PRODUCTION OF POROUS GLASS PREFORM

摘要

PROBLEM TO BE SOLVED: To prevent the occurrence of and deposition of rust on the inside walls of piping of a cooling system and to prevent the degradation in heat exchange efficiency by passing cooling water containing a rust preventive into a cooling medium flow passage provided in a reaction vessel where glass particulates are deposited on a starting base material. SOLUTION: The glass particulates formed by vapor phase hydrolysis of gaseous glass raw material in an oxyhydrogen flame are deposited on a base material glass rod 2 to form a soot body 5 in the reactor 1 having the cooling medium flow passage. A cooling pipe 11 made of stainless steel is installed along the vessel wall 12 of the reactor vessel 1 in parallel with the axis of the base material glass rod 2. Thermally insulating materials 16 are mounted at the vessel wall 12 and the outside wall 15 is provided so as to enclose both. The water containing the rust preventive is passed as a cooling medium into the cooling pipe 11 to cool the reaction vessel 1. The rust preventive containing polycarboxylic acid nitrate or the rust preventive containing polycarboxylic acid nitrite and inorg. nitrogen compd. are used as the rust preventive. The amounts of these rust preventives to the cooling water are preferably specified to about 1 to 10 ppm.