Degradable starch-based agricultural mulch film

Claim 1

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.

Claim 15

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).

Claim 16

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).

Claim 27

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° to 100° C. for about 2 hr., then adding about 0.4 part of NH 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).

Claim 28

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° to 100° C. for about 2 hr., then adding about 0.4 part of NH 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).