Sealable, opaque polyolefinic multilayer film and process therefor

A process for preparing a sealable, opaque polyolefinic multilayer film, comprising the steps of:

• coextruding a base layer and a separate surface layer on each side of said base layer to form the multilayer film, one of said surface layers being sealable and the other of said surface layers being non-sealable;
• biaxially stretching said multilayer film in longitudinal and transverse directions;
• and
• subjecting said non-sealable surface layer to a corona-discharge treatment;
• wherein said base layer is a polypropylene, and includes an additive which is incompatible with said polypropylene, said sealable surface layer is selected from the group consisting of a copolymer of propylene and ethylene, a copolymer of propylene and butene-1, a terpolymer of ethylene, propylene and butene-1, and combinations of the above, and said non-sealable surface layer comprises from about 97.5% to about 99.7% by weight of a propylene homopolymer, and from about 0.3% to about 2.5% by weight of a slip agent;
• wherein the density of said multilayer film is no greater than about 0.85 g/cm.sup.3, and wherein said sealable surface layer has a low minimum sealing temperature.