Patent GB-840663-A (GB)
Title: Improvements in the production of expanded thermoplastic resins
IPC: C08J9/236
Filed: 1957-02-07
Abstract: Lightweight materials in which individual particles of porous thermoplastic resin are surrounded by or enclosed in a solid binding agent are made by mixing particles of a thermoplastic synthetic resin with a blowing agent and with a binding agent which is solid at room temperature, softens at a temperature below the softening range of the thermoplastic resin and which does not dissolve the thermoplastic resin when heated, and thereafter expanding the mixture by heating it to a temperature above the softening range of the thermoplastic resin.  Specified thermoplastic resins are polymethyl methacrylate, polyvinyl chloride, polystyrene and copolymers of styrene with acrylonitrile, vinyl carbazole or small amounts of a divinyl compound (e.g. divinyl benzene).  Specified binding agents are bitumen, glue, paraffin wax, waxes, colophony, shellac and cyclohexanone/formaldehyde resins.  Softeners, fillers, dyestuffs, solvents or diluents may be added to the expandable mixture.  The blowing agent may be a readily volatile liquid, a gas under pressure, a dissolved gas or a compound splitting off a gas.  The lightweight materials may be consolidated together to form shapes, which either as such or as a substrate on other materials may be used for heat, cold or sound insulation, floats, wall or pipe coverings, making boats unsinkable or damping oscillations (see Groups III and X).  In examples the following mixtures are expanded by heating: (1) polystyrene, bitumen and hexane (as blowing agent); (2) polymethyl methacrylate, paraffin wax, a cyclohexanone/formaldehyde resin and petroleum ether (as blowing agent); (3) polystyrene, bitumen and petroleum ether (as blowing agent), the heated mixture being introduced into a spray gun and sprayed on to a flat surface; (4) polystyrene, hide glue, hexamethylene tetramine and petroleum ether (as blowing agent).ALSO:A lightweight material is made by applying to a surface (e.g wood, cardboard or metal) a heated mixture of particles of a thermoplastic synthetic resin, a blowing agent and a binding agent which does not dissolve the synthetic resin, whereby the surface is coated with individual particles of the thermoplastic resin in porous form enclosed in the binding agents.  The binding agent may be bitumen, paraffin wax, waxed, colophony, shellac or cyclohexanone-formaldehyde resins, and the thermoplastic resin may be polymethyl methacrylate, polyvinyl chloride, polystyrene or co-polymers of styrene with acrylonitrile, vinyl carbazole or a divinyl compound.  In Example 3, a surface (e.g. a wall or pipe) is given a coherent porous coating by heating a mixture of polystyrene grains, petroleum ether (as blowing agent) and bitumen, and spraying the mixture on the surface with a heated spray-gun using compressed air heated to 100 DEG  C.  Shaped articles obtained by moulding individual particles of the porous thermoplastic resin surrounded by the binding agent may be coated with a flame-preventing coating or a lacquer.ALSO:Lightweight materials in which individual particles of porous thermoplastic resin are surrounded by or enclosed in a solid binding agent are made by mixing particles of a thermoplastic synthetic resin with a blowing agent and with a binding agent which is solid at room temperature, softens at a temperature below the softening range of the thermoplastic resin and which does not dissolve the thermoplastic resin when heated, and thereafter expanding the mixture by heating it to a temperature above the softening range of the thermoplastic resin.  Specified thermoplastic resins are polymethyl methacrylate, polyvinyl chloride, polystyrene and copolymers of styrene with acrylonitrile, vinyl carbazole or small amounts of a divinyl compound (e.g. divinyl benzene). Specified binding agents are glue, bitumen, paraffin wax, waxes, colophony, shellac and cyclohexanone/formaldehyde resins.  Softeners, fillers, dyestuffs, solvents or diluents may be added to the expandable mixture.  The blowing agent may be a readily volatile liquid, a gas under pressure, a dissolved gas or a compound splitting off a gas.  The lightweight materials may be consolidated together to form shapes. In examples the following mixtures are expanded by heating (1) polystyrene, bitumen and hexane (as blowing agent), (2) polymethyl methacrylate, paraffin wax, a cyclohexanone/formaldehyde resin and petroleum ether (as blowing agent), (3) polystyrene, bitumen and petroleum ether (as blowing agent), the heated mixture being introduced into a spray gun and sprayed on to a flat surface, (4) polystyrene, hide glue, hexamethylene tetramine and petroleum ether (as blowing agent).