阅读说明：本技术 一种抗裂减缩型聚羧酸减水剂及其制备方法 (Anti-cracking shrinkage-reducing polycarboxylate superplasticizer and preparation method thereof ) 是由 卢通 钱珊珊 王学川 赵旭 彭荩影 屈浩杰 于鹏程 郑春扬 于 2021-02-02 设计创作，主要内容包括：本发明公开了一种抗裂减缩型聚羧酸减水剂及其制备方法,其重均分子量(M-w)为10000～100000,结构式为本发明制备方法为：(1)以没食子酸为原料在结构上引入不饱和双键结构制备出没食子酸衍生物不饱和小单体,再将其与含羰基不饱和酸及其衍生物单体进行自由基共聚反应得到减水剂预聚产物；(2)在预聚产物的没食子酸衍生物上引入亲水性聚醚侧链,制备出性能优异的减缩型聚羧酸减水剂。本发明制备得到的抗裂减缩型聚羧酸减水剂稳定性好,适应各种极端天气条件下的储存；在混凝土中分散效果好,减缩效果优异,对由各类收缩引起的开裂情况有非常明显的控制和减缓作用。(The invention discloses an anti-cracking shrinkage-reducing polycarboxylate superplasticizer and a preparation method thereof, wherein the weight-average molecular weight (M) of the anti-cracking shrinkage-reducing polycarboxylate superplasticizer w ) 10000-100000, and the structural formula is)

1. The anti-cracking and shrinkage-reducing polycarboxylate water reducer is characterized by having the following structure:

wherein, P is O, N or NH atom; r₁Is one or the combination of more of H, alkali metal ions, aliphatic groups, alicyclic groups, phenyl and phenyl derivatives; r₂Is one or the combination of several of H, aliphatic group, alicyclic group, phenyl and phenyl derivative; the polymerization degrees n and m are respectively and independently 1-100; the degree of polymerization r is 10 to 200.

2. The preparation method of the anti-cracking and shrinkage-reducing polycarboxylate superplasticizer is characterized by comprising the following steps:

1) preparing an anti-cracking shrinkage-reducing water reducer prepolymerization product: protecting phenolic hydroxyl groups on the gallic acid by using acetic anhydride, stirring and reacting for 3h under the catalysis of concentrated sulfuric acid at 50 ℃, washing with water, and then reacting with chloropropene or bromopropylene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; the obtained small monomer, carbonyl-containing unsaturated acid and derivative monomer thereof, an initiator, a reducing agent and a chain transfer agent are jointly acted in a solvent, oxidation-reduction free radical polymerization reaction is carried out at 10-50 ℃, and a prepolymerization product is prepared after 3-5 hours; wherein, the molar ratio of the unsaturated acid containing carbonyl and the derivative monomer thereof, the unsaturated small monomer of the gallic acid derivative, the initiator, the reducing agent and the chain transfer agent is as follows: (1.5-5) 0.3, (0.01-0.2), (0.01-0.15);

2) preparing an anti-cracking shrinkage-reducing polycarboxylate superplasticizer: and (3) carrying out Williamson ether forming reaction on the obtained product and the halogen-terminated modified polyether in an acetonitrile/water (v/v: 1/20) mixed solvent and an acid-binding agent at the temperature of 10-50 ℃, and reacting for 3-5 h to obtain the anti-cracking and shrinkage-reducing type polycarboxylate water reducer, wherein the molar ratio of the pre-polymerization product of the anti-cracking and shrinkage-reducing type polycarboxylate water reducer to the halogen-terminated modified polyether is 1: 3.

3. The method according to claim 2, wherein the gallic acid derivative unsaturated small monomer structure in step 1) is

4. The method as claimed in claim 2, wherein the carbonyl group-containing unsaturated acid and its derivative monomer in step 1) is one or more of acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, maleic acid, acrylamide, methacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and hydroxy-n-butyl methacrylate.

5. The method according to claim 2, wherein the solvent in step 1) is one or more of methanol, ethanol, tert-butanol, acetonitrile, acetone, Dichloromethane (DCM), chloroform, tetrahydrofuran, dimethyl sulfoxide (DMSO), benzene, toluene, 1, 2-dichloroethane, and N, N-Dimethylformamide (DMF).

6. The method as claimed in claim 2, wherein the initiator in step 1) is one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, azobisisobutyronitrile and azobisisoheptonitrile.

7. The method according to claim 2, wherein the reducing agent in step 1) is one or more of L-ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite and sodium hypophosphite.

8. The method of claim 2, wherein the chain transfer agent in step 1) is one or more of mercaptoethanol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methallylsulfonate, and dodecanethiol.

9. The method of claim 2, wherein the acid-binding agent in step 2) is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, disodium bicarbonate, dipotassium bicarbonate, diethylamine, triethylamine, pyridine, and 4-Dimethylaminopyridine (DMAP).

10. The method of claim 2, wherein the halogen-terminated modified polyether in step 2) has a structure of

,

Wherein the degree of polymerization r is 10-200; x is F, Br or I atom.

Technical Field

The invention relates to the field of polycarboxylic acid water reducing agents for concrete, in particular to an anti-cracking and shrinkage-reducing polycarboxylic acid water reducing agent and a preparation method thereof.

Background

Polycarboxylic acid water reducing agents are widely applied to projects such as railways, bridges and houses, and the market requirements on additives are higher and higher in the aspect of infrastructure. However, due to unavoidable factors, concrete is susceptible to cracking during early hardening and later use, resulting in impaired durability. At present, a series of protective measures for dealing with the cracking phenomenon of concrete, such as improving the rubber components, doping the expanding agent, doping the fiber and establishing a specific curing technology aiming at a specific environment, are also appeared in the market. However, from a comprehensive point of view, internally incorporating concrete shrinkage reducers is the simplest and most effective means.

Shrinkage of concrete not only causes cracking and significantly reduces strength, but also accelerates carbonation and reinforcement corrosion. Based on the above, the concrete shrinkage reducing agent is added to reduce the water evaporation by reducing the surface tension of capillary pores, so that the cracking phenomenon caused by self-shrinkage, drying shrinkage, plastic shrinkage and the like during the hardening of the concrete can be remarkably reduced, and the durability of the concrete is improved.

Some shrinkage reducing agents of alcohols, ethers, alcamines and the like have been reported early on as represented by japan and usa, and such shrinkage reducing agents have no water reducing effect and require a high blending amount, and also cause a side effect of lowering the strength at the later stage, which limits their use. For domestic research, patent CN103724567A discloses a shrinkage-reducing polycarboxylic acid water reducing agent and a preparation method thereof, wherein the preparation method is that free radical polymerization is carried out after esterification, the obtained water reducing agent can remarkably reduce the surface tension of solution in gaps of cement slurry, but the esterification reaction needs to be carried out at high temperature for a long time, which greatly reduces the feasibility of industrial production; patent CN107540795A discloses a shrinkage-reducing water reducing agent prepared by radical polymerization of alkenyl polyether macromonomer, acrylic acid, maleic acid monoalkyl ester and maleic acid polyoxyethylene/polyoxypropylene polydimethylsiloxane and a synthesis method thereof, wherein the synthesized shrinkage-reducing water reducing agent has small influence on the dispersion and slump retaining performance of concrete, but has small reduction of 28-day shrinkage ratio relative to the standard, and is lack of market competitiveness.

Disclosure of Invention

The invention aims to provide an anti-cracking and shrinkage-reducing polycarboxylate superplasticizer.

The invention also aims to provide a preparation method of the water reducing agent.

The technical scheme of the invention is as follows:

an anti-cracking and shrinkage-reducing polycarboxylate water reducing agent with a weight-average molecular weight (M)_w) 10000-100000, and the anti-cracking shrinkage-reducing polycarboxylate superplasticizer has the following structure:

wherein, P is O, N or NH atom; r₁Is one or a combination of more of H, alkali metal ions, aliphatic groups, alicyclic groups, phenyl or phenyl derivatives; r₂Is one or the combination of several of H, aliphatic group, alicyclic group, phenyl and phenyl derivative; the polymerization degrees n and m are respectively and independently 1-100; the degree of polymerization r is 10 to 200.

The invention further provides a preparation method of the anti-cracking and shrinkage-reducing polycarboxylate superplasticizer, which comprises the following specific steps:

1) preparing an anti-cracking shrinkage-reducing water reducer prepolymerization product: protecting phenolic hydroxyl groups on the gallic acid by using acetic anhydride, stirring and reacting for 3h under the catalysis of concentrated sulfuric acid at 50 ℃, washing with water, and then reacting with chloropropene (or bromopropylene) at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; the obtained small monomer, carbonyl-containing unsaturated acid and derivative monomer thereof, an initiator, a reducing agent and a chain transfer agent are jointly acted in a solvent, oxidation-reduction free radical polymerization reaction is carried out at 10-50 ℃, and a prepolymerization product is prepared after 3-5 hours; wherein, the molar ratio of the unsaturated acid containing carbonyl and the derivative monomer thereof, the unsaturated small monomer of the gallic acid derivative, the initiator, the reducing agent and the chain transfer agent is as follows: (1.5-5) 0.3, (0.01-0.2), (0.01-0.15);

2) preparing an anti-cracking shrinkage-reducing polycarboxylate superplasticizer: and (3) carrying out Williamson ether forming reaction on the obtained product and the halogen-terminated modified polyether in an acetonitrile/water (v/v: 1/20) mixed solvent and an acid-binding agent at the temperature of 10-50 ℃, and reacting for 3-5 h to obtain the anti-cracking and shrinkage-reducing type polycarboxylate water reducer, wherein the molar ratio of the pre-polymerization product of the anti-cracking and shrinkage-reducing type polycarboxylate water reducer to the halogen-terminated modified polyether is 1: 3.

Preferably, the unsaturated small monomer structure of the gallic acid derivative in the step 1) is as follows:

preferably, the carbonyl-containing unsaturated acid and derivative monomer in step 1) is one or a combination of acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate, maleic acid, acrylamide, methacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and hydroxy-n-butyl methacrylate.

Preferably, the solvent in step 1) is one or more of methanol, ethanol, tert-butanol, acetonitrile, acetone, Dichloromethane (DCM), chloroform, tetrahydrofuran, dimethyl sulfoxide (DMSO), benzene, toluene, 1, 2-dichloroethane, and N, N-Dimethylformamide (DMF).

Preferably, the initiator in the step 1) is one or a combination of more of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, azobisisobutyronitrile and azobisisoheptonitrile.

Preferably, the reducing agent in the step 1) is one or a combination of more of L-ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite and sodium hypophosphite.

Preferably, the chain transfer agent in the step 1) is one or a combination of more of mercaptoethanol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propenyl sulfonate and dodecanethiol.

Preferably, the acid-binding agent in the step 2) is one or a combination of several of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, disodium bicarbonate, dipotassium bicarbonate, diethylamine, triethylamine, pyridine or 4-Dimethylaminopyridine (DMAP).

Preferably, the halogen-terminated modified polyether in the step 2) has a structure of

Wherein the degree of polymerization r is 10-200; x is F, Br or I atom.

According to the invention, a pre-polymerization product containing a rigid group is obtained through free radical copolymerization, and then a hydrophilic modified polyether side chain is introduced to obtain the anti-cracking and shrinkage-reducing type polycarboxylate water reducer, and the water reducer is endowed with good slump-retaining performance and mechanical property.

The invention has the following beneficial effects:

1) the raw materials of the invention have low price and rich and stable sources;

2) the polycarboxylate water reducer prepared by the invention has an ester group structure, and can be hydrolyzed to release carboxyl, so that the water reducer can have an excellent dispersion retaining effect;

3) according to the polycarboxylic acid water reducing agent prepared by the invention, the hydrophilic modified polyether side chain is introduced on the rigid group with a stable structure, so that the water retention of concrete is increased through the hydrogen bond effect, and the concrete is endowed with excellent anti-cracking and shrinkage reducing performances;

4) the polycarboxylate superplasticizer prepared by the invention can be stored at high and low temperatures for a long time, and can keep excellent and stable performance;

5) the preparation process is safe, reliable, simple and convenient, and the use process is safe and pollution-free.

Detailed Description

The following examples illustrate and describe the technical solutions for the present invention in more detail.

Example 1

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with chloropropene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol) and acrylic acid (3mol) in 50mL of methanol together with ammonium persulfate (0.1mol), sodium bisulfite (0.1mol) and 2-mercaptopropionic acid (0.08mol) at 20 ℃ for 4 hours to prepare a prepolymerization product;

2) adding sodium hydroxide into the obtained prepolymer to enable the pH of the solution to be 7-8, removing the protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w1000g/mol) of 120mL acetonitrile/water (v/v-1/20) mixed solution, and reacting for 5h at 50 ℃ to obtain the anti-cracking shrinkage-reducing polycarboxylic acid water reducing agent (M)_w＝45000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 35, 3 and 23, respectively.

Example 2

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with bromopropylene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol) and methacrylic acid (3.5mol) in 50mL of acetone with hydrogen peroxide (0.15mol), sodium sulfite (0.08mol) and 3-mercaptopropionic acid (0.07mol) for 3.5 hours at 30 ℃ to obtain a prepolymerization product;

2) adding potassium hydroxide into the obtained prepolymer to enable the pH of the solution to be 7-8, removing the protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w800g/mol) of 120mL acetonitrile/water (v/v-1/20) mixed solution, and reacting for 6h at 40 ℃ to obtain the anti-cracking shrinkage-reducing polycarboxylic acid water reducing agent (M)_w＝40000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 34, 3 and 18, respectively.

Example 3

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with chloropropene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol) and acrylamide (4mol) in 50mL of ethanol for 4.5 hours at 30 ℃ under the joint action of potassium persulfate (0.1mol), sodium metabisulfite (0.12mol) and 2-mercaptopropionic acid (0.08mol) to obtain a prepolymerization product;

2) adding triethylamine into the obtained prepolymer to enable the pH value of the solution to be 7-8, removing a protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w3500g/mol) of 120mL acetonitrile/water (v/v 1/20), and reacting at 50 ℃ for 7h to obtain the anti-cracking shrinkage-reducing polycarboxylic acid water reducing agent (M)_w＝60000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 16, 1 and 80, respectively.

Example 4

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with bromopropylene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol) and sodium acrylate (4mol) in 50mL of acetonitrile with sodium persulfate (0.08mol), L-ascorbic acid (0.05mol) and thioglycolic acid (0.1mol) for 4 hours at 25 ℃ to obtain a prepolymerization product;

2) adding sodium bicarbonate into the obtained prepolymer to enable the pH of the solution to be 7-8, removing the protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w3000g/mol) of 120mL of acetonitrile/water (v/v is 1/20), and reacting for 5h at 50 ℃ to obtain the anti-cracking shrinkage-reducing polycarboxylic acid water reducing agent (M)_w＝45000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 13, 1 and 68, respectively.

Example 5

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with chloropropene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol) and potassium acrylate (5mol) in 50mL of toluene for 5 hours at 15 ℃ under the combined action of hydrogen peroxide (0.15mol), sodium sulfite (0.1mol) and 3-mercaptopropionic acid (0.13mol) to obtain a prepolymerization product;

2) adding potassium bicarbonate into the obtained prepolymer to enable the pH of the solution to be 7-8, removing the protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w2400g/mol) of 120mL of acetonitrile/water (v/v-1/20)Mixing the solution, and reacting at 45 ℃ for 5h to obtain the anti-cracking shrinkage-reducing polycarboxylate superplasticizer (M)_w＝45000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 15, 1 and 54, respectively.

Example 6

1) Preparing an anti-cracking shrinkage-reducing water reducer prepolymer product: stirring 1mol of gallic acid and 4mol of acetic anhydride under the catalysis of concentrated sulfuric acid (0.2mL) at 50 ℃ for reaction for 3h, washing with water, and then reacting with bromopropylene at room temperature for 24h to obtain a gallic acid derivative unsaturated small monomer; carrying out free radical polymerization reaction on the obtained small monomer (0.3mol), acrylic acid (2mol) and methacrylic acid (2mol) in 50mL tetrahydrofuran with ammonium persulfate (0.1mol), sodium hypophosphite (0.1mol) and dodecanethiol (0.06mol) for 4 hours at 25 ℃ to obtain a prepolymerization product;

2) adding sodium hydroxide into the obtained prepolymer to enable the pH of the solution to be 7-8, removing the protecting group, and then evaporating to remove the solvent; continuously adding end halogen-based modified polyether (1mol, M) into the obtained product_w1000g/mol) of 120mL acetonitrile/water (v/v-1/20) mixed solution, and reacting for 5h at 45 ℃ to obtain the anti-cracking shrinkage-reducing polycarboxylic acid water reducing agent (M)_w＝35000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n1, n2, m and r are respectively 13, 13, 2 and 23.

Comparative example 1

Mixing acrylic acid (3mol) and polyethylene glycol methacrylate (1mol, M)_w3000g/mol under the combined action of hydrogen peroxide (0.11mol), sodium sulfite (0.08mol) and 3-mercaptopropionic acid (0.08mol), and carrying out free radical polymerization at 25 ℃ for 4.5h to obtain the polycarboxylic acid water reducing agent (M)_w＝30000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 7, 2 and 68, respectively.

Comparative example 2

Mixing sodium acrylate (4mol) and methyl allyl polyoxyethylene ether (1mol, M)_w1500g/mol) under the combined action of sodium persulfate (0.08mol), L-ascorbic acid (0.07mol) and 2-mercaptopropionic acid (0.07mol), the polycarboxylic acid water reducing agent (M) is obtained after the radical polymerization reaction for 3.5h at 20 DEG C_w＝40000g/mol)。

The molecular structural formula is as follows:

wherein the polymerization degrees n, m and r are 17, 4 and 34, respectively.

Test example

1. Cement paste fluidity test

The test refers to GB/T8077-. Wherein the cement is P.I type standard cement, W/C is 0.29, and the folded and fixed admixture amount of the admixture is 0.18 percent of the cement amount. The results show that the embodiment of the invention has no reduction of the initial dispersion and dispersion maintaining effect after introducing other groups, and can achieve the same level with the common polycarboxylic acid water reducing agent.

TABLE 1 Net pulp fluidity and loss over time for different samples

2. Testing of concrete Properties

The concrete slump retaining performance and the mechanical property of the concrete doped with the concrete of the embodiment and the comparative example of the invention are evaluated under the same doping amount condition by referring to GB 8076 + 2008 concrete admixture, and the specific results are shown in Table 2. Wherein the used cement is P.I type standard cement, the folded and fixed amount of the admixture is 0.25 percent of the dosage of the cement, and the designed strength of the concrete is C30.

TABLE 2 concrete slump retaining and mechanical properties of different samples

The result shows that compared with the concrete doped with the common polycarboxylate superplasticizer of the comparative example, the concrete doped with the concrete of the embodiment of the invention has no adverse effect on the dispersing performance and the holding performance, and the compressive strength of 7d and 28d can be improved by about 10%. In addition, the concrete blended with the examples of the present invention has a 28d shrinkage ratio decrease of 56.69% relative to the comparative blended example, that is, the present invention can achieve the object of crack resistance and shrinkage reduction for the concrete.

Finally, it should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto.