JPH0653582B2 - Mold for molding calcium phosphate-based crystallized glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold for molding calcium phosphate-based crystallized glass, and more particularly to a mold for molding which does not cause any inconvenience on the surface or inside of calcium phosphate-based crystallized glass. It is related.

(Prior Art) Calcium phosphate-based crystallized glass has good affinity with living organisms and has physical properties similar to natural teeth. Also, calcium phosphate-based glass is melted and cast into a mold, and then crystallized. Since it can be formed in the same manner as metal by the method of performing, the application as a dental material has been proposed.

In general, as a casting mold for dental metal, since the molten metal (hot water) needs only to enter the casting part of the casting metal part, it is not necessary to consider the shape, and it is usually just a cylinder. It was provided as a void.

However, when such a metal casting mold is used for the calcium phosphate-based glass, during the subsequent crystallization treatment, some bubbles are observed on the surface and inside of the molded product, which damages the shape or breaks it. There are drawbacks such as

As a result of various studies and studies to eliminate such defects and obtain a calcium phosphate-based crystallized glass that does not generate bubbles, the present inventors found that the crystal of the crystallized glass originates from the surface and progresses toward the inside at a fairly uniform speed. However, since crystallized glass has a higher density than ordinary glass, it has been found that voids are generated by the amount of shrinkage due to crystallization at the end of crystallization, which remains as bubbles.

Based on this knowledge, when a calcium phosphate-based crystallized glass molded body has already been obtained by the casting method as a means for creating a cavity in a portion other than the molded body, the diameter of the sprue wire (runner) of the mold is set to the thickness of the glass molded body. It is disclosed in Japanese Patent Application Laid-Open No. 61-7104 that the final crystallization is caused by increasing the size.
Proposed as No. 4.

(Problems to be Solved by the Invention) The method proposed above is certainly an effective means, and there is no problem as an ordinary method for producing this seed crystallized glass.

However, in the case of calcium phosphate-based crystallized glass, the main crystal phase is calcium metaphosphate crystal, and the crystal forms thereof are β crystal and δ crystal, and crystallization is usually performed in the coexistence of these.

Further, in the case of such crystallized glass, it is desirable to make more β crystal in order to obtain glass having water resistance and a transparent appearance. And it is effective to allow the presence of fine crystals of calcium metaphosphate on the surface of the mold in contact with the glass as a means for achieving this, and to make the diameter of the runner of the proposed mold larger than the wall thickness of the glass molding together with this. Unexpectedly, cavities may occur in the molded body when used in combination with
It has been found that simply increasing the diameter of the spray wire is not sufficient to prevent cavities.

(Means for Solving Problems) The present invention has been made based on such findings, and by forming the mold runner into a specific shape, even if a mold having calcium metaphosphate on the surface is used, a cavity is formed in the molded body. It has been found that it does not give rise to.

Thus, the present invention, in the casting mold of calcium phosphate-based crystallized glass, the shortest diameter is larger than the maximum casting wall thickness of the casting part, and the runner of a shape that becomes thicker as it moves away from the forming part. Another object of the present invention is to provide a mold for molding calcium phosphate-based crystallized glass, which is characterized by having.

The present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating the basic structure of a mold for molding calcium phosphate glass according to an example of the present invention. In FIG. 1, 1 is a forming part for forming a cast formed product such as a tooth, and 2 is a runner into which a calcium phosphate glass melt (hot water) is cast into the forming part 1. Reference numeral 3 is an inlet for hot water, and this shape is not particularly limited as long as hot water can be injected.

In the present invention, the runner 2 is required to be connected to the maximum cast wall thickness portion of the cast molding portion 1, and its shape needs to have a larger minimum diameter than the cast wall thickness portion. This is because if the shortest diameter is equal to or smaller than the thick portion, the runner will complete crystallization before the thick portion and bubbles will be generated in the thick portion. The runner 2 has a shape that becomes thicker as it goes away from the forming unit 1. By doing so, the crystallization can be delayed as it gets closer to the injection port 3, and it is possible to reliably prevent the formation of bubbles in the molding part.

Actually, such a shape of the runner 2 is, for example, a truncated cone or a truncated pyramid,
A shape such as a truncated pyramid is used, but it is preferable to use a truncated cone.

The length of the runner 2 (corresponding to the height of the truncated cone) is at least 5
It may be about mm, and the lower end of the heel runner (the tip with a thickened tip) can also serve as the injection port 3.

In the case of a truncated cone, the degree to which the runner 2 becomes thicker is expressed by an inclination angle (angle formed by the generatrix and the central axis), preferably 5 degrees or more, and particularly preferably 15 to 45 degrees. is there.

As a material for forming such a mold, for example, a phosphate-based investment material, an ethylsilicate-based investment material, a gypsum-based investment material, or the like can be appropriately adopted. In particular, the surface of the molding part 1 is a fine particle of boron nitride and calcium metaphosphate. It is preferable that crystals (usually 100 μm or less) be present. By doing so, crystallization of the molded body, particularly growth of β crystal, is remarkable, and mold release can be facilitated.

Boron nitride is 1 ~ 8 within 10μ ~ 1mm from the surface of the mold
It is effective that 0% by weight and fine crystals of calcium metaphosphate are present in an amount of about 1 to 50% by weight within 10 μm to 1 mm from the surface of the mold.

The mold is usually a buried mold such as the Lost Wax method, but other molds such as a split mold can be used.

The calcium phosphate-based glass used in the present invention is preferably one in which calcium metaphosphate crystals are precipitated as a main precipitation crystal phase. For example, those containing 80% by weight or more of calcium phosphate having an atomic ratio Ca / P of calcium to phosphorus of 0.35 to 0.7 are preferable.

In the present invention, in order to actually cast a calcium phosphate-based crystallized glass, for example, a glass melted at 1000 ° C. or higher is cast into a mold by utilizing centrifugal force or a pressure difference in an atmosphere, and then molded into a predetermined shape. Cooled at 70, then 70
A means for performing crystallization by holding at 0 ° C. for 4 hours and then demolding is adopted.

The mold according to the present invention is effective when calcium metaphosphate crystals are allowed to be present on the surface of the molded part in order to promote control of crystallization, but it is also possible to mold a mold without such a control accelerator. It goes without saying that it has the effect of not causing voids in the body.

(Example) A crown having a truncated cone shape with an outer diameter of 30 mm, a height of 18 mm, and a diameter of 3 mm at the top (utility wax manufactured by Ji Dental Industry Co., Ltd.) with a maximum wall thickness of 1.8 mm at the top A wax pattern for forming (the same wax manufactured by the same company) was attached at its maximum wall thickness.

Then, a stainless steel ring having an inner diameter of 30 mm and a height of 50 mm was arranged around it.

On the other hand, 30% by weight of boron nitride powder, 20% by weight of calcium metaphosphate crystals having an average particle size of 5μ, and the balance being a phosphate-based investment material (Bluebest manufactured by Tokuyama Soda Co., Ltd.) were sufficiently mixed to form a slurry according to a conventional method. It flowed into the ring and was left to cure. Then, the wax was incinerated by heating at 800 ° C. for 40 minutes to obtain a mold.

Next, CaO 24.5% by weight, P ₂ O ₅ 74.5% by weight, Al ₂ O
₃ 1.0% by weight of the composition was melted at 1200 ° C. to obtain a calcium phosphate glass, and the glass was centrifugally cast into the mold according to a conventional method. Then 2 at 700 ℃ with the mold
The glass in the mold was allowed to crystallize by holding for a period of time.

After cooling to room temperature, the mold was broken and the crystallized glass was taken out, and the crown molding was cut at the interface with the runner.

In the same manner, a total of 10 tooth crowns were prepared and inspected by the X-ray flaw detection method, respectively, and no cavities existed in any of them.

In addition, large and small cavities were observed in the crystallized glass existing below the runner.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining the basic structure of a mold for molding calcium phosphate glass according to an example of the present invention. 1: forming part, 2: runner, 3: injection port

Claims (1)

[Claims] 1. A casting mold for calcium phosphate-based crystallized glass, comprising a runner having a shape in which the shortest diameter is larger than the maximum casting wall thickness of the casting part, and becomes thicker as the distance from the molding part increases. A mold for molding calcium phosphate-based crystallized glass, which comprises: