GB550703A - Improvements in the degreasing of metal articles - Google Patents

Abstract

550,703. Degreasing non-porous articles. BOOTH, W. E., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. July 18, 1941, No. 9094. [Class 91] In the removal of solvent from a metal or like non-porous article degreased in a bath of a liquid chlorinated aliphatic hydrocarbon solvent capable of forming an azeotrope with water of boiling point lower than that of water, the article is withdrawn from the bath of solvent through a supernatant layer of water of substantial depth at a temperature of below its boiling point but above that of the azeotrope, a zone of vapour consisting of the vapours of water and solvent in azeotropic proportions being maintained above the water layer. Of suitable solvents comprising chloroform, ethylene dichloride, dichloroethylene, and trichloroethylene, the last is preferred, its azeotrope with water boiling at 73‹C. In the usual type of apparatus in which the vapour zone in the upper part of the open topped degreasing vessel 1 is limited by condensing coils 2, the space between the latter and the upper surface 21 of the water layer is connected by a wide duct 4 with a distillation vessel 3. The latter is supplied in azeotropic proportions with water from the aqueous layer overflowing a sloping wall 20 and with solvent from the lower liquid layer through a valved pipe 18, the respective layers in the degreasing vessel being continuously supplemented by the return of water and solvent through pipes 16 and 17 respectively from a separator 14 which collects the mixed condensate from a trough 11 arranged below the condensing coils. The temperatures of the layers of liquid are controlled by a heating coil 10 and a cooling coil 9. The apparatus is particularly applicable for the degreasing and subsequent drying from solvent of metal wool, metal swarf, metal pressings, wire cloth, and wire gauze. Specification 525,995 is referred to.