Polycarboxylate superplasticizer as well as synthesis method and application thereof
By introducing long and short chain block structures and allylated alginate oligosaccharides into polycarboxylate superplasticizers, the synergistic problem between strength and dispersion performance of polycarboxylate superplasticizers was solved, improving the overall performance of concrete and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-14
AI Technical Summary
Existing polycarboxylate superplasticizers are difficult to achieve efficient synergy between improving concrete strength and dispersion performance, and traditional modified materials have high synthesis costs and insufficient batch stability, making them difficult to apply in engineering.
A polycarboxylic acid water-reducing agent was prepared by free radical polymerization of methyl allyl alcohol polyoxyethylene ether macromonomer with ethylene oxide and propylene oxide to form a long-short chain block structure, and short-chain alkyl groups were introduced at the end of the side chain. Allylated alginate oligosaccharides were then combined with the side chain to form a long-short chain block structure.
It improves the dispersion performance and strength of concrete while reducing production costs, achieving a balance between environmental protection and economy, and is suitable for the construction industry.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of concrete technology, specifically relating to a polycarboxylate superplasticizer, its synthesis method, and its application. Background Technology
[0002] Polycarboxylate superplasticizers, as a new generation of high-performance concrete admixtures, possess high water-reducing rates and excellent dispersibility. However, while improving the workability of concrete, they may also limit strength development. To achieve a significant improvement in concrete strength performance, the industry is focusing on the precise design and control of the polycarboxylate molecular structure.
[0003] One of the core ideas of existing technologies lies in reducing air bubbles introduced into the concrete system and assisting in the development of concrete strength through molecular-level optimization, ultimately enhancing the mechanical properties of concrete. Specific methods include screening specific functional monomers, finely adjusting molecular configurations, and optimizing polymerization processes. For example, introducing structural units such as polyether-modified organosilicon into the molecular backbone, or embedding groups such as phosphate triesters and rigid benzene rings, can effectively optimize the density of the slurry structure. Incorporating components such as silane-modified graphene and PAMAM dendritic molecules into the polymerization system, or adjusting the proportion of epoxy alkane in the polyether macromonomer, can improve the uniformity of hydration product distribution. These techniques directly contribute to the increase in the macroscopic strength of concrete by strengthening the microstructure of the cementitious substrate.
[0004] Existing technologies show that a series of modification strategies, such as amidation modification of polycarboxylic acid molecules, introduction of hydrophobic segments, or construction of multi-branched structures, can effectively optimize its application performance, thus providing a reliable technical path for achieving high strength and high performance of concrete. However, in the technical practice of improving the contribution of polycarboxylic acid water-reducing agents to concrete strength through the above methods, the above paths often face the following core contradictions: (1) Insufficient synergy of molecular functions: If hydrophobic structural units (such as ester groups and benzene rings) are introduced to regulate air-entraining behavior, although it helps to enhance the density of the system, it will weaken the solubility and dispersion retention ability of the water-reducing agent; while if hydrophilic segments are excessively maintained to ensure workability, it is difficult to effectively suppress the generation and stability of bubbles, which is not conducive to the final strength development. Therefore, achieving efficient synergy between "gas control" and "plasticity retention" of molecular structure is a key challenge to improve the mechanical properties of concrete. (2) Low feasibility of functional component application: Although novel modified materials such as silane-modified graphene and PAMAM dendritic molecules have potential in improving the density of the system, their synthesis cost is about 5-8 times that of traditional monomers, batch stability is insufficient, and the grafting efficiency with the main chain is generally less than 60%, making it difficult to maintain consistent performance in industrial production, which restricts their reliable application in engineering projects with strict strength requirements. Therefore, starting from the source of molecular structure design, through precise synergistic design of polycarboxylic acid molecular structure, and controlling the balance between the surface activity and steric hindrance of polycarboxylic acid molecules, while ensuring the excellent dispersion performance of polycarboxylic acid water-reducing agents and taking into account the high compressive strength of concrete, this is the core technical challenge to achieve the comprehensive performance improvement of concrete. Summary of the Invention
[0005] The primary objective of this invention is to provide a polycarboxylate superplasticizer that combines high strength with good dispersibility.
[0006] A second objective of this invention is to provide a method for preparing the above-mentioned polycarboxylate superplasticizer.
[0007] A third objective of this invention is to provide the application of the above-mentioned polycarboxylate superplasticizer in the construction field.
[0008] The method for synthesizing the polycarboxylate superplasticizer provided by this invention includes the following steps: S1. Using methyl allyl alcohol polyoxyethylene ether macromonomer as an initiator, ethylene oxide and propylene oxide are polymerized sequentially, and then the ends of the obtained polymer products are capped with short-chain alkyl groups to obtain long and short-chain polyether macromonomers. S2. Introduce unsaturated bonds into the alginate oligosaccharide molecular chain to obtain allylated alginate oligosaccharides. S3. Free radical polymerization of long and short chain polyether macromonomers, allylated alginate oligosaccharides, and unsaturated carboxylic acid monomers yields polycarboxylic acid water-reducing agents.
[0009] Through in-depth and extensive research, the inventors of this invention discovered that the main reason why existing polycarboxylate superplasticizers cannot effectively balance high strength and dispersion performance is as follows: Firstly, there is an inherent constraint in the molecular structure-property relationship. While the polyether side chains in polycarboxylate superplasticizers provide steric hindrance, their surface activity stabilizes adsorbed air bubbles, forming harmful pores that are detrimental to strength development. If the side chains are excessively shortened or unevenly distributed defoaming units (such as siloxane segments) are introduced to suppress air entrainment, the dispersion stability will be weakened or the bubble control will fail, thus affecting the final mechanical properties of concrete. Secondly, small molecule impurities remaining in the polyether macromonomer promote bubble formation and stabilization, increasing the difficulty of controlling air content and adversely affecting strength.
[0010] The key to this invention lies in simultaneously introducing side-chain long and short-chain block structures and alginate oligosaccharide structures into the molecular chain of polycarboxylate superplasticizer, while using short-chain alkyl end caps at the ends of the long and short-chain block structures. This can significantly improve the final strength of concrete while ensuring that the polycarboxylate superplasticizer has good dispersibility. The reasons for this are speculated to be as follows: Firstly, the method of constructing polyethylene oxide and polypropylene oxide segments in the polyether side chains allows for precise control of the hydrophilic-hydrophobic balance of the molecules. The segments closer to the polycarboxylic acid backbone contain a high content of ethylene oxide (EO) units that provide hydrophilic groups, while the segments farther from the polycarboxylic acid backbone contain a high content of propylene oxide (PO) units that provide hydrophobic groups. Furthermore, the introduction of hydrophobic short-chain alkyl groups at the end of the side chains for capping makes the "anchoring-extension" of the side chains on the surface of cement particles more stable, thus synergistically enhancing the dispersibility and durability of concrete. Secondly, the introduction of the bio-based synthetic material "allylated alginate oligosaccharide" as a "rigid spacer unit" into the polycarboxylic acid backbone for the first time can disrupt the stability of the bubble film in concrete. The hydroxyl groups on the pyranose ring can also form hydrogen bonds with the hydration products of cement, enhancing the adsorption force of the backbone on the surface of cement particles, inhibiting the migration of molecules to the gas-liquid interface, thereby playing an auxiliary role in defoaming and increasing the density of the concrete paste.
[0011] The synthesis method of the polycarboxylate superplasticizer provided by this invention does not require complex processes such as amination and high pressure, and can be directly completed in a conventional reactor, possessing extremely high feasibility for industrial production. Furthermore, the synthesis method of the polycarboxylate superplasticizer provided by this invention uses alginate oligosaccharides, a bio-based raw material, as the core component. Compared with traditional petrochemical-based superplasticizers, this effectively reduces the consumption of petrochemical raw materials, and the entire production process generates no toxic or harmful waste, achieving a synergistic balance between environmental protection and economic efficiency. Detailed Implementation
[0012] The method for synthesizing the polycarboxylate superplasticizer provided by this invention includes the following steps: S1. Using methyl allyl alcohol polyoxyethylene ether macromonomer (HPEG) as an initiator, ethylene oxide and propylene oxide are polymerized sequentially, and then the polymer is end-capped with a short-chain alkyl group to obtain long and short-chain polyether macromonomers. S2. Introduce unsaturated bonds into the alginate oligosaccharide molecular chain to obtain allylated alginate oligosaccharides. S3. Free radical polymerization of long and short chain polyether macromonomers, allylated alginate oligosaccharides, and unsaturated carboxylic acid monomers yields polycarboxylic acid water-reducing agents.
[0013] The polycarboxylate superplasticizer obtained by the method provided in this invention has an acrylic acid backbone and a composite molecular structure with both "long and short chain block side chains" and a "rigid main chain". The side chains of this composite molecule are EO-PO long and short chain block polyethers starting with methyl allyl alcohol polyoxyethylene ether macromonomers, with hydrophobic alkyl groups introduced at the ends via short-chain alkyl capping, and allylated alginate oligosaccharides embedded as functional units. This polycarboxylate superplasticizer reduces air bubbles introduced during application through the synergistic effect of different structures, increases the density of the slurry, thereby improving the final strength of concrete, while also maintaining the dispersibility of the superplasticizer. Specifically, the long and short chain polyether macromonomers adopt an EO-PO gradient distribution, with high EO content at the main chain ends and high PO content at the ends. This allows for more stable "anchoring-extension" of the side chains on the cement particle surface, reducing enrichment at the gas-liquid interface, while the short-chain alkyl groups at the ends further disrupt the stability of the bubble film through hydrophobic interaction. Furthermore, the use of allylated alginate oligosaccharides introduces a rigid sugar ring structure, reducing bubble stability and improving adsorption efficiency. The rigid pyran ring structure in the allylated alginate oligosaccharide can interfere with the stability of the bubble film in concrete. The 3-5 hydroxyl groups (-OH) can form hydrogen bonds with cement hydration products, enhancing the adsorption force of the main chain on the cement particle surface and reducing molecular migration to the gas-liquid interface. In summary, the introduction of short-chain alkyl-terminated side-chain long-short-chain block polymers and allylated alginate oligosaccharides ensures gas-entraining properties, while the high EO and PO ends of the short-chain alkyl-terminated side-chain long-short-chain block polymers ensure adsorption performance, thereby guaranteeing dispersibility.
[0014] In the synthesis of the above-mentioned polycarboxylate superplasticizer, the number-average molecular weight of the methyl allyl alcohol polyoxyethylene ether macromonomer is preferably 700-1500, such as 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, etc. The methyl allyl alcohol polyoxyethylene ether macromonomer serves as an initiator and linker for the polyether side chain, and its terminal unsaturated double bonds ensure that the side chain can be covalently grafted onto the main chain. The ethylene oxide (EO) provides hydrophilic groups to ensure dispersibility. Controlling the polymer content of the polyethylene oxide segment to below 15 can avoid excessive surface activity. The propylene oxide (PO) provides hydrophobic groups, forming a gradient distribution with EO and helping to reduce molecular enrichment at the gas-liquid interface. The introduction of short-chain alkyl groups at the end of the long and short-chain polyether macromonomers can disrupt gas film stability, thereby improving the strength and dispersion performance of polycarboxylate superplasticizers.
[0015] In a preferred embodiment, in step S1, the polymerization method includes first performing a first polymerization reaction between the methyl allyl alcohol polyoxyethylene ether macromonomer and ethylene oxide, and then performing a second polymerization reaction between the first polymerization product and propylene oxide. The preferred conditions for the first polymerization reaction between the methyl allyl alcohol polyoxyethylene ether macromonomer and ethylene oxide include: a pressure of 0.3 MPa-0.4 MPa, such as 0.3 MPa, 0.32 MPa, 0.34 MPa, 0.36 MPa, 0.38 MPa, 0.4 MPa, etc.; a temperature of 115℃-145℃, such as 115℃, 118℃, 120℃, 122℃, 125℃, 130℃, 132℃, 135℃, 138℃, 140℃, 142℃, 145℃, etc.; and a time of 2h-4h, such as 2h, 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h, 3.8h, 4h, etc. The preferred conditions for the second polymerization reaction between the first polymerization product and propylene oxide include: a pressure of 0.2 MPa-0.3 MPa (e.g., 0.2 MPa, 0.22 MPa, 0.24 MPa, 0.26 MPa, 0.28 MPa, 0.3 MPa); a temperature of 115℃-145℃ (e.g., 115℃, 118℃, 120℃, 122℃, 125℃, 130℃, 132℃, 135℃, 138℃, 140℃, 142℃, 145℃); and a time of 1.5 h-2.5 h (e.g., 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h). Conducting the first and second polymerization reactions under these preferred conditions effectively controls the degree of polymerization of EO / PO, balances hydrophilicity and hydrophobicity to regulate dispersion and gas entrainment, and further improves strength and dispersion performance.
[0016] In the synthesis process of the above-mentioned polycarboxylate superplasticizer, in step S1, the molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer, ethylene oxide, and propylene oxide is preferably 1:(9-15):(3-5). Specifically, the molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer to ethylene oxide is preferably 1:(9-15), and can be 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc. The molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer to propylene oxide is preferably 1:(3-5), and can be 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4, 1:4.2, 1:4.4, 1:4.6, 1:4.8, 1:5, etc.
[0017] In a preferred embodiment, step S1 further includes pre-activating the initiator methyl allyl alcohol polyoxyethylene ether (HPEG) macromonomer. The pre-activation method is not particularly limited and can be selected from alkali-catalyzed pre-activation, free radical pre-activation, end-group modification pre-activation, etc. In a specific embodiment, the pre-activation method involves placing the HEPG macromonomer and an alkaline catalyst together in a vacuum environment for a dehydration reaction. The preferred conditions for the dehydration reaction include a pressure <-0.05 MPa, such as -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, etc.; a temperature of 105℃-120℃, such as 105℃, 110℃, 115℃, 120℃, etc.; and a time of 1.5h-3h, such as 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h, etc. The alkaline catalyst may include at least one of potassium hydroxide, sodium hydroxide, sodium methoxide, etc. The amount of the alkaline catalyst is 0.6%-1.0% of the mass of the HPEG macromonomer, such as 0.6%, 0.7%, 0.8%, 0.9%, etc.
[0018] In a preferred embodiment, step S1, end-capping the polymer product with a short-chain alkyl group, includes reacting the second polymer product with a short-chain alkyl compound. The conditions for the end-capping reaction preferably include a temperature of 50°C-70°C, such as 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, etc.; and a time of 1h-5h, such as 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc. The molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer to the short-chain alkyl compound is preferably 1:(0.9-1.5), such as 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc. Examples of short-chain alkyl compounds include at least one of propionyl chloride, n-butyryl chloride, isobutyryl chloride, and valerate chloride.
[0019] In the synthesis of the aforementioned polycarboxylate superplasticizer, the alginate oligosaccharide can provide a rigid sugar ring structure containing a pyran ring, which helps to achieve the defoaming effect and is beneficial to improving the strength and dispersion performance of the polycarboxylate superplasticizer. The number average molecular weight of the alginate oligosaccharide is preferably 800-1200, such as 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, etc.
[0020] In the synthesis of the aforementioned polycarboxylate superplasticizer, step S2, introducing unsaturated bonds into the alginate oligosaccharide molecular chain, aims to ensure its copolymerization with the main chain monomer. There are no particular limitations on the method of introducing unsaturated bonds into the alginate oligosaccharide molecular chain; for example, it can include a Williamson etherification reaction between the alginate oligosaccharide and an allyl halide. Specifically, the alginate oligosaccharide can be dissolved in deionized water, the pH of the resulting alginate oligosaccharide solution adjusted to 8-9, and then the allyl halide added for the Williamson etherification reaction. After the reaction is complete, precipitation, filtration, washing, and drying are performed. The preferred mass ratio of the alginate oligosaccharide to deionized water is 1:(4-6), such as 1:4, 1:4.5, 1:5, 1:5.5, 1:6, etc. The preferred conditions for the Williamson etherification reaction include a reaction temperature of 45℃-60℃, such as 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, etc.; a pH of 8-9, such as 8, 8.2, 8.4, 8.6, 8.8, 9, etc.; and a reaction time of 3.5h-5h, such as 3.5h, 3.8h, 4h, 4.2h, 4.5h, 4.8h, 5h, etc. The precipitant used for precipitation can be at least one of ethanol, acetone, methanol, etc. The preferred precipitation conditions include an organic reagent volume of 2.5L or more, such as 2.5L, 3L, 3.5L, 4L, etc.; and a pH of 6.5-7.5, such as 6.5, 7, 7.5, etc. The drying conditions preferably include a pressure of <-0.05 MPa, such as -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, etc.; and a temperature of 35℃-50℃, such as 35℃, 40℃, 45℃, 50℃, etc. The allyl halide may specifically include at least one of allyl chloride, allyl bromide, and allyl iodide.
[0021] In the synthesis process of the above-mentioned polycarboxylic acid water-reducing agent, in step S3, the unsaturated carboxylic acid monomer may include at least one of acrylic acid, methacrylic acid and maleic acid.
[0022] In the synthesis process of the above-mentioned polycarboxylate superplasticizer, in step S3, the preferred mass ratio of the allylated alginate oligosaccharide, long- and short-chain polyether macromonomers, and unsaturated carboxylic acid monomers is (4-9):(60-70):18. Specifically, the mass ratio of the allylated alginate oligosaccharide to the unsaturated carboxylic acid monomers can be (4-9):18, such as 4:18, 4.5:18, 5:18, 5.5:18, 6:18, 6.5:18, 7:18, 7.5:18, 8:18, 8.5:18, 9:18, etc. The mass ratio of the long- and short-chain polyether macromonomers to the unsaturated carboxylic acid monomers can be (60-70):18, such as 60:18, 62:18, 64:18, 66:18, 68:18, 70:18, etc.
[0023] In the synthesis process of the above-mentioned polycarboxylate superplasticizer, the free radical polymerization reaction in step S3 is not particularly limited. Various existing feeding sequences can be followed to mix the materials evenly, and then the resulting mixture is placed under polymerization reaction conditions for reaction. In a preferred embodiment, the free radical polymerization reaction includes mixing unsaturated carboxylic acid monomers, an initiator, and a chain transfer agent to obtain solution A; dissolving allylated alginate oligosaccharides in deionized water to obtain solution B; using long and short chain polyether macromonomers as solution C; simultaneously adding solutions A, B, and C to a reaction vessel for free radical copolymerization, and then adjusting the pH of the resulting free radical copolymerization product to 6-7.5. The initiator can be any existing substance capable of generating free radicals to initiate free radical polymerization, such as at least one of ammonium persulfate, sodium persulfate, hydrogen peroxide / vitamin C, etc. The chain transfer agent can be any existing substance capable of adjusting the molecular weight of the polymer, such as at least one of mercaptoacetic acid, sodium hypophosphite, 3-mercaptopropionic acid, mercaptoethanol, etc.
[0024] In the synthesis process of the above-mentioned polycarboxylate superplasticizer, in step S3, the conditions of the free radical copolymerization reaction preferably include a temperature of 75℃-90℃, such as 75℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, etc.; and a time of 1h-2.5h, such as 1h, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, etc.
[0025] The present invention also provides a polycarboxylate superplasticizer obtained by the above method.
[0026] Furthermore, the present invention also provides the application of the polycarboxylate superplasticizer in the construction field.
[0027] The present invention will be described in detail below through embodiments.
[0028] Example 1 S1. Synthesis of long- and short-chain polyether macromonomers: 100 g (0.125 mol) of HPEG macromonomer with a number-average molecular weight of 800 and 0.8 g of potassium hydroxide were added to a high-pressure reactor and dehydrated at 110 °C and -0.095 MPa for 2 h; then 66 g (1.5 mol) of EO was introduced and reacted at 130 °C and 0.35 MPa for 3 h; then 23.2 g (0.4 mol) of PO was introduced and reacted at 130 °C and 0.25 MPa for 2 h; after the reaction was completed, the temperature was lowered to 60 °C, and 20.5 g (0.192 mol) of n-butyryl chloride was slowly added dropwise, and the reaction was carried out for 1.5 h to obtain butyl-terminated long- and short-chain polyether macromonomers. The average degree of polymerization of the EO segment in this long- and short-chain polyether macromonomer was 12, and the average degree of polymerization of the PO segment was 3.
[0029] S2. Synthesis of allylated alginate oligosaccharides: 100g of alginate oligosaccharides with a number-average molecular weight of 1000 was dissolved in 500mL of deionized water. The pH was adjusted to 8.5 with 30% sodium hydroxide solution while stirring, and the mixture was stirred at 30℃ for 30 minutes. 13.5g of allyl chloride was slowly added dropwise, and the temperature was raised to 50℃ for 4 hours. After the reaction was completed, the pH was adjusted to 7.0 with dilute hydrochloric acid. The reaction solution was poured into 3L of anhydrous ethanol to precipitate the product, filtered, washed twice with ethanol, and dried under vacuum at 40℃ to obtain allylated alginate oligosaccharides.
[0030] S3. Synthesis of polycarboxylate superplasticizer: Add 120g of deionized water to a four-necked flask equipped with a stirrer, thermometer, and dropping device, and heat to 60℃. Mix 18g of acrylic acid, 1.5g of ammonium persulfate (dissolved in 30g of deionized water), and 0.8g of mercaptoacetic acid to form solution A; dissolve 6g of allylated alginate oligosaccharide obtained in step S2 in 50g of deionized water to form solution B; use 65g of long- and short-chain polyether macromonomers obtained in step S1 as solution C. Within 3 hours, slowly add solutions A, B, and C simultaneously to the reaction flask using three dropping funnels. After the addition is complete, maintain the temperature at 80℃ for 1.5 hours. After cooling to 40℃, adjust the pH to 6.5 with 30% wt sodium hydroxide solution to obtain the polycarboxylate superplasticizer.
[0031] Example 2 S1. Synthesis of long- and short-chain polyether macromonomers: 100 g (0.125 mol) of HPEG macromonomer with a number-average molecular weight of 800 and 0.8 g of potassium hydroxide were added to a high-pressure reactor and dehydrated at 110 °C and -0.095 MPa for 2 h; then 82.6 g (1.875 mol) of EO was introduced and reacted at 115 °C and 0.30 MPa for 4 h; then 36.3 g (0.625 mol) of PO was introduced and reacted at 115 °C and 0.30 MPa for 2.5 h; after the reaction was completed, the temperature was lowered to 50 °C, and 12.8 g (0.12 mol) of n-butyryl chloride was slowly added dropwise, and the reaction was carried out for 2 h to obtain butyl-terminated long- and short-chain polyether macromonomers. The average degree of polymerization of the EO segment in this long- and short-chain polyether macromonomer was 15, and the average degree of polymerization of the PO segment was 5.
[0032] S2. Synthesis of allylated alginate oligosaccharides: 100g of alginate oligosaccharides with a number-average molecular weight of 800 was dissolved in 500mL of deionized water. The pH was adjusted to 8 with 30% sodium hydroxide solution while stirring, and the mixture was stirred at 30℃ for 30 minutes. 13.5g of allyl chloride was slowly added dropwise, and the temperature was raised to 60℃ for 3.5h. After the reaction was completed, the pH was adjusted to 7.0 with dilute hydrochloric acid. The reaction solution was poured into 3L of anhydrous ethanol to precipitate the product, filtered, washed twice with ethanol, and dried under vacuum at 40℃ to obtain allylated alginate oligosaccharides.
[0033] S3. Synthesis of polycarboxylate superplasticizer: Add 120g of deionized water to a four-necked flask equipped with a stirrer, thermometer, and dropping device, and heat to 60℃. Mix 18g of acrylic acid, 1.5g of ammonium persulfate (dissolved in 30g of deionized water), and 0.8g of mercaptoacetic acid to form solution A; dissolve 4g of allylated alginate oligosaccharide obtained in step S2 in 50g of deionized water to form solution B; use 70g of long- and short-chain polyether macromonomers obtained in step S1 as solution C. Within 3 hours, slowly add solutions A, B, and C simultaneously to the reaction flask through three dropping funnels. After the addition is complete, maintain the temperature at 75℃ for 2.5 hours. After cooling to 40℃, adjust the pH to 7.5 with 30% wt sodium hydroxide solution to obtain the polycarboxylate superplasticizer.
[0034] Example 3 S1. Synthesis of long and short chain polyether macromonomers: 100 g (0.125 mol) of HPEG macromonomer with a number average molecular weight of 800 and 0.8 g of potassium hydroxide were added to a high-pressure reactor and dehydrated at 110 °C and -0.095 MPa for 2 h; then 50 g of EO (1.125 mol) was introduced and reacted at 145 °C and 0.4 MPa for 2 h; then 29 g (0.5 mol) of PO was introduced and reacted at 145 °C and 0.4 MPa for 1.5 h; after the reaction was completed, the temperature was lowered to 70 °C, and 16.0 g (0. mol) of n-butyryl chloride was slowly added dropwise, and the reaction was carried out for 1 h to obtain butyl-terminated long and short chain polyether macromonomers. The average degree of polymerization of the EO segment in this long and short chain polyether macromonomer was 9, and the average degree of polymerization of the PO segment was 4.
[0035] S2. Synthesis of allylated alginate oligosaccharides: 100g of alginate oligosaccharides with a number-average molecular weight of 1200 was dissolved in 500mL of deionized water. The pH was adjusted to 9 with 30% sodium hydroxide solution while stirring, and the mixture was stirred at 30℃ for 30 minutes. 13.5g of allyl bromide was slowly added dropwise, and the temperature was raised to 45℃ for 5 hours. After the reaction was completed, the pH was adjusted to 7.0 with dilute hydrochloric acid. The reaction solution was poured into 3L of anhydrous ethanol to precipitate the product, filtered, washed twice with ethanol, and dried under vacuum at 40℃ to obtain allylated alginate oligosaccharides.
[0036] S3. Synthesis of polycarboxylate superplasticizer: Add 120g of deionized water to a four-necked flask equipped with a stirrer, thermometer, and dropping device, and heat to 60℃. Mix 18g of acrylic acid, 1.5g of ammonium persulfate (dissolved in 30g of deionized water), and 0.8g of mercaptoacetic acid to form solution A; dissolve 9g of allylated alginate oligosaccharide obtained in step S2 in 50g of deionized water to form solution B; use 60g of long- and short-chain polyether macromonomers obtained in step S1 as solution C. Within 3 hours, slowly add solutions A, B, and C simultaneously to the reaction flask through three dropping funnels. After the addition is complete, maintain the temperature at 90℃ for 1 hour. After cooling to 40℃, adjust the pH to 7 with 30% wt sodium hydroxide solution to obtain the polycarboxylate superplasticizer.
[0037] Example 4: Changing the EO / PO dosage ratio The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the amount of ethylene oxide (EO) was adjusted to 44.0 g and the amount of propylene oxide (PO) was adjusted to 34.8 g, that is, the molar ratio of EO to PO was 10:6. The other conditions were the same as in Example 1, and the polycarboxylate superplasticizer was obtained.
[0038] Example 5: Adjusting the dosage of copolymer raw materials The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the amount of allylated alginate oligosaccharide was adjusted to 9g, the amount of long and short chain polyether macromonomers was adjusted to 62g, the amount of acrylic acid was adjusted to 18g, the amount of ammonium persulfate was adjusted to 1.5g, and the amount of mercaptoacetic acid was adjusted to 0.8g. The other conditions were the same as in Example 1, and the polycarboxylate superplasticizer was obtained.
[0039] Example 6: Isobutyryl chloride instead of n-butyryl chloride for end capping The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the end-capping agent in step S1 was changed from n-butyryl chloride to 18.7g isobutyryl chloride, and the other conditions were the same as in Example 1, to obtain the polycarboxylate superplasticizer.
[0040] Comparative Example 1 Add 120g of deionized water to a four-necked flask equipped with a stirrer, thermometer, and dropping device, and heat to 60℃. Mix 30g of acrylic acid, 1.5g of ammonium persulfate (dissolved in 30g of water), and 1g of mercaptoacetic acid to form solution A; add 150g of HPEG macromonomer as solution B. Over 3 hours, slowly add solutions A and B simultaneously to the reaction flask through two dropping funnels. After the addition is complete, maintain the temperature at 80℃ for 1.5 hours. After cooling to 40℃, adjust the pH to 6.5 with 30% wt sodium hydroxide solution to obtain the polycarboxylate superplasticizer.
[0041] Comparative Example 2 The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the allylated alginate oligosaccharide was replaced with the same amount of acrylic acid by weight, and the other conditions were the same as in Example 1, to obtain the polycarboxylate superplasticizer.
[0042] Comparative Example 3 The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the long and short chain polyether macromonomers were replaced with the same amount of acrylic acid by weight, and the other conditions were the same as in Example 1, to obtain the polycarboxylate superplasticizer.
[0043] Comparative Example 4 The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the EO in step S1 was replaced with the same molar amount of PO, and the other conditions were the same as in Example 1, to obtain the polycarboxylate superplasticizer.
[0044] Comparative Example 5 The polycarboxylate superplasticizer was prepared according to the method of Example 1, except that the PO in step S1 was replaced by the same molar amount of EO, and the other conditions were the same as in Example 1, to obtain the polycarboxylate superplasticizer.
[0045] Comparative Example 6 The polycarboxylate superplasticizer was prepared according to the method in Example 1, except that the order of adding EO and PO in step S1 was reversed. The specific steps are as follows: S1. Synthesis of long and short chain polyether macromonomers: 100g (0.125mol) of HPEG macromonomer with a number average molecular weight of 800 and 0.8g of potassium hydroxide were added to a high-pressure reactor and dehydrated at 110℃ and -0.095MPa for 2h; then 23.2g (0.4mol) of PO was introduced and reacted at 130℃ and 0.25MPa for 2h; then 66g of EO (1.5mol) was introduced and reacted at 130℃ and 0.35MPa for 3h; after the reaction was completed, the temperature was lowered to 60℃ and 20.5g (0.192mol) of n-butyryl chloride was slowly added dropwise and reacted for 1.5h to obtain butyl-terminated long and short chain polyether macromonomers.
[0046] S2. Synthesis of allylated alginate oligosaccharides: 100g of alginate oligosaccharides with a number-average molecular weight of 1000 was dissolved in 500mL of deionized water. The pH was adjusted to 8.5 with 30% sodium hydroxide solution while stirring, and the mixture was stirred at 30℃ for 30 minutes. 13.5g of allyl chloride was slowly added dropwise, and the temperature was raised to 50℃ for 4 hours. After the reaction was completed, the pH was adjusted to 7.0 with dilute hydrochloric acid. The reaction solution was poured into 3L of anhydrous ethanol to precipitate the product, filtered, washed twice with ethanol, and dried under vacuum at 40℃ to obtain allylated alginate oligosaccharides.
[0047] S3. Synthesis of polycarboxylate superplasticizer: Add 120g of deionized water to a four-necked flask equipped with a stirrer, thermometer, and dropping device, and heat to 60℃. Mix 18g of acrylic acid, 1.5g of ammonium persulfate (dissolved in 30g of deionized water), and 0.8g of mercaptoacetic acid to form solution A; dissolve 6g of allylated alginate oligosaccharide obtained in step S2 in 50g of deionized water to form solution B; use 65g of long- and short-chain polyether macromonomers obtained in step S1 as solution C. Within 3 hours, slowly add solutions A, B, and C simultaneously to the reaction flask using three dropping funnels. After the addition is complete, maintain the temperature at 80℃ for 1.5 hours. After cooling to 40℃, adjust the pH to 6.5 with 30% wt sodium hydroxide solution to obtain the polycarboxylate superplasticizer.
[0048] Test case The water reduction rate, air content, bleeding rate ratio, initial setting time difference, and compressive strength of the polycarboxylate superplasticizers obtained in the above examples and comparative examples were tested in accordance with the national standards GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures" and GB / T 50080-2016 "Standard Test Method for Performance of Ordinary Concrete Mixtures". The test conditions included: (1) Reference concrete mix proportion: 360 kg / m³ of PO 42.5 cement, 780 kg / m³ of medium sand, 1020 kg / m³ of crushed stone, and slump controlled at (210±10) mm; (2) Superplasticizer dosage: the dosage was 0.2% of the mass of cementitious materials. The results are shown in Table 1.
[0049] Table 1
[0050] The results in the table show that the polycarboxylate superplasticizer obtained by the method of this invention can improve the water reduction rate and reduce the bleeding rate when applied to concrete, thus demonstrating its good dispersibility. Furthermore, the polycarboxylate superplasticizer obtained by the method of this invention can improve the compressive strength of concrete when applied to concrete.
[0051] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. The present invention is presented above with preferred embodiments, but is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the present invention using the above-displayed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for synthesizing a polycarboxylate superplasticizer, characterized in that, The method includes the following steps: S1. Using methyl allyl alcohol polyoxyethylene ether macromonomer as an initiator, ethylene oxide and propylene oxide are polymerized sequentially, and then the ends of the obtained polymer products are capped with short-chain alkyl groups to obtain long and short-chain polyether macromonomers. S2. Introduce unsaturated bonds into the alginate oligosaccharide molecular chain to obtain allylated alginate oligosaccharides. S3. Free radical polymerization of long and short chain polyether macromonomers, allylated alginate oligosaccharides, and unsaturated carboxylic acid monomers yields polycarboxylic acid water-reducing agents.
2. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, In step S1, the polymerization method includes first performing a first polymerization reaction between the methyl allyl alcohol polyoxyethylene ether macromonomer and ethylene oxide, and then performing a second polymerization reaction between the first polymerization product and propylene oxide. Preferably, the number-average molecular weight of the methyl allyl alcohol polyoxyethylene ether macromonomer is 700-1500; Preferably, the conditions for the first polymerization reaction of the methyl allyl alcohol polyoxyethylene ether macromonomer with ethylene oxide include a pressure of 0.3 MPa-0.4 MPa, a temperature of 115℃-145℃, and a time of 2h-4h. Preferably, the conditions for the second polymerization reaction between the first polymerization product and propylene oxide include a pressure of 0.2 MPa-0.3 MPa, a temperature of 115°C-145°C, and a time of 1.5 h-2.5 h. Preferably, the molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer, ethylene oxide, and propylene oxide is 1:(9-15):(3-5).
3. The method for synthesizing the polycarboxylate superplasticizer according to claim 2, characterized in that, In step S1, the method of end-capping the polymerization product with short-chain alkyl groups includes reacting the second polymerization product with a short-chain alkyl compound for end-capping. Preferably, the conditions for the end-capping reaction include a temperature of 50°C-70°C and a time of 1-5 hours. Preferably, the molar ratio of the methyl allyl alcohol polyoxyethylene ether macromonomer to the short-chain alkyl compound is 1:(0.9-1.5).
4. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, In step S2, the method of introducing unsaturated bonds into the alginate oligosaccharide molecular chain includes Williamson etherification reaction of alginate oligosaccharide with allyl halide. Preferably, the number-average molecular weight of the alginate oligosaccharide is 800-1200; Preferably, the allyl halide is selected from at least one of allyl chloride, allyl bromide and allyl iodine; Preferably, the conditions for the Williamson etherification reaction include a reaction temperature of 45°C-60°C, a pH of 8-9, and a reaction time of 3.5-5 hours.
5. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, The unsaturated carboxylic acid monomer is selected from at least one of acrylic acid, methacrylic acid, and maleic acid.
6. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, In step S3, the mass ratio of the allylated alginate oligosaccharide, long and short chain polyether macromonomers, and unsaturated carboxylic acid monomers is (4-9):(60-70):
18.
7. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, The free radical polymerization reaction includes mixing unsaturated carboxylic acid monomers, initiators, and chain transfer agents to obtain solution A; dissolving allylated alginate oligosaccharides in deionized water to obtain solution B; using long and short chain polyether macromonomers as solution C; simultaneously adding solutions A, B, and C to a reactor to carry out a free radical copolymerization reaction, and then adjusting the pH value of the obtained free radical copolymerization product to 6-7.
5.
8. The method for synthesizing the polycarboxylate superplasticizer according to claim 1, characterized in that, The conditions for the free radical copolymerization reaction include a temperature of 75℃-90℃ and a time of 1h-2.5h.
9. A polycarboxylate superplasticizer, characterized in that, It is prepared by the method of any one of claims 1-8 for the preparation of polycarboxylate superplasticizer.
10. The application of the polycarboxylate superplasticizer according to claim 9 in the construction field.