Alkaline metasilicate prod. used in glass mfr. - made from caustic soda, water and sand, and used as replacement for expensive sodium carbonate

摘要

The prod. contains by wt. 53-55% Na2O, 24-35% SiO2, and 12-21% CO2; and the pref. prod. consists of a flowable, homogeneous mixt. contg. 50-70% of a metasilicate phase Na2SiO3, and 30-50% soda(Na2CO3). The prod. is pref. obtd. starting from a mixt. of 80-85% of NaOH lye (30%) with 8-13% silica or sand. The mixt. is held 20 mins. at 250 deg.C, then cooled to 100 deg.C in a pressure vessel and 4-8% CO2 at 30-40 bars added. After heating 10 mins. at 150 deg.C the prod. is cooled. Conventional glass batches require soda, which is expensive and not always available. The invention reduces the need for soda by making a metasilicate prod. from NaOH.