Poly(hydroxyalkanoic acid) plasticized with poly(trimethylene ether) glycol

1. A polymer composition, comprising a blend of a poly(hydroxyalkanoic acid), an ethylene ester copolymer, and poly(trimethylene ether) glycol wherein, based on the total weight of the composition,

the poly(hydroxyalkanoic acid) is present in the composition from about 50 to 99.8%;

the poly(hydroxyalkanoic acid) comprises polymerized units of one or more hydroxyalkanoic acids selected from the group consisting of 6-hydroxyhexanoic acid, 3-hydroxyhexanoic acid, 4-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, glycolic acid, lactic acid, 3-hydroxypropionic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and combinations of two or more thereof;

the ethylene ester copolymer is present in the composition from about 0.1 to about 40% and comprises, based on the total weight of the ethylene ester copolymer, (a) about 30 to about 99.5 weight % of copolymerized units of ethylene, (b) 0 to about 25 weight % of copolymerized units of at least one ester of the formula CH 2 ═C(R 1 )CO 2 R 2 , and (c) 0 to about 70 weight % of copolymerized units of at least one ester of the formula CH 2 ═C(R 3 )CO 2 R 4 ; provided that the amounts of (b) and (c) in the copolymer are not both 0;

R 1 is hydrogen or an alkyl group having 1-6 carbon atoms; R 2 is a glycidyl group; R 3 is hydrogen or an alkyl group having 1 to 8 carbon atoms; and R 4 is an alkyl group having 1 to 8 carbon atoms; and

the poly(trimethylene ether) glycol is present in the composition from about 0.1 to about 40% and has a hydroxyl number from 20 to 840.

2. The composition of claim 1 wherein the poly(hydroxyalkanoic acid) is selected from the group consisting of poly(glycolic acid), poly(lactic acid), poly(hydroxybutyric acid), poly(hydroxybutyric acid-hydroxyvaleric acid) copolymer, poly(glycolic acid-lactic acid) copolymer, and combinations of two or more thereof.

3. The composition of claim 2 wherein the poly(hydroxyalkanoic acid) is poly(lactic acid), and optionally, a stereo complex of poly(D-lactic acid) and poly(L-lactic acid).

4. The composition of claim 1 wherein the ethylene ester copolymer comprises 0.5 to about 25 weight % of copolymerized units of CH 2 ═C(R 1 )CO 2 R 2 and 0 weight % of copolymerized units of CH 2 ═C(R 3 )CO 2 R 4 .

5. The composition of claim 1 wherein the ethylene ester copolymer comprises of 0 weight % of copolymerized units of CH 2 ═C(R 1 )CO 2 R 2 and 0.5 to about 70 weight % of copolymerized units of CH 2 ═C(R 3 )CO 2 R 4 .

6. The composition of claim 1 wherein the ethylene ester copolymer comprises 0.5 to about 25 weight % of copolymerized units of CH 2 ═C(R 1 )CO 2 R 2 and 0.5 to about 70 weight % of copolymerized units of CH 2 ═C(R 3 )CO 2 R 4 .

7. The composition of claim 3 wherein the ethylene ester copolymer comprises about 40 to about 94% of copolymerized units of ethylene, about 3 to about 20% of copolymerized units of CH 2 ═C(R 1 )CO 2 R 2 , and about 3 to about 70% of copolymerized units of CH 2 ═C(R 3 )CO 2 R 4 .

8. The composition of claim 7 wherein the ethylene ester copolymer comprises about 3 to about 17% of CH 2 ═C(R 1 )CO 2 R 2 , and about 20 to about 35% of CH 2 ═C(R 3 )CO 2 R 4 .

9. The composition of claim 3 wherein the ethylene ester copolymer is selected from the group consisting of ethylene glycidyl methacrylate dipolymer, ethylene butyl acrylate glycidyl methacrylate terpolymer, ethylene butyl acrylate dipolymer and combinations thereof.

10. The composition of claim 8 wherein the ethylene ester copolymer is an ethylene butyl acrylate glycidyl methacrylate terpolymer.

11. A process comprising:

(1) physically blending, based on the total weight of the resulting blend, about 50 to 99.8 weight % of a poly(hydroxyalkanoic acid) polymer, about 0.1 to about 40 weight % of an ethylene ester copolymer, and about 0.1 to about 40% by weight of poly(trimethylene ether) glycol;

(2) melt processing the poly(hydroxyalkanoic acid), ethylene ester copolymer, and poly(trimethylene ether) glycol at a temperature 20 to 40° C. higher than the melt temperature of the poly(hydroxyalkanoic acid) to form a mixture;

(3) cooling the mixture to produce a plasticized polymer composition; and

(4) optionally grinding the plasticized polymer composition; wherein

the poly(hydroxyalkanoic acid) comprises polymerized units of one or more hydroxyalkanoic acids selected from the group consisting of 6-hydroxyhexanoic acid, 3-hydroxyhexanoic acid, 4-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, glycolic acid, lactic acid, 3-hydroxypropionic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and combinations of two or more thereof;

the ethylene ester copolymer comprises, based on the total weight of the ethylene ester copolymer, (a) about 20 to about 95 weight % of copolymerized units of ethylene, (b) 0 to about 25 weight % of copolymerized units of at least one ester of the formula CH 2 ═C(R 1 )CO 2 R 2 , and (c) 0 to about 70 weight % of copolymerized units of at least one ester of the formula CH 2 ═C(R 3 )CO 2 R 4 ; R 1 is hydrogen or an alkyl group having 1-6 carbon atoms, R 2 is a glycidyl group, R 3 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 4 is an alkyl group having 1 to 8 carbon atoms; provided that the amounts of (b) and (c) in the copolymer are not both 0; and

the polytrimethylene ether glycol has a hydroxyl number ranging from 20 to 840.

12. The process of claim 11 wherein the ethylene ester copolymer and the poly(trimethylene ether) glycol are added simultaneously to the poly(hydroxyalkanoic acid).

13. The process of claim 11 further comprising extrusion molding or press molding the plasticized polymer composition.

14. The process of claim 13 wherein the extrusion molding comprises forming an amorphous film or sheet.

15. The process of claim 14 further comprising heating the amorphous film or sheet to above the glass transition temperature (Tg) and below the melting point of the plasticized polymer composition; stretching the film or sheet by vacuum or pressure forming using a mold to provide a stretched article; and cooling the stretched article to provide a finished article.

16. An article comprising the composition of claim 1 .

17. The article of claim 16 wherein the poly(hydroxyalkanoic acid) is poly(lactic acid).

18. The article of claim 17 wherein the article is an amorphous film or sheet.

19. The article of claim 17 wherein the article is thermoformed.

20. The article of claim 17 wherein the ethylene ester copolymer comprises 0.5 to about 25 weight % of CH 2 ═C(R 1 )CO 2 R 2 and either 0 weight % or 0.5 to about 70 weight % of CH 2 ═C(R 3 )CO 2 R 4 .

21. The article of claim 17 wherein the ethylene ester copolymer comprises 0.5 to about 25 weight % of CH 2 ═C(R 1 )CO 2 R 2 and 0.5 to about 70 weight % of CH 2 ═C(R 3 )CO 2 R 4 .

22. The article of claim 17 wherein the ethylene ester copolymer comprises about 40 to about 96% of copolymerized units of ethylene, about 3 to about 20% of copolymerized units of CH 2 ═C(R 1 )CO 2 R 2 , and about 3 to about 70% of copolymerized units of CH 2 ═C(R 3 )CO 2 R 4 .