Polyhydroalkanoate composition exhibiting improved impact resistance

1. A composition comprising polyhydroxyalkanoic acid (PHA) and further comprising:

(A) an elastomeric compound of core-shell type; and

(B) an olefinic copolymer comprising an ethylenic monomer bearing an epoxy function;

wherein the mass ratio (A)/(B) is within the range from 90/10 to 10/90.

2. The composition as claimed in claim 1 , wherein the ethylenic monomer bearing an epoxy function is glycidyl (meth)acrylate.

3. The composition as claimed in claim 1 , wherein (B) is a copolymer of ethylene, of glycidyl methacrylate and optionally of an alkyl (meth)acrylate in which the alkyl chain comprises from 1 to 30 carbon atoms.

4. The composition as claimed in claim 1 , further comprising an additional olefinic polymer (C) other than the olefinic copolymer comprising an ethylenic monomer bearing an epoxy function.

5. The composition as claimed in claim 4 , in which the additional olefinic polymer (C) is a copolymer of ethylene and of an alkyl (meth)acrylate, a copolymer of ethylene and a carboxylic acid vinyl ester, a copolymer of ethylene and of a (meth)acrylic acid or an ionomer.

6. The composition as claimed in claim 4 , in which the mass ratio (B)/(C) is within the range from 90/10 to 10/90.

7. The composition as claimed in claim 1 , in which the amount of ((A)+(B)) is within the range from 1% to 30% by mass of the total composition.

8. The composition as claimed in claim 1 , in which the amount, in polymerized form, of ethylenic monomer comprising an epoxy function is within the range from 0.01% to 2% by mass of the total composition.

9. The composition as claimed in claim 1 , in which the polymer of the core of the core-shell compound (A) has a glass transition temperature of less than 20° C. and the polymer of the shell has a glass transition temperature of greater than 20° C.

10. The composition as claimed in claim 1 , in which the mass amount of core is within the range from 60% to 95% of the total mass of the core-shell compound.

11. The composition as claimed in claim 1 , in which the size of the elastomeric compound of core-shell type is between 50 and 600 nm.

12. The composition as claimed in claim 1 , in which the PHA is chosen from polylactic acid (PLA) and polyglycolic acid (PGA).

13. A process for preparing a composition comprising polyhydroxyalkanoic acid (PHA) and further comprising:

(A) an elastomeric compound of core-shell type; and

(B) an olefinic copolymer comprising an ethylenic monomer bearing an epoxy function;

wherein the mass ratio (A)/(B) is within the range from 90/10 to 10/90, the process comprising a step wherein the mixture of PHA, of (A), and of (B) is prepared by blending or extrusion.

14. A process for preparing a composition comprising polyhydroxyalkanoic acid (PHA) and further comprising:

(A) an elastomeric compound of core-shell type; and

(B) an olefinic copolymer comprising an ethylenic monomer bearing an epoxy function;

wherein the mass ratio (A)/(B) is within the range from 90/10 to 10/90;

wherein the process comprises:

in a first step, preparing a mixture of (A), (B) and optionally an additional olefinic polymer (C) other than the olefinic copolymer comprising an ethylenic monomer bearing an epoxy function to form an impact modifier, and then

in a second step, preparing a mixture of the impact modifier obtained from the first step with PHA.

15. A part or object comprising a composition comprising polyhydroxyalkanoic acid (PHA) and further comprising:

(A) an elastomeric compound of core-shell type; and

(B) an olefinic copolymer comprising an ethylenic monomer bearing an epoxy function;

wherein the mass ratio (A)/(B) is within the range from 90/10 to 10/90.

16. A process for manufacturing a part or object comprising a composition comprising polyhydroxyalkanoic acid (PHA) and further comprising:

(A) an elastomeric compound of core-shell type; and

(B) an olefinic copolymer comprising an ethylenic monomer bearing an epoxy function;

wherein the mass ratio (A)/(B) is within the range from 90/10 to 10/90, wherein the process comprises a step of forming the composition and optionally undergoing an annealing step.

17. The composition as claimed in claim 4 , wherein the additional olefinic polymer (C) is a copolymer of ethylene and an alkyl acrylate with an alkyl chain ranging from 1 to 20.