JPH09273030A - Pitch fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pitch fiber capable of producing a pitch-based fiber excellent in tensile strength, modulus of elasticity, compressive strength and rigidity by conjugately spinning plural pitches having different contents of an optically anisotropic phase. SOLUTION: This pitch fiber is obtained, e.g. by conjugately spinning (A) a pitch obtained by treating heavy oil at 390-450 deg.C and 0.5-3MPa pressure for 1-5 hours and having 80-100% content of an optically isotropic phase as a core part with (B) a pitch obtained by hydrogenating a carbonous pitch in the presence of a hydrogenation catalyst and having 5-40% content of the optically isotropic phase as a sheath part.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pitch fiber having a novel structure.

[0002]

2. Description of the Related Art Pitch is heat-treated to form an optically anisotropic phase, which is melt-spun, infusibilized, carbonized, and graphitized to produce high-strength, high-elasticity carbon fiber. How to do it is known. However, a composite material (CFRP) using pitch-based carbon fibers has a problem that compression properties and shear properties are inferior to CFRP using polyacrylonitrile (PAN) -based carbon fibers. However, even PAN-based carbon fibers tend to deteriorate in compressive physical properties as the elastic modulus increases, and the characteristics of thin materials utilizing the rigidity of carbon fibers cannot be fully utilized.

[0003]

In order to improve the compressed physical properties of CFRP while utilizing the rigidity of carbon fibers, it is necessary to improve the compressed physical properties of carbon fibers themselves. As a result of intensive studies to improve the compressed physical properties of the pitch-based carbon fibers, the present inventors have found that not only excellent tensile strength and elastic modulus but also pitch capable of producing pitch-based carbon fibers having high compression strength The inventors have found a fiber and arrived at the present invention.

[0004]

That is, the present invention relates to a pitch fiber obtained by composite spinning two or more pitches having different optically anisotropic phase contents. Hereinafter, the present invention will be described in detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the composite spinning according to the present invention, preferably, pitches having different optically anisotropic phase contents are spun out from the center and the outside of the nozzle so that the internal cross-sectional structure of the filament has an optically anisotropic phase. The spinning is performed so as to be composed of two or more pitch portions having different contents. The pitch fiber is preferably a core (hereinafter referred to as a core portion)
And a two-layer structure composed of an outer portion of the core (hereinafter referred to as a sheath portion), and the content of the optically anisotropic phase is different between the core portion and the sheath portion. The pitch containing the optically anisotropic phase in the present invention (hereinafter referred to as the optically anisotropic pitch) can be obtained by subjecting the carbonaceous pitch to an appropriate treatment as already known. The carbonaceous pitch used in the present invention is not particularly limited, but petroleum pitch or coal pitch is preferable.

The carbonaceous pitch has a boiling point of 200 when obtained by fluid catalytic cracking of petroleum such as vacuum gas oil.
There are heavy oils at ˜600 ° C., preferably 300˜550 ° C. In addition, as the carbonaceous pitch, the heavy oil is used under the conditions of a temperature of 370 to 480 ° C., preferably 390 to 450 ° C., a pressure of 0.3 to 5 MPa, and preferably 0.5 to 3 MPa for 30 minutes or more. A pitch subjected to heat treatment for 10 hours, preferably 1 to 5 hours can be used. The pitch subjected to the heat treatment as described above is continuously heated to a temperature of 250 to 4
50 ° C, preferably 300-400 ° C, pressure 0.1-1
35 hPa, preferably 1 to 70 hPa, film thickness 0.1
It can also be obtained by performing thin film distillation under the condition of 5 mm. The softening point is usually 40 to 18 by the above steps.
A carbonaceous pitch of 0 ° C. can be obtained.

In the present invention, the pitch forming the core portion is preferably such a pitch that when carbon fiber is used, it exhibits a higher elastic modulus than the sheath portion, and the content of the optically anisotropic phase is higher than that of the sheath portion. It is more preferable that the pitch is as high as possible. Particularly, it is preferable to use a pitch having a content of the optically anisotropic phase of 60 to 100% by heating the carbonaceous pitch in the core portion. The pitch used for the spinning of the core part is, for example, under normal pressure of the carbonaceous pitch, while passing an inert gas such as nitrogen or steam or under reduced pressure, at a temperature of 340 to 450 ° C., preferably 360 to 410 ° C.,
It can be obtained by heating for 1 to 50 hours, preferably 3 to 30 hours. The optically anisotropic pitch for the core portion usually has an optically anisotropic phase content of 60 to
It is preferably 100%, particularly preferably 80 to 100%.
The softening point of the optically anisotropic pitch for the core part is usually 200 to
It is preferably 350 ° C, particularly 240 to 300 ° C.

In the present invention, the pitch forming the sheath portion is preferably such a pitch that when carbon fiber is used, it exhibits higher compressive strength than the core portion, and the content of the optically anisotropic phase is higher than that of the core portion. It is more preferable that the pitch is also small. An optically anisotropic pitch can be used as the pitch used for spinning the sheath portion, but it is preferable that the shrinkage rate during carbonization is almost the same as that of the core portion, so that the optically anisotropic phase is 5 to 5%. It is preferable to use a pitch containing less than 60%, particularly 5 to 40%. Further, the pitch used for the sheath portion has a difference between the pitch used for the core portion and the content of the optically anisotropic phase of usually 10% or more, preferably 40% or more,
More preferably, it is desirable to use a pitch of 50% or more.

Such a pitch can be obtained, for example, by hydrogenating carbonaceous pitch in the presence of a hydrogenation catalyst and heat-treating the hydrogenated pitch under atmospheric pressure or reduced pressure to obtain an optically anisotropic pitch. be able to. Alternatively, the optically anisotropic phase can be adjusted by subjecting the optically anisotropic pitch to solvent extraction or the like. As the hydrogenation catalyst used in the hydrotreatment, an inorganic solid such as zeolite, silica, alumina, silica gel or the like is used as a carrier, and metals such as chromium and molybdenum of Group VIB of the periodic table or cobalt, nickel and palladium are used. It is possible to use a metal of Group VIII in the table in the form of metal or in the form of oxide supported on the carrier. The hydrogenation conditions vary depending on the type of catalyst used, but usually the temperature is 150-45.
The temperature is 0 ° C., the pressure is 2 to 3 MPa, and the liquid hourly space velocity (LHSV) is 0.15 to 3.0. The hydrogenation partially nuclear hydrogenates the aromatic nucleus of the aromatic hydrocarbon in the pitch molecule.
It is desirable to add 2 mol or more, preferably 2 to 18 mol of hydrogen per mol of pitch based on the number average molecular weight.

The hydrogenated pitch as described above is then subjected to heat treatment under normal pressure or reduced pressure to give a pitch having an optically anisotropic phase content of 5 to 100%, preferably 5 to 60%. be able to. The heat treatment is usually 340 to 500
The heat treatment is carried out at a temperature of 370C, preferably 370 to 450C for 1 minute to 30 hours. At the time of heat treatment, it is preferable to perform the heat treatment while aerating an inert gas such as nitrogen. The flow rate of the inert gas is preferably 0.7 to 5.0 scfh / lb pitch. As a more suitable method for obtaining the pitch for the sheath portion, there is a method in which the pitch having an optically anisotropic phase content of 5 to 100% obtained as described above is extracted with a solvent.
In the solvent extraction, the solubility parameter at 25 ° C. is 7.4 to 9.0, preferably 7.6 to 8.4, which is insoluble in an organic solvent, and the solubility parameter at 25 ° C. is 9.2 to 11. 0, preferably 10.0-1
It is preferable to collect pitch that is soluble in an organic solvent of 0.8.

The order of solvent extraction is not particularly limited, but the optically anisotropic pitch is subjected to extraction treatment with an organic solvent having a solubility parameter of 7.4 to 9.0 to collect insolubles,
Subsequently, it is preferable to perform the extraction treatment of the insoluble matter with an organic solvent having a solubility parameter of 9.2 to 11.0 to collect the soluble matter. The extraction treatment with an organic solvent is usually at normal pressure or under pressure, for example, 15 to 230.
It can be carried out at room temperature or under heating. The mixing ratio of the pitch and the organic solvent can be arbitrarily changed depending on the conditions such as pressure and temperature, but 10 to 150 parts by weight of the organic solvent is usually used for 1 part by weight of the pitch.

In the above description, the organic solvent having the solubility parameter of 7.4 to 9.0 is, of course, the organic solvent having the solubility parameter within the range as described above.
Solubility parameter of 7.4-
Those adjusted to have a range of 9.0 can also be used. When two or more organic solvents are mixed and used, each has a solubility parameter of 7.4 to 9.
Even if it is out of the range of 0, the mixing of 7.4 to
The solvent can be used by adjusting it within the range of 9.0. Similarly, for organic solvents having a solubility parameter of 9.2 to 11.0, one type or two types are used.
A mixture of two or more solvents can be used. Specific examples of the organic solvent having a solubility parameter of 7.4 to 9.0 alone (the solubility parameter is shown in parentheses) include carbon tetrachloride (8.6) and 1,1-dichloroethane (8.9). , 1,2-dichloropropane (9.0), methyl ethyl ether (7.6), t-butyl chloride (7.5), diethyl ether (7.4), isobutylamine (8.5), cyclohexane ( 8.2), octane (7.6), xylene (8.8), cumene (8.8)
Is mentioned.

Specific examples of the organic solvent having a solubility parameter of 9.2 to 11.0 alone include carbon dioxide (1
0.0), chloroform (9.3), dichloromethane (9.7), acetone (10.0), methyl ethyl ketone (9.3), pyridine (10.6), dichlorobenzene (10.0), chlorobenzene ( 9.5), benzene (9.2), naphthalene (10.6) and nitrobenzene (10.2). In addition, n-hexane (7.
3), quinoline (11.8), or any combination of two or more kinds of organic solvents may be used to obtain a predetermined solubility parameter. The solubility parameter of the mixed solvent can be obtained by proportional calculation based on each solubility parameter before mixing and each vol%.

Melt spinning can be carried out using the pitches thus adjusted and, for example, a spinning apparatus having a double structure as shown in FIG. In this case, a pitch having a large content of optically anisotropic phase in the melting tank A, preferably a pitch having the same content of 60 to 100%, and a pitch having a small content of optically anisotropic phase in the melting tank B, preferably Is spun with a pitch having the same content of 5 to less than 60%. For example, each pitch can be fed, melted with an external heater, extruded with nitrogen gas, and wound on a bobbin.

In the present invention, the pitch of the core portion may be composed of a single component or two or more components with respect to the content of the optically anisotropic phase. Also, the pitch of the sheath portion may be composed of a single component or two or more components with respect to the optically anisotropic phase content. The sheath portion may be outside the cross section of the core portion. It is preferable that the outer periphery of the core portion is completely covered, but it may be partially covered. At the boundary portion between the core portion and the sheath portion, the content of the optically anisotropic phase may change continuously or discontinuously.

The structure inside the filament of the pitch fiber of the present invention has a composite structure of a core portion and a sheath portion, and the core / sheath area ratio is usually 0.1 to 10, preferably 0.
It is desirable that it is 1-3. The core / sheath area ratio is the area ratio of the pitch fiber cross section perpendicular to the fiber axis.
The area ratio can be determined by carbonizing pitch fibers to form carbon fibers and then observing the cross section of the carbon fibers by SEM. In the SEM observation, the core portion usually has a radial structure and the sheath portion usually has a random structure. The core portion can be formed by the pitch of the melting tank A, and the sheath portion can be formed by the pitch of the melting tank B. The core / sheath area ratio of the pitch fibers during the composite spinning with the above-mentioned device can be controlled by, for example, the extrusion pressure of the pitches forming the respective pitch fibers.

The pitch fiber thus obtained by melt spinning is then subjected to an infusibilizing treatment in an oxidizing gas atmosphere. The oxidizing gas is usually oxygen, ozone, air,
One of oxidizing gases such as nitrogen oxides, halogens, and sulfurous acid gas
Species or two or more species are used. This infusibilization process is
It is carried out under a temperature condition in which the pitch fiber which is the object to be processed is not softened and deformed. Usually 20 to 360 ° C., preferably 100
Infusibilized at ~ 320 ° C. The processing time is usually 5 minutes
10 hours. The infusibilized pitch fiber can then be carbonized in an inert gas atmosphere to form a carbon fiber having a double structure. The carbonization is usually 500-
It is carried out at 3500 ° C., preferably 800 to 3000 ° C. Generally, the time required for carbonization is 0.5 minutes to 10 hours.

The carbon fiber obtained as described above is usually 0.6 GPa or more, preferably 0.7 GPa or more, 5 G or more.
It has a compressive strength of Pa or less. The elastic modulus is usually 3
00 GPa or more, preferably 400 GPa or more, 100
The tensile strength can be 0 GPa or less, and the tensile strength is usually 3 GPa or more, preferably 3.5 GPa or more and 10 GPa or less. The optically anisotropic phase content (%) used in the present specification is a portion of the optical anisotropy obtained by observing under a crossed Nicols with a polarizing microscope and photographing after embedding a pitch in a resin and polishing. The area ratio was measured to determine the optically anisotropic phase content of the spinning pitch. The compressive strength of carbon fiber is determined by the reaction compression method (SR ALLEN J. Mater. Sc) of single fiber.
i. 22 (1987) 853).

The solubility parameter can be expressed by the following equation. δ = {ΔHvRT / V} ^1/2 where δ is the solubility parameter, Hv is the heat of vaporization of the material, R
Is the molar gas constant, T is the Kelvin temperature, and V is the molar volume. Regarding this, J. Hildebrand and R.L. Scott's "Solubility of Non-Electrolytes (Sorugil
it of Non-Electrolyes) ",
Third Edition, Reinhold Publishing Company, New York, 1949.
Year and Prentice Hall "Regular Solutions", New
See Jersey, 1962. The average molecular weight of the pitch is the number average molecular weight.For the benzene soluble content of the pitch, the number average molecular weight is measured as it is with an osmometer, and for the benzene insoluble content of the pitch, after hydrogenation with a catalytic amount of lithium and ethylenediamine, The number average molecular weight was measured with a meter.

[0020]

As is apparent from the examples, the carbon fiber having a double structure of the present invention is not only excellent in tensile strength and tensile elastic modulus, but also has a characteristic of high compressive strength.

[0021]

【Example】

(Example 1) Vacuum light oil 48 was added in the presence of a zeolite catalyst.
Heavy oil having a boiling point of 300 ° C. or higher, which is a by-product of fluid catalytic cracking at 5 ° C. and 0.2 MPa, has a temperature of 405 ° C. and a pressure of 1.3.
Heat treatment was performed at MPa for 3 hours. The solid insoluble matter was centrifuged from the heat-treated oil to adjust the content of the insoluble matter to 5 ppm or less. Next, the heat-treated oil from which solid insoluble matter was separated and removed was subjected to thin film distillation at a temperature of 270 ° C., a pressure of 6.7 hPa, and a film thickness of 2 mm to obtain pitch (1) having a softening point of 100 ° C. This pitch (1) was heat-treated under an inert gas at 390 ° C. for 14 hours to obtain a pitch (2) having an optically anisotropic phase of 90%. The softening point of pitch (2) was 265 degreeC. Next, the pitch (1) was continuously treated on a fixed bed of a nickel-molybdenum-supported catalyst at a temperature of 320 ° C., hydrogen pressure of 15 MPa and LHSV of 0.25, and then the catalyst residue and insoluble solid were 0.5 μm.
By pressure filtration with a filter of No. 2, hydrogenated pitch (3) having a softening point of 40 ° C., in which 8 mol of hydrogen was added per pitch molecule, was obtained.

To this hydrogenated pitch (3) g, nitrogen was added to 6
Stir with aeration at 00 ml / min, 3.5 at 400 ° C
Heat treatment was performed for a time to obtain an optically anisotropic pitch having a softening point of 205 ° C. and an optically anisotropic phase content of 45%. After finely pulverizing this optically anisotropic pitch, 100 g of a mixed solvent (solubility parameter: 8.4) of n-hexane (40 vol%)-benzene (60 vol%) per 3 g of the pitch was added at 60 ° C. Extraction treatment was performed to collect the insoluble matter in the n-hexane-benzene mixed solvent. Next, the n-hexane-
Benzene (75 vo) for 3 g of benzene mixed solvent insoluble matter
1%)-quinoline (25 vol%) mixed solvent (solubility parameter: 9.9) at a ratio of 100 ml was subjected to an extraction treatment at 80 ° C. to collect a benzene-quinoline mixed solvent-soluble component. The solvent was removed from the benzene-quinoline mixed solvent-soluble component to obtain a softening point of 240 ° C. and an optically anisotropic phase content of 35.
% Pitch (4) was obtained. The pitch thus prepared (2)
To the melting tank A of the spinning device shown in FIG. 1, the pitch (4) is put into the melting tank B, the melting tank A is 790 kPa, and the melting tank B is 1
Melt spinning was performed by applying a pressure of 50 kPa to obtain a pitch fiber having a sheath / core structure. Then, pitch fiber is NO
_After heating up to 230 ° C at 1 ° C / min in air containing ₂ vol% of ₂ and holding at 230 ° C for 60 minutes, 5 ° C in nitrogen
The temperature is raised to 750 ° C. at a rate of −1 min / min and held at 750 ° C. for 15 minutes,
Then, the temperature was raised to 2000 ° C. at 100 ° C./min and heat treatment was performed to obtain carbon fibers having a sheath / core ratio of 0.5 at 11 μm. The elastic modulus of the obtained carbon fiber was 520 GPa, the tensile strength was 3.90 GPa, and the compressive strength was 0.85 GPa.

(Example 2) The pitch (2) was placed in the melting tank A,
Pitch (4) is put in melting tank B and melting tank A is set to 625 kP
a, a pressure of 175 kPa was applied to the melting tank B to carry out melt spinning to obtain pitch fibers having a sheath / core structure, and Example 1
A carbon fiber having a sheath / core ratio of 1 and a thickness of 11 μm was obtained in the same manner as in (1). The elastic modulus of the obtained carbon fiber is 420 GPa,
The tensile strength was 3.80 GPa and the compressive strength was 1.0 GPa.

Example 3 Pitch (3) was subjected to heat treatment at 400 ° C. for 12 hours under an inert gas to obtain pitch (5) having an optically anisotropic phase of 95%. The softening point of the pitch (5) was 245 ° C. Pitch (5) is put in the melting tank A, pitch (4) is put in the melting tank B, melting tank A is applied at 285 kPa, and melting tank B is applied at a pressure of 130 kPa to carry out melt spinning to obtain a pitch fiber having a sheath / core structure. A carbon fiber having a sheath / core ratio of 0.38 and a thickness of 10 μm was obtained in the same manner as in Example 1. The elastic modulus of the obtained carbon fiber was 560 GPa, the tensile strength was 4.20 GPa, and the compressive strength was 0.95 GPa.

(Comparative Example 1) The pitch (2) was set to a nozzle diameter of 0.
Spinning was carried out using a spinning machine of 5 mmφ and L / D = 1 to obtain pitch fibers and carbon fibers of 11 μm were obtained in the same manner as in Example 1. The elastic modulus of the obtained carbon fiber was 530 GPa, the tensile strength was 3.90 GPa, and the compressive strength was 0.45 GPa.

(Comparative Example 2) Pitch (5) was made into pitch fibers by the spinning machine used in Comparative Example 1, and 10 μm carbon fibers were obtained by the same method as in Example 1. The elastic modulus of the obtained carbon fiber was 550 GPa, the tensile strength was 3.50 GPa, and the compressive strength was 0.53 GPa.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a spinning device according to the present invention.

[Explanation of symbols]

 1 Melting Tank A 2 Melting Tank B 3 Casting Heater 4 Pitch Discharge Hole 5 Spinning Pressure Adjusting Hole 6 Pitch Fiber Core 7 Pitch Fiber Sheath 8 Pitch Fiber

Claims (1)

[Claims] 1. A pitch fiber obtained by composite spinning two or more pitches having different optically anisotropic phase contents.