RECYCLING BIAXIALLY ORIENTED POLYPROPYLENE FILMS COATED WITH VINYLIDENE CHLORIDE POLYMERS

摘要

It is well known that polyvinylidene chloride (PVdC) coated films are difficult to recycle because they tend to degrade rapidly under typical film reprocessing conditions. This paper reports a novel process that involves treating PVdC coated film with caustic solution, followed by washing and removing the PVdC from the film.The PVdC coating becomes delaminated after being treated with a caustic solution at elevated temperatures. In addition to the caustic treatment, a vigorous mechanical agitation is required to separate the dehydrochlorinated coating from the film substrate. We found that this mechanical agitation can be either combined with the chemical treatment (a one-stage process) or used after transferring the treated film into a water tank (a two-stage process).After being separated from the film substrate, the PVdC coating settles to the bottom as a dark sludge and can be separated through a filter screen. The sludge is an industrial waste and can be land filled. This washed, PVdC-free film shows little discoloration when melt extruded at 250°C using conventional extrusion equipment.