| abstract |
A microporous shaped article is provided. The article comprises ethylene-vinyl alcohol copolymer which has an internal structure of a multiplicity of spaced, randomly dispersed, non-uniform shaped particles of ethylene-vinyl alcohol copolymer. Also provide is process for preparing microporous shaped articles comprising the steps of: (a) melt blending to form a mixture comprising ethylene-vinyl alcohol copolymer and a compatible polymer or compound in which the copolymer will dissolve to form a solution at the melting temperature of the copolymer, but will phase separate on cooling at or below the crystallization temperature of the ethylene-vinyl alcohol copolymer; (b) forming a shaped article of the melt blended mixture; (c) cooling the shaped article to a temperature to cause phase separation to occur between the compatible copolymer or compound and the ethylene-vinyl alcohol copolymer, thereby providing an article comprising an aggregate of a first phase comprising particles of ethylene-vinyl alcohol copolymer in a second phase comprising the compatible polymer or compound with adjacent ethylene-vinyl alcohol copolymer particles being distinct but having a plurality of zones of continuity; and (d)i) collecting said article which has adjacent ethylene-vinyl alcohol copolymer particles which form a network of interconnected micropores therebetween, or ii) extracting the compatible polymer or compound with water and stretching the shaped article in at least one direction while wet to further separate adjacent ethylene-vinyl alcohol copolymer particles from one another and to permanently attenuate the ethylene-vinyl alcohol copolymer in the zones of continuity to form fibrils therebetween and drying, or iii) extracting the compatible polymer or compound with an organic solvent, and optionally stretching. |