US Patent 7875114 Foamed slurry and building panel made therefrom

A gypsum slurry is described that includes water, a hydraulic component comprising at least 50% calcined gypsum by weight based on the dry weight of the hydraulic component, foam, a defoamer, a polycarboxylate dispersant having olefinic unsaturated mono-carboxylic acid moieties and (poly)oxyalkylene moieties, a first portion of a retarder and a second portion of a retarder. In some embodiments of the invention, the defoamer is combined with the dispersant prior to being added to the gypsum slurry. The defoamer and dispersant can be added as a physical mixture, wherein the defoamer is attached onto the dispersant polymer, or a combination thereof. In some embodiments, a gypsum building panel is made from the gypsum slurry.