Abstract: Bringing polymerizates, particularly those comprising styrene polymerized with an equal amount or more acrylonitrile and containing free styrene and acrylonitrile monomers, into contact with carefully selected gases in the near-critical to supercritical state substantially inhibits depolymerization and decomposition while substantially improving residue extraction.

Abstract: The residual monomers, solvents and other impurities particularly in coarse or oversized fat imbibing, fat retaining copolymer beads can be substantially reduced by bringing the copolymer beads into contact with a gas in the supercritical state.

Abstract: Ammonium nitrate activated or catalyzed with certain chromium compounds provides an excellent, low cost blowing or expanding agent(s) for many foamable polymers, including polyethylene(s), polystyrene(s), etc.

Abstract: A method for foaming heat foamable thermoplastic resin preforms and the product produced thereby. Said preforms are foamed in a series of foaming stages, said series comprising at least one stress-relieving foaming stage and at least one additional foaming stage subsequent thereto and at a higher temperature. This method facilitates the production of foam sheets, slabs and planks of better quality than that provided by previously known single stage foaming methods. In an example, a crosslinked, expandable, polyethylene preform is foamed by such a method using two foaming stages.

Abstract: Method for treatment of a solid material submerged in a body of liquid wherein the material is sticky and/or has relatively low tensile strength. The material being treated is supported, while so submerged, by a dynamic boundary layer of a liquid material between the treated material and a stationary porous restraining surface, the layer being created by the forced diffusion of said liquid through the pores of said stationary surface. The method is illustrated by heating and thereby foaming a strip of heat foamable thermoplastic resin while it is held submerged in a denser heat transfer liquid by a dynamic layer of said heat transfer liquid, said layer of heat transfer liquid being created by the forced diffusion thereof through a porous plate in operative communication with a pressurized chamber containing a supply of said liquid.

Abstract: Continuous method and apparatus for treatment of a solid material submerged in a body of liquid wherein the material is sticky and/or has weak tensile strength. The material is supported, while it is so submerged, by a dynamic layer of the liquid lying between the material and a moving surface. The method is illustrated by heating and thereby foaming a strip of heat foamable thermoplastic resin while it is held submerged in a denser heat transfer liquid by a dynamic layer of that liquid generated by a moving belt above the foaming material. In an example, expandable high density polyethylene strip is foamed continuously while it is so held submerged in molten salt.