Gypsum Materials

Abstract

The present invention relates to hydrophobic gypsum and to a process for making gypsum hydrophobic, in particular it relates to a powdered hydrophobing additive, a hydrophobic gypsum composition and method for preparing same using granules containing organosilicon compounds as hydrophobing additives. The invention provides a granulated additive for rendering gypsum material hydrophobic, comprising a particulate carrier on which is deposited an organosilicon component, a binder polymer and an emulsifier for the organosilicon component. Such a granulated hydrophobic additive is able to provide a high initial hydrophobicity to gypsum materials to which it is applied and that the obtained hydrophobicity can last during a long period of time.

1 . A granulated additive for rendering gypsum material hydrophobic, comprising a particulate carrier on which is deposited an organosilicon component, a binder polymer and an emulsifier for the organosilicon component. 
     
     
         2 . The granulated hydrophobing additive according to  claim 1 , characterised in that the organosilicon component is free of organopolysiloxane having Si bonded hydrogen. 
     
     
         3 . The granulated hydrophobing additive according to  claim 1 , characterised in that the particulate carrier is of a nature different from silica. 
     
     
         4 . The granulated hydrophobing additive according to  claim 1 , characterised in that the carrier particle is selected from the group of silicates, calcium carbonates, calcium magnesium carbonate, methyl cellulose, carboxy methyl cellulose, polystyrene beads, sulphates, magnesium oxide, diatomite or calcinated diatomite, calcinated rice and starch residues, and stearates. 
     
     
         5 . The granulated hydrophobing additive according to  claim 1 , characterised in that the emulsifier and the binder are polyvinyl alcohol. 
     
     
         6 . The granulated hydrophobing additive according to  claim 1 , characterised in that the weight ratio of binder versus organosilicon component is comprised between 10:100 and 50:100. 
     
     
         7 . The granulated hydrophobing additive according to  claim 1 , characterised in that the organosilicon component comprises alkoxysilyl groups and alkylsilyl groups. 
     
     
         8 . The granulated hydrophobing additive according to  claim 1 , characterised in that the organosilicon component comprises a silane, an organosiloxane, a condensation product of a silane compound, or a mixture thereof. 
     
     
         9 . The granulated hydrophobing additive according to  claim 1 , characterised in that the organosilicon component comprises a compound of the formula Si (OZ′) 4 , ZSi(OZ′) 3  or Z 2 Si(OZ′) 2  in which Z represents an alkyl, substituted alkyl, aryl or substituted aryl group having 1 to 20 carbon atoms, and each Z′ represents an alkyl group having 1 to 6 carbon atoms and/or a condensation compound obtained by the hydrolysis-condensation of any combination of compounds of the formula Si(OY′) 4 , YSi(OY′) 3  or Y 2 Si(OY′) 2  in which Y represents an alkyl, substituted alkyl, aryl or substituted aryl group having 1 to 20 carbon atoms and each Y′ represents an alkyl group having 1 to 6 carbon atoms. 
     
     
         10 . The granulated hydrophobing additive according to  claim 1 , characterised in that the organosilicon component comprises alkoxysilyl groups having 1 or 2 carbon atoms. 
     
     
         11 . The granulated hydrophobing additive according to  claim 1 , characterised in that the carrier has a mean particle size of 0.1 to 50 micrometers. 
     
     
         12 . A process for preparing a granulated hydrophobing additive for gypsum material, the granulated hydrophobing additive comprising a particulate carrier, an organosilicon component and a binder polymer, the process comprising depositing the organosilicon component on the particulate carrier from an aqueous emulsion. 
     
     
         13 . A granulated hydrophobing additive for gypsum material prepared by the process of  claim 12 . 
     
     
         14 . A gypsum material in powder form, comprising dry gypsum and a granulated hydrophobing additive as defined in  claim 1  in an amount sufficient to give from 0.01 to 2% by weight of the organosilicon component based on the weight of the dry gypsum. 
     
     
         15 . A process for imparting to gypsum material a hydrophobic character, the process comprising mixing into the gypsum material a granulated hydrophobing additive as defined in  claim 1 .