JPH0597464A - Method for molding glass - Google Patents

Abstract

PURPOSE:To obtain a glass molded body having a smoothly finished surface with satisfactory mold releasability. CONSTITUTION:When glass is molded with a metal mold, a coating film of a low m.p. metal or alloy which melts or half-melts at the glass molding temp. but hardly causes evaporation and reaction with the glass at the molding temp. is formed on the surface of the metal mold so that a molten metal or alloy film of Sn, Zn, Pb, etc., is interposed between the glass and the metal mold at the time of molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass molding method or a glass remolding method with improved mold releasability.

[0002]

2. Description of the Related Art Conventionally, a glass molded article is manufactured by melting glass and casting it in an appropriate mold, or a glass remolding method in which a manufactured glass block is put into a mold and pressed. Is used. Since the molding temperature of glass is generally as high as 500 to 1200 ° C., heat-resistant steel is often used as the mold.

Under the condition that steel is repeatedly used at high temperature, it has a problem in durability and has a drawback that mold release is poor. Therefore, instead of steel, a ceramic mold,
A mold in which a precious metal is coated on the surface of the mold has been proposed. Ceramics are superior to steel in heat resistance,
The one coated with a noble metal has improved releasability because the glass and the noble metal hardly react with each other.

[0004]

In the case of a ceramic mold, it is easily welded to a glass material due to its material, and there is a problem in releasability. If the molded body and the mold are welded together, irregularities are formed on the surface of the molded body, resulting in poor quality. Further, although heat resistance is improved, ceramics are brittle, and thus are weak against impact. Ceramic materials are expensive, but can be damaged by thermal shock.

On the other hand, in the case of noble metal coating, abrasion and peeling of the noble metal film occur during use at high temperature,
It will damage the surface of the glass molded body. Like ceramic materials, they are expensive materials, but they have the problem that they cannot withstand repeated use.

It is an object of the present invention to provide a glass molding method in which the mold release is good and the surface of the glass molded body is finished smooth.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a low melting point on the mold surface to such a degree that it exhibits a molten state or a semi-molten state at the glass molding temperature, and at the molding temperature. A film of a metal or an alloy that hardly vaporizes is interposed between the glass and the mold. It is necessary that the metal used is one that does not easily react with glass, and it is more preferable that the metal is inexpensive and widely used.

Tin is an example of a metal that satisfies the above conditions. In the case of tin, the melting point is as low as 232 ° C, which is about 1000
It will be in a molten state at a glass forming temperature of ℃. Since the vapor pressure of tin is as low as 10 ⁻⁴ mmHg even at 1000 ° C., evaporation does not occur. Therefore, pores are not generated between the mold and the molded glass, and the surface condition of the molded glass can be kept good. In addition, tin rarely reacts with glass and is inexpensive and easily available.

As a means for coating the mold with tin, an appropriate method such as plating or spraying and applying molten tin can be considered. Further, not only tin but also a metal or alloy such as zinc, lead or bismuth can be used as a low melting point metal that does not react with glass. On the other hand, for the mold, a mold made of any material capable of coating a metal can be used.

As an example of the present invention, the case of performing glass molding using tin will be described. When heated glass is poured into a tin-coated mold, the tin on the mold surface melts to form a thin and uniform interface layer between the glass and the mold.

When cooled, the cooling proceeds from the surface in contact with the mold, so that tin in a molten state between the glass molded product and the mold forms an interface between the glass molded product and the mold. .. As the tin solidifies, the viscosity of the glass increases. Since the glass does not come into direct contact with the mold and the tin intervenes which hardly reacts with the glass, the glass can be easily released from the mold.

After releasing the mold, tin may adhere to the surface of the glass molded body, but it can be easily removed by pickling or the like. Furthermore, the surface of the glass molded body is finished to be smooth due to the interface between the molten and solidified tin.

[0013]

As described above, a metal or alloy film that has a low melting point, melts at the glass forming temperature, hardly evaporates at the glass forming temperature, and hardly reacts with the glass is formed on the surface of the mold. By this, the mold release can be promoted.

At the time of molding, since the metal or alloy is in a molten-solidified state in contact with the glass at the interface, there is an effect that the surface of the glass molded body is finished to be smooth. Further, since it is possible to re-coat the mold and repeatedly use it, it can be said that it is more advantageous in terms of cost than the conventional means.

Claims (1)

[Claims] 1. In glass molding, a metal or alloy coating that exhibits a liquid phase at a glass molding temperature, has a low vapor pressure, and does not react with glass is provided on the surface of the mold, and the glass and the mold are provided. A glass molding method comprising interposing a film of the metal or alloy.