Biopolymer compositions having improved flexibility

1. A method for increasing the flexibility of a biopolymer comprising mixing a biopolymer and a compatible polyester to form a polymer blend, wherein the polyester comprises repeating units derivable from succinic acid, repeating units derivable from a substituted or unsubstituted C 2 to C 20 aliphatic diol, and one or two terminator units derivable from a substituted or unsubstituted C 1 to C 20 aliphatic alcohol;

wherein the polyester is present in an amount of about 5 to about 30 parts by weight per hundred parts by weight of the biopolymer; and wherein the polymer blend has at least a 10-fold increase in elongation percentage at break compared to the elongation percentage at break of the biopolymer.

2. A polymer blend comprising

(i) a biopolymer, and

(ii) a compatible aliphatic polyester comprising repeating units derivable from succinic acid; repeating units derivable from a substituted or unsubstituted C 2 to C 20 aliphatic diol; and one or two terminator units derivable from a substituted or unsubstituted C 1 to C 20 aliphatic alcohol; wherein the polyester is present in an amount of about 5 to about 30 parts by weight per hundred parts by weight of the biopolymer; and wherein the polymer blend has at least a 10-fold increase in elongation percentage at break compared to the elongation percentage at break of the biopolymer.

3. The polymer blend of claim 2 , wherein the polyester has an acid value of about 8 to about 20 and a hydroxyl value of about 40 to about 110.

4. The polymer blend of claim 2 , wherein the polyester has a number average molecular weight of about 400 to about 10,000 g/mol.

5. The polymer blend of claim 2 , wherein the polyester has an acid value of zero to about 20.

6. The polymer blend of claim 2 , wherein the polyester has an acid value of about 8 to about 20.

7. The polymer blend of claim 2 , wherein the polyester has a hydroxyl value of about zero to about 110.

8. The polymer blend of claim 2 , wherein the polyester has a hydroxyl value of about 40 to about 110.

9. The polymer blend of claim 2 , wherein the biopolymer is selected from the group consisting of polylactic acid, polyhydroxybutyrate, polyvinyl alcohol, polybutylene succinate, polyhydroxyalkanoates, polycaprolactones, aliphatic-aromatic copolyesters, starches, celluloses, and mixtures thereof.

10. The polymer blend of claim 2 , wherein the biopolymer is polylactic acid.

11. The polymer blend of claim 2 , wherein the aliphatic diol is a substituted or unsubstituted C 2 to C 10 aliphatic diol.

12. The polymer blend of claim 2 , wherein the aliphatic diol is a substituted or unsubstituted C 2 to C 4 aliphatic diol.

13. The polymer blend of claim 2 , wherein the aliphatic diol is selected from the group consisting of aliphatic diols having 3 carbon atoms and aliphatic diols having 4 carbon atoms.

14. The polymer blend of claim 2 , wherein the substituted or unsubstituted C 1 to C 20 aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, eicosanol, cis-9-dodecenol, cis-9-tetradecenol, cis-9-hexadecenol, cis-9-octadecenol, cis-cis-9,12-octadecadienol, cis-cis-cis-9,12,15-octadecatrienol, cis-trans-trans-9,11,13-octadecatrienol, octadecatetraenol, cis-11-eicosenol, eicosadienol, eicosatrienol, 5,8,11,14-eicosatetraenol, eicosapentaenol, cis-13-docosenol, docosatetraenol, 4,8,12,15,19-docosapentaenol, docosahexaenol, tetracosenol, 4,8,12,15,18,21-tetracosahexaenol, and mixtures thereof.

15. The polymer blend of claim 2 , wherein the polymer blend has at least a 5% reduction in tensile strength compared to the tensile strength of the biopolymer and at least a 5% reduction in tensile at break compared to the tensile at break of the biopolymer.

16. The polymer blend of claim 2 , wherein the aliphatic polyester has a formula I:

wherein

n is 1 to 1000;

R 1 is —(CH 2 ) 2 —;

R 2 is a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms;

X 1 is selected from the group consisting of —OH,—O 2 C—R 1 —CO 2 H, and —O 2 C—R 1 —CO 2 R 3 ;

X 2 is selected from the group consisting of —H, —R 2 —OH, and R 3 ; and

R 3 is a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms;

with the proviso that if X 1 is —OH or —O 2 C—R 1 —CO 2 H, then X 2 is R 3 .

17. The polymer blend of claim 16 , wherein n is 2 to 40, R 2 is C 1 to C 10 alkyl and R 3 is C 1 to C 20 alkyl.

18. The polymer blend of claim 16 , wherein n is 2 to 20, R 2 is C 3 alkyl and R 3 is C 8 to C 10 alkyl.

19. The polymer blend of claim 16 , wherein R 2 is an alkyl group having from 2 to 4 carbon atoms.

20. The polymer blend of claim 16 , wherein R 2 is selected from the group consisting of —(CH 2 ) 3 —, —CH 2 CH(CH 3 )—, and —CH(CH 3 )CH 2 —.

21. The polymer blend of claim 16 , wherein R 3 is a mixture comprising —(CH 2 ) 7 CH 3 and —(CH 2 ) 9 CH 3 —.

22. The method of claim 1 , wherein the polymer blend has at least a 5% reduction in tensile strength compared to the tensile strength of the biopolymer and at least a 5% reduction in tensile at break compared to the tensile at break of the biopolymer.

23. The method of claim 1 , wherein the polymer blend comprises polymers, the polymers consisting of (i) the biopolymer and (ii) the polyester.

24. The polymer blend of claim 2 , wherein the polymer blend comprises polymers, the polymers consisting of (i) the biopolymer and (ii) the polyester.