Polymer blends with improved notched impact strength Number:7,160,977 from the United States Patent and Trademark Office (PTO) owispatent This invention relates to a blend of biodegradable polymers comprising: (A) about 70% to about 80% by weight of at least one flexible biodegradable polymer (A) having a glass transition less than about 0.degree. C., (B) about 30% to about 20% by weight of at least one rigid biodegradable polymer (B) having a glass transition greater than about 10.degree. C.; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.<H strength, improved, Polymer, blends, , 7160977.html, Patent, pto, 7160977

Title: Polymer blends with improved notched impact strength

Abstract: This invention relates to a blend of biodegradable polymers comprising: (A) about 70% to about 80% by weight of at least one flexible biodegradable polymer (A) having a glass transition less than about 0.degree. C., (B) about 30% to about 20% by weight of at least one rigid biodegradable polymer (B) having a glass transition greater than about 10.degree. C.; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

Patent Number: 7,160,977 Issued on 01/09/2007 to Hale, et al.

Inventors: Hale; Wesley Raymond (Kingsport, TN), Tanner; Candace Michele (Kingsport, TN)
Assignee: Eastman Chemical Company (Kingsport, TN)

Appl. No.: 11/005,587

Filed: December 6, 2004

Current U.S. Class: 528/271 ; 264/176.1; 264/219; 428/411.1; 428/412; 528/193; 528/194; 528/272

Current International Class: C08G 63/00 (20060101)

Field of Search: 264/176.1,219 428/411.1,412 528/193,194,271,272

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Primary Examiner: Boykin; Terressa
Attorney, Agent or Firm: Boshears; B. J. Bernard J. Graves, Jr.

Parent Case Text

RELATED APPLICATIONS

This application claims priority to and the benefit of the following applications; U.S. Patent Ser. No. 60/531,723, filed Dec. 22, 2003, incorporated herein by reference; U.S. Patent Ser. No. 60/531,599, filed Dec. 22, 2003, incorporated herein by reference; and U.S. patent Ser. No. 11/005266 filed on even date herewith entitled "Polymer Blends With Improved Rheology And Unnotched Impact Strength", incorporated herein by reference.

Claims

We claim:

1. An injection molded article comprising a polymer blend comprising: (A) about 60% to about 80% by weight of at least one flexible biodegradable polymer (A) having a glass transition temperature less than about 0.degree. C., and (B) about 40% to about 20% by weight of at least one rigid biodegradable polymer (B) having a glass transition temperature greater than about 10.degree. C.; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

2. The injection molded article according to claim 1, wherein the polymer blend comprises: (A) at least one biodegradable polymer (A) having a Tg of less than about -10.degree. C.; and (B) at least one biodegradable polymer (B) having a Tg of greater than about 20.degree. C.

3. The injection molded article according to claim 2, wherein the polymer blend comprises: (A) at least one biodegradable polymer (A) having a Tg of less than about -20.degree. C.; and (B) at least one biodegradable polymer (B) having a Tg of greater about 30.degree. C.

4. The injection molded article according to claim 3, wherein the polymer blend comprises: (A) at least one biodegradable polymer (A) having a Tg of less than about -30.degree. C.; and (B) at least one biodegradable polymer (B) having a Tg of greater than about 40.degree. C.

5. The injection molded article according to claim 1, wherein the polymer blend comprises about 1% to about 50% by weight of at least one biodegradable additive (C), said percentages being based on the total weight of the polymer blend.

6. The injection molded article according to claim 1 wherein said polymer (A) is selected from the group consisting of aliphatic-aromatic polyesters, aliphatic polyesters comprising repeat units having at least 5 carbon atoms, polycaprolactone, and succinate-based aliphatic polymers.

7. The injection molded article according to claim 1 wherein said polymer (A) is selected from the group consisting of aliphatic-aromatic polyesters, polyhydroxyvalerates, polyhydroxybutyrate-hydroxyvalerates, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, and polyethylene succinate.

8. The injection molded article according to claim 1 wherein said at least one polymer (A) is an aliphatic-aromatic polyester.

9. The injection molded article according to claim 8 wherein said at least one polymer (A) is an aliphatic-aromatic copolyester comprising: (1) diacid residues comprising about 1 to 65 mole percent of one or more aromatic dicarboxylic acid residues; and 99 to about 35 mole percent of one or more non-aromatic dicarboxylic acid residues selected from the group consisting of aliphatic dicarboxylic acids residues containing from about 4 to 14 carbon atoms and cycloaliphatic dicarboxylic acids residues containing from about 5 to 15 carbon atoms; wherein the total mole percent of diacid residues is equal to 100 mole percent; and (2) diol residues of diols selected from the group consisting of one or more aliphatic diols containing about 2 to 8 carbon atoms, polyalkylene ether glycols containing about 2 to 8 carbon atoms, and cycloaliphatic diols containing from about 4 to 12 carbon atoms; wherein the total mole percent of diol residues is equal to 100 mole percent.

10. The injection molded article according to claim 9 wherein the aromatic dicarboxylic acid residues are residues of dicarboxylic acids selected from the group consisting of terephthalic acid, isophthalic acid, and mixtures thereof.

11. The injection molded article according to claim 10 wherein said aliphatic-aromatic copolyester comprises about 25 to 65 mole percent of terephthalic acid residues.

12. The injection molded article according to claim 11 wherein said aliphatic-aromatic copolyester comprises about 35 to 65 mole percent of terephthalic acid residues.

13. The injection molded article according to claim 12 wherein said aliphatic-aromatic copolyester comprises about 40 to 60 mole percent of terephthalic acid residues.

14. The injection molded article according to claim 9 wherein said one or more non-aromatic dicarboxylic acid residues are residues of dicarboxylic acids selected from the group consisting of adipic acid, glutaric acid and mixtures thereof.

15. The injection molded article according to claim 14 wherein said aliphatic-aromatic copolyester comprises about 75 to 35 mole percent of residues of one or more non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid and glutaric acid.

16. The injection molded article according to claim 15 wherein said aliphatic-aromatic copolyester comprises about 65 to 35 mole percent of residues of one or more non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid and glutaric acid.

17. The injection molded article according to claim 16 wherein said aliphatic-aromatic copolyester comprises about 40 to 60 mole percent of residues of one or more non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid and glutaric acid.

18. The injection molded article according to claim 9 wherein one or more diol residue(s) of polyester (A) are residues of diols selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, triethylene glycol, and tetraethylene glycol.

19. The injection molded article according to claim 9 wherein the diol residues of said aliphatic-aromatic copolyester consist essentially of aliphatic diol residues.

20. The injection molded article according to claim 9 wherein the diol residues are residues of diols selected from the group consisting of 1,4-butanediol, 1,3-propanediol, ethylene glycol, 1,6-hexanediol, diethylene glycol, and 1,4-cyclohexanedimethanol.

21. The injection molded article according to claim 20 wherein said aliphatic-aromatic copolyester comprises one or more diol residues of diols selected from the group consisting of 1,4-butanediol, ethylene glycol, and 1,4-cyclohexanedimethanol.

22. The injection molded article according to claim 21 wherein the diol residues of said aliphatic-aromatic copolyester comprise 1,4-butanediol residues.

23. The injection molded article according to claim 22 wherein the diol residues comprise about 80 to 100 mole percent of 14-butanediol residues; wherein the total mole percent of diol residues is equal to 100 mole percent.

24. The injection molded article according to claim 9 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 25 to 65 mole percent of terephthalic acid residues and 75 to about 35 mole percent of non-aromatic dicarboxylic acid residues; and (2) diol residues consisting of aliphatic diol residues.

25. The injection molded article according to claim 24 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 25 to 65 mole percent of terephthalic acid residues and 75 to about 35 mote percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

26. The injection molded article according to claim 25 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 35 to 65 mole percent of terephthalic acid residues and 65 to about 35 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

27. The injection molded article according to claim 26 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 40 to 60 mole percent of terephthalic acid residues and 60 to about 40 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

28. The injection molded article according to claim 1 wherein said polymer (B) is selected from the group consisting of polyesteramides, a modified polyethylene terephthalate, biopolymers based on polylactic acid, polyhydroxyalkanoates, polyhydroxybutyrates, polyhydroxyvalerates, and polyhydroxybutyrate-hydroxyvalerate copolymers.

29. The injection molded article according to claim 28 wherein said at least one polymer (B) is a biopolymer based on polylactic acid.

30. An injection molded article comprising a polymer blend comprising: (A) about 60% to about 80% by weight of at least one polymer (A) having a glass transition temperature less than about 0.degree. C., wherein said polymer (A) is an aliphatic-aromatic copolyester comprising: (1) diacid residues comprising about 1 to 65 mole percent aromatic dicarboxylic acid residues; and 99 to about 35 mole percent of non-aromatic dicarboxylic acid residues selected from the group consisting of aliphatic dicarboxylic acids residues containing from about 4 to 14 carbon atoms and cycloaliphatic dicarboxylic acids residues containing from about 5 to 15 carbon atoms; wherein the total mole percent of diacid residues is equal to 100 mole percent; and (2) diol residues of diols selected from the group consisting of one or more aliphatic diols containing about 2 to 8 carbon atoms, polyalkylene ether glycols containing about 2 to 8 carbon atoms, and cycloaliphatic diols containing from about 4 to 12 carbon atoms; wherein the total mole percent of diol residues is equal to 100 mole percent; (B) about 30% to about 20% by weight of at least one polymer (B) having a glass transition temperature greater than about 10.degree. C., wherein said polymer (B) is a biopolymer based on polylactic acid; said percentages being based on the total weight of the polymer blend; and wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

31. The injection molded article according to claim 30 wherein the polymer blend comprises about 1% to about 50% by weight of at least one biodegradable additive (C), said percentages being based on the total weight of the polymer blend.

32. The injection molded article according to claim 30 wherein said aliphatic-aromatic copolyester comprises about 25 to 65 mole percent of terephthalic acid residues.

33. The injection molded article according to claim 32 wherein said aliphatic-aromatic copolyester comprises about 35 to 65 mole percent of terephthalic acid residues.

34. The injection molded article according to claim 33 wherein said aliphatic-aromatic copolyester comprises about 40 to 60 mole percent of terephthalic acid residues.

35. The injection molded article according to claim 30 wherein the non-aromatic dicarboxylic acid residues are residues of dicarboxylic acids selected from the group consisting of adipic acid, glutaric acid and mixtures thereof.

36. The injection molded article according to claim 35 wherein said aliphatic-aromatic copolyester comprises about 75 to 35 mole percent of residues of non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid, glutaric acid, and mixtures thereof.

37. The injection molded article according to claim 36 wherein said aliphatic-aromatic copolyester comprises about 65 to 35 mole percent of residues of non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid, glutaric acid and mixtures thereof.

38. The injection molded article according to claim 30 wherein said aliphatic-aromatic copolyester comprises about 40 to 60 mole percent of residues of non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid, glutaric acid, and combinations thereof.

39. The injection molded article according to claim 30 wherein one or more diol residue(s) of said aliphatic-aromatic copolyester are residues of diols selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclo-hexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, triethylene glycol, and tetraethylene glycol.

40. The injection molded article according to claim 30 wherein one or more diol residues of said aliphatic-aromatic copolyester consist essentially of aliphatic diol residues.

41. The injection molded article according to claim 30 wherein one or more diol residues of said aliphatic-aromatic copolyester are residues of diols selected from the group consisting of 1,4-butanediol, 1,3-propanediol, ethylene glycol, 1,6-hexanediol, diethylene glycol, and 1,4-cyclohexanedimethanol.

42. The injection molded article according to claim 41 wherein one or more diol residues of said aliphatic-aromatic copolyester are residues of diols selected from the group consisting of 1,4-butanediol, ethylene glycol, and 1,4-cyclohexanedimethanol.

43. The injection molded article according to claim 42 wherein one or more diol residues of said aliphatic-aromatic copolyester comprise 1,4-butanediol residues.

44. The injection molded article according to claim 43 wherein the diol residues comprise about 80 to 100 mole percent of 1,4-butanediol residues; wherein the total mole percent of diol residues is equal to 100 mole percent.

45. The injection molded article according to claim 44 wherein the diol residues comprise about 95 to 100 mole percent of 1,4-butanediol residues; wherein the total mole percent of diol residues is equal to 100 mole percent.

46. The injection molded article according to claim 30 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 25 to 65 mole percent of terephthalic acid residues and 75 to about 35 mole percent of non-aromatic dicarboxylic acid residues; and (2) diol residues consisting of aliphatic diol residues.

47. The injection molded article according to claim 46 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consists essentially of: (1) about 25 to 65 mole percent of terephthalic acid residues and 75 to about 35 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

48. The injection molded article according to claim 47 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 35 to 65 mole percent of terephthalic acid residues and 65 to about 35 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

49. The injection molded article according to claim 48 wherein the diacid and diol residues of said aliphatic-aromatic copolyester consist essentially of: (1) about 40 to 60 mole percent of terephthalic acid residues and 60 to about 40 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues.

50. An injection molded article comprising a polymer blend comprising: (A) about 70% to about 80% by weight of at least one polymer (A), wherein said polymer (A) is an aliphatic-aromatic copolyester comprising: (1) aromatic dicarboxylic acid residues comprising about 35 to 65 mole percent of terephthalic acid residues and 65 to about 35 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol residues; and (B) about 30% to about 20% by weight of at least one polymer (B), wherein said polymer (B) is a biopolymer based on polylactic acid; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

51. The injection molded article according to claim 50 wherein said aliphatic-aromatic copolyester comprises about 40 to 60 mole percent of residues of one or more non-aromatic dicarboxylic acid(s) selected from the group consisting of adipic acid and glutaric acid.

52. The injection molded article according to claims 9, 30, or 50 wherein said aliphatic-aromatic copolyester is branched.

53. The injection molded article according to claims 1, 30, or 50, wherein the polymer blend comprises a plasticizer.

54. The injection molded article according to claim 53 wherein said plasticizer is selected from the group consisting of N-ethyl-o,p-toluenesulfonamide, 2-ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate, tributyl phosphate, t-butylphenyl diphenyl phosphate, tricresyl phosphate, chloroparaffin (60% chlorine), chloroparaffin (50% chlorine), diethyl succinate, di-n-butyl maleate, di-(2-ethylhexyl) maleate, n-butyl stearate, acetyl triethyl citrate, triethyl citrate, tri-n-butyl citrate, acetyl tri-n-butyl citrate, methyl oleate, dibutyl fumarate, diisobutyl adipate, dimethyl azelate, epoxidized linseed oil, glycerol monooleate, methyl acetyl ricinloeate, n-butyl acetyl ricinloeate, propylene glycol ricinloeate, polyethylene glycol 200 dibenzoate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, dimethyl phthalate, diethyl phthalate, di-n-butylphthalate, diisobutyl phthalate, butyl benzyl phthalate, and glycerol triacetate.

55. A polymer blend comprising: (A) 70 to 75% by weight of at least one flexible biodegradable polymer (A) having a glass transition temperature less than about 0.degree. C.; (B) about 25% by weight of at least one rigid biodegradable polymer (B) having a glass transition temperature greater than about 10.degree. C.; and (C) up to 5% by weight of at least one biodegradable additive (C), said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

56. The polymer blend according to claim 55, wherein the polymer (A) is an aliphatic-aromatic copolyester.

57. The polymer blend according to claim 56, wherein the copolyester comprises: (1) about 35 to 65 mole percent of terephthalic acid residues and 65 to about 35 mole percent of residues of adipic acid, glutatic acid, or combinations thereof; (2) diol residues of 1,4-butanediol.

58. The polymer blend according to claim 56, wherein the copolyester is branched.

59. The polymer blend according to claim 57, wherein the polymer (B) is a biopolymer based on polylactic acid.

60. The polymer blend according to claim 59, wherein the biodegradable additive (C) is calcium carbonate.

61. An injection molded article comprising the polymer blend of claim 55.

Description

FIELD OF THE INVENTION

The present invention relates generally to biodegradable polymer blends. Preferably, the present invention relates to blends of two biopolymers, such as biodegradable polyesters and polyester amides, in order to yield blends with improved notched Izod impact strength. The biodegradable polymer blends may be suitable for a number of applications.

BACKGROUND OF THE INVENTION

Biodegradable materials are comprised of components which, by microbial catalyzed degradation, are reduced in strength by reduction in polymer size to monomers or short chains which are then assimilated by the microbes. In an aerobic environment, these monomers or short chains are ultimately oxidized to CO.sub.2, H.sub.2O, and new cell biomass. In an anaerobic environment the monomers or short chains are ultimately oxidized to CO.sub.2, H.sub.2O, acetate, methane, and cell biomass. Successful biodegradation requires that direct physical contact must be established between the biodegradable material and the active microbial population or the enzymes produced by the active microbial population. An active microbial population useful for degrading the films and blends of the invention can generally be obtained from any municipal or industrial wastewater treatment facility in which the influents (waste stream) are high in cellulose materials. Moreover, successful biodegradation requires that certain minimal physical and chemical requirements be met such as suitable pH, temperature, oxygen concentration, proper nutrients, and moisture level.

In response to the demand for biopolymers, a number of new biopolymers have been developed which have been shown to biodegrade when discarded into the environment.

Currently known biopolymers have unique properties, benefits and weaknesses. For example, some of the biopolymers tend to be strong but also quite rigid and brittle. This makes them poor candidates when flexible sheets or films are desired, such as for use in making wraps, bags and other packaging materials requiring good bend and folding capability. For other bipolymers, it is not believed that films can be blown from them.

On the other hand, biopolymers such as PCL, and certain aliphatic aromatic polyesters currently available in the market are many times more flexible compared to the more rigid biopolymers discussed immediately above. However, they have relatively low melting points such that they tend to be self adhering when newly processed and/or exposed to heat. While easily blown into films, such films are difficult to process on a mass scale since they will tend to self adhere when rolled onto spools, which is typically required for sale and transport to other locations and companies. To prevent self-adhesion (or "blocking") of such films, it is typically necessary to incorporate silica or other fillers. As the aforementioned example for blowing films suggests, the molding, extruding, and forming of thicker parts is also extremely difficult.

Another important criterion for injection molded, extruded, or formed parts is temperature stability. "Temperature stability" is the ability to maintain desired properties even when exposed to elevated or depressed temperatures, or a large range of temperatures, which may be encountered during shipping or storage. For example, many of the more flexible biopolymers tend to become soft and sticky if heated significantly above room temperature, thus compromising their ability to maintain their desired packaging properties. Other polymers can become rigid and brittle upon being cooled significantly below freezing (i.e., 0.degree. C.). Thus, a single homopolymer or copolymer may not by itself have sufficient stability within large temperature ranges.

In view of the foregoing, it would be an advancement in the art to provide biodegradable polymer blends with improved notched Izod impact strength which can be readily injection molded, or formed into film and sheets that have increased temperature stability over a broad range of temperatures compared to existing biopolymers.

BRIEF SUMMARY OF THE INVENTION

The present invention discloses specific biodegradable polymer blend composition ranges having improved notched Izod impact strength. Such polymer blends may be injection molded, or formed into films and sheets for use in a wide variety of applications requiring rigidity, toughness, and biodegradability.

The polymer blend of the invention comprises: (A) about 60% to about 80% by weight of at least one flexible biodegradable polymer (A) having a glass transition temperature of less than about 0.degree. C. ; and (B) about 40% to about 20% by weight of at least one rigid biodegradable polymer (B) having a glass transition temperature greater than about 10.degree. C.; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

In another embodiment of the invention, a polymer blend is provided, comprising: (A) about 60% to about 80% by weight of at least one polymer (A) having a glass transition temperature of less than about 0.degree. C., wherein said polymer (A) comprises: (1) diacid residues comprising about 1 to 65 mole percent aromatic dicarboxylic acid residues; and 99 to about 35 mole percent of non-aromatic dicarboxylic acid residues selected from the group consisting of aliphatic dicarboxylic acids residues containing from about 4 to 14 carbon atoms and cycloaliphatic dicarboxylic acids residues containing from about 5 to 15 carbon atoms; wherein the total mole percent of diacid residues is equal to 100 mole percent; and (2) diol residues selected from the group consisting of one or more aliphatic diols containing about 2 to 8 carbon atoms, polyalkylene ethers containing about 2 to 8 carbon atoms, and cycloaliphatic diols containing from about 4 to 12 carbon atoms; wherein the total mole percent of diol residues is equal to 100 mole percent; and (B) about 40% to about 20% by weight of at least one polymer (B), wherein said polymer (B) is a biopolymer derived from polylactic acid; said percentages being based on from the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

In yet another embodiment of the invention is a polymer blend comprising: (A) about 70% to about 80% by weight of at least one polymer (A) ) having a glass transition temperature of less than about 0.degree. C., wherein said polymer (A) consists essentially of: (1) aromatic dicarboxylic acid residues comprising about 35 to 65 mole percent of terephthalic acid residues and 65 to about 35 mole percent of adipic acid residues, glutaric acid residues, or combinations of adipic acid residues and glutaric acid residues; and (2) diol residues consisting of 1,4-butanediol; and (B) about 30% to about 20% by weight of at least one polymer (B), wherein said polymer (B) is a biopolymer derived from polylactic acid; said percentages being based on the total weight of the polymer blend wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

For all of the described embodiments, the polymer blends may comprise about 1 to about 50 weight % of biodegradable additives, based on the total weight of the polymer blend.

These biodegradable polymer blends provide improved notched Izod impact strength which can be readily formed into molded, extruded, or formed parts that have increased temperature stability over a broad range of temperatures compared to existing biopolymer blends.

DETAILED DESCRIPTION

The invention achieves the foregoing improvements by blending at least one biopolymer having relatively high stiffness (rigid), hereinafter also referred to as "biopolymer(s) (B)", with at least one biopolymer (A) having relatively high flexibility, hereinafter also referred to as "biopolymer(s) (A)". The novel blends have improved notched Izod impact strength when compared to the individual polymer components. Moreover, such blends are superior to conventional plastics, which suffer from their inability to degrade when discarded in the environment.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, the ranges stated in this disclosure and the claims are intended to include the entire range specifically and not just the endpoint(s). For example, a range stated to be 0 to 10 is intended to disclose all whole numbers between 0 and 10 such as, for example 1, 2, 3, 4, etc., all fractional numbers between 0 and 10, for example 1.5, 2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10. Also, a range associated with chemical substituent groups such as, for example, "C1 to C5 hydrocarbons", is intended to specifically include and disclose C1 and C5 hydrocarbons as well as C2, C3, and C4 hydrocarbons.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Any of the weight percentages described herein for one embodiment may be used in combination with other embodiments.

The polymer blend of the invention generally comprises the following embodiment as well as others described herein: (A) about 60% to about 80% by weight of at least one flexible biodegradable polymer (A) having a glass transition temperature of less than about 0.degree. C. ; and (B) about 40% to about 20% by weight of at least one rigid biodegradable polymer (B) having a glass transition temperature greater than about 10.degree. C.; said percentages being based on the total weight of the polymer blend; wherein said polymer blend has a notched Izod impact strength according to ASTM D256 of at least 7.5 ft-lbs/in.

In response to the demand for biopolymers, a number of new biopolymers have been developed which have been shown to biodegrade when discarded into the environment. Some of these are aliphatic-aromatic copolyesters, polyesteramides, a modified polyethylene terephthalate, polymers based on polylactic acid, polymers known as polyhydroxyalkanoates (PHA), which include polyhydroxybutyrates (PHB), polyhydroxyvalerates (PHV), and polyhydroxybutyrate-hydroxyvalerate copolymers (PHBV), and polycaprolactone (PCL).

The polymer blends according to the invention include at least one biopolymer having relatively high stiffness and at least one biopolymer having relatively high flexibility. When blended together in the correct proportions, it is possible to derive the beneficial properties from each polymer while offsetting or eliminating the negative properties of each polymer if used separately to molded, extruded, or formed parts for a broad variety of applications. By blending a relatively rigid polymer with a relatively flexible polymer in certain proportions, the inventors have discovered that the notched Izod impact strength of the blend exceed the desirable properties of each polymer when used individually. Thus, the surprising result of an unexpected synergistic effect has been demonstrated.

Biopolymers (A) that may be characterized as being generally "flexible" include those polymers having a glass transition temperature of less than about 0.degree. C. In one embodiments, the flexible biopolymers (A) will have a glass transition temperature of less than about -10.degree. C. In other embodiments of the invention, the flexible biopolymers will have a glass transition temperature of less than about -20.degree. C., and even more preferably, less than about -30.degree. C.

Examples of soft or flexible biopolymers (A) include but are not limited to the following: aliphatic-aromatic copolyesters (such as those manufactured by BASF and previously manufactured by Eastman Chemical Company), aliphatic polyesters which comprise repeating units having at least 5 carbon atoms, e.g., polyhydroxyvalerate, polyhydroxybutyrate-hydroxyvalerate copolymer and polycaprolactone (such as those manufactured by Daicel Chemical, Monsanto, Solvay, and Union Carbide), and succinate-based aliphatic polymers, e.g., polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyethylene succinate (PES) (such as those manufactured by Showa High Polymer).

The term "polyester", as used herein, is intended to include "copolyesters" and is understood to mean a synthetic polymer prepared by the polycondensation of one or more difunctional carboxylic acids with one or more difunctional hydroxyl compounds. Typically the difunctional carboxylic acid is a dicarboxylic acid and the difunctional hydroxyl compound is a dihydric alcohol such as, for example, glycols and diols. The term "residue", as used herein, means any organic structure incorporated into a polymer or plasticizer through a polycondensation reaction involving the corresponding monomer. The term "repeating unit", as used herein, means an organic structure having a dicarboxylic acid residue and a diol residue bonded through a carbonyloxy group. Thus, the dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, or mixtures thereof. As used herein, therefore, the term dicarboxylic acid is intended to include dicarboxylic acids and any derivative of a dicarboxylic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, or mixtures thereof, useful in a polycondensation process with a diol to make a high molecular weight polyester.

The polyester(s) included in the present invention contain substantially equal molar proportions of acid residues (100 mole %) and diol residues (100 mole %) which react in substantially equal proportions such that the total moles of repeating units is equal to 100 mole %. The mole percentages provided in the present disclosure, therefore, may be based on the total moles of acid residues, the total moles of diol residues, or the total moles of repeating units. For example, a copolyester containing 30 mole % adipic acid, based on the total acid residues, means that the copolyester contains 30 mole % adipic residues out of a total of 100 mole % acid residues. Thus, there are 30 moles of adipic residues among every 100 moles of acid residues. In another example, a copolyester containing 30 mole % 1,6-hexanediol, based on the total diol residues, means that the copolyester contains 30 mole % 1,6-hexanediol residues out of a total of 100 mole % diol residues. Thus, there are 30 moles of 1,6-hexanediol residues among every 100 moles of diol residues.

In one embodiment of this invention, the polymer blends of the invention comprise aliphatic-aromatic copolyesters referred to as AAPE herein) constituting component (A) of the present invention include those described in U.S. Pat. Nos. 5,661,193, 5,599,858, 5,580,911 and 5,446,079, the disclosures of which are incorporated herein by reference.

In one embodiment, a "flexible" polymer that may be used in the manufacture of the inventive polymer blends includes aliphatic-aromatic copolyesters manufactured by BASF and sold under the trade name ECOFLEX. The aliphatic-aromatic copolyesters manufactured by BASF comprise a statistical copolyester derived from 1,4-butanediol, adipic acid, and dimethylterephthalate (DMT). In some cases, a diisocyanate is used as a chain lengthener.

The copolyester composition of this invention may comprise one or more AAPE's which may be a linear, random copolyester or branched and/or chain extended copolyester comprising diol residues which contain the residues of one or more substituted or unsubstituted, linear or branched, diols selected from aliphatic diols containing 2 to about 8 carbon atoms, polyalkylene ether glycols containing 2 to 8 carbon atoms, and cycloaliphatic diols containing about 4 to about 12 carbon atoms. The substituted diols, typically, will contain 1 to about 4 substituents independently selected from halo, C6 C10 aryl, and C1 C4 alkoxy. Examples of diols which may be used include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclo-hexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, triethylene glycol, and tetraethylene glycol. Aliphatic diols are preferred in one embodiment. In another embodiment, more preferred diols comprising one or more diols selected from 1,4-butanediol; 1,3-propanediol; ethylene glycol; 1,6-hexanediol; diethylene glycol; and 1,4-cyclohexanedimethanol. In yet another embodiment, 1,4-butanediol, ethylene glycol and 1,4-cyclohexanedimethanol, singly, or in combination, are preferred, but not required.

The AAPE also comprises diacid residues which contain about 35 to about 99 mole %, preferably about 35 to about 75 mole %, more preferably, about 35 to about 65 mole %, and even more preferably, about 40 to about 60 mole %, based on the total moles of acid residues, of the residues of one or more substituted or unsubstituted, linear or branched, non-aromatic dicarboxylic acids selected from aliphatic dicarboxylic acids containing 2 to about 12 carbon atoms and cycloaliphatic dicarboxylic acids containing about 5 to about 10 carbon atoms. The substituted non-aromatic dicarboxylic acids will typically contain 1 to about 4 substituents selected from halo, C6 C10 aryl, and C1 C4 alkoxy. Non-limiting examples of aliphatic and cycloaliphatic dicarboxylic acids include malonic, succinic, glutaric, adipic, pimelic, azelaic, sebacic, fumaric, 2,2-dimethyl glutaric, suberic, 1,3-cyclopentanedicarboxylic, 1,4-cyclohexanedicarboxylic, 1,3-cyclohexanedicarboxylic, diglycolic, itaconic, maleic, and 2,5-norbomanedicarboxylic. In addition to the non-aromatic dicarboxylic acids, the AAPE comprises about 1 to about 65 mole %, preferably about 25 to about 65 mole %, more preferably, about 35 to about 65 mole %, and even more preferably, about 60 to about 40 mole %, based on the total moles of acid residues, of the residues of one or more substituted or unsubstituted aromatic dicarboxylic acids containing 6 to about 10 carbon atoms. In the case where substituted aromatic dicarboxylic acids are used, they will typically contain 1 to about 4 substituents selected from halo, C6 C10 aryl, and C1 C4 alkoxy. Non-limiting examples of aromatic dicarboxylic acids which may be used in the AAPE of our invention are terephthalic acid, isophthalic acid, salts of 5-sulfoisophthalic acid, and 2,6-naphthalenedicarboxylic acid. In another embodiment, the AAPE comprises diol residues comprising the residues of one or more of: 1,4-butanediol; 1,3-propanediol; ethylene glycol; 1,6-hexanediol; diethylene glycol; or 1,4-cyclohexanedimethanol; and diacid residues comprising (i) about 35 to about 99 mole %, preferably about 35 to about 75 mole %, more preferably, about 35 to about 65 mole %, and even more preferably, about 40 to about 60 mole %, based on the total moles of acid residues, of the residues of one or more non-aromatic dicarboxylic acids selected from glutaric acid, diglycolic acid, succinic acid, 1,4-cyclohexanedicarboxylic acid, and adipic acid (preferably, glutaric acid and adipic acid, either singly or in combination); (ii) about 5 to about 65 mole %, preferably about 25 to about 65 mole %, more preferably, about 35 to about 65 mole %, and even more preferably, about 60 to about 40 mole %, based on the total moles of acid residues, of the residues of one or more aromatic dicarboxylic acids selected from terephthalic acid and isophthalic acid. More preferably, the non-aromatic dicarboxylic acid may comprise adipic acid and the aromatic dicarboxylic acid may comprise terephthalic acid. In one embodiment, the diol will comprise about 95 to about 100 mole %, preferably 100 mole %, of 1, 4-butanediol.

In one embodiment, it is preferred that the AAPE comprise terephthalic acid in the amount of about 25 to about 65 mole %, preferably about 35 to about 65 mole %, and even more preferably, about 40 to about 60 mole %. Also, it is preferred that the AAPE comprise adipic acid in the amount of about 75 to about 35 mole %, preferably about 65 to about 35 mole %, and even more preferably, about 60 to about 40 mole %.

Other preferred compositions for the AAPE's of the present invention are those prepared from the following diols and dicarboxylic acids (or copolyester-forming equivalents thereof such as diesters) in the following mole percent, based on 100 mole percent of a diacid component and 100 mole percent of a diol component: (1) glutaric acid (about 30 to about 75%); terephthalic acid (about 25 to about 70%); 1,4-butanediol (about 90 to 100%); and modifying diol (0 about 10%); (2) succinic acid (about 30 to about 95%); terephthalic acid (about 5 to about 70%); 1,4-butanediol (about 90 to 100%); and modifying diol (0 to about 10%); and (3) adipic acid (about 30 to about 75%); terephthalic acid (about 25 to about 70%); 1,4-butanediol (about 90 to 100%); and modifying diol (0 to about 10%).

In one embodiment, one or more modifying diols are selected from 1,4-cyclohexanedimethanol, triethylene glycol, polyethylene glycol and neopentyl glycol. Some AAPE's may be linear, branched or chain extended copolyesters comprising about 50 to about 60 mole percent adipic acid residues, about 40 to about 50 mole percent terephthalic acid residues, and at least 95 mole percent 1,4-butanediol residues. Even more preferably, the adipic acid residues are present in the amount of from about 55 to about 60 mole percent, the terephthalic acid residues are present in the amount of from about 40 to about 45 mole percent, and the 1,4-butanediol residues are present in the amount of from about 95 to 100 mole percent. Such compositions have recently been commercially available under the trademark Eastar Bio.RTM. copolyester from Eastman Chemical Company, Kingsport, Tenn.

Additionally, specific examples of preferred AAPE's include a poly(tetra-methylene glutarate-co-terephthalate) containing (a) 50 mole percent glutaric acid residues, 50 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues, (b) 60 mole percent glutaric acid residues, 40 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues or (c) 40 mole percent glutaric acid residues, 60 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues; a poly(tetramethylene succinate-co-terephthalate) containing (a) 85 mole percent succinic acid residues, 15 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues or (b) 70 mole percent succinic acid residues, 30 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues; a poly(ethylene succinate-co-terephthalate) containing 70 mole percent succinic acid residues, 30 mole percent terephthalic acid residues and 100 mole percent ethylene glycol residues; and a poly(tetramethylene adipate-co-terephthalate) containing (a) 85 mole percent adipic acid residues, 15 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues or (b) 55 mole percent adipic acid residues, 45 mole percent terephthalic acid residues and 100 mole percent 1,4-butanediol residues.

The AAPE preferably comprises from about 10 to about 1,000 repeating units and preferably, from about 15 to about 600 repeating units. The AAPE preferably also has an inherent viscosity of about 0.4 to about 2.0 dL/g, more preferably about 0.7 to about 1.4, as measured at a temperature of 25.degree. C. using a concentration of 0.5 gram copolyester in 100 ml of a 60/40 by weight solution of phenol/tetrachloroethane.

In addition, "flexible" (A) polymers will preferably have a concentration in a range from about 60% to about 80% by weight of the biodegradable polymer blend, and in another embodiment, the rigid polymers (B) will preferably have a concentration in the range of about 70 to about 80% by weight, based on the total weight of the polymer blend.

Any of the biopolymers, including but not limited to the AAPE, optionally, may contain the residues of a branching agent. In one embodiment, the weight percentage ranges for the branching agent are from about 0 to about 2 weight (weight % in this invention refers to weight %), preferably about 0.1 to about 1 weight %, and most preferably about 0.1 to about 0.5 weight % based on the total weight of the AAPE. The branching agent preferably has a weight average molecular weight of about 50 to about 5000, more preferably about 92 to about 3000, and a functionality of about 3 to about 6. For example, the branching agent may be the esterified residue of a polyol having 3 to 6 hydroxyl groups, a polycarboxylic acid having 3 or 4 carboxyl groups (or ester-forming equivalent groups ) or a hydroxy acid having a total of 3 to 6 hydroxyl and carboxyl groups.

Representative low molecular weight polyols that may be employed as branching agents include glycerol, trimethylolpropane, trimethylolethane, polyethertriols, glycerol, 1,2,4-butanetriol, pentaerythritol, 1,2,6-hexanetriol, sorbitol, 1,1,4,4,-tetrakis (hydroxymethyl) cyclohexane, tris(2-hydroxyethyl) isocyanurate, and dipentaerythritol. Particular branching agent examples of higher molecular weight polyols (MW 400-3000) are triols derived by condensing alkylene oxides having 2 to 3 carbons, such as ethylene oxide and propylene oxide with polyol initiators. Representative polycarboxylic acids that may be used as branching agents include hemimellitic acid, trimellitic (1,2,4-benzenetricarboxylic) acid and anhydride, trimesic (1,3,5-benzenetricarboxylic) acid, pyromellitic acid and anhydride, benzenetetracarboxylic acid, benzophenone tetracarboxylic acid, 1,1,2,2-ethane-tetracarboxylic acid, 1,1,2-ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, and 1,2,3,4-cyclopentanetetracarboxylic acid. Although the acids may be used as such, preferably they are used in the form of their lower alkyl esters or their cyclic anhydrides in those instances where cyclic anhydrides can be formed. Representative hydroxy acids as branching agents include malic acid, citric acid, tartaric acid, 3-hydroxyglutaric acid, mucic acid, trihydroxyglutaric acid, 4-carboxyphthalic anhydride, hydroxyisophthalic acid, and 4-(beta-hydroxyethyl)phthalic acid. Such hydroxy acids contain a combination of 3 or more hydroxyl and carboxyl groups. Especially preferred branching agents include trimellitic acid, trimesic acid, pentaerythritol, trimethylol propane and 1,2,4-butanetriol.

The aliphatic-aromatic polyesters of the invention also may comprise one or more ion-containing monomers to increase their melt viscosity. It is preferred that the ion-containing monomer is selected from salts of sulfoisophthalic acid or a derivative thereof. A typical example of this type of monomer is sodiosulfoisophthalic acid or the dimethyl ester of sodiosulfoisophthalic. The preferred concentration range for ion-containing monomers is about 0.3 to about 5.0 mole %, and, more preferably, about 0.3 to about 2.0 mole %, based on the total moles of acid residues.

One example of a branched AAPE of the present invention is poly-(tetramethylene adipate-co-terephthalate) containing 100 mole percent 1,4-butanediol residues, 43 mole percent terephthalic acid residues and 57 mole percent adipic acid residues and branched with about 0.5 weight percent pentaerythritol. This AAPE may be produced by the transesterification and polycondensation of dimethyl adipate, dimethyl terephthalate, pentaerythritol and 1,4-butanediol. The AAPE may be prepared by any conventional method known in the art such as heating the monomers at 190.degree. C. for 1 hour, 200.degree. C. for 2 hours, 210.degree. C. for 1 hour, then at 250.degree. C. for 1.5 hours under vacuum in the presence of 100 ppm of Ti present initially as titanium tetraisopropoxide.

Another example of a branched AAPE is poly(tetramethylene adipate-co-terephthalate) containing 100 mole percent 1,4-butanediol residues, 43 mole percent terephthalic acid residues and 57 mole percent adipic acid residues and branched with 0.3 weight percent pyromellitic dianhydride. This AAPE is produced via reactive extrusion of linear poly (tetramethylene adipate-co-terephthalate) with pyromellitic dianhydride using an extruder.

The AAPE of the instant invention also may comprise from 0 to about 5 weight %, and in one embodiment, from 0.1 to 5 weight %, based on the total weight of the composition, of one or more chain extenders. Exemplary chain extenders are divinyl ethers such as those disclosed in U.S. Pat. No. 5,817,721 or diisocyanates such as, for example, those disclosed in U.S. Pat. No. 6,303,677. Representative divinyl ethers are 1,4-butanediol divinyl ether, 1,5-hexanediol divinyl ether and 1,4-cyclohexandimethanol divinyl ether.

Representative diisocyanates are toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, 2,4'-diphenylmethane diisocyanate, naphthylene-1,5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and methylenebis(2-isocyanatocyclohexane). The preferred diisocyanate is hexamethylene diisocyanate. The weight percent ranges are preferably about 0.3 to about 3.5 wt %, based on the total weight percent of the AAPE, and most preferably about 0.5 to about 2.5 wt %. It is also possible in principle to employ trifunctional isocyanate compounds which may contain isocyanurate and/or biurea groups with a functionality of not less than three, or to replace the diisocyanate compounds partially by tri-or polyisocyanates.

The AAPE's of the instant invention are readily prepared from the appropriate dicarboxylic acids, esters, anhydrides, or sal