Patent Application
20120231171
The present invention generally relates to a composition and a method of applying the composition onto hydrophobic surfaces and retaining the composition on these surfaces. More specifically, the present invention relates to a composition and a method of applying the composition onto materials that impact plant growth such as plant seeds, soil, plant roots and mulch. The composition coats the material surfaces and helps lock in moisture and nutrients that are beneficial to plant growth.
Plant growth requires the presence of moisture and nutrients in the planted seeds and the soil in which the seeds grow. In arid climates and in areas where water is not sufficiently available for irrigation, plant growth may suffer due to loss of moisture around the seeds. Conversely, excessive rain may cause soil erosion and wash away the fertilizers and nutrients in the soil and around the seeds. It would be therefore be desirable to find a way to lock in moisture and nutrients into the environment in which the plant grows including the soil, plant seeds, plant roots, and mulch so that plant growth is enhanced especially in arid climates as well as climates that experience excessive rain.
A number of US patents disclose compositions for improving fiber absorbency and moisture as well as improving water retention of soil and other agricultural materials.
U.S. Pat. Nos. 6,686,414 and 6,984,419 relate to a crosslinked aqueous solution polymer composition consisting of at least one water soluble monomer, preferably an alpha, beta-ethylenically unsaturated carboxylic acid monomer and a crosslinking agent. The polymer solution is sufficiently low enough in viscosity such that it can be applied in aqueous form, yet after crosslinking possesses a fast rate of acquisition and is high absorption capacity. The invention also relates to new methods of enhancing the absorbency of various articles, increasing the humectancy and/or absorbency of a fiber or fibrous matrix, improving the water retention of soil and other agricultural methods, and increasing the open time of cement by incorporating or applying an aqueous superabsorbent polymer composition.
U.S. Pat. No. 7,438,951 teaches a method of increasing the humectancy of a fiber, comprising: a) applying an aqueous polymer composition on a fiber, the composition comprising a polymer derived from monomers consisting of water soluble .alpha.-.beta.-ethylenically unsaturated carboxylic acid monomers neutralized with a base selected from the group consisting of alkali metal hydroxide, alkaline earth metal hydroxide, and combinations thereof and a crosslinking agent, and b) drying the composition.
U.S. Pat. No. number 7,135,135 discloses a multilayer construction that includes a first layer that includes water sensitive thermoplastic polymer and a second layer disposed on the first layer containing a superabsorbent polymer.
While the composition provided in these prior art references can readily attach onto fibers having hydrophilic surfaces, the attachment resulting from the application of this composition onto substantially hydrophobic surfaces appears to be weaker and therefore susceptible to loss and removal. Fibers having relatively hydrophilic surfaces may include wood fibers present in paper, disposable diapers and feminine hygiene products. Surfaces that are generally hydrophobic in the context of the present invention include soil, seeds, mulch and plant roots.
The composition of the present invention comprises at least one superabsorbent for retaining moisture on the surfaces of materials onto which the composition is applied. The composition of the present invention further provides for at least one binder component and a nutrient component. The binder helps attach the composition onto the hydrophobic surfaces of the materials in the environment of the plant in order to enhance plant growth. These materials may include seeds, ground soil, potting soil, plant roots, herbicides, mulch made of untreated and treated saw mill residuals, mulch and biomass residuals from processing cotton, animal manure fibers, switch grass, burr plants, wheat, barley, oats, rye, triticale, sorghum, waste paper, hey and Sudan grass. The nutrient component serves as nourishment to the plant.
The application of the composition onto hydrophobic surfaces results in a film bonded to the surfaces. The film contains a binder, at least one superabsorbent and plant nutrients. The superabsorbent is slow to release any moisture it contains and quick to absorb moisture from rain or irrigation.
In another aspect of the present invention, a method of coating surfaces with a composition for enhancing plant growth, the method comprises: providing an aqueous solution containing at least one superabsorbent polymer, a binder, a cross linking agent and at least one plant nutrient; providing materials in the plant growth environment, the materials having substantially hydrophobic surfaces; applying the aqueous solution onto the surfaces of the materials; removing water from the aqueous solution; and forming a substantially solid film on the surfaces.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The preferred superabsorbent polymer of the present invention is prepared by reacting an ethylenically unsaturated carboxylic acid monomer neutralized with an alkali metal hydroxide to a pH of at least 7 with a crosslinking agent. The monomer is selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic acid anhydride, itaconic acid, fumaric acid and combinations thereof. The preferred crosslinking agent of the present invention comprises ammonium zirconium carbonate.
The preferred binders of the present invention comprise urea having a chemical formula of CO(NH2)2 , pregelatinized starch and ethylenediamine having a chemical formula of C2H4(NH2)2.
The nutrient component of the composition may comprise of mineral source nutrients and carbohydrate source nutrients.
Exemplary embodiments for the mineral source nutrient component of the composition may include urea compounds, anhydrous ammonia, nitrate salts, phosphate salts, ammonium salts and mixtures thereof. The cationic component of the nitrate salts that fall within the scope of the present invention may comprise of sodium, potassium or calcium for which the corresponding salt has a chemical formula of Ca(NO3)2.
Urea compounds that fall within the scope of the present invention include urea having a chemical formula of CO(NH2)2, urea sulfate CH4N2O.H2O4S, urea ammonium nitrate having a chemical formula of NH4NO3+CO(NH2)2+H2O, urea ammonium phosphate CO(NH2)-NH3-H3PO4-H2O, and urea phosphate CO(NH2)2H3PO4.
Phosphate salts that fall within the scope of the present invention include ammonium chloride, ammonium nitrate, ammonium sulfate, Mono-ammonium phosphate, Diammonium phosphate, Ammonium phosphate-sulfate, Ammonium polyphosphate
The ammonium salt mineral source nutrients that fall within the context of the present invention include ammonium chloride NH4Cl, ammonium nitrate NH4NO3, ammonium sulfate (NH4)2SO4, mono-ammonium phosphate NH4H2PO4, ammonium thiosulfate H8N2O3S2, diammonium phosphate (NH4)2HPO4, ammonium phosphate-sulfate (NH4)2(H2PO4)(HSO4) and ammonium polyphosphate (NH4PO3)n.
Generally, the cationic component of the mineral source nutrients may include ammonium, calcium, urea, sodium, ferrous cation, ferric cation, manganese, copper, zinc and molybdenum. The complementary anionic components of the mineral source nutrients may include phosphate, sulfate, chloride, thiosulfate, carbonate, hydroxide, acetate, chelate, oxide, nitrate and sulfide. Additional mineral source nutrients that fall within the scope of the present invention include urea, ammonia, sulfur, citric acid, boric acid, oxalic acid, acetic acid, phosphoric acid and mixtures thereof.
The preferred carbohydrate source nutrient contains oligosaccharides. Examples of oligosaccharides that fall within the scope of the present invention include, but are not limited to, disaccharides, such as sucrose and lactose, trisaccharide raffinose and tetrasaccharide stachyose. The chemical formula of unmodified disaccharides is C12H22O11.
The method of preparation of the composition for coating the surfaces comprises the steps of:
1. Preparing an aqueous monomer solution at a concentration between about 10% to about 25%;
2. Raising the pH of the monomer to at least 7;
3. Blending a crosslinking agent with the monomer solution at between about 2% to about 10% by weight of the active monomer solution, and preferably about 5%;
4. Blending a binder with the monomer solution at between about 5% to about 15% by weight of the active monomer solution;
5. Blending in at least one mineral source nutrient component at between about 5 ppm to about 50 ppm by weight of the active monomer solution; and
6. Blending at least one carbohydrate source nutrient component at between about 5 ppm to about 50 ppm by weight of the active monomer solution.
The method for binding the composition onto hydrophobic surfaces comprises 1) applying an aqueous solution onto these surfaces, 2) removing water from the composition to achieve percent solids of between about 5% to about 20%, and 3) forming a film bound to these surfaces. The application of the aqueous solution may be accomplished by spraying using an irrigation system. Alternatively, the solution may be applied on some materials such as seeds by soaking Water may be removed by allowing the aqueous solution on the surfaces to dry under ambient conditions or by applying heat to expedite the drying.
The scope of the present invention further comprises treating fibers present in the plant environment, such as mulch, to reduce their surface hydrophobicity to further improve binding strength of the composition onto their surfaces. A process for reducing the hydrophobicity of fiber surfaces may be accomplished by treating the fibers and fiber bundles to reduce lignin and hemicelluloses content of these fibers. In an embodiment of the present invention the process comprises the substantially simultaneous steps of:
A treatment apparatus for accomplishing these steps may comprise of a closed chamber adapted for use under pressure. The chamber has a longitudinal central axis, a cylindrical enclosure and a feed opening configured with a fiber feeding device. The inner chamber walls comprise a plurality of channels. A shaft disposed along the longitudinal central axis of said chamber, is configured for rotation around the central axis. A plurality of pins is affixed and configured to protrude from the central axis in a substantially perpendicular relation to the central axis and define a tight clearance with the chamber walls.
The fibers fed into the apparatus are chemically treated in the gas phase with a gaseous mixture containing steam, ammonia and ethylenediamine at a temperature of between about 140 degrees C. and about 180 degrees C. and a pressure of about 2 kilopascals gauge. As the fibers are fed into the chamber, they are chemically softened and macerated in the tight clearance between the pins and chamber walls. The treatment partially dissolves and removes hemi-cellulose and lignin fragments from the cell wall which exposes the more hydrophilic layers of the cellulose components in the fibers.
FTIR data on the films bonded to material surfaces indicates that the superabsorbent polymer, the binder and the nutrients present in the original solution are preserved in the film. This suggests that the bonding of the components is effective.
Composition of the Aqueous Solution:
Monomer: PD8081H from HB Fuller making up about 80% of the active solids neutralized with potassium hydroxide.
Crosslinking agent: BACOTE 20® at a making up about 7% of the active solids.
Binder: Ethylenediamine making up about 10% of the active solids.
Aqueous solution concentration is about 14%.
Mineral nutrients: 15 ppm Diammonium phosphate, 10 ppm Magnesium sulfate and 5 ppm Zinc carbonate.
Carbohydrate nutrient: 40 ppm of sucrose. pH: 8.5
Viscosity: 850 cps.
Composition of Film Applied onto Surfaces of Materials in the Plant Environment:
Material: Plant seeds
Absorbency: 70 g water/gram of composition
FTIR data indicate peaks consistent with the presence of the ethylenediamine, ammonium zirconium carbonate, and sucrose.
Composition of the Aqueous Solution:
Monomer: PD8081H from HB Fuller making up about 80% of the active solids neutralized with potassium hydroxide.
Crosslinking agent: BACOTE 20® at a making up about 7% of the active solids.
Binder: Urea making up about 10% of the active solids.
Aqueous solution concentration is about 10%.
Mineral nutrients: 25 ppm Copper acetate, 15 ppm Molybdenum trioxide and 5 ppm Manganese chloride.
Carbohydrate nutrient: 40 ppm of lactose.
pH: 8.0
Viscosity: 700 cps.
Composition of Film Applied onto Surfaces of Materials in the Plant Environment:
Material: untreated mulch
Absorbency: 40 g water/gram of composition
FTIR data indicate peaks consistent with the presence of the urea, ammonium zirconium carbonate, and lactose.
A germination rate study was conducted by the University of Wisconsin, Green Bay using a composition embodiment consistent with the present invention. A composition comprising a superabsorbent polymer and urea was applied onto perennial rye seeds (PRG) and the germination rates were compared with those of uncoated seeds and those of seeds coated with a composition comprising a superabsorbent polymer only.
The superabsorbent polymer solution was prepared at a concentration of about 15% from PD8081H obtained from HB Fuller in a manner described in the Specification section. This is denoted as PRG/LXL in the results table below. PRG/LXL+urea denotes the superabsorbent polymer solution prepared in the same manner and containing 7% urea based on the active monomer present in the solution.
For the purpose of this example, the urea acts as both the binder and nutrient.
After germination began, seedlings were watered once a day. Humidity varied throughout the experiment. In the first 7 days, the humidity varied from about 0% to about 16% and around 40% thereafter.
The table below shows seedling counts from the day the germination started and represents averages of duplicate readings. The results indicate an increase in the germination counts for the urea containing composition relative to the composition containing only superabsorbent polymer of about 64%, 12% and 9% for 6 days, 11 days and 16 days respectively. The improvement in germination rates performance for the composition containing urea compared to the composition comprising only a superabsorbent polymer appears to be more pronounced at low humidity levels that were prevalent during the first week of the experiments. This indicates that adding a binder and nutrient makes the composition more effective in arid climates where humidity levels tend to be low.
