| 摘要 |
PURPOSE:The drying speed and drying temperature of high silica gel, the hydrolyzate of a metal alkoxide, and the gas input and output are organically linked to control the gel drying speed, thus producing gels, the precursor of optical glass, stably in large quantities. CONSTITUTION:A plurality of vessels 2 contining a metal alkoxide such as Si(OCH3)4, methanol and water in a specific proportion are placed in the chamber 4 and the vessels 2 are heated at, e.g., 50 deg.C to cause the gelation of the mixture. Then, a drying gas such as N2 is introduced from the inlet 1' into the dryer 3 and flown out of the outlet 1'' to condense the alcohol and steam with the water-cooled condenser. At this time, the drying temperature and gas input are controlling so that the rate of weight reduction by gel drying becomes a prescribed one and the control can be made by feeding back the difference in the level between the liquid 20 collecting in the receiver 16 and the moving plate 17 for comparison to the temperature and the gas inlet so as to make the levels equal. Resultingly, gels free from cracks are made readily. |
