GB2152871A

GB2152871A - Spinneret for spinning acetate fibers having a Y-shaped cross-section

Info

Publication number: GB2152871A
Application number: GB08430925A
Authority: GB
Inventors: Toshihiro Koshida
Original assignee: Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Chemical Corp
Priority date: 1983-12-21
Filing date: 1984-12-07
Publication date: 1985-08-14
Also published as: DE3446188A1; GB8430925D0; JPS60134012A

Abstract

Each spinning hole thereof has a cross-section of a modified triangle consisting of three rounded corners and three linear sides connecting the corners to each other. The width l of the corner is 0.006 mm or more and a ratio of the width l relative to a length L of the linear side is 0.30 or less. A distance between centers of the two adjacent holes is 2.5 mm or more. A stable spinning operation can be expected, by which a sharp Y-shaped configuration of the fiber cross-section is maintained even after a long passage of time from the beginning of the spinning operation. <IMAGE>

Description

SPECIFICATION Spinneret for spinning acetate fibers having a Y-shaped cross-section Background of the invention 1. Field of the invention The present invention relates to an improvement of a spinneretfor spinning acetate fibers, such as diacetate or triacetate fibers, which have a Y-shaped cross-section, suitable for use for a yarn for clothing or a tow for cigarette filters.

2. Description of the related art In the conventional method, acetate fibers having a Y-shaped cross-section are produced through a spinneret provided with a plurality of holes, each having a regular triangular cross-section Z as shown in Figure 1. Such a spinneret, however, has a drawback that foreign matter in the spinning solution tends to be caught by the narrow corners of the triangular cross-section of the hole.This results in unstable spinning as well as irregular quality of the resultant fiber, especially in the cross-sectional configuration thereof, after a certain amount of time passage from the initiation of the spinning operation The present inventors proposed a spinneret, in Japanese Unexamined Utility Model Publication (Kokai) No. 58-176968, provided with a plurality of holes, each having a modified triangular cross-section with corners constituted by an arc of a cricule having a center at the centroid of the basic triangle. The present invention relates to an improvement of the above spinneret for achieving further stable spinning by defining a specific numerical limitation to the dimensions of the cross-sectional configuration of the spinning hole.

Summary of the invention It is an object of the present invention to provide a spinneret which ensures stable spinning of acetate fibers having an accurately Y-shaped cross-section even after a long passage of time from the beginning of the spinning operation.

The spinneret according to the present invention includes a plurality of holes having a cross-section of a modified triangle consisting of three rounded corners and linear sides connecting the corners. Each corner is formed by an arc forming part of an imaginary circle having a center thereof at a centroid of a basic regular triangle formed by extensions of the three linear sides. Characteristics of the present invention reside in that a width e of the corner is 0.006 mm or more, a ratio of the width e relative to a length L of the linear side is 0.30 or less, and a distance between centers of the two adjacent holes is 2.5 mm or more.

Preferably, the ratio t/L is within a range of from 0.23 to 0.30.

Not all the holes provided in the spinneret according to the present invention are necessarily of the modified triangular cross-section defined above. Those of other cross-sectional shapes, such as circles, may be mixed with the former.

Brief description of the drawings Other objects and advantages of the present invention will be more apparent from the following description by referring to the attached drawings illustrating a preferred embodiment of the present invention, wherein: Figure 1 illustrates a cross-section of a prior art spinning hole for spinning acetate fibers having a Y-shaped cross-section; Figure 2 is a similar view as Figure 1 of a typical spinning hole according to the present invention; Figure 3 is a plan view of a spinneret utilized in an example of the present invention; Figure 4 illustrates cross-sections of acetate fibers spun from the prior art spinneret, A being that spun at the beginning and B being that spun after the passage oftime; Figure 5 gives similar views to Figure 4 in the case of using a spinneret according to the present invention;; Figure 6 is a front view of a measuring roll for estimating bulkiness of the fiber; and Figure 7 is a schematic view of how the bulkiness is measured.

Description of the preferred embodiments The spinneret 1 according to the present invention is provided with a plurality of spinning holes 2, each having a cross-sectional configuration as shown in Figure 2. The cross-section of the hole 2 is a so-called modified triangle X derived from a regular triangle Z. Each corner of the modified triangle X is constituted by an arc 3 forming part of an imaginary circle 4 depicted by a dotted line and having a center at a centroid 5 of the regular triangle Z. A linear part 6 of the regular triangle Z within the circle 4 corresponds to a part of each side of the modified triangle X.

According to the present invention, the diameter of the imaginary circle 4 must be chosen so that the circle 4 intersects twice with each of the three sides, whereby three rounded corners are provided.

The width e of the arc 3 forming the corner must be 0.006 mm or more and the ratio of the width e relative to the length L of the linear part 6 of the modified triangle X, that is, elL, must be 0.30 or less, preferably from 0.23 to 0.30. If the width e is less than 0.006 mm, the spinning stability of the spinneret deteriorates and, an accurately Y-shaped cross-section of the fiber cannot be ensured as time passes from the beginning of the spinning operation.

On the other hand, if eiL exceeds 0.30, it is difficult to spin a fiber of a Y-shaped cross-section itself and a product manufactured from the resultant fiber becomes poor in bulkiness.

A distance between centers of each two adjacent holes 2 in a spinneret 1 must be 2.5 mm or more. If it is less than 2.5 mm, there is an increased tendencylo yield a fiber cross-section of a deformed Y-shape as the spinning time passes.

As shown in Figure 2, the basic triangle Z of the hole 2 must be a regular triangle because the manufacturing accuracy thereof is rather easily maintained.

In order to obtain a mixed fiber yarn composed of fibers having different kinds of cross-sections, the spinneret 1 may include spinning holes 2 or other than the triangular cross-section, such as circles. Even in such a case, the distance between the centers of the two adjacent holes must be 2.5 mm or more.

The features of the present invention will be more apparent according to the following examples: Example 1 Diacetate fiber yarns of 75d/1 5f were spun by utilizing seven different spinnerets, Nos. 1 to 7, each having 15 holes of triangular cross-s-ction, arranged in a circle at a distance of 3 mm.

The resultant yarns were inspected for the change in the cross-sectional configuration of the composing fiber with the passage of time from the beginning of the spinning operation and the bulkiness as well as yarn breakage during the spinning operation.

The change in the cross-sectionai configuration was judged by comparing the tested sample with standards classified in five grades, in which the first and the fifth grades were defined as the best and the worst ones, respectively, in the test.

The bulkinesss was measured by a device illustrated in Figures 6 and 7. That is, the sample of the as-spun yarn 10 was wound around a measuring roll 11, having cross-sectional dimensions of a--b=c=50 mm, d=e=10 mm and f=5 mm, until it filled up a space between flanges 12 thereof with a constant tension of 0.1 g/d imparted by a magnet tensor 13. Thereafter, an apparent specific volume V of the wound yarn, as a measure of bulkiness, was calculated by the following equation.

V = 78.541W (cm3/g), where W is a weight of the yarn having been wound on the measuring roll 3.

It will be easily understood that the bulkiness is a measure for the interfiber space created by the Y-shaped cross-section of the fiber.

The results thereof are listed on Table 1.

TABLE 1 Dimensions of hole Change in fiber cross-section (grade) Spinneret Shape of hole # L #/L Bulkiness V Varm breakage No. Time passage from beginning (mm) (mm) (cm3/g) end/100 spinnerets/day Beginning 3 days 6 days 9 days 1 as shown in Fig. 1 0 0.060 0 1 3 4 5 1.6 26 2 as shown in Fig. 2 0.004 0.0053 0.08 1 2 3 4 1.6 23 3 same 0.006 0.049 0.12 1 2 3 3 1.6 16 4 same 0.008 0.046 0.17 1 2 2 3 1.6 14 5 same 0.010 0.043 0.23 1 1 2 2 1.6 12 6 same 0.012 0.040 0.30 1 1 2 2 1.5 11 6 same 0.014 0.037 0.38 1 1 1 2 1.4 10 Note: Circled spinneret numbers indicate the present invention and noncircled numbers comparative examples.

Example 2 Diacetate fiber yarns of 75d/1 5f were spun by utilizing four different spinneret Nos. 8 to 11. Spinneret No. 8 has a plurality of holes of a regulartriangular cross-section as illustrated in Figure 1 having L of 0.060 mm and spinneret Nos. 9 to 11 have, respectively, a plurality of holes of a cross-section shown in Figure 2, having the same L of 0.043 mm and # of 0.010 mm (accordingly, elL of 0.23) but having a different distance between the centers of each two adjacent holes.

The same characteristics of the resultant yarns as Example 1 were estimated and listed on Table 2. TABLE 2 Change in fiber cross-section (grade) Spinneret Shape of hole Distance between Bulkiness V Yarn breakage No. centers of two holes Time passage from beginning (mm) (cm3/g) end/100 spinnerets/day Beginning 3 days 6 days 9 days 8 as shown in Fig. 1 3.0 1 3 4 5 1.6 26 9 as shown in Fig. 2 2.0 1 2 3 3 1.6 18 10 same 2.5 1 2 2 2 1.6 13 11 same 3.0 1 1 2 2 1.6 12 Note: Circled spinneret numbers indicate the present invention and noncircled ones comparative examples.

The actual shapes of fiber cross-sections are illustrated in Figures 4 and 5, in which Figure 4 are those obtained from Spinneret No. 8 immediately after the beginning of the spinning operation (A) and 9 days thereafter (B) and Figure 5 are those obtained from Spinneret No. 11 immediately after the beginning of the spinning operation (A) and 9 days thereafter (B). - Example3 Triacetate fiber yarn of 75d/27f was spun from a spinneret having 9 holes, the cross-sections of which are shown in Figure 2, having e of 0.010 mm and L of 0.040 mm (therefore elL of 0.25) and 19 circular holes of 0.030 mm diameter, both being arranged in a manner illustrated in Figure 3 with a distance of centers thereof being 3.0 mm.

The resultant yarn was excellent in resistance to yarn breakage and change in fiber cross-section with the passage of time, as is the case of Spinneret 11 of Example 2.

Claims

1. A spinneret for spinning acetate fibers having a Y-shaped cross-section of a modified regular triangle consisting of three rounded corners and three linear sides connecting said corners to each other, each said corner being formed by an arc forming part of an imaginary circle having a center thereof at a centroid of a basic regular triangle formed by extensions of said three linear sides, characterized in that a width e of said corner is 0.006 mm or more, a ratio of said width e relative to a length L of said linear side is 0.30 or less, and a distance between centers of two adjacent holes is 2.5 mm or more.

2. A spinneret according to claim 1, in which said ratio elL is within a range of from 0.23 to 0.30.

3. A spinneret according to claim 1, in which at least one hole having a cross-section of other than said modified triangle is mixed with the latter.

4. A spinneret substantially as herein described with reference to the accompanying drawings.