JPS6278220A - Production of ribbon-like carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having high tenacity and free from void, fluff, etc., by extruding a spinning pitch through a spinning nozzle having large width/height ratio of the opening part, winding the spun fiber at a specific draft ratio, infusibilizing in oxygen atmosphere and heating in an inert gas at a high temperature. CONSTITUTION:A pitch for spinning is extruded through a spinning nozzle provided with a slit having a width/height ratio of the opening part of 2-300 and continuously wound at a draft ratio of 10-3,000 to obtain a ribbon-like pitch fiber. The fiber is infusibilized in an oxygen-containing atmosphere such as air at 280-440 deg.C and carbonized by heating at 800-3,000 deg.C in an inert gas atmosphere such as nitrogen gas to obtain the objective ribbon-like carbon fiber.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing ribbon-shaped carbon fibers.

Conventional technology and its problems At present, carbon fiber is mainly made of polyacronitrile (hereinafter referred to as P'A
It is produced using N) and pitch as starting materials.

PAN-based carbon fiber has a tensile strength of 300 kq/mm
Two or more are commercially available and are widely used as materials for various high-performance composite materials. However, P.A.
The elastic modulus, which is an important performance as a material for N-based carbon carbon fiber high-performance composite materials, is relatively low, and most commercially available products are around 20 to 3 Q ton/mm", and 4 Q ton/mm".
No material exceeding ton/mm2 has been obtained. This limit in elastic modulus is derived from the PAN-based carbon fiber starting material, as is well known, and is inevitably restricted by crystal growth and orientation within the carbon fiber. Also, PAN
Carbon fibers also have the drawback of high cost due to the low carbonization yield of about 50% of the starting material and the need for tension treatment in the steps after infusibility.

On the other hand, pitch-based carbon fiber does not have the problems of the above-mentioned PAN-based carbon fiber, and is expected to be a cheaper and higher-performance material.

In other words, especially when pitch exhibiting optical anisotropy is used as a raw material, crystal growth and orientation may change as the temperature rises (1000 to 3000°C) during the Europeanization process of the precursor fiber (hereinafter referred to as pitch fiber). 40ton/m1 as it progresses well
Carbon fibers with high elasticity of 2 or more can be easily obtained. In addition, since the starting material is the residue of useful materials used for other purposes, it can be obtained at low cost, and the carbonization yield reaches approximately 90% of the pitch fiber weight, so the manufacturing cost is low. It has advantages. However, such pinch type carbon fibers also have various problems that need to be solved.

(i> In general, molten pitch has a high spinning temperature, a large viscosity change due to temperature, and the strength of pitch!!lra is extremely lower than that of general organic HAH including PAN. It has inferior stable continuous spinning properties compared to Pitch-based carbon 1!! (long fiber), which is currently commercially available.
No finer structuring has been done on an industrial scale.

In addition, commercially available pitch-based carbon fibers have a strength of 200%.
) u+/u2 or less, which is hardly satisfactory.

Therefore, various studies are being conducted to improve the spinnability of such melt pitch and the strength of the resulting carbon fibers. For example, Japanese Patent Application Laid-open No. 57-88016 discloses a technique for improving the spinnability of molten pitch by subjecting the raw material pitch to a reduction treatment in advance prior to the heat treatment step for preparing pitch for spinning. There is. Japanese Unexamined Patent Publication 1987-
The method disclosed in Japanese Patent Application Laid-open No. 100186 also uses a pitch known as a potential anisotropic pitch.
The method disclosed in the publication improves the spinnability of molten pitch by using a pitch called Brimesophase pitch as a spinning pitch, thereby producing carbon fibers with a strength of 200 kmM mm2 or more. It is reported that it can be obtained. However, even with the methods disclosed in these publications, 100 to 200
In multi-hole spinning of one hole or more, the diameter of pitch-based carbon fiber obtained by stable continuous spinning on an industrial scale is up to about 10 μm. In the case of pitch-based fibers, the strength per second unit area generally increases as the fiber diameter decreases.

The above-mentioned fiber diameter of 10 μm or more means that the excellent strength characteristics originally possessed by pitch-based carbon cotton fibers are not fully exhibited.

(ii) Furthermore, pinch type fibers often have the problem that micro-defects such as cracks and warp cracks are likely to occur due to slight variations in the physical properties of the spinning pitch and spinning conditions, which impairs quality stability. There is.

(iii) Furthermore, the strength of pitch fibers is extremely low compared to PAN fibers, which are the same precursor fibers. (partial thread breakage) is likely to occur.

Means for Solving the Problems As a result of intensive research in view of the current state of the technology as described above, the inventor of the present invention has discovered that after extruding spinning pitch from a nozzle having a specific opening shape, the spinning pitch can be extruded at a specific draft ratio. It has been found that the above-mentioned problems of the prior art can be substantially eliminated or greatly reduced if the pinched fibers obtained by winding or ribbon-like fibers are made infusible and then heat treated. That is, the present invention
The spinning pitch is extruded from a spinning nozzle having a slit with an opening width/height ratio of 2 to 300, and the draft ratio is 1.
After winding the ribbon-shaped pinched fiber for one wafer by continuously winding it up to 0 to 3,000, it is rolled in an oxygen-containing atmosphere to 280 to 3,000.
The present invention relates to a method for producing a liphon-like carbon fiber, which is characterized by performing an infusibility treatment at 4/lo'c and then heating at 800 to 3000'C in an inert gas atmosphere.

The spinning pitch used in the present invention is obtained by subjecting a pitch-like material to thermal polycondensation under an inert gas flow.

The pitch-like substance may be any of petroleum-based pitch, coal-based pitch, and pyrolysis residue pitch from organic compounds. In particular, when coal tar or coal-based pitch such as coal tar pitch is used as a raw material, the raw material pitch is subjected to aromatic reducing properties in advance according to the method described in JP-A-57-88016 prior to thermal polycondensation. 350~ depending on the solvent
By heat-treating at 50.0°C, spinnability can be further improved. The pitch for spinning is not particularly limited as long as it can be spun, but especially for high-strength long fibers, pitches with a softening point of 280 to 330'C and an optically anisotropic component amount of 80°C measured at room temperature are recommended. ~100@quantity%
It is preferable that In this application, "softening point" refers to the softening temperature measured using a softening point measurement device manufactured by Mettler, Inc. in the United States, and "optical anisotropic component J" refers to the softening temperature measured using a softening point measuring device manufactured by Mettler, Inc. in the United States, and "optical anisotropic component J" refers to the softening temperature measured using a softening point measuring device manufactured by Mettler, Inc. in the United States. It always gives a bright field when observed under a crossed Nicol prism at room temperature.If the softening point is below 280'C, it tends to be difficult to infusible and carbonize the pitch fibers. On the other hand 330
If it exceeds 'C, the spinnability rapidly decreases, and in either case there is a strong tendency that it becomes difficult to stably produce a high-strength ribbon-like carbon 11li string. Furthermore, if the amount of optically anisotropic component is less than 80% by volume, yarn breakage is likely to occur during spinning, making it difficult to stably and continuously spin ribbon-like pitch fibers, especially under conditions where the trough ratio is large. A tendency arises.

The production of ribbon-like pitch fibers is carried out using a width/height ratio of 2 to 300 at a spinning pinch or at a temperature that exhibits good spinnability (this is easily determined experimentally depending on the type of pitch).
This is done by extruding the pitch from a slit-shaped nozzle and continuously winding it up so that the draft ratio is 10 to 3,000. Here, the draft ratio refers to take-up speed/discharge speed. If the width/height ratio of the slit is less than 2, the ribbon-like effect will be reduced, and the obtained carbon fiber will often contain defects such as vertical cracks and cranks, and the fiber shape itself will become ribbon-like. Therefore, the effects of the invention, which will be described later, will not be sufficiently achieved. On the other hand, if the width/height ratio of the slit exceeds 300, the pinch assimilation point during spinning becomes unstable, and a split phenomenon (discharged pitch melt splits into two or more (separation and winding phenomenon) occurs, making stable continuous spinning difficult. The size in the width direction of the sulin[·-shaped nozzle] can be arbitrarily selected within the range of about 0.10 mm to about 3 cm depending on the shape of the intended ribbon-like carbon fiber. Further, it is preferable that the height of the nozzle to Surin 1 is Q, 2 mm or less. On the other hand, the depth of the nozzle can be selected from a wide range depending on the spinning conditions, the shape of the target ribbon-like carbon fiber, the cross-sectional higher-order structure (the state of molecular arrangement in the cross-section), etc., and there are practically no restrictions. There isn't. If the ratio of the roller 71 is outside the range of 10 to 3000, stable winding becomes difficult.

In the present invention, the ribbon-shaped pitch fibers obtained as described above are made infusible at 280 to 440'C in an oxygen-containing atmosphere, and then heated at 800 to 3000'C in an inert gas atmosphere to form carbon fibers. become

Thus, the carbon fiber of the present invention obtained by 1q has a cross-sectional shape of the fiber, ranging from a shape that is almost similar to the shape of a slit-like nozzle to a shape that has a width/thickness ratio that is significantly reduced.
That is, the width/thickness ratio is within a range of about 1.5 to 300.

Effect of the invention According to the present invention, the following remarkable effects can be obtained.

(i) The ribbon-like carbon fiber finally obtained has almost no microscopic defects such as vertical cracks, cracks, and voids inside it.

(ii) Even when the cross-sectional area of the ribbon-like carbon fiber is large, the strength per unit cross-sectional area is large, 200 kL'mm.
2 or more. For example, the carbon 1.
When preparing f, the strength of a circular carbon fiber with a diameter of 20 μm is 150 km2, whereas the strength of a ribbon-shaped carbon fiber with the same cross-sectional area is 250 to 400 kg/m2.
It reached about m2.

(iii) Therefore, when producing carbon fibers having a strength of over 200 kmMmm2g, it is sufficient to spin pitch fibers with a wider cross-sectional area than conventional ones, and the continuous spinning characteristics have been greatly improved.

(iv) If ribbon-like carbonaceous, p! Even though the fiber cross-sectional area is large, the fiber cord thickness is small, so it is more resistant to deformation such as bending and curling than circular or square cross-section carbon fibers with the same cross-sectional area, and it is more resistant to deformation such as bending and curling after spinning, and during the firing process. The bristling appearance has almost disappeared.

EXAMPLES Examples are shown below along with reference examples and comparative examples to further clarify the characteristics of the present invention.

Reference Example 1 A mixed solution of 1 part by weight of coal tar pitch with a softening point of 110°C, a quinoline soluble content of 0.18%, and a benzene insoluble content of 35% and 2 parts by weight of hydrogenated heavy anthracene oil was heated in an autoclave at 430°C for 60 minutes. After heating with stirring, the mixture was filtered while hot using a pressure filter, and the hydrogenated heavy anthracene oil was removed at a reduced pressure of 300° C. to obtain reduced pitch.

50 kg of the reduced pitch obtained above was placed in a reactor equipped with a gas introduction tube, a thermocouple, a stirrer, and a distillate removal tube, and while stirring and introducing nitrogen gas, low molecular weight components were removed at 410 to 480 °C. and thermal polycondensation. The properties of eight types of thermally polycondensed pitches obtained by selecting reaction times and temperatures are shown in Table 1 as NOs, 1 to 8. Incidentally, the optically anisotropic component content of each pitch was within the range of 67 to 100% by volume.

Reference Example 2 The same coal tar pitch as in Reference Example 1 was subjected to a thermal polycondensation reaction in the same manner as in Reference Example 1 without undergoing heat treatment while mixing with hydrogenated heavy anthracene oil. The properties of the three types of thermally polycondensed pitches obtained are shown as NO, 9 to 11.

Reference Example 3 Petroleum pitch having a softening point of 85°C, 0.2% quinoline solution, and 20% benzene insoluble content was directly subjected to the same thermal polycondensation reaction as in Reference Example 1. The properties of the two types of thermally polycondensed pitches obtained are shown in Table 1 as Nos. 12 and 13.

Table 1 Examples 1 to 13 Using the thermal polycondensation pitches N0.1 to 13 obtained in Reference Examples 1 to 3, respectively, width/height/depth = 3.0 mm10, "1
Ribbon-like pitch fibers were obtained by spinning from a nozzle having a slit of mm/1 and 0 mm at a nozzle temperature of softening point +40° C. and a draft ratio of 800.

Table 2 shows the frequency of thread breakage during spinning.

Ribbon-like pitsuji fiber obtained as above! 441 was infusible at 310'C in air and then heated at 1200'C in N2 gas.
The content of defects such as cracks and voids and the tensile strength measurement results of the ribbon-shaped carbon fibers obtained by heating at ℃ for 10 minutes were
It is also shown in the table.

Table 2 Notes: 1) Based on a 100-hole spinning machine.

As is clear from the results shown in Tables 1 and 2, ribbon-like Stable continuous spinning properties cannot be obtained during pitch fiber spinning.

It is also clear that when coal tar pitch is used as a raw material, stable continuous spinning can be achieved by treating the raw pitch with an aromatic reducing solvent in advance.

Examples 14 to 17 Using the thermal polycondensation pinch NO34 prepared in Reference Example 1, a slit-shaped nozzle with various slit dimensions was used to obtain a nozzle temperature with a softening point of +40°C and a draft ratio of 1000.
Example 1 Ribbon-shaped pitch fibers obtained by spinning under the conditions of
Infusibility and carbonization treatments were carried out in the same manner as in 13 to obtain ribbon-shaped carbon fibers.

Table 3 shows the cross-sectional shape and strength of the ribbon-like carbon fibers.

Using the thermal polycondensation pitch N0.3 prepared in Table 3 Examples 18 to 21 Reference Example], width/height/depth = 0.6 mm 10.05 mm 10.3
After spinning with a nozzle having a slit of mm at a nozzle temperature of softening point +40°C and a draft ratio of 50 to 1500, infusibility and carbonization were performed in the same manner as in Examples 1 to 13 to obtain ribbon-like carbon. Obtained fiber. Table 4 shows the cross-sectional shape and strength of the ribbon-like carbon fibers obtained.

Table 4 Reference Examples 22 to 24 Table 5 shows the physical properties of the fibers obtained by further heating the ribbon-shaped carbon fibers obtained in the same manner as in Example 5 at 1800 to 2500°C for 0 minutes in an inert gas atmosphere. .

Table 5 Comparative Example 1 Using the thermal polycondensation pitch No. 4 prepared in Reference Example 1, a circular nozzle having a nozzle shape with a diameter Q of 2 mm and a depth of 0.4 mm was used to obtain a nozzle temperature of +40°C in softening point. After spinning under the conditions of a draft ratio of 400 and a draft ratio of 400, the pitch fibers were infusible and carbonized under the same conditions as in Examples 1 to 13. Example 4 shows the fuzz occurrence frequency of the obtained continuous long fibers.
A comparison is shown in Table 6.

Table 6 Reference Examples 4 to 6 Three types of ribbon-shaped carbon fibers having different widths/thicknesses were prepared in the same manner as in Examples 18 to 21.

Figure 1 is a scanning electron micrograph (60x) of a ribbon-like carbon fiber with width/thickness = 75, Figure 2 is a scanning electron micrograph (width/thickness = 50).
Figure 3 shows a scanning electron micrograph (1000x) of a ribbon-like carbon fiber with a width/thickness ratio of 10.

Reference Examples 7 to 8 Scanning electron micrographs of the cross-sectional higher-order structure of the ribbon-like carbon fiber 1q obtained in Example 15 are shown in Figure '4 (3300x) and Figure 5 (4000x).

[Brief explanation of drawings]

1 to 5 show scanning electron micrographs of ribbon-shaped carbon fibers obtained in Examples and Reference Examples. (that's all·

Claims (1)

[Claims] (1) Spinning pitch is extruded from a spinning nozzle having a slit with an opening width/height ratio of 2 to 300, and is continuously wound to obtain a ribbon-like pitch fiber with a draft ratio of 10 to 3000. After that, it was heated in an oxygen-containing atmosphere for 28 hours.
A method for producing ribbon-shaped carbon fibers, which comprises performing an infusibility treatment at 0 to 440°C, and then heating at 800 to 3000°C in an inert gas atmosphere.