JPH0633530B2 - 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 and a method for producing the same. More specifically, the present invention relates to a novel carbon fiber having naphthalene as a raw material and having characteristics comparable to those of PAN-based carbon fiber, and a method for producing the carbon fiber.

The carbon fibers currently on the market are classified according to the raw material into PAN-based carbon fibers made of polyacrylonitrile (PAN) and Pitch-based carbon fibers made of pits as a raw material, and generally PAN-based carbon fibers. Since carbon fibers have excellent properties in particular in terms of tensile strength as compared with Pitch-based carbon fibers, PAN-based carbon fibers have hitherto been used as high-performance carbon fibers having high strength and high elastic modulus. It was the mainstream. However, since the PAN-based carbon fiber is expensive and the carbonization yield is poor, it is possible to obtain the same tensile strength and tensile elastic modulus as those of the PAN-based carbon fiber by using the pitch, which is advantageous in terms of economy, as the 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 the menh phase and are non-chicken tropic at 10 to 10 at spinning temperatures. A carbonaceous pitch having a viscosity of 200 poise is spun, the spun fiber is infusibilized in an oxygen-containing atmosphere at 250 to 400 ° C., and the infusible fiber obtained is then at least 1000 ° C. in an inert atmosphere.
By heating to (1100) and then to (1100) and (100) and (1)
01) X-ray diffraction pattern characterized by the presence of lines, ie having a highly three-dimensional structure, a layer spacing of 3.37Å or less, an apparent lamination dimension (La) of 1000Å or more and 1
It has been reported that a graphite fiber having an apparent laminated height (Lc) of 000Å or more is produced (Japanese Patent Laid-Open No. 49-1).
9127).

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 is not necessarily optically anisotropic at the stage of the spinning raw material pitch, but has excellent spinnability and is converted into optically anisotropic at the spinning or firing stage. And methods for producing carbon fibers using the same have 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, mesophase is not substantially formed, and a homogeneous and optically isotropic single phase is formed, and when an external force is applied, it exhibits orientation in that direction. H / C is 0.55.
To 1.2 latent anisotropic pitch (JP-A-57-10018)
6) has been reported. However, any hydrogenation treatment is required. Further, in the former case, there is no example of carbon fiber production using only primomethaze pitch, that is, quinoline-soluble pitch alone, and the spinning pitch contains quinoline-insoluble matter.

In addition, coal tar, coal tar pitches, heavy petroleum oils, residual oil of petroleum at atmospheric pressure, distillation under reduced pressure, and hydrogenation of tar and pits, oil sands or raw materials produced by heat treatment of these residual oils as raw materials. 300 ~ by adding solvent
Heat to 500 ° C for 10-60 minutes, then under reduced pressure 45
A premesophase-containing pitch is heated to a temperature of 0 ° C. or higher for 5 to 60 minutes, the obtained spinning pitch is heated to a temperature higher than the viscosity change temperature, spun, and rapidly cooled, and then heated at 250 to 350 ° C. It is produced by infusibilizing at a temperature and heating the infusibilized fiber to a temperature of 1000 to 1500 ° C. in an inert gas. The orientation angle determined by X-ray diffraction is 30 to 50 °, and the crystal size (Lc) is 12.
~ 80Å, layer spacing (d ₀₀₂ ) is 3.4-3.6Å, tensile strength is at least 200 kgf / mm ² , and module is 1000.
Pitch-based carbon fibers having a weight of 0 kgf / mm ² have been reported (JP-A-59-53717).

In particular, the mesophase pitch-based carbon fiber having a three-dimensional structure of polycrystalline graphite having an orientation angle of less than 30 ° and an apparent size of microcrystals of more than 80Å has high thermal conductivity and electrical conductivity. Shows that the mechanical properties of the fiber are PA
It is reported to be inferior to N-based carbon fibers.

Generally, the mechanical properties of carbon fibers are dominated by higher order structures. For example, it is essential that the high elastic modulus has a fiber structure and has a 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.

The Pitch-based carbon fibers produced by the above-mentioned method are all PA
The graphitization property is superior to N-based carbon fiber, but it is still inferior in tensile strength as a fiber.
The reality is that a Pitch-based carbon fiber having mechanical characteristics equivalent to those of the carbon-based carbon fiber has not yet been provided.

The inventors of the present invention have conducted diligent research to develop a Pitch-based carbon fiber which is equal to or better than the PAN-based carbon fiber in mechanical properties such as tensile strength, tensile modulus and elongation at break. As a result of conducting, heat polymerization under specific conditions using naphthalene as a raw material, using a homogeneous and optically isotropic pitch having a suitable molecular structure and molecular weight obtained by removing light components as a spinning raw material pitch, Pitch-based carbon fibers obtained by spinning, infusibilizing, carbonizing and firing, and high-temperature treatment have an orientation angle of less than 30 ° and an apparent size of microcrystals larger than 80Å. Despite the fiber structure in which the mesh surface is selectively arranged in the fiber axis direction, it does not have the three-dimensional structure peculiar to the conventional Mensophase pitch-based graphitized fiber, and as a result, High strength comparable to AN-based carbon fiber, found to have mechanical properties of high modulus, ItaruTsuta the present invention based on this finding.

That is, in the present invention, the orientation angle (2
Z °) is less than 30 °, the apparent size (Lc ₍₀₀₂₎ ) of the microcrystals is more than 80 Å and 200 Å or less, and the layer interval (d ₀₀₂ ) is 3.371 to 3.440 Å using naphthalene as a raw material. It is an object of the present invention to provide a Pitch-based carbon fiber treated at 2000 ° C or higher. Another object of the present invention is to heat-polymerize naphthalene at 330 ° C. or lower for 0.5 to 100 hours in the presence of a Lewis acid catalyst, remove the catalyst, and then pass 330 to 440 while flowing an inert gas under normal pressure or reduced pressure. Light weight is removed by heating to ℃, softening point is 180 ~ 200 ℃, H / C is 0.6 ~ 0.8, average molecular weight is 800 ~ 1500, benzene insoluble is 35 ~ 45wt%.
And an optically isotropic carbonaceous pitch containing no quinoline insoluble matter is formed, and the produced carbonaceous pitch is spun, infusibilized and carbonized by a conventional method, and then heated at a temperature of 2000 ° C. or higher and It is an object of the present invention to provide a method for producing a Pitch-based carbon fiber having the above-mentioned characteristics by treating 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 °, and an apparent size (Lc ₍₀₀₂₎ ) of microcrystals of 80.
It is more than Å and less than 200 Å, preferably 90 to 170 Å, and the layer interval (d ₀₀₂ ) is 3.371 to 3.440 Å, preferably
3.390 to 3.430Å.

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 in mechanical strength to the conventional Pitch-based carbon fiber. It shows the strength.

Carbon fiber of the present invention has a tensile strength of at least 300 kgf / mm ^2, at least a tensile modulus of 20,000 kgf / 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, the infusibilization reaction proceeds in the surface layer during infusibilization, whereby a fine mosaic structure is formed, In the central part, an excellent fiber structure is provided without disturbing the preferable arrangement of molecules by the infusible reaction.

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 may be used in an amount of 5 to 50 parts by weight, preferably 8 to 20 parts by weight, based on 100 parts by weight of naphthalene. The heating temperature is 330 ℃
Above this, mesophase pitch will be formed, and quinoline insoluble matter will be 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,
Average molecular weight is 800-1500, benzene insoluble matter is 35
˜45% by weight, containing no quinoline insoluble matter, and exhibiting 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 at 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. In addition, the infusibilizing treatment is performed in an oxidizing gas atmosphere at a temperature rising rate of 0.5 to 5 ° C./min for 230 to
It is infusibilized by heating to 300 ° C. and maintaining it for 30 to 60 minutes.

The fiber thus infusibilized 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 0 ° C., then 2000 for example in argon gas
By treating at a predetermined temperature of ℃ or more, it is possible to obtain carbon fibers with a high carbonization yield.

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

(1) Structure-related factors The orientation angle (2Z °), the apparent size of the crystallites in the C-axis direction (Lc), and the layer spacing (d ₀₀₂ ) represent the higher-order structure of the fiber obtained from the wide-angle X-ray diffraction pattern. It is a structure-related factor. The orientation angle (2Z °) indicates the degree of orientation of the crystallites with respect to the fiber axis direction, and the smaller this angle, the more the orientation advances. Apparent size of microcrystal (L
c) represents the apparent stacking height of the carbon microcrystals, and the layer spacing (d ₀₀₂ ) represents the interplanar spacing between the carbon network planes of the microcrystals.

The apparent size (Lc) of the microcrystal is 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 is measured along the diffraction ring and is defined as the half width at half the intensity maximum.

(2) Parameters indicating the characteristics of pitch a) Molecular weight Using pyridine as a solvent, vapor pressure osmometer (VP
O) is used for measurement. As VPO, (Model 117 molecular weight measuring device manufactured by Corona) is used, and pyridine is used as a solvent and benzyl is used as a standard substance.

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

c) Softening point Using a Koka flow tester (Shimadzu Corporation), put 1 g of crushed pitch 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. The temperature is raised at a temperature rising rate of 6 ° C./min, and the temperature at the inflection point of the plasticization curve is taken as the softening point.

d) Solvent insoluble matter It measured based on JIS-K-2425.

(3) Physical properties of carbon fiber The fiber diameter, tensile strength, elongation and tensile modulus of carbon fiber are J
It is measured according to ISR-7601 "Carbon fiber test method". 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
Extruded and spun through the nozzle at N ₂ gas pressure of. The winding speed at this time was about 700 m / min. The pitch fibers obtained as described above were heated to 265 ° C. at a temperature rising rate of about 1 ° C./min in an air atmosphere, and the pitch fibers were held in this atmosphere for about 30 minutes to be infusibilized. .

The fibers thus infusibilized are heated in an N ₂ gas atmosphere at a heating rate of about 5 ° C./min to 900, and then at a heating rate of about 50 ° C./min in an argon atmosphere at 2000.
The sample was heated to 0 ° C. and kept in this atmosphere for about 10 minutes for processing.

Table 2 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 8 μm) determined by X-ray diffraction.

Example 2 The carbon fiber obtained in Example 1 was further heated in an argon gas atmosphere to 2500 ° C. at a temperature rising rate of about 50 ° C./min, and held at this temperature for about 10 minutes for treatment.

Table 3 shows the physical properties and mechanical properties of the obtained carbon fiber determined by X-ray diffraction (diameter: 7.5 μm).

Example 3 The carbon fiber obtained in Example 1 was further heated to 2800 ° C. at a temperature rising rate of about 50 ° C. in an argon gas atmosphere, and kept at this temperature for about 10 minutes for treatment. Table 4 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 7.5 μm) determined by X-ray diffraction.

Example 4 Naphthalene (Kanto Chemical Co., Inc. first-grade reagent) 1000
g and 100 g of AlCl ₃ (Kanto Chemical 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 kg.
f / cm ² G, raise the temperature to 300 ° C with stirring, and
Polymerization was carried out at 0 ° C. for 1 hour. 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 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 with a polarizing microscope, and their characteristics are as shown in Table 5.

Next, the carbonaceous pitch was placed in a cylinder having a nozzle having a diameter of 0.3 mm, heated to 275 ° C., melted, 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 in air atmosphere.
The pitch fibers were heated to 250 ° C. at a temperature rising rate of ° C./min, and the pitch fibers were held in this atmosphere for about 30 minutes for infusibilization treatment.

The fibers thus infusibilized are heated in an N ₂ gas atmosphere to 900 ° C. at a heating rate of about 5 ° C./minute, and then under an argon gas atmosphere at a heating rate of about 50 ° C./minute. The sample was heated to 2000 ° C. and kept in this atmosphere for about 10 minutes for processing.

Table 6 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 7.5 μm) determined by X-ray diffraction.

Example 5 The carbon fiber obtained in Example 4 was further heated in an argon gas atmosphere to 2500 ° C. at a temperature rising rate of about 50 ° C./min, and held in this atmosphere for about 10 minutes for treatment.

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

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

Table 8 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 7 μm) determined by X-ray diffraction.

Example 7 1000 g of naphthalene (first-class reagent manufactured by Kanto Chemical Co., Inc.)
And AlCl ₃ as a catalyst (Kanto Chemical Co., Ltd. first-grade reagent) 1
Charge 00g into a three-necked flask equipped with a stirrer,
Polymerization was carried out for 60 hours. Next, 100 g of AlCl ₃ (first-class reagent manufactured by Kanto Kagaku Co., Ltd.) as a catalyst was further added, and the temperature was maintained at 210 ° C.
Polymerized for hours. After the completion of the polymerization, the catalyst was removed by washing with water (pore size: 0.2 μm) to obtain a pitch.

The obtained pitch was heated at 380 ° C. for 10 Torr for 20 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 9.

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 extrusion 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 fibers obtained as described above are about 1 in 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 for infusibilization.

The infusibilized fiber was heated to 900 ° C. at a heating rate of about 5 ° C./min in an N ₂ gas atmosphere, and then heated to 2000 ° C. at a heating rate of about 50 ° C./min. It was held in the atmosphere for about 10 minutes for processing.

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

Example 8 The carbon fiber obtained in Example 7 was further heated to 2500 ° C. at a temperature rising rate of about 50 ° C./min in an argon gas atmosphere and held in this atmosphere for about 10 minutes for treatment.

Table 11 shows the physical properties and mechanical properties of the obtained carbon fibers (diameter: 7.5 μm) determined by X-ray diffraction.

Example 9 The carbon fiber obtained in Example 7 was further heated to 2800 ° C. at a temperature rising rate of about 50 ° C./min in an argon gas atmosphere, and held in this atmosphere for about 10 minutes to be treated.

Table 12 shows the physical properties and mechanical properties of the obtained carbon fiber (diameter: 7.5 μm) determined by X-ray diffraction.

Claims (2)

[Claims] 1. The orientation angle (2Z °) determined by X-ray diffraction is 3
It is less than 0 ° and the apparent size of the microcrystal (L
_{C (002)} ) exceeds 80 angstroms and 20
20 Å or less and a layer spacing (d ₀₀₂ ) of 3.371-3.440 Å, 20
Carbon fiber made from naphthalene treated at a temperature of 00 ° C or higher. 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,
After being infusibilized and carbonized, it is treated at a temperature of 2000 ° C. or higher, the orientation angle (2Z °) determined by X-ray diffraction is less than 30 °, and the apparent size of the microcrystals (L _{C (002)} ) is greater than 80 angstroms and less than 200 angstroms, and the layer spacing (d
₀₀₂ ) is 3.371-3.440 angstroms.