JPS63156024A - Production of glass ceramic article - Google Patents

Abstract

PURPOSE:To produce the title article by a simple process without causing intrusion of impurities nor impairing the characteristics of the product, by press- molding vitreous raw material powder comprising materials having different softening points at a temp. within the softening range of the powder, softening at lower temp. without using a binder, then executing heat treatment. CONSTITUTION:A powder mixture consisting of vitreous raw material powder having lower softening point (A) and that having higher softening point (B) is molded under compression at a temp. higher than (A) and lower than (B) where the powder (A) is softened but the powder (B) is unsoftened. Both powder (A) and (B) are bonded by softening to compact the mixture, and at the same time crystals are caused to deposit. Then, the molded form is heat-treated. By performing the molding as described above without using a binder, several problems caused by the addition of binder encountered in the conventional process, such as intrusion of impurities, deterioration of the characteristics of the product, obligation of requiring binder, kneading apparatus, drying stage, and stage for removing binder, etc. are eliminated.

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 the powder particles are softened and fused to each other to be integrated and densified, while crystallization is attempted to precipitate mainly elastotonite 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 this method is that during the period of softening and fusion of the glass bodies, if the growth rate of precipitated crystal nuclei is fast and the composition has already entered the period of crystal growth, crystallization may occur. The accompanying increase in viscosity makes it difficult to fuse and integrate the bodies. In other words, there are restrictions on the composition of the glass bodies used, and even if they contain a nucleating agent or a coloring agent that has a nucleating effect, they will not pass.

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 production of large products that are easily damaged during handling, but these binders have little to do with the properties of the finished product (in fact, the residual binder has little to do with the product properties). 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. However, the cost increase caused by this is a problem.

Another problem is the high cost due to the binder itself and the high cost due to the mounting surface 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. It is important to develop means to improve
This invention has been made in response to this 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 is heated to a molding temperature that is above the softening point of the low softening point glassy raw material powder and below the softening point of the high softening point glassy raw material powder, so that the former raw material powder is softened. Then, while the latter powder is still unsoftened, the mixture is pressure-molded to obtain a molded body, and then the molded body is heat-treated to soften and fuse the glassy raw material powders constituting the molded body to make it densified. On the other hand, the point is that 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 has a limited amount of addition, it can be added in a large amount, and therefore a molded article (white ground) with high strength can be obtained even with a relatively small pressing force.

In addition, due to the pressure molding of the softened and unsoftened mixed powder, air trapped between the powders can easily escape, creating a healthy sloping surface. That is, the softened powder deforms to expel air and fill the spaces between the five particles, and the slits between the unsoftened particles act as air passages.

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

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

First, starting with the raw material powder, glass is made into small particles by an appropriate method such as pulverization of molten glass, and this is further used as a powder, and it is called a glassy raw material in the sense that the raw material is made from something that has already become glass. It is called.

By the way, low softening point raw materials have a softening point of 400 to 800°C.
A glassy raw material having a softening point at least 100°C higher than a low softening point raw material is desirable as a high softening point raw material.

In other words, glass that softens below 400℃ (glass-like raw material)
Generally called low-melting glass, it cannot be used 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 pressure forming frames (molds, etc.) during pressure forming. more preferably a softening point of 5.
It is a glassy raw material with a temperature of 00 to 700°C.

On the other hand, the reason why it is desirable that the high softening point glassy raw material has a softening point that is at least 100°C higher than the low softening point glassy raw material is that even if the temperature distribution in the heating furnace is slightly uneven, both powders will still soften. This is to make it possible to maintain the unsoftened difference.

Heating the mixed powder of the above-mentioned glassy raw materials usually does not oxidize the powder, so there is no need to use an inert atmosphere, and various heating methods such as a badge method or a continuous method can be used. During heating and stirring, care must be taken to ensure that the particle size and type distribution of the raw material powder does not become non-uniform.

The mixed powder thus heated to the molding temperature is charged into a molding frame and pressure-molded, and from the viewpoint of molding temperature, pressure, etc., a preferred molding frame is a mold.

FIG. 1 is an explanatory cross-sectional view of an example of mold molding according to an embodiment of the present invention, where ■ is the upper mold of the mold, 2 is the horizontal mold, 3 is the lower mold, and 4 is the upper mold of the mold.
is a mixture of heated glassy raw material powders, and after the mixture 4 is put into a mold, it is press-molded using an upper mold 1.

The softened glassy raw material powder may stick to the mold, and to prevent this, it is desirable to apply a coating mold (zircon sand, graphite, etc.), attach a ceramic sheet, ceramic coating, etc.

The mold can be used either at room temperature or preheated. When used at room temperature, the heat of the input heated raw material powder is taken away by thermal conduction, but there is no problem as long as the time from input to pressure molding is short. As an example of investigation, when the heating temperature of the raw material powder was 600°C and the ambient temperature was 30'C, the average temperature drop of the raw material powder after 30 seconds was 30°C. However, preheating to near the molding temperature is preferred.

Preheating of the mold includes external heating using a gas burner or the like, as well as internal heating using heating wires installed inside the mold.

In this way, when one side of the raw powder mixture is softened and the other is unsoftened, the softened powder acts as a binder, making it possible to obtain a dense press-molded product. can. However, the density of the compact is 50% or more of the true density,
It is appropriate that the bending strength is 1Qkgf/crA or more. This is due to the mutual softening and fusion of both raw material powders in the molded body.
It is a density that allows densification to occur at the lowest possible temperature and reduces volume changes during densification and crystallization, and a strength that allows the molded product to be prevented from being damaged during transportation and heat treatment. .

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

■ First glassy raw material composition (softening temperature 400℃~800℃
°C raw materials) Siot: 55-75%, AmCh: 15% or less, CaO: 5-15%, Na2O+ 20:10-
20% or more as essential ingredients, and 5i02+ JR2
zO* + CaO + Na20 + 20 > 90%
(M content percentage, same below) ■ Second glassy raw material composition (high softening point raw material) SiOz
: 40~60%, 8ρt01:5~20%, Ca
O: 25-45%, the above are essential ingredients, and 5i0218ρ, 0. +Ca
O〉85%.

Note that by including 15% or less of a glass colorant in the second glassy raw material composition, it is possible to make the glass ceramic product colored or colored or patterned.

The remarkable difference between the compositions of the first and second glassy raw materials is that the first glassy raw material contains 10 in Na2O+, but the second glassy raw material does not, and instead has a large amount of CaO. . Of course, the balance of other component contents is also related to the difference in softening point, but the softening point of the second glassy raw material is higher than that of the first glassy raw material mainly due to the difference in composition, and the composition of both is By selective adjustment, a preferable softening temperature difference of 100°C to 400°C can be obtained.

The above-mentioned compositions of the first and second glassy raw materials were designed so that crystallization would be easier when they were fused and integrated than when each was used alone, and now both were 1: The melting surface composition of the particles when mixed and integrated at 1 is 5if2:
47-68%, A901: 2-18%, CaO: 15
-30%, Na20 + K2O: 5 to 10%, which is a composition range in which wollastonite crystals are mainly formed, and anorsite crystals are also formed.

The case where the precipitated crystals are wollastonite or anorthite crystals has been described above, but it is of course possible to use a glassy raw material that precipitates other crystals, such as debitrite crystals.

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 there be a small number of fine particles (50% or less) of 0 mesh or less.

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

In addition, when the glassy raw material with a high softening point is a colored raw material containing a coloring agent, the raw material powder is made into particles of 10 to 200 meshier,
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 meshes 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,
As described above, the mixture is heated to form a press-molded product, and the pressurizing force in this case is 5 kgf/a.
If it is less than J, the necessary strength, that is, the strength capable of maintaining the shape until the next heat treatment, cannot be obtained. Also 300 kg r/
Cj or more is a problem from the viewpoint of mold strength and economy, and there is no need to exceed it.

Next, the heat treatment of the press-molded body will be described.

Heating for heat treatment of the press-molded product may be done by rapidly raising the temperature to the molding temperature, then raising the temperature to the crystallization temperature and maintaining the same temperature. Of course, the molded body may be heated subsequently after pressure molding.

As mentioned above, the pressure 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, a temperature slightly higher than the softening point of the low-temperature softening powder. The softening temperature is a temperature range that exceeds the softening point of the above-mentioned high-temperature softening powder and where 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 softening and fusion of the powder particles, densification, and In other words, sintering and crystallization progress. 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. 2 shows the molding of a press-molded body using the powders of the first and second glass powder raw materials using a conventional method, that is, a binder (PV
The heat treatment curve (solid line) obtained by heat-treating the molded product after kneading it with A melt (using Molten A) and then performing pressure molding at room temperature using a compression molding frame and the heat treatment curve (broken line) of the heat treatment of the present invention. This is a comparison.

In the same figure, (section a1 is a temperature increase section including drying of the compression molded body by the conventional method, section b1 is a debinding section (300℃ to 400℃), and 0 points are the pressure molding temperature according to the present invention (400℃). ℃~800℃), (di section is sintered/
The crystallization section (800° C. to 1000° C.), fe) section is the slow cooling section.

(The two steps of dehydration in section a1 and debinding in section (b) cannot be shortened because rapid processing will have a negative impact on the plain fabric and will eventually deteriorate the physical properties of the product after heat treatment, fa) ~ The entire tel section took over 100 hours.

However, the manufacturing method of the present invention does not require the steps in sections fa) and (b1, and the heat treatment time is about 30 hours, which is 1/1 of the above.
It has been shortened to 3 or less.

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

Example 1゜The glassy raw material had the composition shown in Table 1 below, and the raw materials blended to contain each component were melted, and then this was pulverized to form glassy corpuscles. The material was further ground in a ball mill.

Table 1: The above crushed glassy raw material powder (200 mesh or less)
Mix at a ratio of 1:1 and make soo”c ~ 600 as shown in Table 2.
℃, pressurizing force 30 kgf/ctA, 100
kgf/- by pressure molding using a mold. The swelling and softness of the press-molded body is 150 x 150 x 30 (wm).

However, the mold is not preheated. The coating mold is graphite based and has a thickness of 0.2u+.

Table 2 The above-mentioned white ground was sintered and crystallized at 900° C. for 4 hours, and as a result, anorsite crystals and wollastonite crystals were precipitated. The bending strength of all products is 630kgf
It was /-.

In the above example, the total heat treatment time for heating up the plain ground, crystallization/crystalization heat treatment, and completion of slow cooling was 28 hours.
Compared to the conventional method, which required 101 hours to process white ground (including drying time), this time could be reduced to 1/3.6.

Example 2゜3 Omotega t0%, FeO No. Shingo I Colorless and colored glassy raw materials having the above compositions were used.The colored raw materials had 50 to 60% of 200 mesh or less, and 20 to 5
The colorless raw material is ground into a powder containing 30-40% of 0 meshes, and the colorless raw material is powdered with 98% or more of 200 meshes or less.The two are mixed in a ratio of 1=1, and this is made into a compact under the following conditions, followed by densification and crystallization. It was made into a product by chemical heat treatment.

■ Heating temperature of glassy raw material powder...570℃■ Molded object dimensions...300 x 300 x 25 (mm)■
Mold preheating temperature: 400-500℃ Pressure: 45ksr f/cal Mold coating: Graphite coating, 0.2mm thickness Molded object (white ground) density... 1
．． 68 g/cm Same bending strength...13.8kg
f / cj (This investigation was carried out by slowly cooling to room temperature after molding) ■ The glass-ceramic product in which wollastonite crystals were precipitated as a result of sintering and crystallizing the above-mentioned plain ground at 900°C for 4 hours. became.

■Product properties Density...2.34 g/c11 Bending strength...525 kg f/aJ Water absorption rate...
0.28% These values are sufficiently satisfactory as a building material.

(Effects of the Invention) The present invention is as described above, and it is possible to mold a press-molded body (shiraji) without using a binder, using a low By performing form molding by pressure in the softening region of temperature-softened powder, various problems caused by conventional addition of binders can be solved, such as contamination of impurities, deterioration of product properties, and reduction of binder costs. This solves problems such as the need for a kneading device, a drying process, and a single process for removing binders.Moreover, the strength of the soil can be freely selected by adjusting the heating temperature in the soil forming process, and the pressing force can also be adjusted. We provide glass-ceramic products that are suitable for high-strength building exterior and interior materials, decorative items, etc., and have the advantage of being able to pressurize at a lower temperature than conventional pressurization at room temperature, and can also easily increase the silt density. Therefore, the industrial value of the present invention is significant.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view of an example of molding according to an embodiment of the present invention, and FIG. 2 is a heat treatment curve of a press-formed body according to the present invention and a press-formed body according to a conventional method. 1... Upper mold of the mold, 2... Same horizontal mold, 3... Same lower mold, 4... Mixture of heated glassy raw material powder. Patent applicant Kubota Iron Works Co., Ltd. Figure 1 Figure 2

Claims (2)

[Claims] (1) 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 glassy raw material powder and below the softening point of the high softening point glassy raw material powder, and When the powder is softened and the latter powder is not softened, the mixture is pressure-molded to obtain a molded body, and the molded body is then heat-treated to soften and fuse the glassy raw material powders constituting the molded body. A method for manufacturing a glass-ceramic product, characterized in that it is densified and crystals are precipitated. (2) A method for manufacturing a glass-ceramic product according to claim 1, characterized in that a mixture of glassy raw material powder heated to a molding temperature is charged into a mold and pressure-molded.