Degradable starch-based agricultural mulch film
AssigneeThe United States of America as represented by the Secretary of Agriculture
InventorsFelix H. Otey, Arthur M. Mark
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Abstract
Disclosed herein are plastic film compositions for agricultural mulch which will withstand outdoor weathering conditions for a desired time and then rapidly disintegrate. The film composition comprises starch, poly(vinyl alcohol), glycerol, and a water-resistant coating.
Claims24
A self-supporting, degradable, agricultural mulch film comprising from 1 to 4 parts of polyvinyl alcohol having a degree of hydrolysis of from 85 to 100%, 8 parts of starch, and from 1 to 5 parts of glycerol;
- said film being completely coated with from 5 to 20% of a water-resistant coating composition comprising a mixture of from 0.1 to 0.2 parts of a polyol-toluene-diisocyanate prepolymer containing free isocyanate groups and 1 part of polyvinylidene chloride-acrylonitrile copolymer or 1 part of polyvinyl chloride resin containing a plasticizing amount of a suitable plasticizer, all parts by weight.
A self-supporting, degradable, agricultural mulch film comprising from 2 to 3 parts of polyvinyl alcohol having a degree of hydrolysis of from 98 to 100% and a degree of polymerization of from 1000 to 1700 structural units, 8 parts of starch, from 2 to 4 parts of glycerol, about 0.2 part formaldehyde, about 0.4 part NH.sub.4 Cl, and about 0.1 part of polyethylene sorbitan monooleate;
- said film being completely coated with from 8 to 18% by weight of a water-resistant composition comprising a mixture of from 0.1 to 0.2 part of castor oil-toluene-diisocyanate prepolymer containing from 0.1 to 2 equivalents of excess --NCO groups, 0.01 to 0.03 parts dibutyltin dilaurate, and 1 part polyvinylidene chloride-acrylonitrile copolymer or 1 part polyvinyl chloride containing 20 to 50% by weight dioctyl phthalate.
A method of preparing a self-supporting, degradable, agricultural mulch film comprising the steps of:
- a. reacting, in an aqueous suspension, from 1 to 4 parts of polyvinyl alcohol having a degree of hydrolysis of from 85 to 100%, 8 parts of starch, and from 1 to 5 parts of glycerol;
- b. casting a film from the reaction mixture resulting from step (a);
- c. drying the film resulting from step (b);
- d. reacting a suitable polyol with toluene-diisocyanate in amounts such that the --NCO groups of said toluene-diisocyanate are from 0.1 to 2 equivalents in excess of the amount of --OH groups of said polyol;
- e. preparing a solution containing a suitable solvent, from 0.1 to 0.2 parts of the reaction mixture resulting from step (d), and 1 part polyvinylidene chloride-acrylonitrile copolymer or 1 part polyvinyl chloride containing a plasticizing amount of a suitable plasticizer;
- f. coating the dried film resulting from step (c) with the solution resulting from step (e) in amounts sufficient to provide, after removal of the solvent, a water-resistant coating which is 5 to 20% of the total weight of said self-supporting, degradable, agricultural mulch film;
- and
- g. removing the solvent from the product resulting from step (f).
A method of preparing a self-supporting, degradable, agricultural mulch film comprising the steps of:
- a. reacting, in an aqueous suspension, from 2 to 3 parts of polyvinyl alcohol having a degree of hydrolysis of from 98 to 100% and a degree of polymerization of from 1000 to 1700 structural units, 8 parts of starch, 2 to 4 parts of glycerol, about 0.2 part of formaldehyde, and about 0.1 part of polyethylene sorbitan monooleate at 90.degree. to 100.degree. C. for about 2 hr., then adding about 0.4 part of NH.sub.4 Cl and reacting for an additional 10 min.;
- b. casting a film from the reaction mixture resulting from step (a);
- c. drying the film resulting from step (b);
- d. reacting castor oil with toluene-diisocyanate in amounts such that the --NCO groups of said toluene-diisocyanate are about 0.5 equivalents in excess of the amount of --OH groups of said castor oil;
- e. preparing a solution of methyl ethyl ketone and 0.1 to 0.2 parts of the reaction mixture resulting from step (d), from 0.1 to 0.3 parts dibutyltin dilaurate, and 1 part per polyvinylidene chloride-acrylonitrile copolymer or 1 part polyvinyl chloride containing from 20 to 50% by weight dioctyl phthalate;
- and
- f. coating the dried film resulting from step (c) with the solution resulting from step (e) in amounts sufficient to provide, after removal of the solvent, a water-resistant coating which is 5 to 20% of the total weight of said self-supporting, degradable, agricultural mulch film;
- and
- g. removing the solvent from the product resulting from step (f).
Dependencies are inferred from the claim text.