JPH0144810B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a novel cord suitable for belt reinforcement. More specifically, the present invention relates to a method for producing a cord made of polyester synthetic fiber, which has high modulus, low shrinkage, and excellent fatigue resistance, and is suitable for reinforcing belt structures. Recently, belt products, especially power transmission belts (e.g. V-belts, low-edge V-belts, poly V-belts, conveyor belts, timing belts, polymer belts, etc.) have been used under more severe conditions. Cords used for reinforcement are now required to have even higher physical properties. Conventionally, rayon cords, nylon cords, polyethylene terephthalate cords, glass cords, and steel cords have been used as reinforcing cords for belt products. However, rayon cords have a problem of low strength, and nylon cords have a low Young's modulus. Polyethylene terephthalate is widely used due to its relatively excellent properties, but its modulus, dimensional stability, and fatigue resistance are still insufficient, making it suitable for reinforcing power transmission belts used under harsh conditions. As a material, further improvement in performance is required. As a result of intensive studies to improve the above-mentioned performance of polyethylene terephthalate cords, the present inventors have found that by coding polyester fibers with specific properties and subjecting them to tension heat treatment under specific conditions, they have achieved high modulus, shrinkage properties, and resistance. They discovered that the fatigue resistance was significantly improved and arrived at the present invention. That is, in the present invention, polyester fibers made of polyester having ethylene terephthalate as a main constituent unit and having a maximum heat shrinkage stress of 0.5 to 0.6 g/de are first twisted and/or final twisted, and then twisted under a tension of 5 to 20%. The present invention relates to a method for manufacturing a cord for a belt, characterized in that the cord is heat-treated at a temperature of 200° C. or higher to reduce the maximum thermal shrinkage stress to 55% or less of the fiber. The polyester referred to in the present invention mainly refers to polyethylene terephthalate consisting of a terephthalic acid component and an ethylene glycol component, but it is also a polyester in which a part of the terephthalic acid component, usually 10 mol% or less, is replaced with another dicarboxylic acid component. and/or part of the ethylene glycol component,
It may also be a polyester in which 10 mol% or less of the diol component is usually replaced with another diol component. In addition, modifiers, stabilizers, additives, etc. may be optionally used in the polyester as required. The degree of polymerization of the polyester fiber of the present invention is not particularly limited, but if sufficient strength is required in the final belt structure, the degree of polymerization is preferably 0.65 or more expressed in terms of intrinsic viscosity.
A value of 0.8 or more, particularly preferably 0.83 to 0.95, is particularly preferred. The intrinsic viscosity referred to here was determined using an orthochlorophenol solvent solution at 35°C. The polyester fiber of the present invention must have a maximum heat shrinkage stress of 0.5 to 0.6 g/de, and a cutting strength of 7.5 g/de or more, more preferably 8.5 g/de or more. preferred and also
It is preferable that the dry heat shrinkage rate at 175°C is 9 to 17%. The heat shrinkage stress is initial load: 30 grams, sample length: 11
cm, heating rate: 4° C./min. In addition, for the processing code described below, only the initial load was 60 grams, and the other conditions were the same. For conventional polyester fibers used to reinforce belts, if the maximum thermal shrinkage stress exceeds 0.6 g/de,
Even if the cord is subjected to tension heat treatment after cording, a sufficiently low shrinkage cord cannot be obtained. Also, the maximum heat shrinkage stress is 0.5
If it is less than g/de, even if the tension heat treatment is performed after cording, there will be little effect on improving the shrinkage rate, and in some cases, the shrinkage rate may even increase, making it impossible to obtain a sufficiently low shrinkage cord. do not have. Also, the strength is 7.5g/
For cords with less than de, if the heat shrinkage stress satisfies 0.5 to 0.6 g/de, the tension heat treatment after cording will result in low shrinkage, but a treated cord with sufficient strength and modulus for belt reinforcement will not be obtained. hard. Also,
If the dry yield at 175℃ is less than 9%, the shrinkage rate improvement effect of the tension heat treatment after cording will be small, and 17
%, it tends to be difficult to reduce the shrinkage sufficiently even by tension heat treatment after cording. Therefore, to obtain a cord with sufficient strength, modulus, and low shrinkage for belt reinforcement, the maximum heat shrinkage stress should be 0.5~
Most preferred is a polyester fiber having a strength of 0.6 g/de or more, a strength of 7.5 g/de or more, and a dry yield at 175°C of 9 to 17%. The polyester fiber of the present invention can be obtained by the following method. That is, a polyester having an intrinsic viscosity of 0.70 or more, preferably 0.85 or more, more preferably 0.87 to 1.10 is spun in a molten state into a cooling zone and immediately quenched and solidified, at a drawing speed of 1000 m/min or more,
Birefringence is preferably 2000 to 8000×10 ⁻⁵ , preferably 3000 to 3000, by drawing at preferably 1500 to 5000 m/min
It is produced by obtaining an undrawn yarn of 7000 x 10 ^-5 , more preferably 4000 to 5000 x 10 ^-5 , and drawing it by at least 80%, preferably at least 82%, of the elongation at break of the undrawn yarn. . This stretching may be carried out continuously following spinning, or it may be carried out once after spinning and then stretching. When carrying out continuous spinning following spinning, first the first stage drawing produces a meridian reflection (001) in the X-ray wide-angle diffraction pattern.
It is useful to prepare a single-stage drawn yarn with a birefringence of 0.16 or less, which is then heat-treated for one-stage or multi-stage stretching. In addition, in the case of stretching the filament after it has been wound once after spinning, it is recommended that the first stage of stretching be 75% or less of the total stretching ratio so that the increment in birefringence is 4 times or less, followed by one or more stages of stretching heat treatment. Useful.
In any case, during this stretching (in the case of multi-stage stretching, the first stage stretching), as a heating means, 250
A steam jet method in which heated steam is ejected at ~650°C, preferably 280-600°C, or a heated roller system at 80-120°C can be adopted. In addition, heat treatment can be performed as necessary after stretching, but the maximum heat shrinkage stress of the obtained fiber is 0.5 to 0.6 g/de,
Preferably, the actual heat treatment temperature is 60°C below the melting point so that the dry heat shrinkage rate at 175°C is in the range of 9 to 17%.
It is useful to heat treat at a lower temperature for 0.4 to 1.5 seconds. In order to increase the heat resistance in the rubber of the polyester cord for reinforcing the belt and improve the durability of the belt product, the terminal carboxyl group weight of the above polyester fiber should be 20 equivalents/10 ^{to 6} grams of polymer or less, preferably 15 equivalents/10 Although it is particularly preferable to reduce the amount of polymer to ⁶ grams or less, the following various methods can be adopted for this purpose. That is, (1) A method of reacting phenyl glycidyl ether with molten polyester as in Japanese Patent Publication No. 44-27911. (2) A method of reacting a linear polyester carbonate with molten polyester as in Japanese Patent Publication No. 45-41235. (3) A method of reacting polyester with ethylene oxide, as disclosed in Japanese Patent Publication No. 47-12891. (4) A method of reacting ethylene oxide with polyester, as disclosed in Japanese Patent Publication No. 48-35953. Method of reaction (5) A method of reacting polyester with a cyclic carbonate as described in Japanese Patent Publication No. 48-41713 (6) Method of reacting polyester with diaryl oxalates and/or diaryl malonates as described in Japanese Patent Publication No. 49-5233 (7) A method of reacting polyester with a carbodiimide, as in U.S. Pat. No. 3,193,522. (8) A method of reacting a bis-cyclic imino ether, as in JP-A-55-145734. It is possible to employ it at any time depending on the desired intrinsic viscosity and amount of terminal carboxyl groups. In particular, it avoids coloring of the resulting molded product, does not cause foaming due to decomposition of additives during molding, and does not reduce the degree of polymerization.
A preferred method is to reduce the amount of terminal carboxyl groups to 15 equivalents/10 ⁶ grams of polymer or less. In the present invention, polyester fibers having the above characteristics are subjected to first twisting and/or final twisting according to a conventional method. In this case, setting the K value defined below in the range of 900 to 2600 not only ensures that the treated cord subjected to subsequent heat treatment has high strength, high modulus, and low shrinkage, but also that heat generation in the belt reinforcement Useful for lowering temperature and improving fatigue resistance. K=T√ Here, T is the number of twists per 10 cm length of the cord D is the total denier of the fibers making up the cord In the present invention, the twisted cord is then subjected to tension heat treatment; In order to obtain the desired low shrinkage for belt reinforcement, it is necessary to make the maximum heat shrinkage stress of the treated cord less than 55% of that of the polyester fiber before cording. To reduce the maximum heat shrinkage stress of the treated cord to 55% or less of the polyester fiber before cording, it is sufficient to stretch the cord by 5% to 20% at a temperature of 200 to 260°C, usually for 30 to 240 seconds under high tension. Heat treated with The resulting treated cord has sufficient strength for belt reinforcement, i.e. 6
g/de or more, sufficiently low shrinkage, i.e. dry heat shrinkage at 175℃ of 4.5% or less, high modulus with elongation under 4.5Kg load of 4.5% or less, and tube life of 300 minutes at a bending angle of 90°. It shows high fatigue resistance. As mentioned above, the belt cord of the present invention is strong,
Due to its superior shrinkage, modulus and fatigue resistance, it is suitable for various belt structures such as natural rubber and synthetic materials such as V-belts, low edge belts, poly V-belts, conveyor belts, timing belts, and polymers. It is extremely useful for reinforcing structures such as The present invention will be further explained below with reference to Examples.
In addition, various measured values in the examples are based on the following methods. (1) Δn is a parameter indicating the degree of orientation of molecules in the filament, and was determined by the retardation method using bromonaphthalene as the immersion liquid and a Bereck compensator. For a detailed explanation, please refer to Kyoritsu Shuppan's "Polymer Experimental Course/Physical Properties of Polymers." (2) The load-stretching curve conformed to JISL1017-1963 (5.4). (3) Dry heat shrinkage rate at 175°C complies with JISL1017-1963 (5.12). (4) Tube heat generation temperature and tube life are
Compliant with JISL1017−1963, 1.3.2.1A law. However, the bending angle was 90°C. The exothermic temperature is 90 at the start of operation.
After a few minutes, the temperature of the tube surface was measured using an infrared non-contact thermometer (manufactured by SAN-EI), and the tube life was expressed as the time until tube rupture. Example 1 Polyethylene terephthalate (no titanium oxide content) with an intrinsic viscosity of 1.05 was melted at approximately 290°C, and the pore size was
After being discharged from a spinneret with a size of 0.55 mm and 250 holes,
The discharged yarn is immediately cooled and solidified while blowing cooling air at 25°C at 2.0Nm ³ /min, and then an oil agent is applied with an oiling roller, and then guided to a take-up roller, and immediately interposed between it and a drawing roll without being wound up.2.2
A steam jet of Kg/cm ³ G was sprayed onto the yarn at an angle of 45° to draw it, or the yarn was wound on a heating roll and then stretched to obtain various drawn yarns. At this time, the speed of the take-up roller, the temperature of the steam jet, the stretching ratio,
The temperature of the stretching rolls was varied. All of these drawn yarns have X-ray wide-angle diffraction patterns,
The meridian reflection (001) was clearly observed. Next, these drawn yarns were drawn in a second stage in a heating bath at 325°C, and then subjected to tension heat treatment in a heating bath at 300°C to achieve the total draw ratio shown in Table 1. It is shown in Table 1.

[Table] In addition, in the stretching temperature in the table, SJ indicates the case where a steam jet is used, and HR indicates the case where a heated roll is used. In addition, the intrinsic viscosity [η] and birefringence Δn of the undrawn yarn in the table were measured for the undrawn yarn that was led to a take-off roller at room temperature and then wound without being stretched. In addition, the first stage stretching ratio can be determined by injecting a steam jet interposed between the take-up roller and the stretching roller, or by preheating with a heating roll and then guiding it to the stretching roll.
It is expressed as a ratio (%) of the stretching ratio to the maximum stretching ratio when cutting by gradually increasing the speed of the stretching roller. Using each of the drawn yarns of the above examples, cords were prepared by first twisting and then final twisting each at 49T/10cm (K value approximately 2330), and then heat-treated under tension at dry heat at 240°C for 2 minutes. The performance of the obtained processing code is shown in Table 2. The tension ratio was set in accordance with the physical properties of the drawn yarn so that the elongation of the treated cord at a load of 4.5 kg was approximately 3.5%.

【table】

[Table] Maximum heat shrinkage stress of drawn yarn
Example 2 Using the polyester fiber of Experiment No. 10 in Example 1, a cord was prepared by first twisting and then final twisting, and then subjected to tension heat treatment for 2 minutes. At this time, the physical properties of the treated cord due to the number of twists, degree of tension, and heat treatment temperature are
Shown in the table.

【table】

Claims (1)

[Claims] 1 Made of polyester whose main constituent unit is ethylene terephthalate and has a maximum heat shrinkage stress of 0.5.
~0.6 g/de polyester fibers are first twisted and/or final twisted and then under tension of 5 to 20%.
1. A method for producing a belt cord, characterized by heat treatment at a temperature of 200° C. or higher to reduce the maximum thermal shrinkage stress to 55% or less of the fiber. 2. The method for producing a belt cord according to claim 1, wherein the polyester fiber has a cutting strength of 7.5 g/de or more. 3. The method for producing a belt cord according to claim 1 or 2, wherein the polyester fiber has a 175°C dry heat shrinkage rate of 9 to 17%.