JPH0761884A - Decomposable coated fertilizer - Google Patents

Abstract

PURPOSE:To make a residual coating film after elution not remain in soil by coating the surface of a granular fertilizer with a decomposable coating film consisting essentially of a poly-2-hydroxy-2-alkylacetic acid. CONSTITUTION:A solution of a poly-2-hydroxy-2-alkylacetic acid in an organic solvent is mixed with one or more substances selected from polyvinylidene chloride, polyolefin, rubber, ethylene.vinyl acetate copolymer, PS, polymethyl methacrylate, ethylene.carbon monoxide copolymer, paraffin, hardened oil, solid fatty acid, metal oil, beeswax, Japan wax, low-molecular resinous substance of rosin, etc., and a slightly water-soluble or water-insoluble organic or inorganic powder. The organic solvent solution is sprayed on a granular fertilizer in a fluidized state, a high-speed hot air flow is blown on the fertilizer to remove the solvent, to dry the fertilizer and to coat the surface of the granular fertilizer with a decomposable coating film consisting essentially of the poly-2-hydroxy-2- alkylacetic acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a granular fertilizer coated with a degradable coating and a method for producing the same. More specifically, it relates to the fertilizer coated with a degradable coating containing poly-2-hydroxy-2-alkylacetic acid as an essential resin component and the production method.
The present invention provides a coated granular fertilizer having a coating that is mainly hydrolyzed in soil and / or decomposed by soil microorganisms, and finally does not remain in soil. Various aids or agents can be added to the coating according to the invention to control the elution of the granular fertilizer.

[0002]

2. Description of the Related Art In order to match the elution of fertilizing components of granular fertilizer applied to soil with the requirements of the components accompanying the growth of crops, or to prevent moisture absorption or solidification during the distribution process of granular fertilizers. Various studies have been made. One method is to coat the surface of the granular fertilizer with a polymer. The coating is either thermosetting or thermoplastic. However, a coating film made of such a high molecular polymer also has various problems as described below.

As a method using a thermosetting resin, for example, styrenated alkyd resin and phenol resin (UK Patent 594,555) fatty oil-modified alkyd resin, fatty oil dicyclopentadiene copolymer, diisocyanate-modified fatty oil copolymer. (Japanese Patent Publication No. 40-28927) or phenol resin (Japanese Patent Publication No. 44-28457). Further, as the method using a thermoplastic resin, for example, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyethylene, and polyfluoroalkane or a copolymer composed of two or more of these constituent unit monomers (UK Patent Nos. 815,829) and vinyl acetate emulsion polymerization liquid (Japanese Patent Publication No. 37-15832).

As a problem when a high molecular polymer, especially a thermoplastic resin liquid or an emulsion polymerization liquid thereof is used as a coating material, Japanese Patent Publication No. 42-13681 discloses a liquid or spinnable resin on the surface of a granular material. However, due to the spinnability of the resin, only a few% of the resin is coated, and the particles stick together to form blocks, making it difficult to coat each particle uniformly and thickly. Has been shown to be. JP-A-50-99858, JP-A-51-75674, and JP-A-53-88265 relate to coating methods for granular fertilizers invented by the present inventors. In these publications, properties of resin solutions and drying are described. A method is shown which enables efficient coating in one step without blocking in the coating step depending on the selection of conditions. Japanese Patent Application Laid-Open No. 50-93858 discloses a method of coating a granular fertilizer with a coating material containing a polyolefin as a main component, by spraying a solution of the coating material on the granular fertilizer, and at the same time drying it by a high-speed hot air flow to coat the granular fertilizer. It is shown. The feature of this technique is that it can be uniformly coated with an extremely thin film and that the elution rate can be adjusted by dispersing a surfactant as an elution adjusting agent in the film. JP-A-51-75874 discloses that a polyvinylidene chloride-based resin and an ethylene / vinyl acetate copolymer having a vinyl acetate portion of 5% by weight or less can uniformly coat granular fertilizer as an extremely thin coating together with a polyolefin resin. is doing. Japanese Examined Patent Publication No. 60-37074 discloses that the coating film of a polyolefin resin, an ethylene vinyl acetate copolymer and a surfactant can bring about highly stable dissolution control. In JP-B-60-3040 and JP-A-55-1872, the elution control function is maintained by dispersing an inorganic powder such as talc in the coating film of the polyolefin resin,
At the same time, it is disclosed that the disintegration or decomposition of the residual capsule after elution is promoted. Furthermore, the present inventors
Carbon monoxide copolymer (Japanese Patent Publication No. 2-3516), ethylene / vinyl acetate / carbon monoxide copolymer (Japanese Patent Publication No. 2-23)
515) and other photodegradable copolymers as main coating materials,
We have developed a technology that can control the elution arbitrarily. The fertilizer coated with this technology decomposes extremely slowly in the dark, where the light does not reach the soil, and it decomposes and disintegrates when exposed to the surface layer. The coating could remain. In order to overcome the drawbacks of these coated fertilizers having photodegradability, the present inventors have paid attention to aliphatic polyesters, which are biodegradable resins that undergo degradation in soil where light does not reach, and have 3-hydroxy- A coating technique using 3-alkylpropionic acid has been completed and disclosed (Japanese Patent Publication No. 23517).

[0005]

The present invention has been completed by conducting research on coated fertilizers containing these series of degradable resins as active ingredients, and the residual coating after the purpose elution is mainly hydrolyzed in soil, Another object of the present invention is to provide a coated fertilizer which is decomposed by soil microorganisms and does not leave a coating film in the soil.

[0006]

SUMMARY OF THE INVENTION The present invention has the following main constitution (1) or (6) and (2)-(5) or (7)-
It has the configuration of the embodiment of (9). (1) The surface of granular fertilizer is poly-2-hydroxy-2
-A degradable coated fertilizer, which is coated with a degradable coating containing alkyl acetic acid as an active ingredient. (2) The granular fertilizer according to the above 1, wherein the alkyl group is hydrogen, methyl, or ethyl group. (3) In addition to poly-2-hydroxy-2-alkylacetic acid, the degradable coating is polyvinylidene chloride, polyolefin, rubber, ethylene / vinyl acetate copolymer, polystyrene, polymethylmethacrylate, ethylene / carbon monoxide copolymer Polymer, ethylene / vinyl acetate / carbon monoxide copolymer, or ethylene / ethyl acrylate copolymer,
Resins of ethylene methacrylic acid copolymer, paraffin, hydrogenated oil, solid fatty acid, and metal oil, beeswax, wood wax,
The granular fertilizer according to the above 1st item, which is composed of a low molecular weight resinous substance such as petroleum resin or rosin. (4) The granular fertilizer according to the above 1 or 3, wherein the degradable film contains an inorganic or organic powder that is poorly water-soluble or insoluble. (5) The granular fertilizer according to the above item 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) The organic solvent solution of poly-2-hydroxy-2-alkylacetic acid is added to the granular fertilizer in a fluid state in the form of a spray, and at the time of the addition, the organic fertilizer is added by blowing a high-speed hot air stream onto the granular fertilizer. A method for producing granular fertilizer coated with a degradable coating, which comprises removing the solvent in a solvent liquid and drying. (7) Add poly-2-hydroxy-2- to the organic solvent solution.
In addition to alkyl acetic acid, polyvinylidene chloride, polyolefin, rubber, ethylene / vinyl acetate copolymer, polystyrene, polymethylmethacrylate, ethylene / carbon monoxide copolymer, ethylene / vinyl acetate / carbon monoxide copolymer, or ethylene・ Ethyl acrylate copolymer,
Resins of ethylene methacrylic acid copolymer, paraffin, hydrogenated oil, solid fatty acid, and metal oil, beeswax, wood wax,
7. The method for producing a granular fertilizer according to the above item 6, wherein one or more substances selected from low molecular weight resinous substances such as petroleum resin or rosin are dissolved and used. (8) The method for producing a granular fertilizer according to the above item 6 or 7, wherein an inorganic or organic powder having poor water solubility or insolubility is mixed and dispersed in an organic solvent solution. (9) The method for producing a granular fertilizer according to the above 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 clothylidene diurea. .

The structure and effects of the present invention will be described in detail below. The present invention relates to a poly-degradable aliphatic polyester.
It is characterized in that 2-hydroxy-2-alkylacetic acid (chemical structure I) and its copolymer (chemical structure II) are used as coating materials, and a preferable material is poly-2-hydroxyacetic acid ( Chemical structure III), poly-2-hydroxy-2-methylacetic acid (chemical structure I
V), poly-2-hydroxy-2-ethylacetic acid (chemical structure V), and a copolymer of 2-hydroxyacetic acid and 2-hydroxy-2-methylacetic acid (chemical structure VI).

[0008]

[Chemical 1]

[0009]

[Chemical 2]

[0010]

[Chemical 3]

[0011]

[Chemical 4]

[0012]

[Chemical 5]

[0013]

[Chemical 6]

In the present invention, 2-hydroxy-2-alkyl acetic acid having a chemical structure of [III] to [VI] is used alone or as a mixture as an essential decomposable resin. Further, poly-2-hydroxy- which is an aliphatic polyester essential for the present invention.
The monomer of 2-alkylacetic acid has three types of optical isomers such as L-form, D-form, D, L-form, and any of these can achieve the object of the present invention. Although these aliphatic polyesters essential to the present invention can obtain a very good film in terms of disintegration in soil, the elution period is relatively short, and when the film is coated with a homopolymer, the film becomes hard and brittle. It has functional and physical properties. The general-purpose resin shown below is a range in which the effect of the present invention is not impaired for the purpose of supplementing the properties of the aliphatic polyester essential to the present invention, such as physical property improvement, elution control, extender material, and membrane decomposition adjustment. It is available in the form of a homogeneous mixture or a separate layer of film.

General-purpose resins include polyvinylidene chloride and its copolymers, polyolefin resins, ethylene / vinyl acetate copolymers, ethylene / carbon monoxide copolymers, ethylene / vinyl acetate / carbon monoxide copolymers. Coalescence, ethylene
Examples thereof include ethyl acrylate copolymer, ethylene / methacrylic acid copolymer, rubber-based resin, polystyrene and polymethylmethacrylate. Of these, polymeric materials such as polyvinylidene chloride and its copolymers, polyolefin resins and ethylene / carbon monoxide copolymers are preferable materials for the purpose of delaying elution. On the other hand, as materials that promote elution, ethylene / vinyl acetate copolymers with a particularly high vinyl acetate content (40% by weight or more), natural rubber among rubber resins, polyisoprene, styrene / butadiene random copolymer Etc. Further, preferable wax materials include paraffin, solid fats and oils, especially hardened oil, solid fatty acid and its divalent and trivalent metal salts, beeswax, wood wax, rosin, petroleum resin and the like, and these are materials which delay elution. Is.

In addition to these general-purpose resins, the above-mentioned poly-3-hydroxy-3-alkylpropionic acid,
Although biodegradable aliphatic polyesters such as polycaprolactone have different decomposition rates depending on the types, the effects of the present invention are not impaired even if arbitrarily mixed, and therefore, the purpose of improving physical properties of coatings and extending materials Can be used in.

When these resins are mixed, the physical properties of the film,
Also, the type and ratio of the mixed materials are determined from the viewpoint of degradability of the residual film in soil. Poly-essential to the present invention
Among the 2-hydroxy-2-alkyl acetic acid, the homopolymer composed of a single monomer has the brittle property as mentioned above, and it forms a film when handling and transporting the obtained coated fertilizer. Since there is a risk of cracking, a copolymer having excellent flexibility, or a method of appropriately mixing and using the copolymer, and a copolymer of different optical isomers such as L-form and D, L-form, or this And a homopolymer are appropriately mixed and used, which is a desirable method for improving the physical properties of the coating. Further, in terms of degradability, the copolymer tends to have a faster decomposition rate than the homopolymer, and when a faster decomposition is required, it is a desirable method to use the copolymer. The molecular weight of these is preferably 30,000 or more from the viewpoint of coating strength, and the upper limit is preferably 500,000 or less from the operability of the coating process, but a particularly preferable range is 50,000 to 300,000.

When mixing with other general-purpose resins, the mixing ratio is determined within the range that the physical properties are improved and the biodegradability in soil is not impaired. The physical properties can be improved by blending a hard and brittle homopolymer with a polyolefin polymer or copolymer having excellent flexibility, and by forming an extremely thin reinforcing film in the intermediate or inner and outer layers. It goes without saying that other resins can be used for the same purpose. Furthermore, the elution rate can be controlled by mixing these resins. On the other hand, regarding the degradability of the residual film in soil, the above-mentioned poly-3 was used.
The degradability is not impaired by any mixing of other biodegradable resins such as -hydroxy-3-alkylpropionic acid and polycaprolactone, but in the case of non-degradable resins, it is usually 50% by weight or less, preferably It is desirable to keep it in the range of 30% by weight or less. If it is added in an amount of more than 50% by weight, substantial decomposition of the resin layer does not proceed even if mixing of easily decomposable filler and the like is carried out.

In the present invention, additives such as fillers and surfactants can be used as long as the physical properties of the coating and the elution control function are not impaired. The powder as the filler used in the present invention is a poorly water-soluble or water-insoluble powder, and either inorganic or organic powder may be used, but the particle size thereof is half or less of the coating thickness, preferably Is 1/2
The following are good: These fillers are uniformly dispersed in the coating film, but those having poor dispersibility require surface treatment with silicon or the like or dispersibility improving treatment such as facilitating dispersion with a surfactant or the like. Preferred materials for these inorganic powders include talc, calcium carbonate, clay, diatomaceous earth, silica and its salts, metal oxides, sulfur and the like. Sulfur in these inorganic powders is a material that undergoes microbial decomposition, and has the advantage of being easily decomposed in soil as a component of the composite material of the coating. On the other hand, organic powders are inferior to inorganic ones as fillers, but many are decomposed by microorganisms, and soil decomposition as a composite material has an advantage over sulfur, such as starch and other starchy materials, Slow-release nitrogen fertilizers such as crotylidene diurea, which produces NH ₄ by microbial decomposition in soil, are preferred materials. When these powders are used as fillers, the coating strength tends to decrease as the amount used increases, regardless of which powder is used.

The surfactant which can be used in the present invention may be any of a cationic one, an anionic one, an amphoteric one and a nonionic one. Balance is important. If the hydrophilicity is too strong, the particles do not uniformly disperse in the film and aggregate to cause film defects. Those with strong lipophilicity do not affect the coating, but the elution promoting effect tends to be slightly inferior. HL of these surfactants
B is 15 or less, preferably in the range of 11 to 13.

The present invention is applicable to granules containing any fertilizer component. For example, water-soluble fertilizers such as ammonium sulfate, ammonium salt, ammonium nitrate, urea, potassium chloride, nitrate, sodium nitrate, sodium phosphate, potassium phosphate, lime phosphate, and chelated iron, iron oxide, iron chloride, boric acid, borax, sulfuric acid. It is particularly effective for fertilizers containing a single substance of water-soluble trace elements such as manganese, manganese chloride, zinc sulfate, copper sulfate, sodium molybdate, ammonium molybdate or the like or two or more components. In addition, OMUP (Blackylidene Diurea), IBD
When applied to poorly water-soluble fertilizers such as U (isobutylidene diurea) and oxamide, the effective period of these fertilizers can be extended.

The coating material of the present invention is used by being dissolved or dispersed in an organic solvent. The solvent used at this time dissolves the polymer material and waxes, and the filler is preferably supplied while being dispersed by stirring. Depending on the combination of the coating material and the solvent, the coating may block during the coating and it may not be possible to continue the coating operation. In this case, the method disclosed by the present inventors is preferable as the method for carrying out the present invention.
According to 3140, the combination with a solvent may be changed, or another resin capable of coating, for example, a polyolefin or polyvinylidene chloride resin may be mixed and used in a ratio within the range of the present invention. The present invention will be described below with reference to examples.

[0023]

【Example】

1. Production Example-I of Fertilizer of the Present Invention FIG. 1 shows the jet encapsulation device used in Production Examples-I and II. 1 is a jet tower with a diameter of 250 mm and a height of 200
It has a fertilizer inlet 2 and an exhaust gas outlet 3 with a diameter of 0 mm, a nitrogen gas outlet diameter of 50 mm, and a cone of 50 degrees. The jet nitrogen gas is sent from the blower 10 and reaches the jet tower through the orifice flow meter 9 and the heat exchanger 8. The flow rate is controlled by the flow meter and the temperature is controlled by the heat exchanger, and the exhaust gas is discharged from the exhaust gas outlet 3 to the outside of the tower. Be led to. The granular fertilizer used for the encapsulation treatment is introduced from the fertilizer introduction port 2 through a predetermined hot air (N ₂ gas) to form a jet stream. The temperature of the hot air is T ₁ , the temperature of the particles during encapsulation is T ₂ , and the temperature of the exhaust gas is T _a . When T ₂ reaches a predetermined temperature, the encapsulating liquid is sprayed through the one-fluid nozzle 4 toward the spray particles. The coating liquid is stirred in the liquid tank 11, and when powder is used, it is stirred so that the powder is uniformly dispersed in the coating liquid. When the specified coverage is reached, turn off the blower,
The coated fertilizer is discharged from the outlet 7. In this manufacturing example, a sample was made while maintaining the following basic conditions. One-fluid nozzle: Opening 0.8 mm Full-con type Hot air flow rate: 4 m ³ / min Hot air temperature: 100 ± 2 ° C Fertilizer type: 6-7 mesh granular urea Fertilizer input amount: 10 kg Test solvent: Toluene Coating liquid concentration: Solid content 5.0 wt% Coating liquid supply rate: 0.3 kg / min * Coating liquid is sent from pump 5 to the nozzle, but 80
Superheat with steam so that the temperature does not drop below ℃. Coating time: 73 minutes Encapsulation rate (against fertilizer): 10%

2. Production Example-II of Fertilizer of the Present Invention Using the same coating apparatus as in Production Example-I, in this Production Example, trial production of samples was carried out while maintaining the following basic conditions. One-fluid nozzle: 0.8 mm opening Full-con type Hot air flow rate: 4 m ³ / min Hot air temperature: 100 ± 2 ° C Fertilizer type: 6-7 mesh granular urea Fertilizer input amount: 10 kg Test solvent: Ethyl acetate Coating solution concentration: Solid Min 5.0 wt% Coating liquid supply: 0.3 kg / min * Coating liquid is sent from pump 5 to the nozzle, but 70
Superheat with steam so that the temperature does not drop below ℃. Covering time: 73 minutes Covering rate (against fertilizer): 10%

3. Manufacturing Example III of Fertilizer of the Present Invention FIG. 2 shows the coated granular apparatus used in Manufacturing Example III. To adjust the coating liquid, put the solvent (hexafluoroisopropanol) and coating material in a dissolution tank equipped with a stirrer, heat the solvent (as a standard, the boiling point is 5 to 10 ° C or less under normal pressure of each solvent), and dissolve by stirring. To obtain a resin solution having a solid content of 1% by weight. This solution is constantly stirred even after dissolution, and maintains a uniform dispersed state even when it contains a filler. For fertilizer coating, put granular fertilizer in a rotating pan and roll it, add hot air and the coating liquid in a spray form to the fertilizer particles, evaporate the solvent and form a coating until a predetermined coating rate is reached. Obtain coated granular fertilizer. A sugar-coating machine with a diameter of 30 cm is used as a rotary pan, and 6 to 7 mesh of granular urea is put in this machine.
Rotate at 200 rpm from the hot air jet with a diameter of 5 cm
Hot air of m ³ / HR at 80 ° C. (exit temperature) is blown from about 20 cm from the particle rolling surface. After the coating liquid is dissolved and dispersed in the dissolution tank, it is maintained at about 50 ° C while continuing stirring, and the coating liquid is sent to the spray nozzle attached to the sugar coating machine by a pump and atomized with N ₂ gas for spraying. The rolling particles were continuously added at a feed rate of 2 L / HR so that the particle temperature could be operated in the range of 50 to 55 ° C., and the coating operation was performed until a predetermined coating rate was reached.

4. Example of Elution Rate Measurement of Fertilizer of the Present Invention 10 g of the fertilizer of the present invention produced in each of Production Examples I, II and III was immersed in 200 ml of water and allowed to stand at 25 ° C.
After a predetermined period, it is divided into fertilizer and water, and the amount of urea eluted in water is determined by quantitative analysis. 200 ml of fresh water was added to the fertilizer, and the fertilizer was allowed to stand at 25 ° C again, and the same analysis was performed after a predetermined period. By repeating such operations, the relationship between the cumulative elution of urea eluted in water and the number of days was graphed to create an elution rate curve,
You can know the number of days to reach the dissolution rate. The 24-hour dissolution of the dissolution items in Tables 1 and 2 means 25 ° C and 2 ° C in the above-mentioned dissolution measurement.
It is the elution rate in water after the elapse of 4 hours, and 80% elution days was obtained by preparing an elution rate curve in the above elution rate measurement.

5. Capsule disintegration degree measurement of the fertilizer of the present invention 5 g of the sample of the present invention was used to make pinholes one by one using a sharp needle, and allowed to stand in water at 30 ° C for 2 weeks to elute the urea therein to form empty capsules. create. Put empty capsules separated from the eluate into a resin net (Wakamatsu Ward, Kitakyushu City,
Buried in sandy loam soil. After leaving the capsule for 2 years, observe the condition of the capsule, and for the sample in which the prototype of the capsule is clearly stopped, put the entire amount of the capsule in a V-type mixer with rotating blades and do 3
Stir mix for 0 minutes. Then, the mixture was passed through a 10 mesh sieve, the percentage of the capsules passed through to the test capsules was calculated, and the disintegration degree was shown in Tables 1 and 2. If the original pattern was not retained and only traces or no traces were observed, the above operation was not performed and the degree of collapse was set to 100%.

[0028]

[Table 1]

* 1 Low-density polyethylene MI = 20
d = 0.922 * 2 ethylene / vinyl acetate copolymer MI = 20 V
Ac = 33 wt% * 3 Average particle size 10μ * 4 Ethylene / carbon monoxide copolymer MI = 0.75
CO = 0.95% by weight * 5 Poly (L-2-hydroxy-2-methylacetic acid) Mw = 150,000 * 6 Poly (2-hydroxyacetic acid) Mw = 13
20,000 * 7 Poly (D, L-2-hydroxy-2-methylacetic acid) Mw = 150,000 * 8 Poly (L-2-hydroxy-2-ethylacetic acid) Mw = 150,000 * 9 L -2-Hydroxy-2-methylacetic acid ・ D,
L-2-Hydroxy-2-methylacetic acid copolymer L-2-Hydroxy-2-methylacetic acid: D, L-2
-Hydroxy-2-methylacetic acid = 70:30 Mw
= 130,000 * 10 2-Hydroxyacetic acid / L-2-hydroxy-2-methylacetic acid copolymer 2-Hydroxyacetic acid: L-2-Hydroxy-2
-Methylacetic acid = 30: 70 Mw-100,000 * 11 2-hydroxyacetic acid / L-2-hydroxy-2-methylacetic acid copolymer 2-hydroxyacetic acid: L-2-hydroxy-2
-Methylacetic acid = 50: 50 Mw = 100,000 * 12 2-hydroxyacetic acid / L-2-hydroxy-2-methylacetic acid copolymer 2-hydroxyacetic acid: L-2-hydroxy-2
-Methylacetic acid = 70:30 Mw = 90,000 * 13 Average particle size 10μ * 14 Average particle size 5μ * 15 Copolymer-type atactic polypropylene containing 3% ethylene Mw = 60,000 * 16 Average particle size 10μ * 17 Average Particle size 10μ

[0030]

[Table 2]

* 18 Vinylidene chloride / vinyl chloride copolymer VC1 = 10% by weight * 19 Average particle size 5 μ * 20 HO-CH ₂ -O- [CO- (CH ₂ ) _5- ]
n-OH n = 1000 (average value) * 21 poly-3-hydroxy-3-methylpropionic acid Mw = 750,000 * 22 m.p. p = 69-73 ° C wax

[Brief description of drawings]

1 is a jet encapsulation device used in Production Examples I and II.

FIG. 2 is a granular fertilizer coating device used in Production Example III.

Claims (9)

[Claims] 1. A degradable coated fertilizer in which the surface of a granular fertilizer is coated with a degradable coating containing poly-2-hydroxy-2-alkylacetic acid as an active ingredient. 2. The granular fertilizer according to claim 1, wherein the alkyl group is hydrogen, methyl or ethyl group. 3. The degradable coating is poly-2-hydroxy-2-alkylacetic acid, polyvinylidene chloride, polyolefin, rubber, ethylene / vinyl acetate copolymer, polystyrene, polymethylmethacrylate, ethylene / carbon monoxide. Copolymers, ethylene / vinyl acetate / carbon monoxide copolymers, ethylene / ethyl acrylate copolymers, ethylene methacrylic acid copolymer resins, and paraffins, hardened oils, solid fatty acids, and metal oils, beeswax,
The granular fertilizer according to claim 1, comprising a low molecular weight resinous substance such as wood wax, petroleum resin or rosin. 4. The granular fertilizer according to claim 1 or 3, wherein the degradable film contains an inorganic or organic powder which is poorly water-soluble or insoluble. 5. The inorganic powder is talc, clay, silica,
Diatomaceous earth, metal oxide or sulfur powder,
The granular fertilizer according to claim 4, wherein the organic powder is starch or crotylidene diurea powder. 6. An organic solvent solution of poly-2-hydroxy-2-alkylacetic acid is added to a granular fertilizer in a fluid state in the form of a spray, and at the time of the addition, a high-speed hot air stream is blown onto the granular fertilizer to add it. A method for producing a granular fertilizer coated with a degradable coating, characterized in that the solvent in the organic solvent liquid is removed and dried. 7. An organic solvent solution containing, in addition to poly-2-hydroxy-2-alkylacetic acid, polyvinylidene chloride, polyolefin, rubber, ethylene / vinyl acetate copolymer, polystyrene, polymethylmethacrylate, ethylene.
Resins of carbon monoxide copolymer, ethylene / vinyl acetate / carbon monoxide copolymer, ethylene / ethyl acrylate copolymer, ethylene methacrylic acid copolymer, and paraffin, hardened oil, solid fatty acid, and metal oil The granular fertilizer according to claim 6, wherein one or more substances selected from low molecular weight resinous substances such as beeswax, beeswax, petroleum resin or rosin are dissolved and used. 8. The granular fertilizer according to claim 6 or 7, which is used by mixing and dispersing an inorganic or organic powder having poor water solubility or insolubility in an organic solvent solution. 9. The inorganic powder is talc, clay, silica,
Diatomaceous earth, metal oxide or sulfur powder,
The granular fertilizer according to claim 8, wherein the organic powder is starch or crotylidene diurea powder.