Integrated-preparation and application methods of urea-formaldehyde (UF)-based multi-nutrient biodegradable polymeric slow-release (SR) liquid and granular fertilizers

Patent metadata

Field	Value
Publication number	US-12428355-B2
Application number	US-202519024680-A
Country	US
Kind code	B2
Filing date	Jan 16, 2025
Priority date	Apr 22, 2024
Publication date	Sep 30, 2025
Grant date	Sep 30, 2025

Abstract

A method for integrally preparing urea-formaldehyde (UF)-based multi-nutrient biodegradable polymeric slow-release (SR) liquid and granular fertilizers is provided. A hydroxymethylurea solution is prepared, and a part of the hydroxymethylurea solution is added to a reactor for reaction to obtain the UF-based multi-nutrient biodegradable polymeric SR liquid fertilizer. The rest of the hydroxymethylurea solution is fed into a reaction-extrusion integrated machine for reactive extrusion to obtain a UF polymer through the polycondensation reaction, which is extruded, dried and granulated to obtain the UF-based multi-nutrient biodegradable polymeric SR granular fertilizer. A method for applying such liquid and granular fertilizers is also provided.

First claim

What is claimed is:

1. A method for integrated preparation of a urea-formaldehyde (UF)-based multi-nutrient biodegradable polymeric slow-release (SR) liquid fertilizer and a UF-based multi-nutrient biodegradable polymeric SR granular fertilizer, comprising:
(1) adding urea, formaldehyde, a catalyst, and water to a first reactor followed by a reaction at 50-90° C. for 0.5-3 h to obtain a hydroxymethylurea solution; wherein a molar ratio of the urea to the formaldehyde is 1.2-5:1; the catalyst is 0-5%, excluding 0%, of a total weight of the urea and the formaldehyde; and the water in the first reactor is 15-35% of the total weight of the urea and the formaldehyde; and
(2) adding a first portion of the hydroxymethylurea solution obtained in step (1) to a second reactor containing an acidic suspension followed by a reaction at a first temperature T 1 for a first time t 1 to obtain a viscous UF liquid, wherein the acidic suspension is prepared from an acidic substance, water, and a suspending agent; and adding the viscous UF liquid to a mixed liquid prepared from an alkaline substance, a first fertilizer system containing at least one nutrient element except nitrogen, and a nutrient synergist, followed by mixing to obtain the UF-based multi-nutrient biodegradable polymeric SR liquid fertilizer; and
feeding a second portion of the hydroxymethylurea solution obtained in step (1) and a second fertilizer system containing at least one nutrient element except nitrogen into a twin-screw reaction extruder of a reaction unit of a reaction-extrusion integrated machine, followed by a reactive extrusion process at a second temperature T 2 and a first screw speed R 1 for a second time t 2 to form a reaction mixture, wherein during the reactive extrusion process, hydroxymethylurea is transformed into a UF polymer through a polycondensation reaction; conveying, by the twin-screw reaction extruder, the reaction mixture to a twin-screw extruder of an extrusion unit of the reaction-extrusion integrated machine followed by extrusion at a third temperature T 3 and a second screw speed R 2 to obtain a strip-shaped extrudate; drying the strip-shaped extrudate at a fourth temperature T 4 , followed by granulation to obtain the UF-based multi-nutrient biodegradable polymeric SR granular fertilizer.

2. The method of claim 1 , wherein in step (1), the formaldehyde is selected from the group consisting of a formaldehyde aqueous solution, a solid paraformaldehyde, gaseous formaldehyde, and a combination thereof; and the catalyst is potassium carbonate, potassium hydroxide, or a combination thereof.

3. The method of claim 1 , wherein in step (2), the first portion of the hydroxymethylurea solution is added to the acidic suspension by dripping, mist spraying, or pouring;
the acidic substance is an inorganic acid or an organic acid, and is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid, tartaric acid, and a combination thereof; and
in the acidic suspension, the acidic substance is 0-80 wt. %, except 0 wt. %, of the water; the suspending agent is an inorganic suspending agent or an organic suspending agent, and is selected from the group consisting of attapulgite, bentonite, kaolin, lignin, humic acid, alginic acid, polyvinyl alcohol, colloidal protein, xanthan gum, cellulose, starch, and a combination thereof; and the suspending agent is 0-5 wt. %, except 0 wt. %, of the water.

4. The method of claim 1 , wherein in step (2), the first temperature T 1 ranges from 25° C. to 90° C., and the first time t 1 is 0.1-2 h.

5. The method of claim 1 , wherein in step (2), the alkaline substance is an inorganic base, a strong base-weak acid salt or an organic base, and is selected from the group consisting of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium phosphate, an organic amine compound, and a combination thereof.

6. The method of claim 1 , wherein in step (S2), the second temperature T 2 is 50-130° C.; the first screw speed R 1 is 5-150 rpm; the second time t 2 is 1-30 min; the third temperature T 3 is 50-130° C.; the second screw speed R 2 is 5-150 rpm; and the fourth temperature T 4 is 60-150° C.

7. The method of claim 1 , wherein in step (S2), the first fertilizer system and the second fertilizer system are independently selected from the group consisting of a phosphate, a potassium salt, calcium sulphate, magnesium sulphate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, boric acid, sodium silicate, and a combination thereof;
the phosphate is selected from the group consisting of hydroxyapatite, ammonium dihydrogen phosphate, calcium superphosphate, potassium dihydrogen phosphate, and a combination thereof; and the potassium salt is selected from the group consisting of potassium sulphate, potassium chloride, potassium nitrate, potassium carbonate, potassium silicate, and a combination thereof; and
the nutrient synergist is selected from the group consisting of a humic acid, an amino acid, a seaweed extract, gibberellin, auxin, and a combination thereof.

8. The method of claim 1 , wherein step (S2) further comprises:
sealing a die opening between the reaction unit and the extrusion unit before feeding the second portion of the hydroxymethylurea solution into the twin-screw reaction extruder; and
after feeding the second portion of the hydroxymethylurea solution into the twin-screw reaction extruder, turning on screws of the twin-screw reaction extruder, and simultaneously starting a vacuumization-devolatilization device of the twin-screw reaction extruder to remove water in the reaction mixture; opening the die opening between the reaction unit and the extrusion unit; and turning on the twin-screw extruder of the extrusion unit such that the reaction mixture is conveyed by the twin-screw reaction extruder to the twin-screw extruder.

Assignees

• Univ North China

Inventors

• Liu Yaqing
• Xiang Yang
• Wang Wenqi
• Zhao Guizhe

Classifications

• C05D1/00

  Fertilisers containing potassium (C05D7/00 takes precedence) · CPC title

• C05G5/12

  Granules or flakes · CPC title

• C05C9/005

  Post-treatment · CPC title

• C05G5/20

  Liquid fertilisers (layered or coated C05G5/30; incorporated into a matrix C05G5/40) · CPC title

• C05B1/00

  Superphosphates, i.e. fertilisers produced by reacting rock or bone phosphates with sulfuric or phosphoric acid in such amounts and concentrations as to yield solid products directly · CPC title