JP2005255495A - Method for manufacturing silica glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing silica glass by which bubble-free silica glass is easily manufactured at high yield. <P>SOLUTION: In the method for manufacturing the silica glass, transparent silica glass is manufactured by mixing silica sol with silica powder having 1-10 μm particle diameter in a ratio of 1:2-2.3 by pts.wt., pouring the mixture into a forming die and gelating the mixture to form a silica formed body, drying the silica formed body and primarily firing the dried silica formed body at 1,000-1,400°C under the atmosphere to form a silica porous body and firing the silica porous body at a reduced pressure under an inert gas atmosphere in a vacuum pressurizing firing furnace. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing silica glass, and more particularly to a method for producing silica glass using a sol-gel method.

In the conventional method for producing silica glass using the sol-gel method, as proposed in Patent Document 1, tetraethoxysilane / ethanol / ammonia water is mixed to form a sol solution, which is poured into a mold to form a molded body. In addition, there is described a production method in which a residual organic substance is removed from this molded body at 600 ° C. and then fired at 1350 ° C. in an air atmosphere to form transparent silica glass. However, in the method described in Patent Document 1, it is necessary to severely control (a) temperature and humidity control during drying of the molded body. (B) The gelled compact is fragile and difficult to handle. (C) When the sol is poured into the mold, bubbles are mixed into the silica glass with closed pores. (D) Since there are no open pores when the molded body is dried, shape change and shrinkage are severe and cracks occur. As described above, many improvements are required.
Japanese Patent Laid-Open No. 1-65028 (right column on page 2, lines 5 to 17, FIGS. 4 and 5)

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a method for producing silica glass, which is easy to produce, has a good yield, and can produce bubble-free silica glass.

  In order to achieve the above object, according to one aspect of the present invention, silica sol and silica powder having a particle size of 1 to 10 μm are mixed at a ratio of 1: 2 to 2.3 parts by weight, poured into a mold, and gelled. A silica molded body is prepared, and after the silica molded body is dried, primary firing is performed at 1000 to 1400 ° C. in an air atmosphere to form a porous silica body. There is provided a method for producing silica glass, characterized by firing in an active gas atmosphere to form transparent silica glass. Thereby, the manufacturing method of the silica glass which can manufacture an air-free silica glass with easy manufacture and a good yield is implement | achieved.

  According to the method for producing silica glass according to the present invention, it is possible to provide a method for producing silica glass that is easy to produce, has a good yield, and can produce bubble-free silica glass.

  Hereinafter, an embodiment of a method for producing silica glass according to the present invention will be described with reference to the accompanying drawings.

  In the method for producing silica glass according to the present invention, silica sol and silica powder having a particle diameter of 1 to 10 μm are mixed in a ratio of 1: 2 to 2.3 parts by weight, poured into a mold, and gelled to obtain a silica molded body. After the silica molded body was prepared and dried, primary firing was performed at 1000 to 1400 ° C. in an air atmosphere to form a silica porous body, and this silica porous body was fired in a vacuum pressure and firing furnace under reduced pressure in an inert gas atmosphere. It is the manufacturing method which makes and makes transparent silica glass.

  When hydrolyzing for the first time, the silica sol is set to the acidic side, and ammonia water (alkali) is added to adjust the pH to 4.5 to 5 before mixing the silica powder. The gelation time can be adjusted by adjusting the pH (speeding up). By making the silica powder spherical, the shape change and shrinkage during drying are alleviated, and the generation of cracks can be prevented. The vacuum firing is performed in an inert gas atmosphere with a degree of vacuum of 10 Torr or less, a firing temperature of 1500 ° C. or more. This facilitates transparency.

  According to the method for producing silica glass of the present embodiment, by mixing silica powder and silica sol into a porous silica body, there are innumerable open pores, so shape change and shrinkage during drying are alleviated and cracks are generated. do not do. Moreover, it is a silica porous body molded with silica powder of 1 to 10 μm, and a molded body having high strength and high handling can be obtained. Furthermore, since it is vacuum fired, it can be removed even if bubbles are mixed. Accordingly, it is possible to provide a method for producing silica glass, which is easy to produce, has a good yield, and can produce bubble-free silica glass.

  A silica glass bar with a diameter of 9 mm was produced using the method for producing silica glass according to the present invention.

1. Example 1) Production of porous body: When producing a porous body of φ9 mm silica glass bar, a ratio (volume ratio) of tetraethoxysilane: water: 0.1 N hydrochloric acid = 12.4: 9: 1 was used as a sol adjustment. ) And then propylene glycol is added to the 1.1 N hydrochloric acid 3.1 (volume ratio) to 3.1 N hydrochloric acid, and then 0.01 N ammonia water so that the pH is 4.5 to 5. To obtain a silica sol. To this silica sol, silica powder particles having a particle diameter of 1 to 10 μm are added and mixed in a ratio (weight ratio) of silica sol: silica powder particles = 1: 2, poured into a mold, left to stand for 3 hours, and released from the mold. And The obtained molded body was fired at 1300 to 1400 ° C. for 12 hours in an air atmosphere to obtain a porous silica porous body that was primarily fired.

2) Clarification: The silica porous body obtained in the above 1) was baked in a vacuum pressure sintering furnace under the baking conditions shown in Table 1 under the atmosphere, calcination temperature, and pressure to obtain transparent silica glass.

2. Comparative Example Silica glass was actually produced under suitable conditions using the glass production method described in Japanese Patent No. 2577572 (Patent Document 1).

  Tetraethoxysilane, ethanol, and aqueous ammonia were mixed at a molar ratio of 1: 16: 4 for 3 hours to obtain a silica sol solution. The obtained sol was poured into a mold and gelled. It gelled and released from the mold, and cracks occurred during drying at 70 ° C. with a dryer. Moreover, handling was bad and it shattered when transferred to a baking furnace.

Claims (1)

After mixing silica sol and silica powder having a particle diameter of 1 to 10 μm in a ratio of 1: 2 to 2.3 parts by weight, pouring into a mold and gelling to prepare a silica molded body, and drying this silica molded body A primary firing is performed at 1000 to 1400 ° C. in an air atmosphere to form a porous silica material, and this porous silica material is fired in a vacuum pressure and firing furnace under reduced pressure in an inert gas atmosphere to form a transparent silica glass. A method for producing silica glass.