JPH0461840B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective of the Invention] (Industrial Application Field) The present invention relates to a double-coated sustainable fertilizer and a method for producing the same, and more particularly, a primary coating consisting of a silicate or silicate ester and a second coating consisting of a polymer latex. By applying a second coating to granular fertilizer,
The present invention relates to a double-coated sustainable fertilizer that reduces water permeability and significantly lowers the dissolution rate of fertilizer components into water, and a method for producing the same. (Prior Art) Today, the development of agricultural technology has promoted the mechanization of farming, and it is now required to be able to continuously supply fertilizer components throughout the entire growing period of crops with just one fertilization application. By developing such a sustainable fertilizer, it is possible not only to significantly reduce the labor required for fertilization, but also to reduce the amount of fertilizer runoff after fertilization. Various such sustainable fertilizers have been developed and commercially available, and the general forms of these conventional sustainable fertilizers can be broadly classified into the following three types. (1) Chemically react fertilizer ingredients with other substances,
A chemical reaction type that allows fertilizer components to be gradually hydrolyzed and released after fertilization. (2) A physical mixing type in which fertilizer components are physically mixed with other substances so that the fertilizer components are gradually eluted through the structure of the particles after fertilization. (3) The surface of the fertilizer particles is coated with a thin film,
A coated type that allows fertilizer components to be gradually diffused and released through the coating after fertilization. Representative examples of sustainable fertilizers that belong to the chemical reaction type include those disclosed in U.S. Patent No. 2,592,809 and U.S. Pat. No. 3,322,528, but the manufacturing process of these fertilizers is complicated and it is difficult to obtain a uniform product. It is difficult to
There is a problem that the product price becomes high. Examples of sustainable fertilizers belonging to the physically mixed type include those disclosed in Japanese Patent Publications No. 49-41150 and No. 49-24752, etc., but these fertilizers have simple manufacturing processes. On the other hand, since it contains unnecessary foreign substances other than the active ingredients of the fertilizer, the amount of the active ingredients of the fertilizer is relatively reduced. For this reason, there is a problem in that the product price per amount of active ingredient in the fertilizer increases, and it has not been widely put into practical use. On the other hand, sustainable fertilizers belonging to the coated type can achieve a large sustainable effect even if a small amount of coating material is used. In addition, the elution rate of the fertilizer can be easily adjusted by adjusting the thickness of the coating, incorporating appropriate additives into the coating, and further post-processing the obtained coated fertilizer, so that it is most active. It can be said that this is a form of fertilizer that is undergoing advanced research and development. A typical coated type fertilizer is Osmocote (U.S. Patent No. 3223518), developed by Archer Daniels Midland Company in the United States, which is a fertilizer containing dicyclopentadiene. - Urea particles are coated in multiple layers with a coating material mainly composed of glycerol ester copolymer, and the product has good properties. However, the cost of the coating material is high because a special polymer compound must be used, and the cost of the product is also high because multiple coating processes must be performed. Another important drawback is that the recovery of the organic solvent used in the coating process is complicated and difficult, which may increase product prices and cause environmental pollution due to unrecovered solvent. In addition, Nutricoat, manufactured by Japan's Nihon Asahi Fertilizer Co., Ltd., is a fertilizer made by spraying fertilizer particles with a solution of an olefinic polymer dissolved in a high-temperature organic solvent. There are difficulties in collecting the On the other hand, sulfur coated urea (SCU) was developed by the Tennessee Valley Authority (TVA) in the United States.
Urea) is a product that is completed by spraying sulfur onto preheated urea particles and then filling cracks caused by the sulfur with a wax sealant. This product has the advantage of being inexpensive because it uses inexpensive sulfur as a coating material, but the wax used as a sealant is decomposed by microorganisms in the soil. The problem is that the leaching rate of fertilizer becomes faster and sulfur accumulates in the soil, promoting soil acidification. (Problems to be Solved by the Invention) As mentioned above, the coated sustainable fertilizers developed so far have various problems. In addition, various efforts have been made to adjust the sustainability of the effect of fertilizers after fertilization. For example, Nutricoat (Korean Patent Publication No. 84-2204)
In this case, an appropriate amount of talc powder is included in the film to adjust the rate of elution of fertilizer into water, but there is a problem that talc, which is an inorganic substance, does not disperse well in the polymer solution. Coated urea (SCU)
In this case, the dissolution rate is adjusted by changing the coating amount, but in this case, there is a problem that the fertilizer content changes depending on the product. The present inventors have developed a technology for producing a sustainable fertilizer using water-soluble and inexpensive silicate as a coating material, and published it in US Pat. No. 4,493,725. However, a coating of silicate alone cannot produce a long-lasting fertilizer. Therefore, we developed a technology to additionally coat latex on the silicate coating layer.
I tried to solve the problem of sustainability. On the other hand, we investigated whether it is possible to produce a coated fertilizer using latex alone without performing a primary coating with silicate or silicate ester. If the temperature is too high (over 60℃),
The viscosity of most latexes becomes significant and the fertilizer particles adhere to each other, making coating impossible. On the other hand, if the temperature of the dry hot air is lowered in order to reduce the viscosity of the latex, the water will not completely evaporate and will penetrate into the fertilizer particles, weakening the strength of the fertilizer and making it more likely that the fertilizer will disintegrate during storage. Therefore, it has become clear that there are considerable technical problems when coating fertilizer particles with latex alone without a primary coating. As a result of these various studies, we have arrived at the present invention. (Means for Solving the Problems) The double-coated sustainable fertilizer of the present invention has a primary coating made of silicate or silicate ester on the surface of the granular fertilizer, and a secondary coating made of polymer latex applied thereon. It has a coating. The method for producing a double-coated sustainable fertilizer of the present invention includes:
A step of spraying a silicate or silicate ester aqueous solution with a concentration of 10 to 38% by weight onto the fertilizer and drying it to form a primary film, and suspending a polymer latex with a solid component of 5 to 20% by weight in this primary film. This process consists of spraying a liquid and then drying it to form a uniform secondary coating. Fertilizers used in carrying out the present invention include urea fertilizers, compound fertilizers, etc. Many types of fertilizers can be used regardless of their ingredients, but particle-type fertilizers whose size is not too small are suitable. The one is good. Spherical or near-spherical particles with a diameter of about 1 mm or more are preferred over angular or highly irregular shapes. Examples of silicates or silicate esters used in the present invention include sodium silicate, lithium silicate, potassium silicate, and ethyl silicate. When using sodium silicate, the sodium silicate is obtained from a reaction aqueous solution of silicon dioxide and sodium oxide, and the weight ratio of silicon dioxide to sodium oxide is preferably 3.3-3.4. Silicate or silicate ester granular fertilizer 100
It is coated at a ratio of 1 to 10 parts by weight. Although silicates are generally water-soluble, they do not cause particles to adhere to each other even under dry hot air at high temperatures, so they can be coated on the surface of fertilizer particles instantly, and the strength of the fertilizer particles after coating is , there is no significant difference in strength from before coating. Moreover, since the above-mentioned silicate has good adhesiveness, even in the case of fertilizer particles having a rough surface, a smooth coating like a glass bead without any scratches can be formed on the entire surface of the fertilizer particles. The polymer latex used in the present invention is an emulsion in which a solid component consisting of an insoluble polymer compound is uniformly dispersed in water, and in principle, any type of latex can be used. Although it can be used, those having low viscosity during coating and low water permeability of the coating are preferred. Such examples include natural latex, styrene
Butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, acrylonitrile-butadiene-styrene copolymer latex, styrene-2-ethylhexyl acrylate-acrylonitrile copolymer latex, acrylic copolymer latex, chloroprene copolymer latex , vinyl acetate copolymer latex, isoprene copolymer latex, vinyl chloride copolymer latex, vinylidene chloride copolymer latex, and these compounds can be used alone or in combination of two or more. It is also possible. In addition, a curing agent may be added to improve the physical properties of the polymer. The latex used has a solid content of 5 to 20% by weight, preferably 10 to 15% by weight. Further, the latex is coated at a ratio of 1 to 10 parts by weight per 100 parts by weight of the granular fertilizer. Furthermore, if polyvinyl alcohol, carboxymethyl cellulose, etc., which are water-soluble polymer compounds that can use water as a solvent, are used as the secondary coating material, it is not preferable because the phenomenon of fertilizer particles adhering to each other during coating will occur considerably. . In carrying out the present invention, the following method is used. At this time, a fluidized bed type coating device, which will be described later, can be used. First, in the first step, the concentration of silicate or silicate ester is 10 to 38% by weight, preferably 25 to 38% by weight.
A 30% by weight aqueous solution is sprayed onto the surface of fertilizer particles with a diameter of 0.1-2.0 cm to form a primary coating.
When using the fluidized bed coating device shown in Figure 3, the process conditions include a feed rate of silicate or silicate ester aqueous solution for 500 g of fertilizer.
20ml/min, preferably 5-10ml/min, air pressure of air mixing spray nozzle 0.2-5Kg/ ^cm2 , preferably
0.5 to 1 Kg/cm ² , and the drying air temperature is 20 to 100°C, preferably 60 to 80°C. In addition, a silicate or silicate ester aqueous solution with a concentration of 10 to 38% by weight is supplied at a rate of 2 to 500 g of fertilizer.
When the fertilizer is sprayed at ~20 ml/min for 10 to 150 minutes, the coating amount of silicate or silicate ester is 1 to 10 parts by weight per 100 parts by weight of fertilizer. Here, each process condition is not an independent variable, but influences each other. For example, the concentration of the solution may be lowered by increasing the temperature of the drying air. Furthermore, rather than maintaining the temperature of the drying air constant during the coating process, it is more advantageous for water to evaporate in the initial stage if the initial temperature is high and then gradually lowered. Approximately 30
It is desirable to blow dry air for an additional minute or so to completely dry the primary coating of silicate or silicate ester. Next, in the second step, a latex suspension having a solid content of 5 to 20% by weight, preferably 10 to 15% by weight, is coated using the same fluidized bed coating equipment as in the first step shown in FIG. Then, the fertilizer particles that have undergone the first step are subjected to a second coating. At this time, it is necessary to select the optimum process conditions according to the type of latex.
To prevent adhesion between the latex-coated fertilizer particles, inorganic minerals such as talcum (talc) and kaolin are sprinkled on the fertilizer particles in an amount of 0.1 to 2% by weight, preferably 0.5 to 1% by weight, before drying. Alternatively, add an aqueous solution of a metal salt such as zinc nitrate to 0.1 to 2
It may be applied in an amount of 0.5 to 1% by weight, preferably 0.5 to 1% by weight. Also, in order to perfect the formed film.
10 minutes at a temperature of 50-100℃, preferably 70-80℃
Heat treatment is recommended for 120 minutes, preferably 30 to 60 minutes. In addition, when a latex suspension with a solid content of 5 to 20% by weight is sprayed on 500 g of fertilizer at a feed rate of 2 to 20 ml/min for 20 to 200 minutes, the amount of latex covered is 100 parts by weight of fertilizer. The amount is 1 to 10 parts by weight. FIG. 3 shows an outline of a fluidized bed coating apparatus that can be used in the present invention. First, the fertilizer particles 1 to be coated are put into the fluidized bed 12 of the fluidized coating apparatus main body 2. Subsequently, the coating solution supplied from the coating solution container 3 via the supply pump 4 is spouted upward into the fluid coating device body 2 through a nozzle 5 provided at the bottom of the fluid coating device body 2 . When supplying the coating solution, compressed air is simultaneously supplied to the nozzle 5 through the pressure regulating valve 6.
The supply pressure of compressed air can be controlled by a pressure gauge 7. At this time, the air introduced through the air inlet 8 and heat exchanged to a predetermined temperature by the heat exchanger 9 causes the fertilizer particles to flow, and the moisture on the fertilizer particles after coating can be removed and dried.
Air introduced into the fluidized coating apparatus main body 2 is exhausted to the outside through the exhaust device 10. 11 is a filtering net for preventing the fertilizer particles 1 from coming out together with the exhausted air. Although it is possible to use the same fluidized bed coating device for the first step and the second step,
It is usually best to use separate equipment for each step. [Effects of the Invention] Since the double-coated sustainable fertilizer of the present invention produced as described above uses water as a solvent,
The manufacturing process is simple, as there is no need for equipment for dissolving the polymer in a solvent, equipment for supplying a heated polymer solution, equipment for recovering the solvent that evaporates after spraying the coating solution, etc., which are required in the polymer coating method. It is also inexpensive. Furthermore, since the primary coating of silicate or silicate ester is uniformly secondary coated with latex, the coating formed is uniform and has no pinholes on the surface, and the fertilizer effect continues for a long period of time even after fertilization. This is thought to be due to the fact that during the secondary latex coating, the moisture that has not completely evaporated in the primary coating is completely dried and acts as a barrier to prevent it from penetrating into the fertilizer particles. Further, since various latex coatings can be applied on the primary coating after the primary coating, various latexes can be optionally used to obtain the desired long-lasting fertilizer. In particular, by using a mixture of several types of latex rather than using a single latex, it is possible to arbitrarily change the heat resistance, impact resistance, weather resistance, water dissolution rate, etc. of a sustainable fertilizer. Therefore, more diverse products can be obtained than the existing method of dissolving a polymer compound in an organic solvent and spray coating it. (Example) Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 500 g of spherical urea fertilizer with a particle size of 3 to 5 mm was placed in a fluidized bed coating device (Uni-Glatt, Okawara Seisakusho, Japan), the amount of air introduced was 2 m ³ /min, and the drying air temperature was 70°C. Preheated for 10 minutes while maintaining fluidization at ℃. After preheating, 90 ml of a sodium silicate aqueous solution having a concentration of 25% by weight is supplied into the fluid coating apparatus body for 18 minutes at a flow rate of 5 ml/min through a pump. At this time, the nozzle pressure was 0.1Kg/ ^cm2 , and the hot air at 70℃ was 3.2
It was supplied at a rate of m ³ /min so that spraying, coating and drying were carried out simultaneously. The sodium silicate aqueous solution used here was prepared by diluting a commercially available sodium silicate aqueous solution with a weight ratio of silicon dioxide and sodium oxide of 3.4 and a concentration of 38% by weight with water to a 25% by weight aqueous solution. When the coating with sodium silicate was completed, the temperature of the fluidized bed was lowered to 40°C and drying was performed for an additional 10 minutes in a fluidized state. The coating yield of sodium silicate was 84 to 86%, and there was no phenomenon of solidification of particles during coating, and each fertilizer particle was completely coated with a smooth and transparent film. Next, 500g of fertilizer particles with the above primary coating completed.
was placed in the main body of a fluidized coating apparatus, and 250 ml of a latex suspension diluted to a solid content of 10% by weight of a copolymer of styrene and 2-ethylhexyl acrylate with a molar ratio of 1.5 was gradually stirred. The mixture was supplied to the fluidized bed for 50 minutes at a flow rate of 5 ml/min and a nozzle air pressure of 1 Kg/cm ² for atomization. At the same time, hot air at 40° C. was supplied at a rate of 3.2 m ³ /min so that spray coating and drying of the latex suspension were carried out simultaneously. The latex coating yield of the coated fertilizer was 86 to 89%, and even if the latex coating amount exceeded 15% of the weight of the fertilizer, there was no phenomenon of particles clumping together and uniform coating was achieved. Test Example 1 According to the method of Example 1, when primary coating with sodium silicate, 50 to 150 ml of a sodium silicate aqueous solution with a concentration of 25% by weight was applied at a nozzle pressure of 0.1.
Kg/cm ² , flow rate 5 ml/min, supply time 10 to 30 minutes, hot air temperature 70°C, and hot air flow rate 3.2 m ³ /min. 200 to 350 ml of turbid liquid at nozzle pressure of 1 Kg/cm ² , flow rate of 5 ml/min, supply time of 40 to 70
Each double-coated sustainable fertilizer was prepared with different coverages at a hot air temperature of 40°C and a hot air flow rate of 3.2 ^m3 /min, and latex without a primary coating of silicate or silicate ester. The dissolution rate of fertilizer (urea) in water was compared with that in which only coating was performed according to the method of Example 1. The results are shown in Table 1. If the fertilizer is coated directly with latex without a primary silicate film, the moisture in the fertilizer will be absorbed during the coating process, causing the surface of the fertilizer to dissolve.
Fertilizer components were contained in the latex coating. On the other hand, fertilizers coated with silicate as a primary coating showed no dissolution or disintegration of the fertilizer during the latex coating, allowing a uniform latex coating to be created, and the ability to control the release rate of the fertilizer was also significantly improved. . On the other hand, it has also become clear that the rate of fertilizer dissolution can be arbitrarily delayed by increasing the primary coating amount of silicate. In this case, the dissolution rate of the fertilizer in water at 40°C was measured, but the fertilizer was actually stored at room temperature (25°C).
When used in this case, the elution rate is reduced to 1/2 to 1/3, so it is thought that the fertilizing effect will last 2 to 3 times longer than this.

[Table] Example 2 500 g of urea fertilizer particles which had been primarily coated with sodium silicate in the same manner as in Example 1 were secondly coated with the following latex suspension in accordance with the method of Example 1.

[Table] The latex solution used was 133.3g, diluted to a solid content of 13%, and the coating temperature was 55%.
℃. No adhesion between fertilizer particles was observed at all during coating or in a stagnant state after coating was completed. Test Example 2 In Example 2, the dissolution rates in water of double-coated sustainable fertilizers coated with five types of latexes (A) to (E) were compared, and the results are shown in Table 2. Fertilizers coated with vinyl chloride and vinylidene chloride compound latex exhibit properties that hardly swell in water, and especially vinylidene chloride-vinyl chloride-acrylate copolymer latex coatings have extremely low permeability and are effective as shown in Table 2. It showed excellent ability to adjust fertilizer elution rate.

[Table] Example 3 500 g of urea fertilizer particles that were primarily coated with sodium silicate in the same manner as in Example 1 were treated with a suspension containing two or more of the following latexes according to the method of Example 1. Next coated. 250 g of this mixed latex solution was diluted to have a solid content of 10%.

【table】

[Table] Test Example 3 In Example 3, the dissolution rates in water of the double-coated sustainable fertilizer coated with various latex mixed suspensions were compared, and the results are shown in Table 3. It has good dispersibility between different substances, can form a uniform film during spraying and coating, and has the effect of arbitrarily changing the elution form curve of the coated fertilizer depending on the type and mixing ratio of the mixed latex. Ta.

【table】 [Brief explanation of drawings]

In FIG. 1, a is a schematic cross-sectional view of a granular fertilizer coated by the method of the present invention, and b is a partially enlarged cross-sectional view of a. F: Fertilizer particle layer, S: silicate or silicate ester layer, L: latex layer. Fig. 2 a, b, c and d are schematic diagrams showing the process of forming a film coated by the method of the present invention; The process of forming a dense film,
d shows a state in which the boundaries of dense latex particles have disappeared after sufficient drying. FIG. 3 is a schematic diagram of a fluidized bed type coating device used for coating fertilizer particles in the present invention. 1; Fertilizer particles, 2; Fluid coating device main body, 3; Coating solution container, 4; Supply pump, 5; Nozzle, 6;
Pressure adjustment valve, 7; Pressure gauge, 8; Air inlet,
9; heat exchanger, 10; exhaust device, 11; filtration net,
12; Fluidized bed.

Claims (1)

[Scope of Claims] 1. A double-coated sustainable fertilizer characterized by having a primary coating made of silicate or silicate ester and a secondary coating made of polymer latex on the surface of the granular fertilizer. 2. The ratio of silicate or silicate ester and polymer latex to 100 parts by weight of granular fertilizer is
A double-coated sustainable fertilizer according to claim 1, each containing 1 to 10 parts by weight. 3. The double-coated type according to claim 1, wherein the silicate or silicate ester is at least one selected from the group consisting of sodium silicate, lithium silicate, potassium silicate, and ethyl silicate. Sustainable fertilizer. 4 The polymer latex is natural latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, acrylonitrile-butadiene-styrene copolymer latex, styrene-2-ethylhexyl acrylate-acrylonitrile copolymer latex,
selected from the group consisting of acrylic copolymer latex, chloroprene copolymer latex, vinyl acetate copolymer latex, isoprene copolymer latex, vinyl chloride copolymer latex, vinylidene chloride copolymer latex The double-coated sustainable fertilizer according to claim 1, comprising one or more types of fertilizer. 5 A step of spraying a silicate or silicate ester aqueous solution with a concentration of 10 to 38% by weight onto the fertilizer and then drying it to form a primary film, and a step of forming a primary film with a solid component of 5 to 38% by weight.
A method for constructing a double-coated sustainable fertilizer comprising the steps of spraying and drying a 20% by weight polymer latex suspension to form a uniform secondary film. 6. The method according to claim 5, wherein the concentration of the aqueous solution of silicate or silicate ester is 25 to 30% by weight. 7 The solid component of the polymer latex suspension is 10 to 15
6. A method according to claim 5, wherein the amount is % by weight. 8 The process of spraying an aqueous solution of silicate or silicate ester onto fertilizer to form a primary film is performed on 500 g of fertilizer.
The supply rate of the silicate or silicate ester aqueous solution is 2 to 20 ml/min, and the spray nozzle pressure is 0.1 to 20 ml/min.
5. The method according to claim 5, which is carried out under conditions of 5 kg/cm ² and a drying air temperature of 20 to 100°C. 9 The supply rate of silicate or silicate ester aqueous solution is 5 to 10 ml/min, and the spray nozzle pressure is 0.5 to 1 kg/min.
9. A method according to claim ⁸ , wherein the drying air temperature is between 60 and 80<0>C.