Polymer compositions for the production of articles of biodegradable plastics material and methods of their preparation

• US 5,258,430 A
• Filed: 03/27/1991
• Issued: 11/02/1993
• Est. Priority Date: 08/07/1989
• Status: Expired due to Fees

• Current Assignee: Novamont S.p.a.
• Original Assignee: Novamont S.p.a.
• Inventors: Del Guidice, Luciano, Bastioli, Catia, Lombi, Roberto, Bellotti, Vittorio
• Primary Examiner(s): Michl, Paul R.
• Assistant Examiner(s): DEWITT, LAVONDA R
• Application Number:
  US07/671,766
• Time in Patent Office: 951 Days
• Field of Search: 523/128, 524/52, 524/53, 525/61, 525/344, 525/345, 525/328.4, 525/385
• US Class Current: 524/52
• CPC Class Codes: C08L 23/0861 Saponified vinylacetate
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• 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

Abstract

Polymer compositions useful for the production of articles of biodegradable plastics material with improved biodegradability include destructed starch and a polymer selected from the group consisting of ethylene-vinyl alcohol, polyvinyl alcohol and mixtures thereof wherein at least a portion of the said polymer is modified by the substitution of from 0.1 to 5 molar % of the functional alcohol groups in the polymer chain by X groups in which X is an oxo or an alkyl carbonyl group in which the alkyl group contains from 1 to 4 carbon atoms.

Claims

1. A polymer composition useful for the production of articles of biodegradable plastics material, including a destructured starch and a synthetic polymer selected from the group consisting of ethylene-vinyl alcohol, and polyvinyl alcohol and mixtures thereof, wherein at least a portion of said polymers is modified by the substitution of from 0.1 to 5 molar % of the functional alcohol groups in the polymer chain by X groups in which X is an oxo group or an alkyl carbonyl group in which the alkyl group contains from 1 to 4 carbon atoms.

2. A composition according to claim 1, in which the modified polymer is produced by the reaction of the corresponding polymer with hydrogen peroxide and persulfuric acid.

3. A composition according to claim 1, in which the modified polymer is produced by the reaction of the corresponding polymer with hypochlorite and acetic acid.

4. A composition according to claim 1, including an ethylene-vinyl alcohol copolymer with an ethylene content of from 10 to 40% by weight.

5. A composition according to claim 1, in which the modified polymer is produced by the synthesis of ethylene-vinyl acetate with an ethylene content of from 10 to 50% by weight in the presence of monomers of the ##STR3## type in which R is a C₁ -C₄ alkyl group, and subsequent basic hydrolysis.

6. A composition according to claim 1, wherein the modified polymer is obtained by ozonolysis of polyvinyl alcohol or ethylene-vinyl alcohol copolymers having an ethylene content of from 10 to 40% wt.

7. A composition according to claim 1, wherein the modified polymer amounts to 10-50% wt of the synthetic polymer in the composition.

8. Articles in the form of films made from a polymer composition according to claim 1.

9. Moulded articles made from a polymer composition according to claim 1.

10. A method for the preparation of a polymer composition usable for the production of articles of biodegradable plastics material, comprising the step of:

mixing starch and a synthetic polymer selected from the group consisting of ethylene-vinyl alcohol, polyvinyl alcohol and mixtures thereof, wherein at least a portion of said polymers is modified by the substitution of from 0.1 to 5 molar % of the functional alcohol groups in the polymer chain by X groups in which X is an oxo group or an alkyl carbonyl group in which the alkyl group contains from 1 to 4 carbon atoms, wherein the weight ratio between the starch and total amount of synthetic polymer is of from 19;

1 to 1;

19, with a quantity of a high-boiling plasticizer of from 0.05 to 100% of the weight of the starch, optional in the presence of a destructuring agent selected from the group consisting of urea, alkaline-earth and alkali metal hydroxides, in an extruder which is heated to a temperature and for a period of time sufficient to bring about the destructuring of the starch.

11. A method according to claim 10, wherein the modified polymer is an ethylene/vinyl alcohol copolymer and said copolymer is mixed within the extruder heated to a temperature between 120°

and 170°

C. with a destructured-starch-based component which is prepared beforehand by mixing starch in an extruder with a quantity of a high-boiling plasticizer of from 0.05 to 100% of the weight of the starch, in the presence of a quantity of a destructuring agent selected from the group consisting of urea, alkaline or alkaline-earth hydroxides, and mixtures thereof effective for causing the destructuring of the starch at a temperature below the boiling of the plasticizer and between 120° and

170°

C.

12. A method according to claim 10, in which the high-boiling plasticizer is selected from the group consisting of glycerine, polyethylene glycol, ethylene glycol, propylene glycol, sorbitol, and mixtures thereof.

13. A method according to claim 10, in which the destructuring agent is added in a quantity of from 2 to 20% of the weight of the starch component, in which the mixing operation is carried out with the addition of a quantity of water of from 0.05 to 100% of the weight of the starch component, and in which the water concentration is reduced to a value no greater than 6% of the weight of the whole composition.

14. A method according to claim 11, also including the addition of ammonia.

15. A method according to claim 10, in which the modified polymer is produced by the reaction of the corresponding polymer with hydrogen peroxide and persulfuric acid.

16. A method according to claim 10, in which the modified polymer is produced by the reaction of the corresponding polymer with hypocholorite and acetic acid.

17. A method according to claim 11, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of from 10 to 40% by weight.

18. A method according to claim 11, in which the modified polymer is produced by the synthesis of ethylene-vinyl acetate with an ethylene content of from 10 to 50% by weight in the presence of monomers of the ##STR4## type in which R is a C₁ -C₄ alkyl group, and subsequent basic hydrolysis.