JPS6146563B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention suppresses the generation and growth of foreign matter that accumulates around the nozzle of the spinneret, which is the main cause of poor performance in the spinning process, in melt spinning of high-molecular polymers, improves the quality of the spinning process, and eliminates yarn unevenness. The present invention relates to a melt spinning method for producing fibers with low yarn quality, ie, strong elongation properties. In the melt spinning of high molecular weight polymers, it has been observed that foreign matter accumulates around the nozzle of the spinneret over time, and it is well known that this is the main cause of deteriorating the quality of the spinning process. be. For this reason, the spinning process is maintained in good condition by periodically cleaning the spinneret surface or replacing the spinneret, but this costs...
Labor costs, polymer loss, opportunity losses, etc., can amount to a considerable amount, and reducing the frequency of cleaning the spinneret surface and replacing the spinneret has long been an important issue for textile manufacturing engineers. It was hot. Various methods have been proposed to suppress foreign matter from accumulating around the nozzle of a spinneret. Particularly in the case of polymers whose main component is polyethylene terephthalate, the mechanism of generation and growth of foreign substances is still unknown, but analysis of the foreign substances reveals that they are mainly sublimable, so sublimated particles directly below the mouth surface. It is known that the generation and growth of foreign matter deposited on the mouthpiece surface can be suppressed by discharging an atmosphere containing a large amount of . From this point of view, methods have been proposed to exhaust the atmosphere directly under the mouthpiece surface by suctioning the atmosphere directly under the mouthpiece surface or by blowing gas from outside, but the polymer still solidifies directly under the mouthpiece surface. Since it is in a non-fluid state, blowing or suctioning gas from the outside or giving it any disturbance is undesirable as it will cause uneven threads. Furthermore, if the atmosphere directly below the die surface is exhausted, the temperature directly below the die surface will drop, and the strength and elongation of the resulting fibers will be low, which is also undesirable from this point of view. In the conventionally proposed methods, it has been impossible to suppress foreign matter deposited on the spinneret surface, that is, to improve the quality of the spinning process, and to reduce yarn unevenness and improve yarn quality. The present inventor has arrived at the present invention as a result of intensive studies aimed at reducing foreign matter deposited on the spinneret surface, improving the quality of the spinning process, and obtaining fibers with good yarn unevenness and yarn quality. That is, the present invention provides a method for melt-spinning a high molecular weight polymer using a spinning tube that blows out cooling air for the yarn, in which a space within 30 mm below the spinning pack and a space through which the spun yarn can pass are provided. The space between the spinning pack and the spinning tube is almost closed, and the position where the cooling air blowing speed is maximum is within 300 mm below the top end of the spinning tube, and the average blowing wind speed up to the 300 mm position is It is characterized by making the average blowing wind speed greater than any length of 300mm. Hereinafter, the present invention will be explained based on the drawings. 1st
1 and 2 are a schematic perspective view and a vertical sectional view showing a specific example of the present invention. In the figure, reference numeral 1 has a spinneret 2 for discharging molten polymer from a spinning pack disposed in a spin block 9. Reference numeral 2' denotes spinning holes arranged concentrically in the spinneret 2. 3
This is a shutter for preventing yarn cooling air from flying up toward the spinneret surface and for securing a delayed cooling section, and has a yarn passage hole 3a and is divided into two parts, front and rear from the center. 4 is a spinning tube that blows out yarn cooling air, and 5 is a yarn cooling chamber. Numeral 6 is a spacer made of a metal body, which is composed of split bodies 6a and 6b divided into two parts in the front and rear, similar to the shutter 3. It has a hollow portion 6c as a yarn passage formed to be close to and surround the bundle Y, so as to almost fill the space other than the yarn traveling space (passage) under the spinneret surface. The distance d between the lower surface of the spinning pack 1 and the upper surface of the spacer 6 is 30 mm or less. A magnet 8 attracts, supports and fixes the spacer 6 to the lower surface of the spinning pack 1, and is attached to the spacer 6 directly or indirectly via a fixing means such as an adhesive or a bolt. In addition, 10 is a heat insulating material. Here, the cooling air outlet 4b of the spinning tube 4 has a
A plurality of (4 to 6) 80-mesh wire meshes 4c are stretched, but in the present invention, the cooling air blowing speed reaches its maximum within a downward distance (vertical distance) e = 300 mm from the upper end of the spinning tube 4, and The number of wire meshes between this distance e (300 mm) is smaller than the lower part to reduce the blow resistance so that the average blowing wind speed between the two is higher than the average blowing wind speed of any other 300 mm blow length (vertical distance). (The opening of the wire mesh 4c may be made smaller, or the amount of air supplied may be increased from the lower part). It goes without saying that a current plate such as a honeycomb may be provided in front of the wire mesh 4c. In this way, the cooling air blowing speed is set to 300 mm from the top of the spinning tube.
As will be described later, by limiting the range between these ranges, yarn unevenness and yarn quality can be greatly improved compared to conventional methods, but outside this range, the above-mentioned effects will not occur and on the contrary, yarn unevenness will worsen. In such an apparatus, the yarn Y discharged from the spinneret 2 travels through the space of the delayed cooling section 7 surrounded by the spacer 6, the shutter 3, etc., reaches the cooling chamber 5, and is blown out from the spinning tube 4. It is cooled and solidified by the cooling air. In this case, the yarn polymer discharged from the spinneret 2 carries the surrounding air downward as an accompanying flow for its own running. In the case of conventional spinning devices, which have a fairly wide space under the spinneret surface, most of the air exhausted by the accompanying flow is below the spinneret where the yarn travels at a high speed. Since it is quite slow, a sufficient accompanying flow is not generated, and the atmosphere containing a large amount of sublimate directly under the mouth surface remains stagnant. On the other hand, when the space under the spindle is substantially open only to the yarn running portion as in the present invention, the yarn accompanying flow mainly occurs in the area below the spindle surface where the yarn running speed is high. The atmosphere directly below the mouthpiece is also sucked and exhausted to the outside of the system. That is, by narrowing the yarn traveling space under the mouth surface to a size that allows the yarn bundle Y to pass through, it becomes possible to discharge the atmosphere immediately below the mouth surface to the outside of the system by the accompanying flow. This makes it possible to suppress foreign matter from accumulating on the mouthpiece surface. Therefore, in order to obtain the above effect, it is preferable that the distance between the inner wall surface of the spacer 6 and the yarn bundle Y be as narrow as possible, and usually the distance between the inner wall surface of the spacer 6 and the outermost (spinning) hole 2' of the spinneret 2 is smaller. ₁ is measured by the distance projected on the horizontal plane, and the distance should be 15 mm or less on the cooling air outlet side. As shown in the figure, when using a spinning tube that supplies cooling air from one direction, the yarn (bundle) Y is deflected by the cooling air in a direction away from the cooling air blowing surface 4a, so that the spacer hollow portion 6c is bent. The distance between the inner wall surface and the outermost peripheral hole 2' of the spinneret 2 is the cooling air blowing surface 4.
30mm or less on side ₂ opposite to a, 20mm on side ₃
It is preferable to make it as small as possible by doing the following. Further, it is preferable that the distance between the upper end surface of the spacer 6 and the spinneret surface be as narrow as possible, and should be 30 mm or less. If this value is exceeded, the ventilation effect will be lost and it will not be suitable for suppressing foreign matter adhesion. Furthermore, in the present invention, the air flow is rectified by the yarn accompanying flow in the region where the polymer is in a fluid state directly under the spindle surface, which is the most important area regarding yarn unevenness, and there is no unnecessary space under the spinneret surface other than the yarn running space. Since there is almost no turbulence, there is no disturbance of the atmosphere in this part due to cooling air blowing up from the forced cooling section, etc., which has the effect of reducing yarn unevenness. Furthermore, in the past, when the atmosphere under the nozzle surface was exhausted, the temperature of the atmosphere under the nozzle surface decreased and the strength and elongation of the fibers decreased, in other words, the yarn quality deteriorated. Since the spacer 6 is installed in a high-temperature atmosphere with heat radiation from polymers, spinning packs, spin blocks, etc., the spacer 6 is heated to a high temperature, and the yarn is kept warm due to the radiant heat effect, thus increasing the strength and elongation of the fiber. The level does not decrease, but rather improves. In the present invention, yarn unevenness is effectively improved by regulating the blowing speed of the cooling air within 300 mm below the top end of the spinning tube as described above. This is because the yarn is not solidified at the top of the spinning tube (outlet) and its traveling speed is still slow, so if the blowing air speed here is increased, the cooling air will penetrate through the yarn bundle (between single fibers) enough to create a uniform flow. A fiber with good thread quality, that is, with good thread unevenness and strength and elongation, can be obtained. On the other hand, since the yarn is already in a solidified state at the bottom of the spinning tube (air outlet) and the yarn traveling speed is high, the cooling air here not only does not act effectively on the yarn, but also increases the cooling air speed. This causes the string to sway,
In particular, thread spots become worse. Conventionally, when the blowing air speed at the top of the spinning tube is increased, the cooling air blows up toward the spinneret, disturbing the atmosphere in the delayed cooling section between the spinneret surface and the spinning tube, which worsens yarn unevenness and increasing the blowing air speed at the top of the spinning tube. This is difficult to achieve, and a spinneret with a wind speed distribution that is slower in the upper part than in other parts is usually used. In the present invention, by installing a spacer in the delayed cooling section, it is possible to rectify the flow accompanying the yarn in this space and to prevent the spinning tube cooling air from blowing up. This made it possible to increase the amount. Here, the length of the upper part of the spinning tube (cooling air outlet) that increases the blowout flow rate depends on the length of the delayed cooling section, the denier of the discharged yarn, and the number of filaments, but various experiments have shown that it is approximately before the solidification point. By setting the distance within 300 mm below the top end of the spinning cylinder, fibers with uniform quality can be obtained stably and reliably.If this condition is not met, the effect of the combination with the spacer will not be fully exerted, and the quality of the yarn will deteriorate. It's coming. As described above, the present invention eliminates yarn unevenness by the synergistic effect of the effect of substantially blocking the delayed cooling section between the spinning pack and the spinning tube except for the position immediately below the spinning pack and the yarn path, and the effect of the cooling air blowing speed. This made it possible to produce fibers with extremely good yarn quality. Incidentally, it is preferable that the material of the spacer is a metal substance, but the material is not necessarily limited to this. When using metal, aluminum (aluminum-based material) is most preferable among general-purpose materials because it takes a short time to reach a thermal equilibrium state after installation and has a large radiant heat effect. Furthermore, in order to shorten the time required to reach a thermal equilibrium state, it is preferable to reduce the heat capacity as much as possible, and for this purpose, it is preferable to use a hollow body using a plate as thin as possible. Although various methods can be considered for installing the spacer, it is preferable that the spacer is easily removable and fixed, and the most convenient means for this is to attach it to the bottom surface of the spinning pack via a magnet. In this case, if the spacer is divided into two parts, one on the working surface side of the spinning machine and the other on the non-working surface side, only the working surface side of the spacer needs to be removed when cleaning the nozzle surface or observing the nozzle surface. This is preferred from the standpoint of improving workability. Although the specific example shows the case where four yarns are spun simultaneously, it goes without saying that the present invention is not limited to this and can be similarly carried out when spinning one yarn or any number of yarns. Also shutter 3
may be integrated with the spacer 6, or may be removed or not. When the shutter 3 is attached as in this specific example, it is preferable that the thread passage hole 3a is approximately the same size as the hollow portion of the spacer 6. Further, in order to obtain fibers with good yarn unevenness and yarn quality, it is preferable that the delayed cooling section 7 has an appropriate length of usually 40 to 200 mm. Next, examples will be shown to further specifically explain the effects of the present invention. Example As shown in Figures 1 and 2, a spinning device with a spinning tube from which cooling air is blown out from one direction was used, and the intrinsic viscosity (measured at 35°C in 0-chlorophenol) was
Polyethylene terephthalate and spinning speed of 0.635
Melt spinning was performed at 1200 m/min to obtain a yarn of 50 denier/36 filaments (measured after stretching). A spacer made of a hollow aluminum body was provided on the shutter to provide a space in the delayed cooling section between the spinning pack and the spinning tube. The hollow holes forming the yarn passages had oval cross sections and had different sizes as shown in the table below. Further, the distribution of blowing speed of the spinning tube cooling air was changed by adding one or two pieces of 50-mesh wire mesh. The results are shown in the table below. The length of the delayed cooling section was 100 mm, the pitch circle of the outermost hole of the spinneret was 50 mm, and the cooling air volume was 4 Nm ³ /min.

[Table] Here, ₁ , ₂ , _{and 3} are the distances between the inner wall surface of the spacer hollow hole and the outermost peripheral hole (inner wall surface) of the spinneret, ₁ is on the cooling air blowing surface side, ₂ is on the opposite side to the cooling air blowing surface, ₃ is the distance between the direction of the cooling air blowing surface and the right angle side (lateral side). d is the distance between the bottom surface of the spinning pack and the top surface of the spacer. The spinning process condition is expressed as the average spinneret surface cleaning cycle (unit: days), in which the spinneret surface is cleaned when spinning yarn breakage occurs twice or more in 8 hours. Yarn quality is measured using a drawn yarn, and dyeing spots are visually judged using a 5-point method, and a score of 3.5 or higher is considered to be a good level, but the higher the score, the better. Also, u% is at a good level of 0.7% or less,
The lower the value, the better. As described in detail above, according to the present invention, generation and growth of foreign matter deposited around the nozzle of a spinneret are suppressed, improving the quality of the spinning process, and reducing yarn unevenness.
It becomes possible to stably obtain fibers with good yarn quality. Furthermore, it can be said to be an innovative melt-spinning method in that it satisfies both the suppression of foreign matter deposited on the spinneret surface and the improvement of yarn unevenness and yarn quality, both of which have conventionally been considered contradictory phenomena.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a schematic perspective view and a longitudinal sectional view showing an embodiment of the present invention. 1...Spinning pack, 2...Spinneret, 2'...
Outermost hole, 3...Shutter, 4...Spinning cylinder, 6
...Spacer, 6c...Hollow part, 7...Delayed cooling part.

Claims (1)

[Claims] 1. In a method of melt-spinning high molecular weight polymers using a spinning tube that blows out cooling air for the yarn, the spinning pack is formed by leaving a space within 30 mm below the spinning pack and a space through which the spun yarn can pass. The space between the spinning tube and the spinning tube is almost closed, and the position where the cooling air blowing speed is maximum is within 300 mm below the top end of the spinning tube, and the average blowing wind speed up to the 300 mm point is set at any other 300 mm length. A melt spinning method characterized in that the blowing wind speed is higher than the average blowing wind speed during the spinning period.