| 摘要 |
Water-repellent treatment of gypsum building units is achieved by processing hard wax or hard-wax-containing combinations with solid hydrocarbons with acid numbers >10 together with a metal salt characterised by better dissociation in respect of calcium sulphate and/or hydroxide and a sulphite lye or a modified sulphite lye with gypsum binder and water or di-hydrate and water within a mixing device so as to produce a mixed paste, whereupon the mixed paste is moulded and, if gypsum binder is used, dried, after hardening, at temperatures above the melting point of the wax used approximately to mass constancy, whereas if dihydrate is used the moulded strand of material is dehydrated in a saturated steam atmosphere at >130 DEG C so as to form hemihydrate and is then hardened, in which case thermal treatment after hardening is unnecessary. |
