Expanded articles of biodegradable plastics materials and a method for their production

• US 5,288,765 A
• Filed: 11/04/1992
• Issued: 02/22/1994
• Est. Priority Date: 08/03/1989
• Status: Expired due to Term

• Current Assignee: Spherilene SRL
• Original Assignee: Spherilene SRL
• Inventors: Del Giudice, Luciano, Bastioli, Catia, Rallis, Angelos, Bellotti, Vittorio, Lombi, Roberto
• Primary Examiner(s): Michl, Paul R.
• Assistant Examiner(s): SZEKELY, PETER A
• Application Number:
  US07/972,875
• Time in Patent Office: 475 Days
• Field of Search: 521/84.1, 524/47, 524/52, 524/53, 106/210, 106/211, 106/212, 106/213, 106/214
• US Class Current: 521/84.1
• CPC Class Codes: C08J 2303/02 Starch; Degradation products thereof, e.g. dextrin
• CPC Class Codes: C08J 2403/00 Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
• CPC Class Codes: C08J 9/0061 characterized by the use of several polymeric components
• CPC Class Codes: C08L 2205/03 containing three or more polymers in a blend
• CPC Class Codes: C08L 23/0846 Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
• CPC Class Codes: C08L 23/0861 Saponified vinylacetate
• CPC Class Codes: C08L 23/0869 Acids or derivatives thereof
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: C08L 2666/26 Natural polymers, natural resins or derivatives thereof according to C08L1/00 - C08L5/00, C08L89/00, C08L93/00, C08L97/00 or C08L99/00
• CPC Class Codes: C08L 29/04 Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• CPC Class Codes: C08L 3/02 Starch; Degradation products thereof, e.g. dextrin
• CPC Class Codes: Y10S 521/916 Cellular product having enhanced degradability

Abstract

Expanded articles of biodegradable plastics are produced by the extrusion of a composition including starch, a polymer compatible with starch, in particular, an ethylene-acrylic acid copolymer and/or ethylene-vinyl alcohol copolymer, and an expanding agent. Preferably use is made of sodium bicarbonate as expanding agent in the presence of a polymeric acid.

Claims

1. Expanded articles of biodegradable plastics material comprising a material including starch and a synthetic polymer selected from the group consisting of ethylene-vinyl alcohol, ethylene-acrylic acid, and mixtures thereof, said articles having a closed pore structure and a density of from 0.1 to 0.3 g/cm³.

2. Expanded articles according to claim 1, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of from 10 to 40% by weight and a melt flow index of from 6 to 20.

3. Expanded articles according to claim 1, wherein the ethylene-acrylic acid copolymer is produced by the copolymerization of a mixture including from 3 to 30% by weight of acrylic acid and from 97 to 70% of ethylene.

4. Expanded articles according to claim 1, wherein the starch and the copolymer are in a weight ratio of from 1:

4 to 4;

1.

5. Expanded articles according to claim 1, further including urea and/or a high-boiling plasticizer.

6. Expanded articles according to claim 1, further including a polymeric acid selected from the group consisting of polyacrylic acid, and ethylene-acrylic acid-vinyl alcohol copolymer.

7. Expanded articles according to claim 1, including a filler consisting of granular pyrolized foamed starch or hollow glass microspheres.

8. A method for the production of expanded articles of biodegradable plastics material, comprising the step of extruding a composition including starch and a synthetic polymer selected from the group consisting of ethylene-vinyl alcohol and ethylene-acrylic acid in the presence of a polymeric acid and sodium bicarbonate as the expanding agent.

9. A method according to claim 8, wherein the synthetic polymer is ethylene-vinyl alcohol and the polymeric acid is selected from the group consisting of polyacrylic acid, ethylene-acrylic acid, and ethylene-acrylic acid-vinyl alcohol copolymers.

10. A method according to claim 8 in which the copolymer is produced by a copolymerization of a mixture including from 3 to 30% by weight of acrylic acid and from 97 to 70% of ethylene.

11. A method according to claim 8 wherein the ethylene vinyl alcohol copolymer has an ethylene content of from 10 to 40% by weight and a melt flow index of from 6 to 20.

12. A method according to claim 8 wherein the quantity of sodium bicarbonate added is equal to at least 0.3 equivalents of the bicarbonate for each equivalent weight of free carboxyl groups in the polymeric acid.

13. A method according to claim 8, in which the starch and the copolymer are in a ratio of from 4:

1 to 1;

4.

14. A method according to claim 8, in which the composition includes a quantity of urea of up to 30% by weight of the total weight of the composition and/or a high-boiling plasticizer.

15. A method according to claim 8, wherein the synthetic polymer is ethylene-acrylic acid and the polymeric acid is the ethylene-acrylic acid synthetic polymer and wherein the composition is mixed in an extruder barrel heated to a temperature of between 100°

C. and the temperature of thermal decomposition of the bicarbonate.

16. A method according to claim 8, in which the composition includes a quantity of water of from 10 to 25% by weight of the weight of the dry starch.

17. A method according to claim 8, wherein the synthetic polymer is ethylene-acrylic acid and the polymeric acid is selected from the group consisting of polyacrylic acid, the ethylene-acrylic acid synthetic polymer and ethylene-acrylic acid-vinyl alcohol copolymers.