Layer-forming materials and covering structures

Abstract

The present invention provides a layer-forming material that exhibits a sigmoid curve of sustained release. [Solution] The layer-forming material of the present invention is a layer-forming material comprising an ion crosslinking material and an environmentally degradable tree, wherein the ion crosslinking material comprises at least one of an ion crosslinkable polymer, an ion crosslinking agent, and a crosslinked product of an ion crosslinkable polymer and an ion crosslinking agent, and the change in the urea elution rate in the layer-forming material over time, measured by a predetermined procedure, exhibits a sigmoid curve.

Description

[Technical Field]

[0001] This invention relates to a layer-forming material and a coating structure. [Background technology]

[0002] Various developments have been made regarding layer-forming materials. As an example of this type of technology, the technology described in Patent Document 1 is known. Patent Document 1 describes a coated granular fertilizer having a structure in which a blend layer made by blending different resins, such as biodegradable polyester and polyolefin (thermoplastic resin), is coated with a protective layer containing polyolefin that contains one or more substances that promote the oxidative decomposition reaction of polymers. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-194280 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, our inventors' investigations revealed that, since environmentally degradable resins alone often do not provide sufficient sustained release properties, the change in elution rate over time exhibits a linear curve. [Means for solving the problem]

[0005] Further investigations by the present inventors revealed that by combining an ion-crosslinkable polymer, an ion-crosslinking agent, and at least one of the crosslinked products of the ion-crosslinkable polymer and the ion-crosslinking agent with an environmentally degradable tree, the change in elution rate over time in the layer-forming material containing these materials exhibits a sigmoid curve, thus completing the present invention.

[0006] According to one aspect of the present invention, the following layer-forming material and coating structure are provided.

[0007] Examples of reference formats are provided below. 1. A layer-forming material comprising an ion-crosslinked material and an environmentally degradable tree, The ion-crosslinking material comprises at least one of an ion-crosslinkable polymer, an ion-crosslinking agent, and a crosslinked product of the ion-crosslinkable polymer and the ion-crosslinking agent. A layer-forming material in which the change in urea elution rate over time, measured by the procedure described below, exhibits a sigmoid curve that satisfies either condition (i) or condition (ii) below. Condition (i): The test film thickness is 100 μm, and the time required to reach a urea elution rate of 10% by mass under 35°C water immersion conditions is between 2 days and 55 days. Condition (ii): The test film thickness is 50 μm, and the time required to reach a urea elution rate of 10% by mass under 25°C water immersion conditions is between 1 day and 130 days. (procedure) The layer-forming material is molded to produce a film. The film is punched out to form a circle with a diameter of 15 mm to obtain a test film of a predetermined thickness. Height 1mm, diameter 10mm, volume approximately 78mm 3 The test film is placed on the top and bottom surfaces of the cylindrical urea tablet, and the sides of the urea tablet are fixed with a ring-shaped silicone rubber to produce an evaluation sample. At room temperature (25°C) and atmospheric pressure, the obtained evaluation sample is immersed in water at a predetermined temperature in a polypropylene container. Immediately after immersion, the absorbance of the water at a wavelength of 450 nm is measured over time using an absorbance meter, and the urea elution rate (mass%) is calculated using a calibration curve. 2. The layer-forming material described in 1., A layer-forming material in which the content of the ion crosslinking material is 0.1% by mass or more and less than 20% by mass of 100% by mass of the layer-forming material. 3. A layer-forming material as described in 1. or 2., A layer-forming material in which the total content of the ion-crosslinkable polymer and the ion-crosslinking agent is 0.1% by mass or less of 12% by mass of the layer-forming material. 4. A layer-forming material described in any one of 1. to 3., Contains inorganic fillers, A layer-forming material wherein the inorganic filler comprises one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate. 5. The layer-forming material described in 4. A layer-forming material in which, when the content (mass%) of the ion-crosslinkable polymer contained in the layer-forming material is W1 and the content (mass%) of the inorganic filler is W2, the ratio W1 / W2 is 0.01 or more and 2 or less. 6. A layer-forming material described in any one of 1. to 5., The ion-crosslinkable polymer includes a powdered ion-crosslinkable polymer, A layer-forming material in which the average value of the average width, calculated by dividing the sum of the average values ​​of the maximum width and the average values ​​of the minimum width by 2, using the maximum width and minimum width of each particle contained in the powdered ion-crosslinkable polymer, is 0.01 μm or more and 50 μm or less. 7.6. The layer-forming material described above, A layer-forming material comprising one or more particles having a shape selected from the group consisting of spherical, flattened, fibrous, polyhedral, crushed, and irregular shapes, in which the powdered ion-crosslinkable polymer is. 8. A layer-forming material described in any one of 1. to 7., The ion-crosslinkable polymer comprises at least one of the following components (A) and (B): If the ion-crosslinkable polymer contains the following component (A), the ion-crosslinking agent contains one or more selected from the group consisting of the following components (B), (C), and (D): When the ion-crosslinkable polymer contains the following component (B), the ion crosslinking agent is a layer-forming material containing one or more selected from the group consisting of the following components (A), component (C), and component (D). (A) A polyanion having a monovalent or polyvalent anionic group, or a salt containing the polyanion (B) A polycation having a monovalent or polyvalent cationic group, or a salt containing the polycation (C) An inorganic cation having a monovalent or polyvalent cation, or a salt containing one or more of the inorganic cations (D) An anion monomer having a monovalent or polyvalent anionic group, or an acid containing the anion monomer 9. The layer-forming material according to any one of 1. to 8., The layer-forming material contains one or more hydrophobic substances selected from the group consisting of wax, fats and oils, and fatty acids. 10. The layer-forming material according to any one of 1. to 9., The layer-forming material is used to form a layer on the surface of a coating target containing an agricultural active ingredient. 11. A coating target and A layer covering at least a part of the surface of the coating target, and The coating structure in which the layer contains a layer formed of the layer-forming material according to any one of 1. to 10. 12. The coating structure according to 11., The coating target contains an agricultural active ingredient, the coating structure.

Advantages of the Invention

[0008] According to the present invention, a layer-forming material showing sustained release of a sigmoid curve and a coating structure using the same are provided.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic cross-sectional view showing an example of the configuration of an apparatus for evaluating sustained release.

Embodiments for Carrying Out the Invention

[0010] The outline of the layer-forming material of this embodiment will be described.

[0011] The layer-forming material of this embodiment is a resin composition comprising an ion-crosslinking material and an environmentally biodegradable resin. In this layer-forming material, The ion crosslinking material comprises at least one of an ion crosslinkable polymer, an ion crosslinking agent, and a crosslinked product of the ion crosslinkable polymer and the ion crosslinking agent. A layer-forming material in which the change in urea elution rate over time, measured by the procedure described below, exhibits a sigmoid curve that satisfies either condition (i) or condition (ii) below. Condition (i): The test film thickness is 100 μm, and the time required to reach a urea elution rate of 10% by mass under 35°C water immersion conditions is between 2 days and 55 days. Condition (ii): The test film thickness is 50 μm, and the time required to reach a urea elution rate of 10% by mass under 25°C water immersion conditions is between 1 day and 130 days.

[0012] (Procedure for determining urea elution rate) The layer-forming material is molded to produce a film. The film is punched out to form a circle with a diameter of 15 mm to obtain a test film of a predetermined thickness. Height 1mm, diameter 10mm, volume approximately 78mm 3 The test film is placed on the top and bottom surfaces of the cylindrical urea tablet, and the sides of the urea tablet are fixed with a ring-shaped silicone rubber to produce an evaluation sample. At room temperature (25°C) and atmospheric pressure, the obtained evaluation sample is immersed in water at a predetermined temperature in a polypropylene container. Immediately after immersion, the absorbance of the water at a wavelength of 450 nm is measured over time using an absorbance meter, and the urea elution rate (mass%) is calculated using a calibration curve.

[0013] According to the inventors' findings, by adjusting the blending ratio of ion-crosslinking material to environmentally degradable tree, the sustained-release characteristics of the layer-forming material can be appropriately controlled, and a layer-forming material exhibiting a sigmoid curve in the time-dependent change in urea elution rate can be realized. The detailed mechanism is not clear, but it is presumed to be as follows. Many environmentally degradable trees exhibit very little urea elution. Therefore, when a layer consisting solely of environmentally degradable trees is used, the change in urea elution rate over time shows a senior-type curve. In contrast, by utilizing the hygroscopic properties of ion-crosslinked materials and adjusting the blending ratio of these materials, it is inferred that the change in urea elution rate over time in the layer containing the environmentally degradable resin and ion-crosslinked materials will initially show little or no change, but after a predetermined period, it will change sharply (the urea elution rate will increase), thus exhibiting a sigmoid curve.

[0014] Furthermore, when inorganic fillers are added, factors such as decreased water permeability (which lengthens the sustained release inhibition period) and decreased tensile elongation (which shortens the sustained release inhibition period) complicate the elution mechanism. However, it was found that the sustained release inhibition period (for example, the time to reach 10% by mass of urea elution rate) generally tends to be shortened. Therefore, in layer-forming materials containing inorganic fillers, the sustained release suppression period can be controlled to be extended by adjusting the blending ratio of the ion crosslinking material, thereby achieving a sigmoid-shaped curve of sustained release.

[0015] In this specification, the time required to reach a 10% by mass urea elution rate by water immersion test is defined as T 10 (Japan) Condition (i): T 10 However, it is between 2 days and 55 days, preferably between 3 days and 53 days, and more preferably between 10 days and 50 days. Condition (ii): T 10 However, it is between 1 day and 130 days, preferably between 2 days and 100 days, and more preferably between 3 days and 80 days. Condition (i) in the water immersion test is an accelerated test condition with a higher temperature than condition (ii), and it is possible to measure the time to reach 80% by mass of urea elution rate in a relatively short time. However, by making the test film thicker, it is possible to measure the time to reach 10% by mass of urea elution rate for a relatively longer period. Even if the conditions of the ion crosslinking material are varied, the T of the evaluation sample 10 Since the fluctuations in the value of are relatively gradual, condition (i) allows for stable evaluation of the sustained release properties of the sigmoid curve. Condition (ii) in the water immersion test adopts conditions in which the test film has become thin, so the time required to reach 10% by mass of urea elution rate can be measured in a relatively short time. However, if the conditions of the ion crosslinked material are varied, T 10 The value of this parameter can sometimes fluctuate considerably.

[0016] The layer-forming material of this embodiment can be used to form a thin layer, and is preferably used as a coating material or a film material, for example.

[0017] The layer-forming material can be used as a coating material to form a coating layer on the surface of the object to be coated. An example of a coating layer may be used to form a resin shell structure that encloses one or more objects to be coated. Furthermore, the coating layer can be used to form resin particles having a hollow structure including an inner layer and an outer layer.

[0018] The coating is preferably applied to a material containing agricultural active ingredients, but is not limited to this, and may also contain other water-soluble ingredients. Examples of other water-soluble ingredients include efficacy ingredients used in pharmaceuticals, cosmetics, foods, etc. Agricultural activating ingredients can be any substance used to promote, accelerate, or protect crops, such as fertilizer components and pesticide components. Furthermore, the coating may include fragrances and pigments. Examples of fragrances include synthetic fragrances, natural essential oils, natural fragrances, and animal and plant extracts. Examples of pigments include those used in paints or inks. Furthermore, examples of materials to be covered include air or other gases that have thermal insulation properties. These may be included individually, or any combination of two or more may be included.

[0019] The coating layer can, for example, gradually release the coated material, such as the water-soluble components mentioned above, to the outside. Furthermore, depending on the requirements of the coated material, the coating layer can adjust the permeability of water, air, and / or carbon dioxide into the interior.

[0020] The layer-forming material of this embodiment will be described in detail below.

[0021] (Environmentally degradable resin) Environmentally biodegradable resins can be used if they are decomposed by microorganisms in nature, such as bacteria, and partially or entirely consist of water and carbon dioxide, thus circulating back into nature. Materials that conform to the biodegradability test in accordance with ISO 14855-2 (JIS K 6953-2) are preferred. Furthermore, known environmentally degradable resins can be used.

[0022] The biodegradable resin may contain one or more biodegradable resins of the same and / or different types.

[0023] Specific examples of environmentally degradable resins include biodegradable plastics, such as polyester resins including aliphatic polyester resins, aromatic aliphatic polyester resins, and polyhydroxyalkanol (PHA) resins, as well as non-polyester resins such as natural polymers. These may be used individually or in combination of two or more. Furthermore, aliphatic polyester resins, aromatic aliphatic polyester resins, and PHA resins may each have raw materials that are partially or entirely derived from biomass, or the raw materials may be derived from petroleum. Environmentally degradable resins may contain one of the following: biomass-derived resins, biomass-derived resins, and natural polymers, or they may contain two or more of these, for example, a biomass-derived resin and a petroleum-derived resin. Aliphatic polyester resins may include, for example, one or more of the following: polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxybutyrate, polycaprolactone (PCL), polybutylene succinate / adipate (PBSA), polyethylene succinate, polymalic acid, polyglycolic acid (PGA), polydioxanone, and poly(2-oxetanone). Aliphatic polyester resins may contain these alone or copolymers containing two or more of these. Aromatic aliphatic polyester resins are polyester resins having both aromatic and aliphatic moieties, and may include one or more of the following: polybutylene succinate / terephthalate (PBST), polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate / terephthalate, polyethylene adipate terephthalate (PEAT), etc. PHA-based resins may include, for example, P3HB-based resins containing polyhydroxyalkanoates and / or 3-hydroxybutyrate units. P3HB-based resins may be polymers containing only 3-hydroxybutyrate units, or copolymers containing repeating units other than 3-hydroxybutyrate units. Specific examples of P3HB-based resins include, for example, poly3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate / 3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), (poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) It may contain one or more of the following: poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (PHB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (PHB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (PHB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalate-co-3-hydroxyhexanoate) (PHB3HV3HH). The natural polymer may include one or more of the following: starch, cellulose, cellulose acetate, cellulose ester resin, starch, esterified starch, chitin, chitosan, gluten, gelatin, zein, soy protein, collagen, keratin, etc. The environmentally degradable resin may include, in addition to the polyester resins mentioned above, an environmentally degradable resin having a main chain containing an ester structure, such as polyamides containing an ester structure in the main chain. In addition to the natural polymers mentioned above, the environmentally degradable resin may also include, as a non-polyester resin, polyvinyl alcohol (PVA), polyamide 4 (PA4), aliphatic polycarbonate (PC), and other biodegradable polycarbonates. Here, the environmentally degradable resin may include the same type of resin from aliphatic polyester resins, aromatic aliphatic polyester resins, and PHA resins, or it may include two or more different types. When different types are included, the environmentally degradable resin may include a combination of aliphatic polyester resin and aromatic aliphatic polyester resin, a combination of aliphatic polyester resin and PHA resin, a combination of aromatic aliphatic polyester resin and PHA resin, or a combination of aliphatic polyester resin, aromatic aliphatic polyester resin and PHA resin. In this case, the PHA resin may include at least P3HB resin, or it may include only P3HB resin. Furthermore, the environmentally degradable resin may contain the polyester resin described above alone, but it may also contain a copolymer of the polyester resin and the non-polyester resin, respectively.

[0024] The lower limit of the content of environmentally degradable resin contained in the layer-forming material is, for example, 10% by mass or more, preferably 12.5% ​​by mass or more, and more preferably 15% by mass or more, out of 100% by mass of the total content of ion-crosslinkable polymer, ion-crosslinking agent, and environmentally degradable resin. On the other hand, the upper limit of the content of environmentally degradable resin contained in the layer-forming material is not particularly limited, but may be 99.9% by mass or less, 99.7% by mass or less, or 99.5% by mass or less, out of 100% by mass of the total content of ion-crosslinkable polymer, ion-crosslinking agent, and environmentally degradable resin.

[0025] (Ion crosslinking material) The ion-crosslinking material may contain at least one of an ion-crosslinkable polymer, an ion-crosslinking agent, and a crosslinked product of an ion-crosslinkable polymer and an ion-crosslinking agent. Specifically, it may contain two types, an ion-crosslinkable polymer and an ion-crosslinking agent, and may not contain a crosslinked product, or it may contain three types, an ion-crosslinkable polymer, an ion-crosslinking agent, and a crosslinked product.

[0026] At least one, preferably two, more preferably three, of the ion-crosslinkable polymer, ion-crosslinking agent, and crosslinked product may be water-soluble. At least one, preferably two, more preferably three, of the ion-crosslinkable polymer, ion-crosslinking agent, and crosslinked product may be untreated for hydrophobicity.

[0027] Ion-crosslinkable polymers are polymers that have ion-crosslinking groups. Ionic crosslinking agents are agents that themselves act as crosslinking sites in ionic crosslinking reactions. The ion-crosslinkable polymer and the ion-crosslinking agent may each consist of one type, or two or more types.

[0028] The ionically crosslinkable polymer exists in powder form at room temperature and atmospheric pressure. The ionic crosslinking agent is in powder or liquid form at room temperature and atmospheric pressure, and is preferably in powder form. Any combination of ion-crosslinkable polymers and ion-crosslinking agents can be used, but powdered ion-crosslinkable polymers and powdered ion-crosslinking agents may be used, or powdered ion-crosslinkable polymers and liquid ion-crosslinking agents may be used.

[0029] Furthermore, the ion-crosslinkable polymer preferably contains at least one of the following components (A) and (B). On the other hand, ionic crosslinking agents are If the ion-crosslinkable polymer contains the following component (A), it is preferable that it also contains one or more components selected from the group consisting of the following components (B), (C), and (D): If the ion-crosslinkable polymer contains component (B) below, it is preferable that it also contains one or more components selected from the group consisting of components (A), (C), and (D) below. (A) Polyanions having monovalent or divalent or more anionic groups, or salts containing such polyanions (B) Polycations having monovalent or divalent or more cationic groups, or salts containing such polycations (C) Inorganic cations having monovalent or divalent or more cations, or salts containing one or more of such inorganic cations. (D) An anionic monomer having a monovalent or divalent or more anionic group, or an acid containing said anionic monomer

[0030] In this specification, the valency in (A), (B), and (D) refers to the valency of a single ionic functional group (ionic dissociation group) contained in the monomer or polymer. To illustrate with an example of ionic functional groups in the side chain of a polymer (macromolecule), carboxylic acids are monovalent, and dicarboxylic acids (oxalic acid, fumaric acid, etc.) are divalent. On the other hand, in the case of the valency in (C), sodium ions are monovalent, and calcium ions are divalent. To explain with specific examples, polyacrylic acid polymers are classified as "polyanions having monovalent anionic groups," while alkylphosphonic acid polymers are classified as "polyanions having divalent anionic groups." Furthermore, in polyacrylic acid, or polymers containing acrylic acid as a component, when acrylic acid forms a calcium salt, it is classified as a "polyanion-containing salt" in which a monovalent anionic group forms a salt with a divalent cation. Furthermore, in polymers containing phosphonic acid as a component, if the phosphonic acid forms a sodium salt, it is classified as a "polyanion-containing salt" in which the divalent anionic group forms a salt with a monovalent cation. Basically, polymers whose main chain has repeating structural units α with anionic groups are called "polyanions" (polymer anions). On the other hand, polymers whose main chain has repeating structural units β with cationic groups are called "polycations" (polymer cations). However, when the main chain of a polymer contains both repeating structural units α and β, a polymer is classified as a "polyanion" if the number of repeating structural units α in one molecule is equal to or greater than the number of repeating structural units β, while a polymer is classified as a "polycation" if the number of repeating structural units β in one molecule is greater than the number of repeating structural units α. Furthermore, substances that have an anionic group but do not have a repeating structural unit α that has an anionic group are referred to as "anionic monomers."

[0031] (A) The "polyanion having monovalent or divalent or more anionic groups" preferably includes one or more polyanions A1 selected from the group consisting of polysaccharides containing at least one of carboxylic acids, sulfonic acids, and phosphoric acids in their molecules, and complex carbohydrates containing polysaccharides. It is preferable that polyanion A1 contains at least one of carboxylic acids or sulfonic acids.

[0032] In this specification, a monosaccharide is a sugar composed of one type of sugar. Examples of sugars include glucose, mannose, galactose, glucosamine, galactosamine, xylose, sialic acid, glucuronic acid, iduronic acid, fucose, maltose, trehalose, and lactose. In this specification, a polysaccharide is a sugar composed of two or more monosaccharides linked by glycosidic bonds. A polysaccharide may be a homopolysaccharide, which has only one type of monosaccharide, or a heteropolysaccharide (sometimes called a complex polysaccharide), which has two or more types of monosaccharides. Furthermore, polysaccharides only need to have a sugar chain (main chain) consisting of repeating structures of constituent units derived from monosaccharides, and functional groups may or may not be formed on the side chains within the sugar chain. Examples of functional groups formed on the side chains include polar functional groups such as carboxyl groups, sulfonic acid groups, amide groups, acetyl groups, acetylamide groups, and amino groups. In this specification, a complex carbohydrate is a complex in which a polysaccharide is covalently bonded with other biocompounds other than sugars, such as proteins, lipids, and peptides. Examples of complex carbohydrates include biomacromolecules such as glycoproteins, proteoglycans, and glycolipids.

[0033] The polysaccharide in polyanion A1 may include one or more selected from the group consisting of, for example, alginic acid, carboxymethylcellulose, carrageenan, homogalacturonan, and glycosaminoglycans. Furthermore, the complex carbohydrate in polyanion A1 may include one or more selected from the group consisting of, for example, hyaluronic acid and chondroitin sulfate.

[0034] In another form, (A) "a polyanion having a monovalent or divalent or more anionic group" may include one or more polyanions A2 selected from the group consisting of ligninsulfonic acid and polyglutamic acid. That is, (A) may include polyanion A1 alone, polyanion A2 alone, or both polyanion A1 and polyanion A2. Furthermore, (A) a salt containing a polyanion having a monovalent or divalent or more anionic group may also include a salt of the polyanion with a monovalent cation, that is, an anionic compound formed by the salt formation of the anionic group of the polyanion with a monovalent cation, and may also include a salt of a polyanion having at least one of polyanion A1 and polyanion A2 with a monovalent cation. (A) The salt containing the polyanion may include one or more selected from the group consisting of sodium ions, potassium ions, ammonium ions, and phosphonium ions as the monovalent cation.

[0035] (B) Examples of "polycations having monovalent or divalent or more cationic groups" include polylysine and chitosan. Furthermore, (B) a salt containing a "polycation having monovalent or divalent or more cationic groups" may also include a salt of the polycation with a monovalent anion, that is, a cationic compound formed by a salt between the cationic groups of the polycation and a monovalent anion. (B) The salt containing the polycation may include, as the monovalent anion, one or more selected from the group consisting of chloride ions, hydroxide ions, fluoride ions, bromide ions, iodide ions, acetate ions, and nitrate ions.

[0036] The inorganic cation having a monovalent cation may include, for example, one or more selected from the group consisting of sodium ions, potassium ions, and ammonium ions. (C) The inorganic cation having a cation of 2 or higher valence may include, for example, one or more selected from the group consisting of calcium ions, magnesium ions, and aluminum ions. (C) A salt containing one or more "inorganic cations having monovalent or divalent or higher cations" may also contain a salt of one or more of those inorganic cations with a monovalent or divalent or higher inorganic anion, specifically, an ionic compound containing (C) an inorganic cation having a monovalent cation and / or (C) a divalent or higher inorganic anion and one or more inorganic anions selected from the group consisting of sulfate ions, chloride ions, hydroxide ions, phosphate ions, carbonate ions, fluoride ions, bromide ions, iodide ions, nitrate ions, and acetate ions.

[0037] (D) An anionic monomer having a monovalent or divalent or more anionic group may include an anionic monomer having one or more carboxyl groups, or an anionic monomer having a carboxylate group. (D) Acids containing an anionic monomer having a monovalent or divalent or greater anionic group may also contain an acid in which a proton is bonded to the anionic group of the anionic monomer. (D) Examples of acids containing the anionic monomer include anionic monomers having one or more carboxyl groups, such as oxalic acid, fumaric acid, ethylenediaminetetraacetic acid (EDTA), citric acid, and adipic acid. These may be used individually or in combination of two or more.

[0038] The weight-average molecular weight of at least one of component (A) and component (B) may be, for example, between 1,000 and 10,000,000. The molecular weights of the raw material monomers of component (A), the raw material monomers of component (B), and / or the anionic monomer of component (D) or the acid containing said anionic monomer may be, for example, between 1 and less than 1,000. In this specification, weight-average molecular weight is expressed as the value on a polystyrene basis.

[0039] Furthermore, the layer-forming material may include one or more selected from the group consisting of (X) hydrates of the ionic crosslinking agents described above, (Y) inorganic hydrates other than (X), and (Z) sodium silicate. (Y) The inorganic hydrate is not limited to any inorganic hydrate other than the (X) ion crosslinking agent described above, but it is preferable that it does not contain a salt hydrate containing any of the calcium ions, magnesium ions, and aluminum ions selected from the group. (Y) Specific examples of inorganic hydrates include, for example, sodium carbonate decahydrate, sodium acetate trihydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dihydrate, disodium hydrogen phosphate heptahydrate, disodium hydrogen phosphate octahydrate, disodium hydrogen phosphate dodecahydrate, sodium dihydrogen phosphate monohydrate, sodium dihydrogen phosphate dihydrate, magnesium chloride hexahydrate, cobalt chloride hexahydrate, copper(II) sulfate pentahydrate, cobalt(II) iodide hexahydrate, tin(II) chloride dihydrate, iron(III) oxide hydrate, etc.

[0040] The layer-forming material may include a powdered ion-crosslinkable polymer as an ion-crosslinkable polymer.

[0041] The average width of the average width, calculated by using the maximum and minimum widths of individual particles contained in the powdered ion-crosslinkable polymer and dividing the sum of the average maximum widths and average minimum widths by 2, is preferably, for example, 0.01 μm or more and 50 μm or less.

[0042] In the powdered ion-crosslinkable polymer in the layer-forming material, the upper limit of the average value of the average width is, for example, 50 μm or less, preferably 45 μm or less, and more preferably 40 μm or less. Keeping it below this upper limit improves dispersibility. In the powdered ion-crosslinkable polymer in the layer-forming material, the lower limit of the average width is, for example, 0.01 μm or more, preferably 0.1 μm or more, and more preferably 1 μm or more. A value above this lower limit improves dispersibility and film strength.

[0043] In the powdered ion-crosslinkable polymer in the layer-forming material, the upper limit of the average value of the maximum width is, for example, 95 μm or less, preferably 90 μm or less, and more preferably 85 μm or less. Keeping it below this upper limit improves dispersibility. In the powdered ion-crosslinkable polymer in the layer-forming material, the lower limit of the average maximum width is 0.01 μm or more, preferably 0.1 μm or more, and more preferably 1 μm or more. A value above this lower limit improves dispersibility and film strength.

[0044] Powdered ionic crosslinkable polymers are obtained by grinding and / or classification. Grinding can be performed using known methods such as mixers, ball mills, jet mills, and pin mills. Classification can be performed using known classification methods such as sieving, air classification, and centrifugation. When using a sieve in classification, either the sieved portion or a mixture of the sieved and unsieved portions in a predetermined ratio may be used. The above-described grinding and classification processes may be used when producing powdered ionic crosslinking agents.

[0045] In this specification, the maximum width (μm) and minimum width (μm) of individual particles contained in a powdered ion-crosslinkable polymer are measured based on SEM image observation, and the "average maximum width" and "average minimum width" are calculated using the measurements from 200 particle samples. Using these, the average average width (μm) is calculated based on the formula: [(average maximum width + average minimum width) / 2], and the aspect ratio is calculated based on the formula: (average maximum width / average minimum width). Note that the number of particle samples should be 100 or more.

[0046] At least one of the ion-crosslinkable polymer and the ion-crosslinking agent may contain one or more particles having shapes selected from the group consisting of, for example, spherical, flattened, fibrous, polyhedral, crushed, and amorphous shapes. This improves dispersibility in the environmentally degradable resin. In this embodiment, the shape of individual particles contained in the ion-crosslinkable polymer and ion-crosslinking agent can be measured by imaging observation such as SEM, TEM, AFM, or confocal microscopy. Alternatively, a laser diffraction / scattering particle distribution analyzer may be used. In this specification, "crushed" means a state in which at least a known crushing method has been carried out, and a crushed surface has been formed on at least a portion of the surface of the particles.

[0047] The lower limit of the total content of the ionically crosslinkable polymer and ion crosslinking agent is, for example, 0.1% by mass or more, preferably 1% by mass or more, and more preferably 2% by mass or more, per 100% by mass of the layer-forming material. A content above this lower limit improves seawater degradability. The upper limit of the total content of the ionically crosslinkable polymer and ion crosslinking agent is, for example, 22% by mass or less, less than 10% by mass or less, preferably 8.5% by mass or less, and more preferably 6% by mass or less, per 100% by mass of the layer-forming material. Keeping the content below this upper limit improves the sustained release properties.

[0048] The ion-crosslinked material preferably contains an ion-crosslinked superabsorbent polymer. Ion-crosslinked superabsorbent polymers can absorb water and swell compared to conventional layer-forming materials such as polyolefin resins. Even if the ion-crosslinked superabsorbent polymer gels after absorbing water, it is thought that the fertilizer inside will dissolve in the water in the gel and be released to the outside. Furthermore, the ion-crosslinked superabsorbent polymer only needs to be able to absorb water; it is not necessary for it to absorb oils or other substances besides water. The weight-average molecular weight of the ion-crosslinked material and the ion-crosslinked superabsorbent polymer may be, for example, between 1,000 and 10,000,000.

[0049] For ion-crosslinked superabsorbent polymers, it is preferable to use a polymer salt containing at least two of the following (A') to (D'), and at least one of the following (i) to (vi). (i)(A') and (C'), (ii)(A'), (C'), and (D') (iii) (A'), (B'), and (C') (iv)(A') and (B') (v)(B') and (D') (vi)(A'), (B'), (C'), and (D') (A') Polyanions having monovalent or divalent or more anionic groups (B') Polycation having monovalent or divalent or more cationic groups (C')Polyvalent inorganic cation having a monovalent or divalent or more cation (D') Anionic monomer having a monovalent or divalent or greater anionic group

[0050] The layer-forming material can improve seawater degradability by containing the above-mentioned polymer salt as an ion-crosslinked water-absorbing polymer. Seawater decomposition refers to the property of the polymer salt to become more soluble in aqueous solvents due to an ion exchange reaction between ions present in seawater and ions in the polymer salt. When layer-forming materials dissolve and fragment in seawater, the increased surface area leads to an increased amount of microorganisms in contact with the surface, which is expected to accelerate the decomposition of the environmentally degradable resin.

[0051] The estimated mechanism of seawater degrading will be explained using the example of an ion-crosslinked superabsorbent polymer containing polymer salts (A') and (C') as the combination described in (i) above. However, the ion-crosslinked superabsorbent polymer is not limited to this. Ion-crosslinked polymers, which consist of alginate polymer (a polyanion with a monovalent anionic group) and calcium ions (a polyvalent inorganic cation), form an ionic crosslinked structure in water. However, in saltwater (seawater), the calcium ions exchange with sodium, causing the crosslinks to dissociate, making the polymer soluble in saltwater.

[0052] In another embodiment, it is preferable that the ion-crosslinked superabsorbent polymer is a polymer salt comprising at least one of (A') a polyanion having monovalent or divalent or more anionic groups and (D') an anionic monomer having monovalent or divalent or more anions. More specifically, it is more preferable to use a polymer salt comprising at least one of (i) and (ii) above.

[0053] Furthermore, the layer-forming material may or may not include an ion-crosslinked material obtained by the reaction of the above-mentioned ion-crosslinkable polymer and the above-mentioned ion-crosslinking agent, as an ion-crosslinked superabsorbent polymer.

[0054] The lower limit of the ion crosslinking material content is, for example, 0.1% by mass or more, preferably 1% by mass or more, and more preferably 2% by mass or more, based on 100% by mass of the layer-forming material. A content above this lower limit can improve seawater degradability. The upper limit of the ion crosslinking material content is, for example, less than 20% by mass, preferably 15% by mass or less, and more preferably 12% by mass or less, based on 100% by mass of the layer-forming material. Keeping the content below this upper limit improves the sustained release properties.

[0055] The layer-forming material may contain additives other than ionic crosslinkable polymers, ionic crosslinking agents, and environmentally degradable resins, such as inorganic fillers, surfactants, sizing agents, hydrophobic substances, and functional additives. These may be included individually or in any combination of two or more.

[0056] The inorganic filler can be any inorganic filler that is sparingly soluble or insoluble in water, and may include one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate. Among these, silica, talc, calcium carbonate, clay, mica, etc. are preferred from the viewpoint of price and availability.

[0057] The upper limit of the inorganic filler content is, for example, 50% by mass or less, preferably 49% by mass or less, and more preferably 48% by mass or less, based on 100% by mass of the layer-forming material. This improves the tensile elongation of the layer-forming material. The lower limit of the inorganic filler content is, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the layer-forming material. This allows for low control of moisture permeability due to the water shielding effect.

[0058] In this specification, W1 is defined as the mass %) content of ionically crosslinkable polymer in 100% by mass of the layer-forming material, and W2 is defined as the mass %) content of inorganic filler. In this case, the lower limit of W1 / W2 is, for example, 0.01 or higher, preferably 0.02 or higher, and more preferably 0.04 or higher. A value above this lower limit improves seawater decomposition. The upper limit of W1 / W2 is, for example, 2 or less, preferably 1.35 or less, and more preferably 1 or less. Keeping it below the upper limit improves the sustained release properties.

[0059] The layer-forming material may contain at least one of a surfactant and / or a sizing agent, or it may contain neither. The surfactant and / or sizing agent can be used to control the dispersion state of the ion-crosslinked material. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants and nonionic surfactants are preferred. Other sizing agents include natural sizing agents, synthetic sizing agents, reactive sizing agents, and special sizing agents. Among these, natural sizing agents and synthetic sizing agents are preferred. These may be included individually, or any combination of two or more may be included.

[0060] The layer-forming material may contain one or more hydrophobic substances selected from the group consisting of waxes, oils and fats, and fatty acids. This can suppress blocking and improve spray characteristics. The hydrophobic substance may include one or more selected from the group consisting of hydrophobic substances and fatty acids. That is, the hydrophobic substance may be wax alone, oil alone, or fatty acid alone, or a mixture of wax and oil, a mixture of oil and fatty acid, a mixture of wax and fatty acid, or a mixture of hydrophobic substance and fatty acid. The hydrophobic substance may be a hydrophobic substance, a fatty acid, or a mixture of two or more of these, and may include, for example, one or more selected from the group consisting of hydrocarbon waxes, fatty acid waxes, higher alcohol waxes, glycerin fatty acid esters, and fatty acids. Furthermore, the layer-forming material may contain hydrophobic substances such as polyester polyols or rosin-based resins. The addition of polyester polyols or rosin-based resins allows for control of fluidity and moisture permeability. Biodegradable polyester polyols may also be used. Polyester polyols include, for example, copolymers of at least an organic acid and a glycol. The organic acid may include aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and, if necessary, aromatic dicarboxylic acids. The glycol may include, for example, ethylene glycol, butanediol, hexanediol, etc. Examples of rosin-based resins include rosin esters, hydrogenated rosin esters, modified rosin, maleated rosin, fumarated rosin, maleated rosin esters, disproportionated rosin esters, and polymerized rosin esters.

[0061] Here, the wax may be one of hydrocarbon waxes, fatty acid waxes, or higher alcohol waxes, or a mixture thereof. Fatty acid waxes may include, for example, one or more selected from the group consisting of aliphatic esters, aliphatic ketones, aliphatic amides, and fatty acid metal soaps. Furthermore, any of the following types of wax may be used: natural wax, synthetic wax, or modified wax. Examples of natural waxes include those derived from plants, animals, minerals, and petroleum. On the other hand, examples of oils and fats include glycerin fatty acid esters. Glycerin fatty acid esters may include one of monoglycerin fatty acid esters, diglycerin fatty acid esters, or triglycerin fatty acid esters, or a mixture of two or more of these. Furthermore, glycerin fatty acid esters may also include polyglycerin fatty acid esters, such as those in which one hydroxyl group of glycerin is dimerized by an ether bond. Fatty acids include fatty acids with fewer than 10 carbon atoms and higher fatty acids with 10 or more carbon atoms. Fatty acids may also include straight-chain fatty acids that have a main chain but no side chains, branched fatty acids that have both a main chain and side chains, and / or cyclic fatty acids that contain at least one cyclic structure. Furthermore, fatty acids may also include fatty acid derivatives such as hydroxy fatty acids containing at least one hydroxyl group, and polymers of hydroxy fatty acids. These may be used individually or in combination of two or more. The above fatty acids and aliphatic skeletons each contain saturated and / or unsaturated bonds. The above glycerol fatty acid esters may also include highly purified products obtained by distillation or other means. The hydrophobic substance may include one or more of the following waxes and vegetable oils. Specific examples of waxes include natural waxes such as carnauba wax, beeswax, and rice wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as Fischer-Tropsch wax and polyethylene wax. Specific examples of vegetable oils include palm oil, soybean oil, rapeseed oil, sunflower oil, palm kernel oil, cottonseed oil, peanut oil, olive oil, coconut oil, corn oil, sesame oil, linseed oil, safflower oil, rice bran oil, and perilla oil.

[0062] Here, we will explain the method for manufacturing the layer-forming material.

[0063] One example of a method for producing a layer-forming material may include a step of melt-kneading raw material components, including the above-mentioned ion-crosslinkable polymer, the above-mentioned ion-crosslinking agent, and the above-mentioned environmentally degradable resin, using a kneading device to obtain a solid layer-forming material.

[0064] The order in which the raw material components are supplied to the kneading device is not particularly limited, but after the addition of the environmentally degradable resin, ion-crosslinkable polymers, ion-crosslinking agents, and other additives may be added depending on the application. For example, multiple raw material components may be added simultaneously or sequentially. If necessary, at least two of the components contained in the raw materials may be mixed beforehand before kneading the raw materials.

[0065] The temperature during melt mixing can be adjusted according to the melting or softening point of the environmentally degradable resin used, but for example, it may be 50°C to 300°C, preferably 70°C to 290°C, and more preferably 90°C to 280°C.

[0066] The raw materials may include water contained in each component of the raw materials, and / or water supplied from an external source separately from the raw materials. Examples of water contained in the components include adsorbed water and crystal water.

[0067] Furthermore, another method for producing a layer-forming material may include a step of obtaining a varnish-like layer-forming material comprising raw material components including the above-mentioned ion-crosslinkable polymer, the above-mentioned ion-crosslinking agent, and the above-mentioned environmentally degradable resin, and a solvent. If necessary, the raw materials may contain other additives depending on the intended use.

[0068] The solvent may include a solvent having a boiling point between 30°C and 210°C. As solvents, organic solvents (non-aqueous solvents) are preferred, and examples include halogenated solvents such as chloroform; aromatic solvents such as toluene; aliphatic solvents such as hexane; alicyclic solvents such as cyclohexane; ketone solvents such as acetone and MEK; ester solvents such as ethyl acetate; and alcoholic solvents such as methanol, ethanol, and isopropanol. These may be included individually or in any combination of two or more. In the case of the aqueous emulsion described later, a solvent containing water can be used, for example, one containing 50% or more by mass of water. As a solvent other than water, the non-aqueous solvents mentioned above may also be used. Furthermore, general emulsification processes such as homogenizing or mechanical stirring may be used during the production of aqueous emulsions.

[0069] In the process of obtaining a varnish-like layer-forming material, there are no particular restrictions on the order in which the components of the raw materials are mixed with the solvent. Heating may or may not be performed at any point during the mixing process.

[0070] Furthermore, the varnish-like layer-forming material may consist of a one-component liquid containing at least an ionic crosslinking agent, an ionic crosslinkable polymer, and a second liquid, or it may consist of a two-component liquid containing separately a first liquid containing at least an ionic crosslinking agent and a second liquid containing at least an ionic crosslinkable polymer. In the case of a two-component liquid, the environmentally degradable resin is contained in at least one of the first and second liquids.

[0071] The layer-forming material can take the form of one of the following: solid, varnish, or viscous.

[0072] The solid layer-forming material may be in the form of a powder, granules, pellets, or briquettes. Depending on the form, known methods can be used for molding. Powders and granules can be produced by grinding, cutting, etc. If necessary, they may also be subjected to processing such as classification. Pellets can be manufactured by cutting strands that have been extruded from a molten mixture through a die. Briquettes can be manufactured by methods such as compressing powders or granules, or by molding molten mixtures using molds.

[0073] The viscous layer-forming material may be one in which at least one of its components has absorbed moisture and the forming material has gelled, or it may be one in which the forming material has softened due to the inclusion of a liquid component.

[0074] Next, the covering structure of this embodiment will be described.

[0075] An example of the covering structure of this embodiment is: The above-mentioned items to be covered, The device may also include a coating layer that covers at least a portion of the surface of the object to be coated. The coating layer covers at least a portion or the entire surface of the object to be coated. The coating layer may include at least one layer made of the layer-forming material described above, and may also include one or more layers other than the layer made of the layer-forming material. When the coating layer has a multilayer structure, the layer made of the layer-forming material may be the innermost layer, the outermost layer, or an intermediate layer between the inner and outer layers.

[0076] The form of the material to be covered is solid or liquid in the atmosphere at 25°C. The shape of the material to be coated is not particularly limited, but may be granular, pelletized, briquette-shaped, or other irregular shapes. Among these, the material to be coated may be a granular solid or a granular liquid. The granular solid may be formed from powder or granules, or it may be spherical with a roughly circular or elliptical cross-section. The surface of the granular solid may be smooth or it may have surface irregularities.

[0077] The coating may include agricultural active ingredients such as fertilizer components and pesticide components, as described later. These may be included individually or in any combination of two or more. Furthermore, the material to be coated may contain some gas such as air or a solvent such as water.

[0078] (fertilizer ingredients) As for the fertilizer components, known components can be used, but for example, one or more of nitrogenous fertilizers, phosphorusous fertilizers, and potassiumous fertilizers can be used. Nitrogenous fertilizers include, for example, ammonium salts and nitrates, specifically ammonium sulfate, ammonium chloride, urea, calcium cyanamide, sodium nitrate, and ammonium nitrate. Examples of phosphate fertilizers include superphosphate, double superphosphate, fused phosphate fertilizer, and calcined phosphate fertilizer. Examples of potassium fertilizers include potassium chloride and potassium sulfate. In addition to the three fertilizers mentioned above, the fertilizer may also contain one or more known inorganic compounds containing other fertilizers (such as calcareous fertilizers, silicate fertilizers, manganese fertilizers, boron fertilizers, etc.) or inorganic nutrients.

[0079] The fertilizer components may also contain other components, as long as they do not impair the effects of the present invention. Other components may include, for example, carriers such as clay, kaolin, talc, bentonite, and calcium carbonate; binders such as polyvinyl alcohol, sodium carboxymethylcellulose, and starches; and, if necessary, surfactants such as polyoxyethylene nonylphenyl ether, molasses, animal oils, vegetable oils, hydrogenated oils, fatty acids, fatty acid metal salts, paraffin, waxes, and glycerin. These may be used individually or in combination of two or more.

[0080] For example, the form of the fertilizer component is not particularly limited; it just needs to be solid in the atmosphere at 25°C. An example of the form of fertilizer components would be granular fertilizer.

[0081] Granular fertilizers can be manufactured using known granulation methods such as fluidized bed granulation, rolling granulation, coated granulation, adsorption granulation, and coagulation granulation. However, the manufacturing method of granular fertilizers is not limited to these methods.

[0082] The coating layer that covers the fertilizer components may, if necessary, contain the following functional additives. Functional additives are not particularly limited as long as they are used as layering materials for fertilizers, but examples include fillers other than the inorganic fillers mentioned above, thickeners, adhesion promoters, surface modifiers (such as inorganic fillers), pH adjusters, crosslinking retarders (chelating agents), reinforcing materials, gas barrier agents, magnetic materials, decomposition control agents, defoaming agents, plasticizers, etc. These may be used individually or in combination of two or more. Furthermore, the layer-forming material may contain one or more of the functional additives.

[0083] (Pesticide components) Pesticide components include fungicides, insecticides, and other chemicals (including materials that use such chemicals as raw materials or ingredients and are used for said control) used to control fungi, nematodes, mites, insects, rodents, and other animals, plants, or viruses (hereinafter referred to as "pests and diseases") that harm crops (including trees and agricultural and forestry products; hereinafter referred to as "crops, etc."), as well as plant growth regulators, germination inhibitors, and other chemicals used to enhance or suppress the physiological functions of crops, etc. However, there are no particular restrictions on pesticides as long as they are chemicals used for agricultural purposes, and any of these chemicals may be used, including insecticides, fungicides, and herbicides.

[0084] Next, a method for manufacturing the covering structure of this embodiment will be described.

[0085] An example of a method for manufacturing the coated structure of this embodiment may include a step of forming a coating layer on the surface of the object to be coated using the layer-forming material described above.

[0086] Known methods can be used to form the coating layer. Depending on the formation method, the form of the layer-forming material can be selected from those described above. For example, when using spray treatment as the formation method, a varnish-like form may be selected for the layer-forming material.

[0087] Methods for forming the coating layer can include known methods for coating the surface of solid particles, such as chemical methods including non-aqueous wet methods, aqueous wet methods, gas-phase reaction methods, and mechanical chemical methods, or physical methods such as mechanical surface treatment methods, laser ablation methods, air suspension coating methods, and spray drying methods. When coating an object to be coated with a layer-forming material, it is preferable to use a fluidized bed granulation method or a rolling granulation method. When applying to such manufacturing methods, it is preferable to use a varnish-like layer-forming material. However, it is not limited to this, and when using a solid layer-forming material, it can also be dissolved in a solvent and used in a varnished form. Alternatively, the object to be coated may be coated using an aqueous dispersion emulsion containing the layer-forming material.

[0088] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0089] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0090] <Manufacturing of layer-forming materials> (Preparation of powdered ionic crosslinkable polymer) Commercially available sodium alginate (manufactured by Tokyo Chemical Industry Co., Ltd.) was pulverized using a mixer for 3 minutes, classified using a 53 μm mesh (sieve), and the sieved portion was collected to obtain powdered ion-crosslinkable polymer A.

[0091] For powdered ion-crosslinkable polymer A, the maximum and minimum particle widths (μm) were measured based on SEM imaging. Using the measurements from 200 particle samples, the "average maximum width" and "average minimum width" were calculated. Using these values, the average average width (μm) was calculated based on the formula: [(average maximum width + average minimum width) / 2]. In the powdered ion-crosslinkable polymer A, the average maximum width was 47 μm, and the average average width was 37 μm. Furthermore, SEM imaging confirmed that the powdered ion-crosslinkable polymer A contains fragmented particles with a fractured surface. Furthermore, the above-mentioned ion-crosslinkable polymer A was classified using a mesh (sieve) with an opening of 35 μm, and the portion that passed through the sieve was collected to obtain powdered ion-crosslinkable polymer A'.

[0092] (Example 1) The powdered ion-crosslinkable polymer A' obtained above, aluminum sulfate 14-18 hydrate (manufactured by Fujifilm Wako Pure Chemical Industries) as an ion-crosslinking agent, and calcium carbonate as an inorganic filler were ground and mixed in a mortar to obtain a mixture. The resulting mixture was mixed with polybutylene succinate (PBS) as an environmentally degradable resin while heating to obtain the layer-forming material of Example 1. In Example 1, the content of powdered ion-crosslinkable polymer A' in 100% by mass of the layer-forming material was 1% by mass. (Example 2) The layer-forming material for Example 2 was obtained in the same manner as in Example 1, except that the content of powdered ion-crosslinkable polymer A' in the layer-forming material was changed to 2% by mass. (Example 3) The layer-forming material of Example 3 was obtained in the same manner as in Example 1, except that the content of powdered ion-crosslinkable polymer A' in the layer-forming material was changed to 4% by mass. (Example 4) The layer-forming material of Example 4 was obtained in the same manner as in Example 2, except that powdered ion-crosslinkable polymer A was used instead of the above-mentioned ion-crosslinkable polymer A'. (Example 5) The layer-forming material of Example 5 was obtained in the same manner as in Example 1, except that the content of powdered ion-crosslinkable polymer A' in the layer-forming material was changed to 5% by mass.

[0093] (Comparative Example 1) A layer-forming material of Comparative Example 1 was obtained in the same manner as in Example 1, except that a powdery ion-crosslinkable polymer A and an ion crosslinking agent were not used. (Comparative Example 2) A layer-forming material of Comparative Example 2 was obtained in the same manner as in Example 1, except that the content of the powdery ion-crosslinkable polymer A in the layer-forming material was changed to 20% by mass.

[0094] (Evaluation of Sustained Release by Water Immersion Test) (Preparation of Evaluation Samples) First, each of the layer-forming materials obtained above was molded to produce a layer having a predetermined thickness shown in Table 1, and then punched out into a circular shape with a diameter of 15 mm to obtain 10 test pieces. Subsequently, using a tablet molding machine, solid urea (specific gravity: about 1.3) was tabletted into a cylindrical tablet with a height of 1 mm, a diameter of 10 mm, and a volume of about 78 mm 3 to obtain a cylindrical urea tablet 20 having flat upper and lower surfaces 21. Subsequently, on each of the upper and lower surfaces of the urea tablet 20, the inner surface 13 of the test piece 10 was arranged to face, and their side surfaces 23 were fixed using a ring-shaped silicone rubber (waterproof member 30) to produce an evaluation sample 50.

[0095] (Measurement of Amount of Sustained Release) A standard solution of urea with a known concentration in the range of 1 mg / mL to 12 mg / mL was prepared, and a calibration curve showing the relationship between absorbance and urea concentration was prepared. The above evaluation sample 50 was immersed in distilled water (water 60) having a predetermined liquid temperature shown in Table 1 in a polypropylene container 70 at room temperature of 25 °C and atmospheric pressure as shown in FIG. 1, and water treatment was carried out. During the water treatment, the outer surface 11 of the test piece 10 was continuously contacted with the water 60. Immediately after the water treatment, the absorbance of the water 60 at a wavelength of 450 nm was measured over time using an absorbance meter, and the urea concentration was measured from the calibration curve. From the obtained results, the amount of urea in the urea tablet 20 that moved into the external water 60 (urea elution rate) can be measured. The period T until the obtained urea elution rate reaches 10% by mass 10(Days), and the period until it reaches 80% by mass T 80 The number of days was calculated.

[0096] Table 1 below shows the results of a 25°C water immersion test using a test specimen 10 with a thickness of 50 μm and a water temperature of 25°C, and the results of a 35°C water immersion test (accelerated test) using a test specimen 10 with a thickness of 100 μm and a water temperature of 35°C.

[0097] [Table 1]

[0098] The layer-forming materials of Examples 1-5 showed a change in urea elution rate over time, during period T. 10 It was confirmed that the rise was suppressed until (Sun), followed by a sharp rise in a sigmoid curve. On the other hand, in Comparative Example 1, the change in urea elution rate over time was different from that of Examples 1 to 5. 80 The curve showed a linear type in which the increase was suppressed until (day), and it was confirmed that Comparative Example 2 showed a linear type curve in which the change in urea elution rate over time increased sharply from the beginning. [Explanation of symbols]

[0099] 10 test specimens 11 Exterior 13. Inner self 20 Urea Tablets 23 Side view 30 Waterproofing materials 50 evaluation samples 60 water 70 containers

Claims

1. A layer-forming material comprising an ion-crosslinked material and an environmentally degradable tree, The ion-crosslinking material comprises at least one of an ion-crosslinkable polymer, an ion-crosslinking agent, and a crosslinked product of the ion-crosslinkable polymer and the ion-crosslinking agent. A layer-forming material in which the change over time of urea elution rate, measured by the procedure described below, exhibits a sigmoid curve that satisfies either condition (i) or condition (ii) below. Condition (i): The test film has a thickness of 100 μm, and the time required to reach a urea elution rate of 10% by mass under 35°C water immersion conditions is between 2 days and 55 days. Condition (ii): The test film thickness is 50 μm, and the time required to reach a urea elution rate of 10% by mass under 25°C water immersion conditions is between 1 day and 130 days. (procedure) The layer-forming material is molded to produce a film. The aforementioned film is punched out to form a circle with a diameter of 15 mm to obtain a test film of a predetermined thickness. Height 1 mm, diameter 10 mm, volume approximately 78 mm ３ The test film is placed on the top and bottom surfaces of the cylindrical urea tablet, and the sides of the urea tablet are fixed with a ring-shaped silicone rubber to produce an evaluation sample. At room temperature of 25°C and under atmospheric pressure, the obtained evaluation sample is immersed in water at a predetermined liquid temperature in a polypropylene container. Immediately after immersion, the absorbance of the water at a wavelength of 450 nm is measured over time using an absorbance meter, and the urea elution rate (mass%) is calculated using a calibration curve.

2. A layer-forming material according to claim 1, A layer-forming material in which the content of the ion crosslinking material is 0.1% by mass or more and less than 20% by mass of 100% by mass of the layer-forming material.

3. A layer-forming material according to claim 1 or 2, A layer-forming material in which the total content of the ion-crosslinkable polymer and the ion-crosslinking agent is 0.1% by mass and 22% by mass or less of the layer-forming material by mass.

4. A layer-forming material according to claim 1 or 2, Contains inorganic fillers, A layer-forming material wherein the inorganic filler comprises one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate.

5. A layer-forming material according to claim 4, A layer-forming material in which, when the content (mass%) of the ion-crosslinkable polymer contained in the layer-forming material is W1 and the content (mass%) of the inorganic filler is W2, the ratio W1 / W2 is 0.01 or more and 2 or less.

6. A layer-forming material according to claim 1 or 2, The ion-crosslinkable polymer includes a powdered ion-crosslinkable polymer, A layer-forming material in which the average value of the average width, calculated by dividing the sum of the average values ​​of the maximum width and the average values ​​of the minimum width by 2, using the maximum width and minimum width of each particle contained in the powdered ion-crosslinkable polymer, is 0.01 μm or more and 50 μm or less.

7. A layer-forming material according to claim 6, A layer-forming material comprising one or more particles having a shape selected from the group consisting of spherical, flattened, fibrous, polyhedral, crushed, and irregular shapes, in which the powdered ion-crosslinkable polymer is.

8. A layer-forming material according to claim 1 or 2, The ion-crosslinkable polymer comprises at least one of the following components (A) and (B): If the ion-crosslinkable polymer contains the following component (A), the ion-crosslinking agent contains one or more selected from the group consisting of the following components (B), (C), and (D): If the ion-crosslinkable polymer contains the following component (B), the ion-crosslinking agent is a layer-forming material comprising one or more selected from the group consisting of the following components (A), (C), and (D). (A) Polyanions having monovalent or divalent or more anionic groups, or salts containing such polyanions (B) Polycations having monovalent or divalent or more cationic groups, or salts containing such polycations (C) an inorganic cation having a monovalent or divalent or more cations, or a salt containing one or more of such inorganic cations. (D) An anionic monomer having a monovalent or divalent or more anionic group, or an acid containing said anionic monomer

9. A layer-forming material according to claim 1 or 2, A layer-forming material comprising one or more hydrophobic substances selected from the group consisting of waxes, oils and fats, and fatty acids.

10. A layer-forming material according to claim 1 or 2, A layer-forming material used to form a layer on the surface of a material containing agricultural active ingredients.

11. The object to be covered, The system comprises a layer that covers at least a portion of the surface of the object to be covered, A covering structure wherein the layer includes a layer formed of the layer-forming material described in claim 1 or 2.

12. A covering structure according to claim 11, The aforementioned coated structure contains an agricultural active ingredient.

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