JPH0147575B2 - - Google Patents

Description

[Detailed description of the invention]

a. Industrial Application Field The present invention relates to a high toughness polyester cord that is particularly suitable for industrial use. b. Prior Art Polyester fibers have various excellent properties and are therefore widely used not only for clothing but also for industrial purposes. Polyester fibers, which have particularly high strength and excellent dimensional stability, are useful in industrial applications, and have been used not only for tires but also for non-tire applications and industrial asset applications. however,
Recently, more and more advanced performance is required. For example, in conveyor belts and rubber hose applications, dimensional stability during molding, lower shrinkage, durability under harsh usage conditions, and fatigue resistance are required. There is. Furthermore, in applications such as curing sheets, ropes, and fishing nets, high toughness with high elongation is required. Currently, in these fields, rayon fibers and vinylon fibers, which have a long history, are commonly used, and polyester fibers are also beginning to be used. However, although polyester fibers have high strength, they are insufficient in low shrinkage, durability, and fatigue resistance. If these properties are improved from this point of view, polyester fibers with excellent cost/performance will become increasingly popular as industrial materials. In general, in order to develop high toughness polyester fibers with high elongation, for example,
Using a high degree of polymerization polyester as disclosed in Publication No. 51524, suppressing molecular orientation in the spinning stage and increasing the stretching ratio as much as possible in the stretching stage,
A method is known in which the material is then sufficiently subjected to relaxation heat treatment at a high temperature. However, with this method, drawn fibers with high elongation, high toughness, and low shrinkage can be obtained; If you do so, you will not be able to obtain a product with low shrinkage and high elongation. On the other hand, in order to reduce the shrinkage rate, it is known to use a polyester with a low degree of polymerization as disclosed in, for example, Japanese Patent Laid-Open No. 53-58028. However, with this method, it is difficult to obtain products with high strength and toughness. In addition, both of the above two methods yield products with low fatigue resistance. In order to achieve low shrinkage and improve fatigue resistance, for example, Japanese Patent Application Laid-open Nos. 53-58031 and 53-58032 disclose that the degree of molecular orientation of the drawn yarn is reduced and the work loss is reduced to improve fatigue resistance. Polyester fibers and methods for producing the same have been proposed with the aim of improving. This method is characterized by rapid cooling in a gas atmosphere of 10 to 60°C under a spinneret, but in order to achieve high strength, the yarn is stretched until just before it is cut, resulting in extremely low elongation. It has the disadvantage that thread breakage occurs frequently and stable production is difficult. c Means for Solving the Problem In an attempt to eliminate such drawbacks, the present inventors have made extensive studies and found that although the fibers have a specific degree of polymerization and are highly oriented compared to ordinary undrawn fibers, It has been found that by using undrawn polyester fibers having sufficient elongation at break, a polyester cord with good drawability and desired properties can be obtained. That is, it has high elongation, high toughness, and good fatigue resistance. Surprisingly, when this cord is further heat-treated under tension, it has low shrinkage and increased toughness, making it a polyester cord particularly suitable for non-tire and industrial property applications. The present invention was achieved by discovering the following. That is, the present invention uses ethylene terephthalate as the main component of the repeating structural unit of the molecular chain, is twisted with a twist coefficient of 450 to 1350, and has a twist coefficient of 450 to 1350. This relates to a polyester cord in which the stress increment is zero or negative and the breaking elongation is 15% or more. The polymer constituting the polyester cord of the present invention is a polyester containing 90 mol% or more, preferably 95 mol% or more of ethylene terephthalate repeating units in the molecular chain. Polyethylene terephthalate is suitable as such polyester, but it may contain other copolymer components in a proportion of less than 10 mol%, preferably less than 5 mol%.
Examples of such copolymerization components include isophthalic acid, naphthalene dicarboxylic acid, adipic acid, oxybenzoic acid, diethylene glycol, propylene glycol, trimellitic acid, and pentaerythritol. Further, these polyesters may contain additives such as stabilizers and colorants. Further, in order to obtain high toughness, it is preferable that such a polyester cord has an intrinsic viscosity of 0.80 or more as determined from a ₀ -chlorophenol solution at 25°C. The polyester cord of the present invention has a twist coefficient of
It is necessary that the first twist and/or the final twist of 450 to 1350 are applied. Here, the twist coefficient K is defined by the following formula. K=T√ T is the number of top or bottom twists per 10cm length of cord D is the total denier of the fibers that make up the top or bottom twist If the twist coefficient is less than 450, it will not work even after subsequent high-order processing. Desired elongation and high toughness cannot be obtained, and
If it exceeds 1350, the elongation increases, but the strength decreases, the toughness decreases, and even if a subsequent high-level treatment is applied, low shrinkage cannot be obtained, making it inappropriate. The twist coefficient is determined by considering high-order processing according to the application.
450-1350 is required. Due to its purpose, the polyester cord of the present invention has performance that is significantly different from conventional cords in terms of the shape of the stretching curve. That is, in the load-stretching curve, the stress increment near the cutting point is zero or negative.
The load-stretching curve is JIS L1017-1963 (5.4.)
Measured in accordance with . The characteristic load-stretching curve of this polyester cord is shown in FIG. 1 in comparison with a conventional one. In FIG. 1, A and B are the cutting points of the cord of the present invention and the conventional cord, and slope A' and slope B' indicate the increment of stress (tentatively named terminal modulus) in the vicinity of each cutting point. As is clear from FIG. 1, the polyester cord of the present invention has a negative terminal modulus, which is significantly different from conventional positive cords. When the terminal modulus is negative, surprisingly not only the elongation increases significantly but also the strength increases due to tension treatment and/or heat treatment in the subsequent high-order processing, resulting in significantly increased toughness and low shrinkage. This also improves fatigue resistance. If the same treatment was applied to conventional cords, both strength and elongation would decrease.
Toughness decreases and shrinkage rate also increases. In addition to the above-mentioned characteristic load-stretching curve, the polyester cord of the present invention is required to have a breaking elongation of 15% or more. Below 15%, even if it shows the characteristic load-stretch curve described above,
Due to high-order processing, it is not possible to obtain the desired high elongation and high toughness. The polyester cord also has a cutting strength of 5.5 g/m for the final intended use.
It is preferable to have de or more in order to obtain high toughness. Furthermore, in order for the polyester cord of the present invention to exhibit low shrinkage upon high-level processing, it is preferable that the dry heat shrinkage rate at 150°C is 10% or less. Note that the dry heat shrinkage rate was measured in accordance with JIS L1017-1963 (5.12). The polyester cord of the present invention can be obtained, for example, by the following method. That is, using undrawn fibers that have a specific degree of polymerization, have a higher degree of orientation than normal undrawn fibers, and have sufficient elongation at break, the fibers are drawn at a specific draw ratio; Heat treated to make drawn fibers. The drawn fibers are then twisted into polyester cords using the predetermined twist coefficient in accordance with a conventional method. More specifically, the intrinsic viscosity with ethylene terephthalate as the main repeating unit is 0.80 to 1.0.
or a polyester with an intrinsic viscosity of 0.7 to 0.9 is reacted with a degree of polymerization accelerator, melted and transported by a conventional method, and then drawn from a spinneret to a fineness of 1 to 0.9.
It is discharged onto a thread at a temperature of 20 DE and then rapidly cooled immediately after discharge, kept at a temperature below the melting point and up to the temperature at which crystallization begins, or delayed cooling by exposing it to a heated atmosphere at a temperature above the melting point for a certain period of time. . after that,
The yarn is cooled and solidified, and it is useful to cool and solidify it under the following conditions. 400≦x×√y/-/Q≦1900 [x is the distance from the spinneret surface to the blowing surface of the cooling air (room temperature), which is 450 mm or less, y is the blowing length of the cooling air, 100 to 500 mm, and Q is the cooling air blowing length. 2~ with the amount of blowout
^6Nm2 /min. ] Next, after cooling and solidifying as described above, the oil agent is applied and then taken off at a take-up speed of 1500 m/min or more to obtain a birefringence of 0.02 to 0.07, preferably 0.03 to 0.07.
More preferably 0.035 to 0.050, cutting elongation 100 to 200
% undrawn fiber. The oil agent can be applied by any method such as an oiling roller method or a spray method. Further, as the oil agent, any textile oil agent can be applied as necessary. At this time, in fields where adhesion with rubber is important as a fiber application, it is useful to apply a surface treatment agent to impart adhesion. Next, the undrawn fibers are subjected to drawing heat treatment. This drawing heat treatment step may be performed continuously following spinning, or may be performed as a separate step after winding. When the spinning is followed by continuous drawing, it can be carried out in accordance with the method described in Japanese Patent Application No. 57-88927 previously proposed. In addition, when the yarn is rolled up once after spinning and then stretched, it is possible to
This can be carried out in accordance with the method described in Japanese Patent Application No. 161119 or Japanese Patent Application No. 189094/1983. The latter stretching method is preferred in terms of reducing stretching strain during stretching and heat treatment strain. That is, the undrawn fiber is Tg+15~Tg
After preheating for at least 0.5 seconds at a temperature of +50℃ (where Tg is the glass transition temperature of the undrawn fiber),
The first stage drawing is performed at a magnification of 75% or less to give a birefringence of 1.2 to 3.3 times the birefringence of the undrawn fiber. then 1
The step-drawn yarn is further subjected to multi-step drawing heat treatment. At this time, if the elongation is large and toughness is required, after the first stage drawing, the second stage drawing is performed at a range of the fiber melting temperature -50°C to the melting temperature -110°C as the actual yarn temperature.
Furthermore, if necessary, after multi-stage drawing, a relaxation heat treatment is performed at a temperature of 7% or less while holding the actual fiber temperature in the range of -50°C to -110°C, the melting temperature of the fiber, for 0.4 to 1.5 seconds, and then reduce the drawing ratio to the cutting drawing ratio. It is preferable to set it to 85% or less. In addition, in order to increase the heat resistance of the polyester cord in rubber and improve the durability of products for various uses, the terminal carboxyl group content of the above polyester fiber should be increased to 20%.
It is particularly preferred to have an equivalent weight/10 ⁶ grams polymer or less, preferably 15 equivalents/10 ⁶ grams polymer or less. For this purpose, the following various methods can be adopted. Namely, (1) a method of reacting phenyl glycidyl ether with a molten polyester as disclosed in Japanese Patent Publication No. 44-27911; and (2) a method of reacting a linear polyester carbonate with a molten polyester as disclosed in Japanese Patent Publication No. 45-41235. (3) A method of reacting polyester with ethylene oxide as in Japanese Patent Publication No. 47-12891 (4) A method of reacting a glycol ester of oxalic acid or oxalic acid polyester with polyester as in Japanese Patent Publication No. 48-35953 ( 5) Method of reacting polyester with cyclic carbonate as disclosed in Japanese Patent Publication No. 48-41713 (6) Method of reacting diaryl oxalates and/or diaryl malonates and diaryl carbonates with polyester as disclosed in Japanese Patent Publication No. 49-5233 Reaction method (7) Method of reacting polyester with carbodiimide as in U.S. Pat. No. 3,193,522 (8) Method of reacting with biscyclic imino ether as in JP-A-55-145734, etc. to obtain the desired intrinsic viscosity and terminal carboxyl group. It can be adopted at any time depending on the quantity. 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. Next, this polyester fiber is subjected to the above-described desired first twist and/or final twist according to a conventional method. The polyester cord of the present invention can be used as it is or after knitting and weaving, but depending on the application, it may be further heat-treated under tension, or it may be heat-treated under tension after being treated with an adhesive in order to impart adhesion to rubber. . In case of heat treatment under tension, 200
Heat treatment is sufficient at a temperature of ~260°C, usually for 30 to 240 seconds. The obtained treated cord has sufficient strength suitable for belt reinforcement, i.e., 6 g/de or more, elongation of 13% or more, and toughness (strength x √ elongation) of 25 or more.
Sufficiently low shrinkage, i.e. dry heat shrinkage at 150°C of 4.0% or less, high modulus of elongation under 1.5g/de load of 2.5% or less, and tube life of 300 minutes or more at a bending angle of 90°. Shows fatigue resistance. d Effects As mentioned above, the polyester cord of the present invention has excellent toughness, shrinkage, modulus, and fatigue resistance, so it can be used in various structures such as V-belts, low-edge belts, poly V-belts, and conveyors. It is extremely useful for reinforcing natural rubber and synthetic structures such as belts, timing belts, and small urethane belts. e Examples The present invention will be described in further detail with reference to Examples below.
Note that all parts in the examples indicate parts by weight. Example: 97 parts of dimethyl terephthalate, 69 parts of ethylene glycol, 0.034 parts of calcium acetate monohydrate, and 0.025 parts of antimony trioxide were placed in an autoclave, and the methanol produced as a result of transesterification was heated at 180 to 230°C while slowly passing nitrogen through. After the removal, 0.05 part of a 50% aqueous solution of H ₃ PO ₄ was added and the heating temperature was raised to 280°C, while the pressure was gradually reduced, and it took about 1 hour to reduce the pressure of the reaction system to 0.2 mmHg. Continuing the polymerization reaction for 50 minutes, the intrinsic viscosity was 0.80.
A polymer having a terminal carboxyl group weight of 28 equivalents/10 ⁶ grams was obtained. Add 100 parts of this polymer chip to 2,2'-bis(2-
After dry-blending the amount of Oxazoline (CE) shown in Table 1, it was melted and transported at about 300℃, and the pore size was 0.6 mm.
After being discharged from a spinneret with 250 holes, the discharged yarn was cooled and solidified while blowing cooling air at 25℃ over 300mm at a rate of 4.0Nm ² /min, and then an oil agent was applied with an oiling roller.Table 1 It was rolled up at the stated take-up speed. The properties of the obtained undrawn fibers are shown in Table 1. The undrawn fibers were supplied to rolls heated to 85°C, and after the first drawing with a take-up roll, they were drawn in the second stage through a gas bath heated to 325°C. Thereafter, heat treatment was performed using a heating roller at 130°C and a gas bath at 330°C. The total stretching ratio and the performance of the obtained drawn yarn are also listed in Table 1. Next, three of these drawn yarns are combined to give a Z twist, and then these three are combined to give an S twist to make 1100 de x 9
Got the polyester cord for the book. The performance of the obtained code is also listed in Table 1. Furthermore, these cords were immersed in an adhesive (RFL liquid) and subjected to tension heat treatment at 245°C for 2 minutes. The properties of this treated cord and its heat resistance and strength were measured by embedding it in rubber and vulcanizing it. The results are also listed in Table 1. In addition, for strong heat resistance, this processing cord is embedded in a vulcanization mold at 170°C and a pressure of 50°C.
After accelerated vulcanization at Kg/cm ² for 120 minutes, the treated cord was taken out and its strength was measured.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows the load-stretching curve of polyester cord. Curve 1 is the one according to the invention, and curve 2 is the conventional one. In the figure, A and B are the cutting points, and slopes A' and B' are the increments of stress near the cutting points.

Claims (1)

[Claims] 1. Ethylene terephthalate is the main component of the repeating structural unit of the molecular chain, and the twist coefficient is 450 to 1350.
The first twist and/or the second twist are applied, and the load is -
A polyester cord in which the stress increment near the breaking point in the loading and stretching curve is zero or negative, and the breaking elongation is 15% or more. 2. The polyester cord according to claim 1, which has a dry heat shrinkage rate of 10% or less. 3. The polyester cord according to claim 1 or 2, which has a cutting strength of 5.5 g/de or more.