JP2878832B2 - Manufacturing method of high-purity fine molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a high-purity fine molded product, and in particular, a molded product molded on a graphite substrate by a chemical vapor deposition method can be easily separated from the graphite substrate. The present invention relates to a method for producing a high-purity fine molded body as described above.

(Prior art) Pyrolytic boron nitride (hereinafter abbreviated as PBN), which is widely used as an insulating material having excellent heat resistance, is usually made of ammonia (NH ₃ ) gas and boron trichloride (BC).
l ₃ ) and a boron halide such as boron trifluoride (BF ₃ ) are subjected to a thermal decomposition reaction (CVD reaction) at high temperature and reduced pressure, and the reaction product is placed around a graphite substrate of a desired shape. To form a compact, and then the compact is separated from the graphite substrate.

(Problems to be Solved by the Invention) However, in this method, the graphite base material is sufficiently large, and a sufficient clearance for separating the molded body and the graphite base material due to a difference in thermal expansion coefficient upon cooling after the CVD reaction. Although it is good if it can be obtained, if the target molded body is a thin pipe having a diameter of, for example, 3 mm or less, almost no clearance occurs, so this molded body can be separated from the graphite substrate. However, there is a disadvantage that such a fine compact cannot be produced in practice.

(Means for Solving the Problems) The present invention relates to a method for producing a high-purity fine molded body which solves this disadvantage, and which comprises extruding a graphite member obtained by mixing and firing a binder with graphite. The method is characterized in that a molded body is deposited on a suitable graphite substrate by a chemical vapor deposition method, and then the molded body is separated from the graphite substrate.

That is, the inventors of the present invention have conducted various studies on a method for producing a fine vapor-deposited molded body, which has conventionally been difficult to separate from a graphite substrate, and as a result, the graphite substrate used here was mixed with a binder in graphite and fired. When the graphite member is extruded and formed into a fine material, and a formed body is deposited thereon by a chemical vapor deposition method, the graphite base is softened by the high temperature during the chemical vapor deposition. The inventors have found that they can be easily separated when separated, and have proceeded with research on a method for producing the graphite substrate and the like, thereby completing the present invention.

 This will be described in more detail below.

(Function) The present invention relates to a method for producing a high-purity fine molded body by a chemical vapor deposition method.

For example, a pyrolytic boron nitride (PBN) molded product is prepared by subjecting ammonia and boron halide to 1,450 to 2,000 ° C., particularly to 1,500 to 1,800 ° C. for 0.1 to 20 ° C.
It is made by a method of performing a thermal decomposition reaction under reduced pressure such as Toll, depositing this reaction product on a graphite substrate by a chemical vapor deposition method to form a molded body, and then peeling it from the graphite substrate, The process is carried out in accordance with the PBN manufacturing method.

Since the production of the molded article according to the present invention is also carried out by this method, it can be obtained with high purity.However, as described above, when the molded article is fine, for example, having a diameter of 3 mm or less, a graphite substrate is used. The disadvantage is that this separation becomes difficult because the clearance cannot be obtained.

However, according to the present invention, the graphite substrate is mixed with graphite powder as a ceramic binder, an organic thermoplastic resin or an organic thermosetting resin as a binder, and baked to form a graphite member, which is extruded and formed into a fine particle. Thing, for example, shall be formed into a rod shape with a diameter of 3 mm or less, and the chemical vapor deposition method as described above
When a compact such as PBN is deposited, this compact is naturally fine because the graphite substrate is fine, but the formation of this compact is made by chemical vapor deposition. But usually 1,450 ° C as mentioned above
Since the graphite base is a mixture of a ceramic binder and a synthetic resin as described above, the graphite base is softened at this temperature. The advantage that separation from the substrate is easily performed and a fine molded body is easily obtained is provided.

The binder added to the graphite powder to form the graphite substrate is a ceramic binder, an organic thermoplastic resin, or an organic thermosetting resin, as described above. ₂ O ₃ ),
Select from ceramic binders such as silica (SiO ₂ ), organic thermoplastic resins such as polyvinyl chloride, polyvinyl acetate, polystyrene, and polyethylene, and organic thermosetting resins such as phenolic resin, furfural resin, epoxy resin, and polyester resin. If the amount is less than 10% by weight, the softening effect of the graphite substrate after the high-temperature treatment by the chemical vapor deposition method is small.
If the amount is more than 10% by weight, the high-temperature strength of the graphite base may be insufficient and the graphite may be deformed. Therefore, the amount is preferably in the range of 10 to 30% by weight based on the graphite powder. The extruded material gives a long rod with good dimensional accuracy when extruded, so that it can be molded to a diameter of 0.3 mm.

Further, since the fine graphite substrate thus produced is softened by the high temperature in the chemical vapor deposition method as described above, it is easy to separate from the molded body.
It is also presumed that, since the binder added thereto is volatilized gradually at a high temperature by the chemical vapor deposition method and the base becomes porous, it is easy to separate from the molded body also from this point.

In the production of the molded article according to the present invention, as described above, the graphite substrate on which the molded article is deposited by the chemical vapor deposition method (CVD method) is made fine by extruding a graphite member obtained by adding a binder to graphite powder. Although they are fine, they can be easily separated from the graphite substrate, so that
An ultra-fine pipe having a diameter of 3 mm or less, for example, 1 mm in diameter can be obtained, and this pipe is useful as a pipe insulated through a heater or a thermocouple.

(Examples) Examples of the present invention and comparative examples will be described below.

Examples 1 to 3 and Comparative Examples A graphite composition obtained by mixing an equal mixture of alumina and silica at 30% by volume with isotropic dense graphite was extruded and molded into 50 rod-shaped graphite substrates having a diameter of 2 mm and a length of 300 mm. It is installed upright in a vacuum furnace, and the furnace is kept at 1,800 ° C and 1 Torr or less, and NH ₃ gas is
/ Minute, BCl ₃ gas was supplied at 1 / minute, and the pyrolysis reaction was carried out for 3 hours while adjusting the pressure to 10 Torr or less. After cooling, this was taken out from the vacuum furnace. Since the PBN had been molded, when this PBN compact was separated from the graphite substrate, all 50 could be easily separated, with an inner diameter of 2 mm and a length of 250 mm
50 PBN pipes were obtained.

Also, a graphite composition prepared as a mixture of 30% by weight of polyvinyl chloride and 20% by weight of an epoxy resin in place of the equivalent mixture of alumina and silica in the above, and for comparison, obtained by extrusion molding from graphite to which these binders are not added. The same test as described above was carried out on 50 rod-like graphite substrates, and the results shown in the following Table 1 were obtained.

(Effects of the Invention) The present invention relates to a method for producing a high-purity fine molded article, which comprises mixing a ceramic binder, an organic thermoplastic resin, or an organic thermosetting resin with graphite as described above, and firing the mixture. On a fine graphite substrate obtained by extruding the formed graphite member, a molded body is deposited by a chemical vapor deposition method, and then the molded body is separated from the graphite substrate. According to this, the graphite substrate is softened at a high temperature in the chemical vapor deposition method by the addition of the binder, so that it can be easily separated from the fine compact formed on the fine graphite substrate, and the desired high purity and fineness can be obtained. The advantage is that a compact can be easily obtained.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuhiro Yamaguchi 2-13-1 Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Research Laboratories (58) Field surveyed (Int. Cl. ⁶ , DB Name) B28B 21/42 B28B 1/30 C23C 14/00-16/56

Claims (4)

(57) [Claims] 1. A molded body is deposited by chemical vapor deposition on a fine graphite substrate obtained by mixing a binder with graphite and extruding a calcined graphite member, and then separating the molded body from the graphite substrate. A method for producing a high-purity fine molded body. 2. The high-purity fine particle according to claim 1, wherein the binder is selected from a ceramic binder, an organic thermoplastic resin or an organic thermosetting resin, and the ratio is 10 to 30% by weight. A method for producing a molded article. 3. The molded article is pyrolytic boron nitride.
The method for producing a high-purity fine molded article according to the above. 4. The method according to claim 1, wherein the graphite substrate is a rod-shaped product having a diameter of 3 mm or less.