Preparation method of graft modified salt-tolerant polyacrylamide

Abstract

The invention relates to the technical field of polyacrylamide, in particular to a preparation method of graft-modified salt-tolerant polyacrylamide. The water-soluble acrylic acid water-soluble polymer is prepared from the following raw materials in parts by weight: 60 to 70 parts of acrylamide, 12 to 15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 18 to 20 parts of acrylic acid, 3 to 6 parts of a functional monomer, 2 to 3 parts of modified triblock polyrotaxane, 0.4 to 0.6 part of an initiator, 0.8 to 1 part of an emulsifier, 300 to 350 parts of water and 15 to 20 parts of propylene glycol. A functional monomer and modified triblock polyrotaxane are introduced and participate in the polyacrylamide polymerization process, and in the use process, due to a polyrotaxane structure in a main body, and through host-guest combination, hydrophobic association and mutual synergistic effect of multiple hydrogen bonds among self macromolecules, the polyrotaxane-containing polyacrylamide polymer can be used for preparing the polyacrylamide polymer. Therefore, the problem that existing polyacrylamide is insufficient in salt tolerance is solved, and meanwhile the high temperature resistance and the shear resistance of the polyacrylamide are well improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyacrylamide, and in particular to a preparation method of graft-modified salt-resistant polyacrylamide. Background Art

[0002] With the advancement of deep oil and gas reservoir development, fracturing fluids face extreme conditions of high temperature, high mineralization and strong shear. Polyacrylamide, as an excellent water-soluble polymer, has good thickening properties in water. It has good drag reduction and sand carrying properties when used as a fracturing fluid. However, polyacrylamide polymers have poor salt resistance and are shielded by ions in salt water, dissolving slowly, resulting in a serious decrease in its sand carrying performance, which in turn affects its use as a fracturing fluid. At the same time, due to the effects of high temperature and strong shear, traditional linear or lightly cross-linked polyacrylamide is prone to chain breakage, resulting in a sudden drop in viscosity, which in turn affects its use as a fracturing fluid. For example, patent CN117534789A discloses a polyacrylamide suspension emulsion for fracturing and a preparation method thereof, which prepares polyacrylamide with a linear structure and has high shear resistance, but does not improve its shear resistance under high temperature and strong shear conditions. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing a grafted modified salt-resistant polyacrylamide, by introducing functional monomers and modified triblock polyrotaxanes to make them participate in the polymerization process of polyacrylamide. During use, since its main body contains a polyrotaxane structure, and through the host-guest binding, hydrophobic association and multiple hydrogen bonds between its own macromolecules, the problem of insufficient salt resistance of existing polyacrylamide is solved, and at the same time, its high temperature resistance and shear resistance are also well improved.

[0004] The purpose of the present invention can be achieved by the following technical scheme: A method for preparing graft-modified salt-resistant polyacrylamide, which comprises the following steps: Step S1: weighing the following raw materials in parts by weight: 60-70 parts of acrylamide, 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 18-20 parts of acrylic acid, 3-6 parts of functional monomers, 2-3 parts of modified triblock polyrotaxane, 0.4-0.6 parts of initiator, 0.8-1 parts of emulsifier, 300-350 parts of water and 15-20 parts of propylene glycol; Step S2: acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, functional monomer, modified triblock polyrotaxane, water and propylene glycol are mixed, stirred and an initiator and an emulsifier are added, and then a sodium hydroxide solution is added to adjust the pH value to 8, and the mixture is reacted for 10-12 hours at a stirring rate of 120-140 rpm and a temperature of 35-40° C., rotary evaporated and dried to obtain a grafted modified salt-resistant polyacrylamide; The mass fraction of the sodium hydroxide solution is 30%; The initiator is a combination of sodium persulfate and sodium bisulfite, wherein the weight ratio of sodium persulfate to sodium bisulfite is 2g:1g; The emulsifier is OP-10.

[0005] The functional monomer is prepared by the following steps: Step A1: p-Hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone are mixed, stirred at a stirring rate of 120-140 rpm, at room temperature, stirred for 4-6 hours, filtered with suction, the filter cake is washed with acetone, the filtrate is spin-dried, and recrystallized from ethanol to obtain intermediate 1; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are mixed, stirred at a stirring rate of 120-140 rpm, at room temperature, stirred for 4-6 hours, filtered with suction, and recrystallized from ethanol to obtain intermediate 2; The dosage ratio of p-hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone is 0.01-0.011 mol: 0.02-0.022 mol: 4.12-4.15 g: 30-35 mL; the intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are 1.6-1.65 g: 1.31-1.32 g: 20 mL: 0.8-1.2 mL; During the reaction, the hydroxyl group in p-hydroxybenzaldehyde reacts with the bromine in 3-bromopropyne to form an ether bond to obtain intermediate 1. The aldehyde group in intermediate 1 then reacts with the primary amine in 4-propenylthiosemicarbazide to form a Schiff base structure to obtain intermediate 2.

[0006] Step A2: Mono-6-O-(azido)-β-cyclodextrin, intermediate 2 and dimethyl sulfoxide solution are mixed, stirred at a stirring rate of 120-140 rpm and a temperature of 30-35° C., copper sulfate pentahydrate and sodium ascorbate are added, and the reaction is carried out for 20-24 hours. Dichloromethane and deionized water are then added, and the organic phase is collected and dried with anhydrous sodium sulfate, precipitated with ether, and freeze-dried to obtain a functional monomer; The volume ratio of dimethyl sulfoxide to deionized water in the dimethyl sulfoxide solution is 3:1, and the amount ratio of mono-6-O-(azido)-β-cyclodextrin, intermediate 2, dimethyl sulfoxide solution, copper sulfate pentahydrate and sodium ascorbate is 1.1-1.15 g: 0.35-0.36 g: 10-12 mL: 0.05-0.06 g: 0.1 g; During the reaction, under the conditions of copper sulfate pentahydrate and sodium ascorbate as catalysts, the azide group in mono-6-O-(azido)-β-cyclodextrin reacts with the acetylene group in the intermediate 2 to form a triazole structure, thereby obtaining a functional monomer.

[0007] The modified triblock polyrotaxane is prepared by the following steps: Step B1: polyethylene glycol, triethylamine, 4-dimethylaminopyridine and dichloromethane are mixed, and 2-bromoisobutyryl bromide is added under nitrogen protection, stirring at a rate of 140-180 rpm and a temperature of 0-5°C, and stirred for 30-40 minutes, then heated to room temperature, and the reaction is continued for 24 hours, rotary evaporation, tetrahydrofuran dissolution, filtration, ether precipitation, filtration, and drying to obtain a macromolecular initiator; β-cyclodextrin, the macromolecular initiator and deionized water are mixed, and stirred for 36 hours at a stirring rate of 450-500 rpm and a temperature of room temperature, centrifuged, washed, and freeze-dried to obtain a polypseudorotaxane; The dosage ratio of polyethylene glycol, triethylamine, 4-dimethylaminopyridine, dichloromethane and 2-bromoisobutyryl bromide is 12-13 g: 0.42-0.45 mL: 0.49-0.52 g: 20-25 mL: 1-1.2 mL; the dosage ratio of β-cyclodextrin, macromolecular initiator and deionized water is 0.34-0.35 g: 0.35-0.4 g: 10-15 mL; During the reaction, under the action of triethylamine and 4-dimethylaminopyridine, the double-terminal hydroxyl groups in polyethylene glycol react with the acyl bromide structure in 2-bromoisobutyryl bromide to obtain a macromolecular initiator. Then, in deionized water, due to the unique amphiphilic structure of β-cyclodextrin, which has a hydrophobic inner cavity and a hydrophilic outer side, the macromolecular initiator passes through β-cyclodextrin to obtain a polypseudorotaxane.

[0008] Step B2: Mix polypseudorotaxane, acetone and deionized water, stir at a rate of 80-120 rpm, add acrylamide and pentamethyldiethylenetriamine, stir for 10-15 min, add copper iodide, pass nitrogen protection, react for 10-12 h, dialyze, and freeze-dry to obtain a block polypseudorotaxane; Mix block polypseudorotaxane, acetone and deionized water, stir at a rate of 80-120 rpm, add 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid and pentamethyldiethylenetriamine, stir for 10-15 min, add copper iodide, pass nitrogen protection, react for 10-12 h, dialyze, and freeze-dry to obtain a triblock polyrotaxane; The amount ratio of polypseudorotaxane, acetone, deionized water, acrylamide, pentamethylethylenediamine and copper iodide is 0.48-0.52g: 5-7mL: 5-7mL: 0.2-0.24g: 0.1-0.12g: 0.06-0.07g; the amount ratio of block polypseudorotaxane, acetone, deionized water, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid, pentamethylethylenediamine and copper iodide is 0.32-0.34g: 5-7mL: 5-7mL: 0.08-0.09g: 0.062-0.064g: 0.041-0.043g; During the reaction, under the action of pentamethyldiethylenetriamine and copper iodide, acrylamide and 2-ethyl bromoisobutyrate structures at both ends of the polypseudorotaxane segment undergo atom transfer radical polymerization to obtain a block polypseudorotaxane. Then, under the action of pentamethyldiethylenetriamine and copper iodide, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-acrylic acid and 2-ethyl bromoisobutyrate structures at both ends of the block polypseudorotaxane segment undergo atom transfer radical polymerization to cap the ends, form a polyrotaxane structure, and obtain a triblock polyrotaxane.

[0009] Step B3: Mix the triblock polyrotaxane and deionized water, stir at a rate of 60-80 rpm and room temperature, add sodium hydroxide solution, adjust the pH value to 11, then stir at a temperature of 2-5°C and add glycidyl methacrylate, continue the reaction for 10-12 hours, dialyze, and dry to obtain a modified triblock polyrotaxane; The molar concentration of the sodium hydroxide solution is 1 mol / L, and the amount ratio of the triblock polyrotaxane, deionized water and glycidyl methacrylate is 1.2-1.4 g: 40-50 mL: 3.4-3.5 g; During the reaction, under alkaline conditions, the epoxy group in glycidyl methacrylate reacts with the hydroxyl group on the cyclodextrin structure in the triblock polyrotaxane, thereby introducing a double bond to obtain a modified triblock polyrotaxane.

[0010] Beneficial effects of the invention: The invention discloses a preparation method of a grafted modified salt-resistant polyacrylamide, which participates in the polymerization process of polyacrylamide by introducing functional monomers and modified triblock polyrotaxanes. During use, since the main body contains a polyrotaxane structure, and through the host-guest binding, hydrophobic association and multiple hydrogen bonds between its own macromolecules, the problem of insufficient salt resistance of the existing polyacrylamide is solved, and at the same time, its high temperature resistance and shear resistance are well improved; In the process of using the grafted modified salt-resistant polyacrylamide as the main body of the fracturing fluid, since the grafted modified salt-resistant polyacrylamide is based on the modified triblock polyrotaxane, during the polymerization process, the double bonds in acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid and functional monomers react with the double bonds in the cyclodextrin structure in the modified triblock polyrotaxane, thereby forming a grafted modified salt-resistant polyacrylamide with a polyrotaxane structure as the main body and a polyacrylamide structure as the side chain. Since the sliding ring cross-linking structure of the polyrotaxane allows the molecular chain to reversibly slip under shear, the damage to the grafted modified salt-resistant polyacrylamide caused by high temperature and strong shear is avoided, and its performance loss is reduced; At the same time, since its functional monomer contains a cyclodextrin structure and the end-capping group of the modified triblock polyrotaxane contains an azobenzene structure, it can be used through host-guest inclusion complex during use, and due to the block structure of the modified triblock polyrotaxane itself, it is very easy to undergo hydrophobic association, and it contains thiourea groups, azobenzene structures and triazole structures, which allows it to form a large number of hydrogen bonds, thereby promoting the formation of a dynamic cross-linking network between different macromolecules, thereby improving the salt resistance, temperature resistance and shear resistance of the grafted modified salt-resistant polyacrylamide. DETAILED DESCRIPTION

[0011] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] Example 1 A method for preparing a graft-modified salt-resistant polyacrylamide comprises the following steps: Step S1: weigh the following raw materials in parts by weight: 60 parts of acrylamide, 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 18 parts of acrylic acid, 3 parts of functional monomers, 2 parts of modified triblock polyrotaxane, 0.4 parts of initiator, 0.8 parts of emulsifier, 300 parts of water and 15 parts of propylene glycol; Step S2: acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, functional monomer, modified triblock polyrotaxane, water and propylene glycol are mixed, stirred and an initiator and an emulsifier are added, and then a sodium hydroxide solution is added to adjust the pH value to 8, and the mixture is reacted for 12 hours at a stirring rate of 140 rpm and a temperature of 40° C., and then rotary evaporated and dried to obtain a grafted modified salt-resistant polyacrylamide; The mass fraction of the sodium hydroxide solution is 30%; The initiator is a combination of sodium persulfate and sodium bisulfite, wherein the weight ratio of sodium persulfate to sodium bisulfite is 2g:1g; The emulsifier is OP-10; The functional monomer is prepared by the following steps: Step A1: p-Hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone were mixed, stirred at a stirring rate of 120 rpm, at room temperature for 4 h, filtered with suction, the filter cake was washed with acetone, the filtrate was spin-dried, and recrystallized from ethanol to obtain intermediate 1; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid were mixed, stirred at a stirring rate of 120 rpm, at room temperature for 4 h, filtered with suction, and recrystallized from ethanol to obtain intermediate 2; The dosage ratio of p-hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone is 0.01 mol: 0.02 mol: 4.12 g: 30 mL; the intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are 1.6 g: 1.31 g: 20 mL: 0.8 mL; Step A2: Mono-6-O-(azido)-β-cyclodextrin, intermediate 2 and dimethyl sulfoxide solution were mixed, stirred at a stirring rate of 120 rpm and a temperature of 30° C., copper sulfate pentahydrate and sodium ascorbate were added, and the reaction was carried out for 20 hours. Dichloromethane and deionized water were then added, and the organic phase was collected and dried with anhydrous sodium sulfate, precipitated with ether, and freeze-dried to obtain a functional monomer; The volume ratio of dimethyl sulfoxide to deionized water in the dimethyl sulfoxide solution is 3:1, and the amount ratio of mono-6-O-(azido)-β-cyclodextrin, intermediate 2, dimethyl sulfoxide solution, copper sulfate pentahydrate and sodium ascorbate is 1.1 g: 0.35 g: 10 mL: 0.05 g: 0.1 g; The modified triblock polyrotaxane is prepared by the following steps: Step B1: polyethylene glycol, triethylamine, 4-dimethylaminopyridine and dichloromethane are mixed, and 2-bromoisobutyryl bromide is added under nitrogen protection, stirring at a rate of 180 rpm and a temperature of 0°C, and stirred for 40 minutes, then the temperature is raised to room temperature, and the reaction is continued for 24 hours, rotary evaporation, tetrahydrofuran dissolution, filtration, ether precipitation, filtration, and drying to obtain a macromolecular initiator; β-cyclodextrin, the macromolecular initiator and deionized water are mixed, and stirred at a stirring rate of 450 rpm and a temperature of room temperature for 36 hours, centrifuged, washed, and freeze-dried to obtain a polypseudorotaxane; The dosage ratio of polyethylene glycol, triethylamine, 4-dimethylaminopyridine, dichloromethane and 2-bromoisobutyryl bromide is 13 g: 0.42 mL: 0.52 g: 25 mL: 1 mL; the dosage ratio of β-cyclodextrin, macromolecular initiator and deionized water is 0.34 g: 0.4 g: 10 mL; Step B2: Mix polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 120 rpm and room temperature, add acrylamide and pentamethyldiethylenetriamine, stir for 10 min, then add copper iodide, pass nitrogen protection, react for 12 h, dialyze, and freeze-dry to obtain block polypseudorotaxane; Mix block polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 80 rpm and room temperature, add 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid and pentamethyldiethylenetriamine, stir for 15 min, then add copper iodide, pass nitrogen protection, react for 10 h, dialyze, and freeze-dry to obtain triblock polyrotaxane; The amount ratio of polypseudorotaxane, acetone, deionized water, acrylamide, pentamethylethylenediamine and copper iodide is 0.52g:5mL:7mL:0.2g:0.12g:0.06g; the amount ratio of block polypseudorotaxane, acetone, deionized water, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid, pentamethylethylenediamine and copper iodide is 0.34g:5mL:7mL:0.08g:0.064g:0.041g; Step B3: The triblock polyrotaxane and deionized water were mixed, stirred at a stirring rate of 60 rpm and room temperature, and sodium hydroxide solution was added to adjust the pH value to 11, and then glycidyl methacrylate was added at a temperature of 5°C, and the reaction was continued for 10 hours, dialyzed, and dried to obtain a modified triblock polyrotaxane; The molar concentration of the sodium hydroxide solution was 1 mol / L, and the amount ratio of the triblock polyrotaxane, deionized water, and glycidyl methacrylate was 1.4 g:50 mL:3.4 g.

[0013] Example 2 A method for preparing a graft-modified salt-resistant polyacrylamide comprises the following steps: Step S1: weigh the following raw materials in parts by weight: 70 parts of acrylamide, 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 20 parts of acrylic acid, 6 parts of functional monomers, 2 parts of modified triblock polyrotaxane, 0.4 parts of initiator, 0.8 parts of emulsifier, 350 parts of water and 15 parts of propylene glycol; Step S2: acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, functional monomer, modified triblock polyrotaxane, water and propylene glycol are mixed, stirred and an initiator and an emulsifier are added, and then a sodium hydroxide solution is added to adjust the pH value to 8, and the mixture is reacted for 10 hours at a stirring rate of 120 rpm and a temperature of 35° C., and then rotary evaporated and dried to obtain a grafted modified salt-resistant polyacrylamide; The mass fraction of the sodium hydroxide solution is 30%; The initiator is a combination of sodium persulfate and sodium bisulfite, wherein the weight ratio of sodium persulfate to sodium bisulfite is 2g:1g; The emulsifier is OP-10; The functional monomer is prepared by the following steps: Step A1: p-Hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone were mixed, stirred at a stirring rate of 120 rpm, at room temperature for 4 h, filtered with suction, the filter cake was washed with acetone, the filtrate was spin-dried, and recrystallized from ethanol to obtain intermediate 1; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid were mixed, stirred at a stirring rate of 140 rpm, at room temperature for 4 h, filtered with suction, and recrystallized from ethanol to obtain intermediate 2; The dosage ratio of p-hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone is 0.011 mol: 0.022 mol: 4.12 g: 35 mL; the intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are 1.6 g: 1.31 g: 20 mL: 1.2 mL; Step A2: Mono-6-O-(azido)-β-cyclodextrin, intermediate 2 and dimethyl sulfoxide solution were mixed, stirred at a stirring rate of 140 rpm and a temperature of 30° C., copper sulfate pentahydrate and sodium ascorbate were added, and the reaction was carried out for 24 hours. Dichloromethane and deionized water were then added, and the organic phase was collected and dried with anhydrous sodium sulfate, precipitated with ether, and freeze-dried to obtain a functional monomer; The volume ratio of dimethyl sulfoxide to deionized water in the dimethyl sulfoxide solution is 3:1, and the amount ratio of mono-6-O-(azido)-β-cyclodextrin, intermediate 2, dimethyl sulfoxide solution, copper sulfate pentahydrate and sodium ascorbate is 1.1 g: 0.36 g: 10 mL: 0.05 g: 0.1 g; The modified triblock polyrotaxane is prepared by the following steps: Step B1: polyethylene glycol, triethylamine, 4-dimethylaminopyridine and dichloromethane are mixed, and 2-bromoisobutyryl bromide is added under nitrogen protection, stirring at a rate of 140 rpm and a temperature of 5°C, and stirred for 30 minutes, then the temperature is raised to room temperature, and the reaction is continued for 24 hours, rotary evaporation, tetrahydrofuran dissolution, filtration, ether precipitation, filtration, and drying to obtain a macromolecular initiator; β-cyclodextrin, the macromolecular initiator and deionized water are mixed, and stirred at a stirring rate of 450 rpm and a temperature of room temperature for 36 hours, centrifuged, washed, and freeze-dried to obtain a polypseudorotaxane; The dosage ratio of polyethylene glycol, triethylamine, 4-dimethylaminopyridine, dichloromethane and 2-bromoisobutyryl bromide is 12g:0.42mL:0.49g:20mL:1mL; the dosage ratio of β-cyclodextrin, macromolecular initiator and deionized water is 0.34g:0.35g:10mL; Step B2: Mix polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 80 rpm and room temperature, add acrylamide and pentamethyldiethylenetriamine, stir for 10 minutes, then add copper iodide, pass nitrogen protection, react for 10 hours, dialyze, and freeze-dry to obtain block polypseudorotaxane; Mix block polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 80 rpm and room temperature, add 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid and pentamethyldiethylenetriamine, stir for 10 minutes, then add copper iodide, pass nitrogen protection, react for 10 hours, dialyze, and freeze-dry to obtain triblock polyrotaxane; The amount ratio of polypseudorotaxane, acetone, deionized water, acrylamide, pentamethylethylenediamine and copper iodide is 0.48g:5mL:5mL:0.2g:0.1g:0.06g; the amount ratio of block polypseudorotaxane, acetone, deionized water, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid, pentamethylethylenediamine and copper iodide is 0.32g:5mL:5mL:0.08g:0.062g:0.041g; Step B3: The triblock polyrotaxane and deionized water were mixed, stirred at a stirring rate of 60 rpm and room temperature, and sodium hydroxide solution was added to adjust the pH value to 11, and then glycidyl methacrylate was added at a temperature of 2°C, and the reaction was continued for 10 hours, dialyzed, and dried to obtain a modified triblock polyrotaxane; The molar concentration of the sodium hydroxide solution is 1 mol / L, and the amount ratio of the triblock polyrotaxane, deionized water and glycidyl methacrylate is 1.2 g:40 mL:3.4 g.

[0014] Example 3 A method for preparing a graft-modified salt-resistant polyacrylamide comprises the following steps: Step S1: weigh the following raw materials in parts by weight: 70 parts of acrylamide, 15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 20 parts of acrylic acid, 6 parts of functional monomers, 3 parts of modified triblock polyrotaxane, 0.6 parts of initiator, 1 part of emulsifier, 350 parts of water and 20 parts of propylene glycol; Step S2: acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, functional monomer, modified triblock polyrotaxane, water and propylene glycol are mixed, stirred and an initiator and an emulsifier are added, and then a sodium hydroxide solution is added to adjust the pH value to 8, and the mixture is reacted for 12 hours at a stirring rate of 140 rpm and a temperature of 40° C., and then rotary evaporated and dried to obtain a grafted modified salt-resistant polyacrylamide; The mass fraction of the sodium hydroxide solution is 30%; The initiator is a combination of sodium persulfate and sodium bisulfite, wherein the weight ratio of sodium persulfate to sodium bisulfite is 2g:1g; The emulsifier is OP-10; The functional monomer is prepared by the following steps: Step A1: p-Hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone were mixed, stirred at a stirring rate of 140 rpm, at room temperature for 6 h, filtered with suction, the filter cake was washed with acetone, the filtrate was spin-dried, and recrystallized from ethanol to obtain intermediate 1; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid were mixed, stirred at a stirring rate of 140 rpm, at room temperature for 6 h, filtered with suction, and recrystallized from ethanol to obtain intermediate 2; The dosage ratio of p-hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone is 0.011 mol: 0.022 mol: 4.15 g: 35 mL; the intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are 1.65 g: 1.32 g: 20 mL: 1.2 mL; Step A2: Mono-6-O-(azido)-β-cyclodextrin, intermediate 2 and dimethyl sulfoxide solution were mixed, stirred at a stirring rate of 140 rpm and a temperature of 35° C., copper sulfate pentahydrate and sodium ascorbate were added, and the reaction was carried out for 24 hours. Dichloromethane and deionized water were then added, and the organic phase was collected and dried with anhydrous sodium sulfate, precipitated with ether, and freeze-dried to obtain a functional monomer; The volume ratio of dimethyl sulfoxide to deionized water in the dimethyl sulfoxide solution is 3:1, and the amount ratio of mono-6-O-(azido)-β-cyclodextrin, intermediate 2, dimethyl sulfoxide solution, copper sulfate pentahydrate and sodium ascorbate is 1.15 g: 0.36 g: 12 mL: 0.06 g: 0.1 g; The modified triblock polyrotaxane is prepared by the following steps: Step B1: polyethylene glycol, triethylamine, 4-dimethylaminopyridine and dichloromethane are mixed, and 2-bromoisobutyryl bromide is added under nitrogen protection, stirring at a rate of 180 rpm and a temperature of 2°C, and stirred for 40 minutes, then the temperature is raised to room temperature, and the reaction is continued for 24 hours, rotary evaporation, tetrahydrofuran dissolution, filtration, ether precipitation, filtration, and drying to obtain a macromolecular initiator; β-cyclodextrin, the macromolecular initiator and deionized water are mixed, and stirred at a stirring rate of 500 rpm and a temperature of room temperature for 36 hours, centrifuged, washed, and freeze-dried to obtain a polypseudorotaxane; The dosage ratio of polyethylene glycol, triethylamine, 4-dimethylaminopyridine, dichloromethane and 2-bromoisobutyryl bromide is 13 g: 0.45 mL: 0.52 g: 25 mL: 1.2 mL; the dosage ratio of β-cyclodextrin, macromolecular initiator and deionized water is 0.35 g: 0.4 g: 15 mL; Step B2: Mix polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 120 rpm, and add acrylamide and pentamethyldiethylenetriamine, stir for 15 minutes, then add copper iodide, pass nitrogen protection, react for 12 hours, dialyze, and freeze-dry to obtain block polypseudorotaxane; Mix block polypseudorotaxane, acetone and deionized water, stir at a stirring rate of 120 rpm, and add 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid and pentamethyldiethylenetriamine, stir for 15 minutes, then add copper iodide, pass nitrogen protection, react for 12 hours, dialyze, and freeze-dry to obtain triblock polyrotaxane; The amount ratio of polypseudorotaxane, acetone, deionized water, acrylamide, pentamethylethylenediamine and copper iodide is 0.52g:7mL:7mL:0.24g:0.12g:0.07g; the amount ratio of block polypseudorotaxane, acetone, deionized water, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid, pentamethylethylenediamine and copper iodide is 0.34g:7mL:7mL:0.09g:0.064g:0.043g; Step B3: The triblock polyrotaxane and deionized water were mixed, stirred at a stirring rate of 80 rpm and room temperature, and sodium hydroxide solution was added to adjust the pH value to 11, and then glycidyl methacrylate was added at a temperature of 5°C, and the reaction was continued for 12 hours, dialyzed, and dried to obtain a modified triblock polyrotaxane; The molar concentration of the sodium hydroxide solution is 1 mol / L, and the amount ratio of the triblock polyrotaxane, deionized water and glycidyl methacrylate is 1.4 g:50 mL:3.5 g.

[0015] Comparative Example 1 Compared with Example 3, this comparative example is to remove the functional monomer in the preparation process of the graft-modified salt-resistant polyacrylamide in Example 3, and the other steps are the same.

[0016] Comparative Example 2 Compared with Example 3, this comparative example is different in that the modified triblock polyrotaxane in the preparation process of the graft-modified salt-tolerant polyacrylamide in Example 3 is replaced by the triblock polyrotaxane in Example 3, and the other steps are the same.

[0017] Take the grafted modified salt-resistant polyacrylamide prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2, mix 1.2 g of the grafted modified salt-resistant polyacrylamide with 100 mL of deionized water, and heat at a temperature of 25 ° C and a shear rate of 7.5 s -1 Under the conditions, the apparent viscosity was tested, recorded as the initial apparent viscosity, and then aged for 2 hours at 80°C, left to stand for 20 minutes, and then aged at 25°C and a shear rate of 7.5s -1 The apparent viscosity is tested under the conditions, recorded as the apparent viscosity after heat aging, and the heat aging viscosity retention rate is calculated. The calculation formula is: heat aging viscosity retention rate = apparent viscosity after heat aging / initial apparent viscosity × 100%; Replace 100 mL of deionized water with simulated mineralized water, repeat the above process, measure the apparent viscosity after heat aging, record it as the apparent viscosity after heat aging in brine, calculate its heat aging viscosity retention rate in brine, the calculation formula is: heat aging viscosity retention rate in brine = apparent viscosity after heat aging in brine / initial apparent viscosity × 100%, the sodium ion concentration in the simulated mineralized water is 3.2 g / L, the calcium ion concentration is 0.25 g / L, and the magnesium ion concentration is 0.25 g / L; In saline, at 80°C, at a shear rate of 160s -1 Continue shearing for 20 minutes, then 7.5 seconds -1 Continue shearing for 20 minutes, repeat the above shearing process three times, measure the apparent viscosity after shearing, and calculate the viscosity retention rate after shearing. The calculation formula is: Viscosity retention rate after shearing = apparent viscosity after shearing / initial apparent viscosity × 100%. The test results are as follows: Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Thermal aging viscosity retention rate (%) 85.99 86.12 86.25 73.65 70.31 Thermal aging viscosity retention rate in salt water (%) 82.17 82.15 82.39 67.34 65.56 Viscosity retention after shearing (%) 74.16 75.26 75.42 60.44 51.41 It can be seen from the test results in the table shown that when Example 1, Example 2 and Example 3 are compared with Comparative Example 1 and Comparative Example 2, Comparative Example 1 removes the functional monomer in the preparation process of the grafted modified salt-resistant polyacrylamide in Example 3. Due to the lack of cyclodextrin structure, thiourea structure and triazole structure, its host-guest binding and hydrogen bonding effect are reduced, thereby causing its performance to decline; Comparative Example 2 replaces the modified triblock polyrotaxane in the preparation process of the grafted modified salt-resistant polyacrylamide in Example 3 with the triblock polyrotaxane in Example 3. Due to the lack of double bond modification, its polyacrylamide is grafted on the polyrotaxane structure, thereby causing its performance to decline significantly.

[0018] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0019] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a graft-modified salt-resistant polyacrylamide, characterized in that: The method comprises the following steps: Step S1: weighing the following raw materials in parts by weight: 60-70 parts of acrylamide, 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 18-20 parts of acrylic acid, 3-6 parts of functional monomers, 2-3 parts of modified triblock polyrotaxane, 0.4-0.6 parts of initiator, 0.8-1 parts of emulsifier, 300-350 parts of water and 15-20 parts of propylene glycol; Step S2: acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, functional monomer, modified triblock polyrotaxane, water and propylene glycol are mixed, stirred and an initiator and an emulsifier are added, and then a sodium hydroxide solution is added to adjust the pH value to 8, and the mixture is reacted for 10-12 hours at a stirring rate of 120-140 rpm and a temperature of 35-40° C., rotary evaporated and dried to obtain a grafted modified salt-resistant polyacrylamide; The functional monomer is prepared by the following steps: Step A1: p-Hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone are mixed, stirred at a stirring rate of 120-140 rpm, at room temperature, stirred for 4-6 hours, filtered with suction, the filter cake is washed with acetone, the filtrate is spin-dried, and recrystallized from ethanol to obtain intermediate 1; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid are mixed, stirred at a stirring rate of 120-140 rpm, at room temperature, stirred for 4-6 hours, filtered with suction, and recrystallized from ethanol to obtain intermediate 2; Step A2: Mix mono-6-O-(azido)-β-cyclodextrin, intermediate 2 and dimethyl sulfoxide solution, stir and add copper sulfate pentahydrate and sodium ascorbate at a stirring rate of 120-140 rpm and a temperature of 30-35°C, react for 20-24 hours, then add dichloromethane and deionized water, collect the organic phase and dry it with anhydrous sodium sulfate, precipitate with ether, and freeze-dry to obtain a functional monomer.

2. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 1, characterized in that: In the preparation process of graft modified salt-resistant polyacrylamide: the mass fraction of the sodium hydroxide solution is 30%; The initiator is a combination of sodium persulfate and sodium bisulfite, wherein the weight ratio of sodium persulfate to sodium bisulfite is 2g:1g; The emulsifier is OP-10.

3. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 1, characterized in that: In step A1: the dosage ratio of p-hydroxybenzaldehyde, 3-bromopropyne, anhydrous potassium carbonate and acetone is 0.01-0.011 mol: 0.02-0.022 mol: 4.12-4.15 g: 30-35 mL; intermediate 1, 4-propenylthiosemicarbazide, ethanol and acetic acid 1.6-1.65 g: 1.31-1.32 g: 20 mL: 0.8-1.2 mL.

4. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 1, characterized in that: In step A2: the volume ratio of dimethyl sulfoxide and deionized water in the dimethyl sulfoxide solution is 3:1, and the dosage ratio of mono-6-O-(azido)-β-cyclodextrin, intermediate 2, dimethyl sulfoxide solution, copper sulfate pentahydrate and sodium ascorbate is 1.1-1.15 g: 0.35-0.36 g: 10-12 mL: 0.05-0.06 g: 0.1 g.

5. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 1, characterized in that: The modified triblock polyrotaxane is prepared by the following steps: Step B1: polyethylene glycol, triethylamine, 4-dimethylaminopyridine and dichloromethane are mixed, and 2-bromoisobutyryl bromide is added under nitrogen protection, stirring at a rate of 140-180 rpm and a temperature of 0-5°C, and stirred for 30-40 minutes, then heated to room temperature, and the reaction is continued for 24 hours, rotary evaporation, tetrahydrofuran dissolution, filtration, ether precipitation, filtration, and drying to obtain a macromolecular initiator; β-cyclodextrin, the macromolecular initiator and deionized water are mixed, and stirred for 36 hours at a stirring rate of 450-500 rpm and a temperature of room temperature, centrifuged, washed, and freeze-dried to obtain a polypseudorotaxane; Step B2: Mix polypseudorotaxane, acetone and deionized water, stir at a rate of 80-120 rpm, add acrylamide and pentamethyldiethylenetriamine, stir for 10-15 min, add copper iodide, pass nitrogen protection, react for 10-12 h, dialyze, and freeze-dry to obtain a block polypseudorotaxane; Mix block polypseudorotaxane, acetone and deionized water, stir at a rate of 80-120 rpm, add 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid and pentamethyldiethylenetriamine, stir for 10-15 min, add copper iodide, pass nitrogen protection, react for 10-12 h, dialyze, and freeze-dry to obtain a triblock polyrotaxane; Step B3: Mix the triblock polyrotaxane and deionized water, stir and add sodium hydroxide solution at a stirring rate of 60-80 rpm and room temperature, adjust the pH value to 11, then stir and add glycidyl methacrylate at a temperature of 2-5°C, continue the reaction for 10-12 hours, dialyze, and dry to obtain a modified triblock polyrotaxane.

6. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 5, characterized in that: In step B1, the dosage ratio of polyethylene glycol, triethylamine, 4-dimethylaminopyridine, dichloromethane and 2-bromoisobutyryl bromide is 12-13 g: 0.42-0.45 mL: 0.49-0.52 g: 20-25 mL: 1-1.2 mL; the dosage ratio of β-cyclodextrin, macromolecular initiator and deionized water is 0.34-0.35 g: 0.35-0.4 g: 10-15 mL.

7. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 5, characterized in that: In step B2: the amount ratio of polypseudorotaxane, acetone, deionized water, acrylamide, pentamethylethylenediamine and copper iodide is 0.48-0.52g: 5-7mL: 5-7mL: 0.2-0.24g: 0.1-0.12g: 0.06-0.07g; the amount ratio of block polypseudorotaxane, acetone, deionized water, 2-methyl-6-[4-(2-phenyldiazo)phenoxy]hexyl ester-2-propenoic acid, pentamethylethylenediamine and copper iodide is 0.32-0.34g: 5-7mL: 5-7mL: 0.08-0.09g: 0.062-0.064g: 0.041-0.043g.

8. The method for preparing a graft-modified salt-resistant polyacrylamide according to claim 5, characterized in that: In step B3: the molar concentration of the sodium hydroxide solution is 1 mol / L, and the amount ratio of the triblock polyrotaxane, deionized water and glycidyl methacrylate is 1.2-1.4 g: 40-50 mL: 3.4-3.5 g.