Pendimethalin emulsion and its production process

Abstract

This invention belongs to the field of pesticide formulation technology, specifically relating to a pendimethalin water-in-oil emulsion and its production process. The pendimethalin water-in-oil emulsion, by mass percentage, comprises the following components: 20-40% pendimethalin technical grade, 10-25% organic solvent, 5-12% surfactant, 4-8% stabilizer, 2-4% emulsifier, and the balance water; the emulsifier is a compound of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and a modified sorbitol derivative in a mass ratio of 1:(2-2.8):(0.05-0.1). The production process involves preparing an oil phase from the pendimethalin technical grade, organic solvent, and surfactant; preparing an aqueous phase from the water, stabilizer, and emulsifier; adding the oil phase to the aqueous phase, followed by shear emulsification and filtration to obtain the pendimethalin water-in-oil emulsion. The pendimethalin water-in-oil emulsion obtained by this invention solves the problem of insufficient long-term storage stability of traditional pendimethalin water-in-oil emulsions.

Description

Technical Field

[0001] This invention belongs to the field of pesticide formulation technology, specifically relating to a pendimethalin water-in-oil emulsion and its production process. Background Technology

[0002] Pendimethalin is a highly effective, selective pre-emergence soil-applied herbicide that works primarily by inhibiting cell division in plant meristems. It is widely used in fields of various crops, including corn, soybeans, cotton, and vegetables, to control annual grasses and some broadleaf weeds. Currently, the mainstream formulation of pendimethalin on the market is emulsifiable concentrate (EC). EC formulations are simple to process and have stable efficacy, but their formulations contain large amounts of aromatic organic solvents, posing problems such as flammability, high toxicity, environmental pollution, and health hazards to operators during production and application. To reduce the use of organic solvents, suspension concentrates (SCs) have been developed as a water-based formulation. However, for technical grade herbicides like pendimethalin with low melting points, suspension concentrates are prone to Ostwald ripening under long-term storage or high-temperature conditions, leading to particle enlargement, precipitation, or clumping, resulting in poor physical stability. Furthermore, existing high-concentration suspension concentrate or emulsifiable concentrate production processes often require high temperature or pressure conditions, resulting in high energy consumption and demanding equipment requirements.

[0003] Therefore, developing a new formulation that is environmentally friendly, physically stable, has a simple production process, and maintains the original high-efficiency herbicidal activity of pendimethalin has become an urgent technical problem to be solved in this field. Emulsion-in-water (EW) formulations, as oil-in-water (O / W) liquid preparations, use water as the continuous phase, require less organic solvent, and have advantages such as safety, environmental friendliness, and low cost, making them one of the ideal formulations to replace emulsifiable concentrates. However, pendimethalin EW is a thermodynamically unstable system, prone to stratification, sedimentation, flocculation, and even demulsification and aggregation during long-term storage. This causes the active ingredient, pendimethalin, to separate from the aqueous phase, aggregate, or precipitate at the bottom of the container. During use, even shaking makes it difficult to restore the initial uniform state, resulting in inconsistent concentrations of the sprayed solution. The upper layer of solution has low active ingredient content and poor control effect; the lower layer has excessively high concentrations, which is not only wasteful but may also cause phytotoxicity to crops due to localized overuse.

[0004] Chinese patent CN106259314A discloses a pesticide emulsion, which is composed of the following components by weight percentage: 1-40% active ingredient, 5-20% environmentally friendly solvent, 2-6% special adjuvant, 0-5% antifreeze agent, and the balance being deionized water; the active ingredient is selected from one of thiazophosphonate, imazalil, lambda-cyhalothrin, chlorpyrifos, flusilazole, etc.; the special adjuvant is composed of 50-70% alkyl aryl polyoxyethylene polyoxypropylene ether, 15-30% sodium di-2-octyl maleate sulfonate, 5-10% phenethylphenol polyoxyethylene ether, and 10% epoxidized soybean oil.

[0005] In this patent, the problem of the storage stability of pesticide water-in-oil emulsion is addressed by simply using a combination of nonionic and anionic emulsifiers. Essentially, this is done by reducing the interfacial tension between oil and water to slow down the rate of droplet coalescence. However, during long-term storage, due to factors such as temperature changes, handling, and transportation bumps, the oil-water interfacial film is easily damaged, and the spontaneous phase separation process will occur rapidly, leading to problems such as stratification, sedimentation, and demulsification. Summary of the Invention

[0006] The purpose of this invention is to provide a pendimethalin emulsion to solve the problem of insufficient long-term storage stability of traditional pendimethalin emulsions; this invention also provides a production process for pendimethalin emulsions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The pendimethalin emulsion of the present invention comprises, by mass percentage, the following components: 20-40% pendimethalin technical grade, 10-25% organic solvent, 5-12% surfactant, 4-8% stabilizer, 2-4% emulsifier, and the balance being water; the emulsifier is a compound of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative in a mass ratio of 1:(2-2.8):(0.05-0.1).

[0008] in: The organic solvent is one or more of solvent oil, cyclohexanone, or ethyl acetate; the surfactant is a compound of at least three of alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, phenethylphenol polyoxyethylene ether, and polyacrylic acid, and the hydrophilic-lipophilic balance value of the surfactant is 12-16.5.

[0009] The stabilizing agent is a compound of a dispersant, a thickener, and a pH adjuster in a mass ratio of (5~7):(0.75~1):1. The dispersant is one of glycerol, propylene glycol, or ethylene glycol; the thickener is one of xanthan gum or magnesium aluminum silicate; and the pH adjuster is one of citric acid or sodium dihydrogen phosphate.

[0010] The preparation process of the modified sorbitol derivative is as follows: S1. In a reaction system that has been dehydrated and deoxygenated and is protected by nitrogen, the solvent, D-glucose, zinc powder, ammonium bromide and water are mixed, then allyl bromide is added, and the temperature is raised and maintained under nitrogen protection. S2. After the heat preservation reaction is completed, water is added to the reaction system to dilute it, the pH of the system is adjusted to 3.0~4.0 and then filtered to obtain the first-stage filtrate; the pH of the first-stage filtrate is adjusted to neutral and rotary evaporated under reduced pressure to obtain the crude product; anhydrous ethanol is added to dilute it, and the system is filtered to obtain the second-stage filtrate; the second-stage filtrate is rotary evaporated under reduced pressure to obtain allyl-grafted sorbitol. S3. The solvent, allyl-grafted sorbitol, catalyst and substituted benzaldehyde are mixed and subjected to condensation reaction. After the condensation reaction is completed, the reaction solution is obtained. The reaction solution is diluted with water and filtered. The resulting filter cake is washed and dried to obtain the modified sorbitol derivative.

[0011] In S1, the ratio of solvent, D-glucose, zinc powder, ammonium bromide, water, and allyl bromide is (400~450):100:(60~70):(18~30):(90~120):(250~300), where the solvent and water are in mL, and the D-glucose, zinc powder, ammonium bromide, and allyl bromide are in g; the solvent is anhydrous ethanol; the nitrogen pressure is 0.25~0.4MPa, the heating rate is 2~2.5℃ / min, the holding temperature is 70~80℃, and the holding time is 4~8h.

[0012] In S2, the mass ratio of water to allyl bromide is 4.5 to 6:1, and the mass ratio of anhydrous ethanol to water is 1 to 1.5:1.

[0013] In S3, the solvent is methanol, the catalyst is p-toluenesulfonic acid, and the substituted benzaldehyde is p-hydroxybenzaldehyde; the ratio of solvent, allyl grafted sorbitol, catalyst and substituted benzaldehyde is (1500~1800):450:(16~20):(350~420), where the solvent is in mL, and the allyl grafted sorbitol, catalyst and substituted benzaldehyde are in g; the condensation reaction temperature is 35~45℃, and the condensation reaction time is 6~8h.

[0014] The production process of the dimethomorph water-in-oil emulsion of the present invention includes the following steps: (1) Mix the technical grade of pendimethalin with an organic solvent, then add a surfactant, keep warm and stir to obtain an oil phase; disperse water, stabilizer and emulsifier evenly to obtain an aqueous phase; (2) While stirring, the oil phase is added to the aqueous phase to obtain a mixture. The mixture is then sheared, emulsified, and filtered to obtain pendimethalin emulsion.

[0015] in: In step (1), the heat preservation temperature is 35~45℃ and the stirring time is 15~25min; in step (2), the stirring rate is 250~400rpm, the shear emulsification rate is 2800~3500rpm, and the shear emulsification time is 12~20min.

[0016] When ammonium bromide is used in combination with zinc powder, during the nucleophilic addition of the allyl bromide-zinc intermediate to the aldehyde group of glucose to form the alkoxyzinc intermediate, NH4... + It can gently protonate zinc alkoxy to convert it into the final allyl alcohol product.

[0017] The beneficial effects of this invention are as follows: Traditional pendimethalin emulsions rely solely on the hydrophobic effect of surfactants to reduce interfacial tension. In contrast, the emulsion of this invention incorporates three components: 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and a modified sorbitol derivative. These three components spontaneously form a three-dimensional hydrogen bond network within the pendimethalin emulsion through hydrogen bonding and differences in their solubility between the aqueous phase and pendimethalin-containing oil droplets. This network is the core foundation for the system's stability.

[0018] 2,4,6-Triaminopyrimidine serves as the assembly core, with three primary amino groups on the pyrimidine ring providing hydrogen bond donors (NH) and the N atom on the pyrimidine ring providing strong hydrogen bond acceptors. The triazine ring of chlorobromoisocyanuric acid has carbonyl and NH sites. 2,4,6-Triaminopyrimidine and chlorobromoisocyanuric acid can form hydrogen bond units at the oil-water interface of dimethylpentylamine emulsion through spatial complementarity of hydrogen bond donors and acceptors.

[0019] By grafting allyl sorbitol with p-hydroxybenzaldehyde, two rigid benzene ring structures are endowed to allyl sorbitol. Through the alcohol hydroxyl and phenol hydroxyl groups, they can further combine with the hydrogen bond sites in the hydrogen bond unit to form a continuous three-dimensional hydrogen bond network. Hydrogen bond is a dynamic and reversible non-covalent bond. Therefore, the three-dimensional hydrogen bond network can be rapidly reconstructed after being subjected to mechanical disturbance and temperature fluctuation, giving the system excellent thixotropy and self-healing ability, fundamentally solving the problem of irreversible interfacial film damage in traditional surfactant systems.

[0020] Dimethylpentylene's molecular structure contains nitro groups and substituted benzene ring structures. Once subjected to external disturbances, the three-dimensional hydrogen bond network can bind to dimethylpentylene through hydrogen bonds and π-π stacking interactions, fixing dimethylpentylene in the oil droplets and inhibiting the aggregation and stratification of dimethylpentylene-containing oil droplets through steric hindrance.

[0021] Furthermore, the three-dimensional hydrogen bond network of this invention can be adsorbed at the dimethylpentylene oil droplet-water interface, synergistically with the surfactant in the system. The surfactant adsorption layer provides attachment sites for the three-dimensional hydrogen bond network, thereby forming a stable composite structure between the surfactant adsorption layer and the three-dimensional hydrogen bond network. Traditional surfactant films rely solely on hydrophobic interactions and van der Waals forces for bonding, resulting in low cohesive strength. In contrast, the composite structure possesses multiple hydrogen bonds and a surfactant adsorption layer, significantly improving its cohesive strength, resistance to deformation, and resistance to breakage. Even during transportation and long-term storage, the interfacial film is not easily ruptured, fundamentally inhibiting the aggregation and fusion of oil droplets after collision, and preventing oil separation and demulsification.

[0022] This invention successfully prepared a water-in-oil emulsion with uniform dimethylpentylamine component distribution by compounding a surfactant system with a specific HLB value and combining 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivatives in an aqueous emulsion to construct hydrogen bond self-assembly based on multiple complementary hydrogen bonds. Testing showed that the dimethylpentylamine water-in-oil emulsion product prepared in this invention exhibited no oil separation, no precipitation, and no stratification after 20 days of heat storage at 54℃ and low-temperature storage at -5℃ and -15℃, and its stable period at room temperature was at least 4 years. Detailed Implementation

[0023] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0024] The raw materials used in the following examples and comparative examples are all commercially available products. Alkylphenol polyoxyethylene ether, grade NP-10, was provided by Tianjin Zhonghe Shengteng Chemical Co., Ltd.; fatty acid polyoxyethylene ester, grade AEO-9, was provided by Shandong Yukang Chemical Co., Ltd.; phenethylphenol polyoxyethylene ether, grade 603#, was provided by Nanjing Kehong Chemical Co., Ltd.; polyacrylic acid, with a weight average molecular weight of 12,000, was provided by Zhengzhou Guanda Chemical Products Co., Ltd.; and pendimethalin technical material, with a purity of 95%, was provided by Jiangsu Yong'an Chemical Co., Ltd.

[0025] Example 1 Preparation of modified sorbitol derivatives Nitrogen gas was introduced into the dehydrated and deoxygenated reactor until the gauge pressure reached 0.4 MPa. 4000 mL of anhydrous ethanol was added, and the reactor was stirred. 1000 g of D-glucose, 650 g of zinc powder, 250 g of ammonium bromide, and 900 mL of distilled water were added. After stirring until the materials were completely dissolved, 3000 g of allyl bromide was added. Under nitrogen protection, the temperature was slowly increased to 80 °C at a rate of 2.3 °C / min and the reaction was maintained at this temperature for 4 h.

[0026] After the heat preservation reaction is completed, the reaction system is cooled to room temperature, and distilled water (the mass ratio of distilled water to allyl bromide is 4.5:1) is added for dilution. The pH value of the system is adjusted to 3.4-3.8, and the mixture is filtered to obtain a primary filtrate. The pH value of the primary filtrate is adjusted to neutral, and then rotary evaporated until the system becomes a non-flowing viscous state to obtain a crude product. Anhydrous ethanol (the mass ratio of anhydrous ethanol to distilled water is 1.5:1) is added to the crude product for dilution, and the mixture is filtered to obtain a secondary filtrate. The secondary filtrate is rotary evaporated until no obvious fraction flows out to obtain allyl grafted sorbitol.

[0027] Add 1500 mL of methanol, 450 g of the allyl-grafted sorbitol prepared above, and 18 g of p-toluenesulfonic acid to another clean reaction vessel, and stir until completely dissolved; add 420 g of p-hydroxybenzaldehyde, control the system temperature at 35 °C, and allow the condensation reaction to proceed for 8 h. After the reaction is complete, a reaction solution is obtained; add 2000 mL of water to the reaction solution, stir for 20 min, filter, and wash the filter cake with ethyl acetate and 8 wt% sodium carbonate solution until neutral, then dry to constant weight to obtain the modified sorbitol derivative.

[0028] Preparation of pendimethalin emulsion Weigh out the required raw materials, including 20 parts of pendimethalin technical grade, 10 parts of solvent oil, 5 parts of surfactant, 4 parts of stabilizer, 2 parts of emulsifier, and 59 parts of water.

[0029] The surfactant is composed of 0.8 parts alkylphenol polyoxyethylene ether, 4 parts fatty acid polyoxyethylene ester, and 0.2 parts phenethylphenol polyoxyethylene ether, and its hydrophilic-lipophilic balance value is 12.7. The stabilizer is composed of ethylene glycol, xanthan gum, and sodium dihydrogen phosphate in a mass ratio of 5:0.75:1. The emulsifier is composed of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative in a mass ratio of 1:2:0.05.

[0030] Dimethomorph technical grade was added to the oil phase mixing vessel, along with an organic solvent. The mixture was heated to 35°C and stirred until completely miscible. A surfactant was then added, and the mixture was kept at this temperature and stirred for 15 minutes to obtain the oil phase. Water, stabilizer, and emulsifier were then added to the aqueous phase mixing vessel and stirred until the materials were evenly dispersed to obtain the aqueous phase.

[0031] The water phase mixing vessel was set to a speed of 400 rpm. The oil phase was slowly added to the water phase under continuous stirring. After the addition was complete, a mixture was obtained. The mixture was transferred to a high-speed shear emulsifier and sheared and emulsified at 2800 rpm for 12 minutes to obtain an emulsion. The emulsion was filtered through a polypropylene filter to remove a small amount of impurities. After sampling and testing, it was filled to obtain dimethyl pendimethalin water emulsion.

[0032] Example 2 Preparation of modified sorbitol derivatives Nitrogen gas was introduced into the dehydrated and deoxygenated reactor until the gauge pressure reached 0.36 MPa. 4500 mL of anhydrous ethanol was added, and the reactor was stirred. 1000 g of D-glucose, 600 g of zinc powder, 180 g of ammonium bromide, and 1050 mL of distilled water were added in sequence. After stirring until the materials were completely dissolved, 2680 g of allyl bromide was added. Under nitrogen protection, the temperature was slowly increased to 75 °C at a rate of 2 °C / min, and the reaction was maintained at this temperature for 8 h.

[0033] After the heat preservation reaction is completed, the reaction system is cooled to room temperature, diluted with distilled water (the mass ratio of distilled water to allyl bromide is 5.2:1), and the pH value of the system is adjusted to 3.2~3.6. The system is filtered to obtain a primary filtrate. The pH value of the primary filtrate is adjusted to neutral, and then rotary evaporated until the system becomes a non-flowing viscous state to obtain a crude product. Anhydrous ethanol (the mass ratio of anhydrous ethanol to distilled water is 1.2:1) is added to the crude product for dilution, and the system is filtered to obtain a secondary filtrate. The secondary filtrate is rotary evaporated until no obvious fraction flows out to obtain allyl grafted sorbitol.

[0034] Add 1700 mL of methanol, 450 g of the allyl-grafted sorbitol prepared above, and 16 g of p-toluenesulfonic acid to another clean reaction vessel, and stir until completely dissolved; add 400 g of p-hydroxybenzaldehyde, control the system temperature at 40 °C, and allow the condensation reaction to proceed for 7 h. After the reaction is complete, obtain the reaction solution; add 2500 mL of water to the reaction solution, stir for 18 min, filter, and wash the filter cake with ethyl acetate and 18 wt% sodium carbonate solution until neutral, then dry to constant weight to obtain the modified sorbitol derivative.

[0035] Preparation of pendimethalin emulsion Weigh out the required raw materials, including 40 parts of pendimethalin technical grade, 15 parts of ethyl acetate, 10 parts of cyclohexanone, 8 parts of surfactant, 6 parts of stabilizer, 3 parts of emulsifier, and 18 parts of water.

[0036] The surfactant is composed of 3.9 parts alkylphenol polyoxyethylene ether, 1.8 parts phenethylphenol polyoxyethylene ether, and 2.3 parts polyacrylic acid, and its hydrophilic-lipophilic balance value is 14.3. The stabilizer is composed of propylene glycol, magnesium aluminum silicate, and citric acid in a mass ratio of 6:0.85:1. The emulsifier is composed of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative in a mass ratio of 1:2.8:0.1.

[0037] Dimethomorph technical grade was added to the oil phase mixing vessel, along with ethyl acetate and cyclohexanone. The mixture was heated to 45°C and stirred until completely miscible. A surfactant was then added, and the mixture was kept at this temperature and stirred for 17 minutes to obtain the oil phase. Water, stabilizer, and emulsifier were then added to the aqueous phase mixing vessel and stirred until the materials were evenly dispersed to obtain the aqueous phase.

[0038] The aqueous phase mixing vessel was set to rotate at 330 rpm. The oil phase was slowly added to the aqueous phase under continuous stirring. After addition, a mixture was obtained. The mixture was then transferred to a high-speed shear emulsifier and sheared and emulsified at 3500 rpm for 18 minutes to obtain an emulsion. The emulsion was filtered through a polypropylene filter to remove minor impurities. After sampling and testing to ensure it passed inspection, it was packaged to obtain pendimethalin water-based emulsion.

[0039] Example 3 Preparation of modified sorbitol derivatives Nitrogen gas was introduced into the dehydrated and deoxygenated reactor until the gauge pressure reached 0.25 MPa. 4200 mL of anhydrous ethanol was added, and the reactor was stirred. 1000 g of D-glucose, 700 g of zinc powder, 300 g of ammonium bromide, and 1200 mL of distilled water were added in sequence. After stirring until the materials were completely dissolved, 2500 g of allyl bromide was added. Under nitrogen protection, the temperature was slowly increased to 70 °C at a rate of 2.5 °C / min and the reaction was maintained at this temperature for 6 h.

[0040] After the heat preservation reaction is completed, the reaction system is cooled to room temperature, and distilled water (the mass ratio of distilled water to allyl bromide is 6:1) is added for dilution. The pH value of the system is adjusted to 3.6-4.0, and the mixture is filtered to obtain a primary filtrate. The pH value of the primary filtrate is adjusted to neutral, and then rotary evaporated until the system becomes a non-flowing viscous state to obtain a crude product. Anhydrous ethanol (the mass ratio of anhydrous ethanol to distilled water is 1:1) is added to the crude product for dilution, and the mixture is filtered to obtain a secondary filtrate. The secondary filtrate is rotary evaporated until no obvious fraction flows out to obtain allyl grafted sorbitol.

[0041] Add 1800 mL of methanol, 450 g of the allyl-grafted sorbitol prepared above, and 20 g of p-toluenesulfonic acid to another clean reaction vessel, and stir until completely dissolved; add 350 g of p-hydroxybenzaldehyde, control the system temperature at 45 °C, and allow the condensation reaction to proceed for 6 h. After the reaction is complete, a reaction solution is obtained; add 3000 mL of water to the reaction solution, stir for 15 min, filter, and wash the filter cake with ethyl acetate and 30 wt% sodium carbonate solution until neutral, then dry to constant weight to obtain the modified sorbitol derivative.

[0042] Preparation of pendimethalin emulsion Weigh out the required raw materials, including 30 parts of pendimethalin technical grade, 18 parts of cyclohexanone, 12 parts of surfactant, 8 parts of stabilizer, 4 parts of emulsifier, and 28 parts of water.

[0043] The surfactant is composed of 0.6 parts fatty acid polyoxyethylene ester, 10.1 parts phenethylphenol polyoxyethylene ether, and 1.3 parts polyacrylic acid, and its hydrophilic-lipophilic balance value is 16.5. The stabilizer is composed of glycerol, magnesium aluminum silicate, and sodium dihydrogen phosphate in a mass ratio of 7:1:1. The emulsifier is composed of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative in a mass ratio of 1:2.4:0.07.

[0044] Dimethoprim technical grade was added to the oil phase mixing vessel, followed by cyclohexanone. The mixture was heated to 40°C and stirred until completely miscible. Then, a surfactant was added, and the mixture was kept at this temperature and stirred for 25 minutes to obtain the oil phase. Water, stabilizer, and emulsifier were then added to the aqueous phase mixing vessel and stirred until the materials were evenly dispersed to obtain the aqueous phase.

[0045] The aqueous phase mixing vessel was set to rotate at 250 rpm. The oil phase was slowly added to the aqueous phase under continuous stirring. After addition, a mixture was obtained. The mixture was then transferred to a high-speed shear emulsifier and sheared and emulsified at 3000 rpm for 20 minutes to obtain an emulsion. The emulsion was filtered through a polypropylene filter to remove minor impurities. After sampling and testing to ensure it passed inspection, it was packaged to obtain pendimethalin water-based emulsion.

[0046] Comparative Example 1 Without adding modified sorbitol derivatives, the remaining procedures and raw materials used are the same as in Example 1.

[0047] Comparative Example 2 Without adding chlorobromoisocyanuric acid, the rest of the operation process and raw materials used are the same as in Example 1.

[0048] Comparative Example 3 Without adding 2,4,6-triaminopyrimidine, the remaining procedures and raw materials used are the same as in Example 1.

[0049] Comparative Example 4 The p-hydroxybenzaldehyde was replaced with p-methylbenzaldehyde, and the rest of the operation process and raw materials used were the same as in Example 1.

[0050] Comparative Example 5 Sorbitol was replaced with allyl grafted sorbitol, and the rest of the operation process and raw materials used were the same as in Example 1.

[0051] Implementation effect evaluation Referring to the operating methods in HG / T 2467.9-2003 "Specifications for Writing Standards for Pesticide Water-in-Emulsions" and HG / T 2467.2-2003 "Specifications for Writing Standards for Pesticide Emulsifiable Oils", low-temperature storage stability tests and heat storage stability tests were designed for the pendimethalin water-in-emulsions prepared in the embodiments and comparative examples of this invention.

[0052] Low temperature stability test: Transfer 100 mL of sample to a centrifuge tube and cool it to 0 ± 2 °C in a refrigerator. Maintain the centrifuge tube and its contents at 0 ± 2 °C for 1 hour, stirring every 15 minutes for 15 seconds. Return the centrifuge tube to the refrigerator and continue placing it at -5 °C ± 2 °C for 7 days, then at -15 °C ± 2 °C for 7 days. Remove the centrifuge tube and let it stand at room temperature for 6 hours. Observe for the appearance of layering, precipitation, crystallization, and oily precipitation to determine product homogeneity. Then centrifuge for 15 minutes (the relative centrifugal force at the top of the tube is 500 g ~ 600 g, where g is the acceleration due to gravity). Record the volume of the precipitate at the bottom of the tube. A precipitate volume not exceeding 0.25 mL is considered acceptable.

[0053] Thermal storage stability test: Inject approximately 30 mL of sample into a clean ampoule using a syringe (avoiding contact between the sample and the neck of the ampoule). Place the ampoule in an ice-salt bath to cool it, and then quickly seal it with a high-temperature flame (to prevent solvent evaporation). Seal at least three ampoules, and weigh them after cooling to room temperature. Place the sealed ampoules in a metal container, and then place the metal container in a constant temperature oven at 54℃±2℃ for 20 days. Remove the ampoules and let them cool to room temperature. Wipe the ampoules clean and weigh them separately. For samples whose mass has not changed, observe whether there is any layering, precipitation, local turbidity, or oily precipitation.

[0054] The specific test results for pendimethalin emulsion are shown in Table 1.

[0055] Table 1. Test results of pendimethalin emulsion

[0056] As can be seen from Table 1, the present invention successfully prepared a water-in-oil emulsion with uniform distribution of dimethyl pendimethicone components by compounding a surfactant system with a specific HLB value and combining 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid and modified sorbitol derivatives in the water-in-oil emulsion based on multiple complementary hydrogen bonds to construct hydrogen bond self-assembly, thus completely solving the industry pain point of insufficient long-term storage stability of traditional dimethyl pendimethicone water-in-oil emulsions.

[0057] In Examples 1-3, the three components of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative construct a dynamic and reversible three-dimensional hydrogen bond network based on multiple complementary hydrogen bonds and π-π stacking. In Comparative Examples 1, 2, and 3, if any one of the components is removed, a complete three-dimensional hydrogen bond network cannot be formed, and therefore it is impossible to form a composite interfacial film in synergy with the surfactant.

[0058] Comparative Examples 4 and 5 modified the molecular structure of the modified sorbitol derivatives. In Comparative Example 4, p-hydroxybenzaldehyde was replaced with p-methylbenzaldehyde, and in Comparative Example 5, allyl-grafted sorbitol was replaced with unmodified sorbitol. It can be seen that the thermal storage and low-temperature stability of Comparative Examples 4 and 5 are inferior to those of Examples 1 to 3.

[0059] Unlike phenolic hydroxyl groups, the methyl group of p-methylbenzaldehyde cannot provide hydrogen bonding sites, affecting the formation of a continuous three-dimensional hydrogen bond network from discrete binary units. Furthermore, allyl grafting provides sorbitol with an active site for condensation with p-hydroxybenzaldehyde, while simultaneously regulating the molecular spatial configuration to ensure effective π-π stacking of the benzene ring after grafting. Ungrafted sorbitol cannot introduce a rigid benzene ring structure, thus failing to form a complete three-dimensional hydrogen bond network, leading to decreased stability in the dimethylpentylene aqueous emulsion system.

Claims

1. A pendimethalin water-based emulsion, characterized in that, The product is composed of the following components by mass percentage: 20-40% pendimethalin technical grade, 10-25% organic solvent, 5-12% surfactant, 4-8% stabilizer, 2-4% emulsifier, and the balance being water; the emulsifier is a compound of 2,4,6-triaminopyrimidine, chlorobromoisocyanuric acid, and modified sorbitol derivative in a mass ratio of 1:(2-2.8):(0.05-0.1).

2. The pendimethalin emulsion according to claim 1, characterized in that, The organic solvent is one or more of solvent oil, cyclohexanone, or ethyl acetate; the surfactant is a compound of at least three of alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, phenethylphenol polyoxyethylene ether, and polyacrylic acid, and the hydrophilic-lipophilic balance value of the surfactant is 12 to 16.

5.

3. The pendimethalin emulsion according to claim 1, characterized in that, The stabilizing agent is a compound of dispersant, thickener and pH adjuster in a mass ratio of (5~7):(0.75~1):

1. The dispersant is one of glycerol, propylene glycol or ethylene glycol; the thickener is one of xanthan gum or magnesium aluminum silicate; and the pH adjuster is one of citric acid or sodium dihydrogen phosphate.

4. The dimethomorph emulsion according to claim 1, characterized in that, The preparation process of the modified sorbitol derivative is as follows: S1. In a reaction system that has been dehydrated and deoxygenated and is protected by nitrogen, the solvent, D-glucose, zinc powder, ammonium bromide and water are mixed, then allyl bromide is added, and the temperature is raised and maintained under nitrogen protection. S2. After the heat preservation reaction is completed, water is added to the reaction system to dilute it, the pH of the system is adjusted to 3.0~4.0 and then filtered to obtain the first-stage filtrate; the pH of the first-stage filtrate is adjusted to neutral and rotary evaporated under reduced pressure to obtain the crude product; anhydrous ethanol is added to dilute it, and the system is filtered to obtain the second-stage filtrate; the second-stage filtrate is rotary evaporated under reduced pressure to obtain allyl-grafted sorbitol. S3. The solvent, allyl-grafted sorbitol, catalyst and substituted benzaldehyde are mixed and subjected to condensation reaction. After the condensation reaction is completed, the reaction solution is obtained. The reaction solution is diluted with water and filtered. The resulting filter cake is washed and dried to obtain the modified sorbitol derivative.

5. The dimethomorph emulsion according to claim 4, characterized in that, In S1, the ratio of solvent, D-glucose, zinc powder, ammonium bromide, water, and allyl bromide is (400~450):100:(60~70):(18~30):(90~120):(250~300), where the solvent and water are in mL, and the D-glucose, zinc powder, ammonium bromide, and allyl bromide are in g; the solvent is anhydrous ethanol; the nitrogen pressure is 0.25~0.4MPa, the heating rate is 2~2.5℃ / min, the holding temperature is 70~80℃, and the holding time is 4~8h.

6. The pendimethalin emulsion according to claim 4, characterized in that, In S2, the mass ratio of water to allyl bromide is 4.5 to 6:

1.

7. The dimethomorph water-based emulsion according to claim 4, characterized in that, In S2, the mass ratio of anhydrous ethanol to water is 1~1.5:

1.

8. The pendimethalin emulsion according to claim 4, characterized in that, In S3, the solvent is methanol, the catalyst is p-toluenesulfonic acid, and the substituted benzaldehyde is p-hydroxybenzaldehyde; the ratio of solvent, allyl grafted sorbitol, catalyst and substituted benzaldehyde is (1500~1800):450:(16~20):(350~420), where the solvent is in mL, and the allyl grafted sorbitol, catalyst and substituted benzaldehyde are in g; the condensation reaction temperature is 35~45℃, and the condensation reaction time is 6~8h.

9. A production process for the dimethyl pendimethalin water-based emulsion according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Mix the technical grade of pendimethalin with an organic solvent, then add a surfactant, keep warm and stir to obtain an oil phase; disperse water, stabilizer and emulsifier evenly to obtain an aqueous phase; (2) While stirring, the oil phase is added to the aqueous phase to obtain a mixture. The mixture is then sheared, emulsified, and filtered to obtain pendimethalin emulsion.

10. The production process of the dimethomorph water-in-oil emulsion according to claim 9, characterized in that, In step (1), the heat preservation temperature is 35~45℃ and the stirring time is 15~25min; in step (2), the stirring rate is 250~400rpm, the shear emulsification rate is 2800~3500rpm, and the shear emulsification time is 12~20min.

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