JPH0663131B2 - Method for producing polyester hollow composite fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a side-by-side type hollow composite fiber, more specifically, when two components having different melt viscosities are joined to a side-by-side type and discharged from an orifice. The present invention relates to a method for producing a polyester hollow composite fiber having a high hollowness and an excellent crimping-inhibiting performance, which suppresses a state of being obliquely discharged at an orifice exit (hereinafter referred to as "kneading").

(Prior Art) In recent years, polyester fibers have rapidly increased in place of natural fibers in fields such as futon cotton. This is due to the fact that the polyester fiber has superior properties such as sublimation and dust resistance compared to natural fiber, not to mention the cost of the fiber. Among the polyester fibers, hollow fibers with a hollow central part are excellent in sublime. As a method of obtaining this hollow fiber, for example, Japanese Patent Application Laid-Open No. 61-108707 proposes a method of producing a hollow fiber by using a spinneret in which slits have different widths. However, this method uses a single polymer, discharges the polymer with the same limiting viscosity from orifices with different slit widths, blows cooling air from one direction to cool, and obtains an eccentric hollow fiber. No hollow fiber can be obtained, and thus the sublime expression is poor.

Further, it is known that the composite fiber having a coil spring-like crimp has excellent sublimation property and covering property,
In addition, it is also known that the hollow composite fiber in which the central part of the composite fiber is hollow is further improved in sublime and heat retention.

However, the demand from consumers demands that these various performances be further improved, and among these various performances, there is a strong demand for improvement in sublime.

In order to improve the sophistication performance, it is necessary to increase the crimp development performance and hollowness, and to make the fiber cross-sectional shape and hollow shape more circular.

As a method of increasing the crimp developability, by increasing the difference in intrinsic viscosity and difference in melt viscosity between the two components of the side-by-side type bonded composite fiber, the internal structure of the fiber is greatly changed and the orientation and shrinkage difference are generated. It is known to obtain composite fibers with high crimp performance.

However, when two kinds of polyesters with different melt viscosities are joined together in advance and discharged from the orifice by side-by-side type, kneeing occurs immediately after discharging from the orifice, and the larger the difference in viscosity between the two components, the larger the kneeing angle and the spinning state. Becomes unstable, and in extreme cases, polymer flow adheres to the spinneret surface, causing yarn breakage and making spinning impossible.

Although many means for preventing kneeling have been proposed in the past, few proposals have been made for side-by-side type hollow composite fibers, and mainly those for non-hollow composite fibers have been proposed. In the case of side-by-side type hollow composite fiber, when the viscosity difference is increased, kneeing occurs, the hollowness decreases, the hollow part becomes eccentric to the high viscosity side, and the crimp development performance decreases and it becomes a non-hollow fiber. Compared to it, the high performance is inferior.

As described above, it is difficult to improve the hollow portion ratio when the low-viscosity component is present in the fiber forming step.

Therefore, as a method of removing the influence of the low-viscosity component and improving the hollowness, a method of increasing the viscosity of both components to raise the viscosity level of the low-viscosity component and a method of increasing the viscosity of only the low-viscosity component to reduce the difference in viscosity between the two components. However, in the former case, the cost up of the polymerization reaction cannot be ignored, and in the latter case, the crimping ability is deteriorated, and a fiber having satisfactory performance cannot be obtained.

The present inventors increase the hollowness, that is, the ratio of the hollow part of the hollow composite fiber to the fiber cross-sectional area in order to improve the sublime (the hollowness of 25 to 40% is the best in the sublime). , A method for producing a polyester hollow composite fiber having excellent sublimation by a method with less eccentricity of the hollow portion and less kneeing, and has already been disclosed in JP-A-61-152824.
In the publication, a method was proposed in which a high-viscosity polymer was supplied to the wide slit part on one end of the orifice and a low-viscosity polymer was supplied to the narrow slit part on the other end to obtain a side-by-side type hollow fiber.

In the above method, when the manufacturing accuracy of the melt spinning orifice is good, the hollow part has less eccentricity and a hollow composite fiber close to a perfect circle can be obtained. However, as an orifice, the circumference of the opposing semi-circular slits can be obtained. Since the center point of the outer side surface and the center point of the inner side surface are slightly displaced, it is difficult to accurately and uniformly manufacture many orifices on the spinneret. However, the cross section of the formed fiber also varies, and it is not possible to sufficiently exhibit sublime.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks and reduces the eccentricity of the hollow portion,
Moreover, it is possible to manufacture a polyester hollow composite fiber with excellent sublime by a method with small kneeing, and also to provide a method for manufacturing a polyester hollow composite fiber that can accurately and uniformly manufacture many orifices used in melt spinning. This is a technical issue.

(Means for Solving Problems) That is, according to the present invention, in producing a polyester hollow composite fiber in which two polyester components having different viscosities are arranged side-by-side, the intrinsic viscosity ratio [η _H ] / [Η _L ] (where [η _H ] is the intrinsic viscosity of the high viscosity component, [η _L ] is the intrinsic viscosity of the low viscosity component) is 1.13 to 1.
A circular slit-shaped orifice which uses polyester in the range of 45 and which has two slits each having a substantially semi-circular arc shape facing each other, and each slit has a stepped shape at its central portion,
The wide slit portion 6 of the melt spinning orifice which is formed by sealing one end with the wide sealing portion 4 and the other end with the narrow sealing portion 5 and satisfies the following formulas (I) and (II) A high-viscosity component, a low-viscosity component is supplied to the narrow slit portion 7 to bond the two types of components, and is discharged from a slit-shaped orifice, which is a gist of the method for producing a polyester hollow composite fiber. It is a thing.

However, S _H : Area of wide slit part (mm ² ) S _L : Area of narrow slit part (mm ² ) That is, in the present invention, two semi-circular slits having a wide slit part and a narrow slit part are provided. Uses melt-spinning orifices facing each other and the intrinsic viscosity ratio of the two components is 1.13〜
By spinning a high-viscosity component of 1.45 from a wide slit and a low-viscosity component from a narrow slit, it is possible to produce a composite fiber with little crimping and high crimping performance with no eccentricity.

The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic view showing an example of the shape of an orifice for melt spinning with semi-circular slits facing each other for carrying out the present invention, and FIG. 2 is a general hollow fiber spinning conventionally used. FIG. 3 is a cross-sectional view of the composite fiber obtained by the method of the present invention, and FIG. 4 is a cross-sectional view of the composite fiber obtained by the method of Comparative Example 3 described later.

Also, in Figures 1 and 2, A is the distance between the opposite sealing parts, and D is
The outer circumferential surface arc of diameter, d is the inner circumferential surface arc of the diameter of a conventional orifice, d ₁ is the inner circumferential surface arc of the diameter of the narrow slit portion, the d ₂ represents the diameter of the inner circumferential surface arc of the wide slit portion .

In the present invention, when performing composite spinning using the above melt spinning orifice, it is necessary to place a low viscosity component in the narrow slit portion 7 and a high viscosity component in the wide slit portion 6. When a high-viscosity component is arranged in the narrow slit portion 7, the kneeing is remarkable, and in the cross section of the obtained yarn, the hollow portion is eccentric to the high-viscosity component, and the hollowness also decreases. In addition, in order to obtain a fiber having a high hollowness, a circular cross-section, and a cross-section with little eccentricity in the hollow portion, the intrinsic viscosity ratio of the two components and the shape of the slit-shaped orifice are However, S _H : Wide slit area S _L : Narrow slit area must be satisfied.

That is, the orifice portion (narrow slit portion 7) for discharging the low-viscosity component should be narrow and small in area, and the orifice portion (wide slit portion 6) for discharging high-viscosity component should be wide and large in area. Therefore, it is effective to bring the flow velocities of the low-viscosity component and the high-viscosity component close to each other to reduce the kneeing and make the wall thickness of the fiber outer shell uniform after cooling specificization.

The distance A between the facing sealing portions of the two slits forming the melt spinning orifice is preferably 0.08 to 0.2 mm from the viewpoint of polymer adhesion and the strength of the orifice.

The dimensions D, d ₁ and d ₂ of the orifice may be set according to the viscosity of the polyester used, the target fineness and hollowness, but D / d ₁ is preferably 1.08 to 1.35 and D / d ₂ is 1.12 to 1.40. . If D / d ₁ and D / d ₂ are smaller than the above range, it is difficult to process the orifice, while if it is larger than the above range, the hollowness tends to be lowered.

The melt spinning orifice used in the present invention is concentrically arranged without the need to shift the center points of the outer circumferential arc, the inner circumferential arc of the narrow slit portion and the inner circumferential arc of the wide slit portion. Since it is good, many orifices can be accurately and uniformly manufactured on the spinneret.

The polyester used in the present invention contains ethylene terephthalate units of 85% for both the high viscosity component and the low viscosity component.
% Polyesters, especially polyethylene terephthalate are preferred, but these polyesters are
You may include additives, such as a coloring agent.

In the present invention, a polymer having an intrinsic viscosity ratio of the high-viscosity component and the low-viscosity component in the range of 1.13 to 1.45 is selected in order to produce a conjugate fiber having good spinnability and good expression of a coil spring crimp. There is a need. The intrinsic viscosity ratio of the two components is 1.
When it is less than 13, the expression of the coil spring-like crimp is insufficient, and when it exceeds 1.45, the spinnability is poor in a region where the viscosity of the low-viscosity component is low. It is not preferable because the polymerization cost will increase.

In addition, polyesters with intrinsic viscosities of high-viscosity component and low-viscosity component of 0.82-0.64 and 0.72-0.48, respectively,
And the viscosity difference is 0.06 ~ 0.22, preferably 0.08 ~ 0.2, the difference in melt viscosity at 280 ℃ 700 ~ 3,000 poise, preferably 80
It is desirable to have 0 to 2,500 poise.

The composite fiber obtained by using the high viscosity component and the low viscosity component in the above range has an intrinsic viscosity of 0.55 to 0.75 and a melt viscosity of 700 to 3000 poise at 280 ° C.

Using melt-spinning orifices designed with D, d ₁ and d ₂ so that the hollowness is 25 to 40%, and the high viscosity component with the intrinsic viscosity ratio of the two components of 1.13 to 1.45, the wide slit part,
By spinning the low viscosity component from the narrow slit section,
A fiber having a high crimping performance with less kinking and no eccentricity can be obtained. The obtained fiber is preferably drawn at a low temperature.

That is, the stretching temperature is preferably in the range of the glass transition temperature ± 20 ° C, and the stretching ratio is 65 to 95, which is the maximum stretching ratio.
% Is preferred.

Moreover, it is preferable that the crimp development treatment is performed at a temperature of 140 to 180 ° C. without tension.

In addition, the intrinsic viscosity in the present invention is 20 ° C.
It is the value measured in a mixed solvent of ethane tetrachloride equivalent.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples.

The evaluation value of sublimeness in the examples is 80 g of a web (20 cm × 20 cm) obtained by opening and stacking sample cotton with a card machine when a light load (measurement plate 20 cm × 20 cm, weight 170 g) is applied to a heavy load (measurement). Plate + load 5k
It is a value obtained by measuring the specific volume at the time of g).

A ₁ : Specific volume under light load A ₂ : Specific volume under light load Hollowness was calculated by the following formula.

The knee angle is the outflow angle of the polymer discharged from the orifice.

Examples 1 to 4 and Comparative Examples 1 to 3 Polyethylene terephthalate having two types of limiting viscosities [η _H ] and [η _L ] shown in Table 1 and dimensions (D, d, d ₁ , d ₂ ,
A), the area (S _H , S _L ) melt-spinning orifice is used to discharge the polymer so that the low-viscosity component is placed in the narrow slit, spinning temperature 250 ° C, orifice number 130, orifice After spinning at a single discharge rate of 2.2 g / min and a spinning speed of 1050 m / min, it was drawn at a draw temperature of 85 ° C and a draw ratio of 3.4, and then heat-treated at 170 ° C without tension, cut into 51 mm and cut into polyester. A hollow composite staple was obtained.

As shown in FIG. 3, the typical fiber cross-sectional shape was such that both the fiber cross section and the hollow portion were close to a perfect circle, and the hollow portion had no eccentricity.

Table 2 shows the kneeing angle during spinning, the hollowness of the obtained fiber, and the web sublimation.

As is clear from Table 2, in Examples 1 to 4 of the present invention, the knee angle was small, and the obtained polyester hollow composite fibers were large in both hollowness and sublime.

On the other hand, in Comparative Example 1 in which the K value was large and Comparative Example 3 in which the slit had a uniform diameter, the kneading angle was large, and the hollowness and sublimeness of the obtained fiber were small. Further, in Comparative Example 2 in which the intrinsic viscosity ratio of the two components and the value of K were small, the obtained fiber was poor in sublimation under heavy load, although the knee angle was small.

Example 5 A polyester hollow composite fiber was obtained by spinning and drawing in the same manner as in Example 1 except that the number of orifices was changed to 164 holes. When the cross-sectional shape of each of the 164 single yarns constituting the obtained fiber was judged by a micrograph, it was found that all of the 164 fibers had a high hollowness and had a good cross-sectional shape without eccentricity.

Comparative Example 4 The spinning and drawing were all carried out in the same manner as in Example 5 except that the spinneret for melt spinning had the same die (the number of holes was 164) as in Example 1 of JP-A No. 61-152824. As a result, 11 single yarns in which the hollow portion was broken or the hollow portion was deformed were found in the obtained polyester hollow composite fiber.

(Effects of the Invention) As described above, when the method of the present invention is used, the kneeling is smaller than that of the conventional method and the spinning state is stable, the hollowness is high, and the hollow portion does not have eccentricity. It is possible to obtain a polyester hollow composite fiber having a stable cross-sectional shape, good crimp developability, a large specific volume under light load and a large specific volume under heavy load, and excellent in sublime.

In addition, the melt spinning orifice used in the present invention is arranged concentrically without the need to shift the center points of the outer circumferential arc, the inner circumferential arc of the narrow slit portion and the inner circumferential arc of the wide slit portion. Therefore, a large number of orifices can be accurately and uniformly manufactured on the spinneret, and composite fibers having a substantially uniform cross-sectional shape can be spun from these orifices.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of the shape of an orifice for melt spinning with semicircular slits facing each other for carrying out the present invention, and FIG. 2 is a general hollow fiber spinning conventionally used. FIG. 3 is a schematic view of an orifice, FIG. 3 is a sectional view of a composite fiber obtained by the method of the present invention, and FIG. 4 is a sectional view of a composite fiber obtained by the method of Comparative Example 3. In the figure, 1 is the arc of the outer surface of the semi-circular slit, 2 is the arc of the inner surface of the wide slit, 3 is the arc of the inner surface of the narrow slit, 4
Is a wide sealing portion, 5 is a narrow sealing portion, 6 is a wide slit portion, and 7 is a narrow slit portion.

Claims (2)

[Claims] 1. When producing a polyester hollow composite fiber in which two polyester components having different viscosities are arranged side-by-side, the intrinsic viscosity ratio [η _H ] / [η] of the two components is
_L ] (where [η _H ] is the intrinsic viscosity of the high viscosity component,
[Η _L ] is a polyester with a low viscosity component (intrinsic viscosity) in the range of 1.13 to 1.45, and has a semicircular slit 2
It is a circular slit-shaped orifice with two pieces facing each other, and each slit is formed in a stepped shape at its central part, and is formed by sealing one end with a wide sealing part and the other end with a narrow sealing part. In addition, in the orifice for melt spinning satisfying the following formulas (I) and (II), a high viscosity component is supplied to the wide slit part and a low viscosity component is supplied to the narrow slit part to bond the two components. ，
A method for producing a polyester hollow composite fiber, which comprises discharging from a slit-shaped orifice. However, S _H : Wide slit area (mm ² ) S _L : Narrow slit area (mm ² ) 2. [η _H ] is 0.82 to 0.64 and [η _L ] is 0.72 to
The method for producing a polyester hollow composite fiber according to claim 1, wherein the method is 0.48.