Polycarboxylate superplasticizer with linear water-reducing rate as well as preparation method and application thereof

Abstract

The invention discloses a polycarboxylate superplasticizer with a linear water-reducing rate as well as a preparation method and application of the polycarboxylate superplasticizer. The water reducing agent is prepared from a polyether macromonomer phosphating derivative, a carboxylic acid monomer, a sulfonic acid monomer, an ester slump retaining monomer, a linear regulation and control monomer and other units through a free radical emulsion polymerization process. Compared with a traditional polycarboxylic acid water reducer, the water reducer has more regular side chain arrangement, higher charge density, higher adsorption capacity and more stable dispersing performance, the water-reducing rate can be linearly increased along with the increase of the mixing amount within the effective mixing amount range, and the water-reducing efficiency is improved. The problem that the concrete fluidity is difficult to control due to nonlinear fluctuation of the water reducing rate of a traditional polycarboxylic acid water reducing agent is solved, and the method has important significance on improving the concrete construction stability and the engineering quality. The product provided by the invention has excellent mud resistance and slump loss resistance besides high linear water-reducing rate, is suitable for various cast-in-place and precast concrete projects, and has remarkable economic value and application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of polycarboxylate superplasticizers, specifically relating to a polycarboxylate superplasticizer with linear water reduction rate, its preparation method, and its application. Background Technology

[0002] Polycarboxylate superplasticizers are the third generation of high-performance superplasticizers, developed after ordinary superplasticizers represented by calcium lignosulfonate and high-efficiency superplasticizers represented by naphthalene-based superplasticizers. They offer advantages such as low dosage, high water reduction rate, environmental friendliness, and strong designability of molecular structure, and have been widely used in various concrete projects such as highways, bridges, dams, tunnels, and high-rise buildings in recent years. However, the water reduction rate of traditional polycarboxylate superplasticizers exhibits a non-linear change with increasing dosage. When the dosage is between 0.1% and 0.2%, the water reduction rate increases rapidly (10% → 30%), but when the dosage exceeds 0.2%, the increase in water reduction rate drops sharply (30% → 35%). Even small changes in dosage can lead to significant changes in concrete fluidity, making it difficult to control during construction (for example, slightly higher dosage can easily cause segregation, while insufficient dosage results in poor concrete fluidity). Technicians often struggle to determine the correct dosage of superplasticizer, which can easily lead to concrete quality accidents.

[0003] The root cause of the above problems lies in the molecular structure of traditional polycarboxylate superplasticizers, which consists of a "branched main chain + random side chains." On one hand, the side chains are unevenly distributed, and may even curl or entangle, leading to inconsistent adsorption layer thickness on the cement particle surface and unstable steric hindrance, resulting in unstable dispersion. On the other hand, the main chain adsorption groups are predominantly carboxyl groups, with a low charge density. This not only affects the adsorption capacity and amount of polycarboxylate superplasticizer but also results in a low zeta potential (-10~-15mV) in the cement paste, leading to insufficient electrostatic repulsion. When the dosage is low, the adsorption amount of superplasticizer on the cement particle surface is low, resulting in a low water reduction rate. Only when the dosage reaches a certain level will the adsorption amount increase significantly. The steric hindrance effect causes a sharp increase in dispersion performance, and the water reduction rate rises rapidly at this stage. As the dosage continues to increase, adsorption reaches equilibrium, and the water reduction rate tends to stabilize. Therefore, the water reduction rate of polycarboxylate superplasticizers exhibits a non-linear change with increasing dosage, and there is a period in which the water reduction rate increases sharply with increasing dosage. As a result, the relationship between water reduction rate and dosage is difficult to grasp, which poses a great challenge to the application of polycarboxylate superplasticizers.

[0004] Currently, research in this field mainly focuses on reducing the sensitivity of polycarboxylate superplasticizers. For example, patent CN120025498A discloses a low-sensitivity polycarboxylate superplasticizer that reduces its sensitivity to differences in manufactured sand performance by introducing crosslinking monomers and esterification monomers. Patent CN112707667A discloses another low-sensitivity polycarboxylate superplasticizer that achieves partial crosslinking of the polycarboxylate superplasticizer by introducing silane coupling agent-modified layered calcium-aluminum bimetallic hydroxide, increasing the molecular size and preventing the polycarboxylate from being adsorbed by mud with intercalation structures, thus improving its compatibility with cement and reducing its sensitivity to changes in mud content. Patent CN117777374A discloses a low-sensitivity room-temperature polycarboxylate superplasticizer that improves the problem of poor concrete workability caused by the sensitivity of traditional polycarboxylate superplasticizers by introducing benzene ring polyether structures and phosphate ester structures, while also reducing its sensitivity to ground materials and improving the sensitivity of traditional polycarboxylate superplasticizers to dosage and water usage. Reducing the sensitivity of polycarboxylate superplasticizers can simplify their application. However, within the effective dosage range, the water reduction rate still increases non-linearly with increasing dosage, making dosage control difficult. Therefore, developing a polycarboxylate superplasticizer with linear water reduction characteristics, where the water reduction rate exhibits a linear relationship with dosage, would allow for calculation of the water reduction rate based on dosage. This would significantly reduce the technical difficulty of applying polycarboxylate superplasticizers and is of great importance for improving the stability and quality of concrete construction. Summary of the Invention

[0005] Objective of the Invention: To address the problem of nonlinear variation in water reduction rate with dosage in traditional polycarboxylate superplasticizers, this invention aims to provide a polycarboxylate superplasticizer with linear water reduction rate, its preparation method, and its applications. The polycarboxylate superplasticizer provided by this invention achieves a linear increase in water reduction rate with dosage, while ensuring excellent dispersibility and slump retention.

[0006] Technical Solution: To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] In a first aspect, the present invention provides a polycarboxylate superplasticizer with a linear water reduction rate, wherein the general molecular structure of the polycarboxylate superplasticizer with a linear water reduction rate is as follows:

[0008]

[0009] in:

[0010] Unit A is provided by a phosphating derivative of the polyether macromonomer;

[0011] Unit B is provided by a carboxylic acid monomer;

[0012] Unit C is provided by sulfonic acid monomer;

[0013] The D unit is provided by ester-based slump-retaining monomers;

[0014] The E-unit is provided by a linearly regulated monomer.

[0015] As a specific implementation plan:

[0016] The phosphate derivative of the polyether macromonomer is selected from allyl polyoxyethylene ether (APEG), methyl allyl polyoxyethylene ether (HPEG) or isopentenyl polyoxyethylene ether (TPEG) with a molecular weight of 2000-5000, and isoprenyl polyoxyethylene ether phosphate is obtained by phosphorylation reaction.

[0017] The carboxylic acid monomer is selected from acrylic acid, methacrylic acid, itaconic acid, or maleic anhydride.

[0018] The sulfonic acid monomer is selected from 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium methpropylene sulfonate, or sodium vinyl sulfonate;

[0019] The ester-based slump-retaining monomer is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, or methyl acrylate;

[0020] The linear regulation monomer is selected from N-vinylpyrrolidone (NVP) or acrylamide (ACMO).

[0021] The molar ratio of units A, B, C, D, and E, m:n:o:p:q, is 1:(2-5):(0.5-1.5):(0.5-1.5):(0.2-0.8).

[0022] Secondly, the present invention provides a method for preparing the polycarboxylate superplasticizer with linear water reduction rate, comprising the following steps:

[0023] (a) Using polyether macromonomer phosphating derivative A as raw material, a stable polyether macromonomer phosphating derivative emulsion was prepared by using deionized water and emulsifier, and then an oxidant was added and mixed evenly to obtain solution 1.

[0024] (b) Dissolve carboxylic acid monomer B, sulfonic acid monomer C, ester slump-preserving monomer D, linear regulator monomer E and chain transfer agent in deionized water to obtain solution 2, and dissolve reducing agent in deionized water to obtain solution 3;

[0025] (c) Add solutions 1, 2 and 3 dropwise into the reaction vessel simultaneously, stir and control the reaction temperature. After the addition is complete, continue to keep the temperature to ensure the reaction is complete.

[0026] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7, and the solution is cooled to obtain the finished product.

[0027] As a specific implementation scheme, in step (a), the polyether macromonomer phosphating derivative A is mainly prepared by the following method:

[0028] A polyether macromonomer with a molecular weight of 2000-5000 is added to a reaction vessel. Under inert gas conditions, a phosphorylation reagent is added, and the temperature is raised to the reaction temperature to carry out the reaction. After the reaction is completed, the temperature is lowered to obtain the polyether macromonomer phosphating derivative A.

[0029] Preferably, the polyether macromonomer is selected from allyl polyoxyethylene ether (APEG), methyl allyl polyoxyethylene ether (HPEG) or isopentenyl polyoxyethylene ether (TPEG); the phosphorylation reagent is selected from phosphorus pentoxide (P2O5); the molar ratio of the polyether macromonomer to P2O5 is 2.1-2.5:1; the reaction temperature is 75-85℃, and the reaction time is 3-5 hours.

[0030] As a specific implementation plan, in step (a):

[0031] The mass ratio of the polyether macromonomer phosphating derivative A to deionized water is 1:(1-2).

[0032] The emulsifier is at least one of OP-10, NP-10, or sodium dodecyl sulfate (K12), and its amount is 0.1-0.9% of the mass of the polyether macromonomer phosphate derivative A;

[0033] The droplet diameter of the stable polyether macromonomer phosphating derivative emulsion is <10 μm;

[0034] The oxidant is at least one of hydrogen peroxide (27.5%), ammonium persulfate, and potassium persulfate, and its amount is 0.5-2% of the mass of polyether macromonomer phosphating derivative A.

[0035] As a specific implementation plan, in step (b):

[0036] The carboxylic acid monomer B is at least one of acrylic acid, methacrylic acid, itaconic acid, or maleic anhydride.

[0037] The sulfonic acid monomer C is at least one of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium methpropylene sulfonate, or sodium vinyl sulfonate.

[0038] The ester-retaining monomer D is at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, or methyl acrylate.

[0039] The linear regulating monomer E is at least one of N-vinylpyrrolidone (NVP) or acrylamide (ACMO);

[0040] The chain transfer agent is at least one of mercaptoacetic acid, mercaptopropionic acid, or mercaptoethanol, and its amount is 0.2-0.8% of the mass of the polyether macromonomer phosphating derivative A;

[0041] The reducing agent is at least one of ascorbic acid, sodium formaldehyde sulfoxylate, and sodium bisulfite, and its dosage is 0.1-0.4% of the mass of polyether macromonomer phosphating derivative A;

[0042] The molar ratio of the polyether macromonomer phosphating derivative A, carboxylic acid monomer B, sulfonic acid monomer C, ester slump-retaining monomer D, and linear regulating monomer E is 1:(2-5):(0.5-1.5):(0.5-1.5):(0.2-0.8).

[0043] As a specific implementation plan, in step (c):

[0044] The reaction temperature is 50-70℃;

[0045] The method of drop addition is as follows: the drop addition time of solution 1 and solution 2 is the same and controlled within 2-3 hours to ensure that the concentration of macromonomer (A) and small monomer (B, C, D, E) is constant during the reaction. The drop addition time of solution 3 is extended by 10-30 minutes. After the drop addition is completed, the reaction is kept warm for 1-2 hours to ensure that the reaction is complete.

[0046] Thirdly, the present invention provides the application of the polycarboxylate superplasticizer with linear water reduction rate in the preparation of concrete.

[0047] Fourthly, the present invention provides a type of concrete, wherein the concrete contains the aforementioned polycarboxylate superplasticizer having a linear water-reducing rate.

[0048] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0049] 1. Linear variation of water reduction rate with admixture dosage: To achieve a linear water reduction rate, this invention adopts several technical measures: 1) The polyether macromonomer is phosphorylated, and the hydroxyl groups at the end of the side chain become phosphate esters. After ionization in concrete, these esters can carry two negative charges, which not only effectively increases the adsorption capacity of polycarboxylate superplasticizer, but also effectively increases the zeta potential of cement particles, thereby increasing the electrostatic repulsion effect; 2) An emulsion free radical polymerization process is adopted, and macromonomers and small monomers are added dropwise simultaneously. The concentration and ratio of macromonomers and small monomers are strictly controlled to avoid excessively high local concentrations that lead to the aggregation of reactants. This ensures uniform grafting onto the main chain during free radical copolymerization, achieving an equidistant distribution of side chains. At the same time, the phosphate groups at the ends of the side chains carry negative charges. Electrostatic repulsion between side chains and between side chains and the main chain reduces the possibility of side chains curling or entanglement, thereby further stabilizing the steric hindrance effect of polycarboxylate superplasticizer; 3) The introduction of sulfonic acid monomers, sulfonic acid groups have stronger adsorption capacity than carboxyl groups, which can further enhance the adsorption performance and electrostatic repulsion dispersion effect of polycarboxylate superplasticizer; 4) The introduction of linearly regulated monomers (NVP or ACMO), which can effectively regulate the adsorption rate and steric hindrance effect of polycarboxylate superplasticizer molecules on the surface of cement particles. Through the combined effect of the above technologies, a linear correlation between water reduction rate and dosage can be achieved (within the dosage range of 0.1%-0.3%, the water reduction rate increases linearly from 13% to 40%).

[0050] 2. Excellent dispersion, anti-mud and slump retention properties: By introducing phosphate groups into the side chain and sulfonic acid groups into the main chain, the adsorption performance is not only significantly enhanced, but also the adsorption capacity of clay to polycarboxylate superplasticizer is effectively reduced, thus reducing slump loss. At the same time, the introduction of slump-retaining ester monomers into the main chain releases carboxyl groups after hydrolysis, which can further improve the slump retention performance.

[0051] 3. Good construction stability: The linear water reduction rate allows for precise prediction and control of concrete fluidity as the dosage of water-reducing agent increases. During construction, there is no need to repeatedly adjust the dosage, which reduces the difficulty of construction, avoids segregation and bleeding of concrete under high dosage, and improves the workability of concrete. It is suitable for scenarios that require precise control of the water reduction rate. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Example 1

[0054] (1) Synthesis of polyether macromonomer phosphating derivatives

[0055] Add 1 mol of methyl allyl polyoxyethylene ether (HPEG) with a number average molecular weight of 2000 to the reaction vessel. Purge the air in the vessel with nitrogen 3-5 times. Raise the temperature to 65°C. After the polyether macromonomer melts, start stirring and keep nitrogen continuously flowing through. Slowly add phosphorus pentoxide (P2O5) to the vessel in batches (to avoid local overheating and side reactions). The molar ratio of polyether macromonomer to P2O5 is 2.1:1. Raise the temperature to 80°C and maintain this temperature for 3 hours. When the material in the vessel gradually changes from turbid to a uniform viscous liquid and no obvious bubbles are generated, the reaction is considered to be over. After cooling, a white to pale yellow solid of methyl allyl polyoxyethylene ether phosphate is obtained.

[0056] (2) Synthesis of polycarboxylate superplasticizer with linear water reduction rate

[0057] (a) Mix 1 mol of methyl allyl polyoxyethylene ether phosphate macromonomer with deionized water at a mass ratio of 1:1.5, add 0.5% OP-10 macromonomer by mass, and stir with a high-speed mixer for 10 min (1500 r / min) to form a stable methyl allyl polyoxyethylene ether phosphate emulsion (droplet diameter <10 μm). Then add 0.5% hydrogen peroxide (27.5%) macromonomer by mass and mix well to obtain solution 1.

[0058] (b) Dissolve 2 mol of acrylic acid, 0.5 mol of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 0.5 mol of hydroxyethyl acrylate, 0.2 mol of N-vinylpyrrolidone (NVP), and 0.2% by mass of mercaptoacetic acid (the macromonomer described in step a) in deionized water to obtain solution 2; dissolve 0.1% by mass of ascorbic acid (VC) (the macromonomer described in step a) in deionized water to obtain solution 3;

[0059] (c) Add solutions 1, 2 and 3 dropwise to the reaction vessel simultaneously, stir and control the reaction temperature at 60°C; add solutions 1 and 2 at the same time and control the time to 2 hours to ensure that the concentrations of macromonomer and small monomer are constant during the reaction; extend the time of adding solution 3 by 10 minutes; after the addition is complete, continue to keep the temperature for 1 hour to ensure that the reaction is complete.

[0060] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7 with sodium hydroxide, and the solution is cooled to obtain the finished product.

[0061] Example 2

[0062] (1) Synthesis of polyether macromonomer phosphating derivatives

[0063] Add 1 mol of methyl allyl polyoxyethylene ether (HPEG) with a number average molecular weight of 3000 to the reaction vessel. Purge the air in the vessel with nitrogen 3-5 times. Raise the temperature to 60°C. After the polyether melts, start stirring and keep nitrogen continuously flowing through. Slowly add phosphorus pentoxide (P2O5) to the vessel in batches (to avoid local overheating and side reactions). The molar ratio of polyether macromonomer to P2O5 is 2.2:1. Raise the temperature to 75°C and maintain this temperature for 4 hours. When the material in the vessel gradually changes from turbid to a uniform viscous liquid and no obvious bubbles are generated, the reaction is considered to be over. After cooling, a white to pale yellow solid of methyl allyl polyoxyethylene ether phosphate is obtained.

[0064] (2) Synthesis of polycarboxylate superplasticizer with linear water reduction rate

[0065] (a) Mix 1 mol of methyl allyl polyoxyethylene ether phosphate macromonomer with deionized water at a mass ratio of 1:1.5, add 0.9% of OP-10 macromonomer by mass, and stir with a high-speed mixer for 15 min (1000 r / min) to form a stable methyl allyl polyoxyethylene ether phosphate emulsion (droplet diameter <10 μm). Then add 1.0% of ammonium persulfate macromonomer by mass and mix well to obtain solution 1.

[0066] (b) Dissolve 3 mol of acrylic acid, 1 mol of sodium methacrylate, 1 mol of hydroxypropyl acrylate, 0.5 mol of N-vinylpyrrolidone (NVP), and 0.4% by mass of mercaptopropionic acid (the macromonomer described in step a) in deionized water to obtain solution 2; dissolve 0.2% by mass of ascorbic acid (VC) (the macromonomer described in step a) in deionized water to obtain solution 3;

[0067] (c) Add solutions 1, 2 and 3 dropwise to the reaction vessel simultaneously, stir and control the reaction temperature at 70°C; add solutions 1 and 2 at the same time and control the time to 3 hours to ensure that the concentrations of macromonomer and small monomer are constant during the reaction; extend the time of adding solution 3 by 30 minutes; after the addition is complete, continue to keep the temperature for 2 hours to ensure that the reaction is complete.

[0068] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7 with sodium hydroxide, and the solution is cooled to obtain the finished product.

[0069] Example 3

[0070] (1) Synthesis of polyether macromonomer phosphating derivatives

[0071] Add 1 mol of isopentenyl polyoxyethylene ether (TPEG) with a number average molecular weight of 5000 to the reaction vessel. Purge the air in the vessel with nitrogen 3-5 times. Raise the temperature to 70°C. After the polyether melts, start stirring and keep nitrogen continuously flowing through. Slowly add phosphorus pentoxide (P2O5) to the vessel in batches (to avoid local overheating and side reactions). The molar ratio of polyether macromonomer to P2O5 is 2.3:1. Raise the temperature to 85°C and maintain this temperature for 5 hours. When the material in the vessel gradually changes from turbid to a uniform viscous liquid and no obvious bubbles are generated, the reaction is considered to be over. After cooling, a white to pale yellow isopentenyl polyoxyethylene ether phosphate solid is obtained.

[0072] (2) Synthesis of polycarboxylate superplasticizer with linear water reduction rate

[0073] (a) Mix 1 mol of isopentenyl polyoxyethylene ether phosphate macromonomer with deionized water at a mass ratio of 1:1.5, add 0.1% of NP-10 macromonomer by mass, stir with a high-speed mixer for 15 min (1500 r / min) to form a stable isopentenyl polyoxyethylene ether phosphate emulsion (droplet diameter <10 μm), then add 2% of potassium persulfate macromonomer by mass, mix well to obtain solution 1;

[0074] (b) Dissolve 5 mol of methacrylic acid, 1.5 mol of sodium vinyl sulfonate, 1.5 mol of methyl acrylate, 0.8 mol of acrylmorpholine (ACMO), and 0.8% by mass of mercaptopropionic acid (the macromonomer described in step a) in deionized water to obtain solution 2; dissolve 0.4% by mass of sodium bisulfite (the macromonomer described in step a) in deionized water to obtain solution 3.

[0075] (c) Add solutions 1, 2 and 3 dropwise to the reaction vessel simultaneously, stir and control the reaction temperature at 50°C; add solutions 1 and 2 at the same time and control the time to 2.5h to ensure that the concentrations of macromonomer and small monomer are constant during the reaction, and extend the time of adding solution 3 by 20min. After the addition is complete, continue to keep the temperature for 1.5h to ensure that the reaction is complete.

[0076] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7 with sodium hydroxide, and the solution is cooled to obtain the finished product.

[0077] Example 4

[0078] (1) Synthesis of polyether macromonomer phosphating derivatives

[0079] Add 1 mol of isopentenyl polyoxyethylene ether (HPEG) with a number average molecular weight of 4000 to the reaction vessel. Purge the air in the vessel with nitrogen 3-5 times. Raise the temperature to 60°C. After the polyether melts, start stirring and keep nitrogen continuously flowing through. Slowly add phosphorus pentoxide (P2O5) to the vessel in batches (to avoid local overheating and side reactions). The molar ratio of polyether macromonomer to P2O5 is 2.4:1. Raise the temperature to 80°C and maintain this temperature for 4 hours. When the material in the vessel gradually changes from turbid to a uniform viscous liquid and no obvious bubbles are generated, the reaction is considered to be over. After cooling, a white to pale yellow isopentenyl polyoxyethylene ether phosphate solid is obtained.

[0080] (2) Synthesis of polycarboxylate superplasticizer with linear water reduction rate

[0081] (a) Mix 1 mol of isopentenyl polyoxyethylene ether phosphate macromonomer with deionized water at a mass ratio of 1:1.5, add NP-10 at a mass ratio of 0.4% of macromonomer, and stir with a high-speed mixer for 12 min (1300 r / min) to form a stable isopentenyl polyoxyethylene ether phosphate emulsion (droplet diameter <10 μm). Then add ammonium persulfate at a mass ratio of 1.5% of macromonomer and mix well to obtain solution 1.

[0082] (b) Dissolve 3 mol of acrylic acid, 1 mol of itaconic acid, 1.2 mol of sodium methacrylate sulfonate, 1 mol of hydroxyethyl acrylate, 0.4 mol of N-vinylpyrrolidone (NVP), and 0.6% by mass of the macromonomer (the macromonomer mentioned in step a) in deionized water to obtain solution 2; dissolve 0.3% by mass of sodium formaldehyde sulfoxylate (the macromonomer mentioned in step a) in deionized water to obtain solution 3;

[0083] (c) Add solutions 1, 2 and 3 dropwise to the reaction vessel simultaneously, stir and control the reaction temperature at 65°C; add solutions 1 and 2 at the same time and control the time to 3 hours to ensure that the concentrations of macromonomer and small monomer are constant during the reaction; extend the time of adding solution 3 by 20 minutes; after the addition is complete, continue to keep the temperature for 1 hour to ensure that the reaction is complete.

[0084] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7 with sodium hydroxide, and the solution is cooled to obtain the finished product.

[0085] Example 5

[0086] (1) Synthesis of polyether macromonomer phosphating derivatives

[0087] Add 1 mol of allyl polyoxyethylene ether (APEG) with a number average molecular weight of 3000 to the reaction vessel. Purge the air in the vessel with nitrogen 3-5 times. Raise the temperature to 70°C. After the polyether melts, start stirring and keep nitrogen continuously flowing through. Slowly add phosphorus pentoxide (P2O5) to the vessel in batches (to avoid local overheating and side reactions). The molar ratio of polyether macromonomer to P2O5 is 2.5:1. Raise the temperature to 85°C and maintain this temperature for 5 hours. When the material in the vessel gradually changes from turbid to a uniform viscous liquid and no obvious bubbles are generated, the reaction is considered to be over. After cooling, a white to pale yellow allyl polyoxyethylene ether phosphate solid is obtained.

[0088] (2) Synthesis of polycarboxylate superplasticizer with linear water reduction rate

[0089] (a) Mix 1 mol of allyl polyoxyethylene ether phosphate macromonomer with deionized water at a mass ratio of 1:1.5, add sodium dodecyl sulfate (K12) at a mass ratio of 0.6% of the macromonomer, and stir with a high-speed mixer for 15 min (1500 r / min) to form a stable allyl polyoxyethylene ether phosphate emulsion (droplet diameter <10 μm). Then add hydrogen peroxide (27.5%) at a mass ratio of 1.2% of the macromonomer and mix well to obtain solution 1.

[0090] (b) Dissolve 2.5 mol of methacrylic acid, 1.5 mol of maleic anhydride, 0.8 mol of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 1.2 mol of hydroxypropyl acrylate, 0.6 mol of acrylmorpholine, and 0.5% by mass of mercaptoacetic acid (the macromonomer described in step a) in deionized water to obtain solution 2; dissolve 0.2% by mass of sodium bisulfite (the macromonomer described in step a) in deionized water to obtain solution 3;

[0091] (c) Add solutions 1, 2 and 3 dropwise to the reaction vessel simultaneously, stir and control the reaction temperature at 55°C; add solutions 1 and 2 at the same time and control the time to 2.5h to ensure that the concentrations of macromonomer and small monomer are constant during the reaction, and extend the time of adding solution 3 by 30min. After the addition is complete, continue to keep the temperature for 2h to ensure that the reaction is complete.

[0092] (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7 with sodium hydroxide, and the solution is cooled to obtain the finished product.

[0093] The following experiments illustrate the beneficial effects of this invention:

[0094] Five polycarboxylate superplasticizer samples with linear water-reducing rates synthesized in Examples 1-5 were subjected to water-reducing rate tests and concrete application tests at different dosages, and compared with three commercially available polyether-based polycarboxylate superplasticizers. Comparative Example 1 was a polycarboxylate superplasticizer copolymerized from methyl allyl polyoxyethylene ether (molecular weight 2400), acrylic acid, and hydroxyethyl acrylate, with an acid-ether ratio of 4.0 and an ester-ether ratio of 0.5, prepared via free radical copolymerization. Comparative Example 2 was a polycarboxylate superplasticizer copolymerized from isopentenyl polyoxyethylene ether (molecular weight 2400), acrylic acid, and hydroxyethyl acrylate, with an acid-ether ratio of 4.0 and an ester-ether ratio of 1.0, prepared via free radical copolymerization. Comparative Example 3 was a polycarboxylate superplasticizer copolymerized from methyl allyl polyoxyethylene ether (molecular weight 3000), acrylic acid, and hydroxypropyl acrylate, with an acid-ether ratio of 4.5 and an ester-ether ratio of 1.5, prepared via free radical copolymerization.

[0095] (1) Water reduction rate test under different admixture dosages

[0096] The water reduction rate test referenced the standard GB 8076-2008 "Concrete Admixtures". The concrete mix proportions were: 360 kg of reference cement, 814 kg of sand, 398 kg of 5-10 mm crushed stone, 598 kg of 10-20 mm crushed stone, and 230 kg of reference water. The water-reducing agent dosages (converted to solids) were 0.1%, 0.2%, and 0.3%, respectively. The water reduction rate test data are shown in Table 1.

[0097] Table 1 Water Reduction Rate Test Data

[0098]

[0099] The water reduction rate test results are shown in Table 1. The water reduction rate of all polycarboxylate superplasticizers increases with increasing dosage. Among them, the water reduction rate of the polycarboxylate superplasticizers prepared in Examples 1-5 of this invention shows a highly linear relationship with the dosage, with a linear correlation coefficient R. 2 The linear correlation coefficient between the water reduction rate and the admixture dosage was ≥0.98, while that between the comparative examples 1-3 and the admixture dosage was relatively low (R0.98). 2 ≤0.87). It can be seen that the polycarboxylate superplasticizer prepared by the technical solution of the present invention has a good linear water reduction rate, and the water reduction rate increases linearly with the increase of dosage. In contrast, the water reduction rate of commercially available polycarboxylate superplasticizers increases sharply in the dosage range of 0.1-0.2%, while the increase slows down significantly in the dosage range of 0.2-0.3%.

[0100] (2) Concrete test

[0101] The concrete testing reference standard was GB / T 50080-2016, "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The design strength grade of the concrete was C30, and the mix proportions were: 280 kg of cement, 80 kg of fly ash, 830 kg of sand (fineness modulus 2.6, mud content 5%), 1060 kg of 5-25 mm continuously graded crushed stone, and 162 kg of water. The water-reducing agent dosages (converted to solids) were 0.14%, 0.18%, and 0.22%, respectively. The concrete test data are shown in Table 2.

[0102] Table 2 Concrete Test Data

[0103]

[0104] The concrete test results are shown in Table 2. The data show that, within a narrow dosage range, the slump / spread values ​​of the polycarboxylate superplasticizers prepared in Examples 1-5 of this invention increase relatively steadily with increasing dosage. The concrete fluidity has a good linear correlation with the dosage, and the slump retention effect is also good. In contrast, the slump / spread of the concrete using Comparative Examples 1-3 increases significantly within the range of 0.14-0.18%, while the increase slows considerably within the range of 0.18-0.22%. The fluidity exhibits a non-linear change with dosage, showing a sharp increase in fluidity within a narrow dosage range, making it difficult to control the concrete fluidity through dosage.

[0105] This invention relates to a polycarboxylate superplasticizer with linear water-reducing properties, designed based on a structure-adsorption-dispersion model. By modifying the side chains and main chain of the polycarboxylate superplasticizer, introducing phosphate groups into the side chains and sulfonic acid groups into the main chain (strong adsorption groups), along with ester-based slump-retaining monomers and linear regulating monomers, and employing emulsion free radical polymerization and simultaneous reactant addition processes, the polycarboxylate superplasticizer exhibits a more regular molecular structure, stronger adsorption capacity, higher electrostatic repulsion effect, and more stable steric hindrance effect. Therefore, while providing a high water reduction rate, it also exhibits a linear increase in water reduction rate with dosage, and excellent anti-mud and slump-retaining effects. Its adaptability to various concrete materials is significantly better than traditional polycarboxylate superplasticizers. Thus, this superplasticizer can be more conveniently applied to various types of concrete, and the concrete fluidity can be easily and effectively controlled by adjusting the dosage, greatly reducing the difficulty of admixture compounding and concrete trial mixing, and minimizing concrete quality fluctuations.

[0106] The embodiments of the present invention have been described in detail above with reference to specific examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A polycarboxylate superplasticizer with a linear water-reducing rate, characterized in that, The general molecular formula of the polycarboxylate superplasticizer with linear water reduction rate is as follows: in: Unit A is provided by a phosphating derivative of the polyether macromonomer; Unit B is provided by a carboxylic acid monomer; Unit C is provided by sulfonic acid monomer; The D unit is provided by ester-based slump-retaining monomers; The E-unit is provided by a linearly regulated monomer.

2. The polycarboxylate superplasticizer with linear water reduction rate according to claim 1, characterized in that: The phosphate derivative of the polyether macromonomer is selected from allyl polyoxyethylene ether (APEG), methyl allyl polyoxyethylene ether (HPEG) or isopentenyl polyoxyethylene ether (TPEG) with a molecular weight of 2000-5000, and isoprenyl polyoxyethylene ether phosphate is obtained by phosphorylation reaction. The carboxylic acid monomer is selected from acrylic acid, methacrylic acid, itaconic acid, or maleic anhydride. The sulfonic acid monomer is selected from 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium methpropylene sulfonate, or sodium vinyl sulfonate; The ester-based slump-retaining monomer is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, or methyl acrylate; The linear regulation monomer is selected from N-vinylpyrrolidone (NVP) or acrylamide (ACMO). The molar ratio of units A, B, C, D, and E, m:n:o:p:q, is 1:(2-5):(0.5-1.5):(0.5-1.5):(0.2-0.8).

3. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 1 or 2, characterized in that, Includes the following steps: (a) Using polyether macromonomer phosphating derivative A as raw material, a stable polyether macromonomer phosphating derivative emulsion was prepared using deionized water and emulsifier, and then an oxidant was added and mixed evenly to obtain solution 1. (b) Dissolve carboxylic acid monomer B, sulfonic acid monomer C, ester slump-preserving monomer D, linear regulator monomer E and chain transfer agent in deionized water to obtain solution 2, and dissolve reducing agent in deionized water to obtain solution 3; (c) Add solutions 1, 2 and 3 dropwise into the reaction vessel simultaneously, stir and control the reaction temperature. After the addition is complete, continue to keep the temperature to ensure the reaction is complete. (d) After the heat preservation is completed, the pH of the solution is adjusted to 6-7, and the solution is cooled to obtain the finished product.

4. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 3, characterized in that, In step (a), the polyether macromonomer phosphating derivative A is mainly prepared by the following method: A polyether macromonomer with a molecular weight of 2000-5000 is added to a reaction vessel. Under inert gas conditions, a phosphorylation reagent is added, and the temperature is raised to the reaction temperature to carry out the reaction. After the reaction is completed, the temperature is lowered to obtain the polyether macromonomer phosphating derivative A.

5. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 4, characterized in that, The polyether macromonomer is selected from one of allyl polyoxyethylene ether (APEG), methyl allyl polyoxyethylene ether (HPEG) or isopentenyl polyoxyethylene ether (TPEG); the phosphorylation agent is selected from phosphorus pentoxide (P2O5). The molar ratio of the polyether macromonomer to P2O5 is 2.1-2.5:1; the reaction temperature is 75-85℃, and the reaction time is 3-5 hours.

6. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 3, characterized in that, In step (a), the mass ratio of the polyether macromonomer phosphating derivative A to deionized water is 1:(1-2); The emulsifier is at least one of OP-10, NP-10, or sodium dodecyl sulfate (K12), and its amount is 0.1-0.9% of the mass of the polyether macromonomer phosphate derivative A; The droplet diameter of the stable polyether macromonomer phosphating derivative emulsion is <10 μm; The oxidant is at least one of hydrogen peroxide (27.5%), ammonium persulfate, and potassium persulfate, and its amount is 0.5-2% of the mass of polyether macromonomer phosphating derivative A.

7. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 3, characterized in that, In step (b): The carboxylic acid monomer B is at least one of acrylic acid, methacrylic acid, itaconic acid, or maleic anhydride. The sulfonic acid monomer C is at least one of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium methpropylene sulfonate, or sodium vinyl sulfonate. The ester-type slump-retaining monomer D is at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, or methyl acrylate. The linear regulating monomer E is at least one of N-vinylpyrrolidone (NVP) or acrylamide (ACMO); The chain transfer agent is at least one of mercaptoacetic acid, mercaptopropionic acid, or mercaptoethanol, and its amount is 0.2-0.8% of the mass of the polyether macromonomer phosphating derivative A; The reducing agent is at least one of ascorbic acid, sodium formaldehyde sulfoxylate, and sodium bisulfite, and its dosage is 0.1-0.4% of the mass of polyether macromonomer phosphating derivative A; The molar ratio of the polyether macromonomer phosphating derivative A, carboxylic acid monomer B, sulfonic acid monomer C, ester slump-retaining monomer D, and linear regulating monomer E is 1:(2-5):(0.5-1.5):(0.5-1.5):(0.2-0.8).

8. The method for preparing the polycarboxylate superplasticizer with linear water reduction rate according to claim 3, characterized in that, In step (c): The reaction temperature is 50-70℃; The method of drop addition is as follows: the drop addition time of solution 1 and solution 2 is the same and controlled within 2-3 hours to ensure that the concentration of macromonomer (A) and small monomer (B, C, D, E) is constant during the reaction. The drop addition time of solution 3 is extended by 10-30 minutes. After the drop addition is completed, the reaction is kept warm for 1-2 hours to ensure that the reaction is complete.

9. The application of the polycarboxylate superplasticizer with linear water reduction rate as described in claim 1 or 2 in the preparation of concrete.

10. A type of concrete, characterized in that, The concrete contains the polycarboxylate superplasticizer with a linear water reduction rate as described in claim 1 or 2.

Images