JPH11209190A - Production of coated granular fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a coated granular fertilizer by spray-coating the surface of a granular fertilizer with a liquid containing a sugar polymer o the derivative and a resin and having a specific viscosity by using spray nozzle having a specific aperture. SOLUTION: As the sugar polymer or the derivative, a corn starch, an enzyme denatured starch or a chemically denatured starch each having 1-100 μm particle diameter is preferably used usually by 1-80 wt.% of the resin. As the resin, a polyolefin resin such as thermoplastic PE or PP is desirably used. In addition, if necessary an inorganic material as a filler of the resin, an organic metallic compound accelerating biological decomposition of the resin, a hydrocarbon base or a chlorinated hydrocarbon for dissolving the resin can be used. The viscosity of the liquid is preferably 0.5-100 cP. By using the spray nozzle having 0.9-3.0 mm aperture, the possibility of clogging of a liquid supply pipe line is decreased and the stable production is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a coated granular fertilizer having a controlled dissolution rate.

[0002]

2. Description of the Related Art Conventionally, various types of fertilizers have been used in the field of agriculture. There are even things. Above all, coating (coating) fertilizers that maintain the effect by coating (coating) the fertilizer with a resin or the like have the characteristic that the fertilizer component is gradually released over a long period of time, and the number of times of fertilization can be reduced. For this reason, it has attracted attention as a labor-saving fertilizer that responds to the recent decline in the agricultural population.

For such coatings, polyolefin resins such as polyethylene and polypropylene which are inexpensive and non-biodegradable general-purpose resins, polyvinyl chloride and derivatives thereof are usually used. In particular, in order to physically control the dissolution of fertilizer components applied in soil, coating of the surface of granular fertilizer with a film containing a dissolution rate regulator has been widely studied. Production method of coated fertilizer using
No. 0-99858, Japanese Patent Publication No. 60-3040,
Japanese Patent Publication No. 60-37074) has been put to practical use.

[0004] On the other hand, since the resin film as described above is non-biodegradable, it is accumulated in the soil while maintaining a hollow particle-like morphology, and is likely to run out of the field system during irrigation. A voice is rising. For this reason, various coating fertilizers using a biodegradable resin or material for the film have been studied. Above all, biodegradable resin obtained by mixing starch with resin,
It is in the stage of practical application in the field of molding and processing of general-purpose resins and films, and it is considered that the possibility of application to coating fertilizers is high, and already a film made by adding starch to polyolefin resin or polyvinyl chloride resin. Coating fertilizers have been reported (JP-A-6-87684, JP-A-8-87684).
-333185). The effect of starch in the film is as follows: starch is decomposed and eliminated by amylase secreted from microorganisms in the soil, and microvoids are formed in the film, resulting in a decrease in mechanical strength of the film, an increase in contact area with the soil, Examples of such methods include creating a favorable environment for the survival of microorganisms such as water absorption, and attracting various microorganisms that degrade the resin. Due to such an effect, it has been reported that resins such as polyethylene, which were conventionally considered to be hardly degradable, undergo biodegradation.

[0005]

However, the above-mentioned fertilizer coated with a starch-added resin film is in a research stage, and various problems are expected in its industrial production method. As an industrial production method of a coated fertilizer, generally, a spray coating is used in which a solution in which a resin is dissolved in a solvent or a molten liquid of the resin is sprayed on the raw material fertilizer particles to form a film. When this method was similarly applied to a starch-added resin, the starch was very low in compatibility with the low-polarity organic solvent used for dissolving the resin and the resin itself, and the starch was suspended in the coating solution. It is necessary to spray in a state, and therefore, there is a possibility that a problem peculiar to transfer / spraying of the suspension such as blockage of a spray nozzle or a liquid supply pipe may occur, and stable production may not be performed. In particular, when a solvent is used, aggregation of starch particles is expected to be a problem because the solution has a low viscosity.

[0006]

Means for Solving the Problems The inventors of the present invention have studied a method for performing spray coating in a stable manner, and found that a spray can be stably sprayed by using a spray nozzle having a specific diameter. And arrived at the present invention. That is, the present invention is characterized in that a liquid containing (a) a sugar polymer or a derivative thereof and (a) a resin is spray-coated on the surface of the granular fertilizer using a nozzle having a diameter of 0.9 mm to 3.0 mm. In the method for producing a coated granular fertilizer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. (1) Granular fertilizer to be coated The fertilizer used in the present invention is not particularly limited. urea,
Granular fertilizers containing multiple components such as N, K ₂ O and P ₂ O _{5 in addition} to granular monofertilizers such as ammonium sulfate, salt ammonium chloride, potassium sulfate, ammonium phosphate, etc. used. The particle size and shape of the fertilizer are not particularly limited, but preferably, the average particle size is 0.5 to 4.0 mm, and the shape of the particles is more spherical or nearly spherical than that of the angular or irregular shape. Is more desirable. (2) Coating Material The coating material applied to the present invention is classified into (A) a saccharide polymer or a derivative thereof, (A) a resin, and (C) other optional components. (A) Glycopolymer or derivative thereof Glycopolymer or a derivative thereof is a polysaccharide composed of at least one of hexose such as glucose and fructol and its derivatives, and pentose such as xylose, arabinose and ribose and its derivatives. And a derivative such as starch, cellulose, agar, polysaccharides such as alginic acid, chitin, chitosan, etc., preferably starch or a derivative thereof.

[0008] As the starch, raw starch (corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch, rice starch, legume starch, kuzu starch, bracken starch, lotus starch, sis starch, Starch), physically modified starch (α-starch, fractionated amylose,
Enzyme-modified starch (hydrolyzed starch, enzyme-degraded dextrin, amylose, etc.), chemically degraded starch (acid-treated starch, oxidized starch, dialdehyde starch, etc.), chemically-modified starch derivative (esterified starch, etc.) Etherified starch, cationized starch, cross-linked starch, etc.). Among the chemically modified starch derivatives, esterified starch includes acetate starch, succinate ester, nitrate ester starch, phosphate ester starch, urea phosphate ester starch, xanthate ester starch, and acetoacetate ester. As etherified starch such as acetylated starch,
Allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, and the like. Cationic starches include, for example, a reaction product of starch and 2,3-epoxypropyltrimethylammonium chloride. Examples of the crosslinked starch include formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphate crosslinked starch, and acrolein crosslinked starch.

Among such starches, corn starch, enzyme-modified starch, and chemically-modified starch are preferably used in view of the fact that the lower the viscosity of the gelatinized starch, the easier the melt-molding can be carried out, and the lower the price. As the particle size of starch, as an average particle size,
It is usually from 0.1 to 100 μm, preferably from 1 to 10 μm. Examples of the method of adding starch to a polymer compound include a method of kneading a molten resin and starch, a method of dissolving a resin in a solvent, adding the starch to a solution, and spraying the solution directly on a fertilizer. The amount of starch added to the resin is usually 1 to 8 of the resin, from the viewpoint of achieving both biodegradability of the film and control of dissolution.
0% by weight, preferably 5 to 40% by weight. (A) Resin A resin is used as the coating material, but the type is not particularly limited. For example, polyolefin, polyvinylidene chloride resin, polyvinyl chloride resin, polystyrene resin, polycarbonate, polyamide, polymethyl methacrylate, polyurethane, thermoplastic resin such as ethylene-vinyl acetate, alkyd resin, phenol resin, urea resin, Thermosetting resin such as melamine resin, ABS resin, epoxy resin, silicone resin, other natural rubber, SBR, NB
Synthetic rubber such as R, further decomposable polymers such as polycaprolactone, polybutyric acid, aliphatic polyester, polyglycot, polyvinyl alcohol, polyethylene oxide, polyvinyl alcohol-based resin, sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, etc. Is mentioned. Among them, a thermoplastic resin having a high elution prevention effect even in a small amount due to low moisture permeability is preferable, and a polyolefin resin such as polyethylene and polypropylene is particularly preferable. These resins can be used alone or as a mixture of two or more. (C) Others In addition to the above two kinds of essential components, other inorganic or organic substances may be coexistently coated as long as the purpose of coating is not impaired. For example, when coated with a resin having high water permeability as described above, talc, calcium carbonate, clay, diatomaceous earth, silica,
Organic substances such as surfactants, waxes and plasticizers may be added in addition to inorganic substances such as metal oxides and sulfur. Also,
Substances that promote biodegradation of the resin other than starch, for example, organic metal salts such as iron, aluminum, sodium, potassium, calcium, magnesium, zinc, and manganese, hydroxides, and oxidized oils may be added. (3) Solvent When coating the coating material, a method in which the material is melted and sprayed directly on the granular fertilizer, a method in which the material is dissolved in a solvent and the solution is sprayed, and a prepolymer is sprayed and cured. There is a method, and the method is not particularly limited. However, polymer compounds suitable for the present invention generally have high melting points and high melt viscosities, so they are industrially unsuitable for direct spray coating of melts. Is preferred. At this time, the type of the solvent is not particularly limited, but is appropriately selected in consideration of various conditions. As the judgment material, the dissolving power, dissolving temperature, handleability, ease of recovery, toxicity, safety, price, and the like of the polymer compound serving as the film material can be cited. For example, when a polyolefin resin, particularly low-density polyethylene is used as a coating material, hydrocarbon solvents such as hexane, octane, toluene, xylene, and tetralin, and chlorinated hydrocarbon solvents such as trichloroethylene and perchloroethylene are preferable. . When coating with a water-soluble polymer, emulsion resin, latex, or the like, water is used as a solvent. Most of the saccharide polymers or derivatives thereof used in the present invention hardly dissolve in these solvents, so that they are sprayed in a suspended state.

[0010] The concentration of the solution is not particularly limited.
For example, it is preferable to increase the concentration because the amount of the solvent used is reduced and the processing time is shortened. On the other hand, when the concentration is lowered, the viscosity of the solution is lowered and the handling property is improved.
However, in the case of spray coating, it is necessary to adjust the concentration so as to have a viscosity that allows an appropriate spray state to be obtained according to the spray nozzle and spray pressure used. The viscosity is generally 0.5 to 100 cP, preferably 10 to 100 cP.
５０50 cP. As a specific example, when low-density polyethylene is used as the coating material and perchlorethylene is used as the solvent, the concentration of the solution is usually 1 to 12% by weight, preferably 3 to 10% by weight. Also, in general, polymer compounds are often hardly soluble in solvents when cooled,
Heating is usually required for dissolution. (4) Coating device The coating device applicable to the present invention is not particularly limited as long as the device has a structure and a function of mixing and stirring the particulate matter and sufficiently bringing the particulate material into contact with the air flow. When classified according to the mixing and stirring method, examples of the type of mixing and stirring using stirring blades include a Henschel mixer and a Nauter mixer. Examples of the apparatus that accompanies the particulate matter accompanying the movement of the apparatus itself include a rotary drum type coater (Japanese Patent Laid-Open No. 52-61216), a rotary pan type coater (Japanese Patent Laid-Open No. 5-85873), and a rotary drop type coater. Coater (JP-A-5-139376, JP-A-5-185612, JP-A-5-342527) and the like. In addition, a vibrating fluid device that is stirred by a vibrating force (Japanese Unexamined Patent Publication No.
245847) is preferred because it can vigorously entrain large amounts of particulate matter. Examples of the type of agitation with a viscous force include a Wurster-type or spouted-bed type coater for blowing and circulating and mixing particles, and a fluidized-bed type coater (Japanese Patent Publication No. 4-61840) as a method for floating and flowing particles. The application of the coating solution to the particulate material is usually carried out by spraying to a suitable location in the entrained particles using a one-fluid or two-fluid spray nozzle. The solvent is removed by a hot air flow as described above. As the gas, in addition to air, an inert gas such as nitrogen or carbon dioxide can be used for safety. (5) Spray nozzle The diameter of the spray nozzle is the size of the hole at the tip of the nozzle that sprays the liquid. In the case of a two-fluid nozzle that atomizes the liquid with the jet power of the gas, the hole is usually circular, In this case the bore is the inside diameter. On the other hand, in the case of a one-fluid nozzle of a type in which atomization is performed by the ejection pressure of the liquid itself, the hole is not circular but has a generally used orifice diameter. As described above, in order to spray the suspension stably, the nozzle diameter is set to 0.9 to 3.0 mm, preferably 1.0 to 2.5 mm. If the caliber is smaller than this,
Particles such as starch are easily clogged at the nozzle tip,
Stable, unable to spray suspension continuously.
According to observations of the present inventors, primary particles such as starch usually suspended in a coating solution used in the present invention are:
Although the size is 1/100 or less compared to the nozzle diameter, the pipe through which the liquid flows is squeezed at the nozzle tip,
Just before that, the flow velocity of the liquid decreases and stagnation occurs, and as a result,
It is considered that particles such as starch agglomerate in the pipeline and cause clogging at the nozzle tip. On the other hand, the nozzle diameter is 3.0m
When it is larger than m, the spray droplet diameter becomes large, so that the drying speed of the solvent to which the fertilizer particles are attached becomes slow. As a result, there is a problem that the fertilizer particles aggregate and the quality of the coated fertilizer deteriorates. (6) Manufacturing method The coating material described in (2) is dissolved in a solvent to prepare a coating material solution. On the other hand, the raw material granular fertilizer is charged into the coating device of (4), and the coating material solution is sprayed using a spray nozzle while keeping the product temperature at usually 30 to 100 ° C, preferably 40 to 80 ° C by hot air. The coating is performed by Here, the product temperature refers to a temperature measured by inserting a temperature detection terminal directly into the fertilizer particle group in a sprayed state. The adjustment and holding of the product temperature are performed with hot air for removing the solvent. The temperature of the hot air naturally needs to be higher than the product temperature, and is usually 50 to 150 ° C. The flow rate is determined in consideration of the solvent removal rate, the product temperature, the flow state of the particles, and the like. The amount of coating material (coverage) is usually 3 to 20% by weight, preferably 5 to 15% by weight, based on the granular fertilizer as the raw material. In terms of film thickness, it is usually 10
To 200 μm, preferably 30 to 150 μm. The time of the spray coating is determined by the concentration of the coating solution, the spray rate, the coating rate, and the like.
0 hours, preferably 0.2 to 3 hours. After the coating is completed, the coated fertilizer can be obtained by extracting the fertilizer from the coating apparatus as it is.

[0011]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 (1) Preparation of coating solution Low density polyethylene (density 0.919,
A resin obtained by melting and mixing 90 parts by weight of a melt flow rate 22, melting point of 107 ° C.) and 10 parts by weight of corn starch was used. This is added to the solvent perchlorethylene 5
The coating solution was dissolved at 85 ° C. so as to have a concentration of% by weight to obtain a coating solution. At this time, the starch did not dissolve in the solvent but was in a suspended state. (2) Coating As a coating device, a stirring-rolling fluidized bed type spiral flow SFC5 type (manufactured by Freund Corporation) shown in FIG. 1 was used (inner diameter: 0.26 m). Average particle size as raw material fertilizer 2.
10 kg of 5 mm granular urea was charged into the apparatus, and the temperature was 80 ° C.
Was blown at a flow rate of 500 Nm3 / h to flow the urea particles. Next, the coating solution of the above (1) was sprayed at a flow rate of 30 kg / h for 40 minutes using a metering pump from a spray nozzle installed at a position 40 cm above the fluidized bed surface. The spray time was set to a time for supplying the coating solution in an amount such that the coating rate of the following (4) became 10%. (3) Spray nozzle An external mixing type two-fluid nozzle having a diameter of 0.9 mm was used as the spray nozzle of (2). In the case of a two-fluid nozzle, an appropriate flow rate of nozzle air was supplied simultaneously with the liquid. (4) Quality evaluation of the obtained coated fertilizer After coating is completed, the obtained coated fertilizer is 4 m
With respect to the sieves with and under the sieve of m, the covering ratio (% by weight of the film with respect to the raw urea) and the agglomeration ratio (% by weight of aggregated particles in which two or more particles were agglomerated and bonded) were measured.
The coverage was calculated by crushing 10 g of the coated fertilizer, dissolving and removing only urea therein with water, and measuring the weight of the remaining film. The aggregation rate was calculated by visually selecting the aggregates in 20 g and measuring the weight. The spray could be sprayed stably for 40 minutes, and the coverage of the obtained coated fertilizer was 9.9%, and the agglomeration rate was 1.2%, which was good (see Table 1). Examples 2 to 4 In Example 1, calibers 1.2, 2.2, and 2.8.
mm, and the coating was carried out under the same other conditions. The results are summarized in Table 1. The spray state was stable in each case, and good coating fertilizer was obtained. Comparative Example 1 In Example 1, a two-fluid nozzle having a diameter of 0.7 mm was used, and the other coating was performed under the same conditions.
Spraying was stopped 10 minutes after the start of spraying. When the nozzle was removed and inspected, it was observed that the starch particles were blocked at the nozzle tip (see Table 1). Comparative Examples 2 and 3 In Example 1, coating was performed under the same conditions using one fluid nozzle having a diameter of 0.79 and 0.66 mm, and the spraying was stopped 25 and 5 minutes after the start of spraying, respectively. When the nozzle was removed and inspected, it was observed that the starch particles were blocked at the nozzle tip (see Table 1). Comparative Example 4 The coating was performed in the same manner as in Example 1, except that the two-fluid spray nozzle having a diameter of 3.5 mm was used. As a result, the spray state was stable and spraying was possible for 40 minutes. However, many agglomerated particles were observed in the obtained coated fertilizer, and the aggregation rate was as high as 22% (see Table 1).

[0012]

[Table 1]

[0013]

According to the present invention, a coated granular fertilizer having a coating consisting of (a) a saccharide polymer or a derivative thereof and (a) a resin can be stably produced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a stirred rolling fluidized bed type coating apparatus used for spray coating of fertilizer of Example 1.

Claims (4)

[Claims] 1. A liquid containing (a) a saccharide polymer or a derivative thereof and (a) a resin is coated on a surface of a granular fertilizer with a diameter of 0.9 m.
A method for producing a coated granular fertilizer, comprising spray-coating using a nozzle having a diameter of 3.0 to 3.0 mm. 2. The method for producing a coated granular fertilizer according to claim 1, wherein the sugar polymer or a derivative thereof accounts for 1 to 80% by weight of the resin. 3. The method for producing a coated granular fertilizer according to claim 1, wherein the viscosity of the liquid is 0.5 to 100 cP. 4. The method for producing a coated granular fertilizer according to claim 1, wherein the sugar polymer or a derivative thereof is starch or a derivative thereof.