GB1296649A - - Google Patents

Abstract

1296649 Moulding process; moulds ALPHACO Inc 19 April 1971 [25 March 1970] 21449/71 Heading B3F [Also in Division C3] A foundry moulding comprising a mixture of sand and an organic rosin binder is cured by a noxious organic reagent gas (e.g. triethylamine) by repeating the following steps twice, (1) evacuating a chamber containing the moulding to a pressure of 12-50 mm. Hg. (2) introducing the organic reagent gas to produce a pressure in the chamber of 50-100 mm. Hg., and (3) introducing air or CO 2 to the chamber to produce a pressure below atmospheric pressure (e.g. 730 mm. Hg.). Before opening the chamber it is once again evacuated to purge the gas from the mould and then filled with air to dilute the gas. These two further steps are preferably repeated. When the chamber is opened suction is applied thereto to scavenge the gas. When using triethylamine or trimethylamine the scavenged gas is subjected to neutralizing treatment e.g. by providing a phosphoric acid bath for absorption or by burning with acetylene. The apparatus used includes a chamber with three conduits connected to the atmosphere, a source of reagent gas and a vacuum pump, respectively, and each conduit having an electri cally operated flow valve. The valves are controlled by a stepping relay to automatically effect the process steps in accordance with the pressure in the chamber. Moulds.-The mixture of sand and gas curable organic resin binder may be used to form the facing for the mouldings, whereas their major portions can be formed of coarse sand bonded with sodium silicate which is set by CO 2 . In order to effect hardening the air in stage (3) above of the process is replaced by CO 2 . Alternatively the facing of the moulding can be CO 2 -silicate bonded sand while the back-up material is gas hardened resin-bonded sand.