JP2006111521A - Coated granular fertilizer and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated granular fertilizer having an excellent timed leaching type elution pattern in spite of being a thin coating film and containing much fertilizer components and a method of manufacturing the same without decreasing the productivity. <P>SOLUTION: The coated granular fertilizer has the surface coated with the coating film containing a low density ethylene homopolymer having physical properties of the following (a)-(c) and one or more kinds selected from polysaccharide and its derivatives and has the timed leaching type elution pattern. (a) The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3-6 and the weight average molecular weight (Mw) is 100,000-300,000. (b) The content of a component having the molecular weight of ≤10,000 is <3.5%. (c) The melt mass flow rate is 0.01-2 g/10min. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coated granular fertilizer in which a film is formed with a specific substance on the surface of the granular fertilizer. More specifically, the present invention relates to a coated granular fertilizer having a superior time-dissolving type elution pattern and containing a larger amount of fertilizer components, and a method for producing the same, by using a specific polyethylene resin as a component of the coating, although it is a thin coating.

Coated granular fertilizer coated with granular fertilizer surface with resin, etc. is excellent in elution control of fertilizer components, so it has been recognized that labor saving, labor load reduction and other environmental impact reduction effects, etc., cultivation using coated granular fertilizer Technology is spreading.
Compared with a granular fertilizer that is not coated, the coated granular fertilizer decreases the proportion of the fertilizer depending on the ratio of the coating film. On the other hand, the higher the coating ratio (the thicker the coating thickness), the easier the quality control, such as elution control and maintenance of coating strength, and in order to stably supply high quality coated granular fertilizer, Necessary. In particular, coated granular fertilizers with a timed elution type elution pattern consisting of an elution suppression period in which elution of fertilizer was suppressed for a certain period of time after application and an elution period in which elution continues after a certain period of time elapses during the elution suppression period In order to suppress leakage severely, it has been obtained by a low productivity method such as increasing the thickness of the coating for the purpose of eliminating defects (pinholes, etc.) of the coating, or by thinly coating the coating.
In order to reduce the coating thickness by reducing the coating thickness, the shape of the granular fertilizer should be adjusted, the particle size distribution etc. should be aligned, and if the coating is thinly and carefully applied, a dense thin coating without pinholes should be formed. However, productivity is further reduced.

Among coating materials, an olefin polymer having a low moisture permeability is effective in controlling fertilizer elution, and a coating containing polyethylene (for example, see Patent Document 1) and a coating containing an ethylene / carbon monoxide copolymer (for example, a patent) Document 2), a film containing polyethylene having a melt index of 5 to 50 g / 10 min and a stress brittleness value of 0.5 to 0.1 hours (for example, see Patent Document 3) is disclosed. Further, a film containing a polyethylene homopolymer and a copolymer of polyethylene (see, for example, Patent Document 4), a film containing polyolefin having a weight average molecular weight of 300 to 10,000 and polyethylene having a weight average molecular weight of more than 10,000 (for example, Patent Document 5), density 0.880~0.939g / cm ³ low-density ethylene polymer and density coatings containing high density ethylene polymer of the 0.940~0.975g / cm ³ (e.g. , Patent Document 6), polyethylene having a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw / Mn) of 1 to 6 and a density of 0.865 to 0.945 g / cm ³ A film containing a copolymer of (for example, see Patent Document 7), a film containing a copolymer of ethylene and a conjugated diene compound (for example, see Patent Document 8), Film Hardness by Yurometa D comprises a resin in the range of 54 to 71 (e.g., Patent Document 9 reference) have been disclosed.
In addition, many techniques related to coated granular fertilizer having a timed elution type elution pattern (for example, see Patent Document 10) are also disclosed.
All of these disclose an olefin polymer as an active ingredient of a coating, but disclose a coating material capable of producing a coated granular fertilizer having a time-elution type elution pattern with a thin coating and practical productivity. It was not a thing.

Japanese Patent Publication No.54-3104 JP-B-2-23516 Japanese Patent Publication No. 6-92275 JP 2004-75479 A JP-A-10-231190 Japanese Patent Laid-Open No. 10-236895 Japanese Patent Laid-Open No. 11-92261 JP 2001-89280 A JP 2002-161002 A JP 2000-185991 A

  The present invention provides a coated granular fertilizer having an excellent elution pattern of a timed elution type despite being a thin film and containing more fertilizer components, and a method for producing the same without reducing productivity. Is an issue.

  The present inventors diligently studied to solve the above problems. As a result, a coated granular fertilizer having a time-dissolved elution pattern, the surface of which is coated with a coating containing at least one selected from low density ethylene homopolymers having specific physical properties, polysaccharides and derivatives thereof The above-mentioned problem is solved, and the coating comprises a low-density ethylene homopolymer having specific physical properties, and a coating mixture in which one or more selected from polysaccharides and derivatives thereof are dissolved and dispersed in an organic solvent, Knowing that it is obtained by spraying and adhering to the surface of the granular fertilizer in the fluidized state or rolling state and evaporating the organic solvent from the adhering coating mixture, the present invention has been completed based on this finding.

The present invention is constituted by the following.
(1) A coated granular fertilizer whose surface is coated with a coating, wherein the coating is selected from low density ethylene homopolymers having the following physical properties (a) to (c), polysaccharides and derivatives thereof A coated granular fertilizer which is a film containing seeds or more and has a timed elution type elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is less than 3.5%.
(C) Melt mass flow rate is 0.01 to 2 g / 10 min.

(2) A coated granular fertilizer whose surface is coated with a coating film, wherein the coating film is selected from low density ethylene homopolymers having the following physical properties (a) to (c), polysaccharides and derivatives thereof: A coated granular fertilizer comprising a seed or more, the coating ratio being 3 to 12% by weight based on the coated granular fertilizer, and having a timed elution type elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is 3.0% or less.
(C) Melt mass flow rate is 0.01 to 2 g / 10 min.

(3) The coated granular fertilizer according to (1) or (2), wherein the coating further contains an ethylene copolymer.

(4) The coated granular fertilizer according to any one of (1) to (3), wherein the coating further contains a filler.

(5) The dissolution period of the fertilizer component is defined as d1 (day) until the dissolution rate of the fertilizer component reaches 5% by weight when the coated granular fertilizer is immersed in water at 25 ° C. However, with respect to the total amount of fertilizer components contained in the coated granular fertilizer, d1 / d2 is 0.7 or more when d2 (day) is a period from exceeding 5% by weight to reaching 80% by weight, The coated granular fertilizer according to any one of (1) to (4), wherein d1 + d2 is in the range of 30 to 360 (day).

(6) A coating mixture obtained by dissolving and dispersing in an organic solvent one or more selected from low density ethylene homopolymers having the following physical properties (a) to (c), and polysaccharides and derivatives thereof: The ratio of the coating obtained by spraying and adhering to the surface of the granular fertilizer in the fluidized state or rolling state and evaporating the organic solvent from the adhering coating mixture is 3 to 12% by weight with respect to the coated granular fertilizer. A coated granular fertilizer with a timed elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is 3.0% or less.
(C) The melt mass flow rate is 0.1 to 2 g / 10 min.

(7) The coated granular fertilizer according to (6), wherein the coating mixture further contains an ethylene copolymer.

(8) A method for producing a coated granular fertilizer having a timed elution type elution pattern having the following steps.
1st process: The coating mixture which melt | dissolved and disperse | distributed in the organic solvent 1 or more types chosen from the low density ethylene homopolymer which has the physical property of following (a)-(c), polysaccharide, and its derivative (s). The process of spraying and adhering to the surface of the granular fertilizer in a fluid state or a rolling state.
Second step: a step of evaporating the organic solvent from the coating mixture adhering to the surface of the granular fertilizer to form a film on the surface of the granular fertilizer.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is less than 3.5%.
(C) The melt mass flow rate is 0.1 to 2 g / 10 min.

(9) Jet tower in which spray of coating mixture is provided with a vertical guide pipe installed inside the tower, and a constricted disk having a plurality of jet holes at the bottom of the tower and an opening ratio of 10 to 70% Inside, the spouted layer is formed by the gas ejected from below through the ejection hole of the throttle disk, and is inserted into at least one of the ejection holes from below to the surface of the granular fertilizer in a fluid state The method for producing a coated granular fertilizer according to (8), which is performed using a spray nozzle.

The coated granular fertilizer of the present invention is a coated granular fertilizer that has an excellent elution pattern of a timed elution type in spite of being a thin film and contains more fertilizer components. The method for producing a coated granular fertilizer according to the present invention is a method of producing a thin film having a coating ratio of 3 to 10% by weight in the coated granular fertilizer. For example, the supply rate of the coating mixture during production is 10 kg / h or more in solids. It is a highly productive method that can be manufactured under high conditions.
The coated granular fertilizer of the present invention is not only obtained at a low cost, but also has a d1 / d2 of 0.7 or more, which is an indicator of a timed elution type elution pattern, and is therefore optimal for labor-saving cultivation methods such as fertilization during sowing It is a fertilizer that realizes both low cost and high performance. In addition, since resistance to impact at the time of handling is improved, it is possible to prevent a decrease in the initial elution suppression effect during use.

Hereinafter, the coated granular fertilizer of the present invention will be described in detail.
The coated granular fertilizer of the present invention is a fertilizer having a timed elution type elution pattern in which the entire outer surface of the granular fertilizer is coated with a coating containing at least one selected from a low density ethylene homopolymer, a polysaccharide and a derivative thereof. It is.
In the present invention, the “time elution type elution pattern” means that elution is suppressed within a certain period after fertilization and rapid elution is started after the elapse of the period.

In the present invention, a suppression period during which elution of fertilizer components is suppressed within a certain period after fertilization is referred to as an “elution suppression period” (hereinafter referred to as d1). Specifically, the coated granular fertilizer is submerged in water at 25 ° C. Defined as the number of days until the elution rate of the fertilizer component reaches 5% by weight. The period during which elution of the fertilizer component continues from the start of elution is referred to as an “elution period” (hereinafter referred to as d2). Specifically, the elution rate of the fertilizer component when the coated granular fertilizer is immersed in water at 25 ° C. Is defined as the number of days to reach 80% by weight over 5% by weight. In the present invention, the “timed elution type” elution pattern refers to an elution pattern in which the ratio of d1 / d2 is 0.2 or more.
In the coated granular fertilizer of the present invention, d1 / d2 is preferably 0.7 or more, more preferably 0.7 to 2, and still more preferably 0.75 to 1.5. Moreover, it is preferable that d1 + d2 is 30-360 (days). When d1 and d2 are in the above relationship, the coated granular fertilizer is particularly suitable for fertilization at the time of sowing, and does not cause a concentration disorder or length during seedling raising.

  The film which coat | covers the coated granular fertilizer of this invention contains 1 or more types chosen from the low density ethylene homopolymer, polysaccharide, and its derivative (s). The coating is obtained by coating the surface of a granular fertilizer with a coating mixture in which a coating material containing at least one selected from a low density ethylene homopolymer, polysaccharides and derivatives thereof is dissolved and dispersed in an organic solvent. Formed by evaporating the organic solvent. The coating material is a general term for components obtained by removing an organic solvent from a coating mixture.

The elution suppression mechanism and elution start mechanism of the coated granular fertilizer of the present invention can be explained as follows. That is, the polysaccharide or the derivative in the coating absorbs the moisture that has slightly permeated through the low-density ethylene homopolymer of the coating and starts to swell. The swelling pressure caused by this swelling causes the coating to crack, and the moisture that penetrates from the crack is absorbed by the granular fertilizer that is the core material of the coated granular fertilizer, and the fertilizer component in the granular fertilizer dissolved by water absorption has cracked portions. Begin to elute through. At this time, the time required for the coating to crack is the elution suppression period, and the time required for most of the fertilizer components to complete elution after passing through the crack is the elution period.
The coated granular fertilizer coating of the present invention preferably further contains a filler. The filler in the film suppresses the expansion and contraction of the film due to temperature changes and contributes to the cost reduction of the film material.

The low density ethylene homopolymer used in the coating mixture in the present invention has a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw / Mn) of 3 to 6, and a weight average molecular weight ( Mw) is 100,000 to 300,000. Mw and Mn are measured by gel permeation chromatography (GPC) method. When Mw and Mn satisfy the above conditions, the coated granular fertilizer of the present invention develops a desired time-dissolving elution pattern even though the coating is thin.
Further, from the viewpoint of the elution pattern, the ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) of the low density ethylene homopolymer measured by the GPC method is (Mz / Mw)> ( Mw / Mn) and the value of Mz / Mw is preferably 3 or less.

The low density ethylene homopolymer used in the coating mixture in the present invention has a content of a component having a molecular weight of 10,000 or less of less than 3.5%, preferably 3.0% or less. The molecular weight content is determined from the area ratio of the molecular weight distribution curve measured by gel permeation chromatography (GPC). When the content of the low molecular weight component having a molecular weight of 10,000 or less is less than 3.5%, it is difficult for the elution amount to decrease after the start of elution, and it becomes difficult for the fertilizer to run out. Furthermore, this effect is great. If the fertilizer runs out, the fertilizer components will elute even when they are not needed.
Based on the concept of Nutrient Delivery System (NDS, Nutrient Delivery System) corresponding to the recent Drug Delivery System (DDS) in the pharmaceutical field, delivering the required amount of nutrients (fertilizer components) to the required place when needed As a result, it can be expected to increase fertilization effect, reduce environmental burden, and save labor.

The low density ethylene homopolymer used in the coating mixture in the present invention has a melt mass flow rate (MFR, JIS K7210) of 0.1 to 2 g / 10 min. When the MFR is in the above range, the solution viscosity at the time of dissolving the solvent does not become too large, the coating mixture is uniformly applied in the coating formation, and the coating has sufficient resistance to impact.
The low-density ethylene homopolymer preferably has a crystallization temperature of 105 ° C. or lower and a melting point of 85 to 120 ° C. The crystallization temperature and melting point of the low density ethylene homopolymer are measured by a differential scanning calorimeter (DSC). When the crystallization temperature is 105 ° C. or lower, the spray nozzle is not easily blocked during the spraying process. Also, if the melting point is in the above range, the granular fertilizer does not fuse with each other in the process of forming the coating, and the low density ethylene homopolymer in the coating mixture coming out of the spray nozzle draws the yarn to cover it. It will never be impossible.

The MFR of the low density ethylene homopolymer contained in the coated granular fertilizer coating is in the range of 0.01 to 2 g / 10 min due to the influence of heat and the like during coating.
The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the low density ethylene homopolymer contained in the coating of the coated granular fertilizer is 3-6, and the weight average molecular weight (Mw) is 100, The content of components having a molecular weight of 10,000 or less is less than 3.5%, preferably 3.0% or less.

The low density ethylene homopolymer used for the coating mixture in the present invention preferably has a breaking strength (JIS Z1702) of 20 MPa or more and an elongation (JIS Z1702) of 400% or more. If the breaking strength of the low-density ethylene homopolymer is as described above, the coating may be damaged in mechanical fertilization using a power sprayer, etc., and elution control may not be possible, or the elution suppression period may be shortened. There is no.
The breaking strength of the low density ethylene homopolymer may be any value in the film drawing direction (MD) or vertical direction (TD) in resin processing by extrusion molding.

The low density ethylene homopolymer used for the coating mixture in the present invention preferably has a density (JIS K7112) of 0.88 to 0.93 g / cm ³ . When the density of the low-density ethylene homopolymer is within the above range, the coated granular fertilizer can be easily formed into a film, the solubility in an organic solvent is good, and the coating mixture can be easily prepared.
The low density ethylene homopolymer used in the coating mixture in the present invention can be produced using a production process such as a gas phase method or a slurry method, or a catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.
In the present invention, as the low density ethylene homopolymer, a commercially available low density polyethylene (LDPE) satisfying the above conditions can be selected and used.

  The content of the low density ethylene homopolymer in the coating material is preferably 20 to 75% by weight, more preferably 30 to 70% by weight, and still more preferably 40 to 65% by weight. If the content is in the above range, the elution suppression function is sufficient, and the coated granular fertilizer has good storage stability because there is no decrease in the strength of the coating. A coated granular fertilizer suitable for the above is obtained.

In the present invention, a low density ethylene homopolymer used in a coating mixture for the purpose of improving the accuracy of a timed elution type elution pattern and suppressing elution leakage (also referred to as initial burst) immediately after application by improving the strength of the coating. A part of may be replaced with an ethylene copolymer. As the ethylene copolymer, an ethylene-vinyl acetate copolymer or an ethylene-α-olefin copolymer is preferable from the viewpoint of compatibility with the low density ethylene homopolymer. These may be used alone or in combination, but the ethylene-vinyl acetate copolymer is more advantageous in terms of cost.
The amount of ethylene copolymer used can be used within a range that does not impair the performance of the low density ethylene homopolymer, but from the viewpoint of achieving the intended purpose and cost, 5 to 50% by weight of the low density ethylene homopolymer Preferably, 10 to 40 weight% is more preferable.

As the ethylene-vinyl acetate copolymer, ethylene having a vinyl acetate polymerization component content of 5 to 50% by weight and a weight average molecular weight of 50,000 or more from the viewpoint that the coating strength is sufficient and adhesion is difficult to occur during coating. -Vinyl acetate copolymers are preferred.
The ethylene-α-olefin copolymer is a copolymer of ethylene and one or more α-olefins. Examples of the α-olefin include propylene, 1-butene, 1-pentene, and 2-methyl-1. -Butene, 1-hexene, 1-heptene, 1-octene, 1-dodecene and the like. Among them, a copolymer with propylene or 1-butene having high compatibility with the low density ethylene homopolymer is preferable.

Examples of polysaccharides or derivatives thereof used in the present invention include cellulose, agar, starch, chitin and derivatives thereof, and chitosan and derivatives thereof, among which starch is a low price and a preferable material.
As the starch, those derived from corn, tapioca, wheat, potato, rice and sweet potato can be used. Further, modified starch such as pregelatinized starch obtained by processing these starches may be used. Moreover, the silicon-treated starch etc. which processed the starch surface with the silicone resin etc. and improved the dispersibility and fluidity | liquidity can be used.
These polysaccharides or derivatives thereof can be used alone or in combination of two or more.

  As the polysaccharide or derivative thereof used in the present invention, a powder having a particle size of preferably 50 μm or less, more preferably 5 to 40 μm, still more preferably 6 to 30 μm is suitable. When the particle size is in the above range, the polysaccharide or its derivative powder swells with moisture and causes cracks in the coating, so that the fertilizer components in the granular fertilizer elute through the cracked part, In addition to realizing an elution pattern, problems such as the particle size being too large and peeling of the coating during film formation and clogging of the coating mixture into the spray nozzle or the like are unlikely to occur. However, even if the particle size is large and a part of the powder particles protrudes from the coating surface, if the powder particles are taken into the coating and are thin but the coating covers the powder particles, the intended purpose Is achieved.

  The content of the polysaccharide or derivative thereof in the coating material is preferably 1 to 20% by weight, and more preferably 2 to 15% by weight. When the content is in the above range, the desired effect is obtained, and troubles during production due to poor dispersion in the coating are less likely to occur.

Examples of the filler used as a coating material in the present invention include talc, hydrotalcite, mica, sericite, glass flakes, various metal foils, graphite, plate-like iron oxide, plate-like charcoal, and plate-like aluminum hydroxide. Examples of the filler include calcium carbonate, silica, clay, various ore pulverized products, and sulfur. Preferably, the shape is a flat filler, and more preferably talc.
The particle size of the filler used in the present invention is preferably 100 μm or less, and more preferably 1 to 50 μm. When the particle size is in the above range, problems such as the particle size being too large and the coating film peeling off during film formation or the coating mixture clogging the spray nozzle or the like are unlikely to occur. Even if the filler has a particle size larger than the thickness of the coating and a portion of the filler protrudes from the surface of the coating, the intended purpose can be achieved as long as the filler is partially incorporated into the coating and adhered.

The variation coefficient of filler dispersion in the coating is preferably 50% or less, and more preferably 35% or less. When the variation coefficient is 50% or less, variation in the dissolution pattern between the obtained coated granular fertilizers tends to be small. The coefficient of variation is preferably as close to 0 as possible. However, when the coefficient of variation is less than 5%, it is difficult to measure the following coefficient of variation due to a measurement error due to the shape of the filler. Is preferably 5 to 50%, more preferably 5 to 35%.
The coefficient of variation of the filler dispersion in the coating is an arbitrary value from the cut surface of the coating, with the film thickness direction being vertical and the direction parallel to the film surface being horizontal on the cut surface of one coated granular fertilizer. In addition, the vertical x horizontal = 20 μm x 50 μm range, 10 locations, 20 particles extracted arbitrarily were observed with a scanning electron microscope, the number of fillers present in each location was measured, and obtained from the measurement results (the said Coefficient of variation = standard deviation / average value × 100).

  The content of the filler in the coating material is preferably 5 to 80% by weight, and more preferably 10 to 60% by weight. When the content is in the above range, the desired effect is obtained, and a timed elution behavior is obtained.

  In the present invention, a surfactant can be used as a coating material in order to increase hydrophilicity on the surface of the coated granular fertilizer. Surfactants include nonionic surfactants typified by fatty acid esters of polyols, nonionic surfactants, cationic surfactants, anionic surfactants, and the like, the degree of esterification of surfactants, alkyl groups Can be selected and used in consideration of the chain length, the number of moles of alkylene oxide added and the purity. The content of the surfactant in the coating material is preferably 0.01 to 10% by weight, and more preferably 0.1 to 5% by weight in order to obtain the desired effect.

  In the present invention, various organometallic compounds may be used to decompose the resin in the coating. Examples of organometallic compounds include organometallic complexes and organic acid metal salts. Among these, iron complex and iron carboxylate are preferable because the photodegradability can be easily adjusted. Examples of the iron complex include iron acetylacetonate, iron acetonylacetonate, iron dialkyldithiocarbamate, dithiophosphate, xanthate, and benzthiazole. Examples of the iron carboxylate include iron compounds such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, behenic acid, oleic acid, linoleic acid, and linolenic acid. These may be added alone or in combination of two or more. The content of the organometallic compound in the coating material is preferably 0.0001 to 1% by weight, more preferably 0.001 to 0.5% by weight. When the content is in the above range, the coating is unlikely to collapse or decompose during product storage, and the desired effect can be easily obtained during application.

As fertilizers for granular fertilizers, in addition to nitrogenous fertilizers, phosphate fertilizers, and calcareous fertilizers, fertilizers containing plant essential elements calcium, magnesium, sulfur, iron, trace elements and silicon, etc. Specific examples of nitrogenous fertilizers include ammonium sulfate, urea, and ammonium nitrate, as well as isobutyraldehyde condensed urea and acetaldehyde condensed urea. Phosphorus fertilizer and the like can be mentioned, and examples of the calcareous fertilizer include sulfuric acid potassium, chloride chloride, and silicic acid potassium fertilizer, and the form thereof is not particularly limited. Further, advanced chemical fertilizers and blended fertilizers in which the total amount of the three elements of fertilizers (active ingredients: nitrogen, phosphoric acid, and potassium) is 30% by weight or more, and organic fertilizers may be used. Moreover, the fertilizer which added or made it adhere to a nitrification inhibitor and a pesticide may be sufficient.
Among these, a nitrogenous fertilizer having high water solubility and easily flowing out to the environment is preferable, and urea having a low unit price per fertilizer component is more preferable.

  Although the particle size of the granular fertilizer used as the core material of a covering granular fertilizer is not specifically limited, It is preferable that it is 1.0-10.0 mm. By using a sieve, any particle size range can be selected within the above range.

The shape of the granular fertilizer is not particularly limited, but a spherical shape is preferable in order to develop a time-eluting elution pattern described later. Specifically, the sphericity coefficient obtained by the following formula is preferably 0.90 or more, more preferably 0.92 or more, and still more preferably 0.95 or more. The maximum value of the circularity coefficient is 1. The closer to 1, the closer to the perfect circle, the smaller the circularity coefficient as the shape collapses from the perfect circle.
Circularity factor = (4π × projection area of granular fertilizer) / (contour length of granular fertilizer projection) ²

In the coated granular fertilizer having a timed elution type elution pattern of the present invention, when the granular fertilizer having a circularity coefficient of less than 0.7 increases, the coated granular fertilizer having a timed elution type elution pattern obtained using the granular fertilizer It is preferable that all the circularity coefficients of granular fertilizers are 0.7 or more because the elution suppression at d1 tends to be insufficient and the leakage of fertilizer components tends to occur.
In the present invention, the circularity coefficient is an average value for 100 samples.

  In general, a method for forming a film on the surface of a granular fertilizer includes, for example, a method in which a molten film material is sprayed on the surface of the granular fertilizer, and a coating mixture in which the film material is dissolved and dispersed (or suspended) in a solvent. A method of spraying on the surface of granular fertilizer, a method of adhering granular fertilizer powder to the surface of granular fertilizer and then melting it to form a film, and spraying monomers on the surface of granular fertilizer and reacting on the surface to form a resin (coating ) And a dip method in which granular fertilizer is immersed in the coating mixture.

The manufacturing method of the coated granular fertilizer which has the elution pattern of the time elution type | mold of this invention has the following process in order to implement | achieve high production efficiency, the uniformity of a film, etc.
First step: A coating mixture prepared by dissolving and dispersing one or more selected from the above-mentioned low-density ethylene homopolymer, polysaccharides and derivatives thereof in an organic solvent, in a fluid state or a rolling state A process of spraying and attaching to the fertilizer surface.
Second step: a step of evaporating the organic solvent from the coating mixture adhering to the surface of the granular fertilizer to form a film on the surface of the granular fertilizer.
Details of these steps are disclosed, for example, in the Examples section of Japanese Patent Publication No. 60-3040.

  The productivity of the coated granular fertilizer depends greatly on the production scale, but is greatly influenced by the supply rate of the sprayed coating mixture and the ratio of the coating (material) in the coated granular fertilizer (hereinafter sometimes referred to as the coverage). . That is, it is because a film can be formed in a short time as the amount of the coating mixture supplied per unit time is larger and the required coating mixture is smaller. Increasing the productivity of the coated granular fertilizer can be achieved not only by increasing the supply rate of the coating mixture, but also by increasing the concentration of the coating material in the coating mixture. In order to develop a time-dissolved elution pattern as in the present invention, it is necessary to form a film having no defects. Therefore, it is advantageous to increase the supply rate of the coating mixture without increasing the coating material concentration.

  The viscosity of the coating mixture at that time is preferably in the range of 0.5 to 40 mPa · s, more preferably 0.5 to 30 mPa · s. When the viscosity is in the above range, the dispersion of the filler in the coating is good. The viscosity can be adjusted by the concentration of the coating material in the coating mixture.

  In the present invention, it is preferable to form the coating in a plurality of times, rather than performing the coating in a single operation. Specifically, the first step and the second step are sequentially performed 20 to 160 times. It is preferable to repeat. Further, in the first step, it is preferable that the coating mixture in an amount of 0.1 to 6 μm in thickness by one adhesion is adhered to the surface of the granular fertilizer.

  In the method for producing the coated granular fertilizer of the present invention, the concentration of the coating material in the coating mixture is preferably 3 to 8% by weight from the viewpoint of achieving the formation of a thin coating without an initial burst without reducing the productivity, 4 to 6 weight% is more preferable. The coating mixture supply rate at that time is 10 kg / h or more, preferably 10 to 500 kg / h, more preferably 20 to 350 kg / h in terms of solid content (that is, coating material). If the concentration of the coating material in the coating mixture is in the above range, the time elution type elution pattern can be easily expressed, and mass production with a large facility is possible, so that the cost of the coated granular fertilizer is not increased.

  The large-scale facility here means a manufacturing facility that can realize the manufacturing conditions as described above. As a specific example, a tower-type coating apparatus coated with a spouted bed or a fluidized bed, the tower diameter (inner diameter) is 300 mm or more, the height is 3,000 mm or more, and the coating material concentration in the coating mixture is 3 A production facility having a coating apparatus capable of securing a coating mixture supply rate of 10 kg / h or more as a solid content at ˜8 wt% can be mentioned.

  If the manufacturing method of the coated granular fertilizer of this invention is used, it is possible to express the elution pattern of a time elution type with a thin film also on said coating mixture supply speed conditions. The coverage can be defined as the ratio of the coating (material) to the coated granular fertilizer, preferably 3 to 12% by weight, more preferably 3 to 10% by weight, and even more preferably 3 to 9% by weight. Moreover, although the thickness of a film can be suitably selected with the kind and composition of resin, the magnitude | size of granular fertilizer, and the elution pattern of the intended fertilizer component, it is 10-100 micrometers on average, and 20-70 micrometers is more preferable.

  An example of a coating apparatus that can be used in the solution spraying method will be described with reference to the jet apparatus shown in FIG. In the solution spraying method, it is preferable to vigorously stir the coating mixture in order to uniformly disperse a material insoluble in an organic solvent such as a filler, a polysaccharide or a derivative thereof in the coating mixture.

  This jet apparatus transports the coating mixture to the granular fertilizer 3 in the jet state via the pipe 5, sprays it with the spray nozzle 2, sprays it on the surface of the granular fertilizer 3, and coats the surface simultaneously. Then, a high-temperature gas is caused to flow into the jet tower 1 from below into the guide tube 14, and the organic solvent in the coating mixture adhering to the surface of the granular fertilizer is instantly evaporated and dried by the high-speed hot air flow. The spraying time varies depending on the concentration of the low-density ethylene homopolymer (and ethylene copolymer) in the coating mixture, and the spraying rate, coating rate, etc. of the coating mixture, which should be appropriately selected according to the purpose. It is.

  Coating apparatuses that can be used in the present invention other than the jet apparatus shown in FIG. 1 are disclosed in Japanese Patent Publication Nos. 42-24281 and 42-24282 as fluidized bed type or spouted bed type coating apparatuses. Further, an apparatus for forming a fountain-type fluidized bed of granular fertilizer with a gas body and spraying a coating agent on the granular fertilizer dispersion layer formed in the center can be exemplified. As a rotary type coating apparatus, JP-A-7-31914 can be mentioned. No. 7-195007 and JP-A-7-195007, the drum is rotated by the lifter provided on the inner periphery of the drum by the rotation of the drum and then dropped, and the coating agent is applied to the surface of the falling granule. An apparatus for applying and forming a film can be mentioned.

  Among the above coating apparatuses, a guide tube perpendicular to the axial direction is installed inside the tower, and a throttle disk having a plurality of ejection holes and an aperture ratio of 10 to 70% is installed at the lower part of the tower. In the spouted tower, a coating layer is sprayed on the surface of the granular fertilizer in a fluidized state by forming a spouted layer with the gas spouted from below through the spout hole of the throttle disk, A coating apparatus in which a spray nozzle is inserted into at least one of the ejection holes from below to above is preferable.

It is practically preferable that the number of the ejection holes is normally 4 to 10 and uniformly dispersed in the aperture disk. In addition, at least one spray nozzle is installed from the lower side to the upper side of the ejection hole. In the case of a plurality of spray nozzles, it is desirable to disperse the nozzles as uniformly as possible in the throttle disk. Of course, you may arrange | position for every ejection hole.
Moreover, 10 to 70% is preferable and, as for the aperture ratio of the aperture disk shown by a following formula, 20 to 60% is especially preferable.
Opening ratio (%) = (total area of the upper part of the ejection hole / upper area of the disk before drilling) x 100
When the aperture ratio is in the above range, the granular fertilizer does not accumulate on the upper surface of the squeezing disk, the squeezing action is sufficient, and the desired gas jet velocity can be obtained.

  In the present invention, the gas flow rate in the ejection hole and the gas flow rate in the guide tube are not particularly limited. However, in order to stabilize the quality, when the inert gas is fed into the apparatus from the ejection hole. The gas flow rate in the ejection hole is preferably 5 to 70 m / s, more preferably 20 to 70 m / s, and the gas flow rate in the guide tube is set to 0. 0 which is the terminal velocity of the granular fertilizer circulating and descending along the outside of the guide tube. A method of coating by adjusting to 5 to 3 times is recommended.

  The organic solvent used in the coating mixture in the present invention is not particularly limited, but a low-density ethylene homopolymer contained in the coating material and a solvent capable of dissolving the ethylene copolymer may be selected. . In the present invention, a chlorine-based solvent or a hydrocarbon-based solvent is preferable, and among these, tetrachloroethylene, trichloroethylene, toluene, and ethylcyclohexane are particularly preferable because a dense and uniform film can be obtained.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
1. Measurement method of physical properties The physical properties of the low density ethylene homopolymers of Examples and Comparative Examples were evaluated by the following measurement methods.
(1) Melt mass flow rate (MFR); conformed to JIS K 7210 (190 ° C., 2.16 kg load).
(2) Density: Conforms to JIS K7112. 1 g of the sample was preheated for 2 minutes under the conditions of a press temperature of 180 ° C. and a pressure of 1 kg / cm ² , and then defoaming was repeated several times, and the press temperature of 180 ° C. and a pressure of 150 kg / cm ^{2 was applied} for 4 minutes. After heating and pressurization, the sample was cooled at a rate of 20 to 30 ° C./min, and the sample was pretreated. A pre-treated sample of 2 to 3 mg was cut out, defoamed with an ultrasonic cleaner, and then a density gradient tube having a measurement range of 0.916 to 0.947 g / cm ³ maintained at a temperature density of 23 ± 0.1 ° C. The value when the sedimentation was stopped and the sedimentation completely stopped was taken as the density.
(3) Molecular weight distribution (Mz / Mw, Mw / Mn)
Measured by gel permeation chromatography (GPC) method. Standard polystyrene is manufactured by Tosoh Corporation, and the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) in terms of polystyrene of the polymer are obtained using a calibration curve of elution time and molecular weight, and molecular weight distribution. Mw / Mn and Mz / Mw were determined.
Apparatus: GPC-150C type manufactured by Waters Co. Column: GMH-HT6 manufactured by Tosoh Corporation (7.5 mm ID × 60 cm)
Mobile phase: Orthodichlorobenzene Column temperature: 140 ° C
Flow rate: 1 ml / min
Detector: Differential refractometer (4) Low molecular component Performed in the same manner as the above molecular weight distribution measurement, create a molecular weight distribution curve, determine the area occupied by a molecular weight of 10,000 or less, and divide by the total molecular weight distribution ratio Asked.
(5) Crystallization temperature, melting point Using a differential scanning calorimeter (DSC, DSC-7 manufactured by PerkinElmer Co., Ltd.), a sample 5 ± 0.5 mg was melted by raising the temperature to 200 ° C. at 10 ° C./min. For 5 minutes, the temperature was lowered to −30 ° C. at a temperature lowering rate of 10 ° C./min, held for 10 minutes, and then an endothermic curve when the temperature was raised at a temperature rising rate of 10 ° C./min was obtained to obtain a melting point. Further, the temperature was raised at a rate of temperature increase of 10 ° C./min, held at 200 ° C. for 5 minutes, and then the DSC exothermic peak temperature in the process of cooling at a rate of temperature decrease of 10 ° C./min was used as the crystallization temperature. .
(6) Breaking strength: Conforms to JIS Z 1702. Using a 40 mmφ single-screw extruder with an L / D of 22 and a 180 mmφ inflation die, film forming was performed at an extrusion temperature of 200 ° C. and a tensile speed of 15 to 20 m / min. The film take-up direction was MD, and the vertical direction was TD, and a tube-shaped film molding was obtained. This film was punched with dumbbell No. 1, the distance between the marked lines was 10 cm, the thickness was measured at three locations, and the minimum value was defined as the thickness. The sample was left in a constant temperature room at an ambient temperature of 23 ° C. for 48 hours, and the maximum load until breaking at a tensile speed of 200 mm / min was measured using a strograph (R-3 manufactured by Toyo Seiki Seisakusho). The value divided by was taken as the breaking strength.
(7) Elongation rate: compliant with JIS Z 1702. In the measurement of the breaking strength, the elongation between the marked lines until the breaking occurred was defined as the elongation rate.

The abbreviations and contents of the low density ethylene homopolymers used in Examples and Comparative Examples are as follows. The physical properties are shown in Table 1.
LDPE1: Low density polyethylene Trade name “Suntech-LD M2504” (manufactured by Asahi Kasei Chemicals).
LDPE2: Low-density polyethylene Trade name “Suntec-LD M2713” (manufactured by Asahi Kasei Chemicals).
LDPE3: Low density polyethylene Trade name “Suntec-LD M1920” (manufactured by Asahi Kasei Chemicals).
LDPE4: Low-density polyethylene Trade name “Suntech-LD M2004” (manufactured by Asahi Kasei Chemicals).
LDPE5: Low-density polyethylene Trade name “Suntec-LD M2206” (manufactured by Asahi Kasei Chemicals Corporation).
LDPE6: Low density polyethylene Trade name “Suntec-LD M1703” (manufactured by Asahi Kasei Chemicals).
LDPE7: Low-density polyethylene Product name “Suntech-LD M2270” (manufactured by Asahi Kasei Chemicals), physical properties in Table 1 are catalog values.

Abbreviations and contents of coating materials other than the low-density ethylene homopolymer used in Examples and Comparative Examples are as follows.
EVA: ethylene-vinyl acetate copolymer, trade name “Evaflex 360” (manufactured by Mitsui DuPont Polychemical Co., Ltd.).
Corn starch: particle size 12-18 μm.
Talc: Average particle size 10 μm.
SA: Hexaoxyethylene nonylphenyl ether.
Fe: Iron (III) stearate (manufactured by Kishida Chemical Co., reagent grade, purity 99% or more)

Coated granular material manufacturing apparatus 1
The configuration of the coated granular fertilizer production apparatus 1 used in the examples and comparative examples is the same as that of the flow sheet of FIG. 1, and the spout tower 1 has a tower diameter (inner diameter) of 600 mm, a height of 5,000 mm, and a cone angle of 50 And has a granular fertilizer inlet 15 and a coated granular fertilizer outlet 13. The spray nozzle 2 is a full-contained one-fluid spray nozzle, and 3 is a granular fertilizer (core material). 6 is a solid-gas separator, and 7 is a cooling condenser. 8 is a roots type blower, and 12 is a heater. 9 is a coating mixture adjusting tank (dissolution tank) with a stirrer, and 10 is a diaphragm-type liquid feed pump. Reference numeral 14 denotes a guide tube (diameter 150 mm, length 880 mm, fluororesin-coated product), and 11 denotes a rectifying can. 21 is an aperture disk.
Details of the aperture disk 21 are shown in FIG. In FIG. 2, the diameter is 154 mm, the inner diameter of the ejection hole 23 is 45 mm, the number of ejection holes is 4 (aperture ratio 34%), and the nozzle 2 is provided at the center of each ejection hole 23. The nozzle 2 was arranged on a circle having a diameter of 95 mm with the center of the aperture disk 21 as the center.

Coated granular material production equipment 2
The configuration of the coated granular fertilizer manufacturing apparatus 2 used in the examples and comparative examples is that the tower diameter (inner diameter) of the jet tower 1 is 1,300 mm, the height is 8,500 mm, and the other apparatuses are approximately doubled, The apparatus such as the solid-gas separator, the cooling condenser, and the roots type blower is the same as the case of the manufacturing apparatus 2 except that it is scaled up so as not to interfere with the coating by spraying.

Manufacturing method of coated granular fertilizer Using the manufacturing apparatus 1 or 2, the coated granular fertilizer was manufactured by the following method. The heated airflow flows from the lower part of the jet tower 1 toward the upper part, passes through the solid-gas separator 6, cools the airflow with the condenser 7, and condenses and recovers the organic solvent. The airflow that has passed through the condenser 7 is circulated so as to be heated from the blower 8 through the heater 12 and then led to the jet tower 1 as a high-temperature airflow.
First, granular fertilizer (core material) is introduced from the inlet 15 while air maintained at an airflow temperature of 150 ° C. at the ejection hole is sent to the jet tower 1 using the blower 8, and the granular fertilizer is made into a jet state. Under the present circumstances, the flow volume and temperature of the heated airflow were adjusted so that granular fertilizer temperature might be set to 70 +/- 2 degreeC. The flow rate of the air flow was adjusted while measuring with a flow meter installed between the blower 8 and the rectifying can 11, and the temperature of the heated air flow was adjusted while measuring the granular fertilizer temperature and the jet tower outlet temperature. Circulating air volume 1,000 m ³ / h in the manufacturing apparatus 1, an in the manufacturing apparatus 2 3,000 m ³ / h, the granular fertilizer dosages are 140kg in the manufacturing apparatus 1, a 1,000kg in the manufacturing apparatus 2.
On the other hand, each coating material component having the composition shown in Table 2 and tetrachlorethylene were added to the dissolution tank 9 and mixed and stirred at a liquid temperature of 100 ± 2 ° C. for 1 hour to prepare a uniform coating mixture.
Next, when the granular fertilizer in the tower reaches 70 ° C., the coating mixture supply pump 10 is operated to send the coating mixture in the dissolution tank 9 to the nozzle 2 to start spraying the coating mixture. Note that (coating weight / coated granular fertilizer weight) × 100) is 8.5% of the final coated granular fertilizer, and then the granular fertilizer temperature is maintained at 70 ° C. ± 2 ° C. Drying is performed by blowing only the air flow for 10 minutes while adjusting the temperature of the air flow. When the drying is completed, the blower 8 is stopped, and the coated granular fertilizer is discharged from the outlet 13 and contains an organic solvent. The solvent removal treatment was performed with no airflow, and then the coated granular fertilizer was obtained through the surface treatment for coating the white carbon powder.

Urea (particle size: 3.0 mm to 3.6 mm, average particle size: 3.4 mm) was used as the granular fertilizer.
The circularity coefficient of the granular fertilizer was measured using IMAGE ANAJYZER LUZEX-FS manufactured by NIRECO. The measurement was performed using 100 granular fertilizers taken at random. The measurement result was 0.994.

Examples 1-10, Comparative Examples 1-13
The coated granular fertilizer was manufactured with the coating material composition and manufacturing conditions shown in Table 2.

  About the coated granular fertilizer obtained by the Example and the comparative example, the elution behavior in water and the measurement of the film strength were implemented.

Measurement of dissolution of coated granular fertilizer 10 g of the coated granular fertilizer of Examples and Comparative Examples and 200 ml of distilled water adjusted to 25 ° C. in advance are put into a 250 ml plastic container with a lid, and placed in an incubator set at 25 ° C. I put it. Seven days later, all the water was extracted from the container, and the amount of urea contained in the extracted water (urea elution amount) was determined by quantitative analysis (dimethylaminobenzaldehyde method “detailed fertilizer analysis method second revised edition” Yokendo). The sample after draining water was put into the vessel again, and 200 ml of distilled water was put into the vessel again and left in the same manner. This operation was repeated until the integrated value of the urea elution amount reached 80% by weight of the urea content measured in advance using the same lot of coated granular fertilizer.
Thereafter, the coated granular fertilizer was ground in a mortar, and the content of the fertilizer was dissolved in 200 ml of water, and then the amount of urea remaining was quantitatively analyzed in the same manner as described above. The total amount of urea dissolved and the amount of urea remaining is added to the total amount of urea, and the relationship between the total amount of urea eluted in water and the number of days is graphed, and an elution rate curve is created to determine the number of days to reach 80% by weight elution rate. It was. The results are shown in Table 3. In addition, the number of days from the start of elution measurement until 5% by weight elution was defined as “d1”, and the number of days until 80% by weight elution was performed thereafter as “d2”. The results are shown in Table 3.

As can be seen from these results, in Examples 1 to 10, d1 / d2 was 0 under conditions where the coverage was 10 wt% or less and the coating mixture supply rate was 10 kg / h in terms of solid content and high productivity. It was over 70. This clearly indicates that the fertilizer component after suppressing elution can be supplied only in the required amount at the required time, and that a product containing high performance and more fertilizer components as in the embodiment can be supplied at low cost. Can do.
On the other hand, in Comparative Examples 1 to 12, d1 / d2 is less than 0.70. In particular, when d1 is 40 days or more, or a product in which the sum of d1 and d2 is 100 days or more is manufactured under the conditions of the present invention, d2 is It becomes longer and continues to elute beyond the cultivation period, which is not practical. In Comparative Examples 9 and 10, d1 / d2 is 0.2 or less and does not become a time elution type, and Comparative Example 11 has a too low coverage and the sum of d1 and d2 is 3 days. No, comparative example 12 was coated by carefully spraying the coating material concentration in the coating mixture down to 3% by weight, but d1 / d2 was less than 0.70 as described above.
When a low-density ethylene homopolymer as in Comparative Example 13 was used, the coating was thickened so that the coating rate was 12% by weight and the coating mixture supply rate was 5 kg / h in terms of solid content. If sprayed and coated, an equivalent product of the present invention can be produced, but it is too costly and impractical.

Measurement of coating strength of coated granular fertilizer Using a shoulder-type power spreader (manufactured by Kyoritsu Co., Ltd., DMD-5501-26), spray 10 kg of coated granular fertilizer under the conditions of engine throttle 8 and shutter opening 10 and 10 m or more from the tube tip The discharged coated granular fertilizer was collected. The recovered coated granular fertilizer is shrunk to 50 g with a reducer, and the coated granular fertilizer 10 g before the test, the recovered coated granular fertilizer 10 g, and 200 ml of distilled water adjusted to 25 ° C. in advance and 250 ml of poly with a lid The container was charged and allowed to stand in an incubator set at 25 ° C. Seven days later, all the water is extracted from the container, and the amount of urea contained in the extracted water (urea elution amount) is obtained by quantitative analysis (dimethylaminobenzaldehyde method “Detailed Fertilizer Analysis Method Second Revised Edition” Yokendo). The rate was calculated. A value obtained by subtracting the dissolution rate of the coated granular fertilizer before the test from the dissolution rate of the coated granular fertilizer after the spreader test was determined as a measure of the coating strength. The results are shown in Table 4.

As a result, Examples 1 to 10 were within the range of 1% by weight and showed the strength of the coating strength, but Comparative Examples 1 to 12 expanded to 5 to 15% by weight. This is because the productivity has been higher than before, and in some cases, the spray nozzle became obstructed or blocked during production, and the coating strength was generally weak compared to each example. I think that the. This is presumed to be caused by the fact that the breaking strength and breaking elongation of the low density ethylene homopolymer of the coating material used in the comparative examples are inferior to those of the respective examples.
Therefore, each comparative example is unsuitable for the fertilization method using a machine, or needs attention, and uses are limited.
Although Comparative Example 13 had no problem at the time of production, the film strength was inferior as in each Comparative Example. This is predicted to be affected by a large MFR value.

  The present invention can be effectively used for the production of coated granular fertilizer.

Example flow sheet for equipment used for coating An example of an aperture disk (orifice)

Explanation of symbols

1. Jet tower 2. 2. Spray nozzle Granular fertilizer (core material)
4). Circulating air flow piping5. 5. Mixing supply pipe for coating 6. Solid-gas separator Condenser 8. Blower 9 Dissolution tank 10. Pump 11. Rectification can 12. Heater 13. Outlet 14. Guide tube 15. Granular fertilizer inlet 21. Diaphragm disc 22. Main disc 23. Outlet

Claims (9)

A coated granular fertilizer having a surface coated with a coating, the coating comprising at least one selected from low density ethylene homopolymers having the following physical properties (a) to (c), polysaccharides and derivatives thereof: A coated granular fertilizer which is a coating to be contained and has a timed dissolution type elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is less than 3.5%.
(C) Melt mass flow rate is 0.01 to 2 g / 10 min. A coated granular fertilizer having a surface coated with a coating, the coating comprising at least one selected from low density ethylene homopolymers having the following physical properties (a) to (c), polysaccharides and derivatives thereof: A coated granular fertilizer which is a coating to be contained and has a coating ratio of 3 to 12% by weight with respect to the coated granular fertilizer and has a timed dissolution type elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is 3.0% or less.
(C) Melt mass flow rate is 0.01 to 2 g / 10 min.   The coated granular fertilizer according to claim 1 or 2, wherein the coating further contains an ethylene copolymer.   The coated granular fertilizer according to any one of claims 1 to 3, wherein the coating further contains a filler.   The time elution type elution pattern is d1 (day) until the elution rate of the fertilizer component reaches 5% by weight when the coated granular fertilizer is immersed in water at 25 ° C. D1 / d2 is 0.7 or more, and d1 + d2 is greater than 5% by weight and reaching 80% by weight with respect to the total amount of fertilizer components contained in the granular fertilizer. The coated granular fertilizer according to any one of claims 1 to 4, which is in a range of 30 to 360 (days). A coating mixture in which one or more selected from low density ethylene homopolymers having the following physical properties (a) to (c), and polysaccharides and derivatives thereof are dissolved and dispersed in an organic solvent, The ratio of the coating obtained by spraying and adhering to the surface of the granular fertilizer in the rolling state and evaporating the organic solvent from the adhering coating mixture is 3 to 12% by weight with respect to the coated granular fertilizer, Coated granular fertilizer having an elution pattern.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is 3.0% or less.
(C) The melt mass flow rate is 0.1 to 2 g / 10 min.   The coated granular fertilizer according to claim 6, wherein the coating mixture further contains an ethylene copolymer. The manufacturing method of the covering granular fertilizer which has the elution pattern of a time elution type which has the following process.
1st process: The coating mixture which melt | dissolved and disperse | distributed in the organic solvent 1 or more types chosen from the low density ethylene homopolymer which has the physical property of following (a)-(c), polysaccharide, and its derivative (s). The process of spraying and adhering to the surface of the granular fertilizer in a fluid state or a rolling state.
Second step: a step of evaporating the organic solvent from the coating mixture adhering to the surface of the granular fertilizer to form a film on the surface of the granular fertilizer.
(A) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3 to 6, and the weight average molecular weight (Mw) is 100,000 to 300,000.
(B) The content of components having a molecular weight of 10,000 or less is less than 3.5%.
(C) The melt mass flow rate is 0.1 to 2 g / 10 min.   In the jet tower in which the spray of the coating mixture is installed with a vertical guide pipe inside the tower, and a throttle disk having a plurality of ejection holes at the bottom of the tower and an opening ratio of 10 to 70%, A spray nozzle that is inserted into at least one of the ejection holes from below to above the surface of the granular fertilizer that is in a fluidized state by forming a spout layer with gas ejected from below through the ejection holes of the throttle disk. The manufacturing method of the covering granular fertilizer of Claim 8 performed using.

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