JP2594952B2 - Molded heat insulating material and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a carbonaceous molding for a non-oxidizing atmosphere furnace such as a vacuum heat treatment furnace, a silicon single crystal pulling furnace or a ceramic sintering furnace having excellent heat insulation and durability. The present invention relates to a heat insulating material and a method for manufacturing the same.

<Prior Art> Conventionally, carbon fiber felt (produced by needle-punching a random web of carbon fiber) has been widely used as a heat insulating material for a non-oxidizing atmosphere furnace, but the felt does not have autonomy. Therefore, many supports are required to install in the furnace, and the felt surface is fuzzy,
There are many difficulties such as the broken and scattered carbon fibers contaminating the material to be fired, and the user of the furnace or the manufacturer of the furnace has demanded the development of a heat insulating material having excellent workability.

Various devices and proposals have been made to improve such difficulties.

For example, in order to improve the workability, a method of sewing the felt or impregnating the felt with a resin to be carbonized, hardening and laminating the felt, and then carbonizing the felt to impart rigidity to the carbon fiber felt has been adopted.

<Problems to be Solved by the Invention> However, in the case where the felts of carbon fibers are laminated and used as described above, since the needle-punched thread is perpendicular to the lamination surface, it is used as a heat insulating material. ,
Heat escapes along the vertical yarn, and the amount of heat dissipation increases, and the temperature in the furnace becomes uneven, which has a problem of adversely affecting the fired product.

<Means for Solving the Problems> In view of such problems, the present inventors have conducted intensive studies, and as a result, have used a two-dimensionally randomly oriented carbon fiber web without using carbon fiber felt. As a result, the inventors have found that these problems can be solved, and arrived at the present invention. That is, an object of the present invention is to provide a carbonaceous heat insulating material for a non-oxidizing atmosphere furnace such as a vacuum heat treatment furnace, a silicon single crystal pulling furnace or a ceramic firing furnace which has excellent heat insulation and durability, and a method for producing the same. is there.

 This object is achieved by the following configuration.

(1) A molded heat insulating material obtained by impregnating a carbonized resin into a random web in which carbon fibers are two-dimensionally orientated, laminating and molding, and then firing and graphitizing the laminated heat insulating material. On the heat-insulating surface, the carbon fibers constituting the heat-insulating material are oriented substantially parallel to the laminating surface, and the dimensional change in the direction parallel to the laminating surface before and after firing / graphitization is substantially changed. Molded heat insulation material that does not occur.

(2) Bulk density in which carbon fibers are randomly oriented two-dimensionally 0.01
A dilute solution obtained by dissolving 5 to 25 parts by weight of a resin to be carbonized with respect to 100 parts by weight of alcohol or water having a boiling point of 100 ° C. or less in a random web of about 0.05 g / cm ³ is 250 to 100 parts by weight of the web. A method for producing a molded heat insulating material, comprising: impregnating 450 parts by weight, forming a molded product having a desired thickness while compressing and laminating the same, curing at 150 ° C. or more, and further performing calcination and graphitization treatment.

 Hereinafter, the present invention will be described in detail.

As the carbon fibers used in the present invention, carbon fibers of various raw materials such as carbon fibers made of polyacrylonitrile, carbon fibers made of petroleum pitch and coal pitch, and carbon fibers made of phenol fiber can be used.
In addition, as the type of carbon fiber, infusible fiber, carbonized fiber,
Various materials such as carbon fiber and graphitized fiber can be used. However, care should be taken when using carbonized fiber or infusibilized fiber of a low-temperature fired yarn, since large shrinkage occurs during firing and graphitization of the molded heat insulating material.

The form of the carbon fiber used is not particularly limited, but it is preferable to use a short fiber having a length of about 1 to 10 cm.

As the resin to be carbonized, a resin having a high carbonization yield, such as a phenol resin or a furan resin, which is easily carbonized, is used. Phenolic resin is most suitable in terms of handling and economy.

As a method for producing a two-dimensionally randomly oriented web, a carbon fiber is mechanically converted into a monofilament, which is generally used in spinning, and the web is produced using a random weber for producing the web, or defibrated by air to form a web. There is a manufacturing method.

As the bulk density of the random web, various ones can be taken, but in consideration of handleability, impregnation with a resin to be carbonized, uniformity, etc., 0.01 to 0.05 g / cm ³ is optimal.

The two-dimensionally oriented random web is impregnated with a resin to be carbonized. To make the impregnation uniform, it is desirable that the viscosity (20 ° C.) of the impregnation solution be 10 cps or less, preferably 4 cps or less. For this purpose, a dilute solution in which 5 to 25 parts by weight of a resin to be carbonized is dissolved in 100 parts by weight of alcohol or water having a boiling point of 100 ° C. or lower is used.

The ratio of the carbon fiber to the carbonized and graphitized resin in the molded heat insulating material is preferably 6: 4 to 9: 1 (weight ratio), and particularly preferably 7: 3 to 8: 2.

When the proportion of the resin is higher than the above proportion, the resin undergoes a large shrinkage when carbonized by graphite, which is not preferable because the molded article may undergo a large deformation and shrinkage.

From such a viewpoint, impregnation (adhesion) of the dilute solution
Is preferably selected from 250 to 450 parts by weight based on 100 parts by weight of the web.

Also, in order to keep the resin uniformly in the carbon fiber,
A better molded article can be obtained by laminating and compressing an impregnated web from which the alcohol or water of the solvent has been gradually removed at a temperature of 0 ° C. or lower to obtain a molded article having a desired thickness and shape, and then curing the molded article.

After curing, the formed heat insulating material is obtained by firing and graphitizing according to a conventional method.

The shape of the heat insulating material of the present invention may be a generally used heat insulating material such as a cylindrical shape or a flat plate shape.

If there is a possibility that dust such as carbon fibers may be mixed into the material to be fired in the furnace, apply a coating agent such as graphite cement to the surface of the molded heat insulating material, or use a sheet of expanded graphite, carbon fiber paper, etc. Can be pasted.

<Example> Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 A carbon fiber made from coal pitch was cut to a length of 5 cm,
This chopped strand was defibrated with a random weber to obtain a two-dimensionally randomly oriented random wag having a bulk density of 0.03 g / cm ³ .

Also, resol type phenol resin is added to 100 parts of ethanol.
0 parts was dissolved to prepare a dilute solution of 2.7 cps. The above-mentioned 100 parts of the damdam web was impregnated with 360 parts of the diluted solution. The impregnated web is air-dried until the ethanol concentration becomes 20%, and the air-dried web is laminated.
Cured at 0 ° C. After curing, baking in Ar at 2000 ° C, graphitizing,
A molded body having a bulk density of 0.2 g / cm ³ was obtained. The ratio of the fibers of the molded article to the graphitized resin was 8: 2, and the dimensional change before carbonization shrank by 0.2% in the lamination thickness direction but did not change in the length direction. When the thermal diffusivity of this compact is measured by the step method, it is 500 ° C. in vacuum (10 ⁻² Torr).
1.5 × 10 ⁻³ cm ² / sec at 1000 ° C. and 4.1 × 10 ⁻³ cm ² / sec.

Comparative Example 1 The two-dimensional random web obtained in Example 1 was used with a needling device at 25 lines / inch ² (A), 100 lines / inch ² (B), 1 line.
The felt was manufactured by passing 50 warp yarns / inch ² (C).

Using these three types of felts, impregnation, lamination, curing, firing and graphitization were carried out in the same manner as in Example 1 to obtain molded articles each having a bulk density of 0.2 g / cm ³ .

These three thermal diffusivities were measured by the step method.
The results are shown in Table 1.

Table-1 500 ℃ 1000 ℃
A (50 pcs / inch ² ) 1.8 × 10 ^-3 cm ² / sec 5.0 × 10 ^-3 cm ²
/ sec B (100 / inch ² ) 3.5 × 10 ^-3 cm ² / sec 1.0 × 10 ^-3 cm ² / s
ec C (150 / inch ² ) 5.5 × 10 ^-3 cm ² / sec 1.4 × 10 ^-3 cm ² / se
c Example 2 The same impregnated web as in Example 1 was wound while compressing it into a wooden mold having an outer diameter of 490 mm to form a cylinder having a thickness of 25 mmt, wrapping release paper outside, and wrapping it with metal from above. And cured. After curing, the mold was released, and the cylindrical compact was fired and graphitized to obtain a compact having a bulk density of 0.15 g / cm ³ . The dimensional change from before carbonization was 0.1% shrinkage in the thickness direction, but there was no deformation.

When the thermal diffusivity was measured in a vacuum (10 ^-2 Torr) by the step method, it was found to be 1.3 × 10 ⁻³ cm ² / sec at 500 ° C. and 8.0 at 1000 ° C.
× 10 ⁻³ cm ² / sec.

Comparative Example 2 100 parts of the two-dimensional random web obtained in Example 1 was impregnated with 600 parts of the diluted solution of the phenolic resin obtained in Example 1, and after laminating in a cylindrical shape as in Example 2, curing, firing, Graphitization was performed. The molded article after graphitization was deformed and could not be used as a heat insulating material.

<Effects of the Invention> According to the present invention, a formed heat insulating material having excellent heat insulating properties and durability can be obtained.

Claims (2)

(57) [Claims] 1. A molded heat insulating material obtained by impregnating a carbonized resin into a random web in which carbon fibers are randomly oriented two-dimensionally, laminating and molding the same, and then firing and graphitizing the same. In the laminated heat-insulating surface, the carbon fibers constituting the heat-insulating material are oriented substantially parallel to the laminated surface, and the dimensional change in the direction parallel to the laminated surface before and after firing and graphitization. Substantially no molded insulation. 2. A carbonized resin 5 to 25 parts by weight per 100 parts by weight boiling point 100 ° C. or less of alcohol or water to a random web having a bulk density of 0.01 to 0.05 g / cm ³ which the carbon fibers are oriented in two-dimensional random The web was impregnated with 250 to 450 parts by weight of the dilute solution with respect to 100 parts by weight of the web, formed into a molded product having a desired thickness while being laminated and compressed, and then cured at 150 ° C. or more, and further calcined. A method for producing a molded heat insulating material, which comprises performing a graphitization treatment.