JPH06256767A - Optically isotropic pitch and its production - Google Patents

Abstract

PURPOSE:To obtain the subject pitch capable of shortening the infusibilization treating time by hydrogenating coal tar, etc., or its mixture with a heavy oil having lower aromaticity than that of the coal tar, etc., removing quinoline- insoluble components and then heat-treating the resultant pitch while blowing oxygen and ozone thereinto. CONSTITUTION:This method for producing optically isotropic pitch from coal tar and/or coal tar pitch as a raw material is to hydrogenate the coal tar and/or coal tar pitch or a mixture thereof with at least one of a heavy oil and pitch having lower aromaticity than that of the coal tar and/or coal tar pitch. The resultant hydrogenated substance is then added to the coal tar and/or coal tar pitch and primary quinoline-insoluble components are then removed from the obtained mixture. The obtained substance is subsequently heat-treated at 200-400 deg.C while blowing a gas containing oxygen and/or ozone thereinto. Thereby, the objective optically isotropic pitch having 0.910-0.975 aromaticity index and >=200 deg.C softening point thereof and capable of remarkably shortening the infusibilization time of pitch fiber in producing carbon fiber is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pitch containing an optically isotropic secondary quinoline-insoluble component and a method for producing the pitch. Such a pitch is suitable as a raw material for producing carbon fibers, because the pitch fiber after spinning can be easily infusibilized.

In this specification, the terms "%" and "parts" mean "wt%" and "parts by weight", respectively.

[0003]

2. Description of the Related Art When coal- or petroleum-based pitch is melt-spun, infusibilized, and fired to produce carbon fiber, the ratio of infusibilizing treatment cost to the production cost of carbon fiber is extremely high. Therefore, shortening the infusibilization processing time is extremely important for improving productivity and reducing manufacturing cost.

In particular, pitch fibers made of optically isotropic pitch as a raw material are more difficult to infusibilize than pitch fibers made of optically anisotropic pitch as a raw material. The infusibilizing treatment is carried out under various conditions, for example, by heating the pitch fiber in air at a predetermined temperature rising rate to about 200 to 350 ° C. and holding it for about 1 to 2 hours. There is.

However, such a method has a big problem that the time required for the infusibilizing treatment is long as described above.

Japanese Laid-Open Patent Publication No. 55-654 discloses a pitch fiber of 100 to 400 in an air atmosphere containing NO ₂ gas.
Disclosed is a method of shortening the infusibilization time by treating at inc. For 1 to 4 hours. However, since NO ₂ gas is toxic and corrosive, it causes new problems such as deterioration of working environment and corrosion of devices.

[0007]

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide a new method capable of shortening the infusibilizing treatment time of the pitch fiber.

[0008]

The inventors of the present invention have made extensive studies in view of the problems of the prior art as described above, and as a result, an optically isotropic pitch having new characteristics was used as a spinning raw material. It has been found that when used, the infusibilizing treatment time of the pitch fiber is significantly shortened.

That is, the present invention provides an optically isotropic pitch having the following new characteristics and a method for producing the same.

1. Pitch aromaticity index is 0.910
An optically isotropic pitch having a softening point of 200 ° C. or higher.

2. A method for producing optically isotropic pitch using coal tar and / or coal tar pitch as a raw material, comprising: (a) coal tar and / or coal tar pitch and heavy oil and pitch having a lower aromaticity than that. Hydrogenating a mixture with at least one of (b) coal tar and / or coal tar pitch,
The above is characterized in that after the primary quinoline insoluble component is removed from the mixture obtained by adding this to coal tar and / or coal tar pitch, it is heat-treated at 200 to 400 ° C. while blowing a gas containing oxygen and / or ozone. Item 2. A method for producing an optically isotropic pitch according to Item 1.

The optically isotropic pitch suitable as a raw material for producing carbon fibers according to the present invention has an aromaticity index of 0.910.
~ 0.975 (more preferably 0.920 to 0.975
And a softening point of 200 ° C. or higher (more preferably about 200 to 320 ° C.).

In particular, the aromaticity index is 0.910 to 0.9.
The characteristic of being 75 was not found in the conventional pitch as a raw material for producing carbon fibers, and in this range, the infusible treatment time of the pitch fiber can be shortened. It was first discovered by.

In producing the carbon fiber, the optimum oxygen uptake amount of the pitch fiber at the time of infusibilization is 7 to
It is about 13%.

When the aromaticity index of pitch is less than 0.910, it means that the pitch molecule contains a large amount of an aliphatic compound, a naphthene compound, etc., and a small amount of a condensed polycyclic aromatic compound. According to the research conducted by the present inventor, the higher the amount of aliphatic compounds and naphthenic compounds, the higher the oxygen uptake rate and the amount thereof increases, but the degree of condensation of polycyclic aromatic compounds is low, so that fusion Will be more likely. Therefore, when a pitch having an aromaticity index of less than 0.910 is used, even if the oxygen uptake amount of the pitch fiber is within the above range, infusibilization is not completely performed and the strength of the carbon fiber is descend. On the other hand, when the aromaticity index of the pitch is higher than 0.975, the oxygen uptake rate becomes low, so in order to obtain a predetermined oxygen uptake amount, it is necessary to lengthen the infusibilization treatment time. It becomes difficult to achieve the object of the present invention of shortening the infusibilizing treatment time.

Further, the higher the temperature, the faster the uptake amount of oxygen in the infusibilization of the pitch fiber progresses. Therefore, when the softening point of the pitch is too low, the initial temperature in the infusibilization treatment should be lowered. And the rate of temperature rise must be limited. In other words, if the softening point of the pitch is too low, when the initial temperature in the infusibilizing process is high or the temperature rising rate is fast, the pitch fiber melts or loses its fiber shape by melting. Sometimes. Therefore, the melting point of the pitch is preferably high. However, if the softening point of the pitch is too high, it is necessary to raise the melting temperature of the pitch during spinning, which makes spinning difficult. In consideration of these conditions, the softening point of the pitch in the present invention is 200 ° C. or higher, and more preferably about 200 to 320 ° C.

In the method for producing an optically isotropic pitch according to the present invention, the raw material to be subjected to the heat treatment is (a) coal tar and / or coal tar pitch and heavy oil having a lower aromaticity than that of Or a mixture with pitch (hereinafter referred to as raw material-1) and a mixture of (b) hydrogenated coal tar and / or coal tar pitch with coal tar and / or coal tar pitch (hereinafter referred to as raw material-2) is there.

Coal tar and / or coal tar pitch usually has an aromaticity index of about 0.975 to 0.980. The less aromatic heavy oil and / or pitch to be mixed with coal tar and / or coal tar pitch to prepare feed-1 does not contain quinoline insolubles and has an aromaticity index of 0. 950 or less,
Boiling point is about 200 ° C. or higher. Representative examples of such heavy oils and pitches include petroleum-based heavy oils, petroleum-based pitches, ethylene bottom oils, ethylene bottom oil pitches, and at least one of them is used. The mixing ratio of coal tar and / or coal tar pitch with heavy oil and / or pitch is such that the softening point and aromaticity index of the optically isotropic pitch obtained after the heat treatment of the mixture described below have predetermined values. There is no particular limitation as long as it is selected.

Hydrogenated coal tar and / or coal tar pitch is coal tar and / or
Or raw material prepared by mixing with coal tar pitch-2
May be used. The mixing ratio of this hydride with coal tar and / or coal tar pitch is also selected so that the softening point and aromaticity index of the optically isotropic pitch obtained after the heat treatment of the mixture have predetermined values. However, it is not particularly limited.

The method of the present invention is carried out as follows. After removing the primary quinoline-insoluble component in the raw material-1 or raw material-2, heat treatment is performed at 200 to 400 ° C. while blowing a gas containing oxygen and / or ozone to obtain a desired optically isotropic compound. Get the pitch. The removal treatment of the primary quinoline-insoluble component is performed by the raw material-1 and the raw material-
It may be performed in advance for each of the two types of materials that compose 2. The amount of gas blown into the raw material may be determined according to the properties of the raw material, the desired properties of the pitch, etc. Generally, 1 kg of the raw material is about 0.01 to 5 l / min as oxygen or ozone, and more preferably 0. .1 to 3
It is about 1 / min.

[0021]

When the optically isotropic pitch according to the present invention is used as a raw material for producing carbon fiber, the infusibilizing treatment time of the pitch fiber can be significantly shortened, so that the production cost of carbon fiber can be reduced. Is significantly reduced.

[0022]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention.

Example 1 Coal tar was filtered at 180 ° C. to remove the primary quinoline insoluble component in the coal tar, and then the low boiling point component was removed by vacuum distillation to give a softening point of 8
An optically anisotropic pitch (A) having an aromaticity index of 0.969 was obtained at 1.2 ° C.

Next, 85 parts of the pitch (A) described above was mixed with 15 parts of petroleum-based third-class heavy oil having an aromaticity index of 0.336 containing no free carbon to prepare a raw material-1 and 500 g thereof was added. It was charged in a 1 liter reactor and heat-treated at 330 ° C. for 260 minutes while blowing air at a rate of 5 l / min to give an optically isotropic pitch having a softening point of 280.3 ° C. and an aromaticity index of 0.953. Obtained.

After the above-mentioned optically isotropic pitch is spun to obtain a pitch fiber, the pitch fiber is heated in air from room temperature to 300 ° C. at a temperature rising rate of 5 ° C./min.
The temperature was raised to 0 ° C., the temperature was maintained for 90 minutes, and then the device was taken out of the apparatus.

The oxygen uptake amount of the pitch fiber after the infusibilization treatment was 8.8%, the fibers were completely infusibilized, and the fusion of the fibers was not observed during the firing described below. It was

The infusible fiber thus obtained was fired in a nitrogen atmosphere at 1000 ° C. for 10 minutes, and the tensile strength of the fiber thus obtained was measured. As a result, it was 96.6 kg / mm.
^{Was 2} .

Comparative Example 1 500 g of the pitch (A) obtained in Example 1 was charged in a 1 liter reactor and heat-treated in the same manner as in Example 1 to obtain a softening point of 281.3 ° C. and an aromaticity index of 0.982. To obtain an optically isotropic pitch (B).

The above-mentioned optically isotropic pitch (B) was spun in the same manner as in Example 1 and subjected to infusibilization treatment. The oxygen uptake amount of the pitch fiber after the treatment was 4.6. %, And the infusibilization of the fiber was insufficient.

When the infusible fiber thus obtained was fired in the same manner as in Example 1, the fibers were fused,
The strength could not be measured.

Comparative Example 2 With respect to the pitch fiber obtained in Comparative Example 1, in order to obtain an oxygen uptake amount (8.6%) which is almost the same as that of Example 1, in the infusibilizing treatment, the temperature was changed from room temperature in air to room temperature. 300
It was necessary to raise the temperature to 300 ° C. at a temperature rising rate of 5 ° C./min and hold the same temperature for 180 minutes.

The tensile strength of the carbon fiber obtained by firing the obtained infusible fiber in the same manner as in Example 1 was 83.1.
It was kg / mm ² .

Example 2 Ethylene bottom oil was distilled to obtain an optically anisotropic pitch (C) having a softening point of 83.1 ° C. and an aromaticity index of 0.766.

45 parts of the pitch (A) and 55 parts of the pitch (C) obtained in Example 1 were mixed and heat-treated in the same manner as in Example 1 to obtain a softening point of 279.4 ° C. and an aromaticity index. An optically isotropic pitch (D) of 0.923 was obtained.

The obtained pitch (D) was spun in the same manner as in Example 1, subjected to infusibilization treatment and fired to obtain oxygen fibers. The oxygen uptake amount of the pitch fiber after the infusibilization treatment was 11.2%, and the tensile strength of the carbon fiber after firing was 82.1 kg / mm ² .

Example 3 5 parts of asphalt having an aromaticity index of 0.286 and containing no quinoline insoluble component and the pitch (A) 95 obtained in Example 1
The mixture with the parts was heat treated in the same manner as in Example 1 to obtain an optically isotropic pitch (E) having a softening point of 281.3 ° C. and an aromaticity index of 0.968.

The obtained pitch (E) was spun in the same manner as in Example 1, subjected to infusibilization treatment, and fired. The oxygen uptake amount of the pitch fiber after the infusibilization treatment is 7.9.
%, And the tensile strength of the carbon fiber after firing was 73.
It was 6 kg / mm ² .

Comparative Example 3 A mixture of 85 parts of pitch (A) obtained in Example 1 and 15 parts of asphalt containing no quinoline-insoluble component was heat treated in the same manner as in Example 1 to obtain a softening point of 280.1 ° C. An optically isotropic pitch (F) having an aromaticity index of 0.902 was obtained.

The obtained pitch (F) was spun in the same manner as in Example 1, subjected to infusibilization treatment, and fired. The oxygen uptake amount of the pitch fiber after the infusibilization treatment is 14.
Although it was 6%, a part of fusion was recognized in the carbon fiber after firing, and its tensile strength was 22.1 kg / mm ² .

Claims (2)

[Claims] 1. A pitch aromaticity index of 0.910-0.
An optically isotropic pitch having a softening point of 200 ° C. or higher. 2. A method for producing optically isotropic pitch using coal tar and / or coal tar pitch as a raw material, comprising (a) coal tar and / or coal tar pitch and aromaticity lower than that. A mixture with heavy oil and at least one of pitches or (b) coal tar and / or coal tar pitch was hydrogenated and the primary quinoline insoluble component was removed from the mixture of coal tar and / or coal tar pitch. After that, while blowing a gas containing oxygen and / or ozone,
The method for producing an optically isotropic pitch according to claim 1, wherein the heat treatment is performed at 200 to 400 ° C.