JPS6229525B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for melt-spinning and drawing synthetic fibers, and more particularly to a method for producing polyester fibers having excellent level dyeing properties and improved strength and elongation characteristics by direct spinning and drawing. In recent years, with the aim of improving productivity, a so-called direct spinning and drawing method has been developed in which the spinning process and drawing process are made continuous.
It has been put into practical use industrially. This direct spinning/drawing method involves (1) drawing the spun yarn, which has been melt-spun from a melt spinneret and cooled and solidified, to several times the amount between a first roller (group) and a second roller (group); (2) A method of imparting practical value to the yarn; Independent speed regulation roller(s)
There are two main types of methods: drawing is performed under tension gradients and/or temperature gradients without the intervention of tension and/or temperature gradients, thereby imparting practical value to the yarn. Regarding the latter method, proposals have been made in Japanese Patent Publication No. 1932-1932, Japanese Patent Publication No. 38-2016, etc. In the latter method, once the 80%
Since the spun yarn, which has been cooled and solidified to a temperature below °C, is drawn between the melt spinneret and the first roller (group) under a tension gradient and/or a temperature gradient, the tension and The method and conditions for applying a temperature gradient are one of the important points in silk-spinning technology. As a general means of imparting a tension gradient to a yarn, a method of bringing the yarn into contact with a solid or a liquid is effective and has been practically used industrially. This method is useful when the yarn speed is relatively low, but if such a method is adopted at high speeds, it may cause yarn breakage or single yarn breakage in the case of solid contact during the drawing process, or In this case, liquid scattering occurs and there are many practical problems. In order to solve this problem, a method of drawing the yarn under a temperature gradient is often adopted. However, when drawing is carried out between the melt spinneret and the first roller(s) under a temperature gradient, the drawing condition is usually extremely unstable, and in extreme cases leads to yarn breakage or single yarn breakage, resulting in Yarns have low tensile and elongation properties and have large fluctuations in fiber performance. Furthermore, it is generally difficult to obtain uniform dyeability in knitted fabrics produced by knitting and weaving using threads obtained by this spinning method.
The root of these problems lies in the running state of the yarn in the so-called spinning system and the physical behavior of the yarn from the time it is melt-spun from the melt spinneret until it is taken up by the first roller (group). It is thought that the threads opened, but the direct cause is that the spun yarn melt-spun from the melt spinneret generates a large amount of accompanying airflow along the yarn as the yarn speed increases. However, when the yarn is forcibly removed from the spinning system at the entrance of the heating zone (for example, using an entrainment air separator), it promotes yarn shaking, making the spinning system unstable and causing yarn breakage due to intertwining of yarns. This is thought to lead to the phenomenon of single yarn breakage and a decrease in level dyeing properties. Difficulties in the spinning operability and product performance of this spinning method include the stability of the spinning system, for example, the cooling thinning behavior of the spun yarn melted and discharged from the melt spinneret, and the drawing thinning behavior in the heating zone. behavior changes over time,
are considered to be deeply related. In order to increase the stability of the yarn-spun thread, (a) suppress disturbances to the yarn-spinning system as much as possible. (b) There are two methods to make the responsiveness of the silk spinning system to disturbances as insensitive as possible. Based on the former idea, the present inventors have proposed an attempt to suppress yarn shaking as much as possible by dividing the yarn to smoothly discharge the accompanying airflow generated along the running yarn out of the spinning system. This was proposed in Publication No. 147613/1983. Although it is possible to improve the operability in the direct spinning/drawing method by adopting such a method, the strength and elongation properties and level dyeing properties of the resulting yarn are inferior to those produced by the normal spinning method. low, high level dyeing and/or
Further, its use in the field of textile products requiring high strength and elongation properties is quite limited. The present inventors have devised a method for stably producing yarn with a uniform fiber structure, excellent level dyeing properties, and improved strength and elongation properties by eliminating such drawbacks in the direct spinning/drawing method. ) As a result of intensive research based on the technical idea shown in
In the direct spinning drawing method, in which the yarn is once cooled and solidified, then hot-stretched in a heating zone and immediately taken off, the tension of the running yarn at the exit of the heating zone is maintained within a specific range, resulting in excellent and improved level dyeing properties. The present invention was achieved by discovering the fact that polyester fibers having specific strength and elongation properties can be produced. That is, the present invention involves melt-spinning synthetic linear thermoplastic polyester through a melt spinneret, blowing a cooling air stream onto the spun yarn below the melt spinneret to cool it once to a temperature of 80°C or less, and then heating it. In the direct spinning/drawing method for polyester fibers, which passes through a zone, hot-draws the yarn at a yarn temperature of 80°C or higher, and immediately takes it off at a speed of 3,000 m/min or higher after the stretching, the cooling air stream is heated to a temperature of 55°C or higher. By using an airflow and blowing the cooling airflow across the spun yarn, the tension F (g/d) of the traveling yarn immediately after leaving the heating area is reduced to 22±2℃ as a cooling airflow. With respect to the tension F ₀ (g/d) of the running yarn immediately after leaving the heating zone when using a cooling air flow,
This is a method for producing polyester fiber characterized by satisfying the following formula. 1.05<F/F ₀ <1.70 The synthetic linear thermoplastic polyester suitable for use in the present invention is a fiber-forming polyester in which 85 (mol)% or more of its repeating units are ethylene terephthalate, particularly terephthalic acid or Polyethylene terephthalate prepared from functional derivatives thereof and ethylene glycol or ethylene oxide is preferred. Of course, such polyesters may contain antioxidants, matting agents, coloring agents, dyeability improvers, flame retardancy improvers, crystallization promoters, antistatic property improvers, etc. as necessary. good. Further, there is no particular restriction on the intrinsic viscosity of the polyester, but from the viewpoint of spinning operability regarding single fiber breakage in the spinning section, it is appropriate to increase the intrinsic viscosity of the polymer so that the melt viscosity is preferably as high as possible. It is. These fiber-forming synthetic linear thermoplastic polyesters may be formed into pellets using commonly known methods and conditions and then melted, but particularly preferably they are formed into pellets directly after polymerization without being pelletized. The first step is to adopt a so-called continuous direct spinning system in which the yarn is supplied to the spinning section. In this way, the melt is usually melt-spun through a known melt spinneret, and the spun yarn is once cooled to a temperature below 80°C by blowing a rectified cooling air stream below the melt spinneret. Although the spun yarn is solidified, the first requirement of the present invention is that the temperature of the cooling air stream blown onto the spun yarn at this time is 55° C. or higher. If the temperature of this cooling air stream is below 55°C, even if the other requirements governing the tension of the running yarn are met, the tension ratio F/F ₀ of the running yarn at the exit of the heating zone is determined by the above formula. Not satisfied. On the other hand, if the temperature of the cooling air stream blown onto the spun yarn is too high, even if other requirements are met, the tension of the running yarn at the exit of the heating zone will drop abnormally, resulting in a tension ratio (F/F ₀ ) is outside the range of the above formula. In the present invention, the temperature of the cooling air stream blown onto the spun yarn below the melt spinneret is preferably 55°C or higher, preferably 65°C or higher, and particularly
At around 100°C, the effect on increasing the tension level of the running yarn becomes significant. More surprisingly, as the tension level increases, the temporal variation of the tension, especially the 20-50 Hz tension variation, decreases dramatically.
Of course, as the tension level of the running yarn increases, the yarn swinging phenomenon in the yarn spinning system also decreases. Note that if the cooling air flow temperature exceeds 80°C, the cooling and thinning of the spun yarn discharged from the melt spinneret will be delayed, so if necessary, the cooling air flow should be continuously cooled at room temperature with gaps below the cooling air blowing zone. A cooling zone may also be provided. The length of the zone in which the heated cooling air stream is blown onto the spun yarn melt-spun from the melt spinneret must be at least 5 cm, and the tension of the traveling yarn in the zone less than this length must be at least 5 cm. Even if the other requirements governing F are met, the tension ratio F/F ₀ of the running yarn after hot drawing does not satisfy the above equation. The length of the cooling air blowing zone in the present invention needs to be appropriately selected depending on the so-called spinning conditions such as the amount of polymer discharged per melt spinneret hole and the take-up speed of the first roller (group), but in general, The length is preferably 10 cm or more, more preferably 15 cm or more, but even if the cooling air blowing zone is lengthened unnecessarily, the tension ratio F/F ₀ defined by the above formula will not increase; The length should be limited to 200 cm at most, since the enlargement of equipment would be disadvantageous in terms of cost and spinning operability. In the present invention, it is necessary to blow the heated cooling air flow across the preventive yarn, and it is particularly advantageous to blow the air perpendicularly to the spun yarn in terms of increasing the tension ratio F/F ₀ . However, even if the spun yarn is blown as a cross flow at an upward or downward blowing angle of about ±45° from the direction perpendicular to the spun yarn, the above formula can of course be satisfied. I wish I could. If the spun yarn is cooled and thinned by blowing the spun yarn at an angle other than the above-mentioned blowing angle with cross-flow, parallel flow, or counter-flow, the effect of increasing the tension in the spinning system will be increased even if the cooling air temperature is Even if the tension is increased, it may hardly be noticed or the tension may actually decrease. In the present invention, it is sufficient that the cooling air flow blown onto the spun yarn below the melt spinneret has a flow velocity sufficient to abrade the spun yarn and satisfy the above formula. In order to increase the flow rate, a flow rate of 0.1 m/sec or more is preferable. There is no particular limit to the upper limit of the flow velocity, but if the cooling air velocity is increased unnecessarily, even if the cooling air temperature is increased, the tension ratio F/
Not only is it not possible to increase F ₀ , but it also causes non-uniformity of the microstructure of the fibers in the direction along the yarn diameter in the cross section of the yarn, as well as an increase in fiber unevenness along the length direction. Considering this, it is better to set the speed to 1.0 m/sec or less. A phenomenon in which the tension level of the spinning system increases by blowing a cooling air stream heated to a temperature of 55°C or higher onto the spun filaments melt-spun from a melt spinneret, and further by hot stretching under such high tension. Although the mechanism for improving the strength and elongation properties of the yarn and improving the level dyeing properties is not clear, the following reasons may be considered. That is, the spun yarn discharged from the melt spinneret is cooled and attenuated by blowing a cooling air stream, but the attenuation behavior of the spun yarn depends on the cooling air temperature and/or flow rate conditions. Change. At this time, if the temperature of the cooling air stream becomes high, cooling progresses slowly, and as a result, a uniform microstructure is formed in the fiber, and at the same time, the deformation behavior of the spun yarn during the process of cooling and thinning the spun yarn. Since the movement is slow, it is less susceptible to external disturbances (for example, the influence of vibration of the thread), and as a result, a thread with fewer uneven threads is formed. On the other hand, the phenomenon in which the tension level in a yarn spinning system increases by increasing the temperature of the cooling air flow is due to the fact that the kinematic viscosity coefficient of air increases as the temperature rises, and the frictional resistance force applied to the yarn increases. It is thought that this is deeply related to the development behavior of the birefringence tangent Δn, which is caused by the deformation behavior during thinning and elongation of the yarn in the cooling zone. Further, by applying such reasoning to the hot stretching behavior in the heating zone, it is possible to set suitable conditions for forming the heating zone (so-called temperature gradient). The spun yarn, which has been cooled to a temperature of 80°C or less and finely refined in this manner, is then preferably separated from the spun yarn by a suitable means to separate the high-speed air flow accompanying the spun yarn, and then If necessary, at the same time as the oil treatment, the spun yarn is divided or bundled and then introduced into a heating zone, where the yarn temperature is 80°C or higher, preferably 120°C or higher, more preferably 140℃
Hot stretching is carried out under the above conditions. The upper limit temperature of the yarn in the heating zone should be below the melting point of the yarn, and in particular from the perspective of level dyeing, it is preferably 20° C. lower than the melting point. The yarn thus drawn between the melt spinneret and the first roller(s) under a tension gradient and/or temperature gradient is then taken up by the first roller(s),
The conditions for forming the heating zone provided between the melt spinneret and the first roller (group) as a means for generating this hot drawing are one of the important points in the silk spinning technology. That is, as mentioned above, it is considered important to slow the deformation behavior of the yarn in such a spinning/drawing mode, so the temperature conditions for forming the heating zone, for example, the setting of the temperature gradient, should be set relatively gently. Should. This is clearly different from the conventional concept of applying a temperature gradient to thinning by stretching. In the present invention, there is no particular limitation on the heating zone forming means, but it is preferable to use a non-contact type heating device, and moreover, it has the ability to provide a temperature gradient that actively increases along the yarn traveling direction. A heating device having the following properties is even more suitable. The structure, installation location, temperature conditions, etc. of the heating device are regulated by the discharge amount of molten polymer, cooling air flow temperature, take-up speed, product fineness, etc., but the effect on yarn unevenness, thermal efficiency, and work efficiency are comprehensively taken into consideration. Can be set appropriately. The take-off speed, which is one of the spinning conditions, is an important factor that controls the tension level of the silk-spinning system. Especially when the heating zone is formed using a non-contact heating device, the take-off speed has a great meaning, and the take-off speed is at least 3000 m/min. Above, preferably 4000 m/min or more, particularly preferably 4500 m/min or more. Pick up speed
If the speed is less than 3000 m/min, the yarn obtained by satisfying the above formula has little practical value, and furthermore, the phenomenon of fusion between the yarns occurs in the heating zone, and the operability of spinning and drawing is extremely reduced. In order to prevent such damage, if the temperature of the heating zone is lowered as much as possible, it is virtually impossible to form a drawn yarn. There is no particular upper limit on the take-up speed, but considering the increase in equipment costs associated with higher speeds, silk reeling operability, safety, etc., the upper limit is 8000.
It is best to keep it at around m/min. The yarn taken in this way may be continuously crimped and then cut into staples, or it may be wound up on an appropriate winding device and then subjected to higher processing. good. As described above, the present invention provides yarn that can be obtained by specifying the tension level applied to the yarn in a spinning method in which direct spinning and drawing is performed mainly under a temperature gradient between a melt spinneret and a first roller (group). The purpose is to improve the strength and elongation characteristics of the strips and the level dyeing properties. Then, under the standard spinning conditions, the tension F applied to the yarn _F0 is mainly changed by changing the temperature and flow rate conditions of the cooling air flow, and the value of the tension F when the other yarn spinning conditions are made the same as when calculating _F0 above. /F ₀ is less than 1.05, the effect of the present invention cannot be obtained; conversely, when F 0 is less than 1.70
Although the above method is effective, it cannot be said to be economical because special spinning conditions are required. As described above, the present invention is capable of greatly improving strength and elongation characteristics and level dyeing properties by increasing the tension applied to the running yarn without using means of mass contact or liquid contact with the high-speed running yarn. At the same time, the knitting and weaving properties have also been improved, making it possible to supply fibers that are fully applicable to the clothing field. The present invention will be described in detail below with reference to Examples, but the present invention is of course not limited thereto. Example 1 Intrinsic viscosity [η] measured at a temperature of 30°C in a 6/4 mixed solvent of phenol/tetrachloroethane
However, 0.630 polyethylene terephthalate is passed through a melt spinneret with 96 holes and 0.23 mm diameter spinning holes, and the spinning temperature is 285°C as the amount of polymer discharged so that the fineness of the product fiber is constant at 50d/24f.
0.38, which was melt spun at
A cooling air stream of m/s is blown across a length of 20 cm perpendicularly to the spun yarn, and then the yarn is passed through a cooling zone at room temperature that is continuous below the cooling air outlet zone. Cooled to 30°C. At this time, a cooling air flow temperature of 22°C was used as a blank, and in the case of the present invention whose purpose was to increase the level of tension applied to the yarn, the cooling air flow temperature was kept constant at 100°C. A non-hydrous oil agent is applied to the cooled and finely spun yarn, and then the yarn is divided into four yarn bundles, and then two non-contact cylindrical heating units connected vertically below the melt spinneret are used. The yarn was passed through an apparatus (same as the one described in JP-A-52-55718) for hot stretching, and then the yarn was taken off by a first roller rotating at high speed. The length of each cylindrical heating device is 60 cm, and the temperature of the cylindrical heating device (referred to as the first drawing tank) disposed on the spun yarn introduction side is 120℃
The temperature of a cylindrical heating device (referred to as a second stretching tank) disposed continuously in the stretching tank was kept constant at 320°C. Second
The temperature of the traveling yarn immediately after leaving the drawing tank was determined using a radiation thermometer (RM-2B manufactured by Barnes Engineering Co.).
The measurement was carried out using a mold). The tension of the running yarn at the exit of the second drawing tank is measured using a commercially available tension meter [HF manufactured by Eiko Sokki Co., Ltd.].
-2000STAJ improved model] was used for actual measurements. Regarding the strength and elongation characteristics of the obtained yarn, for example, if the elongation is 40% or less and the strength is 40 g/d or more,
If the strength x elongation ratio is 28.0 or more (strength x elongation ratio for a blank equivalent product is 25 to 27), it can be said that the yarn is usable for practical use and has improved strength and elongation properties. After knitting the dyed spots into a tubular knitted material, dyeing is performed (dye Foron Navy 2GL 2%Owf 100℃ x 90
(minutes), the dyed material is visually judged, and those with no spots are classified as grade 0, and those with the most spots and of no practical value are classified as grade 0.
It is graded as 3.0 grade using 0.5 grade pitch.
Grades 0 to 1.0 indicate passing products.

【table】

[Table] Table 1 shows the strength and elongation properties and level dyeing properties of the yarn obtained in comparison with the take-up speed. As is clear from Table 1, the products belonging to the present invention (Nos. 1 to 4) have strong and elongation properties suitable for use in clothing, and staining spots of 1.0.
It can be seen that it is below grade level and can be used for practical purposes. On the other hand, in the case of the one that does not belong to the present invention (No. 5), fusion of yarns occurs in the heating device, which causes yarn breakage, poor spinning and drawing operability, and the obtained yarn is also uniform. It has poor dyeability and has little practical value. Example 2 Under the yarn spinning conditions of Example 1, the surface speed of the first roller was kept constant at 4000 m/min, and the cooling air flow temperature was varied variously, and the fiber performance was as shown in Table 2.

[Table] From Table 2, those belonging to the present invention (No. 7 to
9) has good strength and elongation properties and satisfactory level dyeing property, whereas in cases outside the present invention (Nos. 6 and 10), only low level dyeing property can be obtained. Recognize. Example 3 Under the spinning conditions of Example 1, the surface speed of the first roller was 4000 m/min, and the cooling air flow temperature was 100°C.
Table 3 shows the results of the fiber performance and tension level when the cooling air flow rate was kept constant and the cooling air velocity was varied.

【table】

[Table] From Table 3, those belonging to the present invention (No. 12 to
It can be seen that No. 13) is satisfactory in both strong elongation properties and level dyeing property, whereas those that do not belong to the present invention (Nos. 11 and 14) have not improved level dyeing property.

Claims (1)

[Claims] 1. Melt-spun a synthetic linear thermoplastic polyester through a melt spinneret, blow a cooling air stream onto the spun yarn below the melt spinneret, and cool it once to a temperature of 80°C or less, Next, the yarn is passed through a heating zone and hot-stretched at a yarn temperature of 80°C or higher, and immediately after the stretching, it is
In the direct spinning and drawing method of polyester fiber, which is drawn at a speed of m/min or more, the cooling air flow is 55℃.
By using a cooling airflow heated to a temperature above and blowing the cooling airflow across the spun yarn, the tension F of the running yarn immediately after leaving the heating zone can be increased.
(g/d) satisfies the following formula for the tension F ₀ (g/d) of the running yarn immediately after leaving the heating zone when a cooling airflow of 22±2°C is used as the cooling airflow. A method for producing polyester fiber, characterized by: 1.05＜F／ _F0 ＜1.70