JPS6363497B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a crystallized glass article suitable for natural stone-like artificial stone for architectural and decorative purposes. [Prior Art] So far known methods for manufacturing natural stone-like crystallized glass articles can be broadly divided into two types. One of them is Special Publication No. 47-1639 and Special Publication No. 47-14839.
No., Special Publication No. 49-36376, Special Publication No. 51-23966, Special Publication No. 53-41693, Special Publication No. 57-20254, Japanese Patent Publication No. 1972
There is a method of directly crystallizing glass formed by a roll-out method, a press method, a pouring method, etc., as typified by publications such as No.-92942 and JP-A No. 59-97551. As proposed in Publication No. 55-29018, after a plurality of granulated glass particles are accumulated, the glass particles are softened, fused, and integrated with each other by heat treatment, and the glass particles are removed from the surface of the glass particles and the fused interface. This is a method called a sintering method in which a crystallized glass article is obtained by precipitating and growing crystals. [Problems to be solved by the invention] In the usual manufacturing method in which glass is formed by a method such as a roll-out method, a press method, or a pouring method, and then heat-treated to crystallize it, the crystals are almost uniform throughout the molded product. Because of this, the resulting crystallized glass products tend to have a uniform and monotonous appearance, making it difficult to obtain a natural stone-like appearance. On the other hand, the coexistence of crystals and glass matrix phases and glass grains 1
Compared to the conventional molding method, the sintering method enhances the beautiful natural stone-like appearance due to the orientation of crystals that grow from each surface or fused interface toward the inside. Although much more preferred, this sintering method also has drawbacks, as discussed below. (a) The glass grains must have a sufficiently low viscosity, and the glass grains must be completely softened, fused, and integrated together before the precipitation and growth of crystals from their surfaces becomes predominant, and the composition range naturally increases. is limited. Moreover, this also limits the types of precipitated crystals and the physical properties of the crystallized glass article within a narrow range. (b) Even if the composition and heat treatment conditions are the same, the progress of softening and crystal precipitation due to heat treatment is different between when powder or fine glass particles are used and when relatively large glass particles are used. Since reproducibility in the surface condition and appearance of crystallized glass articles cannot be obtained, a step is required to smooth the glass particles using a sieve so that the particle size of the glass particles used is almost constant. (c) Glass grains are sufficiently softened by heat treatment. Even when the glass particles are fused, some of the air gaps that exist between the glass particles during accumulation are inevitably incorporated into the crystallized glass article as pores. This means that when processing such as cutting or polishing is performed, the pores are exposed on the surface, making it impossible to obtain a crystallized glass article with a smooth surface, and also reducing mechanical strength. [Objective of the Invention] The present invention has a beautiful natural stone-like appearance due to the coexistence of crystals and matrix glass phases and the orientation of crystals precipitated and grown in the glass, and has the above-mentioned (a).
It is an object of the present invention to provide a method for manufacturing a crystallized glass article for artificial stone, which solves all of the various drawbacks of the sintering method shown in (c). [Means for Solving the Problems] The gist of the present invention, which has been made to achieve the above-mentioned object, is to provide a crystalline material having a property that crystals precipitate and grow from the surface toward the inside when heat treated. A process of forming glass into a desired shape, a process of causing fine cracks in part or the whole of the glass molded product by thermal shock or mechanical shock while maintaining the shape of the glass molded product, and then heat treatment. Due to the coexistence of crystals and matrix glass phases and the orientation of crystals, The present invention provides a method for producing a dense crystallized glass article that has a beautiful natural stone-like appearance and is free of bubbles. The crystalline glass used in the present invention may be of the known composition described in the above-mentioned publication, or may be of other types, and the method of the present invention is not limited by the glass composition. The method of the present invention will be explained in detail below. First, crystalline glass, which has the property of precipitating and growing needle-like or dendritic crystals from the surface to the inside, is melted by heat treatment, and then formed using conventional forming techniques such as roll-out, pressing, and pouring. It is then shaped into a plate or block. Next, while maintaining the shape of the plate-like or block-like glass molded product obtained in this way, a sudden thermal shock or mechanical shock is applied to create fine cracks in the whole or a part of the glass molded product. As a specific example, the following method can be considered. (a) A method in which a molded glass article is cooled in an annealing furnace to a temperature of 300 to 500°C at a rate that does not crack, and then the glass molded article is directly immersed in water to create cracks. If the glass molded product is large and thick, it will easily lose its shape under its own weight, so rather than immersing it in water, it is better to transfer it to a fire-resistant formwork for crystallization heat treatment whose inner surface has been coated with mold release agent powder.
It is preferable to apply water to crack the surface. Moisture is removed by drying before heat treatment. The appearance and fineness of cracks can be controlled by the immersion method, water application method, and quenching temperature difference. (b) The formed glass article is air-blown by the method described, for example, in "Glass Handbook" edited by Masao Sakuhana, Teruo Sakaino, and Katsuaki Takahashi, (September 30, 1980), Asakura Shoten, pp. 485-490. A method of applying a large mechanical impact to the glass molded product by hitting it with a hammer or applying press pressure after cold strengthening to create small cracks. When applying impact, etc., in order to prevent glass particles from scattering or the shape of the molded product to collapse, the front and back surfaces of the tempered glass molded product should be coated with glass shatter prevention spray beforehand, and then the metal formwork should be applied. It is preferable to fix it inside. If the glass molded product is large and thick, it will easily lose its shape under its own weight, so after making the cracks, a binder such as a polyvinyl alcohol aqueous solution is applied to the surface of the cracked glass molded product and dried and solidified. While maintaining its shape, transfer it into a fireproof mold coated with mold release agent powder. Further, in addition to a binder such as a polyvinyl alcohol aqueous solution, an adhesive tape or the like may be used. Of course, the above methods (a) and (b) can be applied to both tempered and untempered glass products. Glass molded products with cracks caused by the above treatment are transferred to a heat treatment furnace together with the refractory mold and heated.
As the cracks inside the glass molded product begin to fuse as the glass softens, needle-shaped, dendritic, etc. crystals move toward the inside of the glass molded product from the surface and the cracks (boundary surfaces) that cover the entire surface of the glass molded product. Once precipitated
When it begins to grow and continues to undergo heat treatment, it becomes an aggregate of coarse crystals. When a crack is placed in a part of a glass molded product, the crystals tend to be unevenly distributed, producing a unique design effect. [Embodiments of the Invention] Examples of the present invention will be described below. FIG. 1 shows a state in which a cracked glass molded product 3 is filled into a refractory mold 1 through a coating layer 2 of mold release agent powder for crystallization heat treatment in the method of the present invention. . 4 is a crack. On the other hand, FIG. 2 shows a case in which glass particles 5 are filled by a sintering method. 6 is a void between glass particles. Example 1 A glass batch was prepared using silica powder, aluminum hydroxide, calcium carbonate, potassium nitrate, zinc white, and arsenic acid as raw materials so as to satisfy the following glass composition, and this was placed in a crucible and heated at a temperature of 1400°C in an electric furnace for about 50 minutes. Time to melt. _SiO2 39.5wt%,
Al ₂ O ₃ 20.0wt%, CaO3 3.5wt%, K ₂ O 0.5wt%,
ZnO6.0wt%, _{As2O30.5wt %} . The obtained molten glass is poured into a metal mold and formed into a plate shape of approximately 300 x 300 x 20 mm. This sheet glass is heated to 650 to 680℃ for 30 minutes in a slow cooling furnace.
After holding for a minute, the temperature was lowered to 300°C at a rate of 1°C/min, and the sheet glass was immediately transferred into a fire-resistant mold whose inner surface was coated with mold release agent powder (see Figure 1). The entire sheet glass molded product is subjected to thermal shock by pouring water on it to create cracks. After that, the cracked glass molded products are dried for each fireproof formwork and transferred to a heat treatment furnace to a temperature of 1050℃.
Heat treatment was carried out by increasing the temperature at a rate of 200°C/hour and holding it at 1050°C for 3 hours. As the temperature rises, cracks inside the glass molded product begin to fuse as the glass softens, but as the temperature rises,
When the temperature exceeds 900℃, dendrite-like crystals begin to grow inward from the surface of the cracked sheet glass and from the crack interface inside the molded product, and as the heat treatment continues, bubbles begin to grow. It became an aggregate of dense, coarse dendrites. Of course, by changing the heat treatment conditions, the crystallization rate can be changed within a certain range. As a result of X-ray diffraction measurement, it was found that the main crystal of the precipitated crystal phase was gehlenite. This natural stone-like pattern is caused by the mixture of crystals and matrix glass phases and the orientation of the crystals, as is the case with the sintering method, but when the upper surface of the crystallized glass product is polished, it creates a beautiful natural stone-like pattern. A pattern appeared and no pores were exposed on the surface. For comparison, a crystallized glass article was manufactured by using a glass composition similar to that of Example 1 and glass grains of about 2 to 6 mm by the sintering method shown in FIG. Conditions such as heat treatment were the same as in Example 1. The results of comparative tests between the above Example 1, Comparative Examples, and natural stones are shown in Table 1 below.

〔Effect of the invention〕

According to the method of the present invention, even if the glass composition does not have a sufficiently low viscosity, the glass regions separated by cracks are in complete contact with each other and are easily fused or sintered, so that heat treatment is not required. As a result, it can be easily integrated and restored to its original shape. Therefore, it is not necessary for the glass composition to have a sufficiently low viscosity, and a wide range of glass compositions can be accommodated. The sintering method requires a step to make the particle size of the glass particles almost constant, and it is especially troublesome to handle the powder or fine glass particles produced during the process, but the manufacturing method of the present invention Although it requires a process to crack the glass molded product,
Since a glass molded product with cracks can be handled as is, there is no need to handle powdered glass or fine glass, and as mentioned above, the type and size of cracks may vary depending on the quenching temperature difference and the degree of air-cooling strengthening. can be easily controlled. Since the glass regions separated by the cracks are in complete contact with each other, it can be said that there are almost no voids between the glass regions compared to the case of the sintering method. Therefore,
The crystallized glass article obtained by heat treatment has a dense structure without pores. This eliminates the difficulty of exposing pores on the surface of the crystallized glass article during processing such as cutting or polishing, and also leads to an increase in mechanical strength. It has various excellent effects such as, and its usefulness is extremely large.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the state of a glass molded article before crystallization heat treatment according to the method of the present invention, and FIG. 2 is an explanatory diagram of a case using a conventional glass grain sintering method.

Claims (1)

[Claims] 1 A process of forming crystalline glass, which has the property of crystallization and growth from the surface toward the inside when heat-treated, into a desired shape, and a process of applying thermal shock or mechanical shock while maintaining the shape of the glass molded product. The method is characterized by comprising a step of creating fine cracks in part or the whole of the glass molded product, and a step of precipitating and growing crystals from the surface of the glass molded product and the interface of the cracks toward the inside through heat treatment. A method for producing a dense crystallized glass article having a beautiful natural stone-like appearance due to the mixture of crystals and matrix glass phases and the orientation of the crystals, and having no air bubbles.