Air-entraining type polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, in particular to an air-entraining type polycarboxylate superplasticizer and a preparation method thereof. The air-entraining type polycarboxylate superplasticizer is formed by polymerizing a polyether macromonomer, a modified active agent and first unsaturated acid through a free radical polymerization reaction, the preparation method comprises the following steps: carrying out condensation reaction on a surfactant, a condensing agent and second unsaturated acid at 60-80 DEG C for 2-3 hours, and removing water in the condensation reaction to obtain the modified active agent. According to the air-entraining type polycarboxylate superplasticizer prepared by the invention, the modified active agent is introduced into the molecules of the air-entraining type polycarboxylate superplasticizer, the adsorption capacity of the polycarboxylate superplasticizer and cement and the specific surface tension of a hydration film are adjusted by utilizing different HLB (Hydrophile-Lipophile Balance) values of the modified active agent, and meanwhile, the flowability of concrete and the air content of the concrete are improved; therefore, the concrete slump rewinding emptying time is shortened, and the concrete compressive strength is kept at a certain good level.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, and in particular to an air-entraining polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] The role of bubbles in the concrete construction process is two-sided. On the one hand, a certain amount of bubbles needs to be introduced during the concrete construction process to meet the needs of concrete construction. For example, an appropriate amount of bubbles during the mixing process is conducive to improving the fluidity of concrete. On the other hand, if there are a large number of bubbles in the mixture, if the harmful bubbles cannot be effectively eliminated and suppressed, a large number of holes will appear on the surface and inside of the concrete, affecting the appearance while also causing deterioration in durability and compressive strength. Therefore, when a large number of bubbles in the concrete have not burst, a defoaming agent needs to be introduced to defoam them.

[0003] Therefore, during the concrete construction process, the air content of concrete needs to be regulated. The usual method is to add defoamers and air entraining agents at different stages. This solution is more common in engineering fields such as hydraulic engineering, port engineering and bridge engineering. Specifically, the common method of controlling the air content is to entrain air first and then defoam, which requires the joint action of multiple additives.

[0004] Machine-made sand concrete is widely used in roads, bridges, tunnels, and high-rise buildings. However, large bubbles of air are also introduced during the concrete mixing process. Due to the variability of raw materials such as machine-made sand and gravel, and the complex and variable concrete construction process, the air content of the mixture obtained in the process of first entraining and then defoaming is variable. When adding defoaming agent and air entraining agent additives, it is necessary to adjust the addition scheme of different additives (adjustment of parameters such as different additive addition periods and ratios) multiple times according to changes in raw materials and construction processes, making it difficult to control, the operation process is complicated, and the controllability is poor. In addition, due to the problems of complex and difficult control and poor controllability, it is easy to cause the air content of air-entrained concrete to fluctuate greatly, batches are unstable, and some batches of concrete are prone to excessive bubbles, resulting in a significant decrease in the compressive performance of concrete.

[0005] In summary, polycarboxylate water-reducing agent is one of the important raw material components of concrete at present. At present, domestic polycarboxylate water-reducing agent manufacturers often mix defoamers and air-entraining agents to meet the requirements of concrete construction. However, the mechanical mixing and compounding of defoamers and air-entraining agents by physical methods has the problems of difficult regulation, complex operation process and poor controllability. Moreover, due to the difficulty in regulation, complex operation process and poor controllability, this solution cannot fundamentally solve the related problems caused by the large fluctuation of air content in concrete.

[0006] Therefore, how to develop a concrete air-entraining polycarboxylic acid water-reducing agent that can avoid the problems of difficult regulation, complicated operation process and poor controllability caused by the air-entraining-before-dissipation method, and make the concrete mixture have good fluidity and maintain good compressive strength to meet application requirements, is the technical difficulty that technical personnel in this field are committed to solving. Summary of the invention

[0007] In order to solve the problems existing in the existing polycarboxylate water-reducing agent mentioned in the above background technology, the present invention provides an air-entraining polycarboxylate water-reducing agent, and its technical solution is as follows:

[0008] The air-entraining polycarboxylic acid water-reducing agent provided by the present invention is prepared by free radical polymerization of a polyether macromonomer, a modified active agent and a first unsaturated acid; the modified active agent is prepared by condensing a surfactant, a condensing agent and a second unsaturated acid at 60-80°C for 2-3h, and then removing water of the condensation reaction; wherein the molar ratio of the second unsaturated acid to the surfactant is (0.95-2.1):1; the mass ratio of the surfactant to the condensing agent is (65-100):(0.1-1.0); the surfactant is one or more combinations of Tween 20, Tween 40, Tween 60, Tween 65, Tween 80, Span 20, Span 40, Span 60 and Span 80; the condensing agent is one or more combinations of trifluoromethanesulfonic acid, boron trifluoride, hydrofluoric acid, fluorosilicic acid, aluminum chloride, stannous octoate, butyl orthotitanate and isopropyl titanate.

[0009] In some embodiments, the mass ratio of the polyether macromonomer, the modified active agent, and the first unsaturated acid is (150-250): (2-15): (10-30); and the temperature of the free radical polymerization reaction is 20-50°C.

[0010] In some embodiments, the preparation process of the modified active agent is: a surfactant and a condensation agent are put into a reaction vessel with a condensation reflux device, the reaction temperature is controlled to be 60-80°C, a second unsaturated acid is added dropwise at 60-80°C and stirred for 2-3 hours, the temperature of the reaction system is increased to 105-110°C and reacted for 0.5-2 hours to remove the water of the condensation reaction, and cooled to room temperature to obtain the modified active agent.

[0011] In some embodiments, when the second unsaturated acid is one or more combinations of acrylic acid and methacrylic acid, the molar ratio of the second unsaturated acid to the surfactant is (2.0-2.1):1; when the second unsaturated acid is one or more combinations of fumaric acid and maleic acid, the molar ratio of the second unsaturated acid to the surfactant is (2.0-2.1):1.

[0012] In some embodiments, the modified active agent is a yellow or yellowish brown transparent liquid with a certain viscosity, the molecular weight of the modified active agent is 300 to 2000, and the viscosity is 100 to 1000 cP.

[0013] In some embodiments, the polyether macromonomer is one or more combinations of isobutyl polyoxyethylene ether, isopentyl polyoxyethylene ether, and 4-hydroxybutyl vinyl ether; the first unsaturated acid and the second unsaturated acid are one or more combinations of acrylic acid, methacrylic acid, fumaric acid, maleic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0014] In some embodiments, the raw materials for preparing the copolymerization reaction include, by weight:

[0015]

[0016]

[0017] In some embodiments, the preparation process is:

[0018] Prepare a mixture of 0.5 to 3 parts of an oxidant and 20 to 40 parts of water by weight to obtain a solution A;

[0019] Prepare a mixture of 0.2-1.0 parts of a reducing agent and 20-40 parts of water by weight to obtain a solution B;

[0020] A mixture of 0.5 to 1.5 parts of a chain transfer agent, 10 to 30 parts of a first unsaturated acid and 20 to 40 parts of water is prepared by weight to obtain a solution C;

[0021] 150-250 parts of polyether macromonomer, 2-15 parts of modified active agent and 200-500 parts of water are added into the reactor, and solution A, solution B and solution C are added dropwise at a reaction system temperature of 20-50° C. for 1-3 hours; then, the reaction is carried out at a constant temperature of 20-50° C. for 0.5-2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0022] In some embodiments, the oxidant is one or more combinations of peroxides and persulfides; the reducing agent is one or more combinations of potassium sulfite, potassium bisulfite, ammonium sulfite, ammonium bisulfite, sodium hypophosphite, potassium hypophosphite, sodium phosphite, and ferrous sulfate; the chain transfer agent is one or more combinations of mercapto alcohol chain transfer agents with a carbon chain length of 2 to 6 and mercapto acid chain transfer agents with a carbon chain length of 2 to 6.

[0023] The present invention also provides an air-entraining polycarboxylate water-reducing agent as described above, which comprises the following steps:

[0024] Prepare a mixture of 0.5 to 3 parts of an oxidant and 20 to 40 parts of water by weight to obtain a solution A;

[0025] Prepare a mixture of 0.2-1.0 parts of a reducing agent and 20-40 parts of water by weight to obtain a solution B;

[0026] A mixture of 0.5 to 1.5 parts of a chain transfer agent, 10 to 30 parts of a first unsaturated acid and 20 to 40 parts of water is prepared by weight to obtain a solution C;

[0027] 150-250 parts of polyether macromonomer, 2-15 parts of modified active agent and 200-500 parts of water are added into the reactor, and solution A, solution B and solution C are added dropwise at a reaction system temperature of 20-50° C. for 1-3 hours; then, the reaction is carried out at a constant temperature of 20-50° C. for 0.5-2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0028] Based on the above, compared with the prior art, the air-entraining polycarboxylate water-reducing agent provided by the present invention has the following beneficial effects:

[0029] The air-entraining polycarboxylate water-reducing agent prepared by the present invention introduces a modified active agent into the air-entraining polycarboxylate water-reducing agent molecule, and adjusts the adsorption capacity of the polycarboxylate water-reducing agent and cement and the specific surface tension of the hydration film by utilizing different HLB values ​​(hydrophile-lipophile balance values) of the modified active agent, and at the same time, improves the fluidity of concrete and the air content of concrete, thereby reducing the emptying time of the concrete slump inverted cone and maintaining the compressive strength of the concrete at a certain good level. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and cannot be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in the present invention.

[0032] The present invention provides a preferred example of a method for preparing an air-entraining polycarboxylate water-reducing agent, which comprises the following steps:

[0033] (1) Based on the mass parts of the substances, a surfactant and a condensing agent are placed in a reaction vessel with a condenser, the temperature of the reaction system is controlled to be 60-80° C., the second unsaturated acid is added dropwise and stirred for 2-3 hours, the temperature is raised to 105-110° C., the reaction is carried out for 0.5-2 hours to remove the water of the condensation reaction, and the mixture is cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, which is recorded as a modified active agent;

[0034] The surfactant is one or more combinations of Tween 20, Tween 40, Tween 60, Tween 65, Tween 80, Span 20, Span 40, Span 60, and Span 80; the condensing agent is one or more combinations of trifluoromethanesulfonic acid, boron trifluoride, hydrofluoric acid, fluorosilicic acid, aluminum chloride, stannous octoate, butyl orthotitanate, and isopropyl titanate. The second unsaturated acid is one or more combinations of acrylic acid, methacrylic acid, fumaric acid, maleic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0035] The molar ratio of the second unsaturated acid to the surfactant is (0.95-2.1):1; the mass ratio of the surfactant to the condensing agent is (65-100):(0.1-1.0); preferably, when the second unsaturated acid is a combination of one or more of acrylic acid and methacrylic acid, the molar ratio of the second unsaturated acid to the surfactant is (2.0-2.1):1; when the second unsaturated acid is a combination of one or more of fumaric acid and maleic acid, the molar ratio of the second unsaturated acid to the surfactant is (2.0-2.1):1.

[0036] (2) preparing a mixture of 0.5 to 3 parts of an oxidant and 20 to 40 parts of water by weight to obtain a solution A;

[0037] (3) preparing a mixture of 0.2 to 1.0 parts of a reducing agent and 20 to 40 parts of water by weight to obtain a solution B;

[0038] (4) preparing a mixture of 0.5 to 1.5 parts by mass of a chain transfer agent, 10 to 30 parts by mass of a first unsaturated acid and 20 to 40 parts by mass of water to obtain a solution C;

[0039] (5) Add 150-250 parts of polyether macromonomer, 2-15 parts of modified active agent, and 200-500 parts of water into the reactor, and dropwise add solution A, solution B, and solution C respectively at a reaction system temperature of 20-50° C. for 1-3 hours; then, react at a constant temperature of 20-50° C. for 0.5-2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0040] Wherein, the polyether macromonomer is one or more combinations of isobutyl polyoxyethylene ether, isopentyl polyoxyethylene ether, and 4-hydroxybutyl vinyl ether;

[0041] The first unsaturated acid is one or more of acrylic acid, methacrylic acid, fumaric acid, maleic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0042] The oxidant is one or more combinations of peroxides and persulfides;

[0043] The reducing agent is one or more combinations of potassium sulfite, potassium bisulfite, ammonium sulfite, ammonium bisulfite, sodium hypophosphite, potassium hypophosphite, sodium phosphite, and ferrous sulfate;

[0044] The chain transfer agent is one or more of a mercapto alcohol chain transfer agent having a carbon chain length of 2 to 6 and a mercapto acid chain transfer agent having a carbon chain length of 2 to 6.

[0045] The present invention also provides the following embodiments and comparative examples:

[0046] Example 1

[0047] (1) Based on the mass parts of the substances, 65 parts (0.1876 mol, 1 eq) of Span 20 and 0.1 parts of trifluoromethanesulfonic acid were placed in a reaction vessel with a condenser, the temperature was controlled at 60° C., 28 parts (0.3886 mol, 2.0711 eq) of acrylic acid were added dropwise and stirred for 2 h, the temperature was raised to 105° C. and the reaction was continued for 0.5 h, the water of the condensation reaction was removed, and the mixture was cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, that is, the modified active agent having a viscosity of 100 cP and a molecular weight of 400;

[0048] (2) Prepare a mixture of 0.5 parts of hydrogen peroxide and 20 parts of water, referred to as solution A.

[0049] (3) Prepare a mixture of 0.2 parts of potassium sulfite and 20 parts of water, referred to as solution B;

[0050] (4) Prepare a mixture of 0.5 parts of mercaptoethanol, 10 parts of acrylic acid and 20 parts of water, by mass, and record it as solution C;

[0051] (5) 150 parts of 4-hydroxybutyl polyoxyethylene ether, 2 parts of modified active agent and 200 parts of water were added into the reactor, and solution A, solution B and solution C were added dropwise at a reaction system temperature of 20° C. for 1 hour; and then, the mixture was reacted at a constant temperature of 20° C. for 0.5 hour to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0052] Example 2

[0053] (1) Based on the mass of the substance, 75 parts of Span 40 (0.1863 mol, 1 eq) and 0.2 parts of aluminum chloride were put into a reaction vessel with a condenser, the temperature was controlled at 65°C, 33.5 parts of methacrylic acid (0.3891 mol, 2.0887 eq) were added dropwise and stirred for 2.5 hours, the temperature was raised to 105°C and reacted for 0.6 hours to remove the water of the condensation reaction, and the mixture was cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, which was recorded as a modified active agent, with a viscosity of 105 cP and a molecular weight of 470;

[0054] (2) Prepare a mixture of 1.0 part sodium peroxide and 30 parts water, referred to as solution A.

[0055] (3) Prepare a mixture of 0.2 parts of sodium hypophosphite and 30 parts of water, referred to as solution B.

[0056] (4) Prepare a mixture of 1 part of thioglycolic acid, 20 parts of acrylic acid, 2 parts of hydroxyethyl acrylate and 30 parts of water, by mass, and record it as solution C;

[0057] (5) 200 parts of 4-hydroxybutyl polyoxyethylene ether, 5 parts of modified active agent and 300 parts of water were added into the reactor, and solution A, solution B and solution C were added dropwise at a reaction system temperature of 30° C. for 1.5 hours; and then, the mixture was reacted at a constant temperature of 30° C. for 1 hour to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0058] Example 3

[0059] (1) Based on the mass fraction of the substance, 85 parts (0.2218 mol, 1 eq) of (Span 20: Tween 80 mass ratio = 1:1) and 0.5 parts of butyl titanate were put into a reaction vessel with a condenser, and the temperature was controlled at 70°C, and 27 parts of maleic acid (0.2326 mol, 1.0486 eq) were added dropwise and stirred for 2.5 hours. The temperature was raised to 110°C and reacted for 1.5 hours. The water of the condensation reaction was removed, and the mixture was cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, which was recorded as a modified active agent, and its viscosity was 500 CP and its molecular weight was 2000;

[0060] (2) Prepare a mixture of 2 parts of ammonium persulfate and 35 parts of water, referred to as solution A;

[0061] (3) Prepare a mixture of 0.5 parts of ferrous sulfate and 35 parts of water, referred to as solution B.

[0062] (4) Prepare a mixture of 1.5 parts of mercaptoethanesulfonic acid, 25 parts of methacrylic acid, 5 parts of hydroxypropyl acrylate and 35 parts of water, by mass, and record it as solution C;

[0063] (5) 220 parts of isopentene polyoxyethylene ether, 8 parts of modified active agent and 400 parts of water were added into the reactor, and solution A, solution B and solution C were added dropwise at a reaction system temperature of 40° C. for 2 hours; then, the mixture was reacted at a constant temperature of 40° C. for 2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0064] Example 4

[0065] (1) Based on the mass fraction of the substance, 100 parts (0.2639 mol, 1 eq) of (Span 60: Tween 40 mass ratio = 1:1) and 1.0 part of boron trifluoride were put into a reaction vessel with a condenser, and 32 parts of fumaric acid (0.2757 mol, 1.0446 eq) were added dropwise at a temperature of 80°C and stirred for 3 hours. The temperature was raised to 110°C and reacted for 2 hours to remove the water of the condensation reaction. The liquid was cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, which was recorded as a modified active agent. The viscosity was 800 and the molecular weight was 3000.

[0066] (2) Prepare a mixture of 3 parts sodium persulfate and 40 parts water, referred to as solution A;

[0067] (3) Prepare a mixture of 1.0 part potassium hypophosphite and 40 parts water, by mass, and record it as solution B;

[0068] (4) Prepare a mixture of 1.5 parts of mercaptopropionic acid, 28 parts of acrylic acid, 2 parts of hydroxyethyl acrylate and 40 parts of water, recorded as solution C;

[0069] (5) 250 parts of isobutylene polyoxyethylene ether, 15 parts of modified active agent and 500 parts of water were added into the reactor, and solution A, solution B and solution C were added dropwise at a reaction system temperature of 50° C. for 3 hours; and then, the mixture was reacted at a constant temperature of 50° C. for 2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0070] Comparative Example 1 (the only difference from Example 1 is that no modified active agent is added to participate in the polymerization)

[0071] (1) Prepare a mixture of 0.5 parts of hydrogen peroxide and 20 parts of water, referred to as solution A.

[0072] (2) Prepare a mixture of 0.2 parts of potassium sulfite and 20 parts of water, referred to as solution B;

[0073] (3) Prepare a mixture of 0.5 parts of mercaptoethanol, 10 parts of acrylic acid and 20 parts of water, recorded as solution C;

[0074] (4) 150 parts of 4-hydroxybutyl polyoxyethylene ether and 200 parts of water were added to the reactor, and solutions A, B and C were added dropwise at 20° C. for 1 hour, and then the reaction was continued at a constant temperature for 0.5 hour to obtain a polycarboxylic acid water reducer.

[0075] (5) After cooling the polycarboxylate water-reducing agent to room temperature, water was added to dilute the solution to a mass content of 10.01%.

[0076] Comparative Example 2 (the only difference from Example 2 is that no modified active agent is added to participate in the polymerization, and the surfactant sodium dodecyl sulfate is subsequently added for compounding)

[0077] (1) Prepare a mixture of 0.5 parts of hydrogen peroxide and 20 parts of water, referred to as solution A.

[0078] (2) Prepare a mixture of 0.2 parts of potassium sulfite and 20 parts of water, referred to as solution B;

[0079] (3) Prepare a mixture of 0.5 parts of mercaptoethanol, 10 parts of acrylic acid and 20 parts of water, recorded as solution C;

[0080] (4) 150 parts of 4-hydroxybutyl polyoxyethylene ether macromonomer and 200 parts of water were added to the reactor, and solutions A, B and C were added dropwise at 20° C. for 1 hour, and then the reaction was continued at a constant temperature for 0.5 hour to obtain a polycarboxylic acid water reducer.

[0081] (5) After the polycarboxylate water reducer is cooled to room temperature, water is added to dilute it to a 10% solution by weight, and sodium dodecyl sulfate is added at a weight of 0.1% of the total weight of the final solution and stirred evenly (the final solution is the sum of the weight of the diluted polycarboxylate water reducer solution and the weight of sodium dodecyl sulfate).

[0082] Comparative Example 3 (the difference from Example 3 is that no modified active agent is added to participate in the polymerization, and rosin air-entraining agent is subsequently added for compounding)

[0083] (1) Prepare a mixture of 0.5 parts of hydrogen peroxide and 20 parts of water, referred to as solution A.

[0084] (2) Prepare a mixture of 0.2 parts of potassium sulfite and 20 parts of water, referred to as solution B;

[0085] (3) Prepare a mixture of 0.5 parts of mercaptoethanol, 10 parts of acrylic acid and 20 parts of water, recorded as solution C;

[0086] (4) 150 parts of 4-hydroxybutyl polyoxyethylene ether and 200 parts of water were added to the reactor, and solutions A, B and C were added dropwise at 20° C. for 1 hour, and then the reaction was continued at a constant temperature for 0.5 hour to obtain a polycarboxylic acid water reducer.

[0087] (5) After the polycarboxylate water reducer is cooled to room temperature, water is added to dilute it to a 10% solution by weight, and a rosin air-entraining agent is added at a weight of 0.1% of the total weight of the final solution and stirred evenly (the final solution is the sum of the weight of the diluted solution of the polycarboxylate water reducer and the weight of the rosin air-entraining agent).

[0088] Comparative Example 4 (the only difference from Example 1 is that the surfactant AEO is used to replace Tween 80)

[0089] (1) Based on the mass parts of the substance, 65 parts of surfactant AEO with a molecular weight of 500 and 0.1 parts of trifluoromethanesulfonic acid are placed in a reaction vessel with a condenser, 15 parts of acrylic acid are added dropwise at a temperature of 60° C. and stirred for 2 h, the temperature is raised to 105° C. and reacted for 0.5 h to remove the water of the condensation reaction, and the mixture is cooled to room temperature to obtain a yellow or yellowish brown transparent liquid with a certain viscosity, which is recorded as a modified active agent;

[0090] (2) Prepare a mixture of 0.5 parts of hydrogen peroxide and 20 parts of water, referred to as solution A.

[0091] (3) Prepare a mixture of 0.2 parts of potassium sulfite and 20 parts of water, referred to as solution B;

[0092] (4) Prepare a mixture of 0.5 parts of mercaptoethanol, 10 parts of acrylic acid and 20 parts of water, by mass, and record it as solution C;

[0093] (5) 150 parts of 4-hydroxybutyl polyoxyethylene ether, 2 parts of modified active agent and 200 parts of water were added into the reactor, and solution A, solution B and solution C were added dropwise at a reaction system temperature of 20° C. for 1 hour; and then, the mixture was reacted at a constant temperature of 20° C. for 0.5 hour to obtain the air-entraining polycarboxylic acid water-reducing agent.

[0094] Performance tests of the products of the embodiments and comparative examples:

[0095] The performance test experiments were carried out on the embodiments and comparative examples, and the experimental materials were as follows:

[0096] Cement: Conch Cement PO 42.5;

[0097] Artificial sand: produced locally in Guizhou, fineness modulus 2.6-3.2;

[0098] Secondary grade crushed stone: produced locally in Guizhou, crushed stone 1 is 5-15mm, crushed stone 2 is 15-35mm;

[0099] The polycarboxylate water reducers prepared in Examples 1, 2, 3, and 4 were uniformly diluted with water to a mass content of 10.1%, and a concrete comparison experiment was conducted with Comparative Examples 1, 2, 3, and 4 under the same mix conditions. A C30 concrete performance experiment was conducted in accordance with GB 8076-2008 "Concrete Admixtures" to compare the concrete performance and compressive strength. The mix ratio is shown in Table 1:

[0100] Table 1C30 concrete experimental mix ratio (unit: kg / m 3 )

[0101]

[0102]

[0103] According to the national standard GB / T 50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures", the concrete viscosity test evaluation was carried out, and the concrete prepared with the formulation ratio in Table 1 was tested according to GB / T 50081-2016 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete". The concrete performance test is shown in Table 2, and the compressive strength is shown in Table 3.

[0104] Table 2 Concrete performance test

[0105]

[0106] Table 3 Compressive strength (unit: MPa)

[0107]

[0108] Among them, the machine status refers to: the concrete flows out of the mixer to a stable and motionless state after being mixed for 2 minutes.

[0109] Analysis of performance test results of products of embodiments and comparative examples

[0110] The raw materials for preparing the air entraining agent regulator in Comparative Examples 1, 2, 3, and 4 are modified based on Example 1, wherein Comparative Example 1 does not add the modified active agent prepared in Example 1 to participate in the polymerization, Comparative Example 2 is compounded with sodium dodecyl sulfate on the basis of Comparative Example 1, Comparative Example 3 is compounded with rosin air entraining agent on the basis of Comparative Example 1, and Comparative Example 4 is prepared by modifying the polycarboxylic acid water reducer with surfactant AEO with reference to Example 1.

[0111] As can be seen from Table 2, compared with Example 1, the initial and 1h slump and expansion of Comparative Example 1 are smaller than those of Example 1, the initial inverted drum emptying time and 1h inverted drum emptying time are relatively increased by 1.5s and 1.7s respectively, and the initial and 1h air contents are 1.5% and 1.0% smaller than those of Example 1. Although the air content of Comparative Example 1 is small due to the poor air entrainment effect compared with the embodiment, so that its compressive strength is maintained at a certain high level, but due to its insufficient air content, the flowability of its mixture is obviously very poor and does not meet the application requirements. It is explained that the flowability and air content of the modified active agent added in the embodiment of the present invention are improved, the concrete inverted drum emptying time is reduced, and it can be seen from the compressive strength data that its compressive strength is maintained well and meets the application requirements.

[0112] It can be seen from Table 2 and Table 3 that, compared with Example 1, Comparative Example 2 has larger initial and 1h slump and expansion than Example 1, and the initial inverted drum emptying time and 1h inverted drum emptying time are relatively shorter by 0.2s and 1.3s, respectively. The initial and 1h air contents are 0.2% and 0.6% larger than those of Example 1, indicating that relative to Example 1, the fluidity and air content of Example 2 with the addition of sodium dodecyl sulfate are improved, and the concrete inverted drum emptying time is reduced, but its 3d, 7d, and 28d compressive strengths are the lowest, and the 3d, 7d, and 28d compressive strengths are most significantly reduced.

[0113] It can be seen from Table 2 and Table 3 that compared with Example 1, the initial and 1h slump and expansion of Comparative Example 3 are larger than those of Example 1, the initial inverted cone emptying time increases by 0.5s, the 1h inverted cone emptying time decreases by 0.9s, and the initial and 1h air contents are 0.1% and 0.6% lower than those of Example 1, indicating that the flowability and air content of Comparative Example 3 with the addition of rosin air-entraining agent are improved compared with Example 1, but its 1h air content is too high, and the 3d, 7d, and 28d compressive strengths are significantly reduced.

[0114] As can be seen from Table 2, compared with Example 1, the initial and 1h slump and expansion of Comparative Example 4 are comparable to those of Example 1, the initial inverted cone emptying time increases by 0.7s, the 1h inverted cone emptying time decreases by 1.2s, the initial air content is 0.1% less than that of Example 1, and the 1h air content is 0.4% greater than that of Example 1, indicating that the flowability and air content of Comparative Example 4 with the addition of surfactant AEO are comparable to those of Example 1, but the 1h air content is too high, and the 3d, 7d, and 28d compressive strengths are significantly reduced.

[0115] It can be seen from Table 2 and Table 3 that compared with Example 1, in Examples 2, 3, and 4, the fluidity and air content of the concrete are improved, the emptying time of the concrete drum is reduced, and the compressive strength at 3d, 7d, and 28d is equivalent.

[0116] Through the above experimental comparison, in Examples 1, 2, 3, and 4, the concrete flow rate is fast, the slurry is sufficient, the concrete drum emptying time is relatively short, and the initial air content is significantly improved, but after 1 hour, the air content can be maintained at a certain level, that is, the air-entraining polycarboxylate water-reducing agent prepared in the present invention can effectively reduce the concrete drum emptying time and improve the concrete fluidity, and keep the compressive strength of the concrete at a certain good level.

[0117] In summary, the air-entraining polycarboxylate water-reducing agent and the preparation method thereof provided by the present invention at least include the following design concepts, action mechanisms and beneficial effects:

[0118] First, the scheme of the present invention obtains a surfactant (modified active agent) containing a double bond by a dehydration condensation reaction of a surfactant such as a Tween series and a Span series with an unsaturated acid. Secondly, the modified active agent is subjected to a free radical polymerization reaction with a polyether macromonomer, an unsaturated acid and other substances under the action of an oxidant, a reducing agent, a chain transfer agent and other substances to obtain a polycarboxylate water reducer. The air-entraining polycarboxylate water reducer prepared by the present invention through a dehydration condensation reaction and a free radical polymerization reaction can effectively reduce the emptying time of the concrete drum and improve the fluidity of the concrete, and the compressive strength of the concrete is maintained at a certain good level. Moreover, compared with the traditional method of adding a defoamer and an air-entraining agent at different stages, the present application adopts the air-entraining polycarboxylate water reducer to achieve the above-mentioned desired effect. While ensuring that the concrete mixture has good fluidity and maintains good compressive performance, it can avoid the problem of complex operation process, large difficulty in regulation and poor controllability caused by the scheme of adding a variety of additives at different times according to actual needs.

[0119] Among them, the main optimization control points for preparing the air-entraining polycarboxylate water-reducing agent of the present invention are:

[0120] (1) Addition of modified active agent

[0121] The present application uses a specific surfactant such as a Tween series and a Span series to carry out a dehydration condensation reaction with an unsaturated acid to prepare a specific structure surfactant (modified surfactant) containing a double bond, and introduces it into a polycarboxylate water reducer through a polymerization reaction:

[0122] Compared with the scheme of the present invention in which the modified active agent is pretreated by condensation reaction and then introduced as a polymerization monomer into the polycarboxylic acid water-reducing agent by polymerization reaction, the scheme in which the raw material surfactant of the modified active agent is directly added as a polymerization monomer to introduce the polycarboxylic acid water-reducing agent by polymerization reaction, the scheme in which the surfactant is directly added does not have an active double bond structure and is purely a simple physical stirring. When the Span surfactant is introduced, the HLB value is too low, resulting in low dispersibility in aqueous solution, and corresponding stratification or surface oil film phenomenon will occur after the milky white liquid is formed.

[0123] In addition, in the preparation process of the modified active agent, the present application optimizes and controls the parameters such as the selection of specific Tween series and Span series of surfactants, condensation reaction temperature, molar ratio of unsaturated acid and surfactant, and catalyst dosage;

[0124] Among them, the water reducer obtained by replacing the specific Tween series and Span series with surfactant AEO cannot achieve the effect of the present application;

[0125] The present application optimizes and controls the condensation reaction temperature. If the reaction temperature is lower than the specified range, the reaction is not sufficient. If it is higher than the specified range, the polymerization is too fast, which is easy to gel or produce too many by-products, and the desired effect of the present application cannot be achieved. Simultaneously, the present application optimizes and controls the molar ratio of the unsaturated acid and the surfactant. If the molar ratio is lower than the specified range, the reaction is not sufficient. If it is higher than the specified range, the raw materials are wasted and too many by-products are produced, and the desired effect of the present application cannot be achieved.

[0126] The present application also optimizes and controls the amount of catalyst used. If the amount of catalyst used is lower than the specified range, it is not conducive to the reaction. If it is higher than the specified range, it is easy to gel or produce too many by-products, and the desired effect of the present application cannot be achieved.

[0127] In summary, the effects of the solution of the present invention are:

[0128] The air-entraining polycarboxylate water-reducing agent prepared by the present invention introduces a modified active agent into the air-entraining polycarboxylate water-reducing agent molecule, and by utilizing different HLB values ​​of the modified active agent (usually, Tween emulsifiers have a higher HLB value, strong hydrophilicity, and belong to water-in-oil emulsifiers with an HLB value of more than 9; Span emulsifiers have a lower HLB value, strong oil-clearing property, and belong to oil-in-water emulsifiers with an HLB value of less than 9; the HLB of the modified emulsifier produced by the reaction of the above two types of emulsifiers with unsaturated acid carboxyl groups is greatly improved, and directly becomes a solubilizer with an HLB value of more than 15), the adsorption capacity of the polycarboxylate water-reducing agent and cement and the specific surface tension of the hydration film are adjusted, and at the same time, the concrete fluidity and the air content of the concrete are improved, thereby reducing the slump of the concrete and the emptying time of the inverted cone, and maintaining the compressive strength of the concrete at a certain good level. In addition, the present invention can avoid the problem of complex operation process, great difficulty in regulation and poor controllability caused by the scheme of adding and matching multiple additives at different times according to actual needs.

[0129] It should be noted that:

[0130] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments of the present invention, but are not intended to limit the present invention. Those skilled in the art may make adaptive adjustments within the scope of the present invention.

[0131] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An air-entraining polycarboxylate water-reducing agent, characterized in that: It is prepared by free radical polymerization of polyether macromonomer, modified active agent and first unsaturated acid; The modified active agent is prepared by reacting a surfactant, a condensing agent and a second unsaturated acid at 60 to 80° C. for 2 to 3 hours and then removing water from the condensation reaction; Wherein, the molar ratio of the second unsaturated acid to the surfactant is (0.95-2.1):1; the mass ratio of the surfactant to the condensing agent is (65-100):(0.1-1.0); The surfactant is one or more combinations of Tween 20, Tween 40, Tween 60, Tween 65, Tween 80, Span 20, Span 40, Span 60, and Span 80; The condensation agent is one or more combinations of trifluoromethanesulfonic acid, boron trifluoride, hydrofluoric acid, fluorosilicic acid, aluminum chloride, stannous octoate, butyl orthotitanate, and isopropyl titanate.

2. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The mass ratio of the polyether macromonomer, the modified active agent, and the first unsaturated acid is (150-250): (2-15): (10-30); The temperature of the free radical polymerization reaction is 20-50°C.

3. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The preparation process of the modified active agent is: A surfactant and a condensation agent are placed in a reaction vessel equipped with a condensation reflux device, the reaction temperature is controlled to be 60-80°C, a second unsaturated acid is added dropwise at 60-80°C and stirred for 2-3 hours, the temperature of the reaction system is increased to 105-110°C and reacted for 0.5-2 hours to remove water from the condensation reaction, and the mixture is cooled to room temperature to obtain the modified active agent.

4. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: When the second unsaturated acid is a combination of one or more of acrylic acid and methacrylic acid, the molar ratio of the second unsaturated acid to the surfactant is (2.0-2.1):1; When the second unsaturated acid is one or more of fumaric acid and maleic acid, the molar ratio of the second unsaturated acid to the surfactant is (1.00-1.05):

1.

5. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The modified active agent is a yellow or yellowish brown transparent liquid with a certain viscosity. The molecular weight of the modified active agent is 300 to 2000, and the viscosity is 100 to 1000 cP.

6. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The polyether macromonomer is one or more of isobutyl polyoxyethylene ether, isopentyl polyoxyethylene ether, and 4-hydroxybutyl vinyl ether; The first unsaturated acid and the second unsaturated acid are one or more combinations of acrylic acid, methacrylic acid, fumaric acid, maleic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate.

7. The air-entraining polycarboxylate water-reducing agent according to claim 1, characterized in that: The raw materials for preparing the copolymerization reaction include, by weight:

8. The air-entraining polycarboxylate water-reducing agent according to claim 7, characterized in that: The preparation process is: Prepare a mixture of 0.5 to 3 parts of an oxidant and 20 to 40 parts of water by weight to obtain a solution A; Prepare a mixture of 0.2-1.0 parts of a reducing agent and 20-40 parts of water by weight to obtain a solution B; A mixture of 0.5 to 1.5 parts of a chain transfer agent, 10 to 30 parts of a first unsaturated acid and 20 to 40 parts of water is prepared by weight to obtain a solution C; 150-250 parts of polyether macromonomer, 2-15 parts of modified active agent and 200-500 parts of water are added into the reactor, and solution A, solution B and solution C are added dropwise at a reaction system temperature of 20-50° C. for 1-3 hours; then, the reaction is carried out at a constant temperature of 20-50° C. for 0.5-2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

9. The air-entraining polycarboxylate water-reducing agent according to claim 7, characterized in that: The oxidant is one or more combinations of peroxides and persulfides; The reducing agent is one or more combinations of potassium sulfite, potassium bisulfite, ammonium sulfite, ammonium bisulfite, sodium hypophosphite, potassium hypophosphite, sodium phosphite, and ferrous sulfate; The chain transfer agent is one or more of a mercapto alcohol chain transfer agent having a carbon chain length of 2 to 6 and a mercapto acid chain transfer agent having a carbon chain length of 2 to 6.

10. An air-entraining polycarboxylate water-reducing agent as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Prepare a mixture of 0.5 to 3 parts of an oxidant and 20 to 40 parts of water by weight to obtain a solution A; Prepare a mixture of 0.2-1.0 parts of a reducing agent and 20-40 parts of water by weight to obtain a solution B; A mixture of 0.5 to 1.5 parts of a chain transfer agent, 10 to 30 parts of a first unsaturated acid and 20 to 40 parts of water is prepared by weight to obtain a solution C; 150-250 parts of polyether macromonomer, 2-15 parts of modified active agent and 200-500 parts of water are added into the reactor, and solution A, solution B and solution C are added dropwise at a reaction system temperature of 20-50° C. for 1-3 hours; then, the reaction is carried out at a constant temperature of 20-50° C. for 0.5-2 hours to obtain the air-entraining polycarboxylic acid water-reducing agent.

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