JPS6183319A - Carbon fiber and its production - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber having high strength and modulus, by thermally polymerizing naphthalene in the presence of a Lewis acid, removing the catalyst, heating the polymer in an inert gas stream to remove the component having low molecular weight, and subjecting the obtained isotropic pitch to spinning, infusibilization, carbonization and high-temperature treatment. CONSTITUTION:Naphthalene is polymerized by heating at <=330 deg.C, preferably 100-300 deg.C for 0.5-100hr in the presence of a Lewis acid catalyst, the catalyst is removed from the product, and the components having low molecular weight are removed by heating the polymer in an inert gas stream at 330-440 deg.C under normal or reduced pressure to obtain an optically isotropic pitch having a softening point of 180-200 deg.C, an H/C ratio of 0.6-0.8, an average molecular weight of 800-1,500, and a benzene-insoluble content of 35-45wt%, and free from quinoline-insoluble component. The objective carbon fiber having an orientation degree (2Z deg.) of <30 deg. determined by X-ray diffraction, an apparent crsytallite size [Cl(002)] of 80-200Angstrom , and an interlayer spacing (d002) of 3.371-3.440Angstrom can be produced by spinning, infusibilizing and carbonizing the above pitch, and heating the fiber at >2,000 deg.C in an inert gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel pitch-based carbon fiber and a method for producing the same. More specifically, the present invention relates to a novel carbon fiber that uses naphthalene as a raw material and has properties comparable to those of PAN-based carbon fibers, and a method for producing the carbon fiber.

Carbon fibers currently on the market are classified by raw material into PAN-based carbon fibers made from polyacrylonitrile (PAN), pitch-based carbon fibers made from pitches, and are generally classified into PAN-based carbon fibers. Since it has superior properties, especially in terms of tensile strength, compared to fiber-based carbon fibers, PAN-based carbon fibers have been the mainstream as high-strength, high-modulus, high-performance carbon fibers. It became.

However, since the raw material for PAN-based carbon fibers is expensive and the carbonization yield is poor, using pitch as a raw material, which has an advantage in terms of economic efficiency, the tensile strength and tensile elasticity of PAN-based carbon fibers, etc. Research has been conducted on methods for producing pitch-based carbon fibers having a high pitch ratio, and several methods have been proposed.

For example, petroleum pitch, coal tar pitch, and acenaphthylene are heated at 350 to 500°C to approximately 40 to 90%
Heating is sufficient to produce % by weight of the men's phase, and the spinning temperature is 10-200 +
carbonaceous pitch having a viscosity of if' Heat to 2000℃, then about 2500℃
By heating above 1°C, an X-ray diffraction pattern characterized by the presence of (112) crossed lattice lines and (100) and (101) lines, i.e. a highly three-dimensional structure, can be obtained by increasing the stacking dimension (La ) and an apparent lamination height r, c) of 100 OA or more has been reported to be produced (Japanese Patent Application Laid-Open No. 19127-1983).
).

As disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 49-19127, conventionally,
Pitch-based high performance carbon u1. In order to manufacture fibers, it was considered essential to use mesophase pitch. This is because when melt-spinning menphase pitch with molecular orientation, microcrystals tend to be aligned parallel to the fiber axis. However, since menphase pitch generally has a high softening point, the melt spinning temperature is high,
It has the disadvantage of being thermally unstable. Also, 0 on the mesophase
Since pitch is a non-uniform mixture of isotropic pitch and pitch liquid crystal, it was considered difficult to obtain uniform pitch fibers.

In order to solve the above-mentioned drawbacks, the spinning material is not necessarily optically anisotropic at the pitch stage, but the spinnability is agitated, and it is converted to optically anisotropic at the spinning or firing stage. A spinning raw material pitch and a method for producing a hydrocarbon fiber using the same have been proposed.

For example, spinning an optically isotropic pre-mesophase carbonaceous material or a pitch-like material mainly composed of an optically isotropic pre-mesophase carbonaceous material under conditions that do not substantially increase the menphase carbon* pawn, Then, after infusibility treatment, carbonization treatment is performed to convert all of the pitch-like material containing pre-mesophase carbonaceous material into substantially optically anisotropic mesophase carbonaceous material (% Kaimei 58-18421) and mesophase The polycyclic polynuclear hydrocarbon present in the pitch has a partially hydrogenated structure and substantially has a quinoline-soluble polycyclic polynuclear skeleton hydrocarbon as a potential anisotropy-forming component,
In the molten state, H/C does not substantially form a menphase, but forms a homogeneous and optically isotropic single phase as a whole, and exhibits orientation in that direction when external force is applied. 0.
Potential anisotropic pitch of 55-1.2 (%, 1986-1
00186) has been reported. However, hydrogenation treatment is essential in both cases. In the former case, there is no example of carbon fiber production using only silimesophase pitch, ie, quinoline-soluble pitch, and the spinning pitch contains quinoline-insoluble matter.

Furthermore, coal tar, coal tar pitch, heavy petroleum oil, atmospheric residual petroleum oil, tar, pitch, and oil sant by-produced by vacuum distillation and heat treatment of these residual oils.
Or add hydrogenated solvent to the raw material of beetumen? :3
00 to 500 °C for 10 to 60 minutes, then heated to a temperature of 450 °C or higher for 5 to 60 minutes under reduced pressure to produce pitch containing premesophase, and the resulting spinning pitch was heated at a temperature higher than the viscosity change temperature. After spinning, the fibers are spun, rapidly cooled, and then infusible at a temperature of 250 to 350°C.
Produced by a wood-fired wood that is heated to a temperature of 30°F. The orientation angle determined by X-ray diffraction is 30 to 5 (f1 crystal size (Lc)
is 12~80A, 1 layer spacing (dno2) is 3.4~3.6
A has been reported to have a tensile strength of at least 200 kyf/ryu2 and a modulus of 20000 kl, t/sho2 (Japanese Patent Laid-Open No. 59-53717).
.

In particular, mesophase pitch-based carbon fibers, which have a three-dimensional structure of polycrystalline graphite with an orientation angle of less than 30° and an apparent size of microcrystals of more than 80x, have high thermal and electrical conductivity. However, the mechanical properties as a fiber are PA
It is reported that it is inferior to N-based carbon fiber.

Generally, the mechanical properties of carbon fibers are controlled by higher-order structure. For example, in order to obtain a high elastic modulus, it is essential that the material has a fiber structure such as fiber structure and high orientation. Conventionally, in order to make highly elastic pitch-based carbon fibers, raw materials such as coal tar and coal tar gitsuchi are heated and polymerized as raw material pitch for spinning, and then qualityified mesophase pitch, latent mesophase pitch, or pre-mesophase is used. The carbon fibers produced using the two-wire method, which required the use of pitch, have superior graphitization properties compared to PAN-based carbon fibers # and 16, but as llR fibers, However, the tensile strength of pitch-based carbon fibers is still inferior, and the reality is that we have not yet reached the point where we can provide pitch-based carbon fibers that have mechanical properties equivalent to those of PAN-based carbon fibers.

The present inventors have conducted extensive research to develop pitch-based carbon fibers that are comparable to or even superior to PAN-based carbon fibers in mechanical properties such as tensile strength, tensile modulus, and elongation at break. As a result, using naphthalene as a raw material, heating and polymerizing it under specific conditions and removing light components, optically isotropic pitch having a homogeneous and appropriate molecular structure and molecular weight of 4 g was used as the spinning raw material pitch. The pitch-based carbon fiber obtained by spinning, infusibility, carbonization firing, and high-temperature treatment has an orientation angle of less than 30° and an apparent size of microcrystals larger than 80X (-1). Despite being endowed with a fiber structure in which the carbon network surface is selectively aligned in the fiber axis direction, it does not have the three-dimensional structure unique to conventional mesophase pitch graphitized fibers. Based on the results, the present invention was completed.

That is, the present invention provides an orientation angle (2) determined by X-ray diffraction.
Z°) is less than 30°, the apparent size of the microcrystal L (! (002)) exceeds 80X, and 200A
The layer spacing (doo2) is 3.371-3.
The purpose is to provide a pitch-based carbon fiber treated at 2000° C. or higher using naphthalene exhibiting 44OA as a raw material. Another object of the present invention is to polymerize naphthalene by heating at 330'C or less for 0.5 to 100 hours in the presence of a Lewis acid catalyst, and after removing the catalyst, under normal pressure or reduced pressure while flowing an inert gas. Light components are removed by heating to 330-440°C, softening point is 180-200°C, H/C is 0.6-0.8, average molecular weight is 800-15001, benzene insoluble content is 35-45% by weight. An optically isotropic carbonaceous pitch containing no quinoline-insoluble matter is produced, and the produced carbonaceous pitch is spun, infusible, and carbonized by a conventional method, and then heated at a temperature of 200°C or higher and insoluble. An object of the present invention is to provide a method for producing pitch-based carbon fibers having the above-mentioned characteristics by processing in an active gas atmosphere.

The carbon fiber of the present invention has an orientation angle (2Z) determined by X-ray diffraction of less than 30°, preferably 15 to 25°,
Apparent size of microcrystal L +1! (002)) is more than 80X and less than 200X, preferably 9° to 170
x, and 4 [(aoo2) Ka 3.371 to 3.44
0X, preferably 3.390 to 3.430^.

The carbon fiber of the present invention, which has the orientation angle, apparent size of microcrystals, and layer spacing as described above, and has a structure in which the crystals are homogeneously arranged, has superior mechanical properties to conventional pitch-based carbon fibers. It shows strength.

The carbon fibers of the present invention have at least 300 klf/mw
r2 tensile strength and at least 20000kff/t2
It has a tensile modulus of elasticity of

Optically isotropic carbonaceous pitch produced by a specific method using naphthalene as a raw material can be melt-spun at a lower temperature than the spinning temperature of mesophase pitch. Homogeneous pitch fibers can be obtained without employing. Furthermore, the basic arrangement of pitch fibers is published by Menface Hotsuchi,
Because it is not strong, when it becomes infusible, the infusibility reaction progresses at the surface layer, forming a fine mosaic-like structure, and the infusibility reaction occurs at the center without disturbing the preferred arrangement of molecules. A fibrous structure is imparted.

Next, the manufacturing method of the present invention will be explained.

The raw material naphthalene is heated to 330% in the presence of a Lewis acid catalyst.
below ℃, preferably 0.5 to 100 at 100 to 300℃
Polymerize by heating for a period of time.

The Lewis acid catalyst used here is AeClh.

Examples include BF5, but AlCl3 is preferred. The Lewis acid catalyst may be used in an amount of 5 to 50 parts by weight per 100 parts by weight of naphthalene, but preferably 8 to 20 parts by weight. It should be noted that if the heating temperature exceeds 330° C., mesophase pitch will be generated and quinoline insoluble matter will be present, which is not preferable. Furthermore, even if 50 parts by weight or more of the Lewis acid catalyst is used, the polymerization efficiency does not change much and removal of the catalyst becomes complicated, which is not economical.

After removing the catalyst from the polymerized naphthalene, it is heated at 330 to 440°C while passing an inert gas under normal pressure or reduced pressure.
Preferably, it is heated to 350 to 420° C. to remove light particles to produce optically isotropic carbonaceous pitch. When the heating temperature exceeds 440℃, menphase pitch is generated,
This is not preferable because it may cause the presence of quinoline-insoluble components.

Carbonaceous pitch thus obtained (spinning raw material pitch)
has a softening point of 180 to 200°C and a H/C of 0.6 to 0.
．． 8. The average molecular weight is SOO~1500°, the Banzen insoluble content is 35~45% by weight, there is no quinoline insoluble content, and it shows isotropy when observed with a polarizing microscope.

The spinning raw material pitch for producing the carbon fibers having excellent mechanical properties of the present invention needs to be a carbonaceous pitch that satisfies the above-mentioned properties.

The obtained carbonaceous pitch is spun and infusible by conventional method I. For example, during spinning, the temperature of carbonaceous pitch when discharged from a spinneret is 70 to 70°C higher than the softening point of carbonaceous pitch.
Set the temperature 90℃ higher, 0.5~2.0k%/
Discharge with crl-a pressure, 300~1ooo
This is done by winding at a winding speed of m/min. In addition, the infusibility treatment is carried out in an oxidizing gas atmosphere with a
b) Infusible treatment is performed by heating to ~300°C and maintaining that temperature for 30 to 60 minutes.

The thus infusible fibers are then heated to 90 °C in an inert gas, for example N2 gas, at a heating rate of 5 to 15 °C/min.
heated to 0°C and then heated to 200°C for example in argon gas.
By processing at a predetermined temperature of 0° C. or higher, carbon fibers can be obtained with a carbonization yield higher than 1.

Next, each index representing the characteristics of fiber and pitch in the present invention will be explained.

(1) Structure-related factors The orientation angle (2z0), the apparent size of the microcrystal in the C-axis direction (Ll), and the interlayer @ (aoo2) are structure-related factors that represent the higher-order structure of the fiber determined from the wide-angle X-ray diffraction pattern. It is. The orientation angle (2Z') indicates the degree of orientation of the microcrystals with respect to the fiber axis direction, and the smaller this angle is, the more advanced the orientation is. Apparent size of microcrystal L
c) represents the apparent stacking height of carbon microcrystals, and layer spacing (doo2) represents the layer spacing between carbon mesh planes of the microcrystals.

The apparent size of microcrystals (Lc) is measured using the simple vibration method (Japan Society for the Promotion of Science, 117th Committee, Carbon, 36.5.196
According to 3).

The orientation angle (2Z') is determined by (002) diffraction by rotating the fiber bundle in which the constituent fibers are aligned in parallel by 180 degrees in the plane perpendicular to the X-ray beam at the position of the diffraction angle that indicates the maximum value of the (002) diffraction intensity. Measure the intensity distribution along the ring,
It is defined as the half-width at the point below the maximum intensity value.

(2) Parameters indicating pitch characteristics a) Molecular weight Pyridine was used as a solvent, and vapor pressure osmometer (vpo
) to measure. As a VPO, (made by Corona)
117 type molecular weight measuring device), using pyridine as a solvent and benzyl as a standard substance.

b) H/C Calculated according to the following formula from elemental analysis measured according to JIS M-8813.

C) Using a flow tester with a high softening point (7N manufactured by Koguruma), put pitch II crushed to 100 mesh or less into a heating cell (inner diameter 10mm, nozzle diameter 1mm), and apply a load of 17d to 10mm from the top. The temperature was increased at a heating rate of 6° C./min, and the temperature at the inflection point of the plasticization curve was defined as the softening point.

d) Solvent-insoluble content Measured in accordance with JIS-2425.

(3) Physical properties of carbon fiber The fiber diameter, tensile strength, elongation, and tensile modulus of carbon fiber are J
Measured according to IS R-7601r Carbon Fiber Test Method. Note that the cross-sectional area method is used to measure the fiber diameter.

The present invention will be explained below with reference to Examples. It should be noted that these examples are merely illustrative and do not limit the present invention.

Example 1 Naphthalene (1st class reagent manufactured by Kanto Kagaku Co., Ltd.) 2000
g and 100 g of AlC15 (first class reagent manufactured by Kanto Kagaku Co., Ltd.) as a catalyst were charged into a glass three-ring flask equipped with a stirrer, and polymerized at 210° C. for 60 hours. After the polymerization was completed, pitch was obtained by washing with water and filtering (pore diameter: 0.2 μm) to remove the catalyst. The resulting pitch is 4
00℃, 150g+',! The light components were removed by heating under N2 flow for 15 minutes.

The carbonaceous pitch thus obtained was optically isotropic when observed under a polarizing microscope, and its properties are shown in Table 1.

Table 1 Next, carbonaceous pitch was put into a cylinder with a nozzle of 0.3 ma+ in diameter, melted in a heating bath at 280°C, and then heated to 1.2 mA.
Extrusion spinning was carried out through the above nozzle at a N2 gas pressure of kpf/da. The winding speed at this time is approximately 700 m/
It was a minute. The pitch fibers obtained as described above are heated to about 265°C in an air atmosphere at a temperature increase rate of about 265°C/minute, and the pitch fibers are held in this atmosphere for about 30 minutes to be infusible. did.

The thus infusible fibers were heated to about 900°C at a temperature increase rate of about 0°C/min in an N2 gas atmosphere, and then the carbon obtained by heating was heated at a heating rate of about 0°C/min to about 900°C. Table 2 shows the physical properties and mechanical properties of the fibers (diameter: 8 μm) determined by X-ray diffraction.

The following margin is Table 2 Example 2 The carbon fiber obtained in Example 1 was further heated in an alcohol gas atmosphere at a heating rate of about 0°C/min to about 2,500°C, and at this temperature it was heated to about 2,500°C. Holding treatment was carried out for 10 minutes.

Table 3 shows the physical properties and mechanical properties of the obtained carbon fibers determined by X-ray diffraction (near diameter, 5 μm).

-19= Table 3 Example 3 The physical properties and mechanical properties determined by X-ray diffraction of the carbon fiber obtained in Example 1 using argon gas (near diameter, 5 μm) are shown in Table 4. show.

Table 4 Example 4 Naphthalene (Class 1 reagent manufactured by Kanto Kagaku Co., Ltd.) 2000
g and catalyst klcls (manufactured by Kanto Kagaku Co., Ltd. 1
grade reagent) 1001! was placed in an autoclave equipped with a magnetic induction stirring device, sealed, and thoroughly replaced with N2 gas.
The internal pressure was set to Oktf/crIG, and the temperature was raised to 300°C while stirring.
The temperature was raised to 300° C. for 1 hour. After the polymerization was completed, pitch was obtained by washing with water and filtering (pore diameter: 0.2 μm) to remove the catalyst. The obtained pitch is a 500c, 1
The light components were removed by heating under N2 gas flow for 3 minutes at 20FF.

When observed with a polarizing microscope, the carbonaceous pitch obtained by this process was found to be optically isotropic and its properties (
It is as shown in Table 5.

Table 5 Next, carbonaceous pitch was put into a cylinder with a nozzle of 0.3 diameter, heated to 275°C to melt it, and then 0.8'j'
Extrusion spinning was carried out through the above nozzle at a N2 gas pressure of f/crlG. The winding speed at this time was about 600 m/min. The pitch fibers obtained as described above were heated to about 250° C. under an air atmosphere at a temperature increase rate of about 250° C./min, and the pitch fibers were held in this atmosphere for about 30 minutes to be infusible.

The thus infusible fibers were heated to about 900°C at a heating rate of about 50°C/minute in an N2 gas atmosphere, and then a Carbon fiber(
Diameter near. Table 6 shows the physical properties and mechanical properties determined by X-ray diffraction (5 μm).

Table 6 Example 5 The carbon fibers obtained in Example 4 were further heated in an argon gas atmosphere to about 2500°C at a temperature increase rate of 0°C/min. The sample was held in a vacuum chamber for about 10 minutes for processing.

Table 7 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter = 7.5 μm) determined by X-ray diffraction.

@7 Table Example 6 The carbon fiber obtained in Example 4 was further heated to about 2800 °C at a heating rate of about 50 °C/min in an argon gas atmosphere, and held in this atmosphere for about 10 minutes. Processed.

Table 8 shows the physical properties and mechanical properties determined by X-ray diffraction of the obtained carbon fiber (near west longitude μm).

Table 8 Example 7 Naphthalene (class 1 reagent manufactured by Kanto Kagaku Co., Ltd.) 2000 g
and AlCl5 (class 1 reagent manufactured by Kanto Kagaku Co., Ltd.) ioog as a catalyst were placed in a three-loaf flask equipped with a stirrer and heated for 10 minutes.
Polymerization was carried out at 0°C for 60 hours. Then the catalyst hlcls
(Class 1 reagent manufactured by Kanto Kagaku Co., Ltd.) 100.9 was further added and polymerized at 210°C for 30 hours. After the polymerization was completed, pitch was obtained by rinsing with water and filtering (pore diameter: 02 μm) to remove the catalyst.

The obtained pitch was heated at 380° C. for 20 minutes under N2 gas flow to remove light components.

The carbonaceous pitch thus obtained was optically isotropic when observed under a polarizing microscope, and its properties are shown in Table 9.

Table 9 Next, carbonaceous pitch was placed in a cylinder with a nozzle with a diameter of 0.3 +n+ and heated to 275°C to melt it.
It was extruded and spun through the above nozzle at a N2 gas pressure of J o of kpf/. The winding speed at this time is
The speed was approximately 500 m/min.

The pitch fibers obtained as described above were heated to 265° C. at a temperature increase rate of about 0.degree. C./min in an air atmosphere, and the pitch fibers were held in this pig enclosure atmosphere for about 30 minutes to be infusible.

The thus infusible fibers were processed at a heating rate of about 5°C/min to about 900°C under a N2 gas atmosphere.

Table 10 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction.

Table 10 Example 8 The carbon fibers obtained in Example 7 were further heated to about 2500°C at a heating rate of about 0°C/min in an argon gas atmosphere, and It was held and processed for about 1°.

Table 11 shows the physical properties and mechanical properties of the obtained carbon fibers (near diameter, 5 μm) determined by X-ray diffraction.

Table 11 Example 9 The carbon fiber obtained in Example 7 was further heated in an argon gas atmosphere to about 2800 degrees Celsius at a heating rate of 0 degrees Celsius/minute, and heated in this atmosphere for about 10 minutes. Retention.

Processed.

Table 12 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter near, 5 μrn) (2) determined by X-ray diffraction.

Table 12 Procedures 111 Official Book October 30, 1985 2. Title of the invention Carbon fiber assembly and method for manufacturing A. 3. Person making the amendment, case and relationship Patent applicant name (110) Kureha Chemical Industry Co., Ltd. 4. Agent 1-14 Shinjuku, Shinjuku-ku, Tokyo
Yamada Building 5, amendment order l old 1 spontaneity 6, number of inventions increased by amendment 7, specification subject to amendment ``l': +l ki'' 6070.31.

Form 74) X Desired 4 Shadow Min' 8. Contents of amendment (1) The scope of claims in the specification Yamanaka is attached to the attached sheet J3
Correct.

■ Page 7, line 4, 1] Page F to line 3 ["1,
Page 11, line 1, page 15, line 3, page 15, line 10
Rows, Table 2 on page 20, Table 3 on page 21, Table 1 on page 22, Table 6 on page 25, Table 7 on page 26, 2
In Table 8 on page 1, Table 10 on page 30, J in Table 11 on page 31, and Table 12 on page 32, [dOO2J] is corrected to "doo2".

(3) On the 4th line of page 8, 1 potential mesoph T-spidge-1 is corrected to ``potential anisotropic bitge''.

(4) In the 7th line from the bottom of page 6, the words ``Peach Komen'' were amended and overwritten as ``1 Biji Komen''.

(5) In the 6th line from the bottom of page 15, the text ``Kuchigi Science Foundation'' is corrected to ``1 Japan Society for the Promotion of Science''.

(6) Page 19, line 5 of the same page, “Approximately 265°Cl No. 19 of 1”
Page 9 ir 11-1 approx. 900°C1, page 19 line 11 line 1-1 approx. 2000°C, page 20 1ζ to 5/line 1 [1-1 approx. 2500°C1 , 1 approx. 2800° C1 in the 4th line from the bottom of No. 21, [approximately 250° Cj in the 4th line of page 24, 7th line of page 24 “Approximately 900°
Cl, page 24, line 9 [approx. 2000°01, 2nd
From the bottom of the 5th member to the 5th, 4th line "] 1 approximately 2500° 01, page 26 F to 0th - 5?jl'l 1 approximately 2800°C -
1, 29th Auto No. 8 t'i r, 1 "about 900 ° (
1, negative') 29 pages 9-10 tjI-1's [about 20
00°C1, 30th white bottom to 0-5th line [1 of [-approx. 24+ 00°C1a-3 and 3111th small color ff
16-□5(-r[I'7) rAbout 1 in about 2800°C1 is deleted 3°2, Claims (1) Orientation hemp determined by X-ray diffraction ( 27') is less than 30° -C, and the apparent (-) size of the microcrystals (1, c (
002)) exceeded 80 people [1'] 200 people were struck, the layer spacing (the next day) decreased to 3.374, and 3.440 people were treated at a temperature of 2000°C or higher. Ij4 fiber eyebrows 1゜■ Naphthalene is heated to 330°C or less in the presence of a Lewis acid catalyst, and 100 to 300°C (from 0.5 to 10
After heating for 0 hours and removing the catalyst, the mixture was heated to 330 to 440°C while flowing inert + I gas under normal broth or under reduced pressure to remove soft components until the softening Jj,i was 180 ~20
0℃C1It/C 0. (i ~ 0.8 Te, average molecular weight 800 ~ + 500 - ('', bempine insoluble content is 35 - 45% by hand) - optically equivalent lJ property that does not contain quinoline insoluble content < r 1! The patent claim requires that the resulting isotropic 171 pitch be spun, infusible, and carbonized by a conventional method, and then treated at a temperature of 2000° or higher. 1] Method for producing carbon fiber assembly according to Scope 1.

Claims (2)

[Claims] (1) The degree of orientation (2Z°) determined by X-ray diffraction is less than 30°, and the apparent size of the microcrystals (Lc_(_0_0
_2_)) is more than 80 Å and less than 200 Å, and the layer spacing (d002) is 3.371 to 3.440 A.
Carbon fiber made from naphthalene treated at temperatures of 2000°C or higher. (2) Naphthalene is polymerized by heating in the presence of a Lewis acid catalyst at 330°C or lower, preferably 100 to 300°C for 0.5 to 100 hours, and after removing the catalyst, an inert gas is passed under normal pressure or reduced pressure. While heating to 330-440°C to remove light components, the softening point is 180-200°C and H/C is 0.
6 to 0.8, an average molecular weight of 800 to 1500, a benzene insoluble content of 35 to 45% by weight, and no quinoline insoluble content. 2. The method for producing carbon fibers according to claim 1, wherein the carbon fiber is spun, infusible, and carbonized by a conventional method, and then treated at a temperature of 2000° C. or higher.