Polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to a polycarboxylic acid water reducer and a preparation method thereof, and the water reducer is prepared from the following raw materials: 45 to 55 percent of isopentenyl polyoxyethylene ether, 28 to 35 percent of acrylic acid, 1.5 to 2.5 percent of modifier, 0.3 to 0.5 percent of ammonium persulfate, 0.03 to 0.06 percent of ascorbic acid, 5 to 8 percent of hydroxyethyl methylacrylate, 0.15 to 0.25 percent of 2, 4-diphenyl-4-methyl-1-pentene and the balance of water. The modifier is prepared from the following raw materials: 1, 5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate and tetramethylpiperidine oxide. The polycarboxylate superplasticizer has excellent neat paste fluidity and fluidity retention capability, has low 1h time-dependent variable slump which is below 18mm and optimally 10mm when applied to concrete, has a water-reducing rate of more than 40% and a gas content of less than 3.8%, and also has more advantages in compressive strength ratio.

Description

Technical Field

[0001] The present invention belongs to the field of concrete admixtures, and more specifically, relates to a polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] Water reducer refers to an admixture that can appropriately reduce the amount of mixing water and improve the strength of concrete under the condition that the slump of concrete and the amount of cement used remain unchanged, or can save the amount of cement under the condition that the workability and strength remain unchanged. It is a high-efficiency water reducer.

[0003] Polycarboxylate superplasticizer is a high-performance water reducer and a cement dispersant used in cement concrete transportation. It is widely used in projects such as roads, bridges, dams, tunnels, and high-rise buildings. Polycarboxylate superplasticizer is non-flammable and non-explosive, making it safe to transport by train and truck. When the water and cement dosages remain unchanged, polycarboxylate superplasticizers can increase concrete slump by 100-200mm, significantly improving concrete fluidity without compromising strength. While maintaining fluidity and cement dosage, polycarboxylate superplasticizers can reduce mixing water by 10%-15%, thereby lowering the water-cement ratio and increasing concrete strength by 15%-20%. While maintaining fluidity and water-cement ratio, reducing mixing water consumption can also reduce cement dosage, saving 10%-15% of cement while maintaining concrete strength, thus reducing project costs. Because the addition of superplasticizers significantly improves the pore structure of concrete, it increases density and reduces water permeability, thereby improving resistance to seepage, frost, chemical corrosion, and rust. Furthermore, the addition of superplasticizers can improve bleeding and segregation in concrete mixtures, delay the setting time of concrete mixtures, slow the exotherm of cement hydration, and prevent cracks caused by internal and external temperature differences. Polycarboxylate superplasticizer is a macromolecular chain compound formed by esterifying polyvinyl alcohol monomethyl ether and methacrylic acid, followed by condensation with methacrylic acid. As a high-molecular-weight compound, polycarboxylate is resinous and possesses excellent strength, toughness, and chemical stability, making it a versatile material. It offers high water-reducing rates at low dosages, maintaining good concrete fluidity, minimizing slump loss, and facilitating broad cement compatibility.

[0004] During the cement hydration process, polycarboxylic acid water-reducing agent molecules will compete for adsorption with sulfates and other substances produced by cement hydration, affecting the adsorption of polycarboxylic acid water-reducing agent and cement, resulting in a decrease in its performance, and then a decrease in the performance of concrete. Most of the methods for synthesizing polycarboxylic acid water-reducing agents are to first synthesize polyethylene glycol mono(meth)acrylate with polymerization activity through esterification or ester exchange, and then copolymerize it with monomers such as methacrylic acid using a solution polymerization process to obtain a polycarboxylic acid-based water-reducing agent. The process route is long, the production is complex, the energy consumption is high, the cost is high, and the quality stability is poor. The dispersion and water-reducing ability of polycarboxylic acid water-reducing agent products are poor, and the slump loss is too fast. Therefore, in view of the shortcomings of the performance of existing polycarboxylic acid water-reducing agents, it is urgent to develop a high-performance polycarboxylic acid water-reducing agent to improve the water-reducing ability of polycarboxylic acid water-reducing agents, reduce the slump loss, meet market requirements, and promote industry development. Summary of the Invention

[0005] The present invention provides a polycarboxylate water-reducing agent and a preparation method thereof, which are used to solve the technical problems of the current polycarboxylate water-reducing agent products, such as poor dispersion and water-reducing ability and high slump loss. By adjusting the components of the polycarboxylate water-reducing agent, a targeted modifier is developed to enable the polycarboxylate water-reducing agent to have excellent net paste fluidity and fluidity retention ability. The prepared polycarboxylate water-reducing agent is applied to concrete, has a low 1h time-varying slump, all below 18mm, and optimally up to 10mm, and has an early strength effect. The concrete maintains good fluidity for a long time, has a water reduction rate of more than 40%, an air content of less than 3.8%, has better air entrainment performance, and has a more advantageous compressive strength ratio.

[0006] In a first aspect, the present invention relates to a polycarboxylate water reducer. The raw materials for its preparation include, by mass percentage, 45-55% of isopentenyl polyoxyethylene ether, 28-35% of acrylic acid, 1.5-2.5% of a modifier, 0.3-0.5% of ammonium persulfate, 0.03-0.06% of ascorbic acid, 5-8% of hydroxyethyl methacrylate, 0.15-0.25% of 2,4-diphenyl-4-methyl-1-pentene, and the balance being water.

[0007] The raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide.

[0008] Preferably, the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinoxide in the raw materials for preparing the modifier is 2.0-3.5:2.5-4.0:1:2.1-2.7:0.13-0.2.

[0009] Preferably, the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinoxide in the raw materials for preparing the modifier is 2.5:3.8:1:2.2:0.18.

[0010] Preferably, the preparation method of the modifier is: mixing the raw materials for preparing the modifier, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinium oxide, reacting at 70-80° C. for 12 to 16 hours, precipitating the product with ethanol, and drying to obtain the modifier powder.

[0011] In a second aspect, the present invention relates to a method for preparing a polycarboxylic acid water reducer, comprising the following steps: (1) adding isopentenyl polyoxyethylene ether and ammonium persulfate into water and mixing them uniformly to form a base material.

[0012] (2) Acrylic acid, hydroxyethyl methacrylate and modifier are prepared into a mixed aqueous solution A.

[0013] (3) Ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene are prepared into aqueous solution B.

[0014] (4) The aqueous solution A and the aqueous solution B are simultaneously added dropwise to the base material solution to react to obtain the polycarboxylate water reducer.

[0015] Preferably, in step (1), isopentenyl polyoxyethylene ether and deionized water are added to a reaction kettle, and after stirring for 5 to 10 minutes, ammonium persulfate is added and stirring is continued for 5 to 10 minutes to form a base material.

[0016] Preferably, in step (4), aqueous solution A and aqueous solution B are added dropwise simultaneously, wherein aqueous solution A is added dropwise for 50 to 70 minutes, and aqueous solution B is added dropwise for 70 to 90 minutes, and the reaction is continued for 40 to 60 minutes after the addition is completed.

[0017] The present invention has the following beneficial effects: by adjusting and optimizing the raw material composition of the polycarboxylate superplasticizer, the isopentenol polyoxyethylene ether main chain contains hydrophilic groups, providing long side chains (polyoxyethylene ether) that disperse cement particles through steric hindrance; the hydroxyethyl methacrylate, whose ester groups slowly hydrolyze to form carboxylic acid, provides a sustained-release effect and extends the slump retention time; and the 2,4-diphenyl-4-methyl-1-pentene, a sulfur-free chain transfer agent, is more environmentally friendly and avoids contamination by byproducts. The ratio of the various components of the polycarboxylate superplasticizer affects the density of hydrophilic and hydrophobic groups and the molecular chain length in the final superplasticizer molecular structure. By adjusting and optimizing the ratio of the components, the resulting polycarboxylate superplasticizer has better overall performance.

[0018] A more suitable modifier component has been developed for polycarboxylate superplasticizers. Upon reaction of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, and ammonium cerium nitrate, the modifier introduces nitro or sulfonic acid groups onto the 1,5-dichloronaphthalene. The naphthalene ring structure of 1,5-dichloronaphthalene exhibits 30% greater steric hindrance than the benzene ring of traditional styrene, increasing molecular chain stretch and extending dispersion retention to over 2 hours. Precisely controlling the molar ratios of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinyl oxide in the modifier maximizes the synergistic effect of the naphthalene ring, nitro, and sulfonic acid groups. This combination creates a ternary system of "charge-steric hindrance-dynamic adsorption," giving the modified polycarboxylate superplasticizer excellent neat slurry fluidity and fluidity retention.

[0019] The preparation method of the polycarboxylate water-reducing agent of the present invention is simple, efficient, rapid, and can react at room temperature, with low energy consumption and significantly reduced costs. The sulfonation of dimethyl sulfate and 2,4-diphenyl-4-methyl-1-pentene replaces traditional sulfonation reagents and mercaptan chain transfer agents, avoiding sulfur-containing byproducts and improving compatibility with clay minerals in cement, enabling sulfur-free production and meeting environmental requirements.

[0020] By optimizing the composition of polycarboxylate superplasticizers and developing targeted modifiers, the polycarboxylate superplasticizers have been endowed with excellent neat paste fluidity and fluidity retention. The resulting polycarboxylate superplasticizers, when applied to concrete, exhibit low 1-hour slump change, consistently below 18mm, with the best reaching 10mm. They also exhibit early strength, maintaining good fluidity over extended periods of time, achieving water reduction rates exceeding 40%, air content below 3.8%, improved air entrainment, and a superior compressive strength ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The present invention discloses a process flow diagram of a polycarboxylate water-reducing agent. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] During the cement hydration process, existing polycarboxylate water-reducers (PCRs) compete for adsorption with sulfates and other substances produced by cement hydration, affecting their adsorption to cement, leading to a decrease in their performance and, in turn, to a decrease in concrete performance. The synthesis of PCRs is complex, energy-intensive, and costly, resulting in poor quality stability. Furthermore, PCRs suffer from poor dispersion and water-reducing capabilities, resulting in rapid slump loss. Therefore, in response to the shortcomings of existing PCRs, there is an urgent need to develop a high-performance PCR to enhance its water-reducing capacity, reduce slump loss, meet market demands, and promote industry development.

[0025] In response to the above technical problems, an embodiment of the present invention provides a polycarboxylate water reducer, wherein the raw materials for preparation include, by mass percentage: 45-55% isopentenyl polyoxyethylene ether, 28-35% acrylic acid, 1.5-2.5% modifier, 0.3-0.5% ammonium persulfate, 0.03-0.06% ascorbic acid, 5-8% hydroxyethyl methacrylate, 0.15-0.25% 2,4-diphenyl-4-methyl-1-pentene, and the balance is water.

[0026] The raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide.

[0027] The raw material for polycarboxylate superplasticizer preparation, isopentenol polyoxyethylene ether, contains hydrophilic groups in its backbone, providing long side chains (polyoxyethylene ether) that disperse cement particles through steric hindrance. The carboxylic acid groups of acrylic acid provide initial dispersing power and reduce cement particle agglomeration through electrostatic repulsion. Hydroxyethyl methacrylate, containing ester groups that slowly hydrolyze to form carboxylic acids, provides a sustained-release effect and extends slump retention time. 2,4-Diphenyl-4-methyl-1-pentene is a sulfur-free chain transfer agent, which is more environmentally friendly and avoids contamination by byproducts. Ammonium persulfate is used as an oxidant, initiating free radical polymerization at low temperatures. Ascorbic acid, a reducing agent, forms a redox system with ammonium persulfate.

[0028] The ratio of the components of polycarboxylate water reducer affects the density of hydrophilic and hydrophobic groups and the length of the molecular chain in the final water reducer molecular structure. By adjusting and optimizing the ratio of the components, the comprehensive performance of the obtained polycarboxylate water reducer is better.

[0029] In one embodiment, the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinoxide in the raw materials for preparing the modifier is 2.0-3.5:2.5-4.0:1:2.1-2.7:0.13-0.2.

[0030] The p-nitrostyrene in the modifier provides a nitro group, a strong electron-withdrawing group that enhances its ability to chelate calcium ions and slows cement hydration. Dimethyl sulfate introduces sulfonic acid groups, creating mild reaction conditions and few byproducts, enhancing hydrophilicity and electrostatic repulsion. The naphthalene ring structure of 1,5-dichloronaphthalene offers greater steric hindrance than the benzene ring, inhibiting intrachain curling through the rigid aromatic ring and enhancing molecular stability. Cerium ammonium nitrate, which combines nitration and oxidation functions, directs the modification of vinyl groups under the catalysis of tetramethylpiperidinium oxide, ensuring a uniform distribution of nitro and sulfonic acid groups. When 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, and cerium ammonium nitrate react, nitro or sulfonic acid groups are introduced to the 1,5-dichloronaphthalene.

[0031] As a strong electron-withdrawing group, the nitro group significantly reduces the electron cloud density of the benzene ring through an inductive effect, thereby increasing the acidity of the adjacent carboxyl or sulfonic acid groups in the modifier molecule. This increased acidity strengthens the chelation effect with cement particles and delays cement hydration. The electron-withdrawing properties of the nitro group promote coordination with metal ions, forming a stable complex that not only delays hydration but also maintains dispersion stability through a dynamic dissociation-readsorption mechanism. The rigid structure of the nitro group inhibits the collapse of the polycarboxylic acid molecular chain, enhancing the steric hindrance effect.

[0032] Sulfonic acid groups, as high-charge-density anionic groups, disrupt the flocculated structure of cement particles through electrostatic repulsion. Sulfonic acid adsorption is reversible, and adsorption sites can be dynamically adjusted during cement hydration. This property enables the modifier to rapidly adsorb onto the cement particle surface while also responding to changes in the hydration environment through dissociation, avoiding fluidity loss caused by excessive adsorption. The synergistic effect of sulfonic acid groups and nitro groups is that the sulfonic acid groups provide strong electrostatic repulsion, while the nitro groups enhance local charge density, creating a gradient charge distribution.

[0033] The rigid structure of the benzene ring prevents the polycarboxylic acid molecular chain from curling inwards through steric hindrance. The naphthalene ring structure of 1,5-dichloronaphthalene has a 30% greater steric hindrance than the benzene ring structure of traditional styrene, increasing the stretchability of the molecular chain and extending the dispersion retention time to over 2 hours. The conjugated system of the benzene ring stabilizes free radical intermediates and reduces side reactions (such as chain breakage) during polymerization. The hydrophilic chain segments of the sulfonic acid group and the rigid structure of the nitro group jointly construct a three-dimensional adsorption network. The ternary coordinated arrangement of the naphthalene ring, sulfonic acid group, and nitro group in the modifier of this application significantly enhances the steric hindrance effect, breaking through the steric hindrance and adsorption capacity bottlenecks of traditional modifiers.

[0034] The tetramethylpiperidinyl oxide serves as a catalyst, specifically catalyzing the reaction of the ammonium cerium nitrate and the p-nitrostyrene to generate nitrovinyl groups.

[0035] Precisely controlling the molar ratios of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide in the modifier maximizes the synergistic effect of the naphthalene ring, nitro group, and sulfonic acid group. The resulting "charge-steric hindrance-dynamic adsorption" ternary system imparts excellent neat paste fluidity and fluidity retention to the modified polycarboxylate superplasticizer. The molar ratios of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide are 2.0-3.5:2.5-4.0:1:2.1-2.7:0.13-0.2.

[0036] In one embodiment, the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinoxide in the raw materials for preparing the modifier is 2.5:3.8:1:2.2:0.18.

[0037] In one embodiment, the preparation method of the modifier is as follows: the raw materials for preparing the modifier, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide, are mixed, reacted at 70-80° C. for 12 to 16 hours, and the product is precipitated with ethanol and dried to obtain a modifier powder.

[0038] like Figure 1 As shown, a method for preparing a polycarboxylic acid water reducer according to an embodiment of the present invention comprises the following steps: (1) adding isopentenyl polyoxyethylene ether and ammonium persulfate into water and mixing them uniformly to form a base material.

[0039] (2) Acrylic acid, hydroxyethyl methacrylate and modifier are prepared into a mixed aqueous solution A.

[0040] (3) Ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene are prepared into aqueous solution B.

[0041] (4) The aqueous solution A and the aqueous solution B are simultaneously added dropwise to the base material solution to react to obtain the polycarboxylate water reducer.

[0042] In one embodiment, in step (1), isopentenyl polyoxyethylene ether and deionized water are added to a reactor, stirred for 5 to 10 minutes, and then ammonium persulfate is added, and stirring is continued for 5 to 10 minutes to form a base material.

[0043] In one embodiment, in step (4), aqueous solution A and aqueous solution B are added dropwise simultaneously, wherein aqueous solution A is added dropwise for 50 to 70 minutes, and aqueous solution B is added dropwise for 70 to 90 minutes, and the reaction is continued for 40 to 60 minutes after the addition is completed.

[0044] The preparation method for the polycarboxylate water-reducing agent provided by the present invention is simple, efficient, and rapid. The reaction can be carried out at room temperature, resulting in low energy consumption and significantly reduced costs. By using dimethyl sulfate sulfonation and 2,4-diphenyl-4-methyl-1-pentene instead of traditional sulfonation reagents / thiol chain transfer agents, the method avoids sulfur-containing byproducts, improves compatibility with clay minerals in cement, and achieves sulfur-free production, meeting environmental requirements.

[0045] By precisely controlling the dripping time of the aqueous solution B and the aqueous solution A, the polycarboxylate water-reducing agent preparation system is controlled to be more uniform, the reaction is more stable, and the production efficiency of the polycarboxylate water-reducing agent and the raw material conversion efficiency are higher.

[0046] The ternary synergy of naphthalene ring, nitro group and sulfonic acid group overcomes the limitations of traditional polycarboxylic acid water-reducing agents that rely on a single functional group. The nitro group enhances adsorption capacity through electronic effects and complexation, the sulfonic acid group dominates the dispersion performance through electrostatic repulsion, and the naphthalene ring enhances structural stability through steric hindrance. The combination of the three forms a ternary system of "charge-steric hindrance-dynamic adsorption", which gives the modified polycarboxylic acid water-reducing agent excellent net paste fluidity and fluidity retention. The prepared polycarboxylic acid water-reducing agent, when applied to concrete, has a low 1-hour slump change, all below 18mm, with the best reaching 10mm, and has an early strength effect. The concrete maintains good fluidity for a long time, with a water reduction rate of more than 40% and an air content of less than 3.8%. It also has better air entrainment performance and a more advantageous compressive strength ratio.

[0047] Example 1: A method for preparing a polycarboxylate water reducer, wherein the raw materials include, by mass percentage: 45% isopentenyl polyoxyethylene ether, 29% acrylic acid, 2.1% modifier, 0.3% ammonium persulfate, 0.03% ascorbic acid, 7% hydroxyethyl methacrylate, 0.15% 2,4-diphenyl-4-methyl-1-pentene, and the balance is water.

[0048] The raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinyl oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinyl oxide is 2:2.5:1:2.5:0.14.

[0049] The preparation method of the modifier comprises the following steps: mixing raw materials for the modifier, namely, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinium oxide, reacting the mixture at 70° C. for 16 hours, precipitating the product with ethanol, and drying the mixture to obtain modifier powder.

[0050] The preparation method of polycarboxylate water reducer comprises the following steps: (1) adding isopentenyl polyoxyethylene ether and deionized water into a reaction kettle, stirring for 5 minutes, adding ammonium persulfate, and continuing to stir for 10 minutes to form a base material.

[0051] (2) Acrylic acid, hydroxyethyl methacrylate and modifier are prepared into a mixed aqueous solution A.

[0052] (3) Ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene are prepared into aqueous solution B.

[0053] (4) Aqueous solution A and aqueous solution B are simultaneously added dropwise to the base material solution to react and obtain the polycarboxylate water reducer; wherein aqueous solution A is added dropwise for 50 minutes, and aqueous solution B is added dropwise for 80 minutes, and the reaction is continued for 50 minutes after the addition is completed.

[0054] Example 2: A method for preparing a polycarboxylate water reducer, wherein the raw materials include, by mass percentage, 50% isopentenyl polyoxyethylene ether, 30% acrylic acid, 1.7% modifier, 0.4% ammonium persulfate, 0.04% ascorbic acid, 6% hydroxyethyl methacrylate, 0.18% 2,4-diphenyl-4-methyl-1-pentene, and the balance is water.

[0055] The raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidin oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidin oxide is 2.5:3.8:1:2.2:0.18.

[0056] The method for preparing the modifier comprises the following steps: mixing raw materials for preparing the modifier, namely, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinium oxide, reacting the mixture at 75° C. for 14 hours, precipitating the product with ethanol, and drying the product to obtain modifier powder.

[0057] The preparation method of polycarboxylate water reducer comprises the following steps: (1) adding isopentenyl polyoxyethylene ether and deionized water into a reactor, stirring for 6 minutes, then adding ammonium persulfate, and continuing to stir for 9 minutes to form a base material.

[0058] (2) Acrylic acid, hydroxyethyl methacrylate and modifier are prepared into a mixed aqueous solution A.

[0059] (3) Ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene are prepared into aqueous solution B.

[0060] (4) water solution A and water solution B are added to the base solution at the same time to obtain the polycarboxylic acid water reducing agent; water solution A is added for 60 min, water solution B is added for 70 min, and after the addition is completed, the reaction is continued for 55 min.

[0061] Example 3: A preparation method of a polycarboxylic acid water reducing agent, the preparation raw materials include, by mass percentage: isoprenyl polyoxyethylene ether 55%, acrylic acid 28%, modifier 1.5%, ammonium persulfate 0.5%, ascorbic acid 0.05%, hydroxyethyl methacrylate 5%, 2,4-diphenyl-4-methyl-1-pentene 0.25%, and the balance is water.

[0062] The preparation raw materials of the modifier contain 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, and tetramethylpiperidinium oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, and tetramethylpiperidinium oxide is 3.5:4.0:1:2.1:0.2.

[0063] The preparation method of the modifier is that the preparation raw materials of the modifier, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, and tetramethylpiperidinium oxide, are mixed, reacted at 80°C for 12 hours, and the product is precipitated by ethanol, dried, to obtain the modifier powder.

[0064] The preparation method of the polycarboxylic acid water reducing agent includes the following steps: (1) isoprenyl polyoxyethylene ether and deionized water are added to a reaction kettle, stirred for 7 min, then ammonium persulfate is added, and stirring is continued for 8 min to form a base solution.

[0065] (2) acrylic acid, hydroxyethyl methacrylate, and the modifier are prepared into a mixed water solution A.

[0066] (3) ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene are configured into a water solution B.

[0067] (4) water solution A and water solution B are added to the base solution at the same time to obtain the polycarboxylic acid water reducing agent; water solution A is added for 60 min, water solution B is added for 70 min, and after the addition is completed, the reaction is continued for 55 min.

[0068] Example 4: A preparation method of a polycarboxylic acid water reducing agent, the preparation raw materials include, by mass percentage: isoprenyl polyoxyethylene ether 52%, acrylic acid 35%, modifier 2.5%, ammonium persulfate 0.4%, ascorbic acid 0.06%, hydroxyethyl methacrylate 8%, 2,4-diphenyl-4-methyl-1-pentene 0.20%, and the balance is water.

[0069] The modifier preparation raw material contains: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, tetramethylpiperidinium oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, tetramethylpiperidinium oxide is 3:3:1:2.7:0.13.

[0070] The modifier preparation method is that the modifier preparation raw materials 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, cerium ammonium nitrate, tetramethylpiperidinium oxide are mixed, reacted at 75℃ for 13 hours, and the product is precipitated by ethanol, dried to obtain the modifier powder.

[0071] The preparation method of the polycarboxylic acid water reducing agent comprises the following steps: (1) adding isopentenyl polyoxyethylene ether and deionized water into a reaction kettle, stirring for 10 min, then adding ammonium persulfate, and continuing to stir for 5 min to form a base material.

[0072] (2) preparing acrylic acid, hydroxyethyl methacrylate and the modifier into a mixed aqueous solution A.

[0073] (3) preparing solution ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene into an aqueous solution B.

[0074] (4) adding the aqueous solution A and the aqueous solution B into the base material solution at the same time to react to obtain the polycarboxylic acid water reducing agent; wherein the aqueous solution A is added dropwise for 60 min, the aqueous solution B is added dropwise for 80 min, and the reaction is continued for 40 min after the dropwise addition is completed.

[0075] Comparative Example 1: The preparation method of the polycarboxylic acid water reducing agent in Comparative Example 1 is different from that of Example 2 only in that the preparation raw material comprises: isopentenyl polyoxyethylene ether 30%, acrylic acid 20%, modifier 1.2%, ammonium persulfate 0.4%, ascorbic acid 0.04%, hydroxyethyl methacrylate 6%, 2,4-diphenyl-4-methyl-1-pentene 0.18%, and the balance is water.

[0076] Comparative Example 2: The preparation method of the polycarboxylic acid water reducing agent in Comparative Example 2 is different from that of Example 2 only in that the preparation raw material comprises: isopentenyl polyoxyethylene ether 60%, acrylic acid 36%, modifier 2.8%, ammonium persulfate 0.4%, ascorbic acid 0.04%, hydroxyethyl methacrylate 6%, 2,4-diphenyl-4-methyl-1-pentene 0.18%, and the balance is water.

[0077] Comparative Example 3: The preparation method of the polycarboxylic acid water reducing agent in Comparative Example 3 is different from that of Example 2 only in that the modifier is replaced by an equal amount of acrylic acid.

[0078] Comparative Example 4: The preparation method of the polycarboxylate water reducer in Comparative Example 4 is different from that in Example 2 only in that: the raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidin oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidin oxide is 1.5:2.3:1:1.2:0.18.

[0079] Comparative Example 5: The preparation method of the polycarboxylate water reducer in Comparative Example 5 is different from that in Example 2 only in that: the raw materials for preparing the modifier contain: 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidin oxide; the molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidin oxide is 4.0:2.3:1:2.9:0.12.

[0080] Comparative Example 6: The preparation method of the polycarboxylic acid water reducer in Comparative Example 6 is different from that in Example 2 only in that: (4) aqueous solution A and aqueous solution B are simultaneously added dropwise to the base solution to react to obtain the polycarboxylic acid water reducer; aqueous solution A is added dropwise for 30 minutes, and aqueous solution B is added dropwise for 50 minutes, and the reaction is continued for 30 minutes after the addition is completed.

[0081] The polycarboxylate water-reducing agents prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were subjected to performance tests. The cement paste fluidity test was conducted according to the national standard GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures" at a dosage of 0.13%. The results are shown in Table 1.

[0082] Table 1 Fluidity performance data of polycarboxylate water-reducing agent cement paste prepared in Examples and Comparative Examples:

[0083] Concrete was prepared using the water-reducing agents in Examples 1-4 and Comparative Examples 1-6 under the same conditions and then tested according to the requirements of GB8076-2008, "Concrete Admixtures." The water-reducing agent was added at a solids-to-solids ratio of 0.13%. Ordinary Portland cement PC32.5 was used, and the concrete mix ratio was cement: fly ash: sand: gravel: water = 310:120:740:1100:175. The measured concrete performance data is shown in Table 2.

[0084] Table 2 Performance data of concrete made from polycarboxylate water-reducing agents prepared in Examples and Comparative Examples:

[0085] As shown in Tables 1 and 2, the water-reducing agents prepared in Examples 1-6 and Comparative Examples 1-4 of the present invention exhibit excellent neat paste fluidity and fluidity retention. When applied to concrete, these polycarboxylate water-reducing agents exhibit low 1-hour slump change, generally below 18 mm, with the highest reaching 10 mm. They also exhibit early strength, maintaining good fluidity over an extended period. With a water reduction rate exceeding 40% and an air content below 3.8%, they also exhibit improved air entrainment properties and a superior compressive strength ratio.

[0086] After adjusting the composition and ratio of the water reducer and modifier, and adjusting the preparation process parameters of the water reducer, the fluidity and fluidity retention ability of the obtained water reducer slurry decreased sharply. After being used in concrete, the water reduction rate decreased, the air content increased, and the compressive strength ratio decreased.

[0087] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A polycarboxylate water reducer, characterized in that: The preparation raw materials include, by mass percentage, 45-55% of isopentenyl polyoxyethylene ether, 28-35% of acrylic acid, 1.5-2.5% of a modifier, 0.3-0.5% of ammonium persulfate, 0.03-0.06% of ascorbic acid, 5-8% of hydroxyethyl methacrylate, 0.15-0.25% of 2,4-diphenyl-4-methyl-1-pentene, and the balance is water; the raw materials for preparing the modifier contain 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate, and tetramethylpiperidinium oxide.

2. A polycarboxylate water reducer according to claim 1, characterized in that, The molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate and tetramethylpiperidinyl oxide in the raw materials for preparing the modifier is 2.0-3.5:2.5-4.0:1:2.1-2.7:0.13-0.

2.

3. A polycarboxylate water-reducing agent according to claim 1, characterized in that: The molar ratio of 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ceric ammonium nitrate and tetramethylpiperidinoxide in the raw materials for preparing the modifier is 2.5:3.8:1:2.2:0.

18.

4. A polycarboxylate water-reducing agent according to any one of claims 1 to 3, characterized in that: The preparation method of the modifier comprises the following steps: mixing the raw materials for preparing the modifier, namely, 1,5-dichloronaphthalene, p-nitrostyrene, dimethyl sulfate, ammonium cerium nitrate, and tetramethylpiperidinium oxide, reacting the mixture at 70-80° C. for 12-16 hours, precipitating the product with ethanol, and drying the product to obtain the modifier powder.

5. The method for preparing a polycarboxylate water-reducing agent according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) adding isopentenyl polyoxyethylene ether and ammonium persulfate into water and mixing them evenly to form a base material; (2) preparing acrylic acid, hydroxyethyl methacrylate and a modifier into a mixed aqueous solution A; (3) preparing a solution of ascorbic acid and 2,4-diphenyl-4-methyl-1-pentene into an aqueous solution B; and (4) simultaneously adding the aqueous solution A and the aqueous solution B into the base material solution to react and obtain the polycarboxylic acid water reducer.

6. The method for preparing a polycarboxylate water-reducing agent according to claim 4, wherein: In the step (1), isopentenyl polyoxyethylene ether and deionized water are added into a reaction kettle, and ammonium persulfate is added after stirring for 5 to 10 minutes, and the stirring is continued for 5 to 10 minutes to form a base material.

7. The method for preparing a polycarboxylate water-reducing agent according to claim 4, wherein: In the step (4), aqueous solution A and aqueous solution B are added dropwise simultaneously, wherein aqueous solution A is added dropwise for 50 to 70 minutes and aqueous solution B is added dropwise for 70 to 90 minutes. After the addition is completed, the reaction is continued for 40 to 60 minutes.

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