Controlled release fertilizer containing ammonium polyphosphate and its preparation methods

Abstract

A controlled release fertilizer containing ammonium polyphosphate includes fertilizer core particles and fertilizer envelopes coated on a surface of the fertilizer core particles respectively. P (phosphorus) is only from ammonium polyphosphate, and ammonium polyphosphate has a degree of polymerization in a range of 5 to 20. A preparation method of the controlled release fertilizer includes steps of (1) weighing the phosphorus source, the nitrogen source, the potassium source and the multiple metallic medium and trace element sources in the above weight parts, pulverizing, and obtaining powders by sieving through a sieve with a mesh number of 80; (2) preparing fertilizer core particles; (3) preparing polyurethane envelopes on a surface of the fertilizer core particles respectively, and (4) adding the agglomerant in the above weight parts into the fertilizer core particles coated with the polyurethane envelopes and cooling to 20° C.

Description

Claims

1. A controlled release fertilizer containing ammonium polyphosphate, wherein: the controlled release fertilizer comprises fertilizer core particles and fertilizer envelopes coated on a surface of the fertilizer core particles respectively;the fertilizer core particles contain phosphorus source, nitrogen source, potassium source and multiple metallic medium and trace element sources;P (phosphorus) in the phosphorus source is only from ammonium polyphosphate which has a degree of polymerization in a range of 5 to 20 and has a chelating effect on metallic medium and trace elements in the multiple metallic medium and trace element sources.

2. The controlled release fertilizer according to claim 1, wherein the multiple metallic medium and trace element sources comprise calcium source, magnesium source, boron source, molybdenum source, iron source, zinc source, manganese source and copper source.

3. The controlled release fertilizer according to claim 1, wherein the controlled release fertilizer contains components in weight parts of: ammonium polyphosphate100-300 parts;nitrogen source400-700 parts;potassium source150-450 parts;calcium source10-50 parts;magnesium source50-100 parts;boron source1-3 parts;molybdenum source1-3 parts;iron source5-20 parts;zinc source0.5-1 part;manganese source1.5-2 parts;copper source and0.5-1 part;an agglomerant5-30 parts.

4. The controlled release fertilizer according to claim 3, wherein the nitrogen source is ammonium nitrate phosphate, and the potassium source is potassium sulfate.

5. The controlled release fertilizer according to claim 4, wherein: the calcium source is potassium calcium magnesium sulfate;the magnesium source is at least one member selected from a group consisting of magnesium sulfate, magnesium nitrate and magnesium chloride.

6. The controlled release fertilizer according to claim 4, wherein: the boron source is at least one member selected from a group consisting of boric acid and sodium borate salt;the molybdenum source is at least one member selected from a group consisting of sodium molybdate and ammonium molybdate.

7. The controlled release fertilizer according to claim 4, wherein: the iron source is a mixture of EDTA (ethylenediaminetetraacetic acid) ferric salt and ferric nitrate, a mixture of EDTA ferric salt and ferric chloride, ferric nitrate or ferric chloride;the zinc source is at least one member selected from a group consisting of zinc sulfate, zinc nitrate and zinc chloride.

8. The controlled release fertilizer according to claim 4, wherein: the manganese source is at least one member selected from a group consisting of manganese sulfate, manganese nitrate and manganese chloride;the copper source is copper sulfate, copper nitrate or copper chloride.

9. The controlled release fertilizer according to claim 1, wherein the fertilizer envelopes are polyurethane envelopes.

10. A preparation method of the controlled release fertilizer according to claim 9, wherein the preparation method comprises steps of: (1) weighing the phosphorus source, the nitrogen source, the potassium source and the multiple metallic medium and trace element sources in the above weight parts, pulverizing, and obtaining powders by sieving through a sieve with a mesh number of 80;(2) preparing fertilizer core particles, which comprises thoroughly mixing the powders obtained by the step (1) in a granulator, introducing atomized water into the granulator through a nozzle, pelletizing, screening, polishing and drying;(3) preparing fertilizer envelopes on a surface of the fertilizer core particles respectively, which comprises putting the fertilizer core particles into a sugarcoating machine, heating at 55-65° C., preparing a coating material by mixing polymerized MDI (diphenyl methane diisocyanate) with vegetable oil-based polyester polyols, coating the coating material on the surface of the fertilizer core particles, forming polyurethane controlled release films by a cross-linking reaction between the coating material and the surface of the fertilizer core particles for increasing viscosity, repeating steps of preparing and coating the coating material and forming the polyurethane controlled release films till a coating rate is in a range of 1.9%-2.1%, and solidifying for 3 to 5 minutes, so that the polyurethane controlled release films are solidified into the fertilizer envelopes on the surface of the fertilizer core particles; and(4) adding the agglomerant in the above weight parts into the fertilizer core particles coated with the fertilizer envelopes, and cooling to 20° C., thus obtaining the controlled release fertilizer containing ammonium polyphosphate.