CN101225148A - A kind of synthetic method of allyl polyether type high performance water reducing agent - Google Patents

Abstract

A method for synthesizing an allyl polyether type high-efficiency water reducer belongs to the field of water reducers. The present invention uses allyl polyoxyethylene ether monomer, maleic anhydride monomer, sodium (meth) allylsulfonate, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, acrylic acid and propylene A mixture of one or several amides, an allyl polyether type high-efficiency water reducer obtained by one-step polymerization initiated by an inorganic peroxide in an aqueous solution system. The final structure of the water reducer does not contain ester bonds, but contains ether bonds, Carboxyl, amide, sulfonic acid and other functional groups, this product is used in various cement and concrete projects. The invention is simple, the process is easy to control, and has no pollution; it solves the disadvantage of low polymerization activity of allyl polyether monomers, and solves the ubiquitous low-temperature crystallization problem of allyl polyether type high-performance water reducers; Higher dispersion and higher retention can be obtained at low dosage; especially in the case of extremely low water-cement ratio, it has better dispersion performance.

Description

A kind of synthetic method of allyl polyether type high performance water reducing agent

technical field

The invention relates to the technical category of preparing a high-performance water reducer for concrete, in particular to a specific synthesis method of an allyl polyether type water reducer.

Background technique

In recent years, with the continuous increase of my country's investment in infrastructure construction, the development of the domestic construction industry is also changing with each passing day, and the demand for concrete superplasticizers is also increasing year by year. Faced with the real problem of high-efficiency superplasticizer foreign raw materials being expensive, the domestic raw material market has been established and is becoming more and more mature. Therefore, my country's construction industry urgently needs high-efficiency water reducer technology and products that adapt to the domestic market and high-performance concrete technology and fully realize the localization of raw materials.

Most of the traditional polycarboxylate superplasticizers use imported methoxypolyoxyethylene ether as the main raw material, and a two-step method is used to synthesize the superplasticizer. The first step of reaction is to generate polymerizable structural units or "building blocks", and the second step of reaction is to generate a certain performance polymer water reducer through condensation or addition polymerization. There are also a small number of patents that use allyl polyoxyethylene ether as a monomer to synthesize high-efficiency water reducers by bulk polymerization.

Patent CN1412175 introduces a high-efficiency water reducer synthesized by using allyl polyoxyethylene ether as a monomer, esterification in the environment of no solvent but the presence of antioxidants, and post-polymerization. Although this patent also uses allyl ether as a synthetic monomer, it is still esterified, the process is cumbersome and the structure is complex;

The patent CN1096774 introduces that in a four-necked flask equipped with a stirring and temperature regulating device, an alkenyl ether (such as: 20 methallyl polyglycol ether, methallyl alcohol with a molar number of 33 Ethylene oxide) 573.0g, Dialkenyl ether (polyoxyethylene diallyl ether, obtained by adding 33 moles of ethylene oxide to allyl alcohol, then adding allyl alcohol to etherification) 55.5g , maleic anhydride 43.9g, benzoyl peroxide 4.5g and toluene 104.8g mixture solution, after installing condenser, N2 gas introduction pipe, thermometer, raise the temperature of the flask to 80～90 ℃, simultaneously in N2 gas atmosphere Stir continuously at 100°C for 7 hours. After the reaction is completed, the temperature is raised, and the toluene is distilled off under reduced pressure at 110° C. under a pressure of about 10 mmHg to obtain a brown copolymer that is solid at room temperature. This admixture is synthesized in an organic solvent, neutralized with lye, diluted to a solution with a solid content of 40%, and can be compounded with naphthalene-based or polycarboxylic acid-based water reducers to make concrete slump It has excellent strength retention performance without affecting the setting and hardening of cement. This method adopts the organic solvent toluene as the reaction medium, the toluene must be recovered after the reaction is completed, the process is complicated, the environment is polluted, and it is not easy to produce on a large scale;

Patent USP5925184 uses short-chain methoxy polyethylene glycol methacrylate (n=4) and long-chain polyethylene glycol methacrylate (n=23) and three monomers such as methacrylic acid to directly copolymerize , synthesized a kind of acrylic water reducer with better slump retention performance and also suitable for sulphoaluminate expansion agent. Put 500 parts of water into the glass reaction vessel of tube and reflux condenser, pass N2 under stirring to remove O2, heat to 80°C under the protection of N2, then drop and mix 350 parts of long chain and 50 parts of short chain within 4 hours Chain, 100 parts of methacrylic acid, 150 parts of water and 2.8 parts of chain transfer agent 3-mercaptopropionic acid monomer aqueous solution, after 40 parts of 10% ammonium persulfate solution is dripped, continue to add dropwise ammonium persulfate aqueous solution within 1 hour, An aqueous polymer solution having a weight average molecular weight of 22,000 was obtained. The active macromonomer used in this invention is methacrylate, and the obtained water reducer is a polyester high-performance water reducer different from the present invention.

Patent CN1847187A discloses a polymerization product obtained by using allyl polyoxyethylene ether or methoxypolyethylene glycol ether as a raw material and using a redox system as an initiator. Add AE, deionized water, and 27% hydrogen peroxide into the four-neck flask, raise the temperature to 50°C, and simultaneously add maleic anhydride, sodium styrene sulfonate aqueous solution and sodium formaldehyde sulfoxylate solution dropwise. The dropping time is controlled at about 90 minutes, and the reaction temperature is 48-52°C. After the dropwise addition, keep warm for 0.5h, and neutralize with 30% sodium hydroxide to about Ph=6.5. This patent uses a redox system as initiation, which is different from the present invention.

The preparation of polycarboxylate water reducers described in most patents requires the synthesis of macromonomers as the first step in the synthesis of water reducers. A macromonomer polymer containing unsaturated double bonds is formed by esterifying or acylating monomers containing polyoxyethylene chains with monomers containing double bonds such as acrylic acid and maleic acid. Then use this esterified product or acylated product as the reaction raw material, polymerize with carboxylic acid containing double bond, and introduce a series of groups that are beneficial to water reduction, such as carboxyl group and sulfonic acid group, in its structure, thereby synthesizing water reducing agent. In our country, this kind of water reducer synthesis method is more popular, and the synthesis of macromonomer affects the performance and quality of water reducer. The synthesis process of macromonomers is complex and difficult to finely control. The overall polycarboxylate high-efficiency water reducer technology has problems such as cumbersome synthesis process, long production cycle, high cost, part of the process does not meet environmental protection requirements, and poor product performance.

Contents of the invention

The present invention proposes a new synthetic method of allyl polyether water reducer, which is characterized in that: using unsaturated allyl polyethylene glycol monomer, and maleic anhydride and (methyl) Sodium allyl sulfonate, 2-acrylamide-2-methylpropane sulfonic acid, itaconic acid, acrylic acid and acrylamide one or more of the mixture, in aqueous solution, using a specific one-step synthesis process, And the high molecular polymer obtained by adjusting the activity of the reaction system by pretreating maleic anhydride and initiating polymerization through ammonium persulfate. The structure of the polyether water reducer obtained by the synthesis method does not contain ester bonds, but contains ether bonds and functional groups such as carboxyl groups, amido groups, and sulfonic acid groups; effectively solves the problem of complex preparation process of polycarboxylate water reducers and high cost. Long production cycle and other issues.

The main operation method of the specific one-step synthesis process adopted in the synthesis of allyl polyether superplasticizer in the present invention is as follows: the temperature of the reaction kettle is raised to 40-60°C, and the unsaturated allyl polyethylene glycol monomer Add the pretreated maleic anhydride aqueous solution into the reaction kettle, and then raise the temperature to 70-90°C to add (meth)allyl sodium sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, The aqueous solution of one or more mixtures of itaconic acid, acrylic acid and acrylamide is added dropwise into the reaction kettle, and the monomer addition time is 45-180 minutes;

Or raise the temperature of the reactor to 40-60°C, put the pretreated aqueous solution of maleic anhydride in the reactor, and then add sodium (meth)allylsulfonate, 2-acrylamide-2-methyl Mix the aqueous solution of one or more mixtures of propanesulfonic acid, itaconic acid, acrylic acid and acrylamide with unsaturated allyl polyethylene glycol monomer, raise the temperature to 70-90°C, and add the mixed monomer dropwise , the dropping time is 45-180 minutes;

While the monomer is being added dropwise, the ammonium persulfate initiator aqueous solution accounting for 70% to 80% of the total mass of the initiator solution is dropped into the kettle in the form of dropwise addition. The time for adding the ammonium persulfate initiator solution is 45 to 180 minutes. Block the reaction for 1 to 2 hours, add the remaining mass of 30% to 20% ammonium persulfate initiator solution, keep the temperature and block the reaction for 30 to 60 minutes, then cool naturally, when the temperature drops below 55°C, use NaOH solution to adjust the pH of the synthetic solution = 6.5±0.5, to obtain the allyl ether concrete high-efficiency water reducer with a mass percentage concentration of 38% to 52%; the concentration can be adjusted according to the water volume;

The above-mentioned maleic anhydride pretreatment method is: using a sodium hydroxide solution with a mass percent concentration of 30-50% to adjust the neutralization degree, and the neutralization degree after the pretreatment reaches 0.2-0.5;

Wherein the molar ratio of maleic anhydride to unsaturated allyl polyethylene glycol monomer is 1.5～4:1, and the molar ratio of ammonium persulfate initiator consumption to unsaturated allyl polyethylene glycol monomer is 0.09～0.45: 1; One or more of sodium (meth)allyl sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, acrylic acid and acrylamide mixed with unsaturated allyl polyethylene glycol The alcohol monomer molar ratio is 0.3-0.7:1.

The key of the invention lies in: using allyl polyethylene glycol as a monomer raw material, adjusting the activity of the reaction system by pretreating maleic anhydride, and adopting a one-step synthesis method. Among them, the concept of "one-step synthesis method" refers to: using the product directly obtained from the ring-opening reaction of ethylene oxide as the basic macromonomer to directly carry out the polymerization reaction. The product obtained by this method is sent to China Metrology Institute for measurement by a DAWN EOS type multi-angle laser light scattering instrument produced by U.S. wyatt company, and the weight average molecular weight obtained is 4000～100000, and the number average molecular weight is 3000～80000.

The unsaturated allyl polyethylene glycol represented by the general formula (a) of the water reducing agent is used as the main reactive monomer, and maleic anhydride, and sodium meth)allyl sulfonate, 2-acrylamide-2 - A mixture of one or more of methylpropanesulfonic acid, itaconic acid, acrylic acid and acrylamide, in an aqueous solution, using a specific one-step synthesis process, a high molecular polymer obtained by polymerization initiated by an inorganic peroxide . The branched structure of the water reducer does not contain ester bonds, but contains ether bonds and functional groups such as carboxyl, amide, and sulfonic acid groups.

H ₂ C=CH-CH ₂ O-CH ₂ -CH ₂  _n OH (a)

n=18, 23, 45

Effect of the present invention:

1. The synthesis adopts a one-step method. The raw material is allyl polyethylene glycol, and the structure contains unsaturated double bonds. The synthesis process avoids the esterification step in the traditional process and avoids high temperature reaction. The aqueous solution polymerization method is adopted, and the operation is simple and convenient, which is beneficial to the implementation of industrial production.

2. In the synthetic method, a pretreatment method is adopted to improve the activity of the reaction system. The unsaturated allyl polyethylene glycol monomer (a) has special activity and is difficult to copolymerize with other monomers. By pretreating maleic anhydride, the polymerization activity of the reaction system is improved, and the method for preparing a high-efficiency water reducer by one-step polymerization is realized. The state of the obtained water reducer product is stable, it does not crystallize when stored at low temperature, and its performance is not affected after low temperature storage.

3. The synthesis method belongs to clean production process. The reaction raw materials are non-polluting, and the reaction process does not require nitrogen protection, avoiding the complicated operation of filling nitrogen and discharging air, reflecting the safety, environmental protection and cleanliness of the whole process.

4. The structure of the polyether water reducer obtained by this synthesis method does not contain ester bonds, but contains ether bonds and functional groups such as carboxyl, amide, and sulfonic acid groups that can provide higher dispersion and retention effects.

5. The water reducing agent synthesized by this method has excellent performance, the reduced solid content is 0.25%, the W/C=0.29, the loss of the cement paste after 2 hours is small, and it is suitable for different manufacturers of cement. In the case of extremely low water-cement ratio W/C=0.20～0.23, when the same dosage as other domestic water reducers, the clean slurry can still maintain a high dispersion performance; it has better working performance when used in the field of concrete.

Detailed ways

"Parts" mentioned in the following examples all refer to mole fractions:

Example 1

Add 16 parts of water to the reaction vessel equipped with stirring, condensation, and effluent reflux. When the temperature is at 40°C, add 1.5 parts of maleic anhydride, and add 0.3 parts of sodium hydroxide solution with a mass percentage concentration of 50%. Perform pre-neutralization. Dissolve 0.25 parts of acrylic acid, 0.05 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 1 part of allyl polyethylene glycol ether (n=18) into 25 parts of water in sequence, and stir well to form a light yellow transparent Monomer mixed solution. Dissolve 0.063 parts of ammonium persulfate in 35 parts of water, raise the temperature to 70°C, and add the monomer mixed solution and initiator aqueous solution dropwise, respectively. The monomer mixed solution was added dropwise in 45 minutes, and the initiator aqueous solution was added dropwise in 60 minutes. Keep the blocking reaction at 70°C for 1 hour. Dissolve 0.027 parts of ammonium persulfate into 15 parts of water, stir evenly, add to the kettle, and seal the reaction at constant temperature for 1 hour. Cool naturally to 50° C., and add NaOH with a concentration of 30% to adjust the pH of the solution to 6.0. The obtained polycarboxylate superplasticizer product 1 is a brownish-yellow transparent liquid with a concentration of 38%.

Example 2

Add 13.4 parts of water to the reaction vessel equipped with stirring, condensation, and effluent reflux, add 2 parts of maleic anhydride at a temperature of 45°C, add 1 part of sodium hydroxide solution with a mass percentage concentration of 30%, and pre-neutralize the maleic anhydride. and processing. 1 part of allyl polyglycol ether (n=23) was added. Dissolve 0.15 parts of acrylic acid, 0.15 parts of acrylamide, and 0.05 parts of sodium (meth)allyl sulfonate into 22.3 parts of water, and stir evenly to obtain a transparent solution. Dissolve 0.147 parts of ammonium persulfate in 46.7 parts of water, raise the temperature to 80°C, and add the monomer solution and the aqueous initiator solution dropwise, respectively. The monomer mixed solution was added dropwise in 90 minutes, and the initiator aqueous solution was added dropwise in 90 minutes. Keep at 80°C to block the reaction for 2 hours. Dissolve 0.063 parts of ammonium persulfate into 20 parts of water, stir evenly, add to the kettle, and keep the reaction at constant temperature for 1 hour. Naturally cool to 50°C, add 30% NaOH to adjust the pH of the solution to 6.5. The obtained polycarboxylate superplasticizer product 2 is a brownish-yellow transparent liquid with a concentration of 40%.

Example 3

Add 8.9 parts of water to the reaction vessel equipped with stirring, condensation, and effluent reflux. When the temperature is at 50°C, add 3.5 parts of maleic anhydride, and add 1.2 parts of sodium hydroxide solution with a mass percentage concentration of 50%. Anhydrides are pre-neutralized. Dissolve 0.5 parts of acrylic acid, 0.05 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 1 part of allyl polyglycol ether (n=45) into 15.6 parts of water in sequence, and stir well to form a light yellow transparent Monomer mixed solution. Dissolve 0.13 parts of ammonium persulfate in 31.2 parts of water, raise the temperature to 85°C, and add the monomer mixed solution and initiator aqueous solution dropwise, respectively. The monomer mixed solution was added dropwise in 150 minutes, and the initiator aqueous solution was added dropwise in 180 minutes. Keep the blocking reaction at 85°C for 1 hour. Dissolve 0.06 parts of ammonium persulfate into 13.4 parts of water, stir evenly, add to the kettle, and keep the reaction at constant temperature for 1 hour. Cool naturally to 55°C, add 30% NaOH to adjust the pH of the solution to 6.5. Prepared polycarboxylate superplasticizer product 3, brownish-yellow translucent liquid, concentration 48%

Example 4

Add 8.9 parts of water to the reaction vessel equipped with stirring, condensation, and effluent reflux. When the temperature is at 50°C, add 3.5 parts of maleic anhydride, add 1.2 parts of sodium hydroxide solution with a concentration of 50% by mass percentage, and perform the reaction on maleic anhydride. Pre-neutralization. 1 part of allyl polyglycol ether (n=45) was added. Dissolve 0.5 parts of acrylic acid and 0.05 parts of 2-acrylamide-2-methylpropanesulfonic acid into 15.6 parts of water in sequence, and stir well to form a light yellow transparent monomer mixed solution. Dissolve 0.13 parts of ammonium persulfate in 31.2 parts of water, raise the temperature to 85°C, and add the monomer mixed solution and initiator aqueous solution dropwise, respectively. The monomer mixed solution was added dropwise in 150 minutes, and the initiator aqueous solution was added dropwise in 180 minutes. Keep the blocking reaction at 85°C for 1 hour. Dissolve 0.06 parts of ammonium persulfate into 13.4 parts of water, stir evenly, add to the kettle, and keep the reaction at constant temperature for 1 hour. Cool naturally to 55°C, add 30% NaOH to adjust the pH of the solution to 7.0. Prepared polycarboxylate superplasticizer product 4, brownish yellow translucent liquid concentration 48%

Example 5

Add 22.3 parts of water to the reaction vessel equipped with stirring, condensation, and effluent reflux, add 4 parts of maleic anhydride at a temperature of 60°C, add 2 parts of 50% sodium hydroxide solution by mass percentage, and pre-neutralize the maleic anhydride. and processing. Add 1 part of M2000 allyl polyglycol ether (n=45). Dissolve 0.5 parts of acrylic acid, 0.15 parts of itaconic acid, and 0.05 parts of 2-acrylamide-2-methylpropanesulfonic acid into 42.3 parts of water in sequence, and stir well to form a colorless and transparent monomer mixed solution. Dissolve 0.315 parts of initiator in 46 parts of water, raise the temperature to 90°C, and separate the low-valent monomer mixed solution and the aqueous initiator solution. The monomer mixed solution was added dropwise in 180 minutes, and the initiator aqueous solution was added dropwise in 180 minutes. Keep the blocking reaction at 90°C for 1 hour. Dissolve 0.135 parts of initiator into 20 parts of water, stir evenly, add into the kettle, and keep the reaction at constant temperature for 0.5 hours. Naturally cool to 54°C, add 30% NaOH to adjust the pH of the solution to 7.0. The obtained polycarboxylate superplasticizer product 5 is a brownish-yellow turbid liquid with a concentration of 52%.

Implementation Effect

1. Fluidity of pulp

In order to compare the plasticizing effects of water reducing agents on different cements, the fluidity of the following water reducing agents on different cement varieties under the same dosage was tested. The test is carried out according to GB/T8077-2000 "Test Method for Homogeneity of Concrete Admixtures", W/C=0.29, and the dosage is the reduced-solid dosage. The test results are shown in Table 1:

Table 1 Flow performance results of different cement pastes

cement type Converted volume (%) Type of superplasticizer Initial fluidity and retention value of clean pulp (mm) 0min 30min 60min 90min 120min JZ cement 0.20 Example 1 280 260 240 240 235 0.20 Example 2 263 260 260 255 240 0.20 Example 3 275 270 270 267 255 0.20 Example 4 275 270 270 270 270 0.20 Example 5 266 265 265 255 245 JD Cement 0.23 Example 1 250 242 238 230 220 0.23 Example 2 265 256 245 240 240

0.23 Example 3 270 260 253 250 245 0.23 Example 4 265 260 255 256 255 0.23 Example 5 280 260 253 248 245 LLH cement 0.23 Example 1 170 200 210 215 220 0.23 Example 2 180 210 230 230 230 0.23 Example 3 190 240 245 251 250 0.23 Example 4 190 250 260 265 270 0.23 Example 5 180 230 230 235 240 HL cement 0.24 Example 1 220 210 212 210 208 0.24 Example 2 215 208 207 205 204 0.24 Example 3 225 220 210 208 212 0.24 Example 4 235 230 230 225 225 0.24 Example 5 210 200 198 200 195

2. Low water-cement ratio net fluidity

The most important feature of this product is that it can still maintain a high dispersibility when it is mixed with other domestic superplasticizers at the very low water-cement ratio W/C=0.20~0.23. The test was carried out in accordance with GB/T8077-2000 "Concrete Admixture Homogeneity Test Method", and different series and different origins of water reducing agents PC-1 and PC-2 were selected as comparison samples. The test results are shown in Table 2:

Table 2 Flow performance results of low cement ratio cement slurry

Water cement ratio sample Dosage   Initial fluidity of clean pulp and its retention value (mm) 0 1 2 0.23 PC-1 0.45% 130 240 250 PC-2 115 255 265 Example 1 185 250 248 Example 2 190 255 250 Example 3 180 240 245 Example 4 195 263 260 Example 5 180 230 235 0.22 PC-1 0.45% - - - PC-2 - - - Example 1 150 220 210 Example 2 165 240 236 Example 3 163 245 243 Example 4 170 255 243 Example 5 155 210 205

3. Mortar water reducing rate

Using 450g of Liulihe 42.5 cement, 1 bag of standard sand, and 220g of blank water, the experimental results of the water-reducing rate of the mortar are shown in Table 3:

Table 3 Experimental results of water-reducing rate of cement mortar

Dosage Example 1 Example 2 Example 3 Example 4 Example 5 0.15 13.4 15.5 15.9 16.5 15.0 0.20 18.9 19.8 20.0 22.0 19.5 0.25 23.4 25.7 25.9 26.2 25.5 0.30 27.2. 28.9 29.1 29.5 28.5 0.40 29.0. 30.8 31.8 32.4 30.5

4. Concrete data:

The product was placed at -15°C for 10 hours, the appearance of the sample did not change, no crystals precipitated at the bottom, and the performance was good. The following is the concrete data of this product:

Admixture Dosage water cement sand pebbles fly ash mineral powder Slump / expansion (mm) strength 0 1h 3 days 7 days 28 days Example 1 0.25% 147 340 713 1070 90 60 210/490 250/520 31.5 53.9 75.8 Example 2 0.25% 147 340 713 1070 90 60 200/450 220/500 32.0 54.1 76.5 Example 3 0.25% 147 340 713 1070 90 60 210/450 230/510 32.3 55.2 76.8 Example 4 0.25% 147 340 713 1070 90 60 230/500 250/520 32.7 56.4 78.5 Example 5 0.25% 147 340 713 1070 90 60 190/430 200/490 31.0 52.4 75.5

Claims (1)

1. a synthetic method of allyl polyether type high-performance water reducer, is characterized in that, comprises the following steps: Raise the temperature of the reaction kettle to 40-60°C, add the unsaturated allyl polyethylene glycol monomer into the reaction kettle with the pretreated maleic anhydride aqueous solution, and then raise the temperature to 70-90°C. (Meth) allyl sodium sulfonate, 2-acrylamide-2-methyl propane sulfonic acid, itaconic acid, acrylic acid and acrylamide in a mixture of one or more aqueous solution drops into the reactor, the monomer Dropping time is 45-180 minutes; Or raise the temperature of the reactor to 40-60°C, put the pretreated aqueous solution of maleic anhydride in the reactor, and then add sodium (meth)allylsulfonate, 2-acrylamide-2-methyl Mix the aqueous solution of one or more mixtures of propanesulfonic acid, itaconic acid, acrylic acid and acrylamide with unsaturated allyl polyethylene glycol monomer, raise the temperature to 70-90°C, and add the mixed monomer dropwise , the dropping time is 45-180 minutes; While the monomer is being added dropwise, the ammonium persulfate initiator aqueous solution accounting for 70% to 80% of the total mass of the initiator solution is dropped into the kettle in the form of dropwise addition. The time for adding the ammonium persulfate initiator solution is 45 to 180 minutes. Block the reaction for 1 to 2 hours, add the remaining mass of 30% to 20% ammonium persulfate initiator solution, keep the temperature and block the reaction for 30 to 60 minutes, then cool naturally, when the temperature drops below 55°C, use NaOH solution to adjust the pH of the synthetic solution =6.5±0.5, the allyl ether type concrete high-efficiency water reducer with a mass percentage concentration of 38% to 52% is obtained; The above-mentioned maleic anhydride pretreatment method is: using a sodium hydroxide solution with a mass percent concentration of 30-50% to adjust the neutralization degree, and the neutralization degree after the pretreatment reaches 0.2-0.5; Wherein the molar ratio of maleic anhydride to unsaturated allyl polyethylene glycol monomer is 1.5～4:1, and the molar ratio of ammonium persulfate initiator consumption to unsaturated allyl polyethylene glycol monomer is 0.09～0.45: 1; One or more of sodium (meth)allyl sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, acrylic acid and acrylamide mixed with unsaturated allyl polyethylene glycol The alcohol monomer molar ratio is 0.3-0.7:1.