JPH0633528B2 - Carbon fiber and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel Pitch-based carbon fiber made of naphthalene as a raw material and a method for producing the same.

Currently available carbon fiber is polyacrylonitrile.
PAN-based carbon fibers made from (PAN) and Pitch-based carbon fibers made from Pitches are classified according to the raw materials.Generally, PAN-based carbon fibers are compared to Pitch-based carbon fibers. In particular, PAN-based carbon fiber has been the mainstream as a high-performance carbon fiber having high strength and high elastic modulus because it has excellent properties especially in terms of tensile strength. However, since PAN-based carbon fiber is expensive and has a low carbonization yield, it is possible to obtain the same tensile strength and tensile modulus as PAN-based carbon fiber by using Pitch, which is advantageous in terms of economy, as a raw material. Research on a method for producing the Pitch-based carbon fiber has been made, and several methods have been proposed.

For example, petroleum-based pitches, coal tar pitches and acenaphthylene pitches are heated at 350-500 ° C. for a time sufficient to produce about 40-90% by weight of mesophases, non-thixotropic at spinning temperatures, A carbonaceous pitch having a viscosity of 200 poise is spun, the spun fiber is made infusible at 250 to 400 ° C. in an oxygen-containing atmosphere, and the infusible fiber obtained is then at least 1000 in an inert atmosphere.
By heating to (.degree. C.) and then to about 2500.degree. C. or above, the (112) cross lattice lines and (100) and (1
01) X-ray diffraction pattern characterized by the presence of lines, that is, having a three-dimensional structure of hardness, a layer spacing of 3.37Å or less, an apparent lamination dimension (La) of 100Å or more and 100 or more.
It has been reported that graphite fibers having an apparent stacking height (Lc) of 0 Å or more are produced (Japanese Patent Laid-Open No. 19197/1974).

As disclosed in Japanese Patent Laid-Open No. 49-19127 described above,
It has been said that the use of mesophase pitch is essential for producing a pitch-based high performance carbon fiber.
This is because when melt-spun mesophase pitches having a molecular orientation, fine crystals are easily aligned parallel to the fiber axis. However, since the mesophase pitch generally has a high softening point, it has a drawback that the melt spinning temperature becomes high and it becomes thermally unstable. Further, since the mesophase pitch is an inhomogeneous mixture in which isotropic pitch and pitch liquid crystal are mixed, it has been considered difficult to obtain uniform pitch fiber.

In order to solve the above-mentioned drawbacks, the spinning raw material pitch which is not necessarily optically anisotropic at the stage of spinning raw material pitch but has excellent spinnability, and which is optically anisotropic during the spinning or firing step, and A method for producing carbon fiber using the same has been proposed.

For example, a pitch-like substance mainly composed of optically isotropic premesophase carbonaceous material or optically isotropic premesophase carbonaceous material is spun under the condition that the mesophase carbon mass is not substantially increased, and then subjected to infusibilization treatment. Then, a method of converting all of the pitch-like substance containing the premesophase carbonaceous material into a substantially optically anisotropic mesophase carbonaceous material by carbonization treatment (Japanese Patent Application Laid-Open No. 58-18421) and a method present in the mesophase pitch. Containing a hydrocarbon of a substantially quinoline-soluble polycyclic polynuclear skeleton having a structure in which the polycyclic polynuclear hydrocarbon is partially hydrogenated, as a potential anisotropy-forming component,
In the molten state, it does not substantially form mesophases, forms a homogeneous and optically isotropic single phase, and exhibits an orientation in that direction when an external force is applied. ~
A latent anisotropic pitch of 1.2 (JP-A-57-100186) has been reported. However, in any case, hydrogenation treatment is required. In the former case, there is no example of carbon fiber production by using only the primomethaze pitch, that is, the quinoline-soluble pitch, and the spinning pitch contains quinoline-insoluble matter.

Generally, the mechanical properties of carbon fibers are dominated by higher order structures. For example, it is essential that a high elastic modulus has a fibrous structure and high orientation. Conventionally, in order to produce highly elastic Pitch-based carbon fiber, raw materials such as coal tar and coal tar pitch are heat-polymerized as a raw material pitch for spinning and then crystallized mesophase pitch, or latent anisotropy. It was necessary to use a pitch or prime mesophase pitch.

All of the Pitch-based carbon fibers produced by the above method are PAN
Although it has superior graphitization characteristics compared to PF-based carbon fibers, it is still inferior in tensile strength as a fiber, and it is necessary to provide Pitch-based carbon fibers with mechanical properties equivalent to PAN-based carbon fibers. The reality is that it has not arrived.

The present inventors have conducted diligent research in order to develop a Pitch-based carbon fiber which is equal to or superior to the PAN-based carbon fiber in mechanical properties such as tensile strength, tensile modulus and elongation at break. As a result, spinning was performed using naphthalene as a raw material, heat-polymerized under specific conditions, and removing light components to obtain an optically isotropic pitch having a proper molecular structure and molecular weight as a spinning raw material pitch. Surprisingly, the Pitch-based carbon fiber obtained by infusibilizing and firing has a fiber structure in which the carbon net surface is selectively arranged in the fiber axis direction, and the conventional Pitch-based high-performance carbon fiber. Based on this finding, the present invention has been accomplished based on the finding that it has mechanical properties of high strength and high elongation, which are not expressed in.

That is, according to the present invention, the orientation angle (2Z
Is greater than 50 ° and the apparent size of the microcrystals (L
_{c (002)} ) is 15 to 50Å, and the layer spacing (d ₀₀₂ ) is 3.43 to
900-1600 using naphthalene showing 3.47Å as raw material
The object is to provide a Pitch-based carbon fiber treated at ° C. Another object of the present invention is to subject naphthalene to heat polymerization in the presence of a Lewis acid catalyst at 330 ° C. or lower for 0.5 to 100 hours to remove the catalyst, and then 330 to 440 while flowing an inert gas under normal pressure or reduced pressure. Heat to ℃ to remove light components, softening point is 180 ~ 200 ℃, H / C is 0.6
-0.8, the average molecular weight is 800-1500, the benzene-insoluble matter is 35-45% by weight, and an optically isotropic carbonaceous pitch containing no quinoline-insoluble matter is produced. According to the present invention, there is provided a method for producing a Pitch-based carbon fiber having the above-mentioned characteristics by performing spinning, infusibilization and carbonization and firing, and then treating at a temperature of 900 to 1600 ° C. under an inert gas atmosphere.

The carbon fiber of the present invention has an orientation angle determined by X-ray diffraction.
(2Z °) is larger than 50 °, preferably 50 to 80 °, and the apparent size of fine crystals (L _{c (002)} ) is 15 to 50.
Å, preferably 20 to 30Å, and the layer spacing (d ₀₀₂ ) is
It is 3.44 to 3.47Å, preferably 3.441 to 3.461Å.

The carbon fiber of the present invention having the orientation angle, the apparent size of microcrystals and the layer spacing as described above, and the structure in which the crystals are uniformly arranged is superior to the conventional Pitch-based carbon fiber in mechanical properties. It shows the physical strength.

Carbon fiber of the present invention has a tensile strength of at least 200 kgf / mm ^2, at least a tensile modulus of 9500kgf / mm ^2.

Optically isotropic carbonaceous pitch produced by a specific method using naphthalene as raw material, compared with the spinning temperature of the mesophase pitch, melt spinning is possible at a lower temperature, and specific spinning conditions during spinning. It is possible to obtain a uniform pitch fiber without adopting. Furthermore, since the basic arrangement of the Pitch fibers is not as strong as the Pitch fibers obtained from the mesophase pitch, during infusibilization, the infusibilization reaction proceeds in the surface layer portion, whereby a fine mosaic structure is formed, In the central part, the infusible reaction does not disturb the preferred arrangement of the molecules and imparts an excellent fiber structure.

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

The raw material naphthalene was added in the presence of a Lewis acid catalyst for 330
Polymerization is carried out by heating at a temperature of not higher than 0.degree. Examples of the Lewis acid catalyst used here include AlCl ₃ and BF _3, but AlCl ₃ is preferable.
The Lewis acid catalyst is 5 to 5 with respect to 100 parts by weight of naphthalene.
Although 0 parts by weight can be used, 8 to 20 parts by weight is preferable. still,
When the heating temperature is higher than 330 ° C., mesophase pitch is generated, and quinoline insoluble matter is present, which is not preferable. Even if 50 parts by weight or more of the Lewis acid catalyst is used, the polymerization efficiency does not change so much and the removal of the catalyst becomes complicated, which is not economical.

After removing the catalyst from the polymerized naphthalene, 330 to 440 ° C. while flowing an inert gas under normal pressure or reduced pressure,
Preferably, it is heated to 350 to 420 ° C. to remove light components to produce an optically isotropic carbonaceous pitch. If the heating temperature exceeds 440 ° C., mesophase pitch is generated and quinoline insoluble matter is present, which is not preferable.

Carbonaceous pitch thus obtained (spinning raw material pitch)
Has a softening point of 180 to 200 ° C., H / C of 0.6 to 0.8, an average molecular weight of 800 to 1500, and a benzene insoluble content of 35 to 35.
It is 45% by weight, contains no quinoline-insoluble matter, and exhibits isotropicity when observed by a polarizing microscope.

The spinning raw material pitch for producing the carbon fiber having excellent mechanical properties of the present invention is required to be a carbonaceous pitch satisfying the above-mentioned various properties.

The obtained carbonaceous pitch is spun and infusibilized by a conventional method. For example, in spinning, the temperature of the carbonaceous pitch at the time of discharging from the spinneret is 70 to 9 above the softening point of the carbonaceous pitch.
It is carried out by setting the temperature to be 0 ° C. higher, discharging under a pressure of 0.5 to 2.0 kgf / cm ² · G, and winding at a winding speed of 300 to 1000 m / min. The infusibilizing treatment is performed by heating to 230 to 300 ° C. at a temperature rising temperature of 0.5 to 5 ° C./min in an oxidizing gas atmosphere and maintaining the temperature for 30 to 60 minutes.

The infusibilized fiber is then heated in an inert gas such as N ₂ gas at a temperature rising rate of 5 to 15 ° C./min to 900
Heated to ℃, then 900 to 1600 ℃ in N ₂ gas
At a prescribed temperature of 900-1 or continuously
Carbon fiber can be obtained with a high carbonization yield by carbonizing and firing at a predetermined temperature of 600 ° C.

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

(1) Structural related factors Orientation angle (2Z °), apparent size of crystallite in C-axis direction (L _c ).
And the layer spacing (d ₀₀₂ ) are structurally related factors that represent the higher order structure of the fiber determined from the wide-angle X-ray diffraction pattern. 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 the orientation is advanced. The apparent size of the crystallites (L _c ) represents the apparent stacking height of the carbon crystallites, and the layer spacing (d ₀₀₂ ) represents the interplanar spacing between the carbon network planes of the crystallites.

The apparent size (L _c ) of the microcrystals was measured by the Gakshin method (Japan Society for the Promotion of Science 117th Committee, Carbon, No. 36, 5, 196).
According to 3).

The orientation angle (2Z °) is (002) By rotating the fiber bundle in which the constituent fibers are aligned in parallel at the position of the diffraction angle showing the maximum value of the diffraction intensity by 180 ° in the vertical plane of the X-ray beam, (002) The intensity distribution along the diffraction ring is measured and defined as the half width at half the intensity maximum.

(2) Parameters indicating pitch characteristics a) Molecular weight Measured using a vapor pressure osmometer (VPO) with pyridine as the solvent. As VPO, (Corona Model 117 molecular weight measuring device) is used, and pyridine is used as a solvent and benzyl is used as a standard substance.

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

c) Softening point Using a high flow tester (Shimadzu Corporation), put 1g of crushed crushed particles of 100 mesh or less into a heating cell (inner diameter 10 ^mm , nozzle diameter 1 ^mm ) and apply a load of 10 kgf / cm ² from the top. Then, the temperature of the inflection point of the plasticization curve is set as the softening point while the temperature is raised at a temperature rising rate of 6 ° C./min.

d) Insoluble matter in solvent Measured in accordance with JIS-K-2425.

(3) Physical properties of carbon fiber The fiber diameter, tensile strength, elongation and tensile modulus of carbon fiber are JI.
Measure according to S R-7601 "Carbon fiber test method". still,
The fiber diameter is measured by the cross-sectional area method.

Hereinafter, the present invention will be described with reference to examples. It should be noted that these examples are merely illustrative and do not limit the present invention.

Example 1 Naphthalene (first-class reagent manufactured by Kanto Chemical Co., Inc.) 1000
g and 100 g of AlCl ₃ (first-class reagent manufactured by Kanto Chemical Co., Inc.) as a catalyst were charged in a glass three-necked flask equipped with a stirrer and polymerized at 210 ° C. for 60 hours. After completion of the polymerization, the catalyst was removed by washing with water and filtration (pore size 0.2 μm) to obtain a pitch. The obtained pitch is 400 ° C, 15 Torr, N for 15 minutes
₂ Heated under circulation to remove light components.

The carbonaceous pits thus obtained are optically isotropic when observed under a polarizing microscope, and their characteristics are as shown in Table 1.

Next, the carbonaceous pitch is put into a cylinder with a nozzle having a diameter of 0.3 mm, heated and melted at 280 ° C., and then 1.2 kgf / cm ² G
It was extruded through the above nozzle and spun at a N ₂ gas pressure of. The winding speed at this time was about 700 m / min. The pitch fiber obtained as described above was added to about 1 in an air atmosphere.
The pitch fibers were heated to 265 ° C. at a temperature rising rate of ° C./min, and the pitch fibers were held in this atmosphere for about 30 minutes to be infusibilized.

The fiber thus infusibilized was heated to 900 ° C. at a temperature rising rate of about 5 ° C./min in an N ₂ gas atmosphere and kept in this atmosphere for about 30 minutes for processing.

Table 2 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8.5 μm) determined by X-ray diffraction.

Example 2 The carbon fiber treated at 900 ° C. obtained in Example 1 was N
1200 ° C at a heating rate of about 50 ° C / min in a ₂ gas atmosphere
It was heated up to and held in this atmosphere for about 10 minutes for processing.

Table 3 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction.

Example 3 Naphthalene (Kanto Chemical Co., Inc. first-grade reagent) 1000
g and 100 g of AlCl ₃ (Kanto Kagaku Co., Ltd. first-class reagent) as a catalyst were charged into an autoclave equipped with a magnet induction stirrer, sealed, and sufficiently replaced with N ₂ gas, and the internal pressure was 0 kgf.
/ cm ² G, raise the temperature to 300 ° C with stirring, and
Polymerization was carried out at 0 ° C. for 1 hour. After the completion of the polymerization, the catalyst was removed by washing with water and filtration (pore size: 0.2 μm) to obtain a pitch.
The obtained pitch was heated at 350 ° C., 12 Torr for 30 minutes under N ₂ gas flow to remove light components.

The carbonaceous pits thus obtained are optically isotropic when observed under a polarizing microscope, and their characteristics are as shown in Table 4.

Next, the carbonaceous pitch was put into a cylinder having a nozzle having a diameter of 0.3 mm, heated and melted at 275 ° C., and then extruded and spun through the above nozzle at a N ₂ gas pressure of 0.8 kgf / cm ² G. The winding speed at this time was about 600 m / min. The pitch fibers obtained as described above are about 1 ° C in an air atmosphere.
The pitch fibers were heated to 250 ° C. at a heating rate of / min, and held in this atmosphere for about 30 minutes for infusibilization.

The fiber thus infusibilized was heated to 900 ° C. at a temperature rising rate of about 5 ° C./min in an N ₂ gas atmosphere and kept in this atmosphere for about 30 minutes for processing.

Table 5 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction.

Example 4 The carbon fiber treated at 900 ° C. obtained in Example 3 was N
1200 ° C at a heating rate of about 50 ° C / min in a ₂ gas atmosphere
It was heated up to and held in this atmosphere for about 10 minutes for processing.

Table 6 shows the physical properties and mechanical properties of the obtained carbon fibers (diameter: 8 μm) determined by X-ray diffraction.

Example 5 Naphthalene (Kanto Chemical Co., Inc. first-grade reagent) 1000
g and 100 g of AlCl ₃ (first-class reagent manufactured by Kanto Chemical Co., Inc.) as a catalyst were charged in a three-necked flask equipped with a stirrer, and 10
Polymerization was carried out at 0 ° C. for 60 hours. Next, 100 g of AlCl ₃ (first-class reagent manufactured by Kanto Chemical Co., Inc.) as a catalyst was further added, and 210
Polymerization was performed at 30 ° C. for 30 hours. After the completion of the polymerization, the catalyst was removed by washing with water and filtration (pore size: 0.2 μm) to obtain a pitch.

The obtained pitch was heated at 380 ° C. for 10 minutes under N ₂ gas flow to remove light components.

The carbonaceous pits thus obtained are optically isotropic when observed under a polarizing microscope, and their characteristics are as shown in Table 7.

Next, the carbonaceous pitch was placed in a cylinder having a nozzle having a diameter of 0.3 mm, heated and melted at 275 ° C., and then extruded and spun through the nozzle at a N ₂ gas pressure of 1.2 kgf / cm ² G.
The winding speed at this time was about 500 m / min.

The pitch fiber obtained as described above was heated to 265 ° C. at a temperature rising rate of about 1 ° C./min in an air atmosphere, and the pitch fiber was held in this atmosphere for about 30 minutes to be infusibilized. .

The fiber thus infusibilized was heated to 900 ° C. at a temperature rising rate of about 5 ° C./min in an N ₂ gas atmosphere and kept in this atmosphere for about 30 minutes to be treated.

Table 8 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction. Example 6 The carbon fiber treated at 900 ° C. obtained in Example 5 was N
1200 ° C at a heating rate of about 50 ° C / min in a ₂ gas atmosphere
It was heated up to and held in this atmosphere for about 10 minutes for processing.

Table 9 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction.

Claims (2)

[Claims] 1. The orientation angle (2Z °) determined by X-ray diffraction is 5
Greater than 0 ° and apparent size of microcrystal (L _{c (002)} )
Is 15-50 angstroms and the layer spacing (d ₀₀₂ ) is 3.44-3.47 angstroms, and the carbon fiber made from naphthalene as a raw material treated at a temperature of 900 ° C-1600 ° C. 2. Naphthalene in the presence of a Lewis acid catalyst 330
After heat-polymerization at 0.5 ° C. or less for 0.5 to 100 hours to remove the catalyst, under normal pressure or reduced pressure while passing an inert gas, 33
Heat to 0-440 ° C to remove light components, softening point 18
0-200 ° C, H / C 0.6-0.8, average molecular weight 800-1500, benzene insoluble content 35-45% by weight
And produce an optically isotropic pitch containing no quinoline insoluble matter, and spinning the produced isotropic pitch,
Orientation angle (2Z °) determined by X-ray diffraction, characterized by being treated at a temperature of 900-1600 ° C after infusibilization
Is larger than 50 ° and the apparent size of the microcrystal (L
_{c (002))} is 15-50 Angstroms method of producing a carbon fiber layer spacing (d ₀₀₂₎ indicates 3.44-3.47 Å.