JP2000159592A - Production of coated granular fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fertilizer excellent in initial leach suppressive ability, having long-term leach suppressive ability, and slight in fertilizer ingredient loss by coating a granular fertilizer of slightly uneven, smooth granular shape with a coating film material. SOLUTION: This coated granular fertilizer is obtained by coating 100 pts.wt. of a granular fertilizer satisfying the relationship: 0<=D120<0.025 with 1-50 pts.wt. of a coating film material; wherein it is defined that, when the granular fertilizer is taken in as a planar image, in the frequency distribution of each of the angles made by three points lying on a straight line on the plane at 100 μm intervals and measured at n>=200 per granule for >=30 granules, D120 represents the sum of the frequency distributions corresponding to angles of <120 deg.. This fertilizer can be manufactured using a rotary granulator, centrifugal granulator, prill granulator, or the like; for example, in the case of ammonium phosphate/nitrate- based fertilizer, such a granulation method as to include 1-2 wt.% moisture therein is preferable. Specifically, this coated granular fertilizer is produced by coating a granular fertilizer with a coating film material using such an apparatus as jet column or rolling tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A variety of slow-release fertilizers have been developed for the purpose of labor saving of fertilization or to exhibit a fertilizing effect according to the growth of plants and to reduce the amount of fertilization. As a typical slow-release fertilizer, there is a coated fertilizer in which the surface of fertilizer particles is coated with various resins or inorganic substances. The present invention relates to a method for producing such a coated granular fertilizer, in particular, without lowering the quality as a fertilizer,
The present invention relates to a method for stably producing a coated fertilizer having excellent initial dissolution inhibiting power and long-term dissolution controllability with little variation among lots and the like with good reproducibility.

[0002]

BACKGROUND OF THE INVENTION An important performance required of coated fertilizers is controllability of dissolution. That is, it is necessary that the elution period be controlled precisely according to requirements, from a short elution period of, for example, several tens of days, to a long-term elution property of several hundred days. It is also important that the initial elution due to film defects or the like is firmly suppressed. If such control is not carried out reliably, the result is that "fertilization" occurs due to elution of excess fertilizer components, and conversely, poor plant growth due to shortage occurs.

As a method for reducing the initial elution, a method of performing two-layer coating as described in Japanese Patent Application Laid-Open No. 9-30883 is known. There is a problem in manufacturing complexity that the coating has to be performed repeatedly. In addition, it is known that the method of prolonging the elution can be achieved by a method of making the substance used in the film hydrophobic, or by increasing the coating amount, that is, by increasing the thickness of the film itself. Have been. However, these methods have disadvantages such as lowering the quality of the fertilizer, and the balance between the initial suppression period and the full-scale elution period cannot be achieved. Furthermore, there is also known a technique of suppressing initial dissolution by a method of appropriately setting temperature conditions and the like when producing a coated fertilizer as described in JP-A-8-225287, and prolonging dissolution. These methods have a disadvantage that productivity is reduced.

On the other hand, fertilizer components for producing coated fertilizer,
That is, from the viewpoint of raw manure, attempts have been made to suppress initial elution. Japanese Patent Application Laid-Open No. 9-30884 discloses a method for producing a coated fertilizer using a granular fertilizer having a short axis / long axis ratio in a certain range. However, in general, the surface shape of the raw manure is complicated, and in this method in which the short axis / long axis ratio is simply in a specific range, excellent initial elution suppressing power and long term can be achieved without deteriorating the quality as a fertilizer. In terms of stably producing a coated fertilizer having a long-lasting elution suppressing power, it was not sufficiently satisfactory. Further, Japanese Patent Application Laid-Open No. H10-158084 discloses a time-eluting type coated fertilizer using fertilizer particles having a "circularity count" calculated from a projected area and a contour length of a projected view within a certain range. ing. However, also in this method, the granular fertilizer often has complicated irregularities,
It was not yet satisfactory in terms of stably producing a coated fertilizer having a long-term dissolution control effect and initial dissolution suppression while satisfying sufficient quality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for stably producing a coated fertilizer having excellent initial dissolution inhibiting power and long-term dissolution control power, and having a small decrease in the amount of fertilizer components. That is.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have focused on the shape of the fertilizer particles used in the coated granular fertilizer and made intensive studies. As a result, the fertilizer particles generally have a complicated shape having concave portions and convex portions, although depending on the manufacturing method, and use only fertilizer particles in which the aspect ratio of the fertilizer particles is within a certain range. However, the dissolution controllability of the coated granular fertilizer has not always been a method capable of producing a satisfactory product. In addition, although the method using "circularity counting" is certainly an appropriate method for evaluating the deformability of fertilizer particles from spheres, it is still excellent in the case where there are concave portions in the particles. In terms of stably producing a coated granular fertilizer having dissolution controllability, the results were not always sufficiently satisfactory.

[0007] In view of the above results, the roundness or concave portion of the whole fertilizer particles can be quantitatively evaluated, and when this is used as a coated fertilizer, variation between lots is small, and it is more preferable. The conditions of the shape of the fertilizer particles that can obtain the dissolution controllability were studied. As a result, when the granular fertilizer is taken as a plane image, the angle formed by three points at a certain interval on a straight line on the plane is measured for a certain number of measurement points and a certain number of particles, and this is statistically measured. When treated, they learned that producing a coated fertilizer using fertilizer particles having a certain distribution could achieve the above-mentioned objectives, and completed the present invention.

[0008] That is, the present invention relates to a method for producing a coated granular fertilizer, which comprises coating 100 parts by weight of a granular fertilizer satisfying the following formula (1) with 1 to 50 parts by weight of a coating material. 0 ≦ D ₁₂₀ <0.025 (1) Here, when the granular fertilizer is taken in as a plane image, D ₁₂₀ is an angle formed by three points on a straight line on the plane at intervals of 100 μm. In the frequency distribution of the angle measured for 200 or more and 30 or more particles per particle, the sum of the frequency distribution of less than 120 degrees is shown.

[0009] First, a description will be given of a measuring method of the D _120. D _120, for example, can be measured using commercially available a "laser three-dimensional shape measurement system." That is, by irradiating the particles with laser light,
Measure the distance from the light source to the surface of the fertilizer particles. On this occasion,
By measuring three distances from any three points at 100-micron intervals where the light source is on a straight line on the same plane to the surface of the stationary fertilizer particles, the angle formed by the three points is calculated. The angle formed by the three points is represented by the angle of 180 degrees or less among the angles formed outside and inside the fertilizer particles. It is preferable to perform this measurement while covering the entire surface of the particles as much as possible. This measurement is randomly measured at 200 points or more per fertilizer particle. Such a measurement is performed on at least 30 fertilizer particles. A frequency distribution of at least 6000 angles measured in this way is created. D ₁₂₀ represents the sum of frequency distributions less than 120 degrees in this frequency distribution. Frequency distribution is less than 0-10, less than 10-20, 20
In the following, distribution is made at intervals of 10 degrees such as less than 30.
In the present invention, in this frequency distribution, the sum of the frequency distributions less than 120 degrees needs to be less than 0.025, and preferably 0.018 or less. The sum of the frequency distribution is 1.

[0010] As described above, the three points on the straight line on the plane image are spaced by 100 microns. In the present invention, as a result of studying this interval, the performance as a coated fertilizer can be more accurately determined by setting the interval to 80 to 120 microns, and the measurement is performed in a range that deviates from the upper limit and the lower limit. Have also found that good results are unlikely to be obtained. In view of these results, in the present invention,
This interval was measured at 100 microns. The particle diameter of the fertilizer particles is usually in the range of 1 to 10 mm, and preferably about 2 to 5 mm, but it is necessary to measure at least 200 points on the surface of one particle. At this time, it is preferable to select any three points that cover the entire surface of the particles as much as possible. If the measurement data is less than 200 per particle, good results cannot be obtained. Furthermore, in the present invention, such measurements are made at random.
Measure on more than one fertilizer particle. As a result, data with less variation can be obtained, and the object of the present invention can be achieved.

Next, a method for producing the coated granular fertilizer of the present invention will be described. The production method of the present invention is a method of coating the surface of a granular fertilizer satisfying the above conditions with a coating material.
The type of granular fertilizer is not particularly limited, and conventionally known ones can be used. Examples of preferred embodiments include urea and formaldehyde condensed urea, aldehyde condensed urea such as isobutyraldehyde condensed urea, guanylurea sulfate, nitrogen-containing organic compounds such as oxamide, ammonium nitrate,
Ammonium compounds such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium sulfate, and ammonium chloride; potassium salts such as potassium nitrate, potassium phosphate, potassium sulfate, and potassium chloride; calcium salts such as calcium phosphate, calcium sulfate, calcium nitrate, and calcium chloride; and nitric acid Magnesium, magnesium chloride, magnesium phosphate, magnesium salts such as magnesium sulfate, ferrous nitrate, ferric nitrate, ferrous phosphate, ferric phosphate, ferrous sulfate, ferric sulfate, ferrous chloride, Iron salts such as ferric chloride, and their double salts, or
One or more composites can be used. These granular fertilizers may contain a conventionally known binder for the purpose of maintaining the form and mechanical strength as granular. Examples of the binder include molasses, ligninsulfonate, and modified products thereof.

These raw manures can be produced using a conventionally known granulator, granulator, etc.
It can be produced by a rotary granulator, a centrifugal granulator, a prill granulator and the like. At the time of granulation, stirring speed,
It is necessary to appropriately set the time for granulation and sizing, the amount of water added to the fertilizer component, and the like according to the type of the fertilizer component. As a condition that more easily satisfies the conditions of the present invention, for example, in the case of a phosphoric acid nitrate-based fertilizer, it has been found that a method of containing 1 to 2% of water and granulating is preferable. It is also preferable to produce a slightly larger particle having a desired particle diameter, and then size the resultant.

Next, the coating material will be described. There is no particular limitation on the type of the coating material, and conventionally known materials can be used. For example, it is possible to use any amount selected from thermoplastic or thermosetting resins, inorganic and organic additives, emulsifiers, colorants, lubricants, oxidation promoters, photodecomposition aids, and the like. . As the above resin,
Polyolefins such as polyethylene and polypropylene,
Polyolefin copolymers such as ethylene / propylene copolymer, ethylene / butene copolymer, ethylene / octene copolymer, ethylene / vinyl ester copolymers such as ethylene / vinyl acetate copolymer, ethylene / (meth)
Acrylic acid copolymer, (letters in parentheses may or may not be read. The same applies hereinafter.) Ethylene / (meth) acrylic acid methyl ester, ethylene / (meth) acrylic acid ethyl ester, ethylene / ( Ethylene / (meth) acrylic acid alkyl ester copolymers such as meth) acrylic acid butyl ester, ethylene / (meth) acrylic acid 2-ethylhexyl ester, ethylene / carbon monoxide copolymer, polystyrene, poly (meth) acrylic acid Polyalkyl (meth) acrylates such as methyl, polyvinyl chloride and its copolymer, polyvinylidene chloride and its copolymer, vinyl chloride / vinylidene chloride copolymer, polybutadiene, polyisoprene, polychloroprene, butadiene. Die such as styrene copolymer, EPDM, styrene / isoprene copolymer Or the like can be used system (co) polymer.

In addition to these, natural resins such as petroleum resin, natural rubber and rosin, hardened oils and fats such as solid fatty acids, and modified products thereof, waxes such as beeswax, wood wax, polyethylene wax and the like are also included. Can be used. Further, thermosetting resins such as conventionally known alkyd resins and urethane resins can also be used. Further, it is also possible to use known biodegradable resins such as polylactic acid, polyhydroxybutanoic acid, polycaprolactone, and aliphatic polyesters. These resins can be used for the purpose of the present invention,
Among these, polyolefins or resins containing the same, in light of the object of the present invention of long-term dissolution control,
It can be used as a suitable material. The use amount of these resins is not particularly limited, but is preferably 30 to 100% by weight, more preferably 40 to 90% by weight in the coating material.

As the inorganic additive, sulfur, talc, clay, calcium carbonate, bentonite, silica, diatomaceous earth, metal oxides such as titanium oxide, sulfur powder and the like can be used. Talc is a preferred example. be able to. As the organic additive, powders such as starch and modified starch, agar, xanthone and the like, and optionally crosslinked polystyrene or polymethyl methacrylate can be used. The content of the inorganic additive such as talc is 80% by weight or less, preferably 70% by weight or less. The content of organic additives such as starch is 30% by weight or less, preferably 15% by weight or less. The type and amount of these additives affect the mechanical strength, dissolution, decomposability, etc. of the film, and the amount should be determined in consideration of this point. For example, an inorganic additive such as talc has an effect of increasing the specific gravity of the film, but if it falls outside the above range, the film strength will be reduced. In addition, since the amount of a hydrophilic polymer such as starch greatly affects the dissolution controllability, the amount should be determined in consideration of this viewpoint.

As the emulsifier, conventionally known emulsifiers can be used, and any of anionic, nonionic and cationic emulsifiers can be used. Among them, a nonionic emulsifier having a polymerization unit of ethylene oxide is mentioned as a preferable example, and ethylene oxide alkyl ether, ethylene oxide alkyl ester and the like can be mentioned as examples. As the colorant, pigments such as carbon black and titanium white, and other known dyes can be used. Further, as the photodecomposition aid, conventionally known organic complexes of transition metals such as iron and nickel can be used. The photodecomposition aid can be added to the film material in a required amount if necessary.

Next, the method for producing the coated granular fertilizer of the present invention will be specifically described. Using granular fertilizer in the range of D ₁₂₀ is described above, it can be prepared by coating the coating material using an apparatus such as jet tower or rolling tank. That is, it is possible to coat the surface of the granular fertilizer by a method of spraying a melt or a melt / dispersion of the coating material while supplying hot air at a predetermined temperature to the granular fertilizer in a jet or rolling state. It is possible. As a device used for coating such as a spout tower or a rolling coating device, a conventionally known device can be used. The coating material can be used by dissolving or dispersing it in an appropriate solvent if necessary. Preferred examples of the solvent include chlorinated solvents such as trichloroethylene and perchlorethylene; aliphatic hydrocarbons such as hexane, heptane and octane; and aromatic hydrocarbons such as benzene, toluene and xylene. It is also possible to use this in a molten state depending on the situation, such as when using a coating material having a low melting point.

When the production method of the present invention is carried out using a jet tower or a rolling device, the coating temperature is not particularly limited, but is usually 30 to 100 ° C., preferably 4 ° C. in terms of product temperature.
0-80 ° C. The concentration of the coating material when supplied in a solution / dispersion state by spraying or the like is not particularly limited, but is usually 1 to 20% by weight, preferably 3 to 10% by weight.
It is preferable to supply under the following conditions. The liquid to spray is
It is preferable to supply the solution by appropriately heating it if necessary. The spray time is not particularly limited, and a condition of about 10 minutes to 3 hours is usually selected. Note that an operation such as heat treatment may be performed after the formation of the film.

The amount of the coating material is 1 to 50 parts by weight based on 100 parts by weight of the granular fertilizer. Below this range, a sufficient elution suppressing effect cannot be obtained. On the other hand, if it exceeds the upper limit, a problem of deterioration in quality as a fertilizer occurs. The amount of the coating material is preferably 2 to 30% by weight, more preferably 4 to 20% by weight. The particle size of the coated granular fertilizer is usually in the range of 1 to 10 mm, preferably 2 to 5 mm.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples and comparative examples will be specifically described below. The dissolution test was performed by the following method. 1
Soak 0 g of the coated fertilizer in 200 ml of deionized water,
It was stored in a thermostat at 25 ° C. The fertilizer component eluted into water after a certain period of time was measured for the concentration of nitrogen, phosphoric acid, potassium, and the like using a total agricultural soil analyzer ZA-II. The elution rate is expressed as a percentage of the eluted component relative to the fertilizer component contained in the original coated fertilizer.

[0021]

Examples 1-3 and Comparative Examples 1 and 2 Potassium phosphate nitrate fertilizers containing 15% each as nitrogen, phosphoric acid and potassium components were used.
While appropriately changing the water content, the mixture is granulated by an Erich granulator, and the granulated product is laser-type three-dimensional shape measuring system MS-3.
D (Sigma Koki Co., Ltd.)
_D120 was measured for 50 particles at 300 points per particle. This resulted five Genpi of different D ₁₂₀ shown in Table 1. Each of these average particle diameters was 3.2.
mm.

Next, using these raw manures, a coated fertilizer was produced. The coating apparatus used was the same as that shown in FIG. 2 of JP-B-54-3104.
Talc / polyethylene (Suntech LD M2270
Mixture 1 having a weight ratio of 50/40/10 = Ethylene-vinyl acetate copolymer (made by Asahi Kasei Kogyo Co., Ltd.) / Ethylene-vinyl acetate copolymer (Evaflex 310 made by Du Pont-Mitsui Polychemical Co., Ltd.)
One part by weight was heated and dissolved / dispersed in perchlorethylene so as to be 5% by weight to prepare a liquid. Next, 10
0 parts by weight of raw manure was charged and adjusted so as to be a stable jet. While adjusting the temperature of the fertilizer particles to be constant at 65 ° C., the above-mentioned perchlorethylene dissolved / dispersed solution was sprayed from the lower part of the jet tower to produce a coated fertilizer. The results of the dissolution test of the obtained coated fertilizer are also shown in Table 1. In addition, when the short axis / long axis ratio of the granular fertilizer obtained in Comparative Example 1 was measured according to the method described in JP-A-9-30884, it was 0.83, and the granular fertilizer obtained in Comparative Example 2 was 0.83. Was measured according to the method described in Japanese Patent Application Laid-Open No. 10-158084, and was found to be 0.75.

[0023]

[Table 1]

As can be seen from Table 1, the coated fertilizer produced by the production method of the present invention has a low elution rate (initial elution rate) on the third day even with the same amount of coating, and has an 80%.
% Elution days are prolonged. Therefore, it was confirmed that the amount of coating for obtaining the same 80% elution days also required a small amount. Also, D ₁₂₀ is 0.025
Less than 3 days, the nitrogen elution rate on day 3 was 3
% Or less, and the number of days of elution with nitrogen 80% was 150 days or more, with good reproducibility.

[0025]

According to the present invention, a coated fertilizer having excellent initial dissolution properties and long-term dissolution control properties can be stably produced without deteriorating the quality as a fertilizer.

Claims (1)

[Claims] 1. A method for producing a coated granular fertilizer, comprising coating 100 parts by weight of a granular fertilizer satisfying the following formula (1) with 1 to 50 parts by weight of a coating material. 0 ≦ D ₁₂₀ <0.025 (1) Here, when the granular fertilizer is taken in as a plane image, D ₁₂₀ is an angle formed by three points on a straight line on the plane at intervals of 100 μm. In the frequency distribution of the angle measured for 200 or more and 30 or more particles per particle, the sum of the frequency distribution of less than 120 degrees is shown.