JPS6197412A - Spinneret for pitch for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain pitch fiber suitable for the production of carbon fiber, preventing the wetting phenomenon, fluctuatioon oft he fiber, welding of fibers, and denier unevenness, by forming a ring groove to the circumference of the opening of the spinning nozzle. CONSTITUTION:A groove 8 is formed to the circumference of the opening 4a of the spinning nozzle 4. The contaminatoion of the spinneret surface in the melt spinning of pitch stored in a pitch reservior, especially the contamination around the spinning nozzle can be prevented, and the difference between the pitch temperature in the spinneret and the pitch temperature at the surface of the spinneret can be decreased. The size of the groove 8 is e.g. d1=0.1-0.3 mm; d2=0.3-0.6 mm; w=0.8 mm; h=0.5-1.0 mm; and H is 3.0 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spinneret used for melt spinning pitch for carbon fibers, and particularly to a spinneret that can be suitably used for spinning optically anisotropic pitch. It is.

2. Description of the Related Art Conventionally, when spinning pitch for carbon fiber to produce pitch-based carbon fiber, a plurality of spinning nozzles (d+:
Melted pitch is inserted into the spinning nozzle 4 under pressure using a spinneret 1 in which 0.15 to 030 r171 and H: 1.2 coral) 4 are formed in one row or in multiple rows concentrically in the circumferential direction. By this process, pitch for carbon fiber was spun.

Such a spinneret 1 is constructed by simply drilling or electron beaming a spinning nozzle 4 into a nozzle plate 2, as shown. The pitch reservoir portion 6 is simply formed by drilling a pitch reservoir portion 6 having an arbitrary shape as desired.

On the other hand, in high-temperature melt spinning such as pitch-based carbon fiber, from the spinning nozzle 4a of the spinning nozzle 4 and the
Volatile low-molecular gas 1, such as oil smoke (heavy oil), is generated from the spun pitch fiber thread through the spinneret and adheres to the spinneret surface 2a around the spinning nozzle spout 4a,
The spinneret 2 is contaminated. The so-called ``talking phenomenon'' was observed.

When such a smearing phenomenon occurs, the spun yarn may sway, causing fusing between each yarn, denier unevenness, or in the worst cases, yarn breakage, which may result in stable spinning over a long period of time. made impossible.

Conventionally, in order to prevent the above-mentioned wetting phenomenon during bath melt spinning, methods have been proposed, such as a method of suctioning and exhausting the gas inside the spinneret, and a method of forcibly spraying cooling gas onto the surface of the spinneret. There is. However, it has been found that in the case of high-temperature melt-protected fiber spinning, such as pitch-based yarn with a similar number of carbon atoms, stable spinning cannot be achieved using the conventional method as described above.

On the other hand, in order to obtain carbon fiber yarn, it is necessary to spin pitch fibers at high temperatures. However, the heat dissipation from the spinneret surface is caused by the air flow (IfIL wake) accompanying the spinning of pitch fibers.
This increases the temperature of the pitch coming out of the spinneret. Therefore, in order to obtain the optimum pitch fiber spinning temperature, K had to increase the pitch temperature in the spinneret pack more than necessary. however,
In some cases, excessive pitch temperature may induce deterioration or foaming of the pitch, narrowing the temperature range in which spinning is possible and making stable spinning difficult.

OBJECTIVES OF THE INVENTION Therefore, the main objective of the present invention is to prevent the "fluffing phenomenon" of the spinneret, that is, the staining of the spinneret surface, especially around the spinning nozzle, and to reduce the pitch temperature difference between the inside of the spinneret and the pitch temperature on the spinneret surface. It is another object of the present invention to provide a spinneret that can reduce the amount of carbon fiber, provide optimum pitch fibers, and perform long-term stable pitch spinning for carbon fibers. In view of the above-mentioned drawbacks of conventional spinnerets, the inventors of the present invention have repeatedly conducted numerous studies and experiments, and have developed an annular concave groove in the vicinity of the spinning nozzle of the spinneret. By this, the above objectives can be completely achieved, that is, the "wetting phenomenon" can be prevented, and yarn shaking, fusion between yarns, and denier unevenness can be eliminated.

It has been found that the optimum pitch fiber for obtaining carbon fiber can be stably spun over a long period of time.

The present invention has been made based on this new knowledge.

To summarize the present invention, 1. The present invention provides a pitch for carbon fiber characterized in that, in a spinneret provided with a spinning nozzle for spinning pitch for carbon fiber, a recess is provided around the spinning nozzle of the spinning nozzle. It is a spinneret for.

According to one embodiment of the invention, the recess is formed annularly around the spinning nozzle, and according to another embodiment, the spinning nozzle is formed by a hollow pipe.

EXAMPLES Example 1 Next, a spinneret according to the present invention will be explained in more detail with reference to the drawings.

Referring to FIG. 1, one embodiment of a spinneret according to the present invention is illustrated. The spinneret 1 is generally made of a stainless steel plate (SUS316 or 6) having a thickness of about 20 mm.
A spinning nozzle 4 and a pitch reservoir 6 connected to the spinning nozzle 4 are formed in the nozzle plate 2 produced in step 30). In the present invention, a space 8 is further provided around the spinning opening 4a of the spinning nozzle 4. In this embodiment.

The cavity 8 is formed by boring an annular hole in the nozzle plate 2 around the spinning nozzle outlet 4a.

The shape of the annular recess 8 may be arbitrary.

- To give an example, d+: O1~0.3 mm (
For example, 0.2 mr).

d2: 0.3 to 0.6 mm (e.g. 0.4 mm)
, w: 0.8 mm.

h: 0.5-1, OynmC e.g. 0.8 mm),
H: 3. It is assumed that Omm.

Examples 2 and 3 FIGS. 2 and 3 show an embodiment in which the spinning nozzle 4 is formed of a pipe 10 made of stainless steel.

In this way, the spinning nozzle 4 was formed using the hollow pipe 10.
If convenient, the spout 1lIII end 10 of the hollow pipe 10
a'! Br, 1 from the nozzle plate 20 surface, for example h=
The present invention can be realized by making the hollow pipe 10 protrude by about 0.5 to 1.0 m (Fig. 2).
The nozzle plate 2 around the spinning outlet side end 10a of
= 0.8 mm and h = 0.5 to LO mrn to form an annular recess 8 (FIG. 3).

The hollow pipe 10 generally has a hole diameter of 0.1 to 0.3 (
d, ), o,: outer diameter (d2) between 3 and 0.6 and H=3
．． Orrrm K and shrink fit into the pilot hole of nozzle plate 2,
Caulking or brazing is used for fitting. In addition, the inlet side of the hollow pipe 10, that is, the connecting part with the pitch reservoir part 6,
Using the spinneret shown in FIGS. 1 to 3 (Examples 1 to 3) and FIG. 4 (Comparative Example), which may be configured to expand slightly as shown, substantially A pitch consisting of a 100 modulus optically anisotropic phase was spun. The specific dimensions of the spinneret 1 at that time are shown in Table 1, and the spinning machine is schematically shown in FIG.

A brief explanation of the spinning machine 100 used in the experiment is as follows.
The spinning machine 100 includes a heating cylinder 102 and a piston 104.
A spinneret 1 is provided on the bottom side of the heating cylinder 102.
was placed. The spinneret 1 was detachably fixed to the heating cylinder 102 by a spinneret presser 108 and bolts 110. In addition, the heating cylinder 102 includes the cylinder 102
The structure was such that the molten pitch P was supplied from a pitch supply pipe 106 provided on the zero side.

During pitch spinning, the molten pitch P is passed through the supply pipe 106
The piston 104 is inserted into the heating cylinder 102.
Pressurized by The pitch P is set so that the yarn after spinning is spun from the spinning nozzle 4 of the spinneret 1 and wound by the first take-up roll 112, so that the yarn after spinning does not sway due to wind or the like. A windshield glass tube 114 was placed surrounding it.

The softening point of the pitch used in this experiment was 258°G,
The pitch was melted at about 330° C. and supplied into the heating cylinder 102 through the pitch supply pipe 106. A long-time spinning test was conducted by closing the pulp and pushing down the piston at a constant speed to wind up the pitch thread flowing down from the nozzle at a rate of 500 m/min.The spinning pitch temperature was controlled at 330°C directly through the nozzle, The extrusion speed was 0.08 gr/min, and the nozzle plate was changed to observe the change in the area around the nozzle opening and the frequency of thread breakage over time. The results are shown in Table 1. Similarly,
In order to compare the spinning temperatures, the pitch temperature was gradually lowered from 330° C. using the same pitch and the spinning temperature was checked, and the results are shown in Table 1.

Margin Table 1 Below Table 1 shows that when the spinneret according to the present invention is used, the frequency of thread cutting is significantly reduced compared to the conventional one, and the structure of Example 3 (Fig. 3) is particularly suitable. .

The spinneret according to the present invention, which is constructed as described above, prevents wetting phenomena, prevents yarn shaking, fusion between yarns, and denier unevenness, and enables stable spinning without yarn breakage over a long period of time. Furthermore, the range of spinning of pitch fibers has been expanded, and it has become possible to spin pitch fibers suitable for making carbon fibers.

Furthermore, the spinneret according to the present invention has a simple structure.

It is easy to manufacture and has the advantage that a spinneret for multifilament can be manufactured relatively easily.

[Brief explanation of the drawing]

1 to 3 are partial cross-sectional views of a spinneret according to the present invention. FIG. 4 is a partial sectional view of a conventional spinneret. FIG. 5 is a schematic sectional view of a spinning machine used in the experiment. 1: Spinneret 2: Nozzle plate 4: Spinning nozzle 6: Pitch reservoir Part 8: Recess 10: Hollow pipe Fig. 4 4a 4 2a Fig. 5 104 '''

Claims (1)

[Claims] 1) A pitch for carbon fiber, characterized in that a spinneret provided with a spinning nozzle for spinning pitch for carbon fiber is provided with a recess around the spinning nozzle of the spinning nozzle. spinneret. 2) The spinneret according to claim 1, wherein the recess is formed in an annular shape around the spinning nozzle. 3) The spinneret according to claim 1 or 2, wherein the spinning nozzle is constituted by a hollow pipe.