JPS6144972B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a discontinuous fiber bundle having crevasses with excellent anti-pilling properties from a continuous fiber bundle, such as a tow or a multifilament. More specifically, while a bundle of continuous fibers is brought into contact with a medium at -5°C or lower, or immediately after contact, a shearing force is applied to an extent that the single fibers do not break, thereby forming a V-shape inside each single fiber constituting the fiber bundle. Generates a crevice-like fissure. This gives a new function to a bundle of continuous fibers with excellent mechanical properties.The mechanical properties of each single fiber are partially reduced to create a bundle of continuous fibers with excellent anti-pilling properties. By applying drawing force and/or shearing force to the fiber bundle to cut each single fiber that makes up the fiber bundle, a bundle of discontinuous fibers, which is an intermediate product for producing spun yarn, has anti-pilling properties. This makes it possible to obtain excellent bundles of discontinuous fibers with industrial advantage. Synthetic fibers have excellent mechanical performance, color development, and good texture, and are widely used in various textile products including clothing. On the other hand, in recent years, demands on textile materials have become extremely wide-ranging and diverse, with demands for beauty in appearance and functionality. However, when widely used for clothing materials, interior decorations, etc., chemical fibers are susceptible to pilling due to their mechanical performance, which significantly impairs the beauty of their appearance. Various methods have been proposed to improve the anti-pilling properties of chemical fibers. In most cases, special polymers, polymerization, spinning, and post-processing are applied at the fiber manufacturing stage to uniformly reduce the mechanical properties of the fibers, which complicates the manufacturing process and lowers productivity. The industrial merit was extremely small. On the other hand, there are Japanese Patent Publication No. 38-5863 and Japanese Patent Application Laid-open No. 128324-1983 which attempt to impart anti-pilling properties by physically damaging textile products, both of which relate to acrylonitrile polymers. After the fibers are heated and softened with a material, pressure is applied using a stuffer box type crimper or the like to reduce the hooking strength while maintaining the tensile strength. However, in order to reduce the strength with this method, it is necessary to make the nip pressure and box pressure of the crimper extremely strong, which causes fusion of fibers and breakage, resulting in poor tow shape. In the spinning process starting from the tow, such as in the turbo method, there is a problem that group breakage, slabs, neps, etc. occur. Furthermore, there has been no method for continuously producing bundles of discontinuous fibers with excellent anti-pilling properties by reducing the strength of a bundle of continuous fibers such as tow or multifilament, and then cutting the bundle by drawing force or the like. The present invention provides a completely new method for producing anti-pilling fibers in order to solve the drawbacks of the conventional methods. In other words, rather than uniformly lowering the mechanical properties of fibers using a special polymer, polymerization, or spinning during the fiber manufacturing process, a bundle of continuous fibers that normally have good mechanical properties is physically processed to randomly weaken them. The object of the present invention is to provide a method for producing a bundle of discontinuous fibers at high speed, which is free from heat fusion, has good quality, and has excellent spinnability and anti-pilling properties by generating sections. As the continuous fiber bundle of the present invention, tow or multifilament is generally used. Continuous fibers include synthetic fibers such as polyamide, polyester, polyacrylic, polymodified acrylic, polyurethane, polyvinyl chloride, and polyvinyl alcohol, semi-synthetic fibers such as acetate, and recycled artificial fibers such as rayon. etc., but acrylic synthetic fibers are particularly preferably used. As fiber bundles, for example, filaments, large filaments and tows with a total denier of 30 d to 2,000,000 d, consisting of single fibers with a denier of 0.1 d to 100 d, are generally used. 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. This bundle of continuous fibers is −
By bringing the fiber into contact with a medium at 5° C. or lower, the elongation of the fiber becomes extremely low. In the present invention, in such a state, a shearing force that does not break the single fibers is applied to generate a crevasse-like tear in the fiber axis direction of each single fiber constituting the fiber bundle. The cracks are generated by applying shearing force while contacting with a medium at −5° C. or lower, or immediately after contact. As the temperature exceeds -5°C and approaches room temperature (around 20°C), the elongation of the fibers increases, and therefore, even if shearing force is applied to cause shear deformation, no tears occur in the fibers. Furthermore, upon cutting, the residual strain of the fiber increases, making it difficult to obtain a spun yarn with a low shrinkage rate. In order to more fully exhibit the effects of the present invention, the temperature is preferably -20°C or lower, more preferably -40°C or lower.
below ℃. Here, conventional fibers with anti-pilling properties have uniformly low hooking strength and elongation, which increases the occurrence of fiber breakage and fly in subsequent processes including the spinning process, as well as poor stability and diagram. There are problems such as: In order to solve these problems, the present invention is designed to prevent crevasse-like tears from occurring in the fibers by using raw cotton with high elongation properties at temperatures below -5°C, as shown in Figure 5. It became possible. Thereafter, it was possible to produce a bundle of discontinuous fibers by applying a drawing force and cutting the fibers. Also, -
When the temperature is lower than 20°C, the amount of cracks generated increases, and even if the shear stress is small, it becomes possible to easily obtain fibers with crevasse-like cracks that suit the intended use and purpose. By applying a drawing force and cutting the fibers, it became possible to obtain a bundle of discontinuous fibers with low shrinkage. Furthermore, by lowering the temperature to -40°C, the amount of crevasse-like fissures is increased, making it possible to obtain a bundle of discontinuous fibers with anti-pilling properties in an extremely stable state. In addition, the lower limit of temperature is up to absolute zero, but this reduces the cost of the medium used,
Due to equipment problems, -20°C to -195°C is preferred. The cooling medium used in the present invention is -5°C
The following can be used, but liquid or vaporized gases such as ammonia, carbon dioxide, air, oxygen, and nitrogen, as well as mixtures of solid carbonic anhydride with alcohols, ethers, etc., as well as ice and zinc chloride, Chloride, nitric acid, and sulfuric compounds such as sodium chloride can be used. It is also possible to use electrical cooling methods. The time of contact with this cooling medium depends on the type of fiber,
It varies depending on the supply method, type of medium, temperature, etc.
Generally, a time of about 0.1 seconds to 10 minutes is used. The method of contact with the cooling medium is not particularly limited, but
There are methods such as bringing a bundle of continuous fibers into contact with the surface of a cooling object, passing the bundle of continuous fibers through a liquid in a gas atmosphere, and dropping a cooling medium onto the bundle of continuous fibers. Shearing force can be measured by passing it between a pair of upper and lower rollers with different surface speeds with a certain contact pressure, by passing it while slipping between a pair of pressure rollers, or by rubbing with a pair of upper and lower rollers with a certain contact pressure. - A method such as passing between rollers can be used. In addition to these, other shearing forces may be used in combination. By applying shearing force to the fibers under these conditions, crevasse-like crevices that cut into the interior of the fibers in a V-shape, as shown in FIGS. 4A and 4B, are generated on the surface of the single fibers. FIG. 4A is a side view of a single fiber 30 in which a crevice-like fissure 31 is present. B is a sectional view taken along line A-A', and the tear portion 31 is cut into the inside of the fiber in a V-shape. The length, width, depth, and number of the fissures 31 vary depending on the magnitude of the shearing force and the temperature of the cooling medium. Generally, the anti-pilling properties improve as the number of cracks increases, but beyond a certain limit, fiber breakage and fly-off occur more frequently during spinning. Therefore, it is desirable to determine the desired shearing force, shearing method, and temperature of the cooling medium experimentally as necessary. In the present invention, the surface of the single fiber has a length of 1 to
It is desirable to select conditions that randomly generate cracks of 100μ and a maximum width of 0.1 to 3μ. When examining the tensile strength and elongation and hooking strength and elongation of a single fiber having this crevasse-like tear at a sample length of 20 mm, it was found that although the decrease in tensile strength and elongation was small, the crevice cut into the interior in a V-shape. A significant decrease in hooking strength and elongation appears. It is preferable that at least half of the discontinuous fibers produced by the method of the present invention have 1 to 10 tears per single fiber. From the viewpoint of anti-pilling properties, it is preferable to have one or more tears per 20 mm, and it is preferable that at least half of the continuous fiber bundles have tears in any 20 mm. Considering the frequent occurrence of fiber breakage and fly-off during the spinning process, the number is more preferably 10 or less. In order to obtain a spun yarn with a low shrinkage rate, it is preferable to cut the bundle of continuous fibers immediately after creating a crevasse-like fissure, but depending on the desired shrinkage rate, cutting the bundle of continuous fibers may be carried out while in contact with a cooling medium. You can do this after contact, or you can do it after contact. If you want to obtain a spun yarn with a medium to high shrinkage rate, first heat-draw a bundle of continuous fibers to give them shrinkage, then contact them with a cooling medium to generate crevasse-like fissures, and then cut them immediately. Alternatively, after creating a crevasse-like fissure as necessary, cutting can be performed at room temperature or in a heated atmosphere. In cutting, each single fiber is cut by applying a drawing force and/or a shearing force to the bundle of continuous fibers. There is no problem in using other cutting forces in addition to these. Specifically, the bundle of discontinuous fibers thus obtained includes slivers, rovings, straight spun yarns, spun yarns, and the like. Figure 7 is a graph of the results of Example 2, in which 100 single fibers with crevasse-like fissures were
It is a figure which shows the relationship between the temperature of a cooling medium and the contraction rate of a single fiber when cutting is performed while contacting with the medium of each temperature under the load of mg/d. As is clear from this graph, according to the present invention, it is possible to achieve any desired shrinkage rate from a low shrinkage rate to a high shrinkage rate. (Graph A) When a desired medium temperature is set during cutting, the shrinkage rate of the single fiber corresponding to that temperature is determined as shown in FIG. FIG. 6A is a diagram showing the temperature of the cooling medium at this time and the strength when cutting a single fiber having a crevasse-like fissure. B is a curve showing the cutting strength of a single fiber before forming a crevasse-like tear. As you can see, even at room temperature, type A with crevasse-like fissures is about 20% larger than type B without it.
The tension required for cutting is reduced. By bringing it into contact with a medium at -20°C or lower, it is possible to cut it with less tension, which is less than half. It was also found that the tip of the cut fiber remained pointed even when cut at an ambient temperature of 20°C or higher. Here, a circular cross section was used, so it was a diagonally cut cylindrical shape. Next, an example of the present invention will be explained with reference to the drawings. 1st
The figure is a process diagram showing one embodiment of the present invention. A bundle 1 of continuous fibers with a uniform thickness divided into single fibers with a constant width is supplied, and the bundle 1 is fed between a back roller 3 and a pair of middle rollers 4 and 4' with different upper and lower surface speed ratios. The elongation of the fibers is kept extremely low by placing them in contact with a cooling medium of -5°C or lower in the cryostat 2, and at the same time applying pressure with the middle rollers 4 and 4', the upper and lower speed ratios are adjusted. After creating a crevasse in each single fiber constituting the continuous fiber bundle 1 by applying shearing force, tensile stress is applied to the fiber bundle between the middle rollers 4, 4' and the front roller 5. The discontinuous fibers are cut into a bundle 6 of discontinuous fibers, which is then stored in a can 8 by a coiler 7. FIG. 2 shows an auxiliary cutting device 10 provided between the middle rollers 4, 4' and the front roller 5.
After creating crevasses in each single fiber constituting the bundle 1 of continuous fibers using middle rollers 4 and 4', the fibers are cut by an auxiliary cutting device 10 to form a bundle 6 of discontinuous fibers. FIG. 3 is a process diagram suitable for producing a bundle 6 of discontinuous fibers with arbitrary shrinkage, in which crevasses are created in each single fiber constituting the bundle 1 of continuous fibers using middle rollers 4, 4'. After that, thermostatic bath 1
At step 1, depending on the desired shrinkage, the fibers are cooled or heated and simultaneously applied with tensile stress and cut to form a bundle 6 of discontinuous fibers. If higher shrinkage is desired, a hot plate 13 may be provided between the feed roller 12 and the back roller 3 to provide hot stretching. Example 1 Composed of acrylic synthetic fiber 3 denier d
A tow of 500,000 d is attached to the device shown in Figure 1, and 25~
Table 1 shows the properties of the single fibers after contacting them with a cooling medium at 120°C and spinning them under the following conditions. Cooling medium Nitrogen gas Atmosphere temperature inside cryostat 25 to -120℃ Front roller 1.05 Top and bottom speed ratio Break draft 2.04 (-20 to -120
℃) 2.56 (0~25℃) Spinning speed 50m/min

[Table] As is clear from this table, by cooling a tow with a total denier of 500,000 and a normal homogeneous cross section, and pressing and shearing it with a pair of upper and lower front rollers with different surface speeds, Crevasse-like fissures could be easily generated in the fibers. Immediately after that, tensile stress was applied to cut the material, and the break draft was 2.04 mm smaller than that of the conventional stretch-braking method. The obtained sliver also had a low shrinkage rate and was able to be produced at high speed with excellent quality in terms of parallelism, neps, and U%. In addition, the cut ends of the fibers with crevasse-like fissures had sharp edges, and the incidence of such fissures exceeded 80% even at -20°C. Next, the above sliver is subjected to a normal spinning process to obtain a ring-spun yarn with a count of 1/40 meter and a number of twists of 500 T/m, and two yarns are knitted into a jersey using the JISL-1076 ICI method (5h). Measured at The results are shown in Table 2.

[Table] Compared to room temperature (25°C) and 0°C, at temperatures below -20°C, small shear deformations easily cause crevasse-like fissures and the hooking strength of single fibers decreases. At -120℃, the amount of shear deformation was relatively high, and there were many fries due to deterioration of physical properties. In this case, it is desirable to further reduce the speed ratio between the top and bottom of the front roller. The spun yarn has sufficient strength and elongation, and the pilling properties of the finished product are -20
At temperatures below 0.degree. C., it was good at grade 4-5. In this way, it has become possible to advantageously obtain products with excellent spinnability, yarn properties, and pilling properties. Example 2 In order to compare the tensile force required for cutting between the present invention and the conventional method, a sample made of acrylic synthetic fiber 3D was
A 500,000 d tow consisting of the 300 d fiber bundle B and the above 3 d was placed in the device shown in Figure 1 and spun under the following conditions, with a crevasse-like fissure taken out at the exit of the middle rollers 4 and 4'. obtained from tow
A 300 d fiber bundle A was pulled using a Tensilon tensile tester at the following ambient temperature, and the temperature distribution of the tensile force required for cutting and the shrinkage rate depending on the temperature were investigated. The results are shown in Figures 6 and 7. Equipment conditions Cooling medium Nitrogen gas Atmosphere temperature in the cryostat -40℃ Residence time 12 seconds Front roller 1.05 Top and bottom speed ratio Tensilon conditions Cooling medium Nitrogen gas Atmosphere temperature 50℃~-120℃ Residence time 30 seconds Initial load 100mg/d Book In this way, the invention applies a shearing force to the bundle of continuous fibers while contacting with a medium at -5°C or lower or immediately after contact to generate a crevasse-like fissure, and then
Since a bundle of discontinuous fibers having crevasse-like fissures is produced by cutting each single fiber by applying drawing force and/or shearing force, 1. Changing the temperature and shearing force of the cooling medium. Accordingly, any crevasse-like crevice can be generated depending on the use and purpose. 2. It is possible to create crevasse-like tears in a bundle of continuous fibers that normally have excellent mechanical performance, thereby imparting anti-pilling properties. 3. By cutting the crevasses after generating them, a spun yarn with low shrinkage can be easily obtained. 4. When producing a bundle of discontinuous fibers by cutting after creating a crevasse, the energy involved in cutting is extremely small. 5. By changing the temperature of the cooling medium, it is possible to produce a spun yarn with any desired shrinkage rate, from low shrinkage to high shrinkage. 6. By performing hot stretching treatment prior to cutting, it becomes possible to change the shrinkage rate as desired. 7 By cutting a crimped continuous fiber bundle at -5°C or lower, a discontinuous fiber bundle that also has crimps after cutting can be obtained. It shows remarkable action and effect.

[Brief explanation of the drawing]

1 to 3 are process diagrams showing an example of a mode suitable for carrying out the present invention. FIG. 4 is a model diagram showing a crevasse-like crevice obtained by the present invention, where A is a side view and B is a sectional view taken along line A-A' of A.
Fig. 5 is a graph showing the results of Example 1, showing the cooling medium temperature and the amount of crevasse-like fissures generated, Figs. 6 and 7 are the results of Example 2, and Fig. 6 shows the results of cutting. FIG. 7 is a diagram showing the relationship between the cooling medium temperature during cutting and the cutting strength, and the relationship between the cooling medium temperature during cutting and the shrinkage rate of the cut single fiber after boiling. DESCRIPTION OF SYMBOLS 1...Bundle of continuous fibers, 2...Cryogenic bath, 3...Back roller, 4, 4'...Middle roller, 5...Front roller, 6...Bundle of discontinuous fibers, 7... Coiler, 8... Kens, 10...
... Auxiliary cutting device, 11 ... Constant temperature bath, 12 ... Feed roller, 13 ... Hot plate, 30 ... Monofilament, 31 ... Crevasse-like tear portion.

Claims (1)

[Claims] 1 While bringing the bundle of continuous fibers into contact with a medium at -5°C or lower, or immediately after contact, apply a shearing force to the bundle of continuous fibers to the extent that the single fibers do not break, and apply V to the single fibers constituting the bundle of fibers. It has a crevasse-like crevice characterized by generating a crevasse-like crevice that is shaped like a letter and cutting into the inside, and then applying a stretching force and/or a shearing force to cut each single fiber constituting the fiber bundle. A method of producing bundles of discontinuous fibers.