Preparation of antibacterial surfactant and its application in pesticide suspending agent

Abstract

The application discloses a kind of preparation of antibacterial surfactant and its application in pesticide suspending agent, belong to pesticide preparation technical field, the method first esterification mPEG500 succinic acid monoester is with pentaerythritol and 12-hydroxystearic acid, condensation is obtained mPEG / hydroxystearic acid co-modification star pentaerythritol, again the product occurs ring-opening reaction with epoxy propyl trimethylammonium chloride under alkaline condition, obtain four functional modification star polymer, and then composite modified silica is prepared antibacterial surfactant;The application is through the dual dispersion mechanism of star structure and modified silica, solves the problem that traditional surfactant is easily contaminated by microorganism, hard water causes particle agglomeration, poor suspended dispersion, improves antibacterial, hard water, wetting and penetration performance, so that surfactant has long-acting stable dispersion and synergistic antibacterial capacity, meets the use requirement of pesticide suspending agent storage and transportation and different water quality farmland.

Description

Technical Field

[0001] This invention belongs to the field of pesticide formulation technology, specifically the preparation of an antibacterial surfactant and its application in pesticide suspensions. Background Technology

[0002] As an important pesticide formulation, pesticide suspension concentrates are widely used in agricultural production due to their advantages of being dust-free, highly effective, safe to use, and environmentally compatible. Stability, as a key performance indicator, directly affects the storage, transportation, and application effects of the product. Surfactants play an indispensable role in this process. They not only disperse pesticide particles by reducing van der Waals forces, preventing particle aggregation and sedimentation to maintain the uniformity and physical stability of the suspension, but also reduce the surface tension of the pesticide solution, promoting its spread and penetration on targets such as leaves and insects to enhance efficacy. They also possess auxiliary functions such as thickening, antifreeze, and defoaming. However, traditional pesticide suspension concentrates and the conventional surfactants they use face the common and challenging problem of microbial contamination and proliferation in actual production and application, becoming a significant bottleneck restricting their performance and application.

[0003] Chinese invention patent CN113457564B discloses an esterified SMA-modified quaternary ammonium / phosphonium salt polymeric antibacterial surfactant and its application. It prepares a polymeric compound with both antibacterial and surface activity by grafting quaternary ammonium / phosphonium salt groups onto esterified styrene-maleic anhydride polymer (SMA). However, due to its rigid aromatic ring skeleton and long-chain polymeric structure, the esterified styrene-maleic anhydride polymer is prone to particle aggregation in the use of pesticide suspensions, resulting in insufficient suspension and dispersion performance of pesticide formulations.

[0004] Chinese invention patent CN119409867B discloses a method for preparing modified polycarboxylate surfactants and their application in pesticide formulations. It introduces strongly polar groups such as carboxyl, sulfonic acid, and phosphate groups, and prepares modified polycarboxylate surfactants through copolymerization to improve the suspension and dispersion properties of pesticide formulations. However, carboxyl, sulfonic acid, and phosphate groups are all strongly polar anionic groups, readily reacting with calcium in hard water. 2+ Mg 2+ When a reaction occurs, insoluble metal salt precipitates are formed, causing pesticide particles to lose their dispersion protection and exhibit aggregation and sedimentation. This prevents the pesticide particles from being evenly dispersed in the pesticide solution, ultimately reducing the effectiveness of the pesticide formulation. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an antibacterial surfactant.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing an antibacterial surfactant includes the following steps:

[0008] Step 1: Pentaerythritol, mPEG500 succinic acid monoester and 12-hydroxystearic acid condense reaction, and then after impurity removal, filtration and washing, mPEG / hydroxystearic acid co-modified star pentaerythritol is obtained.

[0009] Step 2: Then, the mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol is reacted with an epoxy-containing quaternary ammonium salt epoxy ring-opening reaction. After precipitation, washing and drying, a four-functional modified star polymer is obtained.

[0010] Step 3: Modify fumed silica with KH-550 and WD-10 to obtain modified silica functional filler; mix the four-functional modified star polymer and modified silica and dry to obtain antibacterial surfactant.

[0011] Furthermore, the modified silica functional filler is prepared through the following steps:

[0012] Anhydrous ethanol and pretreated fumed silica were added to a reaction vessel and dispersed at 300-400 rpm for 20-30 min. KH-550, WD-10 and anhydrous ethanol were added to a stirred tank, and glacial acetic acid was added to adjust the pH to 4-5. The mixture was stirred for 10-15 min. 8-12 mL of the mixed solution was added dropwise to the reaction vessel and stirred at 50-60℃ and 300-400 rpm for 2-3 h. The mixture was centrifuged at 4500-5500 rpm for 4-6 min, washed 3-5 times with an ethanol-deionized water mixture, and vacuum dried at 90-110℃ for 3-5 h before grinding to obtain the modified silica functional filler.

[0013] Furthermore, the ratio of fumed silica, KH-550 and WD-10 is 8-12g: 1.5-2.5g: 0.5-1g.

[0014] Furthermore, the specific preparation steps of the four-functional modified star polymer are as follows:

[0015] The mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol and a 5% (v / v) acetic acid solution were added to a reaction vessel and stirred at 30-35℃ for 15-20 min. The pH value was adjusted to 8.5-9.5 by adding 1-2 mol / L sodium hydroxide solution dropwise and stirring at 200-300 r / min for 20-30 min. Isopropanol was added and the mixture was stirred and dispersed at 40-50℃ for 15-20 min. A mixture of epoxy-containing quaternary ammonium salt and deionized water was added in 3-5 portions and stirred at 45-55℃ and 300-400 r / min for 5-7 h. Then, 250-350 mL of an acetone-ethanol mixture with a volume ratio of 2:1 was added, and the mixture was washed 3-5 times. The mixture was then vacuum dried at 45-50℃ to obtain the tetrafunctional modified star polymer.

[0016] Furthermore, the ratio of mPEG / hydroxystearic acid co-modified pentaerythritol, 5% acetic acid solution, isopropanol, epoxy-containing quaternary ammonium salt and deionized water is 5-8g: 50-80mL: 100-150mL: 6-12g: 8-15mL.

[0017] Furthermore, the epoxy-containing quaternary ammonium salt is any one of glycidyltrimethylammonium chloride, glycidyltriethylammonium chloride, and glycidyldimethyloctylammonium chloride.

[0018] Furthermore, the specific preparation steps for mPEG / hydroxystearic acid co-modified pentaerythritol are as follows:

[0019] Pentaerythritol, mPEG500 succinic acid monoester, 12-hydroxystearic acid, and dichloromethane were added to a reactor and stirred at 200-300 r / min under nitrogen protection. Then, 0.98-1.83 g of catalyst and 8.2-15 g of condensing agent were added. The mixture was stirred at 20-30℃ under nitrogen protection for 28-32 h. After the reaction was completed, dichloromethane was volatilized to remove the residue, and acetone was used to precipitate the residue. The residue was filtered, and after acetone was volatilized from the filter cake, it was dissolved in chloroform. The solution was washed successively with dilute hydrochloric acid with a pH of 4-6 and distilled water. After evaporating chloroform, the solution was dried under vacuum to obtain mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol.

[0020] Furthermore, the ratio of pentaerythritol, mPEG500 succinate monoester, 12-hydroxystearic acid and dichloromethane is 1.3-1.5g: 12-18g: 1.5-2.5g: 2.8-4.8L.

[0021] Further, the condensing agent is any one of N,N'-dicyclohexylcarboimide, N,N'-diisopropylcarboimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0022] The beneficial effects of this invention are:

[0023] 1. The antibacterial surfactant of this invention adopts a star structure with pentaerythritol as the core and mPEG hydrophilic chains and 18-carbon hydrophobic chains as branches, and is also combined with composite modified silica to form a dual dispersion protection mechanism of molecular steric hindrance and particle synergy. That is, the surfactant forms a three-dimensional steric hindrance layer on the surface of pesticide particles through hydrophilic and hydrophobic chains, and at the same time, it synergistically enhances the steric hindrance effect with modified silica particles through hydrophobic association and weak electrostatic interaction, jointly preventing particle agglomeration. This mechanism can effectively solve the problem that surfactants are prone to react with metal ions in hard water, which leads to unstable agglomeration of pesticide particles, enhances the dispersion stability of pesticide particles, and reduces the occurrence of agglomeration and sedimentation.

[0024] 2. In this invention, the antibacterial surfactant does not react with Ca in hard water because neither its hydrophilic nor hydrophobic chains react with Ca. 2+ Mg 2+ The reaction, and the quaternary ammonium group with core antibacterial activity is a cationic group, has extremely low reactivity with hard water metal ions, making it difficult to form precipitates. Simultaneously, the amino groups on the modified silica surface can weakly adsorb Ca from hard water through lone pair electrons. 2+ Mg 2+ This invention anchors metal ions on the surface of inorganic particles, reducing their direct contact with surfactant molecules and avoiding interference from metal ions on the dispersion function of surfactants. The antibacterial surfactant in this invention can keep pesticide suspensions in a stable dispersion state in hard water in farmland without the need to add additional water softeners or anti-precipitants.

[0025] 3. In this invention, the mPEG hydrophilic chain of the surfactant can significantly reduce the surface tension of the pesticide solution, break through the hydrophobic barrier of the wax layer on the leaf surface, and the 12-carbon hydrophobic chain on the modified silica surface can help the pesticide solution adhere more firmly to the leaf or insect surface, reduce the situation where the pesticide solution turns into small water droplets and rolls off the surface due to uneven surface tension, promote the rapid spread of the pesticide solution into a uniform film and enhance its penetration ability. This effect can reduce the loss of active ingredients in pesticides, improve the absorption efficiency of leaves for effective ingredients, thereby enhancing the control effect of pests and diseases, reducing the amount of pesticide used, and taking into account both efficacy and environmental compatibility.

[0026] 4. This invention introduces a flexible hydroxyethyl isolating segment (-CH2CH(OH)CH2-). When pesticide particles approach each other, these flexible chains can absorb and dissipate collision energy through bending and stretching, thereby more effectively preventing particle aggregation due to van der Waals forces. Furthermore, the flexible chain forms a hydrophilic buffer zone between the hydrophobic chain and the quaternary ammonium group. Its hydroxyl group (-OH) can weakly bind water molecules through hydrogen bonds to the quaternary ammonium group, physically isolating the quaternary ammonium group from the Ca2+ in hard water. 2+ Mg 2+ This avoids the formation of quaternary ammonium salt-metal precipitates; at the same time, the flexible chain makes it easier for the quaternary ammonium groups to approach and adsorb the negatively charged microbial cell membranes, thus improving the sterilization efficiency.

[0027] 5. In this invention, the modified silica, after amino protonation, can work together with the positively charged quaternary ammonium group to enhance the electrostatic adsorption and destruction of the negatively charged microbial cell membrane, thereby achieving a synergistic antibacterial effect. Furthermore, silica itself has a high melting point and excellent thermal stability, which can form a thermally stable spacer layer between pesticide particles, mitigating the problem of increased thermal motion and agglomeration of pesticide particles caused by high temperatures. This helps pesticide suspensions maintain a uniform dispersion state under high-temperature conditions, avoiding failure due to high-temperature stratification and sedimentation. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: A method for preparing an antibacterial surfactant

[0030] S1: Add 20g mPEG-500 and 100mL pyridine to a reaction vessel and stir at 350r / min for 12min. Then add 8g succinic anhydride to the vessel and stir continuously at 60℃ for 2h until the solution gradually turns pale yellow and transparent. Cool down to 45℃ and remove pyridine by vacuum distillation. Then add 150mL benzene to the vessel and stir at 250r / min for 10min. Add 200mL n-hexane dropwise to the reaction vessel and stir continuously for 20min until the white precipitate is completely precipitated. Filter and dissolve the precipitate in double-distilled water. Transfer the precipitate to a dialysis bag with a molecular weight cutoff of 300-500Da for dialyzing. Finally, freeze-dry the dialyzed substance for 48h to obtain mPEG500 succinic acid monoester.

[0031] The terminal hydroxyl group of mPEG-500 undergoes a ring-opening esterification reaction with succinic anhydride in the presence of pyridine, which also acts as a solvent and catalyst, introducing ester groups (-O-CO-) and carboxyl groups (-COOH) at the end of the mPEG-500 chain. The pyridine is then removed by vacuum distillation, small molecules are separated by dialysis, and finally the purified product is obtained by freeze drying.

[0032] S2: 1.4 g pentaerythritol, 16 g mPEG500 succinic acid monoester, 2 g 12-hydroxystearic acid and 3.8 L dichloromethane were added to a reaction vessel and magnetically stirred at 250 r / min under nitrogen protection until the solid was completely dissolved. Then, 1.4 g catalyst 4-dimethylaminopyridine and 11.5 g condensing agent N,N'-dicyclohexylcarboimide were added. The mixture was stirred at 25 °C for 30 h under nitrogen protection. After the reaction was completed, the dichloromethane was volatilized to remove the solids. The residue was precipitated with acetone, filtered, and the filter cake was volatilized to remove the acetone. It was then dissolved in chloroform and washed successively with dilute hydrochloric acid at pH 5 and distilled water. After removing the chloroform, the mixture was dried under vacuum to obtain mPEG / hydroxystearic acid co-modified pentaerythritol.

[0033] Through the action of condensing agents and catalysts, the carboxyl groups (-COOH) of mPEG500 succinic acid monoester and 12-hydroxystearic acid form ester bonds (-COO-) with the hydroxyl groups (-OH) of pentaerythritol, forming a star structure with pentaerythritol as the core and hydrophilic chains of mPEG and 18-carbon hydrophobic long chains as branches; the terminal hydroxyl group of 12-hydroxystearic acid is retained as a new reaction site, and after purification, mPEG / hydroxystearic acid co-modified star pentaerythritol containing hydrophilic chains, hydrophobic chains and new hydroxyl groups is obtained.

[0034] S3: 6.5g of mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol and 65mL of 5% acetic acid solution were added to a reaction vessel and stirred at 32℃ for 18min until dissolved. 2mol / L sodium hydroxide solution was added dropwise to adjust the pH to 9, and the mixture was stirred at 250r / min for 25min. 125mL of isopropanol was added, and the mixture was stirred and dispersed at 45℃ for 18min. A mixture of 9g of glycidyltrimethylammonium chloride and 12mL of deionized water was added in 4 portions. The mixture was stirred for 6h at 50℃ and 350r / min. After the reaction, 300mL of acetone-ethanol mixture (2:1 volume ratio) was added to precipitate the product. The product was washed 4 times and dried under vacuum at 48℃ to obtain the tetrafunctional modified star polymer.

[0035] The hydroxyl group (-OH) in mPEG / hydroxystearic acid co-modified pentaerythritol star is activated under alkaline conditions, losing a proton and transforming into a more nucleophilic alkoxy anion (-O). - The alkoxy anion acts as a nucleophile, attacking the epoxy group in the glycidyltrimethylammonium chloride molecule and initiating the ring-opening reaction of the epoxy ring. After the epoxy ring breaks, the oxygen atom in the original epoxy group combines with a proton to form a flexible segment -CH2CH(OH)CH2-, i.e., the hydroxyethyl isolation segment. At the same time, the quaternary ammonium group in the glycidyltrimethylammonium chloride molecule is connected to the ring-opened segment through a covalent bond, finally yielding a tetrafunctional modified star polymer.

[0036] S4: Add 50 mL of anhydrous ethanol and 10 g of fumed silica pretreated by vacuum drying at 100 °C for 3 h to a reaction vessel and disperse it uniformly at 350 r / min for 25 min. Add 2 g of KH-550, 0.8 g of WD-10 and 10 mL of anhydrous ethanol to a stirred tank, adjust the pH to 4.5 with glacial acetic acid, and stir for 13 min to obtain a mixed solution. Take 10 mL of the mixed solution and add it dropwise to the reaction vessel. Stir the reaction at 55 °C and 350 r / min for 2.5 h. Centrifuge the reaction solution at 5000 r / min for 5 min, wash it 4 times with a 1:1 volume ratio ethanol-deionized water mixture, and then vacuum dry it at 90-110 °C for 3-5 h before grinding to obtain the modified silica functional filler.

[0037] The hydroxyl groups on the surface of fumed silica undergo a condensation reaction with hydrolyzed KH-550 and WD-10, giving the silica surface amino groups and 12-carbon hydrophobic chains.

[0038] S5: Add 12g of the tetrafunctional modified star polymer and 100mL of deionized water to a stirred tank and stir for 25min at 40℃ and 350r / min until completely dissolved. Then add 4g of vacuum-dried modified silica to the tank and ultrasonically disperse for 18min at 550r / min. Then adjust the pH of the system to 7 and continue stirring for 18min. Centrifuge at 3500r / min for 7min and take the supernatant. Vacuum dry at 48℃ for 9h and grind to obtain an antibacterial surfactant.

[0039] Examples 2-4: A method for preparing an antibacterial surfactant, which differs from Example 1 in that the amount of substance added in step S2 is different, while the other steps and parameters remain the same. The specific amounts added are shown in Table 1 below.

[0040] surface Table of Substance Amounts in Step S2

[0041] project Pentaerythritol (g) mPEG500 monosuccinate (g) 12-Hydroxystearic acid (g) Dichloromethane (L) Example 2 1.3 12 1.5 2.8 Example 3 1.4 14 1.9 3.5 Example 4 1.5 18 2.5 4.8

[0042] Examples 5-6: A method for preparing an antibacterial surfactant, the difference from Example 1 is that in step S2, the condensing agent N,N'-dicyclohexylcarboimide is replaced with one of N,N'-diisopropylcarboimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0043] Examples 7-8: A method for preparing an antibacterial surfactant, which differs from Example 1 in that the amount of substance added in step S3 is different, while the remaining steps and parameters remain the same. The specific amounts added are shown in Table 2 below.

[0044] surface Table of Substance Amounts in Step S3

[0045] project mPEG / hydroxystearic acid co-modified pentaerythritol (g) 5% (v / v) acetic acid solution (mL) Isopropanol (mL) Glycidyltrimethylammonium chloride (g) Deionized water (mL) Example 7 5.5 55 110 7 9 Example 8 7.5 75 140 11 14

[0046] Examples 9-10: A method for preparing an antibacterial surfactant, the difference from Example 1 is that in step S3, glycidyltrimethylammonium chloride is replaced by either glycidyltriethylammonium chloride or glycidyldimethyloctylammonium chloride.

[0047] Comparative Example 1: Based on Example 1, pentaerythritol in step S2 was replaced with ethylene glycol, that is, the star structure with pentaerythritol core was replaced with a linear ethylene glycol skeleton. Subsequent steps used the linear ethylene glycol skeleton to prepare a linear surfactant containing quaternary ammonium groups. Other steps and parameters remained unchanged, resulting in an antibacterial surfactant.

[0048] Comparative Example 2: Based on Example 1, glycidyltrimethylammonium chloride in step S3 was replaced with hexadecyltrimethylammonium chloride without epoxy groups, and it participated in subsequent steps to obtain a star-shaped quaternary ammonium surfactant without hydroxyethyl flexible segments. Other steps and parameters remained unchanged, resulting in an antibacterial surfactant.

[0049] Comparative Example 3: Based on Example 1, step S4 was omitted, modified silica was not added in step S5, and other steps and parameters remained unchanged, resulting in an antibacterial surfactant.

[0050] The antibacterial surfactants prepared in Examples 1-10 were used to prepare pesticide suspensions, respectively named Experimental Group 1-Experimental Group 10; the antibacterial surfactants prepared in Comparative Examples 1-Comparative Examples 3 were used to prepare pesticide suspensions, respectively named Control Group 1-Control Group 3. The preparation steps of pesticide suspensions for each experimental group and control group were the same as follows:

[0051] Add 55g of deionized water, 4g of ethylene glycol as an antifreeze, and 0.2g of xanthan gum as a thickener to a mixing tank. Stir for 18 minutes at 200-300 rpm and 35°C. Then add 25g of pesticide active ingredient and stir for 30 minutes at 450 rpm. Next, add 4g of the antibacterial surfactant from the above example / comparative example and continue stirring for 50 minutes. Transfer the mixture to a sand mill, add 0.5-1mm zirconia beads, and grind at 2500 rpm for 1-2 hours until the pesticide particle size is 2-5μm. Then add 0.15g of organosilicon defoamer and stir for 10 minutes at 100-200 rpm to defoam. Adjust the pH to 7, add deionized water to a total mass of 100g, stir for 15 minutes, filter through a 100-mesh filter, and pour into a brown reagent bottle to obtain the pesticide suspension.

[0052] The performance of pesticide suspensions prepared in experimental groups 1-10 and control groups 1-3 was tested. Suspension rate was determined according to GB / T14825-2006 standard; antibacterial activity was determined according to GB / T21510-2008 standard, using the inhibition zone method with *Escherichia coli* and *Mold* as test strains, and the diameter of the inhibition zone was measured to evaluate the antibacterial effect; hard water resistance was determined according to GB / T17767.1-2008 standard, by measuring the suspension rate after standing in 342 mg / L simulated hard farmland water for 7 days to determine hard water resistance; wetting and penetration performance was evaluated by measuring the surface tension of the pesticide solution according to GB / T5549-2010 standard. The test results are shown in Table 3.

[0053] surface Table of Performance Test Results of Pesticide Suspension Concentrates

[0054] Project Group Suspension rate (%) Diameter of the inhibition zone of Escherichia coli (mm) Diameter of the mold inhibition zone (mm) Hard water resistance (%) Surface tension of the drug solution (mN / m) Experimental group 1 95.2 18.3 15.1 92.5 27.3 Experimental group 2 92.1 17.2 14.3 89.3 28.5 Experimental group 3 94.5 17.8 14.8 91.2 27.8 Experimental group 4 96.3 19.1 16.2 93.8 26.7 Experimental group 5 94.1 18.0 15.0 91.0 27.5 Experimental group 6 93.8 17.9 14.9 90.7 27.6 Experimental group 7 93.2 16.8 14.1 90.2 27.9 Experimental group 8 95.5 19.3 16.5 92.8 26.5 Experimental group 9 94.3 17.5 15.2 91.5 27.4 Experimental group 10 95.8 19.5 16.8 93.2 26.3 Control group 1 83.5 14.2 12.1 78.6 34.2 Control group 2 87.3 15.5 13.4 83.8 32.1 Control group 3 78.2 12.3 10.5 73.4 35.6

[0055] As shown in Table 3, the surfactants added in experimental groups 1-10 achieved a dual dispersion and protection mechanism of molecular steric hindrance and particle synergy by using pentaerythritol to co-modify mPEG500 succinic acid monoester and 12-hydroxystearic acid to form a star structure, followed by ring-opening with epoxy-containing quaternary ammonium salt to introduce quaternary ammonium groups and hydroxyethyl flexible segments, and then undergoing composite modified silica treatment. This mechanism also has synergistic antibacterial and efficient wetting and penetration functions. With the increase of the amount of mPEG500 succinic acid monoester, 12-hydroxystearic acid and glycidyltrimethylammonium chloride, the suspension stability, hard water resistance, antibacterial ability and wetting and penetration were further optimized. At the same time, the replacement of the condensing agent in step S2 and glycidyltrimethylammonium chloride in step S3 still maintained good suspension rate, antibacterial and hard water resistance.

[0056] Comparative Example 1, lacking the star-shaped structure construction process based on pentaerythritol, instead employed a linear ethylene glycol framework. This resulted in the absence of the steric hindrance layer provided by the star structure, preventing it from forming an efficient synergistic dispersion mechanism with the subsequently modified silica. Consequently, its suspension rate was significantly lower than that of the experimental group, and its resistance to hard water, wettability, and antibacterial effects were all poor.

[0057] Comparative Example 2, due to the use of non-epoxy group-containing hexadecyltrimethylammonium chloride, cannot form flexible segments through epoxy ring opening. Therefore, it cannot dissipate pesticide particle collision energy through flexible chain bending and stretching to prevent aggregation, nor can it physically isolate the quaternary ammonium groups from the hard water (Ca). 2+ Mg 2+ Therefore, its suspension rate, hard water resistance and antibacterial properties are weaker than those of the experimental group, and its wetting and permeability are also poor.

[0058] Comparative Example 3, by omitting step S4 and not adding modified silica in step S5, lacked the synergistic dispersion effect of modified silica particles and the function of amino groups adsorbing hard water metal ions. At the same time, it lost its synergistic antibacterial effect with quaternary ammonium groups. This result verifies the necessity of composite treatment of modified silica and star-shaped quaternary ammonium modified products to improve the dispersion stability, hard water resistance, synergistic antibacterial effect, and wetting and penetration performance of pesticide suspensions.

[0059] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for producing an antibacterial surfactant, characterized by, Includes the following steps: Step 1: Pentaerythritol, mPEG500 succinic acid monoester and 12-hydroxystearic acid condense reaction, and then after impurity removal, filtration and washing, mPEG / hydroxystearic acid co-modified star pentaerythritol is obtained. Step 2: Then, the mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol is reacted with an epoxy-containing quaternary ammonium salt epoxy ring-opening reaction. After precipitation, washing and drying, a four-functional modified star polymer is obtained. Step 3: Modify fumed silica with silane coupling agent KH-550 and silane coupling agent WD-10 to obtain modified silica functional filler; mix the four-functional modified star polymer and modified silica and dry to obtain antibacterial surfactant.

2. The method for preparing an antibacterial surfactant according to claim 1, characterized in that, The modified silica functional filler is prepared through the following steps: Anhydrous ethanol and pretreated fumed silica were added to a reaction vessel and dispersed at 300-400 rpm for 20-30 min. KH-550, WD-10 and anhydrous ethanol were added to a stirred tank, and glacial acetic acid was added to adjust the pH to 4-5. The mixture was stirred for 10-15 min. 8-12 mL of the mixed solution was added dropwise to the reaction vessel and stirred at 50-60℃ and 300-400 rpm for 2-3 h. The mixture was centrifuged at 4500-5500 rpm for 4-6 min, washed 3-5 times with an ethanol-deionized water mixture, and vacuum dried at 90-110℃ for 3-5 h before grinding to obtain the modified silica functional filler.

3. The method for preparing an antibacterial surfactant according to claim 2, characterized in that, The ratio of the amount of fumed silica, KH-550 and WD-10 is 8-12g: 1.5-2.5g: 0.5-1g.

4. The method for preparing an antibacterial surfactant according to claim 1, characterized in that, The specific preparation steps of the four-functional modified star polymer are as follows: The mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol and a 5% (v / v) acetic acid solution were added to a reaction vessel and stirred at 30-35℃ for 15-20 min. The pH value was adjusted to 8.5-9.5 by adding 1-2 mol / L sodium hydroxide solution dropwise and stirring at 200-300 r / min for 20-30 min. Isopropanol was added and the mixture was stirred and dispersed at 40-50℃ for 15-20 min. A mixture of epoxy-containing quaternary ammonium salt and deionized water was added in 3-5 portions and stirred at 45-55℃ and 300-400 r / min for 5-7 h. Then, 250-350 mL of an acetone-ethanol mixture with a volume ratio of 2:1 was added, and the mixture was washed 3-5 times. The mixture was then vacuum dried at 45-50℃ to obtain the tetrafunctional modified star polymer.

5. The method for preparing an antibacterial surfactant according to claim 4, characterized in that, The ratio of the amount of mPEG / hydroxystearic acid co-modified pentaerythritol, 5% acetic acid solution, isopropanol, epoxy-containing quaternary ammonium salt and deionized water is 5-8g: 50-80mL: 100-150mL: 6-12g: 8-15mL.

6. The method for preparing an antibacterial surfactant according to claim 4, characterized in that, The epoxy-containing quaternary ammonium salt is any one of glycidyltrimethylammonium chloride, glycidyltriethylammonium chloride, and glycidyldimethyloctylammonium chloride.

7. The method for preparing an antibacterial surfactant according to claim 4, characterized in that, The specific preparation steps for the mPEG / hydroxystearic acid co-modified pentaerythritol are as follows: Pentaerythritol, mPEG500 succinic acid monoester, 12-hydroxystearic acid, and dichloromethane were added to a reactor and stirred at 200-300 r / min under nitrogen protection. Then, 0.98-1.83 g of catalyst and 8.2-15 g of condensing agent were added. The mixture was stirred at 20-30℃ under nitrogen protection for 28-32 h. After the reaction was completed, dichloromethane was volatilized to remove the residue, and acetone was used to precipitate the residue. The residue was filtered, and after acetone was volatilized from the filter cake, it was dissolved in chloroform. The solution was washed successively with dilute hydrochloric acid with a pH of 4-6 and distilled water. After evaporating chloroform, the solution was dried under vacuum to obtain mPEG / hydroxystearic acid co-modified star-shaped pentaerythritol.

8. The method for preparing an antibacterial surfactant according to claim 7, characterized in that, The ratio of pentaerythritol, mPEG500 succinic acid monoester, 12-hydroxystearic acid and dichloromethane is 1.3-1.5g: 12-18g: 1.5-2.5g: 2.8-4.8L.

9. The method for preparing an antibacterial surfactant according to claim 7, characterized in that, The condensing agent is any one of N,N'-dicyclohexylcarboimide, N,N'-diisopropylcarboimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

10. The application of an antibacterial surfactant in pesticide suspensions, characterized in that, The antibacterial surfactant is prepared by the preparation method described in any one of claims 1-9.