JPS6374936A - Crystallized glass and production thereof - Google Patents

Abstract

PURPOSE:To readily produce crystallized glass having high strength, by pulverizing a glass raw material containing SiO2, Al2O3, MgO, CaO, Ma2O and K2O of a specific composition, densely compression molding and heat-treating at relatively low temperature. CONSTITUTION:A glass raw material which comprises 65-75wt.% SiO2, 1-5wt.% Al2O3, 1-7wt.% MgO, 5-15wt.% CaO and 10-20wt.% Na2O+K2O as essential components and, if necessary, <=10wt.% glass colorant, is colored and contains SiO2+Al2O3+MgO+Na2O+K2O>90wt.% is pulverized into powder having >=70% particles with <=200 meshes particle size. Then the powder is compression molded into pressed powder having >=55% true density. Then the molded article is heat-treated, the glassy raw material powder is softened and mutually fused, integrated, made dense and made to crystallize. Consequent ly, devitrite crystal is mainly precipitated and high-strength crystallized glass having both characteristics of glass and those of glass ceramic is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to crystallized glass that has the characteristics of glass such as high insulation, chemical resistance, and surface gloss, and the excellent strength of glass ceramics, and the production thereof. Regarding the method.

(Prior Art) Conventional crystallized glass is generally produced by melting a glass raw material containing a nucleating agent, molding it into a desired shape using various molding machines, and then subjecting it to crystallization heat treatment to obtain crystallized glass.

On the other hand, as a method for obtaining crystallized glass without containing a nucleating agent, molten glass is rapidly cooled with water or the like to crush it into glass corpuscles of an appropriate size, and the glass corpuscles are assembled in a mold of a desired shape. A method (hereinafter referred to as the integration method) in which glass bodies are fused together and crystallized by heat treatment has been developed and disclosed in ``Japanese Patent Application Laid-Open No. 78217/1983.''

(Problems to be Solved by the Invention) Generally, glass is a material with a problem in terms of strength, and improvements in its strength are always sought after. The aim is to provide strong glass with special characteristics as crystallized glass, and its manufacturing method solves the following problems of conventional crystallized glass manufacturing methods. It is.

In other words, the problem with the method of crystallization using a nucleating agent is that the nucleating agent is sometimes expensive compared to the raw material, and the integration method that allows crystallization without using a nucleating agent is ,
This method is not suitable for forming any type of crystallized glass; for example, it is not suitable unless the individual glass bodies that are assembled have a sufficiently low viscosity that they can be fused together and integrated at the temperature at which the crystals are precipitated. The problem is that there are limitations to the raw material glass.

In other words, when the accumulated glass bodies are heated, the growth rate of the crystal nuclei that are generated near the softening temperature is fast, and the crystals are already actively growing at the time of the fusion of the bodies. If the glass particles have a certain composition, the viscosity increases due to the growth of crystals, making it difficult to fuse the glass bodies together. On the contrary, the crystals do not break or metastasize and become crystallized glass.

Therefore, raw materials containing a large amount of nucleating agents such as Fe30a, TxOz, ZrO, sulfides, or coloring agents having a nucleating effect such as FeO+ Fe103, Cr Zoo, etc. cannot be used.

Furthermore, the accumulation method produces relatively large bubbles (diameter 0.
It also has the disadvantage that it tends to contain particles (approximately 5 ts).

(Means for Solving the Problems) In order to solve the above problems, in the crystallized glass which is the first invention of the present invention, SiO2:
65-75χ, NtOs: 1-5%, MgO: 1-
7χ, CaO: 5-15χ, NazO+KzO: 1
0 to 20χ as essential components, and 5i02+/V2O3
+MgO+NazO+KzO>90χ, and the glass is mainly composed of debitrite crystals, and in the third invention of the method for producing the same glass, in terms of weight percentage, Sing: 65 to 75χ, N2O3: 1 to
5%, MgO: 1-7%, CaO: 5-15χ, Na
2O+KzO: 10-20χ is an essential component, KatsuS
i Oz+/V, 03 + MgO+Na, O+,
A glassy raw material containing O>90χ, 2
The powder is pulverized into a powder in which particles of 00a+esh or less account for 70% or more, and the powder is compression-molded into a compact having a true density of 55% or more, and then the compact is heat-treated to separate the glassy raw material powders from each other. They are softened and fused, integrated and densified, and crystallized to precipitate mainly debitrite crystals.

(Function) The manufacturing method of the present invention has a remarkable difference in that, compared to the accumulation method, in which glass bodies are simply assembled in a mold and heat-treated, a fine powder of a glassy raw material is compression-molded and then heat-treated. There is.

In other words, in the accumulation method in which coarse glass particles are heated, when the heating temperature reaches the softening point, the softening begins only at the sharp corners of the particles, and almost the entire particle body is softened. In order for the particles to soften and become fused and integrated, it is necessary to heat them at a considerably high temperature above the softening point, e.g. 1100 to 1200°C, depending on the distance between the particles. Attempting to achieve integrated densification at such a low temperature would require a very long time or be difficult to achieve. In contrast, in the fine particle green compact according to the present invention, since each particle is in close contact with each other over a large area compared to its mass,
Fusion, integration and densification proceed at low temperatures that do not significantly exceed the softening point.

The fact that integral densification of glassy raw material particles is possible at low temperatures means that crystal growth can be achieved after integral densification, and the ingredients and composition of the glassy raw material powder facilitate crystal growth. Whether it is a nucleating agent or a coloring agent that has a nucleating effect, there are no hindrances as seen in the integration method.

Figure 1 is a graph conceptually showing the relationship between temperature, nucleation rate, and crystal growth rate when a compression molded body of fine glassy raw material powder is heated, with the nucleation rate and crystal growth rate plotted on the vertical axis. The temperature is plotted on the horizontal axis. The dashed line graph is “
In the "temperature-nucleation rate" curve, the solid line graph is the "temperature-crystal growth rate" curve, s and p indicate the softening point, and M and P indicate the melting point.

As mentioned above, in a compression molded product of fine powder, each glass particle is fused and integrated and densified at a low temperature not much above the softening point, and during this period, nuclei are generated and their number increases. The graph shows that crystal growth increases as the temperature increases.

Next, another effect of compressing fine powder is that it is possible to crystallize even glass with a component composition where crystal growth is slow, that is, glass that is normally not easy to crystallize. be.

In other words, the crystallization rate is expressed as (crystallization rate) = (crystal nucleus number) × (crystal growth rate), and crystal nuclei are likely to occur at the fused interface between glass particles, and in a compacted compact of fine powder. has many fused interfaces,
And it is widespread, so there are many crystal nuclei that occur. Therefore, even if the crystal growth rate is not high, the crystallization rate can be increased as a result, and the crystallization temperature can be lowered.

As described above, compression molding of fine powder of glassy raw materials makes it possible to produce crystallized glass with a wide range of compositions, regardless of the presence or absence of a nucleating agent.

(Example) First, to explain the reason for limiting the components, in the present invention, the crystallization mainly depends on the precipitation of Devitrite crystals (NazO.3CaO.6SiOz), and therefore the component balance is determined by the formation of the Devitrite crystals, The crystallization heat treatment temperature, that is, the temperature at which the crystal growth rate is high in FIG. 1, more specifically, is limited by considering the vicinity of 850°C.

Essential component 5i (h: 65-75χ If it is less than 65χ, the viscosity of the glass is low and it is difficult to maintain the shape of the compression molded product at the above heat treatment temperature. On the other hand, if it exceeds 75χ, the viscosity becomes high and it is difficult to make the compression molded product dense. Also, from the precipitated crystals, if it is less than 65%, Nazo
・2Ca0 ・3SiO1 crystal becomes Si when it exceeds 75χ
O□ crystals begin to precipitate mainly.

AIto3: l~5χ N2O3 has the effect of increasing viscosity, and at least 1χ is necessary to provide the necessary viscosity to the glassy raw material, but if it exceeds 5χ, the viscosity becomes excessive and the compression molded product becomes densified. It becomes difficult.

MgO: 1 to 7χ If it exceeds 7χ, the viscosity becomes excessively high, making it difficult to densify the compression molded body during sintering. 1% or less is required for component balance.

Cab: 5 to 15χ 5 to 15χ is necessary for the balance of soda, lime, and silica glass, and if it exceeds 15χ, acid resistance becomes weak.

Na, O+, O: 10 to 20[chi] When the heat treatment temperature is less than 10[chi], the viscosity of the glass becomes high and the densification of the compression molded product becomes slow. On the other hand, if it exceeds 20χ, the viscosity becomes too low, making it difficult to maintain the shape of the compression molded product during heat treatment.

The above-mentioned essential components are contained in such a way that the total amount is 90% or more, and this limitation is to maintain suitability in physical properties such as strength and moldability.

As components other than the above essential components, ZnO, BaO1Pb
There is no problem when adding O, B2O2, etc. up to about 2χ each, and sb and o act as clarifying agents and may be added in amounts of 1% or less when the raw materials are dissolved.

Also, FeO+FezO:+, CrzO*, NiO5
It is also possible to obtain colored crystallized glass by using a colored glass-like raw material containing 10% or less of a coloring agent such as CuO% Mn01 or CoO. The limitation to 10% or less is determined by the fact that the essential component is 90% or more, but a sufficient coloring effect can be obtained at 10% or less.

Next, the manufacturing method will be explained.

First, the raw materials for the above components are mixed and melted to have a predetermined composition, and this is crushed by a method such as water pulverization to obtain glassy particles, which are used as raw materials.

Of course, a glass-like material having a component composition within a limited range may be crushed by an appropriate means to form small bodies.

The glassy bodies thus obtained are further ground into fine powder using, for example, a ball mill. The particle size at this time is 2
The content of fine particles of 00 mesh or less is 70% or more. This is to ensure the required density of the molded product, and to allow the fusion and integration and densification of the glassy raw material particles to proceed at a temperature slightly above the softening point.

Also, if there are many coarse particles, the product will tend to contain large air bubbles.
This can be prevented by using fine powder as described above.

The glassy raw material fine powder thus obtained is placed in a compression molding frame of a desired shape and molded into a dense green compact having a true density of 55% or more. The limitation of 55% or more is to ensure that the particles are fused and integrated and densified at a low temperature, and to suppress the large shrinkage deformation of the molded product during the same process, and the molding pressure is 20 kgf. /cd or more is appropriate.

In addition, during compression molding, 2 to 3 of polyvinyl alcohol (P, V, A) is added to the glassy raw material powder as a binder in advance.
Adding a χ solution at 5 to 15χ (powder weight ratio) makes it easier to mold a compression molded product and increases its strength.
Effective for preventing damage during transportation and heat treatment. In addition, since the binder is an organic binder, it has the advantage that it is debinding at 200 to 400°C and does not affect the composition or color tone of the material.

In addition, as a binder, in addition to the above-mentioned P, V, and A, one or more of bentonite, alumina cement, and Portland cement is mixed, and the addition amount ratio is 7% or less,
In addition, one in which the amount of added water is 20% or less can be used.

As already mentioned, the compression molded product obtained in this way has
Heat treatment for fusion, integration and densification is performed at a low temperature that does not significantly exceed the softening point of the glassy raw material particles, that is, at a temperature below the softening point and the crystal growth rate. Nucleation is progressing at the contact interface.

Once the compact has been densified, the temperature is further increased to promote crystal growth and crystallization.

However, if the processing temperature is too high, the shape of the green compact cannot be maintained. Therefore, depending on the case, it may be necessary to rely on a processing method that involves holding the material at a certain temperature for a long period of time.

In addition, in the above heat treatment, it is also possible to produce crystallized glass at various stages of crystallization by selecting heat treatment conditions, and as mentioned above, it is possible to use colored glass-like raw materials containing a glass colorant. It is also possible to make colored crystallized glass depending on the method.

Here, I would like to mention the difference between the manufacturing method of ceramics and fine ceramics, which involves the process of compressing fine powder and sintering it, and the manufacturing method of the present invention. While densification is achieved through sintering, the present invention uses raw materials in a glass state and partially crystallizes them, which is fundamentally different.

Next, specific examples of the present invention will be shown.

In weight percentage, 5t (h: 73.2χ, /Vz03
: 1.5X, CaO: 6.8χ, Na, 0: 13
．． A raw material containing 1χ, KzO: 0.9%, and MgO: 4.0χ was melted at 1500°C, and then poured into water to obtain glassy raw material particles. 200 mesh (0,074
mn+) or less, and P is added to the same powder as a binder.
, V, A 3χ solution was added in a weight ratio of 1 oz, mixed well, and then molded using a compression molding frame of 300 x 300 x
A plate-shaped compression molded product having a size of 25 (mn+) was molded. There are three compression pressures: 100 and 200.250 kgf/cal, and the density of the compact at each pressure is 1.62 g/d.
, 1.66g/cffl, 1.7g/Cffl.

The above compression molded body was heat treated at a heating rate of 50°C/h for 4 hours.
After raising the temperature to 00°C and maintaining the same temperature for 4 hours to fuse and integrate the glassy raw material powder and make it dense, the temperature was raised again to 50°C/
The temperature was raised to 850° C. at a rate of 1 h, and the same temperature was maintained for 4 hours to achieve crystallization, and debitrite crystals were precipitated.

The results of measuring the physical properties of the obtained product were a water absorption rate of 0.2 to 0.01χ and a bending strength of 550 to 650 kgf.
/cd.

Note that FIG. 2 shows the heat treatment curve of the above heat treatment.

(Effects of the Invention) As described above, the manufacturing method of the present invention turns a glassy raw material into a fine powder and forms a dense compression molded body, thereby melting the glassy raw material powder constituting the molded body at a relatively low temperature. This makes it possible to integrate and make it more dense.
Therefore, there is no obstacle to particle integration and densification due to increase in viscosity accompanying crystal growth, and crystallization can be performed regardless of the presence or absence of a nucleating agent. It can be carried out at considerably lower temperatures compared to Therefore, the treatment is easy, and by changing the treatment conditions, various stages of crystallization can be obtained.

Furthermore, since it is compression molded from fine powder, it is easy to make crystallized glass of various shapes, and for example, it is easy to create irregularities on the surface.

Furthermore, the product does not contain large bubbles (about 0.5 nm in diameter) unlike in the case of the integrated method.

As is clear from the manufacturing method, the crystallized glass of the present invention, which is provided by a manufacturing method that has many advantages, has the characteristics of ordinary glass, such as high insulation, chemical resistance, and surface In addition to having gloss etc.
It has high strength as a glass ceramic, and as mentioned above, the strength is highly reliable because it does not contain large bubbles.

As described above, the crystallized glass of the present invention having various excellent properties can be applied to insulating materials, chemical-resistant materials, interior and exterior materials of buildings, mechanical parts, etc., and the industrial value of the present invention is enormous.

[Brief explanation of the drawings] Figure 1 shows the "temperature - nucleation rate" curve (dashed line graph) and the "temperature - nucleation rate" curve (dashed line graph) when a compression molded body of glassy raw material fine powder is heated.
FIG. 2 is a heat treatment curve in an example of the present invention. Patent Applicant: Kubota Iron Works Co., Ltd. Figure 2

Claims (5)

[Claims] (1) In weight percentage, SiO_2: 65-75%, Al
_2O_3: 1-5%, MgO: 1-7%, CaO: 5
~15%, Na_2O+K_2O: 10-20% as essential components, and SiO_2+Al_2O_3+MgO+
A crystallized glass characterized by containing Na_2O+K_2O>90% and mainly consisting of debitrite crystals. The crystallized glass according to claim 1, which is colored by containing 10% by weight or less of a glass colorant in component (2). (3) In weight percentage, SiO_2: 65-75%, Al
_2O_3: 1-5%, MgO: 1-7%, CaO: 5
~15%, Na_2O+K_2O: 10-20% as essential components, and SiO_2+Al_2O_3+MgO+
A glassy raw material containing Na_2O+K_2O>90% is pulverized into a powder in which particles of 200 mesh or less account for 70% or more, and the powder is compression-molded into a green compact with a true density of 55% or more. After that, the molded body is heat-treated to soften and fuse the glassy raw material powders to each other, thereby crystallizing them while integrating and densifying them, so that mainly debitrite crystals are precipitated. Production method. (4) Claim 3, characterized in that the glassy raw material is colored by containing 10% or less of a glass colorant.
A method for producing crystallized glass as described in Section 1. (5) Claim 3, characterized in that in compression molding of glassy raw material powder, one or more of polyvinyl alcohol, bentonite, alumina cement, and portland cement are used as a binder in combination. 4. A method for producing crystallized glass according to item 4.