JPS61236605A - Preparation of expanded graphite - Google Patents

Abstract

PURPOSE:To prepare inexpensively and in large amt. expanded graphite which is useful as a material for graphite sheet, etc. by heating raw material pitch, to obtain carbonaceous mesophase, to make a graphite from the mesophase and then oxidizing in the wet state. CONSTITUTION:Heat-treated pitch contg. optically anisotropic carbonaceous mesophase in a raw material pitch is obtd. by heating the raw material pitch (e.g. coal tar pitch) at 350-500 deg.C in inert gas atmosphere. 1pt.wt. said heat- treated pitch is mixed with 0.3pts.wt. org. solvent (e.g. quinoline) and stirred separating the carbonaceous mesophase alone. Unnecessary components are removed by repeating the procedure >=2 times at high temp. Obtd. carbonaceous mesophase is graphitized at 2,400-3,100 deg.C to obtain graphitized product, >=10pts. wt. of which is mixed with a mixture of 9pts.wt. H2SO4 and 1pts.wt. HNO3 and the mixture is oxidized in the wet state at >=50 deg.C for >=2hr.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing expanded graphite, and more specifically, it relates to a method for producing expanded graphite, and more specifically, to a method for producing expanded graphite. The present invention relates to a method for producing expanded graphite using the present invention.

(Prior Art) Expanded graphite is generally produced by oxidizing graphite and firing it. As the graphite, flaky graphite, which is natural graphite, is used, and it is known that when flaky graphite, which has a particularly developed graphite crystal structure, is used, its volume expands several hundred times due to the above-mentioned treatment.

As graphite still has a structure similar to single crystal graphite, quiche graphite or hydrocarbons, which are obtained by precipitation of volutes excessively contained in molten pig iron etc. during cooling, are produced in the gas phase by approximately 20%.
Pyrolytic graphite, etc., which is deposited by passing it over a substrate heated to 00° C. and thermally decomposing it, is known, and it is known that these graphites also expand due to the above-mentioned treatment.

(Problems to be solved by the invention) However, natural graphite, especially flaky graphite, is mainly produced in uneven locations and its reserves are limited, and natural graphite usually contains ash. If the ash content is high, the expansion coefficient will be low and the formability and quality of the obtained expanded graphite will deteriorate. Natural graphite with low ash content, which does not require manipulation, is very expensive.

When Quiche graphite is used, it contains a large amount of impurities such as iron in its crystals, and removal of these impurities is a problem in use, and in the case of pyrolytic graphite, the rate of carbon precipitation,
The problem is that it cannot be produced in large quantities and at low cost due to low yield.

Furthermore, in the case of so-called artificial graphite, which is obtained by coking the heavy oil obtained as a by-product of the coal or petroleum industry, such as coal tar or residual oil, and then graphitizing it, the raw material coal Tar and petroleum-based residual oils have a small content of impurities such as ash, and when removing ash, they turn into a liquid phase, making the removal process easy, but the degree of graphite crystal development is higher than that of natural graphite. Because it is smaller than #1, even if it is subjected to the same oxidation treatment as when using natural graphite, #1 hardly expands, making it impossible to obtain the desired expanded graphite.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have shown that optical anisotropy is generated in the pitch by heat-treating the raw material pitch. Focusing on the fact that carbonaceous mesophase has pseudographite crystals, by using such carbonaceous mesophase as a raw material for expanded graphite, it is possible to easily produce it without the need for a means for removing ash, etc. They discovered this and arrived at the present invention.

That is, an object of the present invention is to provide a method for easily and in large quantities producing expanded graphite, which is a soft graphite useful for producing graphite sheets and the like.

This purpose is achieved by heat-treating the raw pitch at 330 to SOO°C to obtain a heat-treated pitch in which a carbonaceous mesophase is generated, and then solvent-treating the heat-treated pitch using an organic solvent that does not dissolve the carbonaceous mesophase. This is achieved by separating and acquiring the carbonaceous mesophase, graphitizing the obtained carbonaceous mesophase at a temperature range of 0.degree. C. to 3100.degree. C., and then subjecting the obtained graphitized product to a wet oxidation treatment.

The present invention will be explained in detail below.

As the raw material pitch, coal-based coal tar pitch or petroleum-based pitch such as pitch from fluidized catalytic cracking by-product tar, direct distillation residue oil of crude oil, pitch from naphtha pyrolysis by-product tar, etc. is used, but preferably. It is best to use coal tar pitch.

In addition, these raw pitches contain impurities such as free carbon in small amounts, so it is best to remove them from the raw materials in advance using a known method. Good too.

The above raw material pitch was 3!0-50 under an inert gas atmosphere.
0'c:, preferably II 00-1 j 0.0 in a temperature range of 0°C. J- Heat treatment for 20 hours.

By this heat treatment, an optically anisotropic carbonaceous mesophase is generated in the raw material pitch.

Next, the heat-treated pitch containing the carbonaceous mesophase obtained is subjected to solvent treatment with an organic solvent that dissolves pitch components other than the carbonaceous mesophase but does not dissolve the carbonaceous mesophase, whereby only the carbonaceous mesophase is separated and obtained. The organic solvent used to separate the carbonaceous mesophase is a known organic solvent used in producing mesocarbon microbeads, such as quinoline or a mixture of aromatic hydrogenated oil such as anthracene oil and creosote oil. be able to.

This separation operation is performed with the aim of removing pitch components other than the carbonaceous mesophase as much as possible, and specifically, 0.00% of the organic solvent is added to 1 part by weight of the heat-treated pitch.
The carbonaceous mesophase is separated and obtained by mixing and stirring at a ratio of 3 parts by weight or more, preferably 7 to 5 parts by weight, but the above separation operation is repeated at least twice in order to remove pitch components other than the carbonaceous mesophase as much as possible. is preferable.

Note that since pitch itself is a multi-component system of molecules having a complex chemical structure, the solubility of pitch in a solvent depends on temperature, so it is preferable to separate the carbonaceous mesophase at the highest possible temperature. Furthermore, a hydrogenated carbonaceous mesophase obtained by hydrogenating the obtained carbonaceous mesophase can also be used as the carbonaceous mesophase of the present invention. The carbonaceous mesophase obtained by the above separation operation is 2≠
00℃~3100℃, preferably 2roo℃~300℃
A graphitized product is obtained by graphitizing at a temperature of 0°C.

The graphitized product is then subjected to a wet oxidation treatment, which can be carried out by a known method, specifically using a mixed acid of sulfuric acid and nitric acid or a peroxyhalogen acid.

The oxidation conditions, such as the mixing ratio of each line in the mixed acid of sulfuric acid and nitric acid, treatment time, and treatment temperature, are selected and determined as appropriate. The oxidation treatment is carried out using at least the same amount or more for 2 hours or more at a temperature of SO° C. or higher. The graphitized carbonaceous mesophase is expanded by the above oxidation treatment to obtain expanded graphite as a product. In the case of natural graphite, it is sufficiently expanded by oxidation treatment and further expanded by heat treatment at about 1000°C, but the carbonaceous mesophase of the present invention subjected to graphitization treatment requires further heat treatment after oxidation treatment. Even if this is done, there is no particular change in the expansion rate. However, if it is necessary to remove the acidic groups introduced by oxidation treatment, they may be removed by heat treatment.

(Effects) According to the present invention, expanded graphite, which is useful as a raw material for producing graphite films, graphite sheets, etc., can be produced at a lower cost and in larger quantities than when natural graphite or the like is used as a starting material. The present invention is industrially very useful.

(Examples) Hereinafter, the present invention will be explained in more detail using Examples, but the present invention is not limited to the following Examples unless the gist of the present invention is exceeded.

Examples 1 to A About 3 times the amount of quinoline was added to coal tar pitch (softening point 7ff'C, quinoline solubility 44.5% by weight), and the mixture was heated to about 0°C and dissolved. After filtering this with a glass filter, Fi'i! was distilled under reduced pressure to remove quinoline and obtain pitch free of free carbon. This pitch of about 11 oor was placed in a 100 m1 cylindrical glass container and melted in a furnace heated to about 30 OL, then heated to a specified temperature in nitrogen gas with stirring at a heating rate of 3°C per minute. was held for a predetermined period of time.

The thus heat-treated pitch was pulverized, about three times the amount of quinoline was added, and the mixture was heated and dissolved at about 0°C. This was applied to a centrifugal precipitator, the supernatant was removed, fresh quinoline was added, heated, and centrifuged. After repeating this operation five times, benzene was added to the precipitate, the mixture was refluxed for about 1 hour, and then filtered through a glass filter. The filtered product was then thoroughly washed with acetone and dried to collect the quinoline-insoluble matter, which was used as a carbonaceous mesophase.

Table/ shows the heat treatment temperature and time of the raw material pitch, and the obtained carbonaceous mesophase 309 and quinoline 1, Of 3o o
ml autoclave, and after purging the inside with argon, μt was heated at a heating rate of 1°C per minute while stirring.
io''C and held for 60 minutes. After cooling to room temperature, the entire contents were washed out with quinoline and filtered through a glass filter. P hyperactivity was thoroughly washed with quinoline, then benzene and acetone. It was dried. This was used as a quinoline-treated mesophase. The yield for the mesophase by this treatment is also shown in Table 1.

The carbonaceous mesophase obtained as described above was 2≠～≠
Separate it with a sieve of the Kotaira mesh, and align it to λ≠～Hirokonoko mesh degree. This was fired in nitrogen gas at a temperature of about 100° C., then heated to 3000″C in a Tammann furnace and graphitized for 30 minutes.

Approximately 3 f of the obtained graphitized material was accurately weighed and placed in a 1.20 ml measuring cylinder, and after filling the cylinder well, the volume was measured.

Next, put it in a :toOml Erlenmeyer flask and add concentrated sulfuric acid (
Add 3 orae of mixed acid at a ratio of 1 part of concentrated nitric acid (concentration A4'%) and boil in an oil bath at 100°C.
After oxidizing for a minute, the reaction was stopped by pouring it into about a room of water.

This was filtered through a glass filter, dried at about IOθ°C, and the volume was measured using a 1 part weight and 2 parts ml measuring cylinder. Repeat this operation 3 times, and the total temperature is 100℃.
/ oxidized for 0 minutes. The packing density was determined from the weight and volume, and the degree of expansion was expressed as the ratio of the filling density before and after oxidation as the apparent expansion coefficient, as shown by the following formula.

The results obtained are shown in Table 1.

Example 7 Coal tar pitch r00f and anthracene oil similar to Example/-4! 00? and Fe2032r as a catalyst
f was injected into an autoclave with a capacity of 2 t, and the hydrogen pressure /
00 kg/ctil (J and 1~te temperature≠SO℃, 10
After hydrogenation for a minute, the contents were distilled under reduced pressure to obtain hydrogenated pitch. The obtained hydrogenated pitch was heat-treated and solvent-treated in the same manner as in Example 3 to obtain a carbonaceous mesophase as a quinoline solvent. The results are shown in Table/. The obtained carbonaceous mesophase was then subjected to graphitization treatment and wet oxidation treatment in the same manner as in Examples/-t to obtain expanded graphite of the present invention. The results are shown in Table 2.

Example ♂ Carbonaceous mesophase 10V obtained in Example 3 and tetrahydroquinoline 20? was injected into an autoclave with a volume of 300 m1, and heated in an argon atmosphere under autogenous pressure at ppo℃, to
A heat treatment was carried out for a minute (temperature increase rate j° C./min), and the obtained contents were filtered and washed to obtain a hydrogenated carbonaceous mesophase. In addition, the amount of decrease in the concentration of tetrahydroquinoline after the heat treatment was measured, and the amount of hydrogen consumed was calculated from the amount of hydrogen in the generated gas. The results are shown in Table 3.

The obtained hydrogenated carbonaceous mesophase was subjected to graphitization treatment and wet oxidation treatment in the same manner as in Examples 1 to 6 to obtain expanded graphite of the present invention. The results are shown in Table λ.

Comparative Example 1-λ A commercially available graphite material and petroleum coke were graphitized at 3000° C. for 30 minutes, each having a particle size of 2V to λ mesh, and subjected to wet oxidation treatment in the same manner as in Examples/~t. The results are shown in Table-2.

Furthermore, as can be seen from Table 2, the expansion rate is approximately larger in the quinoline-treated mesophase than in the mesophase sampled at 0°C, and the expansion rate is greater in the mesophase treated with quinoline than in the mesophase sampled at 0°C. It can be seen that it is more effective.

Table 3 Applicant: Director of the Agency of Industrial Science and Technology −−□ Others/names

Claims (1)

[Claims] (1) Heat-treated raw pitch is heated at 350 to 500°C to produce a carbonaceous mesophase, and the heat-treated pitch is solvent-treated using an organic solvent that does not dissolve the carbonaceous mesophase. The carbonaceous mesophase was separated and obtained, and the obtained carbonaceous mesophase was
A method for producing expanded graphite, which comprises graphitizing at 00 to 3100°C to obtain a graphitized product, and then subjecting the graphitized product to wet oxidation treatment.