Polyurethane microcapsules, process for their preparation and use

Abstract

This invention provides a polyurethane microcapsule, its preparation method, and its application. The raw materials for preparing the polyurethane microcapsule, by weight, include the following components: 30-50 parts of functionalized polyether polyol, 3-10 parts of amino-containing acrylic monomer, 10-25 parts of isocyanate monomer, 3-6 parts of cationic chain extender, 2-5 parts of small molecule chain extender, 0.5-2 parts of capping agent, 1.5-5 parts of neutralizing agent, 5-15 parts of pesticide active ingredient, 0.1-0.5 parts of initiator, 10-30 parts of organic solvent, and 100-160 parts of water. The raw materials for preparing the functionalized polyether polyol include a ring-opening initiator, functional monomer, and active monomer. This invention improves the adhesion and scouring resistance of polyurethane microcapsules by introducing amino and acrylic structural units into them, resulting in high encapsulation efficiency and rinsing retention rate. Simultaneously, the dense structure of the polyurethane microcapsule achieves a simultaneous improvement in sustained-release performance and adhesion performance.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane materials technology, and particularly relates to a polyurethane microcapsule, its preparation method, and its application. Background Technology

[0002] In agricultural production, pesticides are the primary means of ensuring crop yields and controlling pests and diseases. However, conventional formulations generally suffer from low utilization rates and short durations of effectiveness. Studies have shown that only about 30-40% of the active ingredients in pesticides ultimately act on pests and pathogens after field application. The remainder is lost due to decomposition of active ingredients caused by sunlight, evaporation, and washout by rainwater. Especially in open-field crops and high-humidity environments, the adhesion of pesticides to the leaf surface is insufficient, making the pesticides easily washed away by rainwater. This not only increases the economic cost of frequent re-spraying but also leads to the accumulation of pesticide residues in soil and water bodies, posing a potential risk to the ecological environment.

[0003] To improve pesticide utilization and field persistence, slow-release and carrier technologies have become important development directions in pesticide formulation. Among them, microencapsulation formulations encapsulate active ingredients through polymer walls, forming micron-sized capsules. This can slow down the photolysis and volatilization of active ingredients to a certain extent, achieving slow release, thereby extending the duration of effectiveness and reducing the number of applications.

[0004] CN118160716A discloses a polyurethane pesticide microcapsule and its preparation method, which is prepared by the following steps: An organic solvent is added to the pesticide technical material, followed by the addition of an isocyanate compound, and the mixture is stirred to form an oil phase; an emulsifier and dispersant are weighed and mixed, and deionized water is added, and the mixture is stirred at room temperature to form an aqueous phase; the organic phase is poured into the aqueous phase, and the mixture is stirred to form an oil-in-water emulsion; a chain extender is then added dropwise to the oil-in-water emulsion while stirring; after the addition is complete, stirring continues, followed by centrifugation, washing, and drying to obtain the polyurethane pesticide microcapsule. However, its encapsulation efficiency is 86.33%-88.70%, which needs further improvement.

[0005] CN113016792A discloses a polyurethane pesticide microcapsule suspension and its preparation method, using isophorone diisocyanate, pesticide technical, and organic solvent as the oil phase. The isophorone diisocyanate has a high molecular weight and contains cycloalkane structures, resulting in a stronger solidified network structure compared to other aliphatic isocyanates. This strengthens the microcapsule shell and improves the stability of the polyurethane pesticide microcapsule suspension. An emulsifier and deionized water are used as the aqueous phase. During use, the oil and aqueous phases are directly emulsified and prepolymerized. The prepolymer product then undergoes chain extension by a chain extender, which acts as a capping agent, further stabilizing the microcapsule shell and improving the stability and encapsulation efficiency of the polyurethane pesticide microcapsule suspension. However, the encapsulation efficiency is relatively low, only 73.4%-84.2%.

[0006] CN117502440A discloses a self-dispersible pesticide microcapsule. Its core material is mainly obtained by curing and polymerizing a mixture of polyurethane prepolymer and pesticide, while its encapsulation material is mainly formed by interfacial polymerization of a polyurethane prepolymer containing hydrophilic groups. The pesticide loading is 80-99%, and the particle size is 1-20 μm. The preparation method involves adding hydrophobic and hydrophilic polyurethane prepolymers encapsulating pesticides to water, emulsifying them to obtain an emulsion with the hydrophobic polyurethane prepolymer encapsulating pesticides as the core and the hydrophilic polyurethane prepolymer containing hydrophilic groups as the shell. A curing agent is added to the emulsion, and after interfacial polymerization, pesticide microcapsules are obtained. The pesticide microcapsules are easy to disperse in solvents, have a thin hydration layer, low viscosity, and good stability. However, it is difficult to achieve a balance between controlled-release stability and leaf adhesion in this pesticide microcapsule.

[0007] The leaf adhesion performance of existing microcapsule systems remains significantly insufficient, stemming from limitations in the design of the capsule wall materials and structures. The capsule walls are mostly composed of a single polymer, resulting in a relatively loose structure that makes it difficult to form a dense and stable outer shell. This leads to insufficient spreadability and retention of microcapsules on leaf surfaces, making them highly susceptible to runoff with rainwater. Simultaneously, the low polarity of the capsule walls hinders effective interaction with the waxy layer on the leaf surface, further affecting drug retention and penetration. Although the performance of microcapsules can be improved by introducing hydrophilic or hydrophobic modified monomers, achieving a balance between controlled-release stability and leaf adhesion remains challenging. On the one hand, excessive hydrophilicity leads to capsule runoff with rainwater; on the other hand, excessive hydrophobicity affects the dispersibility of capsules in water and the stability of the emulsion.

[0008] Therefore, developing a polyurethane microcapsule with controlled release properties, dense structure, and good adhesion is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a polyurethane microcapsule, its preparation method, and its application. The present invention copolymerizes an amino-containing acrylic monomer with a polyurethane backbone, introducing amino groups and acrylic structural units into the polyurethane microcapsule. This improves the adhesion and erosion resistance of the polyurethane microcapsule on the leaf surface, while the acrylic structural units enhance the structural density of the capsule wall, achieving a simultaneous improvement in both sustained-release performance and adhesion performance.

[0010] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polyurethane microcapsule, wherein the raw materials for preparing the polyurethane microcapsule comprise the following components by weight: 30-50 parts of functionalized polyether polyol; Contains 3-10 parts of aminoacrylic acid monomers; 10-25 parts isocyanate monomer; 3-6 parts of cationic chain extender; 2-5 parts of small molecule chain extender; 0.5-2 parts of capping agent; Neutralizing agent 1.5-5 parts; 5-15 parts of pesticide active ingredient; Initiator 0.1-0.5 parts; 10-30 parts organic solvent; 100-160 parts water; The raw materials for preparing the functionalized polyether polyol include ring-opening initiators, functional monomers, and active monomers.

[0011] This invention introduces amino-containing acrylic monomers into polyurethane microcapsules. The double bonds in these monomers can copolymerize with functionalized polyether polyols, thereby introducing active amino groups into the capsule wall structure. These amino structures can form multi-point bonds with functional groups on the leaf surface through hydrogen bonding and electrostatic interactions, significantly improving the adhesion and erosion resistance of the polyurethane microcapsules on the leaf surface. Simultaneously, the acrylic structural units enhance the structural density of the capsule wall, achieving synergistic optimization of sustained-release and adhesion properties. The cationic chain extender, on the one hand, forms electrostatic interactions with the negative charges on the leaf surface, improving the erosion resistance of the polyurethane microcapsules and extending the drug's shelf life; on the other hand, the cationic chain extender improves the dispersibility of the components, increases emulsification efficiency, and provides uniform and stable conditions for the polymerization reaction.

[0012] This invention uses specific amounts of each component to copolymerize amino-containing acrylic monomers with functionalized polyether polyols, forming dense and high-performance polyurethane microcapsules. The structure contains amino and acrylic structural units, which significantly improves the density of the polyurethane microcapsules and effectively enhances the sustained-release performance of the drug. At the same time, the polyurethane microcapsules have good adhesion to the interface, which significantly enhances the erosion resistance.

[0013] The amount of the functionalized polyether polyol can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, or 50 parts, etc.

[0014] The amount of the amino-containing acrylic monomer can be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts, etc.

[0015] The amount of the isocyanate monomer can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, or 25 parts, etc.

[0016] The amount of the cationic chain extender can be 3 parts, 4 parts, 5 parts, or 6 parts, etc.

[0017] The amount of the small molecule chain extender can be 2 parts, 3 parts, 4 parts, or 5 parts, etc.

[0018] The amount of the capping agent can be 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc.

[0019] The amount of the neutralizing agent can be 1.5 parts, 2 parts, 3 parts, 4 parts, or 5 parts, etc.

[0020] The dosage of the active ingredient in the pesticide can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts, etc.

[0021] The amount of the initiator can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, etc.

[0022] The amount of the organic solvent can be 10 parts, 15 parts, 20 parts, 25 or 30 parts, etc.

[0023] The amount of water used can be 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 or 160 parts, etc.

[0024] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0025] Preferably, the functionalized polyether polyol contains a double bond structure.

[0026] Preferably, the raw materials for preparing the functionalized polyether polyol include the following components by weight: 2.5-4 parts of ring-opening initiator; 20-55 parts of functional monomers; 70-90 parts of active monomer; The amount of the ring-opening initiator can be 2.5 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, or 4 parts, etc.

[0027] The amount of the functional unit can be 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54 or 55 parts, etc.

[0028] The amount of the active monomer can be 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, or 90 parts, etc.

[0029] Preferably, the ring-opening initiator includes any one or a combination of at least two of ethylene glycol, propylene glycol, diethylene glycol, or dipropylene glycol.

[0030] Preferably, the functional monomer comprises any one or a combination of at least two of glycidyl methacrylate, allyl glycidyl ether, or 4-vinylphenyl glycidyl ether.

[0031] Preferably, the active monomer includes any one or a combination of at least two of ethylene oxide, propylene oxide, butane oxide, or caprolactone.

[0032] This invention prepares functionalized polyether polyols by ring-opening polymerization of ring-opening initiators, functional monomers, and active monomers, so that the side chains contain double bond groups, and then copolymerizes them with amino-containing acrylic monomers to introduce amino and acrylic structural units into polyurethane microcapsules.

[0033] If too much functional monomer is used, it will lead to excessive cross-linking during copolymerization with aminoacrylic monomers, which will further harden the capsule wall in the emulsion stage and affect the stability of the system. The particle size of polyurethane microcapsules will increase and the scouring resistance will decrease. If too little functional monomer is used, the degree of capsule wall densification will be limited and the number of surface active sites will be small, which will reduce the adhesion between polyurethane microcapsules and blades, and thus reduce the encapsulation rate and scouring retention rate.

[0034] Preferably, the raw materials for preparing the functionalized polyether polyol further include a catalyst and / or a monomer stabilizer.

[0035] Preferably, the catalyst comprises any one or a combination of at least two of the following: bimetallic cyanide, stannous octoate, bismuth laurate, bismuth neodecanoate, or bismuth isooctanoate.

[0036] Preferably, the monomer stabilizer comprises any one or a combination of at least two of 2,6-di-tert-butyl-4-methylphenol, hydroquinone monomethyl ether, or benzothiazine.

[0037] Preferably, the preparation method of the functionalized polyether polyol includes the following steps: (1) The functional monomer and the monomer stabilizer are mixed to obtain component A; (2) The ring-opening initiator, active monomer and catalyst are mixed to obtain component B; (3) Mix the A component and the B component and react to obtain the functionalized polyether polyol.

[0038] Preferably, the reaction is carried out in a protective atmosphere.

[0039] Preferably, the protective atmosphere includes any one or a combination of at least two of nitrogen, helium, or argon.

[0040] Preferably, the reaction temperature is 80-120℃, such as 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃.

[0041] Preferably, the reaction time is 2-6 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0042] Preferably, the reaction pressure is 0.3-0.5 MPa, for example 0.3 MPa, 0.4 MPa or 0.5 MPa.

[0043] Preferably, the reaction is followed by filtration.

[0044] Preferably, the catalyst accounts for 30-150 ppm of the total amount of the reaction system, such as 30 ppm, 50 ppm, 70 ppm, 90 ppm, 110 ppm, 130 ppm or 150 ppm.

[0045] Preferably, the monomer stabilizer accounts for 300-800 ppm of the total amount of the reaction system, such as 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm or 800 ppm.

[0046] The preparation method of the functionalized polyether polyol specifically includes the following steps: (1) The functional monomer and the monomer stabilizer are mixed to obtain component A; (2) In a protective atmosphere, add the ring-opening initiator, active monomer and catalyst to the reactor, mix them to obtain component B; (3) Heat the reaction system to 80-120℃ and pressurize it to 0.3-0.5MPa. Add component A to component B at a constant rate. React for 2-6 hours, cool down, and filter under vacuum to obtain the functionalized polyether polyol.

[0047] Preferably, the amino-containing acrylic monomer includes primary amine vinyl (meth)acrylate monomer.

[0048] It should be noted that, in this invention, the primary amine vinyl (meth) acrylate monomer includes primary amine vinyl acrylate monomer and / or primary amine vinyl methacrylate monomer.

[0049] Preferably, the primary amine vinyl (meth) acrylate monomer comprises 2-aminoethyl acrylate and / or 2-aminoethyl methacrylate.

[0050] Preferably, the isocyanate monomer includes any one or a combination of at least two of isoflavone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, or tetramethylphenyl diisocyanate.

[0051] Preferably, the cationic chain extender comprises an alcoholamine.

[0052] Preferably, the cationic chain extender comprises N-methyldiethanolamine and / or N-ethyldiethanolamine.

[0053] Preferably, the small molecule chain extender comprises a small molecule diol.

[0054] Preferably, the small molecule chain extender includes any one or a combination of at least two of ethylene glycol, 1,4-butanediol or hexanediol.

[0055] Preferably, the capping agent comprises a monofunctional alcohol.

[0056] Preferably, the capping agent comprises any one or a combination of at least two of methanol, ethanol, or butanol.

[0057] Preferably, the neutralizing agent comprises a weak acid.

[0058] Preferably, the neutralizing agent includes lactic acid and / or glacial acetic acid.

[0059] Preferably, the active pesticide ingredient includes any one or a combination of at least two of the following: insecticides, fungicides, acaricides, herbicides, or plant growth regulators.

[0060] Preferably, the insecticide includes any one or a combination of at least two of abamectin, emamectin benzoate, imidacloprid, acetamiprid, thiamethoxam, lambda-cyhalothrin, or bifenthrin.

[0061] Preferably, the fungicide includes any one or a combination of at least two of the following: carbendazim, difenoconazole, tebuconazole, propiconazole, triadimefon, or azoxystrobin.

[0062] Preferably, the herbicide includes any one or a combination of at least two of acetochlor, metolachlor, or S-metolachlor.

[0063] Preferably, the initiator includes any one or a combination of at least two of benzoyl peroxide, dicumyl peroxide, azobisisobutyronitrile, or azobisisoheptanenitrile.

[0064] Preferably, the organic solvent includes any one or a combination of at least two of acetone, butanone, or N-methylpyrrolidone.

[0065] In a second aspect, the present invention provides a method for preparing polyurethane microcapsules as described in the first aspect, the method comprising the following steps: (1) The functionalized polyether polyol, isocyanate monomer, cationic chain extender and organic solvent are mixed and reacted to obtain isocyanate prepolymer; (2) Add a small molecule chain extender to react, then add a capping agent to react, and finally add a neutralizing agent to react to obtain a hydrophilic prepolymer; (3) The active pesticide ingredient is added to a hydrophilic prepolymer to obtain an oil phase component. The oil phase component is added to water and emulsified to obtain an O / W emulsion. (4) Add amino-containing acrylic monomers and initiators to the O / W type emulsion and react to obtain the polyurethane microcapsules.

[0066] Preferably, steps (1)-(4) are carried out in a protective atmosphere.

[0067] Preferably, in step (1), the reaction temperature is 80-85℃, such as 80℃, 81℃, 82℃, 83℃, 84℃ or 85℃.

[0068] Preferably, in step (1), the reaction time is 2-3 hours, such as 2 hours, 2.5 hours or 3 hours.

[0069] Preferably, in step (2), the temperature of the reaction of adding the small molecule chain extender is 60-65℃ (e.g., 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃, etc.), and the reaction time is 1-2h (e.g., 1h, 1.5h or 2h, etc.).

[0070] Preferably, in step (2), the temperature of the reaction of adding the capping agent is 55-65℃ (e.g., 55℃, 57℃, 59℃, 61℃, 63℃ or 65℃, etc.), and the reaction time is 0.3-1h (e.g., 0.3h, 0.6h or 1h, etc.).

[0071] Preferably, in step (2), the temperature of the reaction of adding the neutralizing agent is 40-45℃ (e.g., 40℃, 41℃, 42℃, 43℃, 44℃ or 45℃, etc.), and the reaction time is 25-35min (e.g., 25min, 27min, 29min, 31min, 33min or 35min, etc.).

[0072] Preferably, in step (3), the emulsification is carried out under shear conditions.

[0073] Preferably, in step (3), the shearing rate is 1000-3000 rpm, such as 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm, 2800 rpm or 3000 rpm.

[0074] Preferably, in step (3), the emulsification time is 10-30 min, such as 10 min, 15 min, 20 min, 25 min or 30 min.

[0075] Preferably, in step (4), the reaction temperature is 60-80℃, such as 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃.

[0076] Preferably, in step (4), the reaction time is 3-6 hours, for example, 3 hours, 4 hours, 5 hours or 6 hours.

[0077] Preferably, in step (4), the reaction is further followed by filtration.

[0078] The preparation method of the polyurethane microcapsules specifically includes the following steps: (1) In a protective atmosphere, the functionalized polyether polyol, isocyanate monomer, cationic chain extender and organic solvent are mixed and reacted at 80-85°C for 1-2 hours to obtain isocyanate prepolymer; (2) Cool down to 60-65℃, add small molecule chain extender and react for 1-2 hours, then add end capping agent and react at 55-65℃ for 0.3-1 hours, cool down to 40-45℃, add neutralizer and react for 25-35 minutes to obtain hydrophilic prepolymer; (3) The active pesticide ingredient is added to the hydrophilic prepolymer to obtain an oil phase component. The oil phase component is added to water and emulsified at 1000-3000 rpm for 10-30 min to obtain an O / W type emulsion. (4) Add amino-containing acrylic monomers and initiators to the O / W type emulsion, react at 60-80℃ for 3-6h, cool to room temperature, filter, and obtain the polyurethane microcapsules.

[0079] Thirdly, the present invention provides the application of polyurethane microcapsules as described in the first aspect in pesticide formulations.

[0080] Compared with the prior art, the present invention has the following beneficial effects: This invention improves the adhesion and erosion resistance of polyurethane microcapsules on leaf surfaces by introducing amino groups and acrylic structural units into the microcapsules. Simultaneously, the acrylic structural units enhance the structural density of the capsule wall, achieving a simultaneous improvement in both sustained-release performance and adhesion. The polyurethane microcapsules provided by this invention have a particle size between 3.5-4.6 μm, an encapsulation efficiency ≥84%, and a wash-retention rate ≥74%. Detailed Implementation

[0081] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0082] The source information of some raw materials in this embodiment of the invention is as follows: Bimetallic cyanide: Shanghai Sanmei Chemical, bimetallic cyanide catalyst.

[0083] Preparation Example 1 This preparation example provides a functionalized polyether polyol, the raw materials for which the functionalized polyether polyol is prepared include the following components: Ethylene glycol: 3.1 parts; Propylene oxide: 87 parts; Glycidyl methacrylate: 30.4 parts; Bimetallic cyanide: 100 ppm; 2,6-Di-tert-butyl-4-methylphenol: 500 ppm; The preparation method of the functionalized polyether polyol includes the following steps: (1) Glycidyl methacrylate and 2,6-di-tert-butyl-4-methylphenol were mixed to obtain component A; (2) In a protective atmosphere, ethylene glycol, propylene oxide and bimetallic cyanide are added to the reactor and mixed to obtain component B; (3) Heat the reaction system to 100°C and pressurize it to 0.4 MPa. Slowly add component A to component B and react for 4 hours. When the hydroxyl value reaches 51 mg KOH / g, cool down and filter under vacuum to obtain functionalized polyether polyol A.

[0084] Preparation Example 2 This preparation example provides a functionalized polyether polyol, the raw materials for which the functionalized polyether polyol is prepared include the following components: Propylene glycol: 2.5 parts; Butylene oxide: 71 parts; Allyl glycidyl ether: 20 parts; Bimetallic cyanide: 100 ppm; Hydroquinone monomethyl ether: 500 ppm; The preparation method of the functionalized polyether polyol includes the following steps: (1) Mix allyl glycidyl ether and hydroquinone monomethyl ether to obtain component A; (2) In a protective atmosphere, propylene glycol, epoxide and bimetallic cyanide are added to the reactor and mixed to obtain component B; (3) Heat the reaction system to 120°C and pressurize it to 0.3 MPa. Slowly add component A to component B and react for 2 hours. When the hydroxyl value reaches 45 mg KOH / g, cool down and filter under vacuum to obtain functionalized polyether polyol B.

[0085] Preparation Example 3 This preparation example provides a functionalized polyether polyol, the raw materials for which the functionalized polyether polyol is prepared include the following components: Diethylene glycol: 3.8 parts; Caprolactone: 81.7 parts; 4-Vinylphenyl glycidyl ether: 31.5 parts; Stannous octoate 100 ppm; Benzothiazine: 500 ppm; The preparation method of the functionalized polyether polyol includes the following steps: (1) Mix 4-vinylphenyl glycidyl ether and benzothiazide to obtain component A; (2) Under a protective atmosphere, diethylene glycol, caprolactone and stannous octoate are added to the reactor and mixed to obtain component B; (3) Heat the reaction system to 80°C and pressurize it to 0.5 MPa. Slowly add component A to component B and react for 6 hours. When the hydroxyl value reaches 38 mg KOH / g, cool down and filter under vacuum to obtain functionalized polyether polyol C.

[0086] Preparation Example 4 The only difference from Preparation Example 1 is that the amount of glycidyl methacrylate used is 42.6 parts, while the amounts of the other components and the preparation method are the same as in Preparation Example 1, resulting in functionalized polyether polyol D.

[0087] Preparation Example 5 The only difference from Preparation Example 1 is that the amount of glycidyl methacrylate used is 21.3 parts, while the amounts of the other components and the preparation method are the same as in Preparation Example 1, resulting in functionalized polyether polyol E.

[0088] Preparation Example 6 The only difference from Preparation Example 1 is that the amount of glycidyl methacrylate used is 17.7 parts, while the amounts of the other components and the preparation method are the same as in Preparation Example 1, resulting in functionalized polyether polyol F.

[0089] Preparation Example 7 The only difference from Preparation Example 1 is that the amount of glycidyl methacrylate used is 71 parts, while the amounts of the other components and the preparation method are the same as in Preparation Example 1, resulting in functionalized polyether polyol G.

[0090] Example 1 This embodiment provides a polyurethane microcapsule, the raw materials for preparing the polyurethane microcapsule comprising the following components by weight: Functionalized polyether polyol A: 38 parts; 2-Aminoethyl acrylate: 9 parts; Isophorone diisocyanate: 20 parts; N-Methyldiethanolamine: 4.7 parts; 1,4-Butanediol: 2.62 parts; Ethanol: 0.8 parts; Lactic acid: 3.6 parts; Avermectin: 10 parts; Azobisisobutyronitrile: 0.3 parts; N-methylpyrrolidone: 15 parts; Deionized water: 160 parts; The method for preparing the polyurethane microcapsules includes the following steps: (1) In accordance with the above formulation dosage, functionalized polyether polyol A, isoflurone diisocyanate, N-methyldiethanolamine and N-methylpyrrolidone are mixed in a protective atmosphere and reacted at 82°C for 1.5 h to obtain isocyanate prepolymer; (2) Cool down to 65°C, add 1,4-butanediol and react for 1 h, then add ethanol and react at 65°C for 0.3 h, cool down to 43°C, add lactic acid and react for 30 min to obtain a hydrophilic prepolymer; (3) Add abamectin to the hydrophilic prepolymer to obtain an oil phase component. Add the oil phase component to water and emulsify at 2000 rpm for 20 min to obtain an O / W type emulsion. (4) Add 2-aminoethyl acrylate and azobisisobutyronitrile to the O / W type emulsion, react at 70°C for 5 h, cool to room temperature, filter, and obtain the polyurethane microcapsules.

[0091] Example 2 This embodiment provides a polyurethane microcapsule, the raw materials for preparing the polyurethane microcapsule comprising the following components by weight: Functionalized polyether polyol B: 30 parts; 2-Aminoethyl methacrylate: 5 parts; Dicyclohexylmethane diisocyanate: 25 parts; N-Ethyldiethanolamine: 5.2 parts; Hexanediol: 4 parts; Butanol: 1.5 parts; Glacial acetic acid: 2.8 parts; Difenoconazole: 5 parts; Azobisisobutyronitrile: 0.1 part; N-methylpyrrolidone: 20 parts; Deionized water: 150 parts; The method for preparing the polyurethane microcapsules includes the following steps: (1) In accordance with the above formulation dosage, functionalized polyether polyol B, dicyclohexylmethane diisocyanate, N-ethyldiethanolamine and N-methylpyrrolidone were mixed in a protective atmosphere and reacted at 80°C for 2 hours to obtain isocyanate prepolymer. (2) Cool down to 60°C, add hexanediol and react for 1.5 h, then add butanol and react at 60°C for 0.5 h, cool down to 50°C, add glacial acetic acid and react for 25 min to obtain a hydrophilic prepolymer; (3) Add difenoconazole to the hydrophilic prepolymer to obtain an oil phase component. Add the oil phase component to water and emulsify at 3000 rpm for 10 min to obtain an O / W type emulsion. (4) Add 2-aminoethyl methacrylate and azobisisoheptanenitrile to the O / W type emulsion, react at 80°C for 3 hours, cool to room temperature, filter, and obtain the polyurethane microcapsules.

[0092] Example 3 This embodiment provides a polyurethane microcapsule, the raw materials for preparing the polyurethane microcapsule comprising the following components by weight: Functionalized polyether polyol C: 48 parts; 2-Aminoethyl acrylate: 3 parts; Hexamethylene diisocyanate: 10.8 parts; N-Methyldiethanolamine: 3.2 parts; Hexanediol: 2 parts; Methanol: 0.6 parts; Lactic acid: 2.5 parts; Acetochlor: 15 parts; Azobisisobutyronitrile: 0.5 parts; N-methylpyrrolidone: 30 parts; Deionized water: 130 parts; The method for preparing the polyurethane microcapsules includes the following steps: (1) In accordance with the above formulation dosage, functionalized polyether polyol C, hexamethylene diisocyanate, N-methyldiethanolamine and N-methylpyrrolidone were mixed in a protective atmosphere and reacted at 85°C for 3 hours to obtain isocyanate prepolymer. (2) Cool down to 60°C, add hexanediol and react for 2 hours, then add methanol and react at 55°C for 1 hour. Cool down to 40°C, add lactic acid and react for 35 minutes to obtain a hydrophilic prepolymer. (3) Add acetochlor to the hydrophilic prepolymer to obtain an oil phase component. Add the oil phase component to water and emulsify at 1000 rpm for 30 min to obtain an O / W type emulsion. (4) Add 2-aminoethyl acrylate and azobisisobutyronitrile to the O / W type emulsion, react at 60°C for 6 hours, cool to room temperature, filter, and obtain the polyurethane microcapsules.

[0093] Examples 4-7 The only difference from Example 1 is that the functionalized polyether polyol A is replaced with an equal amount of the functionalized polyether polyol DG prepared in Examples 4-7. The amounts of 1,4-butanediol used in Examples 4-7 are 2.75 parts, 2.5 parts, 2.45 parts, and 2.98 parts, respectively. The amounts of other components and the preparation methods are the same as in Example 1.

[0094] Comparative Example 1 The only difference from Example 1 is that the amount of 2-aminoethyl acrylate is 1 part, while the amounts of the other components and the preparation methods are the same as in Example 1.

[0095] Comparative Example 2 The only difference from Example 1 is that 2-aminoethyl acrylate is not added, while the amounts of the remaining components and the preparation methods are the same as in Example 1.

[0096] Performance testing (1) Average particle size: The average particle size of polyurethane microcapsules was determined using a Malvern laser particle size analyzer.

[0097] (2) Encapsulation efficiency: 1.0 g of polyurethane microcapsule emulsion sample was placed in a 100 mL volumetric flask, and ethanol-water solution with a volume ratio of 1:1 was added to bring the volume to 100 mL. After standing, the liquid sample was centrifuged, and the absorbance of the centrifuged liquid was measured by ultraviolet spectrophotometry. The mass of the active ingredient M1 was calculated by referring to the standard curve. Then, the volumetric flask was sonicated for 20 min, and the absorbance of the centrifuged liquid was measured by ultraviolet spectrophotometry. The mass of the active ingredient M2 was calculated by referring to the standard curve. The encapsulation efficiency of the pesticide microcapsule suspension was calculated by the following formula: Encapsulation efficiency of polyurethane microcapsule emulsion = (M2-M1) / M2×100%.

[0098] (3) Rinsing retention rate: The microcapsule preparation to be tested was prepared into a working solution of 100 mg / L based on the effective ingredient, and evenly sprayed onto the surface of clean and dry cucumber leaves, and then allowed to dry naturally at room temperature. After drying, the leaves were divided into an unrinsed group and a rinsed group (3 leaves in each group). The leaves of the unrinsed group were directly cut into pieces for extraction, and the content of the effective ingredient was determined by high performance liquid chromatography, denoted as M. 冲洗前 The leaves in the rinsing group were rinsed with 50 mL of deionized water to simulate the rain washing process. After rinsing, the leaves were collected, chopped, and extracted with acetonitrile. After centrifugation and filtration, the content of the active ingredient was determined by high-performance liquid chromatography and denoted as M. 冲洗后 The flushing retention rate is calculated using the following formula: Flushing retention rate = M 冲洗后 / M 冲洗前 ×100%.

[0099] The polyurethane microcapsules provided in the examples and comparative examples were tested according to the above performance testing methods, and the results are shown in Table 1: Table 1 As shown in Table 1, this invention, by introducing amino-containing acrylic monomers into polyurethane microcapsules, makes the polyurethane microcapsules dense in structure, exhibiting excellent adhesion and erosion resistance, high encapsulation efficiency, and high rinsing retention rate, thus achieving simultaneous improvement in sustained-release performance and adhesion performance. The polyurethane microcapsules provided by this invention have an average particle size between 3.5-4.6 μm, preferably between 3.5-3.8 μm, an encapsulation efficiency ≥84%, preferably ≥89%, and a rinsing retention rate ≥74%, preferably ≥84%.

[0100] A comparison of Examples 1 and 6-7 shows that in Example 6, the amount of functional monomer was too small, resulting in limited densification of the capsule wall and fewer surface active sites, leading to a significant decrease in encapsulation efficiency and rinsing retention rate. In Example 7, the amount of functional monomer was too large, resulting in excessive cross-linking, which caused the capsule wall to harden and produce structural defects, affecting the stability of the system. This was manifested in the increased particle size of the polyurethane microcapsules and the decrease in encapsulation efficiency. At the same time, excessive cross-linking caused the effective amino / cationic interaction sites on the surface to be buried in the capsule wall or consumed, weakening the effective interaction between the polyurethane microcapsules and the leaf surface, thus significantly reducing the rinsing retention rate.

[0101] As can be seen from the comparison between Example 1 and Comparative Example 1, the amount of amino-acrylic monomers used in Comparative Example 1 is relatively small, and the main structure and compactness of the capsule wall do not change much. The microcapsule particle size and encapsulation efficiency remain at a high level. However, due to the reduction in the number of primary amino groups on the capsule wall surface, the interaction between the polyurethane microcapsules and the crop leaf surface is weakened, resulting in a significant decrease in the rinsing retention rate.

[0102] As can be seen from the comparison between Example 1 and Comparative Example 2, since no amino-containing acrylic monomers were introduced in Comparative Example 2, the copolymerization reaction only occurred locally in the polyurethane capsule wall, making it difficult to form an effective functionalized copolymer layer. This resulted in limited capsule wall density and surface adhesion performance, increased particle size, and a significant decrease in encapsulation efficiency and rinsing retention rate. This fully demonstrates that amino-containing acrylic monomers play a key role in improving the adhesion and erosion resistance of polyurethane microcapsules.

[0103] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A polyurethane microcapsule, characterized in that, The raw materials for preparing the polyurethane microcapsules include the following components by weight: 30-50 parts of functionalized polyether polyol; Contains 3-10 parts of amino acrylic monomers; 10-25 parts isocyanate monomer; 3-6 parts of cationic chain extender; 2-5 parts of small molecule chain extender; 0.5-2 parts of capping agent; Neutralizing agent 1.5-5 parts; 5-15 parts of pesticide active ingredient; Initiator 0.1-0.5 parts; 10-30 parts organic solvent; 100-160 parts water; The raw materials for preparing the functionalized polyether polyol include ring-opening initiators, functional monomers, and active monomers.

2. The polyurethane microcapsule according to claim 1, characterized in that, The functionalized polyether polyol contains a double bond structure; The raw materials for preparing the functionalized polyether polyol include the following components by weight: 2.5-4 parts of ring-opening initiator; 20-55 parts of functional monomers; 70-90 parts of active monomer; The ring-opening initiator includes any one or a combination of at least two of ethylene glycol, propylene glycol, diethylene glycol, or dipropylene glycol. The functional monomers include any one or a combination of at least two of glycidyl methacrylate, allyl glycidyl ether, or 4-vinylphenyl glycidyl ether. The active monomer includes any one or a combination of at least two of ethylene oxide, propylene oxide, butane oxide, or caprolactone.

3. The polyurethane microcapsule according to claim 2, characterized in that, The raw materials for preparing the functionalized polyether polyol also include catalysts and / or monomer stabilizers; The catalyst comprises any one or a combination of at least two of the following: bimetallic cyanide, stannous octanoate, bismuth laurate, bismuth neodecanoate, or bismuth isooctanoate. The monomeric stabilizer includes any one or a combination of at least two of 2,6-di-tert-butyl-4-methylphenol, hydroquinone monomethyl ether, or benzothiazine.

4. The polyurethane microcapsule according to claim 2 or 3, characterized in that, The preparation method of the functionalized polyether polyol includes the following steps: (1) The functional monomer and the monomer stabilizer are mixed to obtain component A; (2) The ring-opening initiator, active monomer and catalyst are mixed to obtain component B; (3) Mix the A component and the B component and react to obtain the functionalized polyether polyol.

5. The polyurethane microcapsule according to claim 4, characterized in that, The reaction is carried out in a protective atmosphere; The reaction temperature is 80-120℃; The reaction time is 2-6 hours; The reaction pressure is 0.3-0.5 MPa; The reaction is followed by filtration.

6. The polyurethane microcapsule according to claim 1, characterized in that, The amino-containing acrylic monomers include primary amine vinyl (meth) acrylate monomers; The primary amine vinyl (meth) acrylate monomers include 2-aminoethyl acrylate and / or 2-aminoethyl methacrylate; The isocyanate monomer includes any one or a combination of at least two of isoflavone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate or tetramethylphenyl diisocyanate; The cationic chain extender includes N-methyldiethanolamine and / or N-ethyldiethanolamine; The small molecule chain extender includes any one or a combination of at least two of ethylene glycol, 1,4-butanediol or hexanediol; The capping agent includes any one or a combination of at least two of methanol, ethanol or butanol; The neutralizing agent includes lactic acid and / or glacial acetic acid.

7. The polyurethane microcapsule according to claim 1, characterized in that, The active ingredient of the pesticide includes any one or a combination of at least two of the following: insecticides, fungicides, acaricides, herbicides, or plant growth regulators. The insecticide includes any one or a combination of at least two of the following: abamectin, emamectin benzoate, imidacloprid, acetamiprid, thiamethoxam, cyhalothrin, or bifenthrin. The fungicide includes any one or a combination of at least two of the following: carbendazim, difenoconazole, tebuconazole, propiconazole, triadimefon, or azoxystrobin; The herbicide includes any one or a combination of at least two of acetochlor, metolachlor, or S-metolachlor. The initiator includes any one or a combination of at least two of benzoyl peroxide, dicumyl peroxide, azobisisobutyronitrile, or azobisisoheptanenitrile; The organic solvent includes any one or a combination of at least two of acetone, butanone, or N-methylpyrrolidone.

8. A method for preparing polyurethane microcapsules according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) The functionalized polyether polyol, isocyanate monomer, cationic chain extender and organic solvent are mixed and reacted to obtain isocyanate prepolymer; (2) Add a small molecule chain extender to react, then add a capping agent to react, and finally add a neutralizing agent to react to obtain a hydrophilic prepolymer; (3) The active pesticide ingredient is added to a hydrophilic prepolymer to obtain an oil phase component. The oil phase component is added to water and emulsified to obtain an O / W emulsion. (4) Add amino-containing acrylic monomers and initiators to the O / W type emulsion and react to obtain the polyurethane microcapsules.

9. The preparation method according to claim 8, characterized in that, Steps (1)-(4) are carried out in a protective atmosphere; In step (1), the reaction temperature is 80-85℃; In step (1), the reaction time is 2-3 hours; In step (2), the reaction temperature for adding the small molecule chain extender is 60-65℃, and the reaction time is 1-2h; In step (2), the reaction temperature for adding the capping agent is 55-65℃, and the reaction time is 0.3-1h; In step (2), the temperature of the reaction with the addition of the neutralizing agent is 40-45℃, and the reaction time is 25-35 min; In step (3), the emulsification is carried out under shear conditions; In step (3), the shearing rate is 1000-3000 rpm; In step (3), the emulsification time is 10-30 min; In step (4), the reaction temperature is 60-80℃; In step (4), the reaction time is 3-6 hours; In step (4), the reaction is followed by filtration.

10. The use of a polyurethane microcapsule as described in any one of claims 1-7 in a pesticide formulation.

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