METHOD FOR PREPARATION OF SYNTHETIC VITREOUS SILICA AND APPARATUS FOR HEAT TREATMENT

Title:

METHOD FOR PREPARATION OF SYNTHETIC VITREOUS SILICA AND APPARATUS FOR HEAT TREATMENT

Document Type and Number:

WIPO Patent Application WO/2001/012566

Kind Code:

A1

Abstract:

A method for preparation of a synthetic vitreous silica which comprises a first step comprising ejecting a silicon compound together with a combustion gas containing oxygen and hydrogen from a burner, to hydrolyze the silicon compound in an oxyhydrogen flame and form vitreous silica particles, and depositing the silica particles onto a target being opposed to the burner, to thereby produce a transparent synthetic vitreous silica ingot, a second step of heating the silica ingot to a first holding temperature of 900 °C or higher and holding it at the temperature, and then cooling it to a temperature of 500 °C or less by a temperature-decreasing rate of 10 °C/hr or less, and a third step of heating the resultant glass ingot to a second holding temperature of from 500 °C to 1100 °C and holding it at the temperature, and then cooling it to a temperature 100 °C lower than the second holding temperature by a temperature-decreasing rate of 50 °C/hr or greater.

Inventors:

YAJIMA SHOUJI (JP)
HIRAIWA HIROYUKI (JP)
ISHIDA YASUJI (JP)

Application Number:

PCT/JP2000/005412

Publication Date:

February 22, 2001

Filing Date:

August 11, 2000

Export Citation:

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Assignee:

NIPPON KOGAKU KK (JP)
YAJIMA SHOUJI (JP)
HIRAIWA HIROYUKI (JP)
ISHIDA YASUJI (JP)

International Classes:

C03B8/04; C03B19/14; C03B25/02; C03B32/00; C03C3/06; C03C23/00; (IPC1-7): C03B20/00; C03B8/04

Foreign References:

US5707908A	1998-01-13
JPS62235223A	1987-10-15
JPH06166527A	1994-06-14
JPH07247132A	1995-09-26
JPH11209134A	1999-08-03
JPH10279322A	1998-10-20
JPH08104532A	1996-04-23
US5707908A	1998-01-13

Other References: