Patent ID: 6197235
Filing Date: 2001-03-06
Classification: B28B,Y10T

Abstract:
A method for making textured gypsum fiberboard comprising the steps of:mixing ground gypsum and host particles of a fibrous reinforcement material and sufficient liquid to make a dilute slurry consisting of at least about 70% liquid by weight;calcining said gypsum, in the presence of said host particles, by heating said dilute slurry under pressure, to form acicular calcium sulfate alpha hemihydrate crystals;separating a major portion of said liquid from said calcined gypsum and host particles to form a filter cake;reducing the temperature of the filter cake to the rehydration temperature of said calcined gypsum to begin setting;firstly pressing said filter cake to form aboard and to remove additional water therefrom;providing a flexible die having texture at one side thereof, and secondly pressing said texture of said flexible die against said board while said board is setting and pliable;allowing said board to continue setting while under the pressure of said flexible die;separating said board from said flexible die when the temperature of said board is no greater than about 60% of the temperature rise between the rehydration temperature and the highest temperature reached during rehydration; anddrying said board to remove any remaining free water.