JPS6037074B2 - Coated fertilizer and its manufacturing method - Google Patents

Description

[Detailed Description of the Invention] Conventionally, fertilizer components have been coated with high molecular weight polymers in order to artificially adjust the supply of fertilizer components to meet the needs of plants, or to prevent fertilizer particles from absorbing heat or solidifying. Research and development has been conducted on coated granular fertilizers.

High molecular weight polymers are broadly classified into thermosetting ones and thermoplastic ones, and either type of polymer can be used for the above purpose. For example, British Patent No. 954555 describes styrenated alkyd resins and phenolic resins, Japanese Patent Publication No. 40-28927 discloses fatty oil-modified alkyd resins, fatty oil dicyclobentadiene copolymers, diisocyanate-modified fatty oil polymers,
No. 4-28457 indicates that thermosetting resins such as phenolic resins can be used. Also British patent 8158
No. 29 discloses the use of thermoplastic resins such as polymers or copolymers of styrene, vinyl chloride, vinylidene chloride, acrylonitrileethylene, and fluorinated alkanes as coating materials. Furthermore, Japanese Patent Publication No. 37-15832 discloses the use of a vinyl acetate emulsion polymerization solution as a coating material. As a problem when using high-molecular polymers, especially thermoplastic resin solutions or their emulsions as coating materials, Japanese Patent Publication No. 42-13681 describes coating the surface of granular materials with liquid resin or stringable resin. Due to the stringiness of the resin, the particles adhere to each other and form blocks when only a few percent of the resin is coated, making it impossible to coat them uniformly and thickly, making it difficult to coat the fertilizer with a uniform thickness. It has been shown that it is difficult to slow down the elution rate of the components.

JP-A-50-99858, JP-A-51-75674, and JP-A-53-98265 are related to applications for coating methods for granular fertilizers invented by the inventors of the present application. A method has been shown in which coating can be efficiently performed in one step without causing blocking during the coating process by selecting the properties of and drying conditions.

Samurai Kaisho 50-99858 discloses that when coating granular fertilizer with a coating material mainly composed of polyolefin, a solution of the coating material is applied to the granular fertilizer, and at the same time as coating, preferably 15 m.
A method of coating the granular fertilizer by drying it with hot air at a speed of 1/sec or more is shown. The features of this technology are: (1) it is possible to completely cover the product with an extremely thin film, and (2) the elution rate can be adjusted by appropriately dispersing an elution regulator such as a surfactant within the film. In addition, Tokusei Sho 51-75674 reported that polyvinylidene chloride resin and ethylene monomonovinyl acid copolymer containing less than 5% by weight of vinyl acetate can completely cover granular fertilizer with an extremely thin film, similar to polyolefin resin. Disclosed. The effect of the surfactant is unstable in coated granular fertilizers made by the above-mentioned known technology, in which the dissolution rate is adjusted by uniformly dispersing the surfactant in a film containing polyolefin as the main component, and the surfactant becomes a base material. Polyolefin is relatively inflexible and has weak adhesion to fertilizer particles, so if the product is rapidly cooled or stored outdoors with rapid temperature changes, the film adhering to the recesses may peel off, causing mechanical damage during transportation. If an impact is applied, the coating may wear off and some of the effectiveness of the coating may be lost.

In addition, when a large amount of surfactant is used to increase the elution rate, the results of long-term storage tests of at least two years have shown that cracks may form in the coating even without mechanical impact during long-term storage. Defects were recognized. The reason for this is not clear, but (1) During the coating process, the particles are maintained at a particle size of 50 to 9,000 and are usually handled at room temperature.
The film should be slightly contracted and stretched. ■The main reason for the promotion of ejection by surfactants is the formation of fine cracks, and one possible reason is that the elution rate is affected by slight differences in the properties of the polyolefin resin. In addition, when coating fertilizer particles using polyvinylidene chloride resin, the resin solution turns into a gel with a slight temperature change, making it difficult to use in combination with other resins, such as polystyrene, as the melting characteristics are different from those resins. There are drawbacks. The inventors of the present invention have conducted intensive research to eliminate the above-mentioned drawbacks and further stabilize the storage and transportation properties of coated granular fertilizers. By selecting a specific resin composition from among them and mixing it with an essential third component, the above-mentioned initial objective could be achieved and the present invention was completed.

That is, a surfactant is essential to a resin composition in which a polyolefin resin is used as a first resin component and an ethylene-vinyl acetate copolymer containing 20-4% by weight of vinyl acetate is dispersed as a second resin component. It was found that by coating with a film dispersed as the third component of the resin component, it was possible to obtain various dissolution rates with excellent storage stability depending on the mixing ratio of these resin components and surfactant components, and the present invention was completed. . The main component of the present invention is a resin composition in which an ethylene-vinyl acetate copolymer containing 20-4% by weight of vinyl acetate is uniformly mixed with a polyolefin resin in a range of 10-5% by weight based on the resin composition. A granular fertilizer coated with a film in which a surfactant having an HLB value of 6-20, preferably 9-16 is dispersed as an essential third component in a range of 0.01 to 1% by weight of the resin composition. and its manufacturing method.

The polyolefin resin of the present invention is a general term for olefin polymers, and preferred resins include ethylene polymer, propylene polymer, ethylene-propylene copolymer, etc. without being restricted by the polymerization method or degree of polymerization. Most preferred is low density polyethylene.

The ethylene-vinyl acetate copolymer used in the present invention is a copolymer of ethylene and vinyl acetate, and there are no particular restrictions on the polymerization method or degree of polymerization, and commercially available products can be used as appropriate, but preferred ones are It was obtained by high pressure polymerization method.

Although the mechanism of controlling the elution rate of fertilizer through the film, which is an effect of the present invention, is unknown, polyolefin resins and ethylene-vinyl acetate copolymers are relatively similar in chemical structure, and their compatibility with solvents. There are also many similarities. For example, an ethylene-vinyl acetate copolymer with a low vinyl acetate unit content is treated in the same way as an ethylene copolymer. Therefore, by dissolving both in a solvent or the like, a mixed solution in which they are uniformly dispersed at the molecular level can be created. However, JP-A-50-99
When applied to granular fertilizer etc. using a method such as 858, structural differences occur between a combination consisting of a small vinyl acetate content, ethylene-vinyl acetate copolymer and polyolefin resin, and a combination consisting of a large vinyl acetate content. ,
In other words, copolymers with ethylene that have a low vinyl acetate content and polyolefin have good compatibility between resins and maintain a homogeneous molecular mixture, whereas copolymers with a high vinyl acetate content and polyolefin Since the compatibility of these films is slightly inferior, the molecules repel each other appropriately, and resins of the same type gather together, resulting in a "sea-island" relationship.
In the present invention, the part corresponding to the sea is made of polyolefin resin, and it is thought that the ethylene-vinyl acetate copolymer is located in the position corresponding to the island. A shift occurs in the plane, creating a gap through which ions can pass. However, resins such as polyolefins tend to prevent the free passage of fertilizer components due to their strong hydrophobicity. The surfactant used in the present invention is assumed to act as a lubricant to enhance mutual affinity and facilitate passage of fertilizer components when they pass through the hydrophobic pores of the fertilizer component. The daily LB value of the surfactant used in the present invention is approximately 6 to 20, and the preferred range is 9 to 16.

Generally, if the HLB value is too high, the affinity with the resin will be poor, and the surfactant cannot be uniformly dispersed in the coating, so no effect can be expected. Furthermore, if the HLB value is too low, it will have no affinity with the fertilizer aqueous solution and will not function as a lubricant even if it is uniformly dispersed within the coating. These surfactants can be used alone or in a mixture, but the amount used is 0.01 to 100% based on the weight of the resin composition.
A range of 1% by weight is practical, and below that range no lubricating effect can be expected. Moreover, even if more than that is added, the effect reaches an equilibrium and the additional effect is not clear. Surfactants used in the present invention include (1) Those belonging to nonionic surfactants include M polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether (this polyoxyethylene lauryl ether); The number of moles of oxyethylene is preferably 4 to 15).

(b) Polyoxyethylene alkyl phenyl ethers, such as polyoxyethylene octylphenyl ether (preferably, the number of moles thereof is 4 to 20).

Esters of polyethylene glycol and fatty acids, such as lauric acid monoester (the polyethylene glycol of this lauric acid monoester has a molecular weight of 20
0 to 1000 is preferred).

8. Polyoxyethylene sorbitan fatty acid monoesters, such as polyoxyethylene sorbitan stearate (the polyoxyethylene sorbitan stearate preferably has 2 to 30 moles of oxyethylene). ■ Contains polyoxyethylene amines or amides.

{2) Ionic surfactants include fatty acid salts, such as triethanolamine oleate.

[o} Higher alcohol sulfates, such as palmityl sulfate sodium salt.

1. Dialkyl sulfosuccinates, such as diethylhexyl sulfosuccinate sodium salt.

〇 Alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl phosphates, alkyl amines, alkyloxymethylpyridinium chloride, etc.

Among these, polyoxyethylene alkyl ethers,
Polyoxyethylene alkyl phenyl ethers, ester classes of polyethylene glycol and fatty acids, and polyoxyethylene sorbitan fatty acid monoesters are preferred for the present invention. Specific examples of the elution characteristics of the present invention are as follows.

When low-density polyethylene is used as the PoIJ olefin resin, for example, an ethylene-vinyl acetate copolymer containing 3% by weight of vinyl acetate is mixed with polyethylene in an equal amount,
When granular urea with a diameter of about 3 sides is coated with a coating material containing 0.01% by weight of the total amount of resin, the average thickness of the urea is 25 cm, the time it takes for the dissolution rate in 25 qo water to reach 80% is approximately 100 days. It is days. Further, when a solution containing 4% by weight of vinyl acetate is similarly used, the elution rate is about 20% slower, and when a solution containing 2% by weight of vinyl acetate is similarly used, the elution rate is about 30% slower. The surfactant used in the present invention has an effect of regulating the elution rate, but a rough guide to its effect is that when it is added at 1% to the resin composition, the elution rate is approximately 5%.
~10% farther away.

Although the effect of this surfactant on the elution rate is smaller than when the surfactant is added to the polyolefin resin alone, there is no problem of cracks occurring during storage even if a large amount is used.
The reason for this is that when polyolefin resin is used alone, the dissolution promoting effect of the surfactant is due to the formation of fine cracks.
In the case of the present invention, as described above, this is thought to be because when the aqueous solution passes through the fine hydrophobic pores, it only acts as a lubricant and no cracks are generated. Unlike the case of polyolefin resin alone, the coating of the present invention is relatively flexible, does not peel off in the recessed parts of granular fertilizer due to sudden temperature changes or outdoor storage, is strong against mechanical shock, and has good long-term storage stability. It is. In addition to polyolefins and ethylene-vinyl acetate copolymers, the present invention may be applied to waxes, other polymers soluble in the solvent used in producing the granular fertilizer of the present invention, talc, calcium carbonate, silica, etc. Inorganic fillers such as acid salts can be used as long as the purpose of the present invention is not impaired. The method for producing the granular fertilizer of the present invention is disclosed in Japanese Patent Application Laid-Open No. 50-9
This can be done by a method similar to 9858.

In other words, the solution obtained by dissolving the coating material in a hot solvent of hydrocarbons or chlorinated hydrocarbons is sprayed onto granular fertilizers, and at the same time instant drying is performed without allowing time for the solution to gel. It will be done. The conditions for instant drying are that the resin solution is sprayed onto the fertilizer particles in a stream of dry hot air at a particle temperature of 30 oo or more, preferably 50 qo or more, preferably at a wind speed of 15 m/sec or more. The viscosity of the coating resin solution is preferably 4 ratio p or less, preferably 2 ratio p or less. If a filler such as talc is added, it must be added uniformly so as not to damage the continuous phase of the high molecular weight polymer. When these fillers are used in a coating solution, it is necessary to take care not to impair uniformity. Also, Tokuseki Showa 53-9
It is also possible to uniformly disperse the filler in hot air for drying using a special device as shown in No. 8265. Example 1 This example shows a method for producing samples for comparing the rolling characteristics and storage stability of various coated granular fertilizers.

As an apparatus for carrying out the present invention, a jet coating apparatus was used in order to obtain instant drying conditions. FIG. 1 shows the jet coating apparatus used in this example. 1 is a jet tower with a tower diameter of 2
It is 5 meters tall, 200 meters high, has an air outlet diameter of 5 meters, and has 2 fertilizer inlets and 3 exhaust gas outlets.

The jet air is sent from the blower 10, passes through the orifice flow meter 9 and the heat exchanger 8, and reaches the jet tower.The flow rate is controlled by the flow meter, the temperature is controlled by the heat exchanger, and the exhaust gas is guided outside the tower from the exhaust port. It will be destroyed. The granular fertilizer to be subjected to the coating treatment is introduced from the fertilizer input port while passing a predetermined amount of hot air to form a jet stream. The hot air temperature is T, the coating particle temperature is T2, and the exhaust gas temperature is T.
Detected at 3. In the coating process, after T2 reaches a predetermined temperature, the coating liquid is sprayed in the form of mist through the fluid nozzle 4 toward the jet stream. The coating liquid is prepared by putting a predetermined amount of the coating material and solvent into the liquid tank 11, and stirring the mixture near the boiling point of the solvent to maintain the temperature and coagulation during the coating operation. Coating liquid is pump 5
The system is supplied to the nozzle by a system that is sufficiently insulated to maintain its temperature. After supplying the specified coating liquid, stop the pump and then turn off the blower. The coated fertilizer is taken out from the outlet 7. In this example, coating with granular fertilizer was carried out while maintaining the following basic conditions.
Fluid nozzle: - For fluid, full cone type Sekiguchi 0.8 Skin hot air volume: 4 min Hot air temperature: 10000 Fertilizer type: 5-7 mesh granular urea fertilizer Input amount: 10k9 Coating liquid concentration: Solid content 5% by weight Supply rate: 0.5k9/min Covering time: 2 minutes Coverage rate (relative to fertilizer): 5. (however, the surfactant content is added) Solvent: Tetrachloroethylene Example 2 In this example, a mixture of polyethylene and ethylene vinyl acetate copolymer was used as the fertilizer coating material, and the mixing ratio was varied. This shows that the degree of beach exit can be adjusted.

Table 1 shows the results for resin compositions consisting of various mixing ratios of polyethylene and ethylene vinyl acetate copolymers containing 3% by weight of vinyl acetate prepared by the method shown in Example 1.
．． This shows the film composition of urea coated with a film in which 0.1% by weight of nonionic surfactant (hexaoxyethylene-nnonylphenyl ether) is dispersed and the number of days required for urea to elute 80%. be.

Table 1 The number of days required to dissolve 80% of urea was determined as follows.

The coated product was soaked in 200 ml of water for 10 days, kept in a constant temperature room of 25 ml, and the entire amount of water was refreshed every 10 days. Analyze the urea contained in the replaced water and determine the dissolution rate for 10 days. Using this data, we created a curve (dissolution rate curve) with the number of days on the axis and the cumulative elution rate on the vertical axis, and the cumulative elution rate was 80.
The number of days corresponding to % was calculated. From this example, ethylene-
It can be seen that by mixing vinyl acetate copolymers, products with a wide range of elution days can be obtained.

For additional explanation, one of the samples prepared in this example
The dissolution rate in water on the 0th day was 2% or less in all cases, but the mixture ratio of polyethylene 40 ethylene vinyl acetate copolymer 60% as a reference example was already 20% on the 10th day.
was also eluted.

This indicates that complete coverage is not achieved when the ethylene-vinyl acetate copolymer exceeds 6% by weight. Example 3 In this example, 0.01% by weight of the same surfactant as in Example 2 was dispersed and coated in a resin composition of a fixed ratio of polyethylene and ethylene vinyl acetate copolymer. This figure shows the change in the urea deposition rate when the amount of vinyl acetate in the storage is changed.

Table 2 shows the results. Table 2 From the results, it can be seen that when the amount of vinyl acetate stored in ethylene vinyl acetate is increased from 3% by weight to 4% by weight, the number of days required for elution becomes approximately 80%, and when it is increased to 20% by weight, it becomes approximately 130%.

It seems that a vinyl acetate content of 15% by weight or less is too effective for controlling the elution rate. (If the amount of vinyl acetate is too large, the adhesiveness will increase) Example 4 In this example, the same surfactant as in Example 2 was added to the resin composition of polyethylene-ethylene vinyl acetate with a fixed ratio and composition. 2 shows the change in elution rate when urea is coated with a resin solution dispersed in 2 to 10% by weight.

Table 3 shows the results. Table 3 From the results, it was found that when 1% by weight of surfactant was added to the resin, the elution period was shortened by about 5 to 10%.

(If there is too much surfactant, storage stability will deteriorate.

) Example 5 This example shows an example of checking whether the storage quality is good or not.

Table 4 shows the dissolution rate of the coated granular urea prepared by the method of Example 1 immediately after production and for 3 days in 25 oo water of a sample stored sealed in a 500 ta bottle for 2 years. Table 4: Dissolution test in water: Sample 10 was placed in 200% water, average value of 5 cycles PE: Low density polyethylene M120 EVA: Ethylene-vinyl acetate copolymer, (vinyl acetate 33% by weight) SA: Surfactant Octaoxyethylene-n-nonyl phenyl ether coating composition: The resin composition is PE and EVA, and SA is a percentage of the resin and a number added to the resin.

No. of Table 4 Nos. 1 and 2 showed a remarkable increase in the dissolution rate in water after 3 days after being stored for 2 years, indicating that defects were formed in the film.

NO. 3 to 6 indicate that there is no change in the dissolution rate and no change over time. In order to confirm what kind of defects there are, soak 10 drops of fertilizer in a coloring solution for 1 minute, wash off the coloring solution adhering to the surface with alcohol, and place each grain under a magnifying glass. As a result of observation using a microprocessor, all film defects were colored by the coloring liquid that had penetrated into the film, and their positions could be easily identified, and the defects were all hair cracks on one or two sides. No. 1 is 1 win, no. In No. 2, hair cracks were observed in one sickle, but no hair cracks were observed in other particles. No. No such cracks were observed in samples 3 to 6. The coloring solution is prepared by dissolving 20 parts of p-dimethylaminobenzaldehyde and 100 parts of concentrated hydrochloric acid in alcohol and leaving it for one night to react with urea to produce a yellow color.

The results of the initial elution rate and observation using a magnifying glass are No. 1, 2
Although cracks formed during storage in No. Samples 3 to 6 were determined not to be produced.

Example 6 This example further presents the results of testing the storage stability of a wider range of coating compositions.

FIG. 2 shows the storage stability test results when the sample was left at room temperature for two years using the method of Example 5. As is clear from the figure, it can be seen that as the amount of ethylene-vinyl acetate copolymer increases, storage stability generally improves. Here, film composition: P
E1EVA1SA Coverage rate: PE+EVA set to 5% by weight EVA%: (EVA/PE+EVA) xloo (weight basis) SA%: (SA/PE1EVA) xloo (weight basis) PE: Low density polyethylene (M120 ) EVA: Ethylene vinyl acetate copolymer (M128, vinyl acetate 33% by weight).

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the manufacturing apparatus used in the present invention, and FIG. 2 is a diagram showing the test results of Example 4. 1... Jet tower, 2... Fertilizer input port, 3
...Exhaust gas outlet, 4...Fluid nozzle, 5...
... (for coating liquid supply) pump, 7 ... (coated fertilizer) outlet, 8 ... heat exchanger, 9 ...
Orifice flow meter, 10...Blower, 11.
...Liquid tank (for coating liquid preparation), T. ...Hot air thermometer, T2...Thermometer for coated particles, T3.
...Exhaust gas thermometer. ÷Hino's picture of a spear

Claims (1)

[Claims] 1. Polyolefin resin and vinyl acetate content 20~
The main component is a resin mixture consisting of a mixture with 40% by weight of an ethylene-vinyl acetate copolymer, and the content of the ethylene-vinyl acetate copolymer in the mixture is at least 10% by weight; Furthermore, 0.0 of the main component
A granular fertilizer completely coated with a coating material in which 1 to 10% by weight of a surfactant is added and dispersed. 2 Polyolefin resin and vinyl acetate content 20~
The main component is a resin mixture consisting of a mixture with 40% by weight of an ethylene-vinyl acetate copolymer, and the content of the ethylene-vinyl acetate copolymer in the mixture is at least 10% by weight; Furthermore, 0.0 of the main component
A coating material in which 1 to 10% by weight of a surfactant is added and dispersed is added to a solvent, and the resulting solution is applied to fertilizer particles kept at 30°C or higher and within a temperature range where the coated fertilizer particles do not fuse. At the same time as the spraying, a high-speed hot air flow of 15 m/sec or more is applied to the fertilizer particles on which the resin solution has been sprayed, and the fertilizer particles are instantly dried without giving time for the solution to gel into a jelly. A method for producing a fertilizer coated with the above resin coating material.