JPS6410447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming calcium phosphate glass.

[Conventional technology]

Bioactive ceramics can be used as artificial bone materials,
It has attracted attention as an artificial tooth material, and many reports have been made, such as sintered hydroxyapatite and sintered calcium triphosphate. However, artificial bones, artificial teeth, and the like have complex and uneven shapes, and require high dimensional accuracy. It is very difficult to obtain such a molded body using these sintered bodies.

Therefore, as a ceramic material from which such molded bodies can be obtained, development of crystallized glass materials has proceeded, and calcium phosphate crystallized glass has been reported in Japanese Patent Publication No. 55-11625. In this method, a shape is imparted to a melt of calcium phosphate glass when it is solidified and vitrified, and the glass is crystallized to obtain crystallized glass. It has been reported that gypsum-based investment materials and phosphate-based investment materials can be used as mold materials for molding this calcium phosphate glass (Japanese Patent Application Laid-Open No. 141509-1983). However, gypsum-based investment materials react violently with calcium phosphate glass at approximately 700°C and release SO ₂ gas, making the formed glass more likely to contain air bubbles and lowering the strength of the resulting crystallized glass. In addition, since a reaction layer is formed between the mold material and the glass, it is difficult to separate the glass molded body from the mold, and the resulting glass molded body has a low dimensional accuracy. On the other hand, although the glass molded object obtained using a phosphate-based investment material does not contain air bubbles unlike the case where a gypsum-based investment material is used, it still forms a reaction layer between the mold material and the resulting glass molding. The drawback was that the dimensional accuracy of the body was low.

[Problem to be solved by the invention]

An object of the present invention is to prevent such a reaction between a molding material and molten glass, and to obtain a calcium phosphate glass molded body containing no air bubbles or foreign matter with high dimensional accuracy.

[Means for solving problems]

The present invention was made to solve the above-mentioned problems, and when a melt containing 90% by weight or more of calcium phosphate is poured into a mold, cooled and solidified, and molded, boron nitride is contained on the mold surface by 1% by weight or more. The present invention provides a method for molding calcium phosphate glass, which is characterized by providing a layer of vitreous material.

The calcium phosphate glass of the present invention is not particularly limited as long as it contains 90% by weight or more of calcium phosphate, but the calcium phosphate preferably has an atomic ratio of Ca/P of 0.35 to 0.7. When Ca/P is larger than 0.7, it is difficult to solidify the melt as glass, and 0.35
If the size is smaller, the resulting glass has poor water resistance, making it practically difficult to use it in the atmosphere.

This type of glass melt has a very low viscosity;
It has been found that it is easy to mold due to its high fluidity, but it also has good wettability with the mold material, so it penetrates into the micropores of the mold material and reacts with the mold material, thereby easily forming a reaction layer. As a result of investigating various mold materials that are less likely to cause such reactions, it was discovered that the formation of this reaction layer could be largely suppressed by reducing the wettability of the mold material with glass.
Furthermore, as a result of various studies on how to create a mold material with low wettability with glass, we found that the wettability of the mold with glass could be improved by providing a layer containing boron nitride, carbon, or calcium fluoride on the surface of the mold. It was also found that it significantly reduced
Above, boron nitride or carbon provided on the surface of the mold,
Alternatively, the layer containing calcium fluoride will be referred to as a reaction suppression layer. When we investigated a molding method using a mold with a reaction-suppressing layer on the surface, we found that when molding was performed using a mold with a reaction-suppressing layer containing carbon, the calcium phosphate glass was reduced and the glass was colored red. Bubbles are likely to form due to the generated CO gas, and when molding is performed using a mold with a reaction suppression layer containing calcium fluoride,
It has been found that the generated _F2 gas tends to cause bubbles, and when molding is performed using a mold material with a reaction suppression layer containing boron nitride, there are no bubbles or foreign substances.
Furthermore, it was found that a good glass molded product without forming the reaction layer between the mold and the mold could be obtained.

The content of boron nitride in such a reaction suppressing layer containing boron nitride is suitably 1% by weight or more, preferably 10% by weight or more, particularly preferably 30% by weight or more. If the amount is less than 1% by weight, the effect of reducing the wettability of the mold material due to glass is insufficient. On the other hand, if the content of boron nitride in the reaction suppression layer is high, depending on the method of forming this reaction suppression layer,
In order to maintain the strength of the suppression layer, there is an upper limit to the content. If the reaction suppression layer containing boron nitride on the surface of the mold is formed by a CVD method, sputtering method, etc., and the surface layer has a structure in which boron nitride itself has a bonding force, the boron nitride content is The higher the value, the better. Furthermore, when bonding boron nitride powder using a binder such as gypsum, the surface layer of the mold must not contain more than about 10% by weight of the binder, that is, the content of boron nitride must be less than about 90% by weight. Since the bonding strength of the reaction suppression layer is low, the reaction suppression layer may collapse due to the inflow of the glass melt.

A phosphate-based investment material can also be used as a component other than boron nitride in the reaction suppression layer. The phosphate-based investment material may be one commonly used, such as magnesia (MgO), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), or silicon dioxide (SiO ₂ ).
The following can be mentioned.

In addition, as a result of various studies, the thickness of the reaction suppression layer on the mold surface containing boron nitride was determined to be 1 μm.
It has been found that the formation of the reaction layer can be sufficiently suppressed if the thickness is preferably 10 μm or more. There is no particular limit to the thickness of this reaction suppression layer as long as it is thick, but as can be easily inferred from the above explanation,
Since the effect of the reaction suppressing layer on the mold surface containing boron nitride is expressed only in the part of the mold surface that comes into contact with the molten glass, no further improvement in the effect is observed even if the thickness is 100 μm or more.

There is no particular restriction on the method of forming such a reaction suppression layer, but there are methods for forming the surface layer on the surface of the mold by physical methods such as CVD or sputtering, coating on the surface of the mold, spraying, or forming the surface layer on the surface of the mold. A method of immersing the substrate in a reaction-suppressing layer forming solution is used. In addition, after forming a reaction suppression layer on the pattern surface by coating or spraying on the surface of the pattern surface (wax pattern in the case of the lost wax method), or by immersing the pattern in a reaction suppression layer forming solution, ,
A method of creating a mold may also be adopted.

〔Example〕

EXAMPLE As an example, a method for manufacturing a dental crown by the molding method of the present invention will be described with reference to FIG.

First, as shown in FIG. 1a, a dental plaster mold 1 was filled with heated and melted wax to create a wax pattern 2 for making a dental crown. Next, as shown in FIG. 1B, a sprue wire 3 was attached to this wax pattern 2, and then set on a rubber cone 4.

Phosphate-based investment material (Tokuyama Soda Blue Best)
Add 5 parts of boron nitride powder to 10 parts of the powder, add 20 parts of the special solution for the investment material, mix and stir to obtain about 30 parts of boron nitride.
Uniform slurry containing wt% and wax pattern on the no cone surface uniformly with thickness 0.1~0.5
It was applied to a thickness of about mm (investment material layer 11).
Furthermore, as shown in FIG. 1c, a wax pattern 2 was set in which a slurry 5 of a phosphate-based investment material (Blue Best manufactured by Tokuyama Soda) was applied with an investment material 11 containing boron nitride as described above. metal ring 6
Wax pattern 2 was injected into the cavity according to a conventional method to embed wax pattern 2.

After curing and drying, this was heated to 700°C to incinerate the wax pattern 2 and sprue wire 3. In this way, the lost wax mold 7 for the crown as shown in FIG.
and sprue 8 was formed.

On the other hand, CaO24% by weight, Al ₂ O ₃ 1% by weight, P ₂ O ₅ 75
Glass having a composition of % by weight was melted at 1250°C to prepare a glass melt.

As shown in Fig. 1e, this glass melt 9 was cast through the sprue 8 into the lost wax mold 7 for making dental crowns using a centrifugal casting machine, and then the immersion mold was kept at 680°C for 3 hours in an electric furnace. After the crystallization treatment, the investment material was broken and the molded body was taken out. Then, as shown in FIG. 1f, the sprue 8 was cut along line A-A' to obtain the tooth crown 10 shown in FIG. 1g.

The calcium phosphate-based crystallized glass dental crown obtained in this way has a smooth surface with a luster even without polishing, and when I attached it to the tooth plaster mold 1 used to create the wax pattern, it fit very well. Indicated. The obtained crystallized glass dental crown had a compressive strength of 4000 Kg/cm ² and a bending strength of 1700 Kg/cm ² .

Comparative Example A crystallized glass tooth crown was obtained in the same manner as in the example except that an investment material containing boron nitride was not applied on the wax pattern. The dental crown had a white, rough surface and was poorly compatible with the dental plaster mold 1.

〔Effect of the invention〕

As described above, according to the present invention, since the reaction between the molten glass and the mold material can be suppressed, a calcium phosphate glass molded body with good surface properties and high dimensional accuracy can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example, in which a is an explanatory diagram of the creation of a wax pattern for making a dental crown, b is an explanatory diagram showing the structure of the wax pattern, sprue line, and rubber cone, and c is a wax pattern d is an explanatory diagram showing the configuration of the lost wax mold and sprue; e is an explanatory diagram of the glass melt casting situation; f is a diagram of a tooth crown with a sprue; g is a diagram of a tooth crown. . 1... Plaster mold, 2... Wax pattern, 3... Sprue wire, 4... Rubber cone, 5... Slurry-like investment material, 6... Metal ring, 7... Lost wax mold for crown creation, 8... Sprue, 9 ...Glass melt, 1
0... Dental crown, 11... Investment material layer containing 1% by weight or more of boron nitride.

Claims (1)

[Claims] 1. In a molding method in which a melt containing 90% by weight or more of calcium phosphate is poured into a mold, cooled and solidified, and formed, a reaction suppressing layer containing 1% by weight or more of boron nitride is provided on the surface of the mold. Characteristic method for forming calcium phosphate glass. 2. The method for forming calcium phosphate glass according to claim 1, wherein the thickness of the layer containing boron nitride is 10 μm or more.