JPH0565604B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing side-by-side type hollow composite fibers, in which two components having different melt viscosities are joined side-by-side and discharged from an orifice. The present invention relates to a method for producing polyester hollow conjugate fibers that are prevented from being discharged (hereinafter referred to as kneeing) and have a high degree of hollowness and excellent crimp development performance. (Prior Art) In recent years, synthetic fibers have been rapidly replacing natural fibers in the field of cotton padding such as futon cotton. This is due not only to the cost of the fibers, but also to the fact that synthetic fibers have superior properties such as bulkiness and dust resistance compared to natural fibers. Furthermore, among synthetic fibers, it is known that composite fibers with coil spring-like crimps have even better bulkiness and covering properties, and in addition, hollow composite fibers with a hollow center are It is also known that the bulkiness and heat retention properties are further improved. However, consumers are demanding further improvements in these various performances, and among these performances, there is an even stronger demand for improved bulkiness. In order to increase bulk performance, it is necessary to increase crimp development performance and hollowness. As a method to improve crimp performance, the internal structure of the fibers is greatly changed by increasing the intrinsic viscosity difference and melt viscosity difference between the two components of composite fibers joined side-by-side, thereby reducing the orientation and shrinkage difference. It is known to produce composite fibers with high crimp performance. (Problem to be solved by the invention) However, when two types of polyesters with different melt viscosities are bonded in advance and discharged from an orifice in a side-by-side manner, kneeing occurs immediately after discharge from the orifice, and the difference in viscosity between the two components As the kneeing angle increases, the spinning state becomes unstable, and in extreme cases, the polymer flow adheres to the spinneret surface, causing yarn breakage and making spinning impossible. Although many means for preventing kneeing have been proposed, there have been few proposals for side-by-side type hollow composite fibers, and non-hollow composite fibers have been mainly proposed.
In the case of side-by-side type hollow composite fibers, when the viscosity difference is increased, kneeing occurs, the degree of hollowness decreases, and the hollow part becomes eccentric toward the high viscosity side, resulting in a decrease in crimp performance and the formation of non-hollow fibers. Even when compared, bulk and performance are inferior. As described above, if a low viscosity component is present in the fiber forming process, it is difficult to improve the hollow portion ratio. Therefore, as a method to remove the influence of the low viscosity component and improve the hollowness, there are two methods: increasing the viscosity of both components to raise the viscosity level of the low viscosity component, and increasing the viscosity of only the low viscosity component to reduce the viscosity difference between the two components. Although there are methods for reducing the amount of crimping, the former method involves a non-negligible increase in the cost of the polymerization reaction, and the latter method does not have satisfactory performance because the ability to develop crimp is reduced. (Means for Solving the Problems, Structure of the Invention) In order to improve the bulkiness, the present inventors increased the degree of hollowness, that is, the ratio of the hollow part of the hollow composite fiber to the cross-sectional area of the fiber (the degree of hollowness 25 to 30% is the best bulkiness.) As a result of research into a method for producing polyester hollow composite fibers with excellent bulkiness using a production method with less eccentricity in the hollow part and less kneeing, the present invention was arrived at. . The gist of the present invention is as follows. The present invention has a substantially semi-circular arc shape, with a circular arc 1 on the outer circumferential surface and a circular arc 2 on the circumferential surface located eccentrically, with a wide sealing part 3 at one end and a narrow sealing part 4 at the other end. Two sealed slits are formed with a wide sealing part and a narrow sealing part facing each other, and a high viscosity molten polyester component is applied to the wide slit part 5 of the melt spinning orifice, and the narrow slit part 6 is a method for producing polyester hollow composite fibers characterized by supplying a low-viscosity molten polyester component and discharging it from a slit-like orifice while bonding the two components. That is, when the two semicircular arc-shaped slits are formed facing each other, orifices having different outer diameters, that is, inner diameters, and center points of the inner diameters are used. The polyester used in the present invention is preferably a polyester containing 85 mol% or more of ethylene terephthalate units, and the most suitable polyester is polyethylene terephthalate. Intrinsic viscosity calculated from viscosity is 0.4
~0.8, and preferably has a melt viscosity of 300 to 4000 poise at 280°C. It goes without saying that the polyester may contain additives such as a matting agent and a coloring agent. The method of the present invention will be explained in more detail using the drawings. Fig. 1 shows an example of an orifice in which semicircular arc-shaped slits are opposed to each other for carrying out the present invention, and Fig. 2 is a cross-sectional view of a hollow composite fiber obtained by the method of the present invention. . FIG. 3 is a cross-sectional view of a hollow composite fiber obtained by a conventional method. In Fig. 1, P ₁ is the center point of the circle on the outer peripheral surface 1 when two Orphis chairs are placed facing each other, and P ₂
is the center point of the circle on the inner peripheral surface 2. The outer diameter (of the outer circumferential circle) of the orifice is D, the inner diameter (of the inner circumferential surface) is d,
When the distance P ₁ - P ₂ is l, in the present invention, (D-d)/2≧l≧(D-d)/10 and
It is preferable to satisfy 1.40≧D/d≧1.08, and the low viscosity component L must be placed in the narrow slit portion 6 of the orifice slit. If the high viscosity component H is placed in the narrow slit portion 6 of the orifice slit, kneeing will be significant, and in the cross section of the resulting yarn, the hollow portion will be eccentric toward the high viscosity component, and the degree of hollowness will also decrease. The dimensions D and d of the orifice and the spacing between the joints A and B can be set depending on the viscosity of the polyester used, the target fineness and hollowness, but D/d
is preferably 1.08 to 1.40. If D/d is smaller than 1.08, it will be difficult to process the orifice, and if it is larger than 1.40, the degree of hollowness will decrease. The distance between the joints A and B is preferably 0.08 to 0.2 mm from the viewpoint of polymer adhesion and orifice strength. When the low viscosity component L is placed in the narrow slit part 6 of the orifice slit, l is (D-
d) If it is smaller than /10, kneeing, a decrease in hollowness, and eccentricity of the hollow part will occur, resulting in a shape as shown in FIG. 3, and a yarn with high hollowness and good crimp performance cannot be obtained. When l is larger than (D-d)/2, slits near joint B cannot be formed and the interval between joints B becomes wider, making it impossible to join low-viscosity components or causing abnormal joints, resulting in hollow The result is a thread with a highly unstable cross-sectional shape. In order to make the present invention effective, polyesters with intrinsic viscosities of 0.65 to 0.75 and 0.45 to 0.6 are used for the high viscosity component and the low viscosity component, respectively, and the viscosity difference is reduced.
0.08-0.22, preferably 0.1-0.2, the difference in melt viscosity at 280°C is 1000-3000 poise, preferably
It is desirable to set it to 1500 to 2500 poise. Set D and d so that the degree of hollowness is 20 to 30%, and l is (D-d)/2≧l≧(D-d)/10
When using an orifice designed to
A yarn with high crimp performance and less occurrence of kneeing and no eccentricity can be obtained. It is preferable to draw the obtained yarn at a low temperature. In other words, the stretching temperature is ±20
The temperature is preferably in the range of .degree. C., and the stretching ratio is preferably 65 to 95% of the maximum stretching ratio. The crimp development treatment is preferably carried out at a treatment temperature of 140 to 180°C under no tension. (Example) Hereinafter, the method of the present invention will be specifically explained using Examples. The bulkiness evaluation value in the examples is a web (20 cm x 20 cm, weight 80
g) without load (measuring plate 20cm x 20cm, load 170g)
This is the value measured for the height when loaded (5 kg) and when unloaded (same load as when no load is applied). A ₁ : Height when no load is applied A ₂ : Height when loaded A ₃ : Height when unloaded The degree of hollowness was determined using the following formula. Hollowness ratio (%)=cross-sectional area of hollow part/total cross-sectional area×100 The kneeing angle is the outflow angle of the polymer discharged from the orifice. Example Polyethylene terephthalate with an intrinsic viscosity of 0.69 is used as a high viscosity component (280℃, melt viscosity 3200 poise)
The D of the orifice is 1.6 mm and the d of the orifice is 1.3.
Use an orifice with mm and l of 0.05 mm, an interval of 0.1 mm between joints A at the widest part of the slit, and 0.2 mm between joints B at the narrowest part of the slit. The polymer was discharged so that the low viscosity components were arranged, and after spinning at a spinning temperature of 280°C, a single orifice discharge rate of 2.2 g/min, and a spinning speed of 1050 m/min, it was stretched at a stretching temperature of 85°C and a draw ratio of 3.9. ,
After heat treatment at 160°C under no tension, it was cut to obtain polyester hollow composite short fibers with a single fiber fineness of 6 denier and a fiber length of 51 mm. The cross-sectional shape of the yarn is as shown in FIG.
Table 1 shows the measurement results for kneeing during spinning, yarn hollowness, and web bulkiness. Comparative Example Table 1 also shows the results obtained in the same manner as in the example except that an orifice with l=0 was used. The cross-sectional shape of the yarn is as shown in FIG.

[Table] (Effects of the invention) As described above, if the method of the present invention (example) is used, there will be less kneeing compared to the conventional method (comparative example), the spinning state will be stable, the degree of hollowness will be high, and the hollow portion There is no eccentricity, the cross-sectional shape is stable, and the crimp development performance is also good. A polyester hollow conjugate fiber is obtained which exhibits excellent bulk performance, with high bulk under no load, high bulk under heavy load, and high bulk when unloaded.

[Brief explanation of the drawing]

FIG. 1 is a schematic view showing an example of the shape of an orifice with semicircular arc-shaped slits facing each other for carrying out the present invention, and FIG. 2 is a cross-sectional view of a composite fiber obtained by the method of the present invention. FIG. 3 is a cross-sectional view of a composite fiber obtained by a conventional method. In the figure, 1 is the circular arc of the outer peripheral surface of the semicircular arc-shaped slit;
Reference numeral 2 indicates an arc of the inner peripheral surface, 3 indicates a wide sealing portion, 4 indicates a narrow sealing portion, 5 indicates a wide slit portion, and 6 indicates a narrow slit portion.

Claims (1)

[Claims] 1 It has a substantially semicircular arc shape, and the arc 1 on the outer circumferential surface and the arc 2 on the circumferential surface are eccentrically located, and one end is sealed with a wide sealing part 3 and the other end is sealed with a narrow sealing part 4. A high-viscosity molten polyester component is placed in the wide slit portion 5 of the melt-spinning orifice, which is formed by forming two slits with a wide sealing portion and a narrow sealing portion facing each other.
A method for producing polyester hollow composite fibers, which comprises supplying a low-viscosity molten polyester component to the narrow slit portion 6 and discharging it from a slit-like orifice while bonding the two components.