JPH0651577B2 - Method for producing calcium phosphate-based crystallized glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a calcium phosphate-based crystallized glass,
In particular, it relates to a method of crystallizing a calcium phosphate-based glass molded body without deformation.

(Prior Art) Calcium phosphate-based crystallized glass containing 70% by weight or more of calcium phosphate has been attracting attention in recent years as an artificial tooth or an artificial bone because it is the same as a component of a tooth or bone of a living body.

Conventionally, as a method for producing such a crystallized glass, phosphoric acid or lime is melted into a glass as a raw material, glass is formed into a predetermined shape, and then simply crystallized.

(Problems to be Solved by the Invention) However, in the case of a glass containing 70% by weight or more of calcium phosphate, the glass is considerably low in viscosity near its crystallization temperature, so that the glass is significantly deformed and it is difficult to maintain a predetermined shape. It has drawbacks.

On the other hand, a method has also been proposed in which glass is crystallized while being put in a mold material when it is molded into a predetermined shape.

However, although this method is certainly expected to suppress deformation, the high temperature during crystallization causes a partial reaction layer to form between the molten glass and the mold material, which hinders the formation of uniform crystal nuclei. As a result that crystal nuclei are scattered on the surface of the crystallized glass obtained as a result, they grow individually in four directions and exhibit a large number of chrysanthemum patterns in appearance, and cavities are formed between the nuclei. Presenting no state,
After all, it has a drawback that only crystallized glass having low strength can be obtained.

(Means for Solving Problems) The present inventor has conducted various researches and studies for the purpose of finding out means for eliminating these drawbacks of the conventional method and sufficiently crystallizing the molded body without deformation. It has been found that the above object can be achieved by carrying out the crystallization process which has been carried out until now under a specific condition.

Thus, the present invention is characterized in that a glass molded body containing 70% by weight or more of calcium phosphate is embedded in a powder having heat resistance which does not react with the glass molded body at a temperature of 800 ° C. or less for crystallization. A method of manufacturing a crystallized glass is provided.

The calcium phosphate glass used in the present invention is not particularly limited as long as it contains 70% by weight or more of calcium phosphate, but the atomic ratio Ca / P of calcium to phosphorus is preferably 0.35 to 0.7.

When Ca / P is less than 0.35, the water resistance of the crystallized glass obtained is remarkably low, making it difficult to use in the atmosphere. On the other hand, when it exceeds 0.7, the melt is solidified as a glass. Both are not preferable because they are difficult.

Next, as the powder used in the crystallization step of the present invention,
A material having heat resistance that does not react with the calcium phosphate glass at a temperature of 800 ° C. or lower and does not decompose or melt is used.

Such powders generally have an average particle size of 0.1 to 10
It is suitable to adopt about 0 μm. If the average particle diameter deviates from the above range, the strength of the powder molded product may be insufficient, or the smoothness of the obtained crystallized glass surface may be impaired, which is not preferable.

Examples of such powder include alumina, calcium hydroxide, boron nitride, silicon carbide, zirconia, and silica, and these may be used alone or in combination of two or more.

These powders are put into a suitable container, for example, and the calcium phosphate type glass which has been preformed and cooled to a degree not to be deformed is embedded in the powder and heated to the crystallization temperature for crystallization.

However, rather than simply embedding the glass compact in free-flowing powder, pressurize it further to compact the powder, or add a binder to the powder to solidify the powder. It is more preferable that the deformation during crystallization can be suppressed.

When the powder in which the glass molded body is buried is solidified under pressure, it is generally appropriate to adopt a pressing force of about 1 to 1000 kg / cm ² .

When a powder to which a binder is added is used, it is generally made into a slurry form, which is coated on a glass molded product to a suitable thickness, for example, about 10 to 1000 μm, or glass molded into a suitable shape. It is suitable to put stuff in it, and to make it crystallize by pouring the slurry into it and solidifying it.

In this case, as the binder to be used, for example, silica sol, alumina sol, gypsum, magnesium phosphate, etc. can be appropriately used, and these are generally used in an amount of about 5 to 80% by weight.

When the amount of the binder used is less than the above range, the effect of binding the powder may not be sufficiently obtained, and the deformation preventing effect may be insufficient. On the contrary, when the amount exceeds the above range, the binder may be insufficient. All of them are not preferable because cracks may occur in the powder compact during curing.

Further, the powder to which the binder is added is generally used as a slurry, and the slurry concentration is generally 5 to 9
It is suitable to use about 0% by weight. When the slurry concentration is lower than the above range, it becomes impossible to coat the glass molded product uniformly, and when the slurry concentration is high, the fluidity of the slurry is poor, and voids may occur between the glass molded product and the slurry. However, neither is preferable.

Further, if a crystal powder of calcium metaphosphate is added to the powder in an amount of about 1 to 80% by weight, an effect of accelerating the crystallization of the shaped glass can be expected. As the crystals of calcium metaphosphate, β-type, δ-type and an appropriate mixture thereof are used, and their particle sizes are
About 0.1 to 100 μ is adopted.

Further, calcium metaphosphate may be present as crystals during crystallization of the glass molded body, and therefore, when added to the powder, for example, calcium phosphate glass or CaH ₄ (PO ₄ ) ₂
It is also possible to use those which become crystals during the crystallization operation such as.

Thus, the glass molded body is subjected to crystallization, but the crystallization means is not particularly limited, and for example, a means of holding in an electric furnace kept at about 700 ° C. for 2 hours can be adopted.

When the method of the present invention is adopted, it becomes possible to easily obtain a crystallized glass that requires a strict shape, such as a dental material.

(Example) A molten glass having a composition of 25% by weight of CaO, ₂ % by weight of Al ₂ O _{3 and} 73% by weight of P ₂ O ₅ was cast in a mold using a phosphate-based investment material (Blue Best manufactured by Tokuyama Soda Co., Ltd.). It was cast into a plate, gradually cooled, and then demolded to obtain a prismatic glass of about 3 × 3 × 25 mm.

On the other hand, the powders shown in Table 1 were prepared, and a cylindrical mold of 35 mmφ × 30 mmh was used. In Example 1, the powder was put up to half of the mold, and then the above-mentioned formed prismatic column was formed almost in the center of the mold. The glass was placed horizontally, filled with powder, embedded in the glass, and pressed at a pressure of 300 kg / cm ² to obtain a columnar body containing prismatic glass. On the other hand, in Examples 2 to 8, the prismatic glass molded in the center of the cylindrical mold was held, and the respective slurries were poured into the cylindrical mold to be dried and solidified.
In each case, the cylindrical mold was removed, and each was held in an electric furnace at 700 ° C. for 2 hours for crystallization.

The appearance, dimensional change in the cross-sectional direction and bending strength of the obtained crystallized glass are shown in Table 2.

Claims (3)

[Claims] 1. A calcium phosphate characterized in that a glass molded body containing 70% by weight or more of calcium phosphate is crystallized by being embedded in a powder having heat resistance which does not react with the glass molded body at a temperature of 800 ° C. or less. Of producing a glass-based crystallized glass. 2. The method according to claim 1, wherein the powder is at least one selected from alumina, calcium hydroxide, boron nitride, silicon carbide, zirconia and silica. 3. The method according to claim 1, wherein the powder has an average particle size of 0.1 to 100 μm.