JPS6144973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a discontinuous fiber bundle, which is an intermediate product for producing a spun yarn from a continuous fiber bundle made of acrylic synthetic fibers, such as tow or multifilament. More specifically, a bundle of continuous fibers made of acrylic synthetic fibers is brought into contact with a medium at -20°C or lower while maintaining crimping, and immediately after that, the bundle of continuous fibers is subjected to a drawing force or an auxiliary drawing force. The present invention relates to a method for producing a bundle of discontinuous fibers having crimps by applying a strong shearing force to cut each single fiber. BACKGROUND ART Conventionally, as a method for producing spun yarn, a method is known in which short fibers are produced by a carding process → gill process or drawing process → roving process → spinning process. However, this method has low productivity because it involves a card process. Shrinkage cannot be imparted to the spun yarn during the spinning process In the fiber manufacturing process, a process is required to cut the fibers into lengths that correspond to the purpose of spinning to produce short fibers. In the carding process, neps (tangles of single fibers) and hooks (curved ends of single fibers) occur. Furthermore, since the parallelism is poor, measures such as lengthening the gill process are required. There are some problems. On the other hand, after converting a bundle of continuous fibers such as tow or filament into a bundle of discontinuous fibers, as a method of manufacturing spun yarn, the bundle of discontinuous fibers is manufactured by the parlock method, turbo method, etc. at a temperature around room temperature. There are known ways to do this. The parlock method is a method in which a bundle of continuous fibers is drawn by a roller and each single fiber is cut to obtain a bundle of discontinuous fibers with high parallelism at high speed. When cutting, as shown in the strong elongation curve C of acrylic synthetic fiber (trade name Cashmilon) in Figure 7, the fiber goes through an elastic deformation range with an elongation of 0 to about 5%, and then a plastic deformation range with an elongation of 5% or more. (i) Under normal spinning conditions, there is a large residual strain in the fibers due to stretching, so there is a limit to the production of low shrinkage spun yarns. (ii) Since the strength and elongation, especially the loop strength and elongation, are greatly reduced, fibers are frequently cut and fried in the process of producing spun yarn. (iii) When high elongation fibers are drawn and cut, the disadvantage of (ii) is exacerbated because the parlock method is used to stretch and cut the fibers after preliminary drawing. (iv) The tips of the cut fibers become jittery, which causes unevenness in the spun yarn. There is a problem. The turbo method involves drawing a bundle of continuous fibers,
This is a method of cutting by applying shearing force. In this method, it is not necessary to stretch the fibers to the breaking elongation, but the staple diagram of the cut fibers becomes poor. That is, the content ratio of overlong fibers and short fibers increases. The present invention provides a method to overcome the drawbacks of such conventional methods. That is, in addition to solving the above-mentioned drawbacks in the spinning process, when producing bundles of discontinuous fibers, it can be done with extremely little energy, and spun yarns made of acrylic synthetic fibers with low to high shrinkage rates can be freely produced. The object of the present invention is to provide a method for producing a discontinuous fiber bundle, which can produce spun yarn of extremely excellent quality at high speed, with extremely little occurrence of fiber breakage or fly. As the continuous fiber bundle of the present invention, tow or multifilament is generally used. As a bundle of fibers, the total denier is 30d to 2 million d, consisting of single fiber denier 0.1 to 60d.
filament, large filament and
Applicable to tow etc. Furthermore, it can also be applied to a mixture of the above continuous fiber bundle and a fiber bundle made of short fibers, or a mixture with other types of fibers. One aspect of the present invention is to cool a bundle of continuous fibers made of acrylic synthetic fibers having crimps in a medium at -20°C or lower, preferably -40°C or lower, more preferably at -40°C or lower while maintaining the crimps. is −80
In this method, single fibers are cut immediately after being brought into contact with a medium at a temperature of ℃ or lower. Another invention is to overfeed a bundle of continuous fibers made of acrylic synthetic fibers having crimps into a cooling zone, so that the bundle of continuous fibers made of acrylic synthetic fibers is brought into contact with a cooling medium at the above temperature while maintaining crimps, and then immediately This is a method of cutting single fibers to produce bundles of discontinuous fibers having crimps. Figure 7A shows a state in which a single fiber of acrylic synthetic fiber (product name: Cashmilon) has crimps.
Strength and elongation curve when stretched in contact with nitrogen gas at 100℃ for 45 seconds, B is strength and elongation curve when stretched in contact with the same medium without crimp with tension applied It is a curve. FIG. 8 is a curve showing the breaking strength after being left at each temperature for 1 minute with the crimp maintained, and FIG. 8 is a curve showing the breaking strength after the same treatment was performed with the crimp fully stretched. As can be seen from Figures 7 and 8, if a crimped state is brought into contact with a medium at -20°C or lower to fix the crimped state, then the crimped state is cooled and cut in a stretched state. Approximately 10% compared to
The tension required for cutting is reduced. It can also be cut with the same tension as the conventional stretch braking method. By contacting with a medium at -40℃ or lower, fiber damage is less than that of a continuous fiber bundle, and similarly, there is less fly and shrinkage, physical performance, and quality such as parallelism, unevenness, and neps. An excellent bundle of discontinuous fibers is obtained. By contacting the medium at -80°C or lower, it is possible to cut with less tension, which is less than half that of the conventional stretch-braking method. The state of this crimp is explained using Fig. 4.
The crimps 23 in the longitudinal direction of the single fibers 22 constituting the continuous fiber bundle 21 may exist continuously as shown in A, but they may be crimps 23 in the longitudinal direction of the single fibers 22 constituting the bundle 21 of continuous fibers, but they may be crimps 23 in the longitudinal direction of the single fibers 22 constituting the bundle 21 of continuous fibers. It may have 2 crimps 23. When viewed as a continuous fiber bundle 21, it is desirable that the continuous fibers exist randomly in the length direction. Then, it is preferable to uniformly split the bundle of crimped continuous fibers into single fibers with a constant width and adjust the thickness before supplying the bundle to the cooling zone. In the present invention, when feeding the continuous fiber bundle to the cooling zone, it is more preferable to carry out overfeeding in order to reduce the breaking energy. That is, the fibers are overfed, and while maintaining the crimp of the original fibers as much as possible, the fibers are brought into contact with a medium at −20° C. or lower in a cooling region, and then immediately cut. Figure 10 shows a bundle of continuous fibers made of crimped acrylic synthetic fibers (single fiber denier 3d x 100 fibers) fed to a -100°C cooling zone for 45 seconds at various overfeed rates. It is well understood that the breaking strength decreases as the overfeed rate increases. In the present invention, the single fibers are crimped when fed to the cooling zone, within the length L of the cutting zone, the angle θ of at least one crimp is 0°<θ as shown in FIG.
Preferably, the temperature is ≦120°C. Note that the angle θ was measured with a load of 2 mg/d applied. This crimping can be maintained by feeding the fiber bundle in a relaxed state, or by overfeeding the fiber bundle after it has been tensed. In this way, it is preferable to use a crimped fiber bundle in the present invention, and after sealing with a roller or slit and squeezing to drive out the outside air contained between each single fiber, the fiber bundle is over-fed into a cooling tank. Therefore, by creating crimp and giving the fiber bundle bulkiness, it is possible to increase the cooling efficiency by allowing cold air to pass through or be contained between each single fiber. In addition, the energy required for cutting is reduced, and even after cutting, it has become possible to obtain a bundle of discontinuous fibers that retains its original crimps, is bulky, has low shrinkage, and has good parallelism. As a result, when obtaining a bundle of discontinuous fibers with low shrinkage and crimps using conventional methods, such as the parlock method or turbo method, it is necessary to cut the fibers by causing large plastic deformation and stretching to the breaking elongation. After spinning a bundle of discontinuous fibers with no original crimps and almost no residual elongation, crimps are applied again in a crimper process, and then shrinkage is relaxed and crimps are removed in a setter process. It was necessary to fix it. Furthermore, the bundle of discontinuous fibers thus obtained after setting is tightly packed and has poor opening properties, so a drafter step was required to open the bundle to form a bulky bundle of discontinuous fibers. Therefore, the present invention eliminates the need for the crimper process, setter process, and drafter process for fiber opening used in the conventional method, making it possible to achieve continuity and significantly shortening the process. It has the effect of reducing damage to the fibers caused by bending or buckling deformation in the crimper process in a brittle state with no residual elongation. In addition, in the method of the present invention, in order to remove the high shrinkage that occurs after cutting with large plastic deformation in the conventional method, the method of the present invention applies dry heat and moist heat to the conjugate fibers in addition to fiber shrinkage. This method is very effective against problems such as crimping caused by the structure of the fibers, which causes the bundle of discontinuous fibers to become harder, resulting in increased pullout resistance, poor opening properties, and poor yarn unevenness. As a cooling medium, anything below -20℃ can be used, but vaporized gases or liquids such as ammonia, carbon dioxide, air, oxygen, and nitrogen, and as a cooling agent, alcohol or a mixture of ether and solid carbonic anhydride. In addition, a mixture of ice and a hydrochloric acid, nitric acid, or sulfuric acid compound such as zinc chloride, sodium chloride, sodium nitrate, or sodium sulfate can be used. It is also possible to use electrical cooling methods. The time of contact with this cooling medium varies depending on the type of fiber, feeding method, type of medium, temperature, etc., but generally about 1 to 100 seconds is used. The method of contact with the cooling medium is not particularly limited, but
There are methods such as passing a bundle of continuous fibers through a liquid in a gas atmosphere, dropping a cooling medium onto the bundle of continuous fibers, and bringing the bundle of continuous fibers into contact with the surface of a cooling object. The overfeed rate varies depending on the type of fiber and the cooling temperature, but it is sufficient to relax the tension of the fiber bundle and make it greater than 0%. Generally 1-50%
degree is used. Preferably it is 3 to 10%. In particular, when the fiber bundle is left in a low-temperature bath for a long time, the overfeed rate can be further increased, but the limit is such that the refrigerant can pass between each single fiber of the overfed fiber bundle. Further, the feed roller may be changed depending on the packing density. The continuous fiber bundle is cut immediately after contact with the medium at -20°C or lower. According to the present invention, as the temperature is lowered, the viscous resistance of the fibers increases and the elongation becomes extremely low, so it is possible to obtain a bundle of discontinuous fibers having raw cotton crimps even after cutting. Furthermore, in the present invention, it is preferable to cut the fiber bundle by applying a drawing force or a drawing force and an auxiliary shearing force immediately after cooling the fiber bundle in a crimped state, and cooling the fiber bundle while maintaining the crimps. This increases the cooling efficiency of the fibers and also fixes the crimp. Next, when a stretching force or the like is applied to the fixed crimped portion, it can be cut with a small tension due to the shear stress generated in the crimped portion or the stress generated inside the bent portion. There is no problem in using other cutting forces in addition to these. The resulting bundle of discontinuous fibers will thus have a good staple diagram. Specifically, the bundle of discontinuous fibers produced in this manner includes fiber bundles for sliver, roving direct spinning, and the like. Figure 9 shows the relationship between the temperature of the cooling medium and the shrinkage rate of the single fibers that make up the bundle of discontinuous fibers when cutting acrylic synthetic fibers (product name: Cashmilon) while maintaining crimping. As can be seen from the figure, according to the method of the present invention, it is possible to produce discontinuous fiber bundles with a low shrinkage rate to a medium shrinkage rate. Furthermore, when a required medium temperature is set during cutting, the shrinkage rate of the single fiber corresponding to that temperature is determined as shown in FIG. In that case -20℃
By carrying out stretching, preferably hot stretching, in advance of contact with the following medium, a desired shrinkage ratio can be obtained in accordance with the stretching ratio. FIG. 6C is a diagram showing the change in shrinkage rate when acrylic synthetic fiber (trade name: Cashmilon) is previously hot stretched and then cut while being brought into contact with a medium at -100°C. The shrinkage rate without hot stretching is 4%, but as the hot stretching ratio increases, the shrinkage rate changes from 4 to 28%. On the other hand, D is the shrinkage rate when cutting at 20°C using the Parlock method. In this case, the shrinkage rate is 23%~28
It only changes within a % range. In this way, the present invention produces a bundle of discontinuous fibers by bringing them into contact with a cooling medium of -20°C or lower. Cutting requires very little energy when manufacturing. (b) By changing the temperature of the cooling medium, it is possible to produce a spun yarn with any desired shrinkage rate ranging from low shrinkage to high shrinkage. (c) By performing a stretching process prior to cutting, it is possible to adjust the shrinkage rate to any desired value. (d) The occurrence of flies and fiber breakage in the spinning process is greatly reduced. (e) The spun yarn made from the bundle of discontinuous fibers according to the method of the present invention has extremely little yarn unevenness and high yarn strength. It shows remarkable action and effect. Next, an example of the present invention will be explained with reference to the drawings. FIG. 1 is a process diagram showing an embodiment of a method for cutting while maintaining crimp. The original crimps 32 are removed by overfeeding a bundle 31 of continuous fibers made of single fibers having crimps with a uniform thickness and uniformly splitting the single fibers into a constant width using a back crawler 36. It is supplied into the low temperature chamber 33 while being allowed to recover. By bringing the fibers into contact with a low temperature medium of −20° C. or lower in the low temperature bath 33, the stiffness of the fibers is increased, the fibers are brought into a state with almost no elongation, and the crimp is fixed. Next, give a slight break draft between the middle roller 37 and the break roller 38,
A shearing stress or concentrated stress is generated in the fixed crimped portion, and the single fiber is cut to form a bundle of discontinuous fibers 3.
4, and after being drafted by a front roller 39, it is stored in a can 35. In FIG. 2, a crimper 40 is provided between a back roller 36 and a middle roller 37, and a bundle 31 of continuous fibers with no crimps or with weak crimps is given appropriate crimps 32 to be crimped at a low temperature. 3 is a process diagram for manufacturing a bundle of discontinuous fibers by supplying the fibers into a tank 33 and cutting them by applying a break draft between a middle roller 37 and a break roller 38. FIG. Figure 3 shows a bundle 3 of discontinuous fibers with arbitrary shrinkage.
4, a pair of upper and lower hot plates 42 are provided between the back roller 36 and the stretching roller 41 to heat and soften the continuous fiber bundle 31. At the same time, it is stretched at a stretching ratio suitable for obtaining a predetermined shrinkage. Next, crimps 32 are applied with a crimper 40, and the cryostat 3
3, a slight break draft is applied between the middle roller 37 and the break roller 38 to generate shear stress or concentrated stress in the fixed crimped portion 32, thereby cutting the single fiber. The discontinuous fibers are then stored in a can 35 as a bundle 34 of discontinuous fibers. Next, the present invention will be specifically explained with reference to Examples. Example 1 A 500,000 denier tow made of acrylic synthetic fiber 3D was placed in the apparatus shown in Fig. 1 and spun under the following conditions. Number of crimps 12 (ke/inch) Tow crimp state Degree of crimp 13 (%) Crimp angle 60゜≦θ≦120゜ Overfeed rate 10 (%) Cooling medium Nitrogen gas Ambient temperature in low temperature chamber -100 (℃ ) Residence time 45 (sec) Break draft 1.15 (additional magnification) Spinning speed 100 (m/min) Next, the above tow was placed in an OM tow reactor (manufactured by OM Seisakusho Co., Ltd.) and spinning was performed under the following conditions. The results were compared. Hot plate temperature 120 (℃) Hot drawing ratio 1.281 Residence time 6 (sec) Total draft 6.51 (Break draft) (2.53) Stretch cut zone ambient temperature 20 (℃) Spinning speed 100 (m/min) Furthermore, worsted In the spinning process, staple fiber cut 3D to a bias of 70 to 127 (mm) was supplied to the roller card and spun under the following conditions, and the process performance and sliver physical properties were compared. Spinning speed 30 (m/min)

【table】

[Table] Also, from the above sliver (the tow reactor sliver underwent relaxation set),
Comparisons were also made between ring spun yarns obtained through normal spinning processes and their products.

[Table] By bringing a tow with a total denier of 500,000 into contact with a cooling medium at -100°C, the conventional tow reactor was unable to break through with a break draft less than 2.1 times, whereas the present invention Even after overfeeding by 10%, it was possible to cut with a break draft as low as 1.15 times, and there was less fly and cotton drop, which was better than the conventional card method. The obtained sliver has a low shrinkage rate and maintains its original crimps, so in addition to relaxing it as in the tow reactor method, a setter process is required to fix the crimps added after tension cutting. It's no longer necessary.
Furthermore, compared to card slivers that also do not exhibit shrinkage, it was possible to produce slivers with superior quality in terms of parallelism, neps, and U% at high speed. In terms of yarn physical properties, the method of the present invention has almost no fiber damage and has better count tenacity than the conventional tow reactor method, and is superior in quality such as U% yarn defects compared to the card method. . In addition, in products, as well as the card system,
It had good repellency and good dyeability and heat polishability. Example 2 In order to compare the tensile force required for cutting between the method of the present invention and the conventional method, a 300-denier fiber bundle made of 3D acrylic synthetic fibers (number of crimps: 10/inch/crimp angle: 60°≦θ) was prepared. ≦120°) was stretched with Tensilon under the following conditions, and the respective SS curves were compared. The results are shown in Figure 7. Conventional method Stretch cutting was carried out at an ambient temperature of 20°C. (Graph C) Method of the present invention A bundle of single fibers is slackened by 10% in the length direction, and in a state where crimp is developed, the bundle is exposed to -100°C nitrogen gas at 45°C.
After cooling for seconds, it was stretched and cut. (Graph A) Also, when tension is applied and the crimp is stretched out, -
S- when stretched and cut after cooling to 100℃ for 45 seconds
The S curve was also studied (Graph B) Example 3 Using the same sample as in Example 2, the tensile force required for cutting when the crimp was cooled and fixed with -100°C nitrogen gas and when the crimp was stretched and cooled. We investigated the strong temperature dispersion and the shrinkage rate depending on the temperature. (Figs. 8 and 9) Method of the Invention After cooling for 45 seconds in a state in which crimps were developed by slackening them by 10% in the longitudinal direction, they were stretched and cut. (Graph A) Comparative method After cooling the crimp for 45 seconds in a stretched state, it was stretched and cut. (Graph B) In this way, it was found that by contacting with a cooling medium, it became possible to cut with a very low break draft, and the occurrence of shrinkage was almost eliminated. Furthermore, it has been found that by fixing the crimp and providing a break draft, it is possible to cut with a very small tensile tension, and the shrinkage rate can also be reduced. Example 4 Using the same sample as in Example 2, the relationship between the tensile strength required for cutting and the overfeed rate was shown when the crimp was overfed with nitrogen gas at -100°C and cooled and fixed for 45 seconds. (Figure 10) Example 5 50 made of polyacrylonitrile fiber 3D
A tow of 1,000,000 denier was placed in the apparatus shown in FIG. 3 under the following conditions, and the hot drawing ratio on the hot plate and the shrinkage rate of the obtained sliver were compared with those spun using a conventional tow reactor method. 1 Conditions of the present invention Hot plate temperature 120 (℃) Residence time Approximately 6 (sec) Tow crimp state Number of crimps 12 crimps/inch Crimp angle 60°≦θ≦120° Overfeed rate 10 (%) Cooling medium Nitrogen gas Temperature inside the cryostat -100 (℃) Residence time 45 (ee) Break draft 1.15 Spinning speed 100 (m/min) 2 Tow reactor conditions Hot plate temperature 120 (℃) Residence time approx. 6 (sec) Total・Draft 6.51 (Break draft) (2.53) Spinning speed 100 (m/min) The results are shown in Figure 6. In the conventional method, single fibers are stretched to the breaking elongation because they are cut after hot stretching. must be stretched, and in addition to the shrinkage due to hot stretching, shrinkage due to tension cutting is added. Therefore, the shrinkage ratio is proportional in the region where the hot drawing ratio is relatively high, but in the region where the hot drawing ratio is low, it is not possible to obtain a low shrinkage ratio below a certain value due to additional shrinkage due to tension cutting. . In other words, in the conventional method, the range of shrinkage normally obtained was narrow. In contrast, with the method of the present invention, it is possible to obtain a shrinkage curve that is almost linearly proportional to the hot drawing ratio up to the maximum shrinkage of the fiber, so it is possible to easily produce slivers with arbitrary shrinkage ratios. It turns out that it can be spun.

[Brief explanation of the drawing]

1 to 3 are diagrams showing examples of steps for carrying out the present invention; FIGS. 4A and 4B are schematic diagrams showing the state of crimp;
Figure 5 shows the crimp angle, Figure 6 shows the relationship between hot drawing ratio and shrinkage after boiling, and Figure 7 shows the tensile elongation and tensile strength of acrylic synthetic fiber (product name: Cashmilon). Figure 8 shows the relationship between the temperature of the cooling medium during cutting and the breaking strength. Figure 9 shows the temperature of the cooling medium during cutting and the shrinkage of the cut single fiber after boiling. Figure 10 is a diagram showing the relationship between overfeed rate and breaking strength.

Claims (1)

[Claims] 1. Immediately after a bundle of continuous fibers made of acrylic synthetic fibers having crimps is brought into contact with a medium at -20°C or lower while maintaining the crimps, the bundle of continuous fibers is A bundle of crimped discontinuous fibers made of acrylic synthetic fibers is produced by applying a stretching force or a stretching force and an auxiliary shearing force to cut each single fiber constituting the bundle of continuous fibers. Method. 2 Immediately after contacting a continuous fiber bundle made of acrylic synthetic fibers with crimps to a medium at -20°C or lower while maintaining the crimps by overfeeding the bundle into a cooling zone, Discontinuous fibers with crimps made of acrylic synthetic fibers are produced by applying a stretching force or a stretching force and an auxiliary shearing force to a bundle of continuous fibers to cut each single fiber constituting the bundle of continuous fibers. How to manufacture a bunch of.