Use of setting retarders in plaster, gypsum or anhydrite compositions and process for the preparation of these compositions

摘要

1. Claims for the Contracting States : BE, CH, DE, GB, IT, NL Use in compositions with gypsum or anhydrous plaster base of setting retardants, made up with polymers or water-soluble acrylic copolymers of molecular weight lower than 1000 and having the general formula : see diagramm : EP0011581,P12,F1 in which x and y show the molecular structures of monomers and obtained by polymerisation of : (x) 0 to 40 moles per cent of one or several monomers of the formula : see diagramm : EP0011581,P12,F2 in which : R1 is a hydrogen atom or a methyl radical -CH3 - R2 is : - an acidic group see diagramm : EP0011581,P12,F3 - an ester group see diagramm : EP0011581,P12,F4 in which R4 is a lower alkyl radical containing 1 to 4 carbon atoms - or an amide group see diagramm : EP0011581,P12,F5 - or a nitrile group -C=N (y) 60 to 100 moles per cent of a monomer of the formula : see diagramm : EP0011581,P12,F6 in which R3 is a hydrogen atom or a methyl radical -CH3 , X is an atom of sodium, potassium, lithium, calcium, magnesium or an ammonium group -NH4 . 1. Claims for the Contracting State : AT Process of preparation and production of compositions of gypsum or anhydrous plaster, or plaster based mixtures, characterised in that it consists of pre-mixing dry plaster, when its appearance is of powder form, or adding to the water for the plaster mixture, a setting retardant made up with polymers or water-soluble acrylic copolymers of molecular weight lower than 1000 and having the general formula : see diagramm : EP0011581,P13,F1 in which x and y show the molecular structures of monomers and obtained by polymerisation of : (x) 0 to 40 moles per cent of one or several monomers of the formula : see diagramm : EP0011581,P13,F2 in which : R1 is a hydrogen atom or a methyl radical -CH3 - R2 is : - an acidic group see diagramm : EP0011581,P13,F3 or - an ester group see diagramm : EP0011581,P13,F4 in which R4 is a lower alkyl radical containing 1 to 4 carbon atoms - or an amide group see diagramm : EP0011581,P13,F5 - or a nitrile group -C=N (y) 60 to 100 moles per cent of a monomer of the formula : see diagramm : EP0011581,P13,F6 in which R3 is a hydrogen atom or a methyl radical -CH3 , X is an atom of sodium, potassium, lithium, calcium, magnesium or an ammonium group -NH4 .