JPH05171157A - Production of raw pitch for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject pitch suitable for producing carbon fiber improved in compressive strength, etc., by removing insolubles followed by solubles from specific synthetic pitch using two kinds of solvents having respective specified solubility parameters. CONSTITUTION:The objective pitch can be obtained by removing, from (A) synthetic pitch (containing >=80wt.% of optically anisotropic phase) produced by polycondensation of a condensed polycyclic hydrocarbon using a Lewis acid catalyst, (B) insolubles using a solvent 9.5-11.5 (pref. 10.0-11.0) in solubility parameter (e.g. tetralin, THF) followed by (C) solubles using another solvent 7.0-10.0 (pref. 7.0-9.0) in solubility parameter, with solubility parameter difference by >=0.1 from the former solvent (e.g. toluene/hexane mixture).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a raw material pitch, and more particularly to a method for producing a raw material pitch which is particularly suitable for producing pitch-based carbon fibers.

[0002]

Conventionally, carbonized fiber and graphitized fiber are lightweight,
Due to its excellent properties such as high elasticity and high rigidity, it has been used as a reinforcing material for many composite materials. For example, it is widely used from golf clubs, rackets such as tennis, sports goods such as fishing rods, medical supplies such as artificial hands and artificial legs, to structural materials for vehicles, aerospace vehicles and the like. Polyacrylonitrile (PAN) is a type of high-performance carbon fiber.
It is roughly classified into pitch system and pitch system. Among these, pitch-based carbon fiber and graphite fiber are made from pitch obtained from coal, petroleum, etc. as a raw material, and by using such means as heating, an optically anisotropic phase portion of the liquid crystal that is the precursor structure of the graphite structure is produced. Then, this is spun, infusibilized in an oxidizing atmosphere, then carbonized and, if necessary, graphitized to obtain a high-performance carbon fiber. Here, the reason why the optically anisotropic phase portion is generated is that the optically anisotropic portion, which is a liquid crystal, has orientation, so that the resulting carbon fiber also has excellent orientation and exhibits high strength. This is because it is easy to do. For example, JP-A-49-3617
Japanese Patent Laid-Open No. 0 describes that high-performance carbon fibers can be obtained by using a pitch in which the optically anisotropic phase portion occupies 40 to 90%. From an industrial point of view, the viscosity of the optically anisotropic phase and that of the optically isotropic phase are greatly different. Therefore, the optically anisotropic phase is set to 100% or the optically isotropic phase is changed. It is known that spinning at 100% or either is preferable, and it is also known that the fiber obtained from the optically isotropic phase hardly exhibits high characteristics. Furthermore, in recent years, it has been known to obtain carbon fibers by using a synthetic pitch obtained from a raw material such as naphthalene as a raw material pitch, as described in JP-A-61-83319.

[0003]

However, pitch-based fibers derived from such a synthetic pitch are equivalent to PAN-based fibers in tensile strength, elastic modulus, etc., but are inferior in compressive strength. However, further improvement in this respect has been desired.

[0004]

Means for Solving the Problems The inventors of the present invention have earnestly studied to provide a raw material pitch capable of improving the compressive strength of pitch-based carbon fibers, and arrived at the present invention. That is, an object of the present invention is to provide a method for producing a raw material pitch which is not only excellent in tensile strength and elastic modulus, but can also provide pitch-based carbon fiber which is comparable in compression strength to PAN-based fiber, and such a problem is provided. Is a synthetic pitch obtained by polycondensing a condensed polycyclic hydrocarbon using a Lewis acid catalyst,
The insoluble matter was removed using a solvent having a dissolution parameter of 9.5 to 11.5, and the dissolution parameter of 7.0 to 7.0 was obtained from the obtained pitch.
A method for producing a carbon fiber raw material pitch in which the soluble component is removed using a solvent having a solubility parameter difference of 0.1 or more in the range of 10.0 and used in the above-mentioned treatment,
More specifically, the synthetic pitch obtained by the polycondensation can be easily achieved by the above-mentioned production method in which the optically anisotropic phase is 80% or more.

The present invention will be described in more detail below. First,
In the present invention, the synthetic pitch means a pitch obtained by polycondensing a condensed polycyclic hydrocarbon using a Lewis acid catalyst,
The raw material pitch is the synthetic pitch of the melting parameter 9.5.
The insoluble matter was removed using the solvent of 11.5, and the difference in the solubility parameter from the solvent used in the above treatment was in the range of the solubility parameter 7.0 to 10.0 from the obtained pitch.
It means a raw material pitch for carbon fiber production, in which the soluble component is removed using a solvent of 0.1 or more. Condensed polycyclic hydrocarbons are used as the starting material for the raw material pitch of the present invention.
It is not particularly limited as long as it is a condensed polycyclic hydrocarbon, but preferred are naphthalene, anthracene, phenanthrene, acenaphthene, pyrene, acenaphthylene and alkyl-substituted compounds thereof. These may be used alone or as a mixture of a plurality of them, but it is preferable to use them substantially independently. This is because, for example, naphthalene and anthracene have different morphologies of the polymer when polycondensed under the Lewis acid catalyst, which is the next step. Of these raw material pitches, naphthalene is particularly suitable.

In the present invention, the above-mentioned starting material is polycondensed using a Lewis acid catalyst and used as a synthetic pitch. The Lewis acid catalyst used here is SO ₃ , B
F ₃ , AlCl ₃ , AlBr ₃ , SnCl ₄ , FeCl ₃ ,
ZnCl ₂ , SO ₂ , Li ⁺ , Na ⁺ , Ag ⁺ , Fe ³⁺ , A
l ³⁺ , Cu ²⁺ , Hg ⁺ , H ⁺ , NO ₂ ⁺ , HF · BF _{3, and the} like, among which HF · BF _3, AlCl ₃ , B
F is preferred. The condensed polycyclic hydrocarbons that are the starting materials are
In the presence of such a Lewis acid catalyst, preferably room temperature to 300
Polycondensate at ℃. The polycondensation conditions vary depending on the type of condensed polycyclic hydrocarbon selected and the type of Lewis acid catalyst and are not particularly limited. For example, naphthalene is used as HF / BF.
If one chooses to polymerize in the presence of ₃ , the resulting synthetic pitch will have a Mettler softening point of about 250-290 ° C. and an atomic ratio of hydrogen to carbon of about 0.5-0.7. The synthetic pitch obtained by such a method preferably has a ratio of the optically anisotropic phase of 8 when observed under a polarization microscope at 425 times.
From the viewpoint of spinnability, it is more preferably 0% or more.

In the present invention, the synthetic pitch thus obtained uses two kinds of solvents having a solubility parameter difference of 0.1 or more, is an insoluble component of a solvent having a large solubility parameter, and has a small solubility parameter. A method for producing a synthetic pitch capable of producing a carbon fiber having high compressive strength by extracting and using a soluble component of a solvent. The solvent having a large solubility parameter used in the present invention has a solubility parameter of 9.5 to 11.5, preferably 10.0 to 1
There is no particular limitation as long as it is in the range of 1.0. Specific examples include tetralin, tetrahydrofuran, chlorobenzene, carbon disulfide, nitrobenzene, pyridine,
Naphthalene oil, anthracene oil, creosote oil, cleaning oil. Particularly preferred are pyridine, naphthalene oil, anthracene oil, creosote oil and mixtures thereof. The solvent having a small solubility parameter used in the present invention needs to have a solubility parameter smaller than that of the other (the one having a larger solubility parameter) by 0.1 or more, and has a solubility parameter of 7.0 to 10. ．
0, more preferably in the range of 7.0 to 9.0, specifically, toluene, hexane, xylene, ethylbenzene, kerosene, and mixtures thereof, and these and other solvents having high solubility parameters. And a mixture of kerosene, a mixture of kerosene and kerosene, and a mixture of kerosene and anthracene oil, particularly preferably a mixture of toluene and hexane.

With respect to the step of using the pitch of the present invention as the carbon fiber, the method generally used in the past can be applied as it is. Generally, the spinning is carried out at 200 to 300 ° C., and the spinning is carried out in an oxidizing atmosphere. Preferably, the infusibilizing treatment is performed in an oxygen atmosphere. After that, carbonization and, if necessary, graphitization are performed to obtain carbon fibers so that desired properties can be obtained. Needless to say, various surface treatments may be performed during this step or after obtaining the carbon fibers.

[0009]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 Naphthalene in the presence of a hydrogen fluoride / boron trifluoride catalyst, 2
The polymer was prepared by polymerizing at 00 ° C to 400 ° C, the optical anisotropy was 100% under a polarizing microscope, and the optical anisotropy was "rough flow" structure. The METTLER softening point was 250 ° C and the elemental composition was analyzed. After finely pulverizing a pitch having a value of C: 94.8% by weight and H: 5.2% by weight, pyridine (solubility parameter: 10.6) was added at a ratio of 200 ml to 5 g of this pitch, and at 100 ° C. After extraction, it was filtered through a 0.5 μm membrane filter to remove the pyridine insoluble matter. Then, pyridine was removed from the soluble matter to obtain pyridine-soluble pitch. Then, to 3 g of the pyridine-soluble matter, a mixed solvent of toluene / hexane = 20 vol% / 80 vol% (solubility parameter: 7.6) was added at a rate of 150 ml, and the mixture was extracted at about 70 ° C. and then a 0.5 μm membrane. It was filtered with a filter to remove soluble matter. The solvent was removed from the insoluble matter to obtain a spinning pitch. The obtained spinning pitch was embedded in a resin by a conventional method and then polished, and then, using a polarizing microscope, an objective lens: × 20, a photographing lens for photography: × 5
As a result of observing with a polarization microscope photograph with a magnification of 425 times on the photograph, a large number of optically anisotropic microspheres were observed to be dispersed, and among them, the optical anisotropy with a diameter of 3 μm or more was observed. Microspheres accounted for 30% of the total.

Further, the same sample was put in a gypsum test plate, and objective oil immersion lens: × 100, photographing lens for photography × 5
As a result of observing with a polarization microscope photograph at a magnification of 2700 times on the photograph, a large number of optically anisotropic spheroids having a diameter of 0.3 to 1.0 μm and a diameter of 0.2 to 3 μm are taken. It was dispersed or dense. The above 2700 times, on a polarization micrograph, per 4 cm ² of the photograph (on an actual sample, the diameter of the optically anisotropic spherules in 7.4 μm × 7.4 μm and the number of them are counted, When the optical anisotropy ratio is measured, the optical anisotropy ratio is 40% of the remaining part.
Accounted for volume%.

The temperature at which the spinning pitch had a viscosity of 200 poise was 250 ° C. The spinning pitch was heated in a nitrogen atmosphere on a hot stage and observed with a polarizing microscope with an objective lens of × 20 and an eyepiece lens of × 10. As a result, at 250 ° C. The volume ratio of the anisotropic portion was 1% or less. Next, the spinning pitch is changed to a nozzle diameter of 0.1 mm.
Spinning was performed using an extrusion spinning machine having a nozzle of No. 1 to obtain pitch fibers having a fiber diameter of 11 μm. Next, the pitch fiber was infusibilized at 310 ° C. in air. The fiber thus infusibilized was heated to 2400 ° C. in an argon gas and held for 30 minutes. The obtained carbon fiber has a fiber diameter of 8.6 μm, a tensile strength of 350 kg / mm ² , a tensile elastic modulus of 60 ton / mm ² , and a CFR of Vf60%.
The 0 ° compressive strength of P was 65 kg / mm ² .

Example 2 Naphthalene was added in the presence of a hydrogen fluoride / boron trifluoride catalyst to 2
Optical anisotropy 1 prepared by polymerization at 00 ° C to 400 ° C
Bitch having an elemental compositional analysis value of C: 94.8 wt% H: 5.2 wt% at 00% and a Mettler softening point of 250 ° C. was pulverized, and then pyridine (solubility parameter: 10.6 ) Is added at a ratio of 200 ml, and the temperature is 100 ° C.
After extraction with, the mixture was filtered through a 0.5 μm membrane filter to remove pyridine-insoluble matter. After that, toluene / hexane = 40 vol% / 60 vol with respect to the soluble content of 3 g
% Mixed solvent (solubility parameter: 7.9) 150
After adding at a ratio of ml and extracting at about 70 degrees, 0.5 μm
Insoluble matter was removed by filtration with a Mebrain filter. The solvent was removed from the insoluble matter to obtain a spinning pitch. The pitch thus prepared for spinning was embedded in a resin by a conventional method and polished, and then the objective lens was: × 2 by a polarizing microscope.
0, photographed eyepiece for photography: × 5, and observed with a polarization microscope photograph with a magnification of 425 times on the photograph. As a result, the whole structure has a large flow structure and 100 vol.
It was found to have an optical anisotropy of%.

Then, in the same manner as in Example 1, the spinning pitch was spun by an extrusion spinning machine having a nozzle having a nozzle diameter of 0.1 mm, and then infusible at 310 ° C. in air. Then, it was burned out in argon gas to obtain carbon fibers. The obtained carbon fiber has a fiber diameter of 8.3 μm, a tensile strength of 350 kg / mm ² , a tensile elastic modulus of 65 ton / mm ² , and a CFRP of Vf60% has a 0 ° compressive strength of 5%.
It was 8 Kg / mm ² .

[0015]

Comparative Example 1 Spinning, infusibilization and firing of carbon synthesized from naphthalene, having a pitch of optical anisotropy of 100% and a Mettler softening point of 250 ° C., were carried out in the same manner as in Example 1. Fiber was obtained. The carbon fiber obtained had a fiber diameter of 7.
2 μm, tensile strength 270 kg / mm ² , tensile elastic modulus 53
ton / mm ² , and 0 ° compressive strength of CFRP with Vf 60% was 40 kg / mm ² .

[0016]

Comparative Example 2 Toluene / hexane = 60 vol% with respect to a pitch of 5 g synthesized from naphthalene and having an optical anisotropy of 100% and a Mettler softening point of 250 ° C., which was used in Example 1.
/ 40 vol% mixed solvent (solubility parameter: 8.
2) was added at a rate of 200 ml, extracted at about 70 ° C., and then filtered through a 0.5 μm membrane filter to remove soluble components. The solvent was removed from the insoluble matter to obtain a spinning pitch.

The obtained spinning pitch was observed with a polarization microscope photograph at a magnification of 425 times as in Example 1, and as a result, the whole had a large flow structure and had an optical anisotropy of 100 vol%. I found out that Next, this spinning pitch was spun in the same manner as in Example 1, infusibilized and fired to obtain a carbon fiber. The carbon fiber obtained had a fiber diameter of 9.0 μm.
m, tensile strength is 250 kg / mm ² , tensile elastic modulus is 67 t
on / mm ² and Vf 60% CFRP 0
° Compressive strength was 40 kg / mm ² .

[0018]

[Comparative Example 3] Pyridine (solubility parameter: 1 was used for 5 g of a pitch synthesized from naphthalene used in Example 1 and having an optical anisotropy of 100% and a Mettler softening point of 250 ° C.
0.6) was added at a rate of 200 ml, extracted at 100 ° C., and then filtered through a 0.5 μm membrane filter to remove pyridine-insoluble matter. Then, pyridine was removed from the soluble matter to obtain a pyridine-soluble matter.

The spinning pitch obtained was substantially isotropic under a polarizing microscope. Next, the spinning pitch was spun in the same manner as in Example 1, infusibilized and fired to obtain carbon fibers. The obtained carbon fiber had a fiber diameter of 9.1 μm, a tensile strength of 90 kg / mm ² , and a tensile elastic modulus of 7 ton / mm ² , and a carbon fiber having a high elastic modulus and high strength could not be obtained.

Claims (3)

[Claims] 1. A synthetic pitch obtained by polycondensing a condensed polycyclic hydrocarbon with a Lewis acid catalyst, was obtained by removing insolubles using a solvent having a solubility parameter of 9.5 to 11.5. It is necessary to remove the soluble component by using a solvent having a solubility parameter in the range of 7.0 to 10.0 from the pitch and having a solubility parameter difference from the solvent used in the above-mentioned treatment of 0.1 or more. A method for producing a characteristic carbon fiber raw material pitch. 2. The production method according to claim 1, wherein the synthetic pitch obtained by the polycondensation has an optically anisotropic phase of 80% or more. 3. The solvent used for removing the insoluble matter has a solubility parameter of 10.0 to 11.0, and the solvent for removing the soluble matter has a solubility parameter of 7.0 to 9.0.
The manufacturing method described.