Refractory shell mould - by alternately coating a support with sols of electrically charged colloids and hardeners

摘要

Successive coatings are rapidly applied to a support by immersion in baths containing (1) a sol. of positively or negatively charged inorganic colloidal particles or (2) a solution of an ionic alkali metal silicate followed by a bath of an oppositely charged hardener. For a positive coating the hardener is (a) negatively charged inorganic colloidal particles (b) ionic alkali metal silicate (c) monofunctional organic (6-24C alkyl) acid or salt (d) (in)organic base (e) (in)organic polyfunctional acid or salt or (f) a latex of an anionic surface active agent. For a negative or silicate coating the hardener is (g) positively charged inorganic colloidal particles (h) organic cationic non-polymeric nitrogen cpds. (i) a latex of organic polymer stabilised with cationic surface active agent (j) a basic Al salt Alx(OH)yAz (where x is 1-8, y is 1-20, z is 1-4 and A is acid anion) or (k) a polycationic organic substance. The moulds are free from microfractures and more accurate and are used for lost wax metal moulding processes.