JPH03249218A - High performance carbon fiber and its production - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber having high modulus and strength in high spinnability and yield by spinning a meso-phase pitch produced by the polymerization of a condensed polycyclic hydrocarbon, etc., in the presence of hydrogen fluoride.boron trifluorode. CONSTITUTION:The objective fiber having a tensile strength of >=200kgf/mm<2> and a modulus of >=15tf/mm<2> can be produced by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride.boron trifluoride as a polymerization catalyst, spinning the obtained meso-phase pitch, infusibilizing the fiber by heating in an oxidizing gas (usually air) at 200-370 deg.C and carbonizing by heating to 1000 deg.C in an inert gas (usually nitrogen) preferably at a heating rate of 10-20 deg.C/min.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a high-performance carbon fiber produced from mesoface pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same, and a method for producing the same. Regarding.

(Prior Art) High-performance carbon fibers are generally manufactured industrially using PAN (polyacronitrile) as a raw material.

However, PAN is expensive and its carbonization yield is low.9 In recent years, even when using inexpensive pitch as a raw material, high-performance carbon fibers with properties equal to or better than PAN have been manufactured. It has been discovered that it can be done and is attracting attention.

Pitch for carbon materials includes isotropic pitch and anisotropic pitch. Cheap carbon fibers made from isotropic pitch are
Due to poor molecular orientation, strength is low and high performance products cannot be obtained. On the other hand, carbon fibers made from anisotropic pitch called mesoface pitch have a high degree of molecular orientation and exhibit excellent mechanical properties such as strength and elastic modulus.

For this reason, extensive research is underway to produce mesoface pitch, a raw material for high-performance carbon fiber, from petroleum catalytic cracking oil, petroleum tar pitch, and coal tar pitch.

"Mesophase" is a part that shows an optically anisotropic phase when observed with a polarizing microscope, and the area fraction of this optically anisotropic phase when observed with a polarizing microscope is called the "mesophase content". to be called. If this mesophase content is low,
Since the anisotropic phase and the isotropic phase separate in the molten state and interfere with the spinning operation, it is desirable that the mesophase content be 80% or more, preferably 10 oz. However, increasing the mesophase content generally increases the softening point and viscosity of the pitch, making stable spinning difficult.

In other words, since the softening point and viscosity are high, spinning at high temperatures is difficult, and pitch thermal decomposition and thermal condensation reactions are likely to occur, producing gas and infusible polymer substances, so stable spinning cannot be continued for a long time. is difficult.

Therefore, in order to produce carbon fiber industrially and efficiently, various methods have been proposed to improve the drawbacks of mesoface pitch. For example, Japanese Patent Publication No. 59-30192 describes a method of partially hydrogenating mesophase pitch to moderately weaken the layered state and spinning it into isotropic pitch, and Japanese Patent Publication No. 58-18421 describes describes a method using a unique brimesophase which is isotropic during spinning but changes to anisotropic during carbonization. Furthermore, in JP-A-54-160427, isotropic pi-sochi is extracted with a solvent and the insoluble matter is removed at 200-400'C.
A heating method is described in JP-A-58-136.
No. 835 describes a method of heat-treating isotropic pitch, filtering and separating the generated mesophase, and heat-treating the obtained pitch again. Furthermore, in JP-A No. 57-119984, the pinch is heat treated to reduce the menface content from 20 to 80.
2, a method for settling and recovering mesophase is described.

(Problems to be Solved by the Invention) As mentioned above, various attempts have been made to improve the mesoface pitch in order to make carbon fiber industrially efficient, but each method has the following problems. Satisfactory results have not yet been obtained.

Namely, Japanese Patent Publication No. 59-30192 and Japanese Patent Publication No. 58-18
In the method of No. 421, since spinning is performed at an isotropic stage with weak orientation, the orientation of molecules in the fiber is inferior to that from anisotropic pitch, and performance such as strength and elastic modulus deteriorates. do. Furthermore, the method of hydrogenating a highly viscous pitch in which condensed polycyclic aromatics are laminated is complicated and cannot be said to be an industrially advantageous method.

Furthermore, in the method of JP-A-54-160427, the yield of mesoface pitch is low because less insoluble matter is extracted with the solvent. In the method of JP-A-58-136835, the filtration operation after heat treatment is complicated. Japanese Unexamined Patent Publication 1987-
In the method of No. 119984, it is technically difficult to recover mesophase, and the carbonization yield is low.

In order to efficiently produce high-performance carbon fiber, it is not only necessary to have a high mesoface content in terms of performance such as strength and elastic modulus as described above, but also from the perspective of pitch spinning. It is necessary that 1) the thermal stability during spinning is high, 2) the spun fiber has high infusibility, and 2) the carbonization yield is high.

(Means for solving the problem) The inventors have previously disclosed Japanese Patent Application Laid-Open No. 1-139621 and Japanese Patent Application Laid-Open No. 1-1999.
No. 254,796 and Japanese Patent Application No. 1 to 309,482, mesoface pitch was discovered in which a condensed polycyclic hydrocarbon or a substance containing the same was polymerized in the presence of hydrogen fluoride and boron trifluoride.

The inventors further discovered that high-performance carbon fibers can be easily obtained by spinning this mesoface pitch, making it infusible at low temperatures, and carbonizing it, leading to the present invention.

That is, the present invention provides a mesoface pitch with a tensile strength of 200% obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride.
kgf 7mm2 or more, elastic modulus 15tf/mm” or more, and mesocarbon fibers obtained by polymerizing condensed polycyclic hydrocarbons or substances containing them in the presence of hydrogen fluoride and boron trifluoride. A method for producing high-performance carbon fiber, which is characterized by spinning face pinch, heating it to 200 to 370°C in an oxidizing gas to make it infusible, and then heating it in an inert gas to carbonize it. be.

Note that the mesoface pitch in the present invention has a naphthenic carbon content of 7% or more, or a methyl group carbon content of 4% in all carbons.
z or more, and the atomic ratio of hydrogen to carbon is 0.
The pitch is between 5 and 1.0. The amounts of carbon and hydrogen are measured using an automatic analysis bag fi (CON coder) that applies technology such as detection based on thermal conductivity of combustion gas. In addition, the carbon content of naphthenic carbon and methyl group is N
Measured by MR.

The optically anisotropic phase (mesophase) of this pitch is measured using a polarizing microscope as described above. The mesophase content of this pitch is 80% or more, preferably 90% or more, and it is preferred that substantially all of the pitch is mesophase. If the mesophase content is less than 80χ, the strength and elastic modulus of the carbon fiber will be low. Furthermore, as mentioned above, it is necessary to increase the mesophase content during spinning.

The mesoface pitch used in producing the carbon fiber of the present invention is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same. Examples of the condensed polycyclic hydrocarbons include naphthalene, anthracene, phenanthrene, acenaphthylene, pyrene, and hydrocarbons having these skeletons. Substances containing this include various petroleum fractions, residual oils from petroleum processing processes, and coal tar fractions.

To produce the mesoface pitch used in the present invention, hydrogen fluoride/boron trifluoride is used as a polymerization catalyst. The amount of polymerization catalyst is 0.00% hydrogen fluoride per mole of condensed polycyclic hydrocarbon.
A suitable mesoface pitch can be obtained by carrying out the polymerization reaction at a temperature of 250 to 320°C. The condensed polycyclic hydrocarbon (Ar) forms a complex by polymerizing with a catalyst, and rapidly polymerizes to form a polymer complex.

HF + BF3 ÷ (Nd) = H”
(Nd), BF4 This polymer complex maintains an equilibrium relationship, and the volatile components HF and BF3 are distilled off at the same temperature after the completion of polymerization and recovered as a catalyst. At this time, some low-boiling oil is recovered and, at the same time, polymerized pitch is separated.

The pitch obtained by this polymerization reaction is mesophase pitch with substantially 100χ anisotropy, and has a low melting point of 260 to 3
It can be easily spun at 40''C.The spinning method may be any method such as melt spinning, extrusion spinning, blow spinning, etc.For example, when performing melt spinning, the thickness is 0.1 to 0.5 mm.
Put a pitch in a spinner with a nozzle diameter of 260~3
Heat to 40"C, apply pressure from the top of the pitch, and reduce the spinning speed to 1.
Can be spun at 00 to 1000 m/min.

The spun pitch fibers are made infusible by 2 seconds in an oxidizing gas.
This is carried out by raising the temperature to 00 to 370°C. Air is usually used as the oxidizing gas, and the heating rate is 1 to 5.
°C/min.

The carbonization treatment after infusibility is carried out by raising the temperature to 900'C or higher in an inert gas. Nitrogen gas is usually used as the inert gas, and the temperature increase rate is 1O~20'C/min.
The temperature is generally raised to about 1000°C.

The carbon fiber of the present invention can be heated at 2000°C in an inert gas.
It can also be obtained by graphitization treatment by increasing the temperature above.

The characteristics of the present invention are that spinning can be performed at a low temperature, that infusibility treatment can be easily performed, that carbonization yield is high, and that high-performance carbon fibers of stable quality can be obtained. This seems to be due to the mesophase content of the raw material pitch being approximately 100x and homogeneous, the H/C atomic ratio being high, and the ratio of naphthenic carbon or methyl group carbon to total carbon being high.

(Effects of the Invention) The carbon fiber and the method for producing the same of the present invention have the following characteristics.

(1) Since the mesoface pitch of substantially 100x is spun, the carbon fiber of the present invention has well-developed orientation in the fiber axis direction and has a high elastic modulus.

(2) Since spinning is carried out at a temperature much lower (260 to 340°C) than the temperature at which the thermal decomposition or condensation of the raw mesophase pitch significantly proceeds (approximately 400°C), the spinning is good, and the Stable quality can be obtained because no deterioration occurs.

(3) When spinning the raw material mesoface pitch,
Since there is almost no generation of cracked gas or infusible matter, high-speed spinning can be performed, and the spun fibers have few defects and have high strength.

(4) The raw material mesoface pitch has a high H/C atomic ratio,
Furthermore, since the ratio of naphthenic carbon or methyl group carbon to the total carbon is high, it is highly infusible. Also, a high carbonization yield can be obtained.

As described above, according to the present invention, high-performance carbon fibers can be easily obtained at a high yield, and therefore the present invention has great industrial significance.

(Example) Next, the present invention will be explained in more detail with reference to Examples. Of course, the present invention is not limited to these examples.

Example 1 1 mol of naphthalene, 0.5 mol of liver, and 30.5 mol of BF were charged into a 500 ml acid-resistant autoclave, and the temperature was raised to 260°C while maintaining the reaction pressure at 25 kg/cm2G.
It reacted for 2 hours. Thereafter, the discharge valve of the autoclave was opened, and substantially all of the IP and BF3 were recovered in gaseous form at normal pressure, and then nitrogen was blown into the autoclave to obtain pitch from which low-boiling components had been removed. The yield of the pitch obtained was 76x in terms of weight ratio to the raw material naphthalene.

Further, this pitch was confirmed by a polarizing microscope to be a mesophase having an anisotropy of 100χ.

The softening point of this pitch is 216℃, and the H/C atomic ratio is 0.6.
7. The ratio of naphthenic carbon was 14χ.

This mesoface pitch was put into a melt spinning machine having a nozzle with a diameter of 0.25 mm and spun at 280°C. 500m/
It was possible to spin the yarn without yarn breakage at a winding speed of mtn, and it was easily made infusible by raising the temperature to 270''C at a rate of 5°C/min in air.

Next, this infusible thread was heated to 1000°C at a heating rate of 10''C/min in nitrogen gas to obtain carbon fibers with a thread diameter of 12μ.The carbonization yield during this carbonization treatment was 90χ. The carbon fiber had a tensile strength of 230 kgf/mmz and an elastic modulus of 20 tf/m.

Fork opening I 7 moles of naphthalene, 3 moles of HF, and 1.4 moles of BP were placed in a No. 31 acid-resistant autoclave, heated to 260° C., and reacted for 2 hours. Then, by the same operation as in Example 1, pitch was obtained at a weight yield of 76χ based on naphthalene. This pitch was confirmed by a polarizing microscope to be a mesophase having an anisotropy of 100.chi., the softening point was 229.degree. C., the H/C atomic ratio was 0.66, and the ratio of naphthenic carbon was 13.chi.

This mesoface pitch was put into a melt spinning machine having a nozzle with a diameter of 0.25 mm and spun at 310°C. 500m/
Can be spun without yarn breakage at a winding speed of n+in.
It could be easily made infusible by heating up to 280° C. at a rate of 5°/min in air.

Next, this infusible thread was heated at 10℃/11in in nitrogen gas.
The temperature was raised to 2000° C. at a heating rate of 2,000° C. to obtain carbon fibers with a thread diameter of 9 μm. The carbonization yield during this carbonization process was 90χ, the tensile strength of the carbon fiber was 320kgf/mm2, and the elastic modulus was 50tf/mm'' Comparative Example 1 1 mol of naphthalene, 3 mol of IF, 30.5 mol of BF mol was placed in a 3R acid-resistant autoclave, heated to 80°C, and reacted for 3 hours.Then, the discharge valve of the autoclave was opened, and the autoclave was gradually heated to 180-200°C at normal pressure, and substantially the entire amount of HF BF3 was removed. After recovering the gas in a gaseous state, the pitch was extracted in a molten state.The softening point of this pitch was 72
℃, and the mesophase content was 0χ.

This pitch was heated under normal pressure at 475°C for 50 minutes at 10 Torr.
The pitch was heat-treated at 420° C. under reduced pressure for 30 minutes to obtain pitch having a mesophase content of 100× and a softening point of 250° C. at a yield of 50× based on naphthalene.

The H/C atomic ratio of this pitch was 0.51, and the naphthenic carbon ratio was 4χ. When this pitch was spun at 360° C., it was possible to spin at a winding speed of 300 m/min, but high-speed spinning at 500 m/min was impossible. The pitch fiber obtained by spinning at a winding speed of 300 m/min was heated to 270° C. at a speed of 5° C./min, but could not be made infusible.

In this comparative example, naphthalene was polymerized using an HF BF3 catalyst and mesophase pitch was obtained by heat treatment, but it can be seen that high-speed spinning and infusibility treatment cannot be performed when the ratio of naphthenic carbon is low.

11 juice l α-methylnaphthalene 1 mol, HF 0.5 mol, BF
.

0.2 mol was charged into a 0.542 acid resistant autoclave, heated to 270°C, and reacted for 4 hours.

Thereafter, the discharge valve of the autoclave was opened, and substantially the entire amount of HFBF:l was recovered in gaseous form at normal pressure, and then nitrogen was blown into the autoclave to obtain pitch from which low boiling point components had been removed. The yield of the pitch obtained was 76x in terms of weight ratio to the raw material α-methylnaphthalene.

In addition, this pitch was confirmed to be a mesophase with an anisotropy of 100χ by a polarizing microscope, and the softening point was 2.
The temperature was 40°C, the H/C atomic ratio was 0.65, and the methyl group carbon ratio was 6z.

This mesoface pitch was put into a melt spinning machine having a nozzle with a diameter of 0.25 mm and spun at 310°C. 500m/
No yarn breakage at akin winding speed (can be spun,
It was easily made infusible by increasing the temperature to 270°C at a rate of 5°C/min in air.

Next, this infusible thread was heated at 10° in nitrogen gas (: /n+
The temperature was raised to 1000'C at a heating rate of in, and the yarn diameter was 12μ.
of carbon fiber was obtained. The carbonization yield during this carbonization treatment is 9
0χ, and the tensile strength of carbon fiber is 230 kgf/mm
2. The elastic modulus was 20tf/mm''.

comparison 1 α-Methyl naphtha 171 mol, HF 3 mol, BF.

Pour 0.5 mol into a 3j2 acid-resistant autoclave,
The temperature was raised to 0°C and the reaction was carried out for 3 hours. Thereafter, the discharge valve of the autoclave was opened, and the autoclave was gradually heated to 180 to 200° C. at normal pressure to recover substantially the entire amount of HF BF3 in gaseous form, and then the pitch was extracted in a molten state.

The softening point of this pitch was 72°C, and the mesophase content was Ox.

This pitch was heated under normal pressure at 475°C for 50 minutes at 10 Torr.
A pitch with a mesophase content of 10 oz and a softening point of 250°C was obtained at a yield of 50χ based on naphthalene.

The H/C atomic ratio of this pitch was 0.51, and the ratio of methyl group carbon was 2χ. When this pitch was spun at 360"C, it was possible to spin at a winding speed of 300 m/min, but high speed spinning at 500 m/min was impossible. The pitch fiber obtained by spinning was heated to 270°C at a rate of 5°C/min, but it could not be made infusible.

In this comparative example, α-methylnaphthalene was polymerized using HF BF and a catalyst, and mesophase pitch was obtained by heat treatment, but high-speed spinning and infusibility treatment were not possible when the ratio of methyl group carbon was low. I understand.

Tips ↓ Anthracene 7 mol, IP 3.5 mol, BF 31.0
The moles were charged into a No. 31 acid-resistant autoclave, heated to 240°C, and reacted for 3 hours.

Then, by the same operation as in Example 1, a pinch was obtained with a weight yield of 90x based on anthracene. This pitch was confirmed by a polarizing microscope to be a mesophase having an anisotropy of 100χ, a softening point of 235°C, an H/C atomic ratio of 0.6, and a naphthenic carbon ratio of 11χ.

This mesoface pitch was put into a melt spinning machine having a nozzle with a diameter of 0.25 mm and spun at 315°C. 500m
Can be spun without yarn breakage at a winding speed of /min.
It was easily made infusible by raising the temperature to 300°C at a rate of 5°C/min in air.

This infusible yarn was heated to 1000° C. at a rate of 10° C./min in nitrogen gas to obtain carbon fibers with a yarn diameter of 10 μm. The tensile strength of this carbon fiber was 210 kgf/mm2, and the elastic modulus was 16 tf/mm''.

Claims (3)

[Claims] (1) A tensile strength of 200 kgf/ produced from mesoface pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing it in the presence of hydrogen fluoride and boron trifluoride.
High-performance carbon fiber with elastic modulus of 15tf/mm^2 or more (2) In the presence of hydrogen fluoride and boron trifluoride, mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing it is spun, and in an oxidizing gas,
A method for producing high-performance carbon fiber, characterized by heating it to 0°C to make it infusible and then heating it in an inert gas to carbonize it. (3) Mesoface pitch that contains 7% or more of naphthenic carbon in all carbons, or 4% or more of methyl group carbon in all carbons, and has an atomic ratio of hydrogen to carbon of 0.5 to 1.0. The method for producing high-performance carbon fiber according to claim 2, which comprises spinning