JPS6223082B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a novel method for producing crimped fibers, and particularly provides a novel method for producing crimped synthetic fibers by a melt spinning method. (Prior art) Regarding the manufacturing method of crimped fibers made of thermoplastic synthetic polymers, studies have been actively conducted on continuous spinning, drawing, and crimping for the purpose of reducing production costs and improving productivity. It is being said. However, when the spinning speed is around 1000 m/min, it is necessary to increase the draw ratio several times, and the crimp application speed is unavoidable.
3,000 to 4,000 m/min, and as it is currently not possible to provide satisfactory crimp, the spinning speed is actually reduced to 1,000 m/min.
I had to set it much lower than m/min,
In the end, it was not possible to achieve the intended purpose. In view of the current situation, the inventors of the present invention have conducted intensive studies on high-speed crimp application methods, and have found that with the current level of technology, it is difficult to apply sufficient crimp with a mechanical crimp application device alone, and some kind of auxiliary means is required. For example, even if it were possible to provide sufficient crimp mechanically, the equipment would be extremely expensive, leading to the idea that this would be impractical. (Problems to be Solved by the Invention) The present invention provides a means for producing crimped thermoplastic synthetic fibers having excellent mechanical properties such as strength and elongation and initial Young's modulus, as well as bulkiness, using simplified equipment. The aim is to provide a new method for producing silk at a high speed of 3000 m/min or more with good operability. (Means for Solving the Problems) That is, the present invention provides thermoplastic synthetic fibers that have been melt-spun and then cooled immediately below the spinneret, and are spun together with the spinneret at high speed rotation at a surface circumferential speed of 3000 m/min or more. A process for producing synthetic fibers in which hollow fibers are drawn by passing through a heating zone between take-off rolls and then, if necessary, re-drawn and/or heat treated before being taken off or cut continuously. By using a spinning hole that can be manufactured, configuring the heating zone with a non-contact heating device, and cooling the yarn asymmetrically in the cross-sectional direction directly below the spinneret, the following can be achieved. This is a method for producing a novel crimped fiber having a crimping ability such that the defined potential crimping property 1/ρ is at least 1.5. Latent crimpability 1/ρ: Defined as the reciprocal of the average helical radius ρ (unit: mm) per 10 spiral crimps that occurs when the stretched single fiber is subjected to free shrink heat treatment at 160°C for 60 seconds. . Here, the thermoplastic synthetic fibers may be any fibers made from known polymers that can be melt-spun, but polyamide and polyester polymers are preferred in view of their excellent properties as fibers. . Of course, there are those modified by copolymerization or blending to give special performance,
It may be added with additives or the like. These melt-spun polymers are usually extruded from a spinneret using a known spinning machine to form yarns, but even more effects are exhibited when means such as a direct polymerization spinning method are used. The spinneret used in the present invention does not have a generally used circular (round cross-section) spinning hole, but has a spinning hole that can produce hollow fibers. The reason for using such a spinneret is that the spun yarn is cooled asymmetrically in the cross-sectional direction of the yarn by a cooling air flow directly under the spinneret, thereby imparting a high degree of latent crimp performance to the yarn. It's for a reason. Various types of spinnerets have been proposed in the past, and these known spinnerets can be used in the present invention. In that case, the spinning hole capable of producing hollow fibers should have a fiber hollowness ratio (area of the hollow part of the cross section of the fiber/total area of the cross section of the fiber including the hollow part) of 5 to 40%, especially 10 to 35%. % is better. It is desirable that the arrangement of the spinning holes in the spinneret be carefully considered to avoid unevenness between each single fiber as much as possible. It is best to use a cap like the one suggested in No. 50-71078. The yarn discharged from the spinneret is cooled and solidified asymmetrically in the cross-sectional direction of the yarn by a cooling air flow directly below the spinneret, and then passed through a heating zone installed between the spinneret and a high-speed rotating take-up roll. It is stretched as it passes through. This stretching is performed by frictional force with air under a temperature gradient. Asymmetric cooling of spun yarn is already known, but in the case of high-speed spinning of 3000 m/min or more as in the present invention, it is necessary to increase the blowing speed of the cooling air flow to the yarn to prevent a high degree of latent crimp. This is important in imparting performance, and the blowing speed of the cooling air stream is preferably about 0.5 m/sec or more, particularly 0.5 to 2.5 m/sec. Room temperature air is usually used as the cooling air stream from a thermoeconomic standpoint. The length of the zone in the vertical direction in which the cooling airflow hits the yarn is preferably about 20 to 100 cm. The heating zone is configured with a non-contact heating device from the viewpoint of silk reeling operability and prevention of fuzz generation. Various types of non-contact heating devices are possible, but high-temperature electric furnaces, high-temperature gas furnaces, etc. are particularly preferred. Also, the heating temperature is not particularly limited, but
It is important to set the strength and elongation characteristics after stretching and 1/ρ, preferably 1/ρ is 1.5 or more and the elongation at break is 70% or less, more preferably 50% or less. It is better. In addition, when the speed of the yarn entering the heating zone is high, the amount of cooling gas (air) accompanying the yarn increases significantly and the heat transfer effect to the yarn in the heating zone decreases, so the entrained cooling gas is separated. It is preferable to provide a separation device for this purpose. The potential crimpability 1/ρ in the present invention varies depending on the type of polymer to be melt-spun, the denier of the single fiber, the temperature and blowing speed of the cooling air stream, the take-up speed of the yarn, etc. In order to produce crimped fibers that have satisfactory bulk even without imparting , it is necessary to appropriately select the above-mentioned variable factors so that 1/ρ is 1.5 or more, particularly 2.0 or more. The heated and drawn yarn with latent crimp is then treated with an oil agent if necessary, and then stretched for at least 3000 m/s by a take-up roll rotating at high speed.
The material is taken off at a speed of 3500 m/min or more, but since the latent crimpability increases with the taking speed, it is preferable that the take-up speed by the take-off roll is 3500 m/min or more. The yarn taken up by this take-up roll can be subsequently re-stretched and/or heat-treated as necessary, but preferably it is treated as is or after being subjected to high-temperature treatment in order to develop latent crimp. The filament is wound up with a winding machine and used as a filament, or after being shaken off with a shake-off device, it is cut into short fibers, or after being cut and shaken off, it is used as a staple. Some of the ways in which short fibers are shaken off after being cut are as follows:
This also includes a case where the cutting device also has the capability of functioning as the above-mentioned high-speed rotation take-up roll. When producing a web, the fibers are sucked with a gas jet, opened as appropriate, and dropped onto a net conveyor or the like. When using the already known spunbond method, it is possible to create a very good crimped web due to the room temperature elastic crimping effect of the fibers, and it is also possible to perform subsequent heat treatment if necessary. It is. The crimped fibers produced by the present invention are superior to crimped fibers produced by the conventional high-speed spinning method in which latent crimpable fibers are spun at high speed without providing a heating zone between the spinneret and the high-speed rotation take-up roll. Under the same spinning speed, it has excellent mechanical properties such as strength and elongation, initial Young's modulus, and bulkiness.In particular, because the initial Young's modulus is high, there is little crimping set, and even after long-term use. It has the feature that bulkiness does not decrease, and is extremely practical. Example 1 A product with an intrinsic viscosity of 0.62 (in a mixed solvent of phenol/tetrachloroethane = 6/4) manufactured by a conventional method.
C) with an inner diameter of 0.36 mmφ, an outer diameter of 0.56 mmφ, and a bridge width of 0.1 mm.
The yarn is melt-spun from a spinneret with 30 shaped slit nozzle orifices, cooled by blowing a cooling air stream at room temperature directly below the spinneret from one side of the yarn perpendicular to the yarn, and then heated by an electric heater. After applying an oil agent, the fibers were taken up with a take-up roll rotating at high speed, and then cut into staples of 70 mm in length with a high-speed cutter to produce crimped fibers. The hollowness ratio of the obtained fiber was about 25%. Table 1 shows the spinning conditions, latent crimpability, and properties of the resulting crimped fibers in this example. For comparison, Table 1 also shows the performance of crimped fibers obtained by using a spinneret having 24 circular spinning holes with a hole diameter of 0.3 mmφ and otherwise producing under the same conditions as in this example. Control Example 1 The yarn quality of the crimped fiber produced under the same conditions as Experiment No. 2 of Example 1 except that no heating element such as an electric heater was used was as follows. Potential crimpability 1/ρ = 0.9mm ^-1 , single yarn denier =
2.5d, initial Young's modulus = 24g/d, strength = 2.1g/
d, elongation at break = 69%, number of crimp CN = 8/inch, crimp ratio CI = 13%. These results are also listed in Table 1.

【table】

[Table] As shown in Table 1, the hollow fibers obtained by the present invention (Experiments Nos. 1 to 3) have a high potential crimpability (1/ρ) and can be easily crimped by heat treatment. However, in the case of the solid fiber of the comparative example (experimental
Nos. 4 to 8) have low latent crimp properties, and are in the region where yarn breakage does not occur even if the cooling air blowing speed is increased, with 1/ρ≧
It never reached 1.5. Furthermore, in the case of Comparative Example 1, the mechanical properties such as strength and elongation of the crimped yarn and Young's modulus are inferior, and the crimping performance is also inferior to that of the present invention. (Effects of the Invention) According to the present invention, crimped fibers made of thermoplastic synthetic fibers having excellent mechanical properties such as strength and elongation and initial Young's modulus, as well as bulkiness, can be produced in silk-spinning operations using simplified equipment. It has good performance and can be manufactured at high speeds of 3000m/min or more.

Claims (1)

[Claims] 1. After melt spinning, thermoplastic synthetic fibers are cooled immediately below the spinneret, and the surface circumferential speed is set to 3000.
Manufacture of synthetic fibers by stretching by passing through a heating zone between high-speed rotating take-off rolls at m/min or more, then re-stretching and/or heat treatment as necessary, and then continuously taking off or cutting. In the method, a spinneret with a spinning hole capable of producing hollow fibers is used, the heating zone is configured with a non-contact heating device, and the yarn is asymmetrically shaped in the cross-sectional direction directly under the spinneret. A method for producing a novel crimped fiber having a crimping ability such that a latent crimping property 1/ρ defined below becomes at least 1.5 by cooling the fiber. Latent crimpability 1/ρ: Defined as the reciprocal of the average helical radius ρ (unit: mm) per 10 spiral crimps that occurs when the stretched single fiber is subjected to free shrink heat treatment at 160°C for 60 seconds. .