Gypsum building panel contg. fibrous material, pref. waste paper - is moulded to shaft from di:hydrate with removal of added water, then dried within controlled temp. range

摘要

Panels are made, esp. paperboard, chip board or building panels, where calcium sulphate dihydrate (CSDH) and water are mixed with 5-60 wt. % fibrous material w.r.t. the wt. of the end prod.). The mixt. is moulded with the removal of water, then dried at 95-140 degrees C. Moulding is pref. at room temp., and drying pref. results in 3-10% water content (w.r.t. the chemically unbonded water in the end prod.) The mixt. may also contain 0.5-20 wt.% binder, esp. urea-formaldehyde resin, or aluminium sulphate. The invention permits the use of impure waste dihydrate obtd. e.g. from the chemical industries and/or in phosphate mfr., and without the need to use heat.