Agricultural polymer surfactant and its preparation method

Abstract

The application relates to the field of high-molecular surfactants, and discloses an agricultural high-molecular surfactant and a preparation method thereof. The preparation method comprises the following steps: introducing multiple hydrophilic polyethylene glycol side chains into a sodium lignosulfonate molecule by using an electrophilic substitution reaction to prepare a novel anionic sodium lignosulfonate polyoxyethylene ether, introducing a tetramethylpiperidinamine monomer by using a Mannich reaction to synthesize a novel hindered amine grafted sodium lignosulfonate polyoxyethylene ether, mixing a cationic surfactant hexadecyl trimethyl ammonium bromide with the hindered amine grafted sodium lignosulfonate polyoxyethylene ether to obtain a stable agricultural high-molecular surfactant, and the agricultural high-molecular surfactant has strong surface activity, dispersing performance and photolysis resistance.

Description

Technical Field

[0001] This invention relates to the field of polymeric surfactants, and more specifically to an agricultural polymeric surfactant and its preparation method. Background Technology

[0002] As the final form of pesticide application, formulations directly affect the efficacy and safety of pesticides. Formulation development is moving towards water-based, granular, low-toxicity, and high-efficiency formulations. Dispersants, as the most crucial adjuvant in water-based pesticide formulations, will determine the future development of pesticide formulations.

[0003] Currently, the most commonly used pesticide dispersants include lignin sulfonate-based dispersants, naphthalene sulfonates and their formaldehyde condensates, block copolymers, and polycarboxylic acid comb copolymers. Except for lignin sulfonates, the other dispersants are all derived from petrochemical products, resulting in high costs and even potential harm to human health, failing to meet the needs of sustainable development. Lignosulfonate-based dispersants, mainly derived from papermaking wastewater, possess advantages such as good compatibility with active ingredients, environmental friendliness, complete biodegradability, and low price. Although lignin sulfonates can be applied in various industrial fields, their low molecular weight, insufficient functional groups, and poor surface activity result in generally poor application performance and inadequate dispersion stability when used as specific dispersants. Therefore, improving the application performance of lignin dispersants in pesticide formulations through physical and chemical modification to meet the development needs of novel pesticide formulations is of great significance to the development of pesticide formulations in my country.

[0004] Because biopesticides have poor fast-acting properties and require a long period to exert their effects, the active ingredients of most biopesticides are easily decomposed in the natural environment due to factors such as temperature, light, water pH, and microorganisms, thereby reducing their insecticidal activity and control effect. Increasing the dosage to improve efficacy will also place a greater burden on the environment.

[0005] Existing technologies, such as Chinese patent application CN105557687A, disclose an abamectin aqueous suspension and its preparation method. The method to improve the photostability of pesticides is to directly add the small molecule photostability bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate. This is a non-water-soluble substance, which has poor dispersion in water systems and is easy to migrate, resulting in poor actual effect. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an agricultural polymeric surfactant and its preparation method, wherein the surfactant has strong surface activity, dispersing properties and resistance to photolysis.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing an agricultural polymeric surfactant includes the following steps:

[0009] Step (1): Mix polyethylene glycol, boron trifluoride ethyl ether and epichlorohydrin, and react them. After the reaction is complete, chlorinated polyethylene glycol intermediate is obtained.

[0010] Sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate, the pH was adjusted, and the reaction was carried out. After the reaction was completed, the mixture was purified to obtain sodium lignosulfonate polyoxyethylene ether.

[0011] Step (2): Mix sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine, adjust the pH, add formaldehyde aqueous solution and react. After the reaction is completed, cool and purify to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0012] Step (3): Mix hexadecyltrimethylammonium bromide, hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water, stir, let stand to precipitate, and purify to obtain agricultural polymer surfactant.

[0013] Preferably, in step (1), when preparing the chloropolyethylene glycol intermediate: epichlorohydrin is added slowly dropwise at a rate of 1-2 d / s; the molar ratio of epichlorohydrin to polyethylene glycol is (0.8-1.2):1; the amount of boron trifluoride ether added is 0.1 wt% of the amount of polyethylene glycol added; and the reaction conditions are: reacting at 50-60℃ for 1-3 h.

[0014] Preferably, in step (1), when preparing sodium lignosulfonate polyoxyethylene ether: the mass fraction of sodium lignosulfonate aqueous solution is 30%; the mass ratio of 30wt% sodium lignosulfonate aqueous solution to chlorinated polyethylene glycol intermediate is 3:(0.5-1.5); the pH is adjusted by adding 30wt% sodium hydroxide aqueous solution to adjust the pH to 9-11; the reaction conditions are: reacting at pH=9-11 and 60-80℃ for 2-4 hours.

[0015] Preferably, in step (1), when preparing sodium lignosulfonate polyoxyethylene ether, the purification step is as follows: extract the sodium lignosulfonate polyoxyethylene ether solution with butanone 3-5 times to remove water and unreacted polyethylene glycol, filter to obtain the extraction product, add 8-10 times the mass of the extraction product of ethanol to wash 3-5 times, and dry at 35-45℃ for 20-24h to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0016] Preferably, in step (2): the pH is adjusted by adding 30wt% sodium hydroxide aqueous solution to adjust the pH to 10-12; the formaldehyde aqueous solution added is 10wt% formaldehyde aqueous solution, and the dripping time is 30-40min; the mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:(60-80):(1-4):(2-8); the reaction conditions are: reacting at pH=10-12 and 65-85℃ for 3-5h.

[0017] Preferably, in step (2), the purification step is as follows: add 8-10 times the volume of ethanol to the reaction product to precipitate, filter, take the precipitate, and dry it at 35-45℃ for 20-24h.

[0018] Preferably, in step (3), the mass ratio of hexadecyltrimethylammonium bromide, hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water is 50:(2-10):(150-630):(100-420); the stirring conditions are: stirring at 400-500 rpm for 30-40 min; and the sedimentation time is 20-24 h.

[0019] Preferably, in step (3), the purification step is as follows: take the precipitate, add 8-10 times the mass of the precipitate of deionized water to wash 3-5 times, centrifuge, filter, take the centrifuged precipitate, and dry it at 35-45℃ for 20-24h.

[0020] Preferably, the agricultural polymer surfactant is prepared using the method described above.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The molecular structure of lignin sulfonates contains functional groups such as phenylpropane hydrophobic skeleton, phenolic hydroxyl, alcoholic hydroxyl, carboxyl, and sulfonic acid groups, which have certain dispersing properties. In this invention, multiple hydrophilic polyethylene glycol side chains are introduced into the sodium lignin sulfonate molecule by electrophilic substitution reaction to prepare a novel anionic sodium lignin sulfonate polyoxyethylene ether. The product has anionic functional groups and long hydrophilic polyethylene glycol chains, which increases its molecular weight and improves its surface activity and application performance.

[0023] This invention introduces tetramethylpiperidineamine monomer into sodium lignosulfonate polyoxyethylene ether molecules via the Mannich reaction, synthesizing hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, realizing the polymerization and water-based application of small molecule light stabilizers, and obtaining novel lignin-based water-soluble macromolecular light stabilizers. When used in pesticides, these stabilizers have dual effects of dispersion stabilization and anti-photodegradation enhancement.

[0024] This invention utilizes the electrostatic interaction between the positively charged groups of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and the negatively charged groups of the prepared hindered amine-grafted sodium lignin sulfonate polyoxyethylene ether to prepare a stable cationic and anionic polymeric surfactant. The introduction of a long hydrophilic polyethylene glycol chain increases intermolecular steric hindrance, and the combined effects of steric hindrance and electrostatic interaction prevent flocculation and precipitation. Compared to simple lignin-based anionic surfactants, it exhibits stronger surface activity (surface tension as low as 34.28 mN·m). -1 By determining the critical aggregation concentration, the high-value utilization of lignin sulfonate was achieved, resulting in an agricultural polymer surfactant with strong surface activity, dispersing properties, and resistance to photodegradation.

[0025] The reaction process of this invention is carried out at normal pressure and low temperature, which is easy to operate and control. Since polyoxyethylene ether hydrophilic groups and tetramethylpiperidineamine functional groups are directly introduced into the lignin sulfonate molecule through grafting reaction, there are few side reactions, very little damage to the lignin structure, short reaction time, and the product has good water solubility and is environmentally friendly and non-toxic. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for preparing agricultural polymeric surfactants in this invention;

[0027] Figure 2 This is a bar chart of surface tension in the comprehensive performance test of agricultural polymeric surfactants prepared in Examples 1-5 and Comparative Examples 1-3 of this invention;

[0028] Figure 3 The average particle size histograms of samples 1-8 prepared from Examples 1-5 and Comparative Examples 1-3 of this invention are shown.

[0029] Figure 4 The bar chart shows the suspension rates of samples 1-8 prepared from Examples 1-5 and Comparative Examples 1-3 of this invention.

[0030] Figure 5 This is a bar chart showing the light retention rates of samples 1-8 prepared in Examples 1-5 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0031] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0034] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0035] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 50°C for 3 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0036] The molar ratio of epichlorohydrin to polyethylene glycol is 1.2:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0037] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:1.5. The pH was adjusted to 11 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 80℃ for 2 hours. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0038] The sodium lignosulfonate polyoxyethylene ether solution was extracted five times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed five times with ethanol at 10 times the weight of the extract and dried at 45°C for 20 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0039] Step (2): Prepare hindered amine-grafted sodium lignosulfonate polyoxyethylene ether;

[0040] Sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine (Temp) were mixed, and the pH was adjusted to 12 with 30wt% sodium hydroxide solution. The mixture was stirred at 70℃ for 15 min, and 10wt% formaldehyde aqueous solution was added dropwise over 30 min. After the addition was complete, the mixture was reacted at 85℃ for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Ethanol with a volume of 10 times was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 45℃ for 20 h to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0041] The mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:60:1:2.

[0042] Step (3): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:2:150:100, stir at 500 rpm for 30 min, let stand to precipitate for 24 h, filter, take the precipitate, add 10 times the mass of the precipitate of deionized water to wash 5 times, centrifuge, filter, take the centrifuged precipitate, dry at 45℃ for 20 h to obtain agricultural polymer surfactant.

[0043] Example 2

[0044] This embodiment discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0045] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0046] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 60°C for 1 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0047] The molar ratio of epichlorohydrin to polyethylene glycol is 0.8:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0048] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:0.5. The pH was adjusted to 9 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 60℃ for 4 h. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0049] The sodium lignosulfonate polyoxyethylene ether solution was extracted three times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed three times with ethanol at 8 times the mass of the extract and dried at 35°C for 24 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0050] Step (2): Prepare hindered amine-grafted sodium lignosulfonate polyoxyethylene ether;

[0051] Sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine (Temp) were mixed, and the pH was adjusted to 10 with 30wt% sodium hydroxide solution. The mixture was stirred at 50℃ for 35 min, and 10wt% formaldehyde aqueous solution was added dropwise over 40 min. After the addition was complete, the mixture was reacted at 65℃ for 5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Eight times the volume of ethanol was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 35℃ for 24 h to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0052] The mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:80:4:8.

[0053] Step (3): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:10:630:420, stir at 400 rpm for 40 min, let stand to precipitate for 20 h, filter, take the precipitate, add 8 times the mass of the precipitate of deionized water to wash 3 times, centrifuge, filter, take the centrifuged precipitate, dry at 35℃ for 24 h to obtain agricultural polymer surfactant.

[0054] Example 3

[0055] This embodiment discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0056] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0057] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 52°C for 3 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0058] The molar ratio of epichlorohydrin to polyethylene glycol is 1.1:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0059] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:1.2. The pH was adjusted to 11 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 75℃ for 2 hours. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0060] The sodium lignosulfonate polyoxyethylene ether solution was extracted five times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed five times with ethanol at 10 times the weight of the extract and dried at 42°C for 21 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0061] Step (2): Prepare hindered amine-grafted sodium lignosulfonate polyoxyethylene ether;

[0062] Sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine (Temp) were mixed, and the pH was adjusted to 12 with 30wt% sodium hydroxide solution. The mixture was stirred at 65℃ for 20 min, and 10wt% formaldehyde aqueous solution was added dropwise over 32 min. After the addition was complete, the mixture was reacted at 80℃ for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Ethanol with a volume of 10 times was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 42℃ for 21 h to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0063] The mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:65:2:3.5.

[0064] Step (3): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:2.5:180:120, stir at 475 rpm for 32 min, let stand to precipitate for 23 h, filter, take the precipitate, add 10 times the mass of the precipitate of deionized water to wash 5 times, centrifuge, filter, take the centrifuged precipitate, dry at 42℃ for 21 h to obtain agricultural polymer surfactant.

[0065] Example 4

[0066] This embodiment discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0067] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0068] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 55°C for 2 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0069] The molar ratio of epichlorohydrin to polyethylene glycol is 1:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0070] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:1. The pH was adjusted to 10 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 70℃ for 3 hours. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0071] The sodium lignosulfonate polyoxyethylene ether solution was extracted four times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was washed four times with ethanol at nine times the mass of the extract and dried at 40°C for 22 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0072] Step (2): Prepare hindered amine-grafted sodium lignosulfonate polyoxyethylene ether;

[0073] Sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine (Temp) were mixed, and the pH was adjusted to 11 with 30wt% sodium hydroxide solution. The mixture was stirred at 60℃ for 25 min, and 10wt% formaldehyde aqueous solution was added dropwise over 35 min. After the addition was complete, the mixture was reacted at 75℃ for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Nine times the volume of ethanol was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 40℃ for 22 h to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0074] The mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:70:2.5:5.

[0075] Step (3): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:3:210:140, stir at 450 rpm for 35 min, let stand to precipitate for 22 h, filter, take the precipitate, add 9 times the mass of the precipitate of deionized water to wash 4 times, centrifuge, filter, take the centrifuged precipitate, dry at 40℃ for 22 h to obtain agricultural polymer surfactant.

[0076] Example 5

[0077] This embodiment discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0078] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0079] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 58°C for 1 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0080] The molar ratio of epichlorohydrin to polyethylene glycol is 0.9:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0081] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:0.8. The pH was adjusted to 9 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 65℃ for 4 hours. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0082] The sodium lignosulfonate polyoxyethylene ether solution was extracted three times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed three times with ethanol at 8 times the mass of the extract and dried at 38°C for 23 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0083] Step (2): Prepare hindered amine-grafted sodium lignosulfonate polyoxyethylene ether;

[0084] Sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine (Temp) were mixed, and the pH was adjusted to 10 with 30wt% sodium hydroxide solution. The mixture was stirred at 55℃ for 30 min, and 10wt% formaldehyde aqueous solution was added dropwise over 38 min. After the addition was complete, the mixture was reacted at 70℃ for 5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Eight times the volume of ethanol was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 38℃ for 23 h to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether.

[0085] The mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:75:3:6.5.

[0086] Step (3): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:5:330:220, stir at 425 rpm for 38 min, let stand to precipitate for 21 h, filter, take the precipitate, add 8 times the mass of the precipitate of deionized water to wash 3 times, centrifuge, filter, take the centrifuged precipitate, dry at 38℃ for 23 h to obtain agricultural polymer surfactant.

[0087] Comparative Example 1

[0088] This comparative example discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0089] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0090] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 60°C for 1 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0091] The molar ratio of epichlorohydrin to polyethylene glycol is 0.8:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0092] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:0.5. The pH was adjusted to 9 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 60℃ for 4 h. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0093] The sodium lignosulfonate polyoxyethylene ether solution was extracted three times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed three times with ethanol at 8 times the weight of the extract and dried at 35°C for 24 hours to obtain the anionic polymeric surfactant: sodium lignosulfonate polyoxyethylene ether.

[0094] Comparative Example 2

[0095] This comparative example discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0096] Step (1): Prepare sodium lignosulfonate polyoxyethylene ether;

[0097] Polyethylene glycol was mixed with boron trifluoride ether as a catalyst, and epichlorohydrin was slowly added dropwise at a rate of 1-2 d / s. After the addition was complete, the mixture was reacted at 60°C for 1 h. After the reaction was completed, chlorinated polyethylene glycol intermediate was obtained.

[0098] The molar ratio of epichlorohydrin to polyethylene glycol is 0.8:1, and the amount of boron trifluoride ethyl ether added is 0.1 wt% of the amount of polyethylene glycol added.

[0099] Sodium lignosulfonate was prepared into a 30% aqueous solution. The 30 wt% sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate at a mass ratio of 3:0.5. The pH was adjusted to 9 with 30 wt% sodium hydroxide aqueous solution. The reaction was carried out at 60℃ for 4 h. After the reaction was completed, 0.1 mol / L hydrogen chloride aqueous solution was added to adjust the pH to neutral to obtain sodium lignosulfonate polyoxyethylene ether solution.

[0100] The sodium lignosulfonate polyoxyethylene ether solution was extracted three times with methyl ethyl ketone to remove water and unreacted polyethylene glycol. After filtration, the extract was obtained. The extract was washed three times with ethanol at 8 times the mass of the extract and dried at 35°C for 24 hours to obtain purified sodium lignosulfonate polyoxyethylene ether.

[0101] Step (2): Mix hexadecyltrimethylammonium bromide (CTAB), sodium lignosulfonate polyoxyethylene ether, ethanol, and water in a mass ratio of 50:10:630:420, stir at 400 rpm for 40 min, let stand to precipitate for 20 h, filter, take the precipitate, add 8 times the mass of the precipitate of deionized water to wash 3 times, centrifuge, filter, take the centrifuged precipitate, dry at 35℃ for 24 h to obtain agricultural polymer surfactant.

[0102] Comparative Example 3

[0103] This comparative example discloses an agricultural polymeric surfactant and its preparation method, including the following steps:

[0104] Step (1): Prepare hindered amine-grafted sodium lignosulfonate;

[0105] Sodium lignosulfonate, water, and 2,2,6,6-tetramethylpiperidinamine (Temp) were mixed, and the pH was adjusted to 10 with 30wt% sodium hydroxide solution. The mixture was stirred at 50℃ for 35 min, and 10wt% formaldehyde aqueous solution was added dropwise over 40 min. After the addition was complete, the mixture was reacted at 65℃ for 5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product. Eight times the volume of ethanol was added to the reaction product to precipitate the product. The mixture was filtered, and the precipitate was dried at 35℃ for 24 h to obtain hindered amine-grafted sodium lignosulfonate.

[0106] The mass ratio of sodium lignosulfonate, water, 2,2,6,6-tetramethylpiperidineamine, and 10wt% formaldehyde aqueous solution is 10:80:4:8.

[0107] Step (2): Mix hexadecyltrimethylammonium bromide (CTAB), hindered amine-grafted sodium lignin sulfonate, ethanol, and water in a mass ratio of 50:10:630:420, stir at 400 rpm for 40 min, let stand to precipitate for 20 h, filter, take the precipitate, add 8 times the mass of the precipitate of deionized water to wash 3 times, centrifuge, filter, take the centrifuged precipitate, dry at 35℃ for 24 h to obtain agricultural polymer surfactant.

[0108] In the above examples and comparative examples: polyethylene glycol was from Guangdong Guanghua Science & Technology Co., Ltd., Mw=600, CAS No.: 25322-68-3; boron trifluoride ether was from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 109-63-7; epichlorohydrin was from Shanghai Denuo Chemical Co., Ltd., CAS No.: 106-89-8; sodium lignosulfonate was provided by Jilin Shixian Paper Co., Ltd., derived from poplar acidic sodium sulfite pulping waste liquor, CAS No.: 8061-51-6; sodium hydroxide was from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 14014-06-3; The methyl ethyl ketone (MEK) was from Nanjing Shengqinghe Chemical Co., Ltd., CAS No.: 78-93-3; N,N-dimethylformamide was from Guangdong Guanghua Technology Co., Ltd., CAS No.: 68-12-2; 2,2,6,6-tetramethylpiperidinamine was from Shanghai Aladdin Chemical Reagent Co., Ltd., CAS No.: 36768-62-4; formaldehyde was from Guangzhou Chemical Reagent Factory, CAS No.: 50-00-0; ethanol was from Guangdong Guanghua Technology Co., Ltd., CAS No.: 64-17-5; and cetyltrimethylammonium bromide (CTAB) was from Guangzhou Chemical Reagent Factory, CAS No.: 57-09-0.

[0109] 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, the scope of which is defined by the appended claims and their equivalents.

[0110] Test case

[0111] The surface activity properties of the agricultural polymeric surfactants prepared in Examples 1-5 and Comparative Examples 1-3 were tested. Dimethomorph aqueous suspensions were prepared using Examples 1-5 and Comparative Examples 1-3 as dispersants, designated as samples 1-8. The preparation method included: mixing 40 wt% of the technical grade (dimethomorph) and 4 wt% of the dispersant, filling the remaining volume with water to 100%, and ball milling for 3 hours using a QM-3SP2 planetary ball mill manufactured by Nanjing University Instrument Factory to obtain the dimethomorph aqueous suspension. Specific test results are shown in Table 1.

[0112] Table 1

[0113]

[0114] Table 1 shows the detection methods for each indicator as follows: Surface tension was measured using a DCAT21 surface / interfacial tension meter from Dataphysics, Germany; average particle size was measured using an MS2000 laser particle size analyzer from Malvern, UK, with the average value taken after three measurements, and the heat storage conditions were: placed in a 54℃ oven for 14 days; suspension rate was determined using the test method of GB / T14825-2006, with the heat storage conditions being: placed in a 54℃ oven for 14 days; the light retention rate was tested by irradiating samples 1-8 under a 30W, 310nm UV lamp for 60 hours, then dissolving the UV-irradiated samples 1-8 in 5mL of methanol by ultrasonication, and then detecting the content of the original drug by HPLC, with each sample measured in triplicate and the average value taken.

[0115] As can be seen from the test results in Table 1, the agricultural polymer surfactant prepared by this invention has strong surface activity, dispersibility, and resistance to photolysis.

[0116] In Comparative Example 1, polyethylene glycol was grafted only onto sodium lignosulfonate. The grafting of long polyethylene glycol chains resulted in a more extended and loosely arranged molecule, leading to a more dispersed arrangement of sodium lignosulfonate polyoxyethylene ether molecules at the gas / liquid interface. Simultaneously, the hydrophobic core of sodium lignosulfonate itself also became more porous. Furthermore, due to the stronger hydrophilicity of sodium lignosulfonate polyoxyethylene ether compared to sodium lignosulfonate, its tendency to desorb and dissolve in water increased. These factors resulted in a lower coverage rate at the gas / liquid interface for the sample of Comparative Example 1, leading to poorer surface activity and dispersion performance compared to the examples. Additionally, the lack of hindered amine grafting reduced the photostability of lignin, resulting in a lower light retention rate for sample 6 prepared from Comparative Example 1 compared to samples 1-5.

[0117] In Comparative Example 2, the lack of grafted hindered amine reduced the photostability of lignin, making it unable to inhibit the photo-oxidative decomposition of dimethomorph while acting as a dispersant. Therefore, the light retention rate of sample 7 prepared from Comparative Example 2 was lower than that of samples 1-5.

[0118] In Comparative Example 3, the lack of grafted polyethylene glycol resulted in a lower relative molecular mass and weaker hydrophilicity of the lignin-based polymeric surfactant. Furthermore, the high charge density of lignin sulfonate made it prone to flocculation and precipitation when compounded with cationic surfactants, leading to poor compounding effect. These factors resulted in a lower surface tension in Comparative Example 3 compared to the Examples, causing the average particle size of Sample 8 obtained from Comparative Example 3 to be larger than that of Samples 1-5, while the suspension rate and light retention rate were lower than those of Samples 1-5.

[0119] 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, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an agricultural polymeric surfactant, characterized by, Includes the following steps: Step (1): Mix polyethylene glycol, boron trifluoride ethyl ether and epichlorohydrin, and react them. After the reaction is complete, chlorinated polyethylene glycol intermediate is obtained. The epichlorohydrin was added slowly, with a titration rate of 1-2 drops / s; the molar ratio of epichlorohydrin to polyethylene glycol was (0.8-1.2):1; the amount of boron trifluoride ether added was 0.1 wt% of the amount of polyethylene glycol added; the reaction conditions were: reaction at 50-60℃ for 1-3 hours. Sodium lignosulfonate aqueous solution was mixed with chlorinated polyethylene glycol intermediate, the pH was adjusted, and the reaction was carried out. After the reaction was completed, the mixture was purified to obtain sodium lignosulfonate polyoxyethylene ether. The sodium lignosulfonate aqueous solution has a mass fraction of 30%; the mass ratio of 30wt% sodium lignosulfonate aqueous solution to chlorinated polyethylene glycol intermediate is 3:(0.5-1.5); the pH is adjusted by adding 30wt% sodium hydroxide aqueous solution to adjust the pH to 9-11; the reaction conditions are: reacting at pH=9-11 and 60-80℃ for 2-4 hours. Step (2): Mix sodium lignosulfonate polyoxyethylene ether, water, and 2,2,6,6-tetramethylpiperidineamine, adjust the pH, add formaldehyde aqueous solution and react. After the reaction is completed, cool and purify to obtain hindered amine-grafted sodium lignosulfonate polyoxyethylene ether. The pH was adjusted by adding 30 wt% sodium hydroxide aqueous solution to adjust the pH to 10-12; the formaldehyde aqueous solution added was 10 wt% formaldehyde aqueous solution, and the addition time was 30-40 min; the mass ratio of sodium lignosulfonate polyoxyethylene ether, water, 2,2,6,6-tetramethylpiperidineamine, and 10 wt% formaldehyde aqueous solution was 10:(60-80):(1-4):(2-8); the reaction conditions were: reaction at pH=10-12 and 65-85℃ for 3-5 h. Step (3): Mix hexadecyltrimethylammonium bromide, hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water, stir, let stand to precipitate, purify, and obtain agricultural polymer surfactant. The mass ratio of hexadecyltrimethylammonium bromide, hindered amine-grafted sodium lignosulfonate polyoxyethylene ether, ethanol, and water is 50:(2-10):(150-630):(100-420); the stirring conditions are: stirring at 400-500 rpm for 30-40 min; and the sedimentation time is 20-24 h.

2. The method for preparing an agricultural polymeric surfactant according to claim 1, characterized in that, In step (1), when preparing sodium lignosulfonate polyoxyethylene ether, the purification steps are as follows: extract the sodium lignosulfonate polyoxyethylene ether solution with butanone 3-5 times to remove water and unreacted polyethylene glycol, filter to obtain the extraction product, add 8-10 times the mass of the extraction product of ethanol to wash 3-5 times, and dry at 35-45℃ for 20-24h to obtain purified sodium lignosulfonate polyoxyethylene ether.

3. The method for preparing an agricultural polymeric surfactant according to claim 1, characterized in that, In step (2), the purification step is as follows: add 8-10 times the volume of ethanol to the reaction product to precipitate, filter, take the precipitate, and dry it at 35-45℃ for 20-24h.

4. The method for preparing an agricultural polymeric surfactant according to claim 1, characterized in that, In step (3), the purification step is as follows: take the precipitate, add 8-10 times the mass of the precipitate of deionized water to wash 3-5 times, centrifuge, filter, take the centrifuged precipitate, and dry it at 35-45℃ for 20-24h.

5. An agricultural polymeric surfactant prepared by the method described in any one of claims 1-4.

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