Method for preparing poly-p-dioxanone polymer

Abstract

Poly-p-dioxanone is prepared in a process comprising:(a) heating a reaction mixture comprising p-dioxanone and an effective amount of a polymerization catalyst under conditions of temperature and pressure effective to produce a reaction product mixture comprising molten poly-p-dioxanone and unreacted p-dioxanone;(b) adding to said reaction product mixture a cyclic anhydride under conditions effective for reaction of the poly-p-dioxanone with the cyclic anhydride to form an end-capped poly-p-dioxanone;(c) exposing the reaction product mixture to a temperature within the range of about 50 to about 150.degree. C. under reduced pressure and removing unreacted p-dioxanone from the reaction product mixture; and(d) recovering the end-capped poly-p-dioxanone.The invention process permits the economical production of high molecular weight poly-p-dioxanone in the melt.

Description

Claims

1. A process for melt polymerization of p-dioxanone, the process comprising:

(a) heating a reaction mixture comprising p-dioxanone and an effective amount of a polymerization catalyst under conditions of temperature and pressure effective to produce a reaction product mixture comprising molten poly-p-dioxanone and unreacted p-dioxanone;

(b) adding a cyclic anhydride to said reaction product mixture under conditions effective for reaction of the poly-p-dioxanone with the cyclic anhydride to form an end-capped poly-p-dioxanone;

(c) exposing the reaction product mixture to a temperature within the range of about 50 to about 150.degree. C. under less than atmospheric pressure and removing unreacted p-dioxanone from the reaction product mixture; and

(d) recovering the end-capped poly-p-dioxanone.

2. The process of claim 1 in which the cyclic anhydride is selected from the group consisting of cycloaliphatic anhydrides and aromatic anhydrides.

3. The process of claim 1 in which the cyclic anhydride is pyromellitic anhydride.

4. The process of claim 1 in which the cyclic anhydride is added to the reaction product mixture in an amount within the range of about 0.0001 to about 2 mole percent, based on p-dioxanone.

5. The process of claim 1 in which step (a) is carried out at a temperature greater than 110.degree. C.

6. The process of claim 1 in which step (a) is carried out at a pressure within the range of about 0.05 to about 5 atm.

7. The process of claim 1 in which the poly-p-dioxanone is a copolymer of p-dioxanone and a second cyclic lactone.

8. The process of claim 1 in which the molecular weight of the poly-p-dioxanone is within the range of about 50,000 to about 300,000.

9. The process of claim 1 in which the polymerization catalyst comprises at least one of a tin compound, a zinc compound and an aluminum compound.

10. The process of claim 6 in which said second cyclic lactone is selected from at least one of lactide and glycolide.

11. The process of claim 1 which further comprises recycling the unreacted p-dioxanone from step (c) to the reaction mixture of step (a).