CN107722194B - High-water-reduction polycarboxylic acid cement dispersant and preparation method thereof - Google Patents

High-water-reduction polycarboxylic acid cement dispersant and preparation method thereof Download PDF

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CN107722194B
CN107722194B CN201710968236.8A CN201710968236A CN107722194B CN 107722194 B CN107722194 B CN 107722194B CN 201710968236 A CN201710968236 A CN 201710968236A CN 107722194 B CN107722194 B CN 107722194B
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acid
monomer
polycarboxylic acid
cement dispersant
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CN107722194A (en
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冉千平
李申桐
杨勇
舒鑫
黄振
赵红霞
严涵
翟树英
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Jiangsu Bote New Materials Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F267/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated polycarboxylic acids or derivatives thereof as defined in group C08F22/00
    • C08F267/06—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated polycarboxylic acids or derivatives thereof as defined in group C08F22/00 on to polymers of esters
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/24—Macromolecular compounds
    • C04B24/26—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C04B24/2605—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing polyether side chains
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F285/00—Macromolecular compounds obtained by polymerising monomers on to preformed graft polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/34—Introducing sulfur atoms or sulfur-containing groups
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/30—Water reducers, plasticisers, air-entrainers, flow improvers
    • C04B2103/302—Water reducers

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  • General Chemical & Material Sciences (AREA)
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Abstract

The invention discloses a polycarboxylic acid cement dispersant with high water reduction and a preparation method thereof. The preparation method comprises the following steps: firstly, carrying out copolymerization reaction on a methacrylic acid polyethylene glycol ester monomer and an unsaturated alcohol monomer to obtain a comb-shaped high polymer with a main chain having hydroxyl and a side chain being polyether; then, under the action of an intermediate reagent thiourea, hydroxyl in the comb-shaped macromolecular polymer is converted into sulfydryl to prepare a comb-shaped macromolecular chain transfer agent with a sulfydryl main chain and a polyether side chain; and finally, regulating and controlling an unsaturated acid monomer by using a comb-shaped macromolecular chain transfer agent to carry out free radical polymerization, and finally obtaining the high water-reducing polycarboxylic acid cement dispersant. The high water-reducing polycarboxylic acid cement dispersant has low mixing amount, high water reducing rate and good slump retaining property in concrete application, and can greatly save the production cost of concrete; the production process is green and pollution-free, the process is simple, the production stability is high, and the industrial production is facilitated.

Description

High-water-reduction polycarboxylic acid cement dispersant and preparation method thereof
Technical Field
The invention belongs to the technical field of additives for cement concrete, and particularly relates to a polycarboxylic acid cement dispersant with high water reduction and a preparation method thereof.
Background
The polycarboxylic acid cement dispersant is the most important product in the concrete admixture market at present due to the advantages of low mixing amount, high water reducing rate, good slump retaining property, strong molecular structure adjustability, environmental protection and the like. The research on polycarboxylic acids was first conducted by the Japanese catalyst company, and its patents CN1148329, CN1821149 and CN1303875 describe the synthesis and application technology of polycarboxylic acids in detail. Since the 21 st century, the research on polycarboxylic acids in China has been rapidly developed, and many polycarboxylic acid products with excellent performance have been invented, for example, the synthesis of polycarboxylic acid with large water reducing capacity is reported in patent CN103467671A, the synthesis of polycarboxylic acid with long slump retaining capacity is reported in patent CN102977263A, and the synthesis of polycarboxylic acid with mud resistance is reported in patent CN 104861127A.
With the rapid development of concrete technology, the pursuit of polycarboxylic acid products with more excellent performance is endless. The most important requirement of the current market is that the water reducing capacity of the polycarboxylic acid dispersant cannot be greatly improved? It is also necessary to find a way back to the basic molecular structure of the polycarboxylic acid for this problem, since essentially the water-reducing capacity of the polycarboxylic acid is determined by its molecular structure. The polycarboxylic acid is a comb-shaped polymer, the main chain of the polycarboxylic acid is rich in carboxylic acid groups, the side chain of the polycarboxylic acid is polyoxyethylene ether, when the polycarboxylic acid is added into cement slurry, the negatively charged main chain can be directionally adsorbed on the surface of positively charged cement particles, and the polycarboxylic acid plays a role in dispersion through electrostatic repulsion of the main chain and space repulsion of a hydration adsorption layer formed by polyether side chains. From the above theory, the water reducing ability of the polycarboxylic acid can be improved by increasing the adsorption ability of the main chain or the repulsion force of the side chain. However, practical studies have shown that the repulsive force of the side chains does not increase with increasing molecular weight, as the molecular weight increases, to a certain extent. Therefore, the water-reducing ability of the polycarboxylic acid can be improved only by increasing the adsorption ability of the main chain. By increasing the ratio of carboxyl groups in the main chain of the polycarboxylic acid, the adsorption capacity of the polycarboxylic acid can be obviously improved, thereby improving the water reducing capacity. However, this is not the case because the self-polymerization ratio is greatly increased with the increase in the amount of the carboxylic acid monomer during the synthesis, which in turn lowers the effective component (a random polymer formed by copolymerizing the carboxylic acid monomer and the polyether monomer) in the polycarboxylic acid product and deteriorates the water-reducing ability. In order to solve this problem, patent CN104387536B reports a method for increasing the ratio of carboxyl groups in polycarboxylic acid products by hydrolysis of unsaturated ester monomers, but this method also has the problems of self-polymerization of unsaturated ester monomers and insufficient increase of the ratio of carboxyl groups.
Disclosure of Invention
Aiming at the problem that the water reducing capacity of the existing polycarboxylic acid cement dispersant can not be further improved to meet engineering requirements, the invention provides the polycarboxylic acid cement dispersant with high water reducing capacity and the preparation method thereof, wherein the water reducing rate of the polycarboxylic acid cement dispersant with high water reducing capacity is improved by more than 30% compared with that of the existing polycarboxylic acid product, and the method has the advantages of simple process, low cost, small pollution and the like.
A large number of experiments show that the adsorption capacity of the polycarboxylic acid molecules is an important factor influencing the water reducing capacity of the polycarboxylic acid molecules. Based on the method, a high proportion of carboxylic acid monomers are introduced into polycarboxylic acid molecules through the chain transfer effect of the macromolecular polymer rich in sulfhydryl groups, so that the problem of self-polymerization of the carboxylic acid monomers caused by direct copolymerization of the high proportion of carboxylic acid monomers and polyether monomers is solved, and the polycarboxylic acid cement dispersant with high water reduction is finally prepared.
The invention provides a high water-reducing polycarboxylic acid cement dispersant, which has a molecular structure general formula shown in the specification;
Figure GDA0001538086010000021
wherein R is1is-H or-CH3，R2is-CH2-or-CH2CH2-，R3is-H or-COOH, R4is-H, -CH3or-CH2And COOH, wherein x, y, z and n represent the number of the repeating units of each repeating unit, x is 5-40, y is 2-20, z is 20-40, and n is 22-25.
The weight average molecular weight of the high water-reducing polycarboxylic acid cement dispersant is 15000-50000, and the product performance is deteriorated when the molecular weight is too large or too small.
The invention relates to a preparation method of a polycarboxylic acid cement dispersant with high water reduction, which comprises the following steps:
(1) firstly, carrying out copolymerization reaction on a methacrylic acid polyethylene glycol ester monomer and an unsaturated alcohol monomer to obtain a comb-shaped high polymer with a main chain having hydroxyl and a side chain being polyether;
(2) converting hydroxyl in the comb-shaped high molecular polymer prepared in the step (1) into sulfydryl under the action of an intermediate reagent thiourea to prepare a comb-shaped high molecular chain transfer agent with sulfydryl on the main chain and polyether on the side chain;
(3) and (3) finally, regulating and controlling the unsaturated acid monomer to carry out free radical polymerization by using the comb-shaped macromolecular chain transfer agent prepared in the step (2), so that a macromolecular chain segment generated by polymerization of the unsaturated acid monomer is connected with a sulfur atom in a mercapto group, and finally obtaining the high water-reducing polycarboxylic acid cement dispersant.
The molecular structure of the methyl acrylic acid polyethylene glycol ester monomer conforms to the general formula (1)
Figure GDA0001538086010000031
In the formula (1), n is the number of the repeating units of the repeating unit, and n is 22-45;
the weight average molecular weight of the polyethylene glycol methacrylate monomer is 1000-2000, and the product performance is poor due to too small or too large molecular weight;
the unsaturated alcohol monomer is any one of allyl alcohol, methallyl alcohol and 3-methyl-3-buten-1-ol;
the unsaturated acid monomer is at least one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid or maleic anhydride.
The detailed preparation method of the high water-reducing polycarboxylic acid cement dispersant disclosed by the invention specifically comprises the following three steps:
(1) preparing an unsaturated alcohol monomer and water into a solution with the mass concentration of 40%, heating to 60-80 ℃, then dropwise adding a mixed solution with the mass concentration of 40% and consisting of a methacrylic acid polyethylene glycol ester monomer, an initiator I, a chain transfer agent and water for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped high polymer with the main chain having hydroxyl;
(2) keeping the temperature unchanged, adding thiourea and concentrated sulfuric acid into the comb-shaped high-molecular polymer solution prepared in the step (1), stirring and reacting for 12 hours, and adding a sodium hydroxide solution with the mass concentration of 40% to neutralize the reaction solution, so as to obtain the comb-shaped high-molecular chain transfer agent with the mercapto group on the main chain;
(3) keeping the temperature unchanged, then dropwise adding a mixed solution with the mass concentration of 40% and composed of an unsaturated acid monomer, an initiator II and water into the comb-shaped macromolecular chain transfer agent solution prepared in the step (2), dropwise adding for 1h, then keeping the temperature for 1h, and adding a sodium hydroxide solution with the mass concentration of 40% to neutralize the reaction solution to obtain the high water-reduction polycarboxylic acid cement dispersant;
the molar ratio of the polyethylene glycol methacrylate monomer to the unsaturated alcohol monomer in the step (1) is (2-4): 1, and the amount of the chain transfer agent is 1-4% of the total molar amount of the polyethylene glycol methacrylate monomer and the unsaturated alcohol monomer;
the respective molar dosages of the thiourea, the concentrated sulfuric acid and the sodium hydroxide in the step (2) are the same as the molar dosages of the unsaturated alcohol monomer in the step (1), the conversion of hydroxyl into sulfydryl is not facilitated due to too small dosage, raw material waste is caused due to too high dosage, and the product performance cannot be improved;
the molar ratio of the unsaturated acid monomer in the step (3) to the unsaturated alcohol monomer in the step (1) is (20-40): 1;
the dosage of the initiator I is 0.1-0.5 percent of the total mass of the unsaturated alcohol monomer and the methacrylic acid polyethylene glycol ester monomer, and the dosage of the initiator II is 0.1-0.5 percent of the mass of the unsaturated acid monomer.
The chain transfer agent is one of mercaptoethanol, mercaptoacetic acid and mercaptopropionic acid;
the initiator I and the initiator II are any one of sodium persulfate, potassium persulfate, ammonium persulfate, azobisisobutylamidine hydrochloride (V-50), azobisisobutylimidazoline hydrochloride (VA-044) and azobiscyanovaleric acid (V-501), and the initiators are all dissolved in water.
After the step (3) is finished, the reaction solution can be directly used as a cement dispersant without the steps of purification, concentration, drying and the like. Further, the sodium hydroxide solution with the mass concentration of 40% is used after being neutralized, so that the storage stability of the product is enhanced. This is a technique well known in the art. The amount of the sodium hydroxide is preferably adjusted to adjust the pH value of the reaction product to 6-8. After neutralization, the carboxyl groups contained in the above general structural formula (1) may be partially or completely converted into carboxylate. The present invention ignores the effect of neutralization on the molecular weight of the polycarboxylic acid nanoparticles.
The application method of the high water-reducing polycarboxylic acid cement dispersant of the present invention is the same as that of the known cement dispersant, and the application method is generally known to those skilled in the art.
The high water-reducing polycarboxylic acid cement dispersant has the doping amount of 0.05-0.3 percent of the total mass of the cementing material, the doping amount is the pure solid doping amount, and the percentage is the mass percentage. Too low a content results in deterioration of the performance, and too high a content results in economic waste and performance is not improved.
The polycarboxylic acid cement dispersant with high water reduction can be mixed with other water reducing agents sold in the market, such as lignosulfonate water reducing agents, naphthalene sulfonate water reducing agents, polycarboxylic acid water reducing agents and the like, and can also be added with air entraining agents, retarders, early strength agents, expanding agents, tackifiers, shrinkage reducers and defoamers for use.
Compared with the prior art, the invention has the following advantages:
(1) the high water-reducing polycarboxylic acid cement dispersant has low mixing amount, high water reducing rate and good slump retaining property in concrete application, and can greatly save the production cost of concrete.
(2) The production process of the high water-reducing polycarboxylic acid cement dispersant is green and pollution-free, has simple process and strong production stability, and is beneficial to industrial production.
Detailed Description
The following is a detailed description of the preparation method of the highly water-reducing polycarboxylic acid cement dispersant of the present invention, which is intended to enable one skilled in the art to understand the contents of the present invention and to practice the same, but the examples are by no means intended to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention shall be covered within the scope of the present invention.
In the examples of the invention, the molecular weight of the polymer was measured by means of a Gel permeation chromatograph (GPC, WATERS, USA) equipped with a column of 3Mz-Gel SD plus 10 μm (Agilent, USA), and the mobile phase: 0.01M NaNO3Flow rate of the aqueous solution of (1): 1.0mL/min, sample mass percent concentration: 0.50 percent.
The polyethylene glycol methacrylate monomer (double bond retention value > 98%) used in the embodiment of the invention is produced by Nanjing Bote New Material Co., Ltd, and other raw materials are all commercially available common analytical pure chemical reagents.
Example 1:
11.6g of allyl alcohol and 17.4g of water are added to a reaction flask equipped with a stirrer, mixed homogeneously and heated to 80 ℃ and 400g of polyethylene glycol methacrylate (M)w1000), 1.44g of potassium persulfate, 1.64g of mercaptoethanol and 605g of water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl on the main chain; then adding 15.2g of thiourea and 19.6g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 80 ℃, and after reacting for 12 hours, adding 20g of 40% sodium hydroxide solution to neutralize the reaction solution, thereby obtaining the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution composed of 288g of acrylic acid, 0.288g of potassium persulfate and 430g of water is dripped into the reaction solution, the dripping time is 1h, after the heat preservation is carried out for 1h, 400g of 40 percent sodium hydroxide solution is addedNeutralizing the reaction liquid to obtain the polycarboxylic acid cement dispersant with high water reduction, the solid content of 40.6 percent and the molecular weight Mw＝16200。
Example 2:
4.8g of methyl allyl alcohol and 7.2g of water are added to a reaction flask with a stirrer, mixed uniformly and heated to 60 ℃, and 400g of polyethylene glycol methacrylate (M)w2000), 0.81g of VA-044, 0.54g of thioglycolic acid and 602g of water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl on the main chain; then adding 5.07g of thiourea and 6.53g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 60 ℃, reacting for 12 hours, and adding 6.67g of 40% sodium hydroxide solution to neutralize the reaction solution to obtain the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution composed of 200.6g of methacrylic acid, 0.20g of potassium persulfate and 302g of water is dripped into the reaction liquid, the dripping time is 1h, after heat preservation is carried out for 1h, 233.3g of 40 percent sodium hydroxide solution is added to neutralize the reaction liquid, and the polycarboxylic acid cement dispersant with high water reduction is obtained, wherein the solid content is 40.4 percent, and the molecular weight M isw＝29400。
Example 3:
5.73g of 3-methyl-3-butene-1-ol and 8.6g of water are added into a reaction flask with a stirrer, mixed uniformly and heated to 60 ℃, and then 400g of polyethylene glycol methacrylate (M) is added dropwisew1500), 2.02gV-50, 0.636g of mercaptopropionic acid and 604g of water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl on the main chain; then adding 5.07g of thiourea and 6.53g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 60 ℃, reacting for 12 hours, and adding 6.67g of 40% sodium hydroxide solution to neutralize the reaction solution to obtain the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution consisting of 96g of acrylic acid, 57.3g of methacrylic acid, 0.16g V-50 g of water and 230g of water is dripped into the reaction solution for 1 hour, after heat preservation is carried out for 1 hour, 200g of 40 percent sodium hydroxide solution is added to neutralize the reaction solution, and the high water-reducing polycarboxylic acid cement dispersant with 40.2 percent of solid content and M of molecular weight is obtained, wherein the solid content is 40.2 percentw＝26500。
Example 4:
is provided with a stirrer5.52g of allyl alcohol and 8.29g of water are added to the reaction flask, mixed homogeneously and the temperature is raised to 70 ℃ and 400g of polyethylene glycol methacrylate (M)w1200), 1.62g of potassium persulfate, 1.54g of mercaptopropionic acid and 605g of water, dropwise adding for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl group on the main chain; then adding 7.24g of thiourea and 9.33g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 70 ℃, adding 9.52g of 40% sodium hydroxide solution to neutralize the reaction solution after reacting for 12 hours, and obtaining the macromolecular chain transfer agent with sulfydryl on the main chain; finally, dropwise adding a mixed solution consisting of 309.5g of itaconic acid, 0.31g of potassium persulfate and 465g of water into the reaction solution, dropwise adding for 1h, keeping the temperature for 1h, and then adding 238g of 40% sodium hydroxide solution to neutralize the reaction solution to obtain the polycarboxylic acid cement dispersant with high water reduction, wherein the solid content is 40.5%, and the molecular weight M is 40.5%w＝18700。
Example 5:
adding 7.2g of methyl allyl alcohol and 10.8g of water into a reaction bottle with a stirrer, uniformly mixing, heating to 80 ℃, and then dropwise adding 400g of polyethylene glycol methacrylate (M)w1600 percent), 1.02g ammonium persulfate, 0.594g mercaptopropionic acid and 604g water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the main chain having hydroxyl; then adding 7.6g of thiourea and 9.8g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 80 ℃, adding 10g of 40% sodium hydroxide solution to neutralize the reaction solution after reacting for 12 hours, and obtaining the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution consisting of 352g of acrylic acid, 0.352g of ammonium persulfate and 528g of water is dripped into the reaction liquid, the dripping time is 1h, after the heat preservation is carried out for 1h, 350g of 40 percent sodium hydroxide solution is added to neutralize the reaction liquid, and the high water-reducing polycarboxylic acid cement dispersant with the solid content of 40.8 percent and the molecular weight M is obtained, wherein the molecular weight M is the molecular weight of 40.8 percentw＝40600。
Example 6:
5.97g of 3-methyl-3-butene-1-ol and 8.96g of water are added into a reaction flask with a stirrer, mixed uniformly and heated to 80 ℃, and then 400g of polyethylene glycol methacrylate (M) is added dropwisew1800), 0.81g of ammonium persulfate, 0.728g of mercaptoethanol and 603g of water, and was added dropwiseThe time is 2h, and then the heat preservation is carried out for 1h, thus obtaining the comb-shaped copolymer with the main chain having hydroxyl; then adding 5.28g of thiourea and 6.81g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 80 ℃, adding 6.94g of 40% sodium hydroxide solution to neutralize the reaction solution after reacting for 12 hours, and obtaining the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution consisting of 100g of acrylic acid, 59.7g of methacrylic acid, 0.16g of ammonium persulfate and 240g of water is dripped into the reaction liquid for 1 hour, after heat preservation is carried out for 1 hour, 208g of 40 percent sodium hydroxide solution is added to neutralize the reaction liquid, and the high water-reducing polycarboxylic acid cement dispersant with 40.1 percent of solid content and M of molecular weight is obtained, wherein the solid content is 40.1 percentw＝22700。
Example 7:
4.64g of allyl alcohol and 8.96g of water are added to a reaction flask equipped with a stirrer, mixed homogeneously and heated to 80 ℃ and 400g of polyethylene glycol methacrylate (M)w2000), 1.01g of sodium persulfate, 0.218g of mercaptoethanol and 603g of water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl on the main chain; then adding 6.08g of thiourea and 7.84g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 80 ℃, and after reacting for 12 hours, adding 8g of 40% sodium hydroxide solution to neutralize the reaction solution to obtain the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution composed of 115.2g of acrylic acid, 185.6g of fumaric acid, 0.3g of sodium persulfate and 240g of water is dripped into the reaction liquid for 1 hour, after heat preservation is carried out for 1 hour, 320g of 40% sodium hydroxide solution is added to neutralize the reaction liquid, and the high water-reducing polycarboxylic acid cement dispersant with the solid content of 40.4% and the molecular weight M of 40.4% is obtainedw＝48900。
Example 8:
4.8g of methyl allyl alcohol and 7.2g of water are added into a reaction flask with a stirrer, mixed uniformly and heated to 70 ℃, and then 400g of polyethylene glycol methacrylate (M) is added dropwisew2000), 0.41g V-501, 0.288g of mercaptoethanol and 603g of water, dripping for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl on the main chain; then, 5.07g of thiourea and 6.53g of concentrated sulfuric acid were added to the reaction solution, the reaction temperature was maintained at 70 ℃ and after 12 hours of reaction, 6.67g of a 40% sodium hydroxide solution was added theretoAnd reacting the mixture to obtain a macromolecular chain transfer agent with a mercapto group on the main chain; finally, a mixed solution consisting of 192g of acrylic acid, 0.19g V-501 and 288g of water is dripped into the reaction liquid, the dripping time is 1h, the temperature is kept for 1h, 266.7g of 40 percent sodium hydroxide solution is added to neutralize the reaction liquid, and the polycarboxylic acid cement dispersant with high water reduction, the solid content is 40.3 percent, and the molecular weight M is obtainedw＝42500。
Example 9:
adding 4.3g of 3-methyl-3-butene-1-ol and 6.5g of water into a reaction bottle with a stirrer, uniformly mixing, heating to 80 ℃, and then dropwise adding 400g of polyethylene glycol methacrylate (M)w2000), 0.81g of ammonium persulfate, 1.06g of mercaptopropionic acid and 603g of water, dropwise adding for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped copolymer with the hydroxyl group on the main chain; then adding 3.8g of thiourea and 4.9g of concentrated sulfuric acid into the reaction solution, keeping the reaction temperature at 80 ℃, adding 5g of 40% sodium hydroxide solution to neutralize the reaction solution after reacting for 12 hours, and obtaining the macromolecular chain transfer agent with sulfydryl on the main chain; finally, a mixed solution consisting of 108g of acrylic acid, 0.19g of ammonium persulfate and 162g of water is dripped into the reaction solution, the dripping time is 1h, after the heat preservation is carried out for 1h, 150g of 40 percent sodium hydroxide solution is added to neutralize the reaction solution, and the high water-reducing polycarboxylic acid cement dispersant with the solid content of 40.2 percent and the molecular weight M is obtainedw＝20500。
Comparative example 1:
the product is a polycarboxylic acid cement dispersant with high carboxyl content prepared by hydrolysis of unsaturated ester monomers, synthesized according to the method shown in example 2 of patent CN 104387536B.
Comparative example 2:
to a flask equipped with a stirrer was added methallyl polyoxyethylene ether (M)w2400), 240g of hydrogen peroxide and 240g of water are fully mixed, the temperature is increased to 45 ℃, a mixed solution consisting of 28.8g of acrylic acid, 1.32g of mercaptopropionic acid, 0.44g of L-ascorbic acid and 148g of water is dropwise added, the dropwise addition is finished for 3h, the temperature is kept for 1h, and finally 40g of 40% NaOH solution is added to neutralize the reaction solution, wherein the solid content of the product is 40.2%, and the molecular weight M is 40.2%w30400 this product is a commercially available conventional polycarboxylic acid cement dispersant prepared using conventional procedures.
Comparative example 3:
to a flask equipped with a stirrer was added methallyl polyoxyethylene ether (M)w2400), 240g of hydrogen peroxide, 0.884g of hydrogen peroxide and 240g of water are fully mixed, the temperature is increased to 45 ℃, a mixed solution consisting of 86.4g of acrylic acid, 3.45g of mercaptopropionic acid, 1.14g of L-ascorbic acid and 218g of water is dropwise added, the dropwise addition is finished for 3 hours, then the temperature is kept for 1 hour, and finally 120g of 40 percent NaOH solution is added to neutralize the reaction solution, wherein the solid content of the product is 40.1 percent, and the molecular weight M is 40.1 percentw33100, the product is a polycarboxylic acid cement dispersant with high carboxyl content prepared using conventional processes.
Application examples
In an application embodiment, the adopted cement is Poi 52.5 of a small wild field, the mineral powder is S95 type mineral powder produced by Jiangnan grinding Limited, the fly ash is I-grade fly ash produced by Jiangsu Huaneng electric power company, the sand is medium sand with fineness modulus M of 2.6, and the stones are basalt with continuous gradation of 5-20 mm in particle size.
Application example 1:
the polycarboxylic acid cement dispersant with high water reduction is used for measuring the fluidity of clear paste according to GB/T8077-2000 'test method for homogeneity of concrete admixture', the fixed water-cement ratio is 0.27, the mixing amount of the polycarboxylic acid is adjusted to ensure that the initial fluidity is between 200 and 250mm, and the results are shown in Table 1.
TABLE 1 Cement paste fluidity test results
Figure GDA0001538086010000091
As can be seen from Table 1, the carboxyl group content in the examples is generally 3mmol/g or more, which is more than twice as high as that of comparative example 2(1.49mmol/g) which is a conventional product. From the results of the fluidity of the net slurry of the product, the initial fluidity of the examples 1 to 9 can reach 250mm under the condition that the mixing amount is 0.10 to 0.12 percent, and the fluidity similar to that of the examples can be reached only under the condition that the mixing amount of the comparative example is more than 40 percent higher than that of the example, which proves that the polycarboxylic acid cement dispersant has excellent performances of low mixing amount and high water reduction. It is to be noted that comparative example 3 and the examples have similar carboxyl group contents but poor water-reducing performance, which indicates that the polycarboxylic acid with high carboxyl group content synthesized by the conventional process does not bring about improvement of product performance, and the method of the present invention must be used to synthesize the product with high carboxyl group content and high water-reducing performance.
Application example 2:
the effect of the highly water-reducing polycarboxylic acid cement dispersant of the present invention on fresh concrete was next examined according to the method specified in GB 8076-2008. Fixing the water-cement ratio to be 0.40, adjusting the mixing amount of the polycarboxylic acid to ensure that the initial slump of the concrete is between 21 +/-1 cm, the test temperature is 25 ℃, the humidity is 80 percent, and the mass mixing ratio of the concrete is as follows: the experimental results of cement 267, mineral powder 53, fly ash 60, sand 767, large stone 800, small stone 260 and concrete are shown in Table 2.
TABLE 2 concrete Performance test results
Figure GDA0001538086010000101
As is apparent from the concrete test results in Table 2, examples 1 to 9 had initial and aged fluidity comparable to those of comparative examples 1 to 3 at a lower blending amount, which is in agreement with the net slurry results, indicating that the polycarboxylic acid cement dispersant of the present invention has higher water-reducing ability. In addition, from the test results of gas content and compressive strength, the data of the examples and the comparative examples are similar and have no obvious difference, which indicates that the high water-reducing polycarboxylic acid cement dispersant of the invention does not influence the gas content and the mechanical strength of concrete.
Application example 3:
next, the adsorption amount of the highly water-reducing polycarboxylic acid cement dispersant of the present invention in cement was tested. The test method comprises the following steps: 300g of cement and 81g of an aqueous solution containing 0.45g of a polycarboxylic acid water reducing agent are mixed, the mixture is sampled after being stirred for a certain time, the mixture is quickly diluted by 10 times, the mixture is immediately centrifuged at a high speed (10000r/min) for 2min, 2g of supernatant is taken, 1g of HCl (1mol/L) solution is used for acidification, 17g of deionized water is added for dilution to prepare a sample, the organic carbon content of the sample is measured by a Multi N/C3100 total organic carbon analyzer of Jena company, the adsorption rate of cement particles to polycarboxylic acid molecules is obtained, and the experimental results are shown in Table 3.
TABLE 3 adsorption Rate testing of polycarboxylic acids in Cement
Figure GDA0001538086010000111
As shown in the results of the adsorption rate test in Table 3, the saturated adsorption rate of examples 1-9 at 30min was about 60% while the saturated adsorption rate of the comparative example was only 45% at most. This shows that the polycarboxylic acid cement dispersant of the present invention has a high carboxyl content, thereby improving the adsorption efficiency of the product.

Claims (7)

1. The high water-reducing polycarboxylic acid cement dispersant is characterized by having a molecular structural general formula shown as follows:
Figure FDA0002247346930000011
wherein R is1is-H or-CH3，R2is-CH2-or-CH2CH2-，R3is-H or-COOH, R4is-H, -CH3or-CH2And COOH, wherein x, y, z and n represent the number of the repeating units of each repeating unit, x is 5-40, y is 2-20, z is 20-40, and n is 22-25.
2. The high water-reducing polycarboxylic acid cement dispersant according to claim 1, characterized in that said high water-reducing polycarboxylic acid cement dispersant has a weight average molecular weight of 15000 to 50000.
3. The method for preparing the polycarboxylic acid cement dispersant with high water reduction as claimed in claim 1 or 2, characterized by comprising the steps of:
(1) firstly, a comb-shaped high polymer with a main chain of carbon atoms and side chains of hydroxyl and polyether is obtained through copolymerization reaction of a methacrylic acid polyethylene glycol ester monomer and an unsaturated alcohol monomer;
(2) converting hydroxyl in the comb-shaped high molecular polymer prepared in the step (1) into sulfydryl under the action of an intermediate reagent thiourea to prepare a comb-shaped high molecular chain transfer agent with a main chain of carbon atoms and side chains of sulfydryl and polyether;
(3) finally, regulating and controlling the unsaturated acid monomer to carry out free radical polymerization by using the comb-shaped macromolecular chain transfer agent prepared in the step (2), so that a macromolecular chain segment generated by polymerization of the unsaturated acid monomer is connected with a sulfur atom in a mercapto group, and finally obtaining the high water-reducing polycarboxylic acid cement dispersant;
the molecular structure of the polyethylene glycol methacrylate monomer in the step (1) conforms to the general formula (1)
Figure FDA0002247346930000012
In the formula (1), n is the number of the repeating units of the repeating unit, and n is 22-45;
in the step (1), the unsaturated alcohol monomer is any one of allyl alcohol, methallyl alcohol and 3-methyl-3-buten-1-ol;
in the step (3), the unsaturated acid monomer is at least one of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid or maleic anhydride.
4. The method for preparing polycarboxylic acid cement dispersant with high water reduction according to claim 3, characterized in that the weight average molecular weight of said methacrylic acid polyethylene glycol ester monomer is 1000-2000.
5. The preparation method of the polycarboxylic acid cement dispersant with high water reduction according to claim 3 or 4, which is characterized by comprising the following three steps:
(1) preparing an unsaturated alcohol monomer and water into a solution with the mass concentration of 40%, heating to 60-80 ℃, then dropwise adding a mixed solution with the mass concentration of 40% and consisting of a methacrylic acid polyethylene glycol ester monomer, an initiator I, a chain transfer agent and water for 2 hours, and then preserving heat for 1 hour to obtain the comb-shaped high polymer with the main chain of carbon atoms and the side chain of hydroxyl and polyether;
(2) keeping the temperature unchanged, adding thiourea and concentrated sulfuric acid into the comb-shaped high-molecular polymer solution prepared in the step (1), stirring and reacting for 12 hours, and adding a sodium hydroxide solution with the mass concentration of 40% to neutralize the reaction solution, so as to obtain the comb-shaped high-molecular chain transfer agent with the main chain of carbon atoms and the side chain of sulfhydryl and polyether;
(3) keeping the temperature unchanged, then dropwise adding a mixed solution with the mass concentration of 40% and composed of an unsaturated acid monomer, an initiator II and water into the comb-shaped macromolecular chain transfer agent solution prepared in the step (2), dropwise adding for 1h, then keeping the temperature for 1h, and adding a sodium hydroxide solution with the mass concentration of 40% to neutralize the reaction solution to obtain the high water-reduction polycarboxylic acid cement dispersant;
the molar ratio of the polyethylene glycol methacrylate monomer to the unsaturated alcohol monomer in the step (1) is (2-4): 1, and the amount of the chain transfer agent is 1-4% of the total molar amount of the polyethylene glycol methacrylate monomer and the unsaturated alcohol monomer;
the respective molar usage of the thiourea, the concentrated sulfuric acid and the sodium hydroxide in the step (2) is the same as that of the unsaturated alcohol monomer in the step (1);
the molar ratio of the unsaturated acid monomer in the step (3) to the unsaturated alcohol monomer in the step (1) is (20-40): 1;
the dosage of the initiator I is 0.1-0.5% of the total mass of the unsaturated alcohol monomer and the methacrylic acid polyethylene glycol ester monomer, and the dosage of the initiator II is 0.1-0.5% of the mass of the unsaturated acid monomer.
6. The method for preparing the high water-reducing polycarboxylic acid cement dispersant according to claim 5, characterized in that the chain transfer agent is one of mercaptoethanol, mercaptoacetic acid, mercaptopropionic acid;
the initiator I and the initiator II are any one of sodium persulfate, potassium persulfate, ammonium persulfate, azobisisobutylamidine hydrochloride (V-50), azobisisobutylimidazoline hydrochloride (VA-044) and azobiscyanovaleric acid (V-501).
7. The method for using a polycarboxylic acid cement dispersant with high water reduction as claimed in claim 1 or 2, wherein: the mixing amount of the high water-reducing polycarboxylic acid cement dispersant is 0.05-0.3 percent of the total mass of the cementing material.
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