JPH0431491A - Manufacture of clean carbonaceous pitch - Google Patents

Abstract

PURPOSE:To get rid of structural defect due to ash present in pitch and to obtain clean pitch by filtering a carbonaceous pitch through a specified tubular filter to remove ash. CONSTITUTION:A filter 2 is formed by attaching tubular filters 7 to a partition 8 which divides the interior of a casing 6 comprising a high-pressure vessel into two chambers, wherein the filter 7 is made by laminating a number of etched discs 10 having a through hole in the center and provided around the circumference with many petallike sections 9 having porous grooves 11 which have pores of 0.1-10mum in diameter and are densely arranged in lines in the peripheral part with a spacer put between the discs 10. After raising the pressure to 1-100kgf/cm<2> by a pump 2, a carbonaceous pitch having a viscosity of 0.05-90Pa.s is pumped into the lower part of the casing 6, filtered through the porous grooves 11, passed through a vertical hole 12, and discharged from the upper side of the partition 8 into the upper part of the casing 6, thus giving a carbonaceous pitch having an Fe content of 2ppm or less, an Al content of 1ppm or less, an Si content of 3.3ppm or less, and a total content of Fe, Al, and Si of 5ppm or less. After a certain period of time, high-pressure gas at 1-100kgf/cm<2> is blown into the casing 6 from the top to perform back washing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing clean carbonaceous pitch suitable for producing carbon materials, particularly high-performance carbon fibers.

[Conventional technology]

BACKGROUND ART Conventionally, there has been a demand for the development of high-performance materials having light weight, high strength, high elastic modulus, etc. in various industrial fields such as automobiles, aircraft, and others, and carbon molding materials, carbon fibers, etc. have been attracting attention from this viewpoint.

In particular, the method of manufacturing carbon fiber from carbonaceous pitch is considered important as a method for manufacturing inexpensive and high-performance carbon fiber, and much research has been conducted in recent years, and the performance of carbon fiber obtained from carbonaceous pitch has been has also improved.

However, since pitch fibers obtained from carbonaceous pitch are extremely fragile, many measures have to be taken in handling the yarn in subsequent processes.

Furthermore, in recent years, it has become increasingly clear that the amount of ash remaining in carbonaceous pitch has an extremely large effect on yarn breakage when spinning pitch fibers from carbonaceous pitch and on the physical properties of the final product, carbon fiber. As the number of carbonaceous pitches increases, obtaining clean carbonaceous pitch with low ash content has become an important issue.

As a method to remove ash from carbonaceous pitch.

Due to its ease of use, a method of centrifuging raw tar, which is a raw material for producing carbonaceous pitch, to reduce the ash content in the tar to 0.005% by weight (50 ppm) or less (Japanese Patent Laid-Open No. 5
8-81619) and raw material tar at 50 to 200℃.
A method in which the ash content is removed through an electrostatic precipitator by heating to a temperature of Publication No.) has been disclosed.

On the other hand, a method for directly removing ash from carbonaceous pitch is to centrifuge carbonaceous pitch under high centrifugal force (
Japanese Unexamined Patent Publication No. 60-34619) has been proposed.

[Problem to be solved by the invention]

However, in the method of removing ash from raw material tar, even if the ash content is reduced to, for example, 10 ppm (0,001%), the ash content is reduced to approximately 10 to 100% during the pitch manufacturing process.
It has the disadvantage that it accumulates about 90 times as much and rises to 100 to 900 ppm, and there is also the problem that metal flakes off and gets mixed in due to corrosion or abrasion of reaction vessels, piping, etc. On the other hand, the method of directly removing ash from carbonaceous pitch has the disadvantage that since carbonaceous pitch is a highly viscous substance, it is difficult to remove fine particles and it is difficult to reduce the ash content. Therefore, the residual ash in the pitch after ash removal treatment is
Usually it was about 50 ppr.

In the process of developing carbon fibers with even higher strength and higher modulus, the present inventors discovered that even if the ash content in the pitch was about 50 ppm, it could cause structural defects, especially 2.
It has been found that when high-temperature firing is performed at 000°C or higher, it is difficult to develop strength due to the formation of pores in the fibers.

In addition, in order to develop higher strength, simply increase the ash content by 50%.
It was found that it is not sufficient to reduce the ash content to less than ppm, and that certain elements in the ash have a large effect on the development of strength.

Therefore, in order to eliminate structural defects caused by the ash content in carbonaceous pitch and obtain ultrahigh strength carbon fibers, it has been desired to develop a new ultraclean carbonaceous pitch.

In order to solve these problems, the present inventors previously proposed a method for producing ultra-clean carbonaceous pitch in which carbonaceous pitch is filtered using a sintered metal filter (
(Japanese Patent Application No. 2-79827), it was found that this method has the drawback that the rate of filtration of carbonaceous pitch is slow.

Therefore, it is an object of the present invention to overcome these problems, that is, to provide an extremely low content of specific elements in the ash.
It is an object of the present invention to provide a method for rapidly producing clean carbon pitch by which high-performance carbon fibers can be stably obtained.

[Means to solve the problem]

The above objects are achieved by a method for producing clean carbonaceous pitch according to the present invention.

That is, according to the present invention, carbonaceous pitch containing ash is made of a laminate of etched disks having elaborate pore grooves in a temperature range where the viscosity is from 0.05 Pa-s to 90 Pa-s. Provided is a method for producing clean carbonaceous pitch for carbon materials, characterized in that ash content in the carbonaceous pitch is removed by filtration using a cylindrical filter.

The filtration treatment in this case is carried out under an inert gas atmosphere and at a filtration pressure of 1 to 100 kgf/cm''.

Various shapes of etched disk laminates are used, such as a petal-shaped circular shape, a square shape, and a pleated shape, but the petal-shaped one has a large filtration area compared to the size of the filtration container. preferable.

The petal-shaped etched disk laminate is composed of a stack of etched disks having a large number of petal-shaped parts on the periphery, and the petal-shaped part has a hole in the center through which filtered waves flow, and a solid layer around it. A large number of sophisticated 0.5-1 to filter and separate particles
It has pore grooves of 0μ group. If you use a filter like this.

When placed in a filtration container of the same capacity, the filtration area of the filter can be increased, so the throughput of filtration can be significantly increased, and it is less likely to become clogged.

Through the filtration process using this filter, the ash content in the carbonaceous pitch can be removed, and the Fe content is 2 ppm or less, the Al content is 1 ppm or less, and the Si content is 3.3 ppm or less. The total amount of
An ultra-clean pitch suitable for manufacturing carbon materials with m+ or lower F is rapidly produced.

Note that the Fe content, Al content, and Si content herein are values determined by the following method. That is, the sample pitch is treated with concentrated sulfuric acid, heated and carbonized, and then incinerated at 755±25°C. After melting this ash with sodium carbonate, it is dissolved with hydrochloric acid and water to obtain a sample solution. For this sample solution, the luminescence intensity of each element of Fe, Al, and Si was measured using an inductively coupled plasma emission spectrometer (ICP emission spectrometer), and the concentration of each element in the sample was determined from a calibration curve prepared in advance. were determined, and these were defined as the Fe content, Al content, and Si content, respectively. As the ICP emission spectrometer, a sequential type "rIcPs-1000" manufactured by Shimadzu Corporation was used.

As mentioned above, the carbonaceous pitch obtained by the production method of the present invention has an Fe content of 2 ppm or less and an Al content of 1 ppm.
It is preferable that the ash content is 3.3ppm or less, and the total amount of F8 content, Al content and Si content is 5PP- or less, but the majority of these ash contents are particles with a particle size of 0.
．． It exists as particles of 17a or smaller. Due to such a low content of the above elements, when carbon fibers are produced from the carbonaceous pitch obtained in the present invention according to conventional methods, structural defects in the carbon fibers due to the above elements in the pitch are eliminated, resulting in ultra-high strength. carbon fibers can be obtained stably and easily. The ash content usually contains trace amounts of Ni, Cr, etc. in addition to the Fe, Al, and Si components described above, but as mentioned above, if the Fe content is 2 ppm or less and the Al content is is lP
By setting the P- and Si contents to 3.3 ppm or less, and the total amount of Fe, Al, and Si to 5 ppm or less, high-performance carbon materials, especially carbon with ultra-high strength and high elastic modulus, can be produced. An ultra-clean carbonaceous pitch from which fibers can be produced is obtained.

Furthermore, Fe'J in the pitch is 0.8 ppm or less, Af
It is particularly preferable that 1 minute is 0.5 ppm or less, the Si content is 1.4 ppm or less, and the total amount of Fe, Al, and Si is 2 ppm or less.

In addition, if carbon fibers are manufactured using carbonaceous pitch in which the total amount of Fe content, 0 content, and Sj content exceeds 5 ppm, defects will occur inside the carbon fibers, and carbon fibers with sufficient high strength will not be obtained. In particular, in the case of high-temperature firing of 2,000° C. or higher, the development of strength decreases. Also, although the reason is not clear,
Even if only the Fe content exceeds 2 ppm, strength development is not sufficient. Similarly, if only the Al content exceeds 1 ppm or only the Si content exceeds 3.3 ppm, the strength will not be sufficiently developed.

In order to produce high-performance carbon materials, especially carbon fibers with ultra-high strength and high elastic modulus, the Fe content is 2 ppm or less, the Al content is 1 ppm or less, and the Si content is 3.3 ppm or less, as described above. Furthermore, it is necessary that the pitch be an ultra-clean carbonaceous pitch containing elements below a specific value, such as a total amount of Fe, Al, and Si of 5 ppm or less.

The raw material carbonaceous pitch used in the present invention is a known starting material,
For example, mesophase pitch (optically anisotropic pitch), membrane pitch made from aromatic hydrocarbons, pitch containing an optically anisotropic phase and an optically isotropic phase, or optically isotropic pitch. For example, when producing ultra-high-strength, high-performance carbon fiber from mesophase pitch obtained by pyrolysis polycondensation, the mesophase content is 70%.
~100% mesophase pitches are preferred, particularly mesophase pitches containing substantially 100% mesophases are most preferred.

When producing mesophase pitch by thermally decomposing and polycondensing starting raw materials such as tar, increasing the content of the optically anisotropic phase increases the softening point of the resulting mesophase pitch. Although the spinning temperature inevitably increases,
This makes spinning difficult and prone to yarn breakage.

Therefore, in the production of menface pitch, thermal polycondensation is stopped halfway and the polycondensate is reduced to 350 to 400%.
The optically anisotropic phase (hereinafter referred to as AP phase) with high density is deposited while growing and maturing in the lower layer, and this is deposited in the optical anisotropic phase with lower density in the upper layer. It is preferable to adopt a method in which the isotropic phase (hereinafter referred to as IP phase) is separated from a larger portion and taken out. Details of this method are described in JP-A-57-119984.

A more preferable method for producing mesophase pitch is as described in JP-A-58-180585.
The carbonaceous pitch, which contains a suitable amount of phase and has not yet become excessively heavy, is subjected to a centrifugation operation in a molten state to quickly obtain A.
This is a method in which the P phase portion is allowed to settle.

According to this method, the AP phase accumulates in the lower layer (layer in the direction of centrifugal force) while coalescing, and the AP phase forms a continuous layer with approximately 80% or more of the AP phase, and a small amount of the IP phase is present in the crystalline or The pitch is dispersed in tiny spherical bodies. In this case, the boundary between both layers is clear, the lower layer can be separated from the upper layer, and the AP phase content is high and the softening point is low.
Therefore, membrane pitch that is easy to spin can be produced. According to this method, membrane pitch having an AP phase content of 95% or more and a softening point of 230°C to 320°C can be obtained economically in a short time.

The mesophase pitch obtained in this way has a low softening point despite its homogeneity and high orientation, and therefore has essentially excellent melt spinning properties. However, even when such pitch is used, yarn breakage and fluffing occur during spinning, but this is caused by wear of the catalyst and equipment already mixed in the raw material for producing pitch,
This is largely due to foreign matter that gets mixed in due to corrosion, etc.

In the present invention, the raw material carbonaceous pitch has a viscosity of 0,0
In a temperature range of 5-90 Pa-s, filtration is performed using a filter made of a stack of etched disks with elaborate pore grooves.
The filtration process is carried out using a filter with a diameter of 10 to 10, under an inert gas atmosphere and at a filtration pressure of 1 to 100 kgf/cm''.

As for the shape of the etched disk laminate, various shapes can be used as described above, but a petal-shaped one is preferably used because it can provide a large filtration area.

The petal-shaped etched disk stack will be explained with reference to the drawings. In FIG. 1, the liquid discharged from the pitch storage tank 3 is pressurized by the pump 5 and is supplied to the bottom of the filtration device 2. This filtration device is, for example, a device called Barakotilter (trade name), and is formed by housing several cylindrical filters 7 in a casing 6 made of a high-pressure container, as shown in FIG. That is, the inside of the casing 6 is formed into two upper and lower chambers via the partition plate 8, and each cylindrical filter 7
is attached hanging down with its upper end fixed to the partition plate 8. These cylindrical filters 7 include an etched disk 10 made of a thin metal plate made of stainless steel, copper, or brass (preferably stainless steel) and having a large number of petal-shaped parts 9 on the periphery as shown in FIG. , in Figure 4 (a) (b) (
(Cross-sectional view of the cylindrical filter at the A-A position in Fig. 3)
As shown in the figure, after stacking a large number of sheets with spacers in between and applying a bottom plate to the lower end, a central shaft with a hexagonal cross section is tightened into a hexagonal hole in the center to form an integral columnar shape. In this case, the petal-shaped portion 9 of each disk has a through hole in the center except for the peripheral part, and the peripheral part has fine pore grooves 11 of 1 to 5 pa formed by etching arranged in dense rows. ing. Therefore, as shown in FIGS. 4(a) and 4(b), vertical holes 12 are formed in the etched disk laminate formed in the above manner by the central through-holes of the upper and lower petal-shaped portions 9, respectively. , filtration holes are assembled by the fine pore grooves 11 surrounding these vertical holes 12. That is, this laminate acts as a cylindrical filter.

With this configuration, the raw material liquid that is press-fitted from below the casing 6 is filtered through the filter holes formed by the respective small grooves 11 as shown in FIG. After a certain period of time has elapsed, high pressure gas such as nitrogen gas (1 to 100 kgf/cJG) is blown into the casing 6 from above to backwash it as shown in Figure 4(b). By doing this, the clogging of the filter holes is removed. In FIG. 1, 13 is a nitrogen gas inlet pipe, 14 is a discharge valve for the blown gas, and 16 is a deposited particle outlet.

Etched disks having elaborate pore grooves forming a laminate can be manufactured by a known photoresist method, etc. The pore grooves of the etched disk have a hole diameter of 0.1 to 10. However, if the pore size exceeds 10 pm,
There is a problem that the ash trapping efficiency decreases, and conversely, if the pore diameter is less than 0.1 μm, manufacturing becomes difficult.

Clean carbonaceous pitch can be obtained by performing one stage of filtration treatment on the raw material carbonaceous pitch using the filter, but when obtaining even cleaner pitch, using the filter with a small pore size, This is achieved by performing a filtration operation in two or more stages.

The first stage filter has a pore size of 0.1 to 1
0. The above filter is used. The second stage filtration filter has a pore size of 0.1 to 10. Pitch containing ash is passed through a filter for at least 1 to 3 hours or more in advance, and the filter mesh is moderately clogged with fine ash particles. In addition, if you use a filter that has been used for 1 to 3 hours or more as the second stage filter and then use it as the third stage filter, you will be able to capture even finer particles and obtain a cleaner pitch. .

In this case, the first stage filtration treatment is 1 to 100 kgf#
Under pressure of j, under inert atmosphere, pitch viscosity is 0.0
It is carried out in the range of 5 to 90 Pa-8. In the case of mesophase pitch, it is usually preferable to carry out the reaction at a temperature of 300 to 400°C.

Further, the filtration treatment using the filter pre-coated with ash as described above is preferably carried out under an inert atmosphere, following the first stage filtration treatment, and with a pitch viscosity in the same range as the first stage.

In order to obtain ultra-clean carbonaceous pitch, two steps are usually carried out as described above.
Filtration processing is performed in more than one stage, but in order to increase the filtration speed, the first stage filter is

Each time the filter becomes clogged, it may be backwashed with high-pressure gas to perform filtration while regenerating the filter, and the downstream filter may be used as it is for a long time.

In order to increase the throughput, the -F flow filter should have a configuration in which at least two or more filters are installed in parallel, and two or more filters that have been pre-coated once as a filter for the lower limbs should be used. This can also be done by connecting them in parallel.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is of course not limited thereto.

Example 1 A heavy residual oil with a specific gravity of 0°992, a carbon content of 88.9% by weight, and a hydrogen content of 9.8% by weight, produced by the catalytic cracking of vacuum gas oil, was brought to normal pressure using a vacuum distillation apparatus. Distillation was carried out to 415° C. to obtain a residual tar with a yield of 73 weight.

The resulting tar residue has a specific gravity of 1.062 and a carbon content of 8.
9.1% by weight, hydrogen content 9.7% by weight, ash 0.22
% by weight (2,200 ppm), and the viscosity at 100° C. was 14.7 centistokes.

Put 20kg of this tar into a reactor with an internal volume of 30Q,
3. At 415°C with sufficient stirring under normal pressure nitrogen gas flow.
Heat treated for 5 hours, softening point 240℃, quinoline solubility 13
．． A yield of 23.0 wt. 9 wt. 2 pitch containing about 55% optically anisotropic phase as observed wt under a polarizing microscope was obtained.

This pitch is temperature-controlled at 350°C and a predetermined flow rate of 20-7 is transferred to a cylindrical continuous centrifuge with a rotor effective internal volume of 200-7.
While controlling the rotor temperature at 350° C., the liquid was continuously separated into a heavy liquid and a light liquid using a centrifugal force of 5.0 OOG. The yield of the pitch collected from the heavy liquid outlet was 51% by weight, the softening point was 268°C, the quinolinous content was 28.1% by weight, and the optically anisotropic phase observed with a polarizing microscope was 97%. The ash content in this liquid crystal pitch was 250 ppm.

The obtained mesophase pitch was introduced into a filtration device and filtered. As a filter, a cylindrical filter (manufactured by Pacco Industry Co., Ltd.) with a diameter of 120 mm and a length of 180 layers, which is made of stainless steel and is made of an etched disk laminate having elaborate pore grooves with a pore size of 5 mm, was used. processed.

The liquid crystal pitch obtained by separation using a centrifugal separator was introduced into a filtration device equipped with such a filter at a rate of about 4 kg/hour, and filtration was performed. The atmosphere was a nitrogen gas atmosphere, and filtration was performed under pressure with nitrogen gas. The pressure during filtration is 20kgf/a! I did it. The temperature during filtration was 340°C, and the viscosity of mesophase pitch was 9 Pa-
It was s.

F in the ultra-clean pitch obtained by filtration for 1 hour in this way
E content is 1.6ppm, Afi content is 0.4ppm, S
The i content was 3.0 ppm, and the total amount of the Fe content, 10 minute content, and Si content was 5.0 ppm.

The obtained ultra-clean menface pitch was filled into a spinning machine with a single-hole nozzle with a diameter of 0°3 fat layer, melted at a temperature of 335°C, extruded under nitrogen pressure, wound on a bobbin at the bottom of the nozzle, and then spun for 500 m. The yarn was spun at a take-off speed of /min. During spinning for 1 hour, the yarn did not break even once.

Next, this pitch fiber was made infusible at 230°C in an oxygen atmosphere for 1 hour, and then heated at a rate of 1.500°C at 20°C/min.
Carbonization was performed by raising the temperature to ℃ to obtain carbon fibers. The obtained carbon fiber had a fiber diameter of 10.0. , tensile strength 3, 3
GPa, and the tensile modulus was 260 GPa.

Furthermore, graphite fibers were obtained by firing to 2,500°C.

The obtained graphite fiber has a fiber diameter of 9.8-5 and a tensile strength of 3.6.
GPa and tensile modulus of 740 GPa, indicating extremely high quality.

Example 2 Mesophase pitch separated by a centrifuge was transferred to Example 1.
The same treatment as in Example 1 was carried out, except that the same filtration apparatus used in Example 1 was stacked in two stages in series for filtration.

As the first stage filter, a clean new cylindrical filter (manufactured by Bucco Industries) consisting of a stack of etched disks with five fine pore grooves is installed, and the second stage filter First, the membrane pitch was filtered in advance at a rate of about 4 kg/hour for 1 hour, and the fine ash in the membrane pitch was precoated on a cylindrical filter made of the same etched disk laminate as described above. I installed a filter. The filtration conditions for precoating the second stage filter were a temperature of 340°C and a pitch viscosity of 9 Pa-s. Filtration was performed by gradually increasing the pressure from near atmospheric pressure with nitrogen, and the final pressure was 20 kgf/d.
With such a filter configuration, the liquid crystal pitch obtained by centrifugation was introduced into the filtration device at an average rate of 4 kg/hour to perform filtration. The atmosphere was a nitrogen gas atmosphere, and filtration was performed under pressure with nitrogen gas. The temperature during filtration was 340° C., and the viscosity of the pitch was 9 Pa·S.

The differential pressure during filtration was 20 kgf/ai.

The Fe content in the ultra-clean pitch obtained in this way was 0.3p.
pm, 0.1ppm for 10 minutes, 0.5pp for Si
m, and the total amount of Fe, 10 and Si is 0.
It was 9pp-.

When the obtained ultra-clean mesophase pitch was spun in the same manner as in Example 1, there was no yarn breakage even once during spinning for 1 hour.

Carbon fibers obtained by firing to 1,500°C in the same manner as in Example 1 had an IR fiber diameter of 100 μm and a tensile strength of 3.5.
GPa, tensile modulus is 260 GPa, and 2,500
The graphite fiber obtained by firing to ℃ was of extremely high quality with a fiber diameter of 9.8 μl, tensile strength of 4.4 GPa, and tensile modulus of 750 GPa.

Comparative Example 1 The mesophase pitch (ash content 250 ppm) containing 99% optically anisotropic phase after centrifugation of Example 1 was processed in the same manner as in Example 1, except that it was spun as it was.

In this case, yarn breakage occurred 12 times per hour during spinning.

1. The tensile strength of carbon fiber obtained by firing at 500℃ is 2
．． 4GPa, tensile modulus is 250GPa, 2,
The tensile strength of graphite fiber obtained by firing at 500℃ is 1,
7 GPa, and the tensile modulus was 600 GPa. Compared to Example 1, the tensile strength was significantly lower and the tensile modulus was also lower.

Comparative Example 2 In place of the cylindrical filter of Example 2, which was made of an etched disk laminate with a diameter of 120 mm and a length of 1110 mm.

Example 2 except that a cylindrical sintered metal filter (pore diameter 0.3 pm) with a diameter of 120 + am and a length of 180 cm was used.
It was treated with two-stage filtration in the same manner as above.

In this case, due to the slow filtration rate, the pitch feed rate was reduced by an average of 0.4 kg/hr. In this case, the Fe content in the pitch after completing the second stage filtration is 1.6PPfi1
．． Al content is 0.4ppm+, Si content is 2.8ppm
And the Fe content.

The total amount of Aa and Si was 4.3 ppm.

Moreover, the ash content at this time was 5.9 ppm.

When the obtained pitch was spun in the same manner as in Example 1, there was no yarn breakage once per hour during spinning, which was good.

The carbon fiber obtained by firing to 1,500°C in the same manner as in Example 1 was 4111! Fiber diameter 10.0. m, tensile strength 3
．． 4GPa, tensile modulus of elasticity 260GPa, 2,
The yarn diameter of graphite fibers obtained by firing to 500°C is 9.8. ,
Tensile strength is 3.8GPa, tensile modulus is 740GPa
It was a.

〔Effect of the invention〕

Since the method of the present invention has the above-mentioned structure, the ash content, especially the content of specific elements, is extremely low. Therefore, when carbon fiber is manufactured using the ultra-clean pitch obtained by the method of the present invention, Carbon fibers with high strength and high modulus can be produced. In particular, when fired at high temperatures, defects within the fibers that were conventionally observed do not appear, and graphite fibers with ultra-high strength and high modulus of elasticity can be produced.

Moreover, according to the method of the present invention, such ultra-clean pitch can be filtered much more quickly than in conventional sintered metal filters, so a large amount of ultra-clean pitch can be obtained in a short period of time. I can do it.

As described above, carbon fibers and graphite fibers are manufactured from pitch obtained by the method of the present invention.

Since it has no defects and has the characteristics of high strength and high modulus of elasticity, it can be used extremely effectively as a reinforcing fiber for lightweight structural materials for automobiles, space development, buildings, etc.

Furthermore, the ultra-clean pitch obtained by the method of the present invention is
It can also be used as an excellent matrix material for carbon/carbon composite materials because it has no defects under high temperature firing.

Although the mesophase pitch system has been mainly described above, even when the pitch is optically isotropic, it has the advantage that defect-free general-purpose carbon fibers or other carbon materials can be manufactured.

Furthermore, when the pitch obtained by the method of the present invention is used, it has the advantage that the spinnability in the carbon fiber manufacturing process can be improved more than ever before.

[Brief explanation of drawings]

Fig. 1 shows a flow sheet for an example of the method of the present invention, Fig. 2 is a partially cutaway slope view of the filtration device, Fig. 3 is a plan view of the disk constituting the cylindrical filter, and Fig. 4 ( a
)(b) is an explanatory sectional view showing a part of the cylindrical filter at the position A in FIG. 3. 2... Filtration device, 3... Pitch storage tank, 6... Casing, 7... Cylindrical filter, 9... Petal shaped part,
10... Etched disk, 11... Pore groove, 13
...Nitrogen gas feed pipe.

Claims (4)

[Claims] (1) Carbonaceous pitch is filtered in a temperature range where the viscosity is from 0.05 Pa·s to 90 Pa·s using a cylindrical filter made of a stack of etched disks with elaborate pore grooves. A method for producing clean carbonaceous pitch for producing carbon materials, characterized by removing ash in the carbonaceous pitch. (2) The cylindrical filter made of a laminate of etched disks is made of a laminate of etched disks having a large number of petal-shaped parts on the periphery, and the petal-shaped part has a through hole in the center thereof through which filtering waves flow. The manufacturing method according to claim 1, characterized in that the method uses a material having a large number of pores around the pores for filtering and separating solid particles. (3) The Fe content in the carbonaceous pitch is 2 ppm or less, the Al content is 1 ppm or less, and the Si content is 3.3 ppm or less, by filtration treatment using a cylindrical filter made of a stack of etched disks, The manufacturing method according to claim 1 or claim 2, wherein the total amount of Fe, Al and Si is 5 ppm or less. (4) The manufacturing method according to claim (1), (2) or (3), wherein the carbonaceous pitch is mesophase pitch for manufacturing carbon fibers.