RECOVERED AND RECONDITIONED SAND, MICROWAVE HARDENABLE MOLDING SAND MADE OF SAID SAND AND ITS PRODUCTION

摘要

PURPOSE:To produce molding sand of superior microwave curing performance inexpensively by dry washing recovered sand under application of impact and frictional effect by circulation of said sand in a rotary vessel then adding a thermosetting resin thereto and kneading these. CONSTITUTION:Recovered sand is charged from a hopper 6 into a rotary vessel 1, and under circulation by rotation of the vessel 1, it is scrubbed by the impact and frictional effect of a high speed revolving agitator 4. The impurities on the surfaces of the sand grains are moderately removed by this dry washing, and the sand contg. 0.5-6% clay components and 0.3-5% carbonaceous org. materials is reconditioned. The reconditioned sand is classified, and a thermosetting resin is added at 2-5% to 100pts.wt. reconditioned sand, then these are kneaded. In this way, a large amt. of the reusable reconditioned sand is obtained in a large amt. with low energy. From this reconditioned sand, the microwave curable molding sand having uniform and quick microwave curing performance and having sufficient shell strength without addition of dielectric materials such as carbon black is obtained.