JPH0587480B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a slow-release coated granular fertilizer in which the elution rate of the fertilizer is controlled by coating the surface of the granular fertilizer with a coating material, and a method for producing the same. [Prior Art and Problems to be Solved] Chemical fertilizers are generally water-soluble and therefore fast-acting. However, because it is water-soluble, there is a large loss of components (reduction in utilization rate) due to runoff, denitrification, etc.
It is difficult to maintain the fertilizer effect over a long period of time. Furthermore, when applying fertilizer, there is a risk that concentration disturbances may occur on agricultural crops due to local unevenness of fertilizer application. To prevent this, various slow-release fertilizers have been proposed, and some have even been put into practical use. Slow-release fertilizers are broadly classified into the following two types. IB (isobutyraldehyde processed urea fertilizer),
Slow-release nitrogen fertilizers such as CDU (acetaldehyde-modified urea fertilizer) that are hydrolyzed or microbially decomposed. A coated slow-release fertilizer (coated fertilizer) that is made by covering granular fertilizer with an organic or inorganic coating material. Of these, the latter, especially coating with an organic coating material, is said to be effective in terms of component elution control function. Furthermore, various studies have been made to use various fillers and inorganic powders in the production of coated granular fertilizers for various purposes. For example, as shown below. (1) Slightly soluble inorganic powder such as talc is used to impart disintegrability to the capsule. (Japanese Unexamined Patent Publication No. 54-97260) (2) To reduce the cost of coating materials, powders such as talc, diatomaceous earth, and metal oxides are used. (Special Publication No. 60-102) However, in both cases, problems still remain in terms of membrane performance, price, etc. That is, in method (1), talc is contained in a material such as polyolefin, which is a thermoplastic resin, in a range of 50 to 80% by weight, and the film has excellent disintegration properties, but the addition of talc reduces the concentration of fertilizer components. No elution suppression effect was observed at all. In addition, method (2) also uses a material such as polyolefin, which is a thermoplastic resin, and although the addition of talc etc. can increase the amount, it cannot further improve the effect of suppressing the elution of fertilizer components. It is. Furthermore, there is a problem in that a special method is used to disperse the filler into dry air in a jet device in order to uniformly disperse the filler into the thermoplastic resin. Coated granular fertilizers are more expensive than simple granular fertilizers because of the coating process. The coating material cost accounts for most of the coating process, that is, the incremental processing cost, and it is necessary to reduce the coating material cost in order to produce inexpensive coated granular fertilizer. That is, it is necessary to obtain an inexpensive coated granular fertilizer using an easy coating method and reducing the cost of coating materials. [Means for Solving the Problems] As a result of intensive studies to solve these problems, the inventors of the present invention have found that the cost of covering materials can be drastically reduced by using a composite coating using a selected combination of an inexpensive filler and a resin. achieved. That is, the present invention consists of a resin mainly consisting of a thermosetting resin having a carboxyl group at the end of the surface of the granular fertilizer, and one or more plate-shaped fillers selected from talc, ceritite, and muscovite,
It is a coated granular fertilizer coated with a coating material whose filler volume concentration is in the range of 5 to 25%, and the granular fertilizer is in a flowing or rolling state and heated, and is a thermosetting material with a carboxyl group at the end. Obtained by coating the surface of granular fertilizer by dropping or spraying a solution in which one or more plate-shaped fillers selected from talc, ceritite, and muscovite are dispersed in a resin-containing solvent. I can do it. Thermosetting resins having a carboxyl group at the end include alkyd resins, aminoalkyd resins, polyester resins, thermosetting acrylic resins,
Examples include fatty oil vinyl aromatic copolymers and fatty oil dicyclopentadiene copolymers, but among them, alkyd resins (including modified alkyd resins) are preferred in terms of price, versatility, and wide range of modifications. Most preferred. In addition, it is of course possible to add resins that are compatible with this resin, such as acrylic resin, chlorinated rubber, vinyl chloride, nitrocellulose, and the like. By doing so, it is possible to improve the physical properties and reduce the cost as a total resin. There is no particular limit to the amount of such additive resin added, but in order to fully exhibit the effect of the main resin, a thermosetting resin having a carboxyl group at the end, it is recommended to add 50% by weight of the main resin. The range up to is preferred. In the present invention, a filler is used in addition to these resin components, and by using this filler, the volume increase effect of a general filler, that is, by using an inexpensive filler, the amount of expensive resin used is reduced by the volume thereof. However, the present invention is particularly characterized by using a plate-shaped filler as the filler, and by using the plate-shaped filler, the plate-shaped filler is uniformly dispersed in the coating and bypasses the diffusion path of fertilizer components and water. This produces the same effect as increasing the thickness of the coating, the so-called bypass effect. Due to this bypassing effect, compared to a fertilizer coated with resin alone with the same film thickness, it exhibits a significant elution-suppressing effect. This effect will be explained with reference to FIG. In the figure, the horizontal axis shows the amount of coverage, and the vertical axis shows 80
Shows % elution days. Curves A and B represent the coated granular fertilizer of the present invention, where A represents the resin volume equivalent value of the coating on the abscissa, and B represents the total weight of the resin and talc on the abscissa. C indicates a fertilizer coated solely with resin, which does not contain talc, and the horizontal axis represents the weight of the resin. As is clear from this figure, the amount of coating required to achieve the same effect (elution suppression effect) can be significantly reduced compared to using resin alone. The shape of the plate-like filler used is a plate-like or hexagonal plate-like one, and a flake-like one is particularly preferable, and specifically, the plate-like ratio (particle size/thickness) is 2.
Above, those in the range of 10 or more are particularly preferable. Further, the particle size of the plate-like filler is not particularly limited as long as it has the above shape, but it is usually 0.5 to 50 μm. Such plate-shaped fillers include talc,
Ceritite, muscovite, kaolin, phlogopite, micaceous iron oxide, etc. are included. Among these plate-shaped fillers, the elution suppression effect is completely different depending on the affinity with the main resin, a thermosetting resin having a carboxyl group at the end, and the effect of plate-shaped fillers on the elution performance of the composite coating is The relationship between type and filler volume concentration is shown in Figure 1. As is clear from this figure, talc, ceritite, and muscovite, which have better affinity, have good adhesion between them at the interface.
It is extremely effective in suppressing the elution of fertilizer components. From this point of view, in cases other than these three types of plate-shaped fillers, the surface is modified with a surface treatment agent such as a silane coupling agent or a surfactant, and the filler is used after improving its affinity with the resin. be able to. Next, the composite ratio of a resin mainly composed of a thermosetting resin having a carboxyl group at the terminal and a plate-shaped filler is shown in terms of filler volume concentration (volume % of filler with respect to the total volume of the composite covering material). The optimum filler volume concentration varies depending on the type and combination of resin and plate filler, and the type of granular fertilizer to be coated, but is usually 5 to 25%. Further, it is generally preferable that the coating material made of the resin and the plate-shaped filler be diluted with a solvent before coating. The more diluted it is, the easier it will be to coat it uniformly, but this will increase the cost of drying the solvent and reduce productivity, so it is preferable to coat at a concentration determined from a comprehensive viewpoint that takes these factors into consideration.
Usually it is 3wt~20wt%. There are no particular restrictions on the granular fertilizer as long as it is granular. Ordinary fertilizers, such as simple fertilizers such as ammonium chloride, ammonium sulfate, ammonium nitrate, urea, potassium chloride, NK chemical, chlorophosphoric acid, etc.
Compound fertilizers such as phosphorus sulfate and ammonium potassium can be used. In the present invention, the granular fertilizer can be brought into a fluidized or rolling state by any known method. For example, it can be brought into a fluid state using a flow device or a jet device, and it can be brought into a rolling state using a rotating pan, a rotating drum, or the like. As for the coating temperature, coating can be carried out appropriately within a temperature range of usually 30 to 120°C. In the case of granular fertilizers that contain ingredients that easily decompose or change in quality due to heat,
The coating must be applied at relatively low temperatures. For example, in the case of urea, the temperature is preferably 90°C or lower. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 The average particle size was 3.1 mm in a fluidized coating device with a column diameter of 10 cm.
Nitrogen Potassium Chemical C20 (N: 20%, K ₂ O: 10%)
900g was charged, fluidized with hot air, and maintained at 100°C. On the other hand, a soybean oil-modified alkyd resin (oil length 60) with a solid content concentration of 40 wt% was diluted with a solvent perchlorethylene to a solid content concentration of 7.5 wt%.
A solution was prepared by adding talc (average particle size: 3 μm, platelet ratio: 12) and stirring to uniformly disperse the talc. This solution was dripped onto the fertilizer grains in a fluidized state at the above-mentioned constant temperature using a pump at a constant speed of 5 m/min. After dropping, add another 15 minutes for drying.
The mixture was allowed to flow for a minute to obtain a coated granular fertilizer consisting of a composite coating of alkyd resin and talc. Table 1 shows the results of evaluating the coating amount of alkyd resin and talc, elution performance, etc. of the obtained coated granular fertilizer. Here, each item in Table 1 will be explained. Coverage amount: indicates weight % based on the total weight of resin and filler (resin + filler + granular fertilizer). Coating resin volume conversion value (C): Calculated from the following formula. C=A/da+B/df A: Resin coverage, B: Filler coverage da: Resin density, df: Filler density Number of days for 80% elution (at 25℃): 2.5g of coated granular fertilizer
It is placed in a plastic container that is flooded with water (150% of the maximum water content) and maintained at a constant temperature of 25°C. Drain water from the bottom of the plastic container and replenish water from the top over time. Only the coated granular fertilizer is taken out at regular intervals, and the nitrogen and potassium elution rates are determined by analyzing the nitrogen and potassium remaining in the coated fertilizer granules.
The elapsed number of days until 80% of the nitrogen in the coated granular fertilizer was eluted was defined as the 80% elution number of days. Examples 2 and 3 The same procedures as in Example 1 were carried out except that the filler volume concentration in Example 1 was changed, and the evaluations are shown in Table 1. Examples 4 and 5 The same procedures as in Example 2 were carried out except that talc in Example 2 was replaced with seritite and muscovite, and the evaluations are shown in Table 1. Example 6 The same procedure as Example 2 was carried out except that the resin was a soybean oil-dicyclopentadiene copolymer, and the evaluation was carried out in the first
Shown in the table. Comparative Example 1 The same procedure as in Example 1 was carried out except that the composite coating of alkyd resin and talc was replaced with a single coating of alkyd resin, and the evaluations are shown in Table 1. Comparative Examples 2 and 3 The same procedures as in Example 2 were carried out except that talc in Example 2 was changed to kaolin and phlogopite, and the evaluations are shown in Table 1. Comparative Example 4 The resin is ethylene and ethylene vinyl acetate copolymer resin, and the solid content concentration at the time of coating is 5wt%.
The evaluation was carried out in the same manner as in Example 2 except that
Shown in the table. (Comparative Example 4-1) Comparative Example 4-1 except that the composite coating with talc was changed to a single coating of ethylene and ethylene vinyl acetate copolymer.
The test was carried out in the same manner as in 1, and the evaluation is shown in Table 1. (Comparative Example 4-2) Comparative Example 5 The plate-shaped talc in Example 2 was ground by a ball mill, and the shape was almost isotropic (average particle size
The same procedure as in Example 2 was carried out except that talc of 0.4μ and platelet ratio of 1.6) was used, and the evaluation is shown in Table 1.

[Table] [Effect of the invention] From comparison with the examples and comparative examples shown in Table 1 and FIG. By coating with , a composite coating effect appears and the elution period can be significantly extended compared to the conventional case. Therefore, the amount of coating material used and the cost of the coating material required to produce coated granular fertilizer with the same number of elution days can be significantly reduced compared to the case of conventional coated granular fertilizer. Furthermore, since the coated fertilizer of the present invention contains an inorganic substance with a high specific gravity such as talc in the coating resin, it also has the effect of being difficult to float after fertilization.

[Brief explanation of the drawing]

Figure 1 shows the magnitude of the effect of the type of plate filler and filler volume concentration on the elution performance of composite coatings in Examples 1 to 5 and Comparative Examples 2 and 3. The horizontal axis shows the filler volume concentration. of,
The number of days for 80% elution is plotted on the vertical axis.
Figure 2 shows the relationship between the amount of coverage and the number of days for elution, with the amount of coverage plotted on the horizontal axis and the number of days for 80% elution on the vertical axis.

Claims (1)

[Scope of Claims] 1. The surface of the granular fertilizer consists of a resin mainly consisting of a thermosetting resin having a carboxyl group at the end, and one or more plate-shaped fillers selected from talc, ceritite, and muscovite, and the filler Coated granular fertilizer coated with a coating material having a volume concentration in the range of 5 to 25%. 2. At least one type selected from talc, ceritite, and muscovite is added to the granular fertilizer in a flowing or rolling state and in a heated state in a solvent containing a resin mainly consisting of a thermosetting resin having a carboxyl group at the end. A method for producing a coated granular fertilizer, comprising coating the surface of the granular fertilizer by dropping or spraying a solution in which a plate-shaped filler is dispersed.