GB1062011A - Process for the preparation of synthetic, thermoplastic, expandable substances and for obtaining from these substances porous shaped bodies - Google Patents

Abstract

Expandable particles of thermoplastic polymers include as an expanding agent a chlorofluoro derivative of a hydrocarbon, or a mixture of such derivatives, which is a solvent for the synthetic plastic. Suitable expanding agents, which preferably boil at less than 15 DEG C. at atmospheric pressure, are chlorofluoro-substituted derivatives of aliphatic hydrocarbons with up to 4 carbon atoms and may be used in quantities from 2 to 40% by weight with respect to the weight of synthetic plastic. The synthetic thermoplastic substance used can be polystyrene or a styrene copolymer, containing at least 50% of styrene units by weight, such as with a -methyl styrene, an acrylate, a methacrylate or butadiene. The expanding agent can be introduced into an aqueous suspension of the thermoplastic synthetic polymer particles to form the expandable particles. The aqueous suspension can be a suspension obtained by aqueous suspension polymerization or by grinding a mass of synthetic plastic into small particles and suspending these in water. The expanding agent may be introduced at a temperature from 5 DEG to 40 DEG C. higher than the softening temperature of the synthetic plastic, into the stirred suspension over a period of 30 minutes to 3 hours. The particles can be made into shaped porous bodies by first expanding the particles and then moulding the expanded particles with sintering.