JPS63144134A - Production of glass ceramic article - Google Patents

Abstract

PURPOSE:To obtain the titled article having high strength without necessitating a binder, by mixing glass powder having low softening point with glass powder having high softening point, compression-molding the mixture in a mold at a temperature to soften the former glass powder but to keep the latter glass powder from softening and heat-treating the formed product. CONSTITUTION:Glassy raw material powder having low softening point is mixed with glassy raw material powder having high softening point. The mixture is charged into a mold, heated at a temperature above the softening point of the glassy raw material powder having low softening point and below the softening point of the glassy raw material powder having high softening point and the mixture is compression-molded in a state containing the glassy raw material powder having low softening point in softened state and the glassy raw material powder having high softening point in unsoftened state. The obtained formed article is heat-treated to density the texture of the article by softening and fusing the particles of the glassy raw material powder constituting the formed article and the article is crystallized to obtain the objective glass ceramic article.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing glass-ceramic products.

(Prior Art) The conventional general manufacturing method for glass-ceramic products involves melting a glass raw material containing a nucleating agent, shaping it by various shaping means, and then performing a crystallization heat treatment to precipitate crystals.
It was a glass ceramic product.

In addition, as a method for obtaining glass ceramics without using a nucleating agent, glass particles obtained by crushing molten glass by water cooling or the like are collected in a mold and heat-treated to melt each glass particle. A method of depositing and crystallizing (referred to as an accumulation method) is disclosed in Japanese Patent Publication No. 55-29018.

Further, as disclosed by the present inventors in "Japanese Patent Application No. 60-284150," a glassy raw material having a specific composition (mainly a composition for forming wollastonite crystals) is pulverized, and a green compact of the pulverized powder is heat-treated. Accordingly, there is a method in which powder particles are softened and fused to each other to be integrated and densified, while crystallization is attempted to mainly precipitate wollastonite crystals.

(Problems to be Solved by the Invention) Among the conventional methods described above, the method in which a nucleating agent is included and the glass product is formed and then heat-treated to achieve crystallization is that the nucleating agent is more expensive than the raw material. The problem with the accumulation method is that during the period of softening and fusion of the glass bodies, the growth rate of precipitated crystal nuclei is fast (in the case of a composition that has already entered the period of crystal growth, crystallization may occur). The increase in viscosity associated with this makes it difficult to fuse and integrate the glass bodies.In other words, there are restrictions on the component composition of the glass bodies that can be used, and it is not suitable if the glass bodies contain a nucleating agent or a coloring agent that has a nucleating effect. There isn't.

The following method of pulverizing a glassy raw material and heat-treating the vitreous raw material as a green compact according to the prior invention by the present inventors is to increase the contact area through contact between the fine powders and to lower the softening point through close contact. Softening, fusion, and densification between glass particles can be achieved at temperatures exceeding that of the glass particles. In other words, the softening and fusing of the glass bodies in the accumulation method cannot be achieved unless the temperature is considerably higher than the softening temperature because the glass bodies are coarse particles and in a mere accumulation state, whereas in the prior invention, as described above, the softening point is Therefore, after softening, melting, and densification, the temperature can be further raised to effect crystallization. This also applies when a nucleating agent or a coloring agent having a nucleating effect is included.

Addition of a binder to the molding of the compacted product facilitates molding and improves the strength of the compact (white base), which is effective in preventing damage during transportation and sintering.

Their addition is necessary, especially in the manufacture of large products that are easily damaged, but these binders have little to do with the properties of the finished product, rather the residual binder may reduce the properties of the product. In such cases, it is necessary to incorporate a binder removal step during sintering to actively remove the binder. However, it is often difficult to find a way to remove the binder, and various ideas have been devised, but the resulting increase in costs is a problem.

Another problem is the high cost due to the binder itself and the high cost due to the equipment for uniformly kneading the binder.

PVA (polyvinyl alcohol) is often used as a binder, and other types such as montmorillonite and alumina cement are also used. There has been a strong desire to develop a means to improve this, and the present invention has been made in response to that desire.

(Means for solving the problems) The features of the present invention, which have been made in response to the above-mentioned desire, are as follows:
A mixture of glassy raw material powders with different softening points (low and high softening points) is put into a mold, and then heated to a molding temperature that is higher than the softening point of the low softening point glassy raw material powder and lower than the softening point of the high softening point glassy raw material powder. By heating and press-molding the mixture in a state where the former raw material powder is softened and the latter powder is not softened to obtain a molded body, and then heat-treated the molded body, a glassy raw material powder having a molded body structure is obtained. The point is that they are softened and fused together to become densified, and at the same time, crystals are precipitated.

(Function) A mixture of glassy raw material powders with different softening points is heated to a molding temperature that is above the softening point of the low softening point raw material powder and below the softening point of the high softening point raw material powder, so that the former softens and the latter softens. Since the powder is press-molded in an unsoftened state, the softened powder acts as a binder and integrates the powders. Therefore, the various problems mentioned above caused by the use of conventional non-component binders are solved.

In addition, since the softened powder is the particle itself that constitutes the compact,
Unlike a binder, which is subject to restrictions on the amount added, it is present in a large amount, and therefore forms a molded article (white ground) with high strength even if the pressing force is relatively small.

In addition, since the pressure molding is a mixture of softened and unsoftened powder, the softened particles deform and fill the gaps between the powders, in other words, they act to expel air, while the slits between the unsoftened particles are filled with air. This creates a path for air to escape easily, creating a healthy sloping ground.

If all the powder is pressed and molded in a softened state, the air stagnant between the powders is likely to be trapped (the trapped air expands when the temperature is raised later for crystallization, causing the expansion of the soil). Otherwise, cracks are likely to occur.

In addition to the above, since all of the mixed powders of the raw materials are charged into the mold in an unsoftened state, charging is easy, unlike charging a viscous substance.

(Example) The present invention will be described in detail below along with Examples.

First, let's talk about raw material powder. Glass is made into small particles by an appropriate method such as pulverization of molten glass, and then used as a powder. It is called a shaped raw material.

By the way, the low softening point raw material is preferably a glassy raw material with a softening point of 400 to 800°C, and the high softening point raw material is preferably one having a softening point at least 100°C higher than the low softening point raw material.

In other words, glass that softens below 400℃ (glass-like raw material)
Generally called low melting point glass, it is not suitable as a raw material for glass-ceramic building materials, and glassy raw materials that soften at temperatures above 800°C pose problems in terms of the strength of the forming frame (mold, etc.) during pressure forming. Yes, more preferably a softening point of 500
It is a glassy raw material with a temperature of ~700°C.

On the other hand, the reason why it is desirable that the high softening point glassy raw material has a softening point lower (both 100 degrees Celsius higher) than the low softening point raw material is that even if the heating is slightly uneven, there is still a difference in the softening and non-softening of the two powders. This is to be able to hold the
Deaeration can also be expected over time as the temperature increases from a low softening point to a high softening point.

FIGS. 1 to 3 are cross-sectional views for explaining mold forming according to the present invention, and are shown as examples of molds for manufacturing flat products.

In these figures, the mold l is an upper mold 2, a horizontal mold 3, and a lower mold 4.
A mixture 6 of glassy raw material powder is placed in the same mold 1.
(hereinafter referred to as raw material mixed powder) is added.

The heating of the raw material mixed powder in the mold 1 to the molding temperature is as follows: (1) The raw material mixed powder 6 existing inside the mold 1 is heated to the molding temperature. For this purpose, for example, a soaking oven is used.

(2) The mold 1 is preheated, and the raw material mixed powder 6 introduced into the mold 1 is heated to the molding temperature by the thermal energy possessed by the mold 1. Therefore, the mold only needs to be heated to the molding temperature or slightly above it, and this heating can be done, for example, in a soaking oven or
Alternatively, the mold 1 may have a heat generating device such as a heating wire inside.

(2) The raw material mixed powder 6 is put into the mold 1, and only the surface thereof is heated to the molding temperature.

This heating can be done, for example, by electrothermal radiation.

The raw material mixed powder 6 thus heated to the molding temperature in the mold 1
is pressure-molded between an upper mold 2 and a lower mold 4. FIG. 1 shows a case where the mold 1 has a reinforcing portion 5, which is suitable for the case (2) above. Note that this reinforcing portion 5 does not need to be heated when the mold is heated in a soaking furnace or the like.

In the case of (2) above, the part of the raw material mixed powder 6 in contact with the preheating mold 1 is heated best, and the heating condition becomes worse as it gets further away, but the hatched part of the raw material mixed powder 6 in FIG. The mixed raw material powder near the mold becomes a sufficiently strong base for the molded body, and maintains the shape of the entire molded body without any problems.

Note that the shaded area above is the case where the upper mold 2 is not preheated, and by preheating the upper mold 2, it is also possible to increase the strength near the upper surface part.

When preheating the mold 1 to the molding temperature, it is preferable to select the upper side of the molding temperature range.

In the case of (2), the surface of the raw material mixed powder in the mold is heated, and the powder near the surface, as shown by the hatched area of the raw material mixed powder 6 in Figure 3, becomes a sufficiently strong molded body base, and the entire molded body is heated. It maintains its shape without any problems. In this case as well, it is preferable to heat to the upper end of the molding temperature range, as in case (2).

In any of the above cases, heating in the mold becomes easier if the raw material mixed powder is preheated to a temperature below the softening point of the low softening point glassy raw material powder. In the case of ■■, it is also possible to further heat the mold to the same temperature as above.

Thus, it is preferable to press and mold the raw material mixed powder after heating in an inert atmosphere at the molding temperature, but there are no major problems in the atmosphere or at room temperature.

In other words, the powder hardly oxidizes, and even if the heated powder is placed at room temperature, the temperature drop is small.
The average temperature drop of the powder after 30 seconds after heating the powder to 30° C. together with the mold is 30° C. or less.

It is desirable that the mold be treated with coating (zircon sand, graphite, etc.), application of ceramic seeds, ceramic coating, etc. to prevent adhesion of the glassy raw material powder.

Regarding the molding pressure, it is 5 kgf/cr1 or more to give a bending strength of 10 kgf/crA or more, which is the strength that allows shape retention until heat treatment, and 300 kgf/ad or less from the viewpoint of mold strength and economy. is appropriate.

Next, examples of glassy raw materials suitable for the present invention are illustrated.

A. First glassy raw material composition (low softening point raw material) SiO□
=55-75%, 1vto3: 15% or less CaO:
5-15%, Na, + K2O: 10-20% or more as essential components, and SiO + AJz03 +N
azO+ KzO> 90% (weight percentage, same below)
B. Second glassy raw material composition (high softening point raw material) SiOz
: 40-60%, N2O3 = 5-20%CaO:
25-45% or more as essential ingredients, and 5i02
+Nz03+CaO>85%.

By adding 0.5 to 15% of a coloring agent to the second glassy raw material composition, it is possible to make the glass ceramic product colored or colored or patterned.

The above component composition has a difference in softening point between low and high softening points of at least 100
℃, and a component composition in which both glassy raw material powders are fused is easier to crystallize than each glassy raw material powder alone. In other words, the composition of the ingredients has been carefully considered to ensure that they will not crystallize before fusion, and therefore both powders can be made into a compact and sufficiently densified for post-crystallization.

Glassy raw materials are manufactured by melting raw materials adjusted to have predetermined chemical compositions, and then rapidly cooling and crushing them by a method such as water pulverization to form glassy bodies. Of course, a substance having a predetermined chemical composition and already in the form of glass may be made into a small body by an appropriate means.

The glassy particles obtained in this way are further pulverized using, for example, a ball mill, and the finer the particle size, the more the powder is fused and densified, and the softening point is lowered.
It is carried out at a low temperature that exceeds 20% in the mixed powder.
It is desirable that at least 50% of the particles be 0 mesiosium or less.

On the other hand, the presence of coarse particles of 10 mesh or more should be avoided as they tend to contain air bubbles inside the product.

In addition, when the glassy raw material with a high softening point is a colored raw material containing a colorant, the raw material powder is made into particles of 10 to 200 mesh,
When colorless glassy raw material powder with a low softening point is mixed as a fine powder of 200 mesh or less, the finished product can be made into a product with a colored pattern (mottled pattern). If both are made into fine powders of 200 mesh or less, a uniform ground color will be exhibited and the product will simply be a colored product.

The glassy raw material powder obtained as above is mixed,
The process of heating the mixture to form a press-molded body has already been described, and next, the heat treatment of the molded body will be described.

Heating for heat treatment of the press-molded product may be done by rapidly increasing the temperature to the molding temperature, then increasing the temperature to the crystallization temperature and maintaining the same temperature. Further, the temperature may be raised to the crystallization temperature successively after molding.

As mentioned above, the molding temperature is the temperature at which one of the two types of glassy raw material powder softens while the other remains unsoftened, that is, the temperature slightly above the softening point of the low-temperature softening powder, and the crystallization temperature. is a temperature range exceeding the softening point of the above-mentioned high-temperature softening powder and in which the crystal growth rate is high.

When the compact is heated to the molding temperature, the low-temperature softened powder is softened (re-softened), and when maintained at the crystallization temperature, the high-temperature softened powder also softens, resulting in soft fusion and densification of the powder particles. oxidation, that is, sintering and crystallization. After the crystallization treatment, it is slowly cooled.

In the case of using powders of the first and second glassy raw materials as exemplified above, the molding temperature is 400°C to 800°C, and the crystallization temperature is 800°C to 1000°C.

FIG. 4 shows a conventional method of forming a compression molded body using powders of the first and second glassy raw materials, that is, a binder (PV
After kneading with solution A), the molded body was subjected to pressure molding using a compression molding frame, and the same molded body was heat-treated.
3 shows a comparison between the heat treatment curve (solid line) and the heat treatment curve (broken line) of the heat treatment of the present invention.

In the same figure, (section a1 is the temperature increase section including drying of the compression molded product by the conventional method, section (b) is the debinding section (300°C to 400°C), and 0 point is the pressure molding temperature according to the present invention ( 400° C. to 800° C.), the +d1 section is the sintering/crystallization section (800° C. to 100° C.), and the (e) section is the slow cooling section.

(a) The two steps of dehydration in section (b1) and debinding in section b1 cannot be shortened because rapid processing will have a negative effect on the plain fabric and will eventually deteriorate the physical properties of the product after heat treatment. The entire section from (e) to (e) required more than 100 hours.

However, the manufacturing method of the present invention does not require the step in the (al, ('b) section), and the heat treatment time is about 30 hours, which is longer than the above-mentioned step 1.
/3 or less.

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

[Example 1. ] The glassy raw material has the composition shown in Table 1 below, and the raw material blended so as to contain each component is melted, and then this is pulverized to form glassy corpuscles, which are then further processed. Grind with a ball mill.

a. Chemical composition Table 1 □ A is a low softening point glassy raw material, B is a high softening point glassy raw material; FeO-・Coloring agent, unit is weight %.

(The same applies to Tables 2 and 3) b. Glassy raw material powder particle size A: 200 mesh or less... -98% or more (wt, % or less) B: 20 to 50 mesh... -30 to 40% 200 Less than mesh -50 to 60% C1 powder mixing ratio - A: B = 1; 1 d, compact size - 300 x 300 x 25 (*m
)e, Preheating temperature of raw material mixed powder---111---
300" Cr, mold preheating temperature---------
400'C (Pour the above powder into this mold and heat it together with the mold) g, Pressure force ------50kg f/c
rih, Atmosphere-----1--Atmospheric i, Mold coating mold--Graphite coating mold, 0
．． 2 w thickness j, heating temperature of mold + raw material mixed powder・−・−
-------The molded body that was pressure-molded under conditions of 580°C or higher was gradually cooled to room temperature, and the density and bending strength were measured.The results are as follows.

Apparent density - 4.71 g/cm'' Bending strength - 53, Okgf/ci As a result of heat treating this molded body at 900°C for 4 hours, a glass ceramic product in which wollastonite crystals were precipitated as a main component was obtained. Material property value is apparent density -2,33
g/cm Bending strength - 519 Glare f/d Water absorption rate - 0.32% This value is satisfactory as a building material.

[Example 2. ] Glassy raw material powders were obtained in the same manner as in the examples.

a. Chemical composition No. 2, glassy raw material powder particle size A: 200 mesh or less - -98% or more B: 20-5
o Metshu River 30-40% 200 meshes or less -50~
60% C0 powder mixing ratio... River -A:B=11d, compact size -'-'---300x300 X25 (am)
e, Preheating temperature of raw material mixed powder -... 40'Cf,
Mold preheating temperature: Curve: 650'C (The above mixed powder charged into the mold is heated, the upper mold is 40°C) g, Pressure car: River: -30kgf/csAh, Atmosphere - - - - - - In the air at room temperature, mold coating - -
・−・−Graphite coating mold, 0.2 tm thickness j, elapsed time from adding raw material mixed powder to starting pressure molding−・−−−−−・
The compact is pressure-molded for 25 seconds or more and then slowly cooled to room temperature to determine the density,
Bending strength was measured. (Near the bottom surface) Apparent density - 1
．． 62 g/cm" Bending strength...-14, 5 kg f
/ cA or more was heat-treated at 900° C. for 4 hours, resulting in a glass ceramic product in which wollastonite crystals were precipitated as a main component. The material characteristic values are: Apparent density: -2,36 g/am' Bending strength: -605 kgf/cul Water absorption: -0,18% These values are satisfactory as a building material.

[Example 3. ] Each glassy raw material powder was obtained in the same manner as in Example 1.

Next Leaf A, chemical composition No. 3, glassy raw material powder particle size A: 200 mesh or less...-98% or more B; 20
~50 meshes...30-40%200 meshes or less--50-60%C9 powder mixing ratio...--
・-・A:B=1: 1d, molded object dimensions--・・
------300X300 After putting the above powder into the mold, heat only the surface) g, Pressure car ----30kg f/c
nlh, Atmosphere - - - In the air at room temperature i, Mold coating - - Graphite coating, 0.2 dragon thickness j,
After putting the raw mixed powder into the mold, the heating surface temperature...--1--
The molded body was pressure-molded at 650° C. under conditions of heating method: electric heat radiation or higher, and then slowly cooled to room temperature, and its density and bending strength were measured. (Near the top surface) Apparent density -=4
．． 81 8/am3 When a molded product with a bending strength of -62.5 kgf/aA or more is heat-treated at 900°C for 4 hours,
A glass ceramic product in which crystals mainly composed of wollastonite were precipitated was obtained. Its material properties are: Apparent density - 2,32g/cs' Bending strength - 530kg f/co! Water absorption rate－・－・
-...0.18% This value is satisfactory as a building material.

(Effects of the Invention) The present invention is as described above, and the press-molded product (shiraji) is formed by using a mixture of glassy raw material powders with different softening points in an unsoftened state, instead of using a binder. Depending on the means of charging into the mold, it is easy to charge the mold, and even when the mold is wide and flat, it is easy to achieve a uniform thickness. By setting the temperature below the softening point of the glassy raw material powder, it is possible to obtain a healthy formed body (seraji) without using a binder, and eliminates various problems associated with the use of conventional non-component binders. I was able to resolve it. As a result of the above, the product quality is improved, and the industrial value of the present invention is significant, as it is possible to provide a glass ceramic product with high strength and suitable for use in outside buildings, interior materials, decorations, etc.

[Brief explanation of the drawing]

FIGS. 1 to 3 are cross-sectional views for explaining mold forming according to the present invention. FIG. 4 shows heat treatment curves of the press-molded article according to the present invention and the press-molded article produced by conventional means. 1--mold, 2-upper mold, 3-horizontal mold, 4--lower mold, 5-
- Reinforcement part, 6- Glassy raw material powder mixture (raw material mixed powder). Patent Applicant Kubota Iron Works Co., Ltd. Figure 2 Figure 3Lj Figure 4

Claims (4)

[Claims] (1) A mixture of glassy raw material powders with different softening points (low and high softening points) is put into a mold, and then a mixture of glassy raw material powders with different softening points (low and high softening points) is poured into a mold, and then the mixture is heated to a temperature higher than the softening point of the low softening point glassy raw material powder and lower than the softening point of the high softening point glassy raw material powder. The mixture is heated to a molding temperature, and the mixture is pressure-molded in a state where the former raw material powder is softened and the latter powder is not softened to obtain a molded body, and then the molded body is heat-treated to form a glass-like molded body. A method for manufacturing a glass ceramic product, characterized in that raw material powders are softened and fused together to make them densified, and at the same time, to precipitate crystals. (2) A glass-ceramic product according to claim 1, characterized in that a mixture of glassy raw material powder is put into a mold, and then the powder mixture is heated together with the mold to a molding temperature. Production method. (3) The method for manufacturing a glass-ceramic product according to claim 1, characterized in that the mixture of glassy raw material powders is heated to a molding temperature by being charged into a heated mold. (4) A glass-ceramic product according to claim 1, characterized in that a mixture of glassy raw material powders is put into a mold, and then only the surface of the powder mixture is heated to a molding temperature. manufacturing method.