JPH09309785A - Coated granular fertilizer of time limit elution type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the induction period and elution period of a time limit elution type coated fertilizer. SOLUTION: A coating film coated on the surface of a granular fertilizer core material is formed from a monolayer comprising a thermoplastic resin base material and the powder of a water-absorbing polymer. The water- absorbing polymer is preferably a nonswelling, low swelling or water-soluble substance, more preferably an isobutene-unsaturated dicarboxylic anhydride polymer, etc. The average particle diameter of the water-absorbing polymer powder is a length of 1/8 to 1 time the thickness of the coating film. The content [polymer weight × 100/(polymer weight + thermoplastic resin weight)] of the water-absorbing polymer in the coating film is <50wt.%. The core material is preferably a potassium fertilizer. The coated granular fertilizer enables to remarkably shorten the induction period and elution period of a fertilizer having a high ordinary temperature saturated vapor pressure and a low ordinary temperature water solubility, such as a potassium fertilizer, and the elution pattern of the coated fertilizer is approximately the same, also after preserved for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called "time-eluted coated fertilizer" which does not elute for a predetermined period after application and starts to elute after the elapse of a predetermined period. More specifically, the present invention relates to a time-eluting type coated granular fertilizer characterized in that the surface of a granular fertilizer core material is coated with a coating composed of a single layer in which a water-soluble polymer powder is dispersed in a thermoplastic resin.

[0002]

[Prior art and its problems] It is a specific film that does not elute within a specific period after application, but during that specific period (hereinafter referred to as "induction period") The period of time until the elution period is referred to as “elution period”), and the so-called “time-eluted film” that starts to elute after the elapse of time can include the following description example: ◆ A film in which a sugar polymer is dispersed in a resin is special. Kaihei 6-876
No. 84 (Japanese Patent Application No. 4-237651); ◆ A coating composed of a first layer made of an olefin resin and a water-soluble or water-swellable substance and a second layer made of an olefin resin is disclosed in Japanese Patent Publication No. 5- 29634 (Japanese Patent Application No. 1-20
No. 0256); ◆ A coating or the like composed of a first layer made of a highly water-swellable substance and a second layer made of an olefin resin is disclosed in JP-A-4-202.
Japanese Patent Application No. 079 (Japanese Patent Application No. 2-333822).

As is clear from the examples of the specification, the film disclosed in the above-mentioned JP-A-6-87684 is a fertilizer component such as urea and has a relatively low saturated vapor at room temperature. As long as it is a fertilizer component showing a large solubility in pressure and water, depending on the selection of the coating composition,
An induction period and an elution period of arbitrary length can be realized.

On the contrary, when a fertilizer component having a large saturated vapor pressure at room temperature and a low solubility in water, such as Kali fertilizer, was coated as a core material, it was obtained. It was thought that it would be almost impossible to obtain a coated fertilizer having a short induction period and a short dissolution period, and in particular, a short dissolution period type timed dissolution pattern.

On the other hand, the coatings described in Japanese Patent Publication No. 5-29634 and Japanese Patent Laid-Open No. 4-202079 have the water vapor permeability of the first layer in addition to the selection of the type or amount of the water-swelling substance. It is disclosed that by adjusting the amount, even potassium fertilizer shows a short dissolution pattern in both the induction period and the dissolution period.

However, the coatings described in Japanese Patent Publication No. 5-29634 and Japanese Patent Laid-Open No. 4-202079 are effective time-eluting membranes, but they are improved in that the elution period varies after long-term storage. There was room for it.

Although this is beyond speculation, the first layer is made of a water-swelling resin having a large polarity, or is made of a resin containing the resin, and the surface thereof has a low water-permeability. It has a two-layer structure in which a resin layer having a small size is formed. That is, since it is composed of a resin layer having a very large polarity and a resin layer having a very small polarity, the adhesive surface between the first layer and the second layer undergoes changes such as peeling over time. It is thought that it is because it is.

Further, in order to coat the fertilizer with the above-mentioned two-layer structure coating, the resin material of the first layer and the resin material of the second layer are melted or melted under separate conditions. Therefore, in terms of difficulty in downsizing of manufacturing equipment, material handling during the process, manufacturing cost, etc., it has a larger handicap than the fertilizer coated with a single-layer structure before that. It's hard to avoid doing.

[0009]

As a result of repeated studies in view of the problems of the above-mentioned prior art, the present inventors have completed the following improved technology: Not only for those that show a low saturated vapor pressure and a large solubility in water at room temperature, but also a large saturated vapor pressure at room temperature, such as Kali fertilizer, and a low solubility in water at room temperature. For fertilizer components, a relatively short induction period and elution period can be realized, and in addition, a time-eluting type coated fertilizer that does not easily change even after long-term storage can be formed relatively easily. An intensive study was conducted on the obtained film composition.

As a result, the present inventors have discovered that the coated granular potassium fertilizer obtained by coating the surface of the granular potassium fertilizer with a coating in which a water-absorbing polymer powder is dispersed in a thermoplastic resin exhibits extremely excellent properties. Then, the present invention was completed.

[0011]

The present invention achieves the object by various aspects of the constitutions 1 to 7 described below: (1) In a thermoplastic resin in which the surface of a granular fertilizer core material is a base material Is coated with a single-layer coating in which a water-absorbent polymer powder is dispersed, and the water-absorbent polymer is an isobutylene-unsaturated dicarboxylic acid anhydride copolymer and a polyalkylene oxide-modified resin, acrylic acid-vinyl alcohol. A time-eluting type coated granular fertilizer characterized by being formed from one or more water-soluble polymers selected from copolymers and alkali metal acrylate polymers. (2) The time-eluting coated granular fertilizer according to item 1, wherein the water-absorbing polymer is one or more selected from non-swelling polymers, low-swelling polymers and water-soluble polymers. (3) The above item 1 or 2, wherein the isobutylene-unsaturated dicarboxylic acid anhydride copolymer is an isobutylene-maleic anhydride copolymer and has a weight average molecular weight of 6 × 10 ⁴ to 2 × 10 ^5. Time-eluted coated granular fertilizer. (4) The time-eluting type coated granular fertilizer according to any one of Items 1 to 3, wherein the water-absorbent polymer powder in the coating has an average particle diameter of 1/8 to 1 times the film thickness of the coating. (5) Any of the above items 1 to 4, wherein the content of the water absorbing polymer in the coating film is 0.1 to less than 50% by weight based on the total weight of the thermoplastic resin component amount and the water absorbing polymer component amount. The time-eluting coated granular fertilizer described in Crab. (6) The time-eluting type coated granular fertilizer according to any one of Items 1 to 5, wherein the core material of granular fertilizer is Kari fertilizer.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic resin used as the coated substrate of the present invention is not particularly limited, and it suffices to appropriately select and use a thermoplastic resin material capable of obtaining a desired induction period and elution period. . However, the thermoplastic resin forming the coated substrate for surely suppressing the elution in the initial stage after the fertilizer application is preferably one or more selected from polyolefins (PO) and olefin copolymers having low water vapor permeability. Alternatively, at least one selected from polyvinylidene chloride (PVDC) and vinylidene chloride copolymer is used.

Specific examples of one or more selected from the above-mentioned olefin polymers and copolymers (collective name "PO") include the following: ◆ Polyolefin (PO) and olefin copolymer As polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA; vinyl acetate unit content about 50% by weight or less),
Ethylene-carbon monoxide copolymer (ECO), ethylene-vinyl acetate-carbon monoxide copolymer (EVACO), ethylene-acrylate copolymer, ethylene-methacrylic acid copolymer and its metal salt (ionomer), heat Plastic elastomer, polystyrene, polymethylmethacrylate
(PMMA) and the like.

The above-mentioned various resins (polymers) may be used alone or in combination of two or more kinds, and the combination can elute the fertilizer component from the coated fertilizer in a desired elution pattern. preferable.

The water-absorbent polymer dispersed in the coating film used in the present invention refers to a polymer having an ability to highly absorb water or water vapor upon contact with water or water vapor. The water-absorbing polymer (powder) used in the present invention serves as an elution route (leaching route) to the outside of the film of the fertilizer component dissolved inside the film during the elution period. In order to play this role, it is preferable that the water-absorbent polymer is non-swelling or extremely low swelling. Therefore, the water-soluble resin is preferable among the water-absorbent polymers.

Suitable water-soluble resins include, for example, isobutylene-based polymers, acrylic acid-vinyl alcohol copolymers, alkali metal acrylate-based polymers such as sodium acrylate-based polymers and potassium acrylate-based polymers. Coalescence (commonly called "ionomer") and the like can be mentioned.

Among the above preferred water-absorbing polymers, more preferred are isobutylene-unsaturated dicarboxylic acid anhydride copolymers, particularly isobutylene-maleic anhydride copolymers, the weight average molecular weight of which is usually 6 × 10 ^{4 to} 2 × 1
0 ⁵ things.

In order to set a long induction period for the coated fertilizer, it is preferable to use a water-absorbing polymer (powder) having relatively low hygroscopicity and low swelling property. This induction period is mainly determined by the water vapor permeability of the thermoplastic resin part,
When the water-absorbing polymer powder dispersed in the coating has a large particle size, it is affected by the hygroscopicity and moisture permeability of the water-absorbing polymer powder.

As described above, the water-absorbing polymer powder used in the preparation of the coated granular fertilizer of the present invention is the leaching (bleeding) of the fertilizer component dissolved inside the coating during the dissolution period to the outside of the coating. Since a water-absorbing polymer powder having a large particle size is used, a small amount may be added to the film, and when a water-absorbing polymer powder having a small particle size is used, it may be added in an increased amount. .

From the above relationships, the manufacturer of the coated granular fertilizer of the present invention may arbitrarily select it according to the desired induction period and elution period. However, adding an excessive amount of the water-absorbent polymer powder to the coating tends to cause a reduction in coating strength and difficulty in maintaining the elution function. In order to avoid this, the ratio of the weight of the water-absorbing polymer powder to the total weight of the resin component and the water-absorbing polymer powder is 0.1 to less than 50% by weight (wt%), preferably 1 to 40% by weight. It is preferable that

The coverage of the coated granular fertilizer of the present invention (weight% of the coating material actually used relative to the weight of the coating material required for coating the calculated amount) is usually 3 to 40% by weight, preferably 5 to 20%. When it is set to the weight percent, both the induction period adjustment and the elution period adjustment which are the objects of the present invention can be realized at desired levels.

The "induction period" and "elution period" of the coated fertilizer of the present invention are explained as follows. The granular fertilizer core material absorbs water vapor that has slightly permeated the water-absorbing polymer portion of the resin forming the film, and starts to swell at the same time as absorbing water. The swelling pressure resulting from this swelling causes cracks in the water-absorbent polymer portion, and the granular fertilizer core material, which has absorbed and dissolved permeated water vapor, passes through the water-absorbent polymer powder portion to start elution. Here, the period until the coating film cracks is the "induction period", and the time until the fertilizer finishes the elution after passing through the water-absorbing polymer powder portion is the "elution period".

Therefore, in order to shorten the elution period, it is required that a continuous phase of the water-absorbing polymer powder is formed in the film. In this case, since it is easier to form a continuous phase when the water-absorbent polymer powder has a larger particle size, the particle size of the water-absorbent polymer powder is 1/8 to 1 times longer than the film thickness (equal to the film thickness). It is preferable to select the length.

In this case, the "particle diameter having the same length as the film thickness" means
The two are not necessarily the same numerical value, and even if the particle diameter of the water-absorbing polymer powder is larger than the film thickness and a part of the water-absorbing polymer powder causes the film surface to protrude, it is not If the resin film is incorporated inside and is thin, but the resin film is applied, the object of the present invention can be achieved even if the particle diameter is slightly larger than the film thickness.

When a water-absorbing polymer powder having an average particle diameter approximately equal to the thickness of the coating is used, the coating covering the top of the powder is thinned by the particle diameter of the powder. As a result of facilitating the invasion of water vapor from the portion to the inside of the coating, it is feared that securing (controlling) the induction period becomes difficult.
In this case, it is recommended to select a thermoplastic resin having extremely low water vapor permeability such as polyethylene (resin), polypropylene (resin) or polyvinylidene chloride (resin).

In the present invention, the induction period is determined by the water vapor permeability of the thermoplastic resin used in the present invention. The induction period of the coated fertilizer becomes longer as the thermoplastic resin forming the coating has a low water vapor permeability.

On the other hand, the elution period of the fertilizer component from the coated fertilizer is almost determined by the addition amount of the water-absorbing polymer powder and the particle size. That is, the elution period of the coated fertilizer is shortened as the amount of the water-absorbent polymer powder added is increased or the particle size thereof is increased. The manufacturer of the coated fertilizer of the present invention was able to realize an arbitrary elution period by the control method utilizing this correlation.

The coated fertilizer of the present invention may be obtained by any method. However, as a method for coating a granular fertilizer core material with a thermoplastic resin, Japanese Patent Publication No.
The method disclosed in Japanese Patent No. 3104 is recommended. The coating method disclosed in this patent publication is a method of coating a granular fertilizer core material placed in a jet state by spraying a resin solution, whereby the occurrence of blocking in the coating is small,
A very complete film is formed.

The granular fertilizer core material used in the production of the granular coated fertilizer of the present invention is a granular substance containing any fertilizer component as long as it is water-absorbing, preferably water-soluble, non-swelling or low swelling. Can be done. The coating forming the coated fertilizer of the present invention is effective for controlling the induction period and elution period of a fertilizer whose fertilizer core material contains, for example, the water-soluble compound shown below alone or a combination of two or more components thereof, and particularly, It is very effective for fertilizer core materials such as potassium chloride and sulfuric acid as a coating that can achieve a relatively short induction period and elution period like urea: Nitrogen fertilizers: ammonium sulfate (ammonium sulfate), ammonium chloride (chloride) Ammonium), ammonium nitrate (ammonium nitrate), urea and ammonium phosphate (ammonium phosphate); Phosphate fertilizers: ammonium phosphate (ammonium phosphate), phosphonate (potassium phosphate; potassium phosphate) and lime phosphate (calcium phosphate), lime superphosphate (perphosphate). Calcium Phosphate; Overstone); Kali Fertilizer: Salted (Potassium Chloride; Kali Chloride), Nitrate (Kalium Nitrate; Kari Nitrate), Sodium Nitrate (sodium nitrate)
And phosphorus fertilizer (potassium phosphate; potassium phosphate);
One or more selected from phosphate fertilizer and Kali fertilizer and water-soluble trace elements: chelated iron (chelate complex of iron and various complexing agents), iron oxide, iron chloride, boric acid, borax, manganese sulfate, manganese chloride , One or more selected from zinc sulfate, copper sulfate, sodium molybdate, ammonium molybdate, and the like. Here, examples of the complexing agent include disodium ethylenediaminetetraacetate, 8-oxyquinoline, and acetylacetone.

Further, in the film forming the coated fertilizer of the present invention, a filler (filler) or the like may be added in the film as long as the effect of the present invention is not impaired. By adding a filler, the elution rate of the fertilizer component can be finely adjusted, and if a low-cost filler is selected and used, the cost of the product (coated fertilizer) can be reduced. However, the coating composition should also be determined in mind that the addition of fillers, on the other hand, can result in a loss of coating strength. Although depending on the coating composition, the amount of the filler added is preferably 80% or less of the coating weight, and more preferably 70% or less.

As the inorganic filler, powdery substances such as talc (magnesium silicate), clay (clay), diatomaceous earth, porcelain clay, silicon dioxide (silica), calcium carbonate (limestone or rough lime), zeolite, Metal oxides such as magnesium oxide (magnesia), aluminum oxide (alumina) or sulfur are mentioned, and one or more of them are usually used in powder form.

The organic fillers that can be used are, for example, sugar polymers and their derivatives, cereal flours such as wheat flour,
Barley flour, starch, agar powder, corn starch, cellulose and its derivatives such as carboxymethyl cellulose (CMC), surfactants such as the above CMC, alkylidene diureas such as crotylidene diurea (2-butenylidene diurea), isobutylidene diurea. Polycarboxylic acid polyamide such as oxamide (oxalic acid diamide), and one or more of them are used as powder. Among the organic fillers, "thin wheat flour", CMC and the like are preferable.

<Description Based on the Drawings> An example of an apparatus used for producing the coated fertilizer granules of the present invention will be described below with reference to the drawings. FIG. 1 shows a jet encapsulation device used in the production example of the coated fertilizer of the present invention.

In FIG. 1, reference numeral 1 denotes a jet tower, which is formed by a main body of a cylindrical portion having a tower diameter of 250 mm and a height of 2000 mm and a lower conical portion which is a lower step portion thereof, and the apex angle of the conical surface is 50. °, small-diameter bottomed tubular body 21 connected to the lower end of the cone
And a fluid nozzle 4 for jetting nitrogen gas for jetting is mounted upward in the vicinity of the entrance of the conical portion (11d) through the side wall and
The diameter of the fluid nozzle 4 is 50 mm.

The jet tower 1 is provided with a fertilizer inlet 2 at the lower stage of the left side wall (in the present invention, "upper, left, right, front and back" are expressions for convenience of explanation) and an exhaust gas outlet 3 at the upper end of the right side wall of the jet tower 1.
In addition, in the vicinity of the lower end 7 of the bottomed tubular body 21, a connecting pipe 22 for introducing a jet nitrogen gas (hot air), a heat exchanger 8 at the end of the connecting pipe 22, a subsequent orifice flow meter 9 and hot air thereto. The blower 10 to be supplied is connected.

The nitrogen gas for jet flow is sent from the blower 10 and is sent from the orifice flow meter 9 and the connection pipe 22 following the heat exchanger 8 to the vicinity of the product discharge port 7 at the lower end of the bottomed tubular body 21 and the bottomed tubular body 21. Is blown into the jet tower 1 from its lower end. The flow rate of the jet nitrogen gas is controlled by a flow meter 9, the temperature of the gas is controlled by a heat exchanger 8 which is heated by steam supplied from a steam pipe SL, and the exhaust gas from the jet tower 1 is exhausted from an exhaust gas outlet 3 to a tower. It is discharged outside.

In the encapsulation treatment, the granular fertilizer core material used in the treatment is fed through the fertilizer feed port 2, while the blower 10 is used.
From the fluid nozzle 4 to the lower end region of the jet tower while blowing nitrogen gas (hot air) for jet flow from the above into the bottom of the jet tower 1 via the bottomed tubular body 21 to cause the granular fertilizer core material to flow in the jet tower 1. It is carried out by contacting the atomized coating droplets. The coating liquid is transferred from the coating liquid tank 11 via the pressure pump 6 and the connecting pipe 5.

The bottomed tubular body 21 of the hot air from the blower 10
The temperature T ₁ therein, the particle temperature T ₂ in the encapsulation stage below the main body of the jet tower 1 and the exhaust temperature T ₃ from the exhaust pipe 3 located at the upper end of the main body of the jet tower 1 can be detected by a thermometer (not shown), respectively. . When the temperature T ₂ of the granular fertilizer core material to be coated reaches a predetermined temperature, the coating liquid tank 1
The coating liquid supplied from 1 via the pressure pump 6 and the transfer pipe 5 is sprayed from the fluid nozzle 4 toward the flowing granular fertilizer core material in the jet tower 1 to be encapsulated. The coating liquid for encapsulation is heated in the coating liquid tank 11 by the steam from the steam pipe SL while being stirred, and is maintained at a predetermined temperature.

When the granular fertilizer core material reaches a predetermined coverage, the blower 10 is stopped, and the coated granular fertilizer (capsule granular fertilizer) is taken out from the product withdrawing port 7 at the lower end of the bottomed tubular body 21.

[0040]

When the coated granular fertilizer of the present invention is used, the coated fertilizer has a structure in which the surface of the granular potassium fertilizer is coated in a dispersed state in which the coating forms a continuous phase with the water-absorbing polymer powder in the thermoplastic resin phase. , Not only for fertilizer components with low saturation vapor pressure and large water solubility at room temperature such as urea, but also for fertilizer components with large saturated vapor pressure and low water solubility at room temperature such as Kali fertilizer In addition to being able to set a relatively short induction period and elution period, it became possible to store for a long period of time with almost no fear of causing a change in elution (pattern).

[0041]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

<Evaluation of Measurement Samples> Storage Test Samples (samples) obtained by the above-mentioned trial production were stored and sealed in polyethylene fertilizer bags of 10 kg for each test section, and left indoors for 1 year to prepare “preserved sample”. " Dissolution test Stored sample and untreated sample, 10 g each
Is immersed in 200 ml of water and allowed to stand at 25 ° C. After a lapse of a predetermined period, the solid fertilizer and water are separated, and urea eluted in water is obtained by quantitative analysis. The coated granular fertilizer contains 200 ml of fresh water and is allowed to stand at 25 ° C. again to elute, and the same analysis is performed after a predetermined period of time.

By repeating this operation and plotting the relationship between the total elution amount of urea and potassium dissolved in water and the number of days to prepare an elution rate curve, the number of days to reach the 80% elution rate can be known. Table 1 shows the evaluation results.

[0044]

Example 1 <Manufacturing Example of Fertilizer of the Present Invention><< Manufacturing Conditions >> In this manufacturing example, a sample was made while maintaining the following basic conditions. Fluid nozzle: Opening 0.8 mm Full-con type Hot air flow rate: 4 m ³ / min Hot air temperature: 100 ± 2 ° C Fertilizer shape: Granules of 6-7 mesh Fertilizer input amount: 10 kg Test solvent: Perchlorethylene Coating liquid concentration: Solid content 5.0% by weight Coating liquid supply: 0.3 kg / min Coating composition and fertilizer type: those shown in Table 1.

<Manufacturing Procedure> A granular fertilizer core material having the composition shown in Table 1 is introduced from the granular material inlet 2 provided on the side wall of the jet tower 1, while the granular fertilizer core material is suspended. The fluid for the flow passes through the transfer pipe 22 connected near the lower end of the bottomed tubular body 21, the heat exchanger 8 connected to the upstream side thereof, and the flow meter 9 connected to the upstream side thereof to the upstream side thereof. It was sent into the jet tower 1 from the blower 10 located at.

Urea was selected as the fertilizer core material, and the composition of the first layer coating coated on this was low density polyethylene [density 0.922 g / cc; MI (190 ° C; 21.2) as the thermoplastic resin.
N) 7 g / 10 min] 30% by weight, talc 30% by weight as a filler, and isobutene as a water-absorbing polymer.
Maleic anhydride copolymer (abbreviation "ISO-1") [weight average molecular weight 170,000; trade name: Isoban-10 (manufactured by Kuraray Co.)] 10% by weight of particles (average particle size 30 μm) were blended. It was

The coating liquid for coating the granular fertilizer core material was jetted upward from the coating liquid tank 11 via the pressure pump 6 and the transfer pipe 5 from the fluid nozzle 4 of the jet tower 1. This injection nozzle was installed in the conical part (11d) (lower half part) of the jet tower 1 in the vicinity of the substantially central axis so as to face upward. The temperature of the coating liquid was heated by steam charged in a heating jacket mounted outside the coating liquid tank 11 so as to be maintained at 100 ° C. or higher.

This coating treatment was carried out under the above conditions until the coating rate shown in Table 1 reached 12%. The performance of the obtained time-eluting fertilizer is as shown in Table 1, and the induction period 2
The results were 7 days and the fluctuation rate of 3%, and the dissolution period was 19 days and the fluctuation rate was 2%.

[0049]

Comparative Example 1 The amounts of urea and filler in Example 1 were changed to 43% by weight and 51% by weight, respectively, and the water-absorbing polymer was changed from ISO-1 to weak wheat flour, and the amount was set to 6% by weight. Otherwise, the same operation as in Example 1 was carried out under the same conditions to obtain a coated granular fertilizer. The fertilizer performance was, as shown in Table 1, an induction period of 47 days and a variation rate of 3%, and an elution period of 41 days and a variation rate of 2%.

[0050]

Example 2 A coated granular fertilizer was obtained by the same operation as in Example 1 except that the granular fertilizer core material in Example 1 was changed to sulfuric acid potassium. The performance was 43 days for the induction period and 1% for the variation rate and 48 days for the dissolution period and 2% for the variation rate as shown in Table 1.

[0051]

Comparative Example 2 While forming the first layer coating in Example 2 and changing the amount of the filler to 50% by weight, the water-absorbing polymer was changed from ISO-1 to weak wheat flour, and the amount was changed to 20% by weight. A coated granular fertilizer was obtained by the same operation as in Example 2 except that the above was carried out. The fertilizer performance is shown in Table 1.
, The induction period was 73 days and the variability was 4%, and the dissolution period was 176 days and the variability was 3%.

[0052]

[Example 3] The water-absorbent polymer of Example 2 was replaced with ISO-1.
To ISO-2 [isobutene-maleic anhydride copolymer;
Weight average molecular weight 170,000; trade name: Isoban-10 (manufactured by Kuraray Co., Ltd.)] A coated granular fertilizer was prepared in the same manner as in Example 1 except that particles (average particle size 60 μm) were used. Obtained. As shown in Table 1, the fertilizer performance was as follows: the induction period was 40 days and the variation rate was 2%, and the elution period was 29 days and the variation rate was 1%.

[0053]

COMPARATIVE EXAMPLE 3 In Example 1, except that the amount of sulfuric acid added in Example 1 was changed to 20% by weight and the water-absorbing polymer was changed from ISO-2 to polyethyleneoxide, and the amount was changed to 20% by weight. The same operation was performed under the same conditions to coat the first layer up to a coverage of 9%. The surface was coated with a second layer coating to obtain a two layer coated granular fertilizer. This second layer coating is a low density polyethylene as thermoplastic resin [density 0.922 g /
cc; MI (190 ° C; 21.2N) 7 g / 10 min] 30 wt% and talc 70 wt% as a filler,
The coating was applied until the coverage was 3%.

The fertilizer performance of the obtained two-layer coating is as shown in Table 1, its induction period of 48 days and its fluctuation rate of 26 days.
%, The dissolution period was 59 days, and the fluctuation rate was 12%.

[0055]

[Example 4] The fertilizer core material in Example 1 was changed to potassium chloride, the amount of the filler was 55% by weight, and the water-absorbing polymer was IS.
O-1 to ISO-3 [isobutene-maleic anhydride copolymer; weight average molecular weight 170,000; trade name: isoban-10
(Manufactured by Kuraray Co., Ltd.)] A coated granular fertilizer was obtained under the same conditions as in Example 1 except that the particles (average particle size 80 μm) were changed to 15% by weight. The fertilizer performance was, as shown in Table 1, an induction period of 26 days and a variation rate of 2%, and an elution period of 21 days and a variation rate of 2%.

[0056]

Comparative Example 4 Using sulfuric acid as a fertilizer core material, a maleimide-modified ethylene-maleic anhydride copolymer (abbreviated as “KIG”) was used as a thermoplastic resin forming a first coating layer coated on the surface thereof. [Brand name: KI gel-201K-F2 (Kuraray Co.)] 85% by weight and polyethylene glycol [Brand name: polyethylene glycol 20000 (Nippon Yushi Co., Ltd.)]
The first layer coating material formed at 15% by weight was coated under the same conditions and operations as in Example 1 until a coverage of 9% was reached.

As the thermoplastic resin forming the second layer coating material coated on the surface thereof, low density polyethylene [density: 0.
922 g / cc; MI (190 ° C .; 21.2 N) 7 g / 10 min] 30% by weight and talc 70% by weight as a filler, and the second layer coating is applied to the surface of the first coating until the coverage is 3%. did.

The fertilizer performance was, as shown in Table 1, an induction period of 54 days and a fluctuation rate of 23%, and an elution period of 31 days and a fluctuation rate of 2%. <Calculation of induction period TI and elution period TE> Here, Table 1
The induction period TI is the number of days in the untreated sample from the start of immersion to 10% elution, and the elution period TE is the number of days in the untreated sample from 10% to 80% elution. Further, the variation rate α of the induction period and the variation rate β of the elution period were calculated by the following formulas represented by “general formula (1)” and “general formula (2)”, respectively:

[0059]

[Equation 1]

[0060]

[Equation 2]

[0061]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic longitudinal sectional view of an apparatus system for coating and drying a granular fertilizer core material for producing a coated granular fertilizer of the present invention in a fluid state.

[Explanation of symbols]

 1 Jet Tower 2 Core Material Particle Inlet 3 Exhaust Port from Jet Tower 4 Coating Liquid Injection Nozzle 5 Coating Liquid Transfer Pipe 6 Coating Liquid Pressurizing Pump 7 Coated Granule Fertilizer Outlet 8 Heat Exchanger 9 Orifice Flowmeter 10 Blower 11 Coating liquid tank 21 Bottomed tubular body 22 Bottomed tubular body Connection pipe to the lower end area 11d Conical part that constitutes the lower half of the jet tower T1 Temperature inside the bottomed tubular body T2 Lower stage of jet tower body Temperature in the upper region Temperature in the upper region of the T3 jet tower body

Claims (6)

[Claims] 1. The surface of a granular fertilizer core material is coated with a single-layer coating in which a water-absorbing polymer powder is dispersed in a thermoplastic resin as a base material, and the water-absorbing polymer is isobutylene-
It is characterized by being formed of one or more water-soluble polymers selected from unsaturated dicarboxylic acid anhydride copolymers, acrylic acid-vinyl alcohol copolymers and acrylic acid alkali metal salt-based polymers. Time-eluted coated granular fertilizer. 2. The time-eluting type coated granular fertilizer according to claim 1, wherein the water-absorbing polymer is one or more selected from non-swelling polymers, low-swelling polymers and water-soluble polymers. 3. The isobutylene-unsaturated dicarboxylic acid anhydride copolymer is an isobutylene-maleic anhydride copolymer having a weight average molecular weight of 6 × 10 ⁴ to 2 × 10 ^5. The time-eluted coated granular fertilizer described in. 4. The time-eluted coated granule according to claim 1, wherein the average particle diameter of the water-absorbing polymer powder in the coating is 1/8 to 1 times the film thickness of the coating. fertilizer. 5. The content of the water-absorbing polymer in the coating film is 0.1 to less than 50% by weight based on the total weight of the thermoplastic resin component and the water-absorbing polymer component. The coated granular fertilizer of the timed dissolution type according to any one of 1. 6. The granular fertilizer core material is Kari fertilizer.
~ The time-eluting type coated granular fertilizer according to any one of ~ 5.