Process for making polyetherester elastomer film

Claim 1

A process for preparing an elastic film from a melt blend of a first and second polyetherester elastomer, such elastomer being formed of hard and soft segments made from reactants consisting essentially of poly(tetramethylene ether)glycol, 1,4-butane diol and a phenylene dicarboxylic acid or a derivative thereof, wherein the phenylene dicarboxylic acid consists essentially of at least 70% terephthalic acid and no more than 30% isophthalic acid, the first elastomer amounts to 75 to 85% by weight of the blend and has hard segments amounting to 20 to 25% by weight of said first elastomer and soft segments of 1800 to 2400 number average molecular weight, the second elastomer amounts to 15 to 25% by weight of the blend and has hard segments amounting to 40 to 55% by weight of said second elastomer and soft segments of 850 to 2000 number average molecular weight, and the blend exhibits a melting endotherm over a temperature range that extends from no lower than 120° C. to no higher than 215° C. with a melting peak in the range of 150° to 175° C., the process comprising in sequence compounding finely divided particles of an inorganic anti-blocking agent in the second elastomer in an amount in the range of 3 to 8% by weight of the elastomer blend, melt blending the resultant compounded elastomer with the first elastomer, melt extruding the melt-blended elastomers at a temperature in the range of 180° to 220° C. through a slot orifice to form a thin film, quenching the film to a temperature below 50° C., and advancing the quenched film at a speed that provides the film with a draw-down in the range of 12 to 40.