A multi-branched block copolymer, a preparation method and application thereof

Abstract

A multi-branched block copolymer, a preparation method and application, the multi-branched block copolymer is mainly composed of styrene: allyl polyethylene glycol = 8-9: 0.5-9 by mass ratio; the preparation method is: potassium phosphate, 1-butyl mercaptan, carbon disulfide, acetone are placed in a reaction bottle, after stirring, 1,2,4,5-tetrakis (bromomethyl) benzene is added, after reaction, intermediate product I is obtained, which is reacted with initiator, styrene, dioxane to obtain intermediate product II, which is reacted with initiator, allyl polyethylene glycol, dioxane to obtain the multi-branched block copolymer; the multi-branched block copolymer is applied to the preparation of water coal slurry from low rank coal; the multi-branched block copolymer with hydrophilic group and hydrophobic group is prepared by using reversible addition-fragmentation chain transfer RAFT polymerization, the multi-branched block copolymer with highly controllable structure and molecular weight is used as a water coal slurry dispersant, and the problems of uncontrollable structure, uneven molecular weight distribution, unsatisfactory viscosity reduction effect and unstable slurry preparation of the existing dispersant are solved.

Description

Technical Field

[0001] This invention relates to the field of coal-water slurry dispersants, specifically to a multibranched block copolymer, its preparation method, and its application. Background Technology

[0002] Existing copolymers are generally prepared by random copolymerization or free radical polymerization. For example, the invention with patent number [CN202111068885] entitled "An amphoteric polycarboxylate dispersant with large molecular weight and large branched chain and its preparation method" provides an amphoteric polycarboxylate dispersant with large molecular weight and large branched chain. The polymer is synthesized by free radical polymerization of acrylic acid, sodium styrene sulfonate, methyl allyl alcohol polyoxyethylene ether and trimethyl hexyl ammonium bromide. However, because the free radical polymerization method makes it difficult to control the product structure, the molecular weight distribution of the product is wide, and it has a branched structure, it is impossible to effectively control the molecular weight. Therefore, it has disadvantages such as unsatisfactory viscosity reduction effect, inability to control the ratio of hydrophilic / hydrophobic groups, and unstable pulping. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide a multibranched block copolymer, its preparation method, and its application. By utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization, a multibranched block copolymer with both hydrophilic and hydrophobic groups is prepared. The multibranched block copolymer with highly controllable structure and molecular weight is used as a dispersant for coal-water slurry, solving the problems of uncontrollable structure, uneven molecular weight distribution, unsatisfactory viscosity reduction effect, and unstable slurry preparation of existing dispersants.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A multibranched block copolymer, whose raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of styrene:allyl polyethylene glycol (APEG) = (8-9):(0.5-9).

[0005] The styrene is a hydrophobic group used in low-rank coal-water slurry to contact the surface of low-rank coal; the allyl polyethylene glycol (APEG) is a hydrophilic group to contact water.

[0006] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At -5-0 ℃, tripotassium phosphate: 1-butanethiol: carbon disulfide: acetone = 2:2:6:(2.7-4) by molar ratio, and stir for 1-1.5 h to obtain a mixture. Then, transfer the mixture to room temperature of 20-25 ℃ and continue stirring for 12-13 h to obtain the precursor of intermediate product I. Transfer the precursor of intermediate product I to an environment of -5-0 ℃ and add 1,2,4,5-tetra(bromomethyl)benzene dropwise at a molar ratio of 1,2,4,5-tetra(bromomethyl)benzene:acetone = 1:(2.7-4). Stir for 1-1.5 h to obtain crude intermediate product I. Transfer the crude intermediate product I to 20-25 ℃ and stir for 12-13 h. After purification by rotary evaporation, intermediate product I is obtained. Step 2: Add intermediate product I, styrene, and dioxane sequentially into the reaction vessel, then add the initiator. The mass ratio of intermediate product I: styrene: dioxane is 1:(16-33):(34-102), and the mass ratio of styrene: initiator is 1:(0.03-0.035). Then, evacuate the reaction vessel to a vacuum state and place it in a high-temperature oil bath at 75-85℃. Stir at 800-900 r / min for 24-25 hours. After the reaction is completed, remove the unreacted monomer styrene by reprecipitation to obtain intermediate product II. Step 3: Add intermediate product II, allyl polyethylene glycol (APEG), and dioxane sequentially into the reaction vessel, followed by the initiator. The mass ratio of intermediate product II: allyl polyethylene glycol (APEG): dioxane = 1:(1-3):(2.06-3.315); allyl polyethylene glycol (APEG): initiator = 1:(0.03-0.035). Then, evacuate the reaction vessel to a vacuum state and place it in a high-temperature oil bath at 75-85℃ with a stirring speed of 800-900 r / min for 24-25 h. After the reaction is completed, remove the unreacted monomer allyl polyethylene glycol (APEG) by reprecipitation to obtain the multibranched block copolymer. The reversible addition-fragmentation chain transfer (RAFT) polymerization reaction is then completed.

[0007] The initiator in steps 2 and 3 is azobisisobutyronitrile (AIBN) or azobisisoheptanenitrile (ABVN).

[0008] The above-mentioned multibranched block copolymer is used in the preparation of coal-water slurry from low-rank coal.

[0009] The specific process for preparing coal-water slurry is as follows: coal powder, water and multibranched block copolymer are mixed in a mass ratio of coal powder:water:multibranched block copolymer = (50-60):(39-49.5):(0.5-1), and stirred for 6-10 minutes at 800-1000 r / min to prepare coal-water slurry.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses reversible addition-fragmentation chain transfer polymerization (RAFT) to prepare multibranched block copolymers. Compared with ordinary free radical polymerization and random copolymerization, RAFT polymerization has the advantages of lower polymerization temperature and narrower molecular weight distribution of the obtained polymer. When applied in the field of coal-water slurry dispersants, it has advantages such as regular molecular structure, adjustable number of hydrophilic / hydrophobic groups, good viscosity reduction effect, and high efficiency.

[0011] 2. This invention uses reversible addition-fracture chain transfer polymerization (RAFT) to prepare a multibranched block copolymer dispersant for low-rank coal slurry. Therefore, it has the advantages of adjustable hydrophilic / hydrophobic group ratio and controllable relative molecular mass and structural height. It can adjust the ratio of hydrophilic and hydrophobic groups to address the structural characteristics of Inner Mongolia lignite, which has a high proportion of hydrophilic groups and high internal water content, thereby achieving the goal of improving the fluidity, slurry concentration, and stability of coal-water slurry. This is of great significance for improving energy utilization and enriching the types of coal used in coal-water slurry preparation.

[0012] 3. The multibranched block copolymer proposed in this invention can precisely control the structure of the copolymer and the length of the hydrophilic / hydrophobic segments by adjusting the addition amounts of monomers styrene and allyl polyethylene glycol (APEG), initiators azobisisobutyronitrile (AIBN) and azobisisoheptanenitrile (ABVN), as well as by using a high-temperature oil bath at 75-85℃, stirring at a speed of 800-900 r / min, and precise control of the feed amount. This results in a more regular structure for the multibranched block copolymer. Furthermore, the structure of the multibranched block copolymer can be adjusted by changing the feed ratio according to the inherent structural characteristics of different types of coal, in order to prepare a highly efficient dispersant.

[0013] 4. This invention employs a reversible addition-fragmentation chain transfer polymerization (RAFT) synthesis method, which simplifies the preparation process and equipment. The prepared multibranched block copolymers have highly controllable structure and molecular weight. When applied to low-rank coal-water slurry dispersants, they exhibit excellent dispersing ability, are suitable for large-scale production, and are of great significance for enriching the types of coal-water slurries, improving energy utilization, and have good market potential.

[0014] 5. This invention employs reversible addition-fragmentation chain transfer polymerization (RAFT) to prepare a multibranched block copolymer that simultaneously possesses both hydrophilic and hydrophobic groups. This copolymer is then used as a dispersant for coal-water slurry. The relative molecular mass and structural height of this multibranched block copolymer are highly controllable. The ratio of hydrophilic to hydrophobic groups can be adjusted according to the structural characteristics of low-rank coal, causing the surface of low-rank coal to change from hydrophilic to hydrophobic. At the same time, the hydrogen bonding between oxygen-containing groups or minerals and water is weakened, reducing the content of adsorbed water on the coal surface, thereby improving the slurry-making performance of low-rank coal.

[0015] In summary, this invention utilizes reversible addition-fragmentation chain transfer (RAFT) polymerization to prepare a multibranched block copolymer that simultaneously possesses both hydrophilic and hydrophobic groups. By using this multibranched block copolymer with highly controllable structure and molecular weight as a dispersant for coal-water slurry, the problems of uncontrollable structure, uneven molecular weight distribution, unsatisfactory viscosity reduction effect, and unstable slurry preparation of existing dispersants are solved. Attached Figure Description

[0016] Figure 1 This is a synthetic route diagram for the multibranched block copolymer dispersant in this invention.

[0017] Figure 2 This is an NMR spectrum of an embodiment of the present invention.

[0018] Figure 3 This is the NMR spectrum of intermediate product I of this invention.

[0019] Figure 4 The diagram shows the viscosity-reducing effect of the multibranched block copolymer prepared in the embodiments of the present invention as a dispersant, compared with the common naphthalene sulfonate dispersant sodium lignosulfonate dispersant, on lignite-coal slurry. Detailed Implementation

[0020] The working principle of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] Example 1 See Figure 1 A multibranched block copolymer, whose raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 8:1.5.

[0022] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 2 mol tripotassium phosphate, 2 mol 1-butanethiol, 6 mol carbon disulfide and 2.7 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 20-25 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 1 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude intermediate product I. The crude intermediate product I was then transferred to 20 °C and stirred for 12 h. After rotary evaporation purification, intermediate product I was obtained. Step 2: Add 1380 mg of intermediate product I, 8 g of styrene, and 10.6 g of dioxane to a Schlenk flask, followed by 240 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =5000 intermediate II; the vacuum state is achieved by placing the reagent in step 2 in a Schlenk flask and degassing it through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted styrene monomer; Step 3: Add 1500 mg of intermediate II, 1.5 g of allyl polyethylene glycol (APEG), and 3 g of dioxane to a Schlenk flask sequentially, followed by 45 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), obtaining... M n =10000 multibranched block copolymer; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0023] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 50 g of coal powder, 49.5 g of water, and 0.5 g of the multibranched block copolymer were stirred at 800 r / min for 6 min to prepare a coal-water slurry sample. The slurry was sealed in a 100 mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 3.15%, and no sediment was observed, demonstrating that Example 1 has good dispersibility and the coal-water slurry exhibits good stability.

[0024] Example 2 A multibranched block copolymer, wherein the raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 9:1.5.

[0025] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 4 mol tripotassium phosphate, 4 mol 1-butanethiol, 12 mol carbon disulfide and 8 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 21 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 2 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude product of intermediate product I. The crude product of intermediate product I was transferred to 22 °C and stirred for 12 h. After purification by rotary evaporation, intermediate product I was obtained. Step 2: Add 710 mg of intermediate product I, 9 g of styrene, and 14.7 g of dioxane sequentially to a Schlenk flask reaction vessel, followed by 315 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction vessel to a vacuum state and place it in an oil bath at 75 ºC with stirring at 900 r / min for 25 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =10000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 1500 mg of intermediate II, 1.5 g of allyl polyethylene glycol (APEG), and 4.5 g of dioxane to a Schlenk flask sequentially, followed by 50 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in a 75 ºC oil bath with stirring at 900 r / min for 25 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), obtaining... M n =20000 multibranched block copolymer; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0026] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 60 g of coal powder, 39 g of water, and 1 g of the multibranched block copolymer were stirred at 1000 r / min for 10 min to prepare a coal-water slurry sample. The slurry was sealed in a 100 mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 3.21%, and no sediment was observed, demonstrating that Example 2 exhibits good dispersibility and the coal-water slurry has good stability.

[0027] Example 3 A multibranched block copolymer, wherein the raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 9:0.5.

[0028] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At -4 ℃, 1 mol tripotassium phosphate, 1 mol 1-butanethiol, 3 mol carbon disulfide and 2 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to room temperature of 23 ℃ and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 ℃ and 0.5 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude product of intermediate product I. The crude product of intermediate product I was transferred to 24 ℃ and stirred for 12 h. After rotary evaporation purification, intermediate product I was obtained. Step 2: Add 475 mg of intermediate product I, 9 g of styrene, and 14.4 g of dioxane sequentially to a Schlenk flask reaction vessel, followed by 300 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction vessel to a vacuum state and place it in an oil bath at 85 ºC with stirring at 750 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =15000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 500 mg of intermediate II, 0.5 g of allyl polyethylene glycol (APEG), and 1.5 g of dioxane to a Schlenk flask sequentially, followed by 15 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 750 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), obtaining... M n =30000 multibranched block copolymer; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0029] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 49.7 g of coal powder, 49.5 g of water, and 0.8 g of the multibranched block copolymer were stirred at 1000 r / min for 10 min to prepare a coal-water slurry sample. The slurry was sealed in a 100 mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 4.23%, with slight sedimentation, indicating that Example 3 had poor dispersion performance and poor stability of the coal-water slurry.

[0030] Example 4 A multibranched block copolymer, wherein the raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 9:1.5.

[0031] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 4 mol tripotassium phosphate, 4 mol 1-butanethiol, 12 mol carbon disulfide and 5.4 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 25 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 2 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude intermediate product I. The crude intermediate product I was then transferred to 25 °C and stirred for 12 h. After purification by rotary evaporation, intermediate product I was obtained. Step 2: Add 355 mg of intermediate product I, 9 g of styrene, and 9.5 g of dioxane sequentially to a Schlenk flask, followed by 270 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 900 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =20000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 500 mg of intermediate II, 1.5 g of allyl polyethylene glycol (APEG), and 2 g of dioxane sequentially to a Schlenk flask, followed by 45 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 900 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), yielding... M n =40000 multi-branched block copolymer dispersant; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0032] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 51 g of coal powder, 48.4 g of water, and 0.6 g of the multibranched block copolymer were stirred at 800 r / min for 9 min to prepare a coal-water slurry sample. The slurry was sealed in a 100 mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 4.52%, and no sediment was observed, demonstrating that Example 4 exhibited poor dispersion performance and very poor stability of the coal-water slurry.

[0033] Example 5 A multibranched block copolymer, wherein the raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 9:4.5.

[0034] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At -5 °C, 4 mol tripotassium phosphate, 4 mol 1-butanethiol, 12 mol carbon disulfide and 8 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 20 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 2 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude product of intermediate product I. The crude product of intermediate product I was transferred to 20 °C and stirred for 12 h. After rotary evaporation purification, intermediate product I was obtained. Step 2: Add 1380 mg of intermediate product I, 9 g of styrene, and 10.6 g of dioxane to a Schlenk flask sequentially, followed by 270 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =5000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 1500 mg of intermediate II, 4.5 g of allyl polyethylene glycol (APEG), and 6 g of dioxane to a Schlenk flask sequentially, followed by 135 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), yielding... M n =20000 multibranched block copolymer dispersant, by mass ratio, hydrophilic groups: hydrophobic groups = 3:1; the process of evacuating the reaction bottle to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction bottle, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0035] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 55 g of coal powder, 44.5 g of water, and 0.5 g of the multibranched block copolymer were stirred at 800 r / min for 6 min to prepare a coal-water slurry sample. The slurry was sealed in a 100 mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 2.96%, and no sediment was observed, demonstrating that Example 5 exhibits good dispersibility and the coal-water slurry has good stability.

[0036] Example 6 A multibranched block copolymer, wherein the raw materials include styrene and allyl polyethylene glycol (APEG) in a mass ratio of 9:1.62.

[0037] A method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 2 mol tripotassium phosphate, 2 mol 1-butanethiol, 6 mol carbon disulfide and 2.7 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 21 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 1 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude product of intermediate product I. The crude product of intermediate product I was transferred to 20-25 °C and stirred for 12 h. After purification by rotary evaporation, intermediate product I was obtained. Step 2: Add 540 mg of intermediate product I, 9 g of styrene, and 9.6 g of dioxane sequentially to a Schlenk flask, followed by 280 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =10000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 1500 mg of intermediate II, 1.62 g of allyl polyethylene glycol (APEG), and 6 g of dioxane to a Schlenk flask sequentially, followed by 50 mg of initiator azobisisobutyronitrile (AIBN). Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), obtaining... M n =20000 and a hydrophilic / hydrophobic group mass ratio of 1:3; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

[0038] An application of a multibranched block copolymer in the preparation of coal-water slurry from low-rank coal was described. 52g of coal powder, 47.1g of water, and 0.9g of the multibranched block copolymer were stirred at 800r / min for 6 min to prepare a coal-water slurry sample. The slurry was sealed in a 100mL graduated cylinder, and the water separation rate and presence of sediment were measured after 5 days. The water separation rate was found to be 2.99%, and no sediment was observed, demonstrating that while Example 6 had poor dispersion performance, the coal-water slurry exhibited good stability.

[0039] Structural characterization: See Figure 2 , Figure 3 It can be seen that the peaks with chemical shifts of 7.25-6.82 ppm in the spectrum of the multibranched block copolymer represent hydrogens in different chemical environments within the benzene ring, which is consistent with the NMR spectrum of intermediate product I. Figure 1However, in the spectrum of the multibranched block copolymer, the intensity of the hydrogen peaks in different chemical environments of the -CH=CH2 group in the allyl polyethylene glycol (APEG) molecule structure at chemical shifts of 5.89 and 5.33 ppm was weakened, while the peak of -CH2- appeared in the shift range of 1.3-1.83 ppm, indicating the breaking of the C=C bond. This proves that allyl polyethylene glycol (APEG) and intermediate product II have copolymerized, and the multibranched block copolymer has been successfully prepared.

[0040] The conversion rate was calculated as the ratio of the peak area of ​​hydrogen atoms in different chemical environments on the -CH=CH2 group of the allyl polyethylene glycol (APEG) molecule to the peak area of ​​-CH2-. The controllability of the preparation process was characterized by the relative molecular mass of the multibranched block copolymer. The relative molecular mass of the copolymer was determined using an Agilent 1260 Infinity II gel electrophoresis system, and the results are shown in Table 1. Table 1. Number-average molecular weight and conversion rate of each example Example 1 10000 10767 91.5 Example 2 20000 20536 93.2 Example 3 30000 30042 90.6 Example 4 40000 39842 89.7 Example 5 20000 20876 94.6 Example 6 20000 20361 92.1 As shown in Table 1, the number-average molecular weights of the multibranched block copolymers prepared in Examples 1-6 are basically consistent with the expected design relative molecular mass, and the conversion rates are mostly above 89%, indicating that the controllable preparation of multibranched block copolymers has been successfully achieved. Furthermore, the number-average molecular weights of Examples 1-6 demonstrate that the type of initiator and the reaction temperature in this scheme have little effect on the relative molecular mass of the polymer.

[0041] Performance testing: To characterize the dispersion effect of the multibranched block copolymer dispersant used for low-rank coal-water slurry on Inner Mongolia lignite coal-water slurry, a fixed coal-water slurry concentration of 55 wt% and a dispersant dosage of 0.5 wt% were set. The apparent viscosity of the coal-water slurry was measured using a Chengdu Instrument Factory NXS-4C rotational viscometer, and its flow properties were observed. To characterize the stabilizing effect of the multibranched block copolymer dispersant of the present invention on Inner Mongolia lignite coal-water slurry, the coal-water slurries prepared in the comparative example and the above embodiment were stirred evenly and poured into a 100 mL graduated cylinder (3 cm in diameter). The cylinder was then sealed and placed at 20-25°C for 3 days. The supernatant of the coal-water slurry was drawn out with a syringe and weighed, recorded as m1. The ratio of the mass of the supernatant to the total mass (m0) of the coal-water slurry is the water separation rate. The water separation rate is calculated using the following formula: Water separation rate (wt%) = m1 / m0 × 100%. The water separation rate measurement results are shown in Table 2. Table 2 Performance test results for each embodiment Example 1 10767 55% 0.5 891 No sediment 3.15 Example 2 20536 55% 0.5 696 No sediment 3.21 Example 3 30042 55% 0.5 1196 Slight sedimentation 4.23 Example 4 39842 55% 0.5 1423 More sediment 4.52 Example 5 20876 55% 0.5 595 No sediment 2.96 Example 6 20361 55% 0.5 1089 Slight sedimentation 2.99 blank 55% 0 966 Slight sedimentation 4.33 As shown in Table 2, the performance test results from Examples 1 to 4 indicate that with the gradual increase of the number-average molecular weight of the multi-branched block copolymer, the apparent viscosity of the prepared lignite-coal slurry first gradually decreases and then gradually increases. Therefore, the relative molecular mass of the dispersant suitable for lignite slurry preparation in Inner Mongolia is [value missing]. Mn =20000. Under the condition of optimal relative molecular mass, the ratio of hydrophilic and hydrophobic groups in the polymer was adjusted. The apparent viscosity of the coal-water slurry prepared in Example 5, which is dominated by hydrophilic groups, was significantly lower than that of the coal-water slurry prepared in Example 6, which is dominated by hydrophobic groups.

[0042] See Figure 4 The dispersant prepared in Example 5, which showed the best pulping effect, was compared with common naphthalene sulfonate dispersants and sodium lignosulfonate dispersants used for low-rank coal pulping. The results of the apparent viscosity of the coal-water slurry as a function of shear rate are as follows: It can be seen that when three dispersants are used, the apparent viscosity of the Inner Mongolia lignite coal-water slurry first decreases and then tends to level off with the increase of shear rate, exhibiting pseudoplastic fluid characteristics; when the shear rate is 100 s... -1 At that time, the apparent viscosity of the Inner Mongolia lignite slurry prepared with the dispersant prepared in Example 5 decreased to 595 mPa·s, which was significantly lower than that of the lignite slurry prepared with the other two dispersants, proving that the dispersant prepared in Example 5 has good dispersing and viscosity-reducing ability for lignite.

[0043] In summary, the branched block copolymer dispersant for low-rank coal slurry in this invention has the advantages of adjustable hydrophilic / hydrophobic group ratio and controllable relative molecular mass and structural height. It can adjust the ratio of hydrophilic and hydrophobic groups to suit the structural characteristics of Inner Mongolia lignite, which has a high proportion of hydrophilic groups and high internal water content, thereby achieving the goal of improving the fluidity, slurry concentration and stability of coal-water slurry. This is of great significance for improving energy utilization and enriching the types of coal for coal-water slurry preparation.

[0044] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A multibranched block copolymer, characterized in that, By mass ratio, its raw materials include styrene and allyl polyethylene glycol, with a styrene:allyl polyethylene glycol ratio of 8:1.

5. The method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 2 mol tripotassium phosphate, 2 mol 1-butanethiol, 6 mol carbon disulfide and 2.7 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 20-25 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 1 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude intermediate product I. The crude intermediate product I was then transferred to 20 °C and stirred for 12 h. After rotary evaporation purification, intermediate product I was obtained. Step 2: Add 1380 mg of intermediate product I, 8 g of styrene, and 10.6 g of dioxane to a Schlenk flask, followed by 240 mg of initiator azobisisobutyronitrile. Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =5000 intermediate II; the vacuum state is achieved by placing the reagent in step 2 in a Schlenk flask and degassing it through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted styrene monomer; Step 3: Add 1500 mg of intermediate II, 1.5 g of allyl polyethylene glycol, and 3 g of dioxane to a Schlenk flask sequentially, followed by 45 mg of initiator azobisisobutyronitrile. Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 85 ºC with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol, yielding... M n =10000 multibranched block copolymer; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

2. A multibranched block copolymer, characterized in that, A multibranched block copolymer, comprising, by mass ratio, styrene and allyl polyethylene glycol (APEG), wherein the ratio of styrene to allyl polyethylene glycol (APEG) is 9:1.5; A method for preparing a multibranched block copolymer includes the following steps: Step 1: At 0 °C, 4 mol tripotassium phosphate, 4 mol 1-butanethiol, 12 mol carbon disulfide and 8 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 21 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was transferred to 0 °C and 2 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude product of intermediate product I. The crude product of intermediate product I was transferred to 22 °C and stirred for 12 h. After purification by rotary evaporation, intermediate product I was obtained. Step 2: Add 710 mg of intermediate product I, 9 g of styrene, and 14.7 g of dioxane sequentially to a Schlenk flask reaction vessel, followed by 315 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction vessel to a vacuum state and place it in an oil bath at 75 ºC with stirring at 900 r / min for 25 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =10000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 1500 mg of intermediate II, 1.5 g of allyl polyethylene glycol (APEG), and 4.5 g of dioxane to a Schlenk flask sequentially, followed by 50 mg of initiator azobisisobutyronitrile (ABVN). Then, evacuate the reaction flask to a vacuum state and place it in a 75°C oil bath with stirring at 900 rpm for 25 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol (APEG), yielding... M n =20000 multibranched block copolymer; the process of evacuating the reaction flask to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction flask, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

3. A multibranched block copolymer, characterized in that, By mass ratio, its raw materials include styrene and allyl polyethylene glycol, with a styrene:allyl polyethylene glycol ratio of 9:4.

5. The method for preparing a multibranched block copolymer includes the following steps: Step 1: At -5 °C, 4 mol tripotassium phosphate, 4 mol 1-butanethiol, 12 mol carbon disulfide and 8 mol acetone were placed in a 500 mL flask and stirred for 1 h. The mixture was then transferred to 20 °C and stirred for another 12 h to obtain the precursor of intermediate product I. The precursor of product I was then transferred to 0 °C and 2 mol 1,2,4,5-tetra(bromomethyl)benzene was added dropwise and stirred for 1 h to obtain the crude intermediate product I. The crude intermediate product I was then transferred to 20 °C and stirred for 12 h. After rotary evaporation purification, intermediate product I was obtained. Step 2: Add 1380 mg of intermediate product I, 9 g of styrene, and 10.6 g of dioxane to a Schlenk flask sequentially, followed by 270 mg of initiator azobisisobutyronitrile. Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture containing intermediate product II into a beaker containing a large amount of methanol for reprecipitation to remove unreacted styrene, yielding... M n =5000 intermediate II; the reagent in step 2 is placed in a Schlenk flask and degassed to a vacuum state through three freeze-thaw cycles; the reprecipitation method in step 2 is to pour the mixture into a beaker containing excess methanol to remove unreacted monomer styrene; Step 3: Add 1500 mg of intermediate II, 4.5 g of allyl polyethylene glycol, and 6 g of dioxane to a Schlenk flask sequentially, followed by 135 mg of initiator azobisisobutyronitrile. Then, evacuate the reaction flask to a vacuum state and place it in an oil bath at 80 °C with stirring at 800 r / min for 24 hours. After the reaction is complete, pour the mixture into a beaker containing a large amount of methanol for reprecipitation to remove unreacted allyl polyethylene glycol, yielding... M n =20000 multibranched block copolymer dispersant, by mass ratio, hydrophilic groups: hydrophobic groups = 3:1; the process of evacuating the reaction bottle to a vacuum state in step 3 is as follows: using a Schlenk flask as the reaction bottle, the reagent in step 3 is placed in the Schlenk flask, and degassing is achieved to a vacuum state through three freeze-thaw cycles.

4. The application of any one of the multibranched block copolymers according to claims 1-3, characterized in that, Used for preparing coal-water slurry from low-rank coal.

5. The application of a multibranched block copolymer according to claim 4, characterized in that, The specific process for preparing coal-water slurry is as follows: coal powder, water and multibranched block copolymer are mixed in a mass ratio of (50-60):(39-49.5):(0.5-1) using a stirrer at 800-1000 r / min for 6-10 min to prepare coal-water slurry.

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