Polymerization inhibitor and preparation method thereof, mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution and preparation method thereof

Abstract

The present invention provides a polymerization inhibitor and a preparation method thereof, a mild type sustained-release collapse-resistant polycarboxylate water-reducing agent mother solution and a preparation method thereof. The polymerization inhibitor provided by the present invention has the following structural formula: (CH3OCH2) p ‑C6H4‑OOC(CH2CH2) n SH, wherein n is in the range of 2 or 3 or 4, p refers to the para position of the group, and the relative molecular mass of the polymerization inhibitor is 200 to 320. The present invention uses ethylene glycol monovinyl polyethylene glycol ether to obtain a more flexible polycarboxylate water-reducing agent side chain, and uses a polymerization inhibitor in the reaction to prevent the monomer from self-polymerization and play a role of a chain transfer agent, so that the polycarboxylate water-reducing agent mother liquor finally prepared has the characteristics of high water reduction rate, good slow release and slump retention performance, simple process, good dispersibility, etc. At the same time, the product is safe and stable, does not contain chloride ions, does not corrode steel bars, and does not pollute the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixtures, and particularly relates to a polymerization inhibitor and a preparation method thereof, a mild type slow-release collapse-preserving polycarboxylate water-reducing agent mother liquor and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of my country's construction industry, concrete has become the trend-setter in the construction industry, and water reducers have been used more and more widely. Among them, polycarboxylate water reducers have many advantages such as high water reduction rate, small slump loss, controllable molecular structure and performance, and high economic cost performance, and have attracted much research attention in the construction field. However, monomer self-polymerization is a major problem in the synthesis of polycarboxylate water reducer mother liquor, which not only affects the conversion rate of the monomer, but also has a great impact on the performance of the final polycarboxylate water reducer mother liquor.

[0003] Previously, when 4C polyether and 5C polyether were used in the synthesis experiment of polycarboxylate water-reducing agent, no obvious self-polymerization of monomers was found. However, in the synthesis experiment of slow-release and collapse-preserving polycarboxylate water-reducing agent mother liquor using 6C polyether (ethylene glycol monovinyl polyethylene glycol ether macromonomer EPEG), it was found that a large amount of polyether monomers self-polymerized during the reaction, resulting in a low monomer conversion rate and unstable product performance.

[0004] The patent with publication number CN 114195955 A published on March 18, 2022, discloses a novel GPEG polyether monomer polycarboxylic acid water reducer and its preparation process. The polycarboxylic acid water reducer disclosed in the patent includes the following raw materials in parts by weight: 5.8-7.4 parts of acrylic acid; 16.4-19.0 parts of hydroxyethyl acrylate; 5.8-7.4 parts of polyether macromonomer; 34-45 parts of water; 2.0-2.5 parts of hydrogen peroxide solution; 4.5-5.0 parts of catalyst; 4.5-5.2 parts of reducing agent; 4.5-5.2 parts of oxidant; 4.5-5.0 parts of mercaptopropionic acid. The molecular weight is controlled by adding a chain transfer agent mercaptopropionic acid, but the problem of self-polymerization of a large amount of polyether monomers and unstable product performance cannot be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a polymerization inhibitor and a preparation method thereof, which plays the role of a polymerization inhibitor to inhibit the self-polymerization of polyether macromonomers during the reaction, and also plays the role of a chain transfer agent, so that the final reaction monomer conversion rate is higher.

[0006] Another object of the present invention is to provide a mild sustained-release and collapse-resistant polycarboxylate water-reducing agent mother liquor and a preparation method thereof. The polycarboxylate water-reducing agent mother liquor is prepared by using the above-mentioned polymerization inhibitor, and the synthesized polycarboxylate water-reducing agent mother liquor has excellent performance.

[0007] The specific technical solutions of the present invention are as follows:

[0008] A polymerization inhibitor, the polymerization inhibitor has the following structural formula: (CH3OCH2) p -C6H4-OOC(CH2CH2) n -SH, wherein n is in the range of 2, 3 or 4, p refers to the para position of the group, and the relative molecular mass of the polymerization inhibitor is 200-320.

[0009] The present invention provides a method for preparing a polymerization inhibitor, which specifically comprises:

[0010] p-Hydroxyanisole and concentrated sulfuric acid are uniformly mixed as a base liquid. Under heating conditions, the mixed liquid of mercapto acid and p-hydroxyanisole is dropped into the base liquid, and the mixture is kept warm for reaction. After the reaction is completed, a polymerization inhibitor is obtained.

[0011] In the base liquid, the mass ratio of hydroxyanisole to concentrated sulfuric acid is: 9.5-11:9.0-11; preferably 10:10; in the mixed solution of mercapto acid and p-hydroxyanisole, the mass ratio of mercapto acid and p-hydroxyanisole is:

[0012] 9.0-11.0:9.0-11.5; preferably 10:10; the mass concentration of the concentrated sulfuric acid is 90%-98%;

[0013] The mass ratio of the base liquid to the mixed solution of mercapto acid and p-hydroxyanisole is 1-1.2:1;

[0014] The heating condition refers to: heating at 110-120° C., and after the temperature of the base liquid reaches 110-120° C., dripping the mixed solution of mercaptopropionic acid and p-hydroxyanisole into the base liquid;

[0015] The heat preservation reaction means that the heat preservation reaction time is 1 to 2 hours under the condition of 110 to 120°C;

[0016] The mercapto acid is one or more of mercaptoacetic acid, mercaptopropionic acid or mercaptobutyric acid, preferably mercaptopropionic acid.

[0017] Taking mercaptopropionic acid as an example, the reaction equation of the polymerization inhibitor is:

[0018]

[0019] The present invention provides a mild sustained-release collapse-resistant polycarboxylate water-reducing agent mother solution, comprising the following raw materials:

[0020] Ethylene glycol monovinyl polyethylene glycol ether EPEG is used as monomer A, unsaturated acid is used as monomer B, acrylate is used as monomer C, polymerization inhibitor is used as monomer D, initiator, reducing agent, liquid alkali and water, and the mass ratio of each raw material is monomer A: monomer B: monomer C: monomer D: initiator: reducing agent: liquid alkali: water = (300-430): (10-30): (20-45): (20-40): (1-3): (2-10): (2-8): (566-630).

[0021] The ethylene glycol monovinyl polyethylene glycol ether EPEG has the following chemical structural formula: CH2=C(CH3)-(CH2CH2O) n1 -(CH2CH2O) n2 H, wherein n1 and n2 are the addition moles of ethylene oxide, the sum of n1 and n2 is in the range of 2 to 20, and the addition mole is the molar amount of ethylene oxide polymerized in the addition reaction. And the relative molecular mass of the ethylene glycol monovinyl polyethylene glycol ether EPEG is 1000 to 2500.

[0022] The unsaturated acid is one or more of methacrylic acid, acrylic acid, itaconic acid or maleic anhydride.

[0023] The acrylic acid esters are one or more of methyl acrylate, ethyl acrylate, hydroxyethyl acrylate and hydroxypropyl acrylate.

[0024] The initiator is one or more of ammonium persulfate, hydrogen peroxide, potassium persulfate, sodium sulfite and ammonium thiosulfate.

[0025] The reducing agent is one or more of bleaching agent, L-ascorbic acid or ferrous sulfate.

[0026] The liquid alkali is a sodium hydroxide solution with a mass concentration of 30%;

[0027] The present invention provides a method for preparing a mild sustained-release collapse-resistant polycarboxylate water-reducing agent mother solution, comprising the following steps:

[0028] 1) Add monomer A and 480-510 parts of water, cool to 12-30°C, stir and mix, add initiator, stir, and then drop A material solution and B material solution at the same time. After the dropwise addition is completed, keep warm for reaction;

[0029] 2) Add 8-12 parts of water and liquid alkali, continue stirring and reacting, and obtain a mild type slow-release collapse-preserving polycarboxylate water-reducing agent mother solution.

[0030] Add initiator in step 1) and stir for 20-30 min;

[0031] In step 1), the material A solution is a solution formed by stirring unsaturated acid, polymerization inhibitor, acrylic acid ester and 3-25 parts of water;

[0032] In step 1), the material B solution is a solution formed by stirring a reducing agent and 75-83 parts of water;

[0033] In step 1), the material A solution is added dropwise for 180 to 300 minutes, and the material B solution is added dropwise for 190 to 330 minutes, ensuring that the material A solution is finished dropping 10 to 30 minutes before the material B solution is finished dropping;

[0034] In step 1), after the dripping is completed, the reaction is kept warm for 60 to 180 minutes;

[0035] In step 2), liquid alkali is added to neutralize the solution to pH 7, and stirring is continued for 10 to 20 minutes; the reaction is completed, and finally a mild slow-release collapse-preserving polycarboxylate water-reducing agent mother solution is obtained.

[0036] The invention has a low reaction temperature, a high monomer self-polymerization rate and mild reaction conditions; and the long side chain of the synthesized polycarboxylate water-reducing agent mother liquid macromonomer protects part of the carboxyl groups in the early stage, and has a slow-release effect in concrete application.

[0037] In the preparation of the polymerization inhibitor of the present invention, firstly, phenolic substances are typical chain transfer type polymerization inhibitors, and their mechanism is that under alkaline conditions, phenolic hydroxyl groups are released, and chain free radicals first capture hydrogen atoms on phenolic hydroxyl groups and terminate, and at the same time form phenoloxy free radicals, and then couple with other free radicals to terminate. In the process of synthesizing polycarboxylic acid water reducer from 6C polyether, self-polymerization is easy to occur due to the environment. The use of polymerization inhibitors can effectively prevent its self-polymerization, and the thiol group therein can play a role in chain transfer.

[0038] The present invention uses ethylene glycol monovinyl polyethylene glycol ether EPEG to obtain a more flexible polycarboxylate water-reducing agent side chain, and uses a polymerization inhibitor in the reaction to prevent the monomer from self-polymerization and play a role of a chain transfer agent, so that the polycarboxylate water-reducing agent mother liquor finally prepared has the characteristics of high water reduction rate, good sustained release and collapse retention performance, stability, simple preparation process, good dispersibility, etc. At the same time, the product is safe and stable, does not contain chloride ions, does not corrode steel bars, and does not pollute the environment. DETAILED DESCRIPTION

[0039] Example 1

[0040] A polymerization inhibitor, wherein the preparation method of the polymerization inhibitor is:

[0041] To a three-necked flask equipped with a thermometer and a dropping funnel, add 10 parts of p-hydroxyanisole and 10 parts of 98% concentrated sulfuric acid, and shake evenly to use as a base liquid; to the dropping funnel, add 10 parts of mercaptopropionic acid and 10 parts of p-hydroxyanisole and mix evenly to obtain a mixed liquid, place the three-necked flask in an oil bath and heat at a reaction temperature of 120°C. When the temperature reaches the reaction temperature, start to drop the mixed liquid, and keep the reaction warm for 1.5 hours; after the reaction is completed, obtain polymerization inhibitor monomer D.

[0042] Method for preparing a mild sustained-release collapse-resistant polycarboxylate water-reducing agent mother solution using the polymerization inhibitor of Example 1:

[0043] Add 320 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (1500) and 503.5 parts of water to a four-necked flask equipped with a stirring paddle and a thermometer, turn on the stirring device, and use an ice bag to cool to 15°C. After all the monomer A in the flask is dissolved, add 1.5 parts of ammonium persulfate and stir for 30 minutes. Add the A material solution and the B material solution to the flask at the same time. The A material solution is 12 parts of acrylic acid, 22 parts of polymerization inhibitor, 33 parts of hydroxyethyl acrylate and 23 parts of water. The B material solution is a solution formed by stirring evenly, wherein the A material solution is a solution formed by stirring evenly 2 parts of L-ascorbic acid and 79 parts of water, and the B material solution is added dropwise for 180 minutes and 200 minutes, ensuring that the A material solution is finished dropping 20 minutes before the B material solution is finished dropping. After the dropping is completed, the reaction is kept warm for 100 minutes. After the reaction is completed, 10 parts of water are added, and 5 parts of liquid alkali are added to neutralize the solution to a pH value of 7. The stirring is continued for 15 minutes. The reaction is completed, and finally a mild sustained-release and collapse-preserving polycarboxylic acid water-reducing agent mother liquor is obtained.

[0044] Example 2

[0045] A polymerization inhibitor, wherein the preparation method of the polymerization inhibitor is:

[0046] Add 10 parts of p-hydroxyanisole and 10 parts of concentrated sulfuric acid into a three-necked flask equipped with a thermometer and a dropping funnel, and shake evenly to use as a base liquid; then add 10 parts of thioglycolic acid and 10 parts of p-hydroxyanisole into the dropping funnel and mix evenly to obtain a mixed liquid; place the three-necked flask in an oil bath and heat it at a reaction temperature of 120°C. When the temperature reaches the reaction temperature, start to drop the mixed liquid, and keep the reaction warm for 2 hours; after the reaction is completed, obtain polymerization inhibitor monomer D.

[0047] Method for preparing mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution using the polymerization inhibitor of Example 2:

[0048] To a four-necked flask equipped with a stirring paddle and a thermometer, 340 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (1500) and 496.5 parts of water were added, the stirring device was turned on, and the temperature was cooled to 12°C using an ice bag. After all the monomers in the flask were dissolved, 1.5 parts of hydrogen peroxide were added and stirred for 30 minutes. A material solution and B material solution were added dropwise to the flask at the same time. A material solution was a solution formed by stirring 15 parts of acrylic acid, 22 parts of polymerization inhibitor, 25 parts of ethyl acrylate and 5 parts of water. B material solution was a solution formed by stirring 4 parts of bleaching powder and 79 parts of water. A material solution was added dropwise for 200 minutes, and B material solution was added dropwise for 230 minutes. It was ensured that A material solution was dripped 30 minutes before B material solution was dripped. After dripping, the reaction was kept warm for 80 minutes. After the reaction was completed, 10 parts of water were added, and 5 parts of liquid alkali were added to neutralize the pH value of the solution to 7. Stirring was continued for 20 minutes. The reaction was completed, and the mother liquor of slow-release and collapse-preserving polycarboxylic acid water-reducing agent was finally obtained.

[0049] Example 3

[0050] A polymerization inhibitor, wherein the preparation method of the polymerization inhibitor is:

[0051] To a three-necked flask equipped with a thermometer and a dropping funnel, add 10 parts of p-hydroxyanisole and 10 parts of concentrated sulfuric acid, and shake evenly to serve as a base liquid; then, add a mixture of 10 parts of mercaptobutyric acid and 10 parts of p-hydroxyanisole to the dropping funnel, place the three-necked flask in an oil bath and heat at a reaction temperature of 110°C. When the temperature reaches the reaction temperature, start adding the mixture dropwise, and keep the reaction warm for 1.2 hours; the reaction is completed to obtain a polymerization inhibitor monomer D.

[0052] Method for preparing mild sustained-release collapse-resistant polycarboxylate water-reducing agent mother solution using the polymerization inhibitor of Example 3:

[0053] To a four-necked flask equipped with a stirring paddle and a thermometer, 320 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (2500) and 502 parts of water were added, the stirring device was turned on, and the temperature was cooled to 20°C using an ice bag. After all the monomers in the flask were dissolved, 3 parts of hydrogen peroxide were added and stirred for 25 minutes. A material solution and B material solution were added dropwise to the flask at the same time. A material solution was a solution formed by stirring 12 parts of methacrylic acid, 25 parts of polymerization inhibitor, 35 parts of ethyl acrylate and 8 parts of water. B material solution was a solution formed by stirring 2 parts of ferrous sulfate and 78 parts of water. A material solution was added dropwise for 210 minutes, and B material solution was added dropwise for 230 minutes. It was ensured that A material solution was dripped 20 minutes before B material solution was dripped. After dripping, the reaction was kept warm for 120 minutes. After the reaction was completed, 10 parts of water were added, and 5 parts of liquid alkali were added to neutralize the pH value of the solution to 7. Stirring was continued for 15 minutes. The reaction was completed, and the mother liquor of sustained-release and collapse-preserving polycarboxylic acid water-reducing agent was finally obtained.

[0054] Example 4

[0055] A polymerization inhibitor, wherein the preparation method of the polymerization inhibitor is:

[0056] To a three-necked flask equipped with a thermometer and a dropping funnel, add 10 parts of p-hydroxyanisole and 10 parts of concentrated sulfuric acid, and shake evenly to serve as a base liquid; then, add 10 parts of mercaptopropionic acid and 10 parts of p-hydroxyanisole to the dropping funnel as a mixed liquid, place the three-necked flask in an oil bath and heat at a reaction temperature of 120°C. When the temperature reaches the reaction temperature, start to drop the mixed liquid, and keep the reaction warm for 1.5 hours; after the reaction is completed, polymerization inhibitor monomer D is obtained.

[0057] Method for preparing a mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution using the polymerization inhibitor of Example 4:

[0058] To a four-necked flask equipped with a stirring paddle and a thermometer, 340 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (2500) and 482 parts of water were added, the stirring device was turned on, and the temperature was cooled to 12°C using an ice bag. After all the monomers in the flask were dissolved, 3 parts of ammonium persulfate were added and stirred for 30 minutes. A material solution and B material solution were added dropwise to the flask at the same time. A material solution was a solution formed by stirring 25 parts of maleic anhydride, 30 parts of polymerization inhibitor, 22 parts of hydroxypropyl acrylate and 3 parts of water. B material solution was a solution formed by stirring 3 parts of ferrous sulfate and 77 parts of water. A material solution was added dropwise for 300 minutes, and B material solution was added dropwise for 330 minutes. It was ensured that A material solution was dripped 30 minutes before B material solution was dripped. After dripping, the reaction was kept warm for 120 minutes. After the reaction was completed, 10 parts of water were added, and 5 parts of liquid alkali were added to neutralize the pH value of the solution to 7. Stirring was continued for 10 minutes. The reaction was completed, and the mother liquor of sustained-release and collapse-preserving polycarboxylic acid water-reducing agent was finally obtained.

[0059] Example 5

[0060] A polymerization inhibitor, wherein the preparation method of the polymerization inhibitor is:

[0061] To a three-necked flask equipped with a thermometer and a dropping funnel, add 10 parts of p-hydroxyanisole and 10 parts of concentrated sulfuric acid, and shake evenly to serve as a base liquid; then, add 10 parts of mercaptopropionic acid and 10 parts of p-hydroxyanisole to the dropping funnel as a mixed liquid, place the three-necked flask in an oil bath and heat at a reaction temperature of 120°C. When the temperature reaches the reaction temperature, start to drop the mixed liquid, and keep the reaction warm for 2 hours; the reaction is completed to obtain a polymerization inhibitor monomer D.

[0062] Method for preparing mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution using the polymerization inhibitor of Example 5:

[0063] To a four-necked flask equipped with a stirring paddle and a thermometer, 320 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (2000) and 482 parts of water were added, the stirring device was turned on, and the temperature was cooled to 22°C with an ice bag. After all the monomers in the flask were dissolved, 3 parts of ammonium persulfate were added and stirred for 30 minutes. The A material solution and the B material solution were added dropwise to the flask at the same time. The A material solution was 12 parts of maleic anhydride, 13 parts of acrylic acid, 20 parts of a polymerization inhibitor, 25 parts of hydroxypropyl acrylate and 15 The material B solution is a solution formed by stirring evenly with 5 parts of L-ascorbic acid and 75 parts of water. The material A solution is added dropwise for 220 minutes, and the material B solution is added dropwise for 230 minutes to ensure that the material A solution is finished dropping 10 minutes before the material B solution is finished dropping. After the dropping is completed, the reaction is kept warm for 180 minutes. After the reaction is completed, 10 parts of water are added, and 5 parts of liquid alkali are added to neutralize the solution to pH 7. The stirring is continued for 20 minutes. The reaction is completed, and finally the mother liquor of sustained-release and collapse-proof polycarboxylic acid water-reducing agent is obtained.

[0064] Comparative Example 1

[0065] The method for preparing the mother liquor of polycarboxylic acid water-reducing agent is as follows: 320 parts of monomer A ethylene glycol monovinyl polyethylene glycol ether EPEG (1500) and 503.5 parts of water are added to a four-necked flask equipped with a stirring paddle and a thermometer, the stirring device is turned on, and the temperature is cooled to 15°C with an ice bag. After the ethylene glycol monovinyl polyethylene glycol ether EPEG in the flask is completely dissolved, 1.5 parts of ammonium persulfate are added, stirred for 30 minutes, and the material A solution and the material B solution are added dropwise to the flask at the same time. The material A solution is 12 parts of acrylic acid, 33 parts of The material B solution is a solution formed by stirring 2 parts of hydroxyethyl acrylate and 45 parts of water, and the material A solution is a solution formed by stirring 2 parts of L-ascorbic acid and 79 parts of water. The material A solution is added dropwise for 180 minutes, and the material B solution is added dropwise for 200 minutes. It is ensured that the material A solution is finished dropping 20 minutes before the material B solution is finished dropping. After the dropping is completed, the heat is kept for reaction for 100 minutes. After the reaction is completed, 10 parts of water are added, and 5 parts of liquid alkali are added to neutralize the solution to pH 7. The stirring is continued for 15 minutes. The reaction is completed, and finally the polycarboxylate water-reducing agent mother liquor is obtained.

[0066] In order to evaluate the performance of the slow-release and slump-proof polycarboxylate water-reducing agent mother solution of the present invention, Examples 1 to 5 and Comparative Example 1 were compared with the commercially available polycarboxylate water-reducing agent mother solution, and the standard cement was used, and the amount was 0.25% of the mass of concrete. According to GB8076-2008 "Concrete Admixtures", the concrete water reduction rate and slow-release and slump-proof performance were measured. The cement in this experiment was Conch Cement PO42.5, medium sand with a fineness modulus of 2.5; 5-20mm continuously graded crushed stone. The specific concrete raw materials and mass parts are shown in Table 1; the slump / expansion is shown in Table 2.

[0067] Table 1 Concrete mass mix ratio (parts)

[0068] cement Fly ash Mineral powder medium sand gravel water Water reducing agent 260 60 60 800 1000 170 6.0

[0069] Table 2 Concrete performance comparison

[0070]

[0071]

[0072] The results in Table 2 show that: under the same conditions, compared with Comparative Example 1 and commercially available water reducing agents, the slump and expansion of concrete lost less over time when the preparation examples 1 to 5 of the present invention were added, indicating that the water reducing agent prepared by the present invention has excellent retarding and slump-retaining performance and stable performance.

Claims

1. A polymerization inhibitor, characterized in that The polymerization inhibitor structural formula is as follows: (CH3O) p -C6H4-OOC(CH2) n -SH, wherein n is in the range of 1, 2 or 3, and p refers to the para position of the group.

2. A method for preparing the polymerization inhibitor according to claim 1, characterized in that: The preparation method comprises the following steps: uniformly mixing p-hydroxyanisole and concentrated sulfuric acid as a base liquid, dripping a mixed liquid of mercapto acid and p-hydroxyanisole into the base liquid under heating conditions, and reacting at a heat preservation temperature until the reaction is finished, thereby obtaining a polymerization inhibitor.

3. The preparation method according to claim 2, characterized in that: In the base liquid, the mass ratio of hydroxyanisole to concentrated sulfuric acid is: 9.5-11:9.0-11.

4. The preparation method according to claim 2, characterized in that: In the mixed solution of mercapto acid and p-hydroxyanisole, the mass ratio of mercaptopropionic acid to p-hydroxyanisole is: 9.0-11.0:9.0-11.

5.

5. The preparation method according to claim 2, characterized in that: The mass ratio of the base liquid to the mixed liquid of mercapto acid and p-hydroxyanisole is 1-1.2:

1.

6. The preparation method according to claim 2, characterized in that: The heat preservation reaction refers to: the heat preservation reaction time is 1-2h under the condition of 110-120°C.

7. A mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution, characterized in that: The mild type slow-release collapse-proof polycarboxylate water-reducing agent mother liquor comprises the following raw materials: ethylene glycol monovinyl polyethylene glycol ether as monomer A, unsaturated acid as monomer B, acrylic acid ester as monomer C, polymerization inhibitor as monomer D, initiator, reducing agent, liquid alkali and water, and the mass ratio of each raw material is monomer A: monomer B: monomer C: monomer D: initiator: reducing agent: liquid alkali: water = (300-430): (10-30): (20-45): (20-40): (1-3): (2-10): (2-8): (566-630); the structural formula of the polymerization inhibitor is: (CH3O) p -C6H4-OOC(CH2) n -SH, wherein n is in the range of 1, 2 or 3, and p refers to the para position of the group.

8. The mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution according to claim 7, characterized in that: The relative molecular mass of the ethylene glycol monovinyl polyethylene glycol ether is 1000-2500.

9. A method for preparing the mild sustained-release collapse-preserving polycarboxylate water-reducing agent mother solution according to claim 7 or 8, characterized in that: The preparation method comprises the following steps: 1) Add monomer A and 480-510 parts of water, cool to 12-30°C, stir and mix, add initiator, stir, and then drop A solution and B solution at the same time. After the dropwise addition is completed, keep warm for reaction; 2) Add 8-12 parts of water and liquid alkali, continue stirring and reacting, and obtain a mild type slow-release collapse-preserving polycarboxylate water-reducing agent mother solution; In step 1), the material A solution is a solution formed by stirring unsaturated acid, polymerization inhibitor, acrylic acid ester and 3-25 parts of water; In step 1), the material B solution is a solution formed by uniformly stirring a reducing agent and 75-83 parts of water.

10. The preparation method according to claim 9, characterized in that: In step 1), the A material solution is added dropwise for 180-300 min, and the B material solution is added dropwise for 190-330 min, ensuring that the A material solution is added dropwise 10-30 min before the B material solution is added dropwise.

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