A polyurethane microcapsule emulsion, its preparation method and application

Abstract

This invention relates to a polyurethane microcapsule emulsion, its preparation method, and its application. The raw materials for preparing the polyurethane microcapsule emulsion, by weight, include: 30-50 parts of unsaturated polyester polyol, 10-25 parts of isocyanate monomer, 3-6 parts of hydrophilic monomer, 2-5 parts of small molecule alcohol chain extender, 1.5-5 parts of neutralizing agent, 0.1-0.5 parts of organometallic catalyst, 20-50 parts of organic solvent, 5-15 parts of pesticide active ingredient, 3-10 parts of C6-C15 straight-chain or branched-chain olefin monomer, 0.1-0.5 parts of initiator, and 100-160 parts of water. The polyurethane microcapsule emulsion provided by this invention solves the problems of low crosslinking density, simple structural topology, insufficient hydrophobicity, and poor encapsulation stability of existing pesticide microcapsules, improving the controlled-release performance, capsule wall density, and emulsion system stability of the polyurethane microcapsule emulsion.

Description

Technical Field

[0001] This invention relates to the field of pesticide formulation technology, and in particular to a polyurethane microcapsule emulsion, its preparation method, and its application. Background Technology

[0002] With the increasing demand in agriculture for highly efficient, low-toxicity, and environmentally friendly pesticide formulations, microencapsulation controlled-release technology has been widely used in pesticide formulations due to its ability to prolong efficacy, reduce volatilization, and lower environmental pollution. By encapsulating pesticide active ingredients with polymeric capsule wall materials, microcapsules can achieve sustained-release, improve utilization efficiency, and enhance environmental stability.

[0003] Polyurethane is one of the most widely used microcapsule wall materials for pesticides due to its excellent film-forming properties, stable mechanical properties, and mild reaction conditions. A common method involves reacting isocyanates with polyols to form a prepolymer, which is then further cured in an emulsion system to form the capsule wall. However, existing polyurethane microcapsules still have shortcomings in terms of structural density, controlled release performance, and encapsulation stability, making it difficult to meet the requirements for sustained release under complex environments.

[0004] On the one hand, traditional systems are dominated by linear main-chain structures with limited cross-linking and insufficient capsule wall density, making them prone to problems such as swelling, hydrolysis, or leakage of active ingredients. Some studies have attempted to construct main-chain cross-linking points by introducing unsaturated small-molecule alcohols or polyfunctional alcohols with isocyanates to achieve higher cross-linking density in structure. However, their cross-linking modes are usually relatively simple, making it difficult to form a three-dimensional capsule wall framework with a dense structure, high network complexity, and spatial controllability.

[0005] On the other hand, polyurethane itself has limited hydrophobicity, and water can easily pass through the capsule wall, causing premature release of the drug. In order to improve dispersibility and emulsion stability, existing systems mostly rely on the addition of surfactants or the introduction of conventional hydrophilic monomers. However, due to the lack of system structure synergistic design, the capsule formation process is still easily affected by environmental factors, resulting in poor control of capsule particle size, frequent aggregation and sedimentation, which affects the consistency and storage stability of the product.

[0006] Therefore, it is urgent to construct polyurethane capsule wall systems with high cross-linking density, topological diversity, and hydrophilicity-hydrophobicity regulation capabilities at the molecular structure level to enhance their three-dimensional network stability and environmental adaptability, and improve the sustained-release capacity, structural compactness, and application stability of microcapsules and emulsion systems. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a polyurethane microcapsule emulsion, its preparation method, and its applications. This invention aims to solve the problems of low crosslinking density, simple structural topology, insufficient hydrophobicity, and poor encapsulation stability in existing pesticide microcapsules, thereby improving their controlled-release performance, capsule wall density, and emulsion system stability.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a polyurethane microcapsule emulsion, wherein the raw materials for preparing the polyurethane microcapsule emulsion, by weight, comprise: 30-50 parts of unsaturated polyester polyol (e.g., 30, 35, 40, 45, 50 parts, etc.), 10-25 parts of isocyanate monomer (e.g., 10, 15, 20, 25 parts, etc.), 3-6 parts of hydrophilic monomer (e.g., 3, 4, 5, 6 parts, etc.), 2-5 parts of small molecule alcohol chain extender (e.g., 2, 3, 4, 5 parts, etc.), 1.5-5 parts of neutralizing agent (e.g., 1.5, 2, 3, 4, 5 parts, etc.), and 0.1-0.5 parts of organometallic catalyst. The following components are used: 1 part (e.g., 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, etc.), 20-50 parts organic solvent (e.g., 20 parts, 30 parts, 40 parts, 50 parts, etc.), 5-15 parts pesticide active ingredient (e.g., 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, etc.), 3-10 parts C6-C15 straight-chain or branched-chain olefin monomer (e.g., 3 parts, 4 parts, 5 parts, 6 parts, 8 parts, 10 parts, etc.), 0.1-0.5 parts initiator (e.g., 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.), and 100-160 parts water (e.g., 100 parts, 120 parts, 140 parts, 160 parts, etc.).

[0010] The raw materials for preparing the unsaturated polyester polyol include, by weight, 20-65 parts of polyether polyol (e.g., 20, 30, 40, 50, 60, 65, etc.), 2-6 parts of unsaturated diacid / anhydride (e.g., 2, 3, 4, 5, 6, etc.), and 0.1-1.0 parts of acidic catalyst (e.g., 0.1, 0.2, 0.5, 0.8, 1.0, etc.).

[0011] This invention utilizes unsaturated polyester polyols with carbon-carbon double bonds to react with isocyanate monomers and hydrophilic monomers to generate a polyurethane prepolymer with a hydrophilic structure. Simultaneously, a small molecule alcohol chain extender is introduced to extend the chain, and after neutralization, a stable emulsion-type hydrophilic prepolymer is formed. This emulsion-type hydrophilic prepolymer is mixed with active ingredients and emulsified to form an O / W type emulsion. Then, olefin monomers with long-chain alkane structures and free radical initiators are introduced into the emulsion to initiate free radical cross-linking polymerization. The double bonds on the polyester backbone are used as cross-linking points to construct a dense hydrophobic three-dimensional network structure, forming a polyurethane microcapsule emulsion with sustained-release function.

[0012] This invention, through the synergistic design of unsaturated polyester structures and long-chain olefins, improves the crosslinking density and topological complexity of the capsule wall while maintaining hydrophobicity, effectively enhancing water permeability and release sustainability. Simultaneously, the introduction of hydrophilic monomers imparts excellent emulsion dispersibility to the system, achieving a formulation with uniform particle size and stable storage.

[0013] Preferably, the raw materials for preparing the unsaturated polyester polyol include: polyether polyol, unsaturated diacid / anhydride, and acidic catalyst.

[0014] Preferably, the molar ratio of the polyether polyol to the unsaturated diacid / anhydride is (1.2-2):1 (for example, it can be 1.2:1, 1.5:1, 1.8:1, 2:1, etc.), and more preferably (1.25-1.5):1.

[0015] Preferably, the polyether polyol includes any one or a combination of at least two of polytetrahydrofuran ether diol, polyethylene glycol, or polypropylene glycol.

[0016] Preferably, the molecular weight of the polyether polyol is 600-1500 g / mol (e.g., 600 g / mol, 800 g / mol, 1000 g / mol, 1200 g / mol, 1500 g / mol, etc.), and more preferably 600-850 g / mol.

[0017] Preferably, the unsaturated dicarboxylic acid / anhydride includes any one or a combination of at least two of maleic acid / anhydride, fumaric acid, or itaconic acid, and is more preferably maleic acid / anhydride and / or fumaric acid.

[0018] Preferably, the molar ratio of carbon-carbon double bonds in the C6-C15 straight-chain or branched olefin monomers to unsaturated diacid / anhydride structural units in the unsaturated polyester polyols is (0.8-2.3):1 (e.g., 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2.3:1, etc.), and more preferably (1.5-2):1.

[0019] Preferably, the acidic catalyst is p-toluenesulfonic acid.

[0020] Preferably, the raw materials for preparing the unsaturated polyester polyol also include antioxidants.

[0021] Preferably, the raw materials for preparing the unsaturated polyester polyol further include 0.1-0.5 parts by weight of antioxidant (e.g., 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.).

[0022] Preferably, the antioxidant is butylated hydroxytoluene.

[0023] Preferably, the acid value of the unsaturated polyester polyol is below 2 mg KOH / g.

[0024] Preferably, the unsaturated polyester polyol is prepared by the following method, which includes: mixing and reacting a polyether polyol, an unsaturated diacid / anhydride, an acidic catalyst, and optionally an antioxidant to obtain the unsaturated polyester polyol.

[0025] Preferably, the reaction temperature is 120-160℃ (e.g., 120℃, 130℃, 140℃, 150℃, 160℃, etc.), and the time is 3-5h (e.g., 3h, 3.5h, 4h, 4.5h, 5h, etc.).

[0026] Preferably, the isocyanate monomer includes any one or a combination of at least two of isoflavone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, hydrogenated phenylmethane diisocyanate, or tetramethylphenyl diisocyanate.

[0027] Preferably, the hydrophilic monomer includes dimethylolpropionic acid and / or dimethylolbutyric acid.

[0028] Preferably, the small molecule alcohol chain extender includes any one or a combination of at least two of ethylene glycol, 1,4-butanediol, or hexanediol.

[0029] Preferably, the neutralizing agent comprises a tertiary amine with a boiling point ≤150°C at 1 atm.

[0030] Preferably, the tertiary amine includes any one or a combination of at least two of triethylamine, dimethylethanolamine, or N,N-dimethylethylamine.

[0031] The organometallic catalyst includes organobismuth and / or organotin.

[0032] Preferably, the organic bismuth comprises any one or a combination of at least two of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, or bismuth naphthenate.

[0033] Preferably, the organotin comprises any one or a combination of at least two of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, or di(dodecyl sulfide)dibutyltin. Preferably, the organic solvent comprises any one or a combination of at least two of acetone, butanone, or N-methylpyrrolidone.

[0034] Preferably, the active pesticide ingredient includes any one or a combination of at least two of the following: organophosphorus pesticides, pyrethroid pesticides, neonicotinoid pesticides, amide pesticides, tetracyclic triterpenoid pesticides, or aromatic ketone pesticides.

[0035] Preferably, the active pesticide ingredient includes any one or a combination of at least two of the following: chlorpyrifos, deltamethrin, cypermethrin, deltamethrin, chlorantraniliprole, flonicamid, acetamiprid, thiamethoxam, phoxim, fenthion, rotenone, or azadirachtin.

[0036] Preferably, the C6-C15 straight-chain or branched olefin monomers include α-olefins.

[0037] Preferably, the α-olefin includes any one or a combination of at least two of 1-hexene, 1-octene, 1-decene, or 1-dodecene.

[0038] Preferably, the initiator comprises azobisisobutyronitrile.

[0039] In a second aspect, the present invention provides a method for preparing a polyurethane microcapsule emulsion according to the first aspect, characterized in that the preparation method includes the following steps:

[0040] (1) Unsaturated polyester polyol, isocyanate monomer, hydrophilic monomer, organic solvent and organometallic catalyst are mixed and reacted to obtain polyurethane prepolymer;

[0041] (2) The polyurethane prepolymer and the small molecule alcohol chain extender are mixed and reacted. The system is then mixed with a neutralizing agent to obtain a hydrophilic prepolymer.

[0042] (3) Mix the hydrophilic prepolymer and the active ingredient to form an oil phase; mix and emulsify the oil phase and water to obtain an O / W type emulsion;

[0043] (4) Mix the O / W type emulsion, C6-C15 straight-chain or branched olefin monomer and initiator, and after reaction, obtain the polyurethane microcapsule emulsion.

[0044] Preferably, the temperature of the reaction in step (1) is 80-85℃ (e.g., 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, etc.), and the time is 2-3h (e.g., 2h, 2.2h, 2.5h, 2.8h, 3h, etc.).

[0045] Preferably, the temperature of the reaction in step (2) is 60-65℃ (e.g., 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, etc.), and the time is 1-2h (e.g., 1h, 1.2h, 1.5h, 1.8h, 2h, etc.).

[0046] Preferably, the temperature at which the system and the neutralizing agent are mixed in step (2) is 40-50°C (e.g., 40°C, 42°C, 45°C, 48°C, 50°C, etc.).

[0047] Preferably, the temperature of the reaction in step (4) is 60-80℃ (e.g., 60℃, 65℃, 70℃, 75℃, 8℃, etc.), and the time is 3-6h (e.g., 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, etc.).

[0048] Thirdly, the present invention provides the application of the polyurethane microcapsule emulsion according to the first aspect in the preparation of pesticide formulations.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] This invention, through the synergistic design of unsaturated polyester structures and long-chain olefins, improves the crosslinking density and topological complexity of the capsule wall while maintaining hydrophobicity, effectively enhancing water permeability and release persistence. Simultaneously, the introduction of hydrophilic monomers imparts excellent emulsion dispersibility to the system, achieving a formulation with uniform particle size and stable storage. The polyurethane microcapsule emulsion system provided by this invention is suitable for encapsulating various hydrophobic pesticide active ingredients, significantly improving encapsulation efficiency, controlled-release performance, and field persistence, and possesses good environmental adaptability and industrial application prospects. Detailed Implementation

[0051] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0052] Preparation Example 1

[0053] This preparation example provides an unsaturated polyester polyol, the types and mass fractions of which are shown in Table 1 below:

[0054] Table 1

[0055]

[0056] The method for preparing the unsaturated polyester polyol includes:

[0057] (1) In a four-necked flask equipped with a stirring, temperature control and reflux condenser, add polyether polyol, unsaturated diacid / anhydride and antioxidant in sequence. Start the stirring device and slowly raise the temperature under nitrogen protection. When the system temperature reaches 140°C, add acidic catalyst and maintain the temperature for about 4 hours.

[0058] (2) Take samples to test the acid value of the system. When the acid value drops to less than 10 mg KOH / g, stop the nitrogen flow and vacuum the system for dehydration. When the acid value drops further to less than 2 mg KOH / g, stop heating and cool down to below 100℃ before discharging to obtain unsaturated polyester polyol.

[0059] Preparation Example 2

[0060] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in the mass fraction, as shown in Table 2:

[0061] Table 2

[0062]

[0063] The preparation method is the same as in Preparation Example 1.

[0064] Preparation Example 3

[0065] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in the mass fraction, as shown in Table 3:

[0066] Table 3

[0067]

[0068] The preparation method is the same as in Preparation Example 1.

[0069] Preparation Example 4

[0070] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in that the molecular weight of the polypropylene glycol is Mn=600g / mol and the mass fraction is 32.6 parts, while the rest is the same as Preparation Example 1.

[0071] Preparation Example 5

[0072] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in that the molecular weight of the polypropylene glycol Mn is 1000 g / mol and the mass fraction is 54.3 parts, while the rest is the same as Preparation Example 1.

[0073] Preparation Example 6

[0074] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in that maleic anhydride is replaced with fumaric acid, otherwise it is the same as Preparation Example 1.

[0075] Preparation Example 7

[0076] This preparation example provides an unsaturated polyester polyol, which differs from Preparation Example 1 only in that itaconic acid is used instead of maleic anhydride, while the rest is the same as Preparation Example 1.

[0077] Example 1

[0078] This embodiment provides a polyurethane microcapsule emulsion, the types of components and their mass fractions of which are shown in Table 4 below:

[0079] Table 4

[0080]

[0081] The preparation method of the polyurethane microcapsule emulsion includes:

[0082] (1) Mix unsaturated polyester polyol, isocyanate monomer, hydrophilic monomer and organic solvent, put into a four-necked flask, purge with nitrogen and heat to 85°C, add catalyst, react for 2h to obtain NCO-terminated prepolymer.

[0083] (2) Then the temperature was lowered to 60°C, a small molecule alcohol chain extender was added to the system, the reaction was carried out for 2 hours, and then the temperature was lowered to 40°C, a neutralizing agent was added to neutralize, and a hydrophilic prepolymer with a carboxylic acid ammonium salt structure was formed.

[0084] (3) Add the active pesticide ingredient to the prepolymer to form the oil phase, stir evenly, slowly add the oil phase to deionized water, and emulsify for 15 minutes under high-speed shear (2000 rpm) to obtain an O / W type emulsion with uniform particle size distribution.

[0085] (4) Add C6-C15 straight-chain or branched-chain olefin monomers and initiators to the above emulsion, heat to 70°C, react for 5 hours under stirring, and after the reaction is completed, cool naturally to room temperature (25°C), remove large particles or gels by coarse filtration to obtain polyurethane microcapsule emulsion.

[0086] Example 2

[0087] This embodiment provides a polyurethane microcapsule emulsion, the types of components and their mass fractions of which are shown in Table 5 below:

[0088] Table 5

[0089]

[0090] The preparation method of the polyurethane microcapsule emulsion includes:

[0091] (1) Mix unsaturated polyester polyol, isocyanate monomer, hydrophilic monomer and organic solvent, put into a four-necked flask, purge with nitrogen and heat to 80°C, add catalyst, react for 3h to obtain NCO-terminated prepolymer;

[0092] (2) Then the temperature was lowered to 65°C, a small molecule alcohol chain extender was added to the system, the reaction was carried out for 1 hour, and then the temperature was lowered to 40°C, a neutralizing agent was added to neutralize, and a hydrophilic prepolymer with a carboxylic acid ammonium salt structure was formed.

[0093] (3) Add the active pesticide ingredient to the prepolymer to form the oil phase, stir evenly, slowly add the oil phase to deionized water, and emulsify for 30 minutes under high-speed shear (1000 rpm) to obtain an O / W type emulsion with uniform particle size distribution.

[0094] (4) Add C6-C15 straight-chain or branched-chain olefin monomers and initiators to the above emulsion, heat to 60°C, react for 6 hours under stirring, and after the reaction is completed, cool naturally to room temperature (25°C), remove large particles or gels by coarse filtration to obtain polyurethane microcapsule emulsion.

[0095] Example 3

[0096] This embodiment provides a polyurethane microcapsule emulsion, the types of components and their mass fractions of which are shown in Table 6 below:

[0097] Table 6

[0098]

[0099] The preparation method of the polyurethane microcapsule emulsion includes:

[0100] (1) Mix unsaturated polyester polyol, isocyanate monomer, hydrophilic monomer and organic solvent, put into a four-necked flask, purge with nitrogen and heat to 85°C, add catalyst, react for 2h to obtain NCO-terminated prepolymer.

[0101] (2) Then the temperature was lowered to 60°C, a small molecule alcohol chain extender was added to the system, the reaction was carried out for 2 hours, and then the temperature was lowered to 40°C, a neutralizing agent was added to neutralize, and a hydrophilic prepolymer with a carboxylic acid ammonium salt structure was formed.

[0102] (3) Add the active pesticide ingredient to the prepolymer to form the oil phase, stir evenly, slowly add the oil phase to deionized water, and emulsify for 10 minutes under high-speed shear (3000 rpm) to obtain an O / W type emulsion with uniform particle size distribution.

[0103] (4) Add C6-C15 straight-chain or branched-chain olefin monomers and initiators to the above emulsion, heat to 80°C, react for 3 hours under stirring, and after the reaction is completed, cool naturally to room temperature (25°C), remove large particles or gels by coarse filtration to obtain polyurethane microcapsule emulsion.

[0104] Examples 4-7

[0105] Examples 4-7 each provide a polyurethane microcapsule emulsion, which differs from Example 1 only in that the unsaturated polyester polyol prepared in Preparation Example 1 is replaced with the unsaturated polyester polyol prepared in Preparation Examples 4-7, and the rest is the same as in Example 1.

[0106] Example 8

[0107] This embodiment provides a polyurethane microcapsule emulsion, which differs from Example 1 only in that the amount of 1-octene used is 4 parts, and the rest is the same as in Example 1.

[0108] Example 9

[0109] This embodiment provides a polyurethane microcapsule emulsion, which differs from Example 1 only in that the amount of 1-octene used is 9 parts, and the rest is the same as in Example 1.

[0110] Comparative Example 1

[0111] This comparative example provides a polyurethane microcapsule emulsion, which differs from Example 1 only in that it does not contain 1-octene; otherwise, it is the same as Example 1.

[0112] Test case

[0113] Test items:

[0114] (1) Average particle size: The average particle size of the polyurethane microcapsule emulsion was determined using a Malvern laser particle size analyzer.

[0115] (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:

[0116] ;

[0117] (3) Field trials: To verify the sustained field efficacy of the microcapsule pesticide formulations of the present invention, field efficacy trials were conducted on the chlorantraniliprole microcapsule emulsion formulations prepared in each example and comparative example. The test crop was corn, and the target pest was fall armyworm. The microcapsule emulsion formulations were diluted to a pesticide concentration of 100 mg / L and applied by conventional spraying. Three replicate plots were set up for each treatment. The initial insect population density was recorded before application, and the changes in insect population were observed on the 3rd, 10th, and 15th days after application. The average control efficacy of each treatment was statistically analyzed and calculated.

[0118] The performance data of the polyurethane microcapsule emulsions provided in Examples 1-9 and Comparative Example 1 are shown in Table 7.

[0119] Table 7

[0120]

[0121] As can be seen from Table 7:

[0122] (1) As can be seen from Examples 1 to 9, the polyurethane microcapsule emulsion provided by the present invention has a small particle size (3.0-4.1 μm) and a high encapsulation rate (81.3-90.2%), which improves the sustained release performance and field persistence of the microcapsule emulsion (the control efficacy reaches 71.4-87.9% 30 days after application).

[0123] (2) A comparison of Examples 1 and 4-5 shows that the polyester polyol used in Example 4 was synthesized from polypropylene glycol 600 with a lower molecular weight. The shortened chain length significantly increased the density of double bonds in the main chain, resulting in more complete free radical crosslinking and a denser capsule wall structure, thereby improving the sustained-release performance and field efficacy of the microcapsules. The particle size was slightly reduced, and the encapsulation rate and the control efficacy 30 days after application were slightly improved, showing better structural integrity and controlled-release effect. In contrast, Example 5 used polypropylene glycol 1000 with a higher molecular weight, which led to a larger double bond spacing, a decrease in crosslinking density, and a reduction in capsule wall density, resulting in increased particle size, decreased encapsulation rate, and a significant decrease in control efficacy.

[0124] A comparison of Examples 1 and 6-7 shows that Example 6, by using fumaric acid instead of maleic anhydride to construct an unsaturated polyester, produces a more symmetrical and regular structure, which helps improve the capsule wall aggregation and film-forming ability, exhibiting good controlled-release characteristics and field persistence, with a 30-day efficacy maintained at 84.5%. Example 7, using itaconic acid as an unsaturated acid source, although containing methyl substituents that enhance hydrophobicity and facilitate initial film formation, suffers from increased steric hindrance, leading to decreased free radical crosslinking efficiency and insufficient capsule wall density. Ultimately, this resulted in a decrease in encapsulation efficiency to 85.7% and a 30-day efficacy to 79.8%.

[0125] A comparison of Examples 1 and 8-9 shows that Example 8 reduced the amount of 1-octene, resulting in a lower degree of free radical cross-linking, a looser capsule wall structure, an increased average particle size to 4.0 μm, and a decrease in encapsulation efficiency to 81.3%. Controlled-release performance also declined significantly, with a 30-day efficacy of only 72.5%. Example 9 moderately increased the amount of 1-octene, which led to some enhanced hydrophobic cross-linking, but due to the higher cross-linking density and excessively stiff local film formation, the emulsion particle size slightly increased to 3.6 μm, and the encapsulation efficiency slightly decreased to 87.2%, with a 30-day efficacy of 84.7%, slightly lower than Example 1.

[0126] (3) A comparison between Example 1 and Comparative Example 1 shows that Comparative Example 1 did not introduce long-chain olefin monomers, and the crosslinking of the capsule wall relied solely on the double bonds in the polyester backbone, resulting in a limited degree of crosslinking. This led to a loose structure, an increase in average particle size to 5.4 μm, and a decrease in encapsulation efficiency to 74.2%. In field trials, the 30-day control efficacy of this sample decreased to 58.7%, significantly lower than the 86.2% of Example 1, indicating poor controlled-release and sustained-release performance. This result demonstrates that the present invention, by introducing long-chain olefins to construct a dense hydrophobic three-dimensional crosslinked network, not only increases the crosslinking density but also enhances the barrier to water and pesticide diffusion, thereby achieving higher encapsulation efficiency and more durable field control efficacy.

[0127] The applicant declares that 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 emulsion, characterized in that, The raw materials for preparing the polyurethane microcapsule emulsion include, by weight, 30-50 parts of unsaturated polyester polyol, 10-25 parts of isocyanate monomer, 3-6 parts of hydrophilic monomer, 2-5 parts of small molecule alcohol chain extender, 1.5-5 parts of neutralizer, 0.1-0.5 parts of organometallic catalyst, 20-50 parts of organic solvent, 5-15 parts of pesticide active ingredient, 3-10 parts of C6-C15 straight-chain or branched-chain olefin monomer, 0.1-0.5 parts of initiator, and 100-160 parts of water; The raw materials for preparing the unsaturated polyester polyol include, by weight, 20-65 parts of polyether polyol, 2-6 parts of unsaturated diacid / anhydride, and 0.1-1.0 parts of acidic catalyst; the molecular weight of the polyether polyol is 600-850 g / mol.

2. The polyurethane microcapsule emulsion according to claim 1, characterized in that, The polyether polyol includes any one or a combination of at least two of polytetrahydrofuran ether diol, polyethylene glycol, or polypropylene glycol. The unsaturated dicarboxylic acid / anhydride includes any one or a combination of at least two of maleic acid / anhydride, fumaric acid, or itaconic acid. The molar ratio of carbon-carbon double bonds in the C6-C15 straight-chain or branched olefin monomers to unsaturated diacid / anhydride structural units in the unsaturated polyester polyols is (0.8-2.3):

1. The acidic catalyst is p-toluenesulfonic acid.

3. The polyurethane microcapsule emulsion according to claim 1, characterized in that, The molar ratio of the polyether polyol to the unsaturated diacid / anhydride is (1.2-2):1; The raw materials for preparing the unsaturated polyester polyol also include 0.1-0.5 parts by weight of antioxidant; The antioxidant is butylated hydroxytoluene.

4. The polyurethane microcapsule emulsion according to claim 1, characterized in that, The isocyanate monomer includes any one or a combination of at least two of isoflavone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, hydrogenated phenylmethane diisocyanate, or tetramethylphenyl diisocyanate. The hydrophilic monomers include dimethylolpropionic acid and / or dimethylolbutyric acid.

5. The polyurethane microcapsule emulsion according to claim 1, characterized in that, The small molecule alcohol chain extender includes any one or a combination of at least two of ethylene glycol, 1,4-butanediol or hexanediol. The neutralizing agent includes tertiary amines with a boiling point ≤150°C at 1 atm.

6. The polyurethane microcapsule emulsion according to claim 1, characterized in that, The organometallic catalyst includes organobismuth and / or organotin; The organic bismuth includes any one or a combination of at least two of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, or bismuth naphthenate. The organotin includes any one or a combination of at least two of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, or di(dodecyl sulfide)dibutyltin. The organic solvent includes any one or a combination of at least two of acetone, butanone, or N-methylpyrrolidone.

7. The polyurethane microcapsule emulsion 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: organophosphorus pesticides, pyrethroid pesticides, neonicotinoid pesticides, amide pesticides, tetracyclic triterpenoid pesticides, or aromatic ketone pesticides; The C6-C15 straight-chain or branched olefin monomers are α-olefins; The initiator includes azobisisobutyronitrile.

8. A method for preparing a polyurethane microcapsule emulsion according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Unsaturated polyester polyol, isocyanate monomer, hydrophilic monomer, organic solvent and organometallic catalyst are mixed and reacted to obtain polyurethane prepolymer; (2) The polyurethane prepolymer and the small molecule alcohol chain extender are mixed and reacted. The system is then mixed with a neutralizing agent to obtain a hydrophilic prepolymer. (3) Mix the hydrophilic prepolymer and the active ingredient to form an oil phase; mix and emulsify the oil phase and water to obtain an O / W type emulsion; (4) Mix the O / W type emulsion, C6-C15 straight-chain or branched olefin monomer and initiator, and after reaction, obtain the polyurethane microcapsule emulsion.

9. The preparation method according to claim 8, characterized in that, The reaction in step (1) is carried out at a temperature of 80-85℃ for 2-3 hours. The reaction in step (2) is carried out at a temperature of 60-65℃ for 1-2 hours. The temperature at which the system and neutralizing agent are mixed in step (2) is 40-50℃; The reaction in step (4) is carried out at a temperature of 60-80℃ for 3-6 hours.

10. The use of a polyurethane microcapsule emulsion according to any one of claims 1-7 in the preparation of pesticide formulations.

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