Methods of making and using a superabsorbent polymer product including a bioactive, growth-promoting additive

• US 7,423,090 B2
• Filed: 12/15/2004
• Issued: 09/09/2008
• Est. Priority Date: 12/15/2003
• Status: Active Grant

• Current Assignee: UPL Mauritius Limited
• Original Assignee: Absorbent Technologies, Inc.
• Inventors: Savich, Milan H., Doane, Steven William, Doane, William McKee
• Primary Examiner(s): Jagannathan; Vasu
• Assistant Examiner(s): Mesh; Gennadiy
• Application Number:
  US11/013,664
• Publication Number:
  US 20050159315A1
• Time in Patent Office: 1,364 Days
• Field of Search: None
• US Class Current: 525/242
• CPC Class Codes: A01N 25/10 Macromolecular compounds
• CPC Class Codes: C05G 3/80 Soil conditioners
• CPC Class Codes: C05G 5/40 Fertilisers incorporated into a matrix
• CPC Class Codes: C08F 251/00 Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

A method of and a product formed by entrapping a bioactive, growth-promoting additive in a starch matrix to form a starch-based, superabsorbent polymer product for use in agricultural applications involves (1) graft polymerizing a monomer and a starch to form a starch graft copolymer including a starch matrix; (2) isolating the starch graft copolymer; (3) forming particles of starch graft copolymer; and (4) adding a bioactive, growth-promoting additive such that at least some of the bioactive, growth-promoting additive is entrapped by the starch matrix. Following placement of the starch-based SAP including a bioactive, growth-promoting additive in proximity to a plant, root, seed, or seedling, growth of the plant, root, seed, or seedling is promoted because availability of beneficial nutrients is increased.

Claims

1. A method of forming a superabsorbent polymer product including a bioactive, growth-promoting additive for use in agricultural applications, comprising:

combining a grafting reagent and a starch such that the grafting reagent graft polymerizes onto the starch to form a mixture including starch graft copolymers, the starch graft copolymers forming a starch matrix;

isolating the starch graft copolymers;

forming particles including the starch graft copolymers, the particles sized between about 8 and 25 mesh, wherein forming particles sized between about 8 and 25 mesh comprises extruding the starch graft copolymers into strands and granularizing the strands to form granular, non-powder starch graft copolymer particles sized between about 8 and 25 mesh isolated through screening;

applying an alcohol to the strands to reduce tackiness of the extruded strands of the starch graft copolymers, the alcohol chosen from methanol, ethanol, propanol or isopropanol; and

adding the bioactive, growth-promoting additive while combining the grafting reagent and the starch to form the starch graft copolymers, such that at least some of the bioactive, growth-promoting additive is entrapped by the starch matrix.

2. The method of claim 1, further comprising:

adding a cross-linking agent to the mixture to form cross-linked starch graft copolymers, the cross-linking starch graft copolymers formed prior to extruding the starch graft copolymers into strands; and

neutralizing the cross-linked starch graft copolymers.

3. The method of claim 2, in which the cross-linking agent is selected from a group consisting essentially of glycerides, diepoxides, diglycidyls, cyclohexadiamide, methylene bis-acrylamide, bis-hydroxyalkylamides, bis-hydroxypropyl adipamide, formaldehydes, urea-formaldehyde, melamine-formaldehyde resins, isocyanates, di-isocyanates, tri-isocyanates, epoxy resins, self-cross-linking polymers, derivatives thereof, and mixtures thereof.

4. The method of claim 1, further comprising:

saponifying the mixture.

5. The method of claim 1, in which combining the grafting reagent and the starch involves graft polymerizing a monomer onto the starch in the presence of an initiator.

6. The method of claim 5, in which the monomer is selected from a group consisting essentially of acrylonitrile, acrylic acid, acrylamide, 2-acrylonitrile-2-methyl-propanesulfonic acid, methacrylamide, methacrylic acid, vinyl sulfonic acid, ethyl acrylate, derivatives thereof, and mixtures thereof.

7. The method of claim 5, in which the starch and the monomer are present in a molar ratio of between about 1:

1 and about 1;

6.

8. The method of claim 5, in which the initiator is a cerium salt.

9. The method of claim 1, in which the starch is selected from a group consisting essentially of pure starches, flours, meals, and mixtures thereof.

10. The method of claim 1, in which the starch is a gelatinized starch.

11. The method of claim 1, in which forming the particles involves precipitating the starch graft copolymers by one of (1) adding to the mixture a sufficient amount of an alcohol to cause the starch graft copolymers to form a precipitate, and (2) mechanically manipulating the mixture such that it forms a precipitate.

12. The method of claim 1, in which forming the particles involves drying the mixture.

13. The method of claim 1, in which a ratio of bioactive, growth-promoting additive to starch is between about 0.5 oz.:

1 lb. and about 1.5 oz.;

1 lb.

14. The method of claim 1, in which the bioactive, growth-promoting additive is selected from a group consisting essentially of fertilizers, pesticides, bioactive materials, plant-growth hormones, plant-growth regulators, soil-based nutrients, derivatives thereof, and mixtures thereof.

15. The method of claim 1, further comprising:

adding a material selected from a group consisting essentially of fillers, absorbents, carriers, surfactants, derivatives thereof, and mixtures thereof.

16. The method of claim 1, further comprising:

applying the superabsorbent polymer product including the bioactive, growth-promoting additive to one of (1) a growing substrate in proximity to one of a plant, seedling, root, and seed and (2) to one of a plant, a seedling, a root, and a seed.

33. The method of claim 1, wherein extruding the starch graft copolymers into strands comprises extruding the starch graft copolymers into strands having a diameter of between about 1/16 inch to ¼

inch.

17. A method of forming a superabsorbent polymer product including a bioactive, growth-promoting additive for use in agricultural applications, comprising:

combining a monomer and a starch in the presence of an initiator such that the monomer graft polymerizes onto the starch to form a mixture including starch graft copolymers, the starch graft copolymers forming a starch matrix;

saponifying the mixture;

precipitating the starch graft copolymers from the saponified mixture to form particles of superabsorbent polymer product sized for use in agricultural applications; and

adding the bioactive, growth-promoting additive while precipitating the starch graft copolymers, such that at least a portion of the bioactive, growth-promoting additive is entrapped by the starch matrix;

wherein forming particles of superabsorbent polymer product comprises forcing the starch graft copolymer into strands through a die plate having holes disposed therein with a diameter of between about 1/16 inch to ¼

inch, applying an alcohol to the strands to reduce tackiness of the strands of the starch graft copolymers, the alcohol chosen from methanol, ethanol, propanol or isopropanol, the strands subsequently being granularized to form granular, non-powder starch graft copolymer particles sized between about 8 and 25 mesh isolated through screening.

18. The method of claim 17, in which the monomer is selected from a group consisting essentially of acrylonitrile, acrylic acid, acrylamide, 2-acrylonitrile-2-methyl-propanesulfonic acid, methacrylamide, methacrylic acid, vinyl sulfonic acid, ethyl acrylate, derivatives thereof, and mixtures thereof.

19. The method of claim 17, in which the starch and the monomer are present in a molar ratio of between about 1:

1 and about 1;

6.

20. The method of claim 17, in which the initiator is a cerium salt.

21. The method of claim 17, in which the starch is selected from a group consisting essentially of pure starches, flours, meals, and mixtures thereof.

22. The method of claim 17, in which precipitating the starch graft copolymers involves at least one of (1) adding a sufficient amount of an alcohol to the saponified mixture to cause it to form a precipitate and (2) mechanically manipulating the saponified mixture such that it forms a precipitate.

23. The method of claim 17, in which the bioactive, growth-promoting additive is selected from a group consisting essentially of fertilizers, pesticides, bioactive materials, plant-growth regulators, plant-growth hormones, soil-based nutrients, derivatives thereof, and mixtures thereof.

24. The method of claim 17, further comprising:

applying the particles of superabsorbent polymer product including the bioactive, growth-promoting additive to one of (1) a growing substrate in proximity to one of a plant, seedling, root, and seed and (2) to one of a plant, a seedling, a root, and a seed.

25. A method of forming a superabsorbent polymer product including a bioactive, growth-promoting additive for use in agricultural applications, comprising:

combining a monomer and a starch in the presence of an initiator such that the monomer graft polymerizes onto the starch to form a mixture including starch graft copolymers, the starch graft copolymers forming a starch matrix;

adding a cross-linking agent to the mixture to form cross-linked starch graft copolymers;

neutralizing the mixture;

forming particles of the superabsorbent polymer product for use in agricultural applications, the particles being sized between about 8 and 25 mesh, wherein forming particles sized between about 8 and 25 mesh comprises extruding the cross-linked starch graft copolymers into strands subsequent to forming cross-linked starch graft copolymers;

applying an alcohol to the strands to reduce tackiness of the extruded strands of the starch graft copolymers, the alcohol chosen from methanol, ethanol, propanol or isopropanol, and granularizing the strands to form granular, non-powder starch graft copolymer particles sized between about 8 and 25 mesh isolated through screening; and

adding the bioactive, growth-promoting additive to the starch graft copolymers after forming the superabsorbent polymer particles for use in agricultural applications, such that at least a portion of the bioactive, growth-promoting additive is entrapped by the starch matrix.

26. The method of claim 25, in which the monomer is selected from a group consisting essentially of acrylonitrile, acrylic acid, acrylamide, 2-acrylonitrile-2-methyl-propanesulfonic acid, methacrylamide, methacrylic acid, vinyl sulfonic acid, ethyl acrylate, derivatives thereof, and mixtures thereof.

27. The method of claim 25, in which the starch and the monomer are present in a molar ratio of between about 1:

1 and about 1;

6.

28. The method of claim 25, in which the initiator is a cerium salt.

29. The method of claim 25, in which the starch is selected from a group consisting essentially of pure starches, flours, meals, and mixtures thereof.

30. The method of claim 25, in which forming particles of superabsorbent polymer product involves at least one of (1) adding a sufficient amount of an alcohol to the mixture to cause it to form a precipitate and (2) mechanically manipulating the mixture such that it forms a precipitate.

31. The method of claim 25, in which the bioactive, growth-promoting additive is selected from a group consisting essentially of fertilizers, pesticides, bioactive materials, plant-growth hormones, plant-growth regulators, soil-based nutrients, derivatives thereof, and mixtures thereof.

32. The method of claim 25, further comprising:

applying the particles of superabsorbent polymer product including the bioactive, growth-promoting additive to one of (1) a growing substrate in proximity to one of a plant, seedling, root, and seed and (2) to one of a plant, a seedling, a root, and a seed.

34. The method of claim 25, wherein extruding the neutralized mixture into strands comprises extruding the cross-linked starch graft copolymers into strands having a diameter of between about 1/16 inch to ¼

inch.