GB1005477A - Foamable compositions - Google Patents

Abstract

A foamable composition comprises an unswollen polymer, a finely divided absorbant, the absorbent having absorbed thereon a volatile liquid which is non-reactive with and has not more than a slight solvent action on the polymer, and a nucleating agent. The polymer is preferably in a pelletized form and may be cellulose ethers and esters, homopolymers and copolymers of monomeric compounds containing the CH2=C< grouping such as styrene, ethylene and propylene, vinyl halides, vinyl esters, vinyl ethers, unsaturated carboxylic acids and their derivatives, and interpolymers of the above mentioned vinyl monomers with a ,b -unsaturated polycarboxylic acids and their derivatives. The polymer may also be a rubber, e.g. natural rubber, butadiene (5%)-styrene copolymers, isobutylene-isoprene copolymers; a thermosetting resin, e.g. polyurethanes, phenol-formaldehyde resins, melamine-formaldehyde resin, bisphenol A-epichlorhydrin resin and other epoxy resins. Suitable absorbents are diatomaceous earth, fuller's earth, silica gel, activated alumina, molecular sieves, attapulgus clay and activated carbon. The preferred volatile liquids are aliphatic hydrocarbons boiling between 10 DEG and 100 DEG C. and the nucleating agents are preferably a mixture of two materials which react to form carbon dioxide and water, e.g. a mixture of annomium, alkali metal or alkaline earth carbonates or bicarbonates with an inorganic or organic acid or acid salt which is preferably solid. Wetting agents may also be incorporated in the composition. The polymer and absorbent are preferably dry mixed with the nucleating agent and the mixture fed to the hopper of an extruder. On extrusion, a sheet having a tough skin may be formed by rapidly chilling. The surfaces of the sheet with air blasts or other fluid coolants such as water, a mixture of air and water, nitrogen and argon. The resultant foams are useful in the manufacture of cups, food trays, buckets, plates and face-masks. Specification 998,180 is referred to.