Patent ID: 6093352
Filing Date: 2000-07-25
Classification: C08J,Y10S

Abstract:
Process for preparing a foam product comprising the steps of(A) forming a foamable mixture of (1) an alkenyl aromatic polymer and (2) a blowing agent comprising a major amount of carbon dioxide under a pressure sufficient to prevent prefoaming of the mixture and(B) foaming the mixture into a region of reduced pressure to form the foam product, wherein the difference between the glass transition temperature of the foamable mixture and the foaming temperature is less than about 62.degree. C.;wherein the alkenyl aromatic polymer is selected from the group consisting of (a) a copolymer of styrene and at least one substituted styrene selected from the group consisting of meta-substituted styrene, para-substituted styrene and mixtures thereof, wherein the copolymer is derived from about 5% to about 40% by mole of the substituted styrene, (b) a mixture of (1) a major amount of a polystyrene having a weight average molecular weight of about 45,000 to about 110,000, (2) a minor amount of a polystyrene having a weight average molecular weight of about 190,000 to about 350,000, and (c) mixtures thereof.