JPH0551810A - Spinneret for fiber having modified cross section - Google Patents

Abstract

PURPOSE:The subject spinneret having plural groups of holes, each group consisting of a center hole and plural outer circumferential holes perforated in the outer circumferential direction from the center hole at intervals, and required for the precursors of carbon fibers each having large cross-sectional modification degree, excellent adhesiveness, excellent bending strength, etc. CONSTITUTION:The objective spinneret having plural groups, each group consisting of a center hole 1 and plural outer circumferential holes 2 perforated in the outer circumferential direction of the center hole at intervals L of 0.05-0.15mm. For example, three-five outer circumferential holes are perforated on the substantially same circumference outside the center hole 1 in the rotational symmetry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spinneret for obtaining a modified cross-section fiber, and more particularly to a spinneret for a fine fineness modified cross-section fiber as a precursor of carbon fiber having excellent composite properties. is there.

[0002]

2. Description of the Related Art A modified cross-section fiber has hitherto been used for clothing to improve texture, color developability, improve the waist of a carpet, and the like. As a method for obtaining a modified cross-section fiber, for example,
When the cross section is multi-lobed, a method in which the spinning solution is discharged from a spinneret hole in which slit-shaped holes are radially arranged is generally used.

However, in the slit radial spinneret, in the melt spinning method, the dry spinning method, the dry-wet spinning method, etc., in which the spinning solution is discharged into the air, the spinning solution is circularized by surface tension until it solidifies or solidifies. Therefore, it is difficult to obtain a fiber having a large degree of cross-section irregularity. Further, in wet spinning, it is relatively easy to reflect the hole shape of the spinneret in the fiber cross-sectional shape, but in the case of the modified spinneret, since the outer circumference of the hole is long, the actual spinning draft becomes large and the spinnability is extremely deteriorated. In the extreme case, there is a problem that the coagulation liquid penetrates into the die hole, and it is difficult to obtain a fine fiber.

In the former case, it is necessary to make the slit width as small as possible and lengthen the slit length in order to obtain a fiber having a large degree of cross-section irregularity. However, if the slit width is made small, the processing accuracy is limited. However, there is a problem that the spinnability is extremely poor because the pore area inevitably increases and the discharge linear velocity of the spinning solution decreases.

As a method for improving this, Japanese Patent Laid-Open No. 2-1
In Japanese Patent Publication No. 69710, there is proposed a die for a modified cross section in which three trapezoidal slits having a wide width in the outer peripheral direction are radially arranged. However, even in such a trapezoidal slit hole, discharge stress unevenness occurs due to the four corners of the slit, and the spinnability is poor, and it is particularly difficult to obtain a fine fiber as a precursor fiber for carbon fiber. I understood it.

Further, in Japanese Unexamined Patent Publication No. 64-26712, an acrylonitrile-based polymer has 3 to 5 circular or rectangular small holes, and an angle θ formed by a line connecting each center and the center of the group is 70. A dry acrylic fiber with a modified cross-section is proposed, which is dry-spun through a spinneret having a plurality of small holes arranged so that the intervals between the small holes are 0.03 to 0.70 mm. However, it has been found that when a modified cross-section fiber having an optimum rotational symmetry as a precursor fiber for carbon fiber is obtained, the degree of cross-section modification becomes small.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a modified cross-section yarn having a larger degree of cross-section irregularity than ever before, particularly a precursor fiber for carbon fiber which is excellent in adhesiveness with resin, bending strength and compression strength, That is, it is intended to provide a spinneret for modified cross-section fibers, which is capable of spinning with a high productivity a fine fine yarn having a uniform multileaf shape and each leaf having a bulge shape and having a large specific surface area.

[0008]

The above object of the present invention is to provide a plurality of small hole groups each including a central hole and a plurality of outer peripheral holes perforated at intervals in the circumferential direction of the outer periphery of the central hole. It can be achieved by a spinneret for modified cross-section fibers characterized by having groups.

In the above-mentioned die, the outer peripheral holes are 3 to
In addition to being formed by five pieces, it is preferable that the holes be perforated at positions to be rotated on substantially the same circumference of the outer periphery of the central hole. Further, the distance between the central hole and the outer peripheral hole is 0.
It is preferable to set it to 05 to 0.15 mm.

The present invention will be described in detail below.

As shown in FIG. 1, the present invention has one small hole 1 in the center, and 3 to 5 small holes 2 on the outer side, preferably at rotationally symmetrical positions on the same circumference. The spinning solution is discharged from a spinneret having a plurality of small hole groups 3, and the spinning solution flows discharged from the small holes in each small hole group are merged until the spinning solution is solidified or solidified. , To form a modified cross-section fiber.

As shown in FIG. 2, when there is no central hole in the small hole group, the spinning solution contracts in the cross-sectional direction due to surface tension after joining, so that the cross-sectional shape is circular and a sufficient cross-sectional irregularity is obtained. Inevitably, the object of the present invention cannot be achieved.

That is, the most characteristic feature of the present invention is to have a small hole at the center of the small hole group, which results in a large degree of irregularity in cross section, and each leaf once bulges from the root toward the tip. It is possible to easily obtain a fiber having an irregular cross-section having a characteristic of having a plurality of circles and having substantially the same. The shape of the leaf with this bulge is converted to carbon fiber, and when it is made into a carbon fiber reinforced composite material, the matrix enters between the leaves, and the anchor effect is exhibited unprecedentedly. This is a preferable shape because the tensile strength is further improved.

When the outer peripheral holes are perforated in double or triple concentric circles, the irregularity of the cross section is further increased, but the hole area is increased and it is difficult to obtain fine fibers, and carbon fibers are added. During the conversion process, leaf damage frequently occurs, resulting in poor quality and poor physical properties, which is not preferable. The number of peripheral holes is preferably 3 to 5. If the number is more than 5, the outer peripheral holes are directly joined to each other, and thus the multilobed shape having the bulged leaf as the object of the present invention cannot be maintained, which is not preferable. Further, if the number is less than 3, the effect of the central hole is not exhibited, the difference in the geometrical moment of inertia of the fiber becomes large depending on the rotation angle of the cross section, and the bending stress of the composite material is not improved, which is not preferable. From this point of view, it is preferable that the outer peripheral hole is arranged in a rotationally symmetrical position. That is, if there are three peripheral holes, each small hole should be 1
They are arranged at an interval of 20 ° (symmetry angle), and are arranged at an interval of 90 ° when there are four outer peripheral holes, but there is no problem even if there is a slight deviation as long as the object of the present invention can be achieved.

The distance between the outer peripheral hole and the central hole is 0.05 to 0.
15 mm is preferable, and if it is smaller than 0.05 mm, the degree of irregularity of the cross section is lowered to make it difficult to obtain bulging leaves, and if it is larger than 0.15 mm, it is not preferable because fibers are not sufficiently bonded and do not bond at all. ..

The shape of the small holes is preferably circular, but is not limited to this.

The diameter of the small holes must be optimally designed according to the conditions such as the viscosity of the spinning solution and the discharge amount, but in any case, the area ratio of the outer peripheral hole (one) to the central hole (outer peripheral hole / Center hole) is preferably applied in the range of 0.3 to 3.0.
If it is smaller than 0.3, the leaves are small and the degree of cross-section is reduced, and if it is larger than 3.0, the effect of the existence of the center hole is reduced, so that the outer holes are joined to each other and the degree of cross-section is reduced. Is not preferred. Especially the cross-section irregularity,
From the viewpoint of spinnability, a suitable area ratio is 0.9 to 2.5.
And more preferably in the range of 1.1 to 2.5. ..

With the spinneret of the present invention, it is possible to easily obtain a fiber having a very characteristically-shaped cross section in which each leaf has a bulge from the root to the tip and substantially a plurality of circles are joined. For example, when there are three peripheral holes, the shape is a three-leaf clover shape, and when there are four outer holes, it is a four-leaf clover shape.

The spinning solution is not particularly limited, but if the solution viscosity is too low, it becomes difficult to obtain the desired cross-sectional shape, so the solution viscosity at the temperature discharged from the spinneret is 50 poises or more, Preferably 300 poise or more 1
000 poise or less is preferably applied. In particular, in order to obtain high physical properties as a composite material, a PAN-based spinning solution is used, and dry-wet spinning is preferable in terms of bonding properties and spinning operability.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A 20% by weight DMSO solution of a PAN-based copolymer consisting of 99.3% by weight of acrylonitrile and 0.7% by weight of itaconic acid was used as a spinning solution. The liquid viscosity was 650 poise at 45 ° C. This spinning solution is rotationally symmetrical at a center hole with a diameter of 0.04 mm and three outer peripheral holes with a diameter of 0.055 mm, and the distance between the center hole and the outer peripheral hole (L in FIG. 1) is 0.07 mm (symmetry angle). It is discharged from a spinneret having 500 small hole groups arranged at 120 °), and after passing through a space of 3 mm (air gap), it is led to a coagulating liquid having a DMSO / water weight ratio set to 55/45 and 25 m / Dry-wet spinning was performed at a take-up speed of minutes. After that, washing, stretching and drying are carried out by a conventional method, and then further stretched in pressure steam to perform a total stretching 1
A fiber having a single yarn fineness of 1 denier was obtained by setting the fiber diameter to 0 times. Despite the fineness of the fiber, the fiber had good passability in the yarn forming process and no fluff was observed. Further, the cross-sectional shape of the fiber is uniform, and each leaf has a bulge from the root to the tip as shown in FIG. 2, and the cross-section irregularity (circumscribed circle radius /
The ratio of inscribed circle radii) was 2.0 or more in all cases.

Comparative Example A circular hole having a diameter of 0.06 mm and a center hole of 0.07 m
A rotationally symmetric position on the circumference of a radius of m (symmetry angle 120
A fiber was obtained under the same conditions as in Example 1 except that a spinneret having 500 small hole groups arranged at 3 ° was used. No fluff or the like was found in the obtained fiber, but the cross-sectional shape was a rounded triangle as shown in FIG. 4, and each leaf did not have a bulge and had a cross-sectional irregularity of 1. It was 5 or less.

Examples 2 to 6 Fibers were obtained by changing the distance between the central hole and the outer peripheral hole and the air gap under the conditions of Example 1 and observing the cross-sectional shape,
The results are shown in Table 1.

[0024]

[Table 1]

From the results shown in Table 1, it is possible to obtain a fiber having a cross section in which each leaf has a bulge, by appropriately setting the air gap according to the distance (L) between the central hole and the outer peripheral hole. If the air gap is less than 2 mm, the spinneret immersion trouble may occur in the coagulation bath even with slight waviness. On the other hand, if the air gap is 5 mm or more, yarn breakage trouble may occur at the coagulation bath liquid surface. It is understood that the distance (L) between the central hole and the outer peripheral hole is more preferably 0.05 to 0.15 mm in order to satisfy both the cross-sectional irregularity and the yarn operability.

[0026]

The spinneret of the present invention makes it possible to easily obtain, with high productivity, a modified cross-section fiber having a fineness and uniform multileaf shape, and each leaf having a bulge from the root to the tip. .. When the fiber is used as a precursor fiber for carbon fiber, it is effective for improving composite material properties, particularly for improving 90 ° tensile property, bending property and compression property. Also, due to this characteristic cross-sectional shape, it has a unique texture and luster and can be effectively used for clothing.

[Brief description of drawings]

FIG. 1 shows an example of a small hole group of a die of the present invention. L in the figure
Indicates the distance between the central hole and the peripheral hole.

FIG. 2 one of the cross-sectional morphologies of the fibers obtained according to the invention
Here is an example:

FIG. 3 shows a group of small holes of a die of a comparative example.

FIG. 4 shows a cross-sectional morphology of fibers obtained in a comparative example.

[Explanation of symbols]

 1: Central hole 2: Peripheral hole 3: Small hole group

Claims (3)

[Claims] 1. A modified cross-section fiber having a plurality of small hole groups each comprising a central hole and a plurality of outer peripheral holes perforated at circumferential intervals on the outer periphery of the central hole. Spinneret. 2. The outer peripheral hole is formed by 3 to 5, and the outer peripheral hole of the central hole is perforated at a position to be rotated on substantially the same circumference. 1. The spinneret for modified cross-section fibers according to 1. 3. A distance L between the central hole and the outer peripheral hole is 0.05 to.
The spinneret for modified cross-section fibers according to claim 2, wherein the spinneret is 0.15 mm.