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Abstract

A method for preparing an aqueous gypsum mixture having hydrophobic additive substantially uniformly dispersed therein, which method comprises admixing in water gypsum, a silane of the general formula (RO).sub.3 SiR' or the general formula (RO).sub.2 SiRR' and non-emulsified polysiloxane of the general formula; ##STR1## wherein each R is the same or different and represents a hydrocarbon group having from one to eight carbon atoms, R' represents a lower alkyl group which is optionally substituted by an amino, amino-loweralkylene-amino or dialkylenetriamine group, and a has an average value of between 20 and 200. The silane is preferably N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and the polysiloxane preferably trimethyl end-blocked linear methylhydrogen polysiloxane. The method may further include adding surfactant. Also disclosed is a gypsum product which includes gypsum mixture prepared according to the above method.

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First Claim