Method for preparing and molding expandable, non-equimolar styrene-maleic acid half ester copolymer particles

Claim 2

The process of claim 1 wherein said hydrocarbon blowing agent is used in amounts between 3 and 15 percent by weight based on the copolymer particles.

Claim 3

A process for making foamed structures comprising: a. forming an aqueous suspension of particles of a non-equimolar copolymer of styrene and a minor amount of maleic anhydride, said suspension being stabilized by a suitable suspending agent system; b. adding to the suspension a mixture of an aliphatic or cycloaliphatic hydrocarbon blowing agent containing from one to seven carbon atoms in the molecule and an alcohol having the general formula ROH, wherein R may be alkyl having one to five carbon atoms, halogenated alkyl having one to five carbon atoms, phenyl, alkyl-substituted phenyl, halogenated phenyl, and mixtures thereof; said alcohol being present in an amount equal to or slightly greater than the stoichiometric amount required to react with the anhydride groups of the copolymers to form a half-ester; c. maintaining said hydrocarbon and said alcohol in contact with the suspension at a temperature of between 80* and 150* C. until the hydrocarbon and the alcohol are integrated within said copolymer particles; d. separating said particles from said aqueous suspension; e. partially expanding said particles in the presence of heat; f. subjecting said partially expanded particles to temperatures between 275* and 290* F. in a closed mold, whereby dimensionally staBle, well-fused foamed structures of styrene-maleic half-ester copolymer are produced.