Anhydride Functional Ethylene Copolymers as Compatibilizers for Polyethylene-Rich Mixed Recycle Streams

摘要

Over the past several years, the ability of maleic anhydride grafted polymers to compatibilize polar contaminants with a polyolefin matrix has been confirmed by a number of groups working in this field. These maleic anhydride grafted polymers, typically containing 0.5 to 1.5 weight percent maleic anhydride, improve physical properties of the mixed recycle streams by acting as a compatibilizing agent that binds polar contaminants such as EVOH or nylon to the polymer matrix. This compatibilization is driven by a chemical reaction of the maleic anhydride functional group with co-reactive groups attached to the contaminants such as hydroxyl groups associated with EVOH or amine groups associated with nylon.In this study, we report on next generation additives based on high molecular weight, random copolymers of ethylene and anhydride functional monomers that have been specifically designed for compatibilizing a polyethylene phase with non-polar components in mixed recycle streams.By using a standard high-pressure free radical synthesis technique, DuPont has created a high molecular weight ethylene copolymer with a very high level of reactive functionality (greater than 3 weight percent anhydride). This anhydride-functional-ethylene copolymer has been shown to improve the impact strength of molded or extruded parts made from mixed recycle streams containing EVOH even when the scrap source additionally contains high levels of moisture, lubricant, or nylon. The property improvements provided by the ethylene copolymer additive can be obtained when using the compatibilizing agent at loading levels as low as 0.5 weight percent in the final part. This compares favorably to the higher loadings of traditional anhydride-grafted polymers that are needed to achieve the same performance.This new generation of functional ethylene copolymer additive will allow the industry to provide products with improved performance at reduced cost.