JPH09202683A - Production of coated fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for industrially advantageously producing a sustained release coated fertilizer free from defect of coating film by applying a thermosetting resin to fertilizer. SOLUTION: In this method for producing a granular coated fertilizer coated with a thermosetting resin, the following steps are carried out in the order. (1) Granular fertilizer is kept in rolling state. (2) An uncured liquid thermosetting resin in an amount capable of providing 1-10μm layer thickness is added to the granular fertilizer kept in the rolling state. (3) The surface of each fertilizer granule is coated with the uncured thermosetting resin while keeping the rolling state of the granular fertilizer. (4) The uncured thermosetting resin is cured while keeping the rolling state of the granular fertilizer. (5) Steps from the step (1) to the step (4) are further repeated one or more times.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a slow-acting (sometimes called slow-acting) granular fertilizer. In particular, it relates to a method for producing a slow-release fertilizer resin-coated with a thermosetting resin such as urethane resin or epoxy resin.

[0002]

2. Description of the Related Art A so-called slow-acting granular fertilizer in which granular fertilizer is coated with resin, wax, sulfur or the like and encapsulated to control the elution rate of the fertilizer has a long history, for example, Japanese Patent Publication No. 40-28927 and Japanese Examined Patent Publication. 44-28457, Japanese Patent Publication No. 37-15382, or Japanese Patent Publication No. 42
Various coating materials and coating methods are disclosed in Japanese Patent Publication No. -13681. Regarding the coated fertilizer in which the coating material is a urethane resin composed of a reaction product of a polyisocyanate compound and a polyol compound, U.S. Pat. No. 3,264,089 is known.
No. 3,264,088, and an epoxy resin coating material is disclosed in U.S. Pat. No. 3,264,088. Regarding the method for producing a coated fertilizer comprising a urethane resin as a coating material, in JP-A-1-500661, the urea fertilizer surface is caused to react with an excessive amount of an isocyanate compound to form a base coat, and then the base coat is formed. There is a disclosure of a technique characterized in that a polyol compound is reacted with the excess isocyanate group. In JP-A-7-500560, a mixed resin of a polyisocyanate compound and a polyol compound is applied so that each layer has a layer thickness of 10 to 30 μm, and each layer is cured by treatment with an amine mist. There is disclosure of the technology to do. However, these techniques do not satisfy the purpose of controlled elution of fertilizer with few coating film defects, or have industrially disadvantageous aspects due to complicated manufacturing equipment and processes. There are many.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrially advantageous method for producing a slow-release coated fertilizer coated with a thermosetting resin and free from coating film defects.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. The present invention is as follows. That is, 1. A method for producing a coated fertilizer, which comprises performing the following steps in this order in a method for producing a granular coated fertilizer coated with a thermosetting resin. (1) A step of rolling granular fertilizer. (2) The granular fertilizer in the rolling state has a layer thickness of 1 to 10 μm.
A step of adding a liquid uncured thermosetting resin in an amount of m. (3) A step of maintaining the rolling state of the granular fertilizer and coating the surface of each fertilizer particle with the uncured thermosetting resin. (4) A step of maintaining the rolling state of the granular fertilizer and curing the uncured thermosetting resin. (5) A step of repeating the above steps (1) to (4) one or more times. 2. 2. The method for producing a coated fertilizer as described in 1 above, wherein the thermosetting resin is an epoxy resin or a urethane resin. 3. 3. The method for producing a coated fertilizer as described in 2 above, wherein the urethane resin comprises a diisocyanate compound, a polyol compound and an amine catalyst as essential components. 4. Gel time at the coating temperature of thermosetting resin is 5
The method for producing a coated fertilizer according to the above 1, 2, or 3, wherein the method is a minute or less.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The method for bringing the granular fertilizer into a rolling state is not particularly limited in the device, and known and commonly used ones can be used, and examples thereof include a rotating pan and a rotating drum. In addition, the equipment with heating equipment attached to the device,
It is suitable for improving the accuracy of coating and adjusting the processing time. The granular fertilizer used may be any of the conventional fertilizer granules. Specific examples thereof include urea, ammonium sulfate, ammonium salt,
Nitrogen fertilizers such as ammonium phosphate, ammonium nitrate, lime nitrogen, soda nitrate, acetaldehyde condensed urea, calcined phosphorus fertilizer, processed phosphate fertilizer,
Phosphate fertilizers such as hydrated phosphophosphate, mixed phosphate fertilizer, potassium fertilizer, potassium chloride, potassium sulphate, potassium carbonate, potassium silicate fertilizer and other fertilizers, phosphate fertilizer, nitric acid fertilizer and other chemical fertilizers,
Or a mixture of these fertilizers, such as organic fertilizers,
A granular fertilizer granulated by a method known per se can be mentioned. The particle size of the granular fertilizer is not particularly limited, but 1 to
A range of 5 mm is a preferable range for manufacturing.

The thermosetting resin used will be described. As the thermosetting resin, known resins can be used, and specific examples include epoxy resin, unsaturated polyester resin, phenol resin, alkyd resin, xylene resin,
Examples thereof include thermosetting resins such as melamine resin, furan resin, and silicone resin, and if necessary, two or more selected from these may be mixed and used. Of these, epoxy resins and urethane resins are preferable from the viewpoints of workability and performance, and urethane resins obtained by formulating a diisocyanate compound and a polyol compound with an amine catalyst are particularly preferable.

To further explain the urethane resin,
The urethane resin is a general term for resins which are three-dimensionally cross-linked by reacting a polyisocyanate compound and a polyol compound, and the uncured urethane resin in the present invention refers to the polyisocyanate compound and the polyol compound. A mixture of phenolic compounds, which have not been reacted at all or have been partially reacted in advance so as not to be three-dimensional. It is also a useful technique to add a catalyst to promote the reaction. The form of the uncured resin may be any of a solventless type, a solution type, an aqueous emulsion type, etc.
What is liquid at the processing temperature is suitable. The polyisocyanate compound is not particularly limited, but specific examples thereof include toluene diisocyanate (sometimes referred to as TDI) and diphenylmethane diisocyanate (MD
I), naphthalene diisocyanate,
Trizine isocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate and the like can be exemplified, and a mixture thereof can be used if necessary. Above all, M
DI or TDI or oligomers derived therefrom
The body is preferably used. For the polyol compound,
Although not particularly limited, for example, it is obtained by polymerizing polyetherpolyol or tetrahydrofuran obtained by polyaddition of ethylene oxide or propylene oxide using polyhydric alcohol, amino alcohol or amine as an initiator. Examples include polyether type polyols such as polytetramethylene ether glycol, and polyester type polyols obtained by a method of reacting a polyvalent alcohol with a polyether polyol and a carboxylic acid compound. Can be It is also possible to use an OH group-containing natural product or a modified product thereof in consideration of biodegradability.

As the reaction catalyst, known and conventional ones can be used. Specific examples thereof include triethylenediamine, N-methylmorpholine, N, N-dimethylmorpholine, diazabicycloundecene, 2,4 and 4. 6,-
An amine catalyst such as tris (dimethylaminomethyl) phenol is preferably used. Furthermore, if necessary, it is possible to use pigments or dyes for coloring, or inorganic / organic powders such as talc, mica, silica, carbon black, resin powder, etc. as a filler.

The production method of the present invention includes the step of bringing the granular fertilizer in the rolling state to a predetermined processing temperature. As the processing temperature, the gel time of the uncured resin is within 5 minutes,
More preferably, it is within 3 minutes. In the step of adding and coating the above-mentioned uncured resin to the particles in the rolling state, a resin composition in which a curing agent and a catalyst are mixed and mixed in advance is added by a method such as dropping and spraying. Alternatively, a method may be used in which a main agent, a curing agent, a catalyst, etc. are added separately and each component is mixed when the fertilizer particles are coated with the resin. The amount of resin charged at one time is adjusted so that the coated film thickness is 1 to 10 μm. More preferably, it is in the range of 2 μm or more and 6 μm or less. 1
When the thickness is less than μm, the number of coatings is too large, which is industrially disadvantageous. On the other hand, when the film thickness is 10 μm or more, the following problems occur. In the method of the present invention, a fertilizer in a rolling state is charged with a liquid uncured resin, first, a uniform uncured resin layer is formed on the particle surface by rolling of particles, and at the same time, a curing reaction of the resin occurs. proceed. At this time, the resin gradually thickens with the reaction and becomes spinnable. At that time, the adhesiveness of the resin is increased and the fertilizer particles are adhered to each other by the resin, forming a lump consisting of a large number of particles, which may not be loosened to the original primary particles, or even if loosened, it may damage the resin surface There is. When the resin film is 10 μm or more,
The problems described above occur, and individual particles cannot be uniformly coated with the cured resin. The inventors believe that if the resin film is thick, the force for separating the particles sticking to each other due to the rolling of particles becomes insufficient. In any case, when it is attempted to coat with a thick resin film at once, the above-mentioned inconvenience occurs in the usual rolling type coating method, and it is difficult to produce a desired resin-coated granular fertilizer.

By the steps as described above, the granular fertilizer coated with the uncured resin is maintained in the rolling state as it is, and the resin is cured. The term "curing" as used herein generally refers to a state in which the resin has passed the gel point and loses spinnability, without the need for complete curing. In such a state, the particles are not aggregated together with the adhesiveness of the resin and the particles cannot be disintegrated thereafter. Therefore, the next uncured resin can be added. In the production method of the present invention, by repeating the above-mentioned steps a plurality of times, it is possible to obtain a resin-coated granular fertilizer having a desired film thickness. The coating resin film thickness of the product varies depending on the desired elution pattern, but generally 20 μm to 200 μm is a suitable range. The coated fertilizer coated up to the final layer may optionally include a step of maintaining the resin at a predetermined curing temperature in order to completely cure the resin. It is also a useful technique to add inorganic fine powder such as clay to the surface of the coated fertilizer in order to prevent solidification of the fertilizer and prevention of floating when the fertilizer is applied.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 2 kg of granular urea (average particle size 3.4 mm) was charged into a temperature-controllable inclined pan type rolling granulator (pan diameter 520 mm) equipped with a hot air generator and rotated at 20 to 30 RPM to granulate. The fertilizer was rolled. The temperature of the granular urea charged by heating the apparatus was maintained at 70 to 75 ° C, and the rolling state was maintained. As coating resin, Polymeric MDI (Sumitomo Bayer Urethane, trade name: SUMIJULE 44V1
0) and 4.7 g of branched polyether type polyol (Sumitomo Bayer Urethane, trade name: Sumiphen TM).
3 g and 0.1 g of 2,4,6-tris (dimethylaminomethyl) phenol as an amine catalyst were mixed with stirring and added to the granular urea which was rapidly heated and in a rolling state. The uncured urethane resin composition was liquid at room temperature. The gel time of the uncured urethane resin used in this example was 2 minutes and 30 seconds at 65 ° C.
The amount of resin added was 0.5% by weight based on the fertilizer charged, and when the fertilizer having the particle size was coated, the film thickness of the coat resin was about 3.1 μm. It was confirmed by visual observation that the added resin coats the surface of the granular fertilizer substantially uniformly in about 30 seconds. When a part of the sample was taken out 3 minutes after the addition of the resin, the resin was in a state of having almost lost its tackiness. The above process was repeated 16 times every 3 minutes to coat the fertilizer with 8% by weight. Finally, the resin-coated granular fertilizer was maintained at 70 ° C.-75 ° C. for 10 minutes to completely cure the resin to prepare a urethane resin-coated granular fertilizer. The total process time was about 1 hour, which was an industrially advantageous method. Regarding the coating amount of the resin in the step, it was found from the SEM observation of the cross section of the coated fertilizer that the thickness of the resin film was about 50 μm. The fertilizer elution behavior at 25 ° C. of the resin-coated granular fertilizer prepared by the above process was evaluated. As a result, it was confirmed that 80% of the fertilizer content was eluted from the coated urea in about 85 days, and the coated urea had a sufficient slow-release effect. The fertilizer elution was evaluated according to the method proposed by the Ministry of Agriculture, Forestry and Fisheries Environmental Technology Research Institute (for example, “Detailed Fertilizer Analysis Method” edited by Masayoshi Koshino, 1988).

Example 2 2 kg of granular urea (average particle size 3.4 mm) was put into rolling state in exactly the same manner as in Example 1 and maintained at 65-70 ° C.
As the coating resin, the same components and composition ratios as in Example 1 were used. First, 5.3 g of a polyol component was added with an amine catalyst of 0.
After adding 1 g and thoroughly mixing, it was added to the rolling and warm granular fertilizer. It was visually observed that the amine-containing polyol uniformly coated the fertilizer surface in about 30 seconds. Then, 4.7 g of the polyisocyanate component was added while continuing the rolling and heating of the fertilizer. When a part of the sample was taken out 3 minutes after the addition of the polyisocyanate component, the resin was in a state of almost losing its tackiness. Four
The above process was repeated 16 times every minute to coat the fertilizer with 8% by weight. As a result of evaluating the fertilizer elution behavior at 25 ° C. of the resin-coated granular fertilizer produced by the above-mentioned step in the same manner as in Example 1, 80% of the fertilizer content was eluted in about 70 days, and the coated urea had a sufficient slow-release effect. It was confirmed to have. In addition, it was confirmed from this example that a method of separately adding a polyisocyanate component and a polyol component is also possible.

Example 3 2 kg of granular urea (average particle size 2.9 mm) was put into rolling state in exactly the same manner as in Example 1 and maintained at 65-70 ° C.
As the coating resin, the same components and composition ratios as in Example 1 were used. 15 g of the uncured coating resin that had been sufficiently mixed was added to the granular fertilizer in a heated and rolling state, and the granular fertilizer was coated with a urethane resin. The amount of resin added was 0.
It is 75% by weight, and when it is coated with fertilizer of the particle size,
The resin film thickness is about 4.3 μm. By visual observation, the added resin was coated on the granular fertilizer surface almost uniformly in about 30 seconds.
It was confirmed that When a part of the sample was taken out 3 minutes after the addition of the resin, the resin was in a state of having almost lost its tackiness. The above process was repeated 16 times every 3 minutes to coat the fertilizer with 12% by weight. Finally cut clay 1
0 g was added and maintained at 70-75 ° C. for 10 minutes to prepare a urethane-coated granular fertilizer. The fertilizer elution behavior at 25 ° C. of the resin-coated granular fertilizer prepared by the above process was evaluated in the same manner as in Example 1. As a result, the coated urea was 80 in about 120 days.
% Of fertilizer was eluted, and it was confirmed that the fertilizer had a sufficient slow-release effect.

Comparative Example 1 An attempt was made to produce a resin-coated fertilizer in exactly the same manner as in Example 1 except that the amount of resin added at one time was 40 g. The amount of the resin is 12.4 μm for the granular fertilizer.
It was confirmed by visual observation that the added resin coats the surface of the granular fertilizer substantially uniformly in about 30 seconds. After about 2 minutes,
The resin became thicker and took on a spinnability, and particles agglomerated with each other to form a lump in which a large number of particles agglomerated, and then it became impossible to disintegrate.

Comparative Example 2 An attempt was made to produce a resin-coated fertilizer in exactly the same manner as in Example 1 except that no amine catalyst was added as a resin component. The gel time of the resin when no amine catalyst was added was 20 minutes. When the sample was taken out 3 minutes after the first addition of the resin, the resin did not cure and remained liquid. Further, when a sample was taken out after 10 minutes, a thickening of the resin was observed, but it was a viscous liquid state. When a resin was similarly added to the fertilizer in that state, particles were adhered to each other and a large number of particles were aggregated to form a lump, which was then unable to be crushed.

[0016]

INDUSTRIAL APPLICABILITY According to the present invention, a slow-release coated fertilizer coated with a thermosetting resin and free from coating defects can be industrially produced advantageously.

Claims (4)

[Claims] 1. A method for producing a granular fertilizer coated with a thermosetting resin, which comprises performing the following steps in this order. (1) A step of rolling granular fertilizer. (2) The granular fertilizer in the rolling state has a layer thickness of 1 to 10 μm.
A step of adding a liquid uncured thermosetting resin in an amount of m. (3) A step of maintaining the rolling state of the granular fertilizer and coating the surface of each fertilizer particle with the uncured thermosetting resin. (4) A step of maintaining the rolling state of the granular fertilizer and thermosetting the uncured thermosetting resin. (5) A step of repeating the above steps (1) to (4) one or more times. 2. The thermosetting resin according to claim 1, which is an epoxy resin or a urethane resin.
A method for producing the coated fertilizer described. 3. The method for producing a coated fertilizer according to claim 2, wherein the urethane resin comprises a diisocyanate compound, a polyol compound and an amine catalyst as essential components. 4. The method for producing a coated fertilizer according to claim 1, 2 or 3, wherein the gel time of the thermosetting resin at the coating processing temperature is 5 minutes or less.