CN110790872A - Viscosity-reducing polycarboxylate superplasticizer with micro-crosslinking structure and preparation method thereof - Google Patents

Abstract

The invention discloses a viscosity reduction type polycarboxylate water reducer with a micro-crosslinking structure, which is prepared by taking unsaturated acid, unsaturated anhydride, prenyl polyoxyethylene ether, a crosslinking agent and a reaction type cosolvent as polymerization raw materials and carrying out free radical polymerization under the action of an initiator and chain transfer, wherein the components and the structures have mutual synergistic action. The reactive cosolvent can effectively improve the intermiscibility among monomers, and improve the polymerization efficiency and effective molecular structure arrangement of the polymer. The water reducing agent disclosed by the invention adopts a bifunctional cross-linking agent to improve the molecular structure of the polycarboxylic acid water reducing agent and improve the viscosity reduction performance of the water reducing agent.

Description

Viscosity-reducing polycarboxylate superplasticizer with micro-crosslinking structure and preparation method thereof

Technical Field

The invention relates to the technical field of concrete admixtures, in particular to a viscosity reduction type polycarboxylate superplasticizer with a micro-crosslinking structure based on cement-based materials and a preparation method thereof.

Background

Along with the development of the building industry in China, high-strength and ultrahigh-strength concrete gradually enters the construction market due to the characteristics of high strength, good integrity and small self weight, and can meet the requirements of light weight, high stratification, large span and high durability in modern buildings and infrastructure. However, due to the adoption of a low water-cement ratio and a large amount of cementing material, the viscosity of the concrete mixture is gradually increased, a series of construction problems such as concrete stirring, transportation, pumping and the like are caused, and the popularization and application of high-strength and ultrahigh-strength concrete are limited to a great extent. In addition, the problem of concrete viscosity is more prominent due to the shortage of river sand resources and high-quality admixtures.

How to reduce the viscosity of concrete becomes a key technology for the development of high-strength and ultrahigh-strength concrete. At present, a viscosity reduction method can be mainly developed from two aspects of organic additives and admixtures. At present, the research on the viscosity reducer prepared by synthesis is less, and the viscosity of concrete is reduced by introducing special functional groups, controlling the lengths of a main chain and a side chain and adjusting the thickness of a water film layer of the viscosity reducer on the surface of cement particles. The viscosity reduction type polycarboxylate superplasticizer developed for the purpose of adjusting the viscosity of concrete is mainly used for improving the viscosity of low-water-gel concrete by adjusting rheological parameters such as shear yield stress, plastic viscosity and the like of a concrete system. In the aspect of admixture, the working performance of concrete is improved mainly by adding silica fume, fly ash, micro-beads and the like at present, although the viscosity of concrete can be reduced by adding the admixture, the viscosity reduction effect of high-strength and ultra-high-strength concrete is very limited and the concrete is generally expensive, the single cost of the concrete is increased, and the use of the concrete in commercial concrete is limited. Therefore, the development of a novel viscosity-reducing type polycarboxylate superplasticizer is urgent.

At present, the viscosity of concrete in the stage mainly focuses on factors such as internal friction between cement paste and coarse and fine aggregates, residual polycarboxylate superplasticizer in cement pore liquid, intermolecular chain winding of polycarboxylate superplasticizer and the like, and researchers mostly adopt the following three ways to improve through literature and patents of viscosity reduction type polycarboxylate superplasticizer: (1) reducing the molecular weight of the water reducing agent (2), reducing the length of PEG side chains in polyether monomers and modifying the PEG side chains (3), introducing hydrophobic and rigid groups such as methyl, ester, phenyl and the like into the molecular structure of the water reducing agent, and increasing the hydrophobicity of the product so as to reduce the combination with water, release free water to the maximum extent and reduce the viscosity of concrete. The disadvantage is that short side chain PEG and PEG side chain modification are expensive. The hydrophobic functional group is located on the main chain, and the content of the hydrophobic functional group is limited, and if the content is too high, the air-entraining property is increased.

For example, patent CN109265051A discloses a crosslinking prepolymer prepared by esterifying dibasic acid and dihydric alcohol, and then adding unsaturated acid for further esterification. But the preparation process of the crosslinking prepolymer is complex and the post-esterification rate is low. The crosslinking prepolymer is introduced into a polycarboxylate superplasticizer to form a slow-release polycarboxylate superplasticizer. Patent CN109265052A discloses a bifunctional and trifunctional crosslinking agent prepared from allyl alcohol monomer and butane-2-phosphate-1, 2, 4-tricarboxylate. The cross-linking agent and the 2-methacryloyloxyethyl phosphorylcholine are introduced into a polycarboxylate superplasticizer structure to form a cross-linking viscosity-reducing polycarboxylate superplasticizer, which can effectively reduce the viscosity of concrete, but cannot substantially compare the influence of the cross-linking structure, the phosphate structure and the choline structure on the viscosity-reducing performance.

At the present stage, the viscosity reduction type polycarboxylate superplasticizer cannot increase the thickness of an adsorption layer of an admixture on the surface of cement particles and reduce the residual polycarboxylate superplasticizer in cement pore liquid from the beginning of a molecular structure. If the coverage rate of the polycarboxylate superplasticizer on the surface of cement particles and the thickness of the adsorption layer are increased, the thickness of the solvation layer can be effectively reduced, free water is released, and the viscosity of concrete is reduced. The unadsorbed polycarboxylate superplasticizer in the pore liquid is reduced, so that the viscosity of the pore liquid can be reduced, and the viscosity of concrete can be effectively reduced.

Disclosure of Invention

The invention aims to provide a viscosity-reducing polycarboxylate water reducer with a micro-crosslinking structure based on the molecular structure design of the polycarboxylate water reducer. The water reducer increases the thickness of an adsorption layer of an additive on the surface of cement particles and reduces the residual polycarboxylic acid water reducer in cement pore liquid from the molecular structure of the water reducer, thereby achieving the purpose of viscosity reduction.

The invention also aims to provide a preparation method of the viscosity-reducing polycarboxylate superplasticizer with the micro-crosslinking structure.

The viscosity reduction type polycarboxylate superplasticizer with a micro-crosslinking structure provided by the invention is prepared by taking monomer unsaturated acid, unsaturated anhydride, prenyl polyoxyethylene ether, a crosslinking agent and a cosolvent as polymerization components and polymerizing through free radicals under the action of an initiator and chain transfer. The weight average molecular weight of the water reducing agent is 3-8 ten thousand. The mass percentage of each polymerization monomer component is as follows: 3-20% of unsaturated carboxylic acid, 1-10% of unsaturated anhydride, 78-96% of prenyl alcohol polyoxyethylene ether, 0.5-5% of cross-linking agent and 0.1-1% of reactive cosolvent, wherein the total is 100%.

The cross-linking agent is one or at least two of N, N ' -methylene bisacrylamide, N ' -vinyl bisacrylamide, N ' - (1, 2-dihydroxyethylene) bisacrylamide, ethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1, 4-bis (acryloyloxy) butane, diethylene glycol diacrylate, methacrylic anhydride, diethylene glycol methacrylate phosphate and bismaleic anhydride polyethylene glycol phosphate.

The cosolvent is a reactive cosolvent, and specifically is one or at least two of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

The unsaturated acid is one or at least two of acrylic acid, methacrylic acid, fumaric acid, itaconic acid, and their corresponding alkali metal salts.

The unsaturated anhydride is one or at least two of maleic anhydride, itaconic anhydride, citraconic anhydride, nonyl succinic anhydride and nonenyl succinic anhydride.

The molecular weight of the prenyl alcohol polyoxyethylene ether is 1200-5000, and the prenyl alcohol polyoxyethylene ether is further preferably 1600-4000.

The initiator is one of ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, azobisisopropylimidazoline, benzoyl peroxide, cyclohexanone peroxide and bis (2-phenyl ethoxy) peroxydicarbonate. The addition amount of the initiator is 0.4-4% of the total mass of each reaction monomer (the total mass of the unsaturated carboxylic acid, the unsaturated anhydride, the prenyl polyoxyethylene ether and the cross-linking agent). The preferable addition amount of the initiator is 0.5-3.5% of the total mass of all reaction monomers.

The chain transfer agent is one or at least two of mercaptoethanol, 2-hydroxypropanethiol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptosuccinic acid, dodecyl mercaptan, sodium hypophosphite and sodium formate. The addition amount of the chain transfer agent is 0.02-0.2% of the total mass of all reaction monomers.

The preparation method of the viscosity-reducing polycarboxylate superplasticizer with the micro-crosslinking structure comprises the following steps:

s1, dissolving prenyl alcohol polyoxyethylene ether and unsaturated anhydride in water, and keeping the temperature at 50-80 ℃ to obtain a solution A;

s2, dissolving unsaturated carboxylic acid, a cross-linking agent, a cosolvent and a chain transfer agent in water, and uniformly mixing to obtain a solution B;

s3, dissolving an initiator in water to obtain a solution C;

s4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 1.5-3.0 h, reacting at a constant temperature of 50-80 ℃ for 2-3 h after dropwise adding, and then cooling and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylic acid high-efficiency water reducer.

In the preparation method, in the steps S1-S3, the total addition amount of the solvent water is adjusted by the solid content of the polycarboxylic acid water reducing agent being 30-80%.

Compared with the prior art, the invention has the advantages that:

firstly, a bifunctional cross-linking agent is used for synthesizing the polycarboxylate superplasticizer, and the molecular structure of the polycarboxylate superplasticizer is improved. The conventional comb-shaped structure of the molecular structure of the polycarboxylate superplasticizer is changed into a net-shaped structure. The water reducing agent with the structure can increase the thickness of the adsorption layer on the surface of cement particles, enhance the coverage rate on the surface of the cement particles, reduce the concentration of the residual polycarboxylic acid water reducing agent in cement pore liquid, strengthen the surface activity capacity of the water reducing agent, weaken the interaction force among adsorption interfaces, weaken the intermolecular winding of the non-adsorbed polycarboxylic acid water reducing agent in the cement pore liquid and the rolling of the molecular chain of the polycarboxylic acid water reducing agent per se, and play a role in reducing the viscosity of concrete. Meanwhile, the thickness of a solvation layer on the surface of cement particles can be reduced, free water is released, and the viscosity of concrete is reduced. Compared with the common comb-shaped viscosity reduction type polycarboxylate superplasticizer, the water reducer disclosed by the invention has a smaller hydraulic radius, has less residue in cement pore liquid, and is beneficial to reducing the viscosity.

Secondly, the reaction type cosolvent adopted by the invention can effectively improve the solubility of the oil-soluble cross-linking agent in the unsaturated acid in water, and improve the free radical polymerization efficiency among the cross-linking agent, the unsaturated acid, the unsaturated anhydride and the prenol polyoxyethylene ether. Due to the existence of double bonds, the double bonds are gradually polymerized in the molecular structure of the polycarboxylic acid water reducing agent in the reaction process, no residue is left in the system, and the pollution is reduced. Because the unsaturated ester cosolvent is introduced to adjust the polar type of the polymerized monomer solution, the intermiscibility among polymerized monomers is improved, and the polymerization efficiency and the effective molecular structure arrangement of the polymer are improved. The HLB of the polycarboxylate superplasticizer is regulated and controlled by the type and the amount of the unsaturated ester, so that the micro-crosslinking viscosity-reduction polycarboxylate superplasticizer which is more matched with hydrophilicity and hydrophobicity can be obtained, and the viscosity of concrete can be obviously reduced.

Thirdly, the invention can realize the regulation and control of properties such as slump loss resistance, early strength and the like by changing the type and the dosage of the cross-linking agent, and is beneficial to obtaining the multi-property micro-crosslinked polycarboxylic acid water reducing agent. In addition, the raw materials involved in the invention have low cost, no expensive monomer is needed, the reaction condition is mild, the synthetic process is simple and convenient, the production period is shortened, and the method is environment-friendly and suitable for popularization and application.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.

Example 1

The micro-crosslinking viscosity-reducing polycarboxylate superplasticizer comprises the following polymerization reaction monomer components in percentage by mass: 6% of unsaturated carboxylic acid, 1.3% of unsaturated anhydride, 91% of prenol polyoxyethylene ether, 1.2% of cross-linking agent and 0.5% of reaction type cosolvent, wherein the total is 100%. The preparation method comprises the following steps:

s1, 202g of prenyl alcohol polyoxyethylene ether monomer with the molecular weight of 2400 and 2.88g of maleic anhydride are weighed and dissolved in 205g of deionized water, the temperature is raised to 50 ℃, and the temperature is kept constant to obtain a solution A.

S2, 13.3g of acrylic acid, 2.66g of 2.66g N, N' -methylenebisacrylamide, 1.1g of hydroxyethyl acrylate and 0.38g of chain transfer agent mercaptoethanol were weighed out and dissolved in 30g of water to obtain a solution B.

S3, 1.66g of ammonium persulfate and 0.36g of azodiisobutyl amidine hydrochloride are weighed and dissolved in 30g of water to obtain a solution C;

s4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 2.0h, reacting at a constant temperature of 50 ℃ for 2h after dropwise adding, cooling to room temperature, and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylic acid high-efficiency water reducer, wherein the solid content is 45%, and the molecular structural formula of the water reducer is as follows:

wherein g is 53; a. the ratio of b, c, d and e is 9:1:20:3: 2.

Polyacrylic acid is used as a standard sample, gel chromatography is adopted for determination, and the weight average molecular weight of the water reducing agent is determined to be 35421.

Example 2

The micro-crosslinking viscosity-reducing polycarboxylate superplasticizer comprises the following polymerization reaction monomer components in percentage by mass: 5.7 percent of unsaturated carboxylic acid, 2.4 percent of unsaturated anhydride, 90 percent of prenyl alcohol polyoxyethylene ether, 1.4 percent of cross-linking agent and 0.5 percent of reaction type cosolvent, wherein the total is 100 percent. The preparation method comprises the following steps:

s1, weighing 200g of prenyl alcohol polyoxyethylene ether monomer with the molecular weight of 2400 and 5.33g of maleic anhydride, dissolving in 205g of deionized water, heating to 50 ℃, and keeping the temperature to obtain a solution A.

S2, weighing 12.65g of acrylic acid, 3.1g of N, N' - (1, 2-dihydroxyethylene) bisacrylamide, 0.89g of hydroxyethyl acrylate and 0.38g of chain transfer agent mercaptoacetic acid, and dissolving in 30g of water to obtain a mixed solution B;

s3, weighing 1.46g of ammonium persulfate and 0.4g of sodium persulfate, and dissolving in 30g of water to obtain a mixed solution C;

s4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 2.0h, reacting at a constant temperature of 50 ℃ for 2h after dropwise adding, cooling to room temperature, and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylic acid high-efficiency water reducer, wherein the solid content is 45%, and the structural formula of the water reducer is as follows:

wherein g is 53; a. the ratio of b, c, d and e is 11:1:23:6: 2.

Polyacrylic acid is used as a standard sample, gel chromatography is adopted for determination, and the weight average molecular weight of the water reducing agent is determined to be 41254.

Example 3

The micro-crosslinking viscosity-reducing polycarboxylate superplasticizer comprises the following polymerization reaction monomer components in percentage by mass: 5.7 percent of unsaturated carboxylic acid, 2.1 percent of unsaturated anhydride, 87.2 percent of isoamylol polyoxyethylene ether, 4.5 percent of cross-linking agent and 0.5 percent of reactive cosolvent, wherein the total is 100 percent. The preparation method comprises the following steps:

s1, weighing 193g of prenyl alcohol polyoxyethylene ether monomer with the molecular weight of 2400 and 3.33g of maleic anhydride, dissolving in 205g of deionized water, heating to 50 ℃, and keeping the temperature to obtain a solution A.

S2, 12.65g of fumaric acid, 10g of diethylene glycol methacrylate phosphate, 0.89g of hydroxypropyl methacrylate and 0.38g of the chain transfer agent mercaptopropionic acid were weighed out and dissolved in 30g of water to obtain solution B.

S3, 1.48g of potassium persulfate and 0.2g of azobisisoheptonitrile were weighed and dissolved in 30g of water to obtain solution C.

S4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 1.5h, preserving the heat at 50 ℃ for 2h after the dropwise adding is finished, then cooling to room temperature, and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylic acid high-efficiency water reducer, wherein the solid content is 45%, and the structural formula of the water reducer is as follows:

wherein g is 53; a. the ratio of b, c, d and e is 13:1:18:5: 5.

Polyacrylic acid is used as a standard sample, and the weight average molecular weight of the water reducing agent is 52351 by gel chromatography determination.

Example 4

The micro-crosslinking viscosity-reducing polycarboxylate superplasticizer comprises the following polymerization reaction monomer components in percentage by mass: 7.4 percent of unsaturated carboxylic acid, 2.6 percent of unsaturated anhydride, 84.5 percent of prenyl alcohol polyoxyethylene ether, 4.8 percent of cross-linking agent and 0.7 percent of reactive cosolvent, wherein the total is 100 percent. The preparation method comprises the following steps:

s1, weighing 187.86g of prenyl polyoxyethylene ether monomer with the molecular weight of 3000, 4.67g of maleic anhydride and 1.12g of itaconic anhydride, dissolving in 205g of deionized water, heating to 50 ℃, and keeping the temperature to obtain a solution A.

S2, weighing 12.67g of fumaric acid, 3.78g of methacrylic acid, 10.67g of bismaleimide polyethylene glycol phosphate, 1.56g of hydroxypropyl methacrylate and 0.38g of chain transfer agent dodecyl mercaptan, and dissolving in 30g of water to obtain a solution B;

s3, weighing 1.89g of azodicyano valeric acid and 0.3g of benzoyl peroxide, and dissolving in 30g of water to obtain a solution C;

s4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 1.5h, preserving heat at 50 ℃ for 2h after dropwise adding, and then cooling and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylate superplasticizer, wherein the solid content is 45%, and the molecular structural formula of the superplasticizer is as follows:

wherein g and I are 66 and 10 respectively; a. the ratio of b, c, d, e and f is 6:1:4:5: 11: 1.

polyacrylic acid is used as a standard sample, and the weight average molecular weight of the water reducing agent is 68432 by gel chromatography determination.

Example 5

11. The micro-crosslinking viscosity-reducing polycarboxylate superplasticizer comprises the following polymerization reaction monomer components in percentage by mass: 6% of unsaturated carboxylic acid, 2% of unsaturated anhydride, 89% of prenyl alcohol polyoxyethylene ether, 2.5% of cross-linking agent and 0.5% of reactive cosolvent, wherein the total is 100%. The preparation method comprises the following steps:

s1, weighing 198g of prenyl alcohol polyoxyethylene ether monomer with the molecular weight of 1600 and 4.37g of maleic anhydride, dissolving in 205g of deionized water, heating to 50 ℃, and preserving heat to obtain a solution A.

S2, 11.67g of acrylic acid, 1.65g of methacrylic acid, 5.56g of diethylene glycol methacrylate phosphate, 1.11g of hydroxypropyl acrylate and 0.42g of the chain transfer agent sodium hypophosphite are weighed out and dissolved in 30g of water to obtain solution B.

S3, 1.75g of bis (2-phenylethoxy) peroxydicarbonate is weighed out and dissolved in 30g of water to give solution C.

S4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 1.5h, preserving heat at 50 ℃ for 2h after dropwise adding, and then cooling and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylate superplasticizer with the solid content of 45%, wherein the structural formula is as follows:

wherein g is 35; a. the ratio of b, c, d, e and f is 83:1:29:240:151: 34.

Polyacrylic acid is used as a standard sample, and the weight average molecular weight of the water reducing agent is 68129 by gel chromatography.

Performance test analysis: the micro-crosslinking viscosity-reducing polycarboxylate superplasticizers prepared in examples 1-5 and commercially available concrete viscosity reducers were subjected to concrete working performance and mechanical property tests. The performance of the concrete mixture is tested by referring to the standard of the test method for the performance of the common concrete mixture GB/T50080-2002, the standard of the test method for the mechanical property of the common concrete GB/T50081-2002, the technical specification for the application of self-compacting concrete JGJ/T283-2012 and CECS 203-. The test results are shown in Table 1.

The concrete formula is as follows: 520kg of Lardue P.O 42.5 cement, 90kg of I-grade fly ash, 730kg of machine sand (fineness modulus is 2.9), 1000kg of stones and 0.25 of water-cement ratio.

TABLE 1 comparative data on concrete Properties

Comparative example 1 is a commercial viscosity-reducing polycarboxylic acid water reducer, and comparative examples 2 and 3 are polycarboxylic acid water reducers prepared according to the monomer ratios of example 2 and example 3, respectively, but without adding a crosslinking agent.

As can be seen from Table 1, under the same conditions of the initial state of the concrete, the micro-crosslinking viscosity-reduction type polycarboxylate water reducers in examples 1 to 5 are lower than the commercial viscosity-reduction type water reducer (comparative example 1) and comparative examples 2 and 3 in mixing amount, which shows that the water reducer prepared by the invention has higher water reduction rate. The slump loss time and the T500 time of the water reducing agent without adding the cross-linking agent (comparative example 1 and comparative example 2) are both longer than those of the micro-crosslinking viscosity-reducing water reducing agent prepared by adding the cross-linking agent, which shows that the micro-crosslinking viscosity-reducing polycarboxylic acid water reducing agent prepared by adding the cross-linking agent has better viscosity reduction effect. Compared with a commercial viscosity reduction type water reducer with a good viscosity reduction effect, the water reducer disclosed by the invention can shorten the slump loss time by 57-71%, shorten the T50 time by 2-5 s, and has a remarkable viscosity reduction effect.

In conclusion, the water reducing agent disclosed by the invention forms a micro-crosslinking structure by introducing the bifunctional monomer, and the molecular weight of the water reducing agent is limited to 3-8 ten thousand, so that the thickness and the coverage rate of an adsorption layer of the polycarboxylate water reducing agent on the surface of cement particles are improved, the thickness of a solvation layer on the surface of the cement particles is reduced, and free water is released. Moreover, the water reducing agent of the invention has smaller hydraulic radius than a comb polymer water reducing agent, and has less residue in cement pore liquid than the comb polymer, and the viscosity of the prepared micro-crosslinked polymer is lower than that of the comb polymer, so that the viscosity of the cement pore liquid is reduced. The raw material cost for preparing the water reducing agent is low, the reaction condition is mild, the synthesis process is simple and convenient, the environment is friendly, and the method is suitable for popularization and application.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. The viscosity reduction type polycarboxylate water reducer with a micro-crosslinking structure is characterized by being prepared by polymerizing reaction monomers of unsaturated acid, unsaturated acid anhydride, prenol polyoxyethylene ether, a crosslinking agent and a cosolvent, wherein the crosslinking agent is one or at least two of N, N ' -methylene bisacrylamide, N ' -vinyl bisacrylamide, N ' - (1, 2-dihydroxyethylene) bisacrylamide, ethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1, 4-bis (acryloyloxy) butane, diethylene glycol diacrylate, methacrylic anhydride, diethylene glycol methacrylate phosphate and bismaleic anhydride polyethylene glycol phosphate; the cosolvent is a reactive cosolvent, and specifically is one or at least two of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

2. The viscosity-reducing polycarboxylate superplasticizer with a micro-crosslinking structure according to claim 1, wherein the polymerization reaction monomers are used in the following amounts by mass: 3-20% of unsaturated carboxylic acid, 1-10% of unsaturated anhydride, 78-96% of prenyl alcohol polyoxyethylene ether, 0.5-5% of cross-linking agent and 0.1-1% of reactive cosolvent, wherein the total is 100%.

3. The viscosity-reducing polycarboxylic acid water-reducing agent with a micro-crosslinked structure according to claim 2, characterized in that the weight average molecular weight of the water-reducing agent is 3 to 8 ten thousand.

4. The viscosity-reducing polycarboxylate superplasticizer having a micro-crosslinked structure according to claim 2, wherein said unsaturated acid is one or at least two of acrylic acid, methacrylic acid, fumaric acid, itaconic acid and their corresponding alkali metal salts.

5. The viscosity-reducing polycarboxylic acid water reducer with a micro-crosslinked structure according to claim 2, wherein the unsaturated anhydride is one or at least two of maleic anhydride, itaconic anhydride, citraconic anhydride, nonylsuccinic anhydride and nonylsuccinic anhydride.

6. The viscosity-reducing polycarboxylate superplasticizer with a micro-crosslinking structure as claimed in claim 2, wherein the molecular weight of said prenyl polyoxyethylene ether is 1200-5000.

7. The viscosity-reducing polycarboxylate water reducer with a micro-crosslinking structure as claimed in claim 2, wherein the viscosity-reducing polycarboxylate water reducer is prepared by taking monomer unsaturated acid, unsaturated anhydride, prenyl polyoxyethylene ether, a crosslinking agent and a cosolvent as polymerization components and performing free radical polymerization under the action of an initiator and chain transfer.

8. The viscosity-reduction polycarboxylic acid water reducer having a micro-crosslinked structure according to claim 2, wherein said initiator is one of ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanovaleric acid, azobisisopropylimidazoline, benzoyl peroxide, cyclohexanone peroxide, bis (2-phenylethyloxy) peroxydicarbonate.

9. The preparation method of the viscosity-reducing polycarboxylate superplasticizer with a micro-crosslinked structure according to any one of claims 1 to 8, characterized by comprising the following steps:

s1, dissolving prenyl alcohol polyoxyethylene ether and unsaturated anhydride in water, and keeping the temperature at 50-80 ℃ to obtain a solution A;

s2, dissolving unsaturated carboxylic acid, a cross-linking agent, a cosolvent and a chain transfer agent in water, and uniformly mixing to obtain a solution B;

s3, dissolving an initiator in water to obtain a solution C;

s4, dropwise adding the solution B and the solution C into the solution A at a constant speed for 1.5-3.0 h, reacting at a constant temperature of 50-80 ℃ for 2-3 h after dropwise adding, and then cooling and adding alkali for neutralization to obtain the micro-crosslinking viscosity-reduction type polycarboxylic acid high-efficiency water reducer.

10. The preparation method of the viscosity-reducing polycarboxylate superplasticizer with a micro-crosslinked structure according to claim 9, wherein in steps S1-S3, the total addition amount of solvent water is adjusted to 30-80% of the solid content of the polycarboxylate superplasticizer.