Linear hydroquinone phenoxy polymers and process

Abstract

This invention relates to a process for the preparation of thermoplastic polymers. Specifically it relates to a process for the preparation of a substantially linear, high molecular weight phenoxy resin from substituted hydroquinone, less than 80 mole percent of hydroquinone and optionally up to about 20 mole percent of a second aromatic diol, epichlorohydrin (or another epihalohydrin) and a base, such as sodium hydroxide. Hydroquinone phenoxy resins of this invention are characterized by low permeability to oxygen and carbon dioxide and are, therefore, useful as a gas-barrier layer in multilayer plastic film constructions used in food packaging and beverage bottle applications, for example. For use in such applications, the resin is generally in the form of a thin, uniform film prepared by extrusion, casting, or other such method. It is highly desirable that polymers used in this manner be as free as possible from chain branches or cross-links, as these lead to the formation of gel particles which cause imperfections in the polymer film. These imperfections, in turn, detract from the appearance of the film. Moreover, as is well known, increasing the amount of chain branching in a polymer results in an undesirable reduction of flexibility and toughness.