JPS5935873B2 - Manufacturing method for slow-release coated fertilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a slow-release coated fertilizer, and more specifically, the surface of a granular fertilizer is first coated (inner layer) with a sparingly soluble fertilizer salt, and then an organic material is applied thereon. The present invention relates to a method for producing a slow-release coated fertilizer with significantly improved elution resistance characterized by coating (outer layer).

Commonly used fast-acting fertilizers are essentially water-soluble, so after application, there is a large amount of runoff during rainfall, and if you want to supply the necessary nutrients to crops as they grow, you will need to apply them several times. This means that fertilizer application will have to be divided into two parts.

Furthermore, even under conditions where the amount of leaching is relatively small, if a large amount of quick-release fertilizer is applied at once, it is possible that agricultural crops will be damaged by excessive fertilizer.

In recent years, efforts have been made to develop slow-release fertilizers that compensate for the shortcomings of these quick-release fertilizers, and various proposals have been made.

That is, (1) a method of forming a magnesium phosphate film on a granular fertilizer with MgO, ammonium phosphate, and a concentrated phosphoric acid solution; a method of forming a magnesium phosphate film on a granular fertilizer with Mg(OR)2 and a dilute phosphoric acid solution; (U.S. Patent No. 3392
007, Japanese Patent Publication No. 49-17826), (2) A method of forming a film on granular fertilizer with an organic material such as a mixture of hydrogenated oil and beeswax, nitrofumic acid or its salts, celluloses, resins, etc. Japanese Patent Publication No. 40-27283, Japanese Patent Publication No. 43-781'3), etc. have been proposed, but with the method described in (1) above, pinholes are unavoidable in the coating film, and the coating film does not loosen over a long period of time. It is difficult to say that the organic material is effective, and has the disadvantage that it rapidly dissolves after a certain period of time due to expansion of the pinhole area.Also, in the method described in (2) above, the organic material has poor mechanical strength in water. is weak,
In addition, there are drawbacks such as the inability to maintain the elution suppressing effect over a long period of time due to the poor shape retention of the coating film, and the fact that those that are relatively water resistant are expensive and therefore impractical.

Therefore, the present inventors conducted research to provide a slow-release fertilizer that does not have the above drawbacks, and found that by coating ammonium magnesium phosphate and organic materials in combination, it is possible to coat each of them individually. They discovered that a synergistic effect can be produced compared to the conventional case, and based on this discovery, they came up with the following invention.

That is, the granular fertilizer is first coated with an inner layer (one layer or two or more layers) of a sparingly soluble fertilizer salt consisting of one or more types of ammonium magnesium phosphate by chemical reaction, and then an inner layer (one layer or two or more layers) is coated on the granular fertilizer. The outer layer (one or more layers) is coated with one or more organic materials.

The sparingly soluble fertilizer salt used in the present invention is ammonium phosphate, which can be prepared by any synthetic method.

In addition, organic materials include rosin, paraffin, chlorinated paraffin, mineral and vegetable oils such as hydrogenated oil, boil oil, and drying oil; celluloses such as ethyl cellulose and nitrocellulose; soybean-modified phthalate resin; vinyl acetate, styrene,
Phenol type, urea type, melamine type, coumaron type, epoxy type, polyester type, vinyl type, acrylic type, alkyd type, xylene type, formaldehyde type, polyolefin type, vinyl type, styrene type, polyamide type,
There are synthetic resins such as silicon-based resins.

The coating ratio of the inner layer and outer layer (the ratio of the coating to the coated granular fertilizer expressed in weight%) is 5 to 3, respectively.
0%, 3-20%, preferably 10-20%, 5-10
%.

As a means of coating fertilizer particles with a sparingly soluble fertilizer salt consisting of magnesium ammonium phosphate, simply coating the powder with water granulation does not provide a coating with the excellent properties described below; A robust, slow-release film is formed only when the surface is coated with ammonium magnesium phosphate.

In that case, the means for producing ammonium magnesium phosphate is not particularly limited, and any means may be used as long as easily soluble unreacted substances do not remain in the coated ammonium magnesium phosphate layer, but the following is a preferable example. It will be done.

That is, using Mg(OH)2 or MgO, MgHPO4.3H20 and NH3, MgHP
O4=1.0~1.2- NH3/PO4=0.8~
1,0, MgNH4PO4・H at reaction temperature 60-80℃
2O is produced, in which case the coverage ratio is 5 to 30
%, preferably from 10 to 20%, provides the most homogeneous and robust inner coating layer.

Further, the means for coating the outer layer with the organic material may be any conventional means such as spraying and drying an organic material dissolved in an organic solvent.

In that case, a good outer layer is obtained when the coverage ratio is 3 to 20%, preferably 5 to 10%.

As described above, by first coating the granular fertilizer with an inner layer of hardly soluble fertilizer salt and then coating the outer layer with an organic material,
Even if fragile paraffin, hydrogenated oil, etc. are used as organic materials, the reinforcement effect of ammonium magnesium phosphate can increase water resistance and provide strength.

In addition, when using a water-resistant organic material, it is economical because a thin film of ammonium magnesium phosphate can be coated to close pinholes and increase slow-release properties.

Furthermore, when the fertilizer particles are coated with an inner layer of ammonium magnesium phosphate, it is much easier to coat the fertilizer particles with the organic material than when the inner layer is not coated, and it is possible to coat the fertilizer particles in any desired ratio.

In addition, since ammonium magnesium phosphate is entirely a fertilizer component, it is not only more economical than conventional coatings that mainly contain ingredients other than fertilizers, but also allows the coating thickness to be freely adjusted to prevent floating. can.

Next, the present invention will be explained in more detail by giving examples.

Example 1 While transferring 1 kg of granular compound fertilizer (Salt and Phosphate 14-14-14, hereinafter referred to as granular fertilizer) in a rotary pan,
% phosphoric acid solution (calculated as P2O3) 307g and Mg (
Spray 73g of OH)2 powder alternately, and finally spray NH330.
? An inner layer coating of MgNH4PO4.H2O was formed by adding .

1.183 kg of dried granular fertilizer with a coating ratio of 15.5% (hereinafter referred to as inner layer coated product) obtained in this manner has a melting point of 68
Paraffin wax of ~70°C was melted and coated at 80~90°C, and allowed to cool to obtain a coated fertilizer with an outer layer coverage ratio of 4~9% and a total layer coverage ratio of 19~23%.

Example 2 1 kg of the inner layer-coated product obtained in Example 1 was coated with an outer layer using hydrogenated (fish) oil by the method described in Example 1 to obtain coated fertilizers with arbitrary thicknesses.

Example 3 A 20% toluene solution of 70% chlorinated paraffin was sprayed onto 1 kg of the inner layer-coated product obtained in Example 1, and the mixture was dried (repeatedly) to obtain coated fertilizers with arbitrary thicknesses.

Example 4 1 kg of the inner layer coated product obtained in Example 1 was coated with ethyl cellulose (20% ethanol solution) by the method described in Example 3 to obtain a coated fertilizer.

Example 5 1 kg of the inner coated product obtained in Example 1 was treated with alkyd resin (50% mineral spirit solution) by the method described in Example 3.
was coated to obtain a coated fertilizer.

Comparative Examples 1 to 5 For each of Examples 1 to 5, coated fertilizers with arbitrary thicknesses were obtained by directly coating the organic material layer without coating the inner layer MgNH4PO4.H2O.

Note that the size and hardness of the granular fertilizer used at this time were similar to those of the inner layer coated products of Examples 1 to 5.

Example 6 Salted Rin-an No. 525 (15-12-15) containing urea 1 kg
was coated by the method described in Example 1, and the inner layer coverage ratio was 15.5.
%, and a coated fertilizer with an outer layer coverage ratio of 4 to 10% was obtained.

Example 7 The inner layer-coated product obtained in Example 6 was coated with an outer layer using hardened (fish) oil by the method described in Example 1 to obtain coated products with arbitrary thicknesses.

Example 8 A 20% toluene solution of 70% chlorinated paraffin was sprayed onto the inner layer-coated product obtained in Example 6, and drying was repeated to obtain coated products with arbitrary thicknesses.

Example 9 Coated products of arbitrary thickness were obtained by the method described in Example 8, using a 20% ethanol solution of ethyl cellulose instead of a 20% toluene solution of 70% chlorinated paraffin.

Comparative Examples 6 to 9 For each of Examples 6 to 9, coated fertilizers with arbitrary thicknesses were obtained by directly coating the organic material layer without coating the inner layer MgNI (4PO4.H2O).

In addition, the size and hardness of the granular fertilizer used at this time were similar to those of the inner layer coated products of Examples 6 to 9.

. Comparative Example 10 Granular fertilizer was coated with only MgNH4PO4・H2O (coating ratio 15.5) by the method described in Example 1.
．． 23%) was applied.

As described above, the coated fertilizers 5' obtained in Examples 1 to 9 and Comparative Examples 1 to 10 are as follows. was immersed in 100ml of water and left at 30°C for a certain period of time, and the amount of ammonia nitrogen eluted was measured.

The results are shown in Figures 1-3.

In FIG. 1, curves a, b, and c are respectively of Example 1.2.
．． Graph showing the amount of eluted ammonia nitrogen after one day of the coated fertilizer obtained in step 3, curves a', b/, c
/ is a graph showing the amount of ammonia nitrogen eluted after one day for Comparative Examples 1, 2, and 3, respectively.

Similarly, in FIG. 2, curves a and a' are for Example 4 and Comparative Example 401 days after passing, curves b and b' are for Example 4 and Comparative Example 4 after 7 days, respectively, and curve C9C' and d and d' indicate the results of Example 5 and Comparative Example 5 after 1 day and 7 days, respectively.

Figure 3 shows the dissolution rate after one day, curves a, b, c,
Curves d and d are those of Example 6.7.8.9, respectively, and curves a/b', c', and d' are those of Comparative Example 6.7.8.9, respectively.

The dissolution rate of the coated fertilizer obtained in Comparative Example 10 after one day was 85% and 70.2%.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are graphs showing the dissolution rates of coated fertilizers obtained in Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1. 1 on the surface of the granular fertilizer. It is characterized by coating while producing a sparsely soluble fertilizer salt consisting of magnesium ammonium phosphate produced by the reaction of phosphoric acid, a magnesium compound, and ammonia, and then coating it with one or more organic materials. A method for producing a slow-release coated fertilizer.