Method for preparing biodegradable coating material by ammonolysis modified vegetable oil and application of biodegradable coating material

Abstract

The invention discloses a method for preparing a degradable coating material by an ammonolysis modified vegetable oil and an application of the biodegradable coating material. The method comprises thefollowing steps: firstly preparing the modified vegetable oil by using an ammonolysis method, respectively adding an isocyanate and a polyoxypropylene diol into the modified vegetable oil, adding a chain extender and a catalyst for carrying out a reaction, and finally adding N-methyldiethanolamine for carrying out a reaction to obtain the degradable coating material. A urea-formaldehyde solutionis sprayed on the surface of fertilizer particles during a preheating stage of the coating. The prepared coating material has relatively good micro-porous air-permeability, is relatively convenient for controlling a release rate of a fertilizer, and has relatively good degradable function. At the same time, the surface of the fertilizer particles is modified before coating to eliminate surface crystallization and angularity of the fertilizer particles to make the surface be relatively smooth and further enhance coating effects.

Description

technical field [0001] The invention relates to a preparation method of a fertilizer coating material. Background technique [0002] Vegetable oil has a relatively large number of ester groups containing hydroxyl groups, which react with isocyanate to form water-based polyurethane with a microporous structure. In addition, vegetable oil contains unsaturated double bonds, which can be modified to obtain products with curing properties. Therefore, the use of vegetable oil and water-based polyurethane to prepare fertilizer coating materials has the outstanding characteristics of good film-forming properties and easy control of the release rate of fertilizers. However, since most oils do not contain active hydrogen, they must be modified before they can be used in the preparation of waterborne polyurethane. [0003] The general practice in the prior art is to make the oil possess active groups by copolymerizing the oil and polyurethane, thereby reacting with isocyanate, but th...

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Problems solved by technology

However, since most oils do not contain active hydrogen, they must be modified before they can be used in the preparation of waterborne polyurethane

[0003] The general practice in the prior art is to make the oil have active groups by copolymerizing the oil and polyurethane, so as to react with isocyanate, but the reaction temperature of transesterification is between 240-260°C, and the energy consumption is high

Under such high temperature conditions, even with the protection of nitrogen, the color of the product cannot be guaranteed, which will affect the appearance of the product

[0004] Utilize the modified vegetable oil of different methods as a part of reaction in the existing fertilizer coating material, the method of modification is mainly epoxidation method, the main defect of epoxidation method is: in epoxidation method, epoxide It is difficult to separate from non-double bond vegetable oil molecules, which will have a greater impact on the performance of the product

The main defect of the epoxidation method is: it is difficult to separate the epoxide and the non-double bond vegetable oil molecules, which will have a great impact on the performance of the product, resulting in large differences in the quality of vegetable oils in batches, and the uncertainty of quality has caused a great impact on the industry. production will be adversely affected

In practice, it has been found that since fertilizer particles usually have corners and surface crystals, these corners and surface crystals are difficult to form a film during the coating process, or are easy to break after film formation, resulting in weakened slow-controlled release of the finished product

At present, the main technical means to solve this problem is to increase the amount of film-forming materials, which will lead to an increase in production costs.

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