US 11,667,557 B2
Apparatus and method for producing porous glass preform
Naoto Noda, Ibaraki (JP)
Assigned to Shin-Etsu Chemical Co., Ltd., Tokyo (JP)
Filed by Shin-Etsu Chemical Co., Ltd., Tokyo (JP)
Filed on Dec. 13, 2021, as Appl. No. 17/644,083.
Claims priority of application No. JP2020-207133 (JP), filed on Dec. 14, 2020.
Prior Publication US 2022/0185719 A1, Jun. 16, 2022
Int. Cl. C03B 37/014 (2006.01)
CPC C03B 37/0142 (2013.01) [C03B 2207/22 (2013.01); C03B 2207/36 (2013.01); C03B 2207/81 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A method for producing a glass preform, comprising:
reducing a moisture concentration in a carrier gas with a dryer;
providing the carrier gas from a mass flow controller through two parallel carrier gas supplying pipelines, wherein each of the two parallel carrier gas supplying pipelines have a moisture-reducing apparatus;
further reducing the moisture concentration in the carrier gas with the moisture-reducing apparatus in a selected one of the two parallel carrier gas supplying pipelines to 3 volppm or less;
measuring a dew-point with a dew-point hygrometer on a downstream side of the two parallel carrier gas supplying pipelines;
actuating at least one valve to switch use between one or the other of the two parallel carrier gas supplying pipelines based on an output of the dew-point hygrometer;
mixing organosiloxane in a liquid state being a raw material with the carrier gas having reduced moisture concentration in a vaporizer;
heating this mixture to be vaporized;
supplying this vapor to a burner as a gas raw material;
depositing a glass fine particle produced by combusting the gas raw material on a starting material and thereby producing a porous glass preform;
and sintering the porous glass preform.