Production method for polyurethane enveloped controlled release fertilizer

Abstract

The invention relates to a production method for polyurethane enveloped controlled release fertilizer. The production method comprises the following steps: preheating granulated fertilizer in a fluidized bed in a fluidizing state; atomizing liquid paraffin, and pretreating the surface of the granulated fertilizer; mixing polyatomic alcohol and isocyanate in a nozzle, atomizing the mixture fast, and spraying the mixture onto the surface of the granulated fertilizer; controlling material adding speeds to ensure that polyurethane reaction can be fulfilled fast; adding liquid paraffin and carrying out surface anti-sticking treatment after the filling of reaction materials. According to the invention, the fluidized bed is adopted as enveloping equipment, polyatomic alcohol and isocyanate are used for spraying and enveloping after being premixed, and the adding speeds are regulated in a matched manner, so that the whole enveloping reaction process is fast and continuous. The production method can improve the polyurethane enveloping efficiency to a relatively large extent, and ensure relatively stable and reliable quality of the enveloped fertilizer due to continuous reaction.

Description

technical field [0001] The invention relates to a preparation method of polyurethane coated fertilizer. The method can continuously distribute the reaction materials to the surface of the particles in a fluidized state, can promote the rapid completion of the polyurethane reaction process, make the mixing, coating, reaction and curing process of the reaction materials uniform and rapid, and effectively prevent the particle-to-particle contact. The adhesion between them solves the problem that large-grained fertilizers are easy to bond and damage the controlled-release performance of the film layer during the coating process. The method can continuously atomize castor oil and other vegetable oil polyols and isocyanate onto the surface of fertilizer particles to prepare coated fertilizers with controlled release performance. The method is mainly used for the coating operation of polyurethane reaction film formation, and is especially suitable for continuous production of film-c...

AI Technical Summary

Problems solved by technology

[0006] To sum up, in the process currently used for the production of polyurethane coated fertilizers, the reaction materials are added intermittently, the operation is relatively complicated, and it is difficult to carry out automatically and continuously, and there are some disadvantages:

[0007] 1. Most of the reaction materials are added separately and successively. After each reaction monomer is added, it takes a period of time to make it evenly distributed. There are shortcomings of uneven distribution of reaction materials and difficult control of reaction products;

[0008] 2. The reaction material is added intermittently, and it needs to go through three stages of uniform coating, reaction, and curing film formation. Especially in the curing stage, the viscosity of the polymer suddenly increases, and the phenomenon of particles sticking into groups is prone to occur, which makes the operation Interruption, and strong agitation of the sticky mass is easy to destroy the film layer, so the controlled release performance is very unstable;

[0009] 3. The coating equipment is a drum or a disc, and the particles can only do rolling motion in the drum. The particles are in close contact with each other, and they are prone to adhesion and wear.

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