A multi-block polycarboxylic acid dispersant, its preparation method and application

Abstract

This invention belongs to the field of polymer synthesis and coal-water slurry technology, and relates to a multi-component block polycarboxylic acid dispersant and its preparation method. The raw materials include monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent. Under the action of the chain transfer agent, carbon-sulfur bonds break, and monomer I reversibly adds to the broken carbon-sulfur bonds to obtain product I. The carbon-carbon bonds of monomer II containing carboxyl groups break and reversibly add to the carbon-sulfur bonds of product I to form product II. The carbon-carbon double bonds containing benzenesulfonic acid groups reversibly add to the carbon-sulfur bonds of product II to generate product III, thus obtaining the monomer block polycarboxylic acid dispersant. Compared with polymers prepared by traditional free radical polymerization, the block copolymer prepared by this invention has better dispersibility and slurry stability as a coal-water slurry dispersant.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer synthesis and coal water slurry, and particularly relates to a multi-block polycarboxylic dispersant as well as a preparation method and application thereof. BACKGROUND

[0002] In current industrial applications, especially in the field of coal water slurry, the use of dispersants is crucial for improving the dispersion performance of coal in water and reducing the overall viscosity of the system. With the increasing environmental requirements and the pursuit of efficient energy utilization, it is an important demand of the industry to develop new dispersants with high dispersion efficiency and environmental friendliness. Traditional polycarboxylic dispersants are prepared by random copolymerization method. Although this method is simple, it often encounters problems such as unclear molecular structure, difficult molecular weight control and large polydispersity index (PDI), which leads to large differences in dispersant performance between different batches, seriously affecting its application effect and reliability in the field of coal water slurry and other fields.

[0003] In recent years, reversible addition-fragmentation chain transfer (RAFT) polymerization technology has attracted widespread attention in the field of polymer science due to its excellent molecular weight control ability and designability. RAFT polymerization technology can precisely control the structure of polymers at the molecular level, including molecular weight and molecular weight distribution, thereby significantly improving the performance stability of the final product. In addition, RAFT polymerization technology is not only suitable for polymerization reactions in organic solvents, but also can be carried out in aqueous solutions, providing a new way for the development of environmentally friendly high-performance polymers. However, the application of RAFT technology in aqueous solution, especially in the preparation of multi-block polycarboxylic dispersants, is relatively less studied, and its potential in practical applications such as coal water slurry has not been fully explored. SUMMARY

[0004] The purpose of the present application is to provide a multi-block polycarboxylic dispersant as well as a preparation method and application thereof, which solves the problems of uncontrollable structure, uneven molecular weight distribution, poor viscosity reduction effect and slurry stability of existing dispersants.

[0005] The present application is achieved by the following technical solutions:

[0006] A multi-block polycarboxylic dispersant has the following structural formula:

[0007]

[0008] wherein,

[0009] n is an integer selected from 5-25; n1 is an integer selected from 5-20; n2 is an integer selected from 20-40; and n3 is an integer selected from 10-30.

[0010] Further, the raw material comprises the following components: monomer I containing allyl structure, monomer II containing carboxylic acid functional group, monomer III containing sulfonate functional group, initiator and chain transfer agent;

[0011] The molar ratio of monomer I, monomer II and monomer III is (0.1-2):4:1.

[0012] Further, the monomer I is one or more of allyl polyoxyethylene ether 200, allyl polyoxyethylene ether 400, allyl polyoxyethylene ether 600 and allyl polyoxyethylene ether 1200;

[0013] The monomer II is one or more of acrylic acid, methacrylic acid, methacrylic acid ester and sodium methacrylate;

[0014] The monomer III is one or more of sodium p-styrenesulfonate, sodium methacrylate, sodium 2-acrylamido-2-methylpropanesulfonate;

[0015] The initiator is one or more of azobisdimethylaminoformate hydrochloride, dimethyl azobis isobutyrate and dibenzoyl peroxide;

[0016] The chain transfer agent is one or more of dithiocarbamate, xanthate and trithiocarbonate.

[0017] Further, the number average molecular weight of the multi-block polycarboxylic acid dispersant ranges from 9000 to 97000, and the PDI is controlled in the range of 1.30-2.60.

[0018] The application also discloses a preparation method of the multi-block polycarboxylic acid dispersant, comprising the following steps:

[0019] S1, mixing and stirring monomer I containing allyl structure and deionized water to prepare an initial mixed solution;

[0020] Adding initiator and chain transfer agent to the initial mixed solution and continuing to stir until completely dissolved;

[0021] Carrying out polymerization reaction under nitrogen atmosphere, and carrying out preliminary purification after polymerization is completed to obtain product I;

[0022] S2, mixing product I with deionized water to obtain product I solution, and heating the product I solution;

[0023] Dissolving initiator and monomer II containing carboxylic acid functional group in deionized water respectively to obtain two solutions;

[0024] Under the protection of continuous nitrogen atmosphere, gradually adding the two solutions to the product I solution to carry out polymerization reaction, and obtaining a more purified solution;

[0025] The pH of the purified solution was adjusted to neutral using an alkaline solution, followed by further purification to obtain product II.

[0026] S3. Mix product II with deionized water and stir to obtain a product II solution;

[0027] The initiator and monomer III containing sulfonate functional groups were dissolved in product II solution, and the polymerization reaction was carried out under a nitrogen protective atmosphere. After the polymerization was completed, the multi-component block polycarboxylic acid dispersant was obtained by dialysis and freeze drying.

[0028] Furthermore, in S1, the chain transfer agent is 0.5% to 2.5% of the mass of monomer I;

[0029] The initiator is 0.1%-2.0% of the mass of monomer I.

[0030] Furthermore, in S2, the mass ratio of monomer II to product I is 0.2-0.5:1;

[0031] The initiator is 0.1%-2.0% of the mass of monomer II.

[0032] Furthermore, in S3, the mass ratio of monomer III to product II is 0.15-0.4:1;

[0033] The initiator is 0.1%-2.0% of the mass of monomer III.

[0034] Furthermore, the polymerization reaction temperature is 70-80℃, and the reaction time is 4-8h.

[0035] This invention also discloses the application of the aforementioned multi-block polycarboxylic acid dispersant in the preparation of coal-water slurry.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] This invention discloses a multi-component block polycarboxylic acid dispersant, composed of a hydrophobic long carbon chain and short side chains providing steric hindrance and wetting properties. Allyl polyoxyethylene ether is selected as the macromonomer, and carboxyl functional monomers and sulfonic acid functional monomers providing hydrophilic groups are used as side chain structures. The long carbon chain has a hydrophobic structure for contact with the surface of low-rank coal; the allyl polyoxyethylene ether and R1 containing carboxylic acid functional groups have a hydrophilic structure for contact with water. Through molecular structure design, compared with polymers prepared by traditional free radical polymerization, the block copolymer prepared by this invention has better dispersibility and slurry stability as a coal-water slurry dispersant. The hydrophilic group (-SO3) provided by R2 containing sulfonic acid groups... -The dispersant chelates with the mineral surface through electrostatic repulsion, while the benzene ring interacts with the aromatic rings on the coal surface, thereby enhancing the stability of the dispersant. Furthermore, the long side chains of the dispersant form a large hydration film with water, while the short chains (-SO3)... - ) and (-COO - The dispersant provides electrostatic repulsion, ensuring uniform dispersion of coal particles. Thus, the dispersant not only enhances the dispersion stability of the coal but also improves its flowability. The addition of the dispersant alters the C and O content on the coal surface. The dispersant increases the number of oxygen-containing functional groups on the coal surface and effectively reduces the agglomeration of coal particles. This, in turn, improves product quality, combustion efficiency, and reduces pollution emissions.

[0038] This invention also discloses a method for preparing a multi-component block polycarboxylate dispersant. The method employs a reversible addition-fracture transfer (RAFT) process to synthesize a multi-component block polycarboxylate dispersant in aqueous solution. Compared to traditional free radical polymerization, its structure and molecular weight are controllable, and its molecular weight distribution is uniform. RAFT polymerization allows for controllable reaction rates, design of polymer molecular weight, and the attainment of a lower PDI. By adjusting the reaction conditions, the molecular weight and molecular weight distribution of the polymer can be precisely controlled, thereby preparing a high-performance block polycarboxylate dispersant.

[0039] In S1, monomer I containing an allyl structure, an initiator, and a chain transfer agent undergo a polymerization reaction to polymerize a polycarboxylic acid backbone from carbon-carbon double bonds. This backbone can adsorb onto the hydrophobic portion of the coal surface. The dispersant molecules are adsorbed onto the coal particle surface through interactions such as van der Waals forces. Adding long-chain allyl polyoxyethylene ether, which is linked to the backbone via double bonds, allows it to form hydrogen bonds with water at one end and provide steric hindrance.

[0040] In S2, a functional side chain containing a carboxyl group is added, along with monomer II. The short side chain structure consists of a carboxyl functional monomer providing a hydrophilic group connected to the main chain via a C-C bond. -COO - It comes into contact with water and provides electrostatic repulsion, and can be combined with multiple monomers to exert a synergistic effect.

[0041] In S3, a sulfonic acid functional side chain is added, monomer III is added, and a sulfonic acid functional monomer providing a hydrophilic group is introduced and linked to the main chain via a C-C bond. -SO3 - The hydrophilic groups provide electrostatic repulsion, allowing adsorption onto the mineral surface via chelation. The benzene ring can interact with the aromatic rings on the coal surface, enhancing stability. The dispersant also contains -COO... - and -SO3 - At the same time, the diversity of hydrophilic groups can affect the performance of anionic dispersants. Minerals with -COO - Its adsorption affinity is stronger than that of -SO3- Because -COO - The chelating ability is better than that of -SO3 - -COO - It can be used as an anchoring group, while -SO3 - The groups are oriented towards the aqueous phase.

[0042] Slurry viscosity tests on low-rank coal using block copolymers and random copolymer dispersants showed that, under the conditions of a slurry concentration of 64.0% and a dispersant addition of 0.4%, the coal-water slurry prepared by the block polycarboxylate dispersant had lower viscosity and better stability than the slurry prepared by the random polycarboxylate dispersant due to its structural advantages. Attached Figure Description

[0043] Figure 1 This is the synthetic route for the multi-block polycarboxylic acid dispersant in this invention;

[0044] Figure 2 This is the infrared spectrum of the multi-block polycarboxylic acid dispersant in this invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0046] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0047] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus.

[0048] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0049] These examples demonstrate how experimental conditions or materials can be adjusted based on the original experimental procedures to obtain products with different properties. Two polycarboxylate dispersants (PCs) with different structures were synthesized using APEG, AA, and SSS as monomers via random copolymerization and the RAFT method. r and PC b。 Note that the following content is illustrative and needs to be adjusted according to experimental results and product requirements in actual applications.

[0050] Example 1: (The molar ratio of monomer I, monomer II, and monomer III is 0.5:4:1):

[0051] The multi-component block polycarboxylic acid dispersant prepared in this embodiment comprises the following components: monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent; monomer I is allyl polyoxyethylene ether 600 (APEG600), monomer II is acrylic acid AA, monomer III is sodium p-styrene sulfonate (SSS), the initiator is azobisisobutylamidine hydrochloride (AIBA), and the chain transfer agent is S,S' di(α,α′methylα″acetic acid)-trithiocarbonate TRIT.

[0052] The molar ratio of allyl polyoxyethylene ether 600 (APEG600), AA acrylic acid, and sodium p-styrene sulfonate (SSS) is 0.5:4:1.

[0053] Step 1: In a 250mL three-necked flask equipped with a stirrer and a condenser, add 7.5g of APEG600 and 15g of water to form an initial mixed solution.

[0054] Subsequently, 0.0375 g AIBA and 0.117 g TRIT transfer agent were added to the initial mixed solution, and the mixture was stirred until fully dissolved. The temperature was raised to 70 °C and nitrogen gas was introduced to isolate the air for 30 minutes. The reaction was continued at 70 °C for 8 hours. After the reaction was completed, the solution was dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 3000. The dialyzed product was freeze-dried to obtain product I.

[0055] Step 2: Add product I to a new 250mL three-necked flask, raise the temperature to 70℃ again and continue stirring;

[0056] 0.036 g of AIBA was dissolved in 15 g of water, and 7.2 g of AA was dissolved in 7.8 g of deionized water. Under continuous nitrogen purging, the AIBA and AA solutions were uniformly added to a three-necked flask using a peristaltic pump over a period of 30 minutes. After addition, the reaction was continued at 70°C for 8 hours. After the reaction, the pH was adjusted to approximately 7 using 30% NaOH solution. The product was dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 5000. Following dialysis, the purified dialyzed product was obtained by freeze-drying and designated as product II.

[0057] If AIBA is added directly, a large number of free radicals will be generated during the heating reaction, making the polymerization reaction uncontrollable. Therefore, it should be added dropwise after dissolving to control the free radical initiation rate.

[0058] Step 3: Weigh 6g of product II obtained in Step 2 and 17.45g of water into a 150mL three-necked flask. Stir while heating to 70℃.

[0059] Weigh 0.01137 g AIBA and 2.575 g SSS and dissolve them in deionized water. Add the AIBA and SSS solution to a flask under nitrogen protection. After reacting for 8 hours, dialyze for 24 hours using a dialysis bag with a molecular weight cutoff of 8000. After dialysis, obtain the trimonomer block polycarboxylic acid dispersant PCb1 by freeze-drying.

[0060] like Figure 1 As shown, this reaction can be divided into three stages:

[0061] First stage: Under the action of the chain transfer agent, the carbon-sulfur bond breaks, and monomer I reversibly adds to the broken carbon-sulfur bond to obtain product I.

[0062] Second stage: The carbon-carbon bond with the carboxyl group in monomer II breaks and reversibly adds to the carbon-sulfur bond of product I to form product II.

[0063] The third stage: The carbon-carbon double bond with benzenesulfonic acid group reversibly adds to the carbon-sulfur bond of product II to generate product III, namely the monomer block polycarboxylic acid dispersant.

[0064] Example 2: (Molar ratio of monomer I, monomer II, and monomer III is 0.75:4:1):

[0065] The multi-component block polycarboxylic acid dispersant prepared in this embodiment comprises the following components: monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent; monomer I is allyl polyoxyethylene ether 600 (APEG600), monomer II is methacrylic acid (MA), monomer III is sodium methacrylate sulfonate (SMAS), the initiator is dimethyl azobisisobutyrate, and the chain transfer agent is S,S' di(α,α′methylα″acetic acid)-trithiocarbonate TRIT.

[0066] The molar ratio of allyl polyoxyethylene ether 600 (APEG600), methacrylic acid (MA), and sodium p-methacrylate sulfonate (SMAS) is 0.75:4:1.

[0067] Step 1: In a 250 mL three-necked flask equipped with a stirrer and condenser, add 11.22 g of APEG600 and 20.2 g of water to form an initial mixed solution. Then, add 0.0561 g of dimethyl azobisisobutyrate and 0.175 g of transfer agent TRIT to this mixed solution, and stir until fully dissolved. Raise the temperature to 70 °C and purge with nitrogen to isolate it from air for 30 minutes. Continue the reaction at 70 °C for 8 hours. After the reaction is complete, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 for 24 hours. Freeze-dry the dialyzed product to obtain product I.

[0068] Step 2: Add Product I to a new 250 mL three-necked flask. Raise the temperature back to 70 °C and continue stirring. Dissolve 0.036 g of dimethyl azobisisobutyrate in 15 g of water and 7.2 g of methacrylic acid in 7.8 g of deionized water. Under continuous nitrogen purging, add the dimethyl azobisisobutyrate and methacrylic acid solutions evenly to the three-necked flask using a peristaltic pump, with an addition time set at 30 minutes. After the addition is complete, continue the reaction at 70 °C for 8 hours. After the reaction is complete, adjust the pH to approximately 7 using 30% NaOH solution. Dialyze the product for 24 hours using a dialysis bag with a molecular weight cutoff of 5000. After dialysis, obtain a relatively pure dialysis product, designated as Product II, by freeze-drying.

[0069] Step 3: Weigh 7g of product II obtained in Step 2 and 22.34g of water into a 150mL three-necked flask. Heat to 70℃ while stirring. Weigh 0.01137g of dimethyl azobisisobutyrate and 2.575g of sodium methyl methacrylate according to the molar ratio of Step 1 and Step 2, and dissolve them in deionized water. Add the solution of dimethyl azobisisobutyrate and sodium methyl methacrylate to the flask under nitrogen protection. After reacting for 8 hours, dialyze for 24 hours using a dialysis bag with a molecular weight cutoff of 8000. After dialysis, obtain the trimonomer block polycarboxylic acid dispersant PCb2 by freeze-drying.

[0070] Example 3: (The molar ratio of monomer I, monomer II, and monomer III is 1:4:1):

[0071] The multi-component block polycarboxylic acid dispersant prepared in this embodiment comprises the following components: monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent; monomer I is allyl polyoxyethylene ether 600 (APEG600), monomer II is methacrylate, monomer III is sodium 2-acrylamido-2-methylpropanesulfonate, the initiator is benzoyl peroxide, and the chain transfer agent is S,S' di(α,α′methylα″acetic acid)-trithiocarbonate TRIT.

[0072] The molar ratio of allyl polyoxyethylene ether 600 (APEG600), methacrylate and sodium 2-acrylamido-2-methylpropanesulfonate is 1:4:1.

[0073] Step 1: In a 250 mL three-necked flask equipped with a stirrer and condenser, add 15 g of APEG600 and 29.50 g of water to form an initial mixed solution. Then, add 0.075 g of benzoyl peroxide and 0.234 g of the transfer agent TRIT to this mixed solution, stirring until fully dissolved. Raise the temperature to 70 °C and purge with nitrogen to isolate it from air for 30 minutes. Continue the reaction at 70 °C for 8 hours. After the reaction is complete, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 for 24 hours. Freeze-dry the dialyzed product.

[0074] Step 2: Weigh the same amount of dialysis product as in Step 1 and add it to a new 250 mL three-necked flask. Raise the temperature back to 70 °C and stir continuously. Dissolve 0.036 g of benzoyl peroxide in 15 g of water and 7.2 g of methacrylate in 7.8 g of deionized water. Under continuous nitrogen purging, add the benzoyl peroxide and methacrylate solutions evenly to the three-necked flask using a peristaltic pump, setting the addition time to 30 minutes. After the addition is complete, continue the reaction at 70 °C for 8 hours. After the reaction is complete, adjust the pH to approximately 7 with 30% NaOH solution. Dialyze the product for 24 hours using a dialysis bag with a molecular weight cutoff of 5000. After dialysis, obtain a relatively pure dialysis product by freeze-drying.

[0075] Step 3: Weigh 8g of the dialysis product obtained in Step 2 and 25.67g of water into a 150mL three-necked flask. Heat to 70℃ while stirring. Weigh 0.01137g of methacrylate and 2.575g of sodium 2-acrylamido-2-methylpropanesulfonate according to the molar ratio of Step 1 and Step 2, and dissolve them in deionized water. Add the methacrylate and methacrylate solution to the flask under nitrogen protection. After reacting for 8 hours, dialyze for 24 hours using a dialysis bag with a molecular weight cutoff of 8000. After dialysis, obtain the trimonomer block polycarboxylic acid dispersant PCb3 by freeze-drying.

[0076] Example 4: (Molar ratio of monomer I, monomer II, and monomer III is 1.25:4:1):

[0077] The multi-component block polycarboxylic acid dispersant prepared in this embodiment comprises the following components: monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent; monomer I is allyl polyoxyethylene ether 600 (APEG600), monomer II is acrylic acid AA, monomer III is sodium p-styrene sulfonate (SSS), the initiator is azobisisobutylamidine hydrochloride (AIBA), and the chain transfer agent is S,S' di(α,α′methylα″acetic acid)-trithiocarbonate TRIT.

[0078] The molar ratio of allyl polyoxyethylene ether 600 (APEG600), AA acrylic acid, and sodium p-styrene sulfonate (SSS) is 1.25:4:1.

[0079] Step 1: In a 250 mL three-necked flask equipped with a stirrer and condenser, add 18.75 g of APEG600 and 37.75 g of water to form an initial mixed solution. Then, add 0.0937 g of AIBA and 0.292 g of transfer agent TRIT to this mixed solution and stir until fully dissolved. Raise the temperature to 70 °C and purge with nitrogen to isolate it from air for 30 minutes. Continue the reaction at 70 °C for 8 hours. After the reaction is complete, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 for 24 hours. Freeze-dry the dialyzed product.

[0080] Step 2: Weigh the same amount of dialysis product as in Step 1 and add it to a new 250 mL three-necked flask. Raise the temperature back to 70 °C and stir continuously. Dissolve 0.036 g AIBA in 15 g water and 7.2 g AA in 7.8 g deionized water. Under continuous nitrogen purging, add the AIBA and AA solutions evenly to the three-necked flask using a peristaltic pump, with an addition time set at 30 minutes. After the addition is complete, continue the reaction at 70 °C for 8 hours. After the reaction is complete, adjust the pH to approximately 7 with 30% NaOH solution. Dialyze the product for 24 hours using a dialysis bag with a molecular weight cutoff of 5000. After dialysis, obtain a relatively pure dialysis product by freeze-drying.

[0081] Step 3: Weigh 9g of the dialysis product obtained in Step 2 and 27g of water into a 150mL three-necked flask. Heat to 70℃ while stirring. Weigh 0.01137g of AIBA and 2.575g of SSS according to the molar ratio of Steps 1 and 2, and dissolve them in deionized water. Add the AIBA and SSS solution to the flask under nitrogen protection. After reacting for 8 hours, dialyze for 24 hours using a dialysis bag with a molecular weight cutoff of 8000. After dialysis, obtain the trimonomer block polycarboxylic acid dispersant PCb4 by freeze-drying.

[0082] Example 5: (Molar ratio of monomer I, monomer II, and monomer III is 1.5:4:1):

[0083] The multi-component block polycarboxylic acid dispersant prepared in this embodiment comprises the following components: monomer I containing an allyl structure, monomer II containing a carboxylic acid functional group, monomer III containing a sulfonate functional group, an initiator, and a chain transfer agent; monomer I is allyl polyoxyethylene ether 1200 (APEG1200), monomer II is AA acrylic acid, monomer III is sodium p-styrene sulfonate (SSS), the initiator is azobisisobutylamidine hydrochloride (AIBA), and the chain transfer agent is S,S' di(α,α′methylα″acetic acid)-trithiocarbonate TRIT.

[0084] The molar ratio of allyl polyoxyethylene ether 1200 (APEG1200), AA acrylic acid, and sodium p-styrene sulfonate (SSS) is 1.5:4:1.

[0085] Step 1: In a 250 mL three-necked flask equipped with a stirrer and condenser, add 22.44 g of APEG1200 and 46.36 g of water according to the molar ratio of AA, APEG1200, and SSS of 4:1.5:1 to form an initial mixed solution. Then, add 0.1122 g of AIBA and 0.35 g of transfer agent TRIT to this mixed solution and stir until fully dissolved. Raise the temperature to 70 °C and purge with nitrogen to isolate air for 30 minutes. Continue the reaction at 70 °C for 8 hours. After the reaction is complete, dialyze the solution using a dialysis bag with a molecular weight cutoff of 3000 for 24 hours. Freeze-dry the dialyzed product.

[0086] Step 2: Weigh the same amount of dialysis product as in Step 1 and add it to a new 250 mL three-necked flask. Raise the temperature back to 70 °C and stir continuously. Dissolve 0.036 g AIBA in 15 g water and 7.2 g AA in 7.8 g deionized water. Under continuous nitrogen purging, add the AIBA and AA solutions evenly to the three-necked flask using a peristaltic pump, with an addition time set at 30 minutes. After the addition is complete, continue the reaction at 70 °C for 8 hours. After the reaction is complete, adjust the pH to approximately 7 with 30% NaOH solution. Dialyze the product for 24 hours using a dialysis bag with a molecular weight cutoff of 5000. After dialysis, obtain a relatively pure dialysis product by freeze-drying.

[0087] Step 3: Weigh 12g of the dialysis product obtained in Step 2 and 30.10g of water into a 150mL three-necked flask. Heat to 70℃ while stirring. Weigh 0.01137g of AIBA and 2.575g of SSS according to the molar ratio of Step 1 and Step 2, and dissolve them in deionized water. Add the AIBA and SSS solution to the flask under nitrogen protection. After reacting for 8 hours, dialyze for 24 hours using a dialysis bag with a molecular weight cutoff of 8000. After dialysis, obtain the trimonomer block polycarboxylic acid dispersant PCb5 by freeze-drying.

[0088] Specifically, monomer I is one or more of allyl polyoxyethylene ether 200, allyl polyoxyethylene ether 400, allyl polyoxyethylene ether 600 and allyl polyoxyethylene ether 1200.

[0089] The monomer II is one or more of acrylic acid, methacrylic acid, methacrylate, and sodium methacrylate;

[0090] The monomer III is one or more of sodium p-styrene sulfonate, methylstyrene, styrene, and sodium 2-acrylamido-2-methylpropanesulfonate;

[0091] The initiator is one or more of azobisisobutylamidine hydrochloride, dimethyl azobisisobutyrate, and benzoyl peroxide;

[0092] The chain transfer agent is one or more of dithiocarbamate, xanthate, and trithiocarbonate.

[0093] The materials used are not limited to those in the five embodiments; the principle is the same and will not be repeated here.

[0094] Comparative Example 1: (Molar ratio: 0.5:4:1):

[0095] A magnetic stirrer and condenser were fitted into a 250 mL three-necked flask. Based on a molar ratio of APEG600:AA:SSS = 0.5:4:1, 7.2 g of acrylic acid (AA), 7.5 g of allyl polyoxyethylene ether (APEG600), and 2.575 g of sodium p-styrene sulfonate (SSS) were added to the flask, along with an appropriate amount of deionized water. 0.4% potassium persulfate (KPS) by mass of the total monomers was weighed and dissolved in deionized water as an initiator. The mixture was stirred and heated to 70 °C with nitrogen purging. The KPS and AA solutions were added dropwise to the flask using a peristaltic pump over 1 hour. The reaction was maintained at 70 °C for 6 hours, then cooled, and the pH was adjusted to 7 with a 30% NaOH solution. The random block polycarboxylate dispersant PCr1 was obtained.

[0096] Comparative Example 2 (molar ratio: 0.75:4:1):

[0097] A magnetic stirrer and condenser were fitted into a 250 mL three-necked flask. Based on a molar ratio of APEG600:MA:SMAS = 0.75:4:1, 7.2 g of methacrylic acid (MA), 11.22 g of allyl polyoxyethylene ether (APEG600), and 2.575 g of sodium methacrylate sulfonate (SMAS) were added to the flask, along with an appropriate amount of deionized water. 0.4% potassium persulfate (KPS) by mass of the total monomers was weighed and dissolved in deionized water as an initiator. The mixture was stirred and heated to 70 °C with nitrogen purging. The KPS and MA solutions were added dropwise to the flask using a peristaltic pump over 1 hour. After maintaining the reaction at 70 °C for 6 hours, the mixture was cooled, and the pH was adjusted to 7 with a 30% NaOH solution. The random block polycarboxylate dispersant PCr2 was obtained.

[0098] Comparative Example 3: (Molar ratio: 1:4:1):

[0099] A magnetic stirrer and condenser were fitted into a 250 mL three-necked flask. Based on a molar ratio of APEG600:methacrylate:sodium 2-acrylamido-2-methylpropanesulfonate = 1:4:1, 7.2 g of methacrylate, 15 g of allyl polyoxyethylene ether (APEG600), and 2.575 g of sodium 2-acrylamido-2-methylpropanesulfonate were added to the flask, along with an appropriate amount of deionized water. 0.4% potassium persulfate (KPS) was weighed as an initiator and dissolved in deionized water. The mixture was stirred and heated to 70 °C with nitrogen purging. The KPS and methacrylate solution were added dropwise to the flask using a peristaltic pump over 1 hour. The reaction was maintained at 70 °C for 6 hours, then cooled, and the pH was adjusted to 7 with 30% NaOH solution. The random block polycarboxylate dispersant PCr3 was obtained.

[0100] Comparative Example 4: (Molar ratio: 1.25:4:1):

[0101] A magnetic stirrer and condenser were fitted into a 250 mL three-necked flask. Based on a molar ratio of APEG600:AA:SSS = 1.25:4:1, 7.2 g of acrylic acid (AA), 18.75 g of allyl polyoxyethylene ether (APEG600), and 2.575 g of sodium p-styrene sulfonate (SSS) were added to the flask, along with an appropriate amount of deionized water. 0.4% potassium persulfate (KPS) was weighed as an initiator and dissolved in deionized water. The mixture was stirred and heated to 70 °C with nitrogen purging. The KPS and AA solutions were added dropwise to the flask using a peristaltic pump over 1 hour. The reaction was maintained at 70 °C for 6 hours, then cooled, and the pH was adjusted to 7 with a 30% NaOH solution. The random block polycarboxylate dispersant PCr4 was obtained.

[0102] Comparative Example 5: (Molar ratio: 1.5:4:1):

[0103] A magnetic stirrer and condenser were fitted into a 250 mL three-necked flask. Based on a molar ratio of APEG1200:AA:SSS = 1.5:4:1, 7.2 g of acrylic acid (AA), 22.44 g of allyl polyoxyethylene ether (APEG1200), and 2.575 g of sodium p-styrene sulfonate (SSS) were added to the flask, along with an appropriate amount of deionized water. 0.4% potassium persulfate (KPS) by mass of the total monomers was weighed and dissolved in deionized water as an initiator. The mixture was stirred and heated to 70 °C with nitrogen purging. The KPS and AA solutions were added dropwise to the flask using a peristaltic pump over 1 hour. The reaction was maintained at 70 °C for 6 hours, then cooled, and the pH was adjusted to 7 with a 30% NaOH solution. The random block polycarboxylate dispersant PCr5 was obtained.

[0104] Example of effect description:

[0105] In this invention, the rheological properties of a specific coal-water slurry formulation were evaluated using rheological testing methods. A 64.0% concentration coal-water slurry was prepared using Hongliulin mixed coal according to a multi-peak order, and 0.4% dispersant was added to optimize rheological properties. The viscosity of the coal-water slurry was tested under a constant temperature of 25°C, and measured using a coal-water slurry viscometer at shear rates from 0 s⁻¹. -1 Up to 100s -1 In the 100s -1 It remained stable for a period of time, then started from 100 seconds. -1 Reduced to 0s -1 The shear rate was measured to be stable at 100 s. -1 The average apparent viscosity of coal-water slurry.

[0106] Table 1. Molecular weights of random and block dispersants

[0107]

[0108] As can be seen from Table 1, with the adjustment of the monomer ratio, the relative molecular mass (M) of the two polycarboxylate dispersants... n and M w The molecular weight distribution (PDI) of random polycarboxylic acids and block polycarboxylic acids showed significant differences. The relative molecular mass of random polycarboxylic acids was generally higher than that of block polycarboxylic acids, while the molecular weight distribution of block polycarboxylic acids was relatively narrower.

[0109] This invention demonstrates that precise control of the molecular weight and distribution of polycarboxylic acid dispersants can be achieved by precisely controlling polymerization conditions and monomer ratios. In particular, RAFT polymerization technology, compared with traditional random copolymerization methods, can synthesize block polycarboxylic acids with better molecular weight control and narrower molecular weight distribution, providing a new approach for the development of high-performance polycarboxylic acid dispersants.

[0110] Table 2 Comparison of viscosity between block polycarboxylic acid and random polycarboxylic acid

[0111]

[0112] Table 2 shows that, compared with random polycarboxylate dispersants, block polycarboxylate dispersants can effectively reduce the viscosity of coal-water slurry and improve its stability under the same pulping conditions. With the increase of the proportion of the macromonomer APEG, the viscosity shows a trend of first decreasing and then increasing, with PC... b The minimum viscosity of the dispersant (nAA:nAPEG600:nSSS = 4:1.25:1) is 550 mPa·s. (PC) b 4. Dispersants exhibit better viscosity-reducing and stabilizing effects on low-rank coal-to-water slurry (CWS). Block-structured PC b4 The prepared coal-water slurry exhibits the best stability, possessing both low viscosity and good stability.

[0113] like Figure 2 The image shows the infrared spectra of PCb4 and PCr4 (AA:APEG 600:SSS ratio 4:1.25:1), where APEG600, AA, and SSS are the infrared spectra of the three monomers of the dispersant. Their structures were analyzed, and the image shows a 3310 cm⁻¹... -1 The peak at 2875 cm⁻¹ represents the stretching vibration of the carboxyl hydroxyl group. -1 The peak at 1720 cm⁻¹ represents the symmetric stretching vibration of the saturated methylene group. -1 The peak of the -C=O stretching vibration is located at 1630 cm⁻¹. -1 The absence of characteristic absorption peaks for -C=C on both sides indicates successful polymer polymerization. After adding NaOH, the peak at 1560 cm⁻¹... -1 An absorption peak will appear at 1400 cm⁻¹, transitioning to COONa. -1 The peak at this point represents the bending vibration of the methylene group (CH). Based on the above key structural features, it can be determined that the infrared spectra of PCb4 and PCr4 show a high degree of overlap with the starting material spectra, indicating that the synthesized target products are consistent.

[0114] This invention demonstrates the remarkable performance of block polycarboxylate dispersants in reducing the viscosity and enhancing the stability of low-rank coal-water slurry. It also provides a new technical approach for the efficient preparation of low-rank coal-water slurry, highlighting the great potential of this type of dispersant in future practical applications.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A multi-block polycarboxylic dispersant, characterized by, The structural formula is as follows: Wherein, ； n1 is selected from an integer of 5-20; n2 is selected from an integer of 20-40; n3 is selected from an integer of 10-30; The raw material comprises the following components: monomer I containing allyl structure, monomer II containing carboxylic acid functional group, monomer III containing sulfonate functional group, initiator and chain transfer agent; The molar ratio of monomer I, monomer II and monomer III is (0.1-2):4:1; The monomer I is one or more of allyl polyoxyethylene ether 200, allyl polyoxyethylene ether 400, allyl polyoxyethylene ether 600 and allyl polyoxyethylene ether 1200; The monomer II is one or more of acrylic acid, methacrylic acid, methyl methacrylate and sodium methacrylate; The monomer III is one or more of sodium p-styrenesulfonate, sodium methacrylate and sodium 2-acrylamido-2-methylpropanesulfonate; The preparation method of the multi-block polycarboxylic acid dispersant comprises the following steps: S1, mixing and stirring monomer I containing allyl structure and deionized water to prepare an initial mixed solution; An initiator and a chain transfer agent are added to the initial mixed solution, and stirring is continued until complete dissolution; The polymerization reaction is carried out under a nitrogen atmosphere, and after the polymerization is completed, preliminary purification is carried out to obtain product I; S2, mixing product I with deionized water to obtain product I solution, and heating the product I solution; The initiator and the monomer II containing carboxylic acid functional group are respectively dissolved in deionized water to obtain two solutions; Under the protection of continuous nitrogen atmosphere, the two solutions are gradually added to the product I solution to carry out polymerization reaction, and a more purified solution is obtained; The pH value of the more purified solution is adjusted to neutral by using an alkaline solution, and then deep purification is carried out to obtain product II; S3, mixing and stirring product II with deionized water to obtain product II solution; The initiator and the monomer III containing sulfonate functional group are dissolved in the product II solution, and the polymerization reaction is carried out under the protection of nitrogen atmosphere, and after the polymerization is completed, the multi-block polycarboxylic acid dispersant is obtained by dialysis and freeze-drying treatment.

2. The multi-block polycarboxylic dispersant of claim 1, wherein, The initiator is one or more of azobisdimethylaminoformate hydrochloride, dimethyl azobis-2-methylpropionate and dibenzoyl peroxide; The chain transfer agent is trithiocarbonate.

3. The multi-block polycarboxylic dispersant of claim 1, wherein, The number average molecular weight of the multi-block polycarboxylic acid dispersant ranges from 9000 to 97000, and the PDI is controlled within 1.30-2.

60.

4. The multi-block polycarboxylic dispersant of claim 1, wherein, In S1, the chain transfer agent is 0.5%-2.5% of the mass of monomer I; The initiator is 0.1%-2.0% of the mass of monomer I.

5. The multi-block polycarboxylic dispersant of claim 1, wherein, In S2, the mass ratio of monomer II to product I is 0.2-0.5:1; The initiator is 0.1%-2.0% of the mass of monomer II.

6. The multi-block polycarboxylic dispersant of claim 1, wherein, In S3, the mass ratio of monomer III to product II is 0.15-0.4:1; The initiator is 0.1%-2.0% of the mass of monomer III.

7. The multi-block polycarboxylic dispersant of claim 1, wherein, The polymerization reaction temperature is 70-80℃, and the reaction time is 4-8 h.

8. The multi-block polycarboxylic acid dispersant according to any one of claims 1-7 is applied in the field of preparing coal water slurry.

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