Method for making a heat-shrinkable film containing a layer of crystalline polyamides

Abstract

A process of making a biaxially-oriented multilayer film, comprises extruding a tubular multilayer tape and inflating the tape so that the tape is biaxially oriented by stretching in the transverse direction and machine direction at the same time, so that a tubular multilayer film is formed. The tubular multilayer tape comprises: (i) a first layer comprising a composition comprising a first polyamide and at least one member selected from the group consisting of a first polyolefin and a second polyamide, wherein the first polyamide comprises at least one member selected from the group consisting of nylon 6, nylon 66, and nylon 6/66, and wherein the first polyolefin and the second polyamide each has a different crystal structure than the first polyamide, and wherein the first layer has a thickness of less than about 15 percent, based on a total thickness of the tape; (ii) a second layer comprising a second polyolefin; (iii) a third layer which is an O,-barrier layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinylidene chloride, and polyalkylene carbonate, the third film layer having a thickness of less than about 15 percent, based on a total thickness of the tape; and (iv) a fourth layer comprising a third polyolefin.