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Abstract

A glass manufacturing process using a granular, free-flowing form of alkaline earth metal carbonate, e.g., barium or strontium carbonate, is disclosed. The alkaline earth metal carbonate has a relatively high bulk density and is made without sintering, grinding, or briquetting. The carbonate is prepared from a fine particle size material by the following steps: (a) forming a suspension of the carbonate in water with enough deflocculating agent, e.g., sodium polyacrylate or sodium hexametaphosphate, to substantially completely deflocculate the carbonate; (b) drying the resulting suspension, at a temperature that is elevated, but without heating the carbonate to its sintering point, for example, by spray drying in a spray drier operating at an inlet temperature in the range of about 400.degree. to 600.degree. C., to obtain a granular material primarily passing 10 mesh and held on a 150 mesh screen (Tyler); and (c) heating the granular material to about 600.degree. to 700.degree. C., which causes it to shrink, thereby increasing its bulk density by at least about 5 percent, preferably at least 10 or 20 percent. The resultant alkaline earth metal carbonate is easier to dissolve in the glass melt than are prior art forms, and it is relatively dust-free and easy to handle. The process is especially useful for making television face plates.

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First Claim