Slump-retaining polycarboxylate superplasticizer and preparation method thereof
By modifying polyether macromonomers and carboxylic acid ester monomers and polymerizing them at low temperatures, a slump-retaining polycarboxylic acid superplasticizer was prepared, which solved the problem of high production cost in high-temperature environments and achieved high fluidity and stability of concrete in high-temperature and long-distance transportation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-04-07
AI Technical Summary
Existing slump-retaining polycarboxylate superplasticizers have high production costs and increase energy consumption due to high-temperature synthesis reactions, making it difficult to maintain the fluidity and slump-retaining properties of concrete in high-temperature environments and long-distance transportation.
By modifying polyether macromonomers and carboxylic acid ester monomers and combining them with low-temperature polymerization technology, slump-retaining polycarboxylic acid superplasticizers are prepared to reduce surface tension, enhance steric hindrance effect, control polymerization reaction at low temperature, and suppress side reactions.
It significantly improves the slump retention and dispersion stability of water-reducing agents, reduces production costs, maintains the high fluidity and stability of concrete, and adapts to high temperature and long-distance transportation conditions.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete admixtures, and more specifically, to a slump-retaining polycarboxylate superplasticizer and its preparation method. Background Technology
[0002] With the rapid development of infrastructure construction and the increasing demands for construction performance and durability in concrete engineering, high-slump-retention polycarboxylate superplasticizers can effectively solve the problem of concrete workability loss under high-temperature environments, long-distance transportation, and complex construction conditions, significantly improving the fluidity and slump retention of concrete, and meeting the needs of modern engineering for high-performance concrete.
[0003] The transportation routes within tunnels are complex, with severe water accumulation, potholes, and extremely poor road conditions. Therefore, the engineering community has very high requirements for the slump and fluidity retention capabilities of wet-mixed shotcrete used in tunnels. Long-distance transportation, coupled with extreme heat and the high sand content of the wet-mixed shotcrete, exacerbates the loss of slump and fluidity, necessitating concrete with superior slump retention. Furthermore, the long pouring time for large-volume concrete makes construction difficult due to slump loss; therefore, high-slump-retention water-reducing agents are needed to maintain the concrete's fluidity and reduce segregation and cold joints.
[0004] Currently, polycarboxylate superplasticizers sold on the market, especially imported products, are generally expensive, significantly increasing the production cost of concrete materials. Furthermore, the synthesis reaction of existing slump-retaining superplasticizers is carried out under high-temperature conditions, which further increases the energy consumption and cost burden of industrial production. Therefore, designing a slump-retaining superplasticizer that can maintain good slump-retaining performance while reducing production costs is of significant economic importance. Summary of the Invention
[0005] The purpose of this invention is to provide a slump-retaining polycarboxylate superplasticizer and its preparation method, which can effectively solve the problems of high production costs caused by the selection of raw materials and high-temperature synthesis reactions in existing production technologies while maintaining good slump-retaining performance.
[0006] The technical problem solved by this invention is achieved by the following technical solution.
[0007] On the one hand, embodiments of this application provide a method for preparing a slump-retaining polycarboxylate superplasticizer, comprising the following steps: S1: By weight, select 200-300 parts of modified polyether macromonomer, 100-150 parts of deionized water, 6-8 parts of hydrogen peroxide and 3-5 parts of first chain transfer agent, stir and dissolve at 5-15℃ to obtain the base material; S2: Select 60-75 parts of modified carboxylic acid ester monomers, 10-20 parts of deionized water and 10-15 parts of acrylic acid, mix them to obtain solution A; S3: Select 2-3 parts of second chain transfer agent, 0.3-0.8 parts of ascorbic acid and 20-50 parts of deionized water, mix them to obtain solution B; S4: Add solution A and solution B dropwise to the substrate, dilute with deionized water, and adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
[0008] Furthermore, in step S1, the modified polyether macromonomer is modified methyl allyl polyoxyethylene ether, and the modification step is as follows: by weight, 20-30 parts of 1-octyl isocyanate are added dropwise to 180-270 parts of methyl allyl polyoxyethylene ether, and the reaction is carried out at 60-70℃ for 1-3 hours. After washing, the product is obtained.
[0009] Furthermore, the first chain transfer agent is any one of sodium hypophosphite, isopropanol, and tert-butanol.
[0010] Furthermore, in step S2, the modified carboxylic acid ester monomer is modified hydroxyethyl methacrylate phosphate. The modification steps are as follows: select 60-80 parts by weight of hydroxyethyl methacrylate phosphate and 2-3 parts by weight of ferric sulfate, react at 70-90℃ for 1-1.5h, and adjust the pH to 4-4.2 to obtain the product.
[0011] Furthermore, in step S3, the second chain transfer agent is any one or more of mercaptoacetic acid, mercaptopropionic acid, β-mercaptoethanol, n-dodecyl mercaptoethanol, and tert-dodecyl mercaptoethanol.
[0012] Furthermore, step S4 also includes controlling the reaction temperature at 5-15°C.
[0013] On the other hand, embodiments of the present invention also provide a slump-resistant polycarboxylate superplasticizer, which is prepared by the above preparation method.
[0014] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. This invention modifies the polyether macromonomer, and through the addition reaction between the isocyanate group and the end of the polyether side chain, it significantly reduces the surface tension of the macromonomer and significantly enhances the steric hindrance effect of the polymer side chain; the synergistic effect of the two can more effectively disperse cement particles, thereby significantly improving the workability and slump retention of the water-reducing agent in different aggregate systems; 2. This invention provides a stable hydroxyethyl methacrylate phosphate-iron(III) complex by modifying carboxylic acid ester monomers. This complex participates in copolymerization as a functional monomer. Its iron ion center can be more firmly anchored on the surface of cement particles in the early stage of cement hydration, thereby achieving a slower and more controllable release, giving the water-reducing agent a more durable slump retention effect and excellent early strength promoting ability. 3. By controlling the polymerization temperature within 5-15℃, this invention reduces the activity of the reaction system, thereby precisely controlling the polymerization rate and maximally suppressing side reactions such as molecular chain transfer, crosslinking, and decomposition. Furthermore, the synthesized slump-retaining polycarboxylate superplasticizer exhibits a more significant steric hindrance effect and superior dispersion stability, enabling it to be persistently and efficiently adsorbed onto the surface of cement particles, promoting their dispersion and weakening interparticle interactions, thus forming a highly fluid and stable cement paste. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.
[0017] Example 1 This embodiment provides a slump-retaining polycarboxylate superplasticizer, which is prepared by the following method: S1: By weight, select 200 parts modified methyl allyl polyoxyethylene ether, 120 parts deionized water, 6 parts hydrogen peroxide and 3 parts sodium hypophosphite, control the temperature at 10℃, stir thoroughly to completely dissolve, and obtain the base material.
[0018] The synthesis steps of the modified methyl allyl polyoxyethylene ether are as follows: using organotin as a catalyst, 180 parts of methyl allyl polyoxyethylene ether are dissolved in acetone, and 20 parts of 1-octyl isocyanate are slowly added dropwise. After the addition is completed, the reaction is carried out at 65°C for 2 hours. Then, the acetone is removed by rotary evaporation to obtain the modified methyl allyl polyoxyethylene ether.
[0019] S2: Select 62.5 parts of modified hydroxyethyl methacrylate phosphate, 10 parts of deionized water and 11 parts of acrylic acid, mix them to obtain solution A; The synthesis steps of the modified hydroxyethyl methacrylate phosphate are as follows: 60 parts of hydroxyethyl methacrylate phosphate are mixed with 2 parts of ferric sulfate and reacted at 80°C for 1 hour. Then, 30% sodium carbonate solution is slowly added dropwise to adjust the pH to 4-4.2, thus obtaining the hydroxyethyl methacrylate phosphate-iron complex with ferric ions.
[0020] S3: Select 2.4 parts mercaptoacetic acid, 0.43 parts ascorbic acid and 20 parts deionized water, mix them thoroughly and evenly to obtain solution B; S4: Add the prepared solutions A and B dropwise to the substrate using a peristaltic pump over a period of 2 hours at a reaction temperature of 5°C. After the reaction is complete, dilute with 50 parts of deionized water and finally add 30% sodium carbonate solution to adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
[0021] Example 2 The steps in this embodiment are basically the same as those in Example 1, except that the synthesis steps of the modified methyl allyl polyoxyethylene ether and the modified hydroxyethyl methacrylate phosphate remain unchanged. The difference is as follows: S1: By weight, select 240 parts modified methyl allyl polyoxyethylene ether, 120 parts deionized water, 6 parts hydrogen peroxide and 4 parts sodium hypophosphite, control the temperature at 15℃, stir thoroughly to completely dissolve, and obtain the base material.
[0022] S2: Select 68.4 parts of modified hydroxyethyl methacrylate phosphate, 20 parts of deionized water and 10.8 parts of acrylic acid, mix them to obtain solution A; S3: Select 2.12 parts mercaptopropionic acid, 0.53 parts ascorbic acid and 40 parts deionized water, mix them thoroughly and evenly to obtain solution B; S4: Add the prepared solutions A and B dropwise to the substrate using a peristaltic pump over a period of 2 hours at a reaction temperature of 9°C. After the reaction is complete, dilute with 60 parts of deionized water and finally add 30% sodium carbonate solution to adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
[0023] Example 3 The steps in this embodiment are basically the same as those in embodiment 2, the difference being: S1: By weight, select 300 parts modified methyl allyl polyoxyethylene ether, 150 parts deionized water, 8 parts hydrogen peroxide and 5 parts sodium hypophosphite, control the temperature at 13℃, stir thoroughly to completely dissolve, and obtain the base material.
[0024] S2: Select 72.4 parts of modified hydroxyethyl methacrylate phosphate, 20 parts of deionized water and 14 parts of acrylic acid, mix them to obtain solution A; S3: Select 2.42 parts β-mercaptoethanol, 0.78 parts ascorbic acid and 50 parts deionized water, mix them thoroughly and evenly to obtain solution B; S4: Add the prepared solutions A and B dropwise to the substrate using a peristaltic pump over a period of 2 hours at a reaction temperature of 11°C. After the reaction is complete, dilute with 60 parts of deionized water and finally add 30% sodium carbonate solution to adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
[0025] Example 4 The steps in this embodiment are basically the same as those in embodiment 2, the difference being: S1: By weight, select 200 parts modified methyl allyl polyoxyethylene ether, 100 parts deionized water, 8 parts hydrogen peroxide and 5 parts sodium hypophosphite, control the temperature at 15℃, stir thoroughly to dissolve completely, and obtain the base material.
[0026] S2: Select 70.4 parts of modified hydroxyethyl methacrylate phosphate, 20 parts of deionized water and 12 parts of acrylic acid, mix them to obtain solution A; S3: Select 2.42 parts of n-dodecyl mercaptan, 0.68 parts of ascorbic acid and 30 parts of deionized water, mix them thoroughly and evenly to obtain solution B; S4: Add the prepared solutions A and B dropwise to the substrate using a peristaltic pump over a period of 2 hours at a reaction temperature of 15°C. After the reaction is complete, dilute with 50 parts of deionized water and finally add 30% sodium carbonate solution to adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
[0027] Compare with Example 1: This comparative example uses a commercially available slump-resistant polycarboxylate superplasticizer.
[0028] Compare with Example 2: This comparative example is basically the same as Example 2, except that the reaction temperature is not controlled in step S4 and the reaction temperature is higher than 20°C.
[0029] Compare with Example 3: This comparative example is basically the same as Example 2, except that in step S1, no modified polyether macromonomer is added, and an unmodified polyether macromonomer is used.
[0030] Compare with Example 4: This comparative example is basically the same as Example 2, except that modified hydroxyethyl methacrylate phosphate is not added in step S2.
[0031] Then, the slump-retaining polycarboxylate superplasticizers prepared in Examples 1-4 were selected as samples, and the following comparative experiments were conducted with the slump-retaining polycarboxylate superplasticizers obtained in Control Examples 1-4: 1. Cement Paste Flowability Test: The initial and over-time flowability of cement paste was tested according to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures". The cement used was P·O 42.5 grade ordinary Portland cement, with 300g of cement weighed. The water-cement ratio of the freshly mixed cement paste was 0.29, and the polycarboxylate superplasticizer dosage was 0.3wt%. The mixed cement paste was poured into a truncated conical mold with a top opening of 36mm, a bottom opening of 60mm, and a height of 60mm. After slowly lifting the mold vertically, the maximum diameter of the flowing portion in two mutually perpendicular directions was measured with a ruler, and the average value was taken as the cement paste flowability. The experimental results are shown in Table 1. Table 1: Test results of the fluidity of the paste made with water-reducing agent
[0032] As shown in Table 1, compared with Comparative Example 1, the water-reducing agent involved in this application exhibits superior slump retention and water reduction properties in Examples 1–4. In particular, Comparative Example 2 showed the worst slump retention and flow properties, indicating that the control of reaction temperature has a crucial impact on the polymerization reaction and product performance. Analysis suggests that controlling the polymerization temperature within the range of 5-15℃ reduces the activity of the reaction system, thereby precisely controlling the polymerization rate and maximally suppressing side reactions such as molecular chain transfer, crosslinking, and decomposition. Furthermore, the synthesized slump-retaining polycarboxylate water-reducing agent exhibits a more significant steric hindrance effect and superior dispersion stability, enabling it to persistently and efficiently adsorb onto the surface of cement particles, promoting dispersion and weakening interparticle interactions, thus forming a highly fluid and stable cement paste.
[0033] In addition, Comparative Examples 3 and 4 lacked modified methyl allyl polyoxyethylene ether and modified carboxylic acid ester monomers, respectively, during the reaction process. In Comparative Example 3, the use of unmodified polyether macromonomers weakened the steric hindrance of the polymer side chains, making it difficult for the water-reducing agent molecules to form a well-defined conformation at the cement particle interface, and reducing its effective adsorption capacity. Ultimately, the synthesized product exhibited inferior slump retention and cement paste flowability compared to Examples 1-4. Analysis suggests that the hydroxyl groups in methyl allyl polyoxyethylene ether possess a certain degree of activity, capable of undergoing an addition reaction with octyl isocyanate. This reaction reduces the surface tension of the macromonomer and enhances its steric hindrance effect, thereby improving the slump retention and viscosity reduction effects of the water-reducing agent.
[0034] In Comparative Example 4, due to the lack of modified carboxylic acid ester monomers and insufficient ester group content, the number of carboxyl groups generated by hydrolysis was limited, thus reducing the amount of water-reducing agent adsorbed on the surface of cement particles. Ultimately, this also resulted in a significant decrease in the slump retention and flowability of the product. Analysis suggests that the hydroxyethyl methacrylate phosphate-iron(III) complex, as a functional monomer participating in copolymerization, allows its iron ion centers to be more firmly anchored on the surface of cement particles in the early stages of cement hydration, thereby achieving a slower and more controllable release. This gives the water-reducing agent a more durable slump retention effect and excellent early strength promoting ability.
[0035] 2. Slump Test: Slump and slump changes over 1 hour, 2 hours, and 3 hours were measured according to GB / T 8076-2008 "Concrete Admixtures". The concrete mix proportion was cement:fly ash:sand:aggregate:water = 260:85:720:1150:150, and the polycarboxylate superplasticizer dosage was 1 wt% of the cementitious materials. A slump test bucket with a top opening of 100 mm, a bottom opening of 200 mm, and a height of 300 mm was used. Concrete was poured in two batches. After each filling, the bucket was tamped 20 times evenly from the outside to the inside along the bucket wall. After compaction, the surface was smoothed, and then the bucket was lifted vertically upwards. The concrete slumped due to its own weight. The slump H0 was obtained by subtracting the height of the highest point of the slumped concrete from the bucket height (300 mm). Then, the sample was placed into a sample tube wiped with a damp cloth, the container was covered, and allowed to stand for 1 hour, 2 hours, and 3 hours respectively. After each standing period, the sample was poured out onto an iron plate and stirred thoroughly. The slump was then measured according to the slump test method. The difference between the slump measured at the machine time and at 1 hour, 2 hours, and 3 hours was calculated, yielding the change in slump over time (1 hour, 2 hours, and 3 hours). The experimental results are shown in Table 2. Table 2: Slump Test Results of Water-Reducing Agent
[0036] As shown in Table 2, the initial slump of concrete with the slump-retaining polycarboxylate superplasticizer described in this application is within the range of 225–230 mm. Example 2, exhibiting the best slump retention performance, maintains slumps of 230 mm, 230 mm, and 225 mm at 1 hour, 2 hours, and 3 hours, respectively, with a slump loss of only 5 mm at 3 hours. In contrast, Example 4, with the weakest slump retention effect, experiences a slump loss of 10 mm at 3 hours. In comparison, concrete with a commercially available traditional polycarboxylate slump-retaining admixture has an initial slump of 225 mm, which decreases to 220 mm, 210 mm, and 205 mm at 1 hour, 2 hours, and 3 hours, respectively, with a cumulative loss of 20 mm over 3 hours. Therefore, compared to the slump-retaining polycarboxylate superplasticizers prepared in Examples 1–4 of this application, commercially available polycarboxylate slump-retaining agents exhibit poorer dispersibility, slump retention, and workability in concrete, demonstrating the significant advantages of the product in this application in terms of key performance characteristics.
[0037] 3. Compressive Strength Test: The compressive strength of concrete was tested according to GB / T 8076-2008 "Concrete Admixtures". Prismatic cement mortar specimens of 40mm×40mm×160mm were prepared, using the same mix proportion as in the slump test. The poured specimens were placed in a standard curing chamber for 24 hours. After curing, the specimens were demolded and placed in water at 20℃ for further curing. The compressive strength of the standard specimens was measured after 3 days, 7 days, and 28 days of curing. The experimental results are shown in Table 3. Table 3: Compressive strength test results of water-reducing agents
[0038] It can be seen that, compared with Comparative Examples 1-4, the slump-retaining polycarboxylate superplasticizer provided in Examples 1-4 of this application can significantly improve the compressive strength of concrete specimens formed from concrete mixtures with high mud content in sand and gravel aggregates.
[0039] In summary, the embodiments of the present invention provide a slump-retaining polycarboxylate superplasticizer, which significantly reduces the surface tension of the macromonomer and enhances the steric hindrance effect of the polymer side chain through the addition reaction between the isocyanate group and the end of the polyether side chain by modifying the polyether macromonomer. The synergistic effect of the two can more effectively disperse cement particles, thereby significantly improving the workability and slump-retaining performance of the superplasticizer in different aggregate systems. This invention provides a stable hydroxyethyl methacrylate phosphate-iron(III) complex by modifying carboxylic acid ester monomers. This complex participates in copolymerization as a functional monomer, and its iron ion center can be more firmly anchored on the surface of cement particles in the early stage of cement hydration, thereby achieving a slower and more controllable release, giving the water-reducing agent a more durable slump retention effect and excellent early strength promoting ability. This invention reduces the activity of the reaction system by controlling the polymerization temperature within 5-15℃, thereby precisely controlling the polymerization rate and suppressing side reactions such as molecular chain transfer, crosslinking, and decomposition to the greatest extent. Furthermore, the synthesized slump-preserving polycarboxylate superplasticizer exhibits a more significant steric hindrance effect and superior dispersion stability, enabling it to be persistently and efficiently adsorbed onto the surface of cement particles, promoting their dispersion and weakening interparticle interactions, thus forming a highly fluid and stable cement paste.
[0040] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A method for preparing a slump-retaining polycarboxylate superplasticizer, characterized in that, Includes the following steps: S1: By weight, select 200-300 parts of modified polyether macromonomer, 100-150 parts of deionized water, 6-8 parts of hydrogen peroxide and 3-5 parts of first chain transfer agent, stir and dissolve at 5-15℃ to obtain the base material; S2: Select 60-75 parts of modified carboxylic acid ester monomers, 10-20 parts of deionized water and 10-15 parts of acrylic acid, mix them to obtain solution A; S3: Select 2-3 parts of second chain transfer agent, 0.3-0.8 parts of ascorbic acid and 20-50 parts of deionized water, mix them to obtain solution B; S4: Add solution A and solution B dropwise to the substrate, dilute with deionized water, and adjust the pH to neutral to obtain the slump-resistant polycarboxylate superplasticizer.
2. The method for preparing a slump-retaining polycarboxylate superplasticizer according to claim 1, characterized in that, In step S1, the modified polyether macromonomer is modified methyl allyl polyoxyethylene ether. The modification step is as follows: by weight, 20-30 parts of 1-octyl isocyanate are added dropwise to 180-270 parts of methyl allyl polyoxyethylene ether, and the reaction is carried out at 60-70°C for 1-3 hours. After washing, the product is obtained.
3. The method for preparing a slump-retaining polycarboxylate superplasticizer according to claim 2, characterized in that, The first chain transfer agent is any one of sodium hypophosphite, isopropanol, and tert-butanol.
4. The method for preparing a slump-retaining polycarboxylate superplasticizer according to claim 1, characterized in that, In step S2, the modified carboxylic acid ester monomer is modified hydroxyethyl methacrylate phosphate. The modification steps are as follows: select 60-80 parts by weight of hydroxyethyl methacrylate phosphate and 2-3 parts by weight of ferric sulfate, react at 70-90℃ for 1-1.5h, and adjust the pH to 4-4.2 to obtain the product.
5. The preparation method of the slump-retaining polycarboxylate superplasticizer according to claim 1, characterized in that, In step S3, the second chain transfer agent is any one or more of mercaptoacetic acid, mercaptopropionic acid, β-mercaptoethanol, n-dodecyl mercaptoethanol, and tert-dodecyl mercaptoethanol.
6. The method for preparing a slump-retaining polycarboxylate superplasticizer according to claim 1, characterized in that, Step S4 also includes controlling the reaction temperature at 5-15℃.
7. A slump-retaining polycarboxylate superplasticizer, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.