PL190428B1 - Method of obtaining polymer-coated npk granules - Google Patents

Abstract

1. A method of producing NPK granules covered with a polymer coating. It is characterised in that NPK fertiliser granules are covered with a solution of polysulphone in N,N dimethylformamide at the concentration of 12.5 to 20 percent by mass. The granules coated with polymer are introduced into a gelling bath at the temperature of 15 to 25 degrees Celsius and dried at the temperature of 90 to 105 degrees Celsius to obtain a solid mass.

Description

The subject of the invention is a method of producing NPK granules coated with a polymer layer.

There are known methods of producing fertilizers, especially nitrogen fertilizers with prolonged action, consisting in surrounding the fertilizing components with sulfur or sulfur and paraffin.

There are known methods of reducing nitrogen release by producing urea condensates with formaldehyde or acetaldehyde.

There are also known methods of making slow-release fertilizers coated with polymers. These methods consist in the fact that a known fertilizer, most often nitrogen fertilizer, is covered with a polymer layer, most often by spraying a polymer powder or polymer solution, and then subjected to high temperature. In this way, a polymer film is created, which makes it difficult for the components to pass from the inside of the fertilizer. The applied coating becomes a barrier against the premature release of the fertilizer within a period of several days to several months. The materials used for this purpose have so far been, among others polyacrylamide, polyethylene, polyolefins, polyurethane resins, copolymers of dicyclopentadiene and soybean or linseed oil.

The known methods only make it possible to produce fertilizers with insufficient efficiency or with the use of expensive production methods.

The method of producing NPK granules according to the invention consists in coating the granules with a polymer in the form of a solution of polysulfone in N, N dimethylformamide at a concentration of 12.5 to 20% by weight. The granules coated with the polysulfone solution are introduced into a gelling bath at 15 to 25 ° C and dried at 90% to 105 ° C until constant weight.

Preferably, a double coating with a polysulfone solution of the same or different concentration is used.

Preferably, water is used as the gelling bath.

The fertilizer obtained by the method according to the invention has a porous asymmetric polysulfone shell with a thin skin layer. The resulting layer limits the access of water to the inside of the granule and delays the passage of dissolved salts to the outside.

The fertilizers obtained by the method according to the invention reduce the rate of release of nutrients such as nitrogen, phosphorus, and potassium, thus enabling their more effective use by plants. At the same time, NPK granules coated with polysulfone improve soil structure and aeration.

The advantage of the process according to the invention is the use of a simple phase inversion method to obtain a shell while reducing the process time. In the method according to the invention, the formation of a controlling layer surrounding the NPK granules takes place under mild conditions, without the need for high energy expenditure.

In the method according to the invention, it is possible to control the duration of the fertilizer action by selecting the appropriate concentration of the polymer solution, as well as changing the temperature and composition of the gelling bath. It is also possible to limit the permeability

190 428 coatings double coating of NPK granules with solutions of equal or different concentrations of polysulfone solution.

Example I.

15% by weight of dried polysulfone and 85% by weight of N, N dimethylformamide with a density of 0.95 g / ml were introduced into the vessel. The mixture was then stirred for 6 hours in a sealed vessel while heating it to a temperature of about 50 ° C. A clear, homogeneous polymer solution with a slightly straw color was obtained. In the next stage, the prepared NPK fertilizer was poured with the polysulfone solution and the coated granules were placed in a water bath at 17 ° C. The polymer coated granules were dried at a temperature of 95 ± 1 ° C until a constant weight was obtained.

The product had an average polymer content of 10% by weight, based on the weight of the coated granule, and a shell porosity of 25%. The study of the release rate of NPK fertilizer components from the polymer-coated granules in an aqueous environment showed that after 5 hours of mixing, 74.8% NHf ¹ , 56.36% P2O 5 and 49.28% K by weight in relation to the initial amount were released.

Example II.

18% by weight of dried polysulfone and 82% by weight of N, N dimethylformamide were introduced into the vessel. The mixture was then stirred for 6 hours in a sealed vessel while heating it to a temperature of about 50 ° C. A clear, homogeneous polymer solution with a slightly straw color was obtained. In the next stage, the prepared NPK fertilizer was poured with the polysulfone solution and the coated granules were placed in a water bath at 17 ° C. The polymer coated granules were dried at 104 ± 1 ° C until constant weight.

The product had a polymer content of 13.7% by weight, based on the weight of the coated granule, and a polymer layer porosity of 19.4%. The study of the release rate of NPK fertilizer components from the polymer-coated granules in an aqueous medium showed that after 5 hours of mixing, 44.9% NH4 ⁴ , 38.43% P2O5 and 25.98% K + by weight in relation to the initial amount were released.

Example III.

18% by weight of dried polysulfone and 82% by weight of N, N dimethylformamide were introduced into the vessel. The mixture was then stirred for 6 hours in a sealed vessel while heating it to a temperature of about 50 ° C. A clear, homogeneous polymer solution with a slightly straw color was obtained. In the next stage, the prepared NPK fertilizer was poured with the polysulfone solution and the coated granules were introduced into the bath at a temperature of 21 ° C. The polymer coated granules were dried at 104 ± 1 ° C until constant weight.

Granules coated with one polymer layer were immersed in a film-forming solution at the same concentration as the first polymer layer. The solvent was removed from the second layer of polymer applied to the granules by rinsing it in a gelling bath at 21 [deg.] C, and then the coated granules were dried at 104 [deg.] C until constant weight.

The product had a polymer content of 21% by weight, based on the weight of the coated granule, and a polymer layer porosity of 11.04%. The study of the rate of release of NPK fertilizer components from the polymer-coated granules in an aqueous environment showed that after 5 hours of mixing, 18.99% NH4 +, 8.71% P2O5 and 3.78% K + by weight in relation to the initial amount were released.

Example IV.

18% by weight of dried polysulfone and 82% by weight of N, N dimethylformamide were introduced into the vessel. The mixture was then stirred for 6 hours in a sealed vessel while heating it to a temperature of about 50 ° C. A clear, homogeneous polymer solution with a slightly straw color was obtained. In the next stage, the prepared NPK fertilizer was poured with the polysulfone solution and the coated granules were placed in a water bath at a temperature of 21 ° C. The polymer coated granules were dried at 104 ± 1 ° C until constant weight.

The granules coated with one polymer layer were immersed in a solution with a concentration of 17% by weight of polysulfone and 83% by weight of N, N dimethylformamide. From the second layer of polymer

190,428 applied to the granules, the solvent was removed by rinsing the granules in a gelling bath at 21 ° C, and then the granules with the polymer layered layers were dried at 104 ° C until constant weight.

The porosity of the resulting layers was 13.42%. The study of the rate of release of the fertilizing components from the polymer-coated granules in an aqueous medium showed that after 10 days of static storage, 100% NH4 +, 100% P2 O 5 and 75% K + were rehydrated.

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Claims (3)

Patent claims 1. The method of producing NPK granules coated with a polymer layer, characterized in that the NPK fertilizer granules are covered with a solution of polysulfone in N, N dimethylformamide at a concentration of 12.5 to 20% by weight, and the polymer-coated granules are introduced into a gelling bath at a temperature of 15 to 25 ° C and dried at 90 to 105 ° C until constant weight. 2. The method according to p. The process of claim 1, characterized in that the coating is applied twice with a polysulfone solution of the same or different polymer concentration. 3. The method according to p. The process of claim 1, wherein the gelling bath is water.