JPS62187167A - Manufacture of graphite formed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to the production of a graphite molded body made of graphite powder and mesophase-containing pitch! This is related to Law 1.

[Technical background of the invention]

Conventionally, in the production of graphite molded bodies using graphite as a base material,
Methods of using coal tar pitch, phenol resin, furan resin, etc. as a binder for graphite are known.

When coal tar pitch, phenolic resin, etc. are used as a binder, the melting point of the binder is as low as around 100°C, so it is relatively easy to heat cross-wire and mold with the base material, but on the other hand, these binders The carbonization yield in carbonization up to around 1000℃ is low at 50 to 60% by weight, the amount of shrinkage accompanying carbonization is large, and it has the disadvantage that shrinkage distortion occurs when rapid carbonization is performed. .

Friend, when a formed body with a complicated shape is carbonized, there is a problem that the formed body undergoes complicated deformation due to the difference in the amount of shrinkage.

Phosphoric acid fuel cells, which are being studied on a large scale for practical application in the United States and Japan, use hot phosphoric acid at around 200°C as an electrolyte, so both the electrode substrate and gas separation plate must be resistant to hot phosphoric acid. It is made of a rich carbon material with low electrical resistance. Gas impermeability is strongly required for gas separators used in fuel cells.

[Prior art and its problems]

Glassy carbonaceous materials have been proposed as gas-impermeable carbon materials for use in gas separation plates of fuel cells. For example, JP-A No. 58-150275 describes an example in which glassy carbon alone is used, and JP-A No. 57-72
In Publication No. 273, a constant load is applied to a formed form of graphite and phenolic resin, and carbonization (
The temperature was further increased to 2800°C for 48 hours to obtain a graphitized separator plate. Also, JP-A-59-1
No. 27377 discloses that ultrafine powder of cargen plastic, resin, etc. is added and mixed to furan resin as needed, and after molding to a predetermined thickness, it is cured at room temperature, and the thickness after firing is 0.1 to 1.
A glass-like carbon thin plate is obtained by sandwiching the material 1111 between graphite plates, etc., which have excellent thermal conductivity and shape-retaining properties, and firing while paying attention to uniform firing.

However, in both methods, the temperature of the phenol resin or furan resin, which is the raw material for glassy carbon, is about 1000℃.
No innovative measures have been taken to address the problem of deformation of the molded body due to volumetric shrinkage associated with the carbonization yield of 50 to 60% by weight.

Regarding gas separation plates, in addition to the flat plate disclosed in the above-mentioned technique, a type having subdivided gas flow channels called a separator with lips orthogonally to the front and back sides of the plate has also been proposed. However, the difficulty of manufacturing a gas separation plate with such a complicated shape all at once by carbonization of a formed body using graphite as a base material and phenol resin as a binder is disclosed in Japanese Patent Application Laid-open No. 140977/1983. suggests. That is, according to the publication, in complex-shaped bodies such as separators with lips, plate deformation and warpage occur due to the grooves that constitute a large number of gas flow paths, so the shrinkage coefficient during carbonization of the formed body is A method is disclosed in which powder is measured in advance and the mixing ratio of graphite and phenol is varied for each part, and the powder is filled into a mold and then carbonized. However, other applications by the same applicant (
In JP-A-58-119163), it was pointed out that the yield of the powder filling method was poor, and a method of using a flat gas separation plate was proposed. Furthermore, JP-A-58-150275 discloses a method in which a mold for centrifugal molding is formed in accordance with the shrinkage amount in order to obtain a separator with a lip using furfuryl alcohol resin alone in a predetermined manner. ing.

However, the gas separation plate obtained by the technique described in JP-A-57-72273 must be expensive, and
In the method disclosed in Japanese Patent No. 150275, since the amount of shrinkage, which naturally varies slightly continuously, is approximately captured, it is inevitable that the dimensions become unstable and the work becomes complicated.

In order to utilize phosphoric acid in fuel cells, it is desired that the technical problems described above regarding gas separation plates be fully resolved.

The present inventors have proposed a method for solving this problem, in which the quinoline insoluble content is 70!1 l LIJ or less and the mesophase content is 4.
0- or higher, the upper limit of the heating melting temperature is 400°C, and the carbonization yield at 1000°C is at least 70 Fengmeng. A shaped body produced by pressure molding a powder obtained by mixing mesophase-containing pitch and graphite powder. and further found that by firing the formed body in an inert atmosphere at 700° C. or higher, a graphite shaped body having excellent conductivity and strength and having small changes in volume and weight during carbonization can be obtained, Next, apply for a patent. (
Patent Application No. 199737/1983. ) However, this method still has room for improvement in terms of simplifying the process and improving the gas impermeability of the molded product.

[Purpose of the invention]

An object of the present invention is to provide a simplified method for manufacturing a phosphorescent graphite molded body with better gas impermeability in a subsequent step.

[Summary of the invention]

The present inventors directly pressure-molded the mixed powder of mesophase-containing pitch and graphite powder used in the method of Japanese Patent Application No. 59-199737 at 700 to 3000°C. The inventors have discovered that the impermeability is further improved, a subgraphitic molded body can be obtained in one step, and that a wider range of mesophase-containing pitches can be used in this method, and the present invention has been achieved. That is, the present invention
A powder obtained by mixing mesophase-containing pitch and graphite powder with a quinolino insoluble content of 95% by weight or less, a mesophase content of 35% or more, and a carbonization yield of at least 70% by weight at 1000°C. Pressure molding at a temperature of 1' is a characteristic method for producing a graphite molded body.

[Detailed description of the invention]

As the graphite powder, scale-like natural graphite, earth-like natural graphite, artificial graphite, etc. can be used. Furthermore, in order to make the method of the present invention effective, it is necessary to use graphite powder CFC that can be formed into a compact by pressure molding at room temperature, such as CPB and ASP-1000 (trade name) manufactured by Nippon Graphite Industries Co., Ltd.
It is preferable to use JK8-2.5 (trade name).

Mesophase-containing pitch contains 35% of coal-based or petroleum-based heavy oil such as coal tar, catalytic cracking residue, naphtha cracking residue, etc.
Obtained by heat treatment at 0 to 550°C. Naphtha decomposition residue contains less impurities such as heavy metals and sulfur than other heavy oils, so it is suitable for producing high-purity graphite molded bodies.

In that case, JP-A-58-154792 and 15479
Although the method disclosed in No. 3, in which the material is modified by hydrogen treatment and then heat treated, is suitable for obtaining a molded product with high strength and high density, it is of course possible to use a method that is not modified.

The quinoline-insoluble content of pitch containing menphase is 95% by weight.
or less, preferably 90 weights or less, more preferably 7
It is 0% by weight or less. If the solid/insoluble content exceeds 95 weight S, the strength and gas impermeability of the molded article will decrease. The mesophase content is at least 35%, preferably at least 40%. If it is less than 35%, the compactness of the molded article will be impaired. The carbonization yield is 70% by weight or more, preferably 80% by weight.
That's all. If it is less than 70% by weight, shrinkage during carbonization will be large and the dimensional stability of the molded article will be poor.

The graphite powder and the mesophase-containing pitch can be mixed by various methods, but it is preferable to grind and mix with a gall mill, a vibrating mill, or the like.

The appropriate grinding time is 1 minute to 1 hour.

Menphase-containing pitch can be added in an amount of 5 to 60% by weight, preferably 10 to 40% by weight, based on 100 parts by weight of graphite powder. The optimum addition ratio varies depending on the type of mesophase-containing pitch.

The mixed powder can be hot press-molded using a graphite mold or the like at 700° C. or higher, preferably 900° C. or higher under vacuum or an inert gas atmosphere to obtain a graphite molded body. Other carbon precursors cannot be hot-pressed directly, so pre-calcination is required. (Proceedings of the 11th Annual Meeting of the Carbon Materials Society P, 146 (1984)
) On the other hand, in the case of the graphite-mesophase-containing pitch mixed powder of the present invention, no pre-firing is required, and it does not cause cracks not only when the pressed surface is smooth but also when it has irregularities. Further, direct hot press molding is possible without fusion, which is a major feature of the method of the present invention.

The obtained molded product has excellent strength and conductivity, and is characterized by being gas-impermeable. These properties are achieved by molding at temperatures below 1100°C, although temperatures up to 3000°C can be used depending on further desired properties. The heating rate to reach the specified temperature is 150-3000℃/hour, and the pressure is 5
It can be carried out in the range of 0 to 2000 km3 (gauge).

[Features and application examples of the method of the present invention]

According to the method of the present invention, it is possible to obtain a molded body having a complex shape by direct hot press molding without requiring preliminary firing. 1) The obtained molded product has excellent strength and conductivity, and is also gas-impermeable.

The graphite molded body obtained by the method of the present invention can be used for various types of materials including gas separation plates for fuel cells.

[Embodiments of the invention]

The content of the present invention will be explained in more detail below with reference to Examples and Comparative Examples.

Example 1 [Manufacture of mesophase-containing pitch] Naphtha decomposition residue tar produced by thermal decomposition of naphtha in an autoclave with an internal volume of 16 (normal pressure equivalent boiling point 170°C or higher)
630iP and silica alumina catalyst for fluid catalytic cracking (made by Catalyst Kasei@), alumina content 13g, powder) 30?
was charged, hydrogen was passed at a rate of 100 t/hour (STP), and the temperature was raised from room temperature to 460 °C in 140 minutes while maintaining the reaction pressure at x20 kp/α (r-di).
Hold for 0 minutes and then. After cooling to room temperature, the contents were taken out and solid matter was filtered, and then distilled to remove the fraction below 490°C in terms of normal pressure, and the hydrogen-treated naphtha decomposition residue tar was charged at a yield of 25% by weight based on the raw material. Obtained.

The modified pitch 109'' was obtained as described above with an internal volume of 40-
into a reactor equipped with a cylinder of 300 ml to prevent backflow of distillate into the pitch, and 3 sots of argon per minute.
Tetrahydrokino 1) 7t″ liquid form, 0.13Pbis per minute,
After holding for 10 minutes while supplying the
Next immerse in a molten salt bath and keep at °C. After the pitch was melted in the bath, argon and tetrahydroquinoline were supplied into the liquid pitch, and heat treatment was performed at a reaction temperature of 483° C. for 13 minutes.

As a result, mesophase-containing pitch was obtained at a yield of 52:fflt% based on the modified pitch. The results are as follows:
A sample embedded in an epoxy resin and polished was observed under a polarizing microscope at room temperature to measure the optical anisotropy ratio, that is, the menphase content. As a result, the menphase content of the pitch was approximately 100%. In addition, the quinoline insoluble content (JIS2425 centrifugation method) of this sample was 45% by weight. Further, pitch 101n9 was heated to 1000° C. in a nitrogen gas atmosphere in a differential thermogravimeter to determine the weight loss, and a carbonization yield of 85% by weight was obtained.

[Manufacture of graphite molded body]

The mesophase containing pitch is 0.6? Scale graphite powder manufactured by Nippon Graphite Industries Co., Ltd. (product name CPB) 2.4? Along with this, a Guai Brating Sample Mill manufactured by Hirako Seisakusho (
VIBRATING SAMPLE MILI, ) f7 del chainer (SAMPLE CHAMBER)
Then, grind and mix for 5 minutes to obtain a mixed powder.

The mixed powder approximately 21P11: inner diameter approximately 35. The mixture was filled into a graphite mold, heated to 1020°C in 130 minutes while applying a pressure of 0.4'rON/, (dirge), and held for 1 minute. After cooling to room temperature, the pressure was released to obtain a graphite molded body with a diameter as of 3 m and a thickness of 1.0 m.

The volume resistivity of the molded body in the plane direction by the four-terminal method is 1
．． It had a bending strength of 1 mΩ'w, a bending strength of 575 kg7 cm, and a nitrogen gas permeability of less than 105 I/use at room temperature.

Example 2 In the experiment of Example 1, the amounts of Men7Aze-containing pitch and flaky graphite to be mixed and ground were 0.91 and 2.9%, respectively. I
A graphite molded body was obtained in the same manner except for P. The volume resistivity of the graphite molded body is 1.3 mΩ・cm, and the bending strength is 5.
93 Yu6, the gas permeability was less than 10 cIn/sec.

Example 3 94.1j' of naphtha decomposition residue tar (boiling point of 170°C or higher when converted to normal pressure) generated by thermal decomposition of naphtha was heated to an inner volume of 250
A reactor equipped with an inner cylinder of
The reactor was immersed in a molten salt bath previously maintained at 60° C. while supplying t (s'rP ). Reaction temperature 4 after 15 minutes
After reaching 57°C, it was held for 15 minutes and cooled to obtain mesophase-containing pitch with a yield of 10.5% by weight based on the raw material tar. The pitch has a mesophase content of about 45%, a quinoline insoluble content of 41% by weight, and a carbonization yield of 79% by weight, which is dangerous.

Ta. The molded body has a volume resistivity of 1.1 mΩ, a bending strength of 445 mΩ, and a nitrogen gas permeability of 10 at room temperature.
α/II @ was less than 0.

Example 4 A mesophase-containing pitch was obtained in the same manner as in Example 3 except that the heat treatment temperature was 477° C., and a graphite molded body was obtained. The yield of the pitch is 10.0 wt.
Mesophase content is approximately 80%, quinoline insoluble content is 80%
The carbonization yield was 877% by weight. In addition, the volume resistivity of the obtained T-graphite molded body was 1.1 mΩ·ka, the bending strength was 427 kVcm, and the nitrogen gas permeability at room temperature was 1.
Ivy below 0 cM/sec.

Example 5 In the experiment of Example 3, the heat treatment temperature was set to 487° C., and the other conditions were the same to obtain metsuphase-containing pitch and graphite molded bodies. The yield of the pitch was 10.0% by weight, and the mesophase content was about 90%.

Quinoline insoluble matter is 900% by weight Carbonization yield is 91% by weight
And nine. In addition, the volume resistivity of the graphite molded body is 1.2m.
Ω/F, bending strength of 380 kits, and nitrogen gas permeability at room temperature of less than 10 crR/sec.

Claims (1)

[Claims] A powder obtained by mixing mesophase-containing pitch with a quinoline insoluble content of 95% by weight or less, a mesophase content of 35% or more, and a carbonization yield of at least 70% by weight at 1000°C and graphite powder. A method for producing a graphite molded body characterized by pressure molding at ℃.