JP2810996B2 - Method for producing crystallized glass - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for crystallizing a mother glass when producing crystallized glass, and is particularly suitable for a biomaterial such as a high-strength dental material or an artificial bone. The present invention relates to a method for producing crystallized glass.

[Conventional technology]

Crystallized glass is obtained by reheating a glass body having a predetermined composition and uniformly depositing and growing a large number of microcrystals in the glass. In the manufacturing process of crystallized glass,
The heating method for this crystallization is particularly important,
It is required to precisely control a crystallization furnace having a uniform temperature distribution in the furnace. Obtaining a uniform crystal contributes to improving the strength of the crystal and reducing the form distortion. However, it is very difficult to keep the temperature distribution in the furnace uniform. Therefore, in order to solve this difficulty, a method of heating at a very slow heating rate so as not to cause a temperature difference inside the glass body has been adopted.

Further, since the specific gravity of the crystal is generally larger than that of the glass, the volume shrinks during crystallization. Crystallization is performed by enlarging the glass body in advance in consideration of the volume shrinkage. However, even in this case, if a temperature distribution occurs, the glass body does not shrink uniformly, resulting in crystal distortion or defects such as pores inside. In order to prevent this, a method of crystallizing in a refractory sheath to reduce the way of transmitting heat has been used.

[Problems to be solved by the invention]

Although various methods have been shaken for reducing the temperature distribution as described above, crystallization proceeds from the surface of the glass toward the inside such as a calcium phosphate crystallized glass,
Crystallized glass by a so-called surface devitrification type crystallization term is particularly sensitive to temperature distribution, and a small-sized glass can obtain a substantially uniform crystallized substance by slowly heating it over time. In the case of crystallizing a glass body having a large shape or a plurality of glass bodies at a time, it is almost impossible to realize uniform crystallization by a usual method. In addition, even in the method of crystallizing by putting in a sheath in a glass refractory, the refractory generally has a low thermal conductivity and can reduce the manner of transmitting heat, but cannot realize a uniform temperature distribution.

In order to realize uniform crystallization when the glass body is heated and crystallized, it is necessary to realize a uniform temperature distribution.

[Means for solving the problem]

In a heating furnace generally used for crystallization, heat transfer to the glass body is due to radiation and convection, so the distance between each part of the glass body and the heating element and whether each part of the glass body directly faces the heating element. This inevitably causes a temperature distribution inside the glass body.

Therefore, heating may be performed by conduction heat transfer. In order to realize this, the present invention, when crystallizing the glass, puts the mother glass in a container made of a material having a high thermal conductivity, or the voids in the container have a thermal conductivity of 20 W / m mainly composed of SiC powder or SiC. -Fill with mixed powder of K or more,
Alternatively, crystallization is performed using both of them.

[Configuration of the invention]

The high thermal conductive material used in the present invention is a metal, ceramics or a composite of both,
Thermal conductivity of powder or powder mainly composed of SiC is 20W / m ・ K
It is necessary to be more than the above, and below that, a uniform crystal cannot be obtained in the surface devitrification type. Al, Ag, Cu, A as metal
l, Ir, Mo, W, Cr, Ni, Fe, Pd, Pt, Rh, Si, etc., or alloys based on these are suitable.For ceramics, SiC, BeO, Al
₂ O ₃ , MgO and ceramic mixtures mainly composed of these are suitable. In the case of a metal material, it is also possible to apply a surface coating by a method such as plating, vapor deposition, or thermal spraying to prevent oxidation and corrosion at high temperatures. Ceramic materials are preferred materials from the viewpoint of preventing oxidation and corrosion at high temperatures. In addition, the pores of ceramic materials such as SiC
A composite material such as one in which a metal material such as i is injected, a ceramic material dispersed in a metal material, and a mixture of a metal material and a ceramic material is also suitable.

The container made of a material having a high thermal conductivity may be in the form of a normal box, but from the viewpoint of enhancing the effect of the heat transfer conducted by the object of the present invention, the container wall and the glass body that match the shape of the object to be heated are as close as possible. For example, a container having a shape perforated in a block body is preferable. From the standpoint of increasing the heat uniformity, the container is preferably as thick and dense as possible, but it may be a melt or a sintered body. When filling a mixed powder of SiC powder or a mixed powder mainly composed of SiC and having a thermal conductivity of 20 W / m · K or more, it may be in the form of a lump, a fibrous form, or a mixture thereof, in addition to the powder. It is more efficient to fill to a density, and a method such as using a powder material having a blended particle size is preferable.

In the present invention, only the container made of the high heat conductive material may be used, and the space between the glass body and the container may be left as it is, or may be filled with an arbitrary powder. Alternatively, the container may be made of any material, and the voids may be filled with SiC powder or a mixed powder mainly composed of SiC and having a thermal conductivity of 20 W / m · K or more. However, using a container made of a material with high thermal conductivity, the voids between the glass body and SiC powder or a mixed powder mainly composed of SiC with a thermal conductivity of 20 W / mK or more are packed at a high density. Is the most preferred method.

Further, the method of the present invention is effective in crystallizing one glass body, but is effective in simultaneously crystallizing a plurality of glass bodies. In that case, a plurality of glass bodies may be embedded in the powder filled in the container, or a plurality of holes may be formed in the block body. Especially,
When a plurality of glass bodies are crystallized at one time, the same crystallization state is obtained, and therefore, there is an advantage that a glass with uniform properties such as strength can be obtained.

〔The invention's effect〕

When crystallizing the glass of the present invention, the mother glass is placed in a container made of a material having a high thermal conductivity, or the voids in the container are made of SiC powder or SiC and have a thermal conductivity of 20 W / mK.
According to the method of crystallizing by filling with the above mixed powder or using both together, heat transfer to the glass body becomes uniform, so there is no temperature distribution, and ideal uniform crystallization can be realized It is. In particular, the characteristics are exhibited in the crystallization of surface devitrification-type crystallized glass that is sensitive to temperature distribution, and in particular, calcium phosphate-based crystallized glass used as an artificial crown or an artificial bone material.

Further, it is possible to crystallize a plurality of glass bodies, which has been difficult in the past, so as to have the same crystallization state at once.

Furthermore, by using a high thermal conductive material, it is not necessary to raise the temperature very slowly over time as in the conventional case, and a rapid temperature increase is possible, greatly shortening the time required for the crystallization operation. You.

〔Example〕

Example 1 A SiC-based container was filled with SiC powder having a particle size of 149 μm or less, and a calcium phosphate glass molded body having a composition of 4.3Li ₂ O · 38.5CaO · 9.1Al ₂ O ₃ · 48.1P ₂ O ₅ was filled therein. Five pieces were embedded, the temperature was raised at a rate of 300 ° C./hr, heated at 550 to 650 ° C. for 10 hours, and crystallized to obtain a calcium phosphate crystallized glass. Regardless of the position in the container, the obtained crystallized glass shows the same uniform crystallized state for all five pieces, and has a bending strength of 18
It was as high as ²⁰ to 1980 kg / cm ^2, and its variation was small.

Example 2 A copper block of approximately 90x65x30mm with a diameter of 25mm and a depth of 25
5 holes with a particle size of 14 mm were filled.
The same calcium phosphate-based glass compact as in Example 1 was embedded in 9 μm or less SiC powder, and a copper plate of the same quality (5 m thick)
m), and heated and crystallized under the same conditions as in Example 1 to obtain a calcium phosphate crystallized glass. Also in this case, the obtained crystallized glass shows the same uniform crystallized state for all five pieces regardless of the position in the container, and has a bending strength of 1890 to
It was 1990 kg / cm ² .

Example 3 Calcium phosphate was used in the same manner as in Example 1 using a quartz container filled with quartz powder having a particle size of 149 μm or less and a refractory brick made of alumina-silica filled with a SiC powder having a particle size of 149 μm or less, respectively. A system crystallized glass was obtained. The obtained crystallized glass showed almost the same crystallization state regardless of the position in the container. Measurement of the intensity 1610~1790kg / cm ² in those containers SiC quality as high as 1240~1560kg / cm ² in the container alumina siliceous, but the variation was also relatively small, inferior to Example 1 Did not.

Comparative Example 1 Example 1 was placed on an alumina-silica refractory brick.
5 pieces of the same calcium phosphate-based glass compact were placed, and heated and crystallized under the same conditions as in the example except that the heating rate was very slow, 60 ° C./hr, to obtain a calcium phosphate-based crystallized glass. The obtained crystallized glass shows five different crystallization states depending on the set position on the refractory heat-insulating brick, and each of the crystallized glass itself is exposed to the heating element at a short distance from the upper and lower bricks. A different crystallization state was shown between the contacted portion and the contact portion. Strength 560-980
kg / cm ² , the variation was large depending on the set position, and the strength was small due to the difference in crystallization between each part.

Comparative Example 2 Alumina-silica refractory brick with a particle size of 149 μm
Filling the following quartz powder, calcium phosphate glass 5
The pieces were embedded and heated and crystallized in the same manner as in Example 1 except that the heating rate was set to 60 ° C./hr, to obtain a calcium phosphate crystallized glass. The difference in the crystallization state inside each crystallized glass of the obtained crystallized glass is small.
The crystallized state differs among the five crystallized glasses depending on the set position in the container, and the strength is correspondingly 770 to 103.
It was 0 kg / cm ² .

The thermal conductivity of the materials used was 120 in SiC container, 2.5 in alumina-silica refractory brick container, 0.3 in alumina-silica refractory insulating brick plate, and 350 in copper block in W / mK unit. Both are filled with about 50 SiC and about 0.1 quartz
Met.

────────────────────────────────────────────────── (5) References JP-A-48-100406 (JP, A) JP-A-50-32216 (JP, A) JP-B-42-23038 (JP, B1) (58) Field (Int.Cl. ⁶ , DB name) C03B 32/02 C03C 10/02

Claims (3)

(57) [Claims] 1. A method for producing crystallized glass, comprising: crystallizing a mother glass in a container made of a high heat conductive material having a thermal conductivity of 20 W / m · K or more when crystallizing the glass. 2. When crystallizing glass, the periphery of the mother glass is made of SiC powder or SiC and has a thermal conductivity of 20 W /
A method for producing crystallized glass, characterized by filling and crystallizing with a mixed powder of m · K or more. 3. When crystallizing glass, the mother glass is placed in a container made of a high thermal conductive material having a thermal conductivity of 20 W / m · K or more, and the voids in the container are mainly made of SiC powder or SiC. A method for producing crystallized glass, characterized by filling and crystallizing with a mixed powder having a thermal conductivity of 20 W / m · K or more.