GB402588A - Process for the production of mullite - Google Patents

Abstract

In the manufacture of refractory materials containing a high proportion of mullite from silica or aluminium silicates and added alumina, accelerators are used comprising aluminates, alumino silicates such as the natural or artificial zeolites, and ultramarines such as lapis lazuli are used. The composition is finely ground, moulded and fired at Seger cones 14 to 30 for 2 to 30 hours. In addition, known mineralizers such as fluorine compounds, sulphates, phosphates, cerium and zirconium compounds or already burnt grog may be used. Part of the material may be prefired before the final firing. In the firing it is preferred to slow down the temperature rise between 740 and 860 DEG C. In examples are (1) sillimanite, fused alumina, sodium aluminate, calcium zeolite; (2) fired kyanite, electro-corundum, calcium aluminate, ultramarine blue; (3) anhydrous alumina, quartz sand, sodium permutite, potassium aluminate; (4) fired andalusite, anhydrous alumina, potassium-sodium-aluminate, barium zeolite; (5) fired Rakonitz argillite, alumina hydrate, ultramarine green, barium aluminate; (6) Zinzendorf clay, alumina hydrate, potassium aluminate, natrolite; (7) fired mixture of Example 1, Zinzendorf clay, alumina hydrate, ultramarine green, barium zeolite, sodium aluminate; (8) Zinzendorf clay, anhydrous alumina, ultramarine violet, barium aluminate, mullite grog. Details of fineness, and firing time and temperature are given for each example.