JPH0787848B2 - Mold for molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molding die, and more particularly to a molding die used for molding artificial materials such as dental materials, bones and joints made of calcium phosphate-based crystallized glass. It is a thing.

[Prior Art] In recent years, various artificial materials have been proposed for dental materials, bones, joints, etc., and some of them have been put into practical use.

Of these artificial materials, calcium phosphate-based materials are
Since it is the same as or close to the components of the teeth and bones of the living body,
There is an advantage that it is a preferable material with less rejection reaction from the subject. Among these materials, calcium phosphate-based crystallized glass is expected to be applied as a dental material because of its excellent moldability, particularly because it has physical properties that closely resemble those of natural teeth.

Conventionally, as means for obtaining such a material, molding and crystallization have been performed by casting a calcium phosphate-based material into a magnesium phosphate-based molding material or a silicate-based molding material.

[Problems to be Solved by the Invention] However, in all of these, fine cracks are generated on the surface of the mold material, or the strength of the mold material is insufficient, so that the mold may partially collapse due to the inflow of glass during molding. However, there is a problem in that dimensional accuracy is very unstable because of the occurrence of protrusions, burrs and the like on the surface of the obtained glass molded body.

[Means for Solving the Problems] The present invention eliminates the drawbacks of the conventional method, and finds a mold obtained by molding a molded product having fine dimensional accuracy without causing fine cracks on the surface of the molded product. As a result of various studies and studies for the above purpose, it was found that the above object can be achieved by performing a specific treatment near the molding surface of the mold. Thus, the present invention provides a molding die characterized in that a heat-resistant fibrous substance and boron nitride are present up to a depth of at least 10 μm from the molding surface of the die.

In the present invention, the mold substrate for allowing the fibrous substance to exist is not particularly limited, and for example, magnesium phosphate-based, silicate-based, alumina-based, aluminum phosphate-based, zirconia-based, gypsum-based, etc. are appropriately adopted. obtain.

The fibrous substance has a diameter of 0.1 to 10 μm and a length of 10
It is appropriate to adopt ~ 500μ. If the diameter is less than 0.1 μm, the expected effect is not sufficiently exhibited, and conversely, if it exceeds the above range, the smoothness of the molding surface of the mold may be impaired, which is not preferable. Also, the length is 10μ
If it is less than the above range, the expected effect is not sufficiently exhibited, and conversely if it exceeds the above range, the smoothness of the molding surface of the mold may be impaired.

And within these ranges, the diameter is 0.2-2μ and the length is 20.
It is particularly preferable to employ a thickness of up to 200 μm because the intended purpose can be sufficiently achieved. It is also necessary that such fibers be present at a depth of at least 10μ from the mold surface. If the depth to be present is less than 10 μ, the desired effect cannot be obtained, which is unsuitable. When actually making a mold, it is realistic to mix the fibers with the mold base material and allow the fibers to exist over the entire mold, but in essence, the fibers are up to about 50μ from the surface of the mold. The presence of the above-mentioned object makes it possible to obtain the intended purpose sufficiently and stably. The amount of fibers to be present in the mold is suitably 0.5 to 30% by weight based on the total amount of the amount of the fibers and the amount of the fiber to the depth of the mold. If the existing amount is less than the above range, the intended purpose cannot be sufficiently achieved, and conversely, if it exceeds the above range, the smoothness of the molding surface may be impaired. And when adopting 1 to 10 wt% of these ranges,
It is particularly preferable because the intended purpose can be sufficiently achieved and the smoothness of the surface of the molded body is not impaired.

The fibrous substance used in the present invention is required to be heat-resistant because it is initially a melted material to be molded.
There is no particular limitation as long as it is stable at a high temperature of 800 ° C or higher. Examples of such fibers include silicon carbide, silicon nitride, boron carbide, asbestos, alumina, rock wool, silica and the like. Thus, the molded product molded using the molding die according to the present invention has a smooth surface, no protrusions or burrs, and high dimensional accuracy. However, this alone has some difficulty in releasability. In particular, when the object to be molded is calcium phosphate type glass, the mold and the glass partly react with each other, which tends to make it difficult to release the mold.

The present inventor conducted a study to improve such a point,
It has been found that the presence of boron nitride on the surface of the mold improves the releasability. Boron nitride, like the fibrous material described above, may be present at a depth of at least 10μ from the surface of the mold.

It is appropriate to use boron nitride and fibrous substances in an amount of 10 to 80% by weight of boron nitride and 0.5 to 30% by weight of fibrous substances, based on the total amount of these and the mold base material in which they are present. is there.

When the amount of boron nitride used is less than the above range, a sufficient mold releasing effect cannot be expected, and when it exceeds the above range, the strength of the mold is lowered and the fibrous substance is allowed to exist. None of them are preferable because they may be meaningless.

According to the above indication, boron nitride of 30 to 60% by weight and fibrous substance of 1 to 10% by weight are particularly preferable because the smoothness of the surface of the molded body is good and the releasability is sufficient. . Actually, as a means for obtaining the molding die according to the present invention, for example, a method of forming a mold by premixing the above-mentioned fibrous substance or this and boron nitride in a predetermined amount in a mold base and curing the mixture on the master mold surface , A method of applying the fibrous substance or a base material mixed with boron nitride to the surface of a mold prepared in advance, the above-mentioned method on the mold surface (wax pattern in the case of the lost wax method), A method is also used in which a fibrous substance or a base material mixed with boron nitride is applied or dipped to form a layer containing the fibrous substance or boron nitride and then a mold is formed. You can

Various materials can be used for molding by using the molding die according to the present invention, and calcium phosphate-based glass useful as a biomaterial is particularly suitable. Its composition is, for example, GaO 41 to 49.5 mol%, P ₂ O ₅ 58.5 to 50 mol%, Al ₂ O ₃ 0.
5 to 5 mol% and the atomic ratio represented by Ca / P is 0.35
A value of ˜0.7, preferably 0.35 to 0.49 is suitable.

Further, as a means for molding such a calcium phosphate glass using the molding die according to the present invention, for example, a commonly used means such as the lost wax method or press molding can be appropriately adopted. Further, the glass thus formed can be further crystallized, in which case, for example, 700
Means such as holding for about 2 hours in an electric furnace kept at ℃ is adopted.

[Example] Example 1 A sprue wire was attached to a wax pattern having a crown shape, and the sprue wire was set in a rubber cone. And the diameter is 0.5 ~
2 parts of silicon carbide whiskers having a length of 2 μm and a length of about 20 to 100 μm are mixed with 10 parts of boron nitride powder and 15 parts of an ethyl silicate binder (HAS-6 manufactured by Colcoat Co.) to obtain a uniform slurry, which is used as the wax pattern. Apply on top and apply.
A mold material surface layer having a thickness of about 2 mm was formed. The whole was placed in a metal ring and embedded with a phosphate-based investment material (Blue Vest, manufactured by Tokuyama Soda Co., Ltd.). Then, this was dried and then heated to 700 ° C. to incinerate the wax pattern to obtain a lost wax mold for making a crown.

On the other hand, a composition of 24% by weight of CaO, 1% by weight of Al ₂ O _{3 and} 75% by weight of P ₂ O _{5 was} melted at 1250 ° C. to obtain a glass solution, which was centrifugally cast into the above lost wax mold, and 680 as it was. Crystallization was carried out by keeping at 3 ° C for 3 hours.

Then, the mold was broken to take out the molded body, and the sprue wire was cut to obtain a calcium phosphate crystallized glass dental crown.

The surface of the obtained crown was very smooth and glossy, with no burrs or protrusions. The dimensional change from the wax pattern was 50 μm or less.

Claims (3)

[Claims] 1. A molding die characterized in that a fibrous substance having heat resistance and boron nitride are present up to a depth of at least 10 μm from the molding surface of the die. 2. The abundance of the fibrous substance and boron nitride is 0.5 to 30% by weight of the fibrous substance and 10 to 80% by weight of boron nitride, based on the total amount of the fibrous substance and the mold base on which they are present. The molding die according to claim 1. 3. The fibrous substance has a diameter of 0.1 to 10 μm and a length of 10 to 5
The molding die according to claim 1 or 2, which has a size of 00μ.