JPH0623059B2 - Method for manufacturing glass ceramic products - Google Patents

Description

The present invention relates to a method for producing a glass ceramic product by sintering glass powder.

(Prior Art) A conventional general method for producing a glass-ceramic product is to melt a glass raw material containing a nucleating agent, form it by various forming means, and then perform crystallization heat treatment to precipitate crystals,
It was a glass-ceramic product.

Further, as a method for obtaining glass ceramics without containing a nucleating agent, glass bodies obtained by crushing molten glass by water cooling etc. are accumulated in a mold and heat-treated to melt each glass body. A method of crystallizing while depositing (referred to as an accumulation method) is disclosed in "Tokukaisho 48-78217".

Further, the inventors of the present invention disclosed in Japanese Patent Application No. 60-284150, finely pulverize a glass-like raw material having a specific composition (mainly a wollastonite crystal forming composition), and make the fine powder into a compression molded body at room temperature. There is a method of heat-treating to soften and fuse the powder particles to integrate and densify them, and at the same time, to crystallize and mainly precipitate wollastonite crystals.

(Problems to be Solved by the Invention) Among the above-mentioned conventional methods, in the method of forming a glass product and performing post-heat treatment for crystallization, the nucleating agent is expensive compared to the raw material. The problem is that there are many of them, and the integration method requires crystallization in the case of a composition in which the growth rate of the crystal nuclei of precipitation is high at the time of softening and fusion of the glass bodies and it is already in the growth time as crystals. The accompanying increase in viscosity makes it difficult to fuse and integrate the small bodies. That is, the composition of the glass body used is limited, and it is not suitable when it contains a nucleating agent or a coloring agent having a nucleating action.

The following prior invention by the inventors of the present invention is a method of pulverizing a glassy raw material and heat-treating the fine powder as a powder compact, and increasing the contact area by contact between the fine powders and softening point slightly due to dense contact. The softening fusion and the densification between the glass particles can be performed at a low temperature exceeding the above level. That is, the softening and fusion of the glass particles in the integration method cannot be realized unless the temperature is considerably higher than the softening temperature because of the coarse particles and the simple integration state. The temperature is slightly higher than the above temperature, and therefore, after the softening fusion and the densification, the temperature is further raised to perform the crystallization. This also applies to the case where a nucleating agent or a coloring agent having a nucleating action is included.

As a measure against problems such as deterioration of formability due to increase in size of a molded body (shiraji), transportation, damage at the time of sintering and the like, addition of an organic binder such as polyvinyl alcohol or an inorganic binder such as bentonite may be used. It improves the earth's strength.

However, in press molding at room temperature, there is a limit to the effect of improving the strength by the addition of the above binder, and thus there is a limit to the size of the molded product that can have the required strength.

Furthermore, in the case of adding an organic binder, the larger the amount of the binder added, or the larger the product, the longer the debinding process takes.On the other hand, the addition of a large amount of the inorganic binder prevents shrinkage and densification of the molded body during heat treatment, and The problem is that it adversely affects the product composition.

(Means for Solving Problems) The present invention has been made for the purpose of solving the problems associated with the addition of the above organic or inorganic binders, and is a raw material glass powder made of a glass powder which precipitates crystals by heating. And a mixed powder of a binder glass powder having a softening point of a glass powder lower than the glass of the raw material glass powder, and pressed in a temperature range of the softening point of the binder glass powder or higher and lower than the softening point of the raw material glass powder. After molding, a raw material glass powder is obtained by softening and fusion-bonding the binder glass powder to obtain a molded body, and then heating the molded body to a temperature equal to or higher than the softening point of the raw material glass powder to form a molded body. The raw material glass powder and the binder glass powder are softened and fused to be densified and crystals are precipitated in the raw material glass powder.

(Example) First, a raw glass powder will be described.

In the present invention, the glass used as the raw material glass powder, which is the main raw material for the glass-ceramic product, has a softening point of 600 ° C. or higher, and a glass corresponding to this is, for example, a glass having the following composition.

_{SiO 2: 55 ~75%, Al} 2 O 3: 15% or _{less, CaO: 5~15%, Na 2} O + K 2 O: 10 ~ 20%, as an essential component (% is wt% or less the same.), And SiO ₂ + A
l ₂ O + CaO + Na ₂ O + K ₂ O> 90% SiO ₂ : 40 to 50%, Al ₂ O ₃ : 5 to 20%, CaO: 30 to 40% as essential components, and SiO ₂ + Al ₂
O ₃ + CaO> 85%.

The above glass is a glass that has a higher softening point than glass.

For the production of glass powder having a softening point of 600 ° C. or higher, for example, after melting the raw material adjusted to have the chemical composition as shown in the above example, it is rapidly crushed by a method such as water granulation and crushed into glass particles. Alternatively, glass already having a softening point of 600 ° C. or higher may be made into a small body by an appropriate means, and the small body thus obtained is further ground by, for example, a ball mill. At this time, the finer the particle size, the more the fusion and integration of the powders and the densification are performed at a low temperature of slightly higher than the softening temperature during the sintering of the pressure-molded body. Grain size 2 for powder of compacted body composition
It is desirable that at least 50% of fine particles of 00 mesh or less are contained.

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

One kind or two or more kinds of the powders thus obtained are mixed and used as a raw material glass powder, and a glass powder having a softening point of 500 ° C. or lower, which is lower than the raw material glass powder, such as borate glass or high vanadium glass. Add the above powder as a binder glass powder and mix well. At this time, the particle size of the binder glass powder is preferably 200 mesh or less, and the addition amount is 3 to 15%. That is, if it is less than 3%, the effect as a binder is not exerted, and if it exceeds 15%, the product is adversely affected.

It should be noted here that the case where the product is colored and colored is mentioned.

Colored products can be obtained by using colored glass powder containing a coloring agent. Now, when two kinds of glass powders are mixed and used as a raw material, one of them has a particle size of colored glass containing a coloring agent. ˜200 mesh powder, another one as colorless glass powder of 200 mesh or less, and both are mixed with the binder glass powder. That is, by making the colored glass particles coarse particles, the colored coarse particles form a spot pattern in the product. The mixed powder preferably contains at least 50% of fine particles of 200 mesh or less, which is as described above.

If both the colored glass powder and the colorless glass powder are mixed well at 200 mesh or less, a uniform ground color is exhibited and a mere colored product is obtained.

Even when the binder glass is colored, a colored pattern or a colored product can be obtained depending on the powder particle size. However, it is already mentioned that the binder powder is preferably 200 mesh or less.

The mixed powder obtained by mixing the binder glass powder having a softening point of 500 ° C. or lower as described above is pressure-molded in a temperature range of the softening point of the binder glass powder or higher and lower than the softening point of the raw glass powder, that is, lower than 600 ° C. . Molding temperature is 60
Since it is less than 0 ° C., a normal mold can be used.

If the above pressure molding is carried out above the softening point of the raw glass powder (600
It is not necessary to use the binder glass powder with a low softening point when heated to above (° C or higher), but at 600 ° C or higher, heat-resistant cast steel or graphite mold must be used as a press mold, which is very expensive. It becomes a thing.

It is desirable that the molding is performed by pressure molding so as to have a density of 50% or more of the true density and a bending strength of 10 kgf / cm ² or more. The above conditions are sufficiently satisfied by interposing binder glass powder softened at the above temperature. A satisfactory molded product can be easily obtained.

In addition, the air between the powders is quickly discharged along the particle surface of the raw material glass powder that has not been softened, so that the compacting of the molded body is promoted.

It is desirable for the compact density to be 50% or more of the true density in order to soften and fuse the compact powders of the compacts together and to densify at a temperature as low as possible, and to reduce the volume change during densification and crystallization. The reason is that the bending strength is preferably 10 kgf / cm ² or more because the bending strength can be prevented from being damaged during transportation and heat treatment of the molded body.

Next, the heat treatment of the compact will be described.

The heat treatment is A. heat treatment for softening, fusing and unifying the raw glass powders together, and B. heat treatment for crystallization, and the basic type is a temperature slightly above the softening point of the raw glass powders. It is a two-stage type consisting of a first-stage heat treatment in which the temperature is maintained at the same temperature and the same temperature is maintained, and a second-stage heat treatment in which the temperature is further raised to a crystallization temperature and is maintained. Since the integration progresses to a certain extent through the binder glass particles, the fusion and integration of the raw material glass powders and densification are caused in the process of raising the temperature to the crystallization temperature, and then the crystallization temperature. A one-stage type heat treatment method for holding

In addition to heating from room temperature, the molded body may be heated from the molding temperature without being cooled after the pressure molding.

FIG. 1 shows a heat treatment curve of a basic type (two-step type) heat treatment, and FIG. 2 shows a heat treatment curve of a one-step type heat treatment. In these figures, a broken line portion indicates a “temperature-time curve” in the pressure forming process. The figure shows a mode in which the molding temperature is continuously changed to the heat treatment, and the solid line ab 'indicates the "temperature-temperature" of the part where the pressure-molded body once heated to room temperature is heated to the molding temperature b. The time curve ". Although the figure shows that the same temperature rise is a rapid temperature rise, it is also possible to use such a rapid temperature rise or to select an appropriate temperature rise rate.

Note that many crystallizations can be carried out at 750 to 1000 ° C., and the precipitated crystals are, for example, wollastonite and anorthite when glass powders having the compositions exemplified above are used alone or as a raw material glass powder. , Gerenite, cristobalite, devitrite, etc. are precipitated.

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

The following Table 1 shows the compositions of the raw material glass powder and the binder glass powder used in the examples. The raw material I falls within the range of the above-exemplified composition, and the raw material II has the same composition. It falls into the category. In addition, Fe ₂ O ₃ + FeO in the raw material II is a coloring agent, and thus the raw material II is a colored glass.

The production of each raw material and binder powder was carried out by melting each of the raw materials blended so as to have the composition shown in Table 1 above, then granulating this by water granulation and further crushing it with a ball mill, Each powder was manufactured as 200 mesh or less.

The pressure-molded body was mixed with raw material powder I: raw material powder II = 3: 7 (weight ratio), and pressure-molded using a mold under the conditions shown in Table 2 below. The shape of the molded body is 150 × 150 × 30 (mm).

As the heat treatment, the above-mentioned compact was sintered and crystallized by a one-step heat treatment at 900 ° C. × 10 hr, and as a result, wollast crystals were mainly precipitated.

The bending strength of each product was 520 kgf / cm ² .

The total heat treatment time for the temperature rise, sintering / crystallization heat treatment, and slow cooling of the compact is 46 hours, and the compact is formed by the conventional method using PVA (polyvinyl alcohol) as a binder at room temperature. The processing time (including the drying time) of 1 was required to be 88 hours, while it was able to be reduced to about half as described above.

This effect becomes more remarkable as the product becomes larger.

(Effects of the Invention) The present invention is as described above, and when the mixed powder of the raw material glass powder and the binder glass powder is pressure-molded, the raw material glass powder is attached and integrated through the softened and fused binder glass powder. Therefore, a high-strength molded product can be easily obtained without using an organic or inorganic binder, and a relatively large molded product can be easily handled.

Moreover, during softening and fusion of the binder glass powder during pressure molding and before the softening and fusion of the raw material glass powder is started,
Since the air between the powders is rapidly discharged along the particle surface of the unsoftened raw material glass powder, densification of the molded body is promoted, and consequently a dense crystallized glass-ceramic product without bubbles can be obtained.

[Brief description of drawings]

1 and 2 are heat treatment curves of the pressure-formed body according to the present invention, FIG. 1 is a basic type (two-stage type) heat treatment curve, and FIG. 2 is a one-stage type heat treatment curve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kimura 64, Nishimukaishima-cho, Amagasaki City, Hyogo Prefecture Kubota Iron Works Co., Ltd. Amagasaki Plant (72) Kei Shikata, 64, Nishimukaijima-cho, Amagasaki City, Hyogo Prefecture Kubota Iron Works Co., Ltd. Amagasaki Plant (56) Reference JP-A-54-14813 (JP, A)

Claims (1)

[Claims] 1. A mixed powder of a raw glass powder made of a glass powder which precipitates crystals upon heating and a binder glass powder made of a glass powder having a softening point lower than that of the raw glass powder, After pressure-molding in a temperature range not lower than the softening point and lower than the softening point of the raw material glass powder, a raw material glass powder is adhered and integrated through the softened and fused binder glass powder to obtain a molded body. Glass ceramics characterized by heating to a temperature above the softening point of the raw material glass powder to soften and densify the raw material glass powder and the binder glass powder constituting the molded body and to precipitate crystals in the raw material glass powder. Product manufacturing method.