Article comprising polylactic acid layers and process of making the same
The invention concerns an article comprising layers of polylactic acid and a process of making the same. A layer is of foamed polylactic acid. A layer preferably comprises an impact modifier. The article can be used in the field of packaging.
1. An article comprising a multilayer plastic material comprising:
A) at least one layer A of a non-foamed polylactic acid material A comprising polylactic acid and an impact modifier,
B) at least one layer B of a foamed polylactic acid material B comprising polylactic acid and being substantially free of: (i) expanded microspheres and (ii) impact modifier.
2. The article according to claim 1 , wherein the material B contains at least one adduct of a chemical foaming agent.
3. The article according to claim 2 , wherein the chemical foaming agent comprises at least one of citric acid or sodium bicarbonate.
4. The article according to claim 2 , wherein the adduct is at least one of sodium citrate, cis-aconitic acid, trans-aconitic acid, cis-aconitic anhydride, trans-aconitic anhydride, itaconic anhydride and citraconic anhydride, or a mixture thereof.
5. The article according to claim 1 , wherein the material B has a density of from 0.5 to 1.2 g/cm 3 .
6. The article according to claim 1 , having a density of from 0.75 to 1.2 g/cm 3 .
7. The article according to claim 1 , wherein the impact modifier is a core/shell polymeric compound, an alkyl sulfonate compound, Acetyl TriButyl citrate, Triethyl citrate, Polybutylene Succinate, PVA or ethylene vinyl acetate.
8. The article according to claim 1 , wherein the material A comprises from 0.01% to 30% by weight of the impact modifier.
9. The article according to claim 1 , comprising at least 19% by weight of the at least one layer B.
10. The article according to claim 1 , wherein the article is a three-layer material (first layer A)-(layer B)-(second layer A).
11. The article according to claim 10 , wherein amounts of the layers by distance along an article thickness correspond to the following profile:
the first layer A: from 5 to 45%,
the layer B: from 10 to 90%,
the second layer A: from 5 to 45%,
the total being 100% of the article thickness.
12. The article according to claim 1 , wherein the article is a plastic sheet.
13. The article according to claim 12 , wherein the plastic sheet has a thickness of from 0.5 mm to 2 mm.
14. The article according to claim 1 , wherein the article is a container.
15. The article according to claim 14 , wherein the container is a thermoformed article.
16. The article according to claim 14 , wherein the article is selected from the group consisting of a bottle and a thermoformed cup.
17. A process of making an article according to claim 1 , comprising a step of mixing polylactic acid and a chemical foaming agent to form a mixture, and a step of heating the mixture to generate a gas compound from the chemical foaming agent.
18. The process according to claim 17 , wherein the chemical foaming agent is at least one of citric acid or sodium bicarbonate, and wherein the gas compound comprises CO 2 .
19. The process according to claim 17 , wherein heating is performed at a temperature of from 150 to 250° C.
20. The process according to claim 17 , wherein heating is performed during an extrusion step to form the at least one layer B.
21. The process according to claim 17 , wherein the at least one layer A and the at least one layer B are co-extruded.
22. The process according to claim 17 , wherein the article is a thermoformed container obtained by:
1) co-extruding the at least one layer A and the at least one layer B to obtain a multilayer plastic sheet, and
2) thermoforming the plastic sheet to obtain the thermoformed container.