GB573171A - Improvements in or relating to the manufacture of a binding agent for core sand - Google Patents

Abstract

573,171. Mould and core materials. OEL- & CHEMIE-WERK AKT.-GES. May 18, 1944, No. 9621. Convention date, May 1, 1943. [Class 83 (i)] In making a binding-agent for core sand from sulphite lye, a substance having an acid reaction is added, preferably to the concentrated lye. The mixture may be heated under reduced or increased pressure to increase the viscosity and remove some of the free sulphur-di-oxide. Corrosion inhibitors, e.g. quaternary ammonium compounds, alkaloids, products of condensation of amines with aldehydes, basic petroleum and tar fractions, tannic, mercaptans, urea, thiourea and their derivatives, glue, starch, yeast, molasses, &c. may be added finally. The first addition may be an acid, acid salt, or a substance which produces acid on heating, e.g. organic sulphonic acids or esters, salts of polyvalent metals, or ammonium salts. The sulphur-di-oxide removal may be assisted by blowing air through the mixture, by stirring or by increasing the surface exposed. 100 parts of lye containing about 50 per cent of water may be mixed with 20 parts by weight of 50 per cent sulphuric acid solution and heated to 70‹ C. while blowing or stirring, until the viscosity increases considerably. After cooling, one part of hexamethylene tetramine is added. If solid pulverized lye is used, 100 parts may be mixed with 20 per cent of ammonium sulphate and the mixture used with moist sand or with various proportions of water and sand, with or without other binding agents. Cores should be made with 5 to 6 per cent of the binder and dried for about an hour at 220‹ C., but, unless this temperature is required to generate the required acid, a longer time at a lower temperature may be used.