Abstract: A curing agent isocyanate of a fully bio-based coating material for a polyurethane controlled release fertilizer is a bio-based 1,5-pentane diisocyanate compound. The bio-based 1,5-pentane diisocyanate compound is a compound of a bio-based 1,5-pentane diisocyanate monomer and its polymer, or a compound of different bio-based 1,5-pentane diisocyanate polymers. The bio-based PDI (1,5-pentane diisocyanate) polymer comprises a bio-based PDI trimer and its derivatives, a bio-based PDI tetramer and its derivatives, and other bio-based PDI multimers and their derivatives, which are derived from bio-based materials such as glucose and lysine. The mass percentage of bio-based materials in all raw materials is in a range of 65% to 71%. The coating material is prepared by cross-linking the bio-based polyol and the bio-based 1,5-pentane diisocyanate compound.

Abstract: A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

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.

Abstract: A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

Abstract: Epoxy soybean oil polyol is firstly prepared by open-ring etherification of an epoxy soybean oil and a small molecular alcohol with an organic acid catalyst, and then the epoxy soybean oil polyol is further esterified with an organic acid under an esterification catalyst to prepare a polyester polyol with a high biomass ratio. The polyester polyol includes a compound having an Ñ-type structure and a compound having an Ò-type structure. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer prepared by cross-linking the polyester polyol and MDI on surfaces of the fertilizer. The epoxy soybean oil and the small molecular alcohol can be derived from biomass, so a biomass content is high, the synthesized product is environmentally safe, and product performance is excellent.

Abstract: A method for remodelling granular urea surface, which belongs to the field of resin coated urea manufacturing technology, includes steps of: firstly sending the granular urea with a temperature of 20-80° C. into a drum comprising a shoveling board for rolling in a clockwise or counterclockwise direction; adding reconstituted liquid; dissolving convexes which like peaks and provided on surfaces of granular urea into a reconstituted liquid under a combined effect of mechanical forces and water in the reconstituted liquid; and introducing dry and hot wind, in such a manner that the urea dissolved in the recycled liquid is filled onto concaves of surfaces of the granular urea; wherein after drying is terminated, the granular urea becomes smooth and rounded; uneven surfaces of the convexes which are in a shape of peaks disappear; and the surfaces of the granular urea are shiny and show a mirror effect.

Abstract: A method for remodelling a surface of granular urea, comprising steps of: firstly, sending granular urea into a drum comprising a shoveling board and a heating air duct for rolling in clockwise or counterclockwise direction; then spraying a coating solution slowly and evenly on the surface of the granular urea; wherein moments friction between particles of the granular urea and the drum, particles and shoveling board, particles and particles drive bulges on the surface of the granular urea to be softened or dissolved into the coating solution by external force; drying particles of the granular urea, wherein part of the granular urea that is dissolved into the coating solution crystalizes and fills dents on the surface of granular urea, so the particles of the granular urea becomes smooth and rounded; and drying by air heater until the particles of the granular urea are hardened.