JPS5982418A - Manufacture of high-modulus carbon fiber - Google Patents

Abstract

PURPOSE:To manufacture a high-modulus carbon fiber in high spinnability, by removing light and medium oil components from coal tar, adding a ketone solvent to the coal tar, removing the insuluble components, purifying and hydrogenating the tar, converting to meso-phase by heat-treatment, and subjecting the product to the melt-spinning, conversion to infusible form, and baking. CONSTITUTION:The light and medium oil components are removed from coal tar at a cut point of 270-220 deg.C (boiling point), and the obtained coal tar is mixed with a ketone solvent having a boiling point of <=200 deg.C. The amount of the solvent in the whole mixture is 30-60wt%. The produced insoluble precipitate and then the ketone solvent are removed from the mixture to obtain refined tar. The refined tar or a pitch obtained by the distillation or heat- treatment of the refined tar, is hydrogenated, and the pitch component is removed therefrom to obtain hydrogenated pitch. The product is heat-treted to obtain meso-phase pitch, which is subjected to the melt-spinning, conversion to infusible form, and baking to obtain the objective carbon fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high modulus carbon fiber from coal tar, and in particular involves melt-spinning mesophase pitch containing mesophase pitch in a liquid crystal state, infusible and infusible.
Concerning the method of firing.

When producing high modulus carbon fibers, there is a method that involves passing through mesophase pitch. It is necessary to exhibit a low viscosity below the viscosity.

However, since coal tar originally has high aromaticity and a wide molecular weight distribution, even if the mesophase pitch is simply produced by heat treatment, the mesophase pitch will have a high viscosity.

Therefore, in order to obtain menphase pitch with low viscosity, it is effective to extract only the appropriate components from coal cool and produce menphase pitch from this.

However, in contrast to this method, it has recently been reported that low-viscosity mesophase pitch can be obtained in high yield by hydrogenating coal tar pitch and producing mesophase pitch from it. The idea behind this method is to reduce the excessively large molecular weight components in coal tar pitch to lower molecular weight components by hydrogenation, moderately reduce the high aromaticity of coal tar pitch, and reduce excessive molecular weight during heat treatment. It is thought that this is an attempt to obtain a low-viscosity mesophase as a result while suppressing the formation of a high-viscosity mesophase due to polycondensation.

On the other hand, there are several quinoline-soluble components in coal tar that inhibit spinnability, and even if the above-mentioned hydrogenation treatment method is used, it is difficult to decompose and make it insolubilized, so it is used as a raw material for carbon fiber. Therefore, the method disclosed in Japanese Patent Application Laid-Open No. 56-49791 (hereinafter referred to as the prior method) is effective.

However, according to recent research by the present inventors, it is not sufficient to simply remove quinoline-soluble components as raw materials for menphasic pitch-based carbon fibers, but also components that are insoluble in nitrobenzene and soluble in quinoline. It has become clear that the viscosity of metsuphase pitch is increased and the nitrobenzene fraction is measured according to JISK242.
It is measured by using nitrobenzene instead of quinoline as a solvent in the cool pitch quinoline solution determination method (centrifugation method) of No. 5.

Mata, nitrobenzene exhibits an extraction power intermediate between that of toluene and quinoline.

As described above, the present invention aims to remove not only quinoline-soluble components that cause high viscosity of mesophase pitch, but also nitrobenzene-insoluble to quinoline-soluble components.

In order to achieve this objective, the present inventors attempted various fieldwork and research, and found that the cut point of the starting material, coal tar, was set at 270°C to 220°C, and light and medium oil components were removed. Regarding cool, it was discovered that by using a known method of adding ketones, even components insoluble in nitrobenzene to soluble in quinoline could be aggregated into coarse granular insoluble components, and the present invention was completed.

That is, the present invention sets the cut point to boiling point 270°C ~
Add a ketone solvent with a boiling point of 200°C or less to the coal tar from which light and medium oils have been removed at 220°C.
~ 60 weight ratio of hereditary mixing.In addition to removing the insoluble precipitate formed in the mixed liquid, the ketone solvent is removed from the mixture after removing the insoluble precipitate to obtain purified tar. Refined tar or pitch obtained by distilling or heat-treating the refined tar is subjected to hydrogenation treatment, pitch components are separated from the hydrogenated product to obtain hydrogenated pitch, and this hydrogenated pitch is heat-treated. The method is characterized in that it is made into a mesophase to obtain a mesophase pinch, and then the mesophase and the mesophase pinch are melt-spun, made infusible, and fired.

In the prior method previously disclosed by the present inventors, the boiling point was 2.
If light and medium oils at temperatures below 70°C are removed and a ketone solvent such as acetone with low dissolving power is blended with this, the quinolinone-soluble components will aggregate with components such as β-lenone, forming coarse-grained insoluble components. Therefore, it was a material that could be easily separated.

However, as mentioned above, although this method can separate the quinoline-soluble components, it increases the viscosity of the menphase pitch and ultimately has a negative effect on spinnability. Therefore, the present inventors fundamentally reviewed the previous method and found that the boiling point was 270°C when removing light and medium oil components.
It has become clear that the insoluble matter in nitrobenzene cannot be separated even if it is removed by changing the boiling point to 2], 0° C., for example, the following range is not acceptable. Therefore, to remove light and medium oil components, the boiling point is within a temperature range of 270 to 220°C, preferably 270 to 230°C, and the cut point for removal by distillation is to remove light and medium oil components below this temperature range. is necessary. If the cut point exceeds the boiling point of 270° C., the amount of insoluble components produced increases significantly, and even toluene-insoluble to nitrobenzene-soluble components, which are effective as raw materials for carbon fibers, are removed, which is undesirable.

In fact, if the boiling point is less than 220°C, the insoluble matter in nitrobenzene cannot be removed, resulting in a decrease in spinnability.

On the other hand, the amount of ketone solvent added is also an unimportant factor.The amount added is required to be 30 to 60'ff1t% of the total mixture, based on the coal tar after light and medium oil content has been removed. . If it is less than 30% by weight, nitrobenzene insoluble matter will be mixed into the refined tar. If it exceeds 60% by weight, the insoluble matter becomes a viscous gum-like substance that adheres to other equipment, making operation difficult, and is undesirable because it is removed by effective component removal.

As the extraction solvent, a ketone solvent having a boiling point of 200° C. or lower is used. If a substance with a boiling point exceeding 20° C. is used, it is not preferable because distillation and separation from coal tar becomes difficult. Ketone solvents suitable for the method of the present invention include acetone, methyl ethyl ketone, butyl methyl ketone, noether ketone, and the like.

Thus, the method of the present invention can reduce not only the quinoline-soluble content but also the quinoline-soluble to nitrobenzene-insoluble content, depending on the cut point and the blending amount of the ketone solvent, which has a low dissolving power in the mixture and produces a large amount of insoluble content. It can be completely aggregated into coarse-grained insoluble matter. The aggregated coarse particulate insoluble matter is
It is removed by solid-liquid separation means such as static separation, centrifugal filtration, or filter filtration, and on the liquid side, the ketone solvent is removed by distillation to obtain purified tar that does not contain nitrobenzene-insoluble matter.

The purified tar thus obtained is converted into mesophase pitch through a heat treatment process, but conventional mesophase pitch methods such as simple heat treatment or a combination of vacuum distillation and heat treatment cannot Even if the nitrobenzene-insoluble matter is removed, the viscosity is extremely high and spinning is difficult.

Therefore, in the present invention, hydrogenation treatment is performed prior to the menphasizing heat treatment. Here, the object to be subjected to the hydrogenation treatment may be the above-mentioned purified tar itself, or pitch obtained by subjecting the purified tar to a size such as distillation or heat treatment. Here, the pitch may be not only a pitch consisting only of isogenetic components but also a mesophase pitch.

When such a hydrogenated material is subjected to hydrogenation treatment, the hydrogen introduced into the hydrogenated material reduces the extremely high aromaticity of coal tar pitch and forms menphase pitch during subsequent heat treatment. By making the molecular weights of the components uniform and lower, a mesophase pitch with a low viscosity can be obtained.

Subsequently, the hydrogenated product is produced by mesophase 3
Heat treatment is performed at a temperature of 50 to 450°C. If the temperature is less than 350°C, no polycondensation reaction occurs, and if it exceeds 500°C, the generation of infusible coking substances is undesirable.

Prior to this heat treatment, removing low-molecular-weight components that are slow to convert to menphase through processes such as distillation and solvent extraction will reduce the amount of heating heat and shorten the time required to generate menphase pitch. This is a preferred embodiment in that it brings about effects such as shortening and the resulting reduction in the viscosity of the mesophase pitch.

For the same reason, it is also preferable to remove low molecular weight components by performing reduced pressure treatment or inert bubbling during the mesophasing heat treatment.

The mesophase ho-sochi obtained by kakushi has a low melt viscosity and good spinnability, and can be made into a small-diameter pitch yarn by ordinary melt spinning. This pitch yarn can be easily made into carbon fiber by performing known infusibility and sintering, and the obtained carbon fiber exhibits high elastic modulus and strength, which are characteristics of metsuphase pitch-based carbon fiber.

Next, Examples and Comparative Examples will be shown to further explain the method of the present invention.

(Example 1) Light trade oil with a boiling point of 230°C or less in coal tar is removed by simple distillation, and 50 parts by weight of cut tar containing 32% of quinoline solution is added with 50 parts by weight of coal tar having a boiling point of 56 degrees Celsius. Hereditary ingredients were blended and stirred at room temperature and pressure.

At this time, a dark brown granular solid precipitated. In order to separate this granular solid, the mixed liquid was run in a centrifugal separator with a centrifugal effect of 2000G for 1 minute, and a granulated precipitate was obtained at a yield of 80% based on the raw material, coal-based heavy oil. . Then, acetone was recovered from this supernatant by atmospheric distillation to obtain purified tar.

The obtained purified tar contained no nitrobenzene-insoluble matter.

The purified tar was distilled under reduced pressure to remove components having a boiling point of 500° C. or lower to obtain purified tar. 80 g of the Gitch and 80 g of Tetralin were placed in an autoclave with an internal volume of 500Ω,
1 at 430℃ under N2 atmosphere (initial pressure Okg/cm2・G)
Hydrogenation treatment was carried out by heating for hours.

Next, the hydrogenated product was distilled under reduced pressure to remove components having a boiling point of 500° C. or lower to obtain hydrogenated pitch. The properties of the hydrogenated pitch are shown in Table 1.

Table 1 Next, the hydrogenated pitch was heat-treated at 430°C for 4 hours, resulting in pitch having a menphase content of 80vol% and a viscosity of 120 poise at 350°C.

When the metsuphase pitch was spun at 350° C. using a fixed nozzle spinning machine having a 03φ nozzle, a pitch yarn with a diameter of 15 μm could be spun for a long time. The pitch yarn was heated to 280°C in air at a heating rate of 1°C/min and held for 30 minutes.

The protected carbon fibers were then heated at 1500'C4 at 1°C/min in an Ar atmosphere and held for 10 minutes, resulting in a tensile strength of 250 kL. /in2, tensile modulus 30 ton
It shows high strength and high elastic modulus of 7mm2.

(Comparative Example 1) In Example 1, light oil Cut 2 India was heated at 210°C.
Purified tar was obtained under similar conditions except that: The purified tar contained 0.5% nitrobenzene insoluble matter.

(Comparative Example 2) Purified tar was obtained under the same conditions as in Example 1 except that the blending ratio of acetone was 20% by weight. The purified tar contained nitrobenzene-insoluble matter. After the purified tar was hydrodistilled in the same manner as in Example 1, 43
When heat treated at 0℃ for 3 hours, the non-phase content was 79.
A pinch of vo1% was obtained. The pitch was spun at 350° C. in the same manner as in Example 1, but spinning was not possible. Also, 3
Even at 70°C, a pitch yarn with a diameter of 30μ could only be spun for a short time.

(Example 2) In Example 1, purified pitch was hydrogenated, but a test in which mesophase pitch was hydrogenated was attempted. That is, when the purified pitch of Example 1 was heat-treated at 430° C. for 3 hours, pitch with a menphase content of 80% was obtained. 80g of the menphase pitch and 160g of tetralin
into an autoclave with an internal volume of 500 cc (2) H2
2 Heating to 450℃ at an initial pressure of 5kg/crn2・G, 6
Hydrogenation treatment was carried out by holding for 0 minutes.

When the hydrogenated product was held at 380° C. for 2 hours, pitch with a mesophase content of 85 inches was obtained.

As a result of spinning the pinch yarn at 330°C, a pinch yarn with a diameter of 15 μm could be spun for a long time.

(Example 3) Direct hydrogenation was attempted. That is, purified pitch 10 of Example 1
01/ and 5 g of sulfurized Co-Mo catalyst with an internal volume of 50
Pour into a 0 cc autoclave and set the H2 initial pressure to 100
The mixture was heated at 430° C. for 1 hour using k17 /an2·G for hydrogenation.

The hydrogenated product was extracted with 5 times the amount of quinoline at 80° C. for 30 minutes, and after centrifugation at 2000 G for 1 minute, the supernatant was separated.

The supernatant liquid was distilled under reduced pressure to remove components with a boiling point of 500° C. or lower to obtain hydrogenated pitch.

The hydrogenated pitch was then heat treated at 380° C. for 40 hours, resulting in a pitch with a menphase content of 60%.

The menphase pitch could be spun for a long time at 340° C., and a large amount of pitch yarn with a diameter of 12 μm was obtained.

Claims (1)

[Claims] (1) Coal tar with a boiling point of 270°C to 220°C and light and medium oils removed,
Mix the carbonaceous solvents at 0℃υ to 30 to 60% by weight in the total mixture, remove the insoluble precipitates generated in the mixed solution, and remove the mixed solution after removing the insoluble precipitates. to obtain purified tar by removing the ketone solvent from
The pitch obtained by distilling or heat treating this purified tar or its purified cool is subjected to hydrogenation treatment, the pitch component is separated from the hydrogenated product to obtain hydrogenated pitch, and this hydrogenated pitch is heat treated. Then, the mesophase pitch is obtained by melt-spinning the mesophase pitch.
A method for producing high modulus carbon fiber characterized by infusibility and firing.