Composition comprising expandable thermoplastic material and powdered iron and method for molding same

Claim 1

METHOD FOR EXPANDING INTO A UNIFORM MOLDED FOAM STRUCTURE AN EXPANDABLE GRANULAR THERMOPLASTIC RESINOUS MATERIAL CONTAINING A BLOWING AGENT INCORPORATED IN ITS DISCRETE PARTICLES WHICH COMPRISES DISTRIBUTING A METALLIC MAGNETIC MATERIAL TO BE INCORPORATED WITH THE GRANULES IN APPROXIMATE UNIFORMITY IN AND PHYSICALLY FIXED WITH SAID GRANULES IN THE MASS OF EXPANDABLE THERMOPLASTIC RESINOUS MATERIAL, SAID MAGNETIC MATERIAL BEING IN A FINELY DIVIDED SOLID FORM HAVING AN AVERAGE PARTICLE SIZE SUBSTANTIALLY SMALLER THAN THE PARTICLAR SIZE OF SAID GRANULAR RRESINOUS MATERIAL; PLACING THE MAGNETIC MATERIAL-CONTAINING MASS OF EXPANDABLE THERMOPLASTIC RESINOUS MATERIAL WITHIN THE CONFINING SPACE OF A MOLD FORM; ATTRACTING THE MAGNETIC MAATERIAL-CONTAINING MASS OF EXPANDABLE THERMOPLASTIC RESINOUS MATERIAL BY MEANS OF AT LEAST ONE MAGNETIC FIELD WHICH IS POSITIONED AND DIRECTED IN A MANNER TENDING TO PHYSICALLY POSITION AND DISTRIBUTE THE MASS UNFORMLY WITHIN THE CONFINING SPACE OF THE MOLD FORM; AND SUBJECTING TTE MAGNETICALLY ATTRACTED EXPANDABLE MASS WHILE IT IS UNDER THE INFLUENCE OF THE MAGNETIC FIELD TO AN ADEQUATE QUANTITY OF HEAT TO SOFTEN THE MASS OF THERMOPLASTIC RESINOUS MATERIAL AND CAUSE EXPANSION OF THE BLOWING AGENT IN THE DISCRETE PARTICLES IN THE MASS TO EXPAND THE MASS TO AN INTEGRAL, SUBSTANTIALLY UNFIROM, MOLDED FOAM STRUCTURE.