Reinforced polycarbodiimide modified polyalkylene terephthalate

Abstract

Molding resin compositions comprising a polycarbodiimide modified polyalkylene terephthalate polymer (polypropylene terephthalate, polybutylene terephthalate, or mixtures thereof) and a reinforcing agent such as glass fibers have been found to exhibit improved impact strength and thus are useful in various molding applications in order to prepare articles of manufacture having, e.g., industrial (e.g., gears, bearings), automotive (e.g., automotive distributor caps, distributor rotors), and electrical (e.g., motor end caps, brush holders) applications. These molding resin compositions are particularly useful in certain automotive, industrial, and electrical applications where greater impact strength may be required to extend the useful life of various articles of manufacture which may be subjected to occasional or continuous shock or impact. These molding resin compositions may be prepared by intimately admixing in the molten state a reinforcing agent such as glass fibers with a polycarbodiimide modified polyalkylene terephthalate polymer formed from the reaction between a polyalkylene terephthalate polymer which is the reaction product of terephthalic acid or a dialkyl ester of terephthalic acid and a glycol selected from the group consisting of trimethylene glycol, tetramethylene glycol, and mixtures thereof, and a polycarbodiimide which is both (1) derived from at least one aromatic diisocyanate which is either unsubstituted or contains up to one methyl substituent on each aromatic ring, and (2) contains at least two carbodiimide units per polycarbodiimide molecule. The components of the composition are preferably prepared by charging the polyalkylene terephthalate to the hopper of a melt screw extruder and adding the polycarbodiimide and reinforcing agent downstream in the extruder--e.g., in the vent port or other side feed port of the extruder.