Patent ID: 6120574
Filing Date: 2000-09-19
Classification: C05G

Abstract:
A four-step method of preparing an attrition and shatter resistant fertilizer spike, exhibiting a shape and mechanical strength sufficient to allow the spike to be hammered unsupported into the soil without suffering damage, to provide a source of slow releasing plant nutrients to the soil, the method comprising:(a) sizing particles of plant nutrient compounds, containing one phosphate ion chemically combined with one divalent cation and one monovalent cation, exhibiting a solubility of between 0.01 and 1.0 grams per 100 grams of water at 20.degree. C., so that more than 80 percent of the particles exhibit diameters between 0.5 and 5.0 millimeters;(b) mixing and rolling the sized particles; amounting to between 93 and 98 percent of the weight of the spike, in a coating device and spraying the particles with an aqueous emulsion or dispersion containing between 30 and 70 weight percent of a thermoplastic adhesive which provides adhesion to wet plant nutrients until the particles have been coated with thermoplastic adhesive amounting to between 2 and 7 percent, and free moisture amounting to between 1 and 7 percent of the weight of the spike, the thermoplastic adhesive being selected from the group consisting of vinylidene chloride, 2-ethylhexyl acrylate, acrylic acid, vinyl acetate, butadiene, natural rubber, and combinations thereof;(c) injecting the coated particles into a spike shaped, die at a pressure between 600 and 4000 pounds per square inch, and a temperature greater than the softening temperature of the thermoplastic adhesive and between 50 and 200.degree. C. to form the particles into a fertilizer spike exhibiting the shape and mechanical strength sufficient to allow hammering while unsupported into the soil without suffering damage; and(d) discharging the fertilizer spike from the die and cooling to a temperature less than the softening temperature of the thermoplastic adhesive.