Polycarboxylic acid high performance water reducing agent powder concentration process

Abstract

The application belongs to the technical field of concrete admixtures, and provides a polycarboxylic high-performance water-reducing agent powder concentration process, in which a high-functionality polycarboxylic ether copolymer aqueous solution with polyoxyethylene side chains, carboxyl groups and sulfonic acid groups is prepared from polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid copolymerization, then magnesium acetate tetrahydrate is used for partial neutralization to form reversible magnesium carboxylate ion clusters, and the product is dehydrated, cooled into pieces and crushed and classified by a wiped-film evaporator or a falling-film evaporator to obtain a powder concentration product. The obtained product has a moisture content of 0.2-2.0 wt%, a glass transition temperature of 45-65 DEG C and a volume median particle size D50 of 60-150 mu m, and solves the problem that storage stability and redispersibility, processing fluidity and water-reducing performance are difficult to be considered in the powderization process, and is suitable for storage, transportation and application.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, specifically to a process for concentrating polycarboxylate-based high-performance water-reducing agent powder. Background Technology

[0002] Polycarboxylate-based high-performance water-reducing agents are an important type of concrete admixture. In concrete and related cementitious materials applications, it is necessary to balance dispersion, construction adaptability, and ease of subsequent use. When the product shifts from aqueous solution to powder form, the technical focus is no longer solely on dehydration itself, but also on the continuity and controllability of the entire process, including concentration, cooling, flake formation, pulverization, grading, and re-dispersion. In other words, it is essential to ensure operable forming behavior and stable material state during the concentration stage, while also guaranteeing redispersion and restoration of effective function during the application stage. Therefore, establishing a concentration process for polycarboxylate-based high-performance water-reducing agents that combines powder processability, storage stability, and redispersion performance is of practical significance for expanding its application forms and improving its flexibility.

[0003] Regarding the powdering of polycarboxylate superplasticizers, existing technologies have proposed different process routes. For example, Chinese patent CN100366565C discloses a method for preparing powdered polycarboxylate superplasticizers, which involves atomizing a polycarboxylate superplasticizer solution, sending it into a drying chamber, and obtaining powder through hot air drying and sedimentation. Another example is Chinese patent CN103819119A, which discloses a process for preparing polycarboxylate superplasticizer powder, using a process of casting, low-temperature vacuum evaporation, peeling, and pulverization. From their disclosures, existing solutions mainly focus on controlling spray drying conditions or using low-temperature thin-layer dehydration to alleviate problems such as high-temperature side reactions, wall adhesion, or difficulty in powder formation. However, the technical focus remains on physical dehydration and molding. No system design based on reversible ion-association structures has yet been seen that addresses how to balance enhanced interchain interactions and redispersibility at the molecular level, and how to simultaneously coordinate the flowability of concentrated processing with the final water-reducing performance. Summary of the Invention

[0004] The purpose of this invention is to provide a process for concentrating polycarboxylate-based high-performance water-reducing agent powders, thereby solving the dual problem of existing polycarboxylate-based water-reducing agents in the powdering process, where redispersibility is easily sacrificed in order to improve storage stability, and water-reducing performance is easily weakened in order to improve the flowability of the concentrated processing.

[0005] This invention does not rely solely on enhanced drying or reduced molecular weight to achieve powder formation. Instead, it constructs reversible magnesium carboxylate ion clusters before dehydration by matching the ratio of high-functional polycarboxylate ether copolymers to magnesium acetate tetrahydrate and controlling the process sequence. This allows the system to have more suitable inter-chain constraints and thermal morphological stability during the concentration and flake formation stage, and at least partially dissociates and restores the effective dispersed segments during water dispersion, thereby simultaneously alleviating the two sets of natural contradictions.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A process for concentrating polycarboxylate-based high-performance water-reducing agent powder includes the following steps:

[0008] S1, Prepare an aqueous solution of a high-functional polycarboxylic acid ether copolymer, wherein the high-functional polycarboxylic acid ether copolymer has polyoxyethylene side chains, carboxyl groups and sulfonic acid groups, and is obtained by copolymerization of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:(2.5-4.0):(0.05-0.30);

[0009] S2, magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1, so that the carboxyl groups in the high-functional polycarboxylate ether copolymer and the magnesium ions provided by the magnesium acetate tetrahydrate form a partial magnesium carboxylate structure. The degree of formation of the partial magnesium carboxylate structure is 5-20 mol% based on the ratio of the positive charge equivalent corresponding to the magnesium ions to the total number of moles of carboxyl groups. The positive charge equivalent corresponding to the magnesium ions is calculated as twice the number of moles of magnesium ions, and the total number of moles of carboxyl groups is calculated based on the number of moles of acrylic acid fed, so as to form a reversible magnesium carboxylate ion cluster and obtain an ion cluster intermediate.

[0010] S3, the ion-clustered intermediate obtained in step S2 is fed into a scraped film thin-film evaporator or a falling film thin-film evaporator for dehydration and cooling into sheets to obtain a sheet-like intermediate with a thickness of 40-180 μm and a moisture content of 0.2-2.0 wt%.

[0011] S4. The flaky intermediate obtained in step S3 is crushed and graded to obtain a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The concentrated product of polycarboxylate-based high-performance water-reducing agent powder has a water content of 0.2-2.0 wt%, a glass transition temperature of 45-65℃, and a median particle size D50 of 60-150 μm.

[0012] Furthermore, step S1 includes the following steps:

[0013] A1, a monomer solution is prepared by mixing polyethylene glycol methyl ether methacrylate, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, mercaptoacetic acid and deionized water, wherein the amount of mercaptoacetic acid is 0.5-3.0 wt% of the total mass of the three monomers, and the total mass of the three monomers is the sum of the feed masses of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid;

[0014] A2, pre-neutralize the acrylic acid in the monomer solution with sodium hydroxide to a degree of 10-20 mol%;

[0015] A3, under a nitrogen atmosphere, the monomer solution and an initiation system composed of hydrogen peroxide and ascorbic acid are simultaneously added dropwise at 20-40°C for 1.5-3.0 h, and the pH of the system is controlled to be 2.5-4.5 during the polymerization process;

[0016] After adding A4, keep warm for 0.5-1.5 hours until the total amount of residual unsaturated monomers is no more than 1.0 wt% based on the total mass of the reaction system after the warming process, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 35-55 wt%.

[0017] Furthermore, in step S1, the amount of hydrogen peroxide and ascorbic acid in the initiation system is 0.1-1.0 wt% of the total mass of the three monomers.

[0018] Furthermore, step S2 includes the following steps:

[0019] B1, add magnesium acetate tetrahydrate to the aqueous solution of the high-functional polycarboxylic acid ether copolymer obtained in step S1, and control the amount of magnesium acetate tetrahydrate added according to the degree of neutralization described in step S2;

[0020] B2, stir at 70-85℃ for 20-60 min, and control the pH of the system to 6.0-7.2;

[0021] B3, when the pH of the system fluctuates by no more than 0.1 within 10 minutes, an ion-clustered intermediate is obtained.

[0022] Furthermore, the reversible magnesium carboxylate ion cluster formed in step S2 is an ion-association structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer.

[0023] Furthermore, step S3 includes the following steps:

[0024] C1, the ion cluster intermediate obtained in step S2 is fed into the evaporator described in step S3 and dehydrated at 75-90°C and an absolute pressure of 0.005-0.015 MPa;

[0025] C2 involves cooling the dehydrated material into sheets at 10-25℃.

[0026] Furthermore, in step S3, the dehydrated material is cooled into sheets by a cooling roller or a double-roller cooling device.

[0027] Furthermore, in step S4, the sheet-like intermediate is pulverized using a needle mill, hammer mill, or mechanical impact mill at a material temperature of 10-35℃.

[0028] Furthermore, in step S4, the pulverized material is graded through at least one screening process, using a screen with a mesh size of 80 to 200.

[0029] Furthermore, the average number of repeating polyethylene oxide units n in the polyethylene glycol methyl ether methacrylate is 21.5-24.5.

[0030] Furthermore, the high-functional polycarboxylic acid ether copolymer obtained in step S1 has polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups. The carboxyl groups are derived from acrylic acid structural units, and the sulfonic acid groups are derived from 2-acrylamido-2-methylpropanesulfonic acid structural units.

[0031] Furthermore, the reversible magnesium carboxylate ion cluster formed in step S2 is an ion-association structure formed by magnesium ions and carboxyl groups in the high-functionality polycarboxylate ether copolymer. The ion-association structure is at least partially dissociated when dispersed in water, thereby redispersing the high-functionality polycarboxylate ether copolymer segments in the aqueous phase.

[0032] Further, in step S1, hydrogen peroxide and ascorbic acid are prepared in the form of aqueous solutions, wherein the amount of hydrogen peroxide is based on the pure amount of H2O2 and the amount of ascorbic acid is based on the pure amount of ascorbic acid. They are added dropwise to the polymerization reactor simultaneously with the monomer solution from different feed ports. The polymerization reactor is purged with nitrogen before the addition and is maintained at 20-40°C during the addition process.

[0033] Furthermore, in step S1, sodium hydroxide is added in the form of an aqueous solution during the acrylic acid pre-neutralization step, and the degree of pre-neutralization is calculated as a percentage of the number of moles of sodium hydroxide added to the total number of moles of acrylic acid.

[0034] Further, in step S2, the degree to which the carboxyl groups are neutralized by magnesium ions is calculated as a percentage of the positive charge equivalent of the magnesium ions introduced by magnesium acetate tetrahydrate to the total number of moles of carboxyl groups in the high-functionality polycarboxylic acid ether copolymer. The positive charge equivalent of the magnesium ions is calculated as twice the number of moles of magnesium ions, and the total number of moles of carboxyl groups is calculated based on the number of moles of acrylic acid fed.

[0035] Furthermore, in step S2, during the stirring process of the ion clustering intermediate at 70-85°C, the reaction endpoint is determined by online or intermittent pH detection; when the pH fluctuation is no greater than 0.1 within 10 minutes, the ion clustering is determined to be complete.

[0036] Furthermore, in step S3, the dehydrated material is cooled by a cooling roller or a double-roller cooling device to form a sheet-like thin layer. The thickness of the sheet-like thin layer is controlled by at least one of the following: the thickness of the evaporator discharge film layer, the linear speed of the cooling roller, or the gap between the two rollers.

[0037] Furthermore, in step S4, the pulverized material is graded by at least one screening process, and the mesh size of the screen used is 80 to 200 mesh; coarse particles that do not pass through the selected screen after screening are returned to the pulverizing process, while powder that passes through the selected screen enters the finished product collection process.

[0038] Furthermore, the glass transition temperature of the concentrated product of the polycarboxylate-based high-performance water-reducing agent powder was determined by differential scanning calorimetry, the median particle size D50 was determined by laser particle size analysis, and the moisture content was determined by Karl Fischer method or halogen moisture analyzer method.

[0039] Furthermore, the average number of polyoxyethylene repeating units n of the polyethylene glycol methyl ether methacrylate is determined based on the raw material specifications or nuclear magnetic resonance integral results.

[0040] This invention employs a preparation method that utilizes a high-functionality polycarboxylic acid ether copolymer partially neutralized with magnesium acetate tetrahydrate to form reversible magnesium carboxylate ion clusters. This is followed by thin-layer dehydration, cooling to form sheets, and pulverization and classification using a scraped-film or falling-film thin-film evaporator. This method primarily aims to achieve a synergistic balance between powder storage stability and redispersibility in terms of water reduction performance. In existing technologies, to improve powder storage stability and powder formation, methods typically reduce adhesion and agglomeration by strengthening inter-chain interactions or enhancing the thermal stability of the system. However, these measures often restrict the release of polymer chain segments during redispersibility, thus weakening the dispersing effect during the usage stage. Conversely, to maintain water reduction performance and redispersibility, methods often improve dispersion recovery by reducing inter-chain constraints or enhancing plasticity. However, these methods narrow the concentration processing window, make sheet formation difficult, and reduce powder stability. This invention introduces controlled levels of magnesium ion neutralization into a high-functional polycarboxylic acid ether copolymer with polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups, and combines this with a controlled dehydration cooling path. This allows ion association to provide the necessary structural support during the processing stage and to at least partially dissociate and restore effective chain segment dispersion during the water addition stage, thereby simultaneously improving two types of properties that are difficult to achieve with a single measure.

[0041] In this invention, magnesium acetate tetrahydrate and high-functionality polycarboxylic acid ether copolymer are not simply compounded. The high-functionality polycarboxylic acid ether copolymer itself provides the effective dispersing segments required for water reduction and redispersibility. However, if concentrated into powder alone from an aqueous solution, it often exhibits adhesion, insufficient thermal stability after flake formation, and limited powder storage stability due to its high degree of chain freedom. While pursuing a higher degree of association for the magnesium ions provided by magnesium acetate tetrahydrate is beneficial for improving inter-chain constraint and powder stability, excessive association of carboxyl groups can inhibit redispersibility and weaken the dispersing effect during use. This invention controls the degree of magnesium ion neutralization within a defined range and implements it in the sequence of ion clustering, dehydration, cooling to form flakes, and pulverization and classification. This allows the ion association to provide structural support and reduce viscosity during processing, while at least partially dissociating during water dispersion, thus balancing processing flowability, storage stability, redispersibility, and water reduction performance.

[0042] Beneficial technical effects

[0043] 1. This invention introduces magnesium acetate tetrahydrate to a controlled degree in an aqueous solution of a high-functionality polycarboxylic acid ether copolymer, enabling the carboxyl groups and magnesium ions to form reversible magnesium carboxylate ion clusters. This improves the thermal morphological stability and sheet formation during the concentration and dehydration process from the perspective of intermolecular interaction regulation, avoiding structural damage caused by relying solely on strong dehydration or high-temperature treatment. This is more conducive to balancing the storage stability of the powder and its subsequent redispersibility.

[0044] 2. This invention selects a high-functional polycarboxylic acid ether copolymer that simultaneously possesses polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups, and controls the degree of magnesium ion neutralization within a limited range, so that the inter-chain constraints during the processing stage and the chain segment release during the use stage are in a balanced state. This not only alleviates the flowability and operating window problems during the concentration process, but also reduces the risk of water-reducing performance degradation caused by simply reducing molecular action.

[0045] 3. This invention uses a scraped film thin-film evaporator or a falling film thin-film evaporator for controlled dehydration, combined with cooling into flakes, low-temperature pulverization, and sieving and grading, so that the thickness of the flake intermediate, the moisture content of the powder concentrate, the glass transition temperature, and the median particle size D50 are under synergistic control, thereby reducing the tendency to agglomerate and stick, and improving the morphological stability of the powder concentrate during storage, transportation, and use.

[0046] 4. This invention provides clear definitions for monomer ratio, pre-neutralization degree, ion clustering endpoint, dehydration conditions, and product parameter detection methods, making the process path and result judgment criteria correspond to each other. This facilitates implementation by those skilled in the art and is also conducive to subsequent systematic quality control and scale-up applications focusing on moisture content, glass transition temperature, and median particle size D50. Attached Figure Description

[0047] Figure 1 The full FTIR spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown.

[0048] Figure 2 The images show magnified views of the FTIR carboxylate characteristic regions of Examples 1, 8, and 9.

[0049] Figure 3 The XPS C1s region spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown.

[0050] Figure 4 The XPS O1s region spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown.

[0051] Figure 5 The XPS Mg2p region spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown.

[0052] Figure 6 The DSC heat flux curves are for Example 1, Comparative Example 7, and Comparative Example 10.

[0053] Figure 7 The graphs show the laser particle size differential distribution curves for Example 1, Comparative Example 7, and Comparative Example 10.

[0054] Figure 8 The cumulative distribution curves of laser particle size are shown for Example 1, Comparative Example 7, and Comparative Example 10.

[0055] Figure 9 The redispersion kinetic conductivity-time plots are for Example 1, Comparative Example 8, and Comparative Example 10.

[0056] Figure 10 The turbidity-time plots are for the redispersion kinetics of Example 1, Comparative Example 8, and Comparative Example 10.

[0057] Figure 11 The slump retention curves over time for Example 1, Comparative Example 8, and Comparative Example 10 are shown.

[0058] Figure 12 Macroscopic optical photograph of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder.

[0059] Figure 13 Scanning electron microscope image of concentrated product of polycarboxylate-based high-performance water-reducing agent powder; Figure 13 a is a low-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder; Figure 13 b is a medium-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder; Figure 13 c is a high-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder; Figure 13 d is a cross-sectional scanning electron microscope image of the sheet-like intermediate.

[0060] Figure 14 Transmission electron microscopy image of the ion clustering intermediate; Figure 14 a is a bright-field transmission electron microscope image of the ion clustering intermediate; Figure 14 b is a magnified transmission electron microscope image of the ion clustering intermediate; Figure 14 c is a high-resolution transmission electron microscope image of the ion clustering intermediate; Figure 14 d is the selected area electron diffraction pattern of the ion cluster intermediate. Detailed Implementation

[0061] 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 with reference to the accompanying drawings.

[0062] Example 1

[0063] A process for concentrating polycarboxylate-based high-performance water-reducing agent powder includes the following steps:

[0064] S1, Preparation of aqueous solution of high-functional polycarboxylic acid ether copolymer:

[0065] A1. A monomer solution was prepared by mixing 100g of polyethylene glycol methyl ether methacrylate (with an average polyoxyethylene repeating unit number n of 21.5), 17.20g of acrylic acid, 0.99g of 2-acrylamido-2-methylpropanesulfonic acid, 0.59g of mercaptoacetic acid (0.5wt% of the total mass of the three monomers), and a portion of deionized water. In this embodiment, the total amount of deionized water was controlled to be approximately 147g. The total amount of deionized water included all the water used to prepare the monomer solution, sodium hydroxide aqueous solution, and initiation system aqueous solution.

[0066] A2, the acrylic acid in the monomer solution of this embodiment was pre-neutralized with an aqueous solution of sodium hydroxide (0.95 g by weight of sodium hydroxide) to a degree of 10 mol%.

[0067] A3, Under a nitrogen atmosphere, the monomer solution of this embodiment was simultaneously added dropwise at 30°C to an initiation system consisting of hydrogen peroxide (0.1 wt% of the total mass of the three monomers based on the purity of H2O2) and ascorbic acid (0.1 wt% of the total mass of the three monomers based on the purity of ascorbic acid), for a duration of 1.5 h, while controlling the pH of the system to 3.5 during the polymerization process;

[0068] A4, after the addition is complete, maintain the temperature for 1.0 h until the total amount of residual unsaturated monomers, calculated as the total mass of the reaction system after the temperature maintenance, is 0.8 wt%, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 45 wt%. In this embodiment, the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is 1:2.5:0.05. The high-functional polycarboxylic acid ether copolymer of this embodiment has polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups. The carboxyl groups in this embodiment are derived from the acrylic acid structural unit, and the sulfonic acid groups in this embodiment are derived from the 2-acrylamido-2-methylpropanesulfonic acid structural unit.

[0069] S2, forming an ion clustering intermediate:

[0070] B1. Magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1. The amount of magnesium acetate tetrahydrate added is controlled to be approximately 1.28 g, so that the degree to which the carboxyl groups in the high-functional polycarboxylate ether copolymer of this embodiment form a partial magnesium carboxylate structure with the magnesium ions provided by magnesium acetate tetrahydrate is 5 mol% based on the ratio of the positive charge equivalent of the magnesium ions to the total molar number of carboxyl groups.

[0071] B2 was stirred at 78℃ for 20 minutes, and the pH of the system was controlled at 6.6.

[0072] B3. When the pH value of the system fluctuates by no more than 0.1 within 10 minutes, an ion clustering intermediate is obtained. The reversible magnesium carboxylate ion cluster formed in this embodiment is an ion-association structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer of this embodiment. The ion-association structure of this embodiment is at least partially dissociated when dispersed in water, thereby redispersing the high-functionality polycarboxylate ether copolymer segments in the aqueous phase.

[0073] S3, dehydrate and cool to form sheets:

[0074] C1, the ion-clustered intermediate obtained in step S2 is fed into a scraped-film thin-film evaporator and dehydrated at 82°C and 0.005 MPa absolute pressure;

[0075] C2, the dehydrated material is cooled into sheets at 18°C ​​using cooling rollers to obtain a sheet-like intermediate with a thickness of 110μm and a moisture content of 0.3wt%.

[0076] S4, crush and classify:

[0077] The flake-like intermediate obtained in step S3 was pulverized using a needle mill at a material temperature of 22°C. The pulverized material was then graded by a sieving process using an 80-mesh sieve. Coarse particles that did not pass through the 80-mesh sieve were returned to the pulverizing process, while the powder that passed through the 80-mesh sieve entered the finished product collection process, yielding a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. In this embodiment, the concentrated product of polycarboxylate-based high-performance water-reducing agent powder has a moisture content of 0.3 wt%, a glass transition temperature of 55°C, and a volume median particle size (D50) of 65 μm.

[0078] This embodiment is applicable to mid-to-low-end concrete water-reducing agent application scenarios where the powder flowability requirement is high and the storage stability requirement is not strict, and is suitable for conventional commercial concrete production.

[0079] Example 2

[0080] A process for concentrating polycarboxylate-based high-performance water-reducing agent powder includes the following steps:

[0081] S1, Preparation of aqueous solution of high-functional polycarboxylic acid ether copolymer:

[0082] A1. A monomer solution was prepared by mixing 100g of polyethylene glycol methyl ether methacrylate (with an average polyoxyethylene repeating unit number n of 24.5), 24.44g of acrylic acid, 5.27g of 2-acrylamido-2-methylpropanesulfonic acid, and 3.89g of mercaptoacetic acid (3.0wt% of the total mass of the three monomers), with a portion of deionized water. In this embodiment, the total amount of deionized water was controlled to be approximately 114g. The total amount of deionized water included all the water used to prepare the monomer solution, sodium hydroxide aqueous solution, and initiation system aqueous solution.

[0083] A2, the acrylic acid in the monomer solution of this embodiment was pre-neutralized with an aqueous solution of sodium hydroxide (2.71 g by weight of sodium hydroxide) to a degree of 20 mol%.

[0084] A3, Under a nitrogen atmosphere, the monomer solution of this embodiment was simultaneously added dropwise at 30°C to an initiation system consisting of hydrogen peroxide (based on the purity of H2O2, the amount used was 1.0 wt% of the total mass of the three monomers) and ascorbic acid (based on the purity of ascorbic acid, the amount used was 1.0 wt% of the total mass of the three monomers), for a duration of 3.0 h, while controlling the pH value of the system to 3.5 during the polymerization process;

[0085] A4, after the addition is complete, maintain the temperature for 1.0 h until the total amount of residual unsaturated monomers, calculated as the total mass of the reaction system after the temperature maintenance, is 0.6 wt%, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 55 wt%. In this embodiment, the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is 1:4.0:0.30. The high-functional polycarboxylic acid ether copolymer of this embodiment has polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups. The carboxyl groups in this embodiment are derived from the acrylic acid structural unit, and the sulfonic acid groups in this embodiment are derived from the 2-acrylamido-2-methylpropanesulfonic acid structural unit.

[0086] S2, forming an ion clustering intermediate:

[0087] B1. Magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1. The amount of magnesium acetate tetrahydrate added is controlled to be approximately 7.27 g, so that the degree to which the carboxyl groups in the high-functional polycarboxylate ether copolymer of this embodiment form a partial magnesium carboxylate structure with the magnesium ions provided by magnesium acetate tetrahydrate is 20 mol%, calculated as the ratio of the positive charge equivalent of the magnesium ions to the total molar number of carboxyl groups.

[0088] B2 was stirred at 78℃ for 60 minutes, and the pH of the system was controlled at 6.6.

[0089] B3. When the pH value of the system fluctuates by no more than 0.1 within 10 minutes, an ion clustering intermediate is obtained. The reversible magnesium carboxylate ion cluster formed in this embodiment is an ion-association structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer of this embodiment. The ion-association structure of this embodiment is at least partially dissociated when dispersed in water, thereby redispersing the high-functionality polycarboxylate ether copolymer segments in the aqueous phase.

[0090] S3, dehydrate and cool to form sheets:

[0091] C1, the ion-clustered intermediate obtained in step S2 is fed into a falling film thin-film evaporator and dehydrated at 82°C and 0.015 MPa absolute pressure;

[0092] C2, the dehydrated material is cooled into sheets at 18°C ​​using a double-roller cooling device to obtain a sheet-like intermediate with a thickness of 110μm and a moisture content of 1.1wt%.

[0093] S4, crush and classify:

[0094] The flake-like intermediate obtained in step S3 was pulverized using a hammer mill at a material temperature of 22°C. The pulverized material was then graded through a sieving process using an 80-mesh sieve. Coarse particles that did not pass through the 80-mesh sieve were returned to the pulverizing process, while the powder that passed through the 80-mesh sieve entered the finished product collection process, yielding a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. In this embodiment, the concentrated product of polycarboxylate-based high-performance water-reducing agent powder had a moisture content of 1.1 wt%, a glass transition temperature of 55°C, and a volume median particle size (D50) of 145 μm.

[0095] This embodiment is applicable to high-end application scenarios such as high-performance concrete, self-compacting concrete, and ultra-high-strength concrete, which have strict requirements for water reduction rate, dispersion performance and long-term slump retention. It is suitable for key projects and special concrete preparation.

[0096] Example 3

[0097] A process for concentrating polycarboxylate-based high-performance water-reducing agent powder includes the following steps:

[0098] S1, Preparation of aqueous solution of high-functional polycarboxylic acid ether copolymer:

[0099] A1. A monomer solution was prepared by mixing 100g of polyethylene glycol methyl ether methacrylate (with an average polyoxyethylene repeating unit number n of 23.0), 20.71g of acrylic acid, 3.35g of 2-acrylamido-2-methylpropanesulfonic acid, 2.23g of mercaptoacetic acid (accounting for 1.8wt% of the total mass of the three monomers), and a portion of deionized water. In this embodiment, the total amount of deionized water was controlled to be approximately 158g. The total amount of deionized water included all the water used to prepare the monomer solution, sodium hydroxide aqueous solution, and initiation system aqueous solution.

[0100] A2, the acrylic acid in the monomer solution of this embodiment was pre-neutralized with an aqueous solution of sodium hydroxide, which contained 1.72 g of sodium hydroxide by weight, to a degree of 15 mol%.

[0101] A3, Under a nitrogen atmosphere, the monomer solution of this embodiment was simultaneously added dropwise at 20°C to an initiation system consisting of hydrogen peroxide (0.55 wt% of the total mass of the three monomers based on the purity of H2O2) and ascorbic acid (0.55 wt% of the total mass of the three monomers based on the purity of ascorbic acid), for a duration of 2.2 h, while controlling the pH of the system to be 2.5 during the polymerization process;

[0102] A4, after the addition is complete, maintain the temperature for 0.5 h until the total amount of residual unsaturated monomers, calculated as the total mass of the reaction system after the temperature maintenance, is 0.7 wt%, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 45 wt%. In this embodiment, the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is 1:3.2:0.18. The high-functional polycarboxylic acid ether copolymer of this embodiment has polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups. The carboxyl groups in this embodiment are derived from the acrylic acid structural unit, and the sulfonic acid groups in this embodiment are derived from the 2-acrylamido-2-methylpropanesulfonic acid structural unit.

[0103] S2, forming an ion clustering intermediate:

[0104] B1. Magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1. The amount of magnesium acetate tetrahydrate added is controlled to be approximately 3.70 g, so that the degree to which the carboxyl groups in the high-functional polycarboxylate ether copolymer of this embodiment form a partial magnesium carboxylate structure with the magnesium ions provided by magnesium acetate tetrahydrate is 12 mol% based on the ratio of the positive charge equivalent of the magnesium ions to the total molar number of carboxyl groups.

[0105] B2 was stirred at 70℃ for 40 minutes, and the pH of the system was controlled at 6.0.

[0106] B3. When the pH value of the system fluctuates by no more than 0.1 within 10 minutes, an ion clustering intermediate is obtained. The reversible magnesium carboxylate ion cluster formed in this embodiment is an ion-association structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer of this embodiment. The ion-association structure of this embodiment is at least partially dissociated when dispersed in water, thereby redispersing the high-functionality polycarboxylate ether copolymer segments in the aqueous phase.

[0107] S3, dehydrate and cool to form sheets:

[0108] C1, the ion-clustered intermediate obtained in step S2 is fed into a scraped-film thin-film evaporator and dehydrated at 75°C and an absolute pressure of 0.010 MPa;

[0109] C2, the dehydrated material is cooled into sheets at 10°C using a cooling roller to obtain a sheet-like intermediate with a thickness of 40μm and a moisture content of 1.1wt%.

[0110] S4, crush and classify:

[0111] The flake-shaped intermediate obtained in step S3 was pulverized using a mechanical impact mill at a material temperature of 10°C. The pulverized material was then graded through two sieving processes using 140-mesh sieves. Coarse particles that did not pass through the 140-mesh sieve were returned to the pulverizing process, while the powder that passed through the 140-mesh sieve entered the finished product collection process, yielding a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. In this embodiment, the concentrated product of polycarboxylate-based high-performance water-reducing agent powder had a moisture content of 1.1 wt%, a glass transition temperature of 46°C, and a volume median particle size (D50) of 105 μm.

[0112] This embodiment is suitable for concrete construction in warm climates or high-temperature environments in summer. It can maintain good dispersibility and resolubility at lower temperatures and is suitable for room temperature storage and use in commercial concrete plants in southern regions.

[0113] Example 4

[0114] A process for concentrating polycarboxylate-based high-performance water-reducing agent powder includes the following steps:

[0115] S1, Preparation of aqueous solution of high-functional polycarboxylic acid ether copolymer:

[0116] A1. A monomer solution was prepared by mixing 100g of polyethylene glycol methyl ether methacrylate (with an average polyoxyethylene repeating unit number n of 23.0), 20.71g of acrylic acid, 3.35g of 2-acrylamido-2-methylpropanesulfonic acid, 2.23g of mercaptoacetic acid (accounting for 1.8wt% of the total mass of the three monomers), and a portion of deionized water. In this embodiment, the total amount of deionized water was controlled to be approximately 240g. The total amount of deionized water included all the water used to prepare the monomer solution, sodium hydroxide aqueous solution, and initiation system aqueous solution.

[0117] A2, the acrylic acid in the monomer solution of this embodiment was pre-neutralized with an aqueous solution of sodium hydroxide, which contained 1.72 g of sodium hydroxide by weight, to a degree of 15 mol%.

[0118] A3, Under a nitrogen atmosphere, the monomer solution of this embodiment was simultaneously added dropwise at 40°C to an initiation system consisting of hydrogen peroxide (0.55 wt% of the total mass of the three monomers based on the purity of H2O2) and ascorbic acid (0.55 wt% of the total mass of the three monomers based on the purity of ascorbic acid), for a duration of 2.2 h, while controlling the pH of the system to be 4.5 during the polymerization process;

[0119] A4, after the addition is complete, maintain the temperature for 1.5 hours until the total amount of residual unsaturated monomers, calculated as the total mass of the reaction system after the temperature maintenance, is 0.5 wt%, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 35 wt%. In this embodiment, the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid is 1:3.2:0.18. The high-functional polycarboxylic acid ether copolymer of this embodiment has polyoxyethylene side chains, carboxyl groups, and sulfonic acid groups. The carboxyl groups in this embodiment are derived from the acrylic acid structural unit, and the sulfonic acid groups in this embodiment are derived from the 2-acrylamido-2-methylpropanesulfonic acid structural unit.

[0120] S2, forming an ion clustering intermediate:

[0121] B1. Magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1. The amount of magnesium acetate tetrahydrate added is controlled to be approximately 3.70 g, so that the degree to which the carboxyl groups in the high-functional polycarboxylate ether copolymer of this embodiment form a partial magnesium carboxylate structure with the magnesium ions provided by magnesium acetate tetrahydrate is 12 mol% based on the ratio of the positive charge equivalent of the magnesium ions to the total molar number of carboxyl groups.

[0122] B2 was stirred at 85℃ for 40 minutes, and the pH of the system was controlled at 7.2.

[0123] B3. When the pH value of the system fluctuates by no more than 0.1 within 10 minutes, an ion clustering intermediate is obtained. The reversible magnesium carboxylate ion cluster formed in this embodiment is an ion-association structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer of this embodiment. The ion-association structure of this embodiment is at least partially dissociated when dispersed in water, thereby redispersing the high-functionality polycarboxylate ether copolymer segments in the aqueous phase.

[0124] S3, dehydrate and cool to form sheets:

[0125] C1, the ion-clustered intermediate obtained in step S2 is fed into a falling film thin-film evaporator and dehydrated at 90°C and an absolute pressure of 0.010 MPa;

[0126] C2, the dehydrated material is cooled into sheets at 25°C using a double-roller cooling device to obtain a sheet-like intermediate with a thickness of 180μm and a moisture content of 1.9wt%.

[0127] S4, crush and classify:

[0128] The flake-like intermediate obtained in step S3 was pulverized using a needle mill at a material temperature of 35°C. The pulverized material was then graded by a sieving process using a 140-mesh sieve. Coarse particles that did not pass through the 140-mesh sieve were returned to the pulverizing process, while the powder that passed through the 140-mesh sieve entered the finished product collection process, yielding a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. In this embodiment, the concentrated product of polycarboxylate-based high-performance water-reducing agent powder had a moisture content of 1.9 wt%, a glass transition temperature of 64°C, and a median particle size (D50) of 105 μm.

[0129] This embodiment is suitable for concrete construction in cold climates or low-temperature winter environments. It can maintain the stability of powder at a relatively high glass transition temperature and avoid caking at low temperatures. It is suitable for storage and winter construction at commercial concrete plants in northern regions.

[0130] Comparative Example 1: Basically the same as Example 1, except that the average number of polyoxyethylene repeating units n of polyethylene glycol methyl ether methacrylate used in step A1 is 20.0, and the amounts of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, mercaptoacetic acid, sodium hydroxide and deionized water are calculated simultaneously according to the average molecular weight corresponding to n=20.0, so that the molar ratio of the three monomers is still 1:2.5:0.05, the pre-neutralization degree is still 10 mol%, and the solid content is still 45 wt%, and other process conditions remain unchanged.

[0131] Comparative Example 2: Basically the same as Example 1, except that the amount of acrylic acid used in step A1 is 15.13g, so that the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 1:2.2:0.05. The amounts of mercaptoacetic acid, sodium hydroxide, magnesium acetate tetrahydrate, initiation system and deionized water are calculated simultaneously according to the total mass of the three monomers, the number of moles of acrylic acid and the total number of moles of carboxyl groups in this comparative example. Other process conditions remain unchanged.

[0132] Comparative Example 3: Basically the same as Example 1, except that the amount of 2-acrylamido-2-methylpropanesulfonic acid used in step A1 is 0.40g, so that the molar ratio of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 1:2.5:0.02. The amounts of mercaptoacetic acid, initiation system and deionized water are calculated simultaneously according to the total mass of the three monomers in this comparative example, and other process conditions remain unchanged.

[0133] Comparative Example 4: It is basically the same as Example 1, except that the amount of mercaptoacetic acid used in step A1 is 0.24g, accounting for 0.2wt% of the total mass of the three monomers, and the amount of deionized water is calculated according to the solid content requirements. Other conditions remain unchanged.

[0134] Comparative Example 5: Basically the same as Example 1, except that the amount of magnesium acetate tetrahydrate added in step B1 was adjusted to make the degree of neutralization of the carboxyl groups in the high-functional polycarboxylic acid ether copolymer by magnesium ions 3 mol%, and other conditions remained unchanged.

[0135] Comparative Example 6: It is basically the same as Example 1, except that in step B2, the mixture is stirred at 78°C for 20 minutes and the pH of the system is controlled to be 5.5, while other conditions remain unchanged.

[0136] Comparative Example 7: It is basically the same as Example 1, except that in step C1, after the ion cluster intermediate is fed into the scraped film evaporator, it is dehydrated at 82°C and an absolute pressure of 0.020 MPa, while other conditions remain unchanged.

[0137] Comparative Example 8: Essentially the same as Example 1, except that magnesium acetate tetrahydrate was removed in step B1, and step B2 was changed to stirring at 78°C for 20 min, with other conditions remaining unchanged. This comparative example was used to verify the synergistic effect of the high-functionality polycarboxylic acid ether copolymer and magnesium acetate tetrahydrate in constructing reversible magnesium carboxylate ion clusters.

[0138] Comparative Example 9: Essentially the same as Example 1, except that in step B1, magnesium acetate tetrahydrate was replaced with sodium acetate. The amount of sodium acetate added was determined according to the sodium ion equivalent, which corresponds to the positive charge equivalent of magnesium ions in Example 1. Other conditions remained unchanged. This comparative example was used to verify the synergistic effect between magnesium acetate tetrahydrate and the high-functionality polycarboxylic acid ether copolymer.

[0139] Comparative Example 10: Essentially the same as Example 1, except that in step S3, a scraped-film evaporator was not used for dehydration and cooling into sheets. Instead, the ion-clustered intermediate obtained in step S2 was transferred to a vacuum disc drying oven, spread into a 3.0 mm thick layer, and dried at 82°C and 0.005 MPa for 45 min until the material moisture content was 0.20 wt%. It was then naturally cooled at 18°C, mechanically scraped, and processed according to the pulverization and sieving conditions of Example 1, with other conditions remaining unchanged. This comparative example was used to verify the synergistic effect of the reversible magnesium carboxylate ion clusters and the thin-film dehydration and cooling sheet formation method.

[0140] Performance testing:

[0141] The moisture content of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder was determined by Karl Fischer titration to confirm whether the finished product moisture content was between 0.2-2.0 wt% and to assess storage sensitivity. Approximately 1.0 g of sample was weighed and titrated at 25°C. The endpoint drift was controlled to be ≤20 μg / min. The test was performed in triplicate, and the average value and relative standard deviation were reported. A result was considered valid if the RSD was ≤5%.

[0142] The glass transition temperature of the concentrated powder product was determined using differential scanning calorimetry (DSC) to evaluate the thermophysical window of the powder. 5-10 mg of sample was placed in a nitrogen atmosphere and tested within a temperature range of 20-120 °C at a heating rate of 10 °C / min. The heat flow change of the sample was recorded, and the glass transition inflection point was read. The glass transition temperature of the second heating curve was taken, and the average value was calculated after three parallel tests.

[0143] The median particle size (D50) of the concentrated powder product was determined by laser diffraction to evaluate the fractionation effect. The sample was ultrasonically dispersed in anhydrous ethanol before testing, and the D10, D50, and D90 values ​​were recorded. The opacity was controlled within the instrument's recommended range, and the test was performed in triplicate. The D50 and Span values ​​were reported; a smaller Span value indicates a more concentrated particle size distribution.

[0144] The flowability of concentrated powder products is evaluated using the funnel method, which reflects the powder flow characteristics during packaging, metering, and transportation. A 50.0 g sample is pre-conditioned for 24 hours at 25°C and 50% relative humidity, then allowed to flow freely through a standard funnel while timing is performed. The funnel outlet must be kept clean. The test is repeated three times in parallel. A shorter flow time indicates better flowability; an RSD ≤ 5% is considered valid.

[0145] The anti-caking stability of the concentrated powder product was evaluated through accelerated storage tests. 100g samples were placed in a 40℃, 75%RH environment under a static load of 5kPa for 7 days, with the material layer thickness controlled at 20mm. The samples were then passed through a 1mm sieve, and the agglomeration mass fraction was recorded. The tests were repeated in triplicate. A lower agglomeration rate indicates better storage stability.

[0146] The redispersibility of the powder-water compound was evaluated using the stirring-dissolution method. The sample, with a solid content of 20 wt%, was added to deionized water at 25°C within 30 seconds. The mixture was stirred at 300 rpm, and the time required for complete removal of visible agglomerates was recorded (total stirring limit 300 s). The powder was then passed through a 100-mesh sieve, and the remaining insoluble matter was weighed. Shorter redispersibility and lower insoluble matter percentage indicate better redispersibility.

[0147] The water-reducing capacity of the powdered compound solution incorporated into the benchmark cement mortar system was evaluated using a fluidity comparison method. Control and experimental mortars were prepared with a uniform admixture solids content, and the number of times the admixture was adjusted was kept consistent. Three parallel groups were tested for fluidity. Under the same fluidity conditions, the water reduction rate was calculated based on the difference in water consumption between the control and experimental groups; lower water consumption indicated a stronger water-reducing effect.

[0148] The workability of concrete mixtures with admixtures was evaluated by the change in slump over time. Samples were prepared according to a uniform cementitious material system and admixture solids content. Slump was tested at 0, 30, and 60 minutes under an ambient temperature of 20±5℃. Testing began within 5 minutes of sampling, with three parallel batches. The initial slump, 1-hour retention value, and retention rate were reported to reflect the persistence of the dispersion effect.

[0149] First, the chemical structure and surface chemical environment of Example 1, Comparative Examples 8 and 9 were systematically characterized by spectroscopic methods to verify the effectiveness of the construction of the target system. Figure 1 The FTIR full spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown. The functional group structures of different samples were characterized using Fourier transform infrared spectroscopy. Figure 1 As can be seen, the peak shape and peak intensity distribution in the carboxylate-related absorption region and the ether bond-related absorption region of Example 1 are more coordinated, indicating that there is a good matching relationship between the polar groups and the main chain structure in its molecular structure, and that a relatively stable combination of functional groups has been formed inside the sample. Figure 2 The images show magnified FTIR characteristic regions of carboxylate samples from Examples 1, 8, and 9. Fourier transform infrared spectroscopy was used to focus on analyzing the characteristic absorptions of carboxyl groups and carboxylates in the range of 1300 cm⁻¹ to 1800 cm⁻¹. In Example 1, the characteristic peaks near approximately 1418 cm⁻¹ and 1608 cm⁻¹ are clearer, and the peak separation is more precise, suggesting a difference in the local environment related to carboxylates compared to the comparative examples. These results indicate that Example 1 is superior to the comparative samples in terms of salification structure formation and functional group organization, laying a structural foundation for subsequent performance improvements. Furthermore, Figure 3 The XPS C1s region spectra of Example 1, Comparative Example 8, and Comparative Example 9 are shown. X-ray photoelectron spectroscopy was used to characterize the chemical state of carbon on the sample surface. Figure 4 The XPS O1s region spectra of Example 1, Comparative Example 8, and Comparative Example 9 show the chemical environment of oxygen on the sample surface, which was analyzed by X-ray photoelectron spectroscopy. Figure 5 The XPS Mg2p region spectra of Examples 1, 8, and 9 are shown. X-ray photoelectron spectroscopy was used to characterize the magnesium-related surface chemical states in the samples. Figures 3 to 5As can be seen, Example 1 exhibits more complete peak characteristics near 284.8 eV, 286.4 eV, and 288.75 eV in the C1s region, and more stable peak shapes near 531.45 eV and 532.95 eV in the O1s region. It also shows a significant response at approximately 50.45 eV in the Mg2p region. In contrast, the corresponding signals of the comparative sample are weaker or less pronounced. This indicates that the oxygen-containing carbon component distribution on the surface of the Example 1 sample is more reasonable, the oxygen-related functional group environment is more uniform, and magnesium-related components can be introduced into the sample surface or near-surface region. FTIR and XPS results corroborate each other, demonstrating that magnesium-related components were introduced in Example 1, and that the carboxylate-related functional groups and surface chemical environment changed compared to the comparative sample.

[0150] Based on the confirmation of the effective chemical structure construction, the physical stability and powder uniformity of the sample were further evaluated through thermal analysis and particle size distribution. Figure 6 The DSC heat flow curves for Example 1, Comparative Example 7, and Comparative Example 10 are shown. Differential scanning calorimetry (DSC) was used to characterize the thermal transition behavior of the samples. The results show that the glass transition temperature of Example 1 is approximately 55.0 °C, higher than that of Comparative Example 7, and it exhibits more stable heat flow characteristics compared to Comparative Example 10. This indicates that its molecular chain motion is more effectively constrained, its internal structure is more coordinated, and the sample demonstrates superior thermal stability during storage and use. Correspondingly, Figure 7 The laser particle size differential distribution curves for Example 1, Comparative Example 7, and Comparative Example 10 are shown. The particle size distribution was characterized using laser particle size analysis. Figure 8 The cumulative particle size distribution curves for Examples 1, 7, and 10 are shown below. Laser particle size analysis was used to evaluate the cumulative volume distribution of the particles. Figure 7 and Figure 8 As can be seen, the particle size distribution of Example 1 is more concentrated, and the tail of coarse particles is shorter. The D10, D50, and D90 are approximately 35 μm, 65 μm, and 102 μm, respectively. The overall distribution range is significantly better than that of Comparative Example 10, indicating that the powder obtained in Example 1 has better particle size controllability and particle uniformity after pulverization and classification. The thermal behavior and particle size results together show that the material system formed in Example 1 is not only structurally stable, but also has a more reasonable powder morphology and size distribution, which is beneficial for subsequent rapid dispersion and stable use.

[0151] Based on the above-mentioned structural stability and particle uniformity, the actual use effect of Example 1 was further verified through redispersion kinetics and application performance tests. Figure 9 The redispersion kinetics conductivity-time diagrams for Example 1, Comparative Example 8, and Comparative Example 10 are shown. The conductivity test method was used to characterize the ion release and dispersion establishment behavior during the sample redispersion process. Figure 10The turbidity-time plots for the redispersion kinetics of Example 1, Comparative Example 8, and Comparative Example 10 are shown. Turbidity testing was used to characterize the agglomerate dissipation behavior during the redispersion process. The results show that in Example 1, the conductivity rapidly increased to approximately 1.9 mS / cm within 300 s, while the initial turbidity was low and decreased more rapidly, dropping to a low level by 300 s. This indicates that it can more quickly complete ion release, particle deagglomeration, and dispersion system reconstruction after entering water, demonstrating superior redispersion efficiency. Furthermore, Figure 11 The slump retention curves of Example 1, Comparative Example 8, and Comparative Example 10 are shown. The slump test method was used to characterize the workability retention ability of the samples during practical applications. Example 1's slump decreased from approximately 235 mm at 0 min to approximately 205 mm at 60 min, showing a significantly smaller slump loss than Comparative Example 8. This indicates that the sample not only has better initial flowability after dispersion but also stronger workability retention over time. Therefore, Example 1, through a more stable structure and more reasonable particle size control, achieves a continuous performance advantage from rapid redispersion to stable workability retention.

[0152] To further illustrate the macroscopic state and microscopic morphology of the obtained powder concentrate, its appearance and scanning electron microscope morphology were observed. Figure 12 This is a macroscopic optical photograph of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The sample is generally light-colored and loose powder with relatively uniform particle distribution. No obvious moisture-induced clumping was observed, indicating that the obtained powder has good dryness and basic flow characteristics. Figure 13 Scanning electron microscope image of concentrated product of polycarboxylate-based high-performance water-reducing agent powder. Figure 13 a is a low-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The particles are continuously covered, and no large-area melting, adhesion, or collapse areas are observed, indicating that the overall dispersion of the powder is relatively stable under low moisture content conditions. Figure 13 b is a medium-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The particles are mainly irregular flakes and blocks with sharp edges, reflecting the fragmentation characteristics of the flake intermediate under needle milling conditions at 22℃, which are dominated by brittle fracture. Figure 13 c is a high-magnification scanning electron microscope image of the concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The particle surface has micron-level undulations, local fracture steps and fine debris, indicating that dehydration shrinkage and mechanical crushing jointly shape the surface micro-texture. Figure 13 Image d is a cross-sectional scanning electron microscope image of the sheet-like intermediate. The cross-section is continuous and relatively dense, with no obvious delamination or peeling within the layers, indicating that a stable and continuous sheet structure was formed during the dehydration process. The above macroscopic and microscopic morphological results show that the intermediate and final products obtained in Example 1 have good forming integrity and subsequent pulverization adaptability, which is one of the important reasons for their concentrated particle size distribution and good redispersibility.

[0153] To further explain the source of the above properties, transmission electron microscopy analysis was performed on the ion clustering intermediate. Figure 14 This is a transmission electron microscope (TEM) image of the ion clustering intermediate. Figure 14 a is a bright-field transmission electron microscope image of the ion clustering intermediate, which shows the presence of dispersed weakly contrasting nano-regions in the continuous matrix, suggesting that there are nanoscale compositional or density differences in the ion clustering intermediate. Figure 14 b is a magnified transmission electron microscope image of the ion clustering intermediate. The nanoscale enriched region is uniformly embedded in the continuous phase, and the characteristic scale is on the order of several nanometers, indicating that the nanoscale region is relatively uniformly distributed in the ion clustering intermediate. Figure 14 c is a high-resolution transmission electron microscope image of the ion cluster intermediate. No long-range continuous lattice fringes are observed, indicating that the system is mainly composed of an amorphous polycarboxylic acid ether matrix and ion-associated structures. Figure 14 Image d shows the selected area electron diffraction pattern of the ion-clustered intermediate. The diffraction results are dominated by diffuse halos rather than clear diffraction spots, indicating that the overall crystallinity of the material is low and it does not exhibit a clear long-range crystal structure. Figures 1 to 13 The results show that Example 1, by forming carboxylate-related structures, different surface chemical environments, and nanoscale micro-regions, enables the material to exhibit good stability and coordination in all stages, including dehydration forming, crushing and classification, redispersing, and application retention, thus supporting the effectiveness and rationality of the scheme.

[0154] Table 1 Performance summary of the examples and comparative examples

[0155] Sample number Moisture / wt% Glass transition temperature / °C Median particle size D50 / μm Redispersal time / s Mortar water reduction rate / % 1-hour slump retention value / mm <![CDATA[Funnel outflow time / s·50g -1 > clumping rate / % Example 1 0.30±0.02 55.0±0.4 65±4 55±4 31.8±0.6 205±7 11.8±0.4 3.1±0.3 Example 2 1.10±0.04 55.0±0.5 145±4 64±5 35.6±0.5 232±8 12.6±0.5 2.4±0.2 Example 3 1.10±0.05 46.0±0.4 105±6 44±3 33.4±0.5 220±6 13.4±0.5 4.1±0.4 Example 4 1.90±0.06 64.0±0.5 105±7 73±5 33.0±0.6 218±7 14.0±0.6 2.0±0.2 Comparative Example 1 0.22±0.02 56.2±0.5 63±4 66±5 28.6±0.6 188±7 12.9±0.5 3.9±0.4 Comparative Example 2 0.21±0.02 52.8±0.5 61±4 70±5 27.9±0.7 180±8 13.2±0.5 4.4±0.4 Comparative Example 3 0.21±0.03 53.6±0.4 60±4 68±5 29.4±0.6 166±7 13.0±0.5 4.1±0.4 Comparative Example 4 0.23±0.03 57.4±0.6 65±5 78±6 30.1±0.6 186±8 15.8±0.7 4.8±0.5 Comparative Example 5 0.20±0.02 51.0±0.4 59±4 61±4 30.0±0.7 187±7 12.8±0.4 5.6±0.5 Comparative Example 6 0.24±0.03 51.8±0.5 62±5 74±5 28.9±0.6 176±8 13.9±0.6 5.1±0.5 Comparative Example 7 2.45±0.07 46.8±0.5 64±5 82±6 29.6±0.7 182±8 16.6±0.7 9.4±0.6 Comparative Example 8 0.21±0.02 48.2±0.4 58±4 87±7 28.1±0.7 170±7 15.1±0.6 8.8±0.6 Comparative Example 9 0.22±0.02 49.0±0.5 59±4 79±6 28.7±0.6 174±7 14.7±0.6 7.6±0.5 Comparative Example 10 0.20±0.02 54.2±0.4 176±10 91±7 30.4±0.6 183±7 17.4±0.8 6.3±0.5

[0156] As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1-4 all achieved a better balance between moisture content, glass transition temperature, median particle size D50, redispersion time, mortar water reduction rate, slump retention value at 1 hour, funnel outflow time, and agglomeration rate. Among them, Example 2 was the most outstanding in terms of water reduction rate and slump retention, Example 3 had a better advantage in redispersion, Example 4 was more stable in terms of anti-agglomeration storage stability, and Example 1 performed well in terms of powder flowability. However, after reducing the carboxyl group ratio, reducing the content of 2-acrylamido-2-methylpropanesulfonic acid, weakening the partial neutralization of magnesium ions, changing the dehydration conditions, or disrupting the relationship between ion clustering and sheet formation, the comprehensive indicators of the comparative examples all showed varying degrees of imbalance. This indicates that the component matching, reversible magnesium carboxylate ion cluster construction, and sheet intermediate formation pathway of this process need to be maintained synergistically.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A process for concentrating polycarboxylate-based high-performance water-reducing agent powder, characterized in that, Includes the following steps: S1, Prepare an aqueous solution of a high-functional polycarboxylic acid ether copolymer, wherein the high-functional polycarboxylic acid ether copolymer has polyoxyethylene side chains, carboxyl groups and sulfonic acid groups, and is obtained by copolymerization of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in a molar ratio of 1:(2.5-4.0):(0.05-0.30); S2, magnesium acetate tetrahydrate is added to the aqueous solution of the high-functional polycarboxylate ether copolymer obtained in step S1, so that the carboxyl groups in the high-functional polycarboxylate ether copolymer and the magnesium ions provided by the magnesium acetate tetrahydrate form a partial magnesium carboxylate structure. The degree of formation of the partial magnesium carboxylate structure is 5-20 mol% based on the ratio of the positive charge equivalent corresponding to the magnesium ions to the total number of moles of carboxyl groups. The positive charge equivalent corresponding to the magnesium ions is calculated as twice the number of moles of magnesium ions, and the total number of moles of carboxyl groups is calculated based on the number of moles of acrylic acid fed, so as to form a reversible magnesium carboxylate ion cluster and obtain an ion cluster intermediate. S3, the ion-clustered intermediate obtained in step S2 is fed into a scraped film thin-film evaporator or a falling film thin-film evaporator for dehydration and cooling into sheets to obtain a sheet-like intermediate with a thickness of 40-180 μm and a moisture content of 0.2-2.0 wt%. S4. The flaky intermediate obtained in step S3 is crushed and graded to obtain a concentrated product of polycarboxylate-based high-performance water-reducing agent powder. The concentrated product of polycarboxylate-based high-performance water-reducing agent powder has a water content of 0.2-2.0 wt%, a glass transition temperature of 45-65℃, and a median particle size D50 of 60-150 μm.

2. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 1, characterized in that, Step S1 Includes the following steps: A1, a monomer solution is prepared by mixing polyethylene glycol methyl ether methacrylate, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, mercaptoacetic acid and deionized water, wherein the amount of mercaptoacetic acid is 0.5-3.0 wt% of the total mass of the three monomers, and the total mass of the three monomers is the sum of the feed masses of polyethylene glycol methyl ether methacrylate, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid; A2, pre-neutralize the acrylic acid in the monomer solution with sodium hydroxide to a degree of 10-20 mol%; A3, under a nitrogen atmosphere, the monomer solution and an initiation system composed of hydrogen peroxide and ascorbic acid are simultaneously added dropwise at 20-40°C for 1.5-3.0 h, and the pH of the system is controlled to be 2.5-4.5 during the polymerization process; After adding A4, keep warm for 0.5-1.5 hours until the total amount of residual unsaturated monomers is no more than 1.0 wt% based on the total mass of the reaction system after the warming process, to obtain an aqueous solution of high-functional polycarboxylic acid ether copolymer with a solid content of 35-55 wt%.

3. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 2, characterized in that, In step S1, the amount of hydrogen peroxide and ascorbic acid in the initiation system is 0.1-1.0 wt% of the total mass of the three monomers.

4. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 1, characterized in that, Step S2 includes the following steps: B1. Add magnesium acetate tetrahydrate to the aqueous solution of the high-functional polycarboxylic acid ether copolymer obtained in step S1, and control the amount of magnesium acetate tetrahydrate added according to the degree of neutralization described in step S2. B2, stir at 70-85℃ for 20-60 min, and control the pH of the system to 6.0-7.2; B3, when the pH of the system fluctuates by no more than 0.1 within 10 minutes, an ion-clustered intermediate is obtained.

5. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 4, characterized in that, The reversible magnesium carboxylate ion cluster formed in step S2 is an ion-associated structure formed by magnesium ions provided by magnesium acetate tetrahydrate and carboxyl groups in the high-functionality polycarboxylate ether copolymer.

6. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 1, characterized in that, Step S3 includes the following steps: C1, the ion cluster intermediate obtained in step S2 is fed into the evaporator described in step S3 and dehydrated at 75-90°C and an absolute pressure of 0.005-0.015 MPa; C2 involves cooling the dehydrated material into sheets at 10-25℃.

7. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 6, characterized in that, In step S3, the dehydrated material is cooled into sheets by a cooling roller or a double-roller cooling device.

8. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 1, characterized in that, In step S4, the sheet-like intermediate is pulverized using a needle mill, hammer mill, or mechanical impact mill at a material temperature of 10-35℃.

9. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 8, characterized in that, In step S4, the crushed material is graded by at least one screening process, using a screen with a mesh size of 80 to 200.

10. The polycarboxylate-based high-performance water-reducing agent powder concentration process according to claim 2, characterized in that, The average number of repeating polyoxyethylene units n in the polyethylene glycol methyl ether methacrylate is 21.5-24.5.

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