Preparation method of carboxylate dispersant and application of carboxylate dispersant in suspending agent

Abstract

The invention relates to a preparation method of a carboxylate dispersant and an application of the carboxylate dispersant in a suspending agent, and belongs to the technical field of dispersants.The carboxylate polymer containing carboxyl, polyethylene glycol and slow-release chelating agent nanoparticles are polymerized together to form a comb-shaped structure; the sulfonic acid group on the carboxylate dispersant is ionized into-SO3-, the surfaces of pesticide particles are negatively charged, the electrostatic repulsion in the system is enhanced, the collision among the softened pesticide particles can be weakened, the sedimentation trend of the pesticide nanoparticles is weakened to a certain extent, and the stability of the suspension system is improved. Meanwhile, sodium ethylene diamine tetracetate in the slow-release chelating agent nano-microspheres can be slowly released, the sodium ethylene diamine tetracetate is preferentially chelated with calcium ions and magnesium ions in water, the calcium ions and the magnesium ions are prevented from being combined with sulfonic acid and carboxylic acid groups on the carboxylate dispersing agent, and the comb-shaped structure of the carboxylate dispersing agent has strong steric hindrance, so that the carboxylate dispersing agent can be used for dispersing calcium ions and magnesium ions in water. The effect of physically blocking calcium and magnesium ions can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of dispersants and relates to a preparation method of a carboxylate dispersant and application of the same in a suspending agent. Background Art

[0002] Dispersants, an important class of surfactants, play a crucial role in stabilizing multiphase dispersion systems (such as pigments, dyes, coal-water slurries, and pesticide suspension concentrates). Their core function is to prevent the agglomeration and sedimentation of solid particles, ensuring the uniformity and long-term stability of the system. Traditional small-molecule dispersants (such as lignin sulfonates and naphthalenesulfonate formaldehyde condensates) and some early polymer dispersants, while widely used, have significant drawbacks: their adsorption on particle surfaces is often weak and reversible, and they are prone to desorption, causing the dispersed particles to reaggregate or precipitate due to van der Waals forces. Their stability decreases dramatically, especially under conditions of high ionic strength, extreme pH values, or temperature fluctuations.

[0003] The Chinese invention patent application with publication number CN115403692B discloses a powdered polycarboxylate polymer dispersant, its preparation method, and application. By selecting a specific polymerization monomer compound and compounding it with an organic acid ester, the dispersant's dispersing properties are effectively improved, and it has excellent disintegration, thermal stability, and granulation effects. When styrene or methyl methacrylate and methacrylic acid are used as polymerization monomers in this application, when the mass ratio of the two is 7-9:18-20 and the mass ratio with n-butyl acrylate is 270:6, the lipophilic long molecular chains carried by the corresponding monomers and the specific hydrophilic carboxylate molecules are polymerized, forming a long main carbon chain while effectively increasing the length of the hydrophilic and lipophilic segments and the number of active groups, so that the polymer itself can have excellent carbon chain entanglement and effectively improve the dispersant's water infiltration speed when used in water.

[0004] When the powdered polycarboxylate polymer dispersant in the above scheme is used in hard water, the carboxylate ions in the dispersant easily combine with calcium, magnesium and other ions to form an insoluble metal soap precipitate. The precipitate acts as a "calcium bridge" to strongly cross-link the pesticide particles, resulting in the formation of a rigid agglomeration network between the particles and flocculation and precipitation, which reduces the suspension rate. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a carboxylate dispersant and its application in a suspending agent, by polymerizing slow-release chelating agent nanoparticles, polyethylene glycol and a polymer together to achieve the beneficial effects of stable dispersion in hard water and heat storage.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a carboxylate dispersant comprises the following steps:

[0008] Step 1: Sulfonic acid groups are introduced into alkali lignin by sodium sulfite and formaldehyde to obtain sulfomethylated alkali lignin.

[0009] Step 2: Using sodium ethylenediaminetetraacetic acid as the core material and sulfomethylated alkali lignin as the shell material to obtain slow-release chelating agent nanoparticles.

[0010] Step 3: using maleic anhydride, acrylic acid and sodium styrene sulfonate as monomers to obtain a carboxylate polymer; polymerizing the carboxylate polymer, polyethylene glycol and sustained-release chelating agent nanospheres to obtain a carboxylate dispersant.

[0011] Furthermore, the preparation process of sulfomethylated alkali lignin is as follows:

[0012] Alkali lignin and deionized water are added to a reactor, the pH value is adjusted to 12 with sodium hydroxide solution, sodium sulfite is added at 90-100°C and 500-700 r / min, and then a 10wt% formaldehyde aqueous solution is added dropwise. The mixture is stirred for 4-5 hours and cooled to room temperature to obtain sulfomethylated alkali lignin.

[0013] Furthermore, the usage ratio of alkali lignin, deionized water, sodium sulfite and formaldehyde aqueous solution is 250-300 g: 1-1.5 L: 200-250 g: 500-600 g.

[0014] Furthermore, the preparation process of the sustained-release chelating agent nanoparticles is as follows:

[0015] Hexadecyltrimethylammonium bromide and a 60 vol% ethanol aqueous solution are added to a reactor, sulfomethylated alkali lignin with a concentration of 60 wt% is added to the reactor at 20-25° C. and 700-800 r / min, and sodium ethylenediaminetetraacetate and a 30 vol% tetrahydrofuran aqueous solution are dripped into the reactor within 30 minutes. The reaction mixture is allowed to stand for 24-26 hours, filtered, washed, and dried to obtain slow-release chelating agent nanospheres.

[0016] Furthermore, the usage ratio of hexadecyltrimethylammonium bromide, ethanol aqueous solution, sulfomethylated alkali lignin, sodium ethylenediaminetetraacetate and tetrahydrofuran aqueous solution is 50-60 g: 50-60 mL: 280-300 g: 100-120 g: 700-800 mL.

[0017] Furthermore, the preparation process of the carboxylate polymer is as follows:

[0018] Maleic anhydride and diisopropyl dimethyl ether are added to a reaction kettle, acrylic acid, sodium styrene sulfonate, benzoyl peroxide and diisophenol dimethyl ether are mixed evenly and then added dropwise to the reaction kettle. The mixture is reacted at 80-90°C and 500-700 r / min for 3-4 hours, filtered, washed and dried to obtain a carboxylate polymer.

[0019] Furthermore, the usage ratio of maleic anhydride, diisopropyl dimethyl ether, acrylic acid, sodium styrene sulfonate, benzoyl peroxide and diisophenol dimethyl ether is 98-110 g: 500-600 mL: 72-80 g: 104-110 g: 8-12 g: 500-600 mL.

[0020] Furthermore, the preparation process of the carboxylate dispersant is as follows:

[0021] Carboxylate polymer, polyethylene glycol, slow-release chelating agent nanospheres and acetone are added into a reaction kettle, and then p-toluenesulfonic acid is added as a catalyst. The reaction is carried out at 65-70° C. and 500-700 r / min for 12-14 hours, and rotary evaporation is performed to obtain a carboxylate dispersant.

[0022] Furthermore, the usage ratio of the carboxylate polymer, polyethylene glycol, slow-release chelating agent nanospheres, acetone and p-toluenesulfonic acid is 200-260 g: 200-300 g: 100-120 g: 800-900 mL: 8-15 g.

[0023] The present invention also provides an application of a carboxylate dispersant in a suspending agent.

[0024] Beneficial effects of the present invention:

[0025] 1. The carboxylate dispersant of the present invention is a carboxylate polymer containing carboxyl groups, polyethylene glycol, and slow-release chelating agent nanospheres polymerized together to form a comb-like structure. When used in hard water, the sulfonic acid groups on the carboxylate dispersant will ionize to -SO3 - The surface of the pesticide particles is negatively charged, and the electrostatic repulsion in the system is enhanced, which can weaken the collision between the softened pesticide particles themselves, weaken the sedimentation tendency of the pesticide nanoparticles to a certain extent, and increase the stability of the suspension system. At the same time, the slow-release chelating agent nanospheres will slowly release the internal sodium ethylenediaminetetraacetic acid, and preferentially chelate with the calcium ions and magnesium ions in the water to avoid the combination of calcium and magnesium ions with the sulfonic acid and carboxylic acid groups on the carboxylate dispersants. The comb-like structure of the carboxylate dispersant has a strong steric hindrance, which can physically hinder the calcium and magnesium ions, further inhibit their binding rate with carboxylate ions, and improve the dispersibility of pesticide particles when used in hard water.

[0026] 2. In the present invention, sulfonic acid groups are first introduced into alkali lignin, and then sodium ethylenediaminetetraacetic acid is used as the core material to form microspheres in the form of self-assembly, which are then polymerized with carboxylate polymers. The sulfonic acid groups on the surface of the microspheres and the sulfonic acid groups in the carboxylate polymers jointly increase the charge density of the dispersant and enhance the electrostatic repulsion. In addition, the three-dimensional rigid network of the microsphere structure slows down the dissolution rate of the internal core material, improves the storage stability, and can also inhibit the thermal motion of the chain segments. It synergistically increases the steric hindrance with the comb-like branched structure, thereby improving the dispersibility of the pesticide particles while inhibiting Ostwald ripening and extending the shelf life.

[0027] 3. The maleic anhydride in the polymer of the present invention is hydrolyzed to generate carboxyl groups, which are partially ionized into carboxylate ions in hard water and form a hydrogen bond network with the phenolic hydroxyl groups of the sustained-release chelating agent nanospheres. Polyethylene glycol is grafted onto the carboxylate polymer backbone through ester bonds, making the side chains hydrophilic. The hydrophilic ends extend into the water, thereby enhancing the water solubility of the dispersant. When it encounters water, it can quickly absorb water and swell, making the disintegration of the pesticide particles faster. In addition, the short-chain polyethylene glycol reduces the surface tension of water, promotes the spreading of the pesticide solution on the leaf surface, and improves the bioavailability of the pesticide suspension. DETAILED DESCRIPTION

[0028] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, features and effects of the present invention are described in detail below in combination with preferred embodiments.

[0029] Example 1: This example provides a method for preparing a carboxylate dispersant, comprising the following steps:

[0030] S1: Add 275g of alkali lignin and 1.25L of deionized water into a reactor, adjust the pH value to 12 with sodium hydroxide solution, add 225g of sodium sulfite at 95°C and 600r / min, and then dropwise add 550g of 10wt% formaldehyde aqueous solution. Stir and react for 3.5h. Introduce a sulfonic acid group at the ortho position of the phenolic hydroxyl group of the alkali lignin, and cool to room temperature to obtain sulfomethylated alkali lignin.

[0031] S2: 55g of hexadecyltrimethylammonium bromide and 55mL of 60vol% ethanol aqueous solution were added to the reactor, 290g of 60wt% sulfomethylated alkali lignin was added to the reactor at 22°C and 750r / min, and 110g of sodium ethylenediaminetetraacetic acid and 750mL of 30vol% tetrahydrofuran aqueous solution were dropwise added to the reactor within 30min. The reaction was allowed to stand for 25h. With hexadecyltrimethylammonium bromide as a template, the sulfomethylated alkali lignin molecules self-assembled into microspheres through hydrogen bonding and coated the sodium ethylenediaminetetraacetic acid inside. The mixture was centrifuged and filtered. The precipitate was washed 4 times with deionized water and freeze-dried at -45°C for 7h to obtain sustained-release chelating agent nanospheres with a particle size of 380-410nm.

[0032] S3: 104 g of maleic anhydride and 550 mL of diisopropyl dimethyl ether were added to a reactor, 76 g of acrylic acid, 107 g of sodium styrene sulfonate, 10 g of benzoyl peroxide and 550 mL of diisopropyl dimethyl ether were mixed evenly and then dropped into the reactor. The mixture was reacted at 85°C and 600 r / min for 3.5 h. During the reaction, the carbon-carbon double bonds of acrylic acid, sodium styrene sulfonate and maleic anhydride were opened and polymerized. The mixture was filtered, and the precipitate was washed four times with toluene and dried in vacuo at 42°C for 4.5 h to obtain a carboxylate polymer.

[0033] S4: 230 g of carboxylate polymer, 250 g of polyethylene glycol (molecular weight 500), 110 g of slow-release chelating agent nanospheres and 850 mL of acetone were added to a reactor, and then 11.5 g of p-toluenesulfonic acid as a catalyst was added. The reaction was carried out at 67°C and 600 r / min for 13 h. The carboxylate polymer, polyethylene glycol and slow-release chelating agent nanospheres underwent esterification reaction to form a comb-like product, which was rotary evaporated to obtain a carboxylate dispersant.

[0034] Example 2: This example provides a method for preparing a carboxylate dispersant, comprising the following steps:

[0035] S1: Add 250g of alkali lignin and 1L of deionized water into a reactor, adjust the pH value to 12 with sodium hydroxide solution, add 200g of sodium sulfite at 90℃ and 500r / min, and then drop 500g of 10wt% formaldehyde aqueous solution. Stir and react for 3h. Introduce sulfonic acid group at the ortho position of phenolic hydroxyl group of alkali lignin, and cool to room temperature to obtain sulfomethylated alkali lignin.

[0036] S2: 50g of hexadecyltrimethylammonium bromide and 50mL of 60vol% ethanol aqueous solution were added to the reactor, 280g of 60wt% sulfomethylated alkali lignin was added to the reactor at 20°C and 700r / min, and 100g of sodium ethylenediaminetetraacetic acid and 700mL of 30vol% tetrahydrofuran aqueous solution were dropwise added to the reactor within 30min. The mixture was allowed to stand for 24h. With hexadecyltrimethylammonium bromide as a template, the sulfomethylated alkali lignin molecules self-assembled into microspheres through hydrogen bonding and coated with sodium ethylenediaminetetraacetic acid inside. The mixture was centrifuged and filtered. The precipitate was washed 3 times with deionized water and freeze-dried at -40°C for 6h to obtain sustained-release chelating agent nanospheres with a particle size of 380-410nm.

[0037] S3: Add 98g of maleic anhydride and 500mL of diisopropyl dimethyl ether into a reactor, mix 72g of acrylic acid, 104g of sodium styrene sulfonate, 8g of benzoyl peroxide and 500mL of diisopropyl dimethyl ether evenly, and then drop them into the reactor. React at 80°C and 500r / min for 3h. During the reaction, the carbon-carbon double bonds of acrylic acid, sodium styrene sulfonate and maleic anhydride open and polymerize. Filter, wash the precipitate with toluene three times, and vacuum dry at 40°C for 4h to obtain a carboxylate polymer.

[0038] S4: Add 200g of carboxylate polymer, 200g of polyethylene glycol (molecular weight 200), 100g of slow-release chelating agent nanospheres and 800mL of acetone into a reactor, then add 8g of p-toluenesulfonic acid as a catalyst, and react at 65°C and 500r / min for 12h. The carboxylate polymer undergoes esterification reaction with polyethylene glycol and slow-release chelating agent nanospheres to form a comb-like product, which is then rotary evaporated to obtain a carboxylate dispersant.

[0039] Example 3: This example provides a method for preparing a carboxylate dispersant, comprising the following steps:

[0040] S1: 300 g of alkali lignin and 1.5 L of deionized water were added to a reactor, the pH value was adjusted to 12 with sodium hydroxide solution, 250 g of sodium sulfite was added at 100 ° C and 700 r / min, and then 600 g of 10 wt% formaldehyde aqueous solution was dropwise added. The reaction was stirred for 4 h, and a sulfonic acid group was introduced at the ortho position of the phenolic hydroxyl group of the alkali lignin. The mixture was cooled to room temperature to obtain sulfomethylated alkali lignin.

[0041] S2: 60g of hexadecyltrimethylammonium bromide and 60mL of 60vol% ethanol aqueous solution were added to the reactor, 300g of 60wt% sulfomethylated alkali lignin was added to the reactor at 25°C and 800r / min, and 120g of sodium ethylenediaminetetraacetic acid and 800mL of 30vol% tetrahydrofuran aqueous solution were dropwise added to the reactor within 30min. The reaction was allowed to stand for 26h. With hexadecyltrimethylammonium bromide as a template, the sulfomethylated alkali lignin molecules self-assembled into microspheres through hydrogen bonding and coated the sodium ethylenediaminetetraacetic acid inside. The mixture was centrifuged and filtered. The precipitate was washed with deionized water 5 times and freeze-dried at -50°C for 8h to obtain sustained-release chelating agent nanospheres with a particle size of 380-410nm.

[0042] S3: 110 g of maleic anhydride and 600 mL of diisopropyl dimethyl ether were added to a reactor, 80 g of acrylic acid, 110 g of sodium styrene sulfonate, 12 g of benzoyl peroxide and 600 mL of diisopropyl dimethyl ether were mixed evenly and then dropped into the reactor. The mixture was incubated at 90°C and 700 r / min for 4 hours. During the reaction, the carbon-carbon double bonds of acrylic acid, sodium styrene sulfonate and maleic anhydride were opened and polymerized. The mixture was filtered, and the precipitate was washed 5 times with toluene and dried in vacuo at 45°C for 5 hours to obtain a carboxylate polymer.

[0043] S4: Add 260g of carboxylate polymer, 300g of polyethylene glycol (molecular weight 800), 120g of slow-release chelating agent nanospheres and 900mL of acetone into a reactor, and then add 15g of p-toluenesulfonic acid as a catalyst. React at 70°C and 700r / min for 14h. The carboxylate polymer undergoes esterification reaction with polyethylene glycol and slow-release chelating agent nanospheres to form a comb-like product, which is then rotary evaporated to obtain a carboxylate dispersant.

[0044] Comparative Example 1: Based on Example 1, the slow-release chelating agent nanospheres were removed from step S4, and the remaining steps remained unchanged to prepare a carboxylate dispersant.

[0045] Comparative Example 2: Based on Example 1, styrene was used instead of sodium styrene sulfonate in step S3, and the other steps remained unchanged to prepare a carboxylate dispersant.

[0046] Comparative Example 3: Based on Example 1, sodium edetate was removed from step S2 to prepare lignin nanospheres, which were used to replace the slow-release chelating agent nanospheres in step S4. The remaining steps remained unchanged to prepare a carboxylate dispersant.

[0047] Performance test: The carboxylate dispersants prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to performance tests:

[0048] According to the World Health Organization (WHO) definition of hard water, which is mainly based on the content of calcium ions (Ca+) and magnesium ions (Mg+) in water, experimental hard water is prepared by adding calcium carbonate and magnesium sulfate into the water to prepare standard hard water with a calcium and magnesium ion concentration of 120-180 mg / L.

[0049] Preparation of suspension concentrate: 25 g of pyraclostrobin, 12 g of carboxylate dispersant, 1 g of citric acid and 62 mL of standard hard water were mixed evenly to prepare a suspension with an effective pesticide content of 25 wt.%, a material-bead ratio of 1:3, and a grinding time of 23 h to prepare chlorantraniliprole Nano-SC suspension concentrate.

[0050] Determination of suspension rate: According to the suspension rate determination method for pesticide suspension concentrates in Method 2 of the national standard GB / T 14825-2006, 5g of chlorfenapyr Nano-SC was weighed and placed in a 250mL graduated cylinder containing 100mL of 30±2℃ standard hard water. The cylinder was diluted to the scale with 30℃ standard hard water. The stopper was installed and the cylinder was inverted upside down at a frequency of 2s / time for 1min. The stopper was opened and the cylinder was placed in a constant temperature water bath at 30℃ for 30min. After that, the upper 9 / 10 (225mL) of the suspension in the graduated cylinder was quickly extracted with a vacuum pump. The mass of the active ingredient in the 25mL of suspension concentrate remaining in the bottom of the graduated cylinder was determined by high performance liquid chromatography. The suspension rate W (%) of the active ingredient in the sample is calculated according to the following formula: W (%) = (m1-m2) / m1×10 / 9×100%, where: m1 is the mass of the active ingredient in the Nano-SC taken, g; m2 is the mass of the active ingredient in the 25 mL suspension remaining at the bottom of the measuring cylinder, g; 10 / 9 is the conversion factor.

[0051] Thermal storage stability test: According to the national standard GB / T 19136-2021 for the determination of thermal storage stability of pesticide formulations, the prepared chlorantraniliprole Nano-SC was sealed and placed in a constant temperature drying oven (54±1°C) for 7 days and 14 days respectively. Then, 0.1g of the suspension was added dropwise to the sample tank of the particle size analyzer. The test was carried out in pure water medium. The water circulation and ultrasonic control switches were turned on. After the particle size data stabilized, the D value was recorded. 90 Particle size was measured three times in parallel and the average value was obtained. The test instruments used were: UNE400 electric constant temperature blast drying oven from Memmert GmbH, Germany; and BetterSize 2600 laser particle size analyzer from Better Instrument Co., Ltd., Dandong, Liaoning Province. The test results are as follows:

[0052] Table 1 Performance test list

[0053]

[0054] As shown in Table 1, the suspension rates in Examples 1 to 3 are greater than those in Comparative Examples 1 to 3. In step S4 of Comparative Example 1, the slow-release chelating agent nanospheres are removed. In step S3 of Comparative Example 2, styrene sulfonate is replaced with propylene glycol. In step S2 of Comparative Example 3, sodium ethylenediaminetetraacetate is removed to prepare lignin nanospheres, which are substituted for the slow-release chelating agent nanospheres in step S4. This may be because the sulfonic acid groups on the carboxylate dispersant are ionized to -SO3. - The surface of pesticide particles carries a negative charge, and the electrostatic repulsion in the system is enhanced, which can weaken the collision between the softened pesticide particles themselves, weaken the sedimentation tendency of pesticide nanoparticles to a certain extent, and increase the stability of the suspension system. Ethylenediaminetetraacetic acid preferentially chelates with calcium ions and magnesium ions in water to prevent calcium and magnesium ions from combining with sulfonic acid and carboxylic acid groups on carboxylate dispersants. The two synergistically improve the suspension rate and improve the dispersibility of pesticide particles when used in hard water.

[0055] Thermal storage 0 day D in Example 1-Example 3 90 Particle size, hot storage for 7 days D 90 Particle size, hot storage for 14 days D 90 The particle sizes are all smaller than those of Comparative Examples 1 to 3, and the increase is also smaller. In step S4 of Comparative Example 1, the slow-release chelating agent nanospheres are removed, and in step S3 of Comparative Example 2, styrene propylene is used instead of sodium styrene sulfonate. In step S2 of Comparative Example 3, sodium ethylenediaminetetraacetate is removed to prepare lignin nanospheres, which are used to replace the slow-release chelating agent nanospheres in step S4. This may be because the three-dimensional rigid network of the microsphere structure can inhibit the thermal motion of the chain segments, and synergistically increase the steric hindrance with the comb-like branched structure, thereby improving the dispersibility and prolonging the heat storage time.

[0056] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a carboxylate dispersant, characterized in that: The steps include: Step 1: introducing sulfonic acid groups into alkali lignin by sodium sulfite and formaldehyde to obtain sulfomethylated alkali lignin; Step 2: using sodium EDTA as the core material and sulfomethylated alkali lignin as the shell material to obtain slow-release chelating agent nanoparticles; Step 3: using maleic anhydride, acrylic acid and sodium styrene sulfonate as monomers to obtain a carboxylate polymer; polymerizing the carboxylate polymer, polyethylene glycol and sustained-release chelating agent nanospheres to obtain a carboxylate dispersant.

2. The method for preparing a carboxylate dispersant according to claim 1, wherein The preparation process of the sulfomethylated alkali lignin in step 1 is as follows: Alkali lignin and deionized water are added to a reactor, the pH value is adjusted to 12 with sodium hydroxide solution, sodium sulfite is added at 90-100°C and 500-700 r / min, and then a 10wt% formaldehyde aqueous solution is added dropwise. The mixture is stirred for 4-5 hours and cooled to room temperature to obtain sulfomethylated alkali lignin.

3. The method for preparing a carboxylate dispersant according to claim 2, wherein The usage ratio of the alkali lignin, deionized water, sodium sulfite and formaldehyde aqueous solution is 250-300 g: 1-1.5 L: 200-250 g: 500-600 g.

4. The method for preparing a carboxylate dispersant according to claim 1, wherein The preparation process of the sustained-release chelating agent nanoparticles in step 2 is as follows: Hexadecyltrimethylammonium bromide and a 60 vol% ethanol aqueous solution are added to a reactor, sulfomethylated alkali lignin with a concentration of 60 wt% is added to the reactor at 20-25° C. and 700-800 r / min, and sodium ethylenediaminetetraacetate and a 30 vol% tetrahydrofuran aqueous solution are dripped into the reactor within 30 minutes. The reaction mixture is allowed to stand for 24-26 hours, filtered, washed, and dried to obtain slow-release chelating agent nanospheres.

5. The method for preparing a carboxylate dispersant according to claim 4, wherein: The usage ratio of the hexadecyltrimethylammonium bromide, the ethanol aqueous solution, the sulfomethylated alkali lignin, the sodium ethylenediaminetetraacetic acid and the tetrahydrofuran aqueous solution is 50-60 g: 50-60 mL: 280-300 g: 100-120 g: 700-800 mL.

6. The method for preparing a carboxylate dispersant according to claim 1, wherein The preparation process of the carboxylate polymer in step 3 is as follows: Maleic anhydride and diisopropyl dimethyl ether are added to a reaction kettle, acrylic acid, sodium styrene sulfonate, benzoyl peroxide and diisophenol dimethyl ether are mixed evenly and then added dropwise to the reaction kettle. The mixture is reacted at 80-90°C and 500-700 r / min for 3-4 hours, filtered, washed and dried to obtain a carboxylate polymer.

7. The method for preparing a carboxylate dispersant according to claim 6, wherein: The usage ratio of maleic anhydride, diisopropyl dimethyl ether, acrylic acid, sodium styrene sulfonate, benzoyl peroxide and diisophenol dimethyl ether is 98-110 g: 500-600 mL: 72-80 g: 104-110 g: 8-12 g: 500-600 mL.

8. The method for preparing a carboxylate dispersant according to claim 1, wherein The preparation process of the carboxylate dispersant in step 3 is as follows: Carboxylate polymer, polyethylene glycol, slow-release chelating agent nanospheres and acetone are added into a reaction kettle, and then p-toluenesulfonic acid is added as a catalyst. The reaction is carried out at 65-70° C. and 500-700 r / min for 12-14 hours, and rotary evaporation is performed to obtain a carboxylate dispersant.

9. The method for preparing a carboxylate dispersant according to claim 8, wherein: The usage ratio of the carboxylate polymer, polyethylene glycol, slow-release chelating agent nano-microspheres, acetone and p-toluenesulfonic acid is 200-260 g: 200-300 g: 100-120 g: 800-900 mL: 8-15 g.

10. Use of a carboxylate dispersant obtained by the preparation method of a carboxylate dispersant according to any one of claims 1 to 9 in a suspending agent.

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