JPS6143449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester crimped monofilaments. Conventionally, polyester crimped monofilament (hereinafter sometimes referred to as monofilament)
is produced by a method of performing normal spinning and drawing, followed by false twisting and dividing into individual filaments. In recent years, polyester crimped multifilament (hereinafter sometimes referred to as crimped yarn) for clothing is produced by a method in which melt-spun undrawn yarn is stretched and false-twisted at the same time.It is widely used due to its high productivity and low cost. It has been adopted. For polyester crimped monofilament, a method of stretching and false twisting at the same time as multifilament for clothing has been attempted, but such stretching and simultaneous false twisting (hereinafter sometimes referred to as stretch false twisting) has not been successful. The resulting crimped yarn has extremely poor splitting properties compared to crimped yarn obtained by false twisting ordinary drawn yarn, and has not yet been put to practical use. The present inventors have arrived at the present invention as a result of intensive research into melt spinning conditions and stretching and simultaneous false twisting conditions that provide good fiber splitting properties industrially even when drawing and simultaneous false twisting is performed. That is, in the present invention, polyester is melted and discharged from a spinneret having a plurality of holes, cooled and solidified by cooling air, bundled, oiled, and wound with a high degree of bundle so that the birefringence (△n) is An undrawn multifilament of 0.030 to 0.060 is obtained, and then the undrawn multifilament is taken out in a substantially untwisted state and subjected to simultaneous drawing and false twisting at a draw ratio (DR) that satisfies the following formula. This is a method for producing a bulky polyester monofilament, which is characterized by dividing each filament into crimped monofilaments. −0.664 −1.610 log△n≦DR≦−0.496 −1.617 log△n Here, the polyester referred to in the present invention is primarily polyethylene terephthalate, but within a range that does not essentially change its properties (for example, 10 mol% It may also be a copolyester obtained by copolymerizing a third component with (below). The polyester may contain additives such as a dissipating agent, a coloring agent, a stabilizer, an antistatic agent, and a twist retardant. According to the present invention, in producing a crimped monofilament from the polyester, the polyester is first melted and discharged from a spinneret having a plurality of spinning holes, and then cooled and solidified by cooling air. The fineness of the crimped monofilament produced by the present invention is usually
The fineness of the crimped monofilament is between 10 and 30 deniers.If the fineness of the crimped monofilament is smaller than this range, it will be difficult to separate the fibers after false twisting, and if it is larger, it will cause undesirable winding and unrolling during high-speed winding. . Therefore, in the spinning process, the length of the cooling air blowing section is preferably 70 to 150 cm in order to spin an undrawn multifilament at high speed to produce such a thick denier crimped monofilament. If the length of the cooling air blowing section is smaller than the above range,
Denier spots become larger due to insufficient cooling,
This is undesirable because tension fluctuations increase during false twisting and untwisting tends to occur.
Since such untwisting significantly deteriorates the fiber splitting properties, efforts must be made to minimize the amount of untwisted fibers. The multifilament, which has been cooled and solidified by the cooling air, is focused by a guide, etc., and after oiling,
It is taken up at high speed using a godet roller and wound into a winder as an undrawn multifilament with a birefringence index of 0.030 to 0.06. At this time, the distance L (m) from the spinneret surface to the focusing position in the spinning process
If it is too short, it will be bundled without sufficient cooling, resulting in larger denier irregularities and increased untwisting due to fluctuations in processing tension, and if it is too long, the take-up tension will increase.
The above distance (Lm) is determined by the spinning speed (V
m/min) is preferably within a range that satisfies the following formula. V/600-8/3≦L≦8 The birefringence index (△n) of the undrawn multifilament wound on the winder must be 0.030 to 0.060, and if the birefringence is smaller than the above range, The fiber cross section is flattened by stretching and false twisting,
This causes poor fibrillation properties. On the other hand, if the birefringence is made to be larger than the above range, the spinning speed will become too high and unwinding will increase during winding, which is not preferable. In order to obtain an undrawn polyester multifilament with a predetermined birefringence (△n), it is easy to select the spinning speed. By setting V) to approximately 2,800 to 4,000 m/min, it is possible to manufacture a material with a birefringence (Δn) of 0.030 to 0.060. The package of undrawn multifilament spun and wound as described above is supplied to the creel part of the drawn and simultaneously false-twisted yarn, and is spread within the shaded area shown in Fig. 1 according to its birefringence (△n). A uniformly crimped monofilament can be easily obtained by performing simultaneous stretching and false twisting at a certain draw ratio (DR), and then dividing the fiber into individual filaments and winding them as a monofilament. Figure 1 shows the results of various changes in △n of undrawn multifilament and DR during drawing and simultaneous false twisting, and the degree of scum (white powder) generated during drawing and false twisting and yarn breakage occurring during fiber splitting. This is a graph plotting the results. In Figure 1, high DR draw false twisting that exceeds curve A increases the amount of scum generated, while low DR draw false twist that falls below curve B increases the amount of untwisted yarn in the resulting crimped yarn. During fiber splitting, yarn breakage occurs frequently. In addition, undrawn multifilaments with a height △n exceeding the straight line C, as described above, are difficult to draw due to the fact that when such undrawn multifilaments are manufactured by high-speed spinning, unrolling occurs at the time of spinning and winding. It cannot be subjected to false twisting. On the other hand, in the case of undrawn multifilaments with a low △n below the straight line D, the cross-sectional shape of the fibers is significantly flattened during drawing and false twisting, resulting in frequent breakage during splitting of the resulting crimped yarn, resulting in The crimped monofilament obtained in this manner has large denier irregularities. In this regard, if the relationship between △n of the undrawn multifilament and DR during stretch false twisting satisfies the shaded area shown in Figure 1, the tension during stretch false twisting will cause untwisting. Since the fibers are maintained at a tension that is free from crimps, and the fiber cross section is less flattened, the amount of untwisted yarn remaining in the resulting crimped yarn is reduced, reducing yarn breakage during fiber splitting, and the resulting crimped yarn is Monofilament has small denier irregularities and is uniform. Furthermore, less scum is generated during the stretch false twisting process. Here, the curve A showing the upper limit of the shaded area shown in FIG.
It can be expressed as =-0.664-1.610 logΔn. Therefore, the shaded area shown in FIG. 1 can be expressed by the following formula. −0.664−1.610 log△n≦DR≦−0.496 −1.617 log△n However, 0.03≦△n≦0.06 In order to split the crimped multifilament obtained by drawing and false twisting in this way to make monofilament. When the monofilament leaves the take-up roller of the drawing and simultaneous false twisting machine, it may be separated into individual monofilaments using a splitting guide or splitting roller and wound onto each bobbin. After being wound as a filament yarn, the package of the multifilament yarn may be fed to a splitting machine to separate each monofilament and wind the yarn. According to the method of the present invention as described above, the cross section of the filament is less likely to be flattened during the simultaneous drawing and false twisting process, and the number of untwisted filaments is reduced, so that the splitting property is improved. Furthermore, since the spun yarn is sufficiently cooled and yarn wobbling is small, denier irregularities are reduced, and in this respect, the fiber splitting properties are also improved. On the other hand, regarding the winding shape, even though the single yarn denier is large, there is no winding abnormality such as collapse of the winding. Examples 1 to 3, Comparative Examples 1 to 8 Polyethylene terephthalate containing 0.3% titanium oxide and having an intrinsic viscosity of 0.63 as measured in an O-chlorophenol solution at 35°C was spun from a spinneret having five holes with a pore diameter of 0.55 mm. Discharge rate 60.0 at temperature of °C
Extrude at g/min, 110cm from 10cm below the nozzle
During this time, cooling air was blown almost perpendicularly across the yarn from one side to cool it, and the yarn was converged at a position 6 m below the spinneret, picked up by a godet roller rotating at the circumferential speed shown in Table 1, and wound into a winder. . These unstretched multifilaments were put into a creel of a stretching and simultaneous false twisting machine, taken out in an untwisted state, and subjected to stretching and false twisting simultaneously under the following conditions. Stretching ratio See Table 1 Number of false twists 1991t/m Heater temperature 200℃ Stretching roller circumferential speed 200m/min The obtained false-twisted crimped multifilament was loaded into a fiber splitting machine and split at a speed of 400m/min. The results of the survey are shown in Table 1.

【table】

[Table] As is clear from Table 1, in the case of the present invention, the denier unevenness of the undrawn yarn is small, and the fiber splitting property in the fiber splitting process is excellent. Example 4 Example 2 except that the length of the cooling air blowing section in the spinning process (blowout length) and the length from the spinneret surface to the focusing position (focusing length) were changed as shown in Table 2.
An experiment was conducted under the same conditions as above, and denier unevenness after spinning and yarn breakage during fiber splitting were investigated. The results are shown in Table 2.

【table】

[Table] As is clear from Table 2, the preferred focusing length,
When the blowing length was adopted (Experiments A, B, E, F), the denier unevenness was particularly small and the fiber splitting properties were excellent.

[Brief explanation of the drawing]

Figure 1 shows the scum (white powder) generated during the drawing false-twisting process and the scum (white powder) generated during the splitting process when the birefringence (△n) of the undrawn multifilament and the draw ratio (DR) during the drawing false-twisting process were variously changed. This is a graph in which the degree of yarn breakage that occurs is examined and the results are plotted.

Claims (1)

[Claims] 1. Polyester is melted and discharged from a spinneret having a plurality of spinning holes, cooled and solidified by cooling air, concentrated, oiled, wound at high speed, and the birefringence ( An unstretched multifilament with Δn) of 0.030 to 0.060 is prepared, and then the unstretched multifilament is taken out in a substantially untwisted state and subjected to simultaneous stretching and false twisting at a stretching ratio (DR) that satisfies the following formula. 1. A method for producing a crimped polyester monofilament, the method comprising: separating each filament into crimped monofilaments. −0.664−1.610 logΔn≦DR≦−0.496 −1.617 logΔn [However, Δn represents the birefringence index of the unstretched multifilament, and DR represents the stretching ratio in the simultaneous stretching and false twisting process. 2. The method for producing a crimped polyester monofilament according to claim 1, wherein the monofilament after splitting has a fineness of 10 to 30 deniers. 3. The method for producing a crimped polyester monofilament according to claim 1 or 2, wherein the distance L (m) from the cap surface to the focusing position satisfies the following formula. V/600-8/3≦L(m)≦8 [where L is the distance from the spinneret surface to the focusing position, and V is the spinning speed expressed in m/min. 4. The method for producing a crimped polyester monofilament according to claim 1, 2 or 3, wherein the blowing length of the cooling air is 70 to 150 cm.