JPS59168126A - Production of pitch based carbon fiber - Google Patents

Abstract

PURPOSE:To obtain pitch based carbon fibers having a large specific area and improved adhesive properties when formed into composite materials without causing problems of sticking, combustion, etc. in the infusibilizing treatment, etc., by melt spinning a pitch through a spinneret having holes with modified cross section. CONSTITUTION:A pitch is melt spun through a spinneret having holes with modified cross section, preferably >=2 ratio (R/r) between the radii of a circumcircle having a radius (R) and an inscribed circle having a radius (r) of the cross section of extrusion holes, and the resultant fibers are infusibilized at 250-420 deg.C in the presence of oxygen, e.g. in air, and then carbonized under heating at 800- 1,700 deg.C in a vacuum or an atmosphere of an inert gas and further graphitized under heating at 1,700 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pitch-based fibers having irregular cross sections.

The method of obtaining carbon 11iu and even graphitized fibers by melt spinning pitch is well known. However, all of these techniques use a cap with a circular cross section and form fibers with a circular cross section. However, since such circular cross-section fibers have the smallest specific surface area, there is a problem that the efficiency of oxidation treatment of pitch-based fibers in the infusibility process, which is essential before entering the carbonization process, is low. There has been a problem in that adhesiveness is low when threads or graphitized threads are used in composite materials.

In addition, in the normal infusibility process, pitch-based fibers are aligned in the state of multifilaments 1 to 1 to avoid oxidation, but in this case, fibers with a circular cross section (J adjacent filaments are in continuous contact with each other in the fiber direction, Because it adheres permanently, the contact area is less likely to be oxidized, and in the case of extreme cases, adjacent M&W comrades are fused41), making it even more difficult to oxidize.

Furthermore, when fibers with a circular cross section are closely packed, a closed space is formed between each filament.
As expected, contact with the oxidizing gas becomes poor, the infusibility treatment becomes insufficient, and the removal of the reaction heat due to the oxidation reaction is not successful, causing a heat accumulation phenomenon within one layer of fibers, resulting in problems such as fusion and burning of the fibers. cause problems. When such a problem occurs locally, the monofilament t in that area is broken during the carbonization or graphitization process following infusibility, creating fuzz, which seriously deteriorates the quality of the carbon fiber.

The present invention improves the drawbacks of pitch-based fibers with a circular cross section, solves the problems mentioned above in the infusibility and carbonization processes,
It provides pitch-based fibers, carbon fibers, and graphitized fibers with excellent adhesion and filling rate.

In other words, in this method, after melt-spinning the pitch, it is subjected to infusibility treatment and carbonization treatment or further graphitization treatment to -C carbon 4
This is a method for producing pitch-based carbon fiber, which is characterized in that, when producing J&string, melt spinning is carried out using a die with a modified cross section.

In the present invention, an irregular cross-section means a non-circular cross-section.For example, the various cross-sectional shapes shown in FIG.
There are many things that can be mentioned. It is preferable that such an irregularly shaped cross section has a large degree of irregularity from a circular shape.

This degree of irregularity refers to the circumscribed circle (
Ratio of radius R) to the radius of the circumscribed circle (radius 1゛) (R/r)
The effect increases when this value is around 1.3, preferably 1.7 or more, more preferably 2 or more, which is suitable for the present invention.

As such a discharge hole, it is preferable to adopt various discharge hole shapes shown in FIG. 3, for example. 3 - Mixing various types of fibers obtained from gold with different shapes, or mixing wire scraps obtained from irregular cross-sectional ferrules of the same shape with different cross-sectional areas. Konma phase!
It is possible to increase the exclusion effect by 1.

0? Compared to the carbon wire layer 1 formed from II navy blue fiber with a circular cross section, the carbon fiber formed from the J-C fiber can provide a high filling rate with small voids when made into a composite fiber. .

In order to improve the uniformity of the discharge flow, it is preferable to provide a flow portion with a small cross-sectional area in the 01 outlet hole when using such irregular cross-section [1 gold].

According to the invention, compared to fibers with a circular cross section, (1
) When spun pitch system 41 Iff is infusible and covered, problems such as fusion, combustion (2) have a large specific surface area, and poor adhesion when made into a composite material. Effective pitch fibers can be stably provided.

Thus, the pitch fiber 4 has an irregular cross section of 4jη-
− The string is then infusible treated in the usual way, carbonized,
Graphitized. As the infusibility treatment, for example, a method of oxidizing in the presence of an acid system, usually in air at 250 to 420°C, can be applied. In addition, it is also preferable to use an oxidizing gas such as Δcin or NO2 instead of oxygen in terms of the efficiency of the infusibility treatment. Such infusible fibers are then carbonized,
Although graphitized, such methods can also be applied over conventionally employed methods. Such carbonization treatment includes, for example, a method of heating to 800 to 1700°C in a vacuum or an inert gas atmosphere, and graphitization treatment includes, for example, a method of heating to 1700°C or higher in a vacuum or an inert gas atmosphere. be.

The present invention will be described in more detail below with reference to Examples.

In addition, the measurement method in the examples is based on the method shown below.

[Optical anisotropy] After embedding the sample in epoxy resin, the
l+l! L, Polished surface 1-eit Z Rei made ORT H
Observation was made using an OP LΔN 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 orthotropic part when observed with forward-bending polarized light.

[Quinoline Eluate I J Is-2425] The method was a combination of the centrifugation method and the filtration method specified in IJ Is-2425.

[Glass transition temperature] perkin -E 1mer7t 'IJ [)
The measurement was performed using SC-2 in a nitrogen atmosphere. 2 samples
After heating to 90°C, the sample was cooled to room temperature, heated again to y1 temperature, and measured again, thereby removing one factor that disturbed the baseline such as the dehydration peak.

[Moonan analysis] Using the FIACl-IN Coater MT-3 type manufactured by Yanyu Seisakusho, sample decomposition furnace 900-950℃, oxidation furnace 85℃
0℃, reduction furnace 550℃, helium flow rate 180m+Q/m
Measured under the following measurement conditions.

Example 1 After heating Lutarbidge with a softening point of 80° C. to 410° C. in a nitrogen atmosphere for about 1 hour to avoid melting,
After stirring at 30 ppm and removing insoluble matter by filtration (heat treated at 410°C for 12 hours, pressurized with nitrogen at 380°C and using 200 mesh glass beads), 7'I20°0.5mmH (I Then, the boiling point components were removed.

After embedding the jq pitch in epoxy resin and ωI polishing,
As a result of observation using a reflective polarizing microscope, approximately 90% or more was an optically anisotropic component. The optically anisotropic structure showed a large flow shape. The characteristics of heat-treated pitch are: 63
W[%, softening point 340'C1 glass dislocation rMfS19
The temperature was 5℃, and the elemental analysis results were 93W1% carbon and 3% hydrogen.
．． 7wt%, nitrogen 1. Qwt%.

Using this heat-treated pitch, the degree of irregularity is 3.0 as shown in FIG.
Using a nozzle with a Y-direction cross section of 0, the spinning temperature was 385°C.
, melt spinning at a spindle surface temperature of 360'C, 600m/
A pitch fiber yarn was obtained by taking the yarn at a yarn speed of min.

This yarn was placed in a hot air circulation type A-bun and subjected to infusibility treatment in air. The infusible treated strip 1'1 was warmed to 150° C. for about 5 minutes in a dry room, and kept at 150° C. for 15 minutes from the beginning of heating. Then, the arm was warmed to 150 to 310° C. at a rate of 1° C./min, and the temperature was maintained at 310° C. for 30 minutes to complete infusibility. i! Even when the infusible yarn was held up to a flame, it did not melt ( ), confirming that the infusibility was complete.Also, there was no fusion or combustion during spinning. There was no.This infusible thread was dried in the room.
00%] at a rate of 5°C/min to carbonize and roughly
It was graphitized at 500°C.

The jqed graphitized yarn had no defects such as fusion or fluff and was of good quality. When this graphitized thread was combined with 1-boxy resin, it showed good adhesive properties.

[Brief explanation of drawings]

Fig. 1 is an example showing a cross section of a pitch-based fiber having an irregular cross section according to the present invention, and Fig. 2 is an example showing how to take the circumscribed circle and inscribed circle of an irregular cross-sectional hole when determining the degree of irregularity. FIG. 3 shows eight examples of the irregular cross-section cap of the present invention. R in the figure Radius of the inscribed circle R: Radius of the circumscribed circle Patent applicant Toshi Co., Ltd. Figure 1 Figure 2 Figure 3 Convex + Φ

Claims (1)

[Claims] A method for producing pitch-based carbon fibers, which comprises melt-spinning pitch and then performing infusibility treatment and carbonization treatment or further graphitization treatment to produce carbon fibers using a modified cross-section spinneret.