Process for producing water-impermeable and porous ceramic shaped bodies

摘要

The invention relates to a process for producing water-impermeable and porous, ceramic shaped bodies of clays containing blue conite, illite or bentonite and also blue clays, in which shaped and dried green bodies are fired using exothermic processes and until expansion (swelling, bloating) by liberated gases occurs. It has surprisingly been found that in oxidising firing the swelling process proceeds substantially more quickly and gives products with lower bulk densities if, during firing, the shaped and dried green bodies are subjected to a hold time at from 900 to 100@C and after the hold time the temperature is increased to from 1150 to 1180@C under an oxygen-free atmosphere and is maintained for from 5 to 15 minutes. This hold time, which is dependent on the dimensions of the shaped bodies, should be from one to three hours.