Patent GB-866801-A (GB)
Title: Plastic material drinking cups
IPC: B65D1/26
Filed: 1957-12-13
Abstract: The invention comprises a rigid self-sustaining container suitable for holding hot aqueous liquids having walls formed from a cellular non-porous styrene polymer having a density of less than 10 lbs. per cubic foot and a closed cell structure of which the majority of the cells have a diameter less than 0,05 inch, the walls of the container being at least 0,03 inch thick.  The bottom of the container may be of the same material as the wall or may be of another material such as plastic, metal or paper.  The container can be formed from styrene polymer particles, or (for example using vacuum drape-forming technique) from a sheet of foamed styrene polymer.  The foamed sheets are obtained by extruding a styrene polymer in which there has been incorporated a foaming agent and an alkaline earth metal sulphate of particle size less than 5 microns to reduce the pore size.  Preferred foaming agents are aliphatic and cycloaliphatic hydrocarbons having boiling points between 10 DEG  and 80 DEG C.  In an example the foamed material is prepared by treating polystyrene beads having 6% by weight of pentane incorporated first with an aqueous solution of barium chloride and then with aqueous sodium sulphate. Sodium chloride is washed out and after drying, the beads (coated with barium sulphate) are extruded at 325 DEG F. and 400 lbs./sq. in. to give a product of cell size 0,014 inch.  There may also be used: interpolymers of styrene with 1,3-dienes; a , b -unsaturated carboxylic acids and their functional derivatives; divinyl benzene; a blend or graft polymer of polystyrene and a rubbery diene polymer; or a polymer of a -methylstyrene, o-, m-, or p-methyl or ethyl styrene, or 2,4-dimethylstyrene.  The containers can also be used for packaging ice cream and cottage cheese.ALSO:A rigid self-sustaining container suitable for holding hot aqueous liquids has walls formed from a cellular non-porous styrene polymer having a density of less than 10 lbs. per cubic foot and a closed cell structure of which the majority of the cells have a diameter of less than 0,05 inch, the walls of the container being at least 0,03 inches thick.  The bottom of the container may be of the same material as the wall or may be of another material such as plastic, metal or paper.  The container can be formed from styrene polymer particles, or (for example, using vacuum drape-forming technique) from a sheet of foamed styrene polymer.  The foamed sheets are obtained by extruding a styrene polymer in which there has been incorporated a foaming agent and an alkaline earth metal sulphate of particle size less than 5 microus to reduce the pore size.  Preferred foaming agents are aliphatic and cycloaliphatic having boiling points between 10 DEG  and 80 DEG C. In an example the foamed material is prepared by treating polystyrene beads having 6% by weight of pentane incorporated first with an aqueous solution of barium chloride and then with aqueous sodium sulphate.  Sodium chloride is washed out and after drying, the beads (coated with barium sulphate) are extruded at 325 DEG F. and 400 lbs./sq. in. to give a product of cell size 0,014 inch.  There may also be used: interpolymers of styrene with 1,3-drives; a , b -unsaturated carboxylic acids and their functional derivations; divinyl benzene; a blend or graft polymer of polystyrene and a rubbery diene polymer; or a polymer of a -methylstyrene, o-, m-, or p-methyl or ethylstyrene or 2, 4- dimethylstyrene.