JP2011178650A - Method for producing coated granular water-soluble substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a coated granular water-soluble substance in which initial elution is suppressed, and also, the thinning of a coating film is simultaneously achieved. <P>SOLUTION: In the method for producing a coated granular water-soluble substance, a coating film is formed on a granular water-soluble substance. The method includes a step of feeding at least a polyol liquid containing a polyol compound and an isocyanate liquid containing an aromatic isocyanate compound to the surface of the granular water-soluble substance to form a coating film containing a urethane resin, and the viscosity in the coating temperature of the isocyanate liquid is ≤1/3 the viscosity in the coating temperature of the polyol liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water-soluble particulate material having a surface coated with a urethane resin.

  In recent years, more efficient and more efficient fertilizers and pesticides, and how to use them, in terms of environmental impact due to the runoff of elution components such as granular fertilizers and granular pesticides, and labor saving due to the aging of agricultural workers Is required. Against this background, various elution-controlled fertilizers and pesticides have been proposed and put into practical use.

  The elution control type fertilizer and pesticide are coated granular materials in which the elution of internal components is controlled by coating the surface of the granular fertilizer or the granular pesticide with an organic or inorganic water-permeable coating material. . Among them, coated granular materials using organic coating materials such as resins have a better elution control function, and such molds occupy the mainstream of coated fertilizers and coated pesticides.

  Various types of resin are used as the coating material, but thermosetting resins such as urethane resin use coating film strength, good water resistance, ease of control of elution characteristics, and solvents. It is widely used for the reason that it can be applied without being applied, and the present applicant also disclosed in Patent Document 1 a granular fertilizer whose surface is (A) an aromatic polyisocyanate and a castor oil or a castor oil derivative polyol. A coated granular fertilizer is disclosed in which the isocyanate group-terminated prepolymer obtained from (B) is coated with a film made of a polyurethane resin obtained by curing with castor oil or castor oil derivative polyol and (C) amine polyol. .

  Generally, the coated granular fertilizer as described above has a process of coating (coating) the surface of the granular fertilizer with a coating material in the production process, but on the other hand, coating defects such as defective coating and pinhole defects occur. In order to suppress such defects, various studies have been made on coating methods for coating materials.

  For example, in the method for producing coated granular fertilizer coated with a thermosetting resin, (1) the step of turning the granular fertilizer into a rolling state, (2) the amount of the layer thickness of 1 to 10 μm on the granular fertilizer in the rolling state (3) a step of maintaining the rolling state of the granular fertilizer and coating each fertilizer particle surface with the uncured thermosetting resin, (4) the granular Maintaining the rolling state of the fertilizer and thermosetting the uncured thermosetting resin, (5) repeating the steps (1) to (4) one or more times (1) to (1) to A method for producing a granular fertilizer free from coating defects by performing in the order of (5) is disclosed (Patent Document 2).

  Further, in the method for producing sustained-release fertilizer particles encapsulated with polyurethane, (1) a step of applying an isocyanate-reactive component containing a polyester ether polyol to the fertilizer particles to produce coated fertilizer particles; 2) applying a polyisocyanate component to the coated fertilizer particles of step (1) to produce polyurethane encapsulated fertilizer particles, optionally including these steps of polyurethane of step (2) Using the encapsulated fertilizer particles in place of the fertilizer particles of step (1), repeating as many times as necessary (sequentially), about 2 to about 20% by weight, based on the total weight of the encapsulated fertilizer composition A method of forming polyurethane-encapsulated fertilizer particles containing the polyurethane of is disclosed (Patent Document 3).

  In addition, as a method for improving the operability when producing a coated granular fertilizer, before coating the granular fertilizer, by mixing the polyol compound and the amine catalyst, and then adding the polyisocyanate compound, for coating the granular fertilizer A method for obtaining a prepolymer is disclosed (Patent Document 4).

JP-A-10-265288 Japanese Patent Laid-Open No. 9-202683 Japanese Patent Laid-Open No. 2001-213865 JP 2004-307736 A

  As an elution characteristic of the coated granular water-soluble substance, it is required to suppress elution of initial components after fertilization. One method for suppressing the initial component elution is to suppress the coating defects as described above, and in order to reduce the coating defects, there is a method of forming a plurality of thin coating films. It has been widely studied and implemented (Patent Document 2).

  However, the formation of multiple coating films inevitably increases the film thickness, and as a result, all the internal components of the coated granular water-soluble substance do not elute and remain in the coating film. There was a problem that.

  In addition, since the coating film is formed in multiple layers, the coating process and the heating process must be repeated, resulting in problems such as a long manufacturing time and poor productivity. There is a need for a way to reduce the number.

  Patent Document 3 discloses a technique in which either an isocyanate-reactive component containing a polyester ether polyol or an isocyanate component is coated on fertilizer particles, and the other component is added after coating to form polyurethane. Yes. However, by dividing the process of adding the above two components separately, not only the manufacturing time is prolonged and the productivity is deteriorated, but also when the isocyanate component is coated first, the isocyanate component and the moisture in the air Has reacted, making it difficult to form a uniform coating film.

  In Patent Document 4, the prepolymer is formed before adding to the granular fertilizer, but the coating process itself is the same as the conventional one, and the viscosity of the coating agent increases before coating by prepolymerization. Therefore, the coating defect has not been improved.

  In view of the above, an object of the present invention is to obtain a coated granular water-soluble substance that suppresses initial elution and simultaneously realizes a thin coating film.

  As a result of intensive studies by the present inventors, it has been found that the coating defects can be improved by using a liquid containing a low-viscosity aromatic isocyanate compound as a coating material for forming a coating film.

  On the other hand, in the present invention, when a coating film containing a highly water-absorbent resin is formed, a new problem arises that the elution performance of the initial elution decreases as the coating film thickness decreases. I understood.

  Therefore, as a result of further studies on the new problem described above, it is possible to prevent a decrease in the elution performance of the initial elution by making the particle size of the superabsorbent resin suitable. all right.

That is, the present invention is a method for producing a coated granular water-soluble substance in which a coating film is formed on the granular water-soluble substance,
Supplying a polyol liquid containing at least a polyol compound and an isocyanate liquid containing an aromatic isocyanate compound onto the particulate water-soluble substance to form a coating film containing a urethane resin;
The coated granular material, wherein the viscosity of the isocyanate liquid at the surface temperature of the granular water-soluble substance (hereinafter sometimes referred to as “coating temperature”) is 1/3 or less of the viscosity at the coating temperature of the polyol liquid. This is a method for producing a water-soluble substance.

  When the viscosity at the coating temperature of the isocyanate liquid exceeds 1/3 of the viscosity at the coating temperature of the polyol liquid, the isocyanate liquid is mixed with the polyol liquid before covering the whole granular water-soluble substance without gaps. The suppression effect of coating defects may be reduced. The lower limit is not particularly limited as long as a film can be formed on the surface of the particulate water-soluble substance.

  In the present invention, an isocyanate liquid and a polyol liquid having a difference in viscosity are used to coat the entire granular water-soluble substance without gaps, thereby suppressing coating defects. Generally, granular water-soluble substances such as fertilizers and agricultural chemicals have irregularities, and when a low-viscosity isocyanate liquid and polyol liquid are supplied to these granular water-soluble substances, the coating film formed is the entire surface of the granular water-soluble substance. However, it is not possible to coat the convex portion with a sufficient film thickness. On the other hand, when an isocyanate liquid and a polyol liquid with high viscosity are supplied to these granular water-soluble substances, the formed coating film can cover the convex portions of the surface of the granular water-soluble substance with a sufficient film thickness, but the concave portions are completely covered. Cannot be coated. In addition, when the prepolymerized isocyanate liquid and polyol liquid are supplied to the particulate water-soluble substance, the thermosetting reaction of the urethane resin proceeds before the coating film completely covers the concave portion of the surface of the particulate water-soluble substance. As a result, a coating defect occurs.

  However, as shown in the present invention, the low-viscosity isocyanate liquid containing the aromatic isocyanate compound and the high-viscosity polyol liquid containing the polyol compound are not immediately completely mixed. By easily covering the concave portion of the particulate water-soluble substance before the curing reaction proceeds, the entire surface of the particulate water-soluble substance can be coated, and coating defects can be suppressed. Therefore, even a highly viscous polyol liquid can cover the entire surface of the particulate water-soluble substance, and because of its high viscosity, it can coat the convex part of the surface of the particulate water-soluble substance with a sufficient film thickness. And the entire surface of the particulate water-soluble substance can be coated with a uniform film thickness.

  The polyol liquid is a liquid containing a polyol compound, and may contain one or more arbitrary third components such as a reaction initiator when forming the superabsorbent resin or the urethane resin described above. On the other hand, the isocyanate liquid is a liquid containing an isocyanate compound, and preferably contains only a compound having an isocyanate component without containing an optional third component depending on the reactivity of the isocyanate group.

  In the present invention, the viscosity of the isocyanate liquid at the coating temperature is 50 mPa · s or less.

  The present invention is also characterized in that the isocyanate liquid is diphenylmethane diisocyanate (MDI) which is liquid at the coating temperature.

  In addition, the present invention is characterized in that the polyol liquid has a viscosity at a coating temperature of 20 to 500 mPa · s.

  In the present invention, the granular water-soluble substance has a particle size of 1 to 10 mm.

  Moreover, the present invention is characterized in that the coating film contains a highly water-absorbing resin.

  Moreover, the present invention is characterized in that a 95% diameter in the cumulative particle size distribution of the superabsorbent resin is equal to or less than the average film thickness of the coating film.

  Further, the invention is characterized in that the polyol liquid starts to be supplied between the start of supply of the isocyanate liquid and the end thereof.

  The coated granular water-soluble substance of the present invention has a uniform coating film thickness and suppresses initial component elution. Furthermore, the suitable manufacturing method of the coated granular water-soluble substance of the present invention is a method with good productivity, and it is easy to uniformly coat the surface of the granular water-soluble substance and can suppress coating defects.

It is the figure which showed the elution rate of the urea for every 7 days from Example 1, Example 2, Example 3, and the comparative example 1 to 7 days from the 3rd. It is the figure which showed the elution rate of the urea for every 7 days from Example 4 and the comparative example 2 to 7th to 84th. It is the figure which showed the elution rate of the urea for every 7 days from Example 7 of Example 5, Example 6, and Example 7 to 84 days.

  The present invention maintains a granular water-soluble substance in a fluidized state or a rolling state, and has an isocyanate liquid containing at least a polyol liquid containing a polyol compound and an aromatic isocyanate compound on the surface of the granular water-soluble substance in the fluidized state or rolling state. Is applied to form a coating film containing a urethane resin, and the formed coating film is thermally cured to obtain a coated granular water-soluble substance.

  When the granular water-soluble substance is brought into a fluidized state or a rolling state, the granular water-soluble substance is preheated for a certain period of time with hot air or the like in advance. At this time, the preheating time and the preheating temperature are set so that the water content of the granular water-soluble substance is such that the water content of the granular material does not significantly affect the isocyanate liquid and the polyol liquid, and the temperature of the granular material surface becomes the coating temperature. What is necessary is just to adjust suitably.

  An apparatus such as a fluidized bed or a spouted bed can be used for fluidizing the particulate water-soluble substance, and an apparatus such as a rotating pan or a rotating drum can be used for rolling. By making the particulate water-soluble substance into a fluidized state or a rolling state, it becomes possible to continuously coat the particulate water-soluble substance, and to make the coating film formed on the surface uniform. Become.

  The addition method of the isocyanate liquid and the polyol liquid is not particularly limited as long as it can be dispersed and added efficiently, and examples thereof include spraying and dropping. Particularly, the method of spraying with a two-fluid nozzle using compressed air is a good coating. Since a covering film can be formed, it is preferably used. Further, the method of spraying a mixture of an isocyanate liquid and a polyol liquid in advance is not suitable for the present invention because the difference in viscosity between the isocyanate liquid and the polyol liquid is eliminated.

  Examples of the aromatic polyisocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate (polymeric MDI), phenylene diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate, and the like. Or these modified bodies, for example, urea modified body, dimer, trimer, polymer, carbodiimide body, allophanate modified body, burette modified body, etc. are mentioned. These may be used in combination of two or more, and may be so-called “crude” polyisocyanates used industrially. Of these, MDI, carbodiimidized MDI, polymeric MDI, TDI and the like are particularly preferably used.

  As the aromatic isocyanate compound, liquid MDI has a low viscosity and low vapor pressure, so that stable coating can be performed. Therefore, only liquid MDI may be used, and the viscosity at the coating temperature is 50 mPa · s or less, and MDI is used. As long as it has 20 mass% or more, one or more other aromatic isocyanate compounds may be mixed.

  The isocyanate liquid containing the isocyanate compound preferably has a viscosity at a coating temperature of 50 mPa · s or less. When the viscosity at the coating temperature of the isocyanate liquid exceeds 50 mPa · s, it takes time to coat the surface of the particulate water-soluble substance, and the coating defects may not be suppressed. Moreover, in order to suppress a coating defect more effectively, it is preferable to set it as 30 mPa * s or less.

  Examples of the polyol compound include castor oil and derivatives thereof (for example, castor oil, alkylene oxide adduct of castor oil, polyhydric alcohol modified product of castor oil fatty acid, etc.), alkylene oxide adduct of low molecular polyfunctional alcohol (for example, diols, triols). , Hexaols, glycerin, propylene oxide of trimethylolpropane, butylene oxide, styrene oxide single adduct, coadduct, etc.), low molecular weight polyfunctional carboxylic acid alkylene oxide adduct (eg, propylene oxide of dodecanedioic acid) , Butylene oxide, styrene oxide single adducts, coadducts, etc.), low molecular weight polyfunctional polyester alkylene oxide adducts (for example, propylene oxide of glycerol and dodecanedioic acid polyester) Side, butylene oxide, styrene oxide single adducts, coadducts, etc.), and mixtures of two or more thereof. Among them, castor oil, derivatives obtained by transesterifying castor oil with ethylene glycol or propylene glycol, polyoxyethylene triol, and polyoxypropylene triol may be preferably used.

  The viscosity at the coating temperature of the polyol liquid containing the polyol compound is preferably 20 to 500 mPa · s. When the viscosity at the coating temperature of the polyol liquid exceeds 500 mPa · s, it takes time to coat the surface of the particulate water-soluble substance, and it may be impossible to coat the entire surface of the particulate water-soluble substance. If the viscosity is 20 mPa · s or less, the entire surface of the particulate water-soluble substance cannot be coated with a uniform film thickness. In order to more effectively suppress coating defects and coat with a uniform film thickness, it is preferably 30 mPa · s to 300 mPa · s.

  The said isocyanate liquid and the said polyol liquid are mixed so that the molar ratio represented by the isocyanate group / hydroxyl group of an isocyanate group and a hydroxyl group may be set to 0.5-2.0, Preferably it is 0.00. It may be 5 to 1.5, and in the case of a laminated film, the molar ratio may be changed for each layer. When the molar ratio is less than 0.5 or more than 2.0, the crosslinking between the isocyanate group and the hydroxyl group may be insufficient, and the initial elution may not be suppressed. Furthermore, the molar ratio of the total amount of the coating material used for the coating film may be more preferably 0.6 to 1.3.

  Moreover, it is desirable to add a reaction initiator when supplying the isocyanate liquid and the polyol liquid. As the reaction initiator, an amine compound is preferably used, and the above urethane compound may be contained in the formed urethane resin.

  As the amine compound, alkylamines or amine-based polyols are used. Examples of the alkylamine include trimethylamine, triethylamine, dimethylethylamine, dimethylisopropylamine and the like.

  The amine compound is preferably an amine-based polyol. Examples of such amine-based polyols include low-molecular amine polyols such as di-, tri-, ethanolamine, N-methyl-N, N'-diethanolamine. Or an amine-based polyol obtained by adding an alkylene oxide such as propylene oxide (PO) or ethylene oxide (EO) to an amino compound such as ethylenediamine, 1,3-propanediamine, or 1,6-hexanediamine. Although the ratio of addition is not particularly limited, alkylene oxide is 1 to 200, preferably 1 to 50 per nitrogen atom, but about 2 to 2.4 is a property of controlling the hydrophilic properties of the coating film. Particularly preferred for this purpose. As such, for example, N, N, N ′, N′-tetrakis [2-hydroxypropyl] ethylenediamine, N, N, N ′, N′-tetrakis [2-hydroxyethyl] ethylenediamine, N, N, N ', N'-tetrakis [2-hydroxypropyl] -1,3-propanediamine, N, N, N', N'-tetrakis [2-hydroxyethyl] -1,6-hexanediamine and the like can be mentioned. Particularly preferred are N, N, N ′, N′-tetrakis [2-hydroxypropyl] ethylenediamine and N, N, N ′, N′-tetrakis [2 because of their good reactivity and physical properties. -Hydroxyethyl] ethylenediamine or oxypropylenated ethylenediamine or oxyethylenated ethylenediamine based on them.

  In addition, when the amine-based polyol described above is used as the polyol compound in the present invention, good compatibility with the resin composition can be obtained, and a uniform coating film can be easily formed. Can do. An amine-based polyol is preferable because it accelerates the reaction and also acts as a cross-linking agent and a chain extender to obtain good curability and a tough coating film.

  It is possible to adjust the curing rate of the urethane resin by using the amine polyol in an amount of 0.1 to 50% of the urethane resin mass.

  Moreover, in order to accelerate | stimulate formation of a urethane resin, you may add a catalyst further, for example, organometallic catalysts, such as dibutyltin laurate and lead octenoate, can be used.

  The coating film formed on the surface of the particulate water-soluble substance is formed so that the particulate water-soluble substance is not exposed, and preferably has a uniform film thickness. The coating film may be a single layer film or a laminated film of two or more layers depending on the purpose.

  Further, the coating film is characterized in that a coverage expressed by the mass of the coating film with respect to the mass of the coated granular water-soluble substance is 0.5 to 15% by mass. The coverage is a value represented by the mass of the coating film / the mass of the coated granular water-soluble substance × 100. The larger the value, the more the surface of the granular water-soluble substance is covered with the coating film. Is. The coating rate of the coating film may be preferably 1% by mass or more. When the coating rate of the coating film is less than 0.5% by mass, it becomes difficult to suppress coating defects because the film thickness becomes too thin. Moreover, when it exceeds 15 mass%, the component elution pattern of a covering granular water-soluble substance may be impaired.

  Furthermore, an overcoat layer may be formed on the coating film as long as the elution performance is not impaired. Examples of the overcoat layer include a protective film that prevents the coating film from being damaged, and an anti-adhesion film that prevents mutual adhesion between the coated granular water-soluble substances. Examples of the protective film include those mainly composed of thermosetting resin such as urethane resin, paraffin wax, fine particles having water repellency and hydrophilicity, and the like. Examples of the anti-adhesion film include those containing talc, sulfur, calcium carbonate, silica, zeolite, diatomaceous earth, clay, metal oxide and the like as main components. The above may be used alone or in combination, and both a protective film and an anti-adhesion film may be used.

  When forming a plurality of coating films, it is preferable to supply an isocyanate liquid and a polyol liquid that form the coating film for the next layer when the thermosetting of the urethane resin of the coating film is insufficient. . In a state where the urethane resin is not sufficiently cured, the coating films adhere to each other on the surface, but the adhered coating film and the coating film are not completely integrated. When the isocyanate liquid and the polyol liquid are added, the isocyanate liquid and the polyol liquid enter between the attached coating film and the coating film, and both of them are quickly separated, and peeling that occurs in the coating film, etc. Damage can be suppressed.

  When two or more layers of the coating film are formed, the superabsorbent resin may be included in the layer formed on the inner side. The superabsorbent resin expands by absorbing water that has passed through the coating film, and helps to destroy the coating film. By using the superabsorbent resin, the elution time of the components can be reduced. Further fine control is possible.

  The addition of the superabsorbent resin may be performed simultaneously with the isocyanate liquid or the polyol liquid as long as the isocyanate liquid does not prevent the surface of the particulate water-soluble substance from being coated, but more preferably before adding the high viscosity polyol compound. It is also possible to add a highly water-absorbing resin mixed with a highly viscous polyol compound.

  The highly water-absorbing substance is a substance that swells to more than 5 times its dry volume by absorbing a large amount of water. Particularly preferred is a gel that has low solubility upon water absorption and becomes a gel. Specifically, for example, an acrylate polymer (for example, Sumikagel S, L, R type manufactured by Sumitomo Chemical Co., Ltd., Aqua Keep 10SH, 10SHP, 10SH-NF (20) manufactured by Sumitomo Seika Co., Ltd.) , SA60NTYPE2, Aqua Mate AQ-200, AQ-200B-02, Sanyo Chemical Industries, Ltd. Sunfresh ST-250MPS, ST-500MPSA) manufactured by Sekisui Plastics Co., Ltd., isobutylene polymer (for example, Kuraray KI Gel-201K, KI Gel-201K-F2, KI Gel Solution System, KI Gel Compound), acrylic acid / vinyl alcohol copolymer, polyethylene oxide-modified resin, starch graft polymer, starch (for example, , Potato starch, corn starch, sweet potato starch, soluble starch), carboxymethyl cellulose (CMC), include CMC metal salt and bentonite. Among these, an acrylate polymer, an isobutylene polymer, and starch are preferable, and an acrylate polymer is particularly preferable.

  The particle size of the superabsorbent material is preferably such that the 95% diameter in the cumulative particle size distribution is less than or equal to the average film thickness of the coating film, and low when the particle diameter of the superabsorbent resin is larger than the film thickness of the coating film. The entire superabsorbent resin cannot be covered with a sufficient film thickness with the coating material having a viscosity, and the initial elution of the coated granular water-soluble substance cannot be suppressed. More preferably, the 95% diameter in the integrated particle size distribution of the superabsorbent substance is ½ or less of the average film thickness of the coating film, and more preferably ¼ or less of the average film thickness.

  The addition amount of the superabsorbent material varies depending on the particle size, but is usually 0.1 to 30% by mass of the total mass of the urethane resin and the superabsorbent material, preferably 0.3 to 20% by mass, more preferably Is 0.5 to 10% by mass. If it is less than 0.1% by mass, the change in elution time and elution rate due to the addition of the superabsorbent substance is small compared to the additive-free resin, and it is not effective to adjust the elution characteristics with this. Moreover, when it exceeds 30 mass%, hydrophilicity will become large and adjustment of the elution start time may become difficult. .

  The coating film is usually formed by thermosetting in an atmosphere of room temperature (about 25 ° C.) to 150 ° C., preferably about 40 to 100 ° C. The formation time is the same as that of the isocyanate liquid and the polyol liquid used. What is necessary is just to select suitably according to a kind. Further, in the case of a granular water-soluble substance containing a component that is easily decomposed or altered by heat, it is necessary to form it at a relatively low temperature. In particular, when urea is used, the temperature is preferably 90 ° C. or lower.

  The coated granular water-soluble substance of the present invention can be suitably used as a coated granular fertilizer coated with granular fertilizer because the elution pattern of the eluted components can be adjusted. The coated granular fertilizer may be a water-soluble granular fertilizer, and examples thereof include urea, ammonium sulfate, ammonium sulfate, ammonium nitrate, potassium chloride, potassium sulfate, potassium nitrate, sodium nitrate, potassium phosphate, ammonia phosphate, lime phosphate. And at least one fertilizer or compound fertilizer selected from the group consisting of, and granular organic fertilizer.

  The coated granular water-soluble substance of the present invention is suitably used as a coated granular agricultural chemical coated with a granular agricultural chemical. The coated granular pesticide may be a water-soluble granular pesticide, and examples thereof include various insecticides, insect repellents, fungicides, herbicides, rodenticides, plant growth regulators, and the like.

  Hereinafter, the present invention will be described by way of examples. In addition, this invention is not limited to a following example. The production conditions of the present invention are shown in Table 1.

[Example 1]
10 kg of granular urea (particle diameter: 2.5 to 4.0 mm) was charged in a drum type rolling coating apparatus having a diameter of 600 mm, and the granular urea temperature was maintained at 70 ° C. by a hot air generator while rolling at 15 rpm.

  Next, 40 g of MDI having a viscosity of 2 mPa · s was added dropwise as the isocyanate liquid of the first layer, and after 5 seconds from the start of spraying of the isocyanate liquid, castor oil (hydroxyl value 160 mgKOH / g) and propylene oxide of ethylenediamine were used as the polyol liquid. 65 g (viscosity: 80 mPa · s) of an adduct (propylene oxide / nitrogen atom ratio; 2.2, hydroxyl value; 760 mgKOH / g) mixed so that the molar ratio of the hydroxyl group is 8: 2 is sprayed. A first-layer coating film was formed.

  Next, 3.5 minutes after the addition of the first layer polyol liquid, the same component, the same amount of the isocyanate liquid and the polyol liquid as the first layer coating film are placed in the apparatus at the same timing as the second layer coating film. Sprayed. In order to further accelerate the curing of the thermosetting resin of the coating film, the coating film on the granular urea was cured by rolling for 30 minutes after spraying the second layer of the isocyanate liquid and the polyol liquid. This was cooled to room temperature (about 25 ° C.) to obtain the desired coated granular fertilizer.

[Evaluation of yield rate]
The coated granular fertilizer was taken out and the yield rate was measured. 10 g of the reduced coated urea is sampled, and the coated granular fertilizer is completely immersed in a pre-diluted ink (S-1 (red), manufactured by Sachiachihata) diluted solution (2.5 g / 250 ml pure water). And left to stand at 25 ° C. for 1 hour, and the coated granular fertilizer was recovered by filtration. Subsequently, the ink adhering to the coated granular fertilizer is washed with water, and then the coated granular fertilizer colored with the ink and the coating resin that has been completely dissolved are removed, and the non-colored coated granular fertilizer is obtained from the mass of the coated granular fertilizer that is not colored ((non-colored coated granular fertilizer The mass of fertilizer (g / 10 g × 100) was calculated, and the results are shown in Table 1.

[Measurement of coverage]
The obtained coated granular fertilizer was shrunk and the coverage ((coated film mass / coated granular fertilizer mass) × 100) was calculated.

  As a result, the coverage was 2.0% by mass, and the film thickness at this time was 14.5 μm.

[Example 2]
When forming the coating films of the first layer and the second layer, MDI 40 g having a viscosity of 2 mPa · s as the isocyanate liquid, and a molar ratio of the hydroxyl group of the propylene oxide adduct of castor oil and ethylenediamine as the polyol liquid is 8: 2. A coated granular fertilizer was obtained in the same manner as in Example 1 except that 65 g (viscosity 80 mPa · s) of the mixed liquid was sprayed at the same time. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  From Table 1, it was found that the coating defects could be significantly suppressed as compared with Comparative Example 1 although not equivalent to Example 1. Moreover, the coverage was 2.0 mass% and the film thickness at this time was 14.5 micrometers.

[Example 3]
When forming the coating films of the first layer and the second layer, 32 g of MDI having a viscosity of 2 mPa · s as an isocyanate liquid, and a propylene oxide adduct of castor oil and ethylenediamine as a polyol liquid has a molar ratio of 8: 2. A coated granular fertilizer was obtained in the same manner as in Example 1 except that the liquid thus mixed was changed to 52 g (viscosity 80 mPa · s). The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  The coverage was 1.6% by mass, and the film thickness at this time was 11.6 μm. Although the coverage was lower than Comparative Example 1 from Table 1, the non-defective product rate was higher than Comparative Example 1 and the coating defects were greatly reduced. It turned out that it was able to suppress.

[Example 4]
10 kg of granular urea (particle diameter: 2.5 to 4.0 mm) was charged in a drum type rolling coating apparatus having a diameter of 600 mm, and the granular urea temperature was maintained at 70 ° C. by a hot air generator while rolling at 15 rpm.

  Next, 61 g of polymeric MDI (MDI: 40% by mass) having a viscosity of 25 mPa · s was sprayed as an isocyanate liquid as a coating film for the first layer, and castor oil (as a polyol liquid after 5 seconds from the start of spraying of the isocyanate liquid) Hydroxyl value 160 mgKOH / g) and propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g) were mixed so that the molar ratio of hydroxyl group was 8: 2. 98 g of liquid (viscosity: 140 mPa · s) and 6 g of superabsorbent resin (cross-linked acrylate polymer having a 95% diameter of 20 μm in the cumulative particle size distribution; ST-500MPSA manufactured by Sanyo Chemical Industries) were sprayed twice. Repeated.

  Next, 3 minutes after spraying the polyol liquid in the first layer, 63 g of MDI was sprayed, and after 5 seconds from the start of spraying of polymeric MDI (MDI: 40% by mass), castor oil (hydroxyl value 160 mgKOH / g) and propylene of ethylenediamine 102 g of a liquid in which an oxide adduct (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g) was mixed so that the molar ratio of hydroxyl group was 8: 2 was dropped, and this was repeated three times. Thus, a five-layer coating film was formed.

  In order to further accelerate the curing of the thermosetting resin of the coating film, the coating film on the granular urea was cured by rolling for 30 minutes after the formation of the fifth coating film. This was cooled to room temperature (about 25 ° C.) to obtain the desired coated granular fertilizer. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  From Table 1, it was found that defects in the coating film could be suppressed from the comparative example. The coverage was 7.5% by mass, and the film thickness at this time was 58 μm.

[Example 5]
10 kg of granular urea (particle diameter: 2.5 to 4.0 mm) was charged in a drum type rolling coating apparatus having a diameter of 600 mm, and the granular urea temperature was maintained at 70 ° C. by a hot air generator while rolling at 15 rpm.

  Next, 57 g of polymeric MDI (MDI: 40% by mass) having a viscosity of 2 mPa · s is sprayed as an isocyanate liquid as a coating film for the first layer, and castor oil (as a polyol liquid after 5 seconds from the start of addition of the isocyanate liquid). Hydroxyl value 160 mgKOH / g) and propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g) were mixed so that the molar ratio of hydroxyl group was 8: 2. 101 g of the liquid (viscosity: 140 mPa · s) and 7 g of a highly water-absorbent resin (cross-linked acrylate polymer having a 95% diameter of 40 μm in the cumulative particle size distribution; ST-500MPSA manufactured by Sanyo Chemical Industries) were sprayed.

  Next, 3 minutes after spraying the polyol liquid in the first layer, 59 g of MDI was sprayed, and after 5 seconds from the start of addition of polymeric MDI (MDI: 40% by mass), castor oil (hydroxyl value 160 mgKOH / g) and propylene of ethylenediamine 106 g of a liquid in which an oxide adduct (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g) was mixed so that the molar ratio of hydroxyl group was 8: 2 was dropped, and this was repeated three times. Thus, a four-layer coating film was formed.

  In order to further accelerate the curing of the thermosetting resin of the coating film, the coating film on the granular urea was cured by rolling for 30 minutes after the formation of the fourth coating film. This was cooled to room temperature (about 25 ° C.) to obtain the desired coated granular fertilizer. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  From Table 1, it was found that defects in the coating film could be suppressed from the comparative example. The coverage was 6.0% by mass, and the film thickness at this time was 43.5 μm.

[Example 6]
Example 5 except that when the first layer coating film was formed, a cross-linked acrylate polymer having a 95% diameter of 20 μm in the integrated particle size distribution of the superabsorbent resin; ST-500MPSA manufactured by Sanyo Chemical Industries, Ltd. was used. Coated granular fertilizer was obtained in the same manner as above. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  From Table 1, it was found that defects in the coating film could be suppressed from the comparative example. The coverage was 6.0% by mass, and the film thickness at this time was 43.5 μm.

[Example 7]
Example 5 except that when the first layer coating film was formed, a crosslinked acrylate polymer having a 95% diameter of 10 μm in the cumulative particle size distribution of the superabsorbent resin; ST-500MPSA manufactured by Sanyo Chemical Industries, Ltd. was used. Coated granular fertilizer was obtained in the same manner as above. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate.

  From Table 1, it was found that defects in the coating film could be suppressed from the comparative example. The coverage was 6.0% by mass, and the film thickness at this time was 43.5 μm.

[Comparative Example 1]
10 kg of granular urea (particle diameter: 2.5 to 4.0 mm) was charged in a drum type rolling coating apparatus having a diameter of 600 mm, and the granular urea temperature was maintained at 70 ° C. by a hot air generator while rolling at 15 rpm.

  Next, 55 g (viscosity: 150 mPa · s) of MDI-modified castor oil (isocyanate group-terminated prepolymer in which castor oil is mixed with an excess amount of MDI and the mass of NCO groups is 19% by mass of the total mass) as the first layer isocyanate liquid ), Castor oil (hydroxyl value 160 mgKOH / g) as a polyol liquid, and propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g), the molar ratio of hydroxyl group is 8: The liquid 50 g (viscosity 80 mPa · s) mixed so as to be 2 was mixed for 10 seconds to obtain a total of 105 g of coating material, and the coating material was sprayed.

  Next, 3.5 minutes after the addition of the first layer coating material, the same component and the same amount of coating material as the first layer were sprayed into the apparatus as the second layer coating film at the same timing. In order to further accelerate the curing of the thermosetting resin of the coating film, the coating film on the granular urea was cured by rolling for 30 minutes after spraying the coating material of the second layer. This was cooled to room temperature (about 25 ° C.) to obtain the desired coated granular fertilizer.

  The obtained coated granular fertilizer was measured for non-defective product rate and coverage rate, and the results are shown in Table 1. At this time, the coverage was 2.0 mass%, and the film thickness at this time was 14.5 μm.

[Comparative Example 2]
Granular urea is maintained at 70 ° C., and MDI-modified castor oil (isocyanate group-terminated prepolymer in which castor oil is mixed with an excess amount of MDI to make the mass of NCO group 19% by mass) as the first layer isocyanate liquid 83 g (viscosity 150 mPa · s), castor oil (hydroxyl value 160 mgKOH / g) as a polyol liquid, propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g) 76 g of liquid (viscosity 80 mPa · s) mixed so that the molar ratio is 8: 2, and a highly water-absorbent resin (cross-linked acrylate polymer having a 95% diameter of 20 μm in the particle size cumulative distribution; ST manufactured by Sanyo Chemical Industries, Ltd.) -500MPSA) 6 g for 10 seconds to make a total of 165 g of coating material. It was repeated twice.

  Next, 3 minutes after spraying the coating material of the first layer, MDI modified castor oil as an isocyanate liquid (isocyanate group terminal was prepared by mixing castor oil with an excess amount of MDI to make the mass of NCO group 19% by mass of the total mass). 86 g of prepolymer), castor oil (hydroxyl value 160 mgKOH / g) as a polyol liquid, and propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atoms; 2.2, hydroxyl value; 760 mgKOH / g) The mixture was mixed with 79 g of the liquid so that the ratio was 8: 2 for 10 seconds to obtain a total of 165 g of coating material, and the coating material was sprayed, and this was repeated three times, so that five layers were coated. A coated granular fertilizer was obtained in the same manner as in Example 4. The obtained coated granular fertilizer was evaluated for the yield rate and the coverage rate, and the results are shown in Table 1. The coverage was 7.5% by mass, and the film thickness at this time was 58 μm.

  From the above, coated granular fertilizer with a high yield rate even if the overall coverage is the same by coating the granular material before mixing with the high viscosity polyol compound using a low viscosity aromatic isocyanate It became clear that

[Dissolution test]
The obtained coated granular fertilizer was reduced and subjected to a dissolution test, and the results are shown in FIGS. In the dissolution test, 10 g of the reduced coated granular urea is collected and put into 200 cc of ion-exchanged water, stored in a constant temperature bath at 25 ° C., taken out after a predetermined time, and the amount of urea eluted in water is determined. Asked.

  From FIG. 1, when Example 1 was compared with Comparative Example 1, it was found that initial elution and long-term elution can be suppressed by using a low-viscosity isocyanate. Moreover, when Example 2 and Comparative Example 1 are compared, it is possible to suppress initial elution and long-term elution in Example 3 having a lower coverage than Comparative Example 1 having a higher coverage by using a low-viscosity isocyanate. all right.

  Further, comparing Example 4 with Comparative Example 2 from FIG. 2, even when a highly water-absorbing resin is added to increase the thickness of the coating film, the low-viscosity isocyanate is used to suppress initial elution and long-term elution. I knew it was possible.

  Furthermore, comparing FIG. 5 with Example 6 and Example 7 from FIG. 3, the particle size of the superabsorbent resin is reduced when the superabsorbent resin is added using low-viscosity isocyanate. Thus, it was clarified that initial elution and long-term elution can be suppressed.

Claims (11)

A method for producing a coated granular water-soluble substance in which a coating film is formed on the granular water-soluble substance,
Supplying a polyol liquid containing at least a polyol compound and an isocyanate liquid containing an aromatic isocyanate compound onto the particulate water-soluble substance to form a coating film containing a urethane resin;
A method for producing a coated granular water-soluble substance, wherein the viscosity of the isocyanate liquid at the surface temperature (coating temperature) of the granular liquid substance is 1/3 or less of the viscosity at the coating temperature of the polyol liquid. The method for producing a coated granular water-soluble substance according to claim 1, wherein the isocyanate liquid has a viscosity at a coating temperature of 50 mPa · s or less. The method for producing a coated granular water-soluble substance according to claim 1 or 2, wherein the isocyanate liquid is liquid diphenylmethane diisocyanate (MDI) at a coating temperature. The method for producing a coated granular water-soluble substance according to any one of claims 1 to 3, wherein the polyol solution has a viscosity at a coating temperature of 20 to 500 mPa · s. The method for producing a coated granular water-soluble substance according to any one of claims 1 to 4, wherein a particle diameter of the granular water-soluble substance is 1 to 10 mm. The method for producing a coated granular water-soluble substance according to any one of claims 1 to 5, wherein the coating film contains a highly water-absorbing resin. The method for producing a coated granular water-soluble substance according to claim 6, wherein the 95% diameter in the cumulative particle size distribution of the superabsorbent resin is equal to or less than the average film thickness of the coating film. 8. The coated granular water-soluble composition according to claim 1, wherein the polyol liquid starts to be supplied from the start of supply of the isocyanate liquid to the end of supply of the isocyanate liquid. 9. A method for producing a substance. The coated granular water-soluble substance manufactured using the manufacturing method of the coated granular water-soluble substance of any one of Claim 1 thru | or 8. The coated granular fertilizer according to claim 9, wherein the granular water-soluble substance is a water-soluble fertilizer. The coated granular pesticide according to claim 9, wherein the granular water-soluble substance is a water-soluble pesticide.

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