JPS59168115A - Melt spinning for pitch - Google Patents

Abstract

PURPOSE:In the melt-spinning of pitch, a buffer zone is provided so that the linear speed of the melted pitch becomes slowed down to enable stable formation of multifilaments of pitch carbon fibers without breakage, even when spinning conditions fluctuate. CONSTITUTION:When pitch is melted, extruded and taken up, the melt-spinning is effected so that the average linear speed of the pitch at the spinneret surface becomes slower than the maximum average speed in the holes and less than 1/ 1,500 of the taking-up speed. Namely, for example, a buffer or damping zone 3 is provided beneath the hole 2 so that the cross section of the zone 3 is larger than that of the hole 2 and the linear speed on the spinneret surface becomes less than 1/1,500 of the taking-up speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a melt spinning method for stably producing a vidge-based carbon fiber multifilament.

Conventionally, methods for obtaining carbon fibers by melt spinning pitch have been known, such as a method of extruding molten pitch using a stationary spinneret and a method using rotary centrifugal spinning. However, all of these techniques focus on pitch as a spinning dope, carbonization, and graphitization, and do not even consider the relationship between pitch characteristics and melt spinning.

That is, pitch has (1) extremely high temperature dependence of melt viscosity, and even a slight change in temperature causes a large change in viscosity.

(2) Since pitch is a mixture, it tends to have uneven viscosity.
In particular, in a pitch where an optically anisotropic component is developed, there is a difference in viscosity between the pitch and an optically isotropic part, and there is a strong tendency to cause viscosity unevenness.

(3) At the temperature at which pitch is melt-spun, the viscosity is usually 10
The spinning rate is extremely low at ~300 voids, and stable spinning is possible with normal melt spinning methods.

It is known to correct problems such as

Conventionally, when producing carbon-11 miscellaneous materials from such pitch, when discharging the bit from the mouth surface, a draft is created in the molten pitch by discharging the hip at the discharge linear velocity within the discharge hole and taking it off. It formed a strip.

However, as described above, the pitch has a low melt viscosity immediately after being discharged from the nozzle, and is susceptible to fluctuations in viscosity, temperature, speed, etc., and yarn breakage is likely to occur due to stress changes in the trough. Moreover, since thinning occurs rapidly after dispensing from the nozzle surface, thread breakage can be prevented using the normal dispensing method.
It was a difficult problem to do so.

Unlike ordinary polymers, pitch is a mixture consisting of a very large variety of compounds, and its viscosity is not uniform, and the viscosity during melt spinning is extremely low, exceeding 300 voids, and only a small change in pressure occurs. Even if there is, non-uniformity of flow is likely to occur between each discharge hole. Therefore, in pitch melt spinning,
Although it is extremely important to stabilize and equalize the flow between the discharge holes, in reality it has been difficult to achieve such a uniform flow.

In view of such technical limitations, the present inventors conducted extensive research on the technology to stably and industrially achieve pitch melt spinning, and discovered the fact that it is extremely effective to form a buffer region on the spindle surface. This is what we have investigated and arrived at the present invention.

That is, in the present invention, when the pitch is melted and discharged from the nozzle and then taken off, the average linear velocity of the molten pitch on the nozzle surface is set to be smaller than the maximum average flow velocity in the nozzle hole and 1 of the take-up speed. This is a melt spinning method with a pitch of /1500 or less. (C melt spinning was possible, and pitch-based carbon fiber could be stably produced industrially in the form of multi-noiramen 1.

In the present invention, the average linear velocity of the molten pitch at the mouth surface can be determined from the outflow of the molten pitch and the cross-sectional area of the flow of the molten pitch at the mouth surface. Important points 1 to 1 of the present invention are that the formation is proactive. In other words, this region exerts a buffering effect against various fluctuations. Specifically, there is a method in which a pool of molten pitch having a cross-sectional area larger than the discharge cross-sectional area is formed on the mouth surface. The size of this pool is
The linear velocity at the mouth surface is 1/1500 or less of the drawing speed, preferably 1/2000 or less, more preferably 1
It is necessary to have a cross-sectional area of 15,000 or less.

31 The invention will be explained below with reference to the drawings.

FIG. 1 shows a discharge method with a buffer region according to the present invention. I is a schematic diagram. The molten pitch discharged from the outlet hole 2 provided in the mouthpiece 1 is attached to the face of the mouthpiece to form a reservoir 3, and the yarn 4 is taken from this reservoir 3. The maximum cross-sectional area of the reservoir is preferably made larger as the Tagawa hole cross-sectional area becomes smaller. Furthermore, since a pool is formed at the discharge port, it is also advisable to selectively use a material for the mouth surface that has excellent wetting characteristics against the pitch. It is also preferable to make the mouthpiece outlet a deformed hole to facilitate the formation of a pool.

The present invention produces pitch-based fibers from pitch in an extremely stable manner by providing a region on the spinneret surface that has a buffering effect against various fluctuations during melt-spinning pitch, specifically, a pool of molten pitch. □

According to the present invention, it is possible to industrially produce a multifilament having an extremely low viscosity, for example, a pitch of 20 to 300 poise, and excellent uniformity.

1- In the present invention, fibers having a random structure or fibers having a radial structure can be formed as necessary by selecting the pitch as a raw material and the spinning conditions.

For example, when melt-spinning an optically anisotropic pitch, the shear velocity γ in the die hole shown by equation (1) is set to 550 sec-1 or less in the die discharge hole portion, and the following (2
) A multifilament having a random structure can be obtained by combining the method of melt All spinning with an orientation forming parameter f of 90 T or more.

γ-32Q/πD3・・・・・・・・・(1) f
-γft・・・・・・・・・・・・・・・・・・
...(2) [Q: Bitge style 1d (cm3/sea
) D Niro metal hole diameter (am) t: Average residence time in the mouth hole (sec) ] The average residence time in the mouth hole in the above formula is determined from the following formula (3).

[-πD2ff/4Q (3) [0:
In this method, the quality of the mouthpiece hole is 2505ec.
-1 or more preferably 10 IJ: 150 sec -'
Above-(゛, By selecting and overriding the condition that the orientation formation parameter f is 550 or less, the multi-neuramen 1 with a radially oriented structure is stably jq
It will be done.

In addition, by adopting the following conditions: ``the shedding speed γ is 550 Sac -1 or less and the orientation formation parameter f is 100 or more'', it is possible to form 48 mt with radial orientation.

In the case of radial orientation, the shear speed γ is further 650 se
By selecting a stripe '1' having an orientation formation parameter f of 140 or more, a fiber having a roughly high radial orientation is formed.

This radial structure yarn exhibits excellent performance in terms of elastic modulus, thermal conductivity, electrical conductivity, etc., while the undam structure yarn has excellent strength and elasticity of 1! It has a 1. weaker performance in terms of I″J?.

In addition, in the present invention, when adopting a non-circular [1 gold n1 hole] in a-3 of the present invention, the diameter when converted to a circular hole with the same cross-sectional area is applied to the matching hole in (2) and (b). In addition, according to the present invention, (pulling speed γ is the flow path diameter of the smallest cross-sectional area of the flow path in the nozzle discharge hole portion, and average residence time 1 is the average residence time in the flow path in the Tagawa hole portion. The flow path means the flow path portion beyond the minimum cross-sectional area that is opened to the outside through which pitch is discharged, and does not include the introduction portion that is inserted into a normal mouthpiece.

According to this method, 1q of carbon fiber multifilaments having a random structure or a radial structure can be economically produced at an industrial ear level.

Note that the above-mentioned optical anisotropy pitch refers to optical anisotropy of 1 in the pitch.
! Component I is contained in an amount of 60% or more, preferably 75% or more, more preferably 0% or more.

Although the pitch can be extruded under pressure using a hl pump or an inert gas, extrusion using a 61m pump is preferably applied. It is particularly effective when discharging uniformly (filtration) through two culms using a nozzle with a large number of discharge holes (for forming multifilaments).

l The single fiber diameter after spinning obtained by the method of the present invention is 30
μ or more T is appropriate, preferably 5 to 30μ, and more preferably 7
-20μ range is a? from the viewpoint of thread breakage and strength.
However, diameters other than this are also effective.

The pitch-based IJ Ift thus obtained is then treated to be infusible, carbonized, and graphitized by a conventional method. As the infusibility treatment, for example, a method of oxidizing in the presence of oxygen at 250 to 420°C in normal air can be applied.

Further, it is also preferable to use an oxidizing gas such as A-syn or NO2 as oxygen from the viewpoint of the efficiency of the infusibility treatment. The fibers subjected to such infusibility treatment are then carbonized and graphitized, and a commonly used method can be applied to such a method.

Such carbonization treatment includes, for example, a method of heating to 800 to 1700°C in a vacuum or an inert gas atmosphere.
For graphitization treatment, for example, there is a method of heat treatment at 1700'C or higher in a vacuum or an inert ↑4 electric atmosphere.

Hereinafter, the present invention will be explained in more detail with reference to Examples 8- do.

The measurement method used in the examples is as shown below.

[Optical Anisotropy] After wrapping the sample in poxy resin, it was polished by a conventional method. Polished surface with Leitz ORT HOP [-
Observation was made using a ΔN microscope using a reverse polarization method.

The abundance of the optically anisotropic component was determined from the area ratio of the isotropic part and the anisotropic part when observed under the polarized light described above.

[Quinoline solution] This was carried out by a combination of the pre-centrifugation method and the filtration method specified in JIS-2425.

[Crow transition temperature] Measured in a nitrogen yarn atmosphere using Perkin-E 1mer NE1 DSC-2. By heating the sample to 290°C, cooling it to room temperature, raising the temperature again, and measuring.
Measurements were performed excluding factors that disturb the baseline, such as dehydration peaks.

[Original search analysis] Using Yanagimoto Seisakusho CI-IN coder M-1--3 type L/T, trial rI IWF900-950''G, M
I furnace 850°C, reduction furnace 550°C, helium flow rate 18
The measurement was carried out under the measurement strip A9 of 0 mff, /min.

[Reservoir diameter on the mouthpiece surface] The shape of the molten bit at the outlet of the mouthpiece discharge hole was observed with a long focus W1 microscope, and the diameter was determined.

Example 1 Commercially available petroleum filtrate was pressure filtered at 300°C using 200 mesh glass beads, and then filtered at 310°C and I
Treatment was performed under reduced pressure of Q p+m1-I CI for 30 minutes to remove low boiling point components. The obtained pitch was examined using a polarizing microscope. As a result, it was found to be substantially optically isotropic. This pitch was spun using spinnerets with various hole diameters at a spinning concentration of 280° C. and a spinning speed of 600 m/n+in to obtain pitch fibers with an average diameter of 10 μm. Spinning is 0.01
~2. It was extruded with nitrogen at OK+J/cm2.G. The results are shown in Table 1.

Table 1 0 Gold No. Pore diameter Reservoir diameter Speed ratio Silk spinning situation 1
0.20 No accumulation 1/400 Defective 2
0.20o, 3o 1/9003 0.
30 0,40 1/ +eoo.

4 0.30 0,50 1/2500
Q5 0,/10 0,60 1/36006
0.50 0.80 1/ 64007 0.
70 1,00 1/100008 1.00
1,2 (11/14400 table) Hole diameter: Piper hole diameter (mm) Reservoir diameter and discharge diameter (mm) Speed ratio: Average linear speed at the mouth surface / Take-off 3i degree Poor spinning condition: Many yarn breaks O: Almost no yarn breakage 0: No yarn breakage at all 11 Example 2 After heating and melting rutal bits with a softening point of 80°C in a nitrogen atmosphere for about 1 hour (J) to 410°C, 3
Heat treatment was performed at 410° C. for 12 hours while stirring at 0 rpm. Next, nitrogen pressure was applied at 380°C, and insoluble matter was removed by r-filtration using a 200-mesh Raspice.
A vacuum treatment was performed at 420° C. and 15 mm 1-(o) to remove low-boiling components.

After embedding the obtained pitch in an epoxy resin and polishing it, observation using a reverse polarization microscope revealed that about 90% or more of the pitch was an optically anisotropic component. The optically anisotropic structure showed a large flow shape. The characteristics of heat-treated bits are 53wt of quinoline solution.
%, a softening point of 340°C, a glass transition temperature of 195°C,
The original analysis results were 93 wt% carbon, 3.7 wt% hydrogen,
Nitrogen i, Qwt%.

Using this heat-treated pitch, we use ferrules with various hole diameters,
Spinning was carried out at a spinning concentration of 380° C. and a spinning speed of 600 m/min to obtain pitch-based fibers with an average diameter of 10 μm.

12- Spinning was extruded with nitrogen at 0.01-2.0K (1/am2.G). The results are shown in Table 2.

Experiments Nos. 093 to 8 are examples of the present invention, in which the ratio of the average linear velocity at the spinneret surface to the take-up speed was 1/1500 J: there was no small thread breakage, and the thread reeling properties were good. On the other hand, in experiments Nos. 1 and 2, which are comparative examples, the ratio of the average linear velocity to the take-up speed was less than 1/1500, and stable spinning was not possible due to many yarn breakages.

Table 2 0 Gold No., Pore diameter Reservoir diameter Speed ratio Silk spinning status 9 0
．． 20 No accumulation 1/400 Defective i Q
O, 200, 401/1600 011 0.
30 No accumulation 1/900 Defective 12 0.
30 0.70 1/4900 Ql 3
0.40 0,80 1/640014 (1
,500,901/810015 0.70 1.0
0 1/ 1000016 1.00 1.20
1/14400 Example 3 Using the pitch used in Examples 1 and 2, 2.3
Using 71-karat gold,
Spinning was carried out in the same manner as in Example 1.2. ■The money is pickpocket 9
1 ~ Width a = 0.1111 m, Surin 1 ~ Width - 0.5 m
9/Cl at a nitrogen pressure of 0.01 to 1°0.
Extruded at 112 ・G. The diameter of the reservoir on the mouthpiece surface was approximately 1 mm in each case, and the ratio of the average linear velocity of the molten pitch to the take-up speed was 1/2500, and there was no yarn breakage and the spinning performance was good. When the cross section of the material using W-oriented pitch was observed with a polarizing microscope, it was found to have a random structure.

[Brief explanation of drawings]

FIG. 1 shows an example of yarn spinning in which pitch pools are actively formed on the [-1] metal surface, which is an embodiment of the present invention. FIGS. 2 and 3 show examples of the shape of the mouthpiece outlet preferably applied to the present invention. 1 in the figure: mouthpiece 2; discharge hole 3; pool (buffer area)

Claims (1)

[Claims] When taking the pitch after melting it and discharging it from the nozzle,
The average linear velocity of the molten pitch on the nozzle surface is smaller than the maximum average flow velocity in the nozzle hole, and 1/15 of the take-up speed.
Bituji's melt spinning method, characterized in that the value is 00 or less.