Method of manufacturing fire retardant polystyrene insulating board

Abstract

Fire retardant polystyrene insulating material is manufactured from expandable polystyrene beads in admixture with a phenol-formaldehyde or melamine-for-maldehyde resin in resole form, the resin containing a blowing agent and a surfactant. The insulating material is formed from the bead-resin mix by applying dielectric heating to foam the resin, expand the beads, and cure the foamed resin to a closed cell structure.

I claim: 
     
       1. The method of manufacturing fire retarding insulation material from expandable polystyrene beads containing a heat-activatable expanding agent, .Iadd.said beads being capable of a volumetric expansion of at least 10%.Iaddend., comprising: (a) preparing a moldable mixture of said beads with a heat-foamable thermosetting resin composition, the resin component of said composition being selected from the class consisting of phenol-formaldehyde and melamine-formaldehyde resins, said resin being in resole form and containing a blowing agent and a surfactant, from 5 to 75 parts by volume of said resin being present per 100 parts of said polystyrene beads in said mix; and   (b) applying dielectric heating to portions of said moldable mixture in enclosed molds to obtain integrated molded bodies composed of resin-encapsulated polystyrene beads, said dielectric heating being effective for rapidly foaming said resin, expanding said beads, and curing the foamed resin to a predominately closed cell structure.   
     
     
       2. The method of claim 1 in which said resin is a phenol-formaldehyde resin, and is employed in an amount of from 10 to 50 parts by volume per 100 parts of said polystyrene beads. 
     
     
       3. The method of claim 1 in which said resin is a melamine-formaldehyde resin, and is employed in an amount of from 10 to 50 parts by volume per 100 parts of said polystyrene beads. 
     
     
       4. The method of claim 1 in which said dielectric heating is at a temperature of about 100° to 150° F. and is completed in 10 to 50 seconds. .Iadd. 
     
     
       5.  The method of claim 1 in which said expanding agent is pentane. .Iaddend.