Binder for foundry mould and core matl. - comprising aq alkali silicate and org. colloidal soln e.g. of starch or cellulose ether

摘要

Binder for foundry mould and core material comprises (A) an aq. soln. of alkali metal silicate and (B) an org. colloidal soln. pref. of 10-40 wt.% starch; 0.1-10 wt.% cellulose ethers of 1-10 wt.% polyvinyl alcohol or their mixts. Pref. an H- ion source, e.g. 0.5-8 wt.% p-toluenesulphonic acid, is included and mixt. is prepared by heating components to 60-100 degrees C. When used with sand mixt. which are self hardening or which contain e.g. cement or Fe-Si, the binder improves the ease with which the mixt. can be broken away after casting and increases the hardening speed (about twice that for mixts. contg. only Na silicate). The mixts. prepd. using this binder do not stick to the model or hands. When used with CO2-hardened mixts. a much stronger prod. is obtd., but it can be broken away as easily as those prepared using oil binders.