阅读说明：本技术 一种高和易性水泥分散聚合物及其制备方法 (High workability cement dispersion polymer and preparation method thereof ) 是由 柯余良 方云辉 张小芳 钟丽娜 邱岳涛 于 2020-11-30 设计创作，主要内容包括：本发明涉及建筑外加剂技术领域,特别涉及一种高和易性水泥分散聚合物及其制备方法,所述聚合物包含：a)含酯基的聚合物,所述含酯基的聚合物包含得自单体的聚合物或共聚物,所述单体包括：1)不饱和羧酸酯单体；以及2)不饱和酸单体、不饱和磺酸盐单体中的至少一种；以及b)羧甲基淀粉；和c)聚乙二醇单甲醚。本发明提供了一种高和易性水泥分散聚合物,采用先低温共聚后高温酯化的方法,减少了反应单体双键的破坏,共聚程度提高,生产的水泥分散聚合物减水率高,和易性好,解决了混凝土的泌水、离析和密实度差引起的混凝土质量问题和耐久性问题,特别是对于不同的水泥、掺合料、人工砂、环境温度及混凝土配合比波动都有着优异的适应性。(The invention relates to the technical field of building additives, in particular to a high workability cement dispersion polymer and a preparation method thereof, wherein the polymer comprises the following components: a) an ester group-containing polymer comprising a polymer or copolymer derived from monomers comprising: 1) an unsaturated carboxylic acid ester monomer; and 2) at least one of unsaturated acid monomer, unsaturated sulfonate monomer; and b) carboxymethyl starch; and c) polyethylene glycol monomethyl ether. The invention provides a high workability cement dispersion polymer, which adopts a method of low-temperature copolymerization and high-temperature esterification, reduces the damage of double bonds of reaction monomers, improves the copolymerization degree, produces the cement dispersion polymer with high water reducing rate and good workability, solves the problems of concrete quality and durability caused by poor bleeding, segregation and compactness of concrete, and particularly has excellent adaptability to different cements, admixtures, artificial sand, environmental temperature and concrete mixing ratio fluctuation.)

1. A high workability cement dispersing polymer characterized in that said high workability cement dispersing polymer comprises:

a) an ester group-containing polymer comprising a polymer or copolymer derived from monomers comprising: 1) an unsaturated carboxylic acid ester monomer; and 2) at least one of unsaturated acid monomer, unsaturated sulfonate monomer; and

b) a carboxymethyl starch; and

c) polyethylene glycol monomethyl ether.

2. The high workability cement dispersion polymer of claim 1, wherein the unsaturated carboxylic acid ester monomer comprises one or more of the monomers having the following structures:

CH₂＝CR¹-COOR²；

wherein, R is¹Is H or CH₃，R²Is CH₃Or CH₂CH₃(ii) a The unsaturated carboxylic acid ester monomer accounts for 35 mol% to 50 mol% of the total amount of the polymerized monomers.

3. The high workability cement dispersion polymer of claim 1 wherein the unsaturated acid monomers comprise one or more of the monomers having the following structures:

CH₂＝CH-Ar-R³-COOH；

wherein, R is³Represents an alkyl group having 0 to 2 carbon atoms, Ar represents an aryl group-containing structure of an aryl group having a para-oriented linking group, and the unsaturated acid monomer accounts for 35 to 45 mol% of the total amount of the polymerized monomers.

4. The high workability cement dispersion polymer of claim 1 wherein the unsaturated sulfonate monomers comprise one or more of the monomers having the following structures:

CH₂＝CR⁴-R⁵-SO₃Na

wherein, R is⁴Is H or CH₃，R⁵Is CH₂Or Ar or CONHC (CH)₃)(CH₃)CH₂(ii) a The unsaturated sulfonate monomer is present in an amount of 10 to 30 mole% based on the total amount of polymerized monomers.

5. The high workability cement dispersion polymer according to claim 1, wherein the molecular weight of the polyethylene glycol monomethyl ether is 1200 to 3000.

6. The high workability cement dispersion polymer according to claim 1, wherein the mass ratio of the carboxymethyl starch to the ester group-containing polymer is 1:10 to 20.

7. A method for preparing a high workability cement dispersing polymer, said method comprising:

(1) preparing an ester group-containing polymer comprising a polymer or copolymer derived from monomers comprising: 1) an unsaturated carboxylic acid ester monomer; and 2) at least one of unsaturated acid monomer, unsaturated sulfonate monomer;

(2) carboxymethyl starch, polyethylene glycol monomethyl ether and ester group-containing polymer are subjected to ester exchange under the condition of a catalyst to prepare the high workability cement dispersion polymer.

8. The method for preparing a high workability cement dispersing polymer according to claim 7, characterized in that: the polymerization reaction is carried out under redox-initiated conditions.

9. The method of preparing a high workability cement dispersing polymer according to claim 8 characterized by: the oxidant in the redox initiation system is at least one selected from hydrogen peroxide, potassium persulfate, sodium persulfate or ammonium persulfate.

10. The method of preparing a high workability cement dispersing polymer according to claim 8 characterized by: the reducing agent in the redox initiation system is at least one selected from sodium hypophosphite, L-ascorbic acid, sodium bisulfite and sodium formaldehyde sulfoxylate.

11. The method of preparing a high workability cement dispersing polymer according to claim 8 characterized by: the oxidant in the redox initiation system accounts for 2-5% of the total mass of the polymerization monomers, and the reducing agent accounts for 1-2% of the total mass of the polymerization monomers.

12. The method for preparing a high workability cement dispersing polymer according to claim 7, characterized in that: the catalyst is rare earth solid super acid SO₄ ^2-/TiO₂/Mo⁶⁺。

13. The method for preparing a high workability cement dispersing polymer according to claim 7, characterized in that: the catalyst accounts for 1-2% of the total mass of the polymerization monomers.

14. The method for preparing a high workability cement dispersing polymer according to claim 7, characterized in that: the temperature of the polymerization reaction is 30-40 ℃, and the temperature of the esterification reaction is 120-160 ℃.

Technical Field

The invention relates to the technical field of building additives, in particular to a high workability cement dispersion polymer and a preparation method thereof.

Background

With the continuous popularization of national key engineering projects and the complexity of the structure and the badness of conditions of the structure, great challenges are provided for the quality and the durability of a concrete structure, the temperature inside the concrete rises due to a large amount of hydration heat generated by cement hydration, the hydration heat is accumulated inside the concrete and is not easy to dissipate, and when the tensile stress generated by the internal and external temperature difference at the initial stage of concrete setting exceeds the compressive strength of the concrete, the concrete cracks, so that the strength and the durability of the concrete are seriously affected.

The current possible effective solution is to add materials such as a polycarboxylate water reducer, a hydration regulator and the like to regulate the state and the hydration heat of concrete, but the polycarboxylate water reducer and a sand material have adaptability problem. Therefore, in order to ensure the smooth construction and the engineering quality of the structure, the water reducer which has a good dispersion function and can obviously reduce the hydration heat release rate of the cement is developed, and the water reducer has a wide market prospect.

Maltodextrin is a low degree starch hydrolysate which is a degradation product of starch produced by enzymatic or acid treatment comprising a range of oligosaccharides and polysaccharides with a dextrose equivalent value (DE value) < 20. Maltodextrins with different DE values have different functional properties, such as solubility, thickening properties, acid and salt resistance, etc. The invention takes the maltodextrin as the raw material, has low price, sustainability and environmental protection, and has great significance for developing the high-efficiency water reducing agent by taking the maltodextrin as a resource.

In the prior art, starch substances are introduced into a polycarboxylic acid water reducing agent, so that the problems of poor dispersing performance, overlarge product viscosity and adaptability of the water reducing agent, or the problems of concrete durability and the like caused by the hydration heat release rate of cement cannot be solved.

The publication No. CN104558215A discloses a double-modified maltodextrin high-efficiency water reducing agent, which is prepared by diluting concentrated sulfuric acid by an organic solvent, sulfonating maltodextrin at low temperature, carrying out esterification reaction on a sulfonated product by using dibasic acid anhydride, and finally dissolving the product in water and adding alkali for neutralization.

The publication No. CN108440762A discloses a hyperbranched starch-based water reducing agent, and the adopted hyperbranched polymers with polyamide-amine at the tail end are prepared by the reaction of polybasic acid and amine substances and are reacted with starch to synthesize the hyperbranched starch-based water reducing agent, so that the water reducing efficiency of the water reducing agent can be better improved, the retardation performance is improved, but the preparation process is too complex, the conversion rate of a target product is low, and the industrial production is not facilitated.

The publication No. CN109776022A discloses a composite controllable hydration heat cement-based material, which achieves the purpose of controlling the hydration heat release rate of cement by physically compounding a certain amount of cross-linking agent, organic acid and starch-based macromolecular organic matter, but the product does not have the water reducing effect, and the product is compounded in a liquid-solid manner, so that the actual application process is complex, and the popularization is not facilitated.

The publication No. CN110606922A discloses a preparation method of a polycarboxylate water reducer with hydration heat regulation and control effects, wherein carboxymethyl starch with a substitution degree of 0.3-0.5 and better water solubility is introduced, and is subjected to series of treatments such as pyrolysis, acidolysis and enzymolysis, and then is subjected to esterification reaction with unsaturated hydroxy ester monomers to obtain modified CMS monomers for synthesizing the polycarboxylate water reducer, but the preparation process is too complex and is not beneficial to industrial production.

The publication No. CN111592619A discloses a starch-based polycarboxylic acid water reducer mate and a preparation and use method thereof, wherein modified starch containing unsaturated double bonds, unsaturated polyoxyethylene ether and acrylic monomers are used for preparing the starch-based polycarboxylic acid water reducer mate under the action of an initiator, but the water reduction rate is low, the starch-based polycarboxylic acid water reducer mate needs to be compounded with other water reducers for use, the starch-based polycarboxylic acid water reducer mate has the problem of adaptability to the water reducers, and the starch-based polycarboxylic acid water reducer mate is not beneficial to popularization and.

Disclosure of Invention

To solve the problem of poor workability of the existing water reducing agents mentioned in the above background art, the present invention provides a high workability cement dispersing polymer comprising:

a) an ester group-containing polymer comprising a polymer or copolymer derived from monomers comprising: 1) an unsaturated carboxylic acid ester monomer; and 2) at least one of unsaturated acid monomer, unsaturated sulfonate monomer; and

b) a carboxymethyl starch; and

c) polyethylene glycol monomethyl ether.

On the basis of the above scheme, further, the unsaturated carboxylic ester monomer comprises one or more of the following monomers:

CH₂＝CR¹-COOR²；

wherein, R is¹Is H or CH₃，R²Is CH₃Or CH₂CH₃(ii) a The unsaturated carboxylic acid ester monomer accounts for 35 mol% to 50 mol% of the total amount of the polymerized monomers.

On the basis of the above scheme, further, the unsaturated acid monomer comprises one or more of the following monomers:

CH₂＝CH-Ar-R³-COOH；

wherein, R is³Represents an alkyl group having 0 to 2 carbon atoms, Ar represents an aryl group-containing structure of an aryl group having a para-oriented linking group, and the unsaturated acid monomer accounts for 35 to 45 mol% of the total amount of the polymerized monomers.

Based on the above scheme, further, the unsaturated sulfonate monomer comprises one or more of the following monomers:

CH₂＝CR⁴-R⁵-SO₃Na

wherein, R is⁴Is H or CH₃，R⁵Is CH₂Or Ar or CONHC (CH)₃)(CH₃)CH₂(ii) a The unsaturated sulfonate monomer is present in an amount of 10 to 30 mole% based on the total amount of polymerized monomers.

On the basis of the scheme, the molecular weight of the polyethylene glycol monomethyl ether is 1200-3000.

On the basis of the scheme, the mass ratio of the carboxymethyl starch to the ester group-containing polymer is 1: 10-20.

The present invention provides a method for preparing a high workability cement dispersion polymer, the method comprising:

(1) preparing an ester group-containing polymer comprising a polymer or copolymer derived from monomers comprising: 1) an unsaturated carboxylic acid ester monomer; and 2) at least one of unsaturated acid monomer, unsaturated sulfonate monomer;

(2) carboxymethyl starch, polyethylene glycol monomethyl ether and ester group-containing polymer are subjected to ester exchange under the condition of a catalyst to prepare the high workability cement dispersion polymer.

On the basis of the above scheme, further, the polymerization reaction is carried out under redox initiation conditions.

On the basis of the scheme, the oxidant in the redox initiation system is at least one selected from hydrogen peroxide, potassium persulfate, sodium persulfate and ammonium persulfate.

On the basis of the scheme, the reducing agent in the redox initiation system is selected from at least one of sodium hypophosphite, L-ascorbic acid, sodium bisulfite and sodium formaldehyde sulfoxylate.

On the basis of the scheme, the oxidant in the redox initiation system accounts for 2-5% of the total mass of the polymerized monomers, and the reducing agent accounts for 1-2% of the total mass of the polymerized monomers.

On the basis of the scheme, the catalyst is rare earth solid super acid SO₄ ^2-/TiO₂/Mo⁶⁺。

On the basis of the scheme, the catalyst accounts for 1-2% of the total mass of the polymerized monomers.

On the basis of the scheme, the temperature of the polymerization reaction is 30-40 ℃, and the temperature of the esterification reaction is 120-160 ℃.

Compared with the prior art, the preparation method of the high workability cement dispersion polymer provided by the invention has the following beneficial effects:

1. the cement dispersing polymer synthesized by the invention, which has the functions of improving the workability of fresh concrete and regulating and controlling the hydration heat, can improve the workability of concrete, reduce the hydration heat release rate of cement and delay the appearance of the temperature peak value of concrete, thereby improving the compactness of concrete and reducing the cracking risk of concrete;

2. the carboxymethyl starch is adopted to replace partial polyether monomer for esterification modification, so that the cost is reduced, the cohesiveness and the water-retaining property of the concrete are improved, the problems of concrete quality and durability caused by poor bleeding, segregation and compactness of the concrete are solved, and the carboxymethyl starch has excellent adaptability to different cements, admixtures, artificial sand, environmental temperature and concrete mixing ratio fluctuation.

3. The invention adopts the method of low-temperature copolymerization and high-temperature esterification, reduces the damage of double bonds of reaction monomers, improves the copolymerization degree, and produces the cement dispersion polymer with high water reducing rate and good workability.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following description will clearly and completely describe the embodiments of the present invention, and obviously, the described embodiments are a part of the embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a preparation method of a high workability cement dispersion polymer, which comprises the following steps:

adding an ester-containing polymer and polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding carboxymethyl starch and a catalyst after all water is distilled, heating to 120-160 ℃, simultaneously vacuumizing to react for 2-4 hours under the vacuum degree of 40-80 mbar, slicing the polymer in a molten state, or cooling to below 70 ℃, adding a certain amount of water and 30% sodium hydroxide for neutralization to ensure that the pH is 6-7, thus preparing the cement dispersed polymer with the mass concentration of 50%, wherein the molecular weight is 60000-100000.

Wherein the preparation method of the polymer containing ester groups comprises the following steps:

1) adding 50 parts of deionized water into a reaction kettle;

2) when the temperature is raised to 30-40 ℃, respectively dripping 15-45 parts of an oxidant aqueous solution A with the mass concentration of 10% and 20-40 parts of a reducing agent aqueous solution B with the mass concentration of 5%, and after 10min, dripping a mixed solution C of 30-50 parts of unsaturated carboxylic ester monomers, 35-45 parts of unsaturated acid monomers, 10-30 parts of unsaturated sulfonate monomers and 30 parts of deionized water within 90-120 min;

3) and after the dripping is finished, adding 5 parts of oxidant aqueous solution A with the mass concentration of 10%, finishing the dripping within 20min, and curing for 0.5 hour to obtain the polymer solution with the solid content of 40-50%, the viscosity of 450-800 cps and the weight-average molecular weight of 6000-8000.

To this end, the invention provides the following examples and comparative examples:

example 1

1) Adding 50g of deionized water into a reaction kettle, respectively dropwise adding 25g of 10% hydrogen peroxide aqueous solution A and 35g of 5% L-ascorbic acid aqueous solution B when the temperature is raised to 30 ℃, dropwise adding a mixed solution C of 35g of methyl acrylate, 40g of 4-vinyl benzoic acid, 25g of sodium methallylsulfonate and 30g of deionized water within 100min after 10min,

2) after the dropwise addition, 5g of the solution A was added and the mixture was added within 10min, followed by aging for 0.5 hour to obtain a copolymer solution having a solid content of 45.5%, a viscosity of 660cps and a weight-average molecular weight of 6700.

3) Adding 200g of copolymer and 50g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 20g of carboxymethyl starch and 1g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 40g of water and 37g of sodium hydroxide with the mass concentration of 30% for neutralization, and enabling the pH value to be 6-7, so that the cement dispersed polymer with the mass concentration of 50% is prepared, and the molecular weight is 97600.

Example 2

1) Adding 50g of deionized water into a reaction kettle, respectively dripping 25g of 10 mass percent ammonium persulfate aqueous solution A and 35g of 5 mass percent sodium hypophosphite aqueous solution B when the temperature is raised to 30 ℃, dripping a mixed solution C of 40g of ethyl acrylate, 45g of 4-vinyl phenylacetic acid, 15g of sodium styrene sulfonate and 30g of deionized water within 100min after 10min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% is added, the dropwise addition is completed within 10min, and the mixture is cured for 0.5 hour to obtain a copolymer solution with the solid content of 45.7%, the viscosity of 760cps and the weight-average molecular weight of 7800.

3) Adding 200g of copolymer and 60g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 10g of carboxymethyl starch and 1g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 40g of water and 30g of sodium hydroxide with the mass concentration of 30% for neutralization, and enabling the pH value to be 6-7, so that the cement dispersed polymer with the mass concentration of 50% is prepared, and the molecular weight is 67300.

Example 3

1) Adding 50g of deionized water into a reaction kettle, when the temperature is raised to 35 ℃, respectively dropwise adding 45g of 10 mass percent sodium persulfate aqueous solution A and 30g of 5 mass percent sodium bisulfite aqueous solution B, after 10min, dropwise adding a mixed solution C of 25g of methyl methacrylate, 35g of 4-vinyl benzoic acid, 25g of 2-acrylamido-2-methylpropanesulfonic acid and 30g of deionized water, and completing dripping within 100min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% was added, and the mixture was subjected to dropwise addition within 10 minutes and aged for 0.5 hour to obtain a copolymer solution with a solid content of 45.7%, a viscosity of 650cps and a weight-average molecular weight of 7100.

3) Adding 200g of copolymer and 70g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 15g of carboxymethyl starch and 2g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 30g of water and 30g of sodium hydroxide with the mass concentration of 30% to neutralize, and enabling the pH value to be 6-7, so that the cement dispersed polymer with the mass concentration of 50% is prepared, and the molecular weight is 83800.

Example 4

1) Adding 50g of deionized water into a reaction kettle, respectively dripping 25g of 10 mass percent potassium persulfate aqueous solution A and 35g of 5 mass percent sodium formaldehyde sulfoxylate aqueous solution B when the temperature is raised to 35 ℃, dripping 30g of mixed solution C of ethyl methacrylate, 50g of 4-vinyl phenylacetic acid, 10g of sodium styrene sulfonate and 30g of deionized water within 100min after 10min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% is added, the dropwise addition is completed within 10min, and the mixture is cured for 0.5 hour to obtain a copolymer solution with the solid content of 45.1%, the viscosity of 480cps and the weight-average molecular weight of 6300.

3) Adding 200g of copolymer and 40g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 12g of carboxymethyl starch and 1.5g of rare earth solid super acid SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺The reaction temperature is raised to 140 ℃, vacuum is simultaneously pumped to react for 4 hours under the vacuum degree of 40mbar, the temperature is cooled to below 70 ℃, 30g of water and 35g of water are addedNeutralizing the mixture by using 30% sodium hydroxide to ensure that the pH is 6-7, thus obtaining the cement dispersion polymer with the mass concentration of 50% and the molecular weight of 77400.

Comparative example 1

1) Adding 50g of deionized water into a reaction kettle, when the temperature is raised to 35 ℃, respectively dropwise adding 45g of 10 mass percent sodium persulfate aqueous solution A and 30g of 5 mass percent sodium bisulfite aqueous solution B, after 10min, dropwise adding a mixed solution C of 25g of methyl methacrylate, 35g of 4-vinyl benzoic acid, 25g of 2-acrylamido-2-methylpropanesulfonic acid and 30g of deionized water, and completing dripping within 100min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% was added, and the mixture was subjected to dropwise addition within 10 minutes and aged for 0.5 hour to obtain a copolymer solution with a solid content of 45.7%, a viscosity of 650cps and a weight-average molecular weight of 7100.

3) Adding 200g of copolymer and 70g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, and adding 2g of rare earth solid super acid SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 30g of sodium hydroxide with the mass concentration of 30% to neutralize, and enabling the pH to be 6-7, so that the cement dispersed polymer with the mass concentration of 50% is prepared, and the molecular weight is 43800.

Comparative example 2

1) Adding 50g of deionized water into a reaction kettle, when the temperature is raised to 35 ℃, respectively dropwise adding 45g of 10 mass percent sodium persulfate aqueous solution A and 30g of 5 mass percent sodium bisulfite aqueous solution B, after 10min, dropwise adding a mixed solution C of 25g of methyl methacrylate, 35g of 4-vinyl benzoic acid, 25g of 2-acrylamido-2-methylpropanesulfonic acid and 30g of deionized water, and completing dripping within 100min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% was added, and the mixture was subjected to dropwise addition within 10 minutes and aged for 0.5 hour to obtain a copolymer solution with a solid content of 45.7%, a viscosity of 650cps and a weight-average molecular weight of 7100.

3) Will be provided withAdding 200g of copolymer into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 15g of carboxymethyl starch and 2g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 30g of sodium hydroxide with the mass concentration of 30% to neutralize, and enabling the pH to be 6-7, so that the cement dispersed polymer with the mass concentration of 50% is prepared, and the molecular weight is 63800.

Comparative example 3

1) Adding 50g of deionized water into a reaction kettle, when the temperature is raised to 35 ℃, respectively dropwise adding 45g of 10% sodium persulfate aqueous solution A and 30g of 5% sodium bisulfite aqueous solution B, after 10min, dropwise adding a mixed solution C of 25g of methyl methacrylate, 25g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt and 30g of deionized water, and completing dripping within 100 min;

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% is added, the dropwise addition is completed within 10min, and the mixture is cured for 0.5 hour to obtain a copolymer solution with the solid content of 31.7%, the viscosity of 450cps and the weight-average molecular weight of 6400.

3) Adding 200g of copolymer and 70g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 15g of carboxymethyl starch and 2g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 30g of sodium hydroxide with the mass concentration of 30% to neutralize, and enabling the pH value to be 6-7 to obtain the cement dispersed polymer with the molecular weight of 75100.

Comparative example 4

1) Adding 50g of deionized water into a reaction kettle, when the temperature is raised to 35 ℃, respectively dropwise adding 45g of 10% sodium persulfate aqueous solution A and 30g of 5% sodium bisulfite aqueous solution B, after 10min, dropwise adding a mixed solution C of 25g of methyl methacrylate, 35g of 4-vinylbenzoic acid and 30g of deionized water, and completing dripping within 100min,

2) after the dropwise addition, 5g of the solution A with the mass concentration of 10% is added, the dropwise addition is completed within 10min, and the mixture is cured for 0.5 hour to obtain a copolymer solution with the solid content of 31.5%, the viscosity of 580cps and the weight-average molecular weight of 7400.

3) Adding 200g of copolymer and 70g of polyethylene glycol monomethyl ether into a reaction kettle, heating to 95 ℃, continuously introducing nitrogen, adding 15g of carboxymethyl starch and 2g of rare earth solid super acidic SO after water is distilled₄ ^2-/TiO₂/Mo⁶⁺And raising the reaction temperature to 150 ℃, simultaneously vacuumizing to enable the mixture to react for 3 hours under the vacuum degree of 40mbar, cooling to below 70 ℃, adding 30g of sodium hydroxide with the mass concentration of 30% to neutralize, and enabling the pH value to be 6-7 to obtain the cement dispersed polymer with the molecular weight of 64200.

It should be noted that the specific parameters or some common reagents in the above embodiments are specific examples or preferred embodiments of the present invention, and are not limited thereto; those skilled in the art can adapt the same within the spirit and scope of the present invention.

Samples obtained by synthesis in examples 1-4 and comparative examples 1-4 were tested for water reducing rate, slump loss over time, workability, etc. of concrete using standard cement according to GB 8076 + 2008 "concrete admixture". The concrete mixing proportion is as follows: cement 360kg/m³780kg/m of sand³Stone 1050kg/m³The slump was controlled to 210. + -.10 mm, and the results are shown in Table 1.

TABLE 1 test results of various examples and comparative examples

As can be seen from Table 1, compared with comparative examples 1-4, the cohesiveness of the synthesized examples 1-4 is better than that of comparative examples 1-4, the sample added with carboxymethyl starch is better in workability, small in bleeding distance and better in slump retaining effect, and meanwhile, the concrete is more compact and the concrete shrinkage is reduced by the examples, and the 28d compressive strength is equivalent to or even better than that of comparative examples 1-4.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.