Early-strength polycarboxylate superplasticizer with thickening and water-retaining properties and preparation method thereof

Abstract

The invention discloses an early-strength polycarboxylate superplasticizer with thickening and water-retaining properties and a preparation method thereof, and relates to the technical field of building materials. The early-strength polycarboxylate superplasticizer is prepared from the following components in parts by weight through free radical copolymerization and condensation polymerization: 360 parts of polyether monomer, 20-40 parts of unsaturated carboxylic acid, 0.1-0.5 part of hydrophobic monomer, 1-30 parts of functional additive, 0.5-3 parts of oxidant, 0.1-1 part of reducing agent, 0.5-2 parts of chain transfer agent and 270-460 parts of water. The invention also provides a preparation method of the water reducing agent. By adjusting the structure of the polycarboxylic acid water reducing agent and grafting functional groups with bonding capacity and early strength function, the water reducing agent which is good in application performance and high in water reducing rate is prepared, and the water reducing agent can remarkably improve the wrapping property of concrete, reduce the bleeding property of the concrete and improve the early strength of the concrete.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties and a preparation method thereof. Background Art

[0002] Polycarboxylate water reducer is a high-performance water reducer and a cement dispersant commonly used in cement concrete applications. Due to its large freedom of molecular structure design, multiple synthesis technologies, and large room for high performance, it gives ready-mixed concrete good construction performance, and hardened concrete good strength development and durability. Therefore, polycarboxylate water reducer is widely used in highways, bridges, dams, tunnels, high-rise buildings and other projects.

[0003] However, polycarboxylate water-reducing agents still have obvious application defects, such as strong sensitivity to temperature, strong sensitivity to mud content of sand and gravel aggregates, poor adaptability to machine-made sand, and sensitive dosage affecting construction. Among them, due to the wide range of sources and large differences in preparation processes, sand and gravel aggregates fluctuate greatly in gradation, particle shape, etc., resulting in obvious differences in concrete workability through conventional air entrainment and thickening measures, or even no significant effect. In addition, since the addition of water-reducing agents also affects the hydration process of cement, the setting time of concrete is prolonged, which is not conducive to the development of early strength and cannot meet the production requirements of early-strength concrete. Therefore, the present invention synthesizes a polycarboxylate water-reducing agent with improved concrete workability and early strength. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties and a preparation method thereof. By adjusting the structure of the polycarboxylate water-reducing agent and grafting functional groups with bonding ability and early strength function, a water-reducing agent with good application performance and a high water-reducing rate is obtained, and the water-reducing agent can significantly improve the concrete encapsulation, reduce the concrete water seepage, and improve the early strength of concrete.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties is provided, which is obtained by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of polyether monomer, 20-40 parts of unsaturated carboxylic acid, 0.1-0.5 parts of hydrophobic monomer, 1-30 parts of functional additive, 0.5-3 parts of oxidant, 0.1-1 parts of reducing agent, 0.5-2 parts of chain transfer agent and 270-460 parts of water.

[0006] Furthermore, an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties is obtained by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of polyether monomer, 30 parts of unsaturated carboxylic acid, 0.2 parts of hydrophobic monomer, 10 parts of functional additive, 1 part of oxidant, 0.1-1 parts of reducing agent, 1 part of chain transfer agent and 410 parts of water.

[0007] Furthermore, the polyether monomer is one of isobutylene alcohol polyoxyethylene ether (HPEG), methyl allyl alcohol polyoxyethylene ether (TPEG), ethylene glycol monovinyl polyethylene glycol ether (EPEG) and 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG).

[0008] Furthermore, the unsaturated carboxylic acid is one of acrylic acid, methacrylic acid, itaconic acid and potassium salt and sodium salt thereof.

[0009] The unsaturated carboxylic acid is one of acrylic acid, methacrylic acid, itaconic acid or their corresponding potassium salts and sodium salts.

[0010] Furthermore, the hydrophobic monomer is one of isooctyl acrylate, octadecyl acrylamide and tert-butyl methacrylate.

[0011] Furthermore, the functional additive is prepared by the following method: 2-acrylamide-2-methylpropanesulfonic acid, ethanolamine and deionized water are mixed, stirred and reacted at room temperature for 2-5 hours, heated to 80-110°C, and heat-treated at a constant temperature for 1-10 hours to obtain the functional additive.

[0012] Furthermore, the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, ethanolamine and deionized water is 5-10:5-10:80.

[0013] Furthermore, the ethanolamine is monoethanolamine, diethanolamine or triethanolamine.

[0014] Furthermore, the oxidant is one of hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate; the reducing agent is one of ascorbic acid, E51 and bleaching agent; and the chain transfer agent is one of mercaptoethanol, thioglycolic acid and mercaptopropionic acid.

[0015] The present invention also provides a method for preparing the above-mentioned early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties, comprising the following steps: (1) Under stirring conditions, the polyether monomer, the oxidant and water are mixed to obtain a base material; the functional additive and water are mixed to obtain a solution A; and then the unsaturated carboxylic acid, the hydrophobic monomer and the chain transfer agent are added and mixed to obtain a solution A; Alternatively, the polyether monomer, water and functional additive are mixed under stirring conditions, and an oxidant is added to obtain a base material; unsaturated carboxylic acid, hydrophobic monomer, chain transfer agent and water are mixed to obtain solution A; Alternatively, the polyether monomer, the oxidant and water are mixed under stirring conditions to obtain a base material; the unsaturated carboxylic acid, the hydrophobic monomer, the chain transfer agent and water are mixed to obtain a solution A; (2) Mix the reducing agent and water to obtain solution B; (3) Under stirring conditions, solution A obtained in step (1) and solution B obtained in step (2) are added dropwise to the base material obtained in step (1), and the mixture is kept warm. The remaining components and deionized water are then added, and the mixture is stirred and adjusted to a concentration of 40%, thereby obtaining an early-strength polycarboxylate water-reducing agent having thickening and water-retaining properties.

[0016] Furthermore, in step (3), the dropwise addition time of solution A is 30-120 min, and the dropwise addition time of solution B is 10-30 min longer than that of solution A.

[0017] The functional additive can be added when preparing the base material or solution A, or after adding solution A and solution B dropwise into the base material, the functional additive is added, and then deionized water is added.

[0018] The present invention has the following beneficial effects: 1. The present invention adjusts the structure of polycarboxylate water-reducing agent and grafts functional groups with bonding ability and early strength function to obtain a water-reducing agent with good application performance and high water reduction rate, and the water-reducing agent can significantly improve the concrete encapsulation, reduce the water bleeding of concrete, and improve the early strength of concrete. The early strength polycarboxylate water-reducing agent used in the present invention has the functions of improving the consistency of concrete, improving the water bleeding and workability of concrete, and promoting the development of early strength of concrete in machine-made sand concrete, low-sand and high-stone concrete, and low-cementitious concrete.

[0019] 2. The early-strength polycarboxylate water-reducing agent of the present invention is prepared by a two-step method, has a simple process, easy-to-control conditions, stable performance, no need for organic solvents in the production process, is green and environmentally friendly, and is easy to promote and apply in industrialization. The polymer synthesized under certain process reaction conditions using polyether monomers as the main synthetic units and unsaturated carboxylic acids, hydrophobic monomers, and functional additives contains carboxylic acid groups, sulfonic acid groups, amide groups, alcohol amines and other structures, which have a significant effect on improving the cohesiveness, water retention and early strength of concrete. At the same time, it can be used in combination with other admixtures such as water-reducing agents, air-entraining agents, retarders, defoamers, etc. to achieve better product performance.

[0020] 3. The early-strength polycarboxylate water-reducing agent of the present invention not only provides a carboxyl functional group (-COOH), but also provides a sulfonic acid functional group (-SO 3 ); the two functional groups have different adsorption energies for the hydration products of cement, which not only play a dispersing role but also improve the adaptability of cement and other adhesives. The water reducer contains amide groups and a large number of alcoholamine molecular structures, which promote the hydration of tricalcium aluminate, accelerate the production of calcium sulfate, and significantly improve the early strength of cement paste and concrete.

[0021] 4. The present invention promotes the spontaneous polymerization of AMPS by heating to form a polymer with a high relative molecular mass and a high dispersion index, and after the alcohol amine molecules induce its deprotonation, an electrostatic repulsion effect occurs between the chains, and the polymer molecular chains tend to be in a stretched state. Under a large number of dynamic interactions (such as hydrogen bonds and electrostatic interactions) between the molecular chains, a strong polymer network can be formed, thereby producing a strong bonding effect on cementitious materials and fine aggregates, thereby improving the cohesiveness and water retention of concrete; in addition, the presence of alcohol amine molecules can greatly enhance the hydrogen bond interaction, further enhancing the large number of dynamic interactions between the molecular chains.

[0022] 5. The functional monomers used in the present invention are not affected by the introduction method, and can partially participate in the polymerization process of the polycarboxylate water-reducing agent molecular chain during the synthesis process, and can also synergize with the polycarboxylate water-reducing agent molecular chain. The early-strength polycarboxylate water-reducing agent of the present invention introduces a small amount of hydrophobic structure into the molecular structure to form a hydrophobic associating polymer, which can form a spatial network structure in the solution, can significantly increase the viscosity of the solution, and maintain good solution performance at high temperature and high mineralization. DETAILED DESCRIPTION

[0023] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0024] Example 1 The invention discloses an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties, which is prepared by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of ethylene glycol monovinyl polyglycol ether, 30 parts of acrylic acid, 0.2 parts of isooctyl acrylate, 10 parts of functional additives, 1 part of hydrogen peroxide, 0.6 parts of ascorbic acid, 1 part of mercaptoethanol and 410 parts of water.

[0025] The functional additive is prepared by the following method: 5 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts of diethanolamine and 80 parts of deionized water are mixed, stirred for reaction at room temperature for 3 hours, heated to 110°C, and heat-treated at a constant temperature for 5 hours to obtain the functional additive.

[0026] The preparation method of the above-mentioned early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties comprises the following steps: (1) Under stirring conditions, ethylene glycol monovinyl polyglycol ether, hydrogen peroxide and water are mixed to obtain a base material; functional additives and water are mixed to obtain a base material; acrylic acid, isooctyl acrylate and mercaptoethanol are added and mixed to obtain a solution A; (2) Mix ascorbic acid and water to obtain solution B; (3) Under stirring conditions, solution A obtained in step (1) and solution B obtained in step (2) are added dropwise to the base material obtained in step (1). The addition time of solution A is 40 min, and the addition time of solution B is 60 min longer than that of solution A. After the addition is completed, the mixture is kept warm for 60 min, and then deionized water is added to adjust the concentration to 40%, thereby obtaining an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties.

[0027] Example 2 The invention discloses an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties, which is prepared by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of ethylene glycol monovinyl polyglycol ether, 30 parts of acrylic acid, 0.2 parts of isooctyl acrylate, 10 parts of functional additives, 1 part of hydrogen peroxide, 0.6 parts of ascorbic acid, 1 part of mercaptoethanol and 410 parts of water.

[0028] The functional additive is prepared by the following method: 10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10 parts of diethanolamine and 80 parts of deionized water are mixed, stirred for reaction at room temperature for 3 hours, heated to 90°C, and heat-treated at a constant temperature for 5 hours to obtain the functional additive.

[0029] The preparation method of the above-mentioned early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties comprises the following steps: (1) Under stirring conditions, ethylene glycol monovinyl polyglycol ether, water and functional additives are stirred for more than 30 minutes to mix, and hydrogen peroxide is added to obtain a base material; acrylic acid, isooctyl acrylate, mercaptoethanol and water are mixed to obtain a solution A; (2) Mix ascorbic acid and water to obtain solution B; (3) Under stirring conditions, solution A obtained in step (1) and solution B obtained in step (2) are added dropwise to the base material obtained in step (1). The addition time of solution A is 40 min, and the addition time of solution B is 60 min longer than that of solution A. After the addition is completed, the mixture is kept warm for 60 min, and then deionized water is added. The mixture is stirred and the concentration is adjusted to 40%, thereby obtaining an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties.

[0030] Example 3 The invention discloses an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties, which is prepared by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of ethylene glycol monovinyl polyglycol ether, 30 parts of acrylic acid, 0.2 parts of isooctyl acrylate, 10 parts of functional additives, 1 part of hydrogen peroxide, 0.6 parts of ascorbic acid, 1 part of mercaptoethanol and 410 parts of water.

[0031] The functional additive is prepared by the following method: 10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 10 parts of diethanolamine and 80 parts of deionized water are mixed, stirred for reaction at room temperature for 3 hours, heated to 90°C, and heat-treated at a constant temperature for 5 hours to obtain the functional additive.

[0032] The preparation method of the above-mentioned early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties comprises the following steps: (1) Under stirring conditions, ethylene glycol monovinyl polyglycol ether, hydrogen peroxide and water are mixed to obtain a base material; acrylic acid, isooctyl acrylate, mercaptoethanol and water are mixed to obtain a solution A; (2) Mix ascorbic acid and water to obtain solution B; (3) Under stirring conditions, solution A obtained in step (1) and solution B obtained in step (2) are added dropwise to the base material obtained in step (1). The addition time of solution A is 40 min, and the addition time of solution B is 20 min longer than that of solution A. After the addition is completed, the mixture is kept warm for 60 min, and then functional additives and deionized water are added. The mixture is stirred for more than 30 min and the concentration is adjusted to 40%, thereby obtaining an early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties.

[0033] Comparative Example 1 A polycarboxylate water-reducing agent, the preparation method of which comprises the following steps: (1) Under stirring, 360 parts of ethylene glycol monovinyl polyglycol ether, 1 part of hydrogen peroxide, and 360 parts of water are mixed evenly to obtain a base material; (2) 30 parts of acrylic acid, 1 part of mercaptoethanol and 30 parts of water are thoroughly stirred and mixed to obtain solution A; (3) Mix 0.6 parts of ascorbic acid and 20 parts of water to obtain solution B; (4) Under stirring, add solution A and solution B to the base material. The addition time of solution A is 40 min, and the addition time of solution B is 60 min. (5) After the addition is complete, keep warm for 60 min, add an appropriate amount of deionized water, stir for more than 30 min, and adjust the concentration of polycarboxylic acid water reducer to 40% to obtain polycarboxylic acid water reducer.

[0034] The products obtained in Examples 1-3 and Comparative Example 1 were tested for their mortar water reduction rate, mortar consistency, cement mortar strength, concrete water reduction rate, concrete water bleeding rate ratio, change of concrete air content over time, and concrete compressive strength; the test methods were based on GB8077-2023 "Concrete Admixture Homogeneity Test Method", GB / T 2419-2005 "Mortar Consistency Test Method", GB / T17671-2021 "Cement Mortar Strength Test Method (ISO Method)" and GB / T50080-2016 "Standard for Performance Test Methods of Ordinary Concrete Mixtures". The solid content of polycarboxylate water reducer was 1 wt%, and the test results are shown in Table 1-2.

[0035] Table 1 Mortar performance test

[0036] Table 2 Concrete performance test

[0037] It can be seen from Table 1-2 that the functional additive of the present invention has good synthetic stability and can adapt to different addition methods; at the same time, the early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties of the present invention has good water-reducing and early-strengthening properties, and the concrete water retention and air content stability are also better.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties, characterized in that: The invention is obtained by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of polyether monomer, 20-40 parts of unsaturated carboxylic acid, 0.1-0.5 parts of hydrophobic monomer, 1-30 parts of functional additive, 0.5-3 parts of oxidant, 0.1-1 parts of reducing agent, 0.5-2 parts of chain transfer agent and 270-460 parts of water.

2. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1, characterized in that: The invention is obtained by free radical copolymerization and condensation polymerization of the following components in parts by weight: 360 parts of polyether monomer, 30 parts of unsaturated carboxylic acid, 0.2 parts of hydrophobic monomer, 10 parts of functional additive, 1 part of oxidant, 0.1-1 parts of reducing agent, 1 part of chain transfer agent and 410 parts of water.

3. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1 or 2, characterized in that: The polyether monomer is one of isobutylene alcohol polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether and 4-hydroxybutyl vinyl polyethylene glycol ether.

4. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1 or 2, characterized in that: The unsaturated carboxylic acid is one of acrylic acid, methacrylic acid, itaconic acid and potassium salt and sodium salt thereof.

5. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1 or 2, characterized in that: The hydrophobic monomer is one of isooctyl acrylate, octadecyl acrylamide and tert-butyl methacrylate.

6. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1 or 2, characterized in that: The functional additive is prepared by the following method: 2-acrylamide-2-methylpropanesulfonic acid, ethanolamine and deionized water are mixed, stirred for reaction at room temperature for 2-5 hours, heated to 80-110°C, and heat-treated at a constant temperature for 1-10 hours to obtain the functional additive.

7. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 6, characterized in that: The mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid, ethanolamine and deionized water is 5-10:5-10:80; the ethanolamine is monoethanolamine, diethanolamine or triethanolamine.

8. The early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 1, characterized in that: The oxidant is one of hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate; the reducing agent is one of ascorbic acid, E51 and bleaching agent; and the chain transfer agent is one of mercaptoethanol, thioglycolic acid and mercaptopropionic acid.

9. The method for preparing the early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Under stirring conditions, the polyether monomer, the oxidant and water are mixed to obtain a base material; the functional additive and water are mixed to obtain a solution A; and then the unsaturated carboxylic acid, the hydrophobic monomer and the chain transfer agent are added and mixed to obtain a solution A; Alternatively, the polyether monomer, water and functional additive are mixed under stirring conditions, and an oxidant is added to obtain a base material; unsaturated carboxylic acid, hydrophobic monomer, chain transfer agent and water are mixed to obtain solution A; Alternatively, the polyether monomer, the oxidant and water are mixed under stirring conditions to obtain a base material; the unsaturated carboxylic acid, the hydrophobic monomer, the chain transfer agent and water are mixed to obtain a solution A; (2) Mix the reducing agent and water to obtain solution B; (3) Under stirring conditions, solution A obtained in step (1) and solution B obtained in step (2) are added dropwise to the base material obtained in step (1), and the mixture is kept warm. The remaining components and deionized water are then added, and the mixture is stirred and adjusted to a concentration of 40%, thereby obtaining an early-strength polycarboxylate water-reducing agent having thickening and water-retaining properties.

10. The method for preparing the early-strength polycarboxylate water-reducing agent with thickening and water-retaining properties according to claim 9, characterized in that: In step (3), the dropwise addition time of solution A is 30-120 min, and the dropwise addition time of solution B is 10-30 min longer than that of solution A.

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