface of 2 mm × 3 mm, and held for 2 hours as it was . The stress at the moment of maximum compression was taken as the maximum stress (Tmax), the stress after holding for 2 hours was taken as T, and the stress relaxation rate represented by the following formula was calculated.
Stress relaxation rate (%) = (Tmax-T) / Tmax
(5) Inclination of stress relaxation in rubber-cord composite compression test In the rubber-cord composite compression test shown in (4), the stress from maximum compression to holding for 2 hours is plotted on a logarithmic graph, and the approximate straight line The slope was calculated.

(6) Maximum stress in rubber-cord composite compression test In the rubber-cord composite compression test shown in (4), the stress at maximum compression was regarded as the maximum stress.

(7) Ratio of major axis A to minor axis B in cross section of fiber cord for rubber reinforcement (A / B)
The cord was randomly cut at 20 points, a cross-sectional photograph was taken, the major axis A and the minor axis B were read from the photograph, and the average value of A / B (n = 20) was calculated.

Example 1
A solid content concentration RFL adhesive was prepared by mixing resorcinol formalin precondensate (RF) and rubber latex in a solid content ratio of RF / L = 1/20. The preparation method of the RFL adhesive is as follows. The initial condensation product (RF) of resorcin (R) and formalin (F) was aged at a molar ratio of (R / F) of 1/2 and a solid concentration of 20% by weight under a sodium hydroxide catalyst for 6 hours Resorcinol formalin precondensate was used. Thereafter, the following rubber latex is added, and ion-exchanged water is further added to make the solid content concentration 20% by weight, and after aging for 24 hours, ion-exchanged water is added, and an RFL adhesive having a solid content concentration of 10% by weight Was prepared.
Rubber latex: 2518 FS (manufactured by Nippon Zeon Co., Ltd., Tg = −44 ° C.)
One 1670 dTex polyester multifilament yarn (Toray Industries, Inc. product "Tetron" 1670-288-707C) to which a polyepoxide compound had been imparted in advance was twisted at a twist number of 160 t / m to form an untreated cord.
Polyepoxide compound: EX-421 (manufactured by Nagase ChemteX Co., Ltd.)
The untreated cord is dipped in the above-mentioned RFL adhesive using a computer treater (manufactured by CA Ritzlar Co., Ltd.), then dried at 120 ° C. for 2 minutes (dry treatment), and then continued at 190 ° C. for 0.5 minutes Heat treatment (hot treatment) was performed, and further heat treatment (normalization treatment) was performed at 190 ° C. for 0.5 minutes. The treated cord was mechanically softened under a tension of 3.5 cN / dtex and further wound with flattening at a nip pressure of 1.1 MPa to obtain a rubber reinforcing fiber cord.

  Resin adhesion amount of the treated cord, ratio of major axis A to minor axis B, Gurley cord hardness, initial peel adhesion, heat resistant peel adhesion, stress relaxation rate in rubber-cord composite compression test, stress relaxation inclination, maximum Each stress was measured. The results are shown in Table 2.

(Examples 2 to 7, Comparative Examples 1 to 3)
In Example 1, the RF / L ratio and heat treatment temperature are changed as shown in Table 2, and the conditions are the same as in Example 1 except that the softening conditions and the nip pressure are changed, and the Gurley hardness and flatness are changed. And evaluated similarly. The evaluation results are shown together in Table 2.

  As in the results of Tables 2 and 3, the rubber reinforcing fiber cords of the examples according to the present invention have a stress relaxation rate, maximum stress in a rubber-cord composite compression test, as compared with the conventional rubber reinforcing fiber cords (comparative examples). It can be seen that the stress relaxation slope, initial adhesion and heat resistant adhesion are good.

1 chuck 2 test piece 3 rotary rod 4 scale plate 5 needle W1 load setting hole (25.4 mm (1 inch from the shaft))
W2 load setting hole (50.8 mm (2 inches) from shaft)
W3 load setting hole (101.6 mm (4 inches) from the shaft)
6 cord 7 rubber plate (thickness: same as cord gauge)
8 Rubber plate (Thickness: twice the cord gauge)

Claims (5)

A rubber-reinforcing fiber cord characterized by having a stress relaxation rate of 50% or less in a rubber-cord composite compression test. The rubber-reinforcing fiber cord according to claim 1, wherein the slope of stress relaxation is 27 or less in the rubber-cord composite compression test. The rubber-reinforcing fiber cord according to claim 1 or 2, wherein the maximum stress is 500 N or more in the rubber-cord composite compression test. The rubber reinforcing fiber cord according to any one of claims 1 to 3, wherein a ratio (A / B) of the major axis A to the minor axis B in the cross section of the hose reinforcing fiber is 1.3 or more. Gurley cord hardness is 12 mN or less, The fiber cord for rubber reinforcement according to any one of claims 1 to 4 characterized by the above-mentioned.