Fertilizer coating material, coated granular fertilizer, and method for producing the same.

Abstract

To provide a coating material for a fertilizer which has low moisture vapor permeability of a film, a slow-acting coated granular fertilizer which does not give environmental loads due to a coating shell residue after elusion by coating a granular fertilizer with the coating material for the fertilizer, and a coated granular fertilizer in which floating property is suppressed when used in a paddy field.SOLUTION: A coating material for a fertilizer contains a dehydration condensate of a resin having an OH group and an alkoxysilane condensate.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to fertilizers, and more particularly to coating materials for fertilizers, and to coated granular fertilizers and methods for producing the same. [Background technology]

[0002] Coated granular fertilizers, which are encapsulated by covering their surface with a film material such as resin, have the function of continuously supplying fertilizer components. They offer excellent control over the leaching of fertilizer components and have been recognized for their effects in reducing labor in agricultural work and lowering environmental impact, and have seen remarkable development in recent years. In other words, it is a well-known fact that coated granular fertilizers have remarkable effects, such as preventing excessive fertilization, improving the efficiency of fertilizer utilization by crops, reducing the runoff of fertilizer components into rivers, and reducing the number of fertilization applications, thereby achieving significant results in labor-saving and efficiency improvements in fertilization, as well as environmental conservation.

[0003] However, in recent years, because the resin used as the coating material is non-degradable, there are concerns about the environmental burden caused by the accumulation of coating husks in fields where coated granular fertilizers are applied, and furthermore, by the outflow of these husks into areas outside the field, resulting in their accumulation in ecosystems. Therefore, the early development of coated granular fertilizers that combine excellent leaching control and coating degradability is desired.

[0004] In response to this, various studies have been conducted to improve the degradability of the coating. For example, Patent Document 1 reports a technology in which fertilizer is coated with a coating containing an ethylene copolymer and / or water-repellent starch and metal oxide, resulting in a coating with excellent disintegration and degradability after leaching in soil.

[0005] In addition, in Patent Document 2, a coated granular fertilizer with excellent degradability in soil has been proposed by using a film obtained by combining specific amounts of powders mainly composed of low molecular weight polyethylene and / or petroleum wax having a specific weight average molecular weight, a specific ethylene-α-olefin elastomer, a specific α-olefin polymer, and a sugar polymer or its derivative, respectively. However, in these methods, since a non-biodegradable resin is used as the main component of the film, a part of the film shell remains in the environment after use, which is insufficient for reducing the environmental load. In addition, when used in paddy fields, there is also a problem that the hydrophobic resin component easily floats on water and flows out from the paddy field without staying in the soil.

[0006] On the other hand, technologies using biodegradable resins for the film of coated granular fertilizers have also been proposed. For example, in Patent Document 3, a technology for insolubilizing water-soluble polyvinyl alcohol by heat cross-linking to control the elution rate into the soil is disclosed. However, the method of insolubilizing polyvinyl alcohol by heating described in Patent Document 3 is actually difficult to use because urea used as a granular fertilizer thermally decomposes at about 130 - 140°C. In addition, although various biodegradable resin compositions have been proposed for use in the film of coated granular fertilizers, they are hydrophilic and thus inferior in water resistance, and are insufficient in terms of film stability, elution control, economy, etc.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] As described above, in Patent Documents 1 to 3, it has been difficult to obtain a coated granular fertilizer with sufficiently reduced environmental impact. In the present invention, an object is to provide a coating material for fertilizers having a low moisture permeability. Further, by coating granular fertilizers with this coating material for fertilizers, a sustained-release coated granular fertilizer that does not cause an environmental impact due to the film shell residue after elution is provided. Also, when used in paddy fields or the like, an object is to provide a coated granular fertilizer with suppressed buoyancy.

Means for Solving the Problems

[0009] As a result of intensive studies, the inventors of the present invention prepared a dehydration condensate of a resin having an OH group and a hydrolyzate of an alkoxysilane condensate, and by coating fertilizers with this material, the silanol OH group derived from the alkoxysilane condensate and the resin having an OH group condensed. As a result, it has better water resistance than a simple mixture and can be used as a sustained-release fertilizer. Also, after finishing its role as a fertilizer, it decomposes and only silica, that is, sand, remains in the soil, and an environmentally friendly fertilizer can be obtained, and thus the present invention was achieved.

[0010] That is, the gist of the present invention is as follows. [1] A coating material for fertilizers containing a dehydration condensate of a resin having an OH group and an alkoxysilane condensate. [2] The coating material for fertilizers according to [1], wherein the resin having an OH group is a biodegradable resin. [3] The resin having an OH group is a resin having an alcoholic hydroxyl group or a carboxyl group, The coating material for fertilizers according to [1] or [2]. [4] The coating material for fertilizers according to any one of [1] to [3], having a Si—O—C bond. [5] The coating material for fertilizers according to any one of [1] to [4], wherein the Si content in the coating material for fertilizers is 20% by weight or more and less than 95% by weight in terms of SiO2. [6] The resin having the OH group is selected from the group consisting of polyvinyl alcohol resin, starch, cellulose, lignin, chitin, chitosan, PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), PBAT (polybutylene aditate terephthalate), PCL (polycaprolactone), starch polyester, cellulose acetate, PHB (polyhydroxybutyrate), PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PLA (polylactic acid), polyglycolic acid (PGA), polydioxanone (PDO), and copolymers thereof, as described in any of [1] to [5]. [7] The fertilizer coating material according to any one of [1] to [6], wherein the resin having the OH group is a polyvinyl alcohol resin. [8] The coating material for fertilizer according to any one of [1] to [7], wherein the coating material has a three-dimensional siloxane crosslinking structure derived from an alkoxysilane condensate. [9] The fertilizer coating material according to any one of [1] to [8], wherein the alkoxysilane condensate comprises two or more types of alkoxysilanes.

[10] The fertilizer coating material according to any one of [1] to [9], comprising at least a compound represented by formula (1) as the alkoxysilane condensate. [ka] In formula (1), each of the R1s independently represents an alkyl group with 1 to 10 carbon atoms or an aromatic group with 6 to 15 carbon atoms, and R2 represents a hydrogen atom, a halogen atom, or a monovalent organic group.

[11] The fertilizer coating material according to

[10] , wherein the compound represented by formula (1) is methyltrimethoxysilane. A coated granular fertilizer coated with a film made of the coating material described in any of

[12] [1] to

[11] , wherein the content of the film formed of the coating material is 1% by mass or more and 20% by mass or less in 100% by mass of the coated granular fertilizer.

[13] The coated granular fertilizer according to

[12] , wherein a precoat layer is further provided between the fertilizer and the membrane.

[14] The coated granular fertilizer according to

[12] or

[13] , wherein the precoat layer comprises a biodegradable resin selected from the group consisting of polyvinyl alcohol resin, starch, cellulose, lignin, chitin, chitosan, PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), PBAT (polybutylene aditate terephthalate), PCL (polycaprolactone), starch polyester, cellulose acetate, PHB (polyhydroxybutyrate), PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PLA (polylactic acid), PGA (polyglycolic acid), PDO (polydioxanone) and copolymers thereof.

[15] A method for producing coated granular fertilizer, comprising the steps of mixing a solution containing an alkoxysilane condensate with a solution containing a resin having an OH group, spraying the resulting coating solution onto the fertilizer, and drying it.

[16] A method for producing coated granular fertilizer according to

[15] , comprising heating at 140°C or less during or after the drying process. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a coating material for fertilizers with low moisture permeability of the membrane. Furthermore, by coating granular fertilizers with this coating material, it is possible to provide a slow-release coated granular fertilizer that does not cause environmental burden due to coating residue after leaching. In addition, when used in paddy fields, it is possible to provide a coated granular fertilizer with suppressed buoyancy. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a device for coating fertilizer with a fertilizer coating material. [Figure 2] This is a schematic diagram of a device for coating fertilizer with a fertilizer coating material. [Figure 3]This is a scanning electron microscope image of the coated granular fertilizer according to Comparative Example 8 (photograph used as a substitute for the drawing). [Figure 4] This is a scanning electron microscope image of the coated granular fertilizer according to Example 20 (photograph used as a substitute for drawing). [Modes for carrying out the invention]

[0013] The following describes embodiments of the present invention, but the present invention is not limited to the following. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, and "A~B" means that it is greater than or equal to A and less than or equal to B.

[0014] One embodiment of the present invention is a coating material for fertilizer containing a dehydration condensate (dehydration condensation compound) of a resin having an OH group and an alkoxysilane condensate, and another embodiment is a coated granular fertilizer in which the fertilizer is coated with the fertilizer coating material. In this specification, the dehydration condensate of a resin having an OH group and an alkoxysilane condensate is a reaction product (specifically, a compound obtained by a dehydration condensation reaction) of a resin having an OH group and an alkoxysilane condensate, and is a compound having a structure derived from the resin having an OH group and a structure derived from the alkoxysilane condensate.

[0015] (Resin containing OH groups) The resin having OH groups according to this embodiment is a resin in which silicon and the resin are chemically bonded by reacting with OH groups present in the hydrolysis condensate of the alkoxysilane condensate to form Si-OC bonds. Therefore, carboxyl groups or alcoholic hydroxyl groups are preferred as the OH groups, and alcoholic hydroxyl groups are particularly preferred.

[0016] As for specific resins, those that are biodegradable are preferred. Regarding the specific definition of biodegradability, the Biodegradable Plastics Research Group in 1989 defined it as "a plastic that is broken down in nature by microorganisms into low-molecular-weight compounds that do not adversely affect the environment." This expression is ambiguous, and at the 1993 Annapolis Summit, it was stated that "biodegradable materials are those that are completely consumed by microorganisms, producing only natural by-products (carbon dioxide, methane, water, biomass, etc.)." In this specification, this definition of biodegradability will be used. Specifically preferred resins include polyvinyl alcohol resin, starch, cellulose, lignin, chitin, chitosan, PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), and PBAT (polybutylene aditate tereol). Talate, PCL (polycaprolactone), starch polyester, cellulose acetate, P Examples include those selected from the group consisting of HB (polyhydroxybutyrate), PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PLA (polylactic acid), PGA (polyglycolic acid), PDO (polydioxanone), and copolymers thereof. Of these, PBS (polybutylene succinate) and PBSA (polybutylene succinate adipate) are preferred if environmental considerations are taken into account, as a manufacturing method from biomass raw materials has been established. When heating and melting to coat as a liquid, PCL (polybutylene succinate) is preferred due to its low melting point. Caprolactone is preferred, and from the viewpoint of being able to use natural materials, starch, se Lurose, lignin, chitin, and chitosan are preferred, and PLA (polylactic acid) is preferred because it has excellent physical properties in that it is resistant to breakage when force is applied. However, polyvinyl alcohol resin is most preferred because it has many hydroxyl groups, the level of compounding (Si-OC bonding) can be easily adjusted, and there is a great degree of freedom in its properties. Modified versions of these resins may also be used. In addition, two or more of the above biodegradable resins may be used in mixture form. It is also possible to use the above polymers after crosslinking.

[0017] The coated granular fertilizer according to this embodiment may have multiple coating layers formed by pre-coating the inside of a coating made of a coating material. Furthermore, the coating in the coated granular fertilizer according to this embodiment may include other coating layers to the extent that they do not impede the effects of the present invention. For example, a coating containing fertilizer components such as trace elements, fertilizer efficacy enhancers, pesticide components, etc., on the outermost layer, and a moisture-resistant coating. It is possible to form layers such as a coating that imparts mechanical properties, a coating that suppresses floating under flooded conditions such as paddy fields, or a coating that controls the decomposition of the entire coating.

[0018] Polyvinyl alcohol resin (sometimes referred to as PVA resin below) is a resin having vinyl alcohol structural units, and its specific structure is not particularly limited. Typically, it is obtained by saponifying polycarboxylate vinyl esters obtained by polymerizing vinyl carboxylate monomers such as vinyl acetate, but it is not limited to this. Examples of the aforementioned PVA-based resins include unmodified PVA and modified PVA-based resins. Modified PVA-based resins may be copolymerized modified PVA-based resins synthesized by copolymerizing monomers other than vinyl ester monomers that provide PVA structural units, or they may be modified PVA-based resins obtained by synthesizing unmodified PVA and then modifying the main chain or side chains with appropriate compounds. Examples include Gosenol(R), Gosenex(R), Nichigo G Polymer (manufactured by Mitsubishi Chemical Corporation), Kuraray Poval (manufactured by Kuraray Co., Ltd.), or Erbanol.

[0019] Copolymer monomers (unsaturated monomers) that can be used in copolymer-modified PVA resins include, for example, olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, or α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, or 5-hexen-1-ol, or derivatives thereof such as their acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, or undecylenic acid, or their salts; monoesters or dialkyl esters; diacetone acrylamide, acrylamide, or methacrylic acid Examples include amides such as mid; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, or methallyl sulfonic acid, or their salts; quaternary ammonium salts such as diallyldimethylammonium chloride or diallyldiethylammonium bromide; substituted vinyl acetates such as isopropenyl acetate or 1-methoxyvinyl acetate; or allyl ethers having a poly(oxyalkylene) group, such as polyethylene glycol allyl ether, methoxypolyethylene glycol allyl ether, polypropylene glycol allyl ether, or polyethylene glycol-polypropylene glycol allyl ether.

[0020] Furthermore, copolymer-modified PVA resins include PVA resins having primary hydroxyl groups in their side chains. Examples of such PVA resins include 1,2-diol side-chain modified PVA resins obtained by copolymerizing 3,4-diacetoxy-1-butene, vinylethylene carbonate, or glycerol monoallyl ether; or PVA resins having hydroxymethyl groups in their side chains obtained by copolymerizing and saponifying hydroxymethyl vinylidene diacetates such as 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, or 1,3-dibutyronyloxy-2-methylenepropane. Methods for post-modification of post-modified PVA-based resins include esterification, acetalization, urethaneization, etherization, grafting, phosphate esterification, or oxyalkyleneization of unmodified PVA or the above-mentioned modified PVA-based resin.

[0021] In this embodiment, either unmodified PVA or modified PVA-based resin can be used, but in the case of unmodified PVA, a fully saponified product is preferred, and in the case of modified PVA-based resin, an anionic modified group containing a functional group with excellent hydrophilicity in its side chain, such as a carboxylic acid group or a sulfonic acid group, a cationic modified group containing a quaternary ammonium base, or a nonionic modified group containing a hydroxyalkyl group or an oxyethylene group is preferred.

[0022] When prioritizing the amount of OH groups that react with the silanol group, unmodified PVA is particularly preferred due to its high reaction rate with silicates, as described later. Partially saponified products are preferred for this purpose, and fully saponified products are preferred when the bonding properties between silicate and PVA, i.e., Si-OC bonding, are important.

[0023] The degree of saponification of PVA-based resins is typically 70 mol% or higher, preferably 80 mol% or higher, and more preferably 98 mol% or higher. The upper limit is usually 100 mol% or lower, preferably 99.8 mol% or lower. The degree of saponification is measured using the titration method of JIS K6726. The average degree of polymerization of PVA resins is not particularly limited, but is usually between 200 and 3000, preferably between 250 and 2800, and especially preferably between 300 and 2600. This range prevents the elution of coated fertilizer from becoming too small and also helps prevent the coating film from cracking. This average degree of polymerization is determined by the aqueous solution viscosity measurement method (JIS standard). This value was measured using K 6726.

[0024] PVA resins may be made using only one type of resin, or they may be blended from two or more types of resins. In this case, the structural units may differ, the degrees of saponification may differ, and the average degrees of polymerization may differ. When blended, the average values ​​of the degrees of saponification, average degrees of polymerization, etc., of all PVA resins should be within the above range.

[0025] Furthermore, the PVA resin may be partially modified. If it is modified, the modification rate of the PVA resin is preferably in the range where 90% by weight or more dissolves within 60 minutes after mixing 10 g of the resin particles with 100 g of water at 20°C, dispersing by stirring, and then raising the temperature to 90°C at a rate of 1°C / min while stirring. The type of modification is not particularly limited as long as it has an OH group, but when introducing a group that has strong acidity or basicity in water, it is preferable to use a modification amount that does not show catalytic effects during the compounding process with silicate.

[0026] The weight ratio of components (structures) derived from resin having OH groups to the total weight of the fertilizer coating material (or dehydrated condensate) is usually 1% by weight or more, preferably 4% by weight or more, preferably 6% by weight or more, more preferably 35% by weight or more, even more preferably 45% by weight or more, and usually 85% by weight or less, preferably 82% by weight or less, preferably 75% by weight or less, more preferably 70% by weight or less, and even more preferably 65% ​​by weight or less.

[0027] (Hydrolysis condensate of alkoxysilane condensate) The hydrolysis condensate of the alkoxysilane condensate used in this embodiment combines with a resin having an OH group to form a Si-OC bond. Alkoxysilane condensates refer to compounds obtained by hydrolysis and condensation of alkoxysilanes. Alkoxysilanes are not particularly limited as long as they are silanes having an alkoxy group. Examples of alkoxy groups include aliphatic alkoxy groups having 1 to 10 carbon atoms, such as methoxy, ethoxy, propoxy, or butoxy groups, or aromatic alkoxy groups having 6 to 15 carbon atoms, such as phenoxy or aryloxy groups. Aliphatic alkoxy groups having 1 to 4 carbon atoms are preferable because they allow for easier control of the hydrolysis reaction. Examples of alkoxysilanes include monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, or tetraalkoxysilanes. Tetraalkoxysilanes are preferred because they contain many siloxane bonds that are impermeable to water vapor when hydrolyzed and condensed. Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, or tetrakis(2-ethylhexyloxysilane), and the alkoxysilane condensate may contain one type of alkoxysilane or two or more types. It is preferable to do so. When using these alkoxysilane monomers as raw materials, it is preferable to use alkoxysilane condensates that have undergone a hydrolysis-condensation reaction beforehand, as controlling the condensation reaction is difficult during the hydrolysis reaction. Alkoxysilane condensates are substances having a siloxane bond chain and an alkoxy group, for example, having the structural formula shown in formula (2) below.

[0028] [ka]

[0029] Here, in formula (2), each of the multiple Rs independently represents an alkyl group with 1 to 10 carbon chains or an aromatic compound with 6 to 15 carbon atoms. Among these, alkyl groups with 1 to 4 carbon atoms are preferred because the reaction can be easily controlled by the catalyst species, and methyl groups are particularly preferred because they have a fast hydrolysis reaction rate and are easier to control. n is a repeating structural unit and is not particularly limited, but is preferably 2 or more and 10 or less, may be 2 or more and 8 or less, or 2 or more and 5 or less. Being within this range improves compatibility when a hydrolysis polycondensate is formed and mixed with a solution of a resin having an OH group. From the viewpoint of controlling the reactivity with resins having OH groups, it is preferable that the alkoxysilane condensate used as a raw material itself contains almost no OH groups. Regarding OH in the alkoxysilane condensate, 1 Analysis can be performed using 1H NMR, etc. For example, in the case of condensates of methoxysilanes with 3 to 5 repeating structural units, deuterated dimethyl sulfoxide solvent (hereinafter referred to as DMSO-d6) can be used. 1 ¹H NMR analysis reveals a peak for the methoxy group around δ=3.4 ppm, and if an OH group is present, a broad peak appears around δ=8.0-6.0 ppm. The smaller the integral ratio of the OH group peak to the alkoxy group peak, the smaller the amount of OH group. If the integral value of the OH group is (0.1) or less relative to the integral value of the alkoxy group (100), the alkoxysilane condensate will not self-condense, will exist stably, and its reactivity will not change. Examples of such alkoxysilane condensates include MKC® silicate manufactured by Mitsubishi Chemical Corporation. In this embodiment, the hydrolysis product of the alkoxysilane condensate is combined and mixed with a solution containing a resin having OH groups, coated, and dried to achieve its performance. Another method involves adding the alkoxysilane before hydrolysis to a solution containing a resin having OH groups and hydrolyzing and condensing it in the presence of the resin having OH groups. However, the resin having OH groups may inhibit the hydrolysis and condensation reactions of the alkoxysilane, potentially preventing the sufficient generation of silanol groups necessary to form Si-OC bonds with the resin having OH groups. Furthermore, if the solution containing the resin having OH groups contains a large amount of water, it becomes difficult to control the hydrolysis and condensation reactions of the alkoxysilane, and there is a risk of precipitation of the resin having OH groups due to the consumption of water in the hydrolysis reaction. In this invention, a hydrolyzed polycondensate obtained by hydrolyzing and condensing an alkoxysilane condensate, which is highly safe and allows for easy control of the hydrolysis and condensation reactions, in the presence of a catalyst, and a solution containing a resin having OH groups are prepared and mixed to create a more reactive composite liquid.

[0030] To impart flexibility and strength to the film, a third component can be added in addition to the hydrolyzed product of the alkoxysilane condensate that constitutes the film and the resin having an OH group. The third component undergoes hydrolysis and condensation reactions with the hydrated product of the alkoxysilane condensate during the hydrolysis of the alkoxysilane condensate. It is preferable to use an alkoxysilane that can be bonded in response. Examples of alkoxysilanes include tetraalkoxysilane, trialkoxysilane, dialkoxysilane, or monoalkoxysilane, but trialkoxysilane is most preferred from the viewpoint of having fewer defects in the siloxane bond of the hydrolysis condensate and providing flexibility, and it is particularly preferable that it has a structure represented by the following formula (1). In other words, it is preferable that the coating material contains at least one compound having a structure represented by formula (1) as the alkoxysilane condensate.

[0031] [ka]

[0032] Here, in formula (1), each of the multiple R1s independently represents an alkyl group with 1 to 10 carbon atoms or an aromatic group with 6 to 15 carbon atoms. R2 represents a hydrogen atom, a halogen atom, or a monovalent organic group. The monovalent organic group is not particularly limited and can be, for example, an alkyl group with 1 to 10 carbon atoms, an aromatic group with 6 to 15 carbon atoms, an isocyanate group, a halogenated alkyl group, a urea group, an amino group, a vinyl group, a glycidyl group, an epoxy group, an allyl group, an aryl group, a methacrylate group, a cyclohexyl group, an azide group, a mercapto group, a carbamic acid, an ammonium salt, a succinic anhydride, a phosphine derivative, a naphthalene derivative, a pyridine derivative, etc., and can be selected according to the desired performance. The carbon chain may have a linear or branched structure. These functional groups may have a cross-linked structure such as rubornene. Among these, the compound represented by formula (1) is preferably a functional group that has a low environmental impact, and is preferably methyltrimethoxysilane due to its flexibility and availability as a film.

[0033] From the viewpoint that the object of the present invention is to suppress the premature leaching of fertilizer by coating with a fertilizer coating material, it is preferable that the low crosslinking component, monoalkoxysilane or dialkoxysilane, be used as an additive for imparting functionality, and in the minimum amount that does not promote swelling or dissolution of the resin component having OH groups in the composite particles.

[0034] The alkoxysilane condensate preferably undergoes hydrolysis in the solvent to form a three-dimensional siloxane crosslinked structure as a hydrolyzed polycondensate, and the alkoxysilane condensate may also be a low condensate. Here, a low condensate refers to an oligomer of about 2 to 10 alkoxysilane units, which may be an oligomer of about 2 to 8 units, or an oligomer of about 2 to 5 units. As the solvent, typically methanol, ethanol, or lower alcohols having 1 to 4 carbon atoms such as propanol, or misculations of these with water are used.

[0035] The component (structure) containing the hydrolyzed polycondensate of alkoxysilane contained in the fertilizer coating material of this embodiment has a Si content of 20% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more, and usually less than 95% by weight, preferably 93% by weight or less, in terms of SiO2 equivalent, relative to the total weight of the fertilizer coating material. Here, the SiO2 equivalent is calculated from the molecular weight and amount used of the alkoxysilane condensate, the molecular weight and amount produced of the hydrolyzate of the alkoxysilane condensate, and the molecular weight of SiO2 when all the hydrolyzates of the alkoxysilane condensate have condensed to form SiO2, as shown in formula (3) below. The weight in terms of O2 can be calculated. These Si content values ​​can also be used as the Si content relative to the total weight of the fertilizer coating material.

[0036]

number

[0037] The SiO2 content relative to the total weight of the fertilizer coating material can be quantified using an inductively coupled plasma (ICP) emission spectrometer or similar device after processing the extraction membrane used in the FT-IR analysis described later.

[0038] The resulting fertilizer coating material has a Si-OC structure (bond). This Si-OC structure can be confirmed by Fourier transform infrared spectroscopy. The method for confirming the presence of a Si-OC structure using Fourier transform infrared spectroscopy (FT-IR) is as follows: When FT-IR measurements are performed, the region is 1500-1200 cm⁻¹. -1 The vibrational modes of each atomic group appear in this region. According to Hitachi Review, Vol. 43, No. 5, pp. 90-94 (May 1961), the region is 1430 cm². -1 ±30cm -1 and 1326cm -1 ±25cm -1The coupling between the bending vibrations of the OH groups in PVA and other vibrations is evident. In silicate, there is no peak in the region between 2000 cm⁻¹ and 1300 cm⁻¹. From this, it can be seen that in composite films, when a Si-OC structure is formed, the number of OH groups decreases and the coupling with other vibrations decreases, so this peak decreases or disappears.

[0039] Measurement methods include transmission and reflection, but reflection is preferred, and among reflection methods, the ATR method, which is not affected by the shape of the sample being measured, is particularly preferred. When measuring with the ATR method, a diamond prism is most preferred in terms of the wavenumber range that can be measured. When analyzing with FT-IR, data can be obtained by integrating the results in a single measurement. Integration improves the accuracy of the resulting spectrum, allowing for the acquisition of reliable values. The number of integration steps is 2 to the power of n. There is no particular limit to the number of steps, but it is preferably 64 or more, and particularly preferably 128 or more.

[0040] Furthermore, it is preferable to set the resolution of the spectrum to be measured. The smaller the resolution value set, the more accurate the spectrum becomes, and the more reliable the value obtained. The set resolution value is 4 cm. -1 The following applies: When using FT-IR, it is preferable to perform background measurement when measuring the object being measured. Background measurement refers to a correction to subtract absorbent components such as water vapor and carbon dioxide in the air. This eliminates measurement errors caused by moisture and carbon dioxide in the air. Background measurement should be performed before measurement. The spectrum obtained by FT-IR is phase-corrected. Phase correction is automatically performed by the FT-IR software during measurement. There are no particular restrictions on the phase correction method, but examples include the absolute value method, multiplication method, convolution method, and manual method, and the method can be selected according to the characteristics of the sample being measured. For example, with Thermo Fisher Scientific's iN10MX instrument, you can choose between the Mertz method or the Power Spectrum method. Unless the results are clearly abnormal, Usually, the Mertz method is used.

[0041] The intensity of the spectrum obtained by FT-IR is expressed as absorbance. When the spectrum obtained by FT-IR appears as absorbance, baseline correction is performed. This is because if the baseline of the obtained spectrum is distorted, accurate peak intensity ratios and area values cannot be obtained. The method of baseline correction is not particularly limited, and an appropriate method is used according to the obtained spectrum. For example, in the case of the software OMNIC (Versionsion.8.3 and later) of Thermo Fisher Scientific, the obtained spectrum is analyzed, and the most preferable correction method is automatically selected. In the corresponding software, the linear (first-order) interpolation method, the cubic spline interpolation method (spline), and the polynomial interpolation method can be selected.

[0042] The spectrum obtained by FT-IR is smoothed. This is to prevent minute disturbances in the spectrum from being detected as peaks when performing peak separation described later. By performing smoothing, minute disturbances can be adjusted, and more accurate peak separation calculations can be performed. The method of smoothing is not particularly limited, and examples include the simple moving average method and the Sacutzkey-Golay method. An appropriate method is used according to the obtained spectrum and, in the case of automation, the software used. For example, in the case of the software OMNIC (Version.8.3 and later) of Thermo Fisher Scientific, the obtained spectrum is analyzed, and the most preferable range is automatically selected. Also, in the corresponding software, the interval of wavenumbers when performing smoothing can be specified. If the specified interval of wavenumbers is small, smoothing that maintains the shape of the original spectrum is performed, but the spectral lines are not sufficiently smoothed. Conversely, if the specified interval of wavenumbers is large, the spectral lines become smoother, but they change from the shape of the original spectrum. Therefore, it is important to specify an appropriate interval for smoothing. The specified interval is 9.642 cm -1 or more, 48.212 cm -1The following is preferable, but if the influence of noise or impurities is considered to be significant, use 13.499 cm². -1 Over 28.927cm -1 By using the following range, smoothing can be achieved without damaging the spectral peaks.

[0043] Peak separation is performed on the spectra obtained by FT-IR. This prevents the actual peak intensity from becoming too high due to peak overlap, which would hinder accurate evaluation, and also allows for the calculation of Si-OC bonds from the area ratio of the separated peaks, as described later. There are various methods and techniques for peak separation, and it is also possible to perform the calculation automatically using software. In this specification, peak separation was performed using Thermo Fisher Scientific's software OMNIC (Version 8.3 or later).

[0044] When detecting peaks with the software, specify the number of wavenumbers to separate. The specified range can be the same range used to draw the baseline, such as 4000 cm². -1 From 400cm -1 The range used is 2000 cm. If the baseline within this range is deemed inappropriate, use 2000 cm. -1 From 800cm -1 The specified range is used. Additionally, when detecting peaks within the specified range, an initial value for the peaks to be detected is set. Typically, the half-width is set to 3.857, and peak detection is performed within the specified range. At this time, peaks detected due to baseline disturbances may be removed.

[0045] The distribution function used for peak detection is usually Voigt, but Gaussian, Lorentzian, Gaussian-Lorentzian, and Log Normal may be used depending on the situation. Furthermore, the sensitivity for detecting peaks can be set to a defined half-width. Normally, to prevent unwanted peak detection, the sensitivity is set to low using the instrument's program; however, if no peaks are detected, medium or high sensitivity can be set. This can be done. Peak fitting is performed using the detected peaks. At this time, the acceptable range of the standard deviation between the original spectrum and the resulting composite spectrum can be set in advance and calculated. This acceptable range is treated as noise. The noise can be set from 1 to 10. A larger value results in a larger standard deviation, meaning a larger difference between the resulting spectrum and the original spectrum. A smaller value results in a smaller standard deviation, meaning it is easier to obtain a spectrum that matches the original spectrum. The noise setting is usually 10, but the value may be reduced when the standard deviation is large.

[0046] Furthermore, baseline correction can be performed during peak fitting. While typically a first-order (linear) correction is used, second-order and third-order corrections can be applied depending on the resulting spectrum. The software used performs iterative calculations, so even if the standard deviation of the composite spectrum obtained in the first calculation is greater than the standard, repeating the calculation under the same conditions will produce a composite spectrum closer to the original. Here, the composite spectrum refers to the IR spectrum obtained by summing the calculated isolated spectra. If the standard deviation still exceeds the standard after repeated calculations, it may indicate that the half-width of the detected peaks is different. In this case, the half-width value is changed, peak detection is performed again, and peak fitting is repeated until the standard deviation is below the standard value. A standard deviation of 1.5 or less is preferable, but it is best to use the smallest possible value. Therefore, try values ​​below 1.0 and below 0.7, lowering it to a range where the separated peaks do not disrupt the baseline; the most preferable value is below 0.5.

[0047] The software typically used in this embodiment is OMINC version 8.3 or later, but any software that can detect and calculate peaks by setting the full width at half maximum can be used.

[0048] The sample to be measured by FT-IR varies depending on the measurement method, but it can be measured in the form of coated granular fertilizer, in the form of only the extracted membrane (or in the form of the fertilizer coating material), or using a single membrane prepared under the same conditions as when the coated granular fertilizer was manufactured. If measurement is required urgently, it is preferable to measure in the form of coated granular fertilizer, and if high-precision analysis is required, it is preferable to measure in the form of only the extracted membrane or a single membrane. When measuring in the form of coated granular fertilizer, it can be measured as is, or it may be dried before measurement. There is no specific temperature for drying, but it is preferable that it does not affect the amount of Si-OC bonds in the membrane, and is preferably 120°C or lower.

[0049] The drying time can be adjusted as appropriate depending on the drying temperature. When measuring only the extracted film, there are no particular restrictions on the method of extracting the film, but methods include scraping or placing the coated fertilizer in water, dissolving the fertilizer components, and then washing and drying. Scraping involves scraping the surface of the coated granular fertilizer with a sharp blade or similar tool to extract the film. The other method involves placing the coated granular fertilizer in water, dissolving the fertilizer components, and then extracting only the film. In this case, the water may be heated to improve the efficiency of dissolution. The temperature of the water used to dissolve the urea should be such that it does not affect the amount of Si-OC bonds in the film, and from the viewpoint of efficiency and workability, a temperature of around 20 to 60°C is preferable.

[0050] The extracted membrane is preferably washed with water to remove any remaining fertilizer components. While washing with water is common, washing with an organic solvent is also possible. Examples of organic solvents include alcohols, acetone, or aliphatic hydrocarbons such as heptane; however, there are no particular restrictions as long as the fertilizer components can be washed away. These solvents can also be mixed and used. There are no restrictions on the amount of solvent used for washing, but it is preferable to use an amount sufficient to prevent the detection of fertilizer component-derived spectra during measurement. After washing, drying is preferable to remove moisture from the membrane. The drying temperature should not affect the amount of Si-OC bonds in the membrane and should be sufficient to remove moisture from the membrane; it is not particularly limited, but a temperature of around 80-60°C is preferred.

[0051] 1050 cm in composite membrane-1 ±25cm -1 The peak area of ​​the stretching vibration of the Si-O-Si bond that appears at 1430 cm² -1 ±30cm -1 or 1326±25cm -1 Si-OC bonding can be confirmed by comparing the peak areas in the vicinity. However, the wavenumber of each peak top may vary depending on the measurement conditions and sample state. The peak areas used can be compared using the area values ​​of isolated peaks calculated from the composite spectrum with a standard deviation of 1.0 or less. When the spectral peak ratio is PVA / Si-O-Si, the PVA peak used is typically 1430 cm⁻¹. -1 We will use the peak, but the peak area remains unchanged, so it is 1326 cm². -1 Using the peak is also acceptable. A smaller PVA / Si-O-Si value indicates that more Si-OC bonds are formed, and the value is preferably 0.9 or less, more preferably 0.7 or less, particularly preferably 0.3 or less, and most preferably 0.1 or less.

[0052] In FT-IR, 1430cm -1 ±30cm -1 or 1326cm -1 ±25cm -1 If the peak is not detected, or if the baseline disturbance or spectral noise is significant and accurate values ​​cannot be obtained, then 1H nuclear magnetic resonance spectroscopy (hereinafter, 1 H This problem can be solved by using NMR. normal solution 1 In 1H NMR, peaks are observed that are due to dissolved chemical species, while peaks for insoluble components are not observed. Furthermore, when the OH and Si-OH groups of PVA are bonded via covalent bonds, a three-dimensional network structure is formed, making it insoluble in all solvents. Therefore, when the OH and Si-OH groups of PVA are bonded via covalent bonds, the solution... 1 In 1H NMR, the peak attributable to 1H in PVA is either not observed, or its peak intensity is weaker than expected based on the amount of PVA in the composite film.

[0053] Since the measurement is performed in solution form, the desired form of the object to be measured is either a membrane extracted from the coated granular fertilizer beforehand, i.e., a single membrane prepared under the same conditions as when the coated granular fertilizer was manufactured, or a solution. The method for extracting the membrane and preparing the single membrane is the same as described for FT-IR. There are no particular restrictions on the method of extracting the membrane, but methods include scraping or immersing the coated fertilizer in water to dissolve the fertilizer components, followed by washing and drying. Scraping involves scraping the surface of the coated granular fertilizer with a sharp blade or similar tool to remove the membrane. The other method involves immersing the coated granular fertilizer in water to dissolve the fertilizer components and then removing only the membrane. At this time, the water may be heated to increase the efficiency of dissolution. The temperature of the water used to dissolve the urea should be such that it does not affect the amount of Si-OC bonds in the membrane, and from the viewpoint of efficiency and workability, a temperature of around 20-60°C is preferred.

[0054] By keeping the range within this limit, the effect on the amount of Si-OC bonds in the membrane can be minimized. The extracted membrane is preferably washed with water to remove any remaining fertilizer components. While washing with water is the usual method, washing with an organic solvent can also be used. Examples of organic solvents include alcohols, acetone, or aliphatic hydrocarbons such as heptane, but there are no particular restrictions as long as the fertilizer components can be washed away. These solvents can also be mixed and used. There is no limit to the amount of solvent used for washing, but it is preferable to use an amount that does not allow for the detection of spectra derived from fertilizer components during measurement.

[0055] After washing, it is preferable to dry the film to remove moisture. The drying temperature should not affect the amount of Si-OC bonds in the film and should be sufficient to remove moisture from the film; it is not particularly limited, but a temperature of around 60-80°C is preferred.

[0056] 1When measuring with 1H NMR, there are no particular restrictions on the deuterated solvent used as long as the composite film is soluble in it, but typically, a non-proton-donating deuterated dimethyl sulfoxide solvent is used. Using this solvent allows for measurement without overlapping with spectral peaks originating from the film. The ratio of the substance to the deuterated solvent is 1900% by weight of the deuterated solvent to 100% by weight of the composite film. The weights obtained from this sampling are important because integration normalization will be performed later, and it is preferable that the weights be as uniform as possible.

[0057] 1 When measuring with 1H NMR, it is preferable that the obtained spectrum be integrated. This is because integration reduces noise in the spectrum, resulting in a smoother and more accurate spectrum. Integration is usually performed using a number that is 2 to the power of n. There is no particular limit to the number of integrations; however, increasing the number of integrations will result in a more accurate spectrum. On the other hand, this will increase the measurement time, so it is important to specify an appropriate number of integrations depending on the situation. Preferably, it is 2 to 128 times, more preferably 4 to 128 times, and most preferably 8 to 128 times.

[0058] 1 When performing measurements with 1H NMR, it is necessary to set a relaxation delay (RD) before irradiating the next pulse in order to improve measurement accuracy. This is because the magnetization needs to return to a thermal equilibrium state after excitation. If the delay is too short, the next measurement will start before the magnetization has fully returned to thermal equilibrium, so it is desirable to set an appropriate time. Usually, this is 5 seconds, but a longer time may be used to obtain a more accurate spectrum.

[0059] To perform integral normalization of peaks caused by OH in PVA, it is necessary to add a reference substance when preparing the measurement sample. The reference substance must not overlap with the spectra of the composite film or its raw materials, must be soluble in the deuterated solvent used, and is more preferably non-volatile. Examples include N,N-dimethylformamide (DMF), benzene, benzaldehyde, acetonitrile, chloroform, diethyl ether, methyl ethyl ketone (MEK), heptane, hexane, 2-propanol, pyrrole, toluene, triethylamine (TEA), dimethylacetamide, grease, hexamethylbenzene (HMB), imidazole, hexamethyl phosphate triamide, or pyridine.

[0060] Preferably, the integrated signal value due to the OH groups in the PVA contained in the composite membrane is 50% or less, more preferably 40% or less, particularly preferably 30% or less, and most preferably 20% or less, compared to the integrated signal value due to the OH groups of PVA alone with the same mass as the PVA contained in the composite membrane. Achieving this value suppresses the rapid dissolution of the coated granular fertilizer in water.

[0061] Another method to confirm whether Si-OC bonds have been formed involves immersing the film in a solvent, removing the film after a certain period of time, and evaporating the solvent used for immersion. The solvent is not limited as long as it dissolves the resin that has not reacted with the hydrolysate of the alkoxysilane condensate (hereinafter referred to as the resin with unreacted OH groups). For example, if PVA is used, the unreacted PVA will dissolve in water. On the other hand, if the hydrolysate of the alkoxysilane condensate reacts with PVA to form Si-OC bonds, the film will not dissolve in water even if immersed in water. Therefore, the presence of resin with unreacted OH groups can be confirmed by removing the solvent in which the film was immersed, transferring it to an evaporating dish whose weight has been measured in advance, and observing the weight difference after evaporation to dryness by applying heat. Methods for identifying resins containing unreacted OH groups include immersing the material, along with the substrate, in water after forming a film on it; immersing a separate film prepared under the same drying conditions as the material formed on the substrate using a petri dish or similar method in water; or, in the case of coated granular fertilizers made using a coating material, examining the film after removing the fertilizer components to avoid contamination. The solvent used when immersing the film is not particularly limited as long as it dissolves the resin containing OH groups, but water is preferred in the case of PVA because it dissolves easily. There is no particular requirement for the amount of solvent used, as long as the film is completely immersed in the solvent and the unreacted resin containing OH groups in the film is dissolved. There is no particular requirement for the immersion time in the solvent, but if the immersion time is too short, the unreacted resin containing OH groups may not dissolve sufficiently into the solvent, so it is recommended to immerse the film for 30 minutes or more. This is preferable. At this time, the solution may be stirred or heated for the efficiency of the work. The temperature at which the unreacted resin having OH groups in the film is dissolved should be below the boiling point of the solvent used and should not affect the formation of Si-OC bonds in the film. From the viewpoint of workability and efficiency, 20 to 60°C is preferred. After dissolving the resin containing unreacted OH groups in the film in a solvent, the film that did not dissolve in the solvent is removed. The method of removing the film does not need to be such that any undissolved film remains in the solvent. This can be done by removing it with tweezers, by extracting the solution with a syringe and then connecting a syringe filter to separate the solution from the remaining film, or by using suction filtration to separate the solvent containing the unreacted resin with OH groups from the film. The solvent containing the unreacted OH-group-containing resin is evaporated to dryness. After evaporation to dryness, the weight of the unreacted OH-group-containing resin is obtained by subtracting the weight of the container from the total weight of the unreacted OH-group-containing resin and the container. There are no specific requirements for the container used for evaporation to dryness, but for efficiency, a watch glass or magnetic crucible is recommended. Heat must be applied to completely remove the solvent from the container containing the solvent containing the unreacted OH-group-containing resin, but there are no specific requirements for the method as long as the container can be heated. The temperature is preferably such that the solvent evaporates and the OH-group-containing resin does not decompose. From the viewpoint of workability and efficiency, a temperature of 120°C or lower is preferred. The amount of OH-group-containing resin that did not react with the alkoxysilane condensate hydrolysate obtained by evaporation to dryness is preferably 50 parts by mass or less per 100 parts by mass of the initially immersed film. This range indicates that sufficient Si-OC bonds are present in the film.

[0062] The ratio of the weight of the above-mentioned dehydrated condensate to the total weight of the fertilizer coating material is usually 50% by weight or more, preferably 55% by weight or more, preferably 60% by weight or more, more preferably 65% ​​by weight or more, even more preferably 70% by weight or more, and may also be 100% by weight, 100% by weight or less, 95% by weight or less, 90% by weight or less, or 80% by weight or less.

[0063] (Regarding coated granular fertilizers) In the coated granular fertilizer according to this embodiment, the granular fertilizer that can be used as the core material usually contains one or more fertilizer components: nitrogen, phosphorus, or potassium. Specifically, examples include nitrogenous fertilizers, phosphorusous fertilizers, potassiumous fertilizers, and, if necessary, fertilizers containing trace elements such as calcium, magnesium, sulfur, iron, manganese, molybdenum, copper, zinc, or boron, or silicon. Fertilizers containing nitrification inhibitors, urease inhibitors, or pesticide components are also acceptable. Among these, nitrogenous fertilizers containing ammonium sulfate, urea, or ammonium nitrate, which have high water solubility and are easily released into the environment, potassiumous fertilizers containing potassium sulfate or potassium chloride, and compound fertilizers containing urea, ammoniacal nitrogen, or nitrate nitrogen are preferred, with urea being more preferred due to its low unit cost per fertilizer component.

[0064] The amount of the film made of the fertilizer coating material in the pre-coated granular fertilizer (hereinafter also simply referred to as the "fertilizer coating material film") is not particularly limited, but from the viewpoint of suppressing film defects, it is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and usually 30% by mass or less, and from the viewpoint of increasing the amount of active ingredients in the fertilizer, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0065] (Pre-coat) The core material can be pre-coated. In other words, coated granular fertilizer may have an additional pre-coat layer (film) between the fertilizer and the fertilizer coating material film. The pre-coat material may be wax, nitrification inhibitor, urease inhibitor, biodegradable resin, or anti-caking agent. Examples include functional inorganic particles, surfactants, or formaldehyde. Using a pre-coated core material helps to suppress dissolution and hardening of the core material during coating, enabling stable coating.

[0066] There are no particular restrictions on the biodegradable resins used as precoat materials, but polyvinyl alcohol resin, starch, cellulose, lignin, chitin, chitosan, PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), PBAT (poly Butylene agitate terephthalate, PCL (polycaprolactone), starch polyester The following are selected from the group consisting of tel, cellulose acetate, PHB (polyhydroxybutyrate), PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PLA (polylactic acid), PGA (polyglycolic acid), PDO (polydioxanone), or copolymers thereof. They can be used individually or in combination of two or more.

[0067] There are no particular restrictions on the waxes used as precoat materials, but examples include natural waxes such as plant waxes like castor oil, animal waxes, mineral waxes, or petroleum waxes, as well as synthetic waxes such as polyethylene wax or Fischer-Tropsch wax, and furthermore, compound waxes made from these waxes, oxidized waxes, or hydrogenated waxes such as castor wax. These waxes can be used individually or as mixtures of two or more types.

[0068] The amount of the pre-coat layer calculated from the following formula is not particularly limited, but is usually 0.1% by weight or more and 20% by weight or less relative to the core material. From the viewpoint of suppressing the occurrence of defects in the pre-coat layer, it is preferable to be 1% by weight or more and 20% by weight or less. From the viewpoint of the active ingredients of the fertilizer, a smaller film thickness is preferable, and it is preferable to be 2% by weight or more and 15% by weight or less, and even more preferably 2% by weight or more and 10% by weight or less. Pre-coat layer [weight %] = (weight of pre-coat material / weight of pre-coated core material) × 100

[0069] As described above, the granular fertilizer according to this embodiment may contain one or more fertilizer components such as nitrogen, phosphorus, or potassium. However, as long as the effects of the present invention are not impaired, it may also contain other components such as carriers such as clay, kaolin, talc, bentonite, or calcium carbonate, or binders such as sodium carboxymethylcellulose or starches. Furthermore, if necessary, it may also contain surfactants such as polyoxyethylene nonylphenyl ether, molasses, animal oil, vegetable oil, hydrogenated oil, fatty acids, fatty acid metal salts, paraffin, wax, or glycerin.

[0070] Furthermore, other components such as inorganic or organic fillers may be included in the film, to the extent that they do not impair the effects of the present invention. For example, the fillers include plate-shaped fillers such as talc, mica, or hydrotalcite, calcium carbonate, silica, clay, various crushed ores, or sulfur. In the following paragraphs, when the term "film" is used, unless otherwise specified, it refers to both fertilizer coating material films and pre-coat layers (films).

[0071] Other components besides fillers include, for example, organic substances such as surfactants, polysaccharides and their derivatives. These can be added insofar as they do not affect the above reaction. Examples of surfactants include water-soluble substances such as polyethylene glycol, polypropylene glycol, or polyalkylene glycol obtained by copolymerization of ethylene glycol and propylene glycol, polyvinyl alcohol, ether-type nonionic surfactants such as polyethylene glycol-alkyl ether or polyethylene glycol-branched alkyl ether, ester-type nonionic surfactants such as polyethylene glycol-alkyl ester or polyethylene glycol-branched alkyl ester, and cationic surfactants. Examples include surfactants, anionic surfactants, amphoteric surfactants, or mixtures thereof. Examples of polysaccharides or their derivatives include cellulose, agar, starch, chitin and its derivatives, and chitosan and its derivatives, among which starch is a preferred material due to its low cost. Starch derived from corn, tapioca, wheat, potatoes, rice, sweet potatoes, etc. can be used. Processed starches such as pregelatinized starch may also be used. Starch whose surface has been treated with silicone resin or the like to improve dispersibility and fluidity can also be used. These surfactants, polysaccharides or their derivatives can be used individually or in combination of two or more types.

[0072] The particle size of the filler is preferably 100 μm or less, and more preferably 1 μm or more and 50 μm or less. When the particle size is within the above range, problems such as the film peeling off during film formation due to excessively large particle size, or the film material solution clogging spray nozzles, etc., are less likely to occur. Even if the particle size of the filler is larger than the thickness of the film and a portion of it protrudes from the film surface, the intended purpose is achieved as long as a portion of it is incorporated into the film and adheres to it. The particle size can be measured using known methods, such as the laser diffraction particle size distribution analyzer. When the film material contains the above filler, the proportion is not particularly limited, but it is preferably 0.1 to 70% by mass, and more preferably 1 to 60% by mass, based on 100% by mass of the film material. If the coating material contains other components besides fillers, such as the surfactants and polysaccharides and their derivatives, the proportion is not particularly limited, but is preferably 0.01 to 60% by mass, and more preferably 0.1 to 50% by mass, based on 100% by mass of the coating material.

[0073] In addition, various organometallic compounds and metal oxides may be used as coating materials for purposes such as decomposing the resin in the coating. Examples of usable organometallic compounds include organometallic complexes and organic acid metal salts. Metals with excellent photodegradability include cobalt, iron, manganese, or cerium. In terms of availability, iron complexes and iron carboxylates are preferred. For example, iron complexes include iron acetylacetonate, iron acetonyl acetonate, or iron dialkyldithiocarbamate, dithiophosphate, xanthate, or benzthiazole. Examples of iron carboxylates 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, or linolenic acid. Examples of metal oxides include titanium dioxide or zinc oxide. These may be added individually or in combination of two or more. The content of organometallic compounds in the coating material is preferably 0.0001 to 1% by mass, more preferably 0.001 to 0.5% by mass. When the content is within this range, the coating is less likely to break down or decompose during product storage, and the desired effect is easily obtained upon application. Other biodegradation accelerators and inhibitors can also be added.

[0074] The method for obtaining the fertilizer coating material and coated granular fertilizer according to this embodiment is not particularly limited, but can be obtained by, for example, the method shown below. In the following description, a PVA-based resin will be used. While the PVA-based resin is one example of the most suitable resin in this embodiment, due to the configuration of this embodiment, any resin having an OH group is not particularly limited; for example, starch, chitosan, cellulose derivatives, etc., can also be used. Furthermore, the fertilizer to be coated will be urea granules in the following description. While urea is the most suitable resin in this embodiment, due to the configuration of this embodiment, it is not limited to urea, and known granular chemical fertilizers can be used. Specific examples include aldehyde condensed ureas such as urea, formaldehyde condensed urea, or isobutyraldehyde condensed urea, guanylurea sulfates, calcium cyanamide, ammonium nitrate, ammonium sulfate, ammonium chloride, or ammonium dihydrogen phosphate, phosphate fertilizers such as superphosphate, fused phosphate fertilizer, or calcined phosphate fertilizer, potassium salts such as potassium nitrate, potassium chloride, potassium sulfate, and potassium silicate, calcium phosphate, and calcium sulfate. Examples include calcium salts such as um, calcium nitrate, and calcium chloride; magnesium salts such as magnesium nitrate, magnesium chloride, magnesium sulfate, or magnesium phosphate; iron salts such as ferrous nitrate, ferric nitrate, ferrous phosphate, ferric phosphate, ferrous sulfate, ferric sulfate, ferrous hydrochloride, or ferric hydrochloride; double salts thereof; or combinations of two or more of these.

[0075] In this specification, the types and weights of structures derived from resins having OH groups in fertilizer coating materials, the types and weights of structures derived from alkoxysilane condensates, and the types and weights of structures derived from other components are, for example, 1 The material can be analyzed by 1H-NMR, GPC, or IR, but it may also be identified from the type and quantity of raw materials used.

[0076] This paper details the preparation of a solution of a resin containing OH groups, a hydrolysis solution of an alkoxysilane condensate, and a method for producing a coating using a composite solution combining these, in the formation of a fertilizer coating material using a resin containing OH groups and a hydrolysis condensate of an alkoxysilane condensate. In one example, a fertilizer coating material is obtained by following steps 1) to 5) below. Note that PVA is given as an example of a resin containing OH groups, but this is just one example, and any resin containing OH groups is acceptable. 1) Preparation of the hydrolysis solution (A) of the alkoxysilane condensate 2) Preparation of a solution (B) of a resin having an OH group (e.g., a PVA-based resin) 3) A mixture of (A) and (B) 4) Self-supporting film or coating onto substrate 5) Heat drying When applying the pre-coating described above, the pre-coating step should be included before step 4) coating.

[0077] 1) Preparation of hydrolysis solution (A) of alkoxysilane condensate In this process, the alkoxysilane condensate is mixed with a catalyst and water in the presence or absence of a solvent to hydrolyze it, thereby obtaining a liquid hydrolyzable composition that can be optionally diluted with water or an organic solvent. As solvents, typically methanol, ethanol, or aliphatic lower alcohols having 1 to 4 carbon atoms such as propanol are used. Methanol and ethanol are particularly preferred because they have high compatibility with water and do not easily cause PVA precipitation when mixed with an aqueous solution of PVA resin. Although the condensate of alkoxysilane and water for hydrolysis are not compatible when mixed without a solvent, the added water is consumed as hydrolysis progresses and the corresponding alcohol is produced. Therefore, if the amount of water added is small, a uniform and transparent composition may be obtained even without a solvent. The amount of solvent used is preferably 0.25 to 250 parts by weight per 20 parts by weight of the hydrolyzed alkoxysilane contained in (A) in terms of SiO2 equivalent. This can be appropriately changed depending on the solid content concentration, solvent type, and solvent ratio. After this, if necessary, the mixture may be diluted with water or an organic solvent such as alcohol to achieve the desired concentration.

[0078] In preparing aqueous solution (A), a catalyst and water are used to hydrolyze the alkoxysilane condensate. Such catalysts typically include inorganic acid catalysts such as hydrochloric acid, sulfuric acid, nitric acid, or hydrofluoric acid; organic acid catalysts such as formic acid, acetic acid, maleic acid, fumaric acid, or p-toluenesulfonic acid; and base catalysts such as ammonia. These catalysts may also include organometallic compounds, metal alkoxides, organotin compounds, metal chelate compounds containing any metal such as aluminum or titanium-zirconium, or boron compounds. The resulting hydrolyzed product has many silanol groups, high affinity with PVA-based resins, and the aqueous solution (A) is less likely to gel in a short time, resulting in excellent storage stability. Therefore, acid catalysts, organometallic compounds, metal alkoxides, metal chelate compounds, or boron compounds are preferred.

[0079] The amount of such catalyst is typically relative to the total molar amount of alkoxy groups in the alkoxysilane condensate. The amount is 0.0001 mol% or more and 0.1 mol% or less, preferably 0.0002 mol% or more and 0.09 mol% or less, and particularly preferably 0.0003 mol% or more and 0.8 mol% or less. Using such an amount allows the hydrolysis reaction to proceed at an appropriate rate and enhances the storage stability of the aqueous solution (A). Furthermore, the amount of water used when preparing aqueous solution (A) is usually 0.01 mol% or more, 0.05 mol% or more, preferably 80 mol% or less, relative to the total molar amount of alkoxy groups in the alkoxysilane and / or its condensate. Using such an amount facilitates the hydrolysis reaction and ensures that (A) is uniformly miscible with water when diluted. It also helps to avoid porosity when creating the desired film and avoids wasting heat during drying. Usually, the catalyst and water mixture are added together to the alkoxysilane condensate, but they may also be added separately.

[0080] The hydrolysis reaction of the alkoxysilane condensate during the preparation of solution (A) typically occurs at 10-80°C. If the temperature is too high, the hydrolysis reaction rate increases, making (A) more likely to gel; if it is too low, the reaction tends to proceed slowly. The reaction is usually carried out with stirring. Furthermore, the reaction time varies depending on the scale, but is usually 5 minutes to 24 hours, preferably 10 minutes to 8 hours. This timeframe prevents the aqueous solution (A) from becoming highly viscous or gelling, prevents insufficient reaction, and ensures that it readily and transparently mixes with aqueous solution (B). The concentration of the hydrolysate of the alkoxysilane condensate in solution (A) can be appropriately selected depending on the storage stability of solution (A) and its compatibility with solution (B), which will be described later. The concentration of the hydrolysate of the alkoxysilane condensate in solution (A) is expressed as a solid content concentration using SiO2 equivalent values, and is usually 0.1% by weight or more and 40% by weight or less, preferably 1% by weight or more and 30% by weight or less, and more preferably 5% by weight or more and 25% by weight or less.

[0081] 2) Preparation of a solution (B) of a resin having an OH group In this step, the resin having OH groups is added under stirring to water, a mixed solution of water and a water-soluble organic solvent, a non-water-soluble organic solvent, a mixed organic solvent of two or more types, or these solutions heated as needed, thereby dissolving the resin in the solvent to obtain a solution (B) of the resin having OH groups. Depending on the required solid content concentration of the resin and the corresponding properties of the solvent, for example, when dissolving PVA resin in water, the water temperature is 10°C or higher and 100°C or lower, particularly preferably 25°C or higher and 90°C or lower. This range is appropriately selected according to the solubility characteristics of the solvent used. The resin having OH groups may be added all at once or in stages. To prevent clumping and ensure complete dissolution, the solution may be heated after the addition is complete as needed. Heating may be done immediately after addition, but stirring at room temperature for a certain period of time before heating makes it easier to prevent clumping. Room temperature here refers to a range of 25±5°C. There is no specific time for stirring at room temperature, but it is usually 1 hour or more and 3 hours or less, more preferably 20 minutes or more and 40 minutes or less, and most preferably 10 minutes or more and 15 minutes or less, and can be appropriately selected depending on the properties of the OH group-containing resin used. Alternatively, it may be added while heating.

[0082] The concentration of solution (B) can be appropriately selected depending on the viscosity of solution (B), the solubility characteristics of the resin used, and its compatibility with solution (A), and is usually 1% by weight or more and 30% by weight or less, preferably 2% by weight or more and 25% by weight or less. The solvent of solution (B) is not particularly specified as long as it dissolves the resin having OH groups, does not precipitate the resin having OH groups when mixed with the hydrolysate of the alkoxysilane condensate, and dissolves the hydrolysate of the alkoxysilane condensate. Depending on the solubility characteristics of each material, in addition to water, lower alcohols having 1 to 3 carbon atoms or organic solvents such as acetone may be used, or two or more solvents may be combined. This results in a composite solution in which the resin having OH groups does not precipitate when the two solutions are mixed, and the hydrolysate of the alkoxysilane condensate is dissolved.

[0083] 3) A mixture of (A) and (B) In this step, solutions (A) and (B) prepared using the method described above are mixed to create a homogeneous solution. The mixing method can be either dropwise or by adding all at once. Here, if water is used in solution (B) and the alkoxysilane condensate in solution (A) is in a partially hydrolyzed state, some of the water in (B) is used as water for hydrolysis of the silicate component when solution (A) and aqueous solution (B) are mixed, and further hydrolysis polycondensation proceeds. After mixing aqueous solution (A) and aqueous solution (B), a homogeneous aqueous solution is obtained by aging at room temperature or at a temperature below the boiling point of the mixture for 10 minutes to 24 hours as necessary. This prevents the hydrolysis polycondensate of the alkoxysilane condensate from undergoing excessive condensation reactions, which increases the molecular weight and deteriorates the compatibility between the resin containing the OH group and the solvent.

[0084] 4) Fabrication of a self-supporting film or coating onto a substrate In this step, the solution obtained in the previous step is used as a coating solution to coat a substrate such as a self-supporting film or a plastic film. There are no particular restrictions on the method of forming the coating; any method from conventionally known techniques can be appropriately selected. For example, a self-supporting film can be prepared by mixing solution (A) and solution (B) to obtain a coating solution, spreading it uniformly on a petri dish of the required area for evaluation, drying it for a certain period of time under arbitrary temperature and humidity conditions, and then peeling it off the petri dish. Alternatively, it can be prepared by coating a plastic film coated with a release agent, drying it for a certain period of time under arbitrary temperature and humidity conditions, and then peeling it off the plastic film. The coating method will be explained in the section on coating a substrate such as a plastic film.

[0085] If it is difficult to produce a self-supporting film, a plastic film may be used as the substrate to produce the film. Because the composite liquid has a low solid content, a good film that does not crack even after drying can be obtained depending on the coating method. Composite films are mainly produced using wet film-forming methods. Specifically, these include methods using various means such as spraying, roller coating, bar coating, spin coating, gravure coating, die coating, inkjet, dispenser coating, comma coating, curtain coating, dip coating, silkscreen printing, or flexographic printing. Depending on the thickness of the resulting film and the viscosity and solid content of the coating liquid, the above methods can be appropriately selected. In this specification, spin coating and bar coating methods are used depending on the characteristics of the substrate used.

[0086] Spin coating is a method of coating the surface of a substrate using a rotation process. The substrate to be coated is fixed on the spin coater's stage using a vacuum chuck or the like, the coating liquid is added to the center of the object, and then the substrate is coated by rotating it at a constant rotation speed for a certain period of time. The thickness of the film coated on the substrate depends not only on parameters such as the kinematic viscosity and surface tension of the coating liquid, but also on the rotation speed of the spin coater, so a wide range of thicknesses can be formed depending on the purpose. Therefore, the rotation speed is determined by the characteristics of the composition liquid being evaluated. The rotation time should be determined by the time it takes for the coating liquid to spread across the entire substrate. The spreading speed of the coating liquid is affected by the rotation speed, the kinematic viscosity of the coating liquid, and the wettability to the substrate, so it is determined by the characteristics of the coating liquid being evaluated and the rotation speed. Depending on the resin used to make up the substrate, the flexibility of the resin itself may make it difficult to fix the substrate to the spin coater stage, making the spin coating method difficult to use. Furthermore, the film thickness after deposition may not reach the desired thickness even when considering the rotation speed and the composition of the coating solution. In such cases, the bar coating method can be used.

[0087] The bar coating method is a coating method that uses a shaft called a bar coater. A common bar coater is a so-called wire bar, where a wire is wound around a shaft. The coating principle of the wire bar is that when the coating liquid is applied to the wire bar and pulled, the coating liquid that gets into the gaps between the wires remains on the substrate, thus coating it. The liquid coated on the substrate flows and becomes flat, forming a uniform film. The thickness of the film formed can be controlled not only by the kinematic viscosity of the coating solution but also by the thickness of the wire wound around the shaft. Since thicker films can be formed than with the spin coating method, the appropriate shaft is selected depending on the characteristics of the coating solution and the evaluation items. In recent years, non-wired bars, in which the shaft itself has a uniform textured surface without winding a wire around it, have also come into use. The absence of wire eliminates the risk of wire breakage or displacement, and makes it easier to clean the bar after coating.

[0088] There are no particular restrictions on the substrate material, but it can be paper, nonwoven fabric, or a plastic film made of materials such as polyethylene, polyethylene terephthalate (PET), polyethylene naphthalate, polyethersulfone, polypropylene, polyimide, polycarbonate, polybutylene succinate, or cellulose triacetate. From these, a material with good adhesion to the film after drying should be selected. In addition, the surface of the substrate material may be treated to improve adhesion to the film. There are no specified treatment methods, but conventional techniques include UV irradiation, etching, vapor deposition, sputtering, corona treatment, or plasma treatment, and methods that improve adhesion to the film should be used.

[0089] 5) Heat drying The self-supporting film or the coating film created on the substrate may be dried by applying heat. Applying heat causes the solvent in the coating film to evaporate, forming a protective film. In this process, the OH groups in the hydrolysis products of the alkoxysilane condensate react with the resin containing OH groups to form Si-OC bonds. Any device that can apply heat to remove the solvent from the coating film and cure the film can be used. Examples include forced-circulation dryers, natural convection dryers, and forced-air constant-temperature dryers. The required temperature should not exceed the decomposition temperature of the film or damage the substrate used, and is usually set to 140°C or lower. At this time, two or more drying steps at different temperatures may be included. This prevents the coating film from cracking due to rapid temperature changes. The duration of heating should be sufficient to remove the solvent from the coating film, and there is no specific requirement as the evaporation rate at a given temperature varies depending on the solvent, but it is preferable to perform each step for at least 15 minutes. Furthermore, when preparing self-supporting membranes on a petri dish, rapid drying under unfavorable conditions can cause deformation or cracking of the membrane; therefore, it is possible to add a certain level of humidity. The required humidity is set appropriately depending on the temperature and the solvent composition of the membrane, and is usually below 90% humidity.

[0090] The resulting film exhibits desirable water vapor barrier properties, with a water vapor permeability of 500 g / m² under conditions of 25°C and 90% humidity. 2 ·day or more, ~1000g / m 2 A range of less than 200 g / m² is preferred. 2 ·day or more 500g / m 2 A range of less than 200 g / m² is even more preferable. 2 A release period of less than 1 day is particularly preferable. This range allows for the desired sustained release properties when the compound solution is coated onto the fertilizer.

[0091] <Moisture permeability measurement> The mechanism by which sustained-release coated fertilizers release their components in water is as follows: water turns into water vapor, passes through the coating, comes into contact with the fertilizer, and dissolves it. The water containing the dissolved fertilizer is then released outside the membrane, i.e., into the water, due to osmosis. Therefore, measuring the moisture permeability of the membrane is closely related to the dissolution rate of the sustained-release coated fertilizer. Thus, by checking the moisture permeability of the membrane, the dissolution rate can be estimated before the sustained-release coated fertilizer is manufactured. Moisture permeability can be evaluated using the method specified in JIS Z 0208, and among these methods, evaluation is performed at 25°C and 90% RH to match actual usage conditions.

[0092] <Manufacturing of coated granular fertilizer> The method for producing coated granular fertilizer, which is another embodiment of the present invention, is not particularly limited, but for example, a solution containing an alkoxysilane condensate and a solution containing a resin having an OH group may be mixed. The resulting coating solution can be manufactured by a method that includes the step of spraying it onto fertilizer and drying it. The method for mixing a solution containing an alkoxysilane condensate with a solution containing a resin having an OH group can be similarly applied to the steps described above, from "1) Preparation of hydrolysis solution (A) of the alkoxysilane condensate" to "3) Mixing (A) and (B)". Therefore, the composite solution used for evaluating the moisture permeability measurement described above can be used as the coating solution obtained by this mixing.

[0093] The method of spraying the obtained coating solution onto the fertilizer is not particularly limited. Examples include spraying (applying) a coating solution obtained by mixing aqueous solution (A) and aqueous solution (B) onto the surface of the particles, or immersing the particles in the coating solution. Alternatively, aqueous solution (A) and aqueous solution (B) may be sprayed directly onto the particles simultaneously or separately and mixed on the surface of the particles. Since drying the solvent instantly improves the uniformity of the coating, the spraying method is preferred.

[0094] For spraying, a single-fluid or two-fluid spray can be used, but a two-fluid spray nozzle is preferred as it produces finer spray particles and allows for more uniform film formation. As for the apparatus, various coating devices can be used, such as a rotating drum type, aerated rotating drum type, rotating pan type, rotating drop type, a jet type, or fluidized type, which agitate the granular material in conjunction with the movement of the apparatus itself. This explanation will use the method employing the small fluid-type spray coater 10 shown in Figure 1.

[0095] Here, urea is used as the coating material. Urea particles 3 are placed in the spray coater 10. Adding an appropriate amount of urea makes it easier for the coating solution to uniformly coat the added urea, and also reduces the likelihood of aggregate formation. Next, a gas 4 is introduced from the bottom of the device to blow up the urea. If the gas volume is too low, the urea's fluid state cannot be maintained, and aggregate formation is likely to occur. If the gas volume is too high, the urea will be discharged to the outside of the coater. Once the inside of the coater reaches a predetermined temperature, the spray gas and coating liquid are sprayed from the spray gun 1 at the top through the nozzle 2, thereby coating the urea 3 with the coating liquid. To speed up the drying of the coated urea by the gas 4 blown up from the bottom of the device, the inside of the coater is usually heated to 40-130°C. The gases used for blowing up include air, nitrogen, carbon dioxide, argon, and helium.

[0096] The coating solution is introduced using a liquid delivery pump. If the delivery speed is too fast, the coating solution is introduced before the film dries, causing the urea particles to stick together and making aggregate formation more likely. If the delivery speed is too slow, the coating solution dries in the coater before it can coat the urea, and coated fertilizer cannot be obtained. Examples of gases sprayed together with the coating solution include air, nitrogen, carbon dioxide, argon, and helium. If the coating solution contains organic solvents, there is a risk of ignition, so inert gases such as nitrogen and helium are preferably used. There are no restrictions on the spraying time as long as it does not impair the effects of the present invention, but it is usually 5 to 120 minutes.

[0097] There are no particular restrictions on the method of drying the coating liquid sprayed onto the fertilizer. For example, it may be subjected to a drying treatment, specifically by natural drying or by applying heat. Furthermore, if heat treatment is applied, it may be carried out as part of the drying treatment, or it may be carried out as a separate treatment after drying. The conditions for heat treatment are not particularly limited; for example, the conditions described in "5) Heat drying" above can be applied. However, since the thickness and shape of the film differ between the evaluated coating film and the film covering the granular fertilizer, the heating conditions such as temperature do not necessarily need to be unified. Typically, heat treatment is performed at 140°C or below. Heating is performed below the melting point of the fertilizer components being coated. It is preferable that the material be heated, and if urea is coated, it is preferable that it be heated to 130°C or lower, and more preferably to 90°C or lower. Alternatively, two or more heat treatments may be performed at different temperatures; for example, the first stage may be heated to 90°C or lower, and the second stage drying may be heated to 91°C or higher and 130°C or lower.

[0098] The coverage rate of the fertilizer coating material film in coated granular fertilizer varies depending on the shape and size of the core material, but is preferably 1 to 20% by weight, particularly preferably 2% or more and 15% or less by weight, and even more preferably 2% or more and 10% or less by weight. Here, the coverage rate is defined as the ratio of the coating material (material of the fertilizer coating material film) to the coated granular fertilizer, and is calculated by the following formula. Coverage rate [weight %] = (weight of coating material / weight of coated granular fertilizer) × 100

[0099] Furthermore, the Si content in the fertilizer coating material film is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 50% by weight or more, even more preferably less than 95% by weight, and even more preferably 93% by weight or less. Within this range, the coating is less likely to crack, and the leaching of fertilizer can be further suppressed.

[0100] The form of the coated granular fertilizer described above can be granular, and the average particle size of the coated granular fertilizer is 1.0 mm or more and 10.0 mm or less, preferably 1.0 mm or more and 5.0 mm or less. These particle sizes can also be selected within the above range by using a sieve. Furthermore, from the standpoint of stably controlling the release rate, a shape closer to spherical is more preferable. Specifically, the circularity coefficient calculated by the following formula is preferably 0.7 or higher, more preferably 0.75 or higher, and even more preferably 0.8 or higher, indicating a spherical shape. The maximum value of the circularity coefficient is 1, and the closer it is to 1, the closer the particle is to a perfect circle, and the smaller the circularity coefficient becomes as the particle shape deviates from a perfect circle. Circularity coefficient = {(4π × projected area of ​​the particle) / (length of the outline of the particle projection)} 2}

[0101] B) Pre-coating When pre-coating is performed, this step is included, but the method of performing pre-coating is not particularly limited. The pre-coat material described above is coated onto the surface of the granular fertilizer before the coating step described above. For example, pre-coating can be performed using the coater 20 shown in Figure 2. Specifically, in the coater 20 shown in Figure 2, granular fertilizer (core material, particles) 23 is introduced into the fluidized bed 21, and hot air 26, blown through a heater 25 generated by a blower 24, is used to circulate the blown-up gas into the fluidized bed 21. The fluidized bed 21 is then set to a desired temperature. After confirming that the temperature has reached the target value, the spray solution 29, which contains the pre-coat (pre-coat film) material dissolved in a solvent, is sent from a dissolution tank 28, and the solution is sprayed onto the core material 23 from a two-fluid spray nozzle 22 to perform pre-coating. The blown-up gas is generated by creating an airflow with a blower 24 and sending the heated hot air 26 through the heater 25 into the fluidized bed 21. This blown-up gas is discharged from the exhaust 27. Afterward, the liquid supply is stopped, and the fertilizer is dried while maintaining a constant temperature after the liquid supply is stopped. After lowering the temperature inside the fluidized bed, the blow-up gas is stopped, and the pre-coated fertilizer is removed.

[0102] While there are no particular restrictions on the drying temperature after pre-coating, from the viewpoint of drying efficiency, it is usually 30°C or higher, and preferably 60°C or higher. Furthermore, it is usually 140°C or lower, and from the viewpoint of the melting point of urea, it is preferably 130°C or lower.

[0103] Coated granular fertilizer has desirable slow-release properties, and when immersed in 30°C water, the fertilizer after 24 hours The elution rate of the components is suppressed to 60% or less, preferably 50% by weight or less, and more preferably 10% by weight or less, which meets the official standards for slow-release fertilizers. Furthermore, when the coated granular fertilizer is immersed in water, the initial number of floating particles is preferably 20% or less, and more preferably 10% or less. The elution test and the initial number of floating particles can be determined as follows.

[0104] <Measurement of dissolution rate> Place 1 g of coated urea and 200 mL of pure water in a 250 mL container and allow to stand in an incubator at a constant temperature (30°C). After 24 hours, measure the urea nitrogen concentration in the water. The urea concentration is measured as follows: Mix 50 mL of hydrochloric acid, 250 mL of ethanol, and 700 mL of pure water, dissolve 2.5 g of p-dimethylaminobenzaldehyde, and prepare a reaction solution. Mix 6 mL of the reaction solution with 0.5 mL of urea eluate, allow to stand for 30 minutes, and measure the absorbance at 420 nm using a spectrophotometer. Create a calibration curve using urea aqueous solutions of known concentrations and determine the urea concentration from the absorbance.

[0105] <Measurement of initial floating particle count> Twenty coated urea particles were placed in a petri dish, and pure water was poured in at a rate of 10 mL / min along the side of the dish. After 50 mL of water had been added, the number of particles floating on the surface was measured. Floating rate (%) = Number of floating particles / Number of particles used in the test × 100

[0106] <Method for measuring coverage> 5g of coated urea was crushed in a mortar and placed in a 500mL volumetric flask. Pure water was added to the mark. In addition, the solution was left to stand in a 30°C incubator until the urea was completely dissolved. After standing, the solution was filtered through a 45 μm mesh filter, and the concentration of urea nitrogen was measured using the method described in <Measurement of Elution Rate> above. The coating rate was calculated from the weight of urea in 5 g of coated urea using the following formula. Coverage rate [weight %] = ((weight of covered granular fertilizer - weight of urea) / weight of covered granular fertilizer) × 100 This (weight of coated granular fertilizer - weight of urea) represents the weight of the coating material. [Examples]

[0107] The present invention will be described in detail below using examples, but the present invention is not limited to these examples unless it exceeds the essence of the invention.

[0108] (Device) The fertilizer was coated using a spray coating technique with a small fluidized bed coater, as shown in Figure 1.

[0109] (raw materials) The raw materials used in the examples and comparative examples will be described below. (Alkoxysilane condensate) MS-51 (manufactured by Mitsubishi Chemical): In chemical formula (2), R is a methyl group, and it is an average pentamer compound with a weight-average molecular weight of 800 to 1,000. (Resin containing OH groups) PVA: Modified and unmodified PVA were used. The average degree of polymerization was 400-500, and the degree of saponification was in the range of 39.0 mol% to 100 mol%. As unmodified PVA, we used NK-05R (manufactured by Mitsubishi Chemical Corporation) with a saponification degree of 71.0-75.0 mol% and an estimated average degree of polymerization of 500, GL-03 (manufactured by Mitsubishi Chemical Corporation) with a saponification degree of 86.5-89.0 mol% and an estimated average degree of polymerization of 400, and NL-05 (manufactured by Mitsubishi Chemical Corporation) with a saponification degree of 98.5 mol or higher and an estimated average degree of polymerization of 500. Furthermore, poly(oxyethylene) modified PVA was used as the modified PVA. The degree of saponification was 3 LW-100 (manufactured by Mitsubishi Chemical), which is 9.0 to 46.0 mol% and has an unpublished average degree of polymerization, was used. A product that is usually sold in an aqueous solution form and replaced with a methanol solvent was used. The replacement method used a rotary evaporator (manufactured by Büchi K.K.) to perform distillation under reduced pressure in a hot water bath at 90 °C to remove water, and after cooling, the remaining solid content was dissolved and diluted with methanol (manufactured by Fujifilm Wako Pure Chemical Corporation) to achieve the target solid content concentration. Hydroxypropyl cellulose (hereinafter, HPC): NISSO HPC SSL normal particle products (average particle size 150 to 190 μm) manufactured by Nippon Soda Co., Ltd. were used. The molecular weight determined by GPC is 40,000. Penon PKW: As a modified starch, hydroxypropyl enzyme-modified dextrin manufactured by Nisshin Chemical Co., Ltd. was used. (Third component) Methyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.): From Chemical Formula (1), it has a structure in which R1 and R2 are methyl groups.

[0110] [Example ^{1}] <Preparation of hydrolysis solution of alkoxysilane condensate> 15.4 g of MKC Silicate MS-51 (manufactured by Mitsubishi Chemical), 14 g of methanol, 5.27 g of pure water, and 0.16 g of maleic acid were added and stirred for 5 hours. Then, 46 g of methanol was added and left standing overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 10% in terms of SiO₂. <Preparation of PVA solution> 76.0 g of methanol was added to 19.0 g of pure water, and while stirring, 5 g of polyvinyl alcohol NK-05R (manufactured by Mitsubishi Chemical) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA methanol aqueous solution with a solid content concentration of 5%. <Preparation of composite solution> 7.0 g of the hydrolyzed product of the alkoxysilane condensate was dropped into a container containing 6.0 g of the PVA methanol solution and stirred for 1 hour. As a result, the ratio (SiO₂ / PVA) of the SiO₂ solid content concentration to the PVA solid content concentration in the composite solution was 70 parts by weight / 30 parts by weight.

[0111] [Example 2] <Preparation of hydrolysis solution of alkoxysilane condensate> 13.0 g of MKC Silicate MS-51 (manufactured by Mitsubishi Chemical), 3.6 g of methyltrimethoxysilane (hereinafter, MeTMOS, manufactured by Tokyo Chemical Industry), 23 g of methanol, 6.15 g of pure water, and 0.16 g of maleic acid were added and stirred for 2 hours. Then, 42 g of methanol was added and left standing overnight to obtain a hydrolyzate of an alkoxysilane condensate having a third component with a solid content concentration of 10% in terms of SiO2. <Preparation of composite liquid> 7.0 g of the hydrolyzate of the alkoxysilane condensate having the third component was dropped into a container containing 6.0 g of the PVA methanol solution prepared in [Example 1] and stirred for 1 hour. As a result, the ratio of the SiO2 solid content concentration to the PVA solid content concentration contained in the composite liquid was set to 70 parts by weight / 30 parts by weight.

[0112] [Example 5] <Preparation of hydrolysis solution of alkoxysilane condensate> 15.4 g of MKC Silicate MS-51 (manufactured by Mitsubishi Chemical), 31.2 g of methanol, 3.25 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour. Then, it was left standing overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 20% in terms of SiO2. <Preparation of PVA solution> 47.5 g of methanol was added to 47.5 g of pure water, and 5 g of polyvinyl alcohol GL-03 (manufactured by Mitsubishi Chemical) was added while stirring. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, and a PVA methanol aqueous solution with a solid content concentration of 5% was obtained. <Preparation of composite liquid> 7.0 g of the hydrolyzate of the alkoxysilane condensate was dropped into a container containing 12.0 g of the PVA methanol solution and stirred for 1 hour. As a result, the ratio of the SiO2 solid content concentration to the PVA solid content concentration contained in the composite liquid was set to 70 parts by weight / 30 parts by weight.

[0113] [Example 6] <Preparation of hydrolysis solution of alkoxysilane condensate> 13.0 g of MKC silicate MS-51 (manufactured by Mitsubishi Chemical), 3.6 g of MeTMOS, 28.5 g of methanol, 5.88 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, and then left standing overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 20% in terms of SiO₂. <Preparation of PVA solution> 47.5 g of methanol was added to 47.5 g of pure water, and while stirring, 5 g of polyvinyl alcohol GL-03 (manufactured by Mitsubishi Chemical) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA methanol aqueous solution with a solid content concentration of 5%. <Preparation of composite solution> 7.0 g of the hydrolyzate of the alkoxysilane condensate was dropped into a container containing 12.0 g of the PVA methanol solution and stirred for 1 hour. As a result, the ratio of the SiO₂ solid content concentration to the PVA solid content concentration contained in the composite solution was 70 parts by weight / 30 parts by weight.

[0114] [Example 11] <Preparation of hydrolyzate of alkoxysilane condensate> 15.4 g of MKC silicate MS-51 (manufactured by Mitsubishi Chemical), 31.2 g of methanol, 3.25 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, and then left standing overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 20% in terms of SiO₂. <Preparation of hydroxypropyl cellulose solution> 90 g of methanol was added to a container containing 10.0 g of NISSO HPC SSL (manufactured by Nippon Soda), and stirred at room temperature to dissolve hydroxypropyl cellulose (hereinafter referred to as HPC), obtaining an HPC methanol solution with a solid content concentration of 10%. <Preparation of composite solution> 7.0 g of the hydrolyzate of the alkoxysilane condensate was dropped into a container containing 6.0 g of the HPC methanol solution and stirred for 1 hour. As a result, the ratio of the SiO₂ solid content concentration to the HPC solid content concentration contained in the composite solution was 70 parts by weight / 30 parts by weight.

[0115] [Example 13] <Preparation of Hydrolysis Solution of Alkoxysilane Condensate> 15.4 g of MKC Silicate MS-51 (manufactured by Mitsubishi Chemical), 31.2 g of methanol, 3.25 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, and then allowed to stand overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 20% in terms of SiO2. <Preparation of Modified Starch Solution> 95.0 g of pure water was added to a container containing 5.0 g of Penon PKW (manufactured by Nisshin Chemical), heated to 60 °C, and stirred for 1 hour to dissolve the modified starch, obtaining an aqueous solution of modified starch with a solid content concentration of 5%. <Preparation of Composite Liquid> 7.0 g of the hydrolysis solution of the alkoxysilane condensate was dropped into a container containing 12.0 g of the aqueous solution of modified starch and stirred for 1 hour. As a result, the ratio of the SiO2 solid content concentration to the HPC solid content concentration contained in the composite liquid was 70 parts by weight / 30 parts by weight.

[0116] [Comparative Example 1] <Preparation of Hydrolysis Solution of Alkoxysilane Condensate> 15.4 g of MKC Silicate MS-51 (manufactured by Mitsubishi Chemical), 31.2 g of methanol, 3.25 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, and then allowed to stand overnight to obtain a hydrolyzate of an alkoxysilane condensate with a solid content concentration of 20% in terms of SiO2.

[0117] [Comparative Example 2] <Preparation of PVA Solution> 63.0 g of methanol was added to 27.0 g of pure water, and 10 g of polyvinyl alcohol NK-05R (manufactured by Mitsubishi Chemical) was added while stirring. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA methanol aqueous solution with a solid content concentration of 10%.

[0118] [Comparative Example 3] <Preparation of Hydrolysis Solution of Trimethoxysilane Monomer> ​15.4 g of MeTMOS, 23.1 g of methanol, 6.3 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, then left standing overnight to obtain a hydrolyzate of methyltrimethoxysilane with a solid content concentration of 20% in terms of SiO₂. <Preparation of Composite Liquid> 7.0 g of the hydrolysis condensate of MeTMOS was dropped into a container containing 12.0 g of the PVA methanol solution prepared in [Example 1] and stirred for 1 hour. As a result, the ratio of the SiO₂ solid content concentration to the PVA solid content concentration in the composite liquid was set to 70 parts by weight / 30 parts by weight.

[0119] [Comparative Example 4] <Preparation of PVA Solution> 5 mL of 0.1 mol nitric acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 20.2 g of pure water were added to a container, and 3.4 g of PVA (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., average degree of polymerization 500, saponification degree 86 - 90 mol%) was added while stirring. After stirring at room temperature for about 15 minutes, the temperature was raised to 60 °C and heated for 1 hour. <Preparation of Alkoxysilane Solution> 7.8 g of tetraethoxysilane (manufactured by Tama Chemicals, hereinafter referred to as TEOS. In chemical formula (2), R is an ethyl group and it has no repeating structure, that is, a compound with n = 1.), 2.3 g of methyltriethoxysilane (manufactured by Kishida Chemical Co., Ltd., hereinafter referred to as MeTEOS), and 3.2 g of methanol were added and stirred at room temperature for 1 hour. Thereby, an alkoxysilane mixed solution was prepared. <Preparation of Alkoxysilane / PVA Mixed Solution> The entire amount of the prepared alkoxysilane mixed solution was dropped into a container containing the entire amount of the prepared PVA solution while stirring the PVA solution. After stirring for 3 hours after the dropping was completed, it was further stirred at room temperature overnight. Thereby, an alkoxysilane / PVA mixed solution with a ratio of the SiO₂ solid content concentration to the PVA solid content concentration of 50 parts by weight / 50 parts by weight was prepared.

[0120] Other examples and comparative examples were prepared with the compositions shown in Table 1. [[ID=​Examples 8 to 10, and Example 14 were carried out according to the composition in Table 1 and the preparation procedure in Example 5. [Example 12] was carried out according to the composition in Table 1 and the preparation procedure of [Example 11].

[0121] [Table 1]

[0122] The prepared solutions prepared in [Example 1] to [Example 14] and [Comparative Example 1] to [Comparative Example 4] were used. Next, a coating for the moisture permeability test was formed using the method described below, the film thickness was confirmed, and the moisture permeability test was conducted.

[0123] <Formation of membrane for moisture permeability testing> The coating method used varied depending on the substrate. Spin coating was used when using PET (Toray Industries, Lumirror T60, 25 μm thick), while bar coating was used when using PBS substrates (Mitsubishi Chemical Industries, 30 μm thick).

[0124] <Spin Coating> A 10cm square circuit board was fixed to the base of a spin coater (Mikasa MS-150), and 5mL of solution was added to the center of the board. The lid was closed and the machine was rotated at 750rpm for 45 seconds. After completion, the board was removed from the base, placed on heat-resistant paper, and the corners were secured with heat-resistant tape. It was then placed in a forced-air constant-temperature incubator (Yamato Scientific DKN-400) set to 80°C and heated for 1 hour, after which it was heated for a specified time in a forced-air constant-temperature drying oven (Tokyo Rikakikai WFO-510) set to 105°C. In [Comparative Example 4], after heating to 80°C, the food was heated in a microwave oven (Yamazen, YRB-177, 60Hz) at 500W for 10 minutes.

[0125] <Bar coating> A circuit board cut to 15 cm vertically and 10.5 cm horizontally was secured to heat-resistant paper with cellophane tape. It was placed on a horizontal stand, and the composite liquid was poured onto the top of the circuit board. A wire bar (manufactured by Mitsui Electric Precision Co., Ltd., No. 18) was placed on top of the composite liquid, and after the entire bar was soaked in the liquid, the bar was pulled down to the bottom of the circuit board to coat it. The circuit board, along with the heat-resistant paper, was placed in a forced-air constant-temperature incubator set to 80°C and heated for 1 hour, and then heated in a forced-air constant-temperature drying oven set to 105°C for a specified time.

[0126] <Film thickness measurement> The coating thickness on the obtained coated substrates was confirmed. For substrates coated using the bar coating method, a laser microscope (Keyence) was used to remove the cellophane tape that had been used to fix the substrate, and the difference in height between the uncoated and coated areas was measured to confirm the coating thickness. For substrates coated using the spin coating method, the coating thickness was measured using a film thickness measurement system (Filmetrics, F20). Table 2 shows the conditions under which the coated substrates were fabricated and the thickness of the coating film.

[0127] [Table 2]

[0128] <Moisture Permeability Test> Using the obtained coating substrate, a moisture-permeable cup (manufactured by Yasuda Seiki) was prepared in accordance with JIS Z 0208, and tested in an environmental testing chamber (SH-641, ESPEC) set to 25°C and 90% RH. The details of the test are in accordance with JIS Z 0208.

[0129] After calculating the water vapor permeability in accordance with JIS Z 0208, the water vapor permeability of the individual membrane was calculated using the formula shown below.

number

[0130] The results of the moisture permeability test are shown in Table 3. The symbols for moisture permeability in each table mean the following evaluation results. A: Moisture permeability less than 200 g / m 2 ·day B: Moisture permeability of at least 200 g / m 2 ·day and less than 500 g / m 2 ·day C: Moisture permeability of at least 500 g / m 2 ·day and less than 1,000 g / m 2 ·day [[ID=2L]]D: Moisture permeability of at least 1,000 g / m 2 ·day or more

[0131] [[ID=Z8]]

Table 3

[0132] From the examples, the coating material for fertilizers composed of a resin having an OH group and a hydrolyzate of an alkoxysilane condensate showed low moisture permeability. From [Comparative Example 1] and [Comparative Example 2], it can be seen that the moisture permeability is high with only the hydrolyzate of the alkoxysilane condensate or only the resin having an OH group, and from [Comparative Example 3] and [Comparative Example 4], it can be understood that a coating material for fertilizers with low moisture permeability cannot be obtained with the hydrolyzate of an alkoxysilane.

[0133] [Example 15] <Preparation of silicate hydrolysis solution> 15.4 g of MKC silicate MS-51 (manufactured by Mitsubishi Chemical), 31.2 g of methanol, 3.25 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, and then left standing overnight to obtain a silicate hydrolysis solution with a solid content concentration of 20% in terms of SiO2. <Preparation of PVA aqueous solution> 47.5 g of methanol was added to 47.5 g of pure water, and 5.0 g of polyvinyl alcohol GL-03 (manufactured by Mitsubishi Chemical, average degree of polymerization 400, saponification degree 86.5 - 89.0 mol%) was added while stirring. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, and a PVA methanol aqueous solution with a solid content concentration of 5% was obtained. <Preparation of compound solution> 24.0 g of PVA methanol aqueous solution was mixed with 14.0 g of silicate hydrolysis solution. The ratio of SiO2 solid content concentration to PVA solid content concentration was 70% by weight / 30% by weight. <Coating> 20.0 g of urea was placed in a small fluidized bed coater (Figure 1). A blow-up gas (air) was circulated at 170 NL / min, and the temperature inside the coater was set to 80°C. After confirming that the temperature had reached the target value, a spray gas (nitrogen) was circulated at 7.0 NL / min, and the composite solution was delivered at 0.28 g / min to perform coating. After 48 minutes, the delivery of the composite solution was stopped. After stopping, the coating was dried in the coater for 15 minutes at a constant temperature. After lowering the temperature inside the coater to below 40°C, the blow-up gas and spray gas were stopped, and the coated urea was removed. <Heating (drying) the coating> Coated urea was heated in a constant-temperature forced-air dryer (manufactured by ADVANTEC) at 90°C for 96 hours to obtain coated granular fertilizer.

[0134] [Example 16] A composite solution was obtained in the same manner as in Example 15, except that 32 g of PVA methanol aqueous solution was mixed with 12 g of silicate hydrolysis solution. The ratio of the SiO2 solid content concentration to the PVA solid content concentration of the composite solution was 60% by weight / 40% by weight. The procedure was the same as in Example 15, except that 15.4 g of the composite solution was delivered at 0.28 g / min for 55 minutes. In this method, urea was coated with a compound solution and the coated urea was heated to obtain coated granular fertilizer.

[0135] [Example 17] 27 g of pure water was mixed with 63 g of methanol, and while stirring, 10 g of polyvinyl alcohol NK05R (manufactured by Mitsubishi Chemical) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 60°C and stirred for 1 hour to dissolve the PVA, obtaining a PVA methanol aqueous solution with a solid content of 10%. A composite solution was obtained by mixing 16.0 g of PVA methanol aqueous solution with 12.0 g of silicate hydrolysis solution. The ratio of SiO2 solid content concentration to PVA solid content concentration was 60% by weight / 40% by weight. Except that 9.8 g of the composite liquid was fed at 0.28 g / min for 35 minutes, coating on urea and heating of the coated urea were carried out with the composite liquid in the same manner as in Example 15 to obtain coated granular fertilizer.

[0136] [Comparative Example 5] [Preparation of PVA Aqueous Solution] 27.0 g of methanol was added to 63.0 g of pure water, and while stirring, 10.0 g of polyvinyl alcohol NK-05R (manufactured by Mitsubishi Chemical, average degree of polymerization 500, saponification degree 71.0 - 75.0 mol%) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA methanol aqueous solution with a solid content concentration of 10%. 30.0 g of distilled water was mixed with 40.0 g of this PVA methanol aqueous solution and diluted to a 5.7% PVA methanol aqueous solution.

[0137] [Coating] 20.0 g of urea was placed in a small fluidized bed coater (Figure 1). Dry gas (total air) was circulated at 170 NL / min, and the temperature inside the coater was set to 80 °C. After confirming that the temperature reached the target value, spray gas (nitrogen) was circulated at 7.0 NL / min, and the PVA methanol aqueous solution was fed at 0.28 g / min for coating. After 89 minutes, the feeding of the composite liquid was stopped. After the feeding was stopped, it was dried in the coater for 15 minutes while maintaining a constant temperature. After lowering the temperature inside the coater to 40 °C or below, the dry gas and spray gas were stopped and the urea was taken out. [Heating and Drying of the Coating Film] The coated urea was heated at 90 °C for 96 hours in a constant temperature air blower dryer (manufactured by ADVANTEC) to obtain coated granular fertilizer.

[0138] [Comparative Example 6] [Preparation of PVA / Silica Aqueous Solution] 27.0 g of methanol was added to 63.0 g of pure water, and while stirring, 10.0 g of polyvinyl alcohol NK-05R (average degree of polymerization 500, saponification degree 71.0 - 75.0 mol%) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 60 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA methanol aqueous solution with a solid content concentration of 10%. 21.0 g of this PVA methanol aqueous solution 4.9 g of silicon dioxide (Kanto Chemical Co., Ltd.: precipitated, amorphous, powder) and 25.0 g of distilled water were mixed to achieve a ratio of SiO2 solid content concentration to PVA solid content concentration of 70% by mass / 30% by mass.

[0139] <3D coating> 20.0 g of urea was placed in a small fluidized bed coater (Figure 1). Drying gas (air) was circulated at 170 NL / min, and the temperature inside the coater was set to 80°C. After confirming that the temperature had reached the target value, spray gas (nitrogen) was circulated at 7.0 NL / min, and a PVA methanol aqueous solution was delivered at 0.28 g / min to perform coating. After 37 minutes, the flow of the composite solution was stopped. After stopping the flow, the material was dried inside the coater for 15 minutes at a constant temperature. After lowering the temperature inside the coater to below 40°C, the drying gas and spray gas were stopped, and the urea was removed.

[0140] <Dissolution Test> 1 g of coated urea and 200 mL of pure water were placed in a 250 mL container and left to stand in an incubator at a constant temperature (30°C). After 24 hours, the urea nitrogen concentration in the water was measured. The urea concentration was measured as follows: 50 mL of hydrochloric acid, 250 mL of ethanol, and 700 mL of pure water were mixed, and 2.5 g of p-dimethylaminobenzaldehyde was dissolved to prepare a reaction solution. 6 mL of the reaction solution and 0.5 mL of urea eluate were mixed and left to stand for 30 minutes. The absorbance at 420 nm was then measured using a spectrophotometer. A calibration curve was created using urea aqueous solutions of known concentrations, and the urea concentration was determined from the absorbance.

[0141] <Measurement of initial floating particle count> Twenty coated urea particles were placed in a petri dish, and pure water was poured in at a rate of 10 mL / min along the side of the dish. After 50 mL of water had been added, the number of particles floating on the surface was measured.

[0142] The obtained coated granular fertilizer was analyzed according to the elution test and floating particle count measurement described above. The results are shown in Table 4.

[0143] [Table 4]

[0144] <Dissolution test> In [Example 15] to [Example 17] of the coated granular fertilizer of the present invention, dissolution was suppressed as compared with [Comparative Example 5] and [Comparative Example 6]. In [Comparative Example 5] and [Comparative Example 6], after the start of the dissolution test, the coating film dissolved and disappeared, and accordingly, urea also dissolved, and it completely dissolved 5 minutes after the start of the test and the shape of the fertilizer disappeared.

[0145] <Initial floating granule number> In the measurement of the initial floating granule number, there were no granular fertilizers that initially floated in [Example 15] to [Example 17]. [Comparative Example 5] and [Comparative Example 6] dissolved during the measurement and could not be measured.

[0146] <Measurement of coating rate> In the measurement of the coating rate, [Example 15] to [Example 17] had a coating rate of 6.5%. In [Comparative Example 5] and [Comparative Example 6], the coating film was water-soluble and the coating rate could not be measured.

[0147] Thus, it is clear that the coated granular fertilizer of the present invention maintains the film shape even in water and suppresses the dissolution of the fertilizer components of the coated fertilizer. In addition, the coating film does not cause a problem of initial floating, and the coating film shell after use is difficult to escape from the field. Furthermore, since the coating film shell residue is composed of a biodegradable resin and a silica component with no environmental load, it can be used as a coated granular fertilizer with no environmental load due to residual coating films such as microplastics remaining.

[0148] <Confirmation of Si-O-C bond by FT-IR> The coated urea of [Example 16] and [Comparative Example 5] obtained was measured by FT-IR. Using an FT-IR device iN10MX (manufactured by Thermo Fisher Scientific), the measurement was performed as follows, and the obtained spectrum was analyzed and peak-separated according to the following conditions using the company's analysis software OMINIC (Version.8.3.103). Measurement method) ATR method Shape of measurement sample) Coated urea Prism) Diamond prism (Total number of times) 64 times resolution)4cm-1 (Background correction) Before sample measurement Phase correction) Mertz method (Spectral intensity) Absorbance Baseline Correction) Auto Baseline Correction Smoothing) Auto Smoothing Peak detection: Distribution function) Voigt function Peak detection: Peak detection sensitivity) Low sensitivity Peak detection: (FWHM) 3.857~10 Peak fitting: Noise) 5 Peak fitting (baseline correction): 1st-order (linear) interpolation Peak fitting: (Iterative calculation) Calculation continues until the standard deviation is 1.0 or less.

[0149] <solution 1 H NMR measurement> The coated urea obtained in [Example 16] was in a solution 1 Measurements were taken using 1H NMR. The coated urea prepared in [Example 16] was placed in water and left at room temperature for 3 days. Note that in [Comparative Example 5], the film eluted into the water, so no sample could be obtained. 1 We were unable to proceed to 1H NMR measurement. The sample from which urea had eluted was removed and washed with suction filtration and distilled water. After drying at 100°C for 5 minutes, it was washed again with distilled water, the washing solution was filtered by suction, and it was washed again with distilled water. After drying at 100°C for 5 minutes, 0.050 g of the obtained coating film was added to a 9 mL screw tube, and then 1 drop of DMF as a reference substance was added, and the total volume was diluted with DMSO-d6 solvent to 1.0 g. After shaking the screw tube well to elute unreacted PVA in the film, the sample was placed in an NMR tube until the liquid level was 4 cm above the bottom of the tube. The prepared sample was measured using an NMR spectrometer ECZ-400 (JEOL Ltd.). The measurement conditions were as follows. Magnetic field strength: 9.425T Proton resonance frequency: 400MHz (Number of times totaled) 8 times RD) 20sec

[0150] The obtained spectra were processed using the company's software Delta (Version 5.3.1 or later) to correct for baseline height and phase. Then, the integrated value of the signal of DMF (reference material) (δ = 7.95 ppm) was set to 100, and the normalized integrated value of the peaks attributable to the OH groups of PVA was calculated.

[0151] The elution rate of the membrane into water was confirmed using the composite solutions used in several examples and comparative examples. <Fabrication of individual membranes> 5 to 10 g of the composite solution was added to a 5 cm diameter PTFE petri dish (manufactured by AS ONE) according to its viscosity, and spread evenly throughout the petri dish. For [Example 18], [Example 19], and [Comparative Example 7], the samples were heated at a predetermined temperature for a set time using a forced-air constant-temperature incubator according to Table 5. The resulting films were removed, placed in a container, water was added until the films were submerged, and the container was left at room temperature for at least 3 days. The prepared samples are shown in Table 6.

[0152] [Table 5]

[0153] Using a 10mL plastic disposable syringe (made by AS ONE), draw up 10mL of the solution, and 5 A 15 mL magnetic crucible (made by AS ONE) is fed through a syringe filter with a μm pore size. The solvent was placed in a Wang-made container. The solvent was evaporated over 4 hours using a forced-air constant-temperature incubator set to 120°C. After cooling to room temperature, the weight of the magnetic crucible was measured. FT-IR measurements and solutions of the obtained [Example 16] and [Comparative Example 5] 1 The results of the 1H NMR are shown in Table 6.

[0154] [Table 6]

[0155] Thus, it can be seen that a Si-OC bond was formed in [Example 16], while a Si-OC bond was not formed in [Comparative Example 5].

[0156] Table 7 shows the membrane elution rates obtained for [Example 18], [Example 19], and [Comparative Example 7]. The membrane elution rate was calculated by determining the total weight of eluted PVA in the solution used from the concentration of eluted PVA obtained by evaporation, and then calculating the amount of eluted relative to the weight of the membrane used in the test.

[0157] [Table 7]

[0158] From [Example 18] and [Example 19], it can be seen that the rate of film elution is eliminated by including a heating step for a predetermined time, while from [Comparative Example 7], it can be seen that a PVA film without Si-OC bonds is eluted. This suggests that the OH groups in the hydrolysis product of the alkoxysilane condensate react with the resin containing OH groups to form Si-OC bonds.

[0159] [Comparative Example 8] <Preparation of pre-coated urea> 400.0 g of granular urea was placed in the fluidized bed shown in Figure 1. A blow-up gas (air) was circulated at 1000 NL / min, and the temperature inside the fluidized bed was set to 60°C. After confirming that the temperature had reached the target value, BioPBS was used. TM Pre-coating was performed by supplying a trichloroethylene solution containing FZ71 (manufactured by Mitsubishi Chemical Corporation) at a concentration of 3% by weight at a rate of 50 g / min. After 16 minutes, the supply of the composite solution was stopped. After stopping the supply, the material was dried in a fluidized bed for 15 minutes at a constant temperature. After lowering the temperature in the fluidized bed to below 40°C, the blow-up gas and spray gas were stopped, and the material was removed. The material was heated in a constant temperature forced-air dryer (manufactured by ADVANTEC) at 105°C for 48 hours to obtain pre-coated urea.

[0160] [Example 20] <Preparation of silicate hydrolysate> 13.0 g of MKC silicate MS-51 (manufactured by Mitsubishi Chemical), 28.5 g of methanol, 3.6 g of MeTMOS, 5.88 g of pure water, and 0.16 g of maleic acid were added and stirred for 1 hour, then left standing overnight to obtain a silicate hydrolysis solution with a solid content concentration of 20% in terms of SiO₂. <Preparation of PVA Aqueous Solution> While stirring 95.0 g of pure water, 5.0 g of polyvinyl alcohol NL-05 (average degree of polymerization 500, saponification degree 98.5 mol% or more) was added. After stirring at room temperature for 15 minutes, the temperature was raised to 90 °C and stirred for 1 hour to dissolve PVA, obtaining a PVA aqueous solution with a solid content concentration of 5%.

[0161] <Preparation of Composite Liquid> 4.2 g of the silicate hydrolysis solution was mixed with 11.2 g of the PVA aqueous solution. The ratio of the SiO₂ solid content concentration to the PVA solid content concentration was set to 60 wt% / 40 wt%. <Coating> 20.0 g of the pre-coated urea obtained in Comparative Example 3 was placed in a small fluidized bed coater (Figure 2). The blowing gas (air) was circulated at 170 NL / min, and the temperature inside the coater was set to 90 °C. After confirming that the temperature reached the target value, the spraying gas (nitrogen) was circulated at 7.0 NL / min, and the composite liquid was fed at 0.23 g / min for coating. After 68 minutes, the feeding of the composite liquid was stopped. After the feeding was stopped, it was dried in the coater at a constant temperature for 15 minutes. After lowering the temperature inside the coater to 40 °C or below, the blowing gas and spraying gas were stopped, and the coated granular urea was taken out. <Heat Treatment> The coated urea was heated at 105 °C for 48 hours in a constant temperature air dryer (manufactured by ADVANTEC) to obtain coated granular fertilizer. <Initial Floating Rate> In the same manner as the above urea dissolution rate and initial floating rate, the urea dissolution rate and initial floating rate of the coated granular fertilizers according to Example B and Comparative Example B were measured. <Amount of Membrane> Also, based on the following formula, the amounts (coating rates) of the precoat film and the coating material film for fertilizers were calculated using the following formula. Precoat film [wt%] = (weight of precoat material / weight of pre-coated core material) × 100 Coating material film for fertilizer [wt%] = (weight of coating material / weight of coated granular fertilizer) × 100

[0162]

Table 8

[0163] When the coating material film for fertilizer according to the embodiment of the present invention is overcoated on urea pre-coated with PBS, it can be seen that the release of urea as a fertilizer component is effectively suppressed. Fig. 3 is a scanning electron microscope (SEM photograph) of urea coated with PBS in Comparative Example 8, and defects were observed on the film surface. From the SEM photograph of Example 20 in Fig. 4, it can be seen that the defects are filled by the coating material film for fertilizer. Although no elution suppression was possible at all in Comparative Example 8, by overcoating the pre-coated urea with a film made of the coating material for fertilizer, it was found that the elution period was further delayed compared to the coating material film for fertilizer alone, and the elution control effectively appeared. Thus, when the overcoating of the coating material film for fertilizer according to the embodiment of the present invention is combined with the precoat film, elution suppression can be obtained more effectively, and the floating suppression effect is also good.

Explanation of reference numerals

[0164] 10 Small fluidized bed coater 1 Spray gun 2 Nozzle[[ID=B]] 3 Urea granules 4 Blowing gas 5 Exhaust 20 Coater 21 Fluidized bed 22 Two-fluid spray nozzle 23 Particles 24 Blower 25 Heater 26 Hot air 27 Exhaust 28 Dissolution tank 29 Spray liquid

Claims

1. A coating material for fertilizers containing a dehydrated condensate of a resin having an OH group and an alkoxysilane condensate, The resin having the OH group comprises at least one selected from the group consisting of polyvinyl alcohol resin, hydroxypropyl cellulose, and modified starch. A coating material for fertilizers, wherein the alkoxysilane condensate contains at least a compound represented by formula (2). 【Chemistry 1】 (However, in formula (2), each of the multiple Rs is independently an alkyl group having 1 to 4 carbon atoms, and n is an integer between 2 and 10.)

2. The Si content in the aforementioned fertilizer coating material is SiO ２ The fertilizer coating material according to claim 1, wherein the weight is 20% or more and less than 95% by weight.

3. The fertilizer coating material according to claim 1 or 2, wherein the resin having the OH group is a polyvinyl alcohol resin.

4. The coating material for fertilizer according to any one of claims 1 to 3, wherein the coating material has a three-dimensional siloxane crosslinking structure derived from an alkoxysilane condensate.

5. The fertilizer coating material according to any one of claims 1 to 4, wherein the alkoxysilane condensate contains two or more types of alkoxysilanes.

6. The fertilizer coating material according to any one of claims 1 to 5, wherein the alkoxysilane condensate comprises at least a compound represented by formula (1). 【Chemistry 2】 (However, in equation (1), multiple R １ Each of these independently represents an alkyl group with 1 to 10 carbon atoms or an aromatic group with 6 to 15 carbon atoms, R ２ (This represents a hydrogen atom, a halogen atom, or a monovalent organic group.)

7. The fertilizer coating material according to claim 6, wherein the compound represented by formula (1) is methyltrimethoxysilane.

8. A coated granular fertilizer coated with a film made of the coating material described in any one of claims 1 to 7, wherein the content of the film formed of the coating material is 1% by mass or more and 20% by mass or less in 100% by mass of the coated granular fertilizer.

9. The coated granular fertilizer according to claim 8, wherein a precoat layer is further provided between the fertilizer and the membrane.

10. The aforementioned precoat layer is made of polyvinyl alcohol resin, starch, cellulose, lignin, chitin, chitosan, PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), PBAT (polybutylene aditate terephthalate), PCL (poly Licaprolactone, starch polyester, cellulose acetate, PHB (polyhydroxy The coated granular fertilizer according to claim 9, comprising a biodegradable resin selected from the group consisting of butyrate, PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PLA (polylactic acid), PGA (polyglycolic acid), PDO (polydioxanone) and copolymers thereof.

11. A method for producing coated granular fertilizer, comprising the steps of mixing a solution containing an alkoxysilane condensate with a solution containing a resin having an OH group, spraying the resulting coating solution onto the fertilizer, and drying it. The resin having the OH group comprises at least one selected from the group consisting of polyvinyl alcohol resin, hydroxypropyl cellulose, and modified starch. A coating material for fertilizers, wherein the alkoxysilane condensate contains at least a compound represented by formula (2). 【Transformation 3】 (However, in formula (2), each of the multiple Rs is independently an alkyl group having 1 to 4 carbon atoms, and n is an integer between 2 and 10.)

12. A method for producing coated granular fertilizer according to claim 11, comprising a heating process at 140°C or lower during or after the drying process.

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