Recycling of waste expanded polystyrene foams to give products which may be re-expanded

摘要

The invention relates to a method for the production of re-expandable polystyrene by material recycling of waste expanded polystyrenes. The expanded polystyrene waste is dissolved in a solvent, selected from di-(lower alkylene)glycol di-(lower alkyl) ethers, where lower alkyl = straight- or branched-chain C1 - C12 alkyl, mono- or di-carboxylate di-(lower alkyl) esters with a straight- or branched- carboxylate chain length of C1 - C12, where lower alkyl has the meaning given for the glycol ether, THF, ketones, mixtures of the above solvents and mixtures of said solvents with ethylene carbonate, propylene carbonate, cyclohexane and/or rapeseed oil methyl ester. The polystyrene solution is precipitated using a precipitating agent which has a polarity lower than the employed solvent and the precipitated polystyrene is optionally partly dried, such that the blowing agent incorporated in the polystyrene is not removed. Finally the precipitated polystyrene can be re-expanded by means of a heat-carrier.