Copolymers of polyvinylidene chloride (PVDC), are-well known for their use in demanding barrier packaging applications to minimize the permeation of oxygen, water vapor, and odors. New die designs incorporating patented early encapsulation technology (US Patent 6,685,872, International Publication Number WO 02/06047, US Patent 4,643,927), coupled with temperature isolation technology developed by equipment suppliers, have eliminated degradation problems existing in the typical spiral mandrel dies used in the blown film process. These new die designs, coupled with new resin offerings; enable PVDC resins to be processed on large multilayer blown film dies. Multilayer films incorporating PVDC resins with higher temperature polymers such as Nylon, PP, and LLDPE in the skins are now possible. The advantage of coextruded multilayer films incorporating PVDC are that they offer, in a one step process, a combination of outstanding barrier performance, resistance to in-use conditions such as humidity and flex cracking, and specific physical properties given by the skin polymers. They represent the possibility of increasing product shelf life or down gauging the barrier material as well as reducing processing steps compared to laminated composite products. Its barrier performance being unaffected by humidity makes PVDC well suited for retort applications. In China, PVDC is widely used in retort applications as a monolayer film; and interest in incorporating PVDC in multilayer films for retort is growing.
展开▼
