JPH024693B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a method for producing polyester fibers, and more specifically to a method for producing polyester fibers, which has high modulus, low shrinkage, and excellent fatigue resistance and is suitable for reinforcing rubber structures. Relating to a manufacturing method. (b) Conventional technology Polyester fibers, especially polyethylene terephthalate fibers, have well-balanced and excellent properties in strength, elastic modulus, and dimensional stability, and are therefore widely used for reinforcing rubber structures such as tires, V-belts, and conveyor belts. has been done. In recent years, the fields of its use have expanded, and there has been an increasing demand for high modulus and low shrinkage, especially for use as a substitute for rayon as a carcass material for radial tires and as a substitute for vinylon in industrial applications. Ta. In response to these demands, many methods have been proposed for producing polyethylene terephthalate fibers that have high modulus, low shrinkage, and excellent fatigue resistance (Japanese Patent Application Laid-open Nos. 58032-1982 and 1989-57-1).
Publication No. 154410, Japanese Patent Publication No. 58-203112, Japanese Patent Publication No. Sho
57-161119, JP 58-23914, JP 58-98419, JP 59-1713,
JP-A-59-15513, JP-A-59-21714, JP-A-59-53716, JP-A-59-66515). In these methods, polyethylene terephthalate is melt-spun and then spun at a relatively high spinning speed of 1000 to 3000 m/min under high tension, resulting in a relatively highly oriented material (2000 to 6000 x 10 ^-5 in terms of birefringence). Undrawn yarns are obtained, drawn at a relatively low magnification (1.5 to 4.0 times), and heat treated. The fibers obtained by this method are high-strength type fibers (hereinafter referred to as conventional yarns) based on conventional technical ideas, that is, low-oriented fibers that are melt-spun and then drawn at a low spinning speed of 1000 m/min or less and a low tension. undrawn yarn (birefringence 1000×10 ^-5 or less) at high magnification (4 to 7 times)
Although the strength is slightly inferior to that obtained by stretching and heat treatment, the modulus-shrinkage relationship is extremely superior. For example, when used as a carcass material for radial tires, it greatly contributes to improving tire performance such as ride comfort and handling stability, and to improving productivity by reducing the defective rate of tires. However, although these polyester fibers have such excellent properties, they are more prone to single fiber breakage and yarn breakage during the drawing process than conventional yarns, and there are many fuzz and loops in the product cheese. There is a problem with extremely bad sex. These problems are fatal in the spinning direct drawing process where the drawing speed reaches 4,000 to 6,000 m/min, together with the deterioration in drawing properties due to the increased speed. To address these problems in high-speed direct drawing of high modulus, low shrinkage polyester fibers, improvements in the drawing process and drawing conditions have been proposed. These include improvements in magnification distribution in multi-stage stretching (Japanese Unexamined Patent Application Publication No. 59/1989)
-15513), a method that combines this multi-stage stretching method with a heating steam stretching point fixing device in the first stage (Japanese Unexamined Patent Publication No. 59-66515), a method using hot pins or hot plates (Japanese Unexamined Patent Publication No. 59-1986) -21714), a method of entangling with high-speed fluid in the stretching zone (Japanese Patent Laid-Open Publication No. 21714),
59-53716). however,
None of these measures take into account the characteristics of undrawn yarn, and their effects cannot be said to be sufficient. (c) Object of the Invention The object of the present invention is to provide a method for efficiently straight-drawing high-modulus, low-shrinkage polyester fibers at high speed while maintaining good drawability. (d) Structure of the Invention The method for producing high modulus, low shrinkage polyester fibers according to the present invention is a novel drawing method for high-speed direct drawing of relatively highly oriented undrawn yarns. That is, polyester whose main constituent unit is ethylene terephthalate and has an intrinsic viscosity of 0.85 or more is melt-spun, cooled and solidified, and undrawn yarn with a birefringence of 3000 x 10 ^-5 or more is drawn at a spinning speed of 1800 m/min or more. When subsequently drawing to produce a high modulus, low shrinkage polyester fiber, (a) multi-stage drawing of two or more stages, and (b) the surface temperature of all rollers in the group of drawing rollers except for the final drawing stage roller. (c) The surface temperature of the stretching roller in the final stretching stage is set to 150 to 150°C.
This is a method for producing polyester fiber characterized by heating at 250°C. The polyester used 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 portion of the terephthalic acid component, usually 10 mol% or less, is replaced with another dicarboxylic acid component. It may also be a polyester in which a part of the ethylene glycol component, usually 10 mol % or less, is replaced with another diol component. Furthermore, for example, a modifier, a stabilizer, etc. may be optionally used in the polyester as required. The degree of polymerization of the polyester fiber in the present invention is
In order to demonstrate sufficient strength in the final product and to withstand strength deterioration under harsh usage conditions as a fiber for reinforcing rubber structures, the intrinsic viscosity (IV)
It is preferably 0.8 or more, particularly preferably in the range of 0.83 to 0.98. At the same time, in order to improve chemical stability such as heat resistance, especially hydrolysis resistance, and amine decomposition resistance in rubber as fibers for reinforcing rubber structures, the concentration of terminal carboxyl groups is reduced to 20 equivalents/10 ⁶ grams or less. Therefore, it is preferable, and it is particularly preferable that the amount is 15 equivalents/10 ⁶ grams or less. The undrawn yarn in the present invention has a birefringence of 3000×
10 ^-5 or more is necessary in order to satisfy the required performance of the resulting drawn yarn and further as a product for reinforcing rubber structures. Such undrawn yarn can be obtained by the following method. That is, the intrinsic viscosity is
Polyester of 0.85 or more, preferably 0.90 to 1.15, is spun in a molten state by adjusting the discharge rate so that the single filament denier after drawing heat treatment becomes a predetermined value (usually 1 to 10 denier, preferably 2 to 5 denier). , adjust cooling conditions to solidify, take-up speed 1800m/
It is obtained by drawing at a speed of at least 2000 m/min, preferably at least 2000 m/min. At this time, various methods can be employed to adjust the above carboxyl group concentration. For example, (1) a method of reacting phenyl glycidyl ether with molten polyester as in Japanese Patent Publication No. 44-27911; (2) a method of reacting linear polyester carbonate with molten polyester as 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 polyester with glycol ester of oxalic acid or oxalic acid polyester as in Japanese Patent Publication No. 48-35953. (5) A method of reacting polyester with a cyclic carbonate as in Japanese Patent Publication No. 48-41713, (6) A method of reacting polyester with diaryl oxalates and/or diarylmalonates as in Japanese Patent Publication No. 49-5233. (7) A method of reacting a 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, etc. as desired. It is possible to adopt it at any time depending on the intrinsic viscosity and the amount of terminal carboxyl groups. Particularly preferred is a method in which the amount of terminal carboxyl groups is reduced to 20 equivalents/10 ⁶ grams or less without causing coloring of the resulting molded product, without causing foaming due to decomposition of additives during molding, and without reducing the degree of polymerization. In the present invention, after the undrawn yarn having the above-mentioned characteristics is taken off, it is subsequently drawn. Stretching is carried out by two-stage stretching or more multi-stage stretching. That is, in order to obtain a drawn yarn having the desired strength from the above-mentioned undrawn yarn, it is necessary to draw it by a factor of 1.5 to 3.0 times, and since the spinning speed is 1800 to 3000 m/min in the direct spinning drawing process of the present invention, The speed is extremely high, 4000-6000 m/min. In such a high-speed direct drawing process, the deformation speed is extremely high, so if you try to obtain high-strength yarn with one-stage drawing using the normal roller heating type drawing method, yarn breakage will occur frequently and it will be difficult to reach the desired strength level. I can't. On the other hand, one-stage drawing using a drawing point fixing device such as a steam jet achieves a certain level of strength, but cannot fully absorb the orientation differences between single yarns and between the inner and outer layers of single yarns. , single yarn breakage occurs frequently, and there are many fluffs and loops in the drawn yarn, making it difficult to obtain a product that maintains good quality. The number of drawing stages is most preferably 2 to 3 stages, considering the merit of improving the performance of the drawn yarn obtained, equipment costs, operating costs, etc. The second important component of the present invention is to make the surface temperature of all the rollers, excluding the final stretching roller, of the group of stretching rollers constituting the multistage stretching to be below Tg (Tg is the glass transition temperature). That is, in multistage stretching using conventional heating rollers, the roller surface temperature ranges from Tg+α to Tm−β (Tm: melting point,
A common method is to sequentially heat to higher temperatures from the first stage to the second stage within a range of α: 0 to 50°C, β: 20 to 100°C. However, in the present invention, all Tg
Below, preferably Tg-40 to Tg, more preferably
Adjust to Tg-30~Tg. When the drawing roller temperature is set above Tg as in the conventional drawing method, the relatively highly oriented undrawn polyester yarn used in the present invention exhibits a structural difference between the inner and outer layers, a so-called skin core, and crystallization in the preheated orientation. , and the stretchability is significantly impaired. On the other hand, by setting the stretching roller temperature to Tg or lower, crystallization during the preheating orientation process that impedes uniform stretching is suppressed, and the occurrence of yarn breakage and single fiber breakage during stretching is reduced. The easiest way to control the stretching roller temperature is to adjust the temperature to below Tg by not actively heating it, but in some cases it may be possible to adjust the temperature to below Tg by slightly heating it. . On the other hand, if the roller temperature cannot be controlled below Tg due to heat generation due to yarn stretching or crystallization, it is necessary to use external forced cooling means. The surface temperature of the stretching roller in the final stretching stage is 150 to 250
It is necessary to keep the temperature at ℃. The drawing rollers in the final drawing stage advance the drawing orientation to the ultimate level and provide sufficient heat to promote crystallization after drawing and form the structure of the drawn yarn, at a temperature lower than 150°C. Then, the drawn yarn obtained has an extremely high heat shrinkage rate and becomes unstable. On the other hand, if the temperature is higher than 250°C, the yarn may become fused to the roller surface, resulting in a decrease in operability. Furthermore, although the distribution of stretching ratios in the present invention is not particularly limited, it is preferable that the stretching ratio of a specific stretching stage does not exceed 90% of the total stretching ratio. (E) Effects of the Invention According to the present invention, when producing high-strength, high-modulus, and low-shrinkage polyester fibers from relatively highly oriented undrawn yarns by a high-speed spinning direct drawing method, it is possible to obtain extremely good drawability. , yarn breakage and single yarn breakage can be suppressed, and the resulting product has few fuzz and loops and is of good quality. Furthermore, if a non-heated roller is used to maintain the Tg or lower of the stretching roller, a cost reduction effect due to energy saving is expected. (F) Examples The present invention will be explained below with reference to Examples. Note that the characteristic values described in the above explanation and examples were measured by the following method. (1) Load-stretching curve, dry heat shrinkage rate Measured according to JISL1017. (2) Intrinsic viscosity (IV) Measured using an Ostwald viscometer as an orthochlorophenol solution at 35°C. (3) Birefringence Birefringence was measured using a polarizing microscope and the retardation method using a Pelleck compen center using bromnaphthalene as an immersion liquid. Examples 1 to 4 The stretching apparatus shown in FIG. 1 was used. In the figure, 1 is the spinning tube, 2 is the oiling roller, 3 is the take-up roller (GR ₀ ), 4 is the first drawing roller (GR ₁ ), and 5 is the second drawing roller.
A stretching roller (GR ₂ ), 6 a third stretching roller (GR ₃ ), 7 a relaxation roller (GR ₄ ), 8 a guide roller, and 9 a winder. Polyethylene terephthalate chips with an intrinsic viscosity (IV) of 1.05 are melted at 295°C, discharged from a spinneret with a hole diameter of 0.55 mm and 250 holes, and the discharged yarn is immediately exposed to cooling air at 25°C (4 Nm ³ /min). The mixture is sprayed to cool and solidify rapidly, applied with an oil agent using an oiling roller, and taken off with a take-up roller (GR ₀ ) with a circumferential speed of 2250 to 2450 m/min to obtain an intrinsic viscosity (IV).
An undrawn yarn having a terminal carboxyl group concentration (COOH) of 15, a birefringence (Δn) of 3950×10 ⁻⁵ and a density (ρ) of 1.342 was obtained. The undrawn yarn that has been taken off is not wound up once, but is subsequently passed between the first drawing roller (GR ₁ ).
After applying a pre-stretch of 1.05 times, it is stretched in two stages with a second stretching roller (GR ₂ ) and a third stretching roller (GR ₃ ), and then subjected to a relaxation treatment of 2 to 4% with a relaxing roller (GR ₄ ). Winding at 5000m/min
Various drawn yarns of 1000 denier/250 filament were obtained. Table 1 shows the physical properties, drawing conditions, drawn yarn quality, and drawability of undrawn yarns according to the present invention as Examples 1 to 4. The physical properties of the undrawn yarn were measured on the undrawn yarn taken with a take-up roller GR ₀ . The stretching conditions show roller temperatures GR ₀ to GR ₄ , of which GR ₀ and GR ₁ and GR ₂ of Examples 1 to 4 are unheated, and all other rollers are heated rollers. Further, the stretching ratio is expressed as DR ₀ to _{DR 3} and TDR.
DR ₀ is pre-stretch, GR ₁ lap speed/GR ₀ lap speed,
DR ₁ is the first stage stretching ratio: GR ₂ circumferential speed/GR ₁ circumferential speed,
DR ₂ has GR ₃ circumferential speed/GR ₂ circumferential speed at the second stage stretching ratio,
DR ₃ means GR ₄ circumferential speed/GR ₃ circumferential speed as a shrinkage magnification, and TDR means winding speed/GR ₀ circumferential speed as a total stretching magnification. Furthermore, regarding drawability, single yarn breakage is measured by the number of single yarn breaks per 10,000 m of yarn length on a GR ₄ roller, and yarn breakage rate indicates the number of yarn breaks per ton of yarn output. Comparative Examples 1 to 3 The undrawn yarn was spun under the same spinning conditions as Examples 1 to 4 above, and the drawing rollers GR ₁ and/or GR ₂ were heated under the heated conditions shown in Comparative Examples 1 to 3 in Table 1. It was stretched in stages. The results are shown in Table 1. Comparative Examples 4 and 5 Undrawn yarn under the same spinning conditions as Examples 1 to 4 above was subjected to one-step drawing (Comparative Example 4) and two-step drawing by installing a drawing point fixing device using a steam jet in DR ₁ . (Comparative Example 5) was carried out. 【table】

[Brief explanation of drawings]

FIG. 1 is a diagram showing a typical example of a spinning direct drawing apparatus suitable for carrying out the method of the present invention. 1: Spinning cylinder, Y: Yarn, 2: Oiling roller, 3: GR ₀ (take-up roller), 4: GR ₁ (first drawing roller), 5: GR ₂ (second drawing roller), 6:
GR ₃ (third stretching roller), 7: GR ₄ (relaxation roller), 8: guide roller, 9: winder.

Claims (1)

[Scope of Claims] 1 Polyester whose main constituent unit is ethylene terephthalate and whose intrinsic viscosity is 0.85 or more is melt-spun, cooled and solidified, and taken at a spinning speed of 1800 m/min or more, and has a birefringence of 3000×10 ^-5 or more. When producing a high modulus, low shrinkage polyester fiber by successively drawing the undrawn yarn of The surface temperature of all rollers is set to be below the glass transition temperature of the polyester, and (c) the surface temperature of the stretching rollers in the final stretching stage is set to 150 to
A method for producing polyester fiber characterized by heating at 250°C.