Plant growth aid and method for producing a plant growth aid

Abstract

The object of the present invention is to provide a plant growth aid that exhibits low elution of active ingredients during storage and excellent dispersibility in solvents, in a granular state (powder form), and a method for producing the same. [Solution] A plant growth stimulant comprising sugars and / or sugar alcohols (A), a biodegradable resin (B), and a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, wherein the particles have a median diameter of 1 to 300 nm; a method for producing the plant growth stimulant.

Description

Technical Field

[0001] The present invention relates to a plant growth aid and a method for producing the same.

Background Art

[0002] In agriculture, fertilizers are used to produce crops stably. By being mixed into the soil and absorbed by the roots, fertilizers promote the growth of plants. In recent years, foliar spraying has also been carried out as an auxiliary fertilization method in addition to soil mixing. In any case, fertilizers are generally mixed into the soil or sprayed on the leaves in a liquid form. On the other hand, studies have been made to control the dissolution rate and solubility of active ingredients so that the medicinal effects of active ingredients such as plant growth can be exerted over a long period after fertilization. For example, Patent Document 1 discloses a technique for reducing the usage ratio of active ingredients by using a nanoparticle preparation having relatively high dissolution rate and solubility in a solvent. In recent years, fertilizers are often provided in a form in which particles containing active ingredients as described in Patent Document 1 are dispersed in a solvent (mainly water).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, fertilizers are often stored at the outside air temperature for a long time. In the form of dispersing particles containing active ingredients in a solvent, the active ingredients are gradually released into the solvent during storage, and there is a problem that the performance expected at the fertilization stage cannot be exhibited. Also, when storing the particles as they are and dispersing them in a solvent at the time of fertilization, there is a problem that the dispersibility is poor and uniform fertilization cannot be achieved.

[0005] The object of the present invention is to provide a plant growth aid that exhibits low elution of active ingredients during storage and excellent dispersibility in solvents, in a granular state (powder form), and a method for producing the same. [Means for solving the problem]

[0006] The present inventors have arrived at the present invention as a result of their research to achieve the above objective. Specifically, the present invention relates to a plant growth stimulant in the form of particles with a median diameter of 1 to 300 nm, comprising sugars and / or sugar alcohols (A), a biodegradable resin (B), and a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C; and a method for producing the plant growth stimulant. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a plant growth aid that exhibits low elution of active ingredients during storage in a granular state (powder form) and excellent dispersibility in solvents. [Modes for carrying out the invention]

[0008] The present invention relates to a plant growth stimulant in the form of particles with a median diameter of 1 to 300 nm, containing sugars and / or sugar alcohols (A), a biodegradable resin (B), and a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C.

[0009] <Sugars and / or sugar alcohols (A)> The plant growth aid of the present invention comprises sugars and / or sugar alcohols (A). Examples of sugars in this invention include monosaccharides, disaccharides, polysaccharides of three or more saccharides, and cyclodextrins. Examples of monosaccharides include glucose, galactose, mannose, and fructose. Examples of disaccharides include sucrose, lactulose, maltose, trehalose, cellobiose, isotrehalose, neotrehalose, gentiobilose, mannobiose, galactosucrose, xylobiose, and primevelose. Examples of polysaccharides with three or more components include raffinose, cellulose, mannan, pectin, starch, fructan, galactomannan, acacia gum, talakanto gum, carrageenan, alginic acid, laminaran, galactan, chitin, chitosan, dextran, pullulan, and guar gum. Examples of cyclodextrins include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and their derivatives (methylated, ethylated, hydroxyethylated, hydroxypropylated, maltose-bonded, cationized, quaternary ammoniumated, anionicated, amphoteric, etc.).

[0010] Examples of sugar alcohols include glycerin, sorbitol, erythritol, and mannitol. The sugars and sugar alcohols may be a mixture of two or more types.

[0011] <Biodegradable resin (B)> The plant growth aid of the present invention contains a biodegradable resin (B). The biodegradable resin (B) in this invention is not particularly limited as long as it is a biodegradable resin, that is, a resin that can be degraded by microorganisms, enzymes, or ingested by living organisms. Among these resins, it is preferable to use a resin that satisfies the conditions for easy degradability based on the OECD301C test method for evaluating biodegradability. One type of biodegradable resin (B) may be used alone, or two or more types may be used in combination. From the viewpoint of being easily hydrolyzed and having an excellent balance between the elution and sustained release of the hydrophobic agent (C) from the particles, it is preferable to use at least one resin selected from the group consisting of polylactic acid, polycaprolactone, polyglycolic acid, and lactic acid-glycolic acid copolymers, and resins having a segment made of any of these resins (a segment made of polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer) and a segment made of a resin with an SP value of 5 to 15. In one embodiment, the biodegradable resin (A) is more preferably at least one selected from the group consisting of a resin having segments made of polylactic acid, polycaprolactone, polyglycolic acid or lactic acid-glycolic acid copolymer and segments made of a resin with an SP value of 5 to 15, and polylactic acid, and even more preferably a resin having segments made of polylactic acid and / or segments made of a resin with an SP value of 5 to 15. As segments made of resin with an SP value of 5 to 15, segments made of a homopolymer of ethylene oxide (hereinafter abbreviated as EO), a copolymer of EO and propylene oxide (hereinafter abbreviated as PO) (hereinafter referred to as EO-PO copolymer), or a polymer of an ionic monomer are preferred.

[0012] The weight-average molecular weight (hereinafter abbreviated as Mw) of polylactic acid, polycaprolactone, polyglycolic acid, and lactic acid-glycolic acid copolymer is preferably 1,000 to 200,000, more preferably 20,000 to 150,000, and even more preferably 20,000 to 100,000. If Mw is 1,000 or more, the encapsulation rate of the hydrophobic agent (C) is high and the sustained release properties are good, and if it is 200,000 or less, the elution of the hydrophobic agent (C) from the particles is good.

[0013] In this invention, Mw can be measured by gel permeation chromatography, for example, under the following conditions. Device: "HLC-8120GPC" [Manufactured by Tosoh Corporation] Columns: "Guardcolumn HXL-H" (1 piece), "TSKgel GMHXL" (2 pieces) [both manufactured by Tosoh Corporation] Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 100μL Flow rate: 1mL / min Measurement temperature: 40℃ Detection device: Refractive index detector Reference material: Standard polystyrene

[0014] The polylactic acid, polycaprolactone, polyglycolic acid, and lactic acid-glycolic acid copolymer may be commercially available or produced by known methods. Examples of production methods include ring-opening polymerization using the corresponding cyclic monomer as a catalyst.

[0015] As the biodegradable resin (B), a resin having segments made of polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer and segments made of a resin with an SP value of 5 to 15 is desirable. As the segments made of a resin with an SP value of 5 to 15, it is preferable to use segments made of an EO homopolymer (polyethylene glycol), an EO / PO copolymer (block polymer or random polymer), or a polymer of an ionic monomer. Examples of such resins include those in which an EO homopolymer, an EO / PO copolymer (block polymer or random polymer), or a polymer of an ionic monomer is bonded to the terminal functional groups of polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer. The preferred range of Mw for the polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer constituting the segments is as described above. The method for calculating the SP value in the present invention is based on the method described in the literature by Robert F Fedors et al. (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2 P. 147-154).

[0016] Examples of the ionic monomer in the polymer of the ionic monomer include salts of inorganic acids (such as hydrochloric acid, sulfuric acid, and phosphoric acid) or organic acids (such as acetic acid) such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and allylamine; unsaturated carboxylic acids [(meth) acrylic acid, crotonic acid, maleic acid, and itaconic acid, etc.] and alkali metal salts or ammonium salts of organic sulfonic acids having an unsaturated double bond [vinyl sulfonic acid, styrene sulfonic acid, and 2-(meth) acrylamide-2-methylpropane sulfonic acid, etc.]. “(meth) acrylate” means acrylate or methacrylate, and “(meth) acrylic” means acrylic or methacrylic.

[0017] The production method of the resin having a segment composed of polylactic acid, polycaprolactone, polyglycolic acid, or a lactic acid-glycolic acid copolymer and a segment composed of a resin having an SP value of 5 to 15 is not particularly limited. When using a homopolymer of EO or an EO / PO copolymer, a resin having the above two segments can be obtained by reacting the carboxyl group of polylactic acid, polycaprolactone, polyglycolic acid, or a lactic acid-glycolic acid copolymer (when having only a hydroxyl group, after converting to a carboxyl group with an acid anhydride, etc.) with the hydroxyl group of the homopolymer of EO or the EO / PO copolymer. When using an ionic monomer, for example, a resin having the above two segments can be obtained by reacting an unsaturated carboxylic acid anhydride with the hydroxyl group of polylactic acid, polycaprolactone, polyglycolic acid, or a lactic acid-glycolic acid copolymer to introduce an unsaturated double bond and polymerizing the above ionic monomer thereto.

[0018] Among the homopolymer of EO, the EO / PO copolymer, and the polymer of an ionic monomer, from the viewpoint of the balance between the elution property and the sustained release property of the hydrophobic drug (C) from the particles, the EO homopolymer and the EO / PO copolymer are preferable.

[0019] From the viewpoint of the elution rate of the hydrophobic drug (C), when promoting the elution rate, the weight ratio of EO in the EO / PO copolymer is preferably 50 to 90% by weight, more preferably 65 to 85% by weight. Further, when delaying the elution rate, the weight ratio of EO in the EO / PO copolymer is preferably 2% by weight or more and less than 50% by weight, more preferably 5 to 45% by weight.

[0020] The number average molecular weight (hereinafter abbreviated as Mn) of the EO homopolymer and the EO / PO copolymer is preferably 1,000 to 80,000, more preferably a number average molecular weight of 8,000 to 80,000, still more preferably 9,000 to 75,000. When Mn is 1,000 or more, the elution property of the hydrophobic drug (C) is good, and when it is 80,000 or less, the sustained release property of the hydrophobic drug (C) is good.

[0021] In the present invention, Mn can be measured by gel permeation chromatography under, for example, the following conditions. Apparatus: "Waters Alliance 2695" [manufactured by Waters] Column: "Guardcolumn Super H-L" (1 piece), "a combination of one piece each of TSKgel SuperH2000, TSKgel SuperH3000, and TSKgel SuperH4000 (all manufactured by Tosoh Corporation)" Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 10 μL Flow rate: 0.6 mL / min [[ID=2)3]] Measurement temperature: 40 °C Detector: Refractive index detector Reference substance: Standard polyethylene glycol

[0022] The weight ratio of segments made of polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer in a resin to the weight of segments made of an EO homopolymer, EO / PO copolymer, or polymer of an ionic monomer is preferably 30 to 80% by weight, more preferably 40 to 80% by weight, and even more preferably 50 to 80% by weight. If the segment made of polylactic acid, polycaprolactone, polyglycolic acid, or lactic acid-glycolic acid copolymer is 30% by weight or more, the encapsulation rate of the hydrophobic agent (C) is high and the sustained release properties are good, and if it is 80% by weight or less, the elution of the hydrophobic agent (C) from the particles is good. The content of the biodegradable resin (B) in the particles is preferably 20 to 95% by weight, more preferably 20 to 80% by weight, and even more preferably 30 to 70% by weight, from the viewpoint of controlling the elution of the drug. In one embodiment, when the particles contain at least one selected from the group consisting of polylactic acid, polycaprolactone, polyglycolic acid and lactic acid-glycolic acid copolymer and a resin having a segment made of any of these resins and a segment made of a resin with an SP value of 5 to 15, the total content of polylactic acid, polycaprolactone, polyglycolic acid and lactic acid-glycolic acid copolymer and a segment made of any of these resins is preferably 20 to 80% by weight, and more preferably 30 to 70% by weight, in the particles.

[0023] <Hydrophobic agent (C)> In this invention, hydrophobicity in the hydrophobic agent (C) means that the octanol / water partition coefficient (LogPow) at 25°C is greater than 0. The octanol / water partition coefficient (LogPow) is defined in Pharmaceutical Affairs Bureau Notification No. 291, 62nd Basic Pharmacopoeia, No. 171, OECD Test Guide It can be measured in accordance with the method for measuring the partition coefficient (1-octanol / water) of a chemical substance as specified in ideline ([C(81)30 Final Annex 1])107.

[0024] In the present invention, the hydrophobic agent (C) has an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, from the viewpoint of balancing the sustained release and elution properties of the hydrophobic agent (C) from particles. Examples of hydrophobic agent (C) include pesticides and other chemicals with an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, and known agents for each pesticide effect can be used without particular limitation. The hydrophobic agent (C) used in the present invention is preferably a compound with a molecular weight of less than 2,000. The hydrophobic agent (C) is preferably a compound with an octanol / water partition coefficient (LogPow) of 1 to 8 at 25°C, more preferably a compound with an octanol / water partition coefficient (LogPow) of 1 to 7, and even more preferably a compound with an octanol / water partition coefficient (LogPow) of 1 to 6.

[0025] Preferred hydrophobic agents (C) include, for example, commercially available pesticides such as thiadinil (LogPow=3.68), acibenzolar-S-methyl (LogPow=3.1), isothianil (LogPow=2.96), benzylamine (LogPow=1.09), carpropamide (LogPow=4.2), benomyl (LogPow=1.3), pyroquilon (LogPow=1.42), thiophanate-methyl (LogPow=1.5), thiodicarb (LogPow=1.62), fosthiazate (LogPow=1.68), and thiram (LogP (LogPow=1.73), Metalaxyl (LogPow=1.75), Methidathion (LogPow=2.2), Bensultap (LogPow=2.2), Metminostrobin (LogPow=2.32), Flamethopyr (LogPow=2.36), Fursulfamide (LogPow=2.8), Captan (LogPow=2.8), Felimzon (LogPow=2.89), Mycrobutanil (LogPow=2.9), Fluvalinate (LogPow=2.9), TPN (Chlorothalonil) (LogPow=2.92), Boscalide (LogPow= 2.96), pefrazoate (LogPow=3.0), phthalide (LogPow=3.01), diethofencarb (LogPow=3.02), fluorimide (LogPow=3.04), procymidone (LogPow=3.14), flutolanil (LogPow=3.17), dithianone (LogPow=3.2), cyazofamide (LogPow=3.2), fenbuconazole (LogPow=3.23), mepanipyrium (LogPow=3.28), diazinon (LogPow=3.3), iprobenfos (LogPow=3.37) ), isoprothiolane (LogPow=3.3), diclobentiazox (LogPow=3.4), kresoximmethyl (LogPow=3.4), bifenazate (LogPow=3.4), fenitrothion (LogPow=3.43), pyraclofos (LogPow=3.77), acrinatrin (LogPow=5.25), diflufenican (LogPow=4.9), fipronil (LogPow=4), fluazuron (LogPow=5.1), flufenoxuron (LogPow=4.01), hexaflumuron (LogPow=4.68) Examples include lufenuron (LogPow=5.12), teflubenzuron (LogPow=4.3), tefluthrin (LogPow=6.5), tetraconazole (LogPow=3.53), thiazopil (LogPow=3.89), and transfluthrin (LogPow=5.46) (LogPow values ​​are all at 25°C).

[0026] Furthermore, examples of hydrophobic agricultural agents that promote plant growth (those with a LogPow of 1 to 10 at 25°C) include fat-soluble vitamins, and other agents with a LogPow of 1 to 10 at 25°C that are currently under development include sphingolipids. Hydrophobic agents (C) may be used individually or in combination of two or more.

[0027] <particle> The plant growth aid of the present invention is a particle containing sugars and / or sugar alcohols (A), a biodegradable resin (B), and a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C. The total content of sugars and / or sugar alcohols (A) in the particles is preferably 3 to 95% by weight based on the weight of the particles. When the total weight percentage of sugars and / or sugar alcohols (A) is within this range, the dispersibility of the particles in water is improved. The total content of sugars and / or sugar alcohols (A) in the particles is more preferably 5 to 88% by weight, and particularly desirable to be 5 to 45% by weight based on the weight of the particles.

[0028] The content of the biodegradable resin (B) in the particles is preferably 5 to 80% by weight, based on the weight of the particles. When the weight percentage of the biodegradable resin (B) is within this range, the sustained release rate of the hydrophobic agent is within an appropriate range, and plant growth is improved. The content of the hydrophobic agent (C) in the particles is preferably 0.5 to 15.0% by weight, based on the weight of the particles. When the weight percentage of the hydrophobic agent (C) is within this range, the sustained release rate of the hydrophobic agent is within an appropriate range, and plant growth is improved.

[0029] The weight ratio of the biodegradable resin (B) to the hydrophobic agent (C) in the aforementioned particles [(B):(C)] is preferably 5:1 to 30:1, and more preferably 5:1 to 20:1, from the viewpoint of the elution properties of the hydrophobic agent (C).

[0030] The particles may further contain a surfactant (D) and / or polyvinyl alcohol (PVA) having an HLB value of 3 to 18. Surfactants (D) with an HLB value of 3 to 18 are also referred to simply as surfactant (D) below. Surfactants (D) are preferably compounds with a molecular weight of 2,000 or more, and more preferably compounds with a molecular weight of 2,000 to 80,000. Surfactants (D) may be used alone or in combination of two or more. Compounds with an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C are not included in surfactants (D) in this invention. In this invention, the HLB (Hydrophile-Lipophile Balance) value is a measure indicating the balance between inorganic and organic properties, with a higher HLB value indicating higher inorganic properties. The HLB value used is calculated using the following formula by the Oda method. HLB=10×Inorganic / Organic The Oda method is described, for example, on page 212 of "Introduction to Surfactants" (published by Sanyo Chemical Industries, Ltd. in 2007). The organic and inorganic values ​​for deriving the HLB value can be calculated using the values ​​in the table on page 213 of the aforementioned "Introduction to Surfactants".

[0031] If the particles contain a surfactant (D) and / or polyvinyl alcohol, the weight ratio of the total weight of surfactant (D) and polyvinyl alcohol in the particles to the weight of the hydrophobic agent (C) [((D)+(PVA)):(C)] is preferably 30:1 to 3:1, and more preferably 20:1 to 5:1, from the viewpoint of encapsulation rate. When a surfactant (D) and / or polyvinyl alcohol are used as a dispersant for (C) when mixing a biodegradable resin (B) and a hydrophobic agent (C), the particles contain (D) in a form in which (D) and / or polyvinyl alcohol are present within the particles. Furthermore, the particles can be easily produced, for example, by dissolving a biodegradable resin (B) and a hydrophobic agent (C) in a hydrophilic solvent, and then dropping the mixture into water in which sugars and / or sugar alcohols (A), a surfactant (D), and / or polyvinyl alcohol are dissolved. In this case, the particles contain (D) and / or polyvinyl alcohol in a form in which sugars and / or sugar alcohols (A), surfactants (D), and / or polyvinyl alcohol are adsorbed onto the surface of the particles made of biodegradable resin (B) and hydrophobic agent (C).

[0032] In one embodiment, when at least one resin selected from the group consisting of polylactic acid, polycaprolactone, polyglycolic acid, and lactic acid-glycolic acid copolymer is used as the biodegradable resin (B), it is preferable that the particles contain a surfactant (D) and / or polyvinyl alcohol.

[0033] Examples of surfactants (D) include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants having an HLB value of 3 to 18. However, from the viewpoint of balancing the elution and sustained release of the hydrophobic agent (C) from the particles, nonionic surfactants are preferred, and EO-PO copolymers are particularly preferred.

[0034] In the EO-PO copolymer, the weight percentage of EO is preferably 50-90% by weight, and more preferably 65-85% by weight, from the viewpoint of the elution rate of the hydrophobic agent (C). If the elution rate of the hydrophobic agent (C) is to be accelerated, it is preferably 2% by weight or more and less than 50% by weight, and more preferably 5-45% by weight.

[0035] The number-average molecular weight (hereinafter abbreviated as Mn) of the EO-PO copolymer is preferably 2,000 to 80,000, more preferably 8,000 to 80,000, and even more preferably 9,000 to 75,000. If Mn is 2,000 or more, the elution of the hydrophobic agent (C) is good, and if it is 80,000 or less, the sustained release of the hydrophobic agent (C) is good.

[0036] Examples of polyvinyl alcohol include those that are well known.

[0037] When mixing a biodegradable resin (B) and a hydrophobic agent (C), if a surfactant (D) and / or polyvinyl alcohol are used as a dispersant for (C), the total amount of surfactant (D) and / or polyvinyl alcohol used is preferably 5 to 20 times the weight of the hydrophobic agent (C) from the viewpoint of balancing handling and dispersibility. Furthermore, when dissolving the biodegradable resin (B) and the hydrophobic agent (C) in a hydrophilic solvent during particle production, and then dropping them into water in which surfactant (D) and / or polyvinyl alcohol are dissolved, the total amount of surfactant (D) and / or polyvinyl alcohol used is preferably 5 to 20 times the weight of the hydrophobic agent (C) from the viewpoint of balancing handling and dispersibility.

[0038] The median diameter of the particles is 1 to 300 nm, preferably 5 to 250 nm, and more preferably 10 to 200 nm. Particles with a median diameter of less than 1 nm are difficult to manufacture industrially, and if the diameter exceeds 300 nm, the uptake of the particles by plants becomes insufficient, and the elution of hydrophobic agents (C) from the particles becomes poor. The median diameter in this invention can be measured using a dynamic light scattering measuring device [for example, the LB-550 dynamic light scattering grain distribution analyzer (manufactured by HORIBA), Zetasizer Ultra (manufactured by Malvern Panalytical Corporation), and DelsaMax CORE (manufactured by Beckman Coulter)].

[0039] The contact angle of water with respect to the surface of the particles is preferably 70 to 90°. When the contact angle of water with respect to the surface of the particles is within this range, the dispersion of the particles in water is good. The contact angle of water with respect to the surface of the particles can be adjusted by adjusting the type of polylactic acid, the surfactant, or the EO / PO ratio of the resin.

[0040] <Method for measuring contact angle> In this application, the contact angle of water with respect to the surface of the particles is measured as follows. The aforementioned particles were pressed into a Briquestting Ring (made of polyvinyl chloride, 35 mm in diameter, 5 mm thick) using a Shimadzu Briquest Press MP-35 to create pellets. The contact angle (°) was measured using a Kyowa Interface Chemical Co., Ltd. Dynamic Contact Angle Meter "DMo-701" at 25°C, 30 seconds after a 2.5 μL water droplet landed on the pellet surface.

[0041] Methods for producing the particles include dissolving a biodegradable resin (B) and a hydrophobic agent (C) in a hydrophilic solvent, then dropping the mixture dropwise into water containing a surfactant (D) and / or polyvinyl alcohol under stirring, removing the hydrophilic solvent and other solvents under reduced pressure to form particles, adding sugars and / or sugar alcohols (A), and freeze-drying to produce a powder.

[0042] Examples of hydrophilic solvents include ketone solvents such as acetone and methyl ketone, ester solvents such as ethyl acetate, ether solvents such as dioxane and tetrahydrofuran, and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. Hydrophilic solvents may be used individually or in combination of two or more. In this invention, a hydrophilic solvent means a solvent that dissolves in 20 g or more of water at 20°C.

[0043] From the viewpoint of handling, the ratio of the total weight of (B) and (C) to the weight of the solution obtained by dissolving the biodegradable resin (B) and the hydrophobic agent (C) in a hydrophilic solvent is preferably 0.5 to 5% by weight. The concentration of surfactant (D) and / or the surfactant in the aqueous solution of polyvinyl alcohol is preferably 0.01 to 1% by weight from the viewpoint of handling. When adding a hydrophilic solvent solution of a biodegradable resin (B) and a hydrophobic agent (C) dropwise to an aqueous solution of a surfactant (D) and / or polyvinyl alcohol, it is preferable to add the hydrophilic solvent solution dropwise while stirring at 100 to 500 rpm using a stirrer or the like. [Examples]

[0044] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto. It's not that.

[0045] <Example 1> In a container, 200 mg of polylactic acid [Mw=100,000, manufactured by Tokyo Materials Co., Ltd.] and 10 mg of thiadinyl [LogPow=3.68, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] were dissolved in 16 mL of acetone. 100 mg of polyvinyl alcohol was dissolved in 20 mL of deionized water, and the above aqueous solution at 25°C was stirred at 120 rpm using a magnetic stirrer HS-30D [manufactured by AS ONE Corporation]. The above polylactic acid solution at 25°C was then added dropwise for 5 minutes, and stirring was continued at the same stirring speed at 25°C for 20 minutes. Subsequently, the solvent was removed by vacuum distillation using an evaporator to obtain a particulate aqueous solution (P0-1).

[0046] 17.5 mg of glucose [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] was added to an aqueous particle solution (P0-1), stirred, and then freeze-dried at -80°C for 24 hours to obtain plant growth stimulant particles (P-1). The median diameter in particle (P-1) was 190 nm. The contact angle of water with respect to the surface of particle (P-1) was 78°. Furthermore, a research-grade freeze-dryer, ALPHA2-4LSCplus [manufactured by Kubota Shoji Co., Ltd.], was used for freeze-drying.

[0047] <Examples 2 and 3> Plant growth-promoting particles (P-2) or (P-3) were obtained in the same manner as in Example 1, except that the amount of glycol added to the aqueous particle solution (P0-1) was changed from 17.5 mg to 175 mg or 1750 mg.

[0048] <Example 4> Plant growth-promoting particles (P-4) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of fructose [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0049] <Example 5> Plant growth-promoting particles (P-5) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of galactose [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0050] <Example 6> Plant growth-promoting particles (P-6) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of sucrose [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0051] <Example 7> Plant growth-promoting particles (P-7) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of raffinose [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0052] <Example 8> Plant growth-promoting particles (P-8) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of glycerin [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0053] <Example 9> Plant growth-promoting particles (P-9) were obtained in the same manner as in Example 1, except that 17.5 mg of glucose added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of sorbitol [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.].

[0054] <Example 10> In a container, 120 mg of polylactic acid [Mw=100,000, manufactured by Tokyo Materials Co., Ltd.] and 20 mg of dicloventin azox [LogPow=3.4, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] were dissolved in 16 mL of acetone. 100 mg of polyvinyl alcohol was dissolved in 20 mL of deionized water, and the above aqueous solution at 25°C was stirred at 120 rpm using a magnetic stirrer HS-30D [manufactured by AS ONE Corporation]. The above polylactic acid solution at 25°C was then added dropwise for 5 minutes, and stirring was continued at the same stirring speed at 25°C for 20 minutes. Subsequently, the solvent was removed by vacuum distillation using an evaporator to obtain a particulate aqueous solution (P0-2).

[0055] 17.5 mg of glucose was added to the aqueous particle solution (P0-2), stirred, and then freeze-dried at -80°C for 24 hours to obtain plant growth stimulant particles (P-10).

[0056] <Comparative Example 1> The aforementioned aqueous particle solution (P0-1) was freeze-dried at -80°C for 24 hours to obtain comparative plant growth stimulant particles (RP-1).

[0057] <Comparative Example 2> A comparative plant growth-promoting particle (RP-2) was obtained in the same manner as in Example 1, except that 17.5 mg of glycol added to the aqueous particle solution (P0-1) was replaced with 17.5 mg of polyethylene glycol.

[0058] <Comparative Example 3> The particulate aqueous solution (P0-1) was used as a comparative plant growth stimulant (RP-3).

[0059] <Evaluation of redistribution> For each of the obtained particles (P-1) to (P-10) and (RP-1) to (RP-2), 50 mg of deionized water was added to 50 mg of the particles, and the mixture was stirred for 1 minute using a vortex mixer with a magnetic stirrer HS-30D [manufactured by AS ONE Corporation]. The median diameter was then measured using a dynamic light scattering analyzer [dynamic light scattering particle distribution analyzer Zetasizer Ultra (manufactured by Malvern Panalytical)]. The redispersion rate was defined as the median diameter before freeze-drying divided by the median diameter mentioned above. The results are shown in Table 1.

[0060] <Evaluation of storage properties: Dissolution rate of active ingredients> For the obtained plant growth stimulants P-1) to P-10 and RP-1) to RP-3, 10g of each (10ml for RP-3) was placed at the bottom of a glass container (volume 250mL), the lid of the glass container was closed, and the container was placed in a small environmental test chamber (ESPEC SU-222) set to 40°C and left for 2 months. Two months later, the plant growth stimulants removed from the glass containers were dissolved in water (RP-3 was left as is), and the concentration (ppm) of the hydrophobic agents was measured using a nano-drop spectrophotometer (manufactured by Thermo Fisher Scientific Co., Ltd.). The storage performance was evaluated by dividing the concentration of the hydrophobic agent after the above test by the concentration of the hydrophobic agent measured similarly before the start of the test, and multiplying the result by 100 (%), which was used as the remaining amount of the agent. A higher value is preferable. The results are shown in Table 1. Note that comparative examples 1 and 2, which were not redispersed, could not be measured because they agglomerated and did not dissolve in water.

[0061] [Table 1] [Industrial applicability]

[0062] The plant growth stimulant of the present invention, when dispersed in a solvent and applied as fertilizer, allows plants to efficiently absorb the drug, possesses appropriate drug elution properties from particles, exhibits excellent sustained release properties, and has excellent sustained efficacy. Therefore, it is extremely useful for horticultural and agricultural applications, as it promotes plant growth and growth while suppressing phytotoxicity.

Claims

1. A plant growth stimulant comprising sugars and / or sugar alcohols (A), a biodegradable resin (B), and a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, wherein the particles have a median diameter of 1 to 300 nm.

2. The plant growth aid according to claim 1, wherein the total content of sugars and / or sugar alcohols (A) is 5 to 45% by weight based on the weight of the particles.

3. The plant growth aid according to claim 1, wherein the contact angle of water with respect to the surface of the particles is 70 to 90°.

4. The plant growth aid according to claim 1, wherein the biodegradable resin (B) is at least one resin selected from the group consisting of polylactic acid, polycaprolactone, polyglycolic acid, lactic acid-glycolic acid copolymer, and resins having a segment made of any of these resins and a segment made of a resin having an SP value of 5 to 15.

5. A plant growth support solution containing a biodegradable resin (B), a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, particles with a median diameter of 1 to 300 nm, water, and sugars and / or sugar alcohols (A).

6. A method for producing a plant growth aid according to claim 1, comprising the step of freeze-drying a plant growth aid solution containing a biodegradable resin (B), a hydrophobic agent (C) having an octanol / water partition coefficient (LogPow) of 1 to 10 at 25°C, particles with a median diameter of 1 to 300 nm, water, and sugars and / or sugar alcohols (A).

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