| 摘要 |
<p>Gypsum mouldings are made using an aq. suspension of anhydrite and/or CaSO4.1/2H2O, where the suspension is poured into moulds and the mouldings are extracted and dried. The dynamic viscosity of the suspension is 10,000-40,000 poise, esp. 15,000-30,000 poise, when it is poured into the moulds. The pref. suspension contains 450-4500 g, esp. 1000-3000 g anhydrite and/or CaSO4.1/2H2O per litre of water, and the pref. plant consists of a tiltable vessel provided with vigorous stirrers for the suspension and the rotary blade of a rotating viscometer, using a relay to tilt the vessel when the desired viscosity is attained. The suspension then enters a row of moulds on a casting machine. The rotary blade and shaft on the viscometer are pref. made of Cr-Ni steel, a four-blade rotor being used and located near the surface of the suspension. If the suspension is prematurely poured into the moulds, long setting times are needed and the output of the casting machine is reduced; but if bonding proceeds too far in the stirring vessel, numerous depressions are found in the surface of the mouldings which are therefore scrap. The invention provides max. output of high quality mouldings.</p> |
