Process for the preparation of poly(alkylene terephthalate) employing in situ titanium-containing catalyst and compositions derived therefrom

Abstract

Disclosed is a process for the manufacture of a polyalkylene terephthalate such as polybutylene terephthalate. In particular, the process comprises employing a titanium-containing catalyst formed by the reaction product of tctraalkyl titanate and a complexing agent comprising a phosphorous, nitrogen or boron atom. The process is used to prepare polyalkylene terephthalates characterized by improved hydrostability, as well as compositions derived therefrom.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 677,224, tiled Jul. 30, 2012, which is incorporated herein by reference in its entirety.TECHNICAL FIELD OF THE INVENTION[0002]Disclosed is a process for the manufacture of a polyalkylene terephthalate such as polybutylene terephthalate. In particular, the process comprises employing a titanium-containing catalyst formed by the reaction product of tetraalkyl titanate and a complexing agent comprising a phosphorous, nitrogen or boron atom. The process is used to prepare polyalkylene terephthalates characterized by improved hydrostability, as well as compositions derived therefrom.BACKGROUND OF THE INVENTION[0003]Polybutylene terephthalate (PBT) resin is a well-known polyalkylene terephthalate that is semi-crystalline and has several desirable properties alone or in blends. Compared to amorphous resins such as acrylonitrile butadiene styrene (ABS), polycar...

AI Technical Summary

Benefits of technology

The present invention relates to a process for making polyalkylene terephthalate resin that eliminates the need for catalyst quenchers and improves hydrolytic stability, reduces transesterification reactions, and improves mechanical performance. This is achieved by using an in-situ titanium-based catalyst system during polymerization. The use of scrap PET or modified PBT in the resin composition can provide additional benefits with little or no adverse effects on the resulting properties of the thermoplastic composition.

Problems solved by technology

Unfortunately, an active catalyst in the resin composition can sometimes lead to undesirable reactions in subsequent processing of the polyalkylene terephthalate.

Another problem associated with the presence of the active catalyst is transesterification, which can lead to loss of mechanical properties.

Catalyst quenchers such as phosphoric acid can be added to thermoplastic compositions to prevent such transesterification, but they can also promote degradation of polymer chains and contribute to a decrease in polymer molecular weight as well as greater hydrolytic instability.

The use of phosphite stabilizers is less satisfactory because of the tendency for phosphites to be unstable to both hydrolysis and oxidation.

Insufficient hydrostahility of polyalkylene terephthalate can lead to chain cleavage, the extent of which depends on the exact conditions of exposure to water or humidity.

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