JPS583966B2 - Method for manufacturing graphite compression molded bodies for high-temperature packing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a graphite compression molded body for high-temperature packing.

Conventionally, this type of heat-resistant packing molded body, which is used between joints in tubular atmosphere furnaces such as hydrogen furnaces, nitrogen furnaces, or reduction furnaces, which are widely used in the production of tungsten carbide and other purposes, has been difficult to compression mold. It had major drawbacks in terms of both the lack of high-temperature heat resistance.

That is, from the viewpoint of appropriate elasticity, impact resistance, and heat resistance, conventional so-called expanded graphite (usually with a bulk specific gravity of 0.01 to 0.0
033) has been attracting attention, but not only is the fluidity of the powder extremely poor when feeding it to a molding die, but in press molding, for example, it is difficult to obtain a molded body with a specific gravity of 1.00 and a thickness of 5 mm. The average depth of the mold was 1 m, and in practical terms, the molding operation was so difficult that it was almost impossible, considering the stroke of the press, etc.

Furthermore, the above-mentioned expanded graphite loses weight when heated at temperatures of 500 to 550 DEG C., and the joints of the furnace must be retightened frequently.

In other words, (a) Conventional graphite compacts for packing have low bulk specific gravity and lack fluidity of powder, making it difficult to fill into molds, resulting in poor workability and unsuitability for mass production. .

(b) Expanded graphite itself is fibrous, and if it is as it is, it is almost impossible to uniformly mix it with other additive mixed powders.

Forcible mixing tends to cause separation and segregation.

() Because it is difficult to form into a two-component or multi-component composite, it cannot be modified without compensating for the drawbacks of expanded graphite.

(2) Only small molding densities can be produced.

As described above, conventional methods have had many drawbacks.

The present invention aims to provide a method for producing a compression molded graphite body for high-temperature packing, which eliminates such drawbacks.

That is, the present invention provides fibrous expanded graphite having a bulk specific gravity of 0.01 to 0.033, which is obtained by subjecting graphite powder to a desired expansion process, and which is further pulverized and cut, and then granulated. For expanded graphite powder with a specific gravity of 0.067 to 0.01, L
+aP04, BaHP04 and CaH4(P04)2・
0.1 to 5% by weight of one or more powders of H20,
After adding and mixing as is, or spraying and mixing in a lower alcohol suspension dispersion such as methyl alcohol,
This is a method for producing a graphite compression molded body for high temperature packing, which is cold compression molded into a desired packing mold.

The fibrous expanded graphite used in the present invention is a porous fibrous graphite obtained by greatly expanding normal graphite powder through a desired expansion treatment, and has a bulk specific gravity of 0.1 to 0.03 and a length or particle size. is 1 to 10 mm.

This material is further pulverized using a high-speed rotary pulverizer such as a plastic cutter mill or a colloid mill to cut the fibers.

Or, after pulverizing and cutting in this way, it may be further granulated with a desired granulator and eventually collapsed, with a bulk specific gravity of 0.067 to 0.
01 (15cc/g~100CC/g), particle size 0.1~
Grind into 1 mm expanded graphite powder.

This powder is mixed with a specific phosphate powder in the next step, but in this case, the bulk specific gravity of this expanded graphite powder is 0.
If it is larger than 067, the entanglement between the graphite particles becomes weaker, and the tensile strength after compression molding in the subsequent step becomes weaker, so it is not acceptable.

On the other hand, if the bulk specific gravity is less than 0.01, the fluidity of the powder and the mixability with other types of powder, that is, phosphate powder, will be poor, and the workability will be worse in compression molding in the later process. .

In addition, separation and segregation of particles of other types of substances added and mixed is likely to occur, so this is not possible.

The expanded graphite powder 1 prepared with the bulk specific gravity regulated as described above is put into the container 3 of the mixing device 2 shown in the figure, and compressed air (3 to 5 atm) 5 is supplied from the compressed air inlet 4 at the bottom of the container 3. is blown into the expanded graphite powder 1 in the container 3 through the valve 6.
is allowed to flow, and from another lateral additive inlet 7, as fine a powder 8 (200 mesh) of the phosphate as possible is blown in together with air as shown in the figure.

The phosphates are particularly suitable for Li3PO4, BaHP04 and Ca.
One or more of H4(P04)2H20 is used at a ratio of 0.1 to 5% by weight based on the expanded graphite powder having a bulk specific gravity of 0.067 to 0.01.

In this case, in addition to addition and mixing as is, a suspension obtained by suspending and dispersing these fine phosphate powders 8 in a lower alcohol such as methyl alcohol or ethyl alcohol may be sprayed into the additive inlet shown in the figure. From step 7, a fine spray is blown into the expanded graphite particles to adhere and adsorb them onto the surface of the expanded graphite particles, thereby obtaining uniformity of the mixture.

The mixed powder 9 uniformly mixed in this manner passes through a filter 10, is taken out from an outlet 11, and is collected by a cyclone dust collector or a bag filter (none of which is shown).

When the amount of the phosphate fine powder 8 added to the expanded graphite powder 1 is less than 0.1% by weight, the heat resistance of the molded body, the reduction of heat loss, and the shrinkage of the packing over time (i.e., retightening) are improved.
It is not acceptable because no effects such as reduction in the amount of water, fluidity of the powder, ease of handling, etc. were observed.

On the other hand, if it exceeds 5% by weight, the above-mentioned effect becomes saturated and there is no need to add any more, and the elasticity of the packing also decreases, so 5% by weight is set as the upper limit.

Next, the obtained mixed powder 9 is put into a desired packing mold and cold compression molded to obtain the graphite compression molded body for high temperature packing of the present invention.

In this case, the compression pressure is usually about 3 to 30 ky/cm2, and the bulk specific gravity (0.
067~0.01) is large and the depth of the molding mold is 1/5~
Since it requires only I/1O and the powder has good fluidity, automatic press molding is easily possible.

Of course, roll forming is also possible.

It is also highly practical and economical. The obtained molded product can be used as a molded product for high-temperature packing even at 800° C., and there is almost no need for retightening due to wear even when it is put into practical use, for example, as joint packing for a tube furnace.

A very thin molded article with a thickness of about 0.2 to 0.5 mm can also be made as a molded article for puncturing.

In this case, conventional expanded graphite powder (bulk specific gravity 0.01
~0.033), the roll forming method must be used.

In other words, in press molding, for example, in order to obtain a molded product with a specific gravity of 1.00 and a thickness of 5 mm, the depth of the molding die must be approximately 1 m on average, and considering the stroke of the press, etc., it is difficult to form the mold in practical terms. That would be close to impossible.

The present invention will be further explained with reference to examples.

Example 1 CaH4. (PO4)2
- After 10 g of a 5% methyl alcohol dispersion of H208 was sprayed and adsorbed using the powder mixing device 2 shown in the figure, the obtained mixed powder 9 was press-molded at room temperature to obtain a molded body for packing.

This packing material is used between the joints of a tube furnace, and the temperature is 75
No abnormalities were observed even after continuous use for one week in an atmosphere exposed to 0°C.

That is, there was no need to retighten the packing material due to wear and shrinkage.

In addition, almost the same results were obtained by using a mixed powder 9 in which the CaH4(P04)2.H20 powder 8 was mixed as a powder with the mixing device 2 shown in the figure without using the methyl alcohol dispersion. Obtained.

Furthermore, instead of CaH4(P04)2・H20 powder, L
Substantially similar results were obtained using i3PO4 or BaHP04.

Example 2 Expanded graphite powder 110 pulverized to have a bulk specific gravity of 0.03
After adsorbing 10 g of a 5% ethyl alcohol dispersion of BaHPO48 to 0 g by spraying using the powder mixing device 2 shown in the figure, the obtained mixed powder 9 was press-molded to obtain a packing material.

The packing material of this compact was used between the joints of a tube furnace and was used continuously for one week in an atmosphere exposed to a temperature of 750°C, but no abnormality was observed.

Note that half of the weight of the BaHP04 was replaced with the CaH4 (
Substantially similar results were obtained when PO4)2'H20 was used instead.

Example 3 Expanded graphite powder 1100 pulverized to have a bulk specific gravity of 0.06
20 g of an 8% methyl alcohol dispersion of Lr3P048 was sprayed and adsorbed using the powder mixing device 2 shown in the figure, and the resulting mixed powder 9 was press-molded to obtain a packing material.

The packing material of this compact was used between the joints of a tube furnace and was used continuously for one week in an atmosphere exposed to a temperature of 750°C, but no abnormality was observed.

Note that half of the weight of Ll3PO4 is replaced by BaHPO4
Almost the same results were obtained in both cases where CaH4(P04)2.H20 and CaH4(P04)2.H20 were substituted.

Example 4 Expanded graphite powder 110 pulverized to have a bulk specific gravity of 0.04
For 0 g, Ll3P04, BaHP04 and CaH
100 g of a methyl alcohol dispersion containing 2% each of 4(PO4)2 and H20 (6% in total) was prepared and used, and after adsorption by spraying using the powder mixing device 2 shown in the figure, the obtained mixed powder 9
It was press-molded into a packing material.

The packing material of this molded body is used between the joints of the tube furnace,
When used continuously for one week in an atmosphere exposed to a temperature of 750°C, no abnormalities were observed.

Of course, there was no need to loosen or retighten the packing.

In this case, substantially the same results as above were obtained even when the phosphate powder was added and mixed directly as a powder without using a dispersion.

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view showing a powder mixing device according to the invention. 1... Expanded graphite powder with a bulk specific gravity of 0.067 to 0.01, 2... Powder mixing device, 3... Container, 4... Compressed air Inlet, 5... Compressed air (3 to 5 atm), 6,... ... Valve (pressure reduction control valve), 7... Additive inlet, 8...
Phosphate fine powder, 9... Mixed powder (i.e., a mixture of expanded graphite powder and phosphate powder), 10...
・Filter, 11...Exit.

Claims (1)

[Scope of Claims] 1. Bulk specific gravity obtained by subjecting graphite powder to desired expansion treatment.
Li3PO4, BaHPo4 and CaH4 (
P04) Powder of one or more types of 2/H20 0.1~
A method for producing a graphite compression molded body for high-temperature packing, which comprises adding and mixing 5% by weight as is, and then cold compression molding in a desired packing mold. 2 Bulk specific gravity obtained by subjecting graphite powder to desired expansion treatment: 0.
Li3PO4, BaHPO4 and CaH4 (
P04) Powder of one or more types of 2/H20 0.1~
5% by weight of a lower alcohol suspension dispersion such as methyl alcohol, which is sprayed, added and mixed, and then cold compression molded in a desired packing mold. Production method.