JPS586686B2 - Manufacturing method of graphite molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the manufacturing method of expanded graphite molded bodies, and in particular, improves flexibility, elasticity, and
The object of the present invention is to provide a method for efficiently, easily, and economically producing a dense molded body having extremely excellent heat resistance, chemical resistance, and sealing performance without impairing the working environment.

C between the graphite layers of natural graphite, pyrolytic graphite, kitsch graphite, etc.
Bulk specific gravity 0.003 to 80 to 360 times expanded in the axial direction
Sheet-like or annular molded products made using 0.020 g/cm3 expanded graphite powder alone have flexibility,
It is well known that it is a material with extremely excellent elasticity, heat resistance, chemical resistance, and sealing properties.

Conventionally, the method for manufacturing this type of molded body made of expanded graphite powder alone was to use the expanded graphite powder alone without using any binder, and to take advantage of the self-bonding properties of expanded graphite itself. Dry molding is commonly used.

However, expanded graphite powder has a bulk specific gravity of 0.003 to 0.02.
Since it is a fine powder of about 0 g/cm3 and is extremely light, it easily scatters when filled into a mold, and the dust that flies up significantly worsens the working environment, and the powder has poor fluidity. However, the filling process is difficult due to problems such as adhesion to the mold, and in order to obtain a compact with a relatively high density, it is necessary to fill the powder with up to 360 times the volume of the compact, making the compression molding process using a press extremely difficult. Although it is efficient, it has major drawbacks in terms of productivity and economy, such as the need for large presses and molds.

In order to eliminate these drawbacks, recently expanded graphite sheets (density 1.0 g/cm) made from expanded graphite powder have been developed.
A manufacturing method is used in which a desired weight of 3.0.4 mm thick sample is taken, filled into a mold, and compression molded. However, this method requires two molding steps, and the Uniform filling of the expanded graphite sheet is surprisingly complicated, and when the resulting molded product is used as a packing, there are disadvantages in that rotational torque becomes large.

This invention was made as a result of intensive research to solve the above-mentioned drawbacks, and has a degree of expansion of 200 to 360 times and a bulk specific gravity of 0.
,008g/cm3 or less of expanded graphite powder, 3 to 30 parts by weight of an organic binder, and 50 parts by weight of expanded graphite powder.
The bulk specific gravity is 0.06-0.61/c by completely removing the solvent from a homogeneous kneaded product containing 0-2000 parts by weight of a solvent.
This is a method for producing a graphite molded body, which comprises: kneading a secondary powder of m3, compressing the secondary powder to obtain a molded product, and further heating the molded product to burn out the organic binder.

As is well known, the expanded graphite powder used in this invention refers to graphite layered crystals that expand and exfoliate up to 360 times in the C-axis direction and have a bulk specific gravity of 0.003 to 0.020 g/cm3. In particular, when using expanded graphite powder with a degree of expansion of 200 to 360 times and a bulk specific gravity of 0.008 g/cm3 or less, organic bonding is desirable because the effects of the present invention, which will be described later, can be further exhibited. It is desirable that the material has an affinity with expanded graphite powder, has the ability to moderately agglomerate this powder, and can be easily burned off and removed in the subsequent heating process. Plastic resin, NR, NBR, SB
Latex such as R, starch thereof, animal and vegetable mucilages such as sodium alginate, arabic gum, glue, gelatin, and synthetic mucilages such as methylcellulose, polyvinyl alcohol, sodium polyacrylate, and polybutene are used.

The amount of these organic binders to be added is determined in relation to the bulk specific gravity of the secondary powder, but is usually 3 to 30 parts by weight per 100 parts by weight of expanded graphite powder, and 5 to 10 parts by weight is optimal. .

If it is less than 3 parts by weight, the moldability will not be sufficiently improved, and if it exceeds 30 parts by weight, it will be difficult to remove the organic binder by burning it off in the heating process, which is not desirable.

The amount of solvent such as water for dissolving or dispersing the organic binder is 500 to 2 parts by weight per 100 parts by weight of expanded graphite powder.
000 parts by weight, preferably 800 to 1500 parts by weight.

The first feature of the production method of the present invention is that when producing a dense compact from a single piece of expanded graphite powder by dry molding, an organic binder and an appropriate amount of solvent are added to the expanded graphite powder in advance, and the mixture is uniformly kneaded. Then, by completely removing the solvent from this kneaded product, a secondary powder (bulk specific gravity 0.06 to 0.60 g/ cm3) is obtained,
Second, by using the expanded graphite secondary powder obtained by such a treatment, dense molded bodies can be molded extremely easily and efficiently using the normal dry compression molding method, and the molded bodies obtained can be molded very easily and efficiently. By simply heating and burning off the organic binder added in advance, the various excellent sealing properties inherent to the expanded graphite molded body can be further improved without any loss.

Thirdly, since the bulk specific gravity of the secondary powder is considerably higher than that of the original powder, the amount of powder to be filled and the compression capacity can be small, so there is no need for large-capacity presses or jigs such as large molds. It is economical and efficient, and is particularly convenient for obtaining high-density molded bodies.

Furthermore, since the graphite molded body obtained by the manufacturing method of the present invention is manufactured as described above and finally solvents and organic components other than expanded graphite are removed, the graphite molded body obtained by the manufacturing method of the present invention has the flexibility, elasticity, and heat resistance originally possessed by expanded graphite. The expanded graphite particles in the compact are oriented perpendicularly to the direction of pressure, so they can be used as packing in stuff-in boxes. When used after insertion and tightening, the sealing pressure distribution against the shaft is made uniform, and the rotational torque is particularly small and superior compared to conventional packings formed from sheets.

Example 1 1 100 parts by weight of expanded graphite powder (Japan Graphite EXP-FT) with a bulk specific gravity of 0.005 g/cm3 was added to a mixer (kneader).
A solution obtained by diluting 18 parts by weight of NBR latex (Inu Nippon Ink Kagaku Luxstar 6541G) with 1500 parts by weight of water was added and kneaded for 20 minutes, and then the mixed material was heated and dried in a dryer at 70 to 80°C. Bulk specific gravity 0.10
A secondary powder of expanded graphite with extremely good filling properties and no dust generation of g/cm3 was obtained.

Next, this was filled into an annular mold with an inner diameter of 20 mm, an outer diameter of 30 mm, and a height of 5 mm, approximately 15 times the desired height, and a molding surface pressure of 300 mm was applied.
A molded article having a density of 1.45 g/cm3 was obtained by compression molding at kg/cm2.

Finally, this molded body was taken out from the mold and fired for 1 hour in an electric furnace at 400° C. to obtain a highly flexible graphite molded body with a density of 1.43 g/cm 3 .

Example 2 1 Bulk specific gravity o. 100 parts by weight of expanded graphite powder (Nippon Graphite EXP-FT) with oO3g/cm3 was placed in a mixer, and a solution of 5 parts by weight of polyethylene oxide (Meisei Chemical Industry Alcox E-100) dissolved in 1000 parts by weight of water was added to it. After mixing for 15 minutes, the kneaded material was heated to 70-80℃.
The powder was heated and dried in a dryer to obtain a secondary powder of expanded graphite with a bulk specific gravity of 0.06 g/cm3 and excellent filling properties and no dust generation.

Next, this was filled into a sheet-like mold with a length of 300 mm, a width of 200 mm, and a height of 1 mm, approximately 24 times the desired height, and the molding surface pressure was 3.
Compression molded at 00kg/cm2 and density 1.45g/cm
A molded article No. 3 was obtained.

Finally, this molded body was taken out from the mold and fired in an electric furnace at 400° C. for 1 hour to obtain a highly flexible graphite molded body with a density of 1.43cm 3 .

Example 3 100 parts by weight of expanded graphite powder (Nippon Graphite EXP-FT) with a bulk specific gravity of 0.005 g/cm3 was placed in a mixer, and 7 parts by weight of polyvinyl alcohol (manufactured by Shin-Etsu Chemical) was added to 100 parts by weight of water.
After adding the solution dissolved in 0 parts by weight and kneading for 15 minutes, this kneaded product was heated and dried in a dryer at 70 to 80°C to obtain an expanded product with a bulk specific gravity of 0.10 and extremely good filling properties without generating dust. A secondary powder of graphite was obtained.

Next, this was filled into an annular mold with an inner diameter of 20 mm, an outer diameter of 30 mm, and a height of 5 mm, approximately 15 times the desired height, and a molding surface pressure of 300 k was applied.
Compression molding was performed at a density of 1.45 g/cm 3 to obtain a molded body.

Finally, this molded body was taken out from the mold and fired in an electric furnace at 400° C. for 1 hour to obtain a highly flexible graphite molded body with a density of 1.43 g/cm 3 .

Comparative example bulk specific gravity 0. A predetermined amount of expanded graphite powder (Japanese graphite EXP-FT) of O05g/cm3 was directly heated to an inner diameter of 20mm and an outer diameter of 3.
0 mm and a height of 150 mm into an annular mold with a desired height of approximately 30 mm.
Filling pre-compression (pressure 5-10 kg/c) for 0 times filling
m2) several times to complete the desired filling amount, compression molding was performed at a molding surface pressure of 300 kg/cm2 to obtain a density of 1.43 g/cm2.
A molded body of cm3 was obtained.

Table 1 summarizes the bulk specific gravity of the raw powder and secondary powder and the type of organic binder in Examples 1 to 3 and Comparative Example.

In addition, the expanded graphite molded product obtained by this invention and the conventional product molded from a sheet were placed in a stuff-in box of a valve (valve stem diameter 20 mm, box inner diameter 30 mm) with 6 packings so that each ring had a height of 5 mm. When the relationship between tightening pressure and valve stem rotation torque (kg/Cm) was compared and tested, the results shown in Table 2 were obtained.

Button Conventional molded products are obtained by taking a desired weight of an expanded graphite sheet (thickness 0.4 mm) with a density of 1.0 g/cm3, placing it in a mold, and compression molding it at a pressure of 300 kg/cm2. It is a molded article of 1.43 g/cm2.

As described above, the manufacturing method of the present invention does not use raw expanded graphite powder as it is, but uses secondary powder treated with an organic binder, so there is no deterioration of the working environment due to expanded graphite fine powder that is harmful to health. , no powder adhesion to the mold,
As the weight of powder packed into the mold increases, the work of handling the powder is significantly simplified and becomes more efficient, and the presses and molding jigs can be made smaller and lighter, which significantly shortens the molding work and makes it more economical. It has also been improved.

In addition, it has been extremely difficult to mold high-density molded products from raw powder, but this invention has made it extremely easy to mold.

Furthermore, the graphite molded body obtained by the method of the present invention has the various sealing properties as described above compared to conventional products molded from sheets, and because of its oriented structure, the graphite molded body has particularly low rotational torque and is excellent.

Claims (1)

[Claims] 1. Degree of expansion 200 to 360 times, bulk specific gravity o. oosg/C
The solvent is completely removed from a homogeneous kneaded mixture of 100 parts by weight of expanded graphite powder of m3 or less, 3 to 30 parts by weight of an organic binder, and 500 to 2000 parts by weight of a solvent, resulting in a bulk specific gravity of 0.06 to 0.06. Production of a graphite molded body, characterized in that a secondary powder of 0.60 g/cm3 is obtained, the secondary powder is compressed to obtain a molded product, and the molded product is further heated to burn out the organic binder. Method. 2. The method for producing a graphite molded body according to claim 1, wherein the organic binder is a water-soluble thermoplastic resin, latex, or viscous material.