JPH0223517B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a granular fertilizer coated with a degradable coating and a method for producing the same. More specifically, poly3-
The present invention relates to the fertilizer coated with a degradable film containing hydroxy-3-alkylpropionic acid as an essential resin component, and to a method for producing the fertilizer. The coating according to the present invention is decomposed by soil microorganisms and does not ultimately remain in the soil. Various auxiliary agents or chemicals can be added to the coating according to the present invention in order to control the elution of granular fertilizer. [Prior Art] In order to match the elution of fertilizing ingredients in granular fertilizer applied to soil with the requirements accompanying the growth of crops, or to prevent moisture absorption or caking during the distribution process of granular fertilizer, various methods are used. Research has been done. One method is to coat the surface of granular fertilizer with a high molecular weight polymer. This coating can be either thermoset or thermoplastic. However, coating with such a high molecular weight polymer also has various problems as described below. Methods using thermosetting resins include, for example, styrenated alkyd resins and phenolic resins (British Patent No. 954555), fatty oil-modified alkyd resins, fatty oil dicyclopentadiene copolymers, diisocyanate-modified fatty oil polymers (Japanese Patent Publication No. 1973-1996), 28927) or phenolic resins (Japanese Patent Publication No. 1983-28457). In addition, methods using thermoplastic resins include, for example, polystyrene, polyvinyl chloride,
A copolymer consisting of two or more constituent monomers such as polyvinylidene chloride, polyacrylonitrile, polyethylene and polyfluorinated alkanes or the like (British Patent No. 815829), vinyl acetate emulsion polymerization liquid (Japanese Patent Publication No. 15832-1983) It is shown. As a problem when using a polymer, especially a thermoplastic resin solution or its emulsion polymer solution, as a coating material, Japanese Patent Publication No. 42-13681 describes how to coat the surface of granules with a liquid resin or a stringable resin. Due to the stringiness of the resin, it has been shown that at a length where only a few percent of the resin is coated, the particles stick together and form blocks, making it difficult to coat them uniformly and thickly without forming individual particles. There is. Japanese Patent Publication No. 50-99858, Japanese Patent Publication No. 51-75874, Japanese Patent Publication No. 53-Sho.
-98265 relates to a method for coating granular fertilizer invented by the present inventors, but these publications state that by selecting the properties of the resin solution and the drying conditions, blocking can be avoided during the coating process. A method for efficient coating in one step is shown. Japanese Patent Application Laid-Open No. 50-99858 discloses that when granular fertilizer is coated with a coating material mainly composed of polyolefin, a solution of the coating material is sprayed onto the granular fertilizer, and at the same time the granular fertilizer is coated, it is dried with a high-speed hot air flow to coat the granular fertilizer. It shows how to do this. The characteristics of this technology are that it can be coated uniformly with an extremely thin coating, and that the elution rate can be adjusted by dispersing a surfactant in the coating as an elution regulator. JP-A-51-75674 discloses that a polyvinylidene chloride resin and an ethylene/vinyl acetate copolymer containing 5% by weight or less of vinyl acetate can uniformly cover granular fertilizer as an extremely thin film, similar to polyolefin resin. ing. Japanese Patent Publication No. 60-37074 discloses that coating with a polyolefin resin, an ethylene vinyl acetate copolymer, and a surfactant can provide highly stable elution control. Furthermore, in Japanese Patent Publications No. 60-3040 and No. 55-1672, by dispersing inorganic powder such as talc and sulfur into the polyolefin resin coating, the elution control function is maintained and the residue after elution is reduced. It has been shown to accelerate capsule disintegration and degradation. These series of coating techniques developed by the inventors of the present application have been put into practical use as coated granular fertilizers coated with granular urea or chemical fertilizers, and have come to be widely used as excellent elution control fertilizers. With these fertilizers, elution control can be continuously adjusted for several hours to several years without changing the film thickness.
Basically shows a slow-release elution pattern,
Furthermore, the capsules after the fertilizing ingredients have been eluted tend to deteriorate and decompose when exposed to light or oxygen.
However, there has been a demand from stakeholders for the emergence of coated granular fertilizers, such as slow-release type and time capsule type coated with more advanced microbially degradable materials, in which the capsules are quickly decomposed by microorganisms after the fertilizing ingredients have been eluted. . [Purpose of the Invention] In view of these circumstances, the inventors of the present invention developed a slow-release type fertilizer based on microbially degradable materials that can be controlled at will, and a time capsule type fertilizer that does not elute until a predetermined period of time and then elutes in a short period of time. We conducted research on fertilizers and arrived at the present invention. It was confirmed that poly(3-hydroxy-3-alkylpropionic acid), which is an essential coating material for the present invention, and especially the polymer whose alkyl group is methyl or ethyl, is an excellent microbially degradable polymer material. Later, in order to complete the present invention, attempts were made to coat the material by dissolving it in various solvents. In the case of a certain solvent solution, if it was added in the form of a spray, the coating material would stick and the particles in the coating would stick together, making it impossible to coat a single particle. In addition, in some cases, it was not possible to obtain a tough coating peculiar to polymers. As a result of trial and error, it became possible to coat a single grain with a uniform coating by the method described below, which is based on the coating method disclosed in Japanese Patent Application Laid-Open No. 50-99858 invented by the present inventors, and the method of the present invention has been realized. was discovered and the present invention was completed. In order to complete these technologies, it is necessary to find a polymer material that satisfies all of the following. To find a strong polymer material that is easily decomposed by soil microorganisms. To be able to develop a coating technology using that material. To be able to control elution of materials coated with that material. To combine it with other materials. The elution rate can be controlled over a wide range. The elution rate can be controlled even under conditions where soil microorganisms attack the soil. In the early stages of these search studies, various polymeric materials were investigated and evaluated for their ability to be buried in soil and degraded by soil microorganisms.
It was found that some of these polymeric materials were subject to decomposition. Various coating processes have been investigated using these degradable materials, but in most cases it has not been possible to form a uniform coating that can withstand elution control.
Even those that could be coated into a uniform film were evaluated by the physical properties of the film and an underwater dissolution test, and as a result, most of them could not be put to practical use. The materials screened here can be further combined with other materials to form a composite material, and it has been confirmed through an underwater dissolution test that the dissolution rate can be controlled over a wide range. These materials were also tested for dissolution in soil under conditions where they were degraded by soil microorganisms.
By making composite materials, for example, if there are many polymeric materials that are non-degradable by microorganisms, the decomposition of the capsule itself in the soil could be suppressed, but this is not the case with current slow-release type elution control fertilizers. It was available as such. The present invention was achieved as a result of long-term research and development. As is clear from the above description, an object of the present invention is to provide a granular fertilizer coated with a film decomposable by soil microorganisms and a method for producing the same. [Structure/effect of the invention] The present invention (second invention) has the following main structures (1) and (6).
It has the embodiment configurations of (2) to (5) or (7) to (9). (1) A granular fertilizer coated with a degradable film containing poly-3-hydroxy-3-alkylpropionic acid as an active ingredient. (2) The granular fertilizer according to item (1) above, wherein the alkyl group is a methyl group or an ethyl group. (3) The degradable film is poly-3-hydroxy-3-
In addition to alkylpropionic acids, polyvinylidene chloride, polyolefin, rubber, ethylene/vinyl acetate copolymer, polystyrene, polymethyl methacrylate, ethylene/carbon monoxide copolymer, ethylene/vinyl acetate/carbon monoxide copolymer, or selected from resins such as ethylene/ethyl acrylate copolymer, ethylene methacrylic acid copolymer, and low-molecular resinous substances such as paraffin, hydrogenated oil, solid fatty acids and their metal salts, beeswax, wood wax petroleum resin, or rosin. The above-mentioned substance is made of one or more kinds of substances.
Granular fertilizer as described in (1). (4) The granular fertilizer according to item (1) or item (3) above, wherein the degradable coating is inorganic or organic and contains poorly water-soluble or insoluble powder. (5) The fertilizer according to item (4) above, wherein the inorganic powder is talc, clay, silica, diatomaceous earth, metal oxide, or sulfur powder, and the organic powder is starch or crotylidene diurea powder. (6) An organic solvent solution of poly-3-hydroxy-3-alkylpropionic acid is added to a fluidized granular fertilizer in the form of a spray, and at the time of addition, a high-speed hot air stream is blown onto the granular fertilizer to remove the added organic solvent. A method for producing a granular fertilizer coated with a degradable film, which is characterized by instantaneously removing and drying an organic solvent in a solvent solution. (7) Poly 3-hydroxy-3 in organic solvent solution
-In addition to alkylpropionic acids, polyvinylidene chloride, polyolefin, rubber, ethylene/vinyl acetate copolymer, polystyrene, polymethyl methacrylate, ethylene/carbon monoxide copolymer, ethylene/vinyl acetate/carbon monoxide copolymer , or selected from resins such as ethylene/ethyl acrylate copolymer, ethylene methacrylic acid copolymer, and low-molecular resinous substances such as paraffin, hydrogenated oil, solid fatty acids and their metal salts, beeswax, wood wax petroleum resin, or rosin. The manufacturing method according to item (6) above, wherein one or more substances are dissolved and used. (8) The manufacturing method according to item (6) or item (7) above, wherein an inorganic or organic, poorly water-soluble or insoluble powder is further mixed and dispersed in the organic solvent solution. (9) The method according to item (8), wherein the inorganic powder is a powder of talc, clay, silica, diatomaceous earth, metal oxide, or sulfur, and the organic powder is a powder of starch or crotylidene diurea. The present invention is characterized by using poly-3-hydroxy-3-alkylpropionic acid (chemical structure []) as a soil microorganism-degradable polymer material for forming a degradable film. -Hydroxy-3-methylpropionic acid (chemical structure []), poly-3-hydroxy-3-ethylpropionic acid (chemical structure [])
and a copolymer (chemical structure []) of 3-hydroxy-3-merulpropionic acid and 3-hydroxy-3-ethylpropionic acid. These basically have the following chemical structure, but the bonds in the copolymer [] may be random or block. The granular fertilizer of the present invention can obtain a sufficient elution control function even when coated with these poly-3-hydroxy-3-alkylpropionic acid materials. That is, for example, urea, which has a high deliquescent solubility, can last several tens of days, and potassium sulfate, which has small physical properties, can last several hundreds of days. When elution is to be accelerated by these single materials, the degree of acceleration can be adjusted depending on the amount of dispersion by dispersing the surfactant into the formed film, that is, within the capsule, or by dispersing powder as a filler. However, with these methods, although it is possible to shorten the elution period more than using a single material, it is difficult to extend it. The surfactant that can be used in the present invention may be cationic, anionic, amphoteric, or nonionic, but the balance between hydrophilicity and hydrophobicity of the surfactant is important. It is. If the hydrophilicity is too strong, the particles will not be uniformly dispersed in the film and will aggregate, causing film defects. Those with strong lipophilicity have no effect on the coating, but tend to have a slightly inferior elution promotion effect. The HLB of these surfactants is 15 or less,
Preferably it is in the range of 11-13. The filler powder used in the present invention is a poorly water-soluble or insoluble powder, and either inorganic or organic powders can be used, but the particle size is less than half the thickness of the coating, preferably 1/4. The following are good. These fillers are uniformly dispersed within the film, but those with poor dispersibility require treatment to improve dispersibility, such as surface treatment with silicone or the like, or use of a surfactant to make them easier to disperse. Preferred examples of these inorganic powders include talc, calcium carbonate, clay, diatomaceous earth, silica and its salts, metal oxide sulfur, and the like. Sulfur in these inorganic powders is a material that undergoes microbial decomposition, and as a component of the composite material of the coating, it has the advantage of being easily decomposed in the soil. On the other hand, organic powders are inferior to inorganic fillers as fillers, but they are often easily decomposed by microorganisms, and their soil decomposition as composite materials has advantages over sulfur, such as starch, etc. Preferred materials include starchy materials and slow-release nitrogen fertilizers such as clotilidage urea, which generates NH ⁺ ₄ through microbial decomposition in the soil. When these powders are used as fillers, as the amount used increases, the film strength tends to decrease regardless of which powder is used. Another method of controlling the elution of fertilizing ingredients in the present invention is to use other polymeric materials or waxes as film-forming materials. This method is particularly effective in delaying elution compared to the case of a single material, but it can also be accelerated depending on the selection of composite materials. These methods can be used in conjunction with the first method, which is the promoting effect of incorporating surfactants and fillers, and are often desirable. Degradable coating materials that can be used in combination with poly-3-hydroxy-3-alkylpropionic acid-based materials include polyvinylidene chloride and its copolymers, polyolefin-based resins, ethylene/carbon monoxide copolymers, and ethylene/carbon monoxide copolymers. vinyl acetate copolymer,
These include ethylene/vinyl acetate/carbon monoxide copolymer, ethylene/ethyl acrylate copolymer, ethylene/methacrylic acid copolymer, rubber resin, polystyrene, polymethyl methacrylate, etc. Among these, polymeric materials such as polyvinylidene chloride and its copolymers, polyolefin resins, and ethylene/carbon monoxide copolymers are preferred materials for the purpose of delaying elution. On the other hand, examples of polymeric materials that promote elution include ethylene/vinyl acetate copolymers with a particularly high vinyl acetate content (more than 40% by weight), rubber (rubber-based resins), natural rubber, polyisoprene, and polybutadiene. , a styrene-butadiene random copolymer. On the other hand, preferred wax-like materials to be composited include paraffin, solid fats and oils, especially hydrogenated oils, solid fatty acids and their divalent and trivalent metal salts, beeswax, wood wax, rosin, and petroleum resins. It is a material that delays elution. According to the invention, poly3-hydroxy-3
- Coated granular fertilizers with various functions can be produced by using alkylpropionic acid-based materials as coating materials. Granular fertilizers used as core materials vary in composition, particle size, shape, etc., and even when imparting the same function, the coating state must be changed depending on the type, particle size, and shape of the fertilizer. For example, the practical film thickness of the coated granular fertilizer of the present invention is in the range of 20 to 300 microns, but the coverage to maintain this film thickness varies greatly depending on the particle size (particle size) and shape. When the thickness of these films is less than 20μ, it is difficult to sufficiently suppress elution, and there are almost no cases where a film thickness exceeding 200μ is required. By the way, in the well-known slow-release type, it is usually 20~
The preferred range is 120μ, and 80 to 200μ for time capsule type. Furthermore, the setting of the elution period is greatly influenced by the properties of the granular fertilizer. Even when using the same particle size and shape, the same coating composition, and the same film, the duration of elution can vary by more than 10 times depending on the type of fertilizer (e.g. urea, potassium sulfate, etc.). When designing the coated granular fertilizer of the present invention, first the type, particle size and shape of the fertilizer, which is the core substance, are determined, and then the film thickness and coverage are determined. Under these specific conditions, the sustainability of elution is investigated for slow-release type, but this method is based on the four methods mentioned above: surfactant, filler, specified polymer material, specified Combinations of one or more waxes are possible, and there are many combinations with the same long-lasting composition. For example, in order to obtain a coating that has the same elution-sustaining function as a coating made only of poly-3-hydroxy-3-alkylpropionic acid materials, we first elute polymeric materials such as polyethylene and waxes such as hydrogenated oil. Retardants and poly-3-hydroxy-3
- By mixing alkylpropionic acid-based materials to improve elution sustainability, if fillers and surfactants are added to promote elution, poly-3-hydroxy-3-alkylpropionic acid-based materials can be created. This means that a product with a sustained elution function equivalent to that of Although there are infinite combinations based solely on elution sustainability, there are restrictions from other properties. The first constraint is the strength of the coating; if the filler exceeds 80% of the coating weight, the coating strength will weaken, and the coating may be damaged when handled as a general-purpose fertilizer, impairing the elution control function. . Similarly, waxes such as paraffin and hardened oil used as elution retardants cause problems in film strength if they exceed 50% by weight relative to other polymeric materials. The second constraint is the microbial degradability of the film, and if there are many macromolecules that are not degradable by microorganisms in the film, the decomposition of the film will be inhibited. This varies depending on the presence and amount of microbially degradable filler, but if there is no microbially degradable filler, the microbially non-degradable resin is 40% (by weight) of the polymer material.
It should be kept below 60% even when microbially degradable fillers are used. The coated granular fertilizer of the present invention is covered with a film degradable by microorganisms, and is eroded by soil microorganisms, so it tends to elute more quickly than in water, particularly in soils with strong microbial activity. These trends are
increasing the proportion of microbially non-degradable polymeric materials;
Adjustments can be made by using a disinfectant in combination and by covering the surface with an extremely thin protective film, but it is difficult to provide the same functionality as that covered with a microbially non-degradable film. However, the product of the present invention is useful for today's agriculture as an elution-controlled fertilizer, and is extremely significant as the world's first elution-controlled fertilizer made from a microbially degradable polymeric material. Furthermore, the present invention can also produce a time capsule type fertilizer in which the film is thicker than the slow-release type to suppress elution, and the entire amount is eluted in a short period of time (when the film is broken by microbial decomposition) after a certain period of time. The period of suppression of these elutions can be controlled to some extent by the above-mentioned suppression of decomposition, but it is still incomplete. However, the present invention is also significant as it opens the way to a completely controlled time capsule type fertilizer. The present invention is applicable to granules containing all fertilizer components. In other words, ammonium sulfate, ammonium chloride, ammonium nitrate, urea, potassium chloride, potassium sulfate, potassium nitrate, sodium nitrate, ammonium phosphate, potassium phosphate, lime phosphate, etc. alone or in combination of two or more of these are useful as water-soluble fertilizers. It is particularly effective for fertilizers containing Also OMUP
When applied to poorly soluble fertilizers such as (crotylidene diurea), IBDU (isobutylidene diurea) and oxamide, the effective period of these fertilizers can be extended. The coating material used in the method of the present invention is used after being dissolved or dispersed in an organic solvent. The solvent used at this time is one that dissolves polymeric materials and waxes, and is not soluble when heated to the poly-3-hydroxy-3-alkylprobionic acid-based material essential to the present invention. However, when cold, the polymer precipitates out as fine crystals and becomes cloudy, but it is selected from a group of solvents that form a jelly-like state. The solution for these coatings or the solution in which a predetermined filler is dispersed is kept at a high temperature to prevent the polymeric material in the solution from precipitating or becoming jelly-like, and is sprayed and granulated with a high-speed hot air stream. It is essential that the fertilizer be sprayed and the solvent be dried instantly. The selection of the solvent in the method of the present invention is a necessary condition to prevent particles from becoming blocked and cake-like due to the adhesiveness of the polymeric material during coating, and instant drying by high-speed hot air flow is a necessary condition. This is a necessary condition to avoid evaporation of the solution and precipitation of the polymer during the cooling or concentration process, which would inhibit the film formation inherent to the polymer. The product of the present invention can be obtained by selecting the solvent and maintaining the drying conditions as described above, but the speed of the hot air flow sprayed together with the coating liquid is 10 m/sec or more, preferably 15 m/sec.
The above is necessary. When powder is used as a filler in the coating according to the present invention, it is necessary to forcibly stir the powder in a dissolution tank or the like so that the powder is uniformly mixed in the organic solvent solution without settling or floating. It is necessary to adjust the viscosity of these coating materials so that the viscosity is 50 cp or less at the temperature in which they will be used. If the viscosity is 50 cp or more, even if the solvent is selected as described above, it will not be possible to partially block the resulting coated granular fertilizer, so in this case, the coating solution must be further diluted before use. A spouted bed apparatus is the most suitable and most recommended apparatus for carrying out coating while maintaining these conditions of the method of the present invention. The general shape of a spouted bed device is an inverted conical lower part, the lowermost part of which has an air outlet. When particles are placed in this tank and hot air is ejected from the jet nozzle, the particles are sprayed upward, then fall into the tank and circulate as if being ejected again. . The product of the present invention can be easily obtained by installing a coating liquid spray nozzle at the spout and spraying the sprayed particles. At this time, the temperature of the particles during coating is maintained at an upper limit at which the polymeric material does not fuse or the coating is damaged. The present invention will be explained below with reference to Examples. Example (1) Selection of solvent used in the method of the present invention Poly(3-hydroxy-3
-methylpropionic acid) 0.3g (molecular weight 750000)
Take 30 ml of the test solvent and put it in an oil bath, and while stirring, gradually raise the temperature (°C/min as a guide) and dissolve. At this time, if signs of dissolution are seen, the temperature increase rate is further slowed down to determine the melting temperature. Once completely dissolved, stop stirring, remove from the oil bath, and allow to cool slowly by natural cooling. During this gradual cooling process, some of the solution may become cloudy or jelly-like, and the temperature at this time is considered the gelling point of this solution. Solvents that can be used in the present invention have a gel point. Examples of searches for such solvents are shown in Table 1.

【table】

[Table] (2) Elution promotion effect of filler 1 Figure 1 shows the jet coating device used to manufacture the prototype in this example. 1 is the jet tower and the tower diameter
200mm, height 1500mm, air outlet diameter 45mm, cone angle 50°, fertilizer inlet 2, exhaust gas outlet 3
has. The jet air is sent from the blower 10, passes through the orifice flow meter 9 and the heat exchanger 8, and reaches the jet tower.The flow rate is controlled by the flow meter, the temperature is controlled by the heat exchanger, and the exhaust air is discharged from the exhaust port 3 to the outside of the tower. derived. The granular fertilizer used for coating is introduced from the fertilizer inlet 2 while passing a predetermined hot air to form a jet stream. The hot air temperature is detected by thermometers at T ₁ , the particle temperature in the coating at T ₂ , and the exhaust temperature at T ₃ . When T ₂ reaches a predetermined temperature, the coating liquid is sprayed in the form of a spray through the fluid nozzle 4 toward the jet stream. The coating liquid is stirred in a liquid tank 11, and if powder is used, it is stirred so that the powder is uniformly dispersed in the coating liquid. The coating liquid is sent by the pump 5 and reaches the nozzle, but it is heated with steam so that the temperature does not drop below 80°C. When a predetermined coverage rate is reached, the blower is stopped and the covered fertilizer is discharged from the outlet 7. Sample production in this example was carried out under the following conditions. Solvent: Trichlorethylene single-fluid nozzle: Opening 0.8mm full condenser type Air volume: 2.5m ² /min Hot air temperature: 95℃±3℃ (jet tower inlet) Fertilizer type: 5-8mech granular urea fertilizer Input amount: 3Kg Coating solution concentration: Solid content 2% (weight) Coating solution supply rate: 0.2Kg/min Coating solution supply time: 38min Coverage rate: 5% (relative to fertilizer) 2) Elution rate measurement The elution rate of the prototype sample is as follows. It was determined by the method. Immerse 10 g of the sample in 200 ml of water and leave it at 25°C under sealed conditions. After a predetermined period of time, the sample and water are separated and the urea eluted into the water is determined by quantitative analysis, and the percentage of total urea and eluted urea in the test sample is determined and used as the elution rate. Elution rate = urea dissolved in water / total urea in the test sample x 100 After measuring the elution rate, the sample (coated urea) was immersed again in 200 ml of fresh water, left at 25°C, and then soaked again in the same manner. The elution rate can be determined. The number of days of standing on the horizontal axis and the cumulative dissolution rate on the vertical axis are drawn on a graph and connected with lines to form a dissolution rate curve. 3) The sample coating materials and coating conditions are shown in Table 2.

[Table] The results of elution rate measurement are shown in Figure 2. (3) Example of combined use with waxes Sample preparation and measurement of dissolution rate were carried out in the same manner as in 2 above. The sample coating material and coating situation are as follows.
The table and elution rate measurement results were as shown in Figures 3-1 and 3-2.

[Table] (4) Example of combined use with polymer materials In this example, since a flammable solvent is used, the first
Air-cooled and separated N ₂ gas was piped to the blower 10 shown in the figure, and N ₂ gas was jet-coated instead of air. The conditions for sample production are as follows. Solvent: Toluene nozzle: Opening 0.8mm full con type (fluid nozzle) N2 _amount : ^2.5m2 /min _N2 temperature: 100℃±3℃ (jet column inlet) Fertilizer type: 5-8 mesh granular urea Fertilizer input amount: 3Kg Coating solution concentration: Solid content 2% (weight) Coating solution supply amount: 0.15Kg/min Coating solution supply time: 50min Coverage rate: 5% (relative to fertilizer) Measurement of elution rate of trial sample is as described in the previous section It was carried out in the same manner as in 2. The sample coating materials and coating conditions are shown in Table 4.
The results of elution rate measurement were as shown in FIG.

[Table] (5) Elution in soil and soil decomposition of film 1) Soil elution Paddy soil (sandy loam in Nagano-cho, Minamata) was air-dried and sieved through a 10-mesh sieve, and the bottom of the sieve was tested.
Mix 250 g of dry soil with 2 g of the coated granular fertilizer sample of the present invention, put it in a 500 ml plastic bottle, add 150% of the maximum water capacity, and make it into a paddy field.
Leave it at 25℃. After a predetermined period of time, the entire amount of soil containing the sample is transferred onto a 10 mesh sieve and sieved under water to separate the sample and soil. Carefully discard each grain of the sample remaining on the sieve, transfer the whole amount to a mortar and grind it, dissolve the ground sample in a volumetric flask with water, fill it up to the marked line, and filter it with dry filter paper. The separated urea is analyzed to determine the total amount of urea remaining in the coating. The elution rate in soil is calculated using the following formula. Elution rate in soil = total urea in the test sample - total urea remaining in the film / total urea in the test sample x 100 The results of testing samples Nos. 11 to 14 are shown in Figure 5. 2) Soil decomposition test for the film 5g of the sample of the present invention was placed in water at 30℃ for 2 hours by making a pinhole using a sharp needle.
Leave it for a week to dissolve the urea and create an empty capsule. Empty capsules separated from the eluate
Mix with 400g of the dry soil used in (1), add water to 60% of the maximum water capacity, cover with polyvinylidene chloride film, and leave in a constant temperature bath at 30℃. The capsules are dug out every two months to observe the condition of the capsules, and the evaporated moisture is corrected during this period. Table 5 shows these observation conditions.

【table】

[Table] (6) Table 6: Under the sample production conditions of Example (2)-1), the coating liquid supply time was extended by 76 minutes (double) and the coating rate was 10% (relative to fertilizer). A sample was made using the raw materials shown in the table below. The dissolution rate of this sample in water was determined by the method of Example (2)-2), and the dissolution rate in soil was determined by the method of Example (5)-1). The measurement results for both dissolution rates were as shown in FIG.

【table】 [Brief explanation of drawings]

FIG. 1 is a flow sheet of an apparatus used in the method of the present invention, and FIGS. 2 to 6 are explanatory diagrams of embodiments of the present invention.

Claims (1)

[Scope of Claims] 1. A granular fertilizer coated with a degradable film containing poly-3-hydroxy-3-alkylpropionic acid as an active ingredient. 2. The granular fertilizer according to claim 1, wherein the alkyl group is a methyl group or an ethyl group. 3 The degradable film is poly-3-hydroxy-3-
In addition to alkylpropionic acids, polyvinylidene chloride, polyolefin, rubber, ethylene/vinyl acetate copolymer, polystyrene, polymethyl methacrylate, ethylene/carbon monoxide copolymer, ethylene/vinyl acetate/carbon monoxide copolymer, or ethylene ethyl acrylate copolymer, ethylene methacrylic acid copolymer resins, paraffin, hydrogenated oil, solid fatty acids and their metal salts,
The granular fertilizer according to claim 1, comprising one or more substances selected from low-molecular resin substances such as beeswax, wood wax, petroleum resin, and rosin. 4. The granular fertilizer according to claim 1 or 3, wherein the degradable coating is inorganic or organic and contains poorly water-soluble or insoluble powder. 5. The fertilizer according to claim 4, wherein the inorganic powder is talc, clay, silica, diatomaceous earth, metal oxide, or sulfur powder, and the organic powder is starch or crotylidene diurea powder. 6 Adding an organic solvent solution of poly-3-hydroxy-3-alkylpropionic acid to a fluidized granular fertilizer in the form of a spray, and at the time of the addition, blowing a high-speed hot air stream onto the granular fertilizer to remove the added organic solvent solution. A method for producing granular fertilizer coated with a degradable film, which is characterized by instantly removing the organic solvent therein and drying it. 7 Poly 3-hydroxy-3 in organic solvent solution
-In addition to alkylpropionic acids, polyvinylidene chloride, polyolefin, rubber, ethylene/vinyl acetate copolymer, polystyrene, polymethyl methacrylate, ethylene/carbon monoxide copolymer, ethylene/vinyl acetate/carbon monoxide copolymer , or selected from resins such as ethylene/ethyl acrylate copolymer, ethylene methacrylic acid copolymer, and low-molecular resinous substances such as paraffin, hydrogenated oil, solid fatty acids and their metal salts, beeswax, wood wax petroleum resin, or rosin. 7. The manufacturing method according to claim 6, wherein one or more kinds of substances are dissolved and used. 8. The manufacturing method according to claim 6 or 7, wherein an inorganic or organic, poorly water-soluble or insoluble powder is further mixed and dispersed in the organic solvent solution. 9. The manufacturing method according to claim 8, wherein the inorganic powder is a powder of talc, clay, silica, diatomaceous earth, metal oxide, or sulfur, and the organic powder is a powder of starch or crotylidene diurea.