Pesticide diluent, preparation method and application

Abstract

The invention provides a pesticide diluent which comprises the following components in percentage by mass: 50-90% of a slow-release carrier, 1-10% of a surfactant and 0-40% of water, the slow-release carrier is mixed hydrosol prepared from carboxymethyl chitosan and an acrylic acid-sodium acrylate copolymer according to the mass ratio of (1-3): 1, and the carboxymethyl chitosan and the acrylic acid-sodium acrylate copolymer in the pesticide diluent can remarkably improve the solubility of missible oil and suspending agent type pesticides, so that a stable diluent is formed; according to the present invention, the pesticide spraying uniformity is improved, the volatility of the pesticide in the high temperature environment is reduced through the carboxymethyl chitosan, the adhesion effect of the pesticide is improved through the acrylic acid-sodium acrylate copolymer in the high humidity environment, and the slow release stability of the pesticide is improved through the mutual combination of the carboxymethyl chitosan and the acrylic acid-sodium acrylate copolymer in advance.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide preparation, and specifically relates to a pesticide diluent, a preparation method and an application thereof. Background Art

[0002] A pesticide diluent is an auxiliary substance for adjusting the concentration of pesticides and facilitating their use, which can dilute high-concentration pesticide technical materials into liquid medicines suitable for different application methods and crop requirements. There are various types of commercially available pesticides, such as emulsifiable concentrates, suspension concentrates, microemulsions, soluble liquid formulations, etc. After being mixed and diluted with diluents, problems such as uneven mixing, demulsification, and stratification often occur, affecting the quality of subsequent operations. Currently, the solubility of pesticides is often increased by adding auxiliaries to water.

[0003] Patent CN202110843364.6 discloses a pesticide diluent, which is prepared by uniformly mixing a hydrophilic auxiliary, an adhesive and soft water. This diluent has the advantages of convenient use and ensuring the stability of the physical and chemical properties of pesticides after dilution, can improve the utilization rate of pesticides and reduce the amount of pesticides used. The high temperature and high humidity environment in summer is conducive to the breeding and reproduction of pests and diseases, and field management needs to be strengthened. However, the high temperature environment will accelerate the volatilization of pesticides, reduce the control effect, and even cause poisoning of pesticide applicators; in a high humidity environment such as rainfall, the wet plant surface increases the difficulty of attaching the liquid medicine, and the mechanical action of rainwater causes the attached liquid medicine to flow away, not only reducing the amount of medicine actually acting on the crops, but also causing environmental pollution.

[0004] Although the above diluent introduces chitosan and its derivatives, which are sugar-based biostimulants, as auxiliaries, it mainly plays an auxiliary regulatory function on the nitrogen metabolism of crops, and does not make any elaboration on improving the temperature resistance and humidity resistance of the pesticide system.

[0005] Therefore, there is an urgent need to develop a new slow-release carrier for pesticide diluents, which can improve the stability of the pesticide dilution system, enhance the stability of the liquid medicine system after spraying, enable the liquid medicine to still play its efficacy stably in high temperature and high humidity environments, and reduce the application frequency. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] In view of the deficiencies of the prior art, the present invention provides a pesticide diluent, a preparation method and an application thereof to solve the problems raised in the above background art.

[0008] (II) Technical Solutions

[0009] To achieve the above objectives, the present invention is realized through the following technical solutions: A pesticide diluent, by mass percentage, comprises the following components: 50% - 90% of a slow-release carrier, 1% - 10% of a surfactant, and 0% - 40% of water;

[0010] The sustained-release carrier is a mixed hydrogel of carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer with a mass ratio of 1-3:1;

[0011] Among them, the carboxymethyl substitution degree of the carboxymethyl chitosan is 0.3-0.6, and the molecular weight range of the acrylic acid-sodium acrylate copolymer is 10,000-100,000.

[0012] A preparation method of a pesticide diluent, for preparing the above-mentioned pesticide diluent, comprising the following steps:

[0013] (1) Preparation of carboxymethyl chitosan;

[0014] (2) Preparation of acrylic acid-sodium acrylate copolymer;

[0015] (3) Mix carboxymethyl chitosan, acrylic acid-sodium acrylate copolymer, and water in a mass ratio of 1-3:1:30, stir evenly, and obtain a sustained-release carrier in a sol state;

[0016] (4) Weigh each component according to the following component ratio: 50-90 wt% of the sustained-release carrier, 1-10 wt% of the surfactant, and 0-40 wt% of water, and perform mixing treatment on the weighed components above.

[0017] As a further preference, the preparation of the carboxymethyl chitosan includes the following steps:

[0018] ① Weigh chitosan according to a mass-volume ratio of 1:20-50 (g / mL), add it to an ethanol-water mixed solvent, and slowly add a sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8;

[0019] ② Dissolve chloroacetic acid in a small amount of water, and slowly add it to the alkaline solution of the above chitosan. The molar ratio of chloroacetic acid to chitosan is 2-3:1, the reaction temperature is 50-60 °C, the stirring speed is 300-500 r / min, and the reaction time is 3-6 h;

[0020] ③ After the reaction is completed, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction, then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is neutral, and place the washed product in a vacuum drying oven to dry to constant weight to obtain carboxymethyl chitosan.

[0021] As a further preference, the preparation of the acrylic acid-sodium acrylate copolymer includes the following steps:

[0022] ① Add acrylic acid and sodium acrylate to an aqueous solution according to a molar ratio of 1:1-3, stir to completely dissolve it, prepare a monomer mixed solution, and adjust the pH value of the monomer mixed solution to 6-8 with a sodium hydroxide solution;

[0023] ② Prepare an initiator aqueous solution containing 0.1 - 1 wt% of the total monomer mass;

[0024] ③ Heat the monomer mixed solution to 60 - 80 °C, and during the heating process, slowly dropwise add the initiator solution. After the dropping is completed, carry out the polymerization reaction at this temperature for 2 - 3 h;

[0025] ④ After 1 hour of the polymerization reaction, slowly add the chain transfer agent and stir until the polymerization reaction ends;

[0026] ⑤ After the reaction ends, cool down to terminate the reaction, neutralize the reaction product with sodium hydroxide solution to a pH value of 7 - 8, filter, and freeze-dry to obtain the acrylic acid - sodium acrylate copolymer.

[0027] As a further preference, the total molar concentration of the monomers is 20% - 50%.

[0028] As a further preference, the initiator is one or more of ammonium persulfate and potassium persulfate.

[0029] As a further preference, the chain transfer agent is one or more of mercaptoacetic acid, mercaptoethanol, and isopropanol.

[0030] As a further preference, the usage amount of the chain transfer agent is 0.01 wt% - 0.1 wt% of the total monomer mass.

[0031] An application of a pesticide diluent, using the above pesticide diluent for diluting pesticides, and the pesticides are one or more of commercially available pesticide emulsifiable concentrates, suspension concentrates, microemulsions, and soluble solutions.

[0032] (III) Beneficial effects

[0033] The present invention provides a pesticide diluent, a preparation method, and an application, having the following beneficial effects:

[0034] In the pesticide diluent of the present invention, carboxymethyl chitosan with a substitution degree of 0.3 - 0.6 and an acrylic acid - sodium acrylate copolymer with a molecular weight range of 10,000 - 100,000 are rich in a large number of hydrophilic groups and hydrophilic chains, which can effectively reduce the water - oil interfacial tension and the electrostatic adsorption effect on the surface of solid particles, and improve the stability of emulsifiable concentrates and suspension - type pesticide dilutions;

[0035] Meanwhile, at low temperatures, the molecular chains of carboxymethyl chitosan stretch to evenly disperse the pesticides within the molecular chains. When the temperature rises to a certain threshold, the molecular chains aggregate to form a gel network structure, which wraps the pesticides therein, reduces the volatilization of pesticides in a high - temperature environment, improves the temperature resistance of the pesticide system, and prolongs the effective coverage time of the drug;

[0036] Moreover, in an environment with relatively high humidity, the acrylic acid-sodium acrylate copolymer absorbs moisture in the air, increasing the viscosity of the pesticide diluent, prolonging the residence time of the pesticide on the crop surface, improving the adhesion effect of the pesticide, and avoiding the problem of the liquid medicine falling off due to excessive humidity or rain washing.

[0037] Finally, by pre-combining carboxymethyl chitosan with the acrylic acid-sodium acrylate copolymer to form a slow-release carrier, the mechanical strength of the molecular chain is increased. When the pesticide is sprayed, the molecular chain structure will not be damaged due to spraying and droplet collision, avoiding premature release of the pesticide due to structural damage, and enabling the pesticide to play a continuous and stable role for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the preparation process of the pesticide diluent of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include indirect contact between the first and second features through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicating that the first feature has a lower horizontal height than the second feature.

[0040] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0041] On the one hand, the present invention provides a pesticide diluent, which includes the following components by mass percentage: 50% - 90% of a slow-release carrier, 1% - 10% of a surfactant, and 0% - 40% of water.

[0042] Specifically, the slow-release carrier is a mixed hydrogel of carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer with a mass ratio of 1 - 3:1.

[0043] Further, the preparation steps of the sustained-release carrier are as follows:

[0044] (1) Preparation of carboxymethyl chitosan:

[0045] ① Weigh chitosan according to the mass-volume ratio of 1:20 - 50 (g / mL) and add it to the ethanol-water mixed solvent. Slowly add sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8.

[0046] ② Dissolve chloroacetic acid in a small amount of water and slowly add it to the above-mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 2 - 3:1, the reaction temperature is 50 - 60 °C, the stirring speed is 300 - 500 r / min, and the reaction time is 3 - 6 h. By controlling the molar ratio of chloroacetic acid to chitosan, the carboxymethyl substitution degree of chitosan is adjusted, and its substitution degree is controlled to be 0.3 - 0.6, so that the substituted carboxymethyl chitosan has good solubility in water, can dissolve quickly at room temperature to form a uniform solution, and at the same time, the side reactions caused by excessive chloroacetic acid can be avoided.

[0047] It can be understood that carboxymethyl chitosan with a substitution degree of 0.3 - 0.6 has good solubility in water. Its hydrophobic groups combine with pesticides to improve the mixing uniformity of pesticides and water. At the same time, the hydrophilic groups (such as carboxyl groups, hydroxyl groups, etc.) on the carboxymethyl chitosan molecular chain form hydrogen bonds with water molecules. At low temperatures, these hydrogen bond actions are strong, the carboxymethyl chitosan molecular chain stretches, and the solution is in a sol state. Pesticides are uniformly dispersed inside the molecular chain. When the temperature rises to a certain threshold, the molecular thermal motion intensifies, the hydrogen bonds are broken, the intermolecular interactions of the molecular chain increase, and aggregation occurs to form a gel network structure, which encapsulates the pesticides, reduces the volatilization of pesticides, reduces the loss of pesticides in a high-temperature environment, and at the same time reduces the pollution of the surrounding environment during pesticide application.

[0048] ③ After the reaction is completed, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is close to neutral, and place the washed product in a vacuum drying oven to dry to constant weight to obtain carboxymethyl chitosan.

[0049] (2) Preparation of acrylic acid-sodium acrylate copolymer:

[0050] ① Add acrylic acid and sodium acrylate to the aqueous solution according to the molar ratio of 1:1 - 3, stir to dissolve them completely, and prepare a monomer mixed solution. Adjust the pH value of the monomer mixed solution to 6 - 8 with sodium hydroxide solution, and the total monomer concentration is 20% - 50%. Too high a concentration may cause the polymerization reaction heat to be difficult to dissipate, leading to explosive polymerization, and too low a concentration will result in too slow a reaction rate.

[0051] ② Prepare an aqueous initiator solution containing 0.1 - 1 wt% of the total monomer mass. The initiator can be one or more of ammonium persulfate and potassium persulfate. They can decompose to generate free radicals at a certain temperature, initiating the polymerization of the monomers.

[0052] ③ Heat the monomer mixed solution to 60 - 80 °C, and during the heating process, slowly dropwise add the initiator solution. After the addition is complete, carry out the polymerization reaction at this temperature for 2 - 3 h.

[0053] The polymerization reaction mechanism is as follows:

[0054] Chain initiation:

[0055] Initiator• + CH2=CH-COOH → Initiator-CH2-C•H-COOH;

[0056] Initiator• + CH2=CH-COONa → Initiator-CH2-C•H-COONa;

[0057] Chain growth:

[0058] Initiator-CH2-C•H-COOH + CH2=CH-COOH → Initiator-CH2-CH(COOH)-CH2-C•H-COOH;

[0059] Initiator-CH2-C•H-COOH + CH2=CH-COONa → Initiator-CH2-CH(COOH)-CH2-C•H-COONa;

[0060] Initiator-CH2-CH(COOH)-CH2-C•H-COONa + CH2=CH-COONa → Initiator-CH2-CH(COOH)-CH2-CH(COONa)-CH2-C•H-COONa;

[0061] The acrylic acid free radical can react with acrylic acid or sodium acrylate monomers, and the sodium acrylate free radical can also react with acrylic acid or sodium acrylate monomers. During the reaction process, the free radicals continuously combine with monomer molecules to form longer and longer acrylic acid - sodium acrylate copolymer chains.

[0062] Chain termination:

[0063] Initiator-CH2-C•H-COOH + Initiator-CH2-C•H-COONa → Initiator-CH2-CH(COOH)-CH(CH2-Initiator)-COONa;

[0064] Initiator-CH2-C•H-COOH + Initiator-CH2-C•H-COONa → Initiator-CH2-CH2-COOH + Initiator-CH2=CH-COONa;

[0065] ④ After 1 hour of polymerization reaction, a chain transfer agent was slowly added and stirred until the polymerization reaction ended.

[0066] Among them, the chain transfer agent is one or more of thioglycolic acid, mercaptoethanol and isopropanol. The chain transfer agent has active hydrogen atoms, can react with the growing chain radicals, transfer the radicals to its own molecules, terminate the growth of the polymer chain, and at the same time generate new radicals to continue to participate in the reaction, thereby realizing the regulation and control of the polymer molecular weight.

[0067] Specifically, the usage amount of the chain transfer agent is 0.01wt%-0.1wt% of the total mass of the monomers, and the molecular weight range of the acrylic acid-sodium acrylate copolymer is 10,000-100,000.

[0068] ⑤ After the reaction ended, the reaction was terminated by cooling, and the reaction product was neutralized to pH 7-8 with sodium hydroxide solution, filtered, and freeze-dried to obtain the acrylic acid-sodium acrylate copolymer.

[0069] It can be understood that the acrylic acid-sodium acrylate copolymer contains a large number of carboxylic acid and carboxylate groups, and these groups have a strong affinity for water molecules. In an environment with higher humidity, the acrylic acid-sodium acrylate copolymer will absorb moisture in the air, swell, increase the viscosity of the pesticide diluent, and form a gel-like state. This gel state can slow down the volatilization rate of the pesticide, prolong the residence time of the pesticide on the crop surface, and improve the adhesion effect of the pesticide. When the pesticide diluent is sprayed on the crop surface, the acrylic acid-sodium acrylate copolymer can absorb moisture in the air and retain it on the crop surface, providing a relatively humid environment for the pesticide, enabling the pesticide to maintain its activity for a long time and enhancing the control effect.

[0070] (3)Carboxymethyl chitosan, acrylic acid-sodium acrylate copolymer and water were mixed at a mass ratio of 1-3:1:30, and after stirring evenly, a slow-release carrier in a sol state was obtained.

[0071] Specifically, the carboxymethyl chitosan molecule contains amino groups, and the amino groups will be protonated and carry positive charges in an aqueous solution. The acrylate part of the acrylic acid-sodium acrylate copolymer dissociates carboxylate anions, making the copolymer as a whole negatively charged. When the two are mixed, electrostatic attraction will occur between the groups with opposite charges, promoting them to approach and combine with each other. At the same time, groups such as hydroxyl and amino groups in carboxymethyl chitosan contain active hydrogen atoms, and groups such as carboxyl and carbonyl groups in the acrylic acid-sodium acrylate copolymer have lone pair electrons. Hydrogen bonds will be formed between the active hydrogen atoms and the lone pair electrons. The electrostatic interaction and hydrogen bonds help to improve the degree of combination between the two molecules, thereby improving the stability of the slow-release carrier.

[0072] It is understandable that the hydrophobic parts of the carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer combined with each other in the sustained-release carrier encapsulate the pesticide. When the external humidity is high, such as during rainy weather, the acrylic acid-sodium acrylate copolymer quickly absorbs water and swells, increasing the viscosity of the diluent, enhancing the adhesion to the outside of the crop, reducing the runoff of the liquid medicine due to rain erosion. At the same time, the carboxymethyl chitosan in the sol state controls the drug release rate, improving the utilization rate of the pesticide. When the external humidity is low, the water storage function of the acrylic acid-sodium acrylate copolymer maintains the pesticide activity and provides a moist environment for the carboxymethyl chitosan sol, prolonging the sustained-release effect time. When the external temperature rises, the carboxymethyl chitosan transforms from the sol state to the gel state, and the structure changes from loose to tight, slowing down the pesticide release rate, avoiding the problems of drug waste and environmental pollution caused by the increased volatilization of the pesticide due to the rising temperature, improving the matching degree between drug release and crop absorption, reducing the number of pesticide applications and the total amount of pesticides applied.

[0073] Furthermore, the sol network structure formed by carboxymethyl chitosan is loose. During spraying, the high-speed air flow impact and droplet collision are likely to damage the structure, affecting the stability of pesticide release. The combination of carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer improves the mechanical strength of the hydrophilic chain of carboxymethyl chitosan, reducing the damage to the hydrophilic chain structure caused by spraying and droplet collision, so that the sustained-release carrier still maintains its original function after spraying.

[0074] The present invention also provides a method for preparing a pesticide diluent, which includes the following steps:

[0075] Weigh each component according to the following component ratios: 50 - 90 wt% of the sustained-release carrier, 1 - 10 wt% of the surfactant, and 0 - 40 wt% of water;

[0076] Mix the weighed components above.

[0077] Specifically, the surfactant is one or more of anionic surfactants and non-ionic surfactants. Among them, the anionic surfactant is specifically one or more of sodium dodecylbenzenesulfonate, alkylnaphthalenesulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium dodecyl sulfate. The non-ionic surfactant is specifically one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, and polyoxyethylene sorbitan.

[0078] The present invention also provides an application of the pesticide diluent. Mix the above pesticide diluent and the pesticide according to the required ratio, pour the mixed diluent into the water tank, and spray and cover the crop plants, especially the parts such as leaves and fruits, through a sprayer.

[0079] Specifically, the pesticide can be one or more of commercially available pesticide emulsifiable concentrates, suspension concentrates, microemulsions, and soluble solutions.

[0080] To further understand the present invention, the pesticide diluent provided by the present invention will be described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0081] Example 1

[0082] (1) Preparation of carboxymethyl chitosan:

[0083] ① Weigh chitosan according to a mass-volume ratio of 1:20 (g / mL) and add it to an ethanol-water mixed solvent. Slowly add sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8.

[0084] ② Dissolve chloroacetic acid in a small amount of water and slowly add it to the above-mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 2:1, the reaction temperature is 50 °C, the stirring speed is 300 r / min, and the reaction time is 3 h.

[0085] ③ After the reaction is completed, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is close to neutral, and place the washed product in a vacuum drying oven to dry to a constant weight to obtain carboxymethyl chitosan.

[0086] (2) Preparation of acrylic acid-sodium acrylate copolymer:

[0087] ① Add acrylic acid and sodium acrylate to an aqueous solution according to a molar ratio of 1:1, stir to completely dissolve it, and prepare a monomer mixed solution. Adjust the pH value of the monomer mixed solution to 7 with sodium hydroxide solution, and the total monomer concentration is 30%.

[0088] ② Prepare an aqueous solution of ammonium persulfate containing 0.1 wt% of the total mass of the monomers.

[0089] ③ Heat the monomer mixed solution to 60 °C, and slowly add the aqueous solution of ammonium persulfate during the heating process. After the addition is complete, carry out a polymerization reaction at this temperature for 2 h.

[0090] ④ One hour after the polymerization reaction, slowly add 0.01 wt% of mercaptoacetic acid based on the total mass of the monomers and stir until the polymerization reaction ends.

[0091] ⑤ After the reaction is completed, cool down to terminate the reaction, neutralize the reaction product to a pH value of 7 with sodium hydroxide solution, filter, and freeze-dry to obtain the acrylic acid-sodium acrylate copolymer.

[0092] (3) Mix carboxymethyl chitosan, acrylic acid-sodium acrylate copolymer, and water according to a mass ratio of 1:1:30, stir evenly, and obtain a slow-release carrier in a sol state.

[0093] (4) Weigh by mass fraction: 80% of the slow-release carrier, 1% of sodium dodecylbenzenesulfonate, and 19% of water. Then mix the weighed components to obtain a pesticide diluent.

[0094] Example 2

[0095] (1) Preparation of carboxymethyl chitosan:

[0096] ① Weigh chitosan at a mass-to-volume ratio of 1:50 (g / mL) and add it to an ethanol-water mixed solvent. Slowly add sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8.

[0097] ② Dissolve chloroacetic acid in a small amount of water and slowly add it to the above-mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 3:1, the reaction temperature is 50 °C, the stirring speed is 500 r / min, and the reaction time is 4 h.

[0098] ③ After the reaction is completed, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is close to neutral, and place the washed product in a vacuum drying oven to dry to a constant weight to obtain carboxymethyl chitosan.

[0099] (2) Preparation of acrylic acid-sodium acrylate copolymer:

[0100] ① Add acrylic acid and sodium acrylate to an aqueous solution at a molar ratio of 1:3, stir to completely dissolve them, and prepare a monomer mixed solution. Then adjust the pH value of the monomer mixed solution to 8 with sodium hydroxide solution, and the total monomer concentration is 50%.

[0101] ② Prepare an aqueous solution of potassium persulfate containing 0.5 wt% of the monomer mass.

[0102] ③ Heat the monomer mixed solution to 70 °C, and slowly add the aqueous solution of ammonium persulfate during the heating process. After the addition is complete, carry out a polymerization reaction at this temperature for 3 h.

[0103] ④ After the polymerization reaction for 1 hour, slowly add 0.04 wt% of isopropanol based on the total mass of the monomers and stir until the polymerization reaction is completed.

[0104] ⑤ After the reaction is completed, cool down to terminate the reaction, neutralize the reaction product to a pH value of 7 with sodium hydroxide solution, filter, and freeze-dry to obtain an acrylic acid-sodium acrylate copolymer.

[0105] (3) Mix carboxymethyl chitosan, acrylic acid-sodium acrylate copolymer, and water at a mass ratio of 3:1:30, and stir evenly to obtain a slow-release carrier in a sol state.

[0106] (4)Weigh by mass fraction: 60% of the sustained-release carrier, 5% of sodium dodecylbenzenesulfonate, and 35% of water, and mix the weighed components to obtain a pesticide diluent.

[0107] Comparative Example 1

[0108] (1)Mix chitosan, sodium polyacrylate, and water in a mass ratio of 3:1:30, and stir evenly to obtain a mixed solution.

[0109] (2)Weigh by mass fraction: 60% of the mixed solution, 5% of sodium dodecylbenzenesulfonate, and 35% of water, and mix the weighed components to obtain a comparative diluent.

[0110] Comparative Example 2

[0111] (1)Preparation of carboxymethyl chitosan:

[0112] ① Weigh chitosan at a mass-to-volume ratio of 1:50 (g / mL) and add it to an ethanol-water mixed solvent. Slowly add a sodium hydroxide solution under stirring to adjust the pH value of the solution system to 8.

[0113] ② Dissolve chloroacetic acid in a small amount of water and slowly add it to the above-mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 3:1, the reaction temperature is 50 °C, the stirring speed is 500 r / min, and the reaction time is 4 h.

[0114] ③ After the reaction, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is close to neutral, and place the washed product in a vacuum drying oven to dry to constant weight to obtain carboxymethyl chitosan.

[0115] (2)Mix carboxymethyl chitosan and water in a mass ratio of 1:10, and stir evenly to obtain a mixed solution.

[0116] (3)Weigh by mass fraction: 60% of the mixed solution, 5% of sodium dodecylbenzenesulfonate, and 35% of water, and mix the weighed components to obtain a comparative diluent.

[0117] Comparative Example 3

[0118] (1)Preparation of acrylic acid-sodium acrylate copolymer:

[0119] ① Add acrylic acid and sodium acrylate to an aqueous solution in a molar ratio of 1:3, stir to completely dissolve it, and prepare a monomer mixed solution. Adjust the pH value of the monomer mixed solution to 8 with a sodium hydroxide solution, and the total monomer concentration is 50%.

[0120] ② Prepare an aqueous solution of potassium persulfate containing 0.5 wt% of the monomer by mass.

[0121] ③ Heat the monomer mixed solution to 70 °C, and slowly add an aqueous solution of ammonium persulfate during the heating process. After the addition is complete, carry out a polymerization reaction at this temperature for 3 h.

[0122] ④ After the polymerization reaction for 1 h, slowly add 0.04 wt% isopropanol based on the total mass of the monomers, and stir until the polymerization reaction ends.

[0123] ⑤ After the reaction ends, cool down to terminate the reaction, neutralize the reaction product to pH 7 with sodium hydroxide solution, filter, and freeze-dry to obtain the acrylic acid-sodium acrylate copolymer.

[0124] (2) Mix the acrylic acid-sodium acrylate copolymer and water at a mass ratio of 1:30, and stir evenly to obtain a mixed solution.

[0125] (3) Weigh by mass fraction: 60% of the mixed solution, 5% of sodium dodecylbenzenesulfonate, and 35% of water, and mix the weighed components to obtain a comparative diluent.

[0126] Comparative Example 4

[0127] (1) Preparation of carboxymethyl chitosan:

[0128] ① Weigh chitosan at a mass-to-volume ratio of 1:50 (g / mL) and add it to an ethanol-water mixed solvent. Slowly add sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8.

[0129] ② Dissolve chloroacetic acid in a small amount of water and slowly add it to the above-mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 3:1, the reaction temperature is 50 °C, the stirring speed is 500 r / min, and the reaction time is 4 h.

[0130] ③ After the reaction ends, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is close to neutral, and place the washed product in a vacuum drying oven to dry to constant weight to obtain carboxymethyl chitosan.

[0131] (2) Preparation of acrylic acid-sodium acrylate copolymer:

[0132] ① Add acrylic acid and sodium acrylate to an aqueous solution at a molar ratio of 1:3, stir to completely dissolve it, and prepare a monomer mixed solution. Adjust the pH value of the monomer mixed solution to 8 with sodium hydroxide solution, and the total monomer concentration is 50%.

[0133] ② Prepare an aqueous solution of potassium persulfate containing 0.5 wt% of the total monomer mass.

[0134] ③ Heat the monomer mixed solution to 70 °C, and slowly add an aqueous solution of ammonium persulfate dropwise during the heating process. After the addition is complete, carry out a polymerization reaction at this temperature for 3 h.

[0135] ④ After the polymerization reaction for 1 h, slowly add 0.04 wt% of isopropanol based on the total mass of the monomers, and stir until the polymerization reaction ends.

[0136] ⑤ After the reaction ends, cool down to terminate the reaction, neutralize the reaction product to pH 7 with a sodium hydroxide solution, filter, and freeze-dry to obtain an acrylic acid-sodium acrylate copolymer.

[0137] (3) Weigh by mass fraction: 5.3% of carboxymethyl chitosan, 1.76% of acrylic acid-sodium acrylate copolymer, 5% of sodium dodecylbenzenesulfonate, and 87.94% of water, and mix the weighed components to obtain a comparative diluent.

[0138] Test examples:

[0139] Take the diluents prepared in Examples 1-2 and Comparative Examples 1-4, place them in a transparent container, observe the appearance, and conduct density tests using a densitometer. Test the viscosity at 15 °C and 40 °C using a rotational viscometer. The specific test results are shown in Table 1.

[0140] Wettability test: Drop the diluent on the surface of crop leaves, and measure the contact angle between the liquid droplet and the leaf surface using a contact angle measuring instrument. The specific test results are shown in Table 1.

[0141] Emulsification test: Add a certain amount of oil substances (simulating the oily components in pesticides) to the diluent, stir evenly with a high-speed stirrer, and then observe the stability of the emulsion after standing. The specific test results are shown in Table 1.

[0142] Table 1 Statistical table of physical property tests for each example and comparative example Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Appearance Clear and transparent Clear and transparent Clear and transparent Clear and transparent Clear and transparent Clear and transparent <![CDATA[Density / g / cm 3 > 1.07 1.05 1.04 1.02 1.01 1.05 Viscosity (15°C - humidity 30%) / mPa·s 75 67 235 47 56 69 Viscosity (40°C - humidity 30%) / mPa·s 476 465 227 53 43 479 Viscosity (15°C - humidity 100%) / mPa·s 513 521 233 47 56 69 Viscosity (40°C - humidity 100%) / mPa·s 637 642 229 52 44 632 Contact angle / ° 13 11 46 34 39 17 Emulsion stability No delamination for > 2h No delamination for > 2h Demulsification occurred after > 1h Demulsification occurred after > 2h Demulsification occurred after > 1h Demulsification occurred after > 2h

[0143] For the diluents prepared in Examples 1-2 and Comparative Examples 1-4, after mixing with powdery pesticides, use a mist sprayer to spray on the surface of crop leaves, and respectively test the effective coverage time of the pesticide components and the droplet adhesion rate under the conditions of 15 °C - humidity 30%, 40 °C - humidity 30%, 15 °C - humidity 100%, and 40 °C - humidity 100%. The specific test results are shown in Table 2.

[0144] Table 2 Statistical table of effective coverage time and droplet adhesion rate for each example and comparative example Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Effective coverage time / days 17 16 5.6 7 7.5 8 Adhesion rate / % (15°C - humidity 30%) 85.4 84.8 60.1 58.3 64.2 67.4 Adhesion rate / % (40°C - humidity 30%) 97.2 96.9 60.2 61.5 63.9 73.2 Adhesion rate / % (15°C - humidity 100%) 98.1 97.6 68.4 54.2 78.2 76.1 Adhesion rate / % (40°C - humidity 100%) 99.5 99.8 67.9 56.1 77.9 80.3

[0145] It should be noted that the effective coverage time is calculated based on the total duration when the pesticide concentration in the droplets is not lower than the concentration maintaining the effective control effect under the conditions of 40°C and 100% humidity. The longer the effective coverage time, the fewer the number of pesticide applications, which can effectively save costs. The adhesion rate is determined by measuring the weight change of the leaf surface before and after pesticide application to determine the amount of liquid medicine adhered, and the percentage is calculated based on the amount of pesticide applied. The higher the adhesion rate, the higher the stability of the continuous action of the liquid medicine on the leaf surface and the greater the utilization rate of the pesticide.

[0146] In summary, carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer in the pesticide diluent of the present invention can significantly improve the solubility of emulsifiable concentrate and suspension type pesticides, thereby forming a stable diluent and improving the spraying uniformity. At the same time, when the temperature is low, the molecular chain of carboxymethyl chitosan stretches to evenly disperse the pesticide within the molecular chain. When the temperature rises to a certain threshold, it aggregates to form a gel network structure, encapsulating the pesticide therein, reducing the volatilization of the pesticide. At the same time, in an environment with high humidity, the acrylic acid-sodium acrylate copolymer absorbs moisture in the air, increasing the viscosity of the pesticide diluent, prolonging the residence time of the pesticide on the crop surface, and improving the adhesion effect of the pesticide. And by combining carboxymethyl chitosan and acrylic acid-sodium acrylate copolymer in advance, the mechanical strength of the molecular chain is improved, and the unstable phenomenon of pesticide slow release caused by the destruction of the hydrophilic chain structure due to spraying and droplet collision is reduced.

[0147] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pesticide diluent, characterized in that, By mass percentage, it includes the following components: 50% - 90% of sustained-release carrier, 1% - 10% of surfactant, and 0% - 40% of water; The sustained-release carrier is a mixed hydrogel of carboxymethyl chitosan and acrylic acid - sodium acrylate copolymer with a mass ratio of 1 - 3:1; Among them, the carboxymethyl substitution degree of the carboxymethyl chitosan is 0.3 - 0.6, and the molecular weight range of the acrylic acid - sodium acrylate copolymer is 10000 - 100000.

2. A preparation method of a pesticide diluent, characterized in that, To prepare the pesticide diluent described in claim 1, it includes the following steps: (1) Preparation of carboxymethyl chitosan; (2) Preparation of acrylic acid - sodium acrylate copolymer; (3) Mix carboxymethyl chitosan, acrylic acid - sodium acrylate copolymer, and water in a mass ratio of 1 - 3:1:30, and after stirring evenly, obtain a sustained-release carrier in sol state; (4) Weigh each component according to the following component ratio: 50 - 90wt% of sustained-release carrier, 1 - 10wt% of surfactant, and 0 - 40wt% of water, and perform mixing treatment on the weighed components above.

3. The preparation method of a pesticide diluent according to claim 2, characterized in that: The preparation of the carboxymethyl chitosan includes the following steps: ① Weigh chitosan according to a mass - volume ratio of 1:20 - 50 (g / mL) and add it to the ethanol - water mixed solvent. Slowly add sodium hydroxide solution under stirring conditions to adjust the pH value of the solution system to 8; ② Dissolve chloroacetic acid in a small amount of water, and slowly add it to the above - mentioned alkaline solution of chitosan. The molar ratio of chloroacetic acid to chitosan is 2 - 3:1, the reaction temperature is 50 - 60°C, the stirring speed is 300 - 500 r / min, and the reaction time is 3 - 6h; ③ After the reaction ends, adjust the pH value of the reaction solution to neutral with dilute hydrochloric acid to terminate the reaction. Then, separate the product by filtration, wash it with a large amount of deionized water until the pH value of the washing solution is neutral, and place the washed product in a vacuum drying oven to dry to constant weight to obtain carboxymethyl chitosan.

4. The preparation method of a pesticide diluent according to claim 2, characterized in that: The preparation of the acrylic acid - sodium acrylate copolymer includes the following steps: ① Add acrylic acid and sodium acrylate to the aqueous solution according to a molar ratio of 1:1 - 3, stir to completely dissolve it, prepare a monomer mixed solution, and adjust the pH value of the monomer mixed solution to 6 - 8 with sodium hydroxide solution; ② Prepare an initiator aqueous solution containing 0.1 - 1wt% of the total mass of the monomers; ③ Heat the monomer mixed solution to 60 - 80°C, and during the heating process, slowly dropwise add the initiator solution. After the dropping is completed, carry out a polymerization reaction at this temperature for 2 - 3h; ④ After 1 hour of polymerization reaction, slowly add a chain transfer agent and stir until the polymerization reaction ends; ⑤ After the reaction ends, cool down to terminate the reaction, neutralize the reaction product to a pH value of 7 - 8 with sodium hydroxide solution, filter, and freeze - dry to obtain the acrylic acid - sodium acrylate copolymer.

5. The preparation method of a pesticide diluent according to claim 4, characterized in that: The total molar concentration of the monomers is 20% - 50%.

6. The preparation method of a pesticide diluent according to claim 4, characterized in that: The initiator is one or more of ammonium persulfate and potassium persulfate.

7. The preparation method of a pesticide diluent according to claim 4, characterized in that: The chain transfer agent is one or more of mercaptoacetic acid, mercaptoethanol, and isopropanol.

8. The preparation method of a pesticide diluent according to claim 7, characterized in that: The usage amount of the chain transfer agent is 0.01wt% - 0.1wt% of the total mass of the monomers.

9. An application of a pesticide diluent, characterized in that, Use the pesticide diluent described in any one of 1 - 8 for diluting pesticides in the form of emulsifiable concentrates, suspension concentrates, and microemulsions.

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