JP2007145693A - Sigmoid elution type coated granular fertilizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated granular fertilizer having an excellent sigmoid elution type elution pattern in spite of being a thin coating film. <P>SOLUTION: The coating film having at least two coating film layers of an inner layer containing an ethylene-vinyl acetate copolymer and an outer layer containing an olefin resin is formed in a ratio of 0.05-0.5 wt.% to a fertilizer particle on the surface of the fertilizer particle to be a core. It is preferable that the ratio of the inner layer is 0.1-0.5 wt.%. the content of vinyl acetate in the ethylene-vinyl acetate copolymer contained in the inner layer is 5 wt.% or above but less than 30 wt.%, more preferably 5-25 wt.%, further preferably 5-20 wt.% and the ratio of the outer layer per the fertilizer particle is 2-10 wt.%, more preferably 3-10 wt.% and further preferably 5-9 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a time-dissolved coated granular fertilizer.

  Coated granular fertilizer coated with the surface of fertilizer particles (hereinafter also referred to as “core material”) with resin, etc. has excellent elution control of fertilizer components, achieving labor savings in farm work and environmental impact Effects such as reduction have been recognized, and cultivation techniques using coated granular fertilizer are spreading and expanding.

  Compared with uncoated granular fertilizer, the amount of fertilizer component decreases according to the ratio of the coating, so even if it is multifunctional, the sense of overpricing cannot be wiped off. However, the higher the coating ratio (the thicker the coating thickness), the easier the quality control, such as elution control and maintenance of coating strength, and in order to stably supply high quality coated granular fertilizer, a certain coating thickness is required. Necessary. In particular, coated granular fertilizers with a timed elution type elution pattern consisting of an elution suppression period in which elution of fertilizer was suppressed for a certain period of time after application and an elution period in which elution continues after a certain period of time elapses during the elution suppression period Since it is necessary to strictly control leakage, methods with low productivity such as thickening the coating or recoating the coating are used for the purpose of eliminating defects (pinholes and the like) of the coating.

On the other hand, a method of suppressing defects in the coated granular fertilizer coating by adjusting the shape of the core material has been attempted. As a well-shaped core material used for the manufacture of coated granular fertilizer, a core material manufactured by a continuous granulation method of urea having a good shape (see, for example, Patent Document 1), a particle shape such as a corner or a dent “ The degree of “bitching” is evaluated by the minor axis / major axis ratio of the particles, and the selected core material (see, for example, Patent Document 2), the circularity coefficient calculated from the projected area and the length of the contour of the projected diagram. When the selected core material (for example, refer to Patent Document 3), the area when the raw manure is taken as a planar image is S, and the outer peripheral length is A, A ² / 4πS is 1.00 to 1.15 The core material (for example, refer patent document 4) whose particle | grains which are the range are 60% or more of the whole, the core material (for example, refer patent document 5) etc. which were selected by the transfer machine are disclosed. In addition, attempts to adjust the shape of the core material using wax (for example, see Patent Document 6) are also disclosed. And it is disclosed that the coated granular fertilizer manufactured using the core material with such a shape suppresses generation | occurrence | production of a defective film and the elution suppression effect etc. improve.

However, as part of efforts to reduce agricultural material costs, core materials are required to be produced at low cost by increasing productivity, and to effectively use core materials that tend to deteriorate slightly as a result. . And the coated granular fertilizer which can be manufactured also using such a core material, reduces the ratio of the coating film with respect to the fertilizer component, and has an excellent time elution type elution pattern is expected.
JP 56-79664 A Japanese Patent Laid-Open No. 9-30884 Japanese Patent Laid-Open No. 10-158084 JP-A-10-297899 JP 2005-60119 A JP-A-9-30883

An object of the present invention is to provide a coated granular fertilizer having an elution pattern of an excellent time elution type despite being a thin coating.

  The present inventors diligently studied to solve the above problems. As a result, at least two of an inner layer containing 0.05 to 0.5% by weight of the fertilizer particles and an ethylene-vinyl acetate copolymer and an outer layer containing an olefin resin are formed on the surface of the core fertilizer particles. The above-mentioned problem is solved by a time-dissolved coated granular fertilizer formed by forming a coating film having a coating layer, in particular, the vinyl acetate content of the ethylene-vinyl acetate copolymer in the inner layer is 5% by weight to 30% by weight. If it is less than that, it will be found that the concave portion of the core material surface is filled and the surface is easily smoothed, and the inner layer is excellent in adhesion between the outer layer and the fertilizer particles, and the present invention is completed based on these findings. It came.

This invention is comprised by following (1)-(8).
(1) At least two of an inner layer containing 0.05 to 0.5 wt% of an ethylene-vinyl acetate copolymer and an outer layer containing an olefin-based resin on the surface of the fertilizer particles serving as the core A time-dissolved coated granular fertilizer, characterized in that a coating having a coating layer is formed.

(2) The time-eluting coated granular fertilizer according to (1) above, wherein the ratio of the inner layer to the fertilizer particles is 0.1 to 0.5% by weight.
(3) The time-eluting coating according to (1) or (2) above, wherein the vinyl acetate content of the ethylene-vinyl acetate copolymer contained in the inner layer is 5% by weight or more and less than 30% by weight Granular fertilizer.

  (4) The time-eluting coated granular fertilizer according to (1) or (2) above, wherein the ethylene-vinyl acetate copolymer contained in the inner layer has a vinyl acetate content of 5 to 25% by weight.

  (5) The time-eluting coated granular fertilizer according to (1) or (2) above, wherein the ethylene-vinyl acetate copolymer contained in the inner layer has a vinyl acetate content of 5 to 20% by weight.

(6) The time-eluting coated granular fertilizer according to any one of (1) to (5), wherein the ratio of the outer layer to the fertilizer particles is 2 to 10% by weight.
(7) The time-dissolved coated granular fertilizer according to any one of (1) to (5), wherein the ratio of the outer layer to the fertilizer particles is 3 to 10% by weight.

  (8) The time-dissolved coated granular fertilizer according to any one of (1) to (5), wherein the ratio of the outer layer to the fertilizer particles is 5 to 9% by weight.

  The coated granular fertilizer of the present invention has an excellent elution pattern of a timed elution type even though the film is thin, for example. This provides a coated granular fertilizer that is optimal for labor-saving cultivation methods such as fertilization at the time of sowing, in which d1 / d2 that is an index of the elution pattern of a timed elution type is 0.7 or more. In addition, since the resistance to impact during handling has been improved, the initial elution suppression effect during use can be prevented from being lowered. Furthermore, according to the present invention, a coated granular fertilizer can be produced at a low cost, and thus a coated granular fertilizer that achieves both high performance and low cost is provided.

Hereinafter, the time-dissolved coated granular fertilizer of the present invention will be described in detail.
The time-eluting coated granular fertilizer of the present invention includes an inner layer containing an ethylene-vinyl acetate copolymer having a weight percentage of 0.05 to 0.5% with respect to the core material on the surface of the core material, and an olefin resin. It is a fertilizer having an elution pattern of time elution type by a film having at least two coating layers of the outer layer. In the present invention, the “time elution type elution pattern” means that elution is suppressed within a certain period after fertilization and rapid elution is started after the elapse of the period.

  In the present invention, after a fertilization, a certain period of time during which the elution of fertilizer components is suppressed is referred to as an “elution suppression period”. Is defined as the number of days (d1) until 10% by weight is reached. The period during which the elution of the fertilizer component continues from the start of elution is referred to as an “elution period”. Specifically, the elution rate of the fertilizer component exceeds 10% by weight when the coated granular fertilizer is immersed in water at 25 ° C. The number of days until reaching 80% by weight (d2).

  “Timed elution pattern” refers to an elution pattern in which the ratio of d1 and d2 (d1 / d2) is 0.2 or more. In the time-dissolved coated granular fertilizer, the value of (d1 / d2) is preferably 0.7 or more, more preferably 0.7 to 2, and still more preferably 0.75 to 1.5. Moreover, it is preferable that the value of (d1 + d2) is 30 to 360 (days). When d1 and d2 are in the above relationship, the coated granular fertilizer is particularly suitable for fertilization at the time of sowing, and does not cause a concentration disorder or length during seedling raising. The coated granular fertilizer of the present invention can satisfy the above preferable requirements.

  In the coated granular fertilizer of the present invention, the inner layer has a function of smoothing the surface of the core material and bringing the shape closer to a sphere. Therefore, the inner layer does not need to completely cover the core material. As the coating material for the inner layer, it is preferable to use an ethylene-vinyl acetate copolymer because it is excellent in adhesion to the olefin resin in the outer layer and rubber elasticity which is a characteristic of the resin itself. The vinyl acetate content in the ethylene-vinyl acetate copolymer is not particularly limited. However, if it is within an appropriate range, adhesion between coated fertilizers accompanying a decrease in adhesion due to a decrease in rubber elasticity and adhesion due to an increase in adhesiveness may be observed. Less likely to occur. The vinyl acetate content in the ethylene-vinyl acetate copolymer is preferably 5% by weight or more and less than 30% by weight, more preferably 5 to 25% by weight, and still more preferably 5 to 20% by weight. Furthermore, in consideration of processability, the melt mass flow rate (hereinafter referred to as MFR, measured by JIS K7210) of the ethylene-vinyl acetate copolymer is preferably in the range of 0.1 to 100 g / 10 min.

  The coverage of the inner layer is sufficient so that the core material can be covered sufficiently, and the content of fertilizer components is not excessively reduced so that the cost is not increased, and the elution limit by the outer layer is not affected. From the viewpoint of, for example, a range of 0.05 to 0.5% by weight is preferable, and a range of 0.1 to 0.5% by weight is more preferable. Here, the coverage of the inner layer is defined as the ratio of the coating material of the inner layer to the core material, and is calculated by the following formula.

Inner layer coverage [% by weight] = (inner layer weight / core material weight) × 100
The inner layer weight can be easily measured by removing the core material of the inner layer coated fertilizer (the core material surface having only the inner layer applied). The method for removing the core material is not particularly limited. For example, after making a hole in the coating of the inner layer coated fertilizer with a needle or the like and immersing this in water, the core material is dissolved, and after confirming that all the core material is dissolved And a method of removing moisture from the film obtained by washing with water by drying or the like. The inner layer weight and the core material weight can be calculated by measuring the weight of the inner layer coating fertilizer in advance and then measuring the weight of the inner layer coating.

The outer layer weight and the outer layer coverage are determined if the inner layer weight and the core material weight are known. For example, after producing the inner layer coated fertilizer, the core material weight and the inner layer weight are measured in advance as described above, and then the outer layer is applied to the inner layer coated fertilizer to produce the coated granular fertilizer of the present invention.
By measuring this weight (the sum of the core material weight, the inner layer weight, and the outer layer weight), the outer layer weight can be calculated.

  In the coated granular fertilizer of the present invention, the outer layer is a layer that substantially controls elution. The resin used as the coating material for the outer layer is not particularly limited, and may be either a thermoplastic resin or a thermosetting resin. Specific examples of the thermoplastic resin include olefin polymers, vinylidene chloride polymers, diene polymers, waxes, polyesters, petroleum resins, natural resins, oils and fats, modified products thereof, and urethane resins. it can. Among these, olefin-based resins such as polyethylene and polypropylene are preferable because a film having low moisture permeability can be obtained, and even if thin, the elution preventing effect is high. More preferably, it is a low density polyethylene having an MFR of 0.1 to 2 g / 10 min. If the MFR is in the above range, the solution viscosity at the time of dissolving the solvent does not become too high, the coating mixture (mixture of the coating material and the solvent) is uniformly applied in the coating formation, and the coating has sufficient resistance to impact. become. These resins can be used alone or in combination of two or more. Moreover, in the range which does not impair the effect of this invention, you may add the filler of inorganic substance and organic substance to the coating material for outer layers other than an olefin resin.

  The coating rate of the outer layer is preferably in the range of 2 to 10% by weight, more preferably 3 to 10% by weight, even more preferably 5 to 9% by weight in consideration of elution controllability and productivity. Here, the coverage of the outer layer is defined as the ratio of the coating material of the outer layer to the core material, and is calculated by the following formula.

Covering rate of outer layer [wt%] = (outer layer weight / core material weight) × 100
The content of the olefin resin in the coating material of the outer layer is preferably 20 to 75% by weight, more preferably 30 to 70% by weight, and still more preferably 40 to 65% by weight. If the content is in the above range, the function of elution suppression is sufficient, and there is no decrease in the strength of the coating, so the storage stability of the coated granular fertilizer is good, and the elution behavior of the fertilizer components obtained by the coating is A coated granular fertilizer suitable for the properties is obtained.

  Fillers that can be used as coating materials for the outer layer include plate-like fillers such as talc, mica and hydrotalcite, calcium carbonate, silica, clay, various ore pulverized products, inorganic substances such as sulfur, surfactants and many Organic substances such as sugars or derivatives thereof can be mentioned. Examples of polysaccharides or derivatives thereof include cellulose, agar, starch, chitin and derivatives thereof, and chitosan and derivatives thereof, among which starch is a low price and a preferable material. As the starch, those derived from corn, tapioca, wheat, potato, rice and sweet potato can be used. Further, modified starch such as pregelatinized starch obtained by processing these starches may be used. Moreover, the silicon-treated starch etc. which processed the starch surface with the silicone resin etc. and improved the dispersibility and fluidity | liquidity can be used. These polysaccharides or derivatives thereof can be used alone or in combination of two or more.

  The particle size of the filler is preferably 100 μm or less, and more preferably 1 to 50 μm. When the particle size is in the above range, problems such as the particle size being too large and the coating film peeling off during film formation or the coating mixture clogging the spray nozzle or the like are unlikely to occur. Even if the filler has a particle size larger than the thickness of the coating and a portion of the filler protrudes from the surface of the coating, the intended purpose can be achieved as long as the filler is partially incorporated into the coating and adhered.

In addition, various organometallic compounds may be used as a coating material for the outer layer and / or inner layer for the purpose of decomposing a resin in the coating. Examples of the organometallic compound that can be used include organometallic complexes and organic acid metal salts. Among these, iron complex and iron carboxylate are preferable because the photodegradability can be easily adjusted. Examples of the iron complex include iron acetylacetonate, iron acetonylacetonate, iron dialkyldithiocarbamate, dithiophosphate, xanthate, and benzthiazole. Examples of the iron carboxylate include iron compounds such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, behenic acid, oleic acid, linoleic acid, and linolenic acid. These may be added alone or in combination of two or more. For both the inner layer and the outer layer, the content of the organometallic compound in the coating material is preferably 0.0001 to 1% by weight, more preferably 0.001 to 0.5% by weight. When the content is in the above range, the coating is unlikely to collapse or decompose during product storage, and the desired effect can be easily obtained during application.

  The coating in the coated granular fertilizer of the present invention has two coating layers of an inner layer and an outer layer formed of the above-mentioned coating material, but may further include other coating layers as long as the effects of the present invention are not impaired. . For example, a coating containing a fertilizer component such as a trace element or a fertilizer, an agricultural chemical component, etc. in the outermost layer, a coating imparting mechanical resistance, a coating for suppressing floating under submerged conditions such as paddy fields, A layer such as a coating that controls the degradability of the entire coating can be formed.

  In the coated granular fertilizer of the present invention, as fertilizers that can be used as the core material, in addition to nitrogenous fertilizer, phosphate fertilizer, and nutrient fertilizer, plant essential elements calcium, magnesium, sulfur, iron, trace elements and silicon And the like, and the form is not particularly limited. Moreover, the fertilizer which added or made it adhere to a nitrification inhibitor and a pesticide may be sufficient. Among these, a nitrogenous fertilizer having high water solubility and easily flowing out to the environment is preferable, and urea having a low unit price per fertilizer component is more preferable.

  The particle size of the core material is not particularly limited, but is preferably 1.0 to 10.0 mm. By using a sieve, any particle size range can be selected within the above range.

  The shape of the core material is not particularly limited, but a spherical shape is preferable in order to develop the above-mentioned time-eluting elution pattern. Specifically, the circularity coefficient obtained by the following formula of the core material is preferably 0.90 or more, more preferably 0.92 or more, and still more preferably 0.95 or more. The maximum value of the circularity coefficient is 1, and the closer the value is to 1, the closer to a perfect circle. The circularity coefficient decreases as the shape of the core material collapses from a perfect circle due to irregularities or deformation on the surface of the core material.

Circularity factor = (4π x projected area of granular fertilizer) / (contour length of projected figure of granular fertilizer) ²
Moreover, when the core material with a circularity coefficient of less than 0.7 increases, leakage of fertilizer components from the obtained coated granular fertilizer tends to occur, and elution suppression at d1 becomes insufficient. Therefore, it is preferable that all the circularity coefficients of the core material are 0.7 or more. The above-mentioned “circularity coefficient of the core material” is an average value of 100 samples of the core material.

  The method for forming the coating on the surface of the core is not particularly limited. For example, a method of spraying a molten coating on the surface of the core, a coating mixture in which the coating is dissolved and dispersed (or suspended) in a solvent. Spraying on the surface of the core material (solution spraying method), spraying the monomer onto the surface of the core material, reacting on the surface to form a resin (film formation), and dipping method in which the core material is immersed in the coating mixture A known technique such as can be used. Among these, the solution spray method is preferable.

  A coating apparatus that can be used for the solution spraying method will be described with reference to the jet apparatus shown in FIG. 1 as an example. In the solution spraying method, it is preferable to vigorously stir the coating mixture in order to uniformly disperse a material such as a filler insoluble in the organic solvent in the coating mixture.

  This jet flow device transports the coating mixture to the core material 3 in the jet state via the pipe 5, sprays it with the spray nozzle 2, sprays it on the surface of the core material 3, and at the same time, the hot gas Is introduced into the guide tube 14 from the lower part of the jet tower 1, and the organic solvent in the coating mixture adhering to the surface of the core material is instantly evaporated and dried by this high-speed hot air flow. The spraying time varies depending on the concentration of the ethylene-vinyl acetate copolymer in the coating material and the olefin resin in the outer layer, the spraying rate of the coating mixture, the coating rate, etc., but these should be appropriately selected according to the purpose. It is.

  If the manufacturing method of the above-mentioned coated granular fertilizer is used, the inner layer and the outer layer of the predetermined coverage mentioned above can be formed, and it is possible to express a time-elution type elution pattern with a thin film.

  The thickness of each of the inner layer and the outer layer can be appropriately selected depending on the type and composition of the resin of the coating material, the size of the core material, and the intended elution pattern of the fertilizer component, but is preferably 10 to 100 μm on average, -70 micrometers is more preferable.

  As a coating apparatus that can be used in the present invention other than the jet apparatus shown in FIG. 1, a fluidized bed type or spouted bed type coating apparatus is disclosed in Japanese Patent Publication Nos. 42-24281 and 42-24282. Further, an apparatus for forming a fountain-type fluidized bed of granular fertilizer with a gas body and spraying a coating agent on the granular fertilizer dispersion layer formed in the center can be exemplified. As a rotary type coating apparatus, JP-A-7-31914 can be mentioned. No. 7-195007 and JP-A-7-195007, the drum is rotated by the lifter provided on the inner periphery of the drum by the rotation of the drum and then dropped, and the coating agent is applied to the surface of the falling granule. An apparatus for applying and forming a film can be mentioned.

  Among the above-mentioned coating apparatuses, a guide tube parallel to the axial direction is installed inside the tower, and a throttle disk having a plurality of ejection holes and an aperture ratio of 10 to 70% is installed at the lower part of the tower. In the spouted tower, a coating layer is sprayed onto the surface of the core material in a fluid state by forming a spouted layer with the gas spouted from below through the spout hole of the throttle disk, A coating apparatus in which a spray nozzle is inserted into at least one of the ejection holes from below to above is preferable.

  The number of the ejection holes is usually 4 to 10, and it is practically preferable to disperse them uniformly in the aperture disk. In addition, at least one spray nozzle is installed from the lower side to the upper side of the ejection hole. In the case of a plurality of spray nozzles, it is desirable to disperse the nozzles as uniformly as possible in the throttle disk. Of course, you may arrange | position for every ejection hole.

Moreover, 10 to 70% is preferable and, as for the aperture ratio of the aperture disk shown by a following formula, 20 to 60% is especially preferable.
Opening ratio (%) = (total area of the upper part of the ejection hole / upper area of the disk before drilling) x 100
When the aperture ratio is in the above range, the granular fertilizer does not accumulate on the upper surface of the squeezing disk, the squeezing action is sufficient, and the desired gas jet velocity can be obtained.

  In the present invention, the gas flow rate in the ejection hole and the gas flow rate in the guide tube are not particularly limited, but in order to stabilize the quality, an inert gas is fed into the apparatus from the ejection hole. The flow velocity of the gas in the injection hole is preferably 5 to 70 m / s, more preferably 20 to 70 m / s, and the flow velocity of the gas in the guide tube is circulated and lowered along the outside of the guide tube. A method of coating by adjusting to 0.5 to 3 times is recommended.

  The organic solvent used in the coating mixture in the present invention is not particularly limited, but a solvent capable of dissolving the ethylene-vinyl acetate copolymer, olefin resin, etc. contained in the coating material of the inner layer and the outer layer is used. Just choose. In the present invention, a chlorine-based solvent or a hydrocarbon-based solvent is preferable, and among these, tetrachloroethylene, trichloroethylene, toluene, and ethylcyclohexane are particularly preferable because a dense and uniform film can be obtained.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The “granular fertilizer” in the description of the manufacturing apparatus and the manufacturing method below refers to a core material or an intermediate product in which a part of the coating is applied to the core material surface.

(Manufacturing equipment)
The configuration of the coated granular fertilizer manufacturing apparatus used in the examples and comparative examples is the same as that of the flow sheet of FIG. 1, and the jet tower 1 has a tower diameter (inner diameter) of 600 mm, a height of 5,000 mm, and a cone angle of 50 degrees. And has a granular fertilizer inlet 15 and a coated granular fertilizer outlet 13. The spray nozzle 2 is a full-contained one-fluid spray nozzle, and 3 is a granular fertilizer. 6 is a solid-gas separator, and 7 is a cooling condenser. 8 is a roots type blower, and 12 is a heater. 9 is a dissolution tank (coating mixture adjusting tank with a stirrer), and 10 is a diaphragm type liquid feed pump. Reference numeral 14 denotes a guide tube (diameter 150 mm, length 880 mm, fluororesin-coated product), and 11 denotes a rectifying can. Reference numeral 16 denotes an aperture disk.

  Details of the aperture disk 16 are shown in FIG. In FIG. 2, the diameter is 154 mm, the inner diameter of the ejection hole 22 is 45 mm, the number of ejection holes is 4 (aperture ratio 34%), and the nozzle 2 is provided at the center of each ejection hole 22. The nozzle 2 was arranged on a circle having a diameter of 95 mm with the center of the aperture disk 16 as the center.

(Method for producing coated granular fertilizer)
The coated granular fertilizer was manufactured by the following method using the said manufacturing apparatus. The heated airflow flows from the lower part to the upper part of the jet tower 1, passes through the solid-gas separator 6, is cooled by the condenser 7, and the organic solvent in the airflow is condensed and recovered. The airflow that has passed through the condenser 7 is circulated so as to be heated from the blower 8 through the heater 12 and then led to the jet tower 1 as a high-temperature airflow.

First, using the blower 8, the granular fertilizer (core material) is introduced from the inlet 15 while sending the air whose airflow temperature at the ejection hole is maintained at 150 ° C. to the jet tower 1, thereby bringing the granular fertilizer into a jet state. . At this time, the flow rate and temperature of the heated airflow were adjusted so that the temperature of the granular fertilizer became 70 ± 2 ° C. by a temperature sensor installed in the jet tower so as to contact the granular fertilizer. The flow rate of the air flow was adjusted while measuring with a flow meter installed between the blower 8 and the rectifying can 11, and the temperature of the heated air flow was adjusted while measuring the granular fertilizer temperature and the jet tower outlet temperature. Circulating air volume is 1,000m ³
/ H, the amount of core material input is 140 kg.

  On the other hand, each component of the coating material having the composition shown in Table 1 and tetrachlorethylene were introduced into the dissolution tank 9, and a uniform coating mixture was prepared by mixing and stirring at a liquid temperature of 100 ± 2 ° C. for 1 hour.

  Next, when the granular fertilizer in the tower reaches 70 ° C., the pump 10 for supplying the coating mixture is operated to feed the coating mixture in the dissolution tank 9 to the nozzle 2 and spraying of the coating mixture is started. Spraying was performed by adjusting the supply amount of the coating liquid mixture so that the rate was the ratio shown in Table 1 with respect to the core material.

After the inner layer was coated, the outer layer was continuously coated in the same manner as described above. Thereafter, while keeping the temperature of the coated granular fertilizer at 70 ° C. ± 2 ° C., drying was performed by blowing only the air flow for 10 minutes while adjusting the temperature of the air flow. When the drying is finished, the blower 8 is stopped, the coated granular fertilizer is discharged from the discharge port 13, and after removing the solvent with dry air containing no organic solvent, the surface on which the white carbon powder is coated After the treatment, a coated granular fertilizer was obtained.

The spray rate of the coating mixture was set to 250 kg / h, and the coating material concentration in the mixture was adjusted so that the operation time was 30 minutes for the inner layer and 60 minutes for the outer layer.
As the core material, two types of urea having different shapes (both having a particle diameter of 2.4 mm to 3.6 mm and an average particle diameter of 3.0 mm) were used. Hereinafter, they are called core material A and core material B. The circularity coefficient of each core material was measured using IMAGE ANALYZER LUZEX-FS manufactured by NIRECO. When measurement was performed using 100 randomly extracted core materials, the average circularity coefficient of each was 0.952 (core material A) and 0.810 (core material B). Examples 1-3 and Comparative Examples 1-2 used the core material A, and Example 4 and Comparative Example 3 used the core material B.

In Table 1, the coverage ratio (% by weight) of the inner layer indicates the ratio to the core material, and is calculated by the following formula. Moreover, the coverage (% by weight) of the outer layer is the same, and is calculated by the following formula.
Inner layer coverage [% by weight] = (inner layer weight / core material weight) × 100
Covering rate of outer layer [wt%] = (outer layer weight / core material weight) × 100
Separately from these Examples and Comparative Examples, the same conditions as in Example 1 using an ethylene-vinyl acetate copolymer (melt mass flow rate 20 g / 10 min (JIS K 6760)) having a vinyl acetate content of 30% by weight. The coating operation was performed below, but the sticking operation was interrupted due to severe stickiness in the jet tower.

(Measurement of the number of defective particles)
In order to evaluate the elution performance of the coated granular fertilizer obtained in Examples and Comparative Examples, the following coloring test was performed.

  10 g of each coated granular fertilizer sample was accurately weighed to measure the number of particles (X). These particles are immersed in a red ink liquid (a liquid obtained by weighing 350 g of Yokogawa's pen recorder ink G9620AN and sufficiently dissolved in 10 L of distilled water) and allowed to stand at 23 ° C. for 2 hours. Washed. Thereafter, the moisture on the surface of the particles was evaporated and dried, and the particles were sorted into a white product and a red product (including a part of the film stained), and the number of red particles (Y) was measured. The number ratio of particles colored red was calculated by the following formula.

Red colored particle number ratio (%) = Y / X × 100
It represents that there are few defects of a film, so that the number rate of red colored particles is small.
The results are as shown in Table 2. In the coated granular fertilizers of Examples 1 to 4, the number ratio of red colored particles is as low as 0.1 to 0.3 (%). In these coated granular fertilizers, the irregularities on the surface of the core material become smooth, and pinholes It is considered that no good film was formed. On the other hand, it is considered that the coated granular fertilizers of Comparative Examples 1 to 3 had a higher red colored particle number ratio than Examples 1 to 4, and the coating quality was inferior.

(Measurement of dissolution behavior and coverage of coated granular fertilizer)
10 g of the coated granular fertilizer obtained in Examples and Comparative Examples and 200 mL of distilled water adjusted to 25 ° C. in advance were put into a 250 mL plastic container with a lid and left in an incubator set at 25 ° C. . Seven days later, all the water was extracted from the container, and the amount of urea contained in the extracted water (urea elution amount) was determined by quantitative analysis (dimethylaminobenzaldehyde method “detailed fertilizer analysis method second revised edition” Yokendo). Next, the sample after draining water was put into the container again, 200 mL of distilled water was again put into the container, and left for 7 days, and the amount of urea was determined in the same manner as the previous time. This operation was repeated until the integrated value of urea elution amount reached 80% by weight based on the design value.

  Thereafter, the coated granular fertilizer was ground in a mortar, and the content of the fertilizer was dissolved in 200 mL of water, and then the urea remaining amount was quantitatively analyzed in the same manner as described above. The total urea elution amount and the urea remaining amount are added to the total amount of urea, and the relationship between the total elution amount of urea eluted in water and the number of days is graphed, and an elution rate curve is created. The number of days reaching 80% by weight was determined. The results are shown in Table 2. The number of days from the start of dissolution measurement until the dissolution rate reached 10% by weight was defined as “d1”, and the number of days until the dissolution rate reached 80% by weight thereafter was defined as “d2”. That is, the number of days from the start of elution measurement until the elution rate reaches 80% by weight is d1 + d2.

The coating residue in the mortar was collected, dried at 50 ° C. for 2 hours, cooled to room temperature, and then weighed as the coating material weight. The sample coverage was calculated from the coating weight using the following formula.
Sample coverage [wt%] = (film weight [g] / (10−coating weight [g]) × 100
The difference between the coverage at the time of design (design value of the inner layer + outer layer) and the sample coverage obtained by manufacturing was determined, and the adhesion due to film formation was evaluated. The results are shown in Table 2.

  From the results of the number ratio of the red colored particles and the dissolution rate on the third day, it was confirmed that the coated granular fertilizer of the comparative example was inferior to the initial dissolution. Further, from the comparison of the results of Examples and Comparative Examples 2 and 3, when wax is used for the inner layer (Comparative Examples 2 and 3), the outer layer easily peels from the inner layer during the jet flow in the coating step inside the jet tower. Therefore, the deviation between the actually measured value and the design value of the coverage increases, and on the other hand, when an ethylene-vinyl acetate copolymer is used for the inner layer (Examples 1 to 4), the excellent adhesiveness of the copolymer. As a result, it was considered that the actual measurement value of the coverage was almost as designed.

  The time-dissolved coated granular fertilizer of the present invention has an ethylene-vinyl acetate copolymer as an inner layer, so it absorbs some impact during manufacturing and handling of the fertilizer and suppresses elution in the inner layer even if the outer layer can be damaged. It shows what you can do. In addition, when coating the outer layer that mainly controls elution, the impact resistance of the core material is enhanced by the inner layer in advance, thereby preventing partial crushing and forming a film with fewer defects. it can. That is, when the inner layer of the comparative example is a wax, it is difficult to form a good film because it is not familiar with the outer layer, but a good film can be formed by using the ethylene-vinyl acetate copolymer of the present invention. Show.

  The time-dissolved coated granular fertilizer of the present invention can be suitably used as a fertilizer effect-controlling type fertilizer.

Example flow sheet for equipment used for coating An example of an aperture disk (orifice)

Explanation of symbols

1. Jet tower 2. 2. Spray nozzle Granular fertilizer (core material)
4). Circulating air flow piping5. 5. Coating liquid supply pipe 6. Solid-gas separator Condenser 8. Blower 9 Dissolution tank 10. Pump 11. Rectification can 12. Heater 13. Outlet 14. Guide tube 15. Granular fertilizer inlet 16. Diaphragm disc 21. Main disc 22. Outlet

Claims (8)

  Covering at least two layers of the surface of the fertilizer particles as a core, an inner layer containing 0.05 to 0.5% by weight of the fertilizer particles and containing an ethylene-vinyl acetate copolymer, and an outer layer containing an olefin resin A time-dissolved coated granular fertilizer, characterized in that a film having a layer is formed.   The time-eluting type coated granular fertilizer according to claim 1, wherein the ratio of the inner layer to the fertilizer particles is 0.1 to 0.5 wt%.   The time-eluting coated granular fertilizer according to claim 1 or 2, wherein the ethylene-vinyl acetate copolymer contained in the inner layer has a vinyl acetate content of 5 wt% or more and less than 30 wt%.   The time-dissolved coated granular fertilizer according to claim 1 or 2, wherein the ethylene-vinyl acetate copolymer contained in the inner layer has a vinyl acetate content of 5 to 25 wt%.   The time-dissolved coated granular fertilizer according to claim 1 or 2, wherein the ethylene-vinyl acetate copolymer contained in the inner layer has a vinyl acetate content of 5 to 20% by weight.   The time-eluting coated granular fertilizer according to any one of claims 1 to 5, wherein a ratio of the outer layer to the fertilizer particles is 2 to 10% by weight.   The time-eluting coated granular fertilizer according to any one of claims 1 to 5, wherein a ratio of the outer layer to the fertilizer particles is 3 to 10% by weight.   The time-eluting type coated granular fertilizer according to any one of claims 1 to 5, wherein a ratio of the outer layer to the fertilizer particles is 5 to 9% by weight.

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