Process for producing resin-coated sand particles for use in shell moles

Claim 1

A process of producing resin-coated sand particles for use in shell molds comprising the steps of: a. forming a liquid containing phenol-formaldehyde resin in an initial state of the condensation thereof; b. spraying said liquid prior to complete condensation into a hot zone and maintaining in said hot zone an atmosphere at a temperature higher than the melting point of the initial-condensation product of the resin to form droplets of the liquid; c. causing the droplets sprayed into said hot zone gravitationally to descend into a cold zone below said hot zone; d. maintaining in said cold zone an atmosphere at a temperature lower than the melting point at said initial condensation product to solidify said droplets into generally spherical particles; e. collecting the generally spherical particles solidified in said cold zone; and f. mixing said resin particles with sand particles heated to a temperature higher than the melting point of said resin so as to coat the surface of each sand particle with said resin, said liquid being formed by condensing a phenol component selected from the group which consists of metal-alkyl phenols, metal-alkoxy phenols, meta-halogenated phenols, phenol and resorcinol with an aldehyde component selected from the group which consists of formaldehyde, formalin, peraformaldehyde and furfural in the presence of acidic or alkaline catalyst.