JPH058960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing optically anisotropic small spheres in high yield with controlled particle size.

<Prior art and its problems> When Pits are heat-treated, the polycondensation reaction becomes active as the heat treatment progresses, a huge polycyclic aromatic compound is produced, and optically anisotropic spherules are precipitated from the Pits matrix. It is well known to do so.

The optically anisotropic small spheres are also known as graphite precursors and still have high chemical reactivity, so they can be used as binderless isotropic high-density carbon materials.
It is expected to be used as a raw material for carbon materials such as column packing materials for liquid chromatography.

Conventionally, the production of optically anisotropic small spheres has been carried out using pitches such as tar pitch or heavy petroleum oil.
This was done simply by heat treatment at a temperature of 500°C. However, according to this method, it is difficult to selectively produce optically anisotropic spherules with a high yield, and the yield is only about 30 vol% at most. In that case, it was extremely low at 10 vol%.

As a result of studies to eliminate this drawback, the inventors of the present invention have developed a solvent fractionation method using an aromatic solvent, using pitts containing no free carbon obtained by heat treatment or a combination of heat treatment and hydrogenation treatment as raw materials. After that, the separated solvent-soluble and solvent-insoluble components are recombined in various ratios, or the pitch from which the specific components have been separated is reheated at a temperature slightly lower than the heat treatment described above to achieve a high yield. He discovered that it was possible to produce optically anisotropic small spheres and filed a patent application (Japanese Patent Application No. 278,808/1982).

However, although it was possible to produce optically anisotropic small spheres in high yield according to this method, it was difficult to control the particle size.

As a result of further studies to solve the problems in the patent, the inventors of the present invention found that it is possible to obtain benefits by selecting the above-mentioned recombined pitch or pitch in which specific components are separated, and by selecting a cooling period while stirring after heat treatment. The present invention was based on the discovery that the particle size of the optically anisotropic small spheres can be controlled.

<Object of the Invention> The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide a method for producing optically anisotropic small spheres with a controlled particle size at a high yield.

<Structure of the Invention> The present invention uses pits containing no free carbon obtained by heat treatment or a combination of heat treatment and hydrogenation treatment as a raw material, and uses aromatic solvents to separate them into solvent-soluble components and solvent-insoluble components. Then, the separated solvent-soluble components and solvent-insoluble components are blended again with different ratios, and reheated with stirring at the heat treatment temperature or a temperature range 200°C lower than this to form optically anisotropic spherules. Provided is a method for producing optically anisotropic small spheres, characterized in that the particle size of the small spheres to be formed is controlled by selecting the temperature at which the reheated product is cooled while stirring after forming. It is something to do.

The present invention also uses pitches that do not contain free carbon obtained by heat treatment or a combination of heat treatment and hydrogenation treatment as raw materials, and separates them into solvent-soluble components and solvent-insoluble components using an aromatic solvent. The product from which specific solvent fractionation components have been removed is heated to the above heat treatment temperature or 200℃.
After performing reheat treatment in a low temperature range of ℃ to generate optically anisotropic spherules, further heat treatment with stirring in the reheat treatment temperature range, and select a temperature at which the heat-treated product is cooled while stirring. The present invention provides a method for producing optically anisotropic small spheres, which is characterized by controlling the particle size of the small spheres produced.

The present invention will be explained in more detail below.

The present inventors believe that the formation of optically anisotropic spherules is due to the mutual dissolution between the giant polycyclic aromatic component (i.e., solute) and the Pitzi matrix (i.e., solvent) generated by heat treatment. From this point of view, we discovered a method for producing optically anisotropic spherules in high yield by recombination heat treatment of solvent fractionated components or heat treatment of specific fractionated components, and filed a patent application (Japanese Patent Application No. 59-278808). ).

However, as a result of further investigation, it was discovered that this mutual dissolution effect is strongly influenced by the viscosity, that is, the temperature, of the reheated material. In other words, the formation of optically anisotropic spherules is thought to occur due to the rearrangement of giant aromatic molecules during the cooling process after heat treatment of recombined pitches or pitches obtained by heat-treating specific fractionated components. .

Therefore, stirring is performed when reheating and cooling the reformulated pitch or heat-treated product of specific fractionated components to uniformly disperse the giant aromatic molecules that can form optically anisotropic spherules, and during the cooling process, the giant aromatic molecules are dispersed. The purpose is to control the particle size of the optically anisotropic small spheres produced by stopping stirring at a temperature at which the group molecules rearrange and allowing the mixture to cool.

If the temperature at which stirring is stopped during cooling is increased, the viscosity of the reheated product will be low and the rearrangement of the giant aromatic molecules will be easy, resulting in the formation of optically anisotropic spherules with a large particle size. On the other hand, if the stirring stop temperature is lowered, the viscosity of the reheated product will be high and rearrangement will be difficult and a large number of optically anisotropic small spheres with small particle sizes will tend to occur.

In the present invention, since the relationship between the stirring stop temperature and the particle size differs depending on the remixing pitch or the properties (viscosity) of specific fractionated components, optical anisotropy can be achieved by determining the relationship as necessary each time. control the particle size of the spherules.

In particular, if a specific solvent fractionation component is used, for example, a component that is soluble in a solvent with a weak dissolving power and a component insoluble in a solvent with a strong dissolving power is removed by using this type of solvent with different dissolving power. (In other words, a component consisting of a weak solvent-insoluble component and a strong solvent-soluble component)
has similar properties with a narrow molecular weight distribution, so the properties of the optically anisotropic structural components and the pittsch matrix are more homogeneous compared to the case where the solvent-fractionated components are re-blended. By uniformly dispersing the optically anisotropic tissue components, it is possible to produce optically anisotropic microspheres with smaller particle sizes.

First, the first invention of the present invention will be described.

Coal-based, petroleum-based, etc. pits treated with heat treatment or a combination of heat treatment and hydrogenation are used as raw materials, and the raw material pitches are subjected to solvent separation. Examples of solvents used for solvent fractionation include benzene, toluene, tetrahydrofuran, pyridine, and quinoline. Furthermore, tar-based solvents and the like can also be used.

Next, the solvent-soluble and solvent-insoluble components obtained by solvent fractionation are recombined. The blending ratio varies depending on the raw material pitch and the type of solvent used, and the blending ratio at which optically anisotropic spherules can be selectively generated in high yield under each condition is determined.

The pitches prepared in this manner are heat-treated at the above-mentioned temperature range or 200°C lower than that temperature, more preferably from 50°C to
Reheating is performed while stirring at a temperature 100°C lower to produce optically anisotropic spherules.

Optically anisotropic spherules can be produced more effectively if a reduced pressure treatment or an inert gas bubbling treatment is performed during the reheat treatment.

Subsequently, the mixture is cooled while stirring. During the cooling process, stirring is stopped at a temperature at which the appropriate viscosity is achieved, and the mixture is left to cool.

If the temperature at which stirring is stopped is too high, precipitation of the optically anisotropic phase will occur, and the optically anisotropic phase and isotropic phase will separate. Moreover, if it is too low, a mosaic-like structure will be generated.

Next, the second aspect of the present invention will be described.

The same raw material pitch as above is subjected to solvent fractionation using the same aromatic solvent, and specific solvent fractionation components are removed. Components that are soluble in solvents with relatively weak dissolving power,
Ingredients from which components insoluble in solvents with strong dissolving power have been removed,
In other words, a component consisting of a weakly solvent-insoluble component and a strongly solvent-soluble component is obtained.

This component is reheated at a temperature that is the same as or 200°C lower than the heat treatment temperature used to obtain the raw material pitch described above, preferably 50°C to 100°C lower, to produce optically anisotropic spherules. let

Furthermore, the reheated product containing the generated small spheres is heat treated at a temperature similar to the reheating temperature range while stirring.

This heated product is cooled while stirring, and the stirring is stopped at a temperature at which the appropriate viscosity is achieved during the cooling process.
Leave to cool. Small spheres can be effectively generated by performing a reduced pressure treatment or an inert gas bubbling treatment during the reheat treatment and the subsequent heat treatment. Compared to the first method, this second method has nearly homogeneous component properties, so that it can be uniformly dispersed by heat treatment and produce smaller optically anisotropic spherules.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

(Example 1) Tar pitch was hydrogenated using tetralin at a temperature of 430°C and further heat-treated at 490°C, and the pitch was used as a raw material pitch (BI = 89 wt%, QI = 25 wt%). When observed under a polarizing microscope, this raw material pitch exhibited an optically anisotropic structure over the entire field of view.

This raw material pitch was subjected to solvent fractionation using tetrahydrofuran (THF) and separated into tetrahydrofuran soluble fraction (THFS) and tetrahydrofuran insoluble fraction (THFI). Observation results using a polarized light microscope showed that THFS had an optically isotropic structure, whereas THFI exhibited an optically anisotropic structure over the entire surface.

This THFS, THFI is THFS/THFI=70/30
After mixing in the weight ratio of
The mixture was heated to 440°C to redissolve it.

Cool it as it is while stirring, cooling process 390
Stirring was stopped at 350°C, 320°C, and allowed to stand and cool to room temperature.

When observed with a polarizing microscope, approximately 40 vol% of optically anisotropic spherules were formed in each pitch, and when stopped at 390°C (see Figure 1), most of the particles had a particle size of 70 to 110.
(μm), 30 to 90 (μm) when stopped at 350°C, and 10 to 60 (μm) when stopped at 320°C (see Figure 2).

FIG. 3 shows the relationship between the stirring stop temperature and the average particle size of the optically anisotropic small spheres produced. It is clear that the particle size can be controlled to be small by lowering the temperature at which stirring is stopped (Comparative Example 1) In Example 1, when stirring was stopped at 440°C and left to stand and cool, an optically anisotropic structure was formed. The constituent components precipitated (see Figure 4).

(Comparative Example 2) In Example 1, when the stirring was continued until the pitch was just about to solidify, a mosaic-like structure was generated (see FIG. 5).

(Example 2) The raw material pitch in Example 1 was converted into pyridine soluble (PS) and pyridine insoluble (PI) using pyridine.
The solvent was separated. PS was an optically isotropic structure, and PI was an optically anisotropic structure.

After blending the PS and PI at a weight ratio of PS/PI = 70/30, the mixture was heated to 440° C. with stirring under a nitrogen atmosphere to redissolve it.

After cooling to 390°C, stirring was stopped and the mixture was allowed to stand and cool to room temperature.

When observed with a polarizing microscope, the particle size was 50 to 120.
(μm) optically anisotropic spherules were generated at 70 vol% (see Figure 6).

(Example 3) Using THFI in Example 1, the solvent was fractionated with pyridine, and the soluble fraction was separated from the insoluble fraction in tetrahydrofuran.
It was extracted as a pyridine soluble fraction (THFI-PS).

This THFI-PS was reheated at 440°C under nitrogen bubbling. Nitrogen flow rate is 0.1l/min-g-
It was set as pitch. After cooling to room temperature, observation using a polarizing microscope revealed that optically anisotropic spherules with a particle size of 10 to 50 μm were formed. The reheated product containing the small spheres was further heated under a nitrogen atmosphere to 440°C while stirring, and after cooling to 300°C, the stirring was stopped.
It was allowed to stand and cool to room temperature.

When observed with a polarizing microscope, optically anisotropic spherules with a smaller particle size of 2 to 10 μm were formed (see FIG. 7).

(Example 4) The reheat-treated product containing optically anisotropic small spheres with a particle size of 10 to 50 μm obtained by the reheat treatment of Example 3 was further heat-treated to 440° C. with stirring in a nitrogen atmosphere,
After cooling to 350° C., stirring was stopped and the mixture was allowed to cool, and optically anisotropic small spheres with a particle size of 8 to 20 μm were formed.

<Effects of the Invention> According to the present invention, it is possible to produce optically anisotropic small spheres of various particle sizes to a predetermined particle size (with controlled particle size) from pitches containing no free carbon with high yield. . Since the optically anisotropic small spheres produced according to the present invention have high reactivity, they can be used as raw materials for general carbon materials such as binderless isotropic high-density and high-strength carbon materials and fillers for liquid chromatography. can be expected to be used.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are photographs substituted for drawings showing the particle structure. FIG. 1 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Example 1. FIG. 2 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Example 1. FIG. 3 is a graph showing the relationship between the stirring stop temperature during cooling and the average particle size of the optically anisotropic small spheres produced. FIG. 4 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Comparative Example 1. FIG. 5 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Comparative Example 2. FIG. 6 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Example 2. FIG. 7 is a polarized light micrograph (200x magnification) of the optically anisotropic spherules obtained in Example 3.

Claims (1)

[Scope of Claims] 1 Pitches containing no free carbon obtained by heat treatment or a combination of heat treatment and hydrogenation treatment are used as raw materials, and separated into solvent-soluble components and solvent-insoluble components using an aromatic solvent, The separated solvent-soluble components and solvent-insoluble components are mixed again in different ratios, and reheated with stirring at the heat treatment temperature or a temperature range 200°C lower than this to produce optically anisotropic spherules. A method for producing optically anisotropic small spheres, characterized in that the particle size of the formed small spheres is controlled by selecting a temperature at which the reheated product is cooled while stirring. 2 Pitches that do not contain free carbon obtained by heat treatment or a combination of heat treatment and hydrogenation treatment are used as raw materials, and are separated into solvent-soluble components and solvent-insoluble components using an aromatic solvent. The product from which the solvent fractionation components have been removed is heated to the above heat treatment temperature or 200°C below this temperature.
After performing reheat treatment in a low temperature range to generate optically anisotropic spherules, further heat treatment with stirring in the reheat treatment temperature range, and selecting a temperature at which the heat-treated product is cooled while stirring. A method for producing optically anisotropic spherules, characterized by controlling the particle size of the spherules produced.